Shuttle delivers crucial, and costly, device

CAPE CANAVERAL, Fla. —A mammoth cosmic ray detector arrived at the International Space Station on Wednesday, a $2 billion experiment that will search the invisible universe and help explain how everything came to be.

It's the most expensive cargo ever carried by a space shuttle and almost didn't make it to orbit before the fleet retires this summer. Endeavour, making the second-to-last flight, docked at the space station after doing a slow backflip so cameras could capture any signs of launch damage. NASA said it was taking a closer look at some gouges and nicks on the shuttle's belly but there was no cause for concern.

Two astronaut teams were assigned to attach the Alpha Magnetic Spectrometer to the outside of the space station on Thursday, using a pair of robot arms, where it will stay for the life of the outpost.

The scientists on Endeavour's crew said it will justify the scientific purpose of the space station.

"It's in the same scale of importance as Hubble (Space Telescope)," astronaut Gregory Chamitoff said before the flight. "And it is going to be by far the biggest, most expensive and perhaps the most fundamentally valuable science apparatus we have on the space station."

Physicist Phil Schewe said the experiment is part of a centuries-long tradition of scientists exploring the building blocks of matter, from elements to atoms to subatomic particles.

"This is just a grand extension of trying to answer the question, why we have matter and what it is," said Schewe, a spokesman for the American Institute of Physics.

"Is this a big deal? Especially if they find something, yes it is."

The 7-ton instrument has been 17 years in the making, and involves 600 scientists from 16 countries. The heart of the experiment is a magnet ring 3 feet across.

The made-in-China magnet will bend the path of charged cosmic particles as they pass through eight detectors, enabling scientists to identify their properties.