Re: NROL-76 payload speculation

From: C. Bassa via Seesat-l <>
Date: Sun, 30 Apr 2017 10:44:05 +0200
The intended orbit for the NROL-76 mission, slated for launch on a
Falcon 9 between 11:00 and 13:00UT, today remains a mystery.

These are the facts that we can consider known:
* the launch hazard area is consistent with a 50 deg inclination
* the de-orbit hazard ara is also consistent with a 50 deg inclination
* the launch window is not planar (the April 16 launch date also had
  11:00 to 13:00UT)
* the de-orbit hazard area is valid from 03h38m to 6h15m after launch

All these facts can be considered peculiar. To my knowledge, no NRO
launches have targeted orbits inclined at 50 deg, and all launches,
except perhaps missions to GSO, had planar windows.

Furthermore, the long time between launch and de-orbit is not
compatible with previous Falcon 9 launches. On recent CRS missions (8,
9 and 10), the de-orbit area was valid from about 00h26m to 01h19m
after launch, indicating the second stage was de-orbited before it
completed a full orbit, with the impact point South West of
Australia. The Orbcomm OG-2 mission, targeting a 47deg orbit, had a
similar location and time range for the de-orbit area.

During the Jason 3 and Iridium NEXT missions, the second stage
performed a circularization burn at 00h55m (Jason 3;
1296kmx1321km_at_66deg) and 00h52m (Iridium NEXT; 618kmx627km_at_87deg)
after launch. Here, the de-orbit areas were valid between
01h06m-02h07m and 01h52m-02h48m after launch, respectively.

If NROL-76 targets LEO, why de-orbit the second stage only after about
2.5 orbits?

I wonder if instead NROL-76 targets some sort of MEO/HEO orbit. If so,
it may be expected that perigee is located in the South to allow the
second stage to be de-orbited off the coast of Africa.

Regardless of the target orbit, it'll be an interesting challenge to
locate the NROL-76 payload.

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Received on Sun Apr 30 2017 - 03:44:43 UTC

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