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| Version 0 | Version 1 |
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| Controllers wait on Philae link | Controllers wait on Philae link |
| (about 3 hours later) | |
| No new signals have been picked up from the Philae comet lander since a brief radio contact on Sunday. | No new signals have been picked up from the Philae comet lander since a brief radio contact on Sunday. |
| European Space Agency (Esa) controllers listened again on Tuesday night but heard nothing. | European Space Agency (Esa) controllers listened again on Tuesday night but heard nothing. |
| This was not surprising, they said, given the less than ideal conditions for a radio connection. | This was not surprising, they said, given the less than ideal conditions for a radio connection. |
| Philae called home from Comet 67P on Saturday, its first contact since running out of battery power shortly after landing some seven months ago. | Philae called home from Comet 67P on Saturday, its first contact since running out of battery power shortly after landing some seven months ago. |
| The communication was short - just 85 seconds - and was then followed by an even briefer link-up on Sunday. | The communication was short - just 85 seconds - and was then followed by an even briefer link-up on Sunday. |
| The robot’s mothership Rosetta, which dropped the robot on to the 4km-wide icy dirt-ball, is now being moved closer to facilitate a more effective relay. | The robot’s mothership Rosetta, which dropped the robot on to the 4km-wide icy dirt-ball, is now being moved closer to facilitate a more effective relay. |
| Currently, the satellite is sitting back from the comet at a distance just above 200km. | Currently, the satellite is sitting back from the comet at a distance just above 200km. |
| Controllers have commanded Rosetta to get as close as 180km. They have also told the probe to keep its antenna pointing directly down to aid a stronger radio connection. | Controllers have commanded Rosetta to get as close as 180km. They have also told the probe to keep its antenna pointing directly down to aid a stronger radio connection. |
| Treacherous flying | Treacherous flying |
| The mission has to be cautious, though. Comet 67P is throwing huge quantities of gas and dust into space as its ices melt in the warmth of the Sun. | The mission has to be cautious, though. Comet 67P is throwing huge quantities of gas and dust into space as its ices melt in the warmth of the Sun. |
| If controllers are not careful, this blizzard of material will confuse Rosetta’s navigation systems, potentially tripping the probe into a protective “safe mode” that shuts down all but essential functions. | If controllers are not careful, this blizzard of material will confuse Rosetta’s navigation systems, potentially tripping the probe into a protective “safe mode” that shuts down all but essential functions. |
| This would make communication with Philae impossible but also risk putting Rosetta in some danger because it would no longer be under full control. | This would make communication with Philae impossible but also risk putting Rosetta in some danger because it would no longer be under full control. |
| “It’s like flying your car in a snowstorm. You don’t see anything, and that’s quite dangerous,” said Elsa Montagnon, Esa’s Rosetta deputy flight director. | “It’s like flying your car in a snowstorm. You don’t see anything, and that’s quite dangerous,” said Elsa Montagnon, Esa’s Rosetta deputy flight director. |
| “It’s the same for Rosetta. Its 'eyes' – its star-trackers, which it uses for autonomous orientation - rely on finding stable star patterns that they can follow. | “It’s the same for Rosetta. Its 'eyes' – its star-trackers, which it uses for autonomous orientation - rely on finding stable star patterns that they can follow. |
| “And in this very dusty environment, the trackers can mistake dust particles sometimes for stars and that can lead the spacecraft in the wrong direction.” | “And in this very dusty environment, the trackers can mistake dust particles sometimes for stars and that can lead the spacecraft in the wrong direction.” |
| The immediate plan is to fly Rosetta over the comet in a way that repeats the communication conditions experienced on Saturday. | The immediate plan is to fly Rosetta over the comet in a way that repeats the communication conditions experienced on Saturday. |
| If a stable connection can be established, “housekeeping data”, known to be held on the lander detailing its health, can be downlinked, and new commands uploaded. | If a stable connection can be established, “housekeeping data”, known to be held on the lander detailing its health, can be downlinked, and new commands uploaded. |
| Already, engineers can see from their brief conversations with Philae that it is in good shape. | Already, engineers can see from their brief conversations with Philae that it is in good shape. |
| Its onboard systems appeared to experience no damage during its long slumber and are all working. | Its onboard systems appeared to experience no damage during its long slumber and are all working. |
| Critically, the robot’s internal temperature is rising and this should soon allow it to start charging its battery system. | Critically, the robot’s internal temperature is rising and this should soon allow it to start charging its battery system. |
| For the moment, however, its working day is limited to about three hours of every 12.4-hour “comet day” when sunlight falls on its solar generator. | For the moment, however, its working day is limited to about three hours of every 12.4-hour “comet day” when sunlight falls on its solar generator. |
| Baby steps | Baby steps |
| “For some operations, we do need the battery,” explained Barbara Cozzoni, a lander engineer from the German space agency. | “For some operations, we do need the battery,” explained Barbara Cozzoni, a lander engineer from the German space agency. |
| “The power from the solar arrays is not sufficient, on its own, to drill and analyse cometary samples, for example.” | “The power from the solar arrays is not sufficient, on its own, to drill and analyse cometary samples, for example.” |
| This means the first block of science to be conducted by the awakened Philae, once it can be commanded on a stable link, will involve no mechanical movements. | This means the first block of science to be conducted by the awakened Philae, once it can be commanded on a stable link, will involve no mechanical movements. |
| These first experiments will measure simple parameters like the magnetic and thermal environment around the lander. | These first experiments will measure simple parameters like the magnetic and thermal environment around the lander. |
| Once higher power conditions can be attained, Philae will be told to take some new pictures of its surroundings, and "sniff" the chemical compounds that are wafting past it. | |
| And eventually, Philae will hopefully get sufficient power in its battery to drill into the comet and analyse its make-up. | |
| The washing machine-sized robot landed on Comet 67P on 12 November, and worked for about 60 hours before its primary battery ran flat. | The washing machine-sized robot landed on Comet 67P on 12 November, and worked for about 60 hours before its primary battery ran flat. |
| It emerged that on touchdown, Philae had bounced into a dark ditch, with high walls stopping sunlight from reaching its solar panels. | It emerged that on touchdown, Philae had bounced into a dark ditch, with high walls stopping sunlight from reaching its solar panels. |
| It is only now - seven months later, as the comet has moved closer to the Sun - that illumination conditions have improved to the point where the robot can once again talk to Earth. |