Shuttle's TV antenna quits; repairman a long way away

Before the shuttle's Ku antenna failed, Commander Brian Duffy, left, and Japanese astronaut Kiochi Wakata gathered on the Discovery's flight deck to talk to Japanese officials in this view from television Thursday

From Miles O'Brien
CNN Space Correspondent

(CNN) -- A satellite dish that extends from the cargo bay of the space shuttle Discovery mysteriously failed Thursday morning, leaving the seven-member crew without a radar used for navigation and without any means of transmitting full-motion TV pictures from space.

The Ku band antenna is used as an uplink to a network of NASA satellites in geosynchronous orbit. It is designed to transmit and receive voice and data streams and TV signals and is used as a radar range finder.

The radar system is typically used by shuttle commanders during docking with the International Space Station. It provides accurate data on the relative distance between the two orbiting vehicles during certain phases of the rendezvous. But NASA ground controllers say Friday's planned docking at the station (1:45 PM EDT) will go on as scheduled -- employing several other navigational devices.

"We do not expect any impact to the mission," said lead Flight Director Chuck Shaw. "It does not change anything we want to do for the mission."

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Shuttle crews employ several other systems to safely home in on the station: a "Star Tracker" that focuses on points of light (including docking lights on the station); two laser range finding systems, one built into the orbiter and another handheld device not unlike a police speed detection device; and a camera attached to the docking port that aims at a visual target on the station.

Shuttle crews headed for the station routinely practice dockings in simulators without the help of Ku radar data.

Discovery's crew will be able to communicate with ground controllers using S-Band satellite antennas that are lodged beneath the orbiter's heat shielding tiles. The S-Band system is capable to transmitting "slow scan" video images -- more akin to a slide show.

"Right now I would not bet you are going to get full motion TV back," Shaw said. "I would put it in the irritant category, but its a shame because it (the TV) is fun to watch."

Engineers are not certain what caused the failure, but they and the crew are troubleshooting the problem.

The Ku band system has been a fairly reliable system for NASA, failing only once before -- on a Discovery mission in June 1998. During that mission Discovery performed the ninth -- and final -- shuttle docking at the Russian space station Mir. No TV images were beamed back to Earth during the mission.

This is the 100th mission in space shuttle history. The multinational crew will perform four spacewalks leaving 18,000 pounds of hardware behind at the International Space Station.

They are attaching a piece of lattice-work structure (the Z-1 Truss) that will serve as the platform for the U.S. solar arrays and adding a docking port for future shuttle visits. Two pairs of astronauts will conduct four consecutive spacewalks to connect the components to the station. The mission is slated to last 11 days.

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Shuttle Orbiter Discovery (OV-103)
NASA
Human Space Flight (HSF) - International Space Station

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