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| Rendezvous and Docking |
| Overview |
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Discovery's rendezvous and docking with the International Space Station begins with the precisely timed launch of the shuttle on a course for the station. During the first two days of the mission, periodic engine firings will gradually bring Discovery to the starting point for a final approach. About 2½ hours before the scheduled docking on Flight Day Three, Discovery will reach that point about 50,000 feet -- 9½ miles -- behind the ISS. There Discovery's jets will be fired in a Terminal Intercept (TI) burn to begin the final phase of the rendezvous. Discovery will close the final miles to the station during the next orbit of the Earth. As Discovery closes in, the shuttle's rendezvous radar system will begin tracking the station and providing range and closing rate information to the crew. During the approach, the shuttle can make as many as four, small course corrections at regular intervals. Just after the last correction is completed, Discovery will reach a point about half a mile below the station. At that time, about an hour before the scheduled docking, Commander Scott Horowitz will take manual control of Discovery. Horowitz will slow Discovery's approach and fly to a point about 600 feet directly below the station. There he will begin a quarter-circle of the station, slowly moving to a position in front of the complex, in line with its direction of travel. During the rendezvous, Horowitz will be assisted by Pilot Rick Sturckow. Mission Specialists Dan Barry and Patrick Forrester also will play key roles in the rendezvous, with Barry operating a handheld laser-ranging device and a laptop computer navigation aid assisted by Forrester. Barry also will operate the shuttle's docking mechanism to latch the station and Discovery together after the two spacecraft make contact. Horowitz will slowly close on the station moving at a speed of about a tenth of a mile per hour. Using a view from a camera mounted in the center of Discovery's docking mechanism as a key alignment aid, Horowitz will precisely center the docking ports of the two spacecraft. Horowitz will fly to a point where the docking mechanisms are 30 feet apart, and pause for about five minutes to check the alignment. For Discovery's docking, Horowitz will maintain the shuttle's speed relative to the station at about one-tenth of a foot per second, and keep the docking mechanisms aligned to within three inches of one another. When Discovery makes contact with the station, preliminary latches will automatically attach the two spacecraft together. Immediately after Discovery docks, the shuttle's steering jets will be deactivated to reduce the forces acting at the docking interface. Shock absorber-type springs in the docking mechanism will dampen any relative motion between the shuttle and the station. Once relative motion between the spacecraft has been stopped, Barry will secure the docking mechanism, sending commands for Discovery's mechanism to retract and close a final set of latches between the shuttle and station. Undocking, Separation and Flyaround Once Discovery is ready to undock, Barry will send a command that will release the docking mechanism. The initial separation of the spacecraft will be performed by springs in the docking mechanism that will gently push the shuttle away from the station. Discovery's steering jets will be shut off to avoid any inadvertent firings during this initial separation. Once the docking mechanism's springs have pushed Discovery to a distance of about two feet, when the docking devices will be clear of one another, Sturckow will turn the steering jets back on and fire them to begin very slowly moving away. From the aft flight deck, Sturckow will manually control Discovery within a tight corridor as he separates from the ISS, essentially the reverse of the task performed by Horowitz when Discovery docked. Discovery will continue away to a distance of about 450 feet, where Sturckow will begin a close flyaround of the station, circling the complex 1¼ times. Sturckow will pass directly above the station, then behind, then underneath, then in front and then reach a point directly above it for a second time. At that point, passing above the station for a second time, Sturckow will fire Discovery's jets to separate from the area of the station. The flyaround is expected to be completed a little over an hour after undocking. |
Editorial/Technical Comments: ShuttlePresskit
