Re: NROL-76 payload speculation

From: Jonathan McDowell via Seesat-l <>
Date: Sun, 30 Apr 2017 11:46:42 -0400
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 <>

> 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
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Received on Sun Apr 30 2017 - 10:47:30 UTC

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