Re: weird Omid orbit

From: Bjoern Gimle@GlocalNet (Gimle@GlocalNet)
Date: Sat Feb 28 2009 - 10:24:00 UTC

  • Next message: Scott and Becky Campbell: "Satobs 28 Feb 2009"

    On the dates you mentioned, the mean motion of Omid is
    nearing 16.04, which gives 90 minutes at that (55 d) inclination.
    You can also have 1-day repeat on 96 min (MM ~15), ~103 min (MM ~14) etc.
    Iridiums have a 3-day repeat (3*1440/43=100.465 min nodal), but the also 
    further W.
    Other satellites have repeat patterns of the ground track, like
    China's Shenzhou in two days - every 31 orbit it passed over the landing 
    For 90 degrees a 90 min nodal period object will pass at the
    same RA same time next day, and because of Earth's motion
    around the Sun this will be 1 degree further W on Earth's surface.
    "Sun-synchronous" satellites near 98 degrees can have passes at
    the same time AND altitude, if period is choosen correctly.
    ----- Original Message ----- 
    > Because the shape of the Earth causes the node of the orbit
    > to  precess, the passes seen on different days are further
    > to the west unless the inclation is 90 degrees.
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