Comet lander re-establishes contact with Earth after seven months
After seven months of silence, the European Space Agency’s (ESA) Philae comet lander has emerged from hibernation long enough to relay data back to mission control. On June 13, 14, and 19 the lander successfully transmitted operational data via its mothership, the space probe Rosetta, to the ESA’s European Space Operations Centre, in Darmstadt, Germany.
On Nov. 12, 2014, the ESA made history by landing Philae on the surface of Comet 67P/Ghuryumov–Gerasimenko—no small task considering that Comet 67P is roughly 308 million kilometres away from Earth. Unfortunately, the landing craft’s automated harpoon system did not deploy as planned during touchdown, and, as a result, Philae “bounced” into the shadows where it was unable to adequately charge its solar-powered batteries.
After only 60 hours operating on the surface of the comet, Philae was forced to power down. Seven months later, however, it appears as though Philae may be attempting a comeback.
“We are still examining the housekeeping information…but we can already tell that all lander subsystems are working nominally, with no apparent degradation after more than half a year hiding out on the comet’s frozen surface,” said Dr. Stephan Ulamec, Philae project manager at the Lander Control Center (LCC), in a statement issued by the ESA. “The lander is ready for operations.”
As Comet 67P moves closer to the sun along its elliptical orbit, the sunlight reaching Philae is expected to increase. In fact, data from the recent transmissions have already indicated that sunlight conditions are improving.
“At present, the lander is operating at a temperature of zero degrees Celsius, which means that the battery is now warm enough to store energy,” said Micheal Mailbaum, deputy operations manager at the LCC, in a June 19 press release. “More solar panels were illuminated; at the end of [the most recent] contact, four of Philae’s panels were receiving energy.”
Although communications between Philae and Earth have been brief so far—the longest transmission lasting only 19 minutes—the lander, it turns out, has been intermittently powered on and collecting status information since May. Although “Philae was already awake at this time, [it] could not contact us,” Dr. Ulamec explained in the same LCC release.
The goal for mission control, now, is to maneuver Rosetta into a position to optimize the signal between Philae and the space probe.
“We need a long and stable contact time to conduct research with Philae again as planned,” said Maibaum.
Ideally, project engineers would like to bring the two craft to within 180 km of each other; however, that may not be an easy task.
As Comet 67P approaches perihelion, the point along its orbit in which it is closest to the sun, the comet will begin to release greater amounts of gas and dust as its surface warms. This debris field has the potential to damage Rosetta, and although the increased sunlight will be good for Philae, controllers will have to be careful to avoid placing Rosetta in undue jeopardy.
Once a stronger connection has been established between the two spacecraft, engineers will test sensors that require relatively little energy and have few moving parts—instruments such as cameras and temperature sensors—before the lander resumes the use of any of its more complex scientific instruments. Eventually, the ESA hopes that Philae will be able to drill into the surface of Comet 67P to investigate the chemical composition of the comet’s nucleus. If successful, the results of Philae’s analyses could provide detailed information on some of the oldest material in our planetary system and have far-reaching implications for our understanding of the origin of both the solar system and life on Earth.
Philae has already sent back incredible scientific findings. During its initial 60-hour operating period in November, Philae was able to detect organic molecules in Comet 67P’s atmosphere, using its Cometary Sampling and Composition Experiment (COSAC) instrument.
For those interested in the origins of life on Earth, these findings may lend credence to the hypothesis of panspermia—the idea that all life on Earth, or at least the building blocks of life, is extraterrestrial and was first brought to Earth on comets.
While it remains to be seen if Philae will ever fully recover from its dormant slumber, members of the LCC will be ready and waiting for the next transmission as part of this already ground-breaking feat.