Friday 26 January 2007

More Lacrosse 5, and an old-timer (Kosmos 624) showing up

Having bouts of insomnia is not fun, as it is very tiring. yet the good thing about it, is that it promotes satellite observations.

I was awake very early in the morning yesterday (Jan 25th) after managing only a few hours of sleep. At 5:30 am local time I decided to make something good out of something bad, by checking whether there were any satellite passes to observe. It turned out Lacrosse 3 (97-064A, #25017) made a nice zenith pass, emerging out of eclipse just south of the Big Dipper. So I observed and imaged it.

It was a very dark and transparent, cold night (-0.7 C, the first night with true frost at Cospar 4353 this winter, ridiculously late). Lacrosse 3 was bright, magnitude +2, and I obtained 2 images (hence 4 positions).

As an unanticipated extra, there was a faint second trail on the first image. It was clearly shorter than the Lacrosse trail, so at first I was in some doubt whether it was a satellite at all and not for example a meteor.

I could subsequently positively ID it however as Kosmos 624 (73-104H, # 06992) an old 1973 Soviet Strela-1M communications satellite. Amazing as it "should" have been mag. +7 only (instead it was something like mag. +4, judging from the trail. I did not see it visually)!

The reason the trail was so short, is that its orbit is higher than that of my usual targets: it was at over 1500 km altitude at the time of observation. It must also be the smallest object I imaged so far, as its RCS is only 0.8 m^2.

In the evening I made a second observing run, imaging Lacrosse 5 (05-016A) and Lacrosse 4 (00-047A). Like the previous nights, Lacrosse 5 performed its "disappearance trick" again, this time at 17:23:23 UTC. Before that time is already was somewhat variable, alternating between mag. +1 and +2.5. The observation was done in a blue twilight sky. Upcoming cirrus and a nearby moon prevented me from observing a later second pass of the satellite.

(click images to enlarge)

Successful simultanious observations of Lacrosse 5 "disappearance"!

On January 22 and 24, Philip Masding in the UK and me in the Netherlands managed to observe and time two Lacrosse 5 (05-016A) "disappearances" simultaniously. Phil obtained some marvelous lightcurves showing the brightness behaviour of the satellite during these passes.

Interestingly, the clocked times of disappearance are similar for Phil's location in the UK near Manchester (53.4 N, 2.4 W) and for me in Leiden, the Netherlands (52.2 N, 4.5 E), 485 km to the East of Phil.

Table with 05-016A "disappearance events" on-line

For anyone interested in having a go at modelling the enigmatic "disappearance" events of Lacrosse 5 (05-016A): in addition to the list maintained by Philip Masding at his website, I have posted my own timings of such disappearance event over the past year at:

The list on that URL ( a link to it is in the right-hand sidebar of this blog too) will be updated whenever I time a new event of this type.

Wednesday 24 January 2007

Another Iridium flare, Lacrosse 4 and another Lacrosse 5 "disappearance"

This evening another Iridium flare was predicted for my location. Iridium 76 (98-048B, #25432) was predicted to flare to mag. -4.8 at 18:16:41.7 UTC at virtually the same sky location as yesterdays Iridium 03 flare.

The flare was very fine again. A field of clouds passing by added a dramatic touch to the scene, as can be seen in the photograph below.

(click image to enlarge)

A quarter of an hour earlier, I observed and photographed a fine pass of Lacrosse 4 (00-047A, #26473). It passed close to the Pleiades cluster again, making for a scenic picture (see below). I obtained two images, hence 4 points. Lacrosse 4 was some 0.35s late.

(click image to enlarge)

A minute after the Iridium 76 flare, I switched my attention to Lacrosse 5 (05-016A, #28646). It was bright as it climbed from Cygnus through Andromeda to Cassiopeia. Just before my camera opened for the first exposure, it however did its "disappearance trick" again, this time at 18:18:18 UTC (ugh, if you are nutty enough to believe in numerology (which I don't) that is a Devilish time to do trics for a clandestine sat....6+6+6:6+6+6:6+6+6 !).

