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De-orbiting A Space Station
London - Feb. 3, 2001 Late last year, Yuri Koptev, head of the Russian Space Agency indicated that the preferred re-entry location for Mir was around 2000 kilometres to the East of Australia. Using that information it was possible to make a first stab at calculating the ground track (the Koptev Corridor) and also get a view of the time of day it would likely happen. Mid-January this year, Russia let it be known that the target point for the major pieces of surviving debris was 47 degrees South, 140 degrees West longitude. The choice of date for the re-entry is dictated by the physics of the upper atmosphere. A study undertaken 2000 August for Spaceflight Control Centre in Moscow concluded that the de-orbit manoeuvres could be undertaken by a docked Progress spacecraft but that natural decay would require Mir's orbit to have descended to approximately 200 x 225 kilometres. A fully-loaded Progress tanker would then be able to provide the necessary retro-thrust.
The task of Progress would be to get Mir down to approximately 220 x 160 kilometres with perigee over the southern Pacific Ocean, and then a final burn of the Progress engines would be able to ensure re-entry. The Progress engine burn would need to be of ten minutes duration using the main thrust chamber firing in parallel with the smaller orbit correction thrusters. The smaller thrusters would then continue to fire for a further three minutes, making thirteen minutes of burn time in total. The precision with which Progress will be able to hit the target is dependent very much chance and whether the ground track can be steered into exactly the right position. In reality it is unlikely that Spaceflight Control Centre will be able to hit the spot exactly. The actual parameter which will determine the ground track on re-entry day is where the orbit's first ascending node to the West of 20 degrees East longitude is positioned. For the target location, the ascending node is at 2.5 degrees West - the furthest to West that is possible under the rule. This rule actually precludes use of the "Koptev Corridor" because that particular trajectory results from an ascending node at 19 degrees West. In trying to work out the sequence of events on re-entry day, there are some other pieces of information which prove useful. When NASA presided over the re-entry of the 14-tonne Compton Observatory in 2000, a study was made of the burn-up and fall of debris. Compton started to burn just above 80 kilometres and broke up around 70 kilometres high. Pieces then fell into the Pacific. Spaceflight Control Centre's study also tells us that with the final burn of Progress's engines, the trajectory is such that debris will fall into an area from 1,800 kilometres before the aiming point to 2,600 kilometres beyond it. Compton was aimed at a perigee of 50 kilometres on its re-entry orbit, so if we assume the same for Mir and assume that the perigee will be above the target point then it is possible to map Mir's possible last moments. It has to be emphasised that the map on this page is an estimate only - it will be updated as and when refinements to the re-entry information become available. The precise location of the ground track will only be known a few days before re-entry. With the track now being to the West of the Koptev one, events will take place a little earlier in the day. Retro-fire will be around noon with atmosphere entry about 28 minutes later and it will be all over bar the splashes after another ten minutes. Retro-fire should be completed as Mir flies over the Baikonur Cosmodrome and the Dzhusaly tracking station. Re-entry will occur early-morning local time so the people of Tonga and southward should have a spectacular view of events. Related Links Information on Soviet and Russian Spaceflight SpaceDaily Search SpaceDaily Subscribe To SpaceDaily Express 
Complexity Of Mir Deorbiting Tests Russian Space Skills
Moscow (Interfax) Jan. 27, 2001Several plans have been worked out to bring the Russian space station Mir out of orbit, chief designer of the Russian aerospace corporation Energiya Yuri Semyonov told a Saturday press conference at the mission control center in Korolyov in the Moscow region.
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