MOSCOW, September 13. /TASS/. Russian crew at the International Space Station wil be curtailed to two cosmonauts at a time from the current three cosmonauts as of next spring and will remain curtailed until the commissioning of a Multirole Laboratory Module (MLM), which is scheduled for the end of 2017, a well-informed source in the Russian aerospace industry told TASS.

"In case the endorsed schedule is observed and the MLM gets into operation in December 2017, the curtailment will affect only one Russian crew," the source said. "Otherwise the practice of curtailment will continue until the commissioning of the module."

The Russian state space corporation Roscosmos has to downsize the ISS mission crew as the number of Progress cargo ships launched to the ISS annually will be reduced to three from four at present in the wake of NASA's refusal to continue using the Progresses and to change over to new U.S. cargo carriers instead, the source said, adding that three Progresses a year is not enough to support three cosmonauts working at the ISS permanently.

In this connection, the Russian missile corporation Energiya is developing a new cargo ship that will have a greater payload.

As part of the crew cuttailment plan, Roscomos may swap the crews due to go into space in March and in May.

In March 2017, the Soyuz MS-04 ship is due to take to the ISS the cosmonaus Alexander Misurkin and Nikolai Tikhonov and NASA astronaut Mark Thomas Vande Hei, while the cosmonaut Fyodor Yurchikhin, Nasa astronaut Jack David and the European Space Agency astronaut Paolo Nespoli of Italy are suppsed to head for the ISS in May. foreign partners will receive

The source told TASS Thomas Vander Hei's professional upgrading to Level 1 from 2 Flight Engineer. Should the third place on the Soyuz become vacant, the procedure for replacement of the crews may change and a young Russian cosmonaut may go into space with a visiting crew for a period of several days.

The partners will be familiarized with the final decision right before next launch of a manned space vehicle scheduled for next week, the source said.