Odds of a mag. -7.5 Iridium flare, and twice Lacrosse 5 its tricks

Another clear (and cold) evening, although clouds began to appear at 19h UTC. Positions were obtained on Lacrosse 5 (05-016A, #28646) and Lacrosse 4 (00-047A, #26473), as well as Iridium 03 (98-048A, #25431).

Highlight of the evening was a splendid magnitude -7.5 flare by Iridium 03 at an altitude of 44 degrees and azimuth 28 degrees (north-northeast) at 18:22:50.8 UTC.

(click image to enlarge)

The image above was shot from the street in front of the almshouse complex (it was just too low in the sky to be visible from the courtyard of the complex) with a 10.7s exposure between 18:22:47.1-18:22:57.8 UTC. The flare had a predicted brightness of mag. -7.5, and indeed must have been in that order. The center of the flare path was 4.8 km West of me (while the Iridium satellite was over Denmark, at 785 km altitude and a range of 1069 km north-northwest of me).

Chance had it that the people from Grimbergen observatory in Belgium (Philippe Mollet et al.) located 135.9 km south of my location, observed the same flare from the same Iridium. While I had the center of the flarepath at 4.8 km West of me at 18:22:50.8 UTC, they had the center of the flare path at 4.6 km East of them at 18:22:28.9 UTC. So the geometries were virtually the same (with a predicted brightness of mag. -7.7 for Grimbergen, versus -7.5 for me), they having the flare maximum 20.9s earlier in time than me. What a coincidence!

I observed one pass of Lacrosse 4 (two good images, yielding 4 positions), and two of Lacrosse 5 (3 images, half of the points dropped because of too faint trail ends, hence 3 positions).

Lacrosse 5 (05-016A, #28646) did its "disappearance trick"again at both passes. During the first pass it did it at 17:30:44 UTC, while the camera was open for its second exposure, resulting in the image below. The true end of the trail at the end of the exposure should be at the right of the star near the trail end: it is at the left in the image, as the satellite dropped below the imaging treshold in brightness before the end of the exposure. The drop was rather fast.

(click image to enlarge)

A few tens of seconds after it, I could see the satellite as a very faint object (mag. +4 to +4.5) with the naked eye (before the drop in brightness it had been +2). A third image exposed between 17:31:46.1-17:31:56.8 UTC shows a very faint trail after some image manipulation (see below)

(click image to enlarge)

Lacrosse 5 did the same trick again during a second pass. This time it disappeared some 5 seconds before my camera opened, at 19:13:15 UTC.

Monday 22 January 2007

Lacrosse 5 tricks again, and Lacrosse 4 cruising near the Pleiades

Another clear (and cold) evening. I observed the radar birds Lacrosse 5 (05-016A) and Lacrosse 4 (00-047A) within a minute of each other (making the imaging quite hectic, having to swap the camera to a different part of the sky within a few tens of seconds).

I obtained two images (hence 4 positions) on Lacrosse 4, the first one of which captured the sat cruising at a steady mag. +3 close to the Pleiades cluster (image below):

(click image to enlarge)

A minute earlier I had captured Lacrosse 5 in the act of doing its infamous "disappearance trick" again. The image below shows it fading rapidly, in fact the apparent trail end on the image predates the end of the exposure. Visually, I timed the disappearance at about 18:25:30 (+/- 2s) UTC.

(click image to enlarge)

I dropped the second point on Lacrosse 5 as it probably does not represent the position at the end of the exposure, but rather the point where it became too faint for the camera. The first points suggest it was perhaps some 0.15s late and on-track.

Lacrosse 4 was perhaps some 0.2s late (delta T's vary a bit between 0.05s and 0.30s) and somewhat off-track (about 0.05 degree).

