
Five simple words marked the fulfilment of an extraordinary feat of space exploration yesterday when scientists announced: ‘We are on the comet.’

To cheers and hugs, ecstatic experts delivered the news that a machine the size of a dishwasher had dropped onto an icy rock more than 300 million miles away.

However, they later revealed that the mission is already in jeopardy as it emerged the lander, which was supposed to use harpoons to tether itself to the comet's surface, had been unable to fire them and appeared to be moving around.

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The final approach: This image shows comet 67P/CG from a distance of approximately 3 km from the surface

What's next for Philae: the sensors that will reveal what life on a comet is like

It was a worrying end to an extraordinary day.

At the European Space Agency’s mission control, a faint radio signal came back from the Philae lander at 4pm – proof that it had finally reached the surface of the comet 67P/Churyumov-Gerasimenko after a decade-long chase through space.

Dr Stephan Ulamec, who ran the audacious landing programme, said early tests suggested the craft had bounced softly before turning and settling again.

He said: ‘It touched down and was re-bouncing. So maybe today, we didn’t just land, we landed twice.’

Last night the team were still not sure how securely Philae was fastened after landing thrusters and anchoring harpoons failed to fire.

It was not clear if its three ice screws had deployed either.

Dr Ulamec said: ‘Did we just land in a soft-sand box and everything is fine? Or is there something else happening? We still do not fully understand what has happened.’

Scientists will not know the status of the project until further tests are completed this afternoon.

However, last night they were treating the landing itself as a success.

British scientist Dr Matt Taylor, who played a key role in the mission, said: ‘To see this mountaineering effort, that we’ve descended a lander to the surface of a comet, I can’t put words to it. It’s beautiful.’

And the expert was so confident of success that he had even had an image of the space probe tattooed on his right leg.

Before the attempt yesterday, there was also a good luck message from a man who had once boasted of boldly going into space himself.

Star Trek actor William Shatner sent the team a video in which the 83-year-old said: ‘Good luck Rosetta, Philae’s gonna land.’

One scientist then described the seven hours of ‘terror’ they went through to drop the Philae lander 13.6 miles above the comet from its mothership, Rosetta.

Dr Matthew Genge, of Imperial College London, said during the wait: ‘This is the most difficult landing in space history – like landing a balloon in a city centre on a windy day with your eyes closed.’

Much of the equipment aboard the lander was switched on for the first time after lying dormant during the ten-year journey.

Klim Churyumov, one of the Ukrainians who discovered the comet 45 years ago and named it, said from mission control in Darmstadt, Germany: ‘We saw the first light from this comet in 1969, now we are landing on it. It is a fantastic, outstanding event, the first like it in human civilization.’

The probe is equipped with cameras, a suite of ten instruments, and a drill that can bore out samples to a depth of nine inches.

Although no official images from the surface have been released, this shot spotted by twitter user @coreyspowell appears to show a shot from the surface of the comet. ESA is expected to release the first official shots tomorrow.

Almost there! An image from the lander as it approached the surface

Rosetta's probe, Philae, has successfully landed on its comet 67P/Churyumov-Gerasimenko. Pictured is the mission control team in Darmstadt, Germany celebrating immediately after the announcement

The lander announced its arrival with this historic tweet for its ten year mission

Ptolemy, a British-built laboratory the size of a shoebox, will be used to analyse the composition of samples from the 4.5billion-year-old comet.

Scientists hope the £1billion project will solve some of the greatest puzzles in science – including the origins of life on Earth.

Open University Professor Ian Wright, who helped create Ptolemy, said: ‘The idea that comets may have brought the building blocks of life to Earth is one of the reasons why we want to study them.’

Professor Stanley Cowley, planetary scientist at the University of Leicester, added: ‘It is an interesting relic from that otherwise inaccessible epoch.’

However, controllers have revealed that because harpoons supposed to tether it to the surface had not fired, the lander may have actually bounced, effectively landing twice - and leaving it attached only by screws on its legs.

'It's complicated to land on a comet, and complicated to understand what has happened during this landing,' said Dr Stefan Ulamec, Philae Lander Manager.

