Alan Pickup wrote: ] I agree with Tony Beresford that the thrust available to the ] Iridiums may be too little to force a controlled re-entry. ] And, like Tony, I suspect that the best they can hope for is ] to lower the perigee to somewhere below 300 km where they ] might only last a few weeks or months. At their present ] heights, I would guess that their lifetimes might be 20-50 ] years. Recently I came across an alternate meaning of "deorbit" with respect to geosynchronous satellites, where they are actually raised into a higher orbit, mainly to get them out of the way of operational satellites. I know this is purely speculation, but I wonder how high an orbit would be achievable by Iridium satellites, and how long would they stay in orbit at that height. On the other hand, if they are to re-enter, someone's question was well to the point: will any fragments possibly survive re-entry and reach the ground? According to Mark Wade's Encyclopedia Astronautica, they are the first members of a satellite model called "LM700", cylinders whose length is four meters and diameter is 1.3 meter (not including solar panel and MMAs, of course), and mass is 689 kg: http://www.friends-partners.org/~mwade/craft/lm700.htm If there's little or no chance of any significant fragments reaching the surface, then the primary reason for deorbiting them would be to reduce to whatever degree possible the risk of in-orbit explosion or collision. In this case, the issue is which orbit might they achieve to achieve the most desirable results towards that end. Ed Cannon - ecannon@mail.utexas.edu - Austin, Texas, USA ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Wed Mar 22 2000 - 20:30:00 PST