Saturday, 9 January 2021

First optical observations of the NROL-108 payloads USA 312 and USA 313

In the early morning of January 9, I made the my first optical observations of the two payloads, USA 312 and USA 313 (2020-101A & B)  from the December 19 NROL-108 launch (see my earlier post here for more info on this somewhat enigmatic launch). Both were bright: USA 313 was about magnitude +4.5 and USA 312 about +5.5.

Radio observers already detected one of the payloads on December 20, and the second on January 5th. I used their preliminary TLE's to optically hunt for the objects this morning, which saw a clear frosty sky in Leiden. [edit: as it turns out, Russell Eberst observed both objects one day before me. I somehow had missed that]

USA 313, the leading object, was 13 seconds early and as much as 2.4 degrees off-track relative to the January 5 radio elset. USA 312, the chasing object, was about 1 second early and half a degree off-track relative to the January 5 radio elset.

USA 312 was about 2 minutes behind USA 313. Their orbits are co-planar and on the same orbital altitude, and the true distance between the two was about 900 km at the moment of observation. They are likely meant to operate as a pair, and it will be interesting to see whether they will perform any proximity manoeuvres in the future.

A second fainter object chased USA 312: this turned out to be STARLINK-1632. Their close proximity is almost certainly coincidence, and the result of the increasing number of Starlink satellites on orbit.

The video in the top of this post, shot with a WATEC 902H2 Supreme and Samyang 1.4/85 mm lens, shows USA 313 first, and then USA 312 with Starlink-1632 close by.


Click image to enlarge

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