Daniel R. Adamo Astrodynamics | AIAA Houston Section

Daniel R. Adamo is a longtime member of our NASA/JSC community and an expert in astrodynamics. As of July 27, 2016, when we are starting this public archive of some of his work, he is retired, living in Oregon, and he is a popular Distinguished Lecturer (DL) of AIAA. The DL manual lists his 3 presentations, and he has completed a 4th presentation to be added to that list. As of Sunday, August 26, he added a fifth presentation to that list (below). In April of 2019, Mr. Adamo added a sixth presentation (title and abstract shown below in the sixth bullet), and he first made that presentation in that same month to the AIAA Student Chapter of Pennsylvania State University.

Interplanetary Cruising With Earth-To-Mars Transit Examples
Aquarius, A Reusable Water-Based Interplanetary Human Spaceflight Transport
Questioning The Surface Of Mars As The 21st Century’s Ultimate Pioneering Destination In Space
Depot locations supporting Human SpaceFlight (HSF)
Exploring the Solar System Through Low-Latency Telepresence
“Forty Years on the Bleeding Edge of Technology From an Aerospace Engineer’s Perspective” How did a kid living amid New Hampshire farm fields progress to serve on console in Houston’s Mission Control during 60 Space Shuttle missions? This 1.5-hour autobiographic lecture follows an aerospace career from its roots in the 1970s to present-day freelance consulting on space exploration missions and architectures. Along the way, key “lessons learned” are debriefed with regard to developing, operating, and managing aerospace systems. The lecture concludes with experience-based advice on starting an aerospace career.

Above: A rough image of the business card (and ATIG email signature) of Mr. Adamo, with images of Mr. Adamo in Mission Control Center (MCC) at NASA Johnson Space Center (JSC). (Click to zoom.)

Mr. Adamo has been emailing his Astrodynamics Technical Interchange Group (ATIG) for years. We suggested publishing those outgoing ATIG email notes here on a web page on the website of our Section (initially it was here on the web page of AIAA Houston Section Astrodynamics technical committee), along with the original email notes and attachments (PDF documents, GIFs [image files]), etc. He said yes to our request, so we present a bulleted list below. The first is from 2008, and the latest is from 2016 as we start this project in the fall of 2016. Here is a link to the Dan Adamo ATIG email signature. Mr. Adamo encourages anyone interested in receiving his ATIG email notes to email him at adamod [at] earthlink [dot] net. These Adamo ATIG files are stored in an AIAA Houston Section Horizons (newsletter) directory, not the default WordPress or Bluehost directory, so these files are archived on an AIAA Houston Section directory owned by our hosting service BlueHost.

[2024 02 26] February 26, 2024. A Tale of Two Translunar Aborts, An online Lunch-and-Learn using Zoom in the NASA/JSC community, a presentation by Daniel R. Adamo. We provided the Zoom link in our publicity, and without using any RSVP, attendance was about 100 people.
Date: Monday, February 26, 2024
Time: 11:30 AM – 1:00 PM
Place: Online only (Zoom)
Speaker: Daniel R. Adamo, Astrodynamics Consultant and AIAA Distinguished Speaker
Flyer: (PDF)
Presentation: (PDF) Here are the slides used for this presentation.
Link to the Video Recording: Here is a link to the Zoom video recording of this event. We thank AIAA Houston Section’s SpaceGeekSpeak (Svetlana Hanson) for a convenient place on YouTube to store such a big video file.
Abstract: The recent Peregrine robotic lunar landing abort due to a leaking oxidizer tank was an off-Earth navigator’s nightmare. Overboard vent accelerations were literally all over the sky before attitude control was restored, and an uncontrolled lunar impact was impending before a more responsible disposal strategy was implemented. These dramatic events recall still higher stakes in play after Apollo 13’s onboard explosion aborted its lunar landing attempt in 1970. New insights regarding post-explosion vent accelerations threatening safe Apollo 13 return to Earth will be discussed.
Post-event summary: About 100 people attended this online-only event using Zoom. We recorded the Zoom event. The recording will be stored on the YouTube channel for another AIAA Houston Section event, SpaceGeekSpeak. Dave Hanson was our event co-host for this lunch-and-learn, providing Zoom hosting skills and other kinds of help. Douglas Yazell hosted the event as Chair of the AIAA Houston Section history technical committee. Our Section Chair John Rangel started the recording of the lunch-and-learn with comments about AIAA Houston Section.

