Wednesday, 13 February 2019

USA 290 (NROL-71)

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The photograph above is not the best of images, but it does show the trail (faint) of  USA 290, the payload of the January 19 NROL-71 launch from Vandenberg. I shot it last Monday morning, February 11th.

I wrote about this odd launch earlier (here). Before the launch, it was widely suspected that this was a new electro-optical reconnaissance satellite, a block V KH-11 ADVANCED CRYSTAL ("Keyhole"). So we expected it to go in a 98-degree inclined, ~1000 x 265 km sun-synchronous orbit, the orbit typical for new primary plane additions to the KH-11 constellation.

But then the Maritime Broadcast Warnings for the launch came out, and it became clear that the splashdown and deorbit zones did not fit a launch azimuth consistent with such an orbit (see a previous post where this was discussed). Instead, it suggested a 74-degree inclined, 265 x 455 km non-sunsynchronous orbit. Which was very odd, as it was completely against expectations for a new KH-11.

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The launch was postponed several times, but finally happened on 19 January, a month later than it was originally slated. The launch postponements added a new mystery: the shifting launch window times with each postponement suggested a particular orbital plane with a nodal precession of -2.27 deg/day was aimed for.

The question was: why, if  NROL-71 was going into a 74-degree inclined orbit? Targetting a specific orbital plane only makes sense when the payload is part of a constellation of satellites. But NROL-71 was not targetting the orbital inclination of the existing KH-11 constellation (currently consisting of USA 186, USA 224, USA 245). And it's orbit is (as we will see) not sun-synchronous. It is very odd (and does suggest there will be future objects going into a similar orbit).

After launch on 19:10 UT on January 19th, 2019, there initially was no optical visibility as nighttime passes in the Northern hemisphere were in earth shadow.

But radio observers (a.o. Sven Grahn, Scott Tilley, Cees Bassa, Nico Jansen) quickly picked up the radiosignals of the payload at 2242.5 MHz. These showed that the payload was in a 73.6 degree inclined non-sunsynchronous ~400 km Low Earth Orbit, much as we had gleaned pre-launch from the hazard zones in the Maritime Broadcast Warnings.

As USA 290 slowly emerged from Earth shadow passes, the first optical observations were made by Russell Eberst in Scotland in the morning of 1 February. Next Leo Barhorst in the Netherlands soon followed.

These initial passes were very low in the sky, too low for my urban environment where I need elevations above 20-25 degrees to clear the rooftops. And when as February progressed the passes gradually climbed higher in the sky for my location, weather was not cooperating.

But in the morning of 11 February I finally had a clear sky, and managed to image USA 290, photographically as well as on video. As the illumination angle was not the best, the payload stayed a bit faint, but still was bright enough to register as a faint trail on the photograph (the bright star near the trail is gamma Cygni. Image taken with a Canon EOS 60D + EF 2.0/35 mm lens):

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The object showed up well on the video (WATEC 902H + Canon FD 1.8/50 mm lens), yielding good astrometry:

The optical observations helped to better define the orbit. They show USA 290 is in a 393 x 422 km, 73.6 degree inclined, non-sunsynchronous orbit.

Apart from abandoning the 97.9 degree inclined sun-synchronous orbit of the primary plane KH-11's, it also abandoned the 1000 x 260 km orbital altitude that was previously typical for new primary plane launches. The orbital altitude is closer to the extended mission, secondary plane KH-11's, the sole representative of which (USA186) currently is in a 262 x 452 km orbit.

Of course, in terms of orbital inclination and nodal precession (the non-sunsynchronous character) it doesn't compare to any of the previous KH-11.

(Note: a few year ago I wrote a series of detailed posts analysing the orbital constellation of the KH-11, and the typical changes in orbital plane and orbital altitude when a new addition to the constellation was launched: see the posts here and here).

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So, there is something new under the sun, in more than one way. While the general consensus still is that USA 290 is an electro-optical bird in the ADVANCED CRYSTAL lineage, the radical break with previous orbital structures for this series of satellites is highly interesting. It will be interesting to follow this new object, and see how things develop with future launches.

Over the last two years, the black space program in Low Earth Orbit has become much more exciting, with some new eyebrow-raising additions unlike any previous missions. Examples are USA 276, the failed Zuma launch, and now USA 290, all launches from the past 1.5 years.

I like it: just when we thought things were getting perhaps a tad predictable, we are suddenly treated to a number of surprises, resulting in new stuff to ponder and analyse.

Tuesday, 5 February 2019

Doppler curves

The screenshot above is from a new software program I wrote, Doppler 1.0. As the name already suggests, it calculates the Doppler shift of a radio signal from a satellite TLE and downlink frequency for a given receiving station.

It is a Windows program (64-bits) written in the .NET framework and can be downloaded through my website here.