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  1. #1
    Gregg Hendry's Avatar
    Gregg Hendry Guest

    Default Laser Beams From Space

    The laser altimeter aboard ICESat was powered on again Sept 26th and is
    planned to remain on for 45 days. When atmospheric conditions and
    observer positioning are right, green light from the laser can be easily
    seen from the ground. Thin clouds, numerous scattered clouds, or haze
    should all provide good conditions to observe the laser beam. Clear is
    not good unless the observer is within a few hundred meters of the
    laser’s ground path. To observe the laser in even good conditions it is
    thought best to get close to the satellite’s ground track as the forward
    scattering from the Nadir pointing laser may not be visible more than a
    mile or less off track. The apparition's speed is remarkable as the
    laser spot is moving at orbital velocity.

    (For more info refer to the “Observing ICESat” thread on this newsgroup
    in March of this year)

    Gregg Hendry

  2. #2
    Patty Winter's Avatar
    Patty Winter Guest

    Default Laser Beams From Space

    In article <>,
    Gregg Hendry <> wrote:

    Thanks for the heads-up on this, Greg. I ran out my local ICEsat passes
    on Heavens-Above, and although I'm getting two per night for the
    foreseeable future, they're all way east or west of me. ;-( Guess I'll
    keep checking and hope that some of them get higher in my sky.


  3. #3
    Gregg Hendry's Avatar
    Gregg Hendry Guest

    Default Laser Beams From Space

    ICESat's orbit was changed Saturday 10/4 and is now in a 91 day
    repeating ground track orbit. Assuming the repeating ground tracks get
    evenly spaced around the earth over the 91 days they should be spaced
    approximately 14 miles apart at 40 degrees north. So with some patience
    ICESat should come close to you.

    I have observed the laser three times now and for good viewing suggest
    getting as close to the ground track as possible, hope for some thin
    clouds, and look directly towards zenith.

    When skys were clear observers have reported seeing only a brief green
    flash at zenith but when there is some cloudiness to scatter the beam
    the pass is much more interesting.

    A photograph of a recent pass scattering through clouds is posted at

    Gregg Hendry

    Patty Winter wrote:

  4. #4
    Gregg Hendry's Avatar
    Gregg Hendry Guest

    Default Laser Beams From Space

    The laser altimeter on ICESat (27642) in now off and will likely remain
    off until February or March of 2004.

    Gregg Hendry



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