NROL-45 search elements

From: Ted Molczan via Seesat-l <>
Date: Tue, 9 Feb 2016 06:19:14 -0500
NROL-45 is scheduled for launch on a Delta IV M+(5.2) rocket, from Vandenberg AFB, on 2016 Feb 10, at 11:39 UTC. The
payload is FIA Radar 4, aka Topaz 4. The duration of the launch window has not been made public. If the launch is
delayed to another day, and if the launch window is planar, as seems certain, then the launch window will move later at
the rate of 8.5 min per day of delay.

Spaceflight Now will cover the launch:

That the codename of the FIA Radar series is Topaz was revealed in budget documents leaked by Edward Snowden, which
indicated that five (5) spacecraft are planned, to be succeeded eventually by Topaz Block 2, for which spending was to
begin in U.S. FY2013. The final block 1 launch probably is NROL-47, which is slated for launch from VAFB in the fall of
2017, on a Delta IV M+(5.2).

The Delta IV second stage of NROL-45 will be de-orbited about 140 min. after launch, south of Australia, in a region
centred at 53.8 S, 118.75 E.

The following estimated TLE is derived from our first couple of days of tracking of the second payload of the series,
which employed the same rocket. The epoch is at the first ascending node after launch.

FIA Radar 4                                            1079 X 1096 km
1 76541U          16041.53173366  .00000000  00000-0  00000-0 0    02
2 76541 122.9820 351.2254 0011938 297.0851  62.8894 13.45796211    01

There is good reason to believe that the actual RAAN will be a bit different than that of the above TLE. Below is the
RAAN of the first three payloads of the series, propagated to the epoch of the above TLE.

10046A 37162  86.53418
13072A 39462 176.50206
12014A 38109 266.49981

Note the almost exact 90 deg spacing of successive RAANs. If the fourth payload maintains this progression, then its
initial RAAN will be close to 356.5 deg. That could be achieved by means of yaw-steering during the ascent, to shift the
RAAN east 5.3 deg. A precedent was set by the third launch of the series, which yaw-steered about 4.8 deg east in RAAN.

If FIA Radar 4 yaw-steers to 356.5 deg RAAN, then these will be its approximate elements at first ascending node:

FIA Radar 4                                            1079 X 1096 km
1 76542U          16041.53173367  .00000000  00000-0  00000-0 0    04
2 76542 122.9820 356.5000 0011938 297.0851  62.8894 13.45796211    09

The same RAAN could be achieved without yaw-steering, by delaying lift-off 21 min. Time will tell.

The above TLEs are likely to be uncertain in time by several minutes per 24 h after launch, due to uncertainty in epoch
and mean motion. A wide field of view is recommended for acquisition.

Northern hemisphere observers will have morning visibility. Mid-southern hemisphere observers will have passes near
local midnight.

Alternative pre-launch analyses and TLE estimates are welcome. The more, the merrier.

Happy hunting!
Ted Molczan

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Received on Tue Feb 09 2016 - 05:19:53 UTC

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