RE: ISS rendezvous orbit for Soyuz

From: Thomas Fly (
Date: Sun Apr 18 2004 - 23:44:53 EDT

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    Soyuz launched from the Baikonur Cosmodrome (about 45.4 N, 63.2 E), in
    Kazakhstan, at 3:19 UTC today (Monday) and will rendezvous with the ISS at 5:04
    UTC Wednesday,  representing a total transit time of 2985 minutes.  At launch
    time, the ISS was near the bottom of its orbit, at about 51.16 S, 68.52 W
    (just off the coast of the southern tip of Argentina), so Soyuz is starting out
    offset by 1/2 an orbit from the ISS.
    Assuming that Soyuz will gain (or, less likely, lose) 1/2 an orbit relative to
    the ISS in 2985 minutes, then (using a figure of 92 minutes for the orbital
    period of the ISS), that's about 33 orbits to 32.5 orbits for the ISS, meaning
    that its orbital period is 1 part in 66 less than the ISS, or that it's gaining
    about 46 * 60 / 32.5 = 84.9 seconds on the ISS, for each orbit.
    Another way to state it is to say that Soyuz is starting out 180 out of phase
    with the ISS, and gains/loses about 5.5 per orbit of the ISS, or slightly less
    than 90 of phase per day.
    Assuming that OIG does post TLEs for Soyuz, what would its identifier be?
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