cat's eye in the sky

richard.keen@kingsmarket.com
Mon, 09 Mar 98 20:56:38

                                  
 Flare-watchers -
 I know reports of Iridium flares (flashes? glints?) are getting pretty
routine, but I can't restrain myself...
 I saw a specatuclar double flare this morning about 20 minutes before
sunrise.  An overcast sky in the early hours was beginning to break up,
and the flares occurred right in a clear hole.  First, as usual, the
Iridflar ver. 1.5 output, based on 7- and 5-day-old elements for
Iridiums 38 and 15, respectively:
 Ir  Date    Time     Az  El Range Sun Flare  Vis Peak Stand Obs
           MST (UT-7)         km  elev Angle  Mag  Mag  Mag  Mag
 38 98-3-9  6:06:00.0 158 43 1061 -3.5 0.52  -2.4 -7.6 -3.1  -6
 15 98-3-9  6:06:02.3 158 43 1071 -3.5 0.09  -7.6 -7.6 -8.2  -7
 The event was even better than these predictions would suggest, since
the flare from Iridium 38 occurred 2 seconds later than predicted,
making it precisely simultanous with, and less than half a degree from,
the flare from Iridium 15.  It was also much brighter than predicted. 
The relative positions of the objects were as predicted, so the error
in the Iridium 38 flare was due, I presume, to its MMA's being somewhat
(half a degree or so) off the standard orientation, putting me very
near the center line of the flare's ground track.  Iridium 38 is in a
lower orbit (higher MM) than the standard orbit, so perhaps is not
maintained as closely to the ideal orientation?
 The double flare was visible for 2 or 3 seconds in bright twilight,
and for a moment, reminded me of when I camping in Botswana some years
ago and shined a flashlight at a hyena and his eyes blinked back at me.
 After the double flare, I went back inside, and there was my cat,
blinking into the flashlight.
 Cheers, Rich Keen
 Coal Creek Canyon, Colorado, USA (39.877 N, 105.391 W, elevation 2728m)