96 19C and GPS "C" Objects
Jim Varney (jvarney@mail2.quiknet.com)
Sun, 7 Apr 1996 23:53:38 +0100
For a while now I've been interested in trying to catch any member of a
family of Delta II motors that are used to place the Global Positional
Satellites (GPS). My interest was rekindled with the recent launch
of GPS BIIA-25 (96 19A, 23833).
These motors are in highly eccentric transfer orbits and have very low
perigees. I reasoned that if I could see one near perigee that it would
be near enough to be visible and would cross the sky at high speed.
Catching one of these is a somewhat rare proposition. You have to
wait for the line of apsides, the line of nodes and the mean anomaly
to all be just right to favorably place the satellite for your
location.
The family members are:
GPS BIIA-12 RB 21892 92 09C Inclinations for all objects
GPS BIIA-13 RB 21932 92 19C are between 34.47 and 34.96 deg.
GPS BIIA-14 RB 22016 92 39C
GPS BIIA-15 RB 22110 92 58C Mean motions range from 8.24
GPS BIIA-16 RB 22233 92 79C to 4.06
GPS BIIA-17 RB 22277 92 89C
GPS BIIA-18 RB 22448 93 07C Eccentricities range from 0.37
GPS BIIA-19 RB 22584 93 17D to 0.60
GPS BIIA-20 RB 22659 93 32C
GPS BIIA-21 RB 22702 93 42C All are in different planes,
GPS BIIA-22 RB 22781 93 54C but some planes are close
GPS BIIA-23 RB 22879 93 68C together. Some are roughly 60
GPS BIIA-24 RB 23029 94 16C deg. apart, reflecting the
GPS BIIA-25 RB 23835 96 19C 6-plane GPS constellation.
On April 7 1996 at 0351 UT I observed one of these for the first time:
GPS BIIA-13 RB(C)
1 21932U 92019 C 96095.15624218 .00194969 00000-0 10949-2 0 9494
2 21932 34.4743 34.0349 4479450 135.5577 270.7443 6.71803079 74620
This one is in a 177 x 11137 km orbit with a period of 214 minutes. I
wasn't sure how bright it was going to be; the OIG Satellite
Situation Report lists a radar cross section of 3.103 square meters.
Perigee for this pass was to the east of me over the Caribbean, so
it gained speed during the pass. QuickSat showed an odd effect:
for 20 degrees of azimuth following culmination the closest range of
552 miles very nearly held steady because its increasing downrange
distance was offset by its rapid fall to perigee.
In my 10x50's 92 19C was steady at mag 5.5 (quicksat.mag file -> 5.3)
until it punched into the Earth's shadow. It was a fun satellite to
watch because of its speed -- it scooted across the sky, giving the
impression of falling recklessly towards perigee. If there was ever a
visible demonstration of Kepler's Law, this was it...
If you live too far north, there's always the other end of the orbit.
Maybe someone with a telescope might try for an at or near-apogee
observation?
Good Passes,
Jim
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Jim Varney | 121^ 23' 54" W, 38^ 27' 28" N | Sacramento, CA
Civil Engineer | Elev. 31 ft. |jvarney@mail2.quiknet.com
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