The re-entry of IGS 1B on 26 July 2012

While I was away on holidays, the Japanese spy satellite IGS 1B (03-009B) that malfunctioned in March 2007, re-entered on 26 July 2012, over Polynesia.

The demise of this satellite was covered for over a year on this blog: as the satellite was weighing 1.2 tons and as it had an unknown amount of remnant fuel onboard, the uncontrolled reentry raised some questions and initial concerns (see coverage here).

The last amateur observations of the object were done by Mike Waterman (USA) on July 24th and Alain Figer (France) in evening twilight of July 25th. The last amateur orbital update by Ted Molczan based on a.o. Mike Waterman's observations, showed it to have descended to a 211 x 213 km orbit on July 24th and analysis of this dataset by this author using Alan Pickup's SatEvo suggests reentry on July 26, somewhere between approximately 9:50 and 10:50 UTC.

USSTRATCOM published a final TIP for IGS 1B on July 26th (that they did so for a classified object is unusual), placing re-entry at 26 July 2012, 09:52 +/- 2 min UTC, near 25 S, 186 E, which is near New Zealand. This is at the start of the reentry window given above and hence seems very reasonable even though the reentry coordinates are a verbatim copy (down to one decimal) of a pre-decay prediction issued at 7:34 UTC (only the uncertainty value has changed, from 2 hours to 2 minutes). No details on the orbital development in the final few revolutions were given.

The map below shows the USSTRATCOM determined reentry location and final trajectory. In principle, the re-entry could have been observed from the northern islands of New Zealand and potentially the Fiji-Tonga area. Note that only half a revolution later (about 30 minutes later) it would have passed over NW Europe and next west Africa.

click map to enlarge

The diagram below shows the orbital evolution in terms of apogee and perigee altitudes, from malfunction early 2007 to decay on 26 July 2012. It is based on orbital element sets calculated by Mike McCants and Ted Molczan from amateur observations, including mine:

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IGS 1B was a nice object to observe over the past years: it was bright, and it was interesting to follow its orbital evolution towards decay. The observation that remains the most vivid imprint in my memory is the one that resulted in the picture below: on 2 September 2011, while I was watching and photographing a pass in a slightly hazy sky, the satellite brightly flared to at least magnitude -8 if not more: the brightest satellite flare I have ever seen. I was jumping up and down and yelling "WOOOOOWWWW!!!!" when this happened. It resulted in this wonderful, eerie picture:

click image to enlarge

Update on IGS 1B (10 June 2012)

We are slowly getting closer to the uncontrolled re-entry of the 1.2 tons malfunctioned Japanese spy satellite IGS 1B (2003-009B). The satellite's orbit has by now dropped below 340 km altitude (see second diagram below, perigee/apogee values from orbits calculated by Mike McCants based on amateur observations including mine). That is well below the ISS orbital altitude (ISS is currently in a 392 x 406 km altitude orbit). A mere month ago it was still considerably higher, in a 366 x 368 km orbit: it lost over 25 km or orbital altitude since. It is dropping fast, and the rate increases (see diagram below).

Using the latest amateur orbital elements for the object and Alan Pickup's SatEvo software with the current 10.7 cm solar flux, re-entry is currently estimated to occur between mid-July and early August 2012.

An update on IGS 1B - a spy satellite about to reenter this summer

(updated reentry prediction at the end of this post)

Last year I wrote extensively about the malfunctioned Japanese spy satellite IGS 1B (2003-009B) which is about to reenter, uncontrolled, into the atmosphere soon. The above footage of the object was shot by me last April 13 and 14 and shows two passes over Leiden.

This radar satellite, launched to keep an eye on North-Korea in 2003, malfunctioned in March 2007, halfway though its mission. Since then, it has been steadily coming down (see diagrams below) in a way that clearly shows that the satellite operators do no longer have control over it.

Last year, I pointed to the fact that the 1.2 tons  satellite will reenter in 2012 (so this year), and likely still has some remnant fuel onboard. A subsequent assessment by high-end amateur satellite tracker Ted Molczan showed that this amount of fuel is limited - probably about 14 to 50 kg, an order of a magnitude less than the infamous case of USA 193 in 2008. This assessment is important, as an uncontrolled reentry of a satellite with fuel onboard is a potential hazard (reason why I wrote about it last year) and authorities were (and are) very quiet about it. Ted's assessment, the only public one to date, helped to put the potential risks involved into proper context.

In the autumn of 2011 we temporarily lost track of IGS 1B because it entered winter invisibility for the Northern hemisphere (where most of our observers are located). Early April this year, it emerged from this winter blackout again. I did a failed attempt to recover it on the evening of April 2, and then Russell Eberst successfully recovered it a day later on the evening of April 3. Since then, I observed it on April 13, 14 and 22 (see video footage above of the April 13 and 14 passes) and other amateurs have observed it as well.

Below is a 35-second integration of video frames from the April 13 video (upper right are tail stars of the Big Dipper):

click image to enlarge

Orbital evolution over the winter blackout

When IGS 1B was lost in the winter blackout in the autumn of 2011, it was in a 453 x 455 km orbit. Since then, it has come down considerably: as of 2012 May 1 it is in a 366 x 368 km orbit, almost 100 km lower (and now below the orbital altitude of the ISS). It is coming down at an increasingly fast speed, as the diagrams below show (based on orbital calculations by Mike McCants, derived from amateur observations which include my observations):

click diagrams to enlarge

 

Current Decay Prediction

Using Alan Pickup's SatEvo software with the current orbit and solar activity, I expect the reentry of IGS 1B to occur somewhere during a window that spans from June until August. As the orbit is evolving fast, it is pertinent that we keep close track of the object in order not to lose it (a few days old elements already results in several minutes uncertainty in pass time).