The six astronauts orbiting Earth on space shuttle Discovery are keeping busy during their mission’s first full day in space. Friday, the astronauts spent around six hours conducting a heat shield inspection.

A large piece of foam had fallen away from an external fuel tank after Thursday’s launch, which appeared to then hit the shuttle’s thermal tiles.

But the incident occurred four minutes into the flight — a time, NASA analysts say, that presents far less danger than in the first moments after launch. The foam reportedly did no damage to the tiles.

Via Twitter, NASA said, “We’re rigorously inspecting it, but it occurred late in flight, after window of concern.”

From NPR’s Nell Greenfieldboyce:

The astronauts started their day with a musical wake-up call from Houston — when Mission Control beamed up the song “Through Heaven’s Eyes,” from the soundtrack of the movie Prince of Egypt, to the shuttle.

After breakfast, the crew got to work. They’re using the shuttle’s robotic arm and a set of sensors to do a thorough inspection of Discovery’s heat shield. This has become a routine precaution for shuttle missions, to make sure that no damage occurred during launch.

On their 11-day mission, the astronauts are scheduled to conduct two spacewalks. And around mid-day Saturday (2:19 p.m. ET), Discovery will dock with the International Space Station, bringing the orbiting facility some fresh supplies — and a new storage room.

The weekend rendezvous will present a rare circumstance, says Greenfieldboyce: The space station will be hosting vehicles from all its sponsoring entities. The station already has craft from the space agencies of Europe, Japan and Russia docked to it.

You can track the paths of both Discovery and the ISS at a site called — you guessed it: Real Time Satellite Tracking. On the map, the shuttle follows the orange-red line, while the space station follows the yellow one. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.