Chasing Calipso

From: Gregg Hendry (
Date: Wed Jun 28 2006 - 06:52:33 EDT

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    Laser light from Calipso (29108U) was successfully observed last night (6/28, 09:12:40 UT) in a clear dark sky with maybe a slight amount of haze present.  Two observers about 100 meters apart east west both saw a fan of about 1/2 dozen green beams of light emanating from zenith.  To the western observer the beams were about 20 degrees long.  The eastern observer (me) saw a quick flash of easy to see bright beams at least 40 degrees long.  Both observers had the impression that the beams were passing to the east.  The eastern observer was positioned on Calipso’s geodetic nadir ground track as predicted by STK from a fresh Space-Track element set.
    We may have gotten lucky but with the right amount of cloud cover or haze I predict the Calipso laser should be easy to see for observers within a few hundred meters of the ground track.
    Fresh Space-Track elements and a little luck should be good enough.  Be sure to calculate geodetic position coordinates and not geocentric coordinates as the difference is significant.
    Gregg Hendry
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