impossible accuracy

From: Tony Beresford (
Date: Thu Aug 10 2006 - 00:31:03 EDT

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    I received this request from recently. Given the
    .5 to 1km accuracy of the SGPD4 model I think its impossible
    with TLEs. What accuracy can one expect if one modelled the atmosphere
    with the public domain models and numerically integrated the equations of
    motion using the daily initial conditions provided by NASA?
    I also reminded him that the ISS may be bigger than his FOV (24by 24 arc
    I have an independent question regarding satellites:
    Is there a way to obtain ephemerides for the ISS with
    arcsecond-precision via an online-tool or with freely
    available software?
    The reason I am asking is that I tried to image the
    ISS during my last observing run at Calar Alto with
    the 2.2m telescope and a high-speed camera during dawn.
    (My personal definition of dawn is: the time between
    taking flatfields and doing 'real' science where nobody
    cares what you are using with the telescope for...)
    The camera has an FOV of 24arcsec, delivers 34 frames per
    second, and can easily acquire several 10000 of them.
    I got some TLEs - I think from - and fed
    them into EasySky to get a topocentric ephemeris, pointed
    the telescope to some coordinates where the ISS *should*
    pass, started the acqusition and waited. At least on one
    frame it should have been visible, but I had no luck.
    I guess that either the TLEs were bad or too old (it was
    during the time the Shuttle was docked) or EasySky does not
    work with the required precision.
    Can you recommend me any TLE sources and software for the
    next time?
    Tony Beresford
    Cospar 8597 , -34.9638, 138.6333E
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