RE: Observed Lunar transit -- what did I see?

From: Ted Molczan (molczan@rogers.com)
Date: Thu Oct 16 2003 - 19:34:07 EDT

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    Welcome to the list, David!
    
    Based upon your description and simulated image, the object traversed about 0.3
    deg in 15 to 20 s, equivalent to an angular velocity of 0.02 deg/s. It depends
    upon the type of orbit, but in round numbers, an orbiting object would have to
    be at a range of about 10,000 km to move that slowly.
    
    I know of only one class of very large satellite in a high orbit; it is an
    electronic intelligence gathering satellite, thought to have an antenna about
    100 m in diameter. The U.S.A. launched three such satellites into Molniya orbits
    between 1994 and 1997.
    
    You would have to observe one of those orbits at a range of about 15,000 km to
    yield an angular velocity of 0.02 deg/s. At that range, a 100 m object would
    subtend 1.4 arc sec, far smaller than the 10 to 15 arc sec that you reported,
    and pushing the limit of resolution of a 4 inch telescope, let alone seeing any
    detail.
    
    So, I know of no orbiting object that could explain what you observed.
    
    In a subsequent post, you asked whether or not a LEO object moving toward you at
    low elevation could move that slowly. On an overhead pass, ISS (400 km orbit)
    moves at 0.07 deg/s when it is at the horizon. A Lacrosse satellite (650 km
    orbit), would move at 0.06 deg/s in the same circumstances. So, the answer is
    no.
    
    Thank you for sharing your observation, and please do not hesitate to share any
    future possible satellite sightings.
    
    Ted Molczan
    
    
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