The European Space Agency's comet-chasing Rosetta probe is being woken up from its "deep space hibernation" after two-and-a-half years today.
An internal alarm clock onboard the spacecraft was set to go off at 10am GMT to rouse it from its slumber to resume its mission towards Comet 67P/Churyumov-Gerasimenk.
The Wake Up Call
Rosetta’s computer is programmed to carry out a sequence of events to re-establish contact with Earth when its "alarm clock" goes off:
- First the spacecraft’s startrackers will begin to warm up, taking around six hours.
- Then its thrusters will fire to stop its current slow rotation.
- After a check to ensure its solar arrays are still facing directly towards the Sun, startrackers are switched on to determine the spacecraft’s attitude.
- Next Rosetta will turn directly towards Earth, switch on its transmitter and point its high-gain antenna to send its signal to announce that it is awake.
The first signal from the spacecraft is not expected before 17:30 GMT as it has to travel more than 500 million miles back to Earth.
Since its launch in 2004, Rosetta has been chasing down Comet 67P/Churyumov-Gerasimenko.
The comet is orbiting the Sun once every 6.5 years between the orbits of Jupiter and Earth.
After Rosetta's lander reaches the comet, the main spacecraft will follow the comet for several months as it heads towards the Sun.
The mission's goal is to unravel the secrets of a frozen comet and its transformation by the warmth of the Sun.