ATIG_154__2024_12_16 [December 16, 2024] Parker Solar Probe (PSP) Update
Here is a link to email #154.
ATIG_153__2024_10_23 [October 23, 2024] Europa Clipper’s Earth Departure
Here is a link to email #153.
ATIG_152__2024_10_15 [October 15, 2024] The First Leg Of Hera’s Mission To Dimorphos
Here is a link to email #152.
ATIG_151__2024_09_01 [September 1, 2024] JUICE Departs for Venus with a Moon-Earth Flyby
Here is a link to email #151.
AITG_150__2024_07_07 [July 7, 2024] A Telescope On Phobos?
Here is a link to email #150.
ATIG_149__2024_05_04 [May 4, 2024] ISS Orbit Prediction Accuracy
Here is a link to email #149.
ATIG_148__2024_07_02 [July 2, 2024] Synodic-Resonant Waypoints Supporting Earth/Mars Transits
Here is a link to email #148.
ATIG_147__2024_01_29 [January 29, 2024] An Account of the “Peregrine” Lunar Lander’s Abort
Here is a link to email #147.
ATIG_146__2023_11_05 [November 5, 2023] Luna-25’s Fregat Upper Stage
Here is a link to email #146.
ATIG_145__2023_10_22 [October 22, 2023] The First Leg of Psyche’s Mission
Here is a link to email #145.
ATIG_144__2023_10_09 [September 9, 2023] Insights From Reconstructing Apollo 13’s Abort Trajectory
Here is a link to email #144.
ATIG_143__2023_09_11 [September 11, 2023] Testing A Supplemental Earth Orientation Model
Here is a link to email #143.
ATIG_142__2023_07_16 [July 16, 2023] Targeting Interplanetary Departures And Returns From Lunar NRHO
Here is a link to email #142.
ATIG_141__2023_04_18 [April 18, 2023] JUICE Earth Departure
Here is a link to email #141.
ATIG_140__2023_02_08 [February 8, 2023] A Foray Into Eclipses And AI
Here is a link to email #140.
ATIG_139__2023_01_12 [January 12, 2023] 16 November 2022 UTC Artemis I Launch
Here is a link to email #139.
ATIG_138__2022_11_26 [November 26, 2022] Artemis I Launch Window Anatomy
Here is a link to email #138.
ATIG_137__2022_11_03 [November 3, 2022] “Lucy” Mission’s Centaur Stage
Here is a link to email #137.
ATIG_136__2022_09_19 [September 19, 2022] DART’s Impending Near-Earth Asteroid Impact
Here is a link to email #136.
ATIG_135__2022_12_31 [December 31, 2022] CAPSTONE Status
Here is a link to email #135.
ATIG_134__2022_09_07 [September 7, 2022] Targeting in Parking Orbit Mode (POM)
Here is a link to email #134.
ATIG_133__2022_06_27 [June 27, 2022] Re: 4 March 2022 Lunar Impact
Here is a link to email #133.
ATIG_132__2022_01_16 [January 16, 2022] “Inspiration4” Trajectory Reconstruction.
Here is a link to email #132.
ATIG_131__2022_01_12 [January 12, 2022] Developing Normalized Gravity Models
Here is a link to email #131.
ATIG_130__2021_12_25 [December 25, 2021] JWST’s Earth-Centered Deployment Trajectory
Here is a link to email #130.
ATIG_129__2021_11_26 [November 26, 2021] DART Trajectory Plots
Here is a link to email #129.
ATIG_128__2021_02_18 [February 18, 2022] A Trend in Mars Forward Planetary Protection
Here is a link to email #128.
ATIG_127__2021_11_15 [Novemeber 15, 2021] Ongoing Lucy Mission Commentary
Here is a link to email #127.
ATIG_126__2021_10_26 [October 26, 2021] THEMIS-ARTEMIS Trajectory Odysseys
Here is a link to email #126.
ATIG_125__2021_09_10 [September 10, 2021] Modeling ISS Translations Over Finite Trajectory Arcs.
Here is a link to email #125.
ATIG_124__2021_07_25 [July 25, 2021] An Ambiguity in NASA Apollo Trajectory Elements (NATs)
Here is a link to ATIG email #124.
ATIG_123__2021_07_13 [July 13, 2021] Juno’s Jupiter Odyssey
Here is a link to ATIG email #123.
ATIG_122__2021_06_02 [June 2, 2021] Starlink Sightings
Here is a link to ATIG email #122.
ATIG_121__2021_02_27 [February 27, 2021] SAOCOM 1B Polar Launch by Falcon 9
Here is a link to ATIG email #121.
ATIG_120__2021_01_10 [January 10, 2021] A Global Planisphere
[Here is a link to ATIG email #120.]
ATIG_119__2020_10_17 [October 17, 2020] Surface Map Horizon Graphics
[Here is a link to ATIG email #119.]
ATIG_118__2020_08_09 [August 9, 2020] Three Spacecraft Cruising to Mars
[Here is a link to ATIG email #118.]
ATIG_117__ 2020_07_15 [July 15, 2020] Comet C/2020 F3 “NEOWISE”
[Here is a link to ATIG email #117.]
ATIG_116__2020_07_13 [July 13, 2020] A White Paper Advocating Increased Planetary Defense Preparedness & Resilience
[Here is a link to ATIG email #116.]
ATIG_115__2020_07_12 [July 12, 2020] A White Paper Roadmap for Low-Latency Telepresence at Mars from Deimos
[Here is a link to the ATIG email file #115.]
ATIG_114__2020_07_11 [July 11, 2020] A White Paper Roadmap for Low-Latency Telepresence at Near-Earth Objects
[Here is a link to the ATIG email file #114.]
ATIG_113__2020_04_29 [April 29, 2020] Solar Beta Angle Computation and Simulation
[Here is a link to the ATIG email file #113, Solar Beta Computation and Simulation.]
ATIG_112__2020_11_19 [March 31, 2020, updated August 11, 2021] Statistic Analysis of U.S. COVID-19 Deaths
[Here is a link to the ATIG email file #112, Statistic Analysis of U.S. COVID-19 Deaths.]
ATIG_111__2020_02_15 [February 15, 2020] Discovering Asteroid 2019 OK and Similar Stealthy Earth Approaches
[Here is a link to the ATIG email file #111, Discovering Asteroid 2019 OK and Similar Stealthy Earth Approaches.]
ATIG_110__2019_11_17 [November 17, 2019] Eclipses in a Sun-Synchronous Orbit (SSO)
[Here is a link to the ATIG email file #110, Eclipses in a Sun-Synchronous Orbit.]
ATIG_109__2019_10_11 [October 11, 2019] Surface Map Terminator Graphics
[Here is a link to the ATIG email file #109, Surface Map Terminator Graphics.]
ATIG_108__2019_09_22 [September 22, 2019] Parker Solar Probe Heliocentric Motion, 2018-2021
[Here is a link to the ATIG email file #108, Parker Solar Probe Heliocentric Motion, 2018-2021.]
ATIG_107__2019_07_13 [July 13, 2019] Spheroid Graphics
[Here is a link to the ATIG email file #107, Spheroid Graphics.]
ATIG_106__2019_03_2019 [December 8, 2018] NHATSchecker, A New Mission Planning Utility
[Here is a link to the ATIG email file #106, NHATSchecker, A New Mission Planning Utility.]
ATIG_105__2018_09_01 [September 1, 2018] Interplanetary Reference Body Transformations
ATIG Members- Math behind the subject Galilean transformations is deceptively simple. Even in the context of a proven ephemeris ops concept, I’ve nevertheless found the logic to implement such transformations (for the first time in FORTRAN about 15 years ago; now in Swift) to be daunting. Furthermore, there’s no comprehensive practical guidance on the topic in my astrodynamics library or, from multiple searches I’ve recently conducted, on the Internet. I‘ve therefore taken the initiative to document a strategy with which to transform a position/velocity state vector referenced to one body/barycenter in the Solar System into another state vector expressed relative to any other such body/barycenter. This capability relies on an extensible tree-like hierarchy of ephemerides as detailed in the attached PDF file. Comments on this paper, including citation of relevant documentation to be found elsewhere, are invited. -Dan
[Here is a link to the attached PDF file, SVrefBodyTransformationsR1.pdf.]
[Here is a link to the ATIG email file #105, Interplanetary Reference Body Transformations.]
ATIG_104__2018_05_25 [May 25, 2018] InSight’s VAFB Departure For Mars
ATIG Members- With regard to InSight, NASA’s most recently launched robotic Mars probe, I had several requests to write a paper on how a high inclination launch from Vandenberg AFB can access interplanetary destinations. The short answer is: thanks to an Earth gravity assist in the parking orbit arc between LEO insertion and the trans-Mars injection (TMI) burn. The Russians have been coping with this geometry for years, their biggest problem lately being executing TMI (ref. the Phobos-Grunt ATIG_032 upload archived at http://www.aiaahouston.org/adamo_astrodynamics/). In fact, only higher Earth parking orbit inclinations can access all Mars departure opportunities without occasional performance-robbing “dogleg” TMIs or dedicated plane change impulses post-TMI. The attached white paper on InSight’s Earth departure for Mars on 5 May 2018 documents two trajectories. First, an approximate patched conic design with a purely prograde TMI impulse is developed. An as-flown trajectory is then reconstructed (with its own set of approximations in lieu of proprietary data unavailable for public release) leading to some interesting insights on InSight’s departure, particularly when compared with the patched conic design. Feel free to be in touch with further insights, questions, or comments on this upload. -Dan
[Here is a link to the attached PDF file, InSightDepartureR0.pdf.]
[Here is a link to the ATIG email file #104, InSight’s VAFB Departure For Mars.]
ATIG_103__2018_05_01 [May 1, 2018] An (Inter)Planetary Checkout Monitor
ATIG Members- Those of you with history in trajectory operations at Mission Control-Houston (MCC-H) will be familiar with the MSK 2300 Checkout Monitor display. Since its inception in the 1960s, MCC-H has always had a Checkout Monitor with which to display a state vector’s Cartesian position/velocity components and associated orbit elements/parameters at a specified time. Notably, all states displayed in Checkout Monitor have been geocentric except during the brief period from approximately 1968 to 1972 when MCC-H supported Apollo Program lunar landings. As documented in recent ATIG uploads, my Swift software development exploits with JPL’s planetary ephemerides accessed through the Cspice library have led to the need for a Planetary Checkout Monitor (PCM) to display state vectors/elements/parameters from those ephemerides. An example snapshot of this display’s current incarnation is attached. Interactive widgets at the top of a PCM govern the state vector obtained from JPL ephemerides when the “Fetch State” button is clicked. The fetch epoch may be specified as a UTC date and time or as a dynamic barycentric time (TDB) expressed as a Julian date (JD). Inputs to either fetch epoch option are immediately reflected in the other such that they’re always synchronized. Above the fetch epoch widgets are 3 pop-up menus, each with selectable items for the Solar System barycenter, the Sun, eight planets, Pluto, and the Moon. The “Target Ephem.” menu selects the ephemeris whose state vectors are displayed relative to the ephemeris selected by the “Observer Ephem.” menu. Thus, a position vector in a state displayed by PCM will have the Target object’s center at its “head” and the Observer object’s center at its “tail”. In the specific case of the attached PCM, lunar geocentric states are being displayed. Near the bottom of PCM output, there are exceptions to the Observer-centered theme in order to display Observer nadir position parameters on the Target. The “Source Ephem.” pop-up menu’s input governs PCM processing leading to its final two lines of output. The selected Source object can be regarded as being the source of illumination or other radiation. In the attached example, Moon-Earth-Sun elongation near 147 deg indicates the Moon has a gibbous phase as observed from Earth and illuminated by the Sun. The “Waxing” phase trend (as opposed to “Waning”) indicates full Moon phase is upcoming. The final line’s Source latitude with respect to the Target’s Observer-centered orbit is equivalent to the Sun’s beta angle in MCC-H jargon as applied to a low-Earth orbit. Operationally, all PCM output is mono-spaced text, any segment of which can be copied-and-pasted as desired. You are invited to send comments or questions about this output. Should any of you wish to share lunar geocentric test results at
Ephemeris Fetch UTC = 2017y 246d Sun (09-03) 11:58:50.816
Ephemeris Fetch TDB JD = 2458000.00000000d,
I‘d be interested to see your results. -Dan
[Here is a link to the attached PDF file, coMoonVsEarth2458000jd.pdf.
[Here is a link to the ATIG original #103 email (.eml) file, [NumberSign]103-An_(Inter)Planetary_Checkout_Monitor.eml.
ATIG_102__2018_04_25 [April 25, 2018] Getting Ready To Survey Nearby Solar Systems with TESS
ATIG Members- Launched 18 April 2018 at 22:51 UT, the Transiting Exoplanet Survey Satellite (TESS) is designed to vastly extend discoveries of planets beyond our Solar System. In a manner similar to the Kepler mission (ref. https://www.nasa.gov/mission_pages/kepler/overview/index.html), TESS will identify an exoplanet by observing it transit the star it orbits, thereby slightly reducing the star’s brightness. Such observations are only possible for an exoplanet whose orbit plane happens to nearly contain the Earth. The operational orbit for TESS about Earth is optimized to obtain and transmit exoplanet transit observations, but reaching that orbit will require 2 months of maneuvers, including a lunar flyby with pericynthion on 17 May at 06:30 UT. The attached PDF contains trajectory plots illustrating this process using data posted to JPL’s Horizons ephemeris server (ref. https://ssd.jpl.nasa.gov/?horizons) on 19 April. More information on TESS launch and operations can be found at https://spaceflightnow.com/2018/04/19/all-sky-surveyor-launched-from-cape-canaveral-on-the-hunt-for-exoplanets/. -Dan
[Here is a link to the attached PDF file, TESStraj.pdf.]
[Here is a link to the original ATIG #102 email (.eml) file, [NumberSign]102-Getting_Ready_To_Survey_Nearby_Solar_Systems_with_TESS.eml.]
ATIG_101__2018_02_23 [February 23, 2018] The Interplanetary Roadster
ATIG Members- I hope you’ll enjoy the attached account of Falcon Heavy’s first launch. Feedback is welcome, particularly any insight into what decontamination procedures, including “none”, SpaceX conducted on the Roadster before launch. I’ve contacted planetary protection stakeholders at NASA about this and have had no response a week later. IMHO, it’s arguable North Korea has been more responsible in recent ballistic missile testing than was SpaceX in launching “a red Roadster for the red planet”. -Dan
[Here is a link to the attached PDF file, RoadsterTrajectoryR2.pdf.]
[Here is a link to the original ATIG #101 email (.eml) file, [NumberSign]101-The Interplanetary Roadster.eml.]
ATIG_100__2018_03_06 [March 6, 2018] Accessing JPL Ephemerides From Swift Code Using The SPICE Library
ATIG Members- I‘ve written yet another chapter in the continuing saga of accessing Cspice library functions from Swift code. In the attached “R5” draft, the new material appears in Section 6.0 beginning on p. 8. This version completely supersedes all previously transmitted drafts in this thread. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Sun, 18 Feb 2018 16:32:01 -0800
To: Daniel Adamo <adamod@earthlink.net>
Subject: Re: Accessing JPL Ephemerides From Swift Code Using The SPICE Library
ATIG Members- Continuing with my theme of software development being a humbling life experience, I’m attaching an “R4” draft of the white paper introduced by this thread. This update completely supersedes previous drafts, and it adds a new Section 5.0 addressing how to handle C macros from the Cspice library when developing an application with Swift as its primary programming language. The R4 draft also corrects a typo in Section 4.0. Happy Presidents’ Day! -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Fri, 02 Feb 2018 22:11:57 -0800
Conversation: Accessing JPL Ephemerides From Swift Code Using The SPICE Library
Subject: Re: Accessing JPL Ephemerides From Swift Code Using The SPICE Library
ATIG Members- Thanks to those of you who wrote me commiserating on the fate of FORTRAN, the joys of using SPICE, and applications programming on the bleeding edge. My apologies, but I need to supersede the “R2” draft with the attached “R3”. In Section 3.0 of R2, my contention that “Swift conversion of a user interface text-based String into a Double floating point value… introduces a time skew” is incorrect. This skew really arises in the p. 4 computation of secSinceJ2K, where the difference between two Julian dates, fetchTDB – epochJ2000, is being determined. With modern-day Julian dates having values in excess of 2 million days, this difference limits precision to the order of 0.0001 s in secSinceJ2K. The attached “R3” draft corrects this error with changes confined to Section 3.0 on pages 5 and 6. If anyone would like a version of R3 containing redlines made to R2, a PDF with those markups can be transmitted on request. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Thu, 01 Feb 2018 12:53:13 -0800
Conversation: Accessing JPL Ephemerides From Swift Code Using The SPICE Library
Subject: Accessing JPL Ephemerides From Swift Code Using The SPICE Library
ATIG Members- I‘m sure many of you are marking today as the 15th anniversary of OV-102/Columbia‘s loss, along with her crew. That event, and the resulting stand-down from Space Shuttle flight operations, motivated ATIG’s formation as a series of NASA-JSC seminars beginning later in 2003. Today, I’m celebrating my resurrection from dinosaur status as a FORTRAN programmer with an upload on how to access JPL’s publicly available planetary ephemerides from Swift code using the SPICE library in C (see attached PDF file). Very few people in my network have heard about (let alone developed software with) the new open source Swift programming language, but there’s about a 50% probability any present-day Apple desktop or mobile device runs apps written with it. Swift is showing up on Windows and Linux platforms as well. If you have a reasonably current Mac and want to give Swift a try, the latest compiler and its Xcode IDE can be downloaded free of charge at https://developer.apple.com/download/. You will need to obtain a no-charge Apple ID, if you don’t have one, before you can access the download (see https://developer.apple.com/support/compare-memberships/). If you have questions/comments about the attached PDF or Swift programming in general, be in touch. -Dan
[Here is a link to the attached PDF file, CspiceInSwiftR5.pdf.]
[Here is a link to the original ATIG #100 email (.eml) file.
ATIG_099__2018_04_05 [April 5, 2018] Re: Tiangong-1 Entry Predictions
ATIG Members- Well, Tiangong-1’s orbit lifetime is over. The official word from Space-Track.org is the end came at 2.0 April 2018 UT. At the time, my best entry interface prediction was about an orbit earlier. This end game analysis, together with all the data previously discussed in this thread, are documented in the attached white paper. Enjoy, and feel free to comment. I’m particularly interested in any entry sighting reports, as I’ve heard of no injuries or property damage from falling debris. -Dan
[Here is a link to the attached PDF file, Tiangong-1entryR0.pdf.]
[Here is a link to the original ATIG #99 email (.eml) file.]
From: Daniel Adamo <adamod@earthlink.net>
Date: Sat, 31 Mar 2018 11:41:07 -0700
Conversation: Tiangong-1 Entry Predictions
Subject: Re: Tiangong-1 Entry Predictions
ATIG Members- Analysis of a Tiangong-1 trajectory arc from March 29 @ 13:25 UT to March 31 @ 12:22 UT has further restricted 2-sigma entry interface predictions to a “window” extending from April 1 @ 18:58 UT (95% “heavy” atmosphere) to April 2 @ 00:31 UT (5% “light” atmosphere). Much of this window is spanned by the attached April 1 ground track plot beginning at 19:30 UT and ending at 23:00 UT. The remarkable attribute of this best guess Tiangong-1 terminal ground track prediction is the large portion of it passing over open ocean. At Tiangong-1’s 42.7-deg inclination, it would be hard to target entry ground tracks with better Earth population safety margins than those passing southbound over the Pacific Ocean. Indeed, similar ground tracks are routinely used to dispose of controlled spacecraft such as Progress cargo carriers used by Russia to resupply ISS. Recent news media reports have described Tiangong-1 as “spinning out of control”, but is it? True, there have been no propulsive burns since late 2015, but a Science News report in January suggests Tiangong-1’s trajectory is being controlled by other than propulsive means (ref. https://www.reuters.com/article/us-china-space/chinas-tiangong-1-space-lab-is-not-out-of-control-top-chinese-engineer-idUSKBN1EX09H). -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Fri, 30 Mar 2018 12:01:48 -0700
Conversation: Tiangong-1 Entry Predictions
Subject: Re: Tiangong-1 Entry Predictions
ATIG Members- In the attached entry UT versus anchor UT plot, I’ve tightened both time scales to better illustrate terminal uncertainty for Tiangong-1’s demise. The latest analysis is based on a March 26-29 arc and indicates entry should be in the afternoon hours UT of April 1 with about 2-sigma confidence (no foolin’). Consequently, reports of Tiangong-1 entry will likely be appearing in the media when many on distribution are celebrating Easter. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Tue, 06 Mar 2018 16:18:14 -0700
Conversation: Tiangong-1 Entry Predictions
Subject: Re: Tiangong-1 Entry Predictions
ATIG Members- Attached is a plot with a couple more months of data added to early January’s original upload. It appears my analysis is converging on an early April Tiangong-1 entry at this time. Note how predictions posted at space-track.org have mine pretty well hemmed in. A recent report can be accessed at https://www.theguardian.com/science/2018/mar/06/chinas-tiangong-1-space-station-will-crash-to-earth-within-weeks. Living near 45 deg latitude, I like to think I’m out of the duck-and-cover zone on this event. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Mon, 08 Jan 2018 16:00:26 -0800
To: Daniel Adamo <adamod@earthlink.net>
Subject: Tiangong-1 Entry Predictions
ATIG Members- You’ve probably been reading about the impending demise of China’s first space station, Tiangong-1. If not, a recent report on this event can be found at https://www.nytimes.com/2018/01/04/science/chinese-space-station.html. Since late September 2017, I’ve been making weekly atmospheric drag profile fits to the previous 7 days of Tiangong-1 tracking data posted to https://www.space-track.org/. After averaging a weekly fit with all its predecessors, I coast the latest “anchor” tracking data to atmospheric entry conditions at a geocentric height of +121.92 km. These coasts to entry are performed 3 times for each anchor date using 95% (high density), 50% (medium density), and 5% low density Earth atmosphere predictions posted at https://sail.msfc.nasa.gov/current_solar_report/CurF10.txt. Results of these weekly analyses are summarized in the attached plot. The horizontal axis of this plot reflects the anchor date at which a coast to entry is initiated, and the vertical axis reflects the entry date at which the coast is terminated. Coasts using a common atmosphere prediction are connected and color coded to show trends in 95% (red), 50% (green), and 5% (blue) modeling. Late in December, space-track.org issued its first Tiangong-1 entry prediction, and that’s plotted in the attachment with a black X. I intend to issue a more formal report on my analyses and methodology after Tiangong-1 entry is history. Consider this an interim “teaser” to show consistency with currently widespread predictions of entry in the March timeframe. Given trends in the plot, it’s certainly possible Tiangong-1 could be orbiting into April. Questions and comments on this work are invited. -Dan
ATIG_098__2018_01_04 [January 4, 2018] New Years’ Night Moonrise Over Mount Hood
ATIG Members- One of my favorite archaeoastronomy documentaries is The Mystery of Chaco Canyon, first aired 3/15/12 on PBS. This video focuses on the Anasazi, who mysteriously disappeared from southwestern U.S. settlements circa 1300 A.D. Among their other astronomical accomplishments, there’s evidence the Anasazi knew the 18-year cycle of the Moon’s nodes on the ecliptic plane and its influence on at what times of the year eclipses fall. This cycle is known as the “Saros” (reference https://eclipse.gsfc.nasa.gov/SEsaros/SEsaros.html for more on this topic). Since moving to Salem, Oregon 5 years ago, I’ve been getting more in touch with the current Saros now that I have a broader horizon than subdivision living in Houston, Texas afforded. This Saros has made me wait those 5 years for the Moon to reach a position more than 19.3 degrees north of Earth’s equatorial plane. That finally happened on 1/1/2018, and it meant a nearly full Moon would rise over Mt. Hood’s south slope as seen from my east lawn. These Mt. Hood Moonrises will only get better over the coming decade or so. I’ve attached a sequence of 6 telephoto images I took to record this event. You’ll make out Mt. Hood in the deepening twilight just left of the Moon. Each attached image is named with the local PST at which it was taken in “h;mm;ss” format. All manner of distorting atmospheric effects are apparent in the attachments. In particular, note in the last image how the Moon’s dimension orthogonal to the horizon is foreshortened by atmospheric refraction, giving it a “squashed” appearance. Any extended object near the horizon looks bigger than when overhead because the human brain weights visual impressions that way (probably from success in sighting distant prey or predators throughout our evolution, if I may use the term). Measurements of the rising (or setting) Moon unbiased by human psychology show it’s actually smaller in apparent size than at higher elevations because of atmospheric refraction. BTW, the full Moon early this month will be followed by another “blue” Moon January 31st (in U.S. time zones). This will also be a “super” Moon with its full phase falling near perigee. And, nearly a half year after August 21’s total solar eclipse, this full Moon will occur during total eclipse within Earth shadow. So, the January 31 full Moon is being called a “Super Blue Blood Moon” (reference https://www.forbes.com/sites/trevornace/2018/01/02/supermoon-blue-moon-total-lunar-eclipse-night/#3aefc0cb45b2). Circumstances for the lunar eclipse, which aren’t optimal for most U.S. locations, may be downloaded at http://aa.usno.navy.mil/data/docs/eclipse/L2018Jan31.pdf. -Dan
