HOUSTON — An expensive, ambitious astrophysics experiment 17 years in the making was installed May 19 on the international space station.
From its new perch on the station’s backbone, the $2 billion Alpha Magnetic Spectrometer (AMS) will hunt for clues about some of the universe’s strangest stuff, from dark matter to antimatter.
The instrument was delivered to the orbiting laboratory by the Space Shuttle Endeavour, which launched on its final mission May 16. The shuttle docked at the station May 18, with the AMS packed inside its cargo bay.
“It’s a great milestone for the hundreds of scientists in 16 countries around the world who’ve been working on the AMS for more than a decade,” said shuttle astronaut Greg H. Johnson after the device was attached to the station.
Astronauts used robots to perform the carefully choreographed transfer of the bus-sized experiment from the shuttle to the station.
Robotic maneuvers
At about 2:30 a.m. EDT, astronauts operating the space shuttle’s robotic arm grabbed the AMS and proceeded to lift it out of the cargo bay. Midway along its journey, the experiment was passed from the shuttle arm over to the space station’s robotic arm, which carried the AMS the rest of the way to its permanent home on the station’s backbone-like truss.
The 6,700-kilogram experiment was installed on the space station at 5:46 a.m.
“Your support and fantastic work has taken us one step closer to realizing the science potential of AMS,” the experiment’s principal investigator, Nobel Laureate Samuel Ting of the Massachusetts Institute of Technology, told the crew after the experiment was installed. “With your help, for the next 20 years, AMS on the station will provide us a better understanding of the origin of the universe.”
The AMS is the most expensive science experiment ever flown on the station. It is a product of 17 years of work by more than 500 scientists in 16 countries.
Huge magnet
The giant experiment houses a 1-meter-wide magnet that will bend the paths of cosmic ray particles flying through space, sending them into special detectors that will measure their properties.
“It’s a particle detector,” Johnson said in a preflight NASA interview. “It collects various cosmic particles that can’t come through our atmosphere to Earth, so this particular experiment can’t be on the surface of the planet.”
Scientists hope these particles will include exotic entities such as antimatter and even strange matter, which contains rare particles called strange quarks. The AMS will also search for signs of the elusive dark matter scientists suspect permeates space but have yet to detect directly.
But the most exciting discoveries of the AMS could turn out to be the ones scientists have not even thought to predict.
“You set up these scientific experiments … and you end up learning something that you didn’t expect,” Gary Horlacher, the shuttle’s lead flight director, told reporters May 19. “Hubble’s done that; all the great observatories have ended up surprising us. Just like Hubble, I expect it to rewrite our textbooks for a long time.”
The experiment almost never got the chance to fly. After the 2003 Space Shuttle Columbia accident, the flight slated to launch the AMS was canceled. It took lobbying by hundreds of scientists, and a bill passed by Congress, to add one more space shuttle mission to launch the AMS.
Tricky installation
The installation of the experiment began with astronauts Drew Feustel and Roberto Vittori controlling Endeavour’s robotic arm, called Canadarm 2, to grab onto the AMS and lift it out of the orbiter’s payload bay.
Then the astronauts handed the instrument off to their crewmates, Greg Chamitoff and Johnson, who were controlling the space station’s robotic arm. The station arm attached to the AMS and carried it over to the lab’s starboard-side truss.
“It takes quite a few hours; it’s a tricky operation,” Chamitoff said in a preflight NASA interview. He pointed out that the attachment mechanism used to install the AMS does not have the same level of redundancy, or backup equipment, in place in case it fails. “I’ll be breathing a little better after that’s been completed and I know that it’s attached successfully, just because we don’t have the redundancy there if something does go wrong.”
The instrument was to be turned on shortly after installation, and should begin recording data almost immediately. Results from the experiment, however, will not be available for months because scientists will need time to collect and analyze its many measurements.
Endeavour is in the midst of a 16-day mission to deliver the AMS and other equipment to the international space station. The mission is the 25th and final spaceflight for Endeavour before it is retired this year along with the rest of NASA’s orbiter fleet.
