NASA's plans to provide emergency backup communications support for earth orbiting spacecraft after the closing of four ground stations are examined. Backup support is needed when malfunctions in on-board systems occur and ground intervention is required. The number of spacecraft emergencies that have occurred over the past few years and the reliability of the space-based Tracking and Data Relay Satellite System (TDRSS) White Sands Ground Terminal are also investigated. Spacecraft project managers have expressed the view, based on their professional judgment, that the probability of loss or damage to spacecraft in an emergency, to small spacecraft missions in equatorial orbits, or to launches of expendable rockets would be extremely low, but no formal risk assessments on the ground station closings have been performed. There are no communications support plans for transmission of scientific data from NASA missions should the use of TDRSS be lost. The 11 to 23 earth orbiting spacecraft for which the Goddard Space Flight Center has been responsible have experienced 316 malfunctions that required emergency intervention, about 2.2 per spacecraft per year. Most of these resulted in little or no permanent damage to the spacecraft. White Sands has had numerous outages of the terminal that processes all TDRSS communications. During an outage, spacecraft that normally use TDRSS must rely on ground stations for all communications support. NASA is constructing a second TDRSS ground terminal that is to be opened in 1993. GAO recommends that risk analyses be performed, and support plans for launches of expendable vehicles and Small Explorer missions in equatorial orbits be developed before the four ground stations are closed.
Space Operations: Nasa's Communications Support for Earth Orbiting Spacecraft. Report to Chairman, Subcommittee on Space Science and Applications, Committee on Science, Space and Technology, House of Representatives
1989
36 pages
Report
No indication
English