Saturday 18 June 2016

Mentor 7, the NROL-37 payload, found

Launch of NROL-37 (photo credit: ULA)

On 11 June 2016 at 17:51 UT, after a one-day postponement, the US National Reconnaissance Office (NRO) launched a classified payload from Cape Canaveral under the launch designation NROL-37. It was a launch into geosynchronous orbit using a Delta IV-Heavy rocket.

The NROL-37 payload  has been catalogued under the generic designation USA 268 (2016-036A, 41584). It is widely believed to be a Mentor (Advanced Orion) SIGINT ('eavesdropping') satellite, Mentor 7.

Initial assessments pre-launch indicated a possible orbit insertion of the payload over Southeast Asia. After launch, Paul Camilleri, a novice satellite observer in Australia, was guided by Ted Molczan and me in an attempt to find the payload by means of a dedicated photographic survey.

In the early morning of June 15 (local time -  June 14 in UT), three days after the launch, Paul indeed successfully located the payload! The image below shows one of Paul's initial images, with the NROL-37 payload visible as a bright dot.

Mentor 7 (NROL-37) imaged June 14 by Paul Camilleri in Australia
click to enlarge - photo (c) Paul Camilleri, used with permission

From imagery on June 14 and 15, the following very preliminary orbit was calculated (for the time being, I have fixed a few parameters towards 'round' values here):

Mentor 7
1 41584U 16036A   16166.96303997 0.00000000  00000-0  00000+0 0    06
2 41584   7.5000 353.7000 0046000  41.4155 318.9349  1.00200000    04

rms 0.006, from 7 obs, 2016 June 14.70 - June 15.48 UTC

This places the satellite near longitude 104 E, over the Strait of Malacca, around the time of discovery, in a ~7.5 degree inclined near-geosynchronous orbit.

[edit 19 June 2016, 20:15 UT: I have posted an updated orbit in a later post here]

click map to enlarge

While the Mean Motion still remains somewhat ill defined from this short an observational arc, the satellite appears to be slowly drifting westwards, towards its eventual operational position.  My guess (and no more than that) is that it will eventually stop drifting near either 80 E (south of Sri Lanka) or perhaps 10 E (over central Africa). The reason for the initial placement near 104 E is likely that in this position it is initially well placed for the Pine Gap Joint Defense Facility ground station in central Australia (one of two facilities dedicated to NRO SIGINT payloads) during the initial check-out phase.

Mentor (Advanced Orion) satellites are SIGINT satellites: satellites that "listen" for radio signals. They are "the largest satellite[s] in the World", according to a statement by the then NRO director Bruce Carlson in 2010 at the time of the Mentor 5 (NROL-32) launch. There has been some speculation (it seems to be not more than that) that these satellites might have a huge fold-out mesh antenna some 100 meters wide.

Our observations suggest that these satellites indeed appear to be extraordinarily large. They are very bright (brighter than other geosynchronous payloads), typically of magnitude +8. They are the easiest geosynchronous satellites to photograph: a standard 50mm lens with a 10-second exposure will do.

The other six Mentor satellites, launched between 1995 and 2012, currently make up this configuration:

click map to enlarge

I thank Paul Camilleri for permission to use one of his photographs and for his willingnes to undertake the hunt for Mentor 7

 [edit 19 June 2016, 20:15 UT: an update here]

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