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.

Saturday, 5 January 2019

Fireball seen over New Zealand during cricket match was the reentry of Kosmos 2430 (2007-049A)

image from Fox News broadcast

The image above is a still image from TV-footage shot during the January 5th 2019 cricket match of Sri Lanka against New Zealand at Mount Maunganui, New Zealand. The camera captured a bright, very slow, copiously fragmenting fireball that occurred during the match. Here is the actual footage:

From the video footage, the event had a duration of at last 1 minute, and likely longer. The event was widely seen and reported from New Zealand: more images and more noteworthy video footage, as well as descriptions, can be found in this news article from the New Zealand Herald.

From the footage it is clear that this is a space debris reentry: the event is too slow and of too long duration to be a meteoric fireball.

From a Sri Lankan tv-broadcast of the cricket match, which features a clock in the imagery, the time of the event can be established as 5 Jan 2018 at 07:58 UT (Sri Lanka has a time difference of 5:30 with GMT):

image from Lotus TV broadcast

From the time and location, the event can be identified as the reentry of Kosmos 2430 (2007-049A), a defunct Russian US-K Early Warning satellite launched in 2007. Time and location match well with a near perigee pass of this object over New Zealand. The map below shows its predicted position for 08:00 UT on Jan 5 (movement is from top to bottom):

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CSpOC at the time of writing (5 Jan 2019 14h UT) has a reentry TIP for 6:41 ± 4 m UT on its webportal Space-Track. This is 1h 47m, or one revolution, earlier than the New Zealand sightings.

Nevertheless, I am fully convinced that the event is Kosmos 2430 reentering - the match is too good, and the footage clearly suggests an artificial object reentering from earth orbit. So why the mismatch with the CSpOC TIP?

Kosmos 2430 was in a highly elliptical orbit with perigee over the southern hemisphere. In the diagram below, we see the apogee altitude (the blue line) quickly diminishing in the days before reentry, due to the drag experienced in perigee (diagram based on orbital tracking data from CSpOC):

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The perigee altitude already is very low, near 90-85 km altitude, for days before the reentry and changes minimally untill the actual moment of reentry. The difference between apogee and perigee altitude remains significant up to the last few revolutions, with apogee still at 1000 km only two revolutions before reentry.

This means that, unlike typical objects reentering, Kosmos 2430 only briefly dipped into the upper atmosphere during each orbital revolution, experiencing drag only during brief moments. This is the kind of situation where an object can survive multiple very low perigee passes, and predicting the actual moment of reentry (i.e. during which perigee pass reentry will happen) is difficult. Looking at the CSpOC TIP bulletins for January 5th, this is clear as well as the CSpOC predictions significantly shifted forward in time with the addition of data from each new orbital revolution.

The sightings from New Zealand strongly suggest Kosmos 2430 survived one orbital revolution longer compared to the current (final?) CSpOC TIP estimate.

Note that with such brief but deep dives (well below 100 km) into the upper atmosphere, it is possible that the satellite already developed a plasma tail one or two perigee passes before actual reentry. The copious fragmentation visible in the footage from New Zealand shows that this event, at 7:58 UT was the actual moment of atmospheric reentry and complete disintegration.