Geostationary Solar Eclipses 17/18-FEB-07

From: Gerhard HOLTKAMP (grd.holtkamp@t-online.de)
Date: Sun Feb 11 2007 - 15:46:52 EST

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    Some GEOs at two different locations will experience a solar eclipse on 17/18 
    Feb.07 and the events might be visible indirectly from the ground (Australia, 
    Asia and parts of North America) by observing a dimming of the sats at the 
    time. I give a few day's advanced notice of this so that interested observers 
    can check whether the GEOs in question can be properly viewed at the 
    respective time of day from their positions.
    
    The first event is an annular eclipse for GEOs close to 104.8 East. This would 
    be well placed for observers in Australia and Asia. Of a number of satellites 
    affected the following seem to be the best for observation (times are in UTC 
    on 17-FEB-07):
    ASIASAT 3S (1999-013A , #25657) at 105.4 E
    from 16:30 to 16:59, annularity at 16:44 (for 82 sec)
    
    ASIASTAR (2000-016A  , #26107) at 105.0 E
    from 16:31 to 17:00, annularity at 16:45 (for 84 sec)
    
    KAZSAT 1 (2006-022A, #29230) at 102.9 E   
    from 16:37 to 17:07, annularity at 16:52 (for 38 sec).
    
    In each of the three cases there should be a total drop in apparent brightness 
    by about 2 mag. The final four minutes before (and after) annularity see a 
    change in 1 mag which should be quite obvious.
    
    
    The second event happens a few hours later when GEOs at 145.4 West would 
    experience a total eclipse of the Sun. Unfortunately there are no GEOs at 
    that position but there are some with a partial eclipse. The two best for 
    observation from (parts of) North America are (times in UTC at 18-FEB-07):
    
    ECHOSTAR 1 (1995-073A , #23754) at 147.9 W and ECHOSTAR 2 (1996-055A, #24313) 
    at 147.8 W, will experience a partial solar eclipse from 1:03 to 2:25. 
    Maximum eclipse (0.88) will occur at 1:40 with a total drop by 2 mag. During 
    the last 13 minutes before maximum eclipse until 13 minutes after the change 
    in magnitude should amount to 1 mag. Actually the magnitude change might be 
    somewhat less as the two sats "see" a two-third sunlit Earth with 
    corresponding reflections.
    
    Should there be any deviations in the above numbers due to newer orbit 
    elements I'll post an update a day or two before the events.
    
    Gerhard HOLTKAMP
    Darmstadt, Germany
    
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