Sunday 21 January 2007

Its flaring time again...! (updated)

Drifting fields of clouds made observing a gamble this evening. In between the cloud fields however, it was marvellously clear again.

I had the fortune to observe and photograph another very nice flare of Lacrosse 4 (00-047A, #26473), again just before eclipse entry. It briefly flared to mag. 0 at 19:29:41 +/- 2s UTC, near the Andromeda-Pegasus border. The decline in brightness after the flare was very rapid, unlike the rise to it, perhaps due to the eclipse entry (predicted for 19:29:53 UTC).

(click image to enlarge)

I lost the first pass of Lacrosse 5 (05-016A, #28646) at 17:35 UTC to an untimely pass of a field of clouds (3 minutes after the pass, it was completely clear again...). The same almost happened to the second pass at 19:19 UTC. I did capture it on one image through a hole in the cloud cover though (see below). In fact the second image shows it too, through the cloud cover...but is useless of course for position determinations.

(click image to enlarge)
note: times should read 19:18:36.1 -19:18:46.8 UTC

Update: Like yesterday, 00-047A was 0.8s late, 0.05 degree off-track.
05-016A was exactly on-time and on-track: it doesn't happen every day that you get such results:

STAT__YYday HH:MM:SS.sss___XTRK____deltaT___Perr
4353__07 21 19:18:36.100___0.00____0.00_____0.003
4353__07 21 19:18:46.800__-0.00____0.00_____0.005

Saturday 20 January 2007

A Lacrosse 4 flare, and a Lacrosse 5 "disappearance trick"

This evening was a very clear evening. The storms of the past days (there was another one last night, and there is yet another one predicted for tonight) have blown the atmosphere very transparent. It was a bit windy and chilly, but observing conditions were perfect otherwise.

(click image to enlarge)

Highlight of the evening was a fine short and bright magnitude +0.5 flare by Lacrosse 4 (00-047A, # 26473) at 18:53:00 +/- 1s UTC, just before it entered into eclipse in Taurus.

Earlier that evening, Lacrosse 5 (05-016A, #28646) did the opposite: it did its "disappearance trick" again at 18:31:27 +/- 2 s UTC, some 1.5 minutes before eclipse entry. The camera was open while it happened: the first of below two pictures, where it is already much fainter than before and disappears. The second picture below was taken a minute before the first, and shows just how bright Lacrosse 5 was at that time (about mag. +1.5).

After it disappeared, it did not re-appear visually (naked eye) or photographically.

Update: Lacrosse 4 (00-047A) was about 0.8s late relative to a two week old elset. Lacrosse 5 was on-time.
After image enhancement in Photoshop, the third image does show Lacrosse 5 as well, but barely. It must have been mag. +4 or fainter.
Bruce MacDonald from the UK reports he observed Lacrosse 5 "disappearing"as well on seesat.

(click images to enlarge)

Friday 19 January 2007

Storm over Cospar 4353

A Gale-force storm has been raging in our country yesterday, killing 6 people and bringing all train traffic to a halt. At 11:03 am the first roofing tiles came down here at Cospar 4353. The peak in wind-force was at about 7-8 pm. In Zeeland province, wind speeds of 133 km/h were recorded.

The closest distance to the center of the storm depression for Cospar 4353 was at about 15:30 CET (14:30 UTC), as can be deduced from the above barogram obtained by my courtyard weather-station.

The sky was clear during twilight, but this was also the peak of the storm. A roofing tile had already come down some 2.5 yards from where I normally put my tripod, so I did not dare to risk my head and camera to other plunging roofing tiles. Moreover, the tripod would have blown over I think.

Monday 15 January 2007

Again Lacrosse 5, and a comet observation in daylight!

A poor evening after a nice day. Alas, late in the afternoon and in the early evening cirrus moved in. This after it had been nice and clear blue skies earlier, allowing a rare view of a daylight comet!

