Space

Philae lander goes to "sleep" after batteries die

Philae lander goes to "sleep" ...
Artist's impression of the Philae lander (Image: ESA) (Image: ESA)
Artist's impression of the Philae lander (Image: ESA) (Image: ESA)
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Telemetry readout showing the Philae's drill extended and retracted successfully (Image: ESA)
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Telemetry readout showing the Philae's drill extended and retracted successfully (Image: ESA)
Battery readout from Philae's final hours (Image: ESA)
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Battery readout from Philae's final hours (Image: ESA)
Philae's first landing point from 40 m (Image: ESA)
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Philae's first landing point from 40 m (Image: ESA)
Image of Philae taken by Rosetta during the descent (Image: ESA)
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Image of Philae taken by Rosetta during the descent (Image: ESA)
Image taken of comet 67/P by Philae during its descent (Image: ESA)
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Image taken of comet 67/P by Philae during its descent (Image: ESA)
Diagram of the Philae lander (Image: ESA)
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Diagram of the Philae lander (Image: ESA)
Artist's impression of the Philae lander (Image: ESA) (Image: ESA)
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Artist's impression of the Philae lander (Image: ESA) (Image: ESA)
Image montage fro, Rosetta used to hunt the Philae lander (Image; ESA)
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Image montage fro, Rosetta used to hunt the Philae lander (Image; ESA)
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After its historic landing on a comet, the Philae spacecraft has gone silent. Trapped on its side in a shadowed hole, the unmanned European Space Agency (ESA) lander was unable to receive enough sunlight to recharge its battery and contact was lost today at 00:36 GMT when power levels dropped below critical.

On Wednesday, the washing machine-sized lander made a freefall descent from the Rosetta mothership to the surface of comet 67P/Churyumov-Gerasimenko. Unfortunately, the thruster designed to press it down on the comet and the harpoons to anchor it failed to operate and Philae bounced back into space. After bouncing a second time, it turned on its side and came to rest in a hole or crevice about a kilometer from the original landing site.

In this new position, some of the solar panels that charge the lander’s batteries were buried and the rest only received about 1.5 hours of sunlight per day, which was not sufficient to maintain the systems and keep the spacecraft warm.

Battery readout from Philae's final hours (Image: ESA)
Battery readout from Philae's final hours (Image: ESA)

While engineers worked to find a possible solution to the problem, the Philae science team ordered the lander to activate as many of its experiments as it could and placed priority on returning as much data as possible via the Rosetta mothership. According to ESA, Philae was still able to carry out most of its planned first science sequence experiments and transmit the data back to Earth. In addition, telemetry confirmed that Philae successfully carried out the first ever drilling operation on a comet.

Due to the 60-hour window available before power was lost, the engineers had very limited options for rescuing the trapped spacecraft. They decided against trying to deploy the harpoons for fear of pushing the lander off the comet or damaging it, but about three hour previous to the shutdown, mission control in Darmstadt, Germany ordered the lander to rotate its main body 35 degrees to expose a larger solar panel. The maneuver proved successful, but it was too little too late.

Image taken of comet 67/P by Philae during its descent (Image: ESA)
Image taken of comet 67/P by Philae during its descent (Image: ESA)

ESA says that Philae is now in “idle mode,” where all the scientific experiments and most of the systems are shut down. Contact could still be re-established if enough sunlight falls on the spacecraft, but this is extremely unlikely. However, the Rosetta orbiter has been programmed to listen for a signal on its next pass over the landing site at 10:00 GMT on Saturday.

"Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence," says DLR's Stephan Ulamec, Lander manager. "This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."

