The USAF's TAOS experimental small satellite is back on line, after software revisions following the demise of its inertial system on 19 July (which messed up attitude control and caused a severe power shortage).
Intelsat 703 launched from the Cape by Atlas 2AS on 6 Oct, after a one-day slip due to Atlas battery problems.
Endeavour launched 30 Sept on the second Space Radar Lab mission. The timing was not ideal -- the launch having slipped from mid-August due to the last-second engine abort -- with autumn further advanced in some northern areas than was intended. This mission's primary objective is observing seasonal changes since SRL-1 in April. On the other hand, the new timing happened to coincide with a volcanic eruption in Kamchatka (first spotted by the astronauts, in fact) and an offshore earthquake near Japan, both of considerable interest. Also slated for observation are the two volcanoes that erupted in New Guinea recently (which were observed by SRL-1 before they erupted) and several volcanoes considered possibilities for near-future eruptions; there is hope that radar data might be able to identify changes in water flow accompanying pre-eruption swelling of volcanoes. A new element introduced into the mission since the postponement is an attempt to do radar interferometry with SRL-1 data, by flying some imaging passes along paths exactly duplicating those of SRL-1 passes. So far this seems to be working; the maximum permissible path error is about 300m, but Endeavour has been achieving 50-75m.
Ulf Merbold launched to Mir on 4 Oct, with Viktorenko and Kondakova.
South Africa agrees to abide by the Missile Technology Control Regime, and agrees to terminate its launcher-development project.
China increases its emphasis on satellite remote sensing after a summer of natural disasters. China's highest priority now is radar satellites, since weather in much of southern China is persistently cloudy. China finds western satellite data too expensive, but cannot afford to mount its own development programs, so it is emphasizing cooperative ventures. Western satellite builders are interested but cautious; in particular, they cite problems with figuring out who makes the decisions in China.
Magellan operations prepares to send the spacecraft into its death plunge. Magellan itself is ailing, with interconnections in its solar arrays starting to break from thermal fatigue, reducing available power; the best current guess is that it would have only a couple of months to live. The real limit, however, is that mission-operations money runs out this month, and all funding terminates early next year [and this money came with a condition that it would be the last]. So down she goes.
Up to Oct 10, Magellan will continue its current gravity measurements. In the morning of 11 Oct, thruster firings will lower periapsis to aerobraking altitudes, and this time it will not be raised again. The solar arrays will be set in "windmill" position, as they were for the Sept. windmill experiments (conducted at a higher altitude), with the thrusters fighting the windmill torque to keep the medium-gain antenna pointed at Earth. Windmill configuration will reduce solar power below that needed for spacecraft operation, and the batteries will slowly run down. The signal will be lost sometime the next day, when either the batteries die or the fuel tanks run dry. It will be another day or two before Magellan actually makes its final dive; a few parts, notably the reaction wheels, might reach the surface.
The Sept. windmill experiment, done from the 6th to the 14th, used Magellan's reaction wheels to counter the (much smaller) torques, with the windmill angle varied to assess atmospheric drag. At the 180km altitude of these tests, Venus's atmosphere is mostly atomic oxygen, so the results were relevant to Earth orbiters. At the death-plunge altitude of 140km, the atmosphere should be mostly CO2. Major result will be better values of the accommodation coefficient for aerobraking in CO2. An A.C. of 1 means the molecules all stick to the surface of the craft on impact, while an A.C. of 0 means they bounce off without losing energy. The windmill experiment gave values of about 0.9 at 180km; the best estimates from the 1993 aerobraking at 140km are 0.6-0.7, and the death plunge will refine those values.
Little minds have only room for thoughts | Henry Spencer of bread and butter. --Amundsen | henry@zoo.toronto.edu