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| Rendezvous and Docking Overview |
| Overview |
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Rendezvous and Docking Discovery's rendezvous and docking with the International Space Station actually 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 a point about nine statute miles behind the station, the starting point for a final approach to the station. About two and a half hours before the scheduled docking time on Flight Day Three, Discovery will reach the point about nine statute miles - 48,600 feet -- behind the ISS. At that time, Discovery's engines 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 Earth. As Discovery closes in, the shuttle's rendezvous radar system will continue to track the station and provide range and closing rate information to the crew. During the approach toward the station, the shuttle will have an opportunity to conduct four, small mid-course corrections at regular intervals. Just after the fourth correction is completed, Discovery will reach a point about a half-mile below the station. At that time, about an hour before the scheduled docking, Commander Jim Wetherbee will take over manual control of the approach. Wetherbee will slow Discovery's approach and fly to a point about 600 feet directly below the station, from which 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, Wetherbee will be assisted by Pilot James Kelly in controlling Discovery's approach. Mission Specialists Andy Thomas and Paul Richards also will play key roles in the rendezvous, with Thomas operating the shuttle's docking mechanism and Richards assisting with the rendezvous navigation. Thomas and Richards will use a handheld laser pointed through the shuttle windows to provide supplemental information on the station's range and the shuttle's closing rate. Wetherbee will fly the quarter-circle of the station, starting at a point 600 feet below, while slowly closing in on the complex, stopping at a point a little over 300 feet directly in front of the station. From that point, he will begin slowly closing in on the station - moving at a relative 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, Wetherbee will precisely center the docking ports of the two spacecraft. Wetherbee will fly to a point where the docking mechanisms are 30 feet apart, and pause briefly to check the alignment. For Discovery's docking, Wetherbee 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, 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, Thomas will command the docking ring on Discovery's mechanism to retract, closing latches in the mechanism to firmly secure the shuttle to the station. Undocking, Separation and Fly-Around Once Discovery is ready to undock, Thomas 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. Both Discovery's and the station'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 away to a distance of about two feet, when the docking devices will be clear of one another, Kelly will turn the steering jets back on and fire them to begin very slowly moving away. From the aft flight deck, Kelly will manually control Discovery within a tight corridor as he separates from the ISS, essentially the reverse of the task performed by Wetherbee when Discovery docked. Discovery will continue away to a distance of about 450 feet, where Kelly will begin a close flyaround of the station, circling the complex one and a half times. Kelly will first cross a point directly above the station, then behind, then underneath, then in front and, when he reaches a point directly above the station for the second time, Kelly will fire Discovery's jets to separate the vicinity. The flyaround is expected to be completed a little over an hour after undocking. --end-- |
Editorial/Technical Comments: ShuttlePresskit
