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The European Space Agency's $1.7 billion Rosetta mission and its legions of Internet fans got a lift on Friday when the mission's Philae lander resumed sending back science data from the surface of Comet 67P/Churyumov-Gerasimenko.
The Rosetta team gave the Philae lander a lift as well, in hopes of improving its position for soaking up solar energy. Despite the maneuver, Philae's battery power ran down fast. After sending science data for hours, the lander was switched to standby to conserve energy, ESA said.
The Philae lander made an unprecedented touchdown on the comet on Wednesday, right where it was intended to go — but due to problems with its thruster system and automated harpoons, it took a couple of unfortunate bounces and apparently settled into a shadowed region of the 2.5-mile-wide (4-kilometer-wide) comet.
That location made it difficult for Philae's solar panels to recharge its batteries. "Under the low illumination conditions at Philae’s location, it is unlikely that the secondary batteries will charge up enough to enable extended surface operations," ESA's Daniel Scuka said in a blog posting from the European Space Operations Center in Darmstadt, Germany.
The good news from Friday's communication session was that the lander conducted science operations and sent a flood of data back to Earth across a distance of 317 million miles (511 million kilometers). Philae was even able to drill about 10 inches (25 centimeters) into the comet's surface to start collecting samples.
The bad news was that the battery power dropped dramatically. Scuka said the lander was "racing against the clock" to meet as many science objectives as possible before the power ran out.
"Philae's planned mission is expected to come to an end when batteries are exhausted sometime on Saturday; future contacts are possible if the illumination conditions change as the comet orbits closer to the sun, enabling solar power to flow again," Scuka wrote.
Mission managers tried to improve Philae's situation by having the lander execute a "lift-and-turn" maneuver.
The 100-kilogram (220-pound) probe, which is about the size of a washing machine, was commanded to flex its landing legs. As a result, Philae rose up from the surface, turned about 35 degrees, and settled back down with its solar panels in a potentially improved orientation, ESA said.
The effort didn't fully resolve Philae's immediate power problem. Hours after the communication link was re-established on Friday, the lander was placed into idle mode, in hopes that it can be reawakened when the prospects for solar power improve. Despite the recharging problem, the Rosetta mission team said the Philae landing was "more than 100 percent successful."
"Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence," Philae lander manager Stephan Ulamec was quoted as saying in an ESA blog posting. "This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."
The mission continues
No matter what happens to Philae, the car-sized Rosetta spacecraft will continue its observations of the comet from a distance. Scientists say the data collected by Rosetta and Philae about Comet Churyumov-Gerasimenko will yield insights into the chemical composition of primordial stuff left over from the formation of the solar system, 4.5 billion years ago.
The names of the Rosetta and Philae spacecraft are derived from places associated with the Rosetta Stone, which 19th-century archaeologists used to decipher ancient Egyptian hieroglyphs. Similarly, the Rosetta mission's scientists aim to use cometary data to help decipher our solar system's origins.
Rosetta arrived at Churyumov-Gerasimenko in August after a 10-year, 4-billion-mile (6.4-billion-kilometer) trip, and is expected to track the comet for the next year as it makes its way around the sun.
The mission has captured the attention of millions, particularly on Twitter via the #cometlanding hashtag. "My 8-year-old sat by my side, watching BBC and Twitter for comet landing updates. 'This is so cool, Dad,'" British astronomer Nick Howes tweeted.
"Who needs reality TV and politics when you have @ESA_Rosetta and @Philae2014?" Ben Tuff tweeted from Hong Kong.