WHAT COULD HAVE HAPPENED IF THE THRUSTER DIDN'T WORK? This morning it was revealed that the cold thruster - a nitrogen thruster - on top of the Philae lander was not working properly. This meant the Philae lander relied solely on its screws and harpoons (illustration shown) to ensure it did not bounce off the surface of the comet When Philae touched the surface of the comet it fired harpoons into the surface to keep it anchored there. To keep it attached to the surface a thruster at the top was meant to push it down as the harpoons fired. But this morning, the thruster didn't appear to be working - and it was confirmed the harpoons didn't fire. This meant the lander may have had to rely solely on screws on its legs. The surface was much softer than they expected, so there were some concerns that Philae was not securely fixed on the comet – although from a software point of view things seemed to be fine. Engineers may attempt to fire the anchors again soon in order to keep Philae attached to the surface of the comet. 'It's complicated to land on a comet, and complicated to understand what has happened during this landing,' said Dr Stefan Ulamec, Philae Lander Manager. 'The good news is we touched down, we had a clear signal and recieved data. 'The not so good news is that the anchoring harpoons did not fire. We looked into the data, and we don't fully understand what has happened. We had fluctuations in the radio link, but it always came back again. 'Some of the details indicate the lander may have lifted off again, it is bouncing. 'Two hours later, this stopped. We may have landed not once, but twice.' Advertisement

'The good news is we touched down, we had a clear signal and recieved data.

'The not so good news is that the anchoring harpoons did not fire. We looked into the data, and we don't fully understand what has happened.

We had fluctuations in the radio link, but it always came back again.

'Some of the details indicate the lander may have lifted off again, it is bouncing.

'Two hours later, this stopped. We may have landed not once, but twice.'

In an emotional speech, Esa director general Jean-Jacques Dordain said: 'It's a big step for human civilisation.'

Scientists hope data from the probe will help reveal how the solar system was first created 4.5 billion years ago.

The confirmation of the landing was relayed via Rosetta to Earth and picked up simultaneously by a ground station in Malargüe, Argentina and Madrid, Spain, before being confirmed in Darmstadt.

Ahead of the landing, Rosetta took a number of images of Philae during its daring descent. This view shows the lander's consert antennae deployed. It also shows three lander feet and the Rolis descent camera boom

Overjoyed: The Ukrainian astronomer Klim Tchurjumov (right), one of the discoverers of the comet 67P/Tchurjumov-Gerassimenko, and ESA General Director Jean-Jacques Dordain (left) hug each other at the satellite control center of the European Space Agency (ESA) in Darmstadt, Germany

'Esa and its Rosetta mission partners achieved something extraordinary today,' said Dordain.

'Our ambitious Rosetta mission has secured another place in the history books: not only is it the first to rendezvous with and orbit a comet, but it is now also the first to deliver a probe to a comet's surface.'

'After more than 10 years travelling through space, we're now making the best ever scientific analysis of one of the oldest remnants of our solar system,' added Alvaro Giménez, Esa's director of Science and Robotic Exploration.

'Decades of preparation have paved the way for today's success, ensuring that Rosetta continues to be a game-changer in cometary science and space exploration.'

'Hollywood is good, but Rosetta is better' - said the UK Space Agency CEO Dr David Parker.

At mission control the news was greeted with jubilation and high emotion by staff on the project

Applause: Media and dignitaries from around the world erupt in applause as they hear of Philae's success

However, while the lander has touched down on the comet using its harpoons, scientists said that it had not yet deployed its anchors which meant that it was not completely attached to the surface.

The surface was much softer than they expected, so there were some concerns that it was not securely fixed on the comet – although from a software point of view things seemed to be fine.

Engineers will attempt to fire the anchors again soon in order to keep Philae attached to the surface of the comet.

Esa director general Jean-Jacques Dordain (pictured) said: 'This is a big step for human civilisation'

Bye Rosetta! This image released shows the Philae lander's view of the Rosetta spacecraft 50 seconds after it was released at 08.35am GMT. It is blurry because the probe was rotating at the time

Rosetta has chased comet 67P/Churyumov–Gerasimenko through space for more than ten years in what has been described as 'the sexiest, most fantastic mission ever'

Rosetta has chased comet 67P/Churyumov–Gerasimenko through space for more than ten years in what has been described as 'the sexiest, most fantastic mission ever'.

