RE: Phobos-Grunt: latest two TLEs suggest manoeuvring or venting

From: Ted Molczan (
Date: Fri Nov 11 2011 - 16:38:42 UTC

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    While waiting for new TLEs of the s/c, I have been taking a closer look at the two that indicate an orbit change.
    Interestingly, both nearly intersect with the pre-orbit change TLE at about the time of a pass within range of Baikonur,
    on Nov 10 from ~20:16 to 20:23 UTC. 
    Probably, this will turn out to be a meaningless coincidence, but it does seem interesting in view of efforts to
    communicate with the s/c from that site, so I am putting this out with the caveat that I have been burned lots of times
    by spurious TLEs and various coincidences that later proved meaningless. Subsequent TLEs could make this all go poof!
    Below are the circumstances of the pass. I don't know the coordinates of the telemetry transmitter, so for now, I used
    those of the Zenit pad used for the launch:
    20:15:54 rose above 0 deg elevation
    20:16:17 reached 2 deg
    20:19:36 culminated at ~30 deg
    20:23:06 set below 2 deg
    20:23:31 set below 0 deg
    Closest approach between pre-orbit change TLE and first post-change TLE is ~20:15:52 UTC. Relative the second
    post-change TLE, it is ~20:13:36 UTC. Due to the low delta-V, these times are not well-defined, and uncertainty is at
    least several minutes.
    If there was a single impulse at the point of intersection, then delta-V  was 1.3 to 1.6 m/s (4 to 5 fps).
    Ted Molczan
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