The crew of space shuttle Discovery have been examining in detail the exterior condition of their vehicle.
The orbiter left Florida on Tuesday on a 12-day mission to re-supply the International Space Station (ISS).
On Wednesday, astronauts were spending much of their time imaging the shuttle's wings and nose cap with a camera and laser attached to a boom.
The examinations are designed to show up any damage sustained during the eight-and-a-half-minute climb to orbit.
Soon after lift-off, small pieces of insulating foam were seen to fall away from Discovery's external fuel tank, and US space agency (Nasa) officials want to be sure no damage has been inflicted on the orbiter.
The checks were implemented following the Columbia disaster, in which flyaway foam on launch punched a hole in the ship's left wing.
This allowed fiery gases to enter the spacecraft during its descent back to Earth in 2003. All seven astronauts were killed.
Last year's Discovery crew was the first to try out the new inspection procedures, which can detect damage as small as a third of a centimetre (an eighth of an inch).
The camera and laser are attached to the 15m-long (50ft) Orbiter Boom Sensor System, which is itself affixed to the shuttle's 15m-long robotic arm. The set-up is controlled by the astronauts from inside the shuttle.
"We can detect very, very small damage indeed," said Wayne Hale, the shuttle programme manager.
Some three minutes after Tuesday's take-off from the Kennedy Space Center, about six pieces of foam were seen to fall from the orbiter's external tank.
But Mr Hale said Discovery had been so high when the pieces came off, there was not enough air to accelerate them into the ship and damage it.
"It's all very minor. It's all very late... So at the end of the day, I'm very pleased with the performance of the tank. This is a great improvement from where we were," he said.
When the vehicle nears the space station on Thursday, it will perform a back flip so that the ISS crew can inspect further the shuttle's heat-resistant surfaces, particularly on its belly.
The shuttle's seven astronauts - five men and two women - are making the 115th flight of the American shuttle programme.
Their mission to the ISS will deliver almost 13 tonnes of equipment and supplies.
DISCOVERY SHUTTLE FLIGHT
Mission known as STS-121
Discovery's 32nd flight
18th orbiter flight to ISS
Lift-off: 1438 EDT, 4 July
Location: Kennedy Space Center, Launch Pad 39B
Objective: To test new safety equipment and procedures
Payload: Cargo bay has 12.75t of equipment and supplies
Crew: Lindsey, Kelly, Fossum, Nowak, Wilson, Sellers, Reiter
One crew member - German Thomas Reiter - will be staying aboard the orbiting platform when the others leave in just under two weeks.
His residency raises the number of permanent crewmen on the platform to three. He will also become the first European Space Agency astronaut to get an extended stay on the station.
Two, possibly three, spacewalks will be performed during the Discovery mission. At least one of these will be devoted to testing techniques that could be used to repair small defects on the shuttle's surface tiles.
Discovery is due to return to the Kennedy Space Center on 16 July.