Viewing Iridium flares from the ISS

From: Robert Reeves (
Date: Fri Mar 07 2003 - 01:07:13 EST

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    Hats off to Rob Matson!  He has created a customized program that allows
    predicting Iridium flares as seen from the ISS, and it works!.  Think about
    that.... predicting the interception of an Iridium flare moving at 5 mi/sec
    as seen from another platform in space also moving 5 mi/sec in a different
    plane.  It boggles the mind.
    Anyway, a few weeks ago Rob offered to code up such a program if the guys
    aboard the ISS were willing to look for flares.  Sounds simple enough....
    its never cloudy up there and its night time every 45 minutes.  But
    astronomical observations from the ISS are complicated.  Limited viewing
    angles through the various windows, which may or may not be oriented toward
    the stars, and reflections from station modules and panels which make
    observation of stars impossible when in sunlight have to be taken into
    account.  I sent Don Pettit a note offering to forward any of Rob's
    predictions and by golly, they went for it.
    So Rob coded up the program and I have sent up a number of his predictions
    that Rob filtered for the station's limited viewing angles.  After several
    missed oportunites because of work schedules and solar illumination
    constraints, Don Pettit had a hit today!  The ISS successfully intercepted a
    predicted Iridium flare and it was observed by the Scinece Officer.
    Here is part of a note I got from Don on the ISS this evening.......
    I have been having a great time looking for the IR flashes.  So far I have
    seen one of the predicted events.  The other flashes were predicted to be
    much weaker and came at a time when sunlight was still falling onto parts of
    station hence spoiling viewing contrast.   If the flashes were a few minutes
    later, it would have been dark and I probably could have seen them.
    March 5th  the 10:15 flash at -8:  I looked at my watch after the flash and
    it was 10:16:24.  I estimate the flash to be about -1 magnitude based on the
    stars around.  It was weaker than the pointer stars next to the southern
    cross.  I was watching out the US Lab window at quite an angle.  The flash
    was near the two pointer stars next to the southern cross and was at about
    RA 230  Dec -50.   You should have seen the smile on my face when I saw
    this.  Great job on the calculations.
    This afternoon we changed attitudes again.  We are now LVLH which keeps the
    same side of station pointed towards Earth.  Great for Earth observations
    but bad for stars since most of our windows point "nadir".   However, we
    have two small windows in the Russian segment which point starboard and port
    to our velocity vector so when we are at our highest and lowest latitudes,
    we have views looking due north and south.  This should be good for seeing
    IR flashes since they give views where the satellite orbits converge.  They
    are also great for aurora.  After we get good at predicting and seeing these
    then I will set up a camera and record them.  Maybe I can get a flash with
    Anyway, good work.  If it is not too much trouble, please keep the
    predictions coming.  I will take the time to view as many as I can.  For the
    time being, let us concentrate on brighter ones, say less than 0 mag.
    take care
    I say this is way cool!  Its not every day that someone from the amateur
    community creates something that is used by the guys up in the big bed and
    breakfast in the sky.  I'd say we owe Rob a cold beer on the house!
    Robert Reeves            
    520 Rittiman Rd.         
    San Antonio, Texas 78209    210-828-9036
    USA                                     29.484  98.440  200 meters
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