Where's Philae? Space Agency Narrows Search Area for Lost Comet Lander

Update 5:20 p.m. Friday, Nov. 21:

It's been a week since the European Space Agency's Philae Lander powered down after completing a series of experiments in an unexpected, and as of yet unknown, location on the surface of Comet 67P.

The lander bounced twice and floated more than a kilometer from its intended landing site into a shadier position that hasn't yet allowed enough sunlight for a solar recharge of Philae's batteries.

ESA released a very short audio clip of the lander's initial touchdown Thursday, adding a second track to Philae's astronomical playlist. The first track features oscillations in 67P's magnetic field.

Today, the ESA reports it has narrowed down the search area for the lander using radio wave transmissions between Philae and its mothership, the comet orbiter Rosetta.

The radio wave system on both the orbiter and lander is called the Comet Nucleus Sounding Experiment by Radiowave Transmission, or CONSERT. It was designed to demystify the comet's interior, but it's also proving useful in pinpointing Philae.

Astronomer Gerald McKeegan with the Chabot Space and Science Center has been watching developments of the comet landing this week. He said he's most excited about 67P's interior, which could hold clues about the origin of our solar system.

Initial results from CONSERT suggest the comet's exterior is covered in a layer of dust, then very hard ice. But the core seems to be less dense, something McKeegan says was a bit of a surprise.

"We don’t know exactly what goes on inside a comet," he said. "Comets are samples of the very early solar system, at a time when the solar system was first forming. We’re very interested to know -- what was the composition of that cloud of gas? We’re interested in seeing what all was there."

McKeegan said a prevailing theory is that comets and asteroids delivered water to the Earth early in our planet's life. Philae and Rosetta's analysis of the molecular makeup of the comet's ice could solidify that theory, or turn it upside down.

Philae also "sniffed" molecules containing carbon as it landed on 67P.

"The gases that are blowing off of the comet include some organic compounds, which is not unexpected," McKeegan said, "and they’re still waiting for the results of the drilling operations."

The lander's drill system was the last experiment to deploy before Philae went dark. ESA scientists know the drill went down and came up again, but they don't yet know if it was able to deliver any stuff of which comets are made into the lander's body for analysis.

There's a possibility that the lander will power-up when the comet gets closer to the sun.

"Everybody’s got their fingers crossed that eventually we’ll get enough sunlight to recharge its batteries, and they’ll do some more experimenting," McKeegan said. "There’s some data they don’t have and they’d like to get that. This is still pretty extraordinary. The fact they were able to get it on the comet from 316 million miles away, that’s pretty extraordinary."

Update 5:20 p.m. Friday, Nov. 14:

Philae, we hardly knew ye.

The little comet lander with a lot of luck is completing a lightning round of science experiments on the surface of Comet 67P before it powers down, exhausted and unable to recharge its batteries with solar energy because it ended up in a shadow.

If that sounds not so lucky, consider that Philae bounced twice after hitting the comet initially. A harpoon system intended to blast into the comet's surface and anchor the lander failed to fire.

The European Space Agency reports the lander lifted from the surface for almost two hours and traveled a full kilometer across the comet's surface before touching down again. A shorter, seven-minute lift carried Philae to its final landing.

Philae re-established communication with Rosetta at about 2:30 p.m. PST on Friday and quickly confirmed it had drilled into the comet's surface.

Then it appears to have successfully lifted and righted itself. (Pictures the lander had previously sent back to Earth showed one of its three legs in the air, leading ESA scientists to believe it may have landed on its side.)

But the toils began to take their toll. Philae's battery charge started to plummet after 3:37 p.m. PST.

Still, the lander managed to take another round of images -- that have not yet made it here -- and to measure the core of the comet with its on-board radar.

At 4:09 p.m. PST, Philae began communicating between the Rosetta mothership and its radar instrument, Concert:

And at 4:28 p.m. PST, ESA Operations confirmed Philae had switched to stand-by mode. All its instruments powered down, but it continued to transmit information. The Rosetta Mission acknowledged Philae's hard work.

But take heart; know Philae could rise again, if only briefly. ESA crews are hoping for a window later this year when the comet comes close enough to the sun that Philae will be able to charge up, but still too far away to melt the little lander.

ESA Operations confirmed it had lost communication with Philae at 4:46 p.m. PST.

Update 3:55 p.m. Thursday, Nov. 13:

The European Space Agency's Rosetta spacecraft and the little lander Philae are delivering information from the surface of Comet 67P, despite the inability of ESA crews to locate exactly where the probe settled after bouncing, twice.

But scientists do know the solar-charged Philae may soon run out of power because it appears to be resting in a shadow, according to BBC News.

The ESA may attempt to move Philae, but in its current position, it's estimated to power down sometime Friday or Saturday.

Chabot Space & Science Center astronomer Ben Burress, a KQED Science contributor, detailed the lander's ups and downs today after about 12 incommunicado hours from Philae:

When communication was reestablished, and data from Philae’s ROMAP instrument was analyzed, it was learned that the probe had experienced not one, but three distinct landings. The first landing reported by the data coincided with the initial landing confirmation.

Then, almost two hours later, a second landing event was indicated. The harpoon system, designed to fire an anchor into the comet to tether Philae down, had not functioned, and Philae had bounced.

Seven minutes after the second landing, a third was reported by the data, the lander apparently having bounced a second time. This time, however, it appeared that Philae had come to rest somewhere on the surface. ESA scientists are attempting to triangulate its exact position with instruments on Philae and Rosetta.