Speaking live on TV, Matt Taylor, project scientist of Rosetta, talked about the complexities of the mission.

'I said she was sexy but I never said she was easy,' he said, describing the thruster issue that worried scientists earlier today.

Despite this, after a four billion mile (6.5 billion km) journey, the probe successfully released Philae from its grip to land on the comet, travelling at 1 metre (40 inches) per second.

At 08.35 GMT yesterday, mission control in Darmstadt, Germany, sent a command to release the Philae probe from Rosetta's grip. This picture shows the neck region of Comet 67P/Churyumov-Gerasimenko. It was captured around 4.8 miles (7.7km) from the surface of the comet

Ecstatic: Mission scientists have undergone an agonising seven-hour wait today, as Philae fell to its comet

Success! Scientists were shown looking emotional as they realised they had made space history

'We are extremely relieved to be safely on the surface of the comet, especially given the extra challenge of the comet's unusual shape and unexpectedly hazardous surface,' said Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.

'In the next hours we'll learn exactly where and how we've landed, and we'll start getting as much science as we can from the surface of this fascinating world.'

Engineers were forced to endure a tense wait to discover whether the lander successfully grabbed onto the comet at 3.30pm GMT.

Ahead of the landing, Rosetta captured several images of Philae during its daring mission using its Osiris camera.

One stunning shot showed the lander's antennae deployed, along with all three lander feet and the Rolis descent camera boom that took the photograph of Rosetta.

A view further away taken by Rosetta's Osiris camera. 'It's me… landing on a comet and feeling good!', Philae tweeted

Reflection: Astronomer Klim Ivanovych Churyumov, who discovered the comet 67P/ Churyumov-Gerasimenko in 1969, reacts after the successful landing of the Philae lander on the comet

Immediately after the image was released, Philae tweeted: 'It's me…landing on a comet and feeling good!'.

The separation of Philae from Rosetta was confirmed at 9.03am GMT today, and just after 11am GMT mission control in Darmstadt, Germany received a signal confirming the lander was working.

Throughout the day, the lander has transmitted data and images back to Earth.

'Everything looks really, really good,' said Philae lander manager Stephan Ulamec.

However, the success of the mission hung in the balance because Philae has a faulty thruster, which means it may have had to rely solely on harpoons to attach itself to the surface.

Whether or not it was able to make the thruster work in time has yet to be revealed by Esa.

Tense: Mission director, Paolo Ferri, in the moment he realised the probe had landed on the comet. 'For me this is a dream come true', he told MailOnline

Yup. We’re soft landing on a comet today. Normally my “We” means @NASA. But in this case it’s @ESA, the European Space Agency — Neil deGrasse Tyson (@neiltyson) November 12, 2014

The cold thruster would have been used to push Philae closer to the comet.

Without it, Philae would have been forced to rely on its three landing screws and two harpoons to successfully attach itself to the surface.

However, if the thruster was reactivated and all went to plan, at touchdown a landing gear would have absorbed the force of the landing.

Ice screws in the feet and a harpoon system locked to the comet's surface and the thruster would have pushed it down into the surface to counteract the impact of the harpoon.

Before Philae's release, Esa said there was 'no going back'.

'This is the most difficult landing in space history, like landing a balloon in a city centre on a windy day with your eyes closed,' said Matthew Genge, a senior lecturer in Earth and planetary science at Imperial College London.

At 08.35am GMT the mission control team in Darmstadt, Germany, sent a command to release the Philae probe from Rosetta's grip.

The probe was in free fall for during 'seven hours of terror', before attempting to land on the icy surface of comet 67P/Churyumov-Gerasimenko at a site called Agilkia.

Now in contact with @Philae2014 as it descends to surface of #67P - lander science data download expected to start 13:05CET #CometLanding — ESA Operations (@esaoperations) November 12, 2014

'We'll need some luck not to land on a boulder or a steep slope,' said Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center, ahead of the landing.