Source: ESA

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10 comments
Pierre Collet
Now for the facts: - Originally, it was planned that on the chosen landing site, Philae would get a 7 hours daytime for a 5 hours nighttime. Unfortunately, in its current position, it will get only 1.5 hours daytime for 10.5 hours nighttime. - Originally, the planned working cycle was the following: batteries would deplete in a working session of about 10 hours after which ---on the originally planned landing site--- Philae would take about 4 days to recharge its batteries after which a new 10 hours working session would start again.
Obviously, with a daytime 7/1.5=4.666 times shorter, it will take much longer than 4 days to recharge the batteries, knowing that on a regular day (even on the earth), there is not much sun in the "morning" and in the "evening": solar panels have their best output when the sun is shining vertically over them, which may never be the case...
So unfortunately, it may take much more than 4.666x4days = 18.666 days for the batteries to recharge.
So the working cycle of Philae may be 10 hours / 1 month (or more) rather than the originally planned 10 hours / 4 days.
All this to say that despite the bounces, the mission is still going on, Philae is still working nominally, but will work on a much slower pace than originally planned.
It is hoped that Philae wakes up before the comet gets too close to the sun (and Philae gets too warm to work).
To come back to your article, David, it is necessary to be slightly more precise in your statements (remember that the Devil hides in the details, so this is why scientists need to be extremely precise in their communication).
- When you say "After its historic landing on a comet, the Philae spacecraft has gone silent. Trapped on its side in a shadowed hole, the unmanned European Space Agency (ESA) lander was unable to receive enough sunlight to recharge its battery and contact was lost today at 00:36 GMT when power levels dropped below critical.", this is not the strict facts.
It was always planned that Philae would have blackout periods of 4 days after a 10 hours working session. This is simply what happened. It did not happen *because Philae is trapped on its side in a shadowed hole*. It would also have happened if it had landed correctly.
Therefore, I hope you will understand when I say that the same goes for "In this new position, some of the solar panels that charge the lander’s batteries were buried and the rest only received about 1.5 hours of sunlight per day, which was not sufficient to maintain the systems and keep the spacecraft warm."
Again, when you say "...but about three hour previous to the shutdown, mission control in Darmstadt, Germany ordered the lander to rotate its main body 35 degrees to expose a larger solar panel. The maneuver proved successful, but it was too little too late." The "... but it was too late" part is incorrect. Philae would have passed out even in the original planned landing site. Its instruments consume far more than the energy the solar panels are able to provide. Because the re-orientation of the panels was successful this means that thanks to this last manoeuver, Philae may get a couple more watts than in its original position.
Finally, because Philae was able to complete the drilling and sending back all data, this first this first session went really well. Actually it can be considered that it went even better than planned because Philae's instrument woke up when it first landed, meaning that its working session started just then. Analysis was carried out *throughout the bounces*, meaning that somehow, the failure of the harpoons allowed for the extra-bonus of sampling different areas of the comet (through the dust collected during the bounces), which was not hoped by anyone, even in their wildest dreams (imagine roaming on a comet with such a low gravity).
The price to pay for this extra-bonus was the critical position in which Philae lays now. As ESA says, it is hoped that Philae will be able to wake up again before temperature rises too much.
So the ESA conclusion that you quoted is perfectly right: "Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence," says DLR's Stephan Ulamec, Lander manager. "This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."
Prof. Pierre Collet
Rehab
A true learning experience and no lives were lost. Perhaps comets will become the next gold rush.
SuperFool
that's very cool.
Roland Riese
In 1977, the Voyager 1 spacecraft left Earth on a five-year mission to explore Jupiter and Saturn. Thirty-seven years later it still send data home to earth. None of this would be possible without the spacecraft’s three batteries filled with plutonium-238. It is predicted that Voyager could be sending data for the next 200 years. Philae with nuclear batteries could have been sending pressures data back to earth on its voyage though space for a very long time but the useless solar collectors will enable this wonderful successful mission to only send a very small fraction of the data it could have provided back to earth.
Sven Ollino
Great comment Pierre!
Bob Ehresman
Perhaps incorporating the means to keep "bouncing" might be useful for the future comet explorers. Touch down on the comet. Trigger a pogo manipulator to push off. Fly back out in the weak gravity into sunlight. One might plan for "bounces" to be fairly protracted trajectories in order to gain significant sun time regardless of where an actual touchdown might take place. Bouncing could take the probe to many different locations on the body before some sort of death by misadventure happens.
Darin Selby
What a bunch of self-serving SPACE MORONS to spend $1.4 BILLION just to land on a freaking COMET!!
How about spending that $1.4 billion in CLEANING UP THE ENVIRONMENT AT CAPE CANAVERAL from all of their BS rocket launches! What a concept, eh?
Once again, they had a "V2" when they coulda had a "V8"! :-D
http://usatoday30.usatoday.com/tech/science/space/2011-07-31-nasa-environmental-cleanup_n.htm
Darin Selby
Roland Riese, how soon us humans seem to forget that ROCKETS CONTINUE TO BLOW UP when launched! Where does your PLUTONIUM 238 fit into that scenario, hmm?
Dave Lawrence
Goodnight, Phil . . . . .
Pierre Collet
Looks like Philae is back!
And thanks to the fact that it is in the shade, it should be able to monitor the comet's outgassing during perihelion (which would have been impossible if it had landed on the planned spot, as temperature there was expected to be too hot for Philae as early as last March!)
So it looks like the mishap of the uncontrolled landing is a great bonus, after all!