Europe's comet chaser makes last call home
Europe's comet chaser has now flown a little over 4.5 billion kilometres of its 7.1-billion-kilometre journey that will end in the outer Solar System in May 2014.Paris -- A billion-euro (1.5-billion-dollar) European spacecraft made a final flyby of Earth on Friday, using the planet as a gravitational slingshot to speed to a rendezvous with a comet in 2014.
"Rosetta passed over the ocean, just south of the Indonesian island of Java, at exactly 08:45:40 CET," or Central European Time, which is 0745 GMT and 40 seconds, European Space Agency (ESA) announced.
"The swing-by was pre-planned and fully automated, and the spacecraft was in direct communication with Earth at the time."
The probe sped past Earth at just over 13.3 kilometres per second, equal to 47,800 kph or 29,925 mph.
Thanks to the gravitational catapult, the spacecraft accelerated by a massive 3.6 km/s (12,960 kph, 8,100 mph).
Europe's comet chaser has now flown a little over 4.5 billion kilometres of its 7.1-billion-kilometre (4.4-billion-mile) journey that will take it to Comet 67P/Churyumov-Gerasimenko in the outer Solar System in May 2014.
Rosetta is carrying a fridge-sized lab, Philae, that it will send down to the comet.
Anchored by tiny hooks, Philae will look for clues about the Solar System's primal past, exploring a theory that comets are primitive rubble left over from the making of the Solar System.
Understanding their composition can help explain how planets formed from discs of dust and gas, and maybe even how life was kickstarted on Earth, astronomers believe.
Some of Rosetta's instruments were switched before the flyby, and ESA announced it would release a first batch of images and data later Friday.
The swing-by could also shed light on a curiosity first spotted in 1990: spacecraft get a tiny, unexpected acceleration, of just a few millimetres (fractions of an inch) per second, in a gravity assist.
Some scientists speculate that Earth's rotation may be distorting the fabric of "space-time" more than expected.
If so, this would require a fix to Einstein's theory of general relativity -- the currently accepted theory of gravity.
"It's a mystery as to what is happening with these gravity events" said Trevor Morley, lead flight dynamics specialist at Rosetta's mission control at Darmstadt, Germany.
"Some studies have looked for answers in new interpretations of current physics. If this proves correct, it would be absolutely ground-breaking news."
Two previous flybys used Earth, and another used Mars to gain speed.
The craft is scheduled for a close encounter with a space rock, 21 Lutetia, next July as it hurtles through the asteroid belt.
After that, the spacecraft will be progressively placed in deep-space hibernation, settling down for the coldest leg of her journey to receive a wakeup call only in early 2014.