Manoeuvring KeyHoles and the flashing Iridium 33 wreckage

July 2010 so far yielded a nice series of clear evenings, due to very warm, sunny weather (in most cases allowing observations in shorts and shirt). I observed on July 3, 4, 6, 12, 15, 16, 17 18, 19 and 22.

Two manoeuvring KeyHoles

Prime targets this month were the KH-12 KeyHoles USA 186 (05-042A) and USA 161 (01-044A). These both manoeuvred on the 14th of July, giving us observers a nice task of recovery and renewed tracking.

The manoeuvre of USA 186 (05-042A) was first noted by Pierre Neirinck in France. After some other observers missed it, he observed it being very late, but initially lost his reference points. Ted Molczan next created a number of search orbits, based on different presumed manoeuvre times. Next Alberto Rango and me again recovered the satellite (Alberto first while I still had daytime, then me on the next orbit, in deep twilight), in an orbit very close to one of Ted's search orbits.

Using pre-manoeuvre and post-manoevre orbits calculated by Ted Molczan from our observations, the manoeuvre occurred on July 14th at the ascending equator crossing at about 15:00 UTC, over Indonesia.

Next it turned out that another KH-12 Keyhole, USA 161 (01-044A) had also manoeuvred early on the 14th. Again, Pierre noted it first, observing it 12 minutes late on July 17th. Next Ted and a number of other observers joined the recovery (including me at some point). Using pre- and post-manoeuvre orbits calculated by Ted and Mike from our observations, the manoeuvre ocurred at the ascending equator crossing near 00:20 UTC, July 14th, near Hawaii.


The flashing behaviour of the Iridium 33 wreckage

On 10 February 2009, the American Iridium 33 (97-051C) telephone communication satellite and a defunct Russian satellite, Kosmos 2251, collided in space. A large number of debris pieces were spread over Low Earth Orbit (see here), and the main wreckages of the two objects kept orbiting, now wildly out of control.

The Iridium 33 wreckage (97-051C) made some fine passes last month, displaying the same kind of flashing behaviour due to tumbling that I also observed shortly after the collision in 2009 (see here, here and here). Some of these flashes are easy naked eye flashes, reaching mag. +0. The object interchanges bright flashes like these with (more numerous) fainter flashes in the +4 range.

I targetted the satellite wreckage several times this month to determine the flashing behaviour. In March 2009, it showed a period of 4.7 seconds. Analayses of the imagery of the past few nights, shows this has changed to about 3.1 seconds. Below is one of several images, taken on July 16th, showing a series of fainter and brighter flares:

click image to enlarge

Below are graphic representations of the flare positions (yellow dots) observed on consecutive nights (resp 16-17, 17-18, 18-19 and 22-23 July 2010). Please note: only flares happening during photographic exposures are shown here. There were more flares, but these happened while the camera wasn't open:

click maps to enlarge

(maps made using Heavensat)

An unusual flare was captured on July 17-18, consisting of a triple flare with flares within 0.5 seconds:

click image to enlarge

Other objects besides the KH-12 Keyholes USA 161 and USA 186, and the Iridium 33 wreckage observed last 3 weeks include:

- the geostationary objects Milstar 5, Mentor 2 and Mentor 4 (USA 202);
- the HEO objects USA 184, the USA 40 rk;
- the LEO objects Progress-M 04M, MSX, Lacrosse 5, the Lacrosse 5r, IGS 1B, the IGS 5r, USA 32, the NOSS 3-3 duo and the USA 144 decoy,;
- plus a large number of GEO and LEO strays.

I have yet to analyse the USA 144 decoy (99-028C) data from July 20 for a new tumble period determination.

March 21 Iridium 33 flashes

Like yesterday and 4 days ago, I captured the Iridium 33 wreckage (97-051C) flashing again in a very regular pattern. Like the days before, the flash period was 4.66 seconds:

photo 1:

19:39:02.51
19:39:07.17
19:39:11.85

Photo 2:

19:39:44.46
19:39:49.13

Images with the flashes indicated by arrows below:

(click images to enlarge)

More flashing Iridium 33 wreckage, ISS, USA 200 and other high objects

As I wrote in my previous post with the image of USA 129 flaring, yesterday evening I hauled a rich batch of objects.

It started in twilight with a nice pass of the International Space Station (ISS). The image below shows it rising through Orion:

(click image to enlarge)

Next I photographed passes of Lacrosse 3 (97-064A) and the NOSS 3-4 rocket (07-027B).

The wreckage of Iridium 33 (97-051C) was observed flashing again. Two photographs yielded five flashes, and like 3 days ago they fit a flash periodicity of 4.6 to 4.7 seconds. The timings were derived by measuring the flash positions astrometrically, and fitting the obtained positions to the most recent Iridium 33 tle. Here are the two images, with the flashes indicated:

(click images to enlarge)

I also targeted some HEO (High Earth Orbit) objects again, this time experimenting with different camera settings. USA 200 (08-010A) was captured again, this time somewhat better than 3 days ago:

(click image to enlarge)

I combined 4 of the images into an animated GIF, showing the movement of the sky and the satellite over a 1 minute period:



On the same image series I captured a piece of debris, USA 144 debris (99-028C), as a stray. In addition, I imaged another object in a Molniya orbit, USA 179 (04-034A) and the USA 198 rocket (07-060B) this evening.

