Astronauts aboard space shuttle Atlantis are inspecting the orbiter's heat shield for damage to ensure that the shuttle is capable of re-entering the atmosphere at the end of its servicing mission to the Hubble Space Telescope.

Atlantis's launch yesterday afternoon from Kennedy Space Center in Florida appeared uneventful. But inspection of the shuttle's underside and leading edges is now a routine procedure following the loss of Columbia in 2003, when the shuttle broke up during reentry after sustaining damage to its heat shield from a piece of falling foam insulation at launch.

Initial checks of Atlantis revealed what appeared to be some minor nicking along the right chine, where the wing meets the fuselage, that likely resulted from debris that was detected one minute and 44 seconds into flight. "We did see probably about 21 inches, four tiles in all, with dings in them," lead flight director Tony Ceccacci said in a mission update this afternoon from Johnson Space Center in Houston. Ceccacci added that the damage "looked very minor," in his opinion. NASA will review the inspection data in detail before deciding whether further examination is required.

So how do the astronauts perform the checkup? A boom-mounted sensor attached to the shuttle's robotic arm scans the heat shield, beaming images and laser-ranging data down to mission controllers in Houston, who pore over the pictures.

Astronauts on the shuttle can also look for evidence of missing insulation on the large, orange external tank that fuels the shuttle's main engines during ascent. The tank is jettisoned several minutes into flight, bringing it into view from the shuttle—its fall was captured in a surreal video yesterday by the Atlantis crew.

Since Atlantis is not bound for the safe haven of the International Space Station, as most shuttle missions are, NASA has space shuttle Endeavour standing by at Kennedy Space Center if a crew rescue is deemed necessary.

In the current mission to Hubble, astronauts aim to repair and replace numerous old or faulty components on the aging telescope and install two new scientific instruments. One of them, Wide Field Camera 3, will replace Hubble's workhorse camera, Wide Field Planetary Camera 2 (WFPC2), which has been imaging the cosmos for more than 15 years. To celebrate WFPC2's service, the Hubble team yesterday released the camera's final "pretty picture," a striking photograph of a planetary nebula taken last week.

Photo of Earth from Atlantis: NASA Television