At 14:35 local time (CET) during the clear part of the day, I managed (with difficulty, but certainty) to observe comet C/2006 P1 McNaught with the unaided naked eye in daylight, close to the sun! It was a tiny smudge at a 7-8 o' clock position relative to the sun. Not easy, but once located unmistakable. The sun was covered from direct vision.

Due to the cirrus that came in later today, Lacrosse 5 (05-016A) was the only one of three sats (Lacrosse 2, Lacrosse 5 and USA 193) I tried this evening that was captured. The first point on Lacrosse 5 might be a bit iffy, the second is good I think. delta T is similar to yesterday (+0.2s).

Shortly after this exposure, Lacrosse 5 "disappeared" again. This happened between 17:56:00 and 17:56:30 UTC (I did not see it disappear as I was handling the camera, but when I looked up again after triggering the 2nd image it was gone visually, and it is not visible on the 2nd image either).

Sunday 14 January 2007

Failed Lacrosse flare

Phillip Masding predicted a potential flare by Lacrosse 5 (05-016A, #28646) for my location for 17:06:59 UTC this evening. This was to be in late twilight, and at a favourable sky elevation of 70 degrees (almost in the zenith).

Streaks of cirrus occupied the sky at that time. About 1 minute before Lacrosse 5, I observed Lacrosse 2 (91-017A, #21147) pass through the zenith at a bright mag. +2. A minute later Lacrosse 5 however turned out to be very faint, mag. +3.5 or fainter. It did not flare, and the trail on the photographic image is very marginal. I only used one position of it, as the other one came out as an obvious anomaly.

Lacrosse 2 is visible in the same image, but in a streak of cirrus, and hence very marginal. I did not get usable positions on it.

During the next pass of Lacrosse 5, at 18:50 UTC and 48 degree maximum sky elevation due North, it was brighter (about mag. +2.5) . It easily registered on the photographic image (see below), and added two positions.

The three positions obtained on Lacrosse 5 in total suggest it was on-track, and about 0.2s late relative to a 4-day-old elset.

(click image to enlarge)

Thursday 11 January 2007

Lacrosse 5 flare, and comet C/2006 P1 McNaught

The weather persistently has been very bad since 1 January. Today was the first day I have seen a satellite again.

This evening I observed Lacrosse 5 (05-016A) in a clear sky and saw it briefly flare from mag. +2 to mag. +0.5 during about 2-3 seconds at 18:08:27 ± 5 s UTC.

But allas I have no positions to report. When the camera tried to write the first image to the CF card, a writing error occurred and the image data got corrupted. I had to restart the camera, made a mistake in the settings (forgot the 10 second self-timer), so lost a second imaging opportunity, and then the sat disappeared behind the roof.

Al this while it was very windy. An hour earlier, windforce shortly reached storm values.

Earlier this evening (from another location), during this stormy phase, I caught a glimpse of comet C/2006 P1 McNaught, in deep twilight a few degrees above the horizon. Not very spectacular under these conditions but at least I have seen it. I even could see a short tail by the naked eye.

Monday 1 January 2007

A good start of the new year!

The first evening of 2007 was very clear. Hopefully this sets the trend for 2007!

It was quite windy, and observations were done in twilight and with a near-full moon above the horizon. As a result, the images are quite fogged out.

Targets were Lacrosse 3 (97-064A, #25017) and the International Space Station (see image below)

97-064A did not show up well on the images: faint trails which almost drowned in the background fog. It was about mag. +3. I dropped one point from the second image obtained, as it was obviously in error. Hence 3 positions were left. 97-064A was some 0.5s late relative to a 3 day old elset.

ISS (98-067A) made a nice pass culminating at 40 degrees elevation. I picked it up low in the west, it was mag. -1 throughout the pass (I could not see its low eastern trajectory part though). Around culmination and after it it was a bit orange again. Positions were obtained for calibration purposes. Below is the first of the two images of ISS I took: it is still low in the West here:

(click image to enlarge)