Thursday, 23 March 2017

NOSS 3-8 (NROL-79) components now close to operational separation

In a recent blog post I documented the intricate manoeuvering of the two NROL-79 payloads (NOSS 3-8) over the past three weeks. They were manoeuvering to circularize and synchronize their orbits and manoeuvre to a desired mutual distance.

click image to enlarge

Much of this manoeuvering is now done, and the two spacecraft are now flying in formation at a mutual distance of ~50.5 km. They now look like a typical NOSS pair, as can be seen in the image above shot in the evening of March 21 (the bright star is Procyon).

Below is an updated diagram, showing the evolution of the separation between the two spacraft over time:

click diagram to enlarge

After an initial rapid post-launch separation with a drift of ~31-32 km/day, reaching a maximum separation of ~202 km on day 6 after launch, the separation distance started to decrease post day 6, and is now, by day 20-21 after launch, clearly flattening out to a stable separation distance of about 50 km.

The Mean Motion/orbital period of the two spacecraft are now very similar too, as is their orbital inclination: all signs that they are now close to the desired configuration. The two orbital planes are currently about 0.2 degree separated in RAAN.

click diagram to enlarge
click diagram to enlarge
click diagram to enlarge

While they are now at their operational distance (which looks to be ~50 km in this case) and close to operational configuration, this does not mean that NOSS 3-8 is now fully operational. Over the coming weeks, they will probably undergo extensive check-out tests. I also expect them to continue to make small manoeuvres for a while (but while maintaining a more or less stable mutual distance at ~50 km).

Several amateur satellite trackers contributed data to this analysis, including Leo Barhorst, Cees Bassa, Russell Eberst, Alain Figer, Paul Camilleri, Dave Waterman, Alberto Rango, Brad Young and me.

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