Space Communications:

Better Understanding of Scheduling System Limitations Needed

IMTEC-91-48: Published: Sep 17, 1991. Publicly Released: Sep 20, 1991.

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Samuel W. Bowlin
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Pursuant to a congressional request, GAO reviewed the efficiency and effectiveness of the National Aeronautics and Space Administration's (NASA) system for scheduling usage of the Tracking and Data Relay Satellite System (TDRSS).

GAO found that: (1) since scheduling TDRSS usage is a complicated process, spacecraft project users generate a tentative schedule of the precise contact times and types of TDRSS services needed 3 weeks before service is required; (2) conflicts between users for the same service at the same time are resolved by changing the requested start time, changing the type of service requested, or switching the service requested to a different TDRSS satellite or antenna; (3) the Hubble Space Telescope and the space shuttle are the two biggest sources of schedule disruption; (4) inadequate automated tools have made the conflict resolution process more tedious, labor-intensive, and potentially error-prone than necessary; (5) TDRSS users are concerned that the scheduling system may be inadequate to handle the expected increase in demand for communications services; (6) although TDRSS has been generally very reliable in providing service when needed, TDRSS failure to support user missions could have serious economic and scientific ramifications; (7) developing an efficient scheduling system to accommodate future growth would require an entirely new system design which has been planned but will not be available until fiscal year 1997 at the earliest; and (8) NASA is reluctant to implement enhancements that may streamline the conflict resolution process, because its data were not comprehensive enough to accurately predict the impact of additional TDRSS users on the scheduling process.

Recommendations for Executive Action

  1. Status: Closed - Implemented

    Comments: NASA has collected the data it needs to assess scheduling system limitations.

    Recommendation: The Administrator, NASA, should assess the ability of the current scheduling system to accommodate the additional TDRSS users expected in the near future. Basic measurements to support this assessment would likely include the volume of user requests that are received and rejected at all points in the scheduling process, the number of those requests that must be altered and resubmitted, and the time it takes to reach final resolution of conflicts.

    Agency Affected: National Aeronautics and Space Administration

  2. Status: Closed - Implemented

    Comments: The assessment to reevaluate software enhancements showed no additional software changes are needed.

    Recommendation: The Administrator, NASA, should use the results of the assessment of the current scheduling system to reevaluate its decision not to implement software enhancements that have been identified by scheduling operations personnel as critical to improving productivity.

    Agency Affected: National Aeronautics and Space Administration


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