Hubble Space Telescope
(HST) Archive System
NASA Langley Research Center
Hampton, Virginia
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Returned Hardware
Rate Sensing Units
The rate-sensing units are crucial in pointing of the Hubble Space Telescope during target acquisitions and observations. The pointing control system uses four of the six rate gyros which provide precise angular measurements for short-term stability. The rate gyros report 40 times per second and they are sensitive enough to detect position changes as small as 0.00025 arc second (7 hundred-millionths of a degree). The rate gyros give the computer information about the telescopes's orientation or attitude.
Two pairs of the gyros suffered apparent failures during the HST mission. The rate-sensing units will be visually inspected with particular attention to the connector pins. Photographs and contamination samples will be taken. Electrical interface continuity and isolation tests will be performed. The units will then be returned to Allied Signal for functional testing and evaluations. After testing is completed, the rate sensing units will be refurbished and reflown.
Astronauts remove RSUs during Servicing Mission.
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