Re: NROL-76 payload speculation

From: Jon . via Seesat-l <>
Date: Sun, 30 Apr 2017 11:30:02 +0200
Hello all,

Using the information that Ted and Cees published on this thread I've tried
to build an scenario where all these things can concur.

After some problems trying to build a Molniya orbit using this, reached the
conclusion that a LEO orbit is more probable. This does not discard a
Molniya orbit mission.

Using the NOTAMs and Maritime Restrictions, plus the few available data
about this mission reached the following TLE, assuming launch at 11:15 UTC
(launch was delayed 15 minutes while writing the mail):

NROL-71 scenario #1                                      858 X 858 km
1 70099U 17500B   17120.67709491 0.00000000  00000-0  00000+0 0    04
2 70099  50.0000 280.8604 0000010  73.6430 274.4981 14.10600000    01

The 850 Km height is consistent with the time, location and the track of
the launch and de-orbit restriction and can explain the use of ion-based
satellite bus on a near zero drag enviroment.

It's possible that other orbital solutions can match the data pointed by
Ted and Cees.

If this orbit is near of reality, observers from south hemisphere would
have good dawn passes.


2017-04-30 10:44 GMT+02:00 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
> _______________________________________________
> Seesat-l mailing list

Jon, COSPAR 6242, 42.9453, -2.82839, 623m, Bitoriano, Basque Country.
Seesat-l mailing list
Received on Sun Apr 30 2017 - 04:30:48 UTC

This archive was generated by hypermail 2.3.0 : Sun Apr 30 2017 - 09:30:48 UTC