More flashes from the Iridium 33 wreckage

Yesterday evening, after observing the exciting ISS-Shuttle duo pass (see previous post), I tried to observe flashes from the Iridium 33 wreckage (97-051C) again. Simone had provided some experimental predictions and asked for verification.

The Iridium 33 wreckage did flare: two very bright flashes (both around mag. -1) seen naked eye, and two fainter ones (+4?) found on a photograph. They were off from the experimental predictions, but still cool!

The two -1 naked eye flashed were observed at 17 March, 20:06:56 ± 1s and 20:07:02 ± 5sUTC. The two photographic fainter flashes/glints occurred at 20:07:15.7 and 20:07:20.4 UTC. The time between the latter two is 4.7 seconds, and the first two (the naked eye ones) within their timing uncertainties fit a similar 4.7 second period.

The image with the two faint photographic flashes is below:

(click image to enlarge)

Iridium 33 wreckage photographed, with +4 glint

This evening was quite clear, and I decided to employ my new Canon EF 100/2.8 USM Macro lens to image a pass of the Iridium 33 main wreckage (97-051C). This lens has a bigger aperture than the EF 50/2.5 Marco I normally use, and hence is better for faint objects.

I was lucky and not only captured the very faint, irregular trail of the Iridium 33 wreckage: but also a short glint to mag. +4 at about 19:29:51 UTC (15 March), which I also observed with the naked eye.

The image is below. The inset shows the short glint, close to the end of the trail.

(click image to enlarge)

Iridium 33 and Kosmos 2251 wreckages observed

I visually observed the main wrecks of both Iridium 33 and Kosmos 2251 with the Meade ETX-70 (7 cm F5 refractor) this evening.

The Iridium 33 wreckage (24946, 97-051C) was easy to see and notably irregular in brightness, with many short flashes (several per second, with a brighter one approximately each second. This is an estimate: I did not time them). I observed it as it passed close to Pollux near 19:55:10 UTC (11 March). At its brightest it might have been +6 or +6.5. I did not observe the kind of bright flares as reported by Simone from Italy yesterday.

The Kosmos 2251 wreckage (22675, 93-036A) was much fainter, about +8 at its brightest as it passed close to alpha Uma at 20:11:30 UTC. It too was irregular, but its brightness variation seemed slightly slower than that of the Iridium 33 wreckage.

I also observed Lacrosse 3 in twilight and got 6 positions on it.

Aftermath of a space collision

Over 200 fragments of the Feb 10th collision between Kosmos 2251 and Iridium 33 have now been catalogued. Together, they form two impressive orbital planes filled with debris. The amount of Kosmos 2251 debris catalogued so far is about twice as large as that for Iridium 33 - it seems the Kosmos took the most serious blow.

Most of this debris will stay up for tens of years. About 6% of the Kosmos and 3% of the Iridium debris will decay in the next 2.7 years.

(click images to enlarge)

Feb 15 Texas-Nebraska daylight fireball was NOT satellite debris

Sightings of a bright daylight fireball seen from Texas to Nebraska on February 15th, have been widely reported in the press.

Contrary to what the FAA appears to be stating, this was definitely NOT debris from the collision between the Iridium 33 and Kosmos 2251 satellites on February 10th.

Video footage of the fireball (see below) shows that it moved clearly too fast for that, and was of too short duration, to be decaying satellite debris. In stead it is in line with a meteoritic fireball (asteroidal debris).

There is a clear difference in speed between the two categories: asteroidal/cometary debris moves at at least 11 km/s (and usually much faster) and typically lasts only a few seconds (as this fireball did). Satellite debris decaying moves at 7.5 to 8 km/s, so clearly slower, and typically has a much longer duration (due to the slower speed, but also because it enters at shallow angles). The video footage is incompatible with the appearance of decaying satellite debris. It is completely compatible with a meteoric fireball (asteroidal debris).

In Memoriam: Iridium 33

On 10 February 2009 at 16:56:00 UTC, Iridium 33 (97-051C) collided in orbit with the defunct Russian Kosmos 2251 satellite (93-036A). The collision occurred at 789 km altitude over the Siberian arctic, near 97.9 E, 72.5 N, with an orbital interception angle of 83.5 degrees. A cloud of rapidly spreading debris is now all that remains.

The collision occured at roughly the same altitude as the Chinese ASAT test on Fengyun 1C, and the resulting scenario for the debris cloud will be roughly similar to the latter event. An analysis of the Fengyun 1C debris field formation by Kelso can be read here.

On May 18th 2007, when Iridium 33 was still happy, alive and flaring, I shot the picture below:

(click image to enlarge)