Wednesday 28 January 2009

Observed the flying toolbag

This evening it was clear. Besides photographing the passes of Lacrosse 4 (00-047A) and the NOSS 3-1 duo (01-040A & C), I watched a nice ISS pass together with my neighbour and for the very first time also managed to see the ISS tool bag (98 067BL), the bag with tools lost in space by an astronaut during an ISS EVA in november 2008.

The latter observation was made with my Meade ETX-70 (7 cm refractor) at 13.5x magnification (field-of-view about 4 degrees) during a near-zenith pass at 18:03 UTC (27 Jan), when the object passed close to Algol.

It was faint (mag. +7 to +8) and very fast, zipping through the field of view being gone before you knew it. I had some impression of a slow brightness variation.

It was very nice to finally see it, after a few earlier failed attempts.

Video of the astronaut loosing the toolbag....

Tuesday 27 January 2009

My third Trojan asteroid

As the weather did not allow observations the past week, some news from my asteroid searches. Whenever I want something to do in the evening and it is clouded (so I can't observe satellites) and the TV is dull -which it usually is-, I turn to hunting for new uncatalogued asteroids in NEAT archive imagery.

Today's DOU MPEC 2009-B61 contains four of my new asteroid finds of last week. One of these, 2002 WG29, is a Jovian Trojan, my third Trojan discovery (the other two are 2001 SD355 and (203865) = 2002 WV27).

Jovian Trojans are asteroids that co-orbit with Jupiter in a 1:1 mean motion resonance, as they occupy the stable Lagrange points L4 and L5 in the Jupiter orbit. They are hence a quite special class of asteroids. Currently, some 2900 of these Trojans (including those with temporary designations) have been discovered. Their positions for late 2008 in the two Lagrange points at 60 degrees in front and behind of Jupiter are shown below:

Among the other discoveries of last week are two Hungaria asteroids. Hungaria asteroids are a special class as well: they occupy higher inclinations within 2.0 AU, a region in the main asteroid belt where at lower inclinations a stable orbit isn't possible due to perturbations by Mars. Hungaria's move in a 9:2 mean motion resonance with Jupiter and a 3:2 mean motion resonance with Mars. Hence, they quite stand out among the main belt asteroid population.

Below are two plots showing the positions in the solar system of the objects I discovered for coming February 1st. The new Trojan is the one currently just outside Jupiter's orbit in the top plot.

A full list of my asteroid discoveries can be found here.

(click images to enlarge)

Sunday 18 January 2009

Lacrosse 3 and Uranus

This evening it unexpectedly cleared. I photographed the only available pass of Lacrosse 3 (97-064A) to clearify whether it was still on-time. It was: I obtained two points with delta t resp. 0.03 and -0.08s and delta positions 0.019 and 0.039 degree respectively.

The pass was a very low pass however, the satellite did not come higher than 25 degrees in the sky. This made it difficult, and I only managed to capture it on two images when the satellite was just above rooftop level, in a "gap" between two roofs. On the first image it appears from behind the roof (endpoint measurable), on the second it disappears behind the roof (startpoint measurable).

When astrometrically measuring the images, I noted a relatively bright star near the end of the trail that I could not identify. It was also on the 2nd image. The star was bright enough that it should appear in the database AstroRecord uses, and my Sky Atlas didn't show a star there either. So...?

As I was measuring the image anyway, I decided to measure the star to get a position for it. it yielded (18 Jan 2009, 17:49:12.3 UTC):

RA 350.855, dec -4.751
= 23h 23m 25.2s, -4 45' 03.6" (2000.0)

I checked AstPlot: it did not show a star nor an asteroid on that position. I downloaded a NEAT image of the region: again, no star on that position....

By that time, I was thinking: Oi, what's this?!? A nova?!?

Then I got a hunch. I started up MICA, and obtained accurate positions for Uranus and Neptune. And yes, there it was:

Astrometric Positions Mean Equator and Equinox of J2000.0

Date Time RA Declination
h m s h m s ° ' "
2009 Jan 18 17:49:12.3 23 23 24.115 - 4 45 03.16

So, I accidently "re-discovered" Uranus... 228 years too late... :-p

A reduced resolution crop from one of the images is below, with objects annotated:

(click image to enlarge)

Saturday 17 January 2009

NOSS 3-4 duo through Perseus

An initially very clear evening today allowed observations again. Lacrosse 3 (97-064A) was captured, along with NOSS 2-3D (96-029D) and the NOSS 3-4 duo (07-027A & C). USA 32 (88-078A) was captured as a very faint trail but not measured.

A mistake of one minute in the timing while trying to photograph the 96-029 objects made me miss the C & E objects, but captured the D object at the end of what seems to be a slow flare.

One of the images of the NOSS 3-4 duo, the one where they cross Perseus just below the alpha Persei star association, turned out particularly nice, with lots of stars and two bright trails:

(click image to enlarge)

Sunday 11 January 2009

The glinting behaviour of USA 32 (88-078A)

The year 2009 has started with a period of frost, and hence clear skies. I observed on January 6 and 9 and this evening (the 11th), catching a batch of objects: Lacrosse 3, USA 32, and various NOSS duo's.

The image of USA 32 (88-078A, a SIGINT satellite launched in September 1988) of this evening very nicely shows the glinting behaviour of this satellite. Along the trail, small bright dots (= very short glints) can be seen at regular intervals. They are indicated by the downward pointing arrows in the image (a 10.05 second exposure taken with my Canon EOS 450D and EF 50/2.5 Macro lens at F2.8):

(click image to enlarge)

Below is a brightness profile derived from the pixel brightness along the trail. The same peaks as indicated by the arrows in the photograph, show up well and are labelled A to H:

(click image to enlarge)

Analyzing the position of the glints, shows the following sequence:

1) a series of 4 or more glints at a regular 1.20 second interval;
2) followed by 2.0 seconds of no, or much less bright glints;
3) followed again by 4 or more glints at a regular 1.20 second interval.

Tuesday 6 January 2009

Bright SKYMED 2 surprise

While waiting for USA 32 this evening, I was suprised by a bright object in a north-south trajectory majestically sailing through the zenith at 18:29 UTC. It was magnitude -2 for tens of seconds. I quickly re-aimed the camera and took this photograph:

(click image to enlarge)

On this photograph, where the object disappears behind the roof, it was already slightly less bright than only a few tens of seconds earlier.

It turned out to be SKYMED 2 (07-059A), an Italian Earth Observation Satellite launched a year ago on December 9th 2007.