Thursday, 26 April 2012

April 20 Brazilian fireball was NOT the reentry of an Atlas Centaur r/b

A beautiful, slow, long duration, fragmenting fireball was filmed from Brazil in the evening of April 20 (20 April near 20-21h UT). Movies can be seen here and here.

Soon after the apparition, the question came up: meteoric fireball, or a reentry of "space junk"? Based on the visuals of the two movies available, I noted that it looked like a meteoric fireball, not a reentry.

Subsequently, a piece appeared in Universe Today, claiming it was a reentry: that of an Atlas Centaur rocket, #16102, 85-087B, which launched Intelsat 512 in 1985.

That conclusion is simply wrong however. According to USSTRATCOM the object in question decayed 18.5 hours earlier than the fireball, over the western Pacific at 1:23 UTC (20 April) near 18N, 161 E. It reentered nowhere near Brazil. It did pass over northern Brasil on its final pass an hour before reentry, but that would have been at 00:30 UTC, not 20-21 UTC. Moreover, even that pass would have been too much north to see it from the southern Brasilian location where it was filmed from: it would have passed below the horizon as seen from there.

And even if pieces would have survived longer (highly unlikely in this case), these could not have caused a fireball over Brasil 18.5 hours later: the orbital plane of the r/b was wrongly oriented for that. Around the time of the fireball, any surviving objects in the Centaur orbit would not pass over Brasil but much more north, over Mexico and the Caribean (see below. Note: the object was no longer in orbit at that time!).

So, the object that was filmed was most likely a piece of asteroidal debris, a very nice, very slow and very long duration meteor grazing through the upper atmosphere and breaking to pieces.

Friday, 6 April 2012

FIA Radar 2 (NROL-25) observed - with video

On the night of April 3/4, the NRO launched NROL-25, a new classified satellite. This satellite, FIA Radar 2 (USA 234) is the second of the FIA Radar satellites, and the third launch (assuming that the failed USA 193 was the first) in the Future Imagery Architecture (FIA) series. It received the SSC catalogue entry #38109, international Cospar launch code 2012-014A.

Like its earlier sistership FIA Radar 1, FIA Radar 2 is in an unusual retrograde orbit (proving that it is a radar satellite). Going from estimated search elements by Ted Molczan, Scott Tilley in the US Canada was the first to see the new object on April 4 some 5 hours after the launch. Following that, a.o. Björn Gimle in Sweden, Russell Eberst in Scotland, Alexander Repnoy in Russia and Kevin Fetter and Ted Molczan in Canada observed it.

I was clouded out on Wednesday 4 April, but yesterday evening (5 April) was clear and it was finally my turn: I could observe both evening passes, and film them. The above video provides a compilation of the obtained footage.

The first pass occurred in late twilight near 19:33 UTC , the second at 21:16 UTC (23:16 pm local time). A Near-full moon resulted in a quite light sky.  During the first pass, my GPS time inserter had some trouble maintaining the time signal (see "GPS Bad" message in first part of the footage above) and by coincidence my photo camera malfunctioned as well (due to a mistake with the wire release). Luckily, I had a second pass at 75 degree elevation 1.5 hours later, during which I could obtain a good set of positional data.

FIA Radar 2 was about mag. +4 and steady in brightness. Radio observers report a fading cycle in the radio signal, but visually the object is very steady.

I obtained some photographs as well, during the second pass of the evening. Below is a picture (Canon EOS 450D + EF 2.5/50mm Macro) shot while FIA Radar 2 crossed through the tail of the Big Dipper (Alcor & Mizar in top of the image). It is not the best of images due to the moonlight, but shows the satellite trail well in this 5-second exposure:

click image to enlarge

Over the comings days/weeks the new satellite will probably be actively manoeuvering, so it will be a nice object to keep track off!

Thursday, 5 April 2012

OT: a multistation filmed meteor from 27 March - some results on the trajectory

In the early morning of March 27, while waiting for a pass of ATV-3, I accidentally filmed a nice meteor from Leiden. As it turned out, the same meteor was also filmed by the meteor surveillance video of Martin Breukers in Hengelo. Hence, we have this approximately mag. -1.3 meteor multistation, allowing triangulation to determine the 3-dimensional atmospheric trajectory and orbit in the solar system. Martin used UFOanalyzer software to process the images and arrive at an atmospheric trajectory. I used my orbital spreadsheet Metorb85 to compute a heliocentric orbit for the meteor.

The movie above shows the meteor footage as obtained from Leiden and Hengelo, plus a 360-degree fly-by around the reconstructed atmospheric trajectory.

The meteor started at 51.745 N, 6.267 E, at 100.4 km altitude. It ended at 51.961 N, 6.707 E and 75.2 km altitude. It had an initial velocity of 27.8 km/s.

Above are two integrated frames images of the meteor, a still image showing the 3D trajectory, and images showing the orbit in the solar system. As the convergence angle between the trails as seen from both video stations was not particularly large, the resulting orbit has some inaccuracy. Nominal orbital element values are:

a = 1.87 AU,
q = 0.450 AU,
e = 0.759,
i = 10.47 deg,
omega = 285.84 deg,
node = 6.696 deg.

The geocentric radiant was near RA 198.20 deg, dec. +4.01 deg, Vgeo 25.67 km/s. The radiant position has some leeway due to the low convergence angle. Hengelo saw the meteor appear in Corona Borealis: Leiden in the Aquila-Sagitta-Delphinus border area.

The Nanosail UNID (10-062X) and Lacrosse 5 brightness variation

When NASA's experimental solar sail Nanosail-D was launched by a Minotaur IV rocket in 2010, it was not the only object this launch brought into space. A number of other, classified objects were part of the same launch.

Now Nanosail-D has decayed, four of these objects (RAX, OREOS, FASTSAT, FAST 1) are being tracked by amateur trackers. One additional object of the launch that is being tracked, however cannot be identified reliably with one of the payloads so far. It could be a payload, or a rocket part from the launch. Dubbed the 2010-062 UNID (10-062X) or "Nanosail UNID" by amateur trackers, it is an object near magnitude 4-5, stable in brightness.

The footage above (WATEC 902H + Canon EF 2.0/35mm lens) shows it passing through the tail of Uma (bright stars are epsilon Uma and delta Uma) on April 1st 2012.

I also filmed Lacrosse 5 (05-016A) that evening. The erratic brightness behaviour of this satellite has featured before on this observing blog. Using footage from the April 1st pass and LiMovie, I reconstructed the brightness curve below, showing a  flare at 20:09:14 UTC and a general quite irregular brightness behaviour with what looks like several small peaks. At 20:09:30 UTC, it appears to do it's typical "disappearance trick" again, dropping rapidly in brightness in just a few seconds of time (note: shadow entry was not before 20:12:00 UTC). The profile is very similar to profiles for Lacrosse 5 which Philip Masding previously obtained, also showing the "disappearing trick" being preceeded by a flare.

click diagram to enlarge

The video footage this curve is based on, is this footage (shot with a 12mm wide-angle lens):

More objects were observed the past few nights. Among them USA 129 (96-072A) and Lacrosse 4, while CCD imagery of Prowler (90-097E)  using the "remote" Rigel telescope of Winer observatory was obtained again as well.