Wednesday, March 29, 2006

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.


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