Re: TRMM elsets question

From: Bjoern Gimle (b_gimle@algonet.se)
Date: Sun Jan 23 2000 - 03:17:13 PST

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    >I wonder how reliable the latest of these TRMM elsets is, on day
    >00022?  The drag term is a full order of magnitude larger than
    >...
    >1 25063U 97074A   00022.26301792  .01234510  00000-0  74939-2 0  2440
    >2 25063  34.9883 114.1185 0004108 295.1161  63.3849 15.74011124123838
    >TRMM
    >1 25063U 97074A   00020.86822436  .00088170  00000-0  57889-3 0  2430
    >2 25063  34.9880 123.5957 0001128 290.4556  69.6030 15.74456777123615
    
    ...
    Since e has increased by   0003 and MM decreased by .0044
    (corresponding to an apogee rise of about 4 km) there was
    probably a maneuvre in between. I think TRMM does that.
    In cases like this, with no significant change in perigee,
    it is usually better to set the drag terms to (an average
    of) recent values.
    
    One exception can be the negative drags of Iridiums and other
    satellites, that shortly after launch start a slow climb to
    operational altitude by frequent small adjustments. In these
    cases a 'bad' elset can work better over several days.
    
    
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