Monday, 18 April 2022

NROL-85 observed, but is it an INTRUDER/NOSS or something else? [UPDATED]

click image to enlarge


Yesterday 17 April 2022 at 13:13 UT, SpaceX launched the classified NROL-85 mission for the NRO. Before the launch we widely expected this to be NOSS 3-9, a new pair of INTRUDER/NOSS satellites (see previous post), based on clues as to the orbit it was launched into. 

The orbital inclination and orbital altitude suggested by OSINT infornation on the mission were typical for NOSS/INTRUDER, and the time of launch indicated a launch into the orbital plane of the 10-year-old NOSS duo NOSS 3-6. That is a pattern we have seen before with NOSS missions: a replacement launched into the same orbital plane after 10 years of operational service.

So we expected to observe two objects after launch. 

But NROL-85 had a surprise in store: so far, we detected only one object, not the expected two!

This leads to the question: is NROL-85 a new INTRUDER/NOSS, or not?

NROL-85 was first picked up by me, from Leiden, the Netherlands, some 7 hours after launch, in late evening twilight of 17 April around 19:59 UT (21:59 CEST). It was some 2.5 minutes early on my pre-launch estimated search elset. I subsequently also observed it on a second pass two hours later.

On the first pass, I captured it photographically (see image in top of this post, showing it above the roof of my house along with two old unrelated rocket stages), using a Canon EOS 80D with a Samyang 1.4/35 mm wide angle lens (the exposure is a 2-second exposure at ISO 800). The video system I had set up captured it too, but only very briefly in a corner of the field of view. Only one object was seen, nothwithstanding that I did a photographic plane scan during quite some time.

The second pass was in the northern sky with a less favourable phase angle (so the object was much fainter than during the first pass). I captured it with the video system, and after following it for a minute or so, left the camera stationary to look for a possible second object. None was detected, either before or after the detected object.

Likewise, fellow observers from the Seesat-L list including David Brierley and Eelke Visser, detected only one object too. And Scott Tilley reports that he did not detect radio signals at the frequencies usually used by NOSS.

The absence of a second object could mean that NROL-85 is not a new INTRUDER/NOSS mission after all, but something else, although the orbit is very NOSS-like.

Alternatively, perhaps it is an improved version of INTRUDER that now needs only one satellite, rather than two.

NOSS missions once consisted of three satellites orbiting close together in a triangular formation. In 2001 this changed to two satellites. Maybe now they found a way to do it with one satellite?

The object we detected is in a 1021 x 1191 km, 63.5 degree inclined orbit (update: with a longer observational arc constraining the eccentricity of the orbit better, the new value is ~ 1008  x 1207 km). This orbit is close to the specifications given in a launch contract tender for NROL-85. Below is a preliminary initial elset based on a 5.5 hour observational arc:

NROL-85 (USA 327)
1 70002U 22999A   22108.04497945 0.00000000  00000-0  00000+0 0    07
2 70002  63.5043 123.5866 0114230 185.9890 173.9785 13.40421486    07

rms 0.024 deg

Elset update (20 April 2022): Below is the latest elset based on 114 observations by Cees Bassa, Eelke Visser, David Brearley, Andriy Makeyev and me over a two-day observational arc:

USA 327 (NROL-85)                                      1008 x 1207 km
1 52259U 22040A   22109.98456423 0.00000000  00000-0  00000+0 0    08
2 52259  63.4462 118.5572 0132890 178.9713 181.1610 13.40467640    01

rms 0.011 deg    arc Apr 17.83 UT - Apr 20.01 UT


click to enlarge

As a final note: the post-deorbit-burn fuel vent by the Falcon 9 upper stage used for the launch of NROL-85, which was deorbitted over the Pacific Ocean at the end of the first revolution (see map in previous post), was seen and filmed from Hawaii, showing the characteristic spiral shape:


(a follow-up post is here)

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