Showing posts with label disappearance. Show all posts
Showing posts with label disappearance. Show all posts

Tuesday, 29 September 2009

The Lacrosse 5 "disappearance trick", and a BWGS meeting

On Saturday 26 September, a small number of BWGS satellite observers gathered at the house-boat of Leo Barhorst (Cospar 4253) at Almere. Present were, besides Leo Barhorst, BWGS president Bram Dorreman and me. A number of active BWGS observers alas could not come, hence the rather small group this time.

In the afternoon we exchanged some information, looked at some software, my collection of "black space program" mission, launch and unit patches, and Leo's collection of space-related postal stamps. I demonstrated how I astrometrically measure my satellite photographs for positions, and how I get brightness curves from an image.

The plan was to try some joint observations that evening (we could stay for the night at Leo's boat), and as it was sunny, we started preparations in the early evening. I took below photograph of Leo (seen frontal) and Bram (seen on the back) while they were making their preparations

click image to enlarge


The sky was not perfect (and would progressively deteriorate later that evening). From a small green a few tens of yards from Leo's boat, we started by watching Iridium 80 flare to mag. -3.5 close to epsilon Cyg in the eastern wingtip of Cygnus. I took the picture below, a 10-second exposure with the EF 100/2.8 Macro USM:

click image to enlarge


Immediately after that I rushed to re-aim the camera and capture the USA 144 decoy (99-028C) passing close to vega in the next minute. Predictions had put the track just west of Vega, and while Bram and Leo were watching there with binoculars I made a series of images. Strangely enough, Bram and leo did not pick it up: and the reason was, after a look at my photographs, that it passed east of Vega, not west! After a puzzled "huh?!?" it dawned upon me: the coordinates of my prediction software were still set on my Leiden locality!

Next up were the objects related to the recent launch of a Russian Meteor weather satellite. Bram and Leo indeed picked one up with their binoculars.

Shortly after that, we watched a nice pass of the SAR Lacrosse 5 (05-016A) with the naked eye. As we watched it, it did it's infamous "disappearance trick" again. It did so during an exposure, that captured the quick loss of brightness very well. It was the first time I imaged the phenomena with my Canon EOS 450 DSLR. It yielded this very nice diagram of the brightness variation (constructed from two images):

click image to enlarge


Note how quick the brightness drop is (it takes a mere 4 seconds) and how sharp the turnpoints in the diagram are.

Next up were passes of the KH-12 optical reconnaisance Keyhole USA 186 (05-042A), which briefly attained naked eye visibility and was of course photographed; and the NOSS 3-3 duo (05-004A & C) which were faintly visible to the naked eye as they crossed Cygnus, and yielded two very fine pictures, one of which is below:

click image to enlarge


Note the difference in brightness between the A and C components. (note: I mistakenly labelled the C component as 'B' in the image...)

After this, Leo and Bram observed the NOSS 3-3 rocket, which is a flasher. As the sky quality rapidly deteriorated, we called it quits after that and went inside to reduce the observational data.

It was nice to meet and observe together. Leo was a perfect host, and his cat Bankie kept my feet warm later that night.

Friday, 23 March 2007

A Lacrosse 5 Disappearance and Re-appearance

Yesterday evening at about 20:20 UTC I saw Lacrosse 5 (05-016A) do its "disappearance trick" again: this time however followed by a re-appearance about half a minute later.

Disappearance - I observed it being very bright (mag. 0) while ascending in the sky. Just when I was aiming my camera and about to trigger it, it disappeared in a few seconds time. Completely out of naked-eye range. This was at about 20:19:30 UTC, but this time can be somewhat off for reasons stated below.

Re-appearance - At 20:19:50 ± 5 seconds UTC (I am more certain of this time) it re-appeared again in a few seconds time, close to Capella, attaining a brightness of magnitude +1. From that moment on it was steady, gradually fading to mag. +2, crossing the Big Dipper and Draco untill I lost it behind the building.

The photograph below was taken within half a minute of it re-appearing again and shows that it was very bright again.

The observation was a bit chaotic because my neighbour started a chat with me and I was explaining my observations to her when Lacrosse 5 disappeared (hence why the time of that event did not entirely stuck in my memory). Moreover her cat tried to hug my tripod, so I gently had to scoop the animal away.

I also catched USA 129 (96-072A) and USA 186 (05-042A) last evening, but the trails were very faint and I could not get unambiguous positions from them.

I also have a late report to make on the evening of March 14th, when I gathered a total of 6 positions on Lacrosses 2 & 3.

(click image to enlarge)