UARS returns home
29 Sep 2011 by Evoluted New Media
NASA’s decommissioned Upper Atmosphere Research Satellite (UARS) satellite re-entered the Earth’s atmosphere and crash-landed last week – trouble was nobody knew where.
The precise re-entry time and location of the debris impacts were hard to determine – NASA’s best estimate was that it came down at 04.16 GMT, somewhere in the Pacific Ocean. The satellite orbited the Earth between 57° North and 57° South – so the satellite could have crash-landed anywhere.
“Because we don’t know where the re-entry point actually was, we don’t know where the debris field might be,” said Nick Johnson, NASA’s chief scientist for orbital debris at the Johnson Space Centre. “If the re-entry point was at the time the Joint Space Operations Centre (JSpOC) has its best guess of 04.16 GMT, then all that debris wound up in the Pacific Ocean.”
The JSpOC weren’t too far off – NASA confirm yesterday (28th September) that the decommissioned satellite crashed into the Pacific Ocean at 14.1° South latitude and 170.2° West longitude, engaging with the atmosphere at 04.01 GMT.
UARS was deployed in 1991 by the Space Shuttle Discovery, and was used to study the Earth’s atmosphere over the next 14 years. It was the first multi-instrumented satellite to observe numerous chemical components of the atmosphere and have helped us understand the chemistry of the ozone layer and the cooling effect of volcanoes.
Scientists believe around 500kg of the 6.5 tonne satellite reached the Earth, with the rest breaking away and burning up on re-entry into the Earth’s atmosphere. Debris could be scattered over an 800km path.
Tracking stations like JSpOC witness at least one uncontrolled return of debris every day, and one defunct spacecraft or rocket each week. They see something the size UARS once a year, but larger objects such as space station cargo ships return from orbit several times a year.
