International Space Station (ISS) Expedition 31 Flight Engineer Don Pettit: “My star trail images are made by taking a time exposure of about 10 to 15 minutes. However, with modern digital cameras, 30 seconds is about the longest exposure possible, due to electronic detector noise effectively snowing out the image. To achieve the longer exposures I do what many amateur astronomers do. I take multiple 30-second exposures, then ‘stack’ them using imaging software, thus producing the longer exposure.” Donald Pettit worked as a scientist at the Los Alamos National Laboratory until 1996, when he was selected as an astronaut candidate. Pettit's first space mission was as a mission specialist on ISS Expedition 6 in 2002 and 2003. He was Mission Specialist 1 on the STS-126 mission to deliver equipment and supplies to the ISS and performed experiments on board ISS related to clumping of solid particles in microgravity. Pettit again launched to the International Space Station on December 21, 2011 as part of the Expedition 30/31 crew. He and fellow crewmembers Oleg Kononenko and André Kuipers arrived at the ISS on December 23. On May 25, 2012, Pettit and Kuipers operated the Canadarm2 to grapple the SpaceX Dragon and berth it to the Harmony module. Pettit was the first to enter the unmanned supply ship on May 26, making him the first astronaut in the history of space exploration to successfully enter a commercially-built and operated spacecraft docked in the ISS in orbit.