Re: Flaring Geo sats.

From: Bjoern Gimle (
Date: Sun Mar 04 2001 - 23:16:26 PST

  • Next message: Rod Sladen: "Re: Iridium double-flare"

    Most observers use star maps and RA/Dec to find (and identify) satellites,
    so most prediction programs provide that info (even the Heavens-Above site).
    SkyMap by Rob Matson star map, coordinates, satellite tracks and track
    information in one graphic display.
    Without personal experience of equinox geoflashers, I would summarize the
    discussion like this:
    The active geosynch population traces a declination band given by a formula
    found in previous mails, and by prediction programs, or about -latitude/7.
    If their solar arrays are tracing the Sun in RA, but not in Dec, they should
    point roughly at the equator, and the most reflections should be seen at the
    same declination as the Sun, but 180 degrees (12 h) away in RA. This point
    is closest to the geosynch band at the dates now discussed - around the
    Unfortunately, the shadow cone, which casts a circular shadow patch of 12000
    km dia at the 36000 km geosynch distance (ie about 20 degrees) also meets
    this point at the equinoxes. But while the Sun is below the equator, the
    center of the cone is above it, though shifted south by parallax for a
    northern observer. This provides a chance to see reflections near midnight.
    The Earth also rotates W-E during the night, so there is a parallax in RA as
    well. Observers closer to the equator can see reflections before shadow
    entry to the right (W) of the cone in the evening, and to the left after the
    morning shadow exit.
    All these facts can be visualized in SkyMap, using a range filter of
    33000-44000 km if not running a dedicated Geo TLE file, and a magnitude
    limit of 20. Use a prediction period of 1-2 hours to avoid 'smearing' the
    edges of the shadow patch. The position of the 'Anti-Sun' position can be
    added to the deepsky.txt file to show in the plot.
    I have sent two samples to Richard Bassan, and will generate some for you,
    -- (office)                         --
    -- (home) --
    -- COSPAR 5919, MALMA,    59.2576 N, 18.6172 E, 23 m         --
    -- COSPAR 5918, HAMMARBY, 59.2985 N, 18.1045 E, 44 m         --
    > How do you know where (exactly) to look?  Do you use detailed star charts
    > the geo arc and then predict their location in right ascension and
    > declination?  What programs provide sat locations in RA and declination?
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    This archive was generated by hypermail 2b29 : Sun Mar 04 2001 - 23:49:36 PST