How you can help wake up a sleeping spacecraft

By Bob McDonald, Quirks & Quarks
This weekend, you can add your voice to a global shout-out to a sleeping spacecraft more than 600 million kilometres from Earth. 

The "Wake Up Rosetta" campaign is looking for personal messages that will be beamed to the spacecraft on Jan. 20. There are even prizes to be given out for the best message.

Rosetta is one of the most ambitious robotic missions ever conceived by the European Space Agency. Launched in 2004, it has been roaming the solar system, gaining momentum so it can rendezvous and make the first-ever landing on a comet later this year. The spacecraft will then stay with the comet and record all the activity as the comet develops a tail while making a journey around the sun.

When it was launched a decade ago, Rosetta did not have enough energy to travel uphill, away from the sun, out beyond Jupiter, where Comet 67P/Churyumov-Gerasimenko (named after its co-discoverers) currently resides.

To gain speed, the spacecraft has circled the sun five times, like a discus thrower winding up for a toss. Each time it passed close to Earth and Mars, it gained gravitational energy from the planets, which flung it out to deep space. 

Along the way, it flew past two never-before-seen asteroids: Steins and Lutetia, so it has already sent back valuable information about small bodies in the solar system.

But now it's time to get down to the real business. For the last 2.5 years, Rosetta has been in hibernation mode as it completed the last leg of its journey. 

Since there was nothing for the spacecraft to do in empty space, most of its instruments were turned off to save power. Thermal blankets and heaters, powered by solar panels that receive less and less power as they get farther from the sun, have kept the robot alive ... hopefully.

Scientists at mission control in Darmstadt, Germany, will be holding their breath next Monday at 10 a.m. GMT (5 a.m. ET) as computers on board begin a complicated sequence of commands to bring the spacecraft back to life. 

It must make sure the solar panels are pointed directly at the sun to absorb all the energy they can; warm up the instruments; turn them on; orient itself in space and find the Earth; then beam a signal back home to verify that it's awake. 

At Rosetta's distance, that signal will take almost an hour to reach Earth. If the spacecraft does not come to life, the careers of scientists who have been working on the project for more than a decade could be lost.

As a gesture to make sure Rosetta remembers the date, scientists are sending a loud wake-up call, made up of video messages from people around the world that will be blasted out into space using one of ESA's deep space radio antennae.

f you join in, your shout, "Wake up, Rosetta!" could win you a prize of space souvenirs; and two winners will be invited to mission control for the comet encounter next November.

And what an encounter that will be. The icy nucleus of the comet is only four kilometres across, a remarkably small target after such a long journey. 

The gravity on this dirty snowball is a million times less than what we feel on Earth. If you stood on the surface, even the smallest step would send you floating upwards, and it would take a minute or so before you floated back down. Pick up a stone and you could throw it into orbit with a soft pitch.

With such low gravity, Rosetta will have to match speed with the comet and go into a lazy orbit, circling around at about a walking pace. That will happen in August. 

Then in November, it will release a probe named Philae that will gently land on the surface and hang on to record activities as the comet approaches the sun. Both spacecraft will stay with the comet for about a year.

If all goes as planned, it should be a spectacular mission, hitch-hiking a ride on a comet, all the way around the sun. So, send in your shout and keep your eyes on Rosetta.