When the first pictures came in they showed what looks like a jagged, dusty, even gravely cliff face, and no framing horizon. Philae was not level with the ground, but resting at a tilted angle. Later, additional images sent back were assembled into the first panoramic view from the comet.

Despite the excursions from a perfect landing scenario, Philae has landed, and we are there, thanks to the telepresence the washing-machine-sized robot has given us.

Philae is delivering more than just photos in what could be its very short life. Listen below to 67P's soundscape:

The chirping is thought to be generated by oscillations in the comet's magnetic field. The sound wave is below the frequency that can be heard by a human ear, but ESA boosted the frequency in the track.

Update 6:35 p.m. Wednesday, Nov. 12:

Philae's landing on Comet 67P might have been a little bumpier than first reported. The lander may have bounced off the comet after initial contact, according to European Space Agency officials, and a harpoon system designed to blast an anchor into the surface appears to have failed to fire.

Here's a video from ESA showing how Philae's landing was supposed to go down:

Despite those small mishaps, the lander has settled for now and is likely doing science experiments while it waits for its mother ship Rosetta to appear on the horizon and re-establish contact with Earth. Learn more about its systems, technology and mission from this graphic:

Click to enlarge.

Update 10:35 a.m. Wednesday, Nov. 12:

Here are previous photos from the European Space Agency.

Original post Wednesday, Nov. 12:
Bill Chappell
NPR

Hundreds of millions of miles from Earth, a man-made object was flung at a comet Wednesday — and now it's sticking to the rock as it hurtles through space.

"We are on the comet," Stephan Ulamec, Philae Lander Manager, announced Wednesday, marking a historic achievement.

The news came after the European Space Agency endured tense hours of uncertainty following the lander's separation from the Rosetta spacecraft, as scientists awaited a message from the lander that would tell them whether it landed safely -- or suffered a calamity.

As Ulamec said that the lander was secured to the comet's surface by ice screws that had been shot by the craft's harpoons — and that it was now doing its job and communicating with Earth — he sparked an uproar of applause from workers and spectators at the European Space Operations Center in Darmstadt, Germany.

But while the European agency says the lander is in "great shape," it also says that additional analysis suggests that Philae's harpoons did not fire, and that the agency is looking at trying again. (see update below).

It took 10 years for the Philae Lander to reach a point where it could be sent toward Comet 67P/Churyumov-Gerasimenko. The ESA said this morning that it had received a signal from the lander as it headed toward its rendezvous with the comet, indicating that if all went well, the lander would be able to communicate and send photos from the comet's surface.

We'll update this post with developments from space. You can also follow the news at the ESA's Rosetta page, and at NASA TV, starting at 9 a.m. ET.

Update at 11:50 a.m. ET: 'Harpoons Did Not Fire'

After analyzing telemetry data from the Philae lander, ESA says it seems that the craft's harpoons didn't fire as first thought.

Adding that the lander is in "great shape," the agency says its engineers are looking into options for retrying the harpoon operation, which is meant to secure the craft to the comet's surface.

In a tweet, the agency says the lander "made a fairly gentle touch down on #67P based on amount of landing gear damping."

Update at 11:05 a.m. ET: Philae Has Landed

In a first, the Philae lander is on the comet's surface. We've updated the top of this post to reflect the news.

Update at 10:15 a.m. ET: New Images, And 'A Boot'

"Everything looks really, really good," says Stephan Ulamec, Philae program manager at DLR, in a progress report.

The ESA has released new images from the area around the comet, including one shot of Philae breaking away from the Rosetta craft and heading toward 67P.

Another image shows the lander from the view of its parent spacecraft.

The two scientists who discovered the comet 45 years ago — Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko — are in the unique position today of watching humanity's attempt to land on it.

Churyumov and Svetlana Ivanovna Gerasimenko took part in an event hosted by the ESA that was equal parts news conference and viewing party.

When Gerasimenko was asked the tongue-in-cheek question of how she likes the comet that she and her colleague spotted decades ago, she responded by saying, "I like the form very much — it reminds me of a boot."

Today's comet operation was also being monitored by other space veterans.

Our original post continues:

Comet 67P has several surprising qualities. First of all, it smells really bad.

"It stinks," researcher Kathrin Altwegg told NPR's Geoff Brumfiel last month.

That's because of a mixture of ammonia, hydrogen sulphide, formaldehyde and methanol.

The comet also emits "a mysterious song," according to the ESA blog.

"The comet seems to be emitting a 'song' in the form of oscillations in the magnetic field in the comet's environment," the ESA says. "It is being sung at 40-50 millihertz, far below human hearing, which typically picks up sound between 20 Hz and 20 kHz. To make the music audible to the human ear, the frequencies have been increased by a factor of about 10,000."

Here's what that sounds like — close your eyes and you might be able to pick out "Flight of the Bumblebee":

As Geoff reports, scientists here on Earth see Philae, which is about the size of a refrigerator, as "our remote hands." The lander will take many readings from the comet's surface, in addition to drilling into it.

But before any tests can occur, Geoff notes, the comet's rocky and uneven surface could make the landing very tricky — and that's why the lander has harpoons.

"Moments after its feet touch down, the harpoons will fire," Geoff says, "along with some thrusters to keep the lander grounded. Then screws in the feet will try to get a grip."