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I SUPPLEMENTARY NOTES1s. ABSTRACT IThis note briefly reviews the Skylab attitude and pointing control system (APCS) requirements and the way in which they became altered during the prelaunch phase of development. The actual flight mission (including mission alterations during flight) is described. The serious hardware failures that occurred, beginning during ascent through the atmosphere, also are described. The APCS's ability to overcome these failures and meet mission changes are presented. The large around-the-clock support effort on the ground is discussed. Finally, salient design points and software flexibility that should afford pertinent experience for future spacecraft attitude and pointing control system designs are included.

Approved for public release; distribution is unlimited. 4. PERFORMING ORGANIZATION REPORT NUMBER(S) 5. MONITORING ORGANIZATION REPORT NUMBER(S) AFWAL-TR-88-3038 6a. NAME OF PERFORMING ORGANIZATION Control Dynamics Company 6b. OFFICE SYMBOL (If applicable) 7a. NAME OF MONITORING ORGANIZATION Flight Dynamics Lab (AFWAL/FDSGC) AF Wright Aeronautical Labs 6c. ADDRESS (City. State, and ZIP Code

Vigorous efforts to reduce costs, coupled with changes in Space Telescope (ST, formerly LST) guidelines, took place in the fall of 1974. These events made possible a new design of the ST and its Pointing and Attitude Control System. The major design changes are summarized as : an annular Support Systems Module; removal of image motion compensation; reaction wheels instead of control moment gyroscopes; and a magnetic torquer system to perform the emergency and backup functions, eliminating the previously required mass expulsion system. Preliminary analysis indicates the Low Cost ST concept has met the newly defined requirements and results in a significantly reduced development cost.