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Aviation History
1995
1995 - 0448.PDF
SPACEFLIGHT The Mir rendezvous 'X^ ^ In the Shuttle mock-up and integration laboratory are (left to right) James Wetherhee, Eileen Collins, Bernard Harris, Michael Foa/e, Janice Ford, and Vladimir Titov. involve manoeuvring the Spartan satellite by hand in the payload bay. The astronauts will also place themselves on the end of the RMS and be positioned directly above the payload bay, facing away from the Earth to assess new units in the environmen tal-control system which have been fitted to prevent the overheating experienced in previ ous spacewalks. The other major payload aboard the Discovery is the Spacehab mid-deck extension module, being flown on its third mission. It was the need to ensure that the Spacehab 3 would carry a reasonably full complement of NASA-sponsored and commercial experi ments which delayed the STS63 mission. NASA EXPERIMENTS The Spacehab is fitted with experiments from NASA, the US Department of Defense and National Institute of Health, and Canada's space agency. While the crew is not monitor ing Spacehab experiments on future flights, scientists will be able to observe or interact with their experiments using the Charlotte, a robot developed by McDonnell Douglas, which will be assessed during the STS63 mis sion during a series of prescribed experiment- support tasks. Other experiments being operated on the STS63 mission, mounted in the payload bay and in the Shuttle mid-deck, include the Orbital Debris Radar Calibration Spheres experiment, in which three metal "Spaceballs" and three dipoles, ranging in size from 50mm to 150mm diameter or length, will be deployed from the payload bay for calibr ating ground- based radar and optical systems. Q After the STS63 night-launch, followed by two orbital-manoeuvring system fir ings,the Discovery will undertake the five planned engine burns to place it on a course to arrive at a point 75km (40nm) behind the Mir 1 space station at the same altitude. At about T+3d 9h, the Discovery will be fired to direct it on a course which will end with an initial approach to within about 14.8km, during a firing will be conducted to initiate an actual rendezvous sequence. This will be calculated by the orbiter's onboard flight-control computers using onboard navigation information derived from star tracker sightings of the Mir. On arrival at the 14.8km point, at T+3d lOh, the next firing will begin the Discovery's final-phase rendezvous and terminal interception of the Mir. This will take about 90min, during which the Discovery's radar system will begin to provide navigation information, Discovery's range and closing rate. Four mid-course corrections burns can be made during this period, if required. At T+3d 12h, manual control by commander Jim Wetherbee will begin at about 0.9km below the Mir. Wetherbee, using the flight controls on the aft deck, will take the orbiter up and around towards the front of the station, braking his approach, aligning the orbiter's course to bring it within 121m, directly in front of the Mir. As the orbiter comes within 304m, the Discovery's thrusters will be fired in a mode called Low Z, an approach which fires jets which are slighdy offset to the Mir, rather than point ing direcdy at the station, to avoid contamination or damaging the station. As the orbiter come within close proximity to the Mir, the Trajectory Control Sensor, a laser-ranging device mounted in the payload bay, provides information on the distance and closing rate to the Mir. Wetherbee will manually control the flight for the next 2h 40min for approach and close-proximity operations. At T+3d 12h, the Discovery reaches the V Bar, an imaginary line drawn along Mir's direction of travel, or a point about 121m directly in front of the station. Wetherbee will first stationkeep at that point relative to the Mir and begin a slow approach. He will fly from 12 lm to a point 10m from the Mir — no further, at Russian insistence — aligning with the station's Kristall docking module in a rehearsal for the STS71 mis sion docking. (During the STS71 flight, its commander Robert "Hoot" Gibson, must ensure that the Atlantis is not tilted with respect to the Kristall airlock by more than 2° as he approaches at a speed of just 30mm/sec. He will rely on a critical television camera on the US/Russian androgynous docking system mounted in the forward payload bay of the Atlantis, although there will be two other cameras in the payload bay to provide assistance. Gibson will have a 4min window in which to perform the docking over the Russian tracking station failure means that it will be delayed for one orbit.) To assist with his approach and alignment, STS63's Wetherbee will watch the view from a centreline television camera, mounted in the upper window of the Spacehab module, on a monitor in the aft-flight deck. When within about 600mm of the Mir, air-to-air communications using a VHF radio system will begin between the Discovery and the Mir. At 100m from the docking port, Wetherbee will again stationkeep, rehearsing a manoeuvre to orient die Discovery prop erly to the docking port, before backing slowly away from the Mir along the same route he approached. When the Discovery is again 121m from the Mir, depending on the amount of fuel left, Wetherbee will start a slow fly-around to verify flight techniques, communications and navigation air sensor interfaces, keeping the distance to about 137m above the station, then the same dis tance behind, below, and in front respectively, and again to a point 137m above the station. At this point, at T+3d 14h, a firing will begin the orbiter's separation from the Mir, putting the Discovery on a course which will eventually take it ahead of the Mir and constantly opening the distance between the two spacecraft. A day later, a new firing will circularise the orbit to prepare for the Spartan retrieval rendezvous. FLIGHT INTERNATIONAL 25 - 31 January 1995 31
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