Speaking to Astronomy Now, Head of Mission Operations Paolo Ferri said they had received both positive and negative readings from the thruster.

'We don't know whether the motor is working or not. We have inconsistent readings,' he said at the time.

This picture from mission control shows the team preparing to receive confirmation from the Philae lander that it had separated from Rosetta earlier this morning

This graphic details how the Philae lander will touchdown on the surface of comet 67P. Without its cold thruster on top, however, the landing was due to be even more risky than thought

TO BOLDLY GO WHERE NO SPACECRAFT HAS GONE BEFORE William Shatner, who played Captain James T. Kirk in the TV series Star Trek, has wished the Rosetta team good luck ahead of the landing attempt in a video recorded by himself. 'Good luck Rosetta, Philae's gonna land,' he says in the video. 'I am so excited and I wish you such good luck. 'Good wishes from all of us here in Los Angeles.' Shatner posted the video to his Twitter page, to which Esa responded: 'Thank you captain!' While the 83-year-old is known around the world as Captain Kirk from the fictional show Star Trek, he is also a big proponent of real space exploration. In the past he has spoken with Nasa and Esa on Twitter, occasionally 'checking in' to see how the agencies are doing. Back in August he tweeted: 'How is @NASA doing today?' Nasa responded: '@WilliamShatner Good day, Captain. #ISS is in standard orbit and Commander Swanson has the conn. Hope you're having a great weekend!' To which Shatner replied: '@NASA Very good news!' Shatner played Kirk in Star Trek: The Original Series but also reprised his role elsewhere including in seven movies. Shatner is pictured left in his 20-second-long video wishing the Rosetta team good luck, and right in Star Trek: The Original Series back in 1967. Since taking on the role, he has shown a keen interest in space Advertisement

The team in Darmstadt, Germany, are pictured here celebrating as news of Philae's separation from Rosetta was received earlier this morning. Since then, the probe has landed and scientists around the world celebrate

TIMELINE OF THE LANDING Time is when confirmation on Earth will be received. All times in GMT 0903 - Philae will separate from the main Rosetta spacecraft. 0904 - First 'farewell images' received from Philae of Rosetta. 0912 - Philae will be 100 metres from Rosetta. 0943 - Loss of signal expected due to manoeuvre of spacecraft. 1053 - Signal link re-stablished. 1458 - Philae's harpoon anchor system will be turned on. 1501 - Images of landing site will be taken. 1517 - Final pre-touchdown operations. 1522 - Start of lander's touchdown window. 1602 - Expected time of landing on the surface. 1607 - First images of the surface sent back to Earth. Advertisement

Philae's cold thruster is nitrogen-powered and is designed to fire on landing in order to prevent the probe from flying off into space due to the comet's weak gravity.

In order to prepare cold-gas jets, scientists use one of two pins to puncture a wax seal on the thruster's gas tank.

Experts detect success by the change in pressure in the piping system.

However, this morning mission controllers did not see pressure increases after two attempts with each of the two pins.

But according to the industry provider, there may still be a chance that retrying the puncture of the wax seal would succeed, even after four failed attempts.

The comet is currently 300 million miles away (480 million km), and is travelling through space at about 34,000 mph (55,000 km/h).

Yesterday flight managers gave their 'OK' to the first of four checks that must be carried out before the probe Philae can descend from its orbiter craft onto a comet in deep space this afternoon.

WHY DOES COMET 67P LOOK LIKE A 'DOUBLE' COMET? When comet 67P/Churyumov-Gerasimenko was first imaged, scientists were shocked that it seemed to have two sections. It appeared to have a smaller and a larger lobe, which earned it the nickname 'rubber duck comet' owing to its appearance. Scientists aren't quite sure why it has this odd shape, but it may be the result of something known as a 'contact binary'. This occurs when two comets come into contact at very low velocity before slowly melding together over many years. This would mean comet 67P was actually once two comets. Or it may have just been a single comet that was pulled into an odd shape by the gravitational pull of large bodies like Jupiter and the sun. Alternatively it could have been shaped in such a way by ice evaporation on its surface or an impact with another object. Advertisement

