The fourth day of the mission will focus on the installation of the Alpha Magnetic Spectrometer-2 (AMS), a particle physics detector. The AMS is a 2-ton ring of powerful magnets and ultrasensitive detectors built to track, but not capture, cosmic rays in a search for various types of unusual matter. The 15,251-pound instrument will be connected to the outside of the International Space Station, tilted a bit so it will not interfere with any of the station's mechanisms and storage platforms. It will be operated remotely from Earth and should not require any attention from astronauts in orbit.
The mobile transporter is in position. The crew will extract AMS using the space shuttle robotic arm at 1:56 a.m. Shortly thereafter, the station crew will wake, and at 3:01 a.m., the shuttle robotic arm will transfer AMS to the station's robotic arm. At 3:41 a.m., the crew will manipulate the station arm to install AMS onto the starboard side of the station's truss structure on the zenith side.
Later this morning, the crew will participate in interviews.
Toward the end of the flight day, the crew will review procedures for the mission's first spacewalk, and spacewalkers Drew Feustel and Greg Chamitoff will begin their camp out at a reduced air pressure, a procedure that helps purge nitrogen from their bloodstreams and prevents the “bends” when they exit the airlock.