Hi, I have a question about atmospheric drag, and it seems like someone here probably knows the answer, or can point me in the right direction ... I'm working on the Mars Gravity Biosatellite, planned for launch in 2005, flying about a dozen mice on a rotating spacecraft to study the effects of a partial gravity environment. This is a volunteer project involving MIT, U of Washington, and U of Queensland. Since we have a re-entry capsule, this would be in low LEO -- possibly repeating groundtracks at mean motion 16, or possibly slightly higher (up to about 15.75). We are trying to estimate propellant requirements for orbit adjustment under various strategies for handling drag and re-entry phasing. The major unknown is a good estimate of the rate of altitude decay. Also relevant is how this would increase if we were away from solar minima (making sure we can support a long launch delay without re-design). If there is empirical decay data out there, we can adjust for the differences in ballistic co-efficient. I've seen the Starshine decay curve, but that was near solar maximum ... I've also seen ISS/Mir altitude graphs, but we're lower than these (well, lower than Mir was then ...) Something closer to our phase in the solar cycle would be helpful. If there are atmospheric models that give atmospheric density, of course, we can do the math from there. I know that atmospheric drag is highly variable. I'm not out for good predictions, just an average, and some sense of how much variance to expect in real life. Anyone know of anything useful? If replying off the list, please use the address "mars at golux d.t org", which goes to my folder for this project. PS: for visual interest, this spacecraft will spin at about 30 rpm, so I'm hoping we can include a nice mirror! Sean Sullivan Lead engineer for Guidance, Navigation & Control Mars Gravity Biosatellite http://www.marsgravity.org ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www.satellite.eu.org/seesat/seesatindex.html
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