London/Washington: The European Space Agency's (ESA) Rosetta mission is set to complete its historic 12-year journey in a controlled descent to the surface of its comet on Friday.
The spacecraft arrived at its destination comet on Aug 6, 2014, becoming the first mission in history to rendezvous with a comet and escort it as it orbits the Sun.
The final hours of descent will enable Rosetta to make several once-in-a-lifetime measurements, including analysing gas and dust closer to the surface than ever possible before.
The spacecraft will also take very high-resolution images of the comet nucleus, including the open pits of the Ma'at region where the spacecraft is expected to make its controlled impact.
"These data should be returned during the descent up to the moment of final impact, after which communication with the spacecraft will not be possible," the ESA said in a statement on Thursday.
The Rosetta spacecraft arrived at Comet 67P/Churyumov-Gerasimenko following a ten-year journey through the solar system after its launch on March 2, 2004.
The Philae lander was sent down to the surface of the comet on November 12, 2014.
After two years living with the comet, returning an unprecedented wealth of scientific information during its closest approach to the Sun, Rosetta and the comet are now heading out beyond the orbit of Jupiter again.
"Travelling further from the Sun than ever before, and faced with a significant reduction in solar power that it needs to operate, Rosetta's destiny has been set: it will follow Philae down onto the surface of the comet," the ESA said.
Rosetta has provided many important clues for scientists to put together to solve key questions regarding the comet's origin and evolution, its place in the early solar system, and the possible role of comets in delivering ingredients considered crucial for the emergence of life on Earth, including water and organic materials.
NASA Television and the agency's website will air the conclusion of Rosetta mission, with commentary, interviews and analysis of the successful mission.
Rosetta was launched carrying 11 science instruments, with several contributions from NASA.
ESA is ending the mission because the spacecraft's ever-increasing distance from the Sun has resulted in significantly reduced solar power to operate the spacecraft and its instruments.
Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed.