But the ceremony -- to be performed during a transmission between the International Space Station (ISS) and Earth -- is likely to draw the wrath of Malenchenko's military superiors in Russia.

When 41-year-old Malenchenko first announced three weeks ago that he planned to marry 26-year-old Yekaterina Dmitriyeva during his ISS mission, Russia's space agency opposed the plans.

The reason is that Colonel Malenchenko is an active-duty officer in Russia's armed forces and as such, he is prohibited from marrying a foreigner.

"He knows certain secrets. To change his family situation, he must first make a declaration to his superiors," Sergei Gorbunov, spokesman for the Rosaviakosmos agency, said then.

Dmitriyeva, who emigrated from the Soviet Union at age four, is a US citizen and currently lives in Houston, Texas.

But Malenchenko apparently pressed ahead with his plans and when news of the upcoming wedding appeared this week, the agency was "very surprised," but decided to adopt a neutral tone in the matter, a spokesman told AFP Friday.

While the cosmonaut will likely have to answer some questions on his return to Earth, "he won't be thrown into prison for this," the spokesman said.

When the unprecedented ceremony takes place Sunday, Malenchenko will be dressed for the solemn affair -- he received a tuxedo and a wedding ring aboard a Progress cargo vessel that refueled the ISS in June.

The ceremony could also be quite lucrative for the newlyweds as well -- according to a source close to Rosaviakosmos, Dmitriyeva has reportedly negotiated with an American television station to air the blessed event live.

The couple will not have to pay the cost of the transmission -- between 8,000 and 10,000 dollars (7,100 to 8,800 euros) for 10 minutes -- because cosmonauts are allowed to speak with their close ones for free while in orbit, according to Rosaviakosmos.

Malenchenko, who divorced several months ago, proposed to Dmitrieva in December before blasting off for the ISS in April along with US astronaut Eduard Lu.

The couple plans to marry in a church in Russia when Malenchenko returns to Earth from the heavens, before going on to a honeymoon in Australia.

SPACE.WIRE