Astrogator Mike has worked a lot recently on a re-purposing plan for the Express-AM4 spacecraft, and is quoted extensively in this article.
Don’t splash the bird!
Russians to decide on Polar Broadband Plan
This could be a great mission for science, and involved some decent Earth-orbiting astrogation. Stay tuned for more details of this orbit once we hear the fate of the bird. Don’t miss the associated video here:
Lawrence Livermore National Laboratory (LLNL) and the Air Force Joint Space Operations Center (JSpOC) came up with a new approach to predicting re-entry while trying to track Phobos-Grunt. Article here:
A New Approach to Predicting Re-Entry
Basically their approach was to take a supercomputer and give it access to the best real-time tracking available. Sounds like their results were pretty good.
(Follow-up from Dan Adamo)
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.
The following is from Dan Adamo, guest astrogator and a former Flight Dynamics Officer at JSC. Dan runs a mail list called the ATIG (Astrodynamics Technical Interchange Group). Last year he graciously allowed me(Mike) to be a part of the group, and since then I get interesting articles from him every month or so. This month, Dan sent the following, which I thought was a great topic for the guild.
Dan Adamo
Earth Risk Corridor Computations for 2011 AG5 on 5 February 2040
Introduction
The near-Earth object (NEO) designated 2011 AG5 is currently associated with a relatively high linearized Earth impact probability of 0.001557 (odds of 1-in-642.3) during its predicted 5 February 2040 close approach to Earth. This probability appears in Table 1 (reference the P_i/p column), together with data pertaining to other near-term 2011 AG5 planetary approaches closer than 0.1 AU (15 million km). These predictions are obtained from JPL’s Horizons on-line solar system data and ephemeris computation service* using the current JPL#45 orbit solution for 2011 AG5. Note that coordinate time (CT) is a uniform time scale void of leap seconds and used as the fundamental ephemeris argument by Horizons. To a precision of ±0.002 s, CT is related to atomic time (TAI) by CT = TAI + 32.184 s.
The recent uncontrolled reentry of the UARS spacecraft got a lot of attention last week as NASA and the JSpOC tried to track the vehicle as it reentered.
It doesn’t have to be done this way, however. On March 13, 2011, a commercial spacecraft was purposefully reentered into the Pacific ocean 3000 miles southeast of Hawaii. Top-notch Astrogator and Guild member Tim Craychee of Applied Defense Solutions provides a description of the process of the reentry in his 2011 paper here:
Mitigating Potential Orbital Debris: The Deorbit of a Commercial Spacecraft
The paper tells us:
“While it is not known if any spacecraft debris survived reentry, the design of the final orbit was such that potentially surviving debris would impact within a “safe zone” in the Pacific Ocean.
SSN #27838 Impact Zone
On a previous post I mentioned that contrary to what a lot of the recent news reports imply, NASA itself is not in the business of tracking uncooperative or (in the case of UARS) dead spacecraft. NASA normally will determine a satellite’s orbit (called “Orbit Determination”) via communications with the spacecraft. Both ranging (measuring the time for signals to get up and back from the spacecraft) and range-rate (measuring the doppler shift of signals) are used to track a satellite. Sometimes spacecraft also have on-board systems (such as GPS receivers) that help. Once a spacecraft is dead NASA quickly runs out of options for tracking. NASA doesn’t have a lot of radar or other assets to track dead objects, that’s done by the Joint Satellite Operations Center or JSpOC.
Discovery.Com
Universe Today
Skymania
CollectSpace
I am helping Nick Howes and his students in the UK (and elsewhere) to try and locate Snoopy, the ascent stage of the Apollo 10 Lunar Module that was sent into a solar orbit back in 1969.
After the previous post, I had contacts from several twitter followers with suggestions for improving my predictions. In particular @Marco_Langbroek suggested that 120 km (rather than 80 or 75 km) was the magic number for atmospheric contact, and he further suggested that the 4:16 UTC time originated with the the Joint Space Operations Center (www.space-track.org). It turned out I had an account there already, so I could all but verify that was the source. This makes sense really, because NASA doesn’t have much in the way of assets to track non-cooperative spacecraft. NASA normally tracks spacecraft in the course of communicating with them, and if a spacecraft goes dead, they rely on our military to use radar and other assets for tracking. So any solution you see attributed to NASA in this case very likely came from the JSpOC, and NASA is just the messenger.
