* Astronomy

During a special Change of Command Ceremony aboard the International Space Station, the reins of the International Space Station were passed from Expedition 24 Commander Alexander Skvortsov to Expedition 25 Commander Doug Wheelock. Expedition 24 crew membersTracy Caldwell Dyson and Mikhail Kornienko will return to Earth on Sept. 24.

Expedition 24 astronauts Doug Wheelock and Tracy Caldwell Dyson conducted the first of two planned spacewalks needed to replace a failed ammonia pump module that helps cool the International Space Station on Aug. 7. They will conduct a second spacewalk no earlier than Aug. 11, and possibly a third to continue the pump replacement effort.

Expedition 24 Soyuz Commander Fyodor Yurchikhin and NASA Flight Engineers Doug Wheelock and Shannon Walker arrived at the International Space Station June 17, docking their craft to the aft port of the Zvezda Service Module on the Russian segment of the station. A few hours later, the hatch opened and Yurchikhin, Wheelock and Walker were greeted by Alexander Skvortsov, Mikhail Kornienko and Tracy Caldwell Dyson, who've been on the station since April. The three newcomers were also welcomed by officials gathered at the Russian Mission Control Center outside Moscow.