Re: observations of Phobos-Soil (Fregat) engine burns

From: Denis Denisenko (
Date: Wed Nov 02 2011 - 15:58:23 UTC

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    Ted Molczan wrote:
    > The Phobos-Soil Project has requested precise positional observations 
    > of the spacecraft during the two engine burns that will propel it out 
    > of its LEO parking orbit and send it to Mars
    Since I am working at IKI in Moscow, I've talked to our Deputy Director, 
    and he explained that one of the main tasks for observers is to record 
    (and  to report) the time of engine firings and cut-offs during two 
    active parts of trajectory.  This is important to make sure the booster 
    has worked the correct amount of time required for the trajectory 
    > There are challenges for prospective observ/ers:
    > - the spacecraft will be in eclipse (Earth's shadow) for nearly the 
    > entire portion of both burns visible from land.
    > Fortunately, the exhaust plume is expected to be sufficiently bright 
    > to be observed from the ground.
    I think SeeSat readres can help in bringing the light to the 
    plausibility of such observations!  The booster for sending Phobos-Soil 
    to the orbit will be Fregat.  This booster has been already used for 
    launching several satellites into orbit before, though in Soyuz-Fregat 
    configuration.  (Phobos-Soil will be launched by Zenit-Fregat combo).  
    There are some modifications made to the "base" version of Fregat since 
    that (Fregat-SB means "Fregat with detachable tanks"), but this is still 
    a similar hardware.  Wikipedia says Fregat booster was used for 18 
    successfull launches before, so chances are high someone on this list 
    has observed it before in different conditions (I mean, sunlit or eclipsed).
    This is why I think the following questions are important:
    - Has anybody observed Fregat booster firings (engine burns) before 
    during Soyuz-Fregat launches?  Was the exhaust plume visible in the 
    Earth's shadow?  If yes, what was its visual magnitude then?
    - If anybody has seen Fregat booster both before and after engine 
    firing, what was the difference in magnitude?
    The answer to this questions will at least allow to estimate what 
    equipment will be necessary for the observations of booster in Earth 
    shadow.  There's a lot of difference between naked-eye object and 
    binocular or telescopic visibility!
    To Ted: can you please estimate if the engine firing and cut-off can be 
    both visible from the same observing site (at least on one of the two 
    Also, I suppose the plots posted here before (1eb_04.jpg and 2eb_01.jpg) 
    need some explanations for the coloration used.  This page: explains what the thin and 
    bold black and red parts of trajectory actually mean.
    And finally, the direct link to the page with TLE would be nice to have:
    Best regards,
    Denis in Moscow
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