Live In Orbit: Astronauts Scan Shuttle Heat Shield

Discovery's astronauts are scanning their spaceship's heat shield to make certain micrometeorites or space junk did no critical damage during its eight-day stay at the International Space Station.

Shuttle pilot Tony Antonelli and mission specialist Joe Acaba -- a former Melbourne High School science teacher -- limbered up the shuttle's robot arm earlier this morning and grappled a 50-foot extension that is equipped with a TV camera and laser sensors.

The astronauts are using the Orbital Boom Sensor System -- or OBSS -- to scan the shuttle's nose cap and its wing panels, all of which are made of composite carbon that is susceptible to damage from micrometeorites or space junk.

The daylong operation has been a standard procedure since NASA returned the shuttle fleet to service after the 2003 Columbia accident. Accident investigators recommended that NASA provide crews with a means of inspecting their spaceships and making repairs in orbit if necessary.

The OBSS was developed as a result of that recommendation and astronauts now also have a rudimentary capability to repair minor damage in orbit.

Discovery's astronauts are in the midst of a three-day trip back to Earth, one that is scheduled to culminate with a 1:42 p.m. Saturday landing at Kennedy Space Center. The weather forecast for landing looks pretty good.

The National Weather Service's Spaceflight Meteorology Group at NASA's Johnson Space Center in Houston issued a forecast today that calls for scattered clouds over the three-mile KSC runway and sustained winds of 13 knots with gusts to 21 knots. Visibility will be seven miles.

The wind direction would pretty much make for a headwind for a landing on Runway 33 on the south end of the landing strip of a tailwind for a landing on Runway 15 on the north end of the landing strip.

No flight rule violations are expected.

The weather forecast for Sunday is considerably worse. Meteorologists say there is a chance of electrically charged clouds and thunderstorms within 30 miles. A sustained crosswind of 13 knots is expected with gusts up to 21 knots -- conditions that all would violate flight rules.