Saturday 31 May 2014

[AGAIN UPDATED] USA 161 recovered (?) - and new ideas on changes in the KH system

CORRECTION 1 June 2014: The object I observed on May 31 turns out to be NOT the KH USA 161, but one of the IGS objects, IGS 8R (2013-002C) which we had 'lost' in the winter blackout, just like USA 161. Their orbital planes happen to be very close (with a few tenths of a degree in inclination and a few degrees in RAAN) at the moment.

This renders the whole story below incorrect and hence moot.

Luckily, Russell Eberst did observe the real USA 161 last night (June 1) and his observations fit with Leo's observations from May 23. More in a new post later. (this new post is up now here)

ML, 01/06/2014

- STOP PRESS - (31 May 2014, 19:00 UT). Okay. Cees Bassa thinks last night's object is not USA 161. See here. So read the story below with caution: the jury is still out on all this.

Although it all was/is a bit confusing, it appears USA 166 (2001-044A), the secondary East plane KH-11 Keyhole/CRYSTAL has finally been recovered. [UPDATE: OR PERHAPS NOT???]. It had not been positively observed since August 2013 and over the past half year had been hiding in the northern hemisphere winter blackout.

USA 161 ?. IGS 8R last night
(click image to enlarge)

Initially, Leo Barhorst in Almere (NL) appeared to have recovered it on May 23. However, his observed object now turns out to not have been USA 161 but an unidentified other object.

Last night it was clear, after a very rainy week. Suffering from a bout of insomnia, I took advantage of the clear skies by conducting a 30 minute plane search, from 01:00 UT to 01:31 UT (May 31), using the EF 2.0/35 mm wide angle lens.

Just as I was about to abandon the effort at 01:30 UT, a bright and fast satellite appeared with a direction that was correct for USA 161 in a generally correct area of the sky. I managed to capture it on two images, the second one of which is depicted above. The object was about mag +2 when I first visually picked it up, and then becoming brighter as it produced a slow flare to mag -2 near 01:30:27 UTC. The image above shows the slow flare moment. It moved fast, producing long trails on the 10 second images with the 35 mm wide angle, so it evidently was near perigee.

The object could not be matched to any known object, but did appear to move in the general secondary East orbital plane of the KH-11. Visually, the slow bright flare it showed was quite typical for the KH-11 too. So I was (and am) fairly certain it is USA 161. Or not? Problem was, my observation was difficult to match with Leo's observation a week earlier...

After I reported my observations, Ted Molczan next managed to positively match my object to a UNID observation by Björn Gimmle in Sweden on April 22 (so over a month earlier), proceeding to fit a very reasonable orbit. The suggestion of this all is, that Leo's object from May 23 was something else, as it does not fit well with the other observations.

The preliminary orbit calculated by Ted, which needs to be refined by further observations, suggests that USA 161 made a manoeuvre into a (compared to the orbit it was last seen in in 2013) slightly higher orbit of 411 x 425 km, with the orbital inclination changed by half a degree to 97.52 degrees. This is the same orbital inclination as USA 129 (1996-072A), the former secondary West plane KH which we have recently "lost" and which is suspected to have been de-orbitted, was orbiting in.

Like the drifting secondary West plane KH USA 186 (2005-042A, see several previous posts on this blog for a discussion), USA 161 is no longer sun-synchronous as a result of this manoeuvre, and hence in what appears to be a plane transfer orbit. Its distance in RAAN relative to the primary East plane KH-11, USA 224 (2011-002A), has increased and will keep increasing steadily until it makes a corrective manoeuvre (which I suspect will happen near June 12, see below).

The orbital constellation for May 31 looks like this:

(image removed)
click image to enlarge

The current situation is that the two new primary plane objects, USA 224 and USA 245, are keeping a more or less steady plane distance (in terms of RAAN) of 48.5 degrees. The two (older) secondary plane satellites, USA 186 and USA 161 however have now both lost sun-synchronicity, and are both drifting outwards with respect to the orbital planes of their corresponding primary plane satellite.

Frequent readers of this blog will remember that I initially expected USA 186 to manoeuvre back into a non-drifting sun-synchronous orbit when the RAAN difference with USA 245 was 10 degrees, early February. That didn't happen. As a secondary option, I then thought it would manoeuvre when the difference was 20 degrees, early May. That didn't happen either. I then was at a loss as to what "they" were planning to do with USA 186.

Now USA 161 has been recovered and turns out to have been manoeuvered into a drifting plane-changing orbit as well, just like USA 186, I am getting a possible idea again about what they might intend. Please note: I have been wrong twice before, so my track-record in these kind of predictions is not quite good :-p

Nevertheless: assuming that symmetry is what is being aimed for, I think both objects (USA 186 and USA 161) will manoeuvre back into a non-drifting, sun-synchronous orbit on or near June 10 to June 12.

On May 31 the RAAN difference between USA 245 (primary West) and USA 186 (drifting secondary West) was 23.0 degrees. The RAAN difference between USA 224 (primary East) and USA 161 (drifting secondary East) was 23.7 degrees. Their rate of drift is different: it is -0.11 degrees/day for USA 186 and +0.056 degrees/day for USA 161 (i.e., USA 186 is drifting twice as fast as USA 161). These differential drift rates mean that at some point in time, both satellites will reach a matching value in RAAN difference with their primary partner, at similar RAAN distances from their primary partner on the same day. This is depicted in the diagram below:

(image removed)
click diagram to enlarge

What can be seen from the diagram, is that this moment will occur in about 10-12 days from now, near June 10-12. On June 12, both satellites (USA 186 and USA 161) will reach a matching difference in RAAN of 23.3 degrees with their primary partners USA 245 and USA 224. Interestingly, this value is very close to 0.5 times the RAAN difference between the primary plane satellites, USA 224 and USA 245 which are 48.5 degrees apart in RAAN.