[Here is a link to a thumbnail preview of those six images.]
[Link 1: Photo 1, (Filename 1_PST4;51;37p.jpg)
[Link 2: Photo 2, (Filename 2_PST4;51;59p.jpg)
[Link 3: Photo 3, (Filename 3_PST4;52;28p.jpg)
[Link 4: Photo 4, (Filename 4_PST4;53;00p.jpg)
[Link 5: Photo 5, (Filename 5_PST4;54;00p.jpg)
[Link 6: Photo 6, (Filename 6_PST4;55;00p.jpg)
[Here is a link to the original ATIG #98 .eml (email) file.]
ATIG_097__2017_10_27 [October 27, 2017] Our First Interstellar Interloper
ATIG Members- The first object in human history observed to fly through the Solar System on an interstellar trajectory was discovered on 19 October 2017. Currently designated A/2017 U1, the object was originally dubbed C/2017 U1 when thought to be a comet immediately after discovery. Its heliocentric orbit eccentricity is 1.2, and its heliocentric asymptotic speed in nearby interstellar space is 25.5 km/s. You can read more about A/2017 U1 at https://www.jpl.nasa.gov/news/news.php?feature=6983 and at http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/. The attached PDF file plots heliocentric motion for A/2017 U1, Mercury, and Earth from 4 August 2017 to 12 November 2017. Perspective is that of an observer at ecliptic longitude 270 deg; latitude 47 deg S. This viewpoint is very nearly normal to A/2017 U1’s plane of hyperbolic heliocentric motion. From the plot, it’s evident A/2017 U1 was difficult to observe from Earth before closest approach because its direction was too close to the Sun in our sky. This important discovery, coming only 5 days afterward, is indeed fortuitous.-Dan
[Link to PDF file, ATIG_097_A_2017_U1helio.pdf]
[Here is a link to the original ATIG #97 .eml (email) file.]
ATIG_096__2017_09_30 [September 30, 2017] Near-Earth Object (NEO) 2012 TC4
ATIG Members- Those of you who were subscribed to this distribution list 5 years ago will recall an upload documenting the subject NEO’s discovery and close Earth encounter at that time (reference Upload #040 in the ATIG archive at http://www.aiaahouston.org/adamo_astrodynamics/). On October 12 this year, the same NEO will return to Earth at half that distance. This celestial déjà vu is related in the attached update. Comments and corrections are welcome! -Dan
[Link to PDF file, ATIG_096_RevisitFrom2012_TC4r1.pdf]
[Here is a link to the original ATIG #96 .eml (email) file.]
ATIG_095__2017_21_2017 [September 21, 2017] OSIRIS-REx Earth Flyby Update
ATIG Members- The attached geocentric trajectory plot for September 22’s OSIRIS-REx Earth gravity assist targeting near-Earth asteroid (101955) Bennu (1999 RQ36) serves as an update to the ATIG_082 upload made 2016 September 12 (CST) and archived at http://www.aiaahouston.org/adamo_astrodynamics/. The Earth flyby plot in last September’s upload has a prelaunch planning pedigree and has been refined in the attachment to reflect the as-flown trajectory posted to JPL’s Horizons server on 2017 September 15. In the attached plot, note how OSIRIS-REx approach to Earth on September 22 closely parallels the ecliptic plane before the flyby directs spacecraft motion into Bennu’s orbit plane inclined 6.0 degrees to the ecliptic. Arrival at Bennu remains scheduled for October 2018. -Dan
[Link to PDF file, ATIG_095_ORgeoEGA.pdf]
[Here is a link to the original ATIG #95 .eml (email) file.]
ATIG_094__2017_09_17 [September 17, 2017] Considerations For Space Exploration Via Orbiting Low-Latency Telepresence (LLT)
ATIG Members- The attached white paper is my primary technical input to a Keck Institute for Space Studies (KISS) report on space exploration enhanced by LLT. Workshops associated with the “study” mentioned in this paper were held in October 2016 (ref. http://kiss.caltech.edu/workshops/telepresence/telepresence.html) and in July 2017 (ref. http://kiss.caltech.edu/workshops/telepresence/telepresence2.html). The report is expected to have a principle focus on enhanced science returns from LLT as opposed to more traditional human exploration paradigms such as Apollo Program lunar EVAs. My input seeks to provide motivation for LLT with humans in an orbiting habitat proximal to an off-Earth exploration destination at which robotic surrogates have been emplaced. Criteria serving to select an optimal orbit for such LLT are also suggested. As always, corrections and comments on this paper are welcome. I’m hopeful the KISS study report will be published before 2018, and I’ll pass along a copy or download URL when that milestone is achieved. -Dan
[Link to PDF file, ATIG_094_OrbitalLLTr1.pdf]
[Here is a link to the original ATIG #94 .eml (email) file.]
ATIG_093__2017_09_03 [September 3, 2017] An Account of Oregon’s Total Solar Eclipse
ATIG Members- It’s hard for me to believe I spent a couple minutes in the Moon’s umbra on my acreage not quite two weeks ago. Conditions for the spectacle were nearly ideal here in Salem, and I’m still pinching myself to awake from this dream come true. My bucket list is one item shorter this month. I’ve promised a number of you a copy of my illustrated eclipse account, so I’m sharing it with all in the attached PDF file. Enjoy! I hope this note finds its many recipients in greater Houston well on the road to recovery from Harvey. An entire year’s worth of rainfall in 3 days is too much of a good thing. -Dan
[Link to PDF file, ATIG_093_SalemEclipseAccountR0.pdf]
[Here is a link to the original ATIG #93 .eml (email) file.]
ATIG_092__2017_08_14 [August 14, 2017] Draft Article on “Cassini” Disposal at Saturn
ATIG Members- The attached PDF file is a draft article intended for publication by AIAA-Houston Section in their Horizons newsletter (not to be confused with the JPL server of that name cited in the draft). Many of you know me to be a Cassini groupie, and multiple ATIG uploads on this mission have been issued since the spacecraft entered Saturn orbit in 2004. You’re invited to send feedback on the draft, particularly if I’ve erred or inadvertently anthropomorphized this robotic explorer at any point. -Dan
[Link to PDF file, ATIG_092_CassiniEndGameR0.pdf]
[Here is a link to the original ATIG #92 .eml (email) file.]
ATIG_091__2017_07_22 [July 22, 2017] Green Flash Sunrise Over Mt. Hood
ATIG Members- Many of you have heard me wax rhapsodic regarding the beauty of green flash phenomena seen over the Cascade Mountains from my residence at sunrise. Attached is an account of a particularly spectacular example. I’ll hope to do as well photographing August 21’s total solar eclipse from here. -Dan
[Link to PDF file, ATIG_091_Juy21_2017sr.pdf]
[Here is a link to the original ATIG #91 .eml (email) file.]
ATIG_090__2017_06_18 [June 18, 2017] A Critical Essay On “The Humans To Mars Report 2017”
ATIG Members- The attached PDF document is the latest installment in my growing body of commentary as self-appointed “Mars or bust” curmudgeon. I tend to get critical and suspicious of any specific off-Earth human destination advocacy because our state of ignorance about the habitability and return on investment (both monetary and human) among such destinations is truly profound. If you’ve volunteered to be a Mars One settler (ref. https://en.wikipedia.org/wiki/Mars_One) or are ready to invest in SpaceX’s Interplanetary Transport System (ref. https://en.wikipedia.org/wiki/Interplanetary_Transport_System), you have my sincere condolences. Happy Fathers’ Day to all! -Dan
[Link to PDF file, 10 pages, 145 KB, H2MR2017commentaryR0.pdf]
[Here is a link to the original ATIG #90 .eml (email) file.]
ATIG_089__2017_04_28 [April 28, 2017] Repeating Ground Tracks In LEO
ATIG Members- The attached white paper was drafted in response to an astronaut’s unofficial inquiry regarding the nature of repeating ground tracks. I hope you’ll find it useful. As always, questions and feedback are invited. -Dan
[Link to PDF, 7 pages, 289 KB, RepeatGTr0.pdf]
[Heree is a link to the original ATIG #89 .eml (email) file.]
ATIG_088__2017_04_15 [April 15, 2017] Cassini’s Final Titan Gravity Assist
ATIG Members- On April 22 at 06:08 UT, NASA’s prolific Saturn orbiter Cassini will perform its final “T-126” Titan flyby and receive a gravity assist lowering perichrone from just outside the F-ring to just inside the C-ring, setting the stage for the mission’s Grand Finalé phase. I was gratified to share insights on Titan gravity assists with local high school physics students this past week, and charts from that presentation are attached. You’ll recognize some of these charts from the 2016 Dec 1 ATIG upload (#084 in the archives at http://www.aiaahouston.org/adamo_astrodynamics/), but the last 2 charts are new and specifically detail the T-126 trajectory. This past week, a 3.7-minute video documenting the Grand Finalé phase was posted at https://saturn.jpl.nasa.gov/news/3016/making-cassinis-grand-finale/. Enjoy the majesty of Saturn and its environs, courtesy of Cassini! -Dan
[Link to PDF file, 10 pages, 727 KB, TitanGAs.pdf]
[Here is a link to the original ATIG #88 .eml (email) file.]
ATIG_087__2017_03_27 [March 27, 2017] Lunar Surface Logistics From Selenocentric Equatorial Orbits (SEOs)
ATIG Members- With a new Presidential administration in Washington D.C., debate over what orbit to select for human space flight (HSF) infrastructure in the “cislunar proving ground” has only intensified since 2017 January 20. In assessing lunar landings from the subject SEOs, the attached white paper makes no assumptions regarding their accessibility from Earth in the context of any SLS/Orion or other specific logistics system design. Nevertheless, as the attached paper is reviewed, I’d urge any HSF policy stakeholders among us to consider two conclusions from my previous cislunar trajectory research since 2008. 1) Particularly in a HSF context, cislunar orbit accessibility from Earth isn’t exclusively dependent on a cherry-picked optimal total change-in-velocity. Rather, the frequency with which loiter-free viable transits between Earth and a cislunar orbit can be initiated and concluded must be considered too. Opportunities to begin and end such transits arise on a daily basis for SEOs with radii near 10,000 km. 2) Retrograde SEOs (a subset of lunar distant retrograde orbits) are the closest stable orbits to Earth from which multiple interplanetary transits may begin and end without undue propulsive penalties or delays. If the cislunar infrastructure is to serve as an interplanetary gateway logistics node, placing it in an orbit not well aligned with the Moon’s geocentric motion will render it a logistic albatross in the long run. Given the investment being contemplated in cislunar HSF infrastructure, the virtues of a stable orbit venue cannot be overestimated. I’ll be happy to supply papers supporting these conclusions on request, but they’re probably also accessible from the ATIG archives at http://www.aiaahouston.org/adamo_astrodynamics/. -Dan
[Link to PDF file, 4 pages, 281 KB, SEOtoLunarSurfaceR0.pdf]
[Here is a link to the original ATIG #87 .eml (email) file.]
ATIG_086__2017_03_11 [March 11, 2017] A Near Miss From 2017 EA
ATIG Members- The article at https://cneos.jpl.nasa.gov/news/news194.html relates the brief observational history of near-Earth object (NEO) 2017 EA prior to its passage only 14,500 km above the Eastern Pacific Ocean on 2 March 2017 at 14:04 UT. If 2017 EA had reached this point in its heliocentric orbit only 8 to 15 minutes later, a collision with Earth would have occurred. Because this NEO is estimated to be only 3 m in diameter, however, such a collision would have caused no damage on Earth’s surface. The resulting airburst from 2017 EA’s destruction in Earth’s atmosphere would have generated far less energy than the Chelyabinsk bolide on 15 February 2013 (reference ATIG archive #042-Chelyabinsk Bolide Trajectory Reconstruction). The Chelyabinsk bolide had an estimated diameter of 17 m prior to Earth encounter. Its airburst injured over 1100 Chelyabinsk inhabitants in Russia. Because this bolide approached Earth from the Sun’s direction, it evaded detection until entering Earth’s atmosphere. In the case of 2017 EA, Earth was approached from its nightside, and discovery was made 6 hours before perigee despite this NEO’s small size. Geocentric and heliocentric plots of 2017 EA’s motion are attached. -Dan
[Link to PDF file, 2 pages, 158 KB, 2017 EA.pdf]
Here is a link to the original ATIG #86 .eml (email) file.
ATIG_085__2017_01_07 [January 7, 2017] ATIG Upload Archives Open For Access
ATIG Members- Some of you already know I’ve been working since July 2016 to establish an archive of all ATIG uploads I’ve made since retirement from conventional employment in July 2008. The archive was suggested by Douglas Yazell, an active member of the American Institute of Aeronautics and Astronautics (AIAA) Houston Section and longtime ATIG member. With support from Al Jackson, AIAA Houston Section’s Astrodynamics Technical Committee Chair and another ATIG member, the archive idea was recently accepted by Houston Section leadership for hosting on their website. Douglas has applied his webmaster skills to transform the series of 84 ATIG uploads issued beginning 18 August 2008 into a reverse-chronology of cover letter emails with links to associated attachments. This blog-like webpage can be accessed at http://www.aiaahouston.org/adamo_astrodynamics. You may also access a similar (but chronologic) list of archived ATIG uploads in their original .eml format at https://spideroak.com/browse/share/DanAdamo/ATIGuploads/ATIGuploads/. Although the SpiderOak archive could lapse or migrate in the future for a number of reasons, there’s hope the aiaahouston.org archive will enjoy substantial institutional longevity. Each archive will continue to record ATIG uploads, this email eventually becoming the 85th. My hope is these will be useful to many ATIG members, particularly those who joined after 2008. Either ATIG archive is open to anyone with Internet access. -Dan
Here is a link to the original ATIG #85 .eml (email) file.
ATIG_084__2016_12_01 [December 1, 2016] Cassini’s Final Titan Flybys
ATIG Members- This week, NASA’s robotic explorer Cassini entered the ring-grazing phase of its planned 13 years in Saturn orbit. Flybys of Saturn’s largest moon Titan have played a primary role in managing Cassini’s tour of Saturn, its rings, and its moons. Only one of these flybys, the 126th, remains. When it’s performed next April, Cassini will be in its grand finalé phase and on a path to disposal in Saturn’s atmosphere 15 September 2017. Details regarding Cassini’s endgame, and how Titan flybys enable it, are provided in the attached PDF file. Happy holidays to all as we boreals approach 2016’s winter solstice! -Dan
[Link to PDF, 10 pages, 544 KB, FinalTitanFlybysR0.pdf]
Here is a link to the original ATIG #84 .eml (email) file.
ATIG_083__2016_11_17 [November 17, 2016] A Survey of Interplanetary HSF Transport Mars Orbit Geometries
ATIG Members- Last month, I had the pleasure of conversing with members of NASA’s Evolvable Mars Campaign (EMC), an architecture effort that recently studied what HSF might explore during an extended stay on Phobos, the inner moon of Mars. Although funding limitations precluded a similar EMC study of a HSF mission to that other moon of Mars, Deimos, I was more concerned to learn the Phobos study intentionally assumed the Mars approach and departure trajectories, together with the nearly equatorial orbit of Phobos, are coplanar. The EMC’s assumption inspired me to survey planar geometries associated with arrivals at and departures from Mars for Earth roundtrips during a 15-year synodic cycle. This amounts to studying eight successive Mars missions to even begin comprehending geometric variations in these arrivals and departures. The attached draft paper documents my survey’s results. Comments are welcome, as always. Before closing, let me recognize that a lot of ATIG members are located in Greater Houston. My itinerary is still preliminary, but let me give you a heads-up that AIAA’s Houston Section will be hosting me for multiple presentations at local venues. Current planning has me at Gilruth Center for a Lunch & Learn on Friday, January 27 and at the UH Main Campus on Saturday, January 28. I hope to see many of you during my first trip to Houston since moving to Oregon 4 years ago. -Dan
[Link to PDF file, 13 pages, 771 KB, Asymptote-DefinedPlanesR0.pdf]
Here is a link to the original ATIG #83 .eml (email) file.
ATIG_082__2016_09_12[September 12, 2016] OSIRIS-REx Trajectory Planning
ATIG Members- The robotic sample return mission OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security Regolith Explorer) launched as planned on 8 September 2016 at 23:05 UT. This mission’s destination is (101955) Bennu (1999 RQ36), a carbonaceous near-Earth object (NEO) about 500 m in diameter. Reports and details about the mission are available at http://www.asteroidmission.org/. Due to its on time launch, planned trajectory data for OSIRIS-REx posted 31 August 2016 to JPL’s Horizons ephemeris server at http://ssd.jpl.nasa.gov/?horizons are reasonably valid for visualization purposes. The attached 5-page PDF file reflects these data and contains inertial geocentric, heliocentric, and Bennu-centered trajectory plots. Note the fifth plot in the attachment illustrating Bennu-centered motion at OSIRIS=REx arrival is very preliminary and subject to change as the asteroid’s gravity field and spin state are determined in this time frame. However, the basic arrival strategy appears to involve surveying Bennu from above its terminator with a brief dayside equatorial flyby at close range circa 24 November 2018. Bennu-centered positions for the fifth plot were sampled from Horizons at hourly intervals. -Dan
[Link for PDF attachment (5 pages, 436 KB)]
Here is a link to the original ATIG #82 .eml (email) file.
ATIG_081__2016_09_06 [September 6, 2016] Orthographic Trajectory Plots
ATIG Members- I‘ve been sharing the subject plots with some of you since ATIG was formed in 2003. Over the years, I’ve received a few inquiries regarding the method behind these plots. The most recent of these inquiries motivated the attached explanation. Please respond with any corrections, omissions, or questions you’d like addressed. -Dan
[Link: OrthoTrajPlottingR0.pdf, 360 KB, 3 pages.]
Here is a link to the original ATIG #81 .eml (email) file.
ATIG_080__2016_07_28 [July 28, 2016] “Aquarius” Proposal
ATIG Members- Those of you on ATIG distribution in March 2014 will recall receiving a draft paper titled “Aquarius, A Reusable Water-Based Interplanetary Human Spaceflight Transport”. Since then, the paper has morphed into an American Institute of Aeronautics and Astronautics (AIAA) distinguished lecture I present at venues across the U.S. As of today, 28 July 2016, the paper has been published as a peer-reviewed article in Acta Astronautica Vol. 128 (2016) pp. 160-179. Until 16 September 2016, you may download a “final version” of the published article at http://authors.elsevier.com/a/1TSDrLWHFg814 free of charge. [That links to this PDF: 1-s2.0-S0094576516300868-main.pdf. (2.8 MB, 20 pages)] Many ATIG members contributed helpful feedback on Aquarius, and I believe at least one of you served as a peer reviewer for Acta. This feedback has been very helpful to the subject proposal’s maturation and is greatly appreciated. In the final version, a parenthetical sentence appears at the end of many figure captions. The “web version” to which readers are referred in this sentence is one and the same with the “final version” available for download. Enjoy! -Dan
Here is a link to the original ATIG #80 email file.
ATIG_079__2016_07_08 [July 8, 2016] Juno’s Journey
ATIG Members- Attached (PDF, 304 KB) are Sun and Jupiter-centered plots of Juno’s trajectory extending from shortly after launch on 2011 Aug 5 through this week’s Jupiter orbit insertion (JOI) burn and ending on 2016 Aug 26.0 UT. Juno trajectory data are imported from JPL’s Horizons ephemeris server at http://ssd.jpl.nasa.gov/?horizons as posted on 12 May 2016 and should effectively be “as flown” at the plots’ scales. A retrograde burn is scheduled on 19 Oct 2016 to reduce Juno’s orbit period about Jupiter to 14 days. -Dan
Here is a link to the original ATIG #79 email file.
ATIG_078__2016_06_24 [June 24, 2016] Earth Pseudo-Moons
ATIG Members- This month, I’ve received multiple inquiries concerning dynamics associated with near-Earth object (469219) 2016 HO3. These are explained and visualized in the attached (PDF, 798 KB, 11 pages) white paper, together with those of another more remote object undergoing similar geocentric motion. Your questions and comments on this paper are welcome. -Dan
Here is a link to the original ATIG #78 email file.
ATIG_077__2016_06_09 [June 9, 2016] Trajectory Reproduction Of A Proposed Apollo Era Piloted Venus Flyby
ATIG Members- With the subject proposal originating circa 1967 at the facility now known as NASA-JSC, it’s fitting I was introduced to alternate space history author Jerry Brennan by JSC colleagues in November 2015. Since then, I’ve collaborated with Jerry to reproduce an example trajectory in accord with the Apollo Era proposal, helping substantiate the technical basis for his latest story titled Island of Clouds. The attached paper documents this Venus flyby trajectory reproduction in detail. Your questions and comments on this paper are welcome. -Dan
[Link: 14 pages, 389 KB, PDF]
Here is a link to the original ATIG #77 email file.
ATIG_076__2016_05_29 [May 29, 2016] Embarking on a 2016-17 Stint as Oregon Eclipse Docent
ATIG Members- With less than 15 months to go before the Moon’s umbra sweeps across my part of Oregon, I inaugurated an educational outreach campaign on safely watching the 2017 August 21 solar eclipse in a May 24 visit to nearby Amity Middle School Presentation charts from the Amity visit are attached, and I wish clear skies to anyone planning some “umbra time” in 2017. Happy Memorial Day! -Dan
[Link: 13 pages, 840 KB]
Here is a link to the original ATIG #76 email file.
ATIG_075__2016_05_18 [May 18, 2016] Re: ISS Nears a 6-Figure Orbit Count
ATIG Members- With Orbit 100,000 entered in ISS logbooks earlier this week, I’ve added a Section 4 to the white paper you received last September. The new section begins on p. 5 in the attached PDF file and documents a best-estimate reconstruction of the actual milestone. This is certainly an event worth celebrating! -Dan
[Link to PDF of May 18, 2016: 6 pages, 340 KB]
From: Daniel Adamo
Date: Wed, 16 Sep 2015 16:43:06 -0700
Conversation: ISS Nears A 6-Figure Orbit Count
Subject: ISS Nears A 6-Figure Orbit Count
ATIG Members– In a low-Earth orbit context, orbit count is typically defined as a tally of northbound equator crossings or ascending nodes. A satellite logging more than 16 ascending nodes per day is about to enter earth’s atmosphere and end its orbit lifetime. Since its first element Zarya was launched in 1998, ISS has been logging over 15 ascending nodes per day. Only through a dedicated international planning and logistics effort has it been possible to maintain ISS orbit lifetime for 17 years such that it’s about to reach an orbit count of 100,000. Robotic spacecraft have attained 6-figure orbit counts before, but probably not in less than 20 years after launch. The attached white paper attempts to predict when the 100,000-orbit milestone will occur for ISS. All URLs in the attachment should be clickable if your PDF reader supports this behavior, but you may have to manually copy and paste URLs into your web browser if they occupy multiple lines in the PDF. As always, comments are welcome. -Dan
Here is a link to the original ATIG #75 email file.
ATIG_074__2016_05_07 [May 7, 2016] Solar Eclipses in GEO
