Fobos-Grunt: decay estimate

From: Ted Molczan (
Date: Wed Dec 14 2011 - 18:10:14 UTC

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    The mean rate of decay of the semi-major axis of the twenty-one (21) USSTRATCOM TLEs from epoch 11343.54617215 to
    11348.50789148 (2011 Dec 09 13:06 - Dec 14 12:11 UTC) was 1.4287 km/d. 
    Using the STOAG propagator and actual space weather during that period, I found that the mean rate of decay could be
    accounted for using A/m = 0.001399 m▓/kg and Cd = 2.2. 
    Using those values with predicted space weather, STOAG propagates the orbit to decay on 2012 Jan 10. Estimated
    uncertainty is +/- 5 days, based on the rule of thumb of 20 percent of the time remaining to decay.
    I extracted the actual and estimated space weather data required by STOAG, from data provided by, which
    compiles data issued by official sources (mainly NOAA) and presents it in a convenient format:
    Ted Molczan
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