Re: HST orbit

From: Tony Beresford (
Date: Mon Feb 07 2000 - 21:18:32 PST

  • Next message: Bjoern Gimle: "ETS-6 05.Feb."

    At 10:06 8/02/00 , wrote:
    >Since I started satellite watching, last May of 1999, the Hubble ST has been 
    >in the morning sky, low on the southern horizon; about 20 degree elev.
     You are mistaken, this is not HST's visibility behaviour
    >maximum. But just recently--Feb 5--it began appearing in the evening sky. (i 
    >get all my times from Heavens above). However, in just another 10 days from 
    >now, it seems to stop appearing all together. 
    >What kind of orbit is Hubble in such so that it can stay either in morning or 
    >evening for such a long time? -Ben
    Ben, HST is in a 28.5 degree circular orbit, 650Km above surface.
    Which means its always to the South of you, and to the North of me at 34.9S.
    It makes appearances alternatively as a morning and evening object,
    with periods on invisibility in between,as the orbit rotates under
    the influence of the oblate shape of the Earth.
    The passes around midnight in winter will be in shadow. During your summer
    the shadow height stays below the orbit height of HST for much longer.
    However the shadow height at 28.5 N at midnight in midsummer is
    above HST orbit.
    Tony Beresford
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