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Problems Surface During TDRS I Orbit Raising

More Information:

The TDRS I (Tracking and Data Relay Satellite), launched on March 8, lost pressure in one of its four onboard propellant tanks four days after liftoff, possibly stranding the satellite in its geosychronous transfer orbit.

Engineers at Boeing Satellite Systems are investigating the problem. Four propellant tanks feed the onboard thrusters, but there is a problem with the supply in one of those tanks. Boeing remains optimistic that they will be able to deliver the satellite to its proper orbit, after which they will turn operations of TDRS I over to NASA and the spacecraft will be renamed TDRS 8. TDRS I probably had an initial propellant load of about 1660 kg (Boeing has not released the dry mass of the satellite, but it is probably about 1540 kg). About 140 kg is required for geostationary stationkeeping and maneuvers.

At launch, the spacecraft was injected into a 247 x 29,135 km x 27.1 degree orbit. On March 11 a burn of the apogee motor raised the orbit to 433 x 29,146 km x 26.4 degrees. On March 13 a perigee burn raised the apogee to geostationary altitude, 429 x 35,800 km. No further burns were made until March 19, when the orbit was raised to 3,521 x 35,789 km and the inclination lowered to 21.4 deg. However, Boeing is reporting that the most recent orbital parameters have the satellite with a perigee of 8,000 km (4,319 nmi) and an apogee of 35,800 kilometers (19,330 nmi).

TDRS I was insured for the cost of replacement.

TDRS I is the second spacecraft to be launched as part of an US$840 million three satellite upgrade program requisitioned by NASA's Goddard Space Flight Center in Greenbelt, Md. The satellite network provides a communications link between ground stations and the space shuttle, International Space Station, Hubble Space Telescope and many NASA satellites. The TDRS network is used to relay television signals, telemetry, research data and other signals between space and Earth.

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March 22, 2002