A Russian spacecraft has undocked from the International Space Station for a three-week scientific mission before it is buried in the Pacific, officials said.

The Progress M-15M unmanned cargo spacecraft undocked early Tuesday, RIA Novosti reported.

"The undocking was carried out at 01.16 Moscow time," Russia's Mission Control said. "The spacecraft will conduct a series of scientific experiments under the Radar-Progress project."

That project is intended to study the impact of space engines on the Earth's ionosphere.

"After the project is completed the space freighter will be de-orbited and sunk in the Pacific," Mission Control announced.

The freighter, which arrived at the ISS in April, undocked July 23 to test an upgraded Russian automated rendezvous system.

The first attempt to re-dock with the ISS using the Kurs-NA system resulted in failure, but the spacecraft successfully docked on a second attempt July 29 after Russian engineers had reprogrammed the system.

Russia is planning to launch its next space freighter, the Progress M-16M, from the Baikonur space center in Kazakhstan on Aug. 1 to deliver some 2 tons of food, water and fuel supplies to the ISS, RIA Novosti reported.