Astronauts unload space-scanner at station

“Houston, we’ve got a challenge!”

WASHINGTON – Astronauts installed a massive physics experiment at the International Space Station on Thursday, the fourth day of the US shuttle Endeavour’s 16-day mission to spruce up the orbiting lab.

The Alpha Magnetic Spectrometer-2 is a $2-billion, 15,000-pound (7,000-kilogram) particle detector that will remain at the ISS to scour the universe for hints of dark matter and antimatter over the next decade.

“At 5:46 am EDT, the Alpha Magnetic Spectrometer-2 (AMS) was installed successfully on the outside of the International Space Station’s right side,” NASA said.

“Mission Specialists Andrew Feustel and Roberto Vittori used the space shuttle’s robotic arm to extract it from Endeavour’s payload bay. They handed it off to the space station’s Canadarm2,” it said.

“Pilot Greg Johnson and Mission Specialist Greg Chamitoff then used the robotic arm to install AMS on the starboard side of the station’s truss.”

The detector, part of a 16-nation collaboration that aims to discover how the universe began, is expected to send information to scientists on Earth for the next 10 years.

“It is certainly a challenging operation any time you are moving around large masses like this,” said NASA official LeRoy Cain, though he declined to say it was the “most challenging” project ever done at the space lab.

Meanwhile, NASA managers at mission control in Houston were busily inspecting the shuttle’s heat shield after seven tiles appeared to have been damaged during the orbiter’s ascent Monday.

Three tiles are getting extra attention because they appear to have the most damage, Cain said, adding that the inspection was a routine matter.

“We don’t have any reason for concern or alarm,” he said. “Overall the vehicle is very clean.”

NASA was able to capture high-resolution photos of the shuttle’s exterior when it approached the International Space Station, doing a nine-minute, 360-degree flip before docking at the lab.

The crew is equipped with kits to repair damaged tiles if needed. Shuttle managers will know more about what steps, if any, should be taken in the coming days, Cain said.

Endeavour blasted off on its final mission Monday with six astronauts on board — five Americans and one Italian — and docked at the ISS on Wednesday.

After the Endeavour crew of six greeted the six astronauts already at the orbiting space lab, the team’s first order of business was to transfer the Express Logistics Carrier from Endeavour’s robotic arm to the ISS.

The carrier holds extra parts for the space station, including an ammonia tank, a high-pressure gas tank, a cargo transport container, and a spare arm for the Canadian robot Dextre.

The Endeavour mission is being commanded by astronaut Mark Kelly, the husband of US Representative Gabrielle Giffords, who is recovering after being shot in the head at a January political meeting with local voters.

The shuttle will remain at the space station until May 30, returning to the United States on June 1.

The 30-year US space shuttle program formally ends later this year with the flight of Atlantis, leaving Russia’s space capsules as the sole option for world astronauts heading to and from the orbiting research lab.