Meeting other satellite observers

Yesterday I travelled to Belgium to meet some other satellite observers out of the BWGS at the home of Bram Dorreman. The meeting was as well a BWGS meeting, a birthday meeting for Bram Dorreman, and a meeting to celebrate his 40th anniversary as a satellite observer.

Leo picked me up by car at Vleuten and we then continued to fetch Wim and a Belgian lady Marieke. Other joining at Bram's house were Tristan and Kurt. The meeting was very pleasant and informal, we were cared for very well in terms of drinks and food by Bram and his wife. For me, this was the first time I met other satellite observers except of Bram.

Wim brought some bulletins out of the "old box" with him. Kurt demonstrated the latest development of his internet PPAS database. Bram brought us back to the early days, by demonstrating the 'ancient' and time consuming graphic technique for predicting satellite passes of yesteryear. Ah, so much has changed...

It was a fun meeting.

The weather is very bad here the past week. Heavy rain showers and thick cloud cover.

Yesterdays Lacrosse 3 data

Russell Eberst reported data for Lacrosse 3 (97-064A) from last night as well, from a later pass. Our results quite agree:


STA___XTRK___deltaT___Perr

4353___0.04___-0.83___0.450
4353___0.02___-0.74___0.416
2420___0.02___-0.86___0.448

(STA = station, with 2420 being Russell; XTRK = cross-track error in degrees; deltaT = timing error in seconds, with negative meaning 'early'; Perr = positional error in degrees)

Relative to elset 06125.89779354, the satellite was some 0.8 seconds early.

Lacrosses and IGS 1B, and veil clouds

Summer has arrived: it is very sunny the past week, and I finally can leave my jacket at home and walk about in shorts and shirt, even observe in a T-shirt.

Nevertheless, sky conditions are not optimal. There is a thin veil in the skies, which in an urban environment like Leiden (and with moonlight now entering as well) is deadly to photographic observations. This was shown again last night: sat passes that were visible with the naked eye, drowned in the background fog on the photographic image. So I have seen Lacrosse 2, Lacrosse 3 and IGS 1B, but can only present positions for Lacrosse 3 as the other images did not yield measurable trails. The result on Lacrosse 3 was obtained in strong twilight before the thin veil clouds arrived. The image too is fogged, by twilight, but did yield a measurable trail and enough stars so I measured it and reported it.

USA 129 under very bad conditions

Just when I was about to start my observing activities in late dusk yesterday evening, a thin motled cloud cover came in.

Much to my surprise, I did manage to get some results on USA 129 (96-072A) . The trail is visible through the cloud cover. Below a (reduced quality) shot of the Astrorecord screen: negative for clarity, and some image contrast enhancement has been performed before loading the image into Astrorecord.

(click image for larger picure)

As can be seen, not quite an ideal catch! Normally I would not have reported data from such a marginal cloud-interfered trail. Yet in this case I did do because I hoped they migth be of help to analysts and Bjorn Gimle after his post here.

IGS 1B, bad luck with the KH's

Managed to get 2 images (4 positions) on IGS 1B yesterday evening. It was 3s early and clearly off in cross-track relative to elset 06115.87140454.

Had bad luck with the Keyholes. I missed a pass of USA 129 as the sky was obscured by an untimely pach of clouds. I did see USA 186 with the naked eye, but lost the image, because an error occurred while the camera was writing the data to the memory card.

Lacrosse 3 & Lacrosse 5 rocket, plus IGS 1B

After 20 days of forced non-activity, I managed to obtain some data again last night. Weather conditions were instable. It had been clouded much of the day, but cleared around dusk. Yet large fields of cumulus would come and go. I missed passes of Keyholes USA 129 and 186 due to this, and one of two passes of Lacrosse 3.

I did catch Lacrosse 3 during another pass, although Murphy almost struck again. The battery of the camera turned out to be near-empty, so it quit after the first image.