ATIG Members- From my readings into space-based solar power (SBSP) proposals, I’ve encountered some wishful thinking about 24/7/365 sunlight in geosynchronous Earth orbit (GEO). So, I decided to research solar eclipses in GEO to quantify how they’d affect SBSP generation from that venue. In the process, I’ve come up with an infrastructure deployment strategy reducing cumulative time spent in GEO solar eclipses. This research is captured in the attached PDF file. As always, your feedback on this work is invited and appreciated. Those of you on ATIG distribution as of September 16, 2015 will recall an upload on that date with subject “ISS Nears A 6-Figure Orbit Count”. As predicted at that time, ISS will tally Orbit Number 100,000 just before midnight CDT on May 15, 2016. I intend to reconstruct this event after it’s history and will issue an “as-flown” revision to the September 16 upload later in May. -Dan
[Link tp PDF: 536 KB, 9 pages]
Here is a link to the original ATIG #74 email file.
ATIG_073__2016_03_14 [March 14, 2016] Apollo 15 Trans-Earth Trajectory Reconstruction
ATIG Members- Since February 24, I’ve had the pleasure of working with an ESA researcher on documenting Apollo 15’s trajectory during its homeward journey from the Moon in 1971. As many veterans from the Apollo Era can attest, as-flown trajectory data for crewed lunar missions are hard to come by, particularly with temporally dense content. There are horror stories I’ve been told about retaining magnetic tapes with Apollo tracking data on them until weekly justification forms had to filed, the NASA data archivist gave up the paper chase, and the tapes were released by default to be overwritten. I’m reasonably assured Federal record-keeping has more integrity these days, but don’t ever let someone trash your flight data! The attached white paper documents the Apollo 15 trajectory reconstruction, its motivation, and a rare opportunity to spot-check some reconstructed positions with archived data whose pedigree is reasonably authoritative. As always, your feedback on this research is welcome. -Dan
[Link to PDF: 8.2 MB, 7 pages]
Here is a link to the original ATIG #73 email file.
ATIG_072__2016_01_16 [January 16, 2016] “Cassini” Heads for Higher Inclinations at Saturn
ATIG Members- Happy 2016! During most of 2015, NASA’s Cassini spacecraft orbited Saturn very near the planet’s equatorial plane. This enabled close flybys of moons other than Saturn’s largest (Titan), including Enceladus with its ice geysers (ref. http://planetaria.ca/2015/02/cassini-data-indicates-enceladus-ocean-similar-to-soda-lakes-on-earth/). Cassini began departing Saturn’s equator to progressively greater inclinations the evening of 2016 Jan 15 (U.S. local time) with its 115th targeted Titan flyby (T-115) since achieving orbit about Saturn in 2004. The effects of T-115 on Cassini’s Saturn-centered motion are illustrated in the attached trajectory plot. The gravity assist associated with T-115 increased Cassini’s orbit inclination with respect to Saturn’s equatorial plane from 1.3 deg to 4.1 deg. It also increased Cassini’s orbit period from 12.85 days to 15.95 days. The orbit period of Titan is 15.95 days, so Cassini is, for the time being, in a 1 : 1 resonance with this moon and its power to further evolve the spacecraft’s orbit. For details on where Cassini is headed next, see http://saturn.jpl.nasa.gov/mission/saturntourdates/. -Dan
[Link to PDF: 1 page, 100 KB]
Here is a link to the original ATIG #72 email file.
ATIG_071__2015_11_29 [November 29 2015] Hayabusa-2’s Journey to Ryugu
ATIG Members- At 4:22 UT on 3 Dec 2014, Japan launched Hayabusa-2, its second ion-propelled spacecraft designed to visit a near-Earth asteroid (NEA). The destination for this mission is a volatile-rich NEA recently named Ryugu (dubbed 1999 JU3 when discovered) and estimated to be 920 m in diameter. For the last year, Hayabusa-2 has been in a slightly more elliptical orbit than Earth’s about the Sun. This orbit also has a 1 : 1 resonance with Earth’s, facilitating an Earth flyby and gravity assist into Ryugu’s orbit plane on 3 Dec 2015. Thereafter, Hayabusa-2 will slowly close with Ryugu from behind and sunward of it, arriving in mid-2018. This week’s Earth flyby trajectory, together with a series of yearly heliocentric trajectory plots, are attached to illustrate Hayabusa-2’s outbound journey. Trajectory data are based on a 28 Nov 2015 update to JPL’s Horizons ephemeris server at http://ssd.jpl.nasa.gov/?horizons. After about 18 months surveying and sampling Ryugu, Hayabusa-2 is to begin a one-year journey back to Earth in late 2019. The return date, when samples are to be delivered by an atmospheric entry capsule, will be very close to 3 Dec 2020. The attached heliocentric plots illustrate why major Hayabusa-2 mission events involving Earth tend to fall on December 3. This point in Earth’s orbit is only about 240,000 km (roughly 60% of the Moon’s geocentric distance) from Ryugu’s ecliptic plane descending node. On 29 Dec 2020, Ryugu will be very close to this node and only 9 million km from Earth. That geometry makes Hayabusa-2’s return propulsion requirements easy to satisfy, even if Ryugu departure date is postponed. As this may be 2015’s last ATIG upload, I’ll take the opportunity to wish you happy holidays and a joyous 2016! -Dan
[Links: Five PDF files, each one page, each less than 120 KB. (1) Hayabusa2ega.pdf (2) Hayabusa2helio14-15.pdf (3) Hayabusa2helio15-16.pdf (4) Hayabusa2helio16-17.pdf (5) Hayabusa2helio17-18.pdf
Here is a link to the original ATIG #71 email file.
ATIG_070__2015_10_29 [October 29, 2015] Cislunar Artifact WT1190F
ATIG Members- Attached are some trajectory plots and predictions I’ve made for WT1190F, currently thought to be debris from an unidentified lunar mission. News reports are concentrating on its predicted entry Friday, 13 November 2015 at 06:20 UT. The acronym formed by alphabetic components of “WT1190F” is also attracting humorous remarks. But I’m thinking WT1190F’s lasting legacy is to human space flight architects and mission planners working on visits to NASA’s “Proving Ground” in cislunar space. We need to minimize abandoned artifacts and debris sent through the Proving Ground because a hypervelocity hit to spacecraft or habitats days from Earth return is potentially more hazardous to crew survival than are hits aboard ISS. What debris we do send into cislunar space needs to be catalogued and tracked as diligently as are those ISS threats. And what we cannot reliably track due to its small size and great distance must be shielded against with added spacecraft/habitat mass. Comments on the attachment and these remarks are welcome. -Dan
[Link to PDF file, 322 KB, 5 pages, WT1190F#29trajR0.pdf. To make the link work properly, I changed # to [numbersign]…]
Here is a link to the original ATIG #70 email file.
ATIG_069__2015_10_22 [October 22, 2015] NASA’s Journey to Mars Document
ATIG Members- Attached is another of my seemingly ceaseless essays commenting on our culture’s fixation with sending humans to Mars. It’s a great dream, even if its rationale is elusive, but some of the strategies and associated rhetoric being used to implement it are turning the dream into a nightmare for me. How about you? There’s one poorly supported tidbit appearing at the top of p. 6 in my essay on which I’d particularly like feedback to confirm or refute it. What’s become of NASA’s open competition to develop “advanced” boosters with liquid or solid propellant for the evolved SLS? If this competition has been indefinitely frozen, SLS may never evolve beyond capability to deliver 105 t mass to low Earth orbit. That shortfall could be a game-changer, even in the cislunar “Proving Ground”. In that event, my chief consolation would be the Saturn 5 retaining its status as “the most powerful [and capable] rocket ever built”. -Dan
[Link to PDF, 142 KB, 7 pages, JTMcommentaryR0.pdf]
Here is a link to the original ATIG #69 email file.
ATIG_068__2015_09_16 [September 16, 2015] ISS Nears A 6-Figure Orbit Count
ATIG Members- In a low-Earth orbit context, orbit count is typically defined as a tally of northbound equator crossings or ascending nodes. A satellite logging more than 16 ascending nodes per day is about to enter earth’s atmosphere and end its orbit lifetime. Since its first element Zarya was launched in 1998, ISS has been logging over 15 ascending nodes per day. Only through a dedicated international planning and logistics effort has it been possible to maintain ISS orbit lifetime for 17 years such that it’s about to reach an orbit count of 100,000. Robotic spacecraft have attained 6-figure orbit counts before, but probably not in less than 20 years after launch. The attached white paper attempts to predict when the 100,000-orbit milestone will occur for ISS. All URLs in the attachment should be clickable if your PDF reader supports this behavior, but you may have to manually copy and paste URLs into your web browser if they occupy multiple lines in the PDF. As always, comments are welcome. -Dan
[Link to the PDF document, 176 KB, 4 pages, ISSorb100kR0.pdf]
Here is a link to the original ATIG #68 email file.
ATIG_067__2015_06_30 [June 30, 2015] Space News Editorial on FBC
ATIG Members- Several in this group have asked to be notified when the op-ed draft sent your way on May 21 was published. It was posted earlier on June 30 at http://spacenews.com/op-ed-humans-to-mars-in-20-years-a-faster-better-cheaper-sequel/. As always, I appreciate any feedback on these words, but mainly editorial changes have been applied since the May 21 draft. To those who inspired these changes, please accept my sincere thanks! -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Thu, 21 May 2015 17:27:24 -0700
Conversation: An Op-Ed On Our Headlong Rush To Mars
Subject: An Op-Ed On Our Headlong Rush To Mars
ATIG Members- In an attempt to put my essay on the AM II report in a broader context, I’m drafting an op-ed intended for publication in Space News (see the attached PDF file). It’s arguable that risks associated with Apollo Moon landings were justified by national prestige during the Cold War. I see nothing approaching this level of justification for taking even bigger risks in sending humans to Mars using an “affordable”, minimalist architecture. From bitter experience in the Shuttle Program, I’ve learned to appreciate affordability not just in monetary terms. There’s a human cost to affordability too. I welcome feedback on this op-ed. In particular, let me know if you’ve found any “unobtainium” on Mars only humans can extract. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Tue, 14 Apr 2015 12:04:40 -0700
Conversation: An Essay Commenting On The AM II Report
Subject: An Essay Commenting On The AM II Report
ATIG Members- I became aware of the second in a series of Affording Mars workshops (AM II) when its proceedings and findings were reviewed at the Future In-Space Operations (FISO) telecon of 4 February 2015. You can download charts and an audio transcript of this telecon at http://spirit.as.utexas.edu/%7Efiso/telecon/Thronson-Cassady_2-4-15/.
The FISO presentation refers its audience to an AM II report. Since I took issue with much of the presentation’s material, I felt compelled to review the report in detail. My commentary from this review is attached in the subject essay. Your feedback on the essay is invited, and you are welcome to share it with stakeholders and other interested parties in your network. Please note I’ve already sent the essay to all the report’s editors whose email addresses I could find. I invite feedback from all essay readers, and I hope this dialog helps foster future workshops with greater integrity and ability to build a broader, more informed consensus on the why/how/when of human Mars exploration. -Dan PS: if your organization would like to hear more about the “why” or the “how” of human Mars exploration, I’d be willing to personally share my research on either subject in a one-hour presentation. All I ask in compensation is reimbursed travel expenses.
Here is a link to the original ATIG #67 email file.
ATIG_066__2015_06_22 [June 22, 2015] Re: “Dawn” Achieves Ceres Orbit
ATIG Members- A first update to the March 30 Dawn ephemeris (referenced in the plot accompanying April 4’s ATIG upload below) was posted to JPL’s Horizons server circa June 18. This reflects initial as-flown trajectory reconstruction of arrival in the RC3 orbit (13,600 km in altitude) and a spiral down to the Survey orbit (4400 km in altitude), completed on June 3. These milestones are plotted with respect to Ceres, as viewed from its equatorial plane, in the attached PDF. On June 22, Dawn is completing her sixth southbound data collection pass over the dayside of Ceres in the Survey orbit. After the eighth Survey orbit is complete late in June, Dawn is to begin lowering her altitude once again. -Dan
[Link to PDF, 122 KB, 1 page, CeresAppR3.pdf]
From: Daniel Adamo <adamod@earthlink.net>
Date: Sat, 04 Apr 2015 12:11:40 -0700
Conversation: “Dawn” Achieves Ceres Orbit
Subject: Re: “Dawn” Achieves Ceres Orbit
ATIG Members- Updating Dawn’s approach to (1) Ceres, the attached plot of Ceres-centered motion has SEP thrusting modeled into the mid-April time frame. This plot is viewed from Ceres’ equatorial plane in a direction looking “up” in the plot sent March 8. From the updated trajectory, SEP thrusting to achieve Dawn approach over Ceres’ north rotational pole is evident. Planned SEP thrusting in late April (not modeled in this plot’s ephemeris) will achieve a circular “RC3” orbit at 13,500 km altitude on April 23. You can read more about Dawn’s Ceres approach at http://dawnblog.jpl.nasa.gov/?p=2437. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Sun, 08 Mar 2015 21:45:51 -0700
Conversation: “Dawn” Achieves Ceres Orbit
Subject: “Dawn” Achieves Ceres Orbit
ATIG Members- About the time most of us in the U.S. were arising on Friday morning, March 6, the Dawn spacecraft was achieving orbit about dwarf planet asteroid (1) Ceres. Because Dawn uses solar electric propulsion (SEP), its thrust duty cycles are highly flexible and equally uncertain because of the low accelerations exerted. The attached plot of Dawn’s Ceres-centered motion depicts orbit capture, but SEP thrusting doesn’t appear to be modeled much after March in the associated ephemeris posted March 6 to http://ssd.jpl.nasa.gov/?horizons. According to http://dawnblog.jpl.nasa.gov/2015/03/06/dawn-journal-march-6/, Dawn should be in its circular RC3 orbit about Ceres (13,500 km altitude, polar inclination, ascending node at local midnight) on April 23. I’ll attempt to pass along subsequent plots reflecting SEP thrusting leading to RC3 as they become available. -Dan
Here is a link to the original ATIG #66 email file.
ATIG_065__2015_05_21 [May 21, 2015] An Op-Ed On Our Headlong Rush To Mars
ATIG Members- In an attempt to put my essay on the AM II report in a broader context, I’m drafting an op-ed intended for publication in Space News (see the attached PDF file). It’s arguable that risks associated with Apollo Moon landings were justified by national prestige during the Cold War. I see nothing approaching this level of justification for taking even bigger risks in sending humans to Mars using an “affordable”, minimalist architecture. From bitter experience in the Shuttle Program, I’ve learned to appreciate affordability not just in monetary terms. There’s a human cost to affordability too. I welcome feedback on this op-ed. In particular, let me know if you’ve found any “unobtainium” on Mars only humans can extract. -Dan
[FBCtheSequelR2A.pdf, 3 pages, 90 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Tue, 14 Apr 2015 12:04:40 -0700
Conversation: An Essay Commenting On The AM II Report
Subject: An Essay Commenting On The AM II Report
ATIG Members- I became aware of the second in a series of Affording Mars workshops (AM II) when its proceedings and findings were reviewed at the Future In-Space Operations (FISO) telecon of 4 February 2015. You can download charts and an audio transcript of this telecon at http://spirit.as.utexas.edu/%7Efiso/telecon/Thronson-Cassady_2-4-15/.
The FISO presentation refers its audience to an AM II report. Since I took issue with much of the presentation’s material, I felt compelled to review the report in detail. My commentary from this review is attached in the subject essay. Your feedback on the essay is invited, and you are welcome to share it with stakeholders and other interested parties in your network. Please note I’ve already sent the essay to all the report’s editors whose email addresses I could find. I invite feedback from all essay readers, and I hope this dialog helps foster future workshops with greater integrity and ability to build a broader, more informed consensus on the why/how/when of human Mars exploration. -Dan
PS: if your organization would like to hear more about the “why” or the “how” of human Mars exploration, I’d be willing to personally share my research on either subject in a one-hour presentation. All I ask in compensation is reimbursed travel expenses.
Here is a link to the original ATIG #65 email file.
ATIG_064__2015_04_14 [April 14, 2015] An Essay Commenting On The AM II Report
ATIG Members- I became aware of the second in a series of Affording Mars workshops (AM II) when its proceedings and findings were reviewed at the Future In-Space Operations (FISO) telecon of 4 February 2015. You can download charts and an audio transcript of this telecon at http://spirit.as.utexas.edu/%7Efiso/telecon/Thronson-Cassady_2-4-15/. The FISO presentation refers its audience to an AM II report. Since I took issue with much of the presentation’s material, I felt compelled to review the report in detail. My commentary from this review is attached in the subject essay. Your feedback on the essay is invited, and you are welcome to share it with stakeholders and other interested parties in your network. Please note I’ve already sent the essay to all the report’s editors whose email addresses I could find. I invite feedback from all essay readers, and I hope this dialog helps foster future workshops with greater integrity and ability to build a broader, more informed consensus on the why/how/when of human Mars exploration. -Dan
[AffordingMarsIIcommentaryR0.pdf, 13 pages, 199 KB]
PS: if your organization would like to hear more about the “why” or the “how” of human Mars exploration, I’d be willing to personally share my research on either subject in a one-hour presentation. All I ask in compensation is reimbursed travel expenses.
Here is a link to the original ATIG #64 email file.
ATIG_063__2015_04_04 [April 4, 2015] Re: “Dawn” Achieves Ceres Orbit
ATIG Members- Updating Dawn’s approach to (1) Ceres, the attached plot of Ceres-centered motion has SEP thrusting modeled into the mid-April time frame. This plot is viewed from Ceres’ equatorial plane in a direction looking “up” in the plot sent March 8. From the updated trajectory, SEP thrusting to achieve Dawn approach over Ceres’ north rotational pole is evident. Planned SEP thrusting in late April (not modeled in this plot’s ephemeris) will achieve a circular “RC3” orbit at 13,500 km altitude on April 23. You can read more about Dawn’s Ceres approach at http://dawnblog.jpl.nasa.gov/?p=2437. -Dan [CeresAppR2.pdf, 1 page, 93 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Sun, 08 Mar 2015 21:45:51 -0700
Conversation: “Dawn” Achieves Ceres Orbit
Subject: “Dawn” Achieves Ceres Orbit
ATIG Members- About the time most of us in the U.S. were arising on Friday morning, March 6, the Dawn spacecraft was achieving orbit about dwarf planet asteroid (1) Ceres. Because Dawn uses solar electric propulsion (SEP), its thrust duty cycles are highly flexible and equally uncertain because of the low accelerations exerted. The attached plot of Dawn’s Ceres-centered motion depicts orbit capture, but SEP thrusting doesn’t appear to be modeled much after March in the associated ephemeris posted March 6 to http://ssd.jpl.nasa.gov/?horizons. According to http://dawnblog.jpl.nasa.gov/2015/03/06/dawn-journal-march-6/, Dawn should be in its circular RC3 orbit about Ceres (13,500 km altitude, polar inclination, ascending node at local midnight) on April 23. I’ll attempt to pass along subsequent plots reflecting SEP thrusting leading to RC3 as they become available. -Dan
Here is a link to the original ATIG #63 email file.
ATIG_062__2015_03_23 [March 23, 2015] Possible Post-Pluto Flybys For “New Horizons”
ATIG Members- Last October, I first learned HST had discovered Kuiper Belt objects (KBOs) potentially accessible to New Horizons (NH) following its Pluto flyby on 2015 July 14. The news came to me in a report by NH Principal Investigator, Alan Stern (see http://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_10_23_2014). Unfortunately, the KBO flyby candidates were referred to as “PT1”, “PT2”, and “PT3” in the article. This is not standard provisional nomenclature for small bodies in the solar system, so I wasn’t able to study potential KBO flyby trajectories at that time. My appeal for meaningful identification of the KBO flyby candidates was sent to <NewHorizons@jhuapl.edu> on 2014 October 23, but no response was received. Thanks to some help from NASA’s Small Bodies Assessment Group (SBAG), it now appears the candidates were only informally identified following their discoveries because anybody with access to the HST observations had insufficient skills or time to reduce those observations into orbit solutions. This month’s 46th Lunar and Planetary Science Conference apparently reordered some priorities, and orbit solutions are now available for the only 2 viable KBO flyby candidates remaining: 2014 MU69 and 2014 PN70. My assessment of KBO flyby prospects for NH is documented in the attached 2 PDF files. One PDF documents the 2014 MU69 flyby option, and one PDF documents the 2014 PN70 flyby option. In each PDF, a zoomed-in heliocentric trajectory plot is followed by two pork chop charts (PCCs). The first PCC tabulates post-Pluto change in velocity magnitude (Dv) required to achieve KBO intercept from the coasted NH trajectory. The second PCC tabulates the resulting flyby speed with respect to the KBO. Boxed cells in the PCCs pertain to the corresponding plotted flyby case. Other than KBO intercept trajectories I generated as heliocentric conics, all NH and KBO data are from ephemerides computed by JPL’s Horizons server at http://ssd.jpl.nasa.gov/?horizons. You can read more about New Horizons planning for Pluto flyby and thereafter from downloadable charts at http://www.lpi.usra.edu/sbag/new_horizons/. Enjoy! -Dan
[NHto2014 MU69.pdf, 127 KB, 3 pages, NHto2014 PN70.pdf, 125 KB, 3 pages]
Here is a link to the original ATIG #62 email file.
ATIG_061__2015_03_08 [March 8, 2015] “Dawn” Achieves Ceres Orbit
ATIG Members- About the time most of us in the U.S. were arising on Friday morning, March 6, the Dawn spacecraft was achieving orbit about dwarf planet asteroid (1) Ceres. Because Dawn uses solar electric propulsion (SEP), its thrust duty cycles are highly flexible and equally uncertain because of the low accelerations exerted. The attached plot of Dawn’s Ceres-centered motion depicts orbit capture, but SEP thrusting doesn’t appear to be modeled much after March in the associated ephemeris posted March 6 to http://ssd.jpl.nasa.gov/?horizons. According to http://dawnblog.jpl.nasa.gov/2015/03/06/dawn-journal-march-6/, Dawn should be in its circular RC3 orbit about Ceres (13,500 km altitude, polar inclination, ascending node at local midnight) on April 23. I’ll attempt to pass along subsequent plots reflecting SEP thrusting leading to RC3 as they become available. -Dan
[CeresAppR1.pdf, 1 page, 131 KB]
Here is a link to the original ATIG #61 email file.
ATIG_060__2015_01_02 [January 2, 2015] Hayabusa-2’s Odyssey: The First Leg
ATIG Members- Happy 2015! Japan’s Hayabusa-2 robotic mission to visit and retrieve samples from near-Earth asteroid (162173) 1999 JU3 began with launch on 2014 Dec 3. The attached Sun-centered inertial plot illustrates coasted Hayabusa-2 motion during the first year following launch, together with that of Earth and Venus. The initial solar orbit for Hayabusa-2 has a semi-major axis of 1.002 AU, bringing it near to Earth a year after launch, as seen in the attached plot. Thanks to Hayabusa-2’s ion thrusters, the plot’s coasted trajectory is to undergo progressive modification in the coming months such that a close encounter with Earth will occur in late 2015. Orientation of a Sun-centered orbit plane can be specified by its inclination with respect to the ecliptic (IN) and by ecliptic longitude of its ascending node (ELAN). In the attached plot, Earth’s orbit coincides with the ecliptic plane, and the arrow pointing rightward from the Sun annotates the direction toward zero ecliptic longitude. The following table indicates Hayabusa-2’s current orbit is very nearly coplanar with that of 1999 JU3.