Esa also revealed this new image showing how the comet would dwarf London

This is an artist's impression Philae, showing how it made its way to the surface of the comet today

Pictured is a separate Esa Rosetta control team in Toulouse, France awaiting news of the separation

Anxious: Scientists (mission controller Paolo Ferri pictured in foreground) faced a gruelling seven-hour wait to discover if the Philae probe had managed to safely land on the comet it has chased for 10 years

Esa has now successfully made contact with the Philae lander after it separated from the Rosetta spacecraft this morning at 08.35am GMT. It is now heading towards the comet and is expected to attempt to land on the surface at 4pm GMT. Pictured right is Paolo Ferri, Head of Mission Operations, celebrating making contact

The checklist was preceded by a brief moment of worry when Philae 'took a bit longer than expected' to be activated, said Paolo Ferri, mission leader at Darmstadt.

'We were a bit worried at first that the temperature would be wrong (for the descent) but it all worked out. We didn't lose any time,' Ferri said.

No one has ever attempted such a daring feat, and even Esa engineers admit they initially thought it sounded more like science fiction.

Scientists hope that Rosetta and Philae could help unravel secrets of how the solar system formed 4.5 billion years ago.

WHAT IS A COMET? Comets are remnants of the early solar system that remain in orbit around the sun. Most are found in two specific regions of the solar system. The first region is the Kuiper belt, just beyond the orbit of Neptune, which is thought to contain about 200 million objects. Much further out, extending to 50,000 times the distance from Earth to the sun, is a vast region known as the Oort Cloud where hundreds of millions of comets are present. Comet are often called 'dirty snowballs' because they are made of ice and rock. At their core they have a solid nucleus. But as they approach the sun, the ice on their surface melts and a 'coma' of gas forms around the comet. They also have two main tails. The dust tail is made of small, solid particles that are pushed back from the sun. The gas tail, meanwhile, forms behind the comet from the melted ice on its surface. A third tail known as a sodium tail has been detected around some comets, but less is known of it. Advertisement

Rosetta has also been aiming to work out the plasma characteristics of the comet (illustrated)

At 0835am GMT the team in Darmstadt, Germany (picture from mission control shown) sent a command to release the Philae probe from Rosetta's grip

WHAT IS THE MIDAS INSTRUMENT? The Midas instrument on Philae is designed to study the dust particles flung from the comet Midas is the Micro-Imaging Dust Analysis System. It is designed to study the dust particles flung from the comet as it is heated by the sun and becomes active. When comets pass through the inner solar system, the ices buried below their dark surface are gradually heated. As this gas streams away from the comet's surface, it drags along dust particles – themselves tiny pieces of rock, ice and organic material. Sunlight reflected from billions of such particles result in the beautiful dust tails seen from Earth on particle population, size, volume and shape. Midas is one of several instruments that will study cometary dust. To collect particles Midas has a funnel, which usually points towards the comet. Behind this is a wheel with sticky targets mounted around its circumference. After dust has been collected, the wheel is rotated to move the dust to the microscope for analysis. By scanning over the dust grain, line by line, scientists can build a 3D picture. Knowing the size, shape and structure of these particles tells us about how and where these particles formed. These particles are remnants of when the solar system formed 4.5 billion years ago and could reveal how planets formed, and perhaps on life came to be on Earth. Advertisement

Engineers at Rosetta mission control have made history by landing the Philae probe on comet 67P. Pictured is an artist's impression

WHY ARE COMETS IMPORTANT? Comets are of great interest to scientists because they are the oldest and most primitive bodies in the solar system that we know of. They preserve the earliest record of material from the nebula from which our sun and planets formed. While the planets in the solar system have gone through chemical transformations, comets have remained almost unchanged in the 4.5 billion year history of the solar system. It is also thought that they brought certain elements to planets, including water. They also carry complex organic molecules that may triggered life on Earth. Advertisement

Emotions at mission control were running high ahead of the landing. 'This, for me, is a wonderful dream come true,' Paolo Ferri, mission director told MailOnline. 'Just thinking about it…I have tears in my eyes.

'You spend a lot of your time in very odd situations with [Rosetta], working weekends, and getting calls in the middle of the night. It's not fair to compare it to a relationship with a human, but it's very close.'

When it was launched in 2004, Rosetta was so far from 67P that it had to pass Earth three times and Mars once, so that it could use the planets' gravity to slingshot its way deep into the solar system.

The spacecraft will spend more than a year studying the comet, which is made up of material left over from when our solar system was first created 4.5 billion years ago.

Ahead of the landing, Esa has published a series 'beauty shots', taken by Rosetta's navigation camera, revealing the varied and dramatic terrain of the mysterious rock.

TOUCHDOWN ON THE COMET: PHILAE'S DETAILED LANDING TIMELINE Rosetta will release Philae at 08:35 GMT/09:35 CET on 12 November at a distance. Pictured is an artist's impression of the lander on Comet 67P Rosetta released Philae at08:35 GMT/09:35 CET on 12 November at a distance of 14 miles (22.5km) from the centre of the comet. The landing took place about seven hours later at around 15:30 GMT/16:30 CET. During the descent, Philae took images and conducted science experiments, sampling the dust, gas and plasma environment close to the comet. It also took a 'farewell' image of the Rosetta orbiter shortly after separation. Philae is due to take a panorama of its surroundings. Again, this is expected back on Earth several hours later. Longer-term study of the comet by Philae will depend on for how long and how well the batteries are able to recharge, which is related to the amount of dust that settles on its solar panels. It is expected that by March 2015, as the comet moves closer in its orbit towards the sun, temperatures inside the lander will have reached levels too high to continue operations, and Philae's science mission will come to an end. But the Rosetta orbiter's mission will continue for much longer. It will accompany the comet as it grows in activity until their closest approach to the sun in August 2015 and then as they head back towards the outer solar system. Advertisement

Rosetta's target comet, 67P/Churyumov–Gerasimenko, is about 2.48 miles (4km) wide. Here it is shown alongside some of Earth's landmark

Illustrated here are the various scientific instruments on the Philae lander that will be used to study the comet when it is attached to the surface

Rosetta has chased comet 67P/Churyumov–Gerasimenko through space for more than ten years in what has been described as 'the sexiest, most fantastic mission ever' (illustration of solar system shown)

The images shows a raised plateau on the larger lobe of Comet 67P/Churyumov-Gerasimenko. It was captured from a distance of 6 miles (9.8 km) from the center of the comet

The mission began as a concept about three decades ago and was the brainchild of Gerhard Schwehm, former Rosetta Project Scientist (pictured in the 1980s)

Incredibly, many of the images were taken at less than six miles (10km) from the comet's surface, and highlight what a challenging task Philae engineers have ahead of them.

The Philae probe aims to analyse the comet in more detail than Rosetta ever could. The results, Esa claims, could completely rewrite the history of how the Earth formed.

As Philae descends, it will be travelling at walking speed of 3ft (one metre) per second relative to 67P while the duck-shaped rock is rotating constantly.

Philae will need to be released with pinpoint accuracy as its landing site contains a mix of sheer cliffs and deep craters – any of which could scupper its chances.

Scientists are aiming to land on a spot named 'Agilkia' on the smaller 'head' lobe of 67P after Philae is released from a distance of 14 miles (22.5km) from the centre of 67P.



Rosetta has been taking scientific readings of the comet since it arrived, including measurements of the magnesium on the surface (shown)

The daring descent Philae (artist's impression shown) will take seven hours from separation. It will be exactly nine years that a similar landing attempt on an asteroid by Japan's Hayabusa failed in 2005

This image shows the Agilkia landing site on Comet 67P/ChuryumovGerasimenko, taken with Rosetta's navigation camera on 6 November. It was captured at a distance of 22 miles (35.5km)

Jose Pellon-Bailon, one of eight flight engineers responsible for Rosetta, told MailOnline there are a number of things that could go wrong during the descent.

For instance, Rosetta might not release Philae at the right spot if the thrusters are activated at the wrong time.

