Astronauts aboard the space shuttle Endeavour are installing a particle physics detector on the International Space Station, NASA said on Thursday.

The $2-billion Alpha Magnetic Spectrometer (AMS) was delivered to the ISS by Endeavour on Wednesday.

The AMS is a 2-ton ring of powerful magnets and ultrasensitive detectors built to track cosmic rays in a search for various types of unusual matter, including anti-matter and dark matter.

The astronauts are using robotic arms both on the shuttle and on the station to install the instrument onto the starboard side of the station's truss structure.

After the installation the AMS will be operated remotely from Earth for the remaining service life of the orbital station.