Orbit IN (deg) ELAN (deg)
Hayabusa-2 6.8 250.5
1999 JU3 5.9 251.6

As dotted blue lines projecting position onto the ecliptic plane indicate in the attached plot, Hayabusa-2’s current descending node is very close to the ecliptic longitude Earth occupies around December 3. On 2015 Dec 3.0 UTC, Earth’s ecliptic longitude will be 70.259 deg, very near the descending node for 1999 JU3 (251.6 – 180 = 71.6 deg). Current perihelion distance for Hayabusa-2 is 0.915 AU, again very close to 1999 JU3’s value of 0.963 AU. Thus, the gravity assist imparted to Hayabusa-2 from a properly targeted Earth encounter around 2015 Dec 3.0 UTC will easily enable rendezvous with 1999 JU3, currently set for July 2018. The precise rendezvous date is largely dependent on how closely the trajectory following Earth gravity assist matches 1999 JU3’s semi-major axis of 1.190 AU and on how aggressively this residual is reduced by ion propulsion. All Hayabusa-2 and 1999 JU3 data provided in this narrative and its attached plot are traceable to JPL’s Horizons server. This facility is accessible at http://ssd.jpl.nasa.gov/?horizons. -Dan
[CoastedHayabusa2.pdf, 1 page, 65.5 KB]
Here is a link to the original ATIG #60 email file.
ATIG_059__2014_12_17 [December 17, 2014] Re: A Proposed Launch Performance Standard
ATIG Members- Many thanks to those of you who commented on the standard. I’ve incorporated that feedback, together with additional research, into a white paper on this topic. It may be downloaded from the Space Enterprise Institute (SEI) website at http://www.spaceenterpriseinstitute.org/2014/12/an-objective-launch-vehicle-performance-standard/. The SEI site does require you to register as a user before you can obtain its free downloads. This requires a name and email address, neither of which must be valid. Registration information is intended to suppress spam on the site and is employed to send you emailed alerts when new SEI material becomes available. Happy holidays! -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Sun, 07 Dec 2014 17:06:58 -0800
Conversation: A Proposed Launch Performance Standard
Subject: A Proposed Launch Performance Standard
ATIG Members- Many of you who correspond with me on “rocket science” matters are familiar with my rant on absence of a performance standard for launch vehicles such that “apples versus apples” comparisons may be made. I couldn’t tell you if a Delta IV Heavy delivers more performance than an Ariane V because they launch from different locations into different orbits. There are also claims regarding “the most powerful rocket ever flown” floating around out there. Just how powerful is that compared to other launch vehicles? And what is meant by “power” anyway? Thrust at liftoff is likely a poor metric for what really counts: initial mass delivered to low Earth orbit by a single launch (IMLEO). So, here’s my proposed standard for an IMLEO-based launch performance metric. First, some relevant background is warranted. Forty-two years ago today, on 7 Dec 1972, a Saturn V launched the Apollo XVII mission from KSC LC 39A (28.608 deg N Lat, 80.604 deg W Lon, -32.0 m Alt) at an azimuth of 91.5 deg E of N. Some 11.9 min after launch, insertion into a 166.7 km altitude circular orbit (reckoned with respect to an Earth radius of 6378.2 km) was achieved. Inclination of this orbit was 28.526 deg. See Apollo: The Definitive Sourcebook (Orloff & Harland, 2006), p. 511 for these statistics. Additional data from the Sourcebook infer a total Apollo XVII vehicle mass of 140,345 kg at orbit insertion. This IMLEO achievement has never been surpassed by a single launch, whether from Earth’s surface or a carrier aircraft. Launch service providers with accurate simulation capabilities are invited to duplicate the Apollo XVII launch circumstances, achieve a similar orbit with their launch vehicle (whether operational or under design), and report their IMLEO values via email along with the launch vehicle configuration simulated. These IMLEO results will be cited with the proposed standard at http://spaceenterpriseinstitute.org/, facilitating an “apples versus apples” performance comparison between launch vehicles. I‘d be very interested in any commentary regarding the proposed standard. In particular, is anyone aware of a similar or somehow better standard? One data point I might contribute would be from a MacMECO simulation of a Shuttle launch into the Apollo XVII orbit. Just how much Orbiter mass can be inserted into this orbit without incurring a low level MPS cutoff? If I have to use OMS-2 to circularize at 166.7 km, that propellant will come out of the IMLEO I report. But I will report “useless” IMLEO mass like the Orbiter’s wings. -Dan
Here is a link to the original ATIG #59 email file.
ATIG_058__2014_12_07 [December 7, 2014] A Proposed Launch Performance Standard
ATIG Members- Many of you who correspond with me on “rocket science” matters are familiar with my rant on absence of a performance standard for launch vehicles such that “apples versus apples” comparisons may be made. I couldn’t tell you if a Delta IV Heavy delivers more performance than an Ariane V because they launch from different locations into different orbits. There are also claims regarding “the most powerful rocket ever flown” floating around out there. Just how powerful is that compared to other launch vehicles? And what is meant by “power” anyway? Thrust at liftoff is likely a poor metric for what really counts: initial mass delivered to low Earth orbit by a single launch (IMLEO). So, here’s my proposed standard for an IMLEO-based launch performance metric. First, some relevant background is warranted. Forty-two years ago today, on 7 Dec 1972, a Saturn V launched the Apollo XVII mission from KSC LC 39A (28.608 deg N Lat, 80.604 deg W Lon, -32.0 m Alt) at an azimuth of 91.5 deg E of N. Some 11.9 min after launch, insertion into a 166.7 km altitude circular orbit (reckoned with respect to an Earth radius of 6378.2 km) was achieved. Inclination of this orbit was 28.526 deg. See Apollo: The Definitive Sourcebook (Orloff & Harland, 2006), p. 511 for these statistics. Additional data from the Sourcebook infer a total Apollo XVII vehicle mass of 140,345 kg at orbit insertion. This IMLEO achievement has never been surpassed by a single launch, whether from Earth’s surface or a carrier aircraft. Launch service providers with accurate simulation capabilities are invited to duplicate the Apollo XVII launch circumstances, achieve a similar orbit with their launch vehicle (whether operational or under design), and report their IMLEO values via email along with the launch vehicle configuration simulated. These IMLEO results will be cited with the proposed standard at http://spaceenterpriseinstitute.org/, facilitating an “apples versus apples” performance comparison between launch vehicles. I‘d be very interested in any commentary regarding the proposed standard. In particular, is anyone aware of a similar or somehow better standard? One data point I might contribute would be from a MacMECO simulation of a Shuttle launch into the Apollo XVII orbit. Just how much Orbiter mass can be inserted into this orbit without incurring a low level MPS cutoff? If I have to use OMS-2 to circularize at 166.7 km, that propellant will come out of the IMLEO I report. But I will report “useless” IMLEO mass like the Orbiter’s wings. -Dan
Here is a link to the original ATIG #58 email file.
ATIG_057__2014_08_26 [August 26, 2014] Launches From Brownsville, TX
ATIG Members- My recent research on LEO launch trajectories from Brownsville, TX is documented in the attached white paper, and I hope you’ll find it interesting. A major source of information for this paper is an FAA environmental impact statement (EIS) on Brownville launches. Please note the EIS link provided in the paper’s footnote on p. 6 is clickable but has too many imbedded line breaks to work in my browser. When I copy-and-paste this URL into my browser, however, it works. As usual, I welcome feedback on the paper. But I also have an open issue with this research on which I’d like input. The EIS doesn’t appear to raise any range safety issues with Brownsville launches to LEO. But, as documented in my paper, second stage underspeeds could conceivably scatter debris over land, even at the most benign targeted LEO inclination documented in the EIS. Is the FAA aware of this possibility? The potential threat of land impact would not arise in U.S. airspace, and the threatened impact footprint might also lie well outside U.S. airspace in many cases. Would a second stage underspeed impact threat then be outside FAA’s regulatory jurisdiction? If so, would any Federal agency have regulatory authority over this scenario? On request, I’ll keep the source of any feedback/input anonymous. -Dan
[B’villeLaunchesR0.pdf, 6 pages, 285 KB]
Here is a link to the original ATIG #57 email file.
ATIG_056__2014_08_17 [August 17, 2014] To Explore Or Pioneer?
ATIG Members- You’ll recall my critique of the NAS Pathways to Exploration report. As with most critiques, it had to ramble a bit. Attached is an initial op-ed draft, ultimately targeted for Space News publication, that’s more focused on how I feel NASA’s HSF strategy needs to change. I won’t be sending this off for publication until next week in order to collect feedback from you and others. Many thanks for whatever you care to send. -Dan
[ExploreOrPioneerOpEdR0.pdf, 3 pages, 94 KB]
Here is a link to the original ATIG #56 email file.
ATIG_055__2014_07_20 [July 20, 2014] “Pathways” Critique
ATIG Members- Attached is the latest draft of a critique I’ve written on last month’s National Academies Press publication Pathways to Exploration–Rationales and Approaches for a U.S. Program of Human Space Exploration. Your questions and comments on this critique and the Pathways report are invited. -Dan
[PathwaysCommentaryR2.pdf, 9 pages, 178 KB]
Here is a link to the original ATIG #55 email file.
ATIG_054__2014_07_09 [July 9, 2014] Selenocentric Distant Retrograde Orbits (SDROs) Paper
ATIG Members- Earlier today, the attached paper was submitted to the 2014 AIAA/AAS Astrodynamics Specialist Conference (see http://www.aiaa-space.org/), a segment of AIAA’s SPACE 2014 Conference. A good portion of this paper was first distributed in the ATIG upload of 15 September 2013 PDT. The conference paper documents additional research concerning SDRO applications other than as a destination for redirected asteroids. Comments and questions on the paper are welcome. This publication has been approved by NASA-GSFC for public distribution. -Dan
[InnovativeSDROsR6A.pdf, 19 pages, 1.6 MB]
Here is a link to the original ATIG #54 email file.
ATIG_053__2014_05_07 [May 7, 2014] STS-16
ATIG Members- No, this isn’t a blast from the past or a reenactment of the STS 51-D mission. It’s the return-to-flight for students at Russell Elementary School in Smyrna, GA. Their 28-hour “long sim” begins this Thursday, May 8. A YouTube broadcast schedule for the simulation and associated links can be accessed at http://russellroadrunners.typepad.com/space/youtube-broadcast-schedule.html. Back in the 1990s, student-run simulations like this were being performed regularly across the U.S., primarily in middle schools and high schools. They promoted interdisciplinary STEM education through the motivation of creative applied study, together with fulfillment from teamwork and mission accomplishment, before the acronym was even invented. Over the next decade, however, “teach to test” and the funding shortfall from No Child Left Behind left little time or financial support for these simulations. It’s my sincere hope that STS-16 will mark a turnaround in this trend. I‘d be interested in your comments about the Russell Space Team and their latest mission, particularly if you can watch some of their YouTube broadcasting. If you advocate space exploration, this is the future. -Dan
“That the powerful play goes on, and you may contribute a verse.” -Walt Whitman
Here is a link to the original ATIG #53 email file.
ATIG_052__2014_03_25 [March 25, 2014] Aquarius Proposal
ATIG Members- Attached is a reasonably mature draft proposal for a water-based interplanetary human transport architecture. Trajectory designs in Section III make repeated use of the “aid” from the last ATIG upload on 27 January. My co-author Dr. Jim Logan and I hope this proposal helps human spaceflight stakeholders focus on a synergistic interplay of technologies and strategies critical to a sustainable presence far beyond low Earth orbit. As always, your questions and comments are welcome. -Dan
[AquariusProposalR2.pdf, 34 pages, 1.5 MB]
Here is a link to the original ATIG #52 email file.
ATIG_051__2014_01_27 [January 27, 2014] An Aid To Interplanetary Trajectory Design
ATIG Members- I hope you’re enjoying a happy and prosperous 2014. This year, I find myself designing yet another precision round-trip trajectory from Earth to Mars and back. I expect to be sharing details of this design and its associated mission concept with you in the near future. During the patched conic phase of interplanetary trajectory design, I’ve found planet-centered departure or arrival hyperbolic trajectories can often be conveniently defined using asymptotic velocity imposed by the heliocentric transfer trajectory, together with specified periapsis distance and declination. The attached PDF details how to define and sample planet-centered hyperbolic trajectories using these data in a variety of mission design contexts. For those wishing to implement this technique, a numeric example is included for the context of arrival at Mars. As always, questions and comments on the attached documentation are welcome. -Dan
[HyperDef+Samp.pdf, 7 pages, 1.6 MB]
Here is a link to the original ATIG #51 email file.
ATIG_050__2013_11_02 [November 2, 2013] Potentially Hazardous Object (PHO) 2013 TV135
ATIG Members- The attached white paper details a preliminary analysis of collision prospects between near-Earth object 2013 TV135 and Earth in year 2032. Such events play out very much in the same way as do potential collisions between ISS and debris orbiting Earth. The major difference is possible interplanetary collisions with Earth are typically first predicted decades in advance of impact, while those threatening ISS are rarely forecast more than a few days before closest approach. In both cases, collision probability Pc typically increases before it suddenly drops to zero, and statistics behind this behavior are explained in the paper. Of course, the typical ISS debris avoidance impulse of about 1 m/s would be unthinkably difficult to impart to the Earth. In the unlikely event 2013 TV135 Pc approaches near-certain levels, it would have to be diverted or exploded to avert an impact currently estimated at 3250 megatons. October 31’s Pc estimate for 2013 TV135 collision with Earth on 26.36 August 2032 UT is 0.00016, or 1-in-6250. At this Pc level, an ISS avoidance maneuver would be considered near-mandatory, but planning and executing such a maneuver can take a day or more with at most 3 days’ notice before potential collision. We have about a decade to refine 2013 TV135’s orbit before any worst-case scenario would precipitate action to mitigate collision with Earth. As always, feedback on this paper is invited. -Dan
[PHO2013 TV135r1.pdf, 7 pages, 377 KB]
Here is a link to the original ATIG #50 email file.
ATIG_049__2013_09_16 [September 16, 2013] Selenocentric Distant Retrograde Orbits (SDROs)
ATIG Members- As many of your are aware, an SDRO is the intended end state for NASA’s contemplated Asteroid Redirect Mission (ARM). Earlier this year, I was in discussions with some of you regarding just how distant and how stable ARM’s SDRO would be. The attached white paper will hopefully answer these questions and make more clear the nature of SDROs. I welcome feedback from anyone who cares to read it. The attached PDF is bookmarked to facilitate navigation. I’ve tested all URLs to verify they’re functional, but the one in the second footnote on p. 1 won’t work with my web browser because line wrapping in Acrobat inserts some superfluous characters when it’s clicked. The URL reads correctly in the PDF and is reproduced here as http://www.nasa.gov/pdf/756122main_Asteroid%20Redirect%20Mission%20Reference%20Concept%20Description.pdf in case anyone wants to download this document but can’t use the PDF’s URL. Enjoy! -Dan
[DROassessmentsR0.pdf, 24 pages, 2.9 MB]
Here is a link to the original ATIG #49 email file.
ATIG_048__2013_09_07 [September 7, 2013] LADEE Trajectory to LOI
ATIG Members- Friday night, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft was launched from the Wallops Flight Facility by a Minotaur V rocket on a month-long multi-orbit trajectory to the Moon. Liftoff was on time September 6 at 11:27 PM EDT, and the reported trans-lunar trajectory was nominal. I’m therefore enclosing Earth-centered and Moon-centered inertial trajectory plots of the planned nominal trajectory leading to lunar orbit insertion (LOI) on October 6. Data supporting these plots were posted to JPL’s Horizons ephemeris service on August 30. According to a report posted to http://www.nasa.gov/LADEE/#.Uis62OB0org at 3:40 AM EDT on September 7, mission controllers are working an anomalous shutdown of LADEE’s attitude control reaction wheels, but communications with the spacecraft are still being maintained. The nominal trans-lunar trajectory appears to be very flexible in achieving LOI, so there is ample time to work this problem. If any significant trajectory updates are posted, I’ll make every effort to pass along updated plots. -Dan
[LADEEprelaunchGeo.gif, 1 page, 150 KB, LADEEprelaunchSel.gif, 1 page, 110 KB]
Here is a link to the original ATIG #48 email file.
ATIG_047__2013_07_24 [July 24, 2013] Reusable Infrastructure In Earth Orbit Supporting Multiple Mars Departures
ATIG Members- I‘m sure many of you are aware of space architectures, such as propellant depots, offering support to human spaceflight (HSF) beyond low Earth orbit (LEO). Such infrastructure would likely provide more return on investment if it could be reused to facilitate multiple departures from LEO bound for deep space. Earlier this year, I researched how reusable infrastructure in Earth orbit might assemble and service Mars-bound payloads during successive departure seasons in 2020 and 2022. The attached PDF file documents this research and its findings. It is bookmarked to aid navigation. Your questions, suggestions, and discussion of this work are invited. -Dan
[MultipleMarsDeparturesR1.pdf, 24 pages, 1.6 MB]
Here is a link to the original ATIG #47 email file.
ATIG_046__2013_06_15 [June 15, 2013] Rendezvous Endgame
ATIG Members- About 8 hours before ATV-4 docked with ISS at 7:07 AM PDT on June 15, the attached image was obtained from my home south of Salem, Oregon. Both spacecraft are recorded moving southeastward past the star Deneb in the constellation Cygnus. The 30-second exposure began at 11:14:42 PM PDT on June 14 with ISS leading ATV-4 at a point near its closest approach to Deneb. For those unfamiliar with constellations, I’ve “connected the dots” for Cygnus, alias The Northern Cross, using faint gray lines. Note how much closer the two trails are to overlaying each other in this late phase of rendezvous than they were in the image obtained a week earlier. Because ISS elevation above the horizon is similar in both images, about 40 degrees, the ATV-4 trail has shifted closer to that of ISS in the later image due to its increased orbit altitude. This is a typical signature in “rendezvous from below and behind” operations. In the endgame, the spacecraft about to dock with ISS progressively reduces its catch-up rate by incrementing its orbit altitude to more closely match that of ISS. By carefully timing these increments, ATV-4 achieved an altitude match just as it caught up with ISS, allowing docking operations to proceed safely at low relative speeds. Yet another faint unidentified satellite trail is visible in the attached image. For scale, assign angular distance d to the apparent separation between Deneb and the star Gamma Cygni at which the two Northern Cross members intersect. From Gamma Cygni, proceed in the 4 o’clock direction about 0.7 d to the trail, which is about 0.2 d in length. Because the trail is so short compared to those of ISS and ATV-4, it’s undoubtedly from a satellite at much higher altitude. Congratulations to ESA for a successful (and picturesque) rendezvous and docking with ISS! -Dan
[IMG_1156ann.JPG, 645 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Sat, 08 Jun 2013 11:36:36 -0700
Conversation: Highway In The Sky (Speed Limit: 7.7 km/s)
Subject: Highway In The Sky (Speed Limit: 7.7 km/s)
ATIG Members- The attached photo was taken from my home looking north toward the city of Salem, Oregon with the state capitol about 10 km away, so please forgive a little light pollution. It shows an early stage of the European Space Agency’s (ESA’s) Automated Transfer Vehicle-4 (ATV-4, christened Albert Einstein, see http://esamultimedia.esa.int/HSO/Publications/ATV4-EN/) rendezvous with the International Space Station (ISS). The photo’s exposure began on June 7 at 10:28:59 PM PDT when only ATV-4 (dimmer, lower trail) was in the camera’s field of view, and exposure was terminated 55 sec later when only ISS (brighter, higher trail) was in the field of view. Because the two spacecraft are orbiting in nearly the same plane with ATV-4 at a slightly lower altitude and higher speed, their trails are parallel but displaced during the exposure. Orbit motion among the stars is down and to the right in the photo, which shows a maple and a fir tree in silhouette against Salem’s sky-glow at bottom. There’s also a very faint trail at lower left running nearly perpendicular to that of ISS, but I have no idea what Earth satellite caused it. For those unfamiliar with constellations, I’ve “connected the dots” for Ursa Minor, alias The Little Dipper, using faint gray lines. The star at the end of the Dipper’s handle, and closest to the end of the ISS trail, is Polaris. Launched on June 5 at 2:52 PM CDT, ATV-4’s docking with ISS is planned for June 15 at 6:46 AM PDT. The attached June 7 PDT photo catches ATV-4 just after it had “lapped” ISS and moved ahead of it in orbit. On the previous PDT evening, ATV-4 was on the other side of Earth from ISS, making a single exposure capturing both spacecraft impossible for Earthbound photographers. The following table shows daily differences in the times ISS and ATV-4 appear in Salem’s sky after sunset. This Dt is reckoned by subtracting the ISS time from the ATV-4 time for a particular PDT evening, so a negative value implies ISS trails ATV-4. The concept of trailing or leading degenerates near +45 min or -45 min Dt when ISS and ATV-4 are on opposite sides of the Earth.

