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Philae found -just in time for Rosetta’s finale

There can be no doubt that the European Space Agency ROSETTA mission, to study Comet Churyumov-Gerasimenko (or “CG” as I’m going to call it from now on because I am not typing that out every time, sorry!), has been an astounding success. Since arriving at the comet on August 6th 2014 it has revolutionised our understanding of what comets are, how they behave and, of course, what they look like. It has sent back tens of thousands of stunningly detailed images, most of which (after a very shaky and controversial start by the OSIRIS team) have now been released for everyone to admire and study and drool over, and the many instruments on the orbiter have told us what the comet is made of and how it “works”. Thanks to ROSETTA we will never look at comets in the same way again. And no matter how many missions fly to comets in the future, ROSETTA’s place in history is assured: it was the first probe to rendezvous with a comet and study it as it rounded the Sun.

But the end is nigh. After more than two years studying Comet CG, ROSETTA’s historic mission will end on September 30th when the orbiter descends to the comet’s surface, either “landing” or “crashing”, depending on which way you want to look at it. As the dust settles on the surface of 67P, covering whatever’s left of the probe after impact, and the mission controllers confirm the final loss of signal, I’m sure the army of scientists who have worked on the mission all these years, and many of the reporters and jourtnalists who have followed it too, will be swept up in a tsunami of emotions: sadness that the mission has ended, relief that it was such a success, excitement at the prospect of all the data yet to study, and more. Many will feel a profound sense of loss, maybe enough to move them to tears, as a very significant chapter in their scientific careers comes to a very sudden and very public end.

I hope Monica Grady has bought a huge box of tissues, she’s going to need every one of them…

But not only scientists will feel moved on that day. Around the world many thousands of fans and supporters of the mission, who have faithfully followed the adventure all these months, will feel a real sense of loss too. Thanks to the tremendous and tireless efforts of the mission’s social media, education and outreach teams, ROSETTA has enjoyed probably the highest profile and most enthusiastic public  support of any ESA mission to date. Through their competitions, blogs and hugely-popular animated films they have brought ROSETTA to life in a way no other ESA mission has enjoyed. The stunning short SF  film “Ambition” must, by now, have been shown to the audiences of thousands of outreach events all over the world. (I have lost count of the number of times I’ve shown it as part of my Outreach work, and just for my own pleasure.) Let’s be frank here – ESA’s Outreach efforts used to suck. And I mean suck. They just didn’t seem to “get” how important it was for the public to feel involved with their missions, and to share the results of those missions – particularly the images taken by their spacecraft – with them. But now… now they definitely do Get It, and ROSETTA has been one of the most popular missions flown by any space agency.

Another reason why, when ROSETTA’s time orbiting CG ends, it will be a sad, sad day.

But, thanks to a picture taken by the probe on September 2nd, perhaps not as sad as we all thought it was going to be…

Because as successful as ROSETTA has been, one part of the mission didn’t go according to plan. When the little PHILAE lander descended from the orbiter on Nov 12th 2014 it was supposed to land on the comet’s surface, securing itself to the icy ground with harpoons, and then begin a programme of intensive science. Instead, its harpoons failed and the lander bounced off the comet, cartwheeling away from its landing site and heading off into the great unknown.

Measurements suggest that if it had bounced a little harder, and gone faster, PHILAE would have flown off into space altogether, and all its precious science would have been lost. But we now know that the lander bounced twice, like a stone skimming a pond, before finally coming to rest –

Well, that was the problem: we didn’t know where it eventually came to rest. We knew it had come down somewhere, because it sent back a handful of pictures soon after landing, frustrating images suggesting it was surrounded by cliffs of ice or stone. But as for where on the comet’s surface it had come down… no idea.

Despite its “non optimal landing orientation”, PHILAE survived for three precious days, long enough to send back priceless data from most of its payload of instruments, before its energy reserves ran out and it went into hibernation. We watched that happen live, online, and it was both thrilling to watch the scientists squeezing every possible last drop of science out of the lander’s short life before its batteries drained, and heartbreaking to watch the traces on the power graph suddenly drop like a stone…

Since then PHILAE has been, effectively, Missing In Action. It called out forlornly a few times, like a cat trapped down a well, raising hopes that it could be roused from its slumber and commanded to do more science, but those hopes were dashed when, admitting defeat, ESA finally stopped listening for signals from the lander, accepting the need to concentrate their efforts on keeping the orbiter operating as efficiently as possible, doing as much science as possible, during the time it had left.

And that was hard for many people. It was bad enough that PHILAE’s mission had been cut so cruelly short in the first place, but not knowing where it even was felt like the comet was rubbing salt in our wound. Every time we looked at an image of the comet we wondered “Where are you?” Even when amazing detective work by ROSETTA scientists revealed that PHILAE had in fact landed on its side, with its legs sticking in the air, not knowing where the lander was felt… awful. At least when the Mars Exploration Rover Spirit “died” on Mars we knew where she was, because we could see her on HiRISE photos. And when Beagle 2 was spotted on more images of Mars taken from orbit, many of us let out a sigh of relief, as it told us that at least the probe had made it TO the surface, and hadn’t burned up in the atmosphere like a piece of bacon left under a grill too long, as we had feared.

But PHILAE was just missing. We put “Have You Seen This Lander?” flyers up on lamp posts, offered rewards, but nothing. There was no sign of her, and that was troubling; as they say on the TV news a lot now, because it’s very trendy and fashionable, there was no “closure” without a photo showing PHILAE at its final resting place.

And, you know, with no photo of its grave it was hard to believe PHILAE had actually…. well… gone

Then, on Monday, just three weeks before the ROSETTA mission is due to come to an end, we finally got that “closure”. ESA released an image, taken on September 2nd, showing a craggy, rugged area of the comet. The image showed what looked like a close-up photo of a spilled bag of muesli, or a sack of builders’ rubble emptied out on a tabletop  – a truly chaotic landscape, with a steep hillside, its slopes strewn with boulders, rocks and outcrops, and caves, caves as dark and foreboding as anything found in Tolkien’s books…

But there, over on the far right of the image, just visible in one of those caves, half hidden in shadow, half bathed in sunlight, was… something. Something clearly artificial, metallic. I’ve ringed it on the image below so you don’t spend the next two hours straining your eyes looking for it. Enlarging the image by clicking on it will make it easier to see…


( credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0 )

If you zoom in on that, this is what you see…


(Original image ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam – CC BY-SA,  IGO 3.0 Processing by Stuart Atkinson)

Look at that… There, in the dark shadow of that cave, beneath that huge, over-hanging boulder, is a machine of some sort.

Look even more closely, and you see this…


(Original image ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam – CC BY-SA,  IGO 3.0 Processing by Stuart Atkinson)

I looked at that and thought “Oh, you poor thing… look at you…look where, and how, you ended up…” Because there’s no mistaking it, is there? That’s it. That’s PHