Re: CALIPSO Laser Observation

From: Gregg Hendry via Seesat-l <>
Date: Tue, 3 Mar 2015 16:46:22 -0700
The CALIPSO LIDAR ground track is virtually always east of the
sub-satellite track.
Occasionally the satellite is pointed elsewhere but to date this has not
been often or long lasting.

The laser is nominally directed 3 degrees forward along the satellite's
velocity vector, not to the side.  This 3 degree look ahead angle puts the
laser pulses hitting the ground about 37 km ahead of the satellite's nadir
point.  The satellite takes about 5 1/2 seconds to get to where the laser
pulse landed but in the meantime the earth rotates east placing the
satellite ground track west of the laser track. I calculate 1950 meters at
40 degrees latitude.

The best place to look for laser spots in the atmosphere is directly to
zenith.  Small green flashes at the satellite's position appear 3 degrees
to the north of zenith along the satellite's track through the stars,
roughly azimuth 8 deg, altitude 87 deg.

Note:  A CALIPSO apparition is not an event to be viewed directly through a
telescope as the laser was designed to be eye safe by only a factor of 2 in
10 x 50 binoculars.  Also the spot trail and beams can subtend 30 degrees
or more of the sky and would be missed if viewed through optics.

Gregg Hendry

On Mon, Mar 2, 2015 at 12:09 AM, Vladislav Gooba via Seesat-l <> wrote:

> >Applying some rusty geometry to the photograph calculates the LIDAR ground
> >track passing 2000 meters east of the satellite track.
> Is this always so? I have read that the laser is directed at an angle of 3
> degrees from nadir. So the best opportunities to look is 87 deg. altitude
> pass westward? Is it directed eastward all time or it changes it's
> direction?
> Sincerely
> Vlad
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Received on Tue Mar 03 2015 - 17:46:54 UTC

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