Comet probe on cusp of history

A spacecraft is on course to make history by landing the first probe on a comet, but first it must end its two-year hibernation. Rosetta, operated by the European Space Agency, has been dormant since Jul 2011 and its alarm clock is set for 10am GMT on Jan 20.

It blasted off more than 10 years ago, and the input of two Irish companies is critical to it achieving its objective of landing on comet 67P/Churyumov–Gerasimenko.

Captec in Malahide, Dublin, developed the support system software that allows Rosetta communicate with Philae, the comet lander, while Space Technology Ireland at Maynooth University built the hardware unit that will handle data returning from the lander.

Comets are leftovers from the solar system’s construction 4.5bn years ago and thought to have ferried to Earth the ingredients that helped life evolve. With the lander and the fact Rosetta will orbit the comet — another first — for 17 months, scientists hope to learn more about the early evolution of the solar system, while also seeing how a comet is transformed by the Sun.

As it approaches the comet, Rosetta — named after the stone that led to the deciphering of Egyptian hieroglyphics almost 200 years ago — will determine a landing site, then approach to within 1km of its target next month. Using harpoons to keep it in place, the lander will gather samples for examination by automatic onboard microscopes and take images.

Firstly, though, the Rosetta team is excitedly preparing for the spacecraft to wake up, warming its navigation instruments, before pointing its antenna at Earth to let the ground team know it is still operational.

“We don’t know exactly at what time Rosetta will make first contact with Earth, but we don’t expect it to be before about 17:45 GMT [on Jan 20]”, said Fred Jansen, Rosetta mission manager. “We are very excited to have this important milestone in sight, but we will be anxious to assess the health of the spacecraft after Rosetta has spent nearly 10 years in space.”

After wake-up, the spacecraft will still have about 9m km to travel. By May, it will be 2m km from its target, and will manoeuvre to line up for rendezvous with the comet in August. The first images of 67P/Churyumov–Gerasimenko are expected at this time.