An Upside Down ‘Star Wars’ Test of Shuttle Fails : Wrong Data Given to Crew, Causing Laser Beam to Miss ‘Target’
An effort to use the space shuttle as a “cooperative target” for a “Star Wars” missile defense experiment failed Wednesday when the Discovery flew over the Hawaiian island of Maui upside down.
Chagrined flight controllers at Mission Control here said the wrong “attitude change information” was supplied to the crew. When that information was fed into the shuttle’s guidance system, it caused the vehicle to roll the wrong way and the Discovery passed over a laser tracking station with a critical window pointing up instead of down. That prohibited the laser beam from hitting a mirror mounted inside the window.
“Sorry about that,” Mission Control told the Discovery’s crew.
Crewmen aboard the shuttle reported seeing the low power laser beam, which was bright blue, so the experiment might have worked if the Discovery had been in the right position. The Discovery will try again when it passes over the same spot Saturday morning.
A Disappointing Turn
It was a disappointing turn in an otherwise flawless mission, following the successful launch of a third communications satellite earlier in the day. The satellite, owned by American Telephone & Telegraph Co., was released from the shuttle’s cargo bay and is on its way to an orbit 22,300 miles above the Earth. At that altitude the satellite will appear stationary relative to the ground, serving the communications needs of AT&T;'s customers in the United States.
The first clue that something was wrong with the laser experiment came as the shuttle approached the Hawaiian Islands. A NASA official said it looked like the ship was “180 degrees” out of position with its right wing pointed down instead of its left.
A mirror already had been mounted inside a window near the nose of the craft. The shuttle was supposed to be positioned so that the mirror would be aimed at the ground. That should have permitted the mirror to reflect the laser beam transmitted from an Air Force station on top of Haleakala Crater on Maui.
After the mix-up, officials with the National Aeronautics and Space Administration huddled in privacy as one official wandered up and down the halls of the press center, muttering “port left, starboard right.”
“We’re still trying to sort out what happened,” James Wetherbee, the shuttle communicator at Mission Control, told the crew.
“Steve (Nagel) and I are taking some amount of static from our commander and pilot,” astronaut John M. Fabian responded. Both Nagel and Fabian are Air Force officers. Daniel C. Brandenstein, the commander, and John O. Creighton, the pilot, are both Navy. The laser experiment is an Air Force operation.
“Roger that, John,” Wetherbee answered. “But I bet you’re not getting half the static that the flight director is passing out.”
Error Occurred on Ground
As it turned out, the error occurred on the ground, not on the shuttle.
A statement issued by NASA said the attitude change information was supplied to the crew in units of feet. Those figures were correctly fed into the on-board guidance system, which was expecting units in nautical miles, not feet.
The laser experiment is the shuttle’s first known participation in the “Star Wars” project. It was designed to see if a low energy laser could be used to track a high speed target about 200 miles above the earth. By its failure Wednesday, NASA unwittingly proved what the Air Force already knew--that the laser would only work on a “cooperative target"--and is not likely to be useful as a tracking device for enemy missiles.
However, this and future experiments should help the Air Force understand the effects of atmospheric interference on lasers, a crucial element in any possible use of lasers as weapons against missiles. It could also demonstrate that lasers could be used to track and control space-based components of a U.S. anti-missile system, including giant mirrors that would reflect high energy lasers onto enemy targets.
Width of Laser Beam
The experiment uses a laser that is about the width of a pencil at its point of origin on Maui. The beam spreads to about 15 feet across by the time it reaches the altitude of the shuttle.
If the beam hits the mirror, when the experiment is tried again Saturday, it should be reflected back to exactly the same spot on Maui.
At that point, the laser will take over control of the Air Force tracking system, locking radar and optical instruments on the shuttle for at least one minute, according to Army Lt. Col. Lee DeLorme, spokesman for the Strategic Defense Initiative Organization.
Researchers hope the experiment will help them in their effort to overcome minor atmospheric interference with laser beams. Heavy cloud cover appears to make use of ground lasers impossible, but some scientists believe it should be possible to get around that problem by placing laser facilities in widely scattered locations, thus increasing the chances that at least some of them would be useful at any given time.