Re: NROL-76 payload speculation

From: Jon . via Seesat-l <seesat-l_at_satobs.org>
Date: Sun, 30 Apr 2017 11:35:12 +0200
Forgot to mention that information from Marco Langboek was used too. Sorry.


Jon.

2017-04-30 11:30 GMT+02:00 Jon . <jonmikelk_at_gmail.com>:

> 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.
>
>
> Jon.
>
>
> 2017-04-30 10:44 GMT+02:00 C. Bassa via Seesat-l <seesat-l_at_satobs.org>:
>
>> 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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>> http://mailman.satobs.org/mailman/listinfo/seesat-l
>>
>
>
>
> --
> Jon, COSPAR 6242, 42.9453, -2.82839, 623m, Bitoriano, Basque Country.
>



-- 
Jon, COSPAR 6242, 42.9453, -2.82839, 623m, Bitoriano, Basque Country.
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Received on Sun Apr 30 2017 - 04:35:36 UTC

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