PDT Date Dt (min)
June 5 +10
June 6 -44
June 7 0
June 8 +44
June 9 -11
June 10 +40
June 11 -3
June 12 -43
June 13 +16
June 14 0

From data in the foregoing table, ATV-4 can be inferred to pass beneath ISS on multiple occasions at roughly 2-day intervals prior to about a day before docking. If you’re interested in sighting opportunities for ISS, ATV-4, or various other satellites from your location, point your web browser at http://spaceflight.nasa.gov/realdata/sightings/index.html to obtain predictions. Wishing you clear skies! -Dan
Here is a link to the original ATIG #46 email file.
ATIG_045__2013_06_08 [June 8, 2013] Highway In The Sky (Speed Limit: 7.7 km/s)
ATIG Members- The attached photo was taken from my home looking north toward the city of Salem, Oregon with the state capitol about 10 km away, so please forgive a little light pollution. It shows an early stage of the European Space Agency’s (ESA’s) Automated Transfer Vehicle-4 (ATV-4, christened Albert Einstein, see http://esamultimedia.esa.int/HSO/Publications/ATV4-EN/) rendezvous with the International Space Station (ISS). The photo’s exposure began on June 7 at 10:28:59 PM PDT when only ATV-4 (dimmer, lower trail) was in the camera’s field of view, and exposure was terminated 55 sec later when only ISS (brighter, higher trail) was in the field of view. Because the two spacecraft are orbiting in nearly the same plane with ATV-4 at a slightly lower altitude and higher speed, their trails are parallel but displaced during the exposure. Orbit motion among the stars is down and to the right in the photo, which shows a maple and a fir tree in silhouette against Salem’s sky-glow at bottom. There’s also a very faint trail at lower left running nearly perpendicular to that of ISS, but I have no idea what Earth satellite caused it. For those unfamiliar with constellations, I’ve “connected the dots” for Ursa Minor, alias The Little Dipper, using faint gray lines. The star at the end of the Dipper’s handle, and closest to the end of the ISS trail, is Polaris. Launched on June 5 at 2:52 PM CDT, ATV-4’s docking with ISS is planned for June 15 at 6:46 AM PDT. The attached June 7 PDT photo catches ATV-4 just after it had “lapped” ISS and moved ahead of it in orbit. On the previous PDT evening, ATV-4 was on the other side of Earth from ISS, making a single exposure capturing both spacecraft impossible for Earthbound photographers. The following table shows daily differences in the times ISS and ATV-4 appear in Salem’s sky after sunset. This Dt is reckoned by subtracting the ISS time from the ATV-4 time for a particular PDT evening, so a negative value implies ISS trails ATV-4. The concept of trailing or leading degenerates near +45 min or -45 min Dt when ISS and ATV-4 are on opposite sides of the Earth.

PDT Date Dt (min)
June 5 +10
June 6 -44
June 7 0
June 8 +44
June 9 -11
June 10 +40
June 11 -3
June 12 -43
June 13 +16
June 14 0

From data in the foregoing table, ATV-4 can be inferred to pass beneath ISS on multiple occasions at roughly 2-day intervals prior to about a day before docking. If you’re interested in sighting opportunities for ISS, ATV-4, or various other satellites from your location, point your web browser at http://spaceflight.nasa.gov/realdata/sightings/index.html to obtain predictions. Wishing you clear skies! -Dan
[IMG_1144annotated.JPG, 521 KB]
Here is a link to the original ATIG #45 email file.
ATIG_044__2013_05_18 [May 18, 2013] A Special Earthlike Orbit: NEO 2013 BS45
ATIG Members- At heliocentric (a, e) coordinates (0.998 AU, 0.084) on the V-plot sent last month is the newly discovered NEO 2013 BS45. With a semi-major axis nearly the same as Earth’s, this NEO’s heliocentric phase rate with respect to Earth is so small that some very strange things happen to its orbit as it closes in on our planet. Read all about 2013 BS45’s remarkable orbit in the attached PDF file. Could a small NEO in an orbit like 2013 BS45’s be captured and retrieved by a robotic spacecraft with ion engines? Such a target would not be easy to find with enough lead time to launch a rendezvous mission before it escapes the reach of our current retrieval technology. -Dan
[Horseshoe2013bs45r3.pdf, 10 pages, 968 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Mon, 22 Apr 2013 09:39:16 -0700
Conversation: Near-Earth Objects (NEOs) In Earthlike Orbits
Subject: Near-Earth Objects (NEOs) In Earthlike Orbits
ATIG Members- The attached PDF file is effectively a 2-page caption for the “V-plot” graphic at its conclusion. To clearly view annotations on this graphic, you’ll need a zoom factor of about 250%. As humanity begins to explore the most accessible interplanetary destinations in an era prior to the first comprehensive NEO survey, a current V-plot is akin to maps of the New World published circa 1500 AD. As you study the V-plot, be sure to note the location of 2013 BS45. This recently discovered NEO is in a very interesting orbit and will be the subject of an ATIG upload in the next month or so. -Dan
Here is a link to the original ATIG #44 email file.
ATIG_043__2013_04_22 [April 22, 2013] Near-Earth Objects (NEOs) In Earthlike Orbits
ATIG Members- The attached PDF file is effectively a 2-page caption for the “V-plot” graphic at its conclusion. To clearly view annotations on this graphic, you’ll need a zoom factor of about 250%. As humanity begins to explore the most accessible interplanetary destinations in an era prior to the first comprehensive NEO survey, a current V-plot is akin to maps of the New World published circa 1500 AD. As you study the V-plot, be sure to note the location of 2013 BS45. This recently discovered NEO is in a very interesting orbit and will be the subject of an ATIG upload in the next month or so. -Dan
[Vplot2013mar11r1.pdf, 3 pages, 356 KB]
Here is a link to the original ATIG #43 email file.
ATIG_042__2013_03_02 [March 2, 2013] Chelyabinsk Bolide Trajectory Reconstruction
ATIG Members- Greetings from sunny (today at least) Salem, Oregon! I hope you’ll enjoy my first ATIG contribution from the Pacific Northwest in the attached PDF file. It is inspired by celestial events on February 15, but the fog surrounding those events only started to clear about a week ago. Another report released earlier today can be found at http://neo.jpl.nasa.gov/news/fireball_130301.html. -Dan
[ChelyabinskBolideReconR1.pdf, 3 pages, 144 KB]
Here is a link to the original ATIG #42 email file.
ATIG_041__2012_11_03 [November 3, 2012] 2012 UV136 And Its Subjective Accessibility For HSF
ATIG Members- Last month, yet another near-Earth object (NEO) was discovered in an orbit very similar to Earth’s. As the attached report details, this NEO is highly accessible for human space flight (HSF) over the next decade or so, but that accessibility is fleeting. Your comments are welcome. -Dan
[2012 UV136discoveryR1.pdf, 4 pages, 264 KB]
Here is a link to the original ATIG #41 email file.
ATIG_040__2012_10_17 [October 17, 2012] Last Friday’s Flyby
ATIG Members- Last Friday, 12 October, another bit of interplanetary flotsam flew between us and the Moon. According to best estimates, it’ll be back to visit us 12 October 2017. On that occasion, it could reach a perigee distance anywhere from 464,700 km (just outside the Moon’s orbit) to 13,000 km (well inside GEO altitude). Be careful out there! -Dan
[GravityAssistTo2012 TC4r1.pdf, 3 pages, 237 KB]
Here is a link to the original ATIG #40 email file.
ATIG_039__2012_09_29 [September 29, 2012] Comet ISON
ATIG Members- If Comet ISON’s discovery is news to you, the article at http://www.space.com/17762-newfound-comet-dazzling-2013-display-c2012s1.html provides useful background. As with any long-period comet coming to its first perihelion in human history, ISON could be a dazzler or a dud. Nevertheless, I hope the attached PDF file will convey an appreciation for its orbit and Earthly viewing geometry. May we all require sunglasses to see it near perihelion! As some of you already know, my wife and I are on a path to relocation in Salem, Oregon late this year, fulfilling a retirement vision of ours after years of searching the Willamette Valley for our dream home. You can perhaps appreciate my motivation by browsing to http://www.redfin.com/OR/Salem/8119-Kloshe-Ct-S-97306/home/26352434. This is indeed the land of milk and honey (if you can manage a few brambles and gophers). I intend to retain my EarthLink address through my relocation, ISPs permitting. And, as most of you can attest, I never leave my trajectory analysis tools behind. Keep in touch! -Dan
[CometISONin2013+14.pdf, 2 pages, 204 KB]
Here is a link to the original ATIG #39 email file.
ATIG_038__2012_08_10 [August 10, 2012] A Notional Round Trip to EML2
ATIG Members- Some of you are aware of trajectory studies being conducted by NASA-JSC’s Flight Dynamics Division in which the translunar libration point (EML2) is the Orion crew’s destination. During an educational outreach effort at JSC this month, a notional Orion mission to EML2 was presented to secondary school teachers from around the U.S. This presentation consisted of a descriptive illustrated PDF file, together with a 3-D simulation rendered by Celestia. The simulation was subsequently turned into a QuickTime movie of 6 min 49 sec duration. Both the PDF file and QuickTime movie are archived at https://spideroak.com/browse/share/DanAdamo/EML2roundTrip as a downloadable package about 120 MB in size. I hope you enjoy this flight of fancy and look forward to any comments you may have. -Dan
[AIAA is also providing links to those two files here: EML2roundTripR1.mov, 128 MB, 6:49 (minutes:seconds), EML2roundTripR2.pdf, 6 pages, 456 KB.]
Here is a link to the original ATIG #38 email file.
ATIG_037__2012_08_01 [August 1, 2012] Apollo Hardware In Solar Orbit
ATIG Members- I‘ve talked with some of you about a consulting contract I’ve been working this year under which I’ve reconstructed Apollo Program trajectories pertaining to jettisoned hardware placed in solar orbit. The primary deliverable for this contract is a report describing reconstruction methodology and results. My JPL customer has kindly granted permission to distribute the finalized report without restriction, so it’s attached. The tentative plan for Space Launch System (SLS) upper stage disposal is similar to that used on Saturn IV-B (S-IVB) upper stages during the Apollo 8 through 12 missions and documented in the report. Back in the Apollo Era, S-IVB stages could be tracked post-TLI only as long as batteries could power the onboard radio transponder (less than a day). Consequently, these stages were lost well before they entered interplanetary space. Today, the situation is different. Planetary radars at Goldstone, California and Arecibo, Puerto Rico can likely skin track an SLS upper stage for weeks after TLI. This could result in a sufficiently accurate orbit to support recovery when the upper stage returns to Earth’s vicinity. Because upper stages disposed in interplanetary space tend to enter solar orbits very similar to Earth’s, there is high value in maintaining knowledge of their trajectory status over time. If this is done, the stages will not be mistaken for potentially hazardous objects (PHOs) threatening Earth impact. Nor will they be mistaken for highly accessible near-Earth asteroids (NEAs) warranting robotic or human visits. I‘m considering writing an op-ed advocating funding planetary radar tracking of disposed SLS upper stages as they head for solar orbit. If anyone has comments or information on this concept they can share, I’d appreciate hearing from you. -Dan
[ApolloEarthDeparturesR7.pdf, 49 pages, 3.3 MB]
Here is a link to the original ATIG #37 email file.
ATIG_036__2012_07_24 [July 24, 2012] Re: Mars Science Lab (MSL) Entry/Descent/Landing (EDL)
ATIG Members- With help from one among our ranks, I’ve traced the 3-min skew to an error on my part in converting events from solar system barycentric time to UTC. As penance, I shall attend this Friday’s Trajectory Think Tank discourse on time measurement by JSC-DM/Brian Kubena. This error has been corrected in the attached “r1” revision to my 22 July upload, which is hereby completely superseded. Happy landings! -Dan
[MSL’sEDLr1.pdf, 3 pages, 251 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Sun, 22 Jul 2012 08:27:32 -0500
Conversation: Mars Science Lab (MSL) Entry/Descent/Landing (EDL)
Subject: Mars Science Lab (MSL) Entry/Descent/Landing (EDL)
ATIG Members- You’ll find attached my analysis of what I believe to be the latest and most authoritative MSL EDL data available to the public at this time. Those of us who attended JSC-DM/Gavin Mendeck’s excellent presentation on this topic at June 29’s Trajectory Think Tank will note EI (and presumably other events) in the attachment is about 3 min later than in Gavin’s Chart #10. I’m suspicious this time skew is by design and is an attempt to delay MSL landing in order to obtain better EDL real time data relay coverage. The relay function is provided through Mars Odyssey, which recently suffered a reaction wheel failure and may otherwise be unable to establish contact with MSL until after landing. I‘ve been unable to verify the 3-min skew is real beyond a well written 16 July report on the relay difficulty by Jonathan Amos at http://www.bbc.co.uk/news/science-environment-18861463. Reports at http://mars.jpl.nasa.gov/msl/news/whatsnew/ are terse and do not confirm or refute the skew’s existence. If anyone’s in a position to provide better EDL planning data to me, I’m willing to revise the attached PDF accordingly and distribute to ATIG. -Dan
Here is a link to the original ATIG #36 email file.
ATIG_035__2012_04_22 [April 22, 2012] NEA to EML2
ATIG Members- My apologies to those of you I’m contacting about the subject concept for the second time, but I’d like to share it with the broadest possible community. Many of you have already heard the hype surrounding launch of Planetary Resources on April 24. The science and engineering behind this corporate startup is likely documented in a Keck Institute for Space Studies (KISS) report available for download at http://kiss.caltech.edu/study/asteroid/asteroid_final_report.pdf. If this asteroid capture and return (ACR) venture becomes viable, EML2 may not be “just an empty point in space” by the time humans arrive there. -Dan
Here is a link to the original ATIG #35 email file.
ATIG_034__2012_03_07 [March 7, 2012] Re: The Risk Corridor
ATIG Members- It seems Nature has supplied a timely footnote for my 2011 AG5 risk corridor analysis. Attached are heliocentric and geocentric plots spanning NEO 2012 DA14’s close Earth approach on 15 Feb 2013. Recent Horizons prediction data (reference ephemeris JPL#15) for that event appear in the following table.

