From my friend at NASA:
Astronaut Ron Garan took this image during the spacewalk conducted on Tues., July 12, 2011. It shows the International Space Station with Space Shuttle Atlantis docked on the right and a Russian Soyuz on the far left. In the foreground is the Alpha Magnetic Spectrometer (AMS) experiment installed during the STS-134 mission. AMS is a state-of-the-art particle physics detector designed to use the unique environment of space to advance knowledge of the universe and lead to the understanding of the universe’s origin by searching for antimatter and dark matter, and measuring cosmic rays.