USA 159 r elements

From: Ted Molczan (
Date: Fri Aug 17 2001 - 10:00:23 PDT

  • Next message: Matson, Robert: "RE: Geodetic precision"

    I derived the following using data from Ed Cannon, Paul Gabriel and U.S.
    Spacecom, between 2001 Aug 14 - 17:
    USA 159 r1       9.8  3.0  0.0  4.8 v
    1 26881U 01033B   01229.08166667  .00286333  00000-0  35779-3 0    08
    2 26881  28.6540 176.3098 0378059 193.7583 165.2471 15.39571766    00
    Mean residuals are about 0.02 deg.
    I used Paul's preliminary observations. He prefers to hold off posting them to
    SeeSat-L until he is more certain of their accuracy. Overall, they look pretty
    good to me, but 2 of his 5 points have somewhat higher residuals than the
    others, so his caution may prove warranted.
    I believe that Paul uses the same method that I use when I need/want to obtain
    many points on a pass: he does not stop after each observation to sketch the
    reference stars, but relies on memory, perhaps assisted by a tape recorder. To
    find our reference stars for the purpose of observation reduction, we compute
    the expected position of the object at the time of each observation, using the
    best available elements, and look for the stars in an atlas. If the elements
    are reliable, then the reference stars should be readily identifiable. However,
    in this case, Paul had only preliminary elements, which may not be sufficiently
    accurate to unambiguously reveal the correct reference stars, hence his caution
    about posting his obs.
    Regarding my data credit to U.S. Spacecom, I refer to their 2nd elset:
    1 26881U 0133B    01226.28993968  .00000349  00000-0  62037-5 0    21
    2 26881  28.6968 195.6121 0243087 165.2938 177.1552 15.22595359  1228
    I agree with Mike McCants that although this elset is largely erroneous, it
    probably does have some basis in reality. I assumed that this elset is accurate
    at its epoch, so I generated a fictitious point, looking straight up from the
    sub-satellite point at the epoch.
    Ted Molczan
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