Date (CT) Body CA Dist MinDist MaxDist Vrel TCA3Sg Nsigs P_i/p
A.D. 2013 Feb 15.81141 Earth 0.000182 0.000181 0.001436 8.195 73.09 2013.0 0.000000

Converting CA Dist, MinDist, and MaxDist from AU to km units, I couldn’t help noticing the nominal perigee distance of 27,200 km is nearly the same as the minimum possible perigee (to 3-sigma confidence) of 27,100 km and yet is appreciably removed from the maximum possible perigee (to 3-sigma confidence) of 214,800 km. Perigee distance uncertainty is confirmed by TCA3Sg’s value. At 73.09 minutes, that’s a lot of potential Earth-relative motion! The attached geocentric plot gives geometric perspective on perigee distance uncertainty. The line of variations (LOV) is effectively the plotted trajectory, and it’s nearly perpendicular to Earth’s heliocentric velocity (directed roughly out of the plot at the viewer). Thus, variations in the time of perigee can affect perigee distance, but they can’t appreciably decrease the current best guess for that distance. So, as indicated by the P_i/p value, there is no credible prospect for Earth collision (nor for a risk corridor plot) associated with this approach. -Dan
[2012 DA14hel#14.gif, 166 KB, 2012 DA14geo#15.gif, 138 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Sun, 04 Mar 2012 15:43:58 -0600
Conversation: The Risk Corridor
Subject: The Risk Corridor
ATIG Members- Arguably the most compelling reason for space exploration (human or robotic) is planetary defense from impact by potentially hazardous objects (PHOs), comprised of near-Earth objects (NEOs) and long-period comets. The attached white paper is motivated by NEO 2011 AG5’s possible Earth impact in 2040 (reference http://www.space.com/14683-big-asteroid-2011-ag5-threat-earth.html), which if it actually took place, would then be confined to a 15-km-wide locus of terrestrial locations called the risk corridor. A non-conventional risk corridor generation method documented by the paper is inspired by a strategy ATIG members familiar with Shuttle ascent/entry onboard state vector management will recognize: to correct a down-track navigation error (the most common type), simply modify the state vector time tag as appropriate. In applying this strategy to risk corridor computation, the time bias is varied to systematically sample a PHO’s one-dimensional uncertainty region for the subset of conditions resulting in Earth impact. I welcome feedback on this paper and its implications for planetary defense. -Dan
Here is a link to the original ATIG #34 .eml (email) file.
ATIG_033__2012_03_04 [March 4, 2012] The Risk Corridor
ATIG Members- Arguably the most compelling reason for space exploration (human or robotic) is planetary defense from impact by potentially hazardous objects (PHOs), comprised of near-Earth objects (NEOs) and long-period comets. The attached white paper is motivated by NEO 2011 AG5’s possible Earth impact in 2040 (reference http://www.space.com/14683-big-asteroid-2011-ag5-threat-earth.html), which if it actually took place, would then be confined to a 15-km-wide locus of terrestrial locations called the risk corridor. A non-conventional risk corridor generation method documented by the paper is inspired by a strategy ATIG members familiar with Shuttle ascent/entry onboard state vector management will recognize: to correct a down-track navigation error (the most common type), simply modify the state vector time tag as appropriate. In applying this strategy to risk corridor computation, the time bias is varied to systematically sample a PHO’s one-dimensional uncertainty region for the subset of conditions resulting in Earth impact. I welcome feedback on this paper and its implications for planetary defense. -Dan
[RiskCorr2011 AG5r2.pdf, 8 pages, 319 KB]
Here is a link to the original ATIG #33 email file.
ATIG_032__2012_01_31 [January 31, 2012] Re: Draft Phobos-Grunt Article
ATIG Members- Looks like the 15 Jan landing date was reasonably accurate. Now if somebody can just figure out where the debris really ended up, or at least release some terminal observations without compromising U.S. space-based space surveillance capability. As some of you have already noticed, Lindley Johnson and I are cited in an article on inane Russian explanations for Phobos-Grunt’s failure by Jim Oberg (not something I’ll be putting on my résumé) at http://www.thespacereview.com/article/2016/1. One reviewer of my “R0” Phobos-Grunt draft article requested I look into a recovery strategy involving 4 TMI burns. The first two raise apogee, the third does a plane change at apogee to null the accumulated TMI steering angle targeting Mars, and the last burn achieves Earth departure. This strategy is akin to one developed by the Constellation Program to enable “anytime” Earth return from low lunar orbit. If I’ve done my Phobos-Grunt performance bookkeeping correctly, the 4-burn TMI would have enabled mission recovery as late as 9 days after launch. As you’ll recall from the R0 draft, a standard 2-burn TMI with simultaneous planar steering would have supported mission recovery for only 3 days after launch. The attached PDF incorporates the 4-burn TMI strategy (modeled as 3 impulses) in a new section beginning at the bottom of p. 8 and completely supersedes R0. Other changes to R0 are relatively minor. This “R1” draft is what I intend to submit before the 8 Feb newsletter deadline, but I’ll do my best to incorporate any feedback you may have. If it’ll expedite your review, I can send a PDF with all R1 redlines to an R0 baseline on request. Enjoy! -Dan
[Phobos-GruntTMIr1.pdf, 11 pages, 989 KB]
From: Daniel Adamo <adamod@earthlink.net>
Date: Thu, 29 Dec 2011 20:33:27 -0600
Conversation: Draft Phobos-Grunt Article
Subject: Draft Phobos-Grunt Article
ATIG Members- Attached is a draft article intended for publication in AIAA-Houston Section’s Jan-Feb 2012 newsletter (author deadline is 8 Feb). I believe this to be the most lucid account of when Phobos-Grunt could have departed Earth for Mars under at least two scenarios which became hopelessly confused during November 2011. Except for the “TBS” Phobos-Grunt orbit decay date on p. 2 (current predictions are converging on 15 Jan), I believe this draft is complete. Any corrections or suggestions you care to send are invited. -Dan
Here is a link to the original ATIG #32 email file.
ATIG_031__2012_01_09 [January 9, 2012] X-37B Flyby of Tiangong-1
ATIG Members- Welcome to 2012! Attached is a somewhat rambling account, but it’s to the point. Doing the analysis, I somehow felt the veil of secrecy about X-37B operations had been (legally) lifted to a degree, at least hypothetically. I’ll be interested in anyone’s reasoned take on whether or not you think the 10 January flyby will be on X-37B’s flight plan. -Dan
[X-37Bflyby.pdf, 6 pages, 632 KB]
Here is a link to the original ATIG #31 email file.
ATIG_030__2011_12_29 [December 29, 2011] Draft Phobos-Grunt Article
ATIG Members- Attached is a draft article intended for publication in AIAA-Houston Section’s Jan-Feb 2012 newsletter (author deadline is 8 Feb). I believe this to be the most lucid account of when Phobos-Grunt could have departed Earth for Mars under at least two scenarios which became hopelessly confused during November 2011. Except for the “TBS” Phobos-Grunt orbit decay date on p. 2 (current predictions are converging on 15 Jan), I believe this draft is complete. Any corrections or suggestions you care to send are invited. -Dan
[Phobos-GruntTMIr0.pdf, 8 pages, 965 KB]
Here is a link to the original ATIG #30 email file.
ATIG_029__2011_12_18 [December 18, 2011] Comet Lovejoy Solar Graze
ATIG Members- The attached account of last week’s solar graze is an attempt at public outreach which I’m also circulating among colleagues. From imagery posted at SpaceWeather.com and other sites, laypersons may be under the impression Comet Lovejoy tunneled through the Sun. A less geocentric perspective gives a clearer understanding. Feel free to share with others. Happy holidays to all! -Dan
[LovejoyGraze.pdf, 2 pages, 154 KB]
Here is a link to the original ATIG #29 email file.
ATIG_028__2011_12_06 [December 6, 2011] A Peek at “Cassini”
ATIG Members- Attached is another astrodynamics draft article intended for the AIAA-Houston Section’s next newsletter. Comments and corrections are invited, as always. I’ve heard rumors Cassini may not make it to the planned mission termination date in 2017. Apparently JWST is consuming so much of NASA’s science budget that serious consideration is being given to shutting down operations for Cassini and other functioning missions this fiscal year. I resisted the temptation to lobby on Cassini’s behalf in the article and simply let a few pictures do the talking. Happy holidays! -Dan
[CassiniAfter7yearsR0.pdf, 7 pages, 1.4 MB]
Here is a link to the original ATIG #28 email file.
ATIG_027__2011_11_05 [November 5, 2011] A Salvo for the ATIG
ATIG Members- Attached are 3 PDFs documenting recent research. The first relates to NEO 2005 YU55’s Earth encounter at 9.0 November 2011 UTC, and is the most perishable material. I hope you’ll agree this encounter has broader implications for planetary defense and interplanetary astronautics. This initial draft may morph into an article appearing in the AIAA-Houston Section’s newsletter a couple months hence. The next two PDFs are peer-reviewed references I’ve produced as follow-on actions from my 3 weeks as a volunteer mentor at JSC’s High School Aerospace Scholars (HAS) workshops this past summer. Some of you participated in this review, and I’m grateful for your help. An introduction to interplanetary trajectory design and mission analysis appears in the Interplanetary Cruising reference, while the Radiation Shielding reference discusses the interplanetary environment, NASA standards, and a possible mitigation strategy in that context. I hope you’ll find all this reference material useful and will be using it sooner than you may currently believe! As always, comments and corrections regarding the PDFs are welcome and appreciated. -Dan
[2005 YU55,TheCycler.pdf, 3 pages, 224 KB, InterplanetaryCruisingR2.pdf, 17 pages, 1.8 MB, RadShieldingMassR2.pdf, 5 pages, 118 KB]
Here is a link to the original ATIG #27 email file.
ATIG_026__2011_10_17 [October 17, 2011] Asteroid 2009 TM8
ATIG Members I‘m impressed: after I sent out the notice at the bottom of this thread 2 years ago, one among us added an appropriate event to her calendar for today and has inquired what’s become of 2009 TM8. Good question, Pam! Just before noon CDT today, I polled JPL’s Small Bodies Database (SBDB) and found 2009 TM8’s record hasn’t received another observation since the 48 leading to its discovery. Because these observations extended over only 2 days (close to a 2-deg heliocentric arc), the integrity of the current 2008 TM8 orbit elements would be equivalent to those from low speed ground NAV tracking a Shuttle for half a minute. Indeed, the SBDB’s Orbital Condition Code (OCC) for this NEO is 6, meaning 2009 TM8 is effectively lost. According to Harvard’s Minor Planet Center, OCC = 6, is equivalent to a heliocentric downtrack error between 1692 and 7488 arc-seconds per decade. Consequently, in the two years since 2009 TM8 was discovered, its predicted heliocentric mean anomaly is probably in error from 0.1 to 0.4 deg. Since humanity insists on observing NEOs only from Earth, a very close approach by 2009 TM8 is required because its diameter is almost certainly less than 10 m. When mapped into a close-up geocentric viewing geometry, heliocentric position uncertainty places 2009 TM8 virtually anywhere in our sky this week. I‘ll be in touch with further details if this celestial needle in a haystack is rediscovered. Fortunately, an object less than 10 m in diameter won’t do much damage if it enters Earth’s atmosphere. -Dan
From: Daniel Adamo <adamod@earthlink.net>
Date: Wed, 21 Oct 2009 12:12:37 -0500
Subject: Asteroid 2009 TM8
ATIG Members- Last Friday evening Oct 16 CDT, yet another asteroid briefly came closer to Earth than the Moon. Flyby geometry for the interloper, provisionally designated 2009 TM8, is illustrated in the attached geocentric plot. With the Moon and Sun roughly to the left of Earth in the geocentric plot, 2009 TM8 crossed Earth’s heliocentric orbit ahead of our path around the Sun. Earth flyby geometry therefore caused 2009 TM8 to lose some heliocentric orbit energy. This is apparent from the heliocentric plot spanning 2009 and 2010. Note the shift to lower aphelion as the 2009 TM8 plot begins and ends. As of October 18, JPL’s orbit solution for 2009 TM8 contained 36 observations over a 2-day arc. By October 20, 48 observations had been processed over the same arc. Because (2009 TM8)’s Earth departure was toward the Sun, I’m speculating the observation arc won’t be extended later in time very much. The only significant improvement in the orbit solution would come from a serendipitous pre-discovery observation. Nevertheless, current knowledge of (2009 TM8)’s post-flyby heliocentric orbit places its period very near two years. To a 3-sigma uncertainty of 23.9 hours in closest approach time, the next Earth conjunction will be (you guessed it) early on 2011 Oct 17 UTC. Depending on how the statistics play out, perigee could be as low as 178,600 km on that occasion. I imagine interest in reacquiring (2009 TM8) will be high during the summer/fall of 2011. -Dan
Here is a link to the original ATIG #26 email file.
ATIG_025__2011_10_05 [October 5, 2011] International Astronautical Congress (IAC) 2011
ATIG Members- The attached paper is being presented by NASA Associate Administrator Bill Gerstenmaier at this year’s IAC on October 7. Feel free to feed comments or questions to me. -Dan
[IAC_2011_A5.4.7_RevD.pdf, 12 pages, 637 KB]
Here is a link to the original ATIG #25 email file.
ATIG_024__2011_10_02 [October 2, 2011] *Responsible* Human Space Flight
ATIG Members- The attached PDF is an op-ed draft inspired by NASA’s recent heavy lift Space Launch System announcement. Assuming this system to loft humans beyond LEO goes operational, we’ll have enough capability to be dangerous. The issue I’m trying to confront is: will we provide the responsible strategies, infrastructure, and trained personnel to go with this capability? I’m hoping this piece will soon be published in Space News. Thanks to those among you who have helped me pull this draft together. -Dan
[ResponsibleHSFr1.pdf, 2 pages, 85 KB]
Here is a link to the original ATIG #24 email file.
ATIG_023__2011_09_25 [September 25, 2011] GRAIL to the Moon
ATIG Members- The attached PDF is a draft article on GRAIL’s trans-lunar coast and lunar orbit insertion trajectory intended for publication in AIAA-Houston Section’s November-December newsletter. Any feedback is welcome at any time, but my newsletter deadline is September 30. -Dan
[GRAILtoMoonR1.pdf, 6 pages, 504 KB]
Here is a link to the original ATIG #23 email file.
ATIG_022__2011_09_18 [September 18, 2011] Dawn Reaches HAMO
ATIG Members- Just before 2011 Sep 1.0 UTC, Dawn began lowering its orbit altitude about (4) Vesta from 2700 km to 680 km. At the same time, Dawn rotated the descending node of its orbit on Vesta’s equator from 15 deg west of local solar noon about 15 deg westward toward Vesta’s sunrise terminator. Thanks to a September 15 posting on JPL’s Horizons server, this transition from Dawn’s survey orbit to its high altitude mapping orbit (HAMO) about Vesta is chronicled by the attached plot. This plot’s plane very nearly coincides with that of the HAMO. If the transition went according to the posted plan, HAMO was reached around 2011 Sep 17.6 UTC. -Dan
[DawnVsVestaR5.gif, 267 KB]
Here is a link to the original ATIG #22 email file.
ATIG_021__2011_08_10 [August 10, 2011] NEO Accessibility Paper
ATIG Members- The attached bookmarked PDF is a paper I presented to the AAS/AIAA Astrodynamics Specialist conference last week. It will also be the subject of a presentation I’m scheduled to make at the June 26 Trajectory Think Tank (T3) seminar. Any feedback on the paper is welcome, including any questions or topics you’d like addressed at T3. This is definitely ongoing research! -Dan
[AAS 11-449r3.pdf, 20 pages, 1.4 MB]
Here is a link to the original ATIG #21 email file.
ATIG_020__2011_07_19 [July 19, 2011] Dawn Arrival at Main Belt Asteroid (4) Vesta
ATIG Members- I‘ve never looked into traj ops for a spacecraft with solar electric propulsion (SEP), so I resolved to get a taste of them with Dawn’s historic arrival in orbit about Vesta this month. Talk about TIG slip capability! Even terminal approach burns with durations measured in weeks can easily be postponed by days with no ill effects. The attached draft article is to be published in the August issue of the AIAA Houston Section’s newsletter. Be in touch if you run across any errors or glaring omissions, as these can probably be corrected over the next week or so. I remain unconvinced that electric propulsion, even with a nuclear reactor as its power source, is advisable on a crewed spacecraft. However, this technology could play important supporting roles in HSF, particularly when those roles are not time-critical. -Dan
[DawnVestaArrivalR1.pdf, 4 pages, 258 KB]
Here is a link to the original ATIG #20 email file.
ATIG_019__2011_06_02 [June 2, 2011] The Red Baron Scenario
ATIG Members- I‘ve agreed to author a series of informal articles dealing with astrodynamics themes for publication by the AIAA-Houston Section in its Horizons newsletter. Newsletter editor Douglas Yazell has graciously permitted me share the initial draft of my first article, titled “The Red Baron Scenario In An Interplanetary Context”, with all of you. Kindly review the attached PDF and forward any comments or corrections to me in the next week, if possible. Many thanks! -Dan
[RedBaronScenarioR1.pdf, 6 pages, 387 KB]
Here is a link to the original ATIG #19 email file.
ATIG_018__2011_03_17 [March 17, 2011] Mercury Orbit Insertion (MOI)
ATIG Members- After nearly 7 years of interplanetary cruise, the MESSENGER robotic probe will become the first artifact to orbit Mercury at 8 PM CDT tonight (http://messenger.jhuapl.edu/mer_orbit.html). A heliocentric trajectory plot showing the end of interplanetary cruise is attached, along with a Mercury-centered plot showing terminal approach, MOI, and the first orbit of Mercury (actually Orbit 0 and the first half of Orbit 1 the way JHU-APL controllers reckon it). -Dan
[MOImerc.gif, 150 KB, MOIhelio.gif, 148 IB]
Here is a link to the original ATIG #18 email file.
ATIG_017__2011_01_10 [January 10, 2011] Accessible NEOs Paper
ATIG Members- Happy 2011! According to my records, a preliminary draft of the attached paper was uploaded on December 7, 2009 to those of you who were ATIG members then. Since that initial upload, the paper benefitted from multiple peer review cycles and was published in the November-December 2010 issue of AIAA’s Journal of Spacecraft and Rockets (Vol. 47, No. 6). The published version may be accessed via www.aiaa.org. Unfortunately, the JSR baseline suffers from errata I couldn’t correct and absence of color due to lack of funding. The attached version attempts to correct those deficiencies and may be freely distributed without charge to recipients. I hope you find use for this research from the heady days of the 2009 Augustine Commission and inception of The Flexible Path. The paper is already starting to show its age, but that’s what being “on the cutting edge” is all about. 😉 -Dan
[AccessibleAsteroidsR0.pdf, 17 pages, 1 MB]
Here is a link to the original ATIG #17 email file.
ATIG_016__2010_10_14 [October 14, 2010] Propellant Depot Locations
ATIG Members- Many of you familiar with my lunar surface rendezvous (LSR) rants would likely count me as a propellant depot advocate. Last month, I appeared on The Space Show (read summaries and hear recordings at http://www.thespaceshow.org/ for Sep/7/2010 and Sep/23/2010) twice to qualify that advocacy. These appearances led to a more formal and technical propellant depot presentation at GSFC/Harley Thronson’s Future In-Space Operations (FISO) telecon on October 13. I think many of you will find the attached FISO charts of interest. As always, I welcome feedback or questions, including any invitations to present this material at a time and place we coordinate. Enjoy! -Dan
[PropDepotChartsFISOr1.pdf, 16 pages, 419 KB]
Here is a link to the original ATIG #16 email file.
ATIG_015__2010_10_02 [October 2, 2010] “Mars Approach and Deimos Rendezvous” on YouTube
ATIG Members- As some of you know, I attended my first International Space Development Conference (ISDC) in Chicago this May. At the ISDC, my colleague Jim Logan and I presented a 3-hour seminar on interplanetary travel with foreseeable technology. One of the high points in the seminar was a video of Mars approach and rendezvous with its outer moon Deimos. The video’s premier at the ISDC had no audio track, as I simply narrated what was being rendered. As a follow-on action, Jim and I have packaged the video for YouTube posting with 2 minutes of shameless self-promotion, followed by 6.5 minutes explaining how Mars can be explored by humans using Deimos as a convenient observation post and habitat. If your PC is HD-capable, I recommend selecting 720pHD and full-screen from controls at the lower right of YouTube’s video player. The URL is http://www.youtube.com/watch?v=X10GAqA4Ky4. Enjoy! -Dan
Here is a link to the original ATIG #15 email file.
ATIG_014__2010_08_13 [August 13, 2010] An Opinion On Initial Steps Toward NEO Exploration
ATIG Members- During June and July, I had the honor of ghost writing an editorial on where U.S. priorities should lie with respect to near-Earth object (NEO) exploration in the near term. I learned a lot from some very smart people and wanted to share that knowledge with those of you who haven’t seen the result. The attached PDF is shamelessly scanned from August 2’s issue of Space News. I invite any feedback on it you’d care to send my way. Until our next seminar, keep ’em flying! -Dan
[AsPublishedOpEd.pdf, 2 pages, 314 KB]
Here is a link to the original ATIG #14 email file.
ATIG_013__2009_12_07 [December 7, 2009] Accessible Near Earth Objects (NEOs)
ATIG Members- Attached is a draft paper documenting how prospective NEO human exploration opportunities were identified and assessed under auspices of the Augustine Commission earlier this year. This PDF is bookmarked to facilitate navigation, and I welcome questions or comments regarding it. Please refrain from further distribution of the PDF because it will soon be submitted to a peer-reviewed journal. Those desiring a PDF copy who aren’t on ATIG distribution may be referred to me for an upload. A Happy 2010 to all of you! -Dan
[NEOmissionSurveyR2.pdf, 15 pages, 1.1 MB]
Here is a link to the original ATIG #13 email file.
ATIG_012__2009_10_21 [October 21, 2009] Asteroid (2009 TM8)
ATIG Members- Last Friday evening Oct 16 CDT, yet another asteroid briefly came closer to Earth than the Moon. Flyby geometry for the interloper, provisionally designated (2009 TM8), is illustrated in the attached geocentric plot. With the Moon and Sun roughly to the left of Earth in the geocentric plot, (2009 TM8) crossed Earth’s heliocentric orbit ahead of our path around the Sun. Earth flyby geometry therefore caused (2009 TM8) to lose some heliocentric orbit energy. This is apparent from the heliocentric plot spanning 2009 and 2010. Note the shift to lower aphelion as the (2009 TM8) plot begins and ends. As of October 18, JPL’s orbit solution for (2009 TM8) contained 36 observations over a 2-day arc. By October 20, 48 observations had been processed over the same arc. Because (2009 TM8)’s Earth departure was toward the Sun, I’m speculating the observation arc won’t be extended later in time very much. The only significant improvement in the orbit solution would come from a serendipitous pre-discovery observation. Nevertheless, current knowledge of (2009 TM8)’s post-flyby heliocentric orbit places its period very near two years. To a 3-sigma uncertainty of 23.9 hours in closest approach time, the next Earth conjunction will be (you guessed it) early on 2011 Oct 17 UTC. Depending on how the statistics play out, perigee could be as low as 178,600 km on that occasion. I imagine interest in reacquiring (2009 TM8) will be high during the summer/fall of 2011. -Dan
[(2009 TM8)helio.gif, 71 KB, (2009 TM8)geo.gif, 61 KB]
Here is a link to the original ATIG #12 email file.
ATIG_011__2009_09_17 [September 17, 2009] MESSENGER Mercury Flyby #3
ATIG Members- This is coming to you a bit early, but I thought I’d get trajectory plots of MESSENGER’s third Mercury flyby in your email before Cathy Osgood retires from 50 years of service to the US space program and her address is deactivated. Closest approach to Mercury will be just before 5 PM CDT on September 29. This mission’s final gravity assist sets the stage for MESSENGER to achieve orbit about Mercury on March 18, 2011. Launch was August 3, 2004. -Dan
[Mrec3helio.gif, 66 KB, Merc3merc.gif, 62 KB]
Here is a link to the original ATIG #11 email file.
ATIG_010__2009_09_05 [September 5, 2009] LCROSS Status
ATIG Members- Many of you are already familiar with the Lunar CRater Observation and Sensing Satellite (LCROSS) mission to impact a permanently shaded “cold trap” near the Moon’s south pole and detect any substantial water deposits there. http://www.nasa.gov/mission_pages/LCROSS/main/index.html. Two weeks ago, LCROSS declared a spacecraft emergency after attitude control malfunctions expended nearly all the spacecraft’s propulsion margin while out of contact with NASA’s Deep Space Network (DSN). This incident occurred at one of the mission’s worst possible intervals, when LCROSS was far south of the celestial equator and virtually invisible from two of the three DSN sites (only the site near Canberra, Australia is in the southern hemisphere). After some heroics by operations personnel, LCROSS stood down from emergency status on September 3. Just before the Labor Day weekend, dedicated JPL personnel (in the FDO/TOPO tradition) posted an LCROSS ephemeris update to their Horizons website reflecting tracking into September 3. Coasting from a terminal Horizons state 431 sec beforehand, I infer a lunar impact on October 9 at 11:26:05 UTC near 67.9 deg S; 58.5 deg W. If I coast from a September 4.0 Horizons state, impact is 11:27:26 UTC near 69.6 deg S; 55.8 deg W. From these two coasts, it appears there are no future LCROSS maneuvers in Horizons, but it won’t take much propulsion to hit the target impact point when it’s selected on or about September 10. I’m frankly amazed the attitude “control” impulses 2 weeks ago didn’t introduce more impact trajectory error. Attached are a couple trajectory plots from the September 4.0 coast. Feel free to share these with colleagues if you wish. -Dan
[Sep3ancGeo.gif, 78 KB, Sep3ancSel.gif, 64 KB]
Here is a link to the original ATIG #10 email file.
ATIG_009__2009_09_01 [September 1, 2009] Human Max Altitude Record
ATIG Members- If you happened to view the Air & Space Museum’s Apollo 11 Fortieth Anniversary Gala (televised on NASA TV this past July 20), you’ll recall remarks by MC Dr. Neil deGrasse Tyson regarding Apollo 13’s crew holding the subject record. Having already published research on reconstructing Apollo 13’s trajectory, I resolved to verify this claim and possibly refine the record’s value/pedigree. Results of this work are attached as a bookmarked PDF file. Please note this is a preliminary draft of a paper intended for your review and comment prior to formal publication. I therefore request you not redistribute this file. If others are interested in a copy, please refer them to me, and I’ll supply them with the latest. I hope you find this paper useful, and thanks for any corrections or other comments you care to send my way. -Dan
[ApolloMaxH.pdf, 11 pages, 1.2 MB]
Here is a link to the original ATIG #09 email file.
ATIG_008__2009_06_20 [June 20, 2009] LCROSS Trajectory Plots
ATIG Members- Although NASA posts all kinds of detailed as-tracked trajectory data for Shuttle and ISS (I used to help do that job in my former FDO life), there’s the usual dearth of this information available following Thursday’s LRO/LCROSS launch. All I could find was a planned LCROSS trajectory posted on JPL Horizons. Although these planned data assume an on-time Thursday launch 20-min earlier than the actual event, the attached plots should be reasonably accurate for purposes of gross situational awareness. In the LCROSSgeo Earth-centered plot, lunar encounter is evident from the trajectory’s S-turn as the nearly stationary LCROSS and attached Centaur upper stage are overrun by the Moon at a geocentric speed 5 times greater. The resulting lunar gravity assist flings LCROSS/Centaur into a longer period Earth orbit at greater ecliptic inclination from which lunar impact will be targeted for 2009 October 9. The LCROSS lunar gravity assist is plotted at greater detail in the LCROSSsel attachment. Perspective for this plot is orthogonal to the Moon-centered trajectory’s plane from a direction very close to Earth’s. As indicated by the Moon’s shading, its geocentric phase is just past new. According to the USNO, new Moon is 2009 June 22 @ 19:35 UTC. If LCROSS is able to operate its visible and IR cameras during closest approach to the Moon, some spectacular imagery of rugged terrain at low solar elevation directly below the spacecraft would be obtained. These images might include the eventual impact site near the Moon’s south pole. -Dan
[LCROSSsel.gif, 63 KB, LCROSSgeo.gif, 61 KB]
Here is a link to the original ATIG #08 email file.
ATIG_007__2009_06_04 [June 4, 2009] Lunar Surface Rendezvous (LSR) Lunch ‘n Learn
ATIG Members- Per the attached flyer, AIAA Houston Section’s Astrodynamics Technical Committee (ATC) will host a Lunch ‘n Learn seminar next Friday, June 12, at noon in B16/R111. I will lead a 45-minute discussion of my LSR research. Anticipating many questions/comments on this work, the room has been reserved until 1:30 PM. The last time I circulated my LSR white paper among all ATIG members, it was Revision 2 last November 20. The latest Revision 6 is attached for your reference as the Augustine Commission’s tenure begins. It commences with a single-page executive summary and is bookmarked to facilitate navigation. I’m indebted to the ATC’s chair, Al Jackson, for coordinating this seminar at a very timely juncture and hope schedules will permit many of you to attend. -Dan
[LSRvirtuesR6.pdf, 14 pages, 339 KB, LSRflyerLnL.pdf, 1 page, 301 KB]
Here is a link to the original ATIG #07 email file.
ATIG_006__2009_04_13 [April 13, 2009] Twenty Years & Counting…
ATIG Members- As a confirmed NEOphyte, I would be remiss in not noting it’s twenty years today until potentially hazardous asteroid (99942) Apophis misses Earth by ~31800 km on Friday the 13th of April 2029. Depending largely on what happens then, there’s something like a 1-in-40000 chance of Apophis Earth impact on (Roman) Easter Sunday April 13, 2036. This is all unabashed promotion for my two presentations at the AIAA Houston Section’s Annual Technical Symposium on May 15, 2009. Facsimile abstracts for the two presentations are attached. Hope to see you at Gilruth Center for these presentations (assuming they’re accepted). -Dan
[AdamoApophisAbstract.pdf, 1 page, 72 KB, AdamoLSRabstract.pdf, 1 page, 65 KB]
Here is a link to the original ATIG #06 email file.
ATIG_005__2009_03_20 [March 20, 2009] Venus Pix
ATIG Members- As illustrated in the attached GIF’s J2000.0 ecliptic plane plot of Earth and Venus motion about the Sun, a line of sight from Earth to the Sun is in the +X direction today, and Spring is here. This line also passes very close to Venus, making it dangerous for me to continue taking daytime images of our sister planet without frying my telescope’s optics. Venus will “lap” Earth (in the heliocentric sense) on March 24, an event known as inferior conjunction. The attached JPEG is a montage of 4 daytime Venus images obtained at an effective magnification of 62x during the GIF plot’s time span. Each image is cropped to 615 px in horizontal dimension and 397 px in vertical dimension to maintain a consistent scale illustrating progressively smaller Venus geocentric distance during the sequence. To state image scale in more absolute terms, Venus apparent angular diameter in the March 20 image is 58 arc-sec, approaching resolution capability of the unaided human eye. Of course, don’t even think about looking for Venus in the daytime with a line of sight this close to the Sun! Each image in the JPEG is oriented with celestial north upward to demonstrate rotation of the Venus morning terminator as its phase evolves from “quarter Moon” to crescent. The “horns” of this crescent clearly become biased in a northerly direction as inferior conjunction approaches. This is because Venus lies more than 3 deg north of the ecliptic plane on March 20. Currently, the orbit of Venus has a descending node on the ecliptic at a heliocentric longitude occupied by Earth in early June each year. In 2012, Venus descending nodal passage will occur near enough to inferior conjunction to produce a transit of Venus across the Sun as observed from Earth. If the attached files won’t download in your copy of Outlook, they will in NASA WebMail. -Dan
[Earth+Venus.gif, 53KB, Venus2009.jpg, 161 KB]
Here is a link to the original ATIG #05 email file.
ATIG_004__2009_03_13 [March 13, 2009] Curious Cassini Conundrum
ATIG Members- In reading March 12’s issue of Cassini Significant Events, a weekly JPL PAO newsletter, I ran across the following riddle.

