The time and location of re-entry cannot be predicted precisely. At present, scientists expect the X-ray satellite, which completes an Earth orbit in about 90 minutes, to re-enter in early November 2011.Currently, this date can only be calculated to within plus/minus five weeks.This time slot of uncertainty will be reduced as the date of re-entry approaches. However, even one day before re-entry, the estimate will only be accurate to within plus/minus five hours .All areas under the orbit of ROSAT, which extends to 53 degrees northern and southern latitude could well be affected by its re-entry. The bulk of the debris will impact near the ground track of the satellite. However, isolated fragments could fall to Earth in a 80 kilometre wide path along the track.
The latest studies reveal that it is possible that up to 30 individual pieces weighing a total of 1.6 tons may reach the surface of the Earth. The largest single fragment will probably be the telescope's mirror, which is very heat resistant.
Interesting, thanks for bringing this to attention.How big exactly is the biggest piece? I assume they mean the mirror here; from wikipedia I read the largets piece might be as heavy as 400 kg; is this the mirror?
What delta-v is needed to bring satellites down 2 or 3 orbits early?So we can ensure that they land in the sea.
Currently the ESA http://twitter.com/#!/ROSAT_Reentry is predicting reentry around Oct 23, while Space-Track has Oct 11. I'm guessing the ESA value is better.
Quote from: Silmfeanor on 09/23/2011 12:07 pmInteresting, thanks for bringing this to attention.How big exactly is the biggest piece? I assume they mean the mirror here; from wikipedia I read the largets piece might be as heavy as 400 kg; is this the mirror?Yes, the primary mirror. It consist of several barrel shaped mirrors assembled in to one barrel-like construction. Weighs roughly 400 kg, is made of high-temperature resistant materials (glass ceramics). Could possibly survive re-entry nearly intact.
Quote from: A_M_Swallow on 09/23/2011 05:23 pmWhat delta-v is needed to bring satellites down 2 or 3 orbits early?So we can ensure that they land in the sea.Not applicable here. ROSAT will re-enter uncontrolled. There is no active attitude control, nor any contact with the satellite. Those systems shut-down long ago.
Quote from: woods170 on 09/23/2011 12:28 pmQuote from: Silmfeanor on 09/23/2011 12:07 pmInteresting, thanks for bringing this to attention.How big exactly is the biggest piece? I assume they mean the mirror here; from wikipedia I read the largets piece might be as heavy as 400 kg; is this the mirror?Yes, the primary mirror. It consist of several barrel shaped mirrors assembled in to one barrel-like construction. Weighs roughly 400 kg, is made of high-temperature resistant materials (glass ceramics). Could possibly survive re-entry nearly intact. To be specific, the primary mirror assembly is a pair of four nested cylindrical mirrors. Similar systems have been made from Schott Zerodur, a glass and ceramic matrix with nearly zero coefficient of thermal expansion, which is moderately dense (2.53 g/cm^3) . It would seem probable that the 400 kg assembly would come apart into eight roughly equal mass parts. Whether this increases or decreases the small probablility of doing harm is beyond my ability to guess.
According to DLR:Re-entry now estimated to happen between October 20 and October 25, plus-or-minus three days.
ROSAT to crash into earth at the end of October?!?! maybe this link will help us see the bright side of this incident! German satellite, 20 years old, where will it land? Nobody know!!!
DLR has updated the re-entry timeframe again: Re-entry expected between 21 and 25 October.And that fit's nicely with the prediction made by Comga