Jets of gas spewing from the comet could also cause problems during, moving Philae off course.

Another concern is the strange duck-shape of the comet, which means Philae could crash land, damaging its instruments.

ESA'S BIZARRE SUPERSTITIONS During the landing of the Mars rover Curiosity, space engineers underwent what they described as 'seven minutes of terror.' In that time, bottles of peanuts started to appear, and people mission control calmed their nerves by munching on the snack. Now, whenever a difficult space mission is taking place, both Nasa and Esa have peanuts to hand to make sure the mission doesn't fail. Paolo Ferri, mission director for Rosetta, says he will also be wearing the same tie that he did during the launch of Rosetta ten years ago. 'It appears at all these moments,' he told MailOnline. 'So it was there for the flyby of Mars, it was there at the wake up, and it will be there at the 12th of November for Philae. I'm very superstitious.' Advertisement

And even if Philae lands safely, it will need to attach itself to the comet using harpoons.

Philae is able to withstand temperatures of 150°C (300°F), but it could become too hot to operate as the comet travels towards the sun.

But if it all goes to plan, it could trigger more mission to comets in the future.

'The other scientific instruments are collecting a huge amount of data and I'm sure they'll provide to the scientific community a humongous richness,' Pellon-Bailon said.

At the moment, communication between Rosetta and mission control take 28 minutes and 20 seconds each way – the time it takes for a signal to travel 315 million miles (510 million km) to Earth.

'It's difficult, in the sense that you are commanding something and you are seeing the effects almost one hour later,' says Pellon-Bailon. 'If we land on the comet, it will be very emotional.'

Ferri's biggest fear isn't that Philae will be damaged during the descent, but that it could fail to send a signal back at all.

'This would be a huge disappointment,' he says. 'Of course, the landing mission would be off, but also we wouldn't have learned why.'

The landing has been described by Esa as 'ridiculously difficult'.

'Imagine the comet as Mont Blanc,' says Ferri.

'You fly with an aircraft at 13.6 miles (22km) in altitude - so twice the altitude of a normal airline.

'At a certain point you have to drop a box and hope that it lands on the mountain within a square km.'

Pellon-Bailon says his team are fully prepared, even down to what they will eat on the day.

67P/CHURYUMOV-GERASIMENKO The comet is named after astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko who identified it in 1969. It is believed to originate from the Kuiper Belt, a large reservoir of small icy bodies located just beyond Neptune. Scientists describe it as a 'Jupiter class' comet which takes 6.45 years to complete one full circuit of the sun The icy core, or nucleus, is about 2.4 miles (4km) across and the comet takes around 12.4 hours to rotate fully. The comet has now been observed from Earth on seven approaches to the Sun: in 1969, 1976, 1982, 1989, 1996, 2002 and 2009. Over an entire year, as it approaches the sun, Rosetta will orbit the comet, mapping its surface and studying changes in its activity. As its ices evaporate, instruments on board the orbiter will study the dust and gas particles that surround the comet and trail behind it Advertisement

Peanuts are crucial. 'We found out that people at Nasa eat peanuts on the day of the special activity. In a mission that is problematic, they will always have peanuts on the table.'

Esa has inherited the superstition, and Ferri confirms that it's vital to the success of the mission. 'I'll also be wearing the same tie I wore when Rosetta launched ten years ago,' he says.

The bizarre rituals at mission control are hoped to steady nerves as engineers perform complex manoeuvres around the comet.

Pellon-Bailon says when he first got involved in the mission in the early 1990s, it sounded to him like science fiction. Even now, he can't quite believe they've reached the comet.

'It sounds crazy when you say it out loud,' says Ferri. 'Sometimes I sit back and think, there's a two cubic metre box flying half a billion kilometres away, that is now sending a very faint signal.

'That signal is picked up in Australia, and now I'm looking at it. Then I think, how is it possible?'

But it has been possible, and even if Philae doesn't make it on tomorrow, the mission has already achieved its main objective.

'You have to remember, and we have to remember, this landing is spectacular, but it is only one part of the mission,' says Ferri.