Remember Philae? The little lander has been sitting in a hole between cliffs on Comet 67P/Churyumov-Gerasimenko, but as George Harrison sang – Here Comes the Sun.
Philae (FEE-lay) bounced off the comet’s surface twice while attempting to touch down. On the first bounce, it rebounded at a speed of 15 inches per second, sending it sailing over half a mile above 67P’s surface. Had the lander exceeded 17 inches per second it would have escaped the comet’s gravity!
To get a feel for the alien beauty of Comet 67P, press play to take a flyover.
It finally came to rest on November 12, 2014 after a second bounce. Had the lander’s harpoons worked properly, it would have affixed itself upright on the surface on its first attempt.
Unfortunately, Philae landed in the shadows of cliffs with its solar panels steeped in shadow most of day. With too little sunlight to provide the energy to charge the lander’s batteries, the probe’s primary battery provided only 60 hours power before it shut down. Philae conducted as much data-gathering as it could and then powered down into hibernation mode on Nov. 15. No one’s heard from it since.
That might be the end of the story, but mission scientists are hopeful that as seasons change as 67P orbits the Sun (just like they do on Earth), sunlight will filter down between the steep hills at Philae’s location and provide the needed energy for the solar panels to power up the lander’s batteries. The intensity of sunlight has also been increasing as 67P gets closer to the Sun. A few days of sunlight on the solar panels is all it would take to resume collecting data according to Philae landing manager Stephan Ulmanec.
Already the lander is receiving twice as much solar energy as it did last November. Optimistic mission managers recently switched on the communication unit on the Rosetta orbiter to call the lander.
Philae’s like a hibernating black bear during its winter sleep. Before the craft wakes up, its interior temperature has to “warm up” to -49° F (-45° C). Since the mean temperature of the comet’s nucleus is -94° F (-70° C), this bear will sleep a while longer.
At its landing site, named Abydos, after one of the oldest cities in ancient Egypt, only a little sunlight shines down each day. Once the solar panels can generate 5.5 watts – less than a typical night light uses – the probe will finally have enough power to begin the wake-up process.
Once the sleep is gone from its eyes, Philae’s next task is to switch on its receiver to listen for Rosetta’s signal. True two-way communication can’t begin until the panels can generate 19 watts of power. Once the link has been reestablished, Rosetta will send the good news back to Earth. For all we know, Philae’s back up in low-power mode but doesn’t have the energy yet for a two-way conversation.
Rosetta tried signaling the lander and listening for a response during a favorable alignment between starting March 12th and ending on the 20th. The next chance to hear a possible signal from the lander will be during the first half of April.
Before it went dark, Philae did a stellar job deploying its instruments and gathering as much information as it could about the comet’s alien surface and atmosphere. On its first touchdown attempt and also at its present site, the probe discovered a large amount of water ice beneath the dust-covered surface.
Attempts were made to drill into the crust, gather a sample of soil and deliver it to the lander’s ovens for analysis, but nothing was ever turned up. It’s thought that the lander’s cockeyed position prevented the drill from making contact with the surface. Another instrument, which banged the surface with a hammer, suggest that a veneer of dust 4-8 inches (10-20 cm) thick overlays a thick layer of ice. Organic molecules with carbon and hydrogen were found in the comet’s atmosphere, too.
We’re eager to hear more from Philae, but the long winter of its discontent must first yield to what passes for spring on a comet.