Lageos2 Deployment

Although the mission was not quite as long as the two weeks Columbia spent aloft during STS-50, several EDO components remained on board: most notably the

LAGEOS-2 deployment 171

LAGEOS-2 deployment 171

LAGEOS-2 leaves Columbia's payload bay on 23 October 1992.

RCRS carbon dioxide-removal system, which had behaved erratically during its maiden outing. On STS-52, by complete contrast, it operated perfectly: the astronauts switched it on at 6:11 pm, an hour after reaching orbit, and it flawlessly scrubbed the cabin's atmosphere of exhaled carbon dioxide for the remainder of the mission. During the first day of their mission, the crew activated several scientific experiments stored in Columbia's middeck.

The first major objective, however, was deployment of LAGEOS-2, under Jernigan's supervision. ''Houston, we see a good deploy,'' she told Mission Control as the satellite and Columbia parted company at 2:57:24 pm on 23 October. Forty-five minutes later, the IRIS booster - built by the Italian Alenia Aerospazio company - fired to deliver LAGEOS-2 into a 297 x 5,923 km orbit, inclined 41 degrees to the equator. Then, at around 5:30 pm, the satellite's own LAS motor fired to insert itself into a near-circular orbit of 5,617 x 5,950 km, inclined at 52.6 degrees.

Overall, the procedure was almost identical to that followed for the deployment of the SBS-3, ANIK-C3 and Satcom Ku-1 satellites in Columbia's early days: the Pacman-like sunshade was opened and a turntable imparted the required 60-rpm rotation rate on LAGEOS-2 before pyrotechnic bolts fired and spring actuators pushed the payload free. Meanwhile, Veach used cameras on the RMS to monitor the ignition of the IRIS and Wetherbee and Baker fired the Shuttle's OMS engines to lower her orbit to 287 km to maintain a safe separation distance and better support USMP-1 operations.

Entirely appropriately, the six astronauts were awakened on 24 October to the strains of Joe Turner's 'Shake, Rattle and Roll', in honour of the plate motions that LAGEOS-2 was expected to measure. The satellite, according to Miriam Bartuck, had already been successfully tracked by four ground-based laser stations by 2:00 pm that day. During the course of its mission, it has been tracked on a more-or-less-daily basis by 10 NASA-operated Satellite Laser Ranging (SLR) stations and 35 National Satellite Laser Ranging Committee coordinated sites around the world.

Unlike LAGEOS-1, which had been inserted into a 109.9-degree orbit, the inclination of its successor was chosen to enable it to provide better coverage of the seismically active Mediterranean basin, as well as California. It was also hoped to clear up several irregularities that had cropped up with LAGEOS-1's orbital position; these seemed to be linked to erratic spinning of that satellite. After reaching its correct orbital slot, LAGEOS-2 underwent a month-long checkout to precisely calculate its orbit by laser ranging, after which scientific operations got underway in earnest.

''[The satellite] will reduce the problems caused by cloudy weather and will enhance our modelling of Earth's gravity field,'' said Bartuck before the mission. ''Its orbit has been designed to improve coverage of the Mediterranean, a poorly understood and geologically complex area that is naturally of great interest to our Italian partners.''

In fact, LAGEOS-2's orbit is so stable that it will not be dragged into Earth's atmosphere for perhaps eight million years! It should remain 'operational' for about half a century and the only limiting factor is the degradation of its retroreflector prisms. In view of the long time it would spend aloft, NASA asked planetary scientist Carl Sagan - who chaired the team which produced the Voyager plaques - to make a stainless-steel disk for LAGEOS-2. This contained three maps of Earth: as it appeared 268 million years ago, how it looks 'today' and how it may be eight million years hence.

Interestingly, the 'future' map includes the eventual drift of California way out into the Pacific Ocean. ''A being need only compare its view of Earth to the depictions of Earth's past, present and future to determine its place in time relative to the Earth's,'' said NASA spokesman James Hartsfield before STS-52 set off. Plans already exist for a third LAGEOS, which will involve collaboration between the

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