Sleep well, Philae! Scientists give up latest attempt to make contact with space probe
- European Space Agency has begun attempting to contact the lost probe
- Philae has been missing since November when it landed on Comet 67p
- Scientists believe the lander bounced into a ditch in the shade of a cliff
- But they say it may already be awake but not yet able to send messages
- The probe needs 19 Watts of power from its solar panels to communicate
- As the comet gets closer to the sun the lander may receive more sunlight
- Scientists have sent commands to Philae for it to begin warming itself up
- They will attempt to contact the lander with Rosetta over the next 8 days
Experts have abandoned an eight-day vigil for a wakeup call from the robot lander Philae, but remained hopeful the scout will revive as it rides on a comet nearing the Sun.
Monitoring for the lander, which has been hibernating since November, will resume next month, the mission said.
'Perhaps it is still too cold for the Philae lander to wake up on Comet 67P/Churyumov-Gerasimenko,' the German Aerospace Centre (DLR) said in a blog posted by the European Space Agency (ESA).
ESA scientists have renewed efforts to contact the Philae lander on Comet 67p, shown in the illustration above
ROSETTA MISSION REFRESHER
The Rosetta probe, which was carrying Philae, launched into space in 2004, using the gravity of Earth and Mars to slingshot its way towards comet 67P.
It chased comet 67P/Churyumov–Gerasimenko through space for more than ten years, and entered orbit in August 2014.
After a four billion mile (6.5 billion km) journey, the probe then successfully released the Philae lander from its grip to land on the comet on 12 November 2014, travelling at 1 metre (40 inches) per second relative to the comet.
But when it first made contact with the surface it failed to fire harpoons that would have kept it attached to the comet.
This resulted in it bouncing to a height of 0.62 miles (1km) above the comet before again landing on the surface. It then bounced again, but to a much lower altitude.
Scientists recently said that water on the comet was different to that on Earth - suggesting water on our world came from an asteroid, not a comet.
'Maybe its power resources are not yet sufficient to send a signal to the team at the DLR Lander Control Center.'
There has been no news of Philae for more than four months.
That was when the battery ran down on the 100-kilogram (220-pound) lab after it bumped down in a rugged, shadowed part of the comet.
Philae had just enough juice to carry out a 54-hour roster of core experiments before going into shutdown mode.
The hope is that as the comet races towards the Sun, more light will bathe the probe's solar panels, enabling it to power up again and resume work.
Its mother ship Rosetta sent down Philae on November 12 after a 10-year trek around the Solar System.
It began to listen out for signals on March 12 as it launched a schedule of orbital swoops around the spot where Philae is believed to have landed.
But there was only silence, and at 0400 GMT on Friday, Rosetta's communication unit was switched off, the ESA blog said.
'It was a very early attempt,' said DLR Project Manager Stephan Ulamec.
'We will repeat this process until we receive a response from Philae. We have to be patient.'
Engineers saw an early chance in March when comet and lander were about 300 million kilometers (187 million miles) from the Sun, and the amount of solar radiation had nearly doubled compared to November.
The next chance to receive a signal is during the first half of April, the blog said.
Philae needs an internal temperature of more than minus 45 degrees Celsius (minus 49 degrees Fahrenheit) and at least five watts of power to automatically turn on.
Until it can generate 19 watts, it cannot send signals to Earth via the orbiter.
Philae has 10 instruments, including a drill, chemistry sets and imaging tools.
It is the crowning feat in a 1.3-billion-euro ($1.4-billion) mission to unlock the secrets of comets, which some astrophysicists believe may have 'seeded' Earth with some of the ingredients for life.
The Rosetta orbiter took a number of images of Philae as it bounced, with its final suspected resting place in the top right. However, further attempts to find the lander at the foot of the cliff have failed to find the probe
Philae touched down on 67P/Churyumov-Gerasimenko on 12 November, but rather than landing softly, the failure of its harpoons and thrusters saw it bounce twice.
It first bounced to a height of 0.62 miles (1km) and then 65ft (20 metres) before finally coming to rest at an angle on uneven ground.
Blurry images captured the the spacecraft movement through the air.
Scientists described the comet's surface as being more like a trampoline, causing the probe to rebound so far.
It is thought the probe settled in a ditch beneath a cliff after bouncing more than half a mile from its original landing site.
The duck-shaped comet 67p/Churyumove-Geraismenko is moving closer to the sun and warming up as it does
This image sent back by the Philae lander shows one of its three feet next to what appears to be a cliff face
Scientist have been pouring over photographs of the landing area using the mothership Rosetta in an attempt to find the missing probe.
Philae was able to send back a photograph - the first taken from the surface of a comet - of an overhanging cliff face that is thought to be obscuring the lander.
Before its batteries finally ran out, Philae managed to send back data on the few experiments it was able to conduct along with some images.
Among the discoveries to have been released so far is that the comet's surface appears to be made of a very hard 'sintered' ice.
This graphic shows how Philae bounced twice after it failed to anchor itself to the surface of the comet
Researchers also revealed that they had found organic molecules - the basic building blocks of life.
From several miles above the comet, Rosetta has also continued to provide a constant stream of images and data since it arrived.
But there are some fears that dust thrown up by the landing and movement of the comet itself could have covered the lander's solar panels.
This would mean it may struggle to get enough light to power its communication units and the experiments it is carrying on board.
The image above is a composite of four pictures taken by the Rosetta probe while flying 12 miles above the surface of the 2.4 mile wide comet 67p and shows the dramatic landscape that surrounds the Philea lander
Comet 67p is due to reach its closest point to the sun in August this year and this is when scientists believe they have the best chance of hearing back from the stricken lander.
Philae requires its internal temperature to reach at least -45 degrees C before it can wake up.
It will also require at least 5.5 watts from its solar panels to wake up.
Once awake, Philae will turn on its receiver every 30 minutes and listens for a signal from the Rosetta orbiter.
Koen Guerts, part of the Philae lander team at the DLR Control Centre, said the probe may have already woken up but is yet to send a signal home.
He said: 'Philae is designed so that, since November 2014, it has been using all the available solar energy to heat up.'
'At this time, we do not yet know that the lander is awake.To send us an answer, Philae must also turn its transmitter – and that requires additional power.'
This blurry image captures the moment Philae bounced from the comet's surface after failing to anchor itself
Philae needs a total of 19 watts to begin operating and allow two-way communication.
Over the next eight days the Rosetta orbiter is due to transmit signals to its lander and listen for the response during a series of 11 flybys.
Engineers have also sent new commands to the lander to optimise the heating and provide energy savings to improve its chances of communication with Earth.
Once Philae wakes up and can also transmit, it will first send data about its 'health' to Earth.
The scientific work with the 10 instruments on board Philae also depends on these results.
If sufficient energy cannot be stored in the battery, the solar energy available during the comet daytime will determine whether a reduced version of the measurements can be performed.
Currently, scientists believe that Philae is in sunlight for 1.3 hours - just a fraction of the 12.4 hour long day that the comet enjoys.
Mr Ulamec added: 'Once we can communicate with Philae again, the scientific work can begin.'
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