5 Oct 2011

Image of the Day - End of ROSAT


Today's Image of the Day for 5/10/11 - End of ROSAT

ROSAT all-sky survey sourtesy of xray.mpe.mpg.de
ROSAT (short for Röntgensatellit, in German X-rays are called Röntgenstrahlen, in honour of Wilhelm Röntgen) is a defunct German Aerospace centre-led satellite X-Ray telescope, with instruments built by Germany, the UK and the US. It was launched on 1 June 1990, on a Delta II rocket from Cape Canaveral, on what was initially designed as an 18 month mission, with provision for up to 5 years of operation. ROSAT actually operated for over 8 years, finally shutting down on 12 February 1999.
       ROSAT is expected to re-enter the Earth's atmosphere at some point between October and December. In February, it was reported that the 2,400 kg satellite was unlikely to burn up entirely while re-entering the earth atmosphere due to the large amount of ceramics and glass used in construction. Parts as heavy as 400 kg could impact the surface intact. If you thought that Nasa's odds of one in 3,200 that someone somewhere on the Earth would be struck by a piece of the falling UARS satellite were worrying, then the next major satellite decay poses even more of a risk. The German Aerospace Center puts the equivalent odds for Rosat, the Roentgen Satellite, at one in 2,000. In fact, your personal odds of being hit are more like 1 in 14 trillion, so it is probably safe to put away that tin hat. If you live north of the Wash, then you are out of the "danger zone" which extends to 53° N and S of the equator. Equipped with an 84cm mirror, it completed an X-ray survey of the sky, finding more than 150,000 objects.
         It followed up with targeted observations of interesting objects from galaxies, to neutron stars and even comets. It is about three weeks away from re-entry as it's orbit decays, though it could survive into November. Rosat is less than half as massive as UARS, but more than half of it is thought likely to survive re-entry. The expectation is that this will drop harmlessly into an ocean. The US tracking authorities took more than two days to confirm the details of UARS' plunge into the Pacific, so let us hope that they do better with ROSAT.

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