Rosetta Probe Revived after 31-month Slumber for Comet Rendezvous

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Updated Jan. 24 at 1:32 p.m. EDT

PARIS — Europe’s Rosetta comet-chaser satellite on Jan. 20 awakened itself on schedule after a 31-month hibernation and began preparations for a spring rendezvous with a comet and a fall attempt to attach a probe to it.

First using NASA’s Deep Space Network and then adding the European Space Agency’s own ground antennas, mission managers said all systems appeared functioning onboard Rosetta, which has set a record for the longest satellite hibernation followed by a successful restart.

“Everything seems to be OK,” said Matthew Taylor, Rosetta project scientist at the 20-nation European Space Agency. In a Jan. 24 press briefing with NASA officials, Taylor said the satellite’s instruments would be gradually switched on in March and April, with observations to begin in May.

Launched in March 2004, Rosetta and its small Philae lander are now some 800 million kilometers from Earth. The mission was placed into hibernation in June 2011 because it was too far from the sun to permit its solar arrays to provide full power. All but those essential services needed to keep the instruments from freezing were powered down.

Several dozen officials had their eyes trained on a screen Jan. 20 showing a readout of signals from NASA’s Goldstone, Calif., Deep Space Network antenna. NASA’s Canberra, Australia, facility then joined the hunt. The signal remained flat before spiking some 48 minutes after its expected communications window opened at 12:30 p.m. EST following the Goldstone signal receipt.

“A spectacular few moments of torture,” Martin Kessler, science operations manager, said after the signal was confirmed.

Gerhard Schwehm, long-time Rosetta mission manager, reflecting the stress of the 48-minute wait, said: “What is three-quarters of an hour to wait after 31 months of hibernation?”

In the coming months, Rosetta’s payload of 11 instruments on the satellite and nine on the Philae lander will be activated and tested.

During this time, NASA’s Deep Space Network, Goldstone chief among them using 34- and 70-meter antennas, will track Rosetta for a bit more than eight hours per day for the rest of 2014, and 14 hours daily in 2015, according to Art Chmielewski, U.S. Rosetta project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

NASA has several instruments onboard Rosetta.

ESA’s antennas will take up the balance of the Rosetta observing time.

In May, Rosetta will be inserted into an orbit to follow Comet 67P/Churyumov-Gerasimenko as the path of the comet, which measures 3 kilometers by 5 kilometers, carries it toward the sun.

Starting in August, Rosetta will make numerous looping surveys of Comet 67P as it studies, from different angles, its composition and especially its topography to determine the best place for Philae to land. These maneuvers are not without risk as Comet 67P makes its way closer to the sun and begins spewing off water and other materials, processes that could slightly modify its trajectory and pose challenges for Rosetta as it escorts the comet.

Philae’s landing is scheduled to occur in November after an analysis of the Rosetta data indicates the most favorable landing spot.

Comet 67P’s gravity is so slight — officials described its force as similar to dropping a sheet of paper to the floor — that Philae will not so much land as attach itself to the surface via harpoons.

European Space Agency officials said they are aware of the difficulty involved in the Philae mission, which will operate for just five days on the comet’s surface assuming the mission operates successfully.

Rosetta cost ESA and its participating member states some 1.3 billion euros ($1.75 billion), a figure that includes the Airbus Defence and Space-built satellite, the Philae lander, launch aboard a European Ariane rocket and its planned operations.