WASHINGTON — After two spacewalks, one fewer than NASA thought it would take, astronauts replaced a balky valve in the international space station’s cooling system, setting the stage for Orbital Sciences Corp. to launch a cache of supplies to the outpost Jan. 7.

The valve, which began acting up Dec. 11, is designed to regulate the temperature of the ammonia in the station’s main cooling system. The malfunction forced NASA to temporarily deactivate some science equipment and postpone Orbital’s resupply mission to allow spacewalking astronauts to replace the faulty hardware.

The repair work was carried out by crewmen Rick Mastracchio and Mike Hopkins during spacewalks Dec. 21 and Dec. 24. Japanese astronaut Koichi Wakata assisted the procedures, operating the station’s Canadian-built robotic arm from the outpost’s interior.

The replacement valve passed preliminary checks Dec. 24 and appears to be functioning properly, NASA said in a statement posted on its website.

On the Dec. 21 spacewalk, water entered Mastracchio’s spacesuit. NASA, in a press release, said the malfunction was unrelated to a July incident in which the spacesuit worn by European Space Agency astronaut Luca Parmitano — who was not injured — flooded. Nevertheless, Mastracchio used a different suit for the Dec. 24 spacewalk.

NASA’s impromptu spacewalks pushed Orbital Sciences Corp.’s first contracted cargo delivery mission to the space station from mid-December to January. Dulles, Va.-based Orbital is now set to launch its Antares rocket and Cygnus space capsule to station no sooner than Jan. 7 — six days earlier than the company thought it would fly when NASA first postponed the mission to stage the holiday spacewalks.

Orbital, on its website, said it moved the launch up because of “a conflict with a previously scheduled operation” at NASA’s Wallops Flight Facility on Wallops Island, Va., from which the company launches its space station resupply missions.

After Orbital, the Russian space agency, Roscosmos, will make its own cargo delivery to station using a Progress freighter slated to launch from the Baikonur Cosmodrome in Kazakhstan Feb. 5. Space Exploration Technologies Corp., the only NASA contractor able to return cargo from station, will be next. The Hawthorne, Calif., company is slated to fly Feb. 22 at the earliest.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.