Russian unmanned spacecraft docks on second try

MOSCOW (Reuters) - An upgraded Russian unmanned spacecraft successfully linked up with the International Space Station on Sunday on its second attempt to test a new docking system, Russia's space agency said.

The docking set aside doubts over the new Kurs-NA rendezvous system that will deliver astronauts and future cargoes to the orbital station after a botched first test when the equipment malfunctioned due to low temperatures earlier this week.

The operating system functioned properly after it was allowed to warm up, according to a statement from the U.S. space agency NASA.

Kurs-NA is an upgrade of the Kurs docking gear used for years on Russia's manned Soyuz and robotic Progress spacecrafts.

The system consolidates five antennas into one, has updated electronics and is designed to improve safety and use less power, according to NASA.

The Progress ship re-docked with the Pirs module at 0100 GMT (9 p.m. EDT on Saturday), the Russian space agency Roscomos said in a statement, for a brief final stay before the single-use craft, laden with space station trash, is due to burn up on re-entry over the Pacific Ocean on July 30.

Since the retirement of the U.S. space shuttles last year, the United States has been dependent on Russia and is paying $60 million per person to fly astronauts to the ISS, a $100 billion research complex orbiting 240 miles above Earth.

Moscow is struggling to restore the prestige of its once-pioneering space program after a string of launch mishaps last year, including the failure of a mission to return samples from the Martian moon Phobos.

Six astronauts are currently aboard the orbital outpost: American Sunita Williams, Japan's Akihiko Hoshide and Russian Yury Malenchenko joined cosmonauts Gennady Padalka and Sergei Revin and US astronaut Joseph Acaba earlier this month.

(Reporting By Alissa de Carbonnel, editing by Tim Pearce)