RE: Brightness of GRACE Satellites

From: Brad Young (
Date: Thu Oct 26 2006 - 17:36:04 EDT

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    My last two observations of the GRACEs have been steady in a 70 deg altitude
    W pass, with nice flares to +2 then fading to inv. to the naked eye in a 80
    deg altitude E pass. Each acted just like the other, to me.
    -----Original Message-----
    From: Gerhard HOLTKAMP [] 
    Sent: Thursday, October 26, 2006 4:22 PM
    Subject: Brightness of GRACE Satellites
    A friend sent me two pictures showing the trails of a pair of satellites on 
    related orbits taken at 19:02 UTC, 16-OCT-06 asking for identification. 
    Checking the positions on the pictures and the respective timings I get a 
    perfect match with the pair of GRACE satellites (2002-012A and 2002-012B). 
    What I find strange is that they fluctuate strongly in brightness (even 
    during the 20 sec exposures). The visual report (they were also observed 
    through binoculars) mentioned the leading satellite fluctuating between mag
    and less than mag 8 (then disappearing) and the trailing satellite was 
    between mag 3 and mag 5. I would have thought that the GRACE satellites have
    a controlled attitude. Have they gone out of service and are tumbling now?
    Gerhard HOLTKAMP
    Darmstadt, Germany
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