The newest generation Tracking and Data Relay Satellites (TDRS) will provide vital communication links with the Space Shuttle, International Space Station, Hubble Space Telescope and other spacecraft and launch vehicles.

"The average age of the existing fleet is more than 10 years, which is beyond the mission design lifetime," said Anthony Comberiate, TDRS Project Manager at NASA's Goddard Space Flight Center, Greenbelt, MD. "The new series will replenish our existing fleet and allow users to migrate to the new Ka-band," allowing a threefold increase in data throughput.

The Tracking and Data Relay Satellite-H, or TDRS-H, will be launched June 29 aboard a Lockheed Martin Atlas IIA rocket from Cape Canaveral Air Force Station, FL, during a 40-minute launch window, which opens at 8:38 a.m. EDT.

Engineers will insert the spacecraft into a geosynchronous orbit about 22,300 miles above the Earth. Maintaining its fixed position above Earth, TDRS-H will provide nearly continuous communication links with controllers and researchers on the ground.

Total cost for the TDRS-H mission is $395 million, which includes the spacecraft, launch vehicle and modifications to the White Sands Complex. (The White Sands, NM, ground terminal is the TDRS operational control center, which also provides customer telecommunications services.) Cost for all three satellites (TDRS-H, -I and -J) is $485 million and includes the White Sands Complex modifications. NASA plans to launch TDRS-I and TDRS-J in 2002 and 2003, respectively.

After testing and acceptance of the spacecraft, TDRS-H will be called TDRS-8, relaying enormous volumes of user data -- voice, television and science -- from various orbiting scientific and manned missions to ground control centers. The spacecraft also will track user satellites, determining their exact location in space.

TDRS-8 features the following new and improved services:

• S-band Single Access: Two 15-foot diameter steerable antennas used at the 2.0 to 2.3 GHz (Giga Hertz) band will supply robust communications to user satellites with smaller antennas and receive telemetry and range-safety data from expendable rockets during launch.

• Ku-band Single Access: The same two large antennas, operating at 13.7 to 15.0 GHz, will provide high data-rate support to the International Space Station with high-resolution digital television, and will dump large volumes of data at rates up to 300 Mbps (Megabits per second). This rate is more than 5,000 times faster than the standard "56K" (56 Kilobytes per second) home-computer modem.

• Ka-band Single Access: A new higher-frequency (22.5 to 27.5 GHz) service that increases data rate capabilities to 800 Mbps will provide communications with missions like the International Space Station and future multi-spectral instruments for earth science applications.

• Multiple Access: Using a phased array antenna and operating in the 2.0 to 2.3 GHz range, the system receives and relays data simultaneously from five lower data-rate users and transmits commands to a single user.

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