Later that night I also managed to get two pictures on IGS 1B (during the same pass) and a picture of the Lacrosse 5 rocket. In all, a nice set of data

IGS 1B crossing the Big Dipper amidst flying clouds

Visit Bram Dorreman

Today noted satellite observer Bram Dorreman, chair of the BWGS, payed me a visit. It was good to meet one of the frequent names from SeeSat list in real. For several hours, we talked about observing activities, astronomy and a few personal things. Bram showed a bit of the kind of observational data he collects, and I demonstrated the basics of my photographic technique of positional measurements.

Keyhole Flare Galore!

(click photo for full size image)

Yesterday evening was a fine clear evening again, with several interesting passes. I got treated with a nice set of Keyhole flares.

Most spectacular was USA 186 (2005-042A, #28888). I saw it and photographed it while it was producing two short brilliant flares of mag. -1.5 within 10 seconds while passing just below the tail of the Big Dipper. See the photograph above (30:17:46.8 should read 20:17:46.8, sorry for that typoe).

Next was another Keyhole, USA 129 (1996-072A, #24680), which produced a slow long flare up to mag. +0.5 in the N-NW at 21:11:10 +/- 5s UTC.

I got two good positions on USA 186, and one on USA129. In addition, I got two positions on the Japanese IGS 1B. With the latter I was lucky, as an untimely very local patch of clouds almost threatened to obscure it (see photograph below). It was very bright again at mag +1.5, while coming out of eclipse.

The points on both USA 186 and USA 129 agree very well in delta T and cross-track with the latest elsets for these satellites; however the points on IGS 1B are clearly off (0.1 degree) in cross-track compared to elset 06096.85488870 and I believe this is a true deviation, not a measurement error. These points are also some 2 seconds early.

IGS 1B

A late report on yesterday evening, due to circumstances.

Good clear sky again. First tried to cover the passes of USA 186 and USA 129. Both were too faint this time however. USA 129 nevertheless made one short bright flash (mag. 0) at 21:17:32 UTC.

Over the past two days, other observers (e.g. Pierre, Bruce) too commented on the irregular brightness behaviour of 2005-042A (USA 186), just as I did in my previous post and report on my April 4th observation.

Yesterday I did catch IGS 1B (2003-009B), the Japanese radar Intelligence Gathering Satellite. It starts to slowly get higher in the sky during passes, and hence slowly into view. I viewed and photographed it as it emerged out of eclipse just above the roof of the opposite building. It was very bright, mag.+1.5 and brightening. On the photograph, the trail ends behind the roof, so hence I could only measure the startpoint. the trail is clear and crisp on the image, and the resulting point is almost exactly 1s early with regard to elset 06093.83849704.

Two Keyholes

Yesterday evening I spotted two Keyholes, an old one and a new one: USA 129 (96-072A, #24680) and USA 186 (05-042A, #28888).

USA 186 was the first, and I saw it emerging from eclipse at 40 degrees altitude under the tail of the Big Dipper at 20:13 UTC. It was very irregular in brightness and made at least two flashes, the brightest of which was about mag. +1 at 20:13:05 +/- 3 sec UTC. I caught only a very faint marginal trail on the photograph,marginall also afteer some digital image enhancement. The endpoint was undeterminable, the startpoint I hope is indeed the startpoint...

Half an hour later USA 129 made a zenith pass around 20:47 UTC. It was too faint to be either seen or photographed in the actual zenith (20:46:40 UTC) but clearly showed up a minute later, well past the zenith. Good trail on the image, no problems measuring it.

Nice bright USA 129 pass captured

Beautiful clear sky this first April evening. USA 129 made a nice bright zenith pass, easily visible by the naked eye at mag. +2.5. I obtained 3 images, hence 6 points. The trail on the 3rd image is faint, so the last two points should be used with care.

4 out of 6 points are about 3.4 to 3.5 seconds late with respect to Mike's elset 06088.79862438, and clearly off cross-track again by some 0.10 to 0.15 degrees. Lutz Schindler reports similar results from the same pass.

