Re: Statistics on prediction accuracies

From: Björn Gimle (bjorn.gimle@gmail.com)
Date: Fri Apr 08 2011 - 10:19:26 UTC

  • Next message: Russell Eberst: "2011APR7-8.OBS"

    Even moderate drag has a large effect over time.
    Consider orbit data (which you can view on H-A) e.g. for ISS,
    which may start this: 1 25544U 98067A   11097.75640206  .00060054 ...
    
    30 days after the Epoch (11097...) ie day 127 ie May 7 the cumulative
    drag is 30*30*.00060054 = 0.54 orbits or about 50 minutes.
    The error in this "average" is often 10-20%, 5-10 minutes in this case.
    Over a few days, the atmospheric density may vary a lot more than 20%,
    and this could cause elset data to be grossly misleading when
    extrapolated over longer time.
    
    /Björn
    
    
    
    2011/4/8 Marco Langbroek <marco.langbroek@wanadoo.nl>
    
    > Op 8-4-2011 05:52, George Roberts schreef:
    >
    > > All the orbits from sattrack are spot on.
    >
    > I beg to differ on this one.
    >
    > - Marco
    >
    > -----
    > Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
    > e-mail: sattrackcam@wanadoo.nl
    >
    > Cospar 4353 (Leiden):   52.15412 N, 4.49081 E (WGS84), +0 m ASL
    > Cospar 4354 (De Wilck): 52.11685 N, 4.56016 E (WGS84), -2 m ASL
    > SatTrackCam: http://home.wanadoo.nl/marco.langbroek/satcam.html
    > Station (b)log: http://sattrackcam.blogspot.com
    > -----
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    >
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