Thursday, March 5 (DOY 064):

How is it that at one moment Cassini can be found nearly at apoapsis, the farthest point from Saturn in an orbit, and within a day, be at periapsis, the closest point to Saturn in an orbit, when its orbital period is around 16 days? Well, it is happening at the end of March this year. On DOY-86, Mar. 27, the Titan 51 targeted flyby will occur. Just a few hours later, apoapsis and the start of orbit #107 would have occurred. However, because of the gravitational influence of Titan during the flyby, Cassini’s orbit is modified such that apoapsis on the new Saturn centered orbit occurs prior to the Titan encounter, on an orbit different from the one Cassini actually flew. For orbit 107, on DOY-87, Mar. 28, Cassini is now at the closest point to Saturn in that orbit. The above scenario is unique in the history of the project and will not occur again before the end of the extended mission. The fact that Cassini’s orbit about Saturn is very nearly circular at this time is what enables this rather curious sequence of events.

Saturn-centered geometry pertaining to Titan-51’s 180-deg apsidal shift is illustrated in the attached CassiniVsSaturn GIF. The viewpoint for this trajectory plot is nearly normal with respect to Cassini orbit planes before and after the Titan-51 flyby. Note Saturn’s north pole, just visible from this perspective and emerging from nearly 15 Earth years of winter darkness, is pointed downward. The attached CassiniVsTitan trajectory plot is also viewed from nearly normal to the Cassini plane of motion, but in a Titan-centered reference frame. In this case, Titan’s south pole is visible and pointed downward. Periapsis height for this flyby is planned at +960 km. If Outlook won’t download these GIFs, remember that NASA WebMail will. -Dan
[CassiniVsTitan.gif, 62 KB, CassiniVsSaturn.gif, 74 KB]
Here is a link to the original ATIG #04 email file.
ATIG_003__2009_02_23 [February 23, 2009] LSR Mission Design
ATIG Members- Happy 2009! Following through on my latest research indicating lunar surface rendezvous (LSR) is a practical Moon exploration architecture with two Ares V launches, I’ve spent the last couple months generating and documenting an illustrative mission design. Notionally staged in 2019 to coincide with Apollo 11’s fiftieth anniversary, this particular LSR mission targets a landing near Aristarchus Crater where planetary science interest is high. Crew lunar surface operations are deliberately planned for one week duration in order to pose nearly worst-case geometry to lunar orbit rendezvous and Earth return due to 90 deg of lunar rotation/revolution of a mid-latitude location. As documented in the attached mission design paper (packaged as a bookmarked PDF), nominal LSR mission design is free from geometric performance “humps” from event timing. In addition to the nominal LSR mission design, the paper documents associated trans-lunar, low lunar orbit, and no-LOI abort options. It concludes with a deep space crew rescue mission design. Both nominal and anomalous trajectories are demonstrated to be in accord with vehicle performance specifications developed in the original LSR white paper, indicating this architecture is operationally viable and robust. Your feedback on the attached paper is requested. As always, I’m willing to discuss this research in our usual seminar format at any venue to which I have access. As a further demonstration of LSR capability, I next intend to plan an LSR landing at a lunar surface location nearly inaccessible to current 1.5-launch architecture due to performance limitations. I posit this mission’s nominal LSR performance demands will differ very little from those of the nominal Aristarchus mission. In this manner, LSR’s capability to fully and robustly satisfy the “land anywhere; leave anytime” US Space Exploration Policy requirement will be further demonstrated. Suggestions for this “performance-challenged” mission’s landing site coordinates are certainly welcome. In lieu of any better input, I’ve tentatively selected the center of a performance “hole” in CxP temporal availability contour plots (reference pp. 20 – 23 of [7] in the attached paper) at 55 deg S lat; 25 deg W lon. As Sir Arthur would have it, this location is ~90 km NW of the NW rim of Clavius Crater. -Dan
[LSRin2019.pdf, 34 pages, 2 MB]
Here is a link to the original ATIG #03 email file.
ATIG_002__2008_11_08 [November 8, 2008] LSR, Anyone? [LSR: Lunar Surface Rendezvous]
ATIG Members- Many of you have known me to make occasional quixotic forays into the realm of lunar exploration architecture. Retirement from conventional employment only affords more opportunities for such adventures. Since the 2005 Exploration System Architecture Study (ESAS) put us on the current “1.5-launch” architecture path, a series of Ares I performance setbacks have imposed compensating Ares V performance upgrades. In terms of single-launch Ares V payload injection capacity into a trans-lunar trajectory (no Ares I payload assist via LEO rendezvous), September 2008 performance data indicate a 15% increase with respect to an ESAS-vintage baseline. The attached white paper proposes a means by which enhanced Ares V performance may be used to implement a Lunar Surface Rendezvous (LSR) “2.0-launch” architecture. Multiple vulnerabilities in the current 1.5-launch architecture are mitigated using the proposed LSR mission profile, and the paper documents these in some detail. As stated in the paper’s Introduction, the attached bookmarked PDF may be freely distributed provided it is not altered. As always, your feedback on the paper’s content is invited, and I would be honored to discuss it at any venue to which I’m provided access. -Dan
[Link: LSRvirtuesR2.pdf, 236 KB, 10 pages.]
Here is a link to the original ATIG #02 email file.
ATIG_001__2008_08_18 [August 18, 2008] Rosetta’s Flyby Of Asteroid 2867 Steins
ATIG Members- Per the attached trajectory plots of ESA’s Rosetta spacecraft, its first asteroid encounter is being targeted for September 5, when an approach to 800 km is planned. Per the Rosetta web page at URL http://www.esa.int/SPECIALS/Rosetta/index.html, the targeting process is an active one. A period of optical navigation being conducted from August 4 to September 4 is being used to refine Steins’ orbit uncertainty from 100 km to 2 km in the Rosetta B-plane (plane orthogonal to Rosetta’s Steins-relative velocity vector). Highest resolution in images obtained during the Steins flyby is expected to approach 10 m. -Dan Adamo
[Links: RosettaSteins.gif (57 KB), RosettaSteinsHelio.gif (63 KB)]
Here is a link to the original ATIG #01 email file.