USA 129 too faint this time

I had clear skies again this evening. The only potentially interesting pass though was that of USA 129 at 20:23 UTC.

I did see it visually, with the naked eye, as it crossed the Big Dipper: it was very faint though. Magnitude +4 I guess. There is a hint of a trail on the photograph, but nothing measurable alas.

He's back! USA 129 and Solar Eclipse

Bjorn Gimle recovered the keyhole satellite USA 129 (96-072A, #24680) on the 23rd when it came out of its winter dark period. Following this, it was observed by Lutz Schindler, Alberto Rango and yesterday evening finally by me.

I obtained two points with one very lucky picture. It was obtained amidst flying cloud cover: the one moment the sky was clear, 2 minutes later covered, then clear again etc..... The Big Dipper cleared only a minute before USA 129 would cross it! A minute after the passage it was clouded over again...! Only part of the resulting photographic image was not clouded, but that part yielded well enough stars for a good astrometric solution (I measured 100 stars). So, a lucky shot!

Could see the satellite by the naked eye easily at about mag. +2.5

These two points are almost exactly on time (both delta T -0.06s) with regard to Mike's elset 06085.80344161. The cross-track devation is however 0.17 resp 0.19 degrees (a factor 10 larger than usual, usual is 0.01 to 0.03).

I believe this is a real deviation value, not a measurement inaccuracy. The trail on the image was not very bright, but crisp.

So clearly, the updated orbit still needs some fine tuning.

Screenshot from Astrometrica showing extend of cloud cover on image. Green dots are measured reference stars, blue dots are start and end of satellite trail

Detail of USA 129 trail crossing Big Dipper (click for larger image)

Today around noon, there was a partial solar eclipse visible from my country. Much of the country had cloud cover and we started cloudy here too, but around the eclipse we got clear skies here in the coastal area. Inbetween several appointmeents I managed to snap a few pictures. Below is a compilation.

Lacrosse 4 Flare and missing Lacrosse 5

Conditions were poor this evening: haze due to very thin high altitude clouds lowered the limiting magnitude considerably. Still, some work could be done. And I was rewarded for the effort with observing and imaging a nice short-duration magnitude 0 flare by Lacrosse 4 (2000-047A, #26473). The image above shows the flare: the start of the trail coincides within a second or so with peak brightness, and the satellite then can be seen fading rapidly. Stars visible are in Leo.

Only the bright start of the trail was measurable and hence yielded one point. It is 0.3 seconds early with regard to Mike's 9 day old elset 06072.38962997. It corresponds quite well in delta T to the series of positions on 2000-047A obtained by Scott Campbell 20 hours earlier (delta T also -0.3 sec). Both Scott and mine are however a few tenths of a second different in delta T from a position reported by Russell Eberst, while a position Lutz Schindler reported only minutes after my observation is different by as much as 2 seconds in delta T. Which shows the human factor in this work.

That became evident in another way this evening too. I tried to observe Lacrosse 5 during its 19:30 UTC pass and failed to see it. This while Philip Masding from the UK and Lutz Schindler from Germany did see it only minutes before and after my attempt! Maybe it were the observing conditions, although I really would have expected to see Lacrosse 5 at its usual brightness of mag. +2, the more since I was able to see Lacrosse 4 at a similar brightness (before it flared) 20 minutes later.

Update: Pierre Neirinck from France reports he initially couldn't see it either on that pass, eventually picking it up rather late at 19:33 UTC. So he believes Lacrosse 5 did its "disapparance trick" again between the observations of Philip and Lutz.

Clear skies, nice Lacrosse 5 pass

After a few grey days, this monday turned into a very clear day. Bright blue skies in the daytime, good dark sky in th evning. I had only one good pass this evening, but a nice one: Lacrosse 5 (2005- 016A, #28646), one of my regular targets lately, made a near-zenith pass at 19:38 UTC.

Lacrosse 5 was bright and steady, appearing in the west-northwest, crossing over Cassiopeia and climbing towards the zenith and Ursa Major, at magnitude +2.0 to +1.5. No "disappearance tricks" this time.

