RE: Unknown object observed through galaxy M51

From: Ted Molczan (
Date: Mon Aug 15 2005 - 18:25:07 EDT

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    I agree with Rob Matson's finding that the object is Radsat (1972-076B / 6217).
    I question whether the broken trail of its image is due to flashing by Radsat.
    The NASA URL on Radsat found by Allen Thomson states that its "spin period was 5
    I do not know whether or not any of its instruments still operate; however, I
    doubt that it still spins. Jean-Pierre Rohart visually observed it to be steady
    in Jul 1998, as did Russell Eberst in Aug 2000. Russell did report it varying
    irregularly in Mar 2004, but that is not the same as a regular variation.
    I estimate the length of Radsat's track in the image at 0.22 deg (scaled
    relative the 0.072 deg separation between M51 and NGC 5195). Radsat's angular
    velocity at the time was 0.38 deg/s; therefore, it transited in about 0.58 s.
    Therefore, the 50-60 pulses in its trail occurred at the rate of about 100 Hz.
    Is there anything about the instrument that could have caused a 100 Hz pulse or
    interruption in the satellite's trail?
    Ted Molczan
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