NASA Begins Countdown for Shuttle Mission

NASA began the countdown Sunday for a space shuttle mission that will feature the first spacewalk by Americans in nearly a year and delivery of a giant communications satellite.

“I’m chomping at the bit and ready to light off those (rockets) and fly,” shuttle commander John Casper said after arriving here with his crew.

The countdown clocks began ticking at 1 p.m. EST toward a Wednesday morning liftoff of the Endeavour. It will be the year’s first shuttle launch--eight are planned for 1993--and the 53rd since shuttles began flying in 1981.

“Everybody’s geared up, anxious for a good on-time launch Wednesday morning,” said shuttle test director Mike Leinbach.

Tucked inside the National Aeronautics and Space Administration’s newest spaceship is a $200-million Tracking and Data Relay Satellite. Endeavour’s five astronauts are to release the satellite six hours after liftoff, and, soon afterward, a rocket is to propel the craft into a 22,300-mile-high orbit.

Four such satellites are already in orbit, transmitting data from other satellites to ground controllers and vice versa. Each TDRS can track up to 32 satellites and relay the equivalent of a 20-volume encyclopedia in one second through just one of its channels.

Once the satellite is freed from the shuttle cargo bay, the astronauts will conduct plant, rat and fire experiments until the next major event, a five-hour spacewalk by two crew members on the fifth day of the flight.

NASA added the spacewalk to the mission just two months ago, long after the crew began training for the flight.

The agency wants more spacewalking experience before astronauts start building an orbiting space station in 1996. The spacewalk by Mario Runco Jr. and Gregory Harbaugh is also expected to contribute to preparations for a mission to repair the Hubble Space Telescope at the end of this year.

NASA hopes to add a spacewalk to at least one other shuttle flight before the Hubble mission.

The extra outings should improve the efficiency of future spacewalks by up to 10%, and that would reduce the number of spacewalks needed to build the space station, said Ron Farris, head of NASA’s spacewalking section.