The problem with the gyros is partly one of radiation damage and subatomic particles. An early experiment in the space age detonated a nuclear weapon in LEO. The subatomic particles from this explosion now appear to form in a region called the South Atlantic Anomaly (SAA). Hubble Space Telescope flies through the SAA quite often. Additionally to radiation problems the control law of the spacecraft can't change significantly due to memory limitations. Early analysis of the HST revealed that oscillations from solar panels flapping about required the spacecraft to fight them. Necessarily the gyros are working harder than designed and the spacecraft within a couple years lost all redundant gyros mostly attributed to the SAA problem.
Military intelligence community spacecraft spend a good deal of their time 'safed' with instruments shielded and the spacecraft oriented with maximum shielding head first into the wave. The HST cannot do this to attain necessary long exposures for good science. A further aside: HST by my last account of the project had a 386 level processor on it with about as much memory as a Texas Instruments 83 graphing calculator. I recall reading in the 'Hubble Wars' . Engineers at NASA Goddard attempted to damp out the oscillations from the panels by using the gyros. I think the programs were too large however to readily fix the problem and this left the structure flapping about for 10 minutes every 90 minute orbit. Orbits: Yes the orbits are indeed different. The inclination of the ISS is 51.6339 degrees and the HST is 28.4657 degrees. Granted this is an over simplification of the problem, but to move something the mass of the Orbiter would require the orbiter to have a lot of fuel on board for specifically this purpose, thus reducing the mass of the payloads it can carry into space. HST 1 20580U 90037B 03240.42254663 .00001224 00000-0 86788-4 0 6071 2 20580 28.4657 237.5645 0004265 134.7336 347.0128 14.98413118531289 ISS (ZARYA) 1 25544U 98067A 03241.08614583 .00017750 00000-0 20687-3 0 4121 2 25544 51.6339 13.2008 0007188 177.9097 163.8647 15.61726755272389 _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
