Re: Calipso questions

From: Gregg Hendry (
Date: Sat Feb 28 2009 - 07:24:06 UTC

  • Next message: Bjoern Gimle@GlocalNet: "Re: Calipso questions"

    On Fri, Feb 27, 2009 at 10:30 AM, Paul Bridges <> wrote:
    > Amateur/Lurker here in California. I have some Calipso passes over the next few months and would like to try to observe/photograph the green laser. I see that the laser is down for most of Mar/Apr due to a leak, but I have good passes in May. I would be appreciative if someone could clear up some of these questions...
    > 1. I normally usually use Heavens-Above and HeavenSat to spot ISS, STS, and Iridiums.  Is there a better tool (using Windows) for making ground tracks?  H-Above provides little detail. SeeSat archives mention, but this appears to be only historical data, and I don't know how to make a ground track from it.
    The best source for the laser ground track is from the web site
    mentioned (
    It usually, but not always contains up to date information.
    I have found the most up-to-date 1 second files by highlighting the
    "10 Second Products" tab and scanning down to the "1-SIXTEEN-DAY-FILE"
    section.  The first file in the list is the most current.  The latest
    16 day file is however out of date today (2/27) but the latest
    1-minute file is current.  Hopefully the 1 second files will be
    updated when normal operations resume.
    For the last year or so the laser has been pointed 3 degrees ahead of
    the satellite's nadir which results in a laser ground track about 2000
    meters east of the sub-satellite ground track.
    For plotting the satellite ground track I use an old copy of STK
    running on XP but it is easiest to rely on the NASA web site.
    Whatever software is used to generate the satellite's position make
    sure the output is in geodetic coordinates and not geocentric
    coordinates as it makes a difference of over 3 miles at mid-latitudes.
    > 2. I see mentions of "orbit raise" and "drag make-up maneuver". What is the difference?  Is it safe to assume they only affect timing by a few seconds and not the ground track?
    I think "orbit raise" and "drag make-up" are referring to the same
    operation.  The ground track of the laser is not significantly changed
    from 2000 meters east of the sub-satellite track due to the maneuver
    but the sub-satellite ground track moves around over time by plus or
    minus 3 miles or more.
    > 3. Since the beam width on ground is only 70 meters, how do I fine tune or verify position?  How would I generate coordinates for use with GPS?
    I fine tune my position using the LIDAR ground track files from the
    web site mentioned above by plotting the 1 second points as a route on
    mapping software.  I use the National Geographic TOPO! software.
    I then find a suitable location on the map and record the coordinates
    in a GPS receiver.
    Plotting the points on GoogleEarth also works well to plan an observation.
    Hopefully this helps,
    Gregg Hendry
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