I obtained a series of 3 images during this pas, hence 3 trails to measure and 6 positions in total. Relative to Mike McCants' elset 06074.84503776, I get the following residues:

xtrk dltaT dlpos
(deg) (sec) (deg)
0.02 0.24 0.086
0.00 0.31 0.114
0.01 0.22 0.120
0.02 0.18 0.105
0.01 0.02 0.013*
0.01 -0.08 0.045*

The last two (marked by an asterisk) deviate from the rest of the set by some 0.2 seconds in delta T. This means I might have been a tad slow in pressing the shutter release button for the last image.

Playing hide & seek with Lacrosse 5

Got a nice bunch of data on Lacrosse 5 (2005-016A, #28646) last evening. I observed two passes (19:08 and 20:50 UTC) , under poor conditions (moonlight, veil of very thin high altitude clouds with more solid patches in it). Nevertheless obtained some good trails: 3 out of 4 photographs yielded useful points (6 points reported in total, 5 of which are consistent).

Observations on March 11 & 12 had suggested to me that Lacrosse 5's "disappearance trick" might occur when it reached 64-65% illumination. If that would be correct it should do the trick again at about 19:09:30 UTC. In fact, it did at 19:09:41 +/- 3 s UTC, the satellite having reached 65% illumination at 19:09:39 UTC. This is very intrestinng: what is happening at 65% illumination thatt could cause this behavour?

At the next pass, I observed it being bright (+1.5, brighter than the previous pass when it was +2.0 to +2.5), at illuminatons between 68% and 70%. So wat ver happens it to 'dsappear"at 65% illumination, the effect is gone again by 68% illumination.

An attempt to also capture Lacrosse 2 failed as a thick patch of clouds occupied the part of the sky where it would pass.

Lacrosse 5 disappearance trick & timing problem gone?

I observed Lacrosse 5 doing its disappearance trick this evening. I think this explains my non-observation of March 6th in combination with Peter Wakelin seeing it easily only minutes before.

Saw it making a nice pass here around 19:11-19:15 UTC (obtained two good trail photographs during this pass), easily visible at mag. +1.5 to +1.0 or so. Just after the last of my two exposures ended (19:14:51 UTC), and well before it should get into eclipse, it suddenly disappeared from naked eye view, within maybe 3-5 seconds so very fast. This was at about 19:15:00-19:15:10 UTC or so.

I think this might happened at March 6th as well, just before I started to look for it.

I obtained two pictures during this pass, hence 4 points. One point (point two of photograph 1) was clearly anomalous (delta T +0.35), the other three are very consistent both internally and with Mike Mccant's latest elset for Lacrosse 5. The -0.3s delta T deviation of the previous week (see the previous post) has gone, even though I did not make an extra time correction!

Pierre Neirinck noted that Lutz Schindler, who also used the DCF77 time signals, had a similar time deviation last week. So I am now starting to believe that the problem was not with the camera at all: but with the Frankfurt time signals!

Oh, how I love Japanese electronics... (timing error issues)

Yep, it seems have a ~0.3 second timing devation again against other stations. Here's two messages I sent out in our tracking network today, summing up the issue:

-----
Hmmm,

I am starting to worry again. Since resuming my observational activities here at the new site, I seem to be some 0.25-0.3 second off in timing again. E.g. these two sets:

Lacrosse 5 Rk
STA AZ EL ASP XTRK deltaT Perr
( 1) 2420 78.35 66.69 108.86 0.00 -0.06 0.035 <-- Russell, 5 Mar
( 2) 2420 106.00 72.99 104.58 0.00 -0.06 0.041 <-- Russell, 5 Mar
( 3) 4353 324.85 79.48 80.67 0.02 -0.29 0.207 <-- me, 6 Mar
( 4) 4353 5.83 84.79 87.43 0.01 -0.33 0.237 <-- me, 6 Mar

Lacrosse 5:

