Avionics failure to delay Endeavour launch at least a week

February 1, 2000
Web posted at: 2:19 p.m. EST (1919 GMT)

From Space Correspondent Miles O'Brien

CAPE CANAVERAL, Florida (CNN) -- A problem with a critical avionics box has forced NASA to scrub Tuesday's planned launch of the Endeavour. The earliest the space shuttle can now launch is February 9th.

Bad weather first delayed the launch on Monday, but during the countdown a potential problem was discovered in one of two so-called Master Events Controllers. After eight hours of troubleshooting late into the night, NASA engineers were unable to make the glitch repeat. As a result, mission managers decided early Tuesday to scrub the launch and replace the 65-pound box.

It is "absolutely critical that they (the Master Events Controllers) work," said Ron Dittemore, manager of the shuttle program. Space shuttles are equipped with a pair of redundant Master Events Controllers. The microwave oven-sized avionics boxes relay critical commands from the shuttle's onboard computer system to jettison the twin solid rocket boosters and the external fuel tank.

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NASA has a firm rule not launch if there are any concerns about a controller. The loss of one would leave the shuttle only one failure away from a so-called "Criticality One" failure, meaning the catastrophic loss of the vehicle and crew.

The suspect controller failed a routine health check with 20 minutes remaining in the countdown. During the check, computers send the avionics boxes a series of commands that prompted a reply. In this case the response was not what was expected.

"It's looking for a particular pattern of ones and zeroes. If it recognizes the right pattern, you pass the health check. And if it looks like the ones and zeros are in the wrong places, you fail the health check," Dittemore said.

The balky controller passed a second health check, but that was not enough to satisfy the launch team.

The change-out is relatively complex and will take at least a week. Technicians will have to disconnect the pyrotechnic devices linked to the controllers before removing the device.

The controller is located in the aft engine compartment of the shuttle. It can be accessed, but not easily, while the vehicle sits on the pad.

While the shuttle could be ready to fly in a week, the Cape Canaveral launch range may not. The launch of an unmanned Delta rocket may conflict with the shuttle timetable. Nevertheless, NASA hopes to secure a slot to fly on February 9th.

Endeavour's 14th mission is the 97th flight of a space shuttle. Using a sophisticated radar mapping device, Endeavour's six-person crew will spend 11 days in orbit, creating a detailed 3-D map of about 70-percent of the Earth's surface.

The Pentagon's National Imagery and Mapping Agency is NASA's primary customer on this $600 million mission. NIMA creates maps that are used to guide missiles, warplanes and ground troop deployments.

Space Correspondent Miles O'Brien contributed to this report.