Saturday, 14 January 2012

[Updated] Summary of Phobos-Grunt reentry predictions as off 14 Jan, 13:00 UTC

Current predictions by various sources for the reentry of the failed Russian Mars probe Fobos-Grunt all still have a very large uncertainty window. Therefore, it is still impossible to provide any realistic statements about the when and especially where the reentry will happen. Suggestions in the press such as these only demonstrate a continuing and thorough misunderstanding of the whole issue among some journalists.

Perhaps as a result of this, USSTRATCOM has changed the way it presents it's Fobos-Grunt reentry predictions. While for other objects they still use the classical TIP format (time with uncertainty interval, and position at the nominal time), they altered the presentation for F-G: they only list the uncertainty interval, without positions or nominal time. Given the way that TIP messages were taken completely out of context and misinterpreted in the press recently (e.g. the notorious and utterly misinformed Novosti-RIA publication here), this is all a very understandable precaution.

A summary of the current predictions (round-up of predictions at 14 Jan, 13:45 UTC. Listed are: source; time/date prediction was issued; predicted time plus uncertainty interval, or uncertainty interval only):

USSTRATCOM (13  Jan 15:30 UTC): 15 Jan 08:25 - 16 Jan 03:37 UTC
Harro Zimmer (13 Jan 11:51 UTC): 15 Jan 17:05 +/- 3 hrs UTC
Ted Molczan (14 Jan 08:35 UTC): 15 Jan 22:31 +/- 8 hrs UTC
Celestrak (T.S. Kelso, 14 Jan 11:00 UTC): 17 Jan 10:04 +/- 1 day UTC
AeroSpace Corp. (13 Jan 10:40 UTC): 15 jan 17:52 +/- 14 hrs UTC
Roscosmos (14 Jan UTC):  15 Jan  21:51 17:51 UTC (no uncertainty window listed)

[added 15:45 UT, 14 Jan] My own estimate, using Alan Pickup's SatEvo and the current space weather (F10.7 cm flux) and the Jan 14.54 orbit, is for 15 Jan, 21:50 +/- 7 hrs UTC.

PLEASE take note of the large uncertainty windows on all these predictions! The uncertainty amounts to many revolutions of F-G around the Earth, so it is impossible to even indicate a Continent or Ocean (as some media sources do) where F-G will end up, at this moment.

Most of the predictions favour the 2nd part of Sunday Jan 15th.

No comments: