SBIRS GEO Flight 4 prelaunch elements

From: C. Bassa via Seesat-l <seesat-l_at_satobs.org>
Date: Wed, 17 Jan 2018 23:09:41 +0100
An Atlas 5 in the 411 vehicle configuration will launch SBIRS GEO
Flight 4 into a geostationary transfer orbit on January 19 between
00:52 and 01:32UTC. The Centaur upper stage will be deorbited.

The mission booklet states that the targeted transfer orbit will be
185x35851km inclined at 16.88 degrees. Space craft separation will be
42 minutes after launch, followed by the deorbit burn and fuel dump at
about 74 to 79 minutes after launch. The Centaur will impact 9.5 hours
after launch.
(http://www.ulalaunch.com/uploads/docs/Mission_Booklets/AV/av_sbirsgeo4_mob.pdf)

Based on the target orbit and the map in the mission booklet, I
estimate this orbit for the payload:

SBIRS GEO F4
1 72001U          18019.05646528  .00000000  00000-0  00000-0 0    08
2 72001  16.8800 325.0000 7309693 178.0000   2.0000  2.27834097    02

The orbit of the Centaur upper stage after the deorbit burn is the
following, requiring a delta-v of about 175 m/s for the deorbit burn.

SBIRS GEO F4 r
1 70002U          18019.08781481  .00000000  00000-0  00000-0 0    08
2 70002  16.9283 324.6884 7270734 173.1245  32.4469  2.64261228    09

Both elsets are valid for a launch at the start of the window.

Unfortunately the deorbit burn and fuel dump will not be visible as
the ground track of the payload and upper stage will be near the
latitude and longitude of the sub-solar point. Due to the reduced
insertion inclination of 16.88 degrees, the stack will also not be
visible from South Africa after the insertion burn.

The upper stage has very limited visibility during the half hour prior
to impact from the Eastern side of Australia. The payload has better
visibility from Australia, assuming it did not perform a perigee
raising manouver at the first apogee.

Regards,
   Cees
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Received on Wed Jan 17 2018 - 16:10:29 UTC

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