CAPE CANAVERAL, Fla. -- A NASA communications satellite has reached its proper orbit over the equator despite a problem with the spacecraft that delayed the maneuver several weeks.
Built for NASA by Boeing Integrated Defense Systems, the Tracking and Data Relay Satellite (TDRS-I) was launched atop an Atlas 2A rocket from Cape Canaveral on March 8.
The satellite delivery mission successfully inserted the spacecraft into an egg-shaped geosynchronous transfer orbit. The high end of the orbit was at the proper altitude of 22,300 miles (35,897 kilometers) but the low end still needed to be raised until the orbit was shaped like a circle.
Thrusters aboard TDRS-I were supposed to do the job, relying on two fuel tanks to supply the needed propellant. The trouble came when one of those two tanks would not pressurize, so there was no way to force half the propellant into the thrusters to complete the maneuver.
In a procedure that Boeing officials described as being like a "remote control coronary bypass," engineers routed the helium gas used to pressurize the tanks through the plumbing so they bypassed a stuck valve, which was to blame for the trouble.
A series of thruster firings during the past four months ended on Sept. 30 with TDRS-I in its final, proper orbit.
"The TDRS-I recovery effort was an incredible feat that demonstrates the inherent design robustness of our products and the incredible space operation knowledge and experience of our team," Randy Brinkley, president of Boeing Satellite Systems (BSS), said in a prepared statement.
During the next eight weeks controllers will order the satellite to deploy its antennas and run TDRS-I through a series of routine tests. Based on the remaining amount of propellant, the satellite is expected to fulfill its contractually required 15-year service life, Boeing officials said.
TDRS-I was launched as part of an $840 million program to eventually replace six aging sister craft, which are considered critical to every major NASA spaceborne program from the International Space Station to the Hubble Space Telescope.
The first of the three, TDRS-H, was launched by an Atlas 2A rocket in June 2000. TDRS-I marked the second and the third, TDRS-J, is to be lofted by an Atlas 2A on Nov. 20 between 10:36 and 11:16 p.m. EST (0236 to 0316 GMT Nov. 21).
The trio of enhanced spacecraft include improvements that will allow high-resolution TV signals to be beamed between a space shuttle and the ground. It will also relay enormous amounts of data at speeds 5,000 times faster than a typical 56K home computer modem.
Television, science data, radio signals, spacecraft telemetry and even e-mail is relayed between Earth and space thanks to this network of spacecraft, the first of which was launched into orbit by the space shuttle Challenger in 1983.
Demand has grown for the aging TDRS fleet. Initially designed to last seven years, they are on average now more than 12 years old, NASA in 1995 began an effort to orbit three modernized and more capable TDRS.
Once TDRS-I is declared operational and ownership is turned over to NASA, the satellite will be known as TDRS-9.
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