But please be advised: until now, I was wrong each time I thought I could make sense of it....

Wednesday 21 May 2014

USA 224 recovered, USA 186 still drifting, and looking for GPS IIF-6 20 minutes after launch

For various reasons, I am a bit late in keeping the reader up to what is happening to the KH-11 Keyhole/CRYSTAL system of optical reconnaissance satellites.

USA 186 (2005-042A), the secondary West plane KH-11, is still in a non sun-synchronous orbit and hence still drifting westwards. It is drifting for over half a year now. The difference in RAAN with USA 245, the primary West plane KH-11, is now over 20 degrees (21.8 degrees on May 19th). I am very curious as to when the drifting will stop, if ever. If it continues to drift for many weeks to come, we should contemplate whether perhaps the satellite is "dead", i.e. has lost manoeuverability. Problem is that NW European observers temporarily have lost visibility of the satellite, due to the current short nights. Tracking all comes down now to observers in the US and southern Europe.

Meanwhile, Russell Eberst in Scotland recovered USA 224 (2011-002A), the primary East plane KH-11, on May 9th. It is in a 260 x 1006 km orbit, which means it has slightly lowered its apogee. Before the winter blackout it was in a 258 x 1023 km orbit. The difference in RAAN with USA 245, the primary West plane KH-11, is now 48.5 degrees.

My own first observation of USA 224 was in the night of May 16-17. The image below shows it crossing through Corona borealis:

click image to enlarge

USA 161 (2001-044A), the secondary East plane KH-11, has still not emerged out of the winter blackout. Meanwhile, USA 129 (1996-072A) has gone missing since April 24 (see a previous post). There is a good chance it has been de-orbitted.

The current KH-11 constellation now looks like this (where the current orbital configuration of USA 161, in red, is uncertain, and USA 129 left out as it is no longer in its old orbit, and presumed de-orbitted):

click images to enlarge

In the early morning of May 17 (evening of May 16 in the US) and after a one day delay due to bad weather, a new GPS satellite, GPS II-F6 was launched from Cape Canaveral on a Delta IV rocket. It would pass over the Netherlands some 20 minutes after launch, still ascending and still attached to the 2nd stage. A number of search orbit had been published, but it looks like none of these was very accurate. I visually observed a bright UNID near 00:24:00 UT (May 17) moving just a few degrees to the 'right' of Altair on a trajectory parallel to the predicted ones but some 20 degrees cross-track in a southern direction. It was already descending over the roof when I picked it up, so I had no time to snap a picture alas. It did not match any known object so I am quite confident it was GPS II F-6 on its way to orbit. It was bright, about mag +1 to 0.

Monday 5 May 2014

KH-11 USA 129 is missing, USA 186 has still not manoeuvered

USA 129 (96-072A), the oldest of the KH-11 Keyhole/CRYSTAL/KENNAN optical reconnaisance satellites, has gone missing. The last observers to see it were me on April 22 and Russel Eberst on April 24. The photo below shows one of my images from April 22, with USA 129 passing near Castor and Pollux:

click image to enlarge

Somewhere between that date and May 1, when various observers noted it missing, it disappeared.

There is a possibility that it has been de-orbitted, as it is over 17.5 years old now and appears to be 'redundant' after the launch of USA 245 and plane move of USA 186 (see various earlier posts on this blog). On the other hand, we should be cautious and not too hasty: in the recent past (Feb 2014) we erroneously wrote USA 129's eulogy before, and it turned out it had just manoeuvered. Maybe it did this time as well. A dedicated plane watch I did in the evening of 3 May between 20:41 -21:05 UT yielded nothing.

Meanwhile, we had expected USA 186 (2005-042A) to manoeuvre early May. But up to yesterday May 4th it hasn't. Maybe it will do in the coming days. On May 1st the difference in RAAN with the main West plane KH, USA 245, was 19.8 degrees. At a drift rate of 0.11 degrees/day, it reached 20 degrees the past weekend. If it hasn't manoeuvered by the end of the coming week, it will become interesting. Unfortunately, it is disappearing in evening twilight for my location these days.

The image below shows USA 186 crossing Canis minor in deep evening twilight of May 2nd:

click image to enlarge

I imaged USA 245 (2013-043A), the current main West plane KH-11, last Saturday evening. In evening twilight, it was visible in the same camera field with FIA Radar 1 (2010-046A):

click image to enlarge

Sunday 4 May 2014

Imaging SWARM A and C

On 22 November 2013, ESA launched SWARM, a group of three futuristically looking scientific satellites (2013-007A, B and C) whose purpose is to map the strength, variation and structure of the Earth's magnetic field. Two of the three operate as a close pair in a similar orbital plane at 460 km altitude, the third at 530 km altitude will eventually orbit at an angle to the orbit of the other two (the orbital plane is currently still quite similar, but that will change over the coming years).

The satellites look like a cross between a techno aardvark and a vacuum cleaner:

image credit: ESA

On the night of May 3-4 I was taking images with the EF 2.0/35mm wide field  in an attempt to recover KH-11 USA 224. I did not recover USA 224 but my images showed a number of objects. Including a serendipitous catch of the SWARM A & C duo (2013-007B & C) crossing through Cygnus near 23:32:02 UTC.

click image to enlarge

The yellowish whisps in the image are clouds. SWARM C shows a bright flare near the start of its trail, then the brightness suddenly drops. SWARM A is faint.