Fobos-Grunt: decay estimate

From: Ted Molczan (
Date: Sun Dec 11 2011 - 19:56:29 UTC

  • Next message: Kevin Fetter: "COBE = nice flasher"

    The mean rate of decay of the semi-major axis of the twenty-two (22) USSTRATCOM TLEs from epoch 11340.4411995 through
    11345.46978193 (2011 Dec 06 10:35 - Dec 11 11:16 UTC) was 1.3285 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 = 0.001264 mē/kg and Cd = 2.2. 
    Using those values with predicted space weather, STOAG propagates the orbit to decay on 2012 Jan 11. Estimated
    uncertainty, based on the rule of thumb of 20 percent of the time remaining to decay, is +/- 6 days.
    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
    Seesat-l mailing list

    This archive was generated by hypermail 2b29 : Sun Dec 11 2011 - 19:58:00 UTC