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This is NASA's press kit for Space Shuttle mission STS-75, dated February 1996 and later edited by Richard W. Orloff. It covers Columbia's planned 13-day flight carrying the Italian Tethered Satellite System reflight (TSS-1R) and the third United States Microgravity Payload. The kit sets out launch and landing plans, abort modes, the timeline, payload weights, crew duties, the tether's science objectives and investigators, and crew biographies. It does not mention any unidentified objects.
“NASA”22 pages
Edited by Richard W. Orloff, 01/2001/Page 20 about nine miles away. From this point, the speed with which the tether is fed out will gradually decrease through the rest of the procedure, coming to a stop almost five and a half hours after the initial movement, when the satellite is a little more than 12.8 miles, or 20.7 kilometers, from Columbia. Just prior to the satellite's arrival at its most distant point, the quarter-revolution spin will be stopped briefly to measure tether dynamics. Then, a seven-tenths-of- a-revolution-per-minute spin will be imparted. At full deploy, the tension on the tether, or the pull from the satellite, is predicted to be equivalent to about 12 pounds of force. The tether is 13.7 miles, or 22 kilometers, long, allowing an extra mile, or 1.3 kilometers, of spare tether that is not planned to be unwound during the mission. Dynamics Functional Objectives During the deploy of TSS, several tests will be conducted to explore control and dynamics of a tethered satellite. Models of deployment have shown that the longer the tether becomes, the more stable the system will be. The dynamics and control tests that will be conducted during deploy also will aid in preparing for retrieval of the satellite and will serve to verify the ability to control the satellite during that operation. During retrieval, it is expected that the stability of the system will decrease as the tether is shortened, opposite the way stability increased as the tether was lengthened during deploy. The dynamics tests involve maintaining a constant tension on the tether and correcting any of several possible disturbances to it. The possible disturbances include: a bobbing motion, also called a plumb bob, where the satellite bounces slightly on the tether, causing it to alternately slacken and tighten; an oscillation of the tether, called a libration, resulting in a pendulum-like movement of tether and satellite; a pendulous motion of the satellite, rolling and pitching motion of the satellite at the end of the tether; and a lateral string mode disturbance, a motion where the satellite and Shuttle are stable, but the tether is moving back and forth in a "skip rope" motion. All of these disturbances may occur naturally and are not unexpected. Some disturbances will be intentionally induced. The first test objective will be performed when the satellite is 250 yards from Columbia, and will involve small firings of the satellite's steering jets to test the response of the satellite's automatic rate damping system. Other methods of controlling the satellite and tether motion can be performed by the crew when needed. Those methods include using visual contact with the satellite or telemetry information from it to manually stabilize TSS from aboard the Shuttle by remotely firing the satellite's attitude thrusters. Another test will be performed when the satellite is about 2.5 miles from Columbia. Columbia's autopilot will be adjusted to allow the Shuttle to drift by as much as 10 degrees in any direction before steering jets automatically fire to maintain Columbia's orientation. The 10-degree deadband will be used to judge any disturbances that may be imparted to the satellite if a looser attitude control is maintained by Columbia. The standard deadband, or degree of allowable drift, set in the Shuttle's digital autopilot for Tethered Satellite operations is two degrees of drift. Tests using the wider deadband will allow the crew and flight controllers to monitor the amount of motion the satellite and tether impart to Columbia. When the satellite is fully deployed and on station at 12.8 miles, Columbia will perform jet firings to judge disturbances imparted to the tether and satellite at that distance. The satellite is planned to remain at that distance, called On Station-1 (OST-1), for about 22 hours. Damping of any motion which is expected to occur in the tether and satellite while at 12.8 miles and during the early portion of retrieval will be accomplished using electrical current flow through the tether. During the later stages of retrieval, damping will be accomplished using a combination of the Shuttle's steering jets, a built-in damping system at the end of the deploy boom and the satellite's steering jets.
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