WASHINGTON, Jan. 25 (Xinhua) -- Two astronauts on Saturday finalized the repair of a cosmic particle detector in searching for dark matter and antimatter after a spacewalk outside the International Space Station (ISS).

European Space Agency astronaut Luca Parmitano and U.S. space agency NASA astronaut Andrew Morgan wrapped up their six-hour-16-minute spacewalk at 1:20 p.m. U.S. Eastern Time, completing repairs on a cooling system for the Alpha Magnetic Spectrometer (AMS).

The 7.5-ton device, launched to the space in 2001, was developed by a 600-member multinational team. It features a thermal control system developed by Chinese scientists. The duo had completed three complex spacewalks to repair the cosmic ray detector.

This time, they conducted leak checks for the cooling system on the AMS and opened a valve to being pressurizing the system, according to NASA.

NASA's ground teams will work over the next several days to fill the new AMS thermal control system with carbon dioxide, allow the system to stabilize, and power on the pumps.

The astronauts also completed an additional task to remove degraded lens filters on two high-definition video cameras.