NROL-47 search elset and identity

From: Marco Langbroek via Seesat-l <>
Date: Tue, 9 Jan 2018 17:57:36 +0100
Hi all,

We might have another classified payload going into an unusual orbit tomorrow.

NROL-47 is slated to launch from Vandenberg SLC-6 tomorrow January 10. The
Maritime Broadcast Warning window opens at 20:30 UT and ends January 9 at 1:26 UT.

The launch hazard areas and Upper Stage deorbit hazard area from the Broadcast
Warnings point to an unusual orbital inclination: 108.6 degrees.

Some websites (e.g. Spaceflight 101) have speculated NROL-47 is the fifth TOPAZ
(FIA Radar) based on the fact that it is launched westwards into retrograde orbit.

If so, it is going into a different kind of orbit than the previous four ones,
both regarding inclination (the four FIA satelites have an orbital inclination
of 123.0 deg) and orbital altitude.

The launch azimuth from the launch hazard areas published differs by 20 degrees
from previous FIA launches. And there is no need for a dogleg manoeuvre, as
previous FIA launches launched directly into a 123.0 degrees inclination orbit.

From what appears to be the Upper Stage de-orbit hazard area near Antarctica and
the time it opens (23:23 UT) as well as its shape, an orbital altitude near 1500
km is indicated. Previous FIA are in 1100 km orbits.

So the identity of NROL-47 remains a questionmark and I am not convinced it must
be a FIA/TOPAZ. It could be some other new radar (the retrograde orbit suggests
it is a radar satellite).

Here is an orbit estimate for launch on 10 January 20:30 UT:

NROL-47  launch 2018-01-10 20:30 UT                    1495 x 1505 km
1 70000U 18999A   18010.85416667  .00000000  00000-0  00000-0 0    09
2 70000 108.6398 105.5134 0006347 166.4011 308.2684 12.41559515    01

Here is an alternative orbit for an 1100 km orbital altitude (FIA, but in a
different orbital plane):

NROL-47  launch 2018-01-10 20:30 UT                    1100 x 1110 km
1 70001U 18999A   18010.85416667  .00000000  00000-0  00000-0 0    00
2 70001 108.5831 105.5134 0006682 166.4011 304.1188 13.41149813    06

Allow for several minutes difference in pass time and several degrees cross-track.

South Africa might have visibility on the first pass near 21:38 UT and the
second pass near 23:30 UT.

- Marco

Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.

Cospar 4353 (Leiden):     52.15412 N, 4.49081 E (WGS84), +0 m ASL
Cospar 4355 (Cronesteyn): 52.13878 N, 4.49937 E (WGS84), -2 m ASL
Station (b)log:
Twitter: _at_Marco_Langbroek
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Received on Tue Jan 09 2018 - 16:57:36 UTC

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