STA AZ EL ASP XTRK deltaT Perr
( 1) 2701 231.94 31.12 39.72 0.01 -0.00 0.012 Mar 03
( 2) 2701 235.93 49.68 54.66 0.00 -0.02 0.008 Mar 03
( 3) 2701 236.19 50.53 55.39 0.00 0.00 0.003 Mar 03
( 4) 6226 325.33 24.24 96.83 0.00 -0.01 0.004 Mar 04
( 5) 6226 327.32 24.03 98.43 0.00 -0.02 0.006
( 6) 6226 328.97 23.82 99.76 0.01 0.01 0.008
( 7) 6226 333.11 23.20 103.11 0.02 0.04 0.017
( 8) 2018 165.10 15.25 59.66 0.00 -0.02 0.006
( 9) 2018 147.53 20.13 74.61 0.01 -0.05 0.016
(10) 2018 136.04 21.67 84.19 0.00 -0.06 0.018
(11) 2018 132.70 21.89 86.95 0.01 -0.06 0.019
(12) 2018 120.60 21.84 96.93 0.01 -0.02 0.008
(13) 710 147.36 37.57 83.08 0.01 -0.36 0.141
(14) 2018 98.36 18.25 115.52 0.00 -0.04 0.009
(15) 4353 242.78 47.55 52.67 0.01 -0.28 0.102 <-- me, Mar 04
(16) 4353 243.07 51.50 55.99 0.00 -0.30 0.119 <-- me, Mar 04

I did not alter anything in my camera settings this time, as far as I am aware of. I will re-check the GPS measurement of my new location, although I doubt a small error in that would lead to a 0.3s time difference...

- Marco :-/
-----

I just did a new GPS measurement on the courtyard. Got a good fix, and it yields the same coordinates with differences only in the second decimal of the arcseconds. So no problem there it seems.

Also checked the DCF77 radio-controled clock I use. It seems to be okay when I check it against my computer clock, which is synchronized each 5 minutes by an NSTP server.

So it must be the camera again, or the person pushing the camera button (me). Interestingly, it is again an ~0.3 second error, just as the last time such a deviation popped up, half a year ago. Oh, how I love Japanese electronics....

I realized I *did* alter my camera settings shortly in December, while taking night-time images of snow in Delft. But I changed them back to the old settings again afterwards, as far as I am aware of. Again: oh, how I love Japanese electronics... From now on I'll refrain from doing anything to the manual settings again.

Well, I guess I have to work with another empirical 0.3 seconds correction again from now on. By making such a correction to the datasets I reported the past two weeks, my data come quite in line with the other data again.

- Marco
-----

A no-show of Lacrosse 5, and timings off again?

Quicksat predicted two good near-zenith passes this evening, of both the Lacrosse 5 Rocket stage (2005-016B, #28647) and the payload itself, Lacrosse 5 (2005-016A, #28646).

The rocket stage indeed made a fine pass: it was easily visible at magnitude ~ +2 with the naked eye, being somewhat irregular in brightness. The trail shows up well on the image with no dificulty in the measurements. It was about 0.3 seconds early according to my data: as my latest Lacrosse 5 data obtaineed a few nights ago were some 0.25 seconds early too, I start to worry again...

The payload, Lacrosse 5 itself, made a no-show an hour later. Predicted to be mag. +2.1 it should have been easily visible: but I failed to see it with the naked eye and there is no trace of it on the obtained image too.

Flaring Lacrosse 5

This image was obtained by me this evening and shows Lacrosse 5 (2005-016A, #28646) while flaring. Here, it goes from about mag. +1.0 to +0.5. It reached peak brightness of about mag. 0 some 5 seconds after the end of this exposure, short before shadow entry.

The trail is well defined, so no trouble measuring it. A good set of data, no doubt. Useful data, as it seems Lacrosse 5 has just manouvred (see posts by Scott Campbell and Ted Molczan on the SeeSat-list here and here) and its brightness behaviour is odd the past few days (see messages here and here).