Two and a half years is a long time to sleep—even for a machine. That's how long Rosetta has slumbered in its decade-long journey towards the comet where it will land. But in the dead of the night, at 2am PST tomorrow morning, Rosetta will awaken. Here's how its alarm clock works.
Rosetta is many millions of miles away from Earth by now, well on its way towards the Churyumov-Gerasimenko comet, where it'll land in May of this year. Rosetta has been "chasing" the comet for years, building up the speed it has taken to get near enough the comet to attempt a landing. In 2011, the solar-powered craft got so far away from the Sun that the ESA put it into a "deep-space slumber," spinning slowly at a rotation of once every minute. Now, Rosetta's close enough to the Sun again to be fully powered and awake.
In the video above, the ESA explains how it's all going to happen, thanks to what it describes as "the most important alarm clock in the solar system." At 10:00 GMT tomorrow, the onboard computer will carry out a sequence of events that will rouse its systems. First, its startrackers will begin warming up—these are the sensors that let Rosetta navigate towards the comet. That'll take about six hours. Then, the craft's thrusters will fire, slowing down the stabilizing rotation I mentioned earlier. It'll also reorient its solar arrays to better capture solar energy.
Finally, the startrackers will be switched on, and Rosetta will be able to turn towards Earth and begin communicating for the first time in years. Because it's so incredibly far away from us, there'll be a 45 minute lag between when it sends its first message and when NASA's tracking dishes in Goldstone, California, will receive it:
Image via Wikipedia.
Are the ESA and NASA nervous? Absolutely. Agency advisor Mark McCaughrean put it this way to Raw Story:
If the alarm fails and Rosetta does not rouse itself, we will be in trouble. On the day, we will all be waiting in the control room, anxious to hear a signal from Rosetta. However, it will take several hours for the craft to complete its wakeup procedures before it transmits a message to Earth to let us know it is alive and well. It will be a nerve-wracking day.