Alarm call set to wake comet probe

An alarm clock in deep space was expected Monday to wake up the comet probe Rosetta ahead of a key phase in its 10-year mission, European scientists said. Rosetta's onboard computer was programmed to give the wakeup call at 1000 GMT, but it would take at least seven hours for mission control to get confirmation it has worked, they said. The craft was launched in 2004 on a trek of seven billion kilometres (4.3 billion miles) around the inner Solar System. Its goal is to rendezvous in August with a comet, 67P/Churyumov-Gerasimenko, and in November send down a lander to carry out experiments on the icy wanderer. Comets are clusters of ice and dust which are believed to be remnants from the very birth of our star system. Analysing this primeval matter should unlock secrets of how the Solar System formed and possibly how life on Earth was kickstarted. Alvaro Gimenez Canete, the European Space Agency's director of science and robotic exploration, referred to the carved stone that in the early 19th century unlocked Egyptian hieroglyphics and revealed the life of the Pharaohs. "Rosetta and the comet 67/P may become the Rosetta Stone for planetary science," he said. Rosetta was placed in hibernation for 31 months because it was so far from the Sun that light was too dim to power its solar array. The wakeup procedure should take a number of hours, followed by a tiny "all is well" signal, which will take 45 minutes to cross a distance of more than 800 million km (500 million miles). "The window in which we expect the nominal signal, if everything goes according to plan, is of about an hour, between 1730 and 1830 GMT," Paolo Ferri, ESA's head of solar and planetary missions, told AFP by phone from mission control in Darmstadt, Germany. Rosetta will progressively carry out braking and steering manoeuvres designed to get it on track with Comet "C-G." In August, the craft will be inserted into an orbit just 25 kilometres (15 miles) above the comet, using 11 cameras, radar, microwave, infrared and other sensors to scan its surface. The billion-dollar craft carries a fridge-sized robot laboratory, Philae, designed to harpoon itself to the "dirty snowball" surface and carry out experiments. "We want to know everything about the comet -- magnetic field, composition, temperature, everything," said Amalia Ercoli-Finzi, in charge of one of the 10 instruments aboard Philae. Over the last quarter-century, 11 unmanned spacecraft have been sent on missions to comets, most of them flybys. Successes include the US Stardust probe, which brought home dusty grains snatched from a comet's wake, and Europe's Giotto, which ventured to within 200 km (120 miles) of a comet's surface. If Rosetta succeeds, it would cap them all in terms of its sampling size and proximity. Thomas Reiter, ESA's director of human spaceflight and operations on Monday described the Rosetta venture as "one of the superlatives". "It's truly unique and in William Shakespeare's words, 'stuff dreams are made of.'"