The late deorbit is indeed interesting. I suspect it is related to the suspected low mass of the primary payload and the resulting excess capacity in some way: either stage 2 will be used after payload separation by SpaceX for experiments (related to tech development for stage 2 recovery perhaps?) or there are secondary payloads to be deployed. Observers should therefore be on the lookout for the possibility of additional objects in orbit. - Jonathan On 30 April 2017 at 04:44, C. Bassa via Seesat-l <seesat-l_at_satobs.org> wrote: > 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. > > Regards, > Cees > _______________________________________________ > Seesat-l mailing list > http://mailman.satobs.org/mailman/listinfo/seesat-l > _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Sun Apr 30 2017 - 10:47:30 UTC
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