Shorterthanplanned Freeflight

Since even a few atoms could have detrimental effects on the factory's ability to grow ultra-pure films, the wake side had to be very carefully cleaned before being installed into the Shuttle's payload bay. Further cleansing was also necessary just prior to its deployment in space. On the afternoon of 22 November, Jones powered-up Columbia's RMS for the second time and grappled WSF-3 at 7:25 pm. Shortly afterwards, Mission Specialist Tammy Jernigan activated the Canadian-built Space Vision System (SVS) to carefully track the satellite's position and Cockrell oriented Columbia in a gravity gradient attitude to minimise disturbances.

Meanwhile, Jones' next task after unberthing the satellite was to 'cleanse' its wake side for two-and-a-half hours with the atomic oxygen prevalent in low-Earth orbit; to do this, he 'hung' it over the port-side payload bay wall with its underside facing into Columbia's direction of travel. Then, at 11:45 pm, he manoeuvred WSF-3 across the bay and positioned it over the starboard wall, this time with its underside facing away from the direction of travel, in order to check out its Automatic Data Acquisition and Control System (ADACS) and attitude-control thrusters.

Finally, he oriented the satellite high above the payload bay, again with its underside facing away from Columbia's direction of travel, to await the opening of the first, 41-minute-long deployment 'window' at 1:06 am on 23 November. After a slight delay, he released WSF-3 at 1:38 am as the Shuttle sailed over the western Pacific. Shortly afterwards, the satellite's ground controllers commanded it to fire a tiny nitrogen thruster, which produced 45 grams of thrust and pushed it clear of Columbia. This made it the first 'self-deploying' payload; the Shuttle's own thrusters having been temporarily disabled to reduce possible contamination.

The firing, which lasted for 19 minutes, positioned WSF-3 some 30-50 km away from the Shuttle and set it up for three days of autonomous operations; at this stage, ORFEUS-SPAS-2 was approximately 93 km 'behind' Columbia. By 2:00 pm on 23 November, the first of a planned seven semiconductor-processing runs was underway; however, a potential problem would lead to an earlier-than-scheduled retrieval on the 26th. The crew was awakened early on 24 November to the news that ORFEUS-SPAS-2 seemed to be closing on WSF-3 at a faster-than-expected rate.

Original plans called for Cockrell and Rominger to perform as many as two manoeuvres per day to maintain the proper separation distance from both satellites, and for the Wake Shield to fire one of its thrusters daily. This, it was expected, would keep both some 30-40 km away from the Shuttle, and approximately the same distance from one another. After a lengthy period of tracking analysis and predictions of the satellites' positions, Mission Control decided that their separation distance was well within limits, but Columbia's crew were nevertheless instructed to retrieve WSF-3 three hours ahead of schedule.

The early retrieval did not impact the facility's semiconductor-growth runs; all seven films had been successfully processed on 25 November and WSF-3 was grappled at 12:01 am the following morning. Throughout the rendezvous and retrieval procedure, Columbia drew no closer than 10 km of ORFEUS-SPAS-2, which was exactly as had been predicted by flight controllers and well within safety margins. Yet

Was this article helpful?

0 0

Post a comment