Re: almost time for the ISS marathon-TONY

From: amstuart (
Date: Mon May 19 2008 - 12:36:17 UTC

  • Next message: Tony Beresford: "Re: almost time for the ISS marathon-TONY"

    Thank you, Tony. I did not realize the shadow constraint. Having used HA, I
    know the sky charts resolve the transit path for a location based on the ISS
    first rising above the local horizon and terminate with the ISS entering
    shadow. In retrospect, TheSky and Satellite Tracker do not discern
    visibility along a transit path, only report "if" the ISS is visible.
    If you use HA to select the ISS from the select a
    satellite option, and ask for all passes in the 10 day interval
    that includes sunday may 18 for your location ,
    you will see that their is a pass culminating at
    21:35 EDT or may 19, 01:35 UT. Its just that HA
    reckons its in shadow. The other software programmes
    you used obviously disagreed. Its hard to
    calculate a satellite illumination accurately when the trajectory is
    nearly tangent to the shadow cone. Differences in
    the effective shadowing radius of the Earth that is
    assumed can result in differing results from
    different programmes. I remember doing some observations
    utilizing Echo 1 (1960 9A) or Echo2 ( 1964 4A )
    at the request of Moonwatch HQ to help decide the
    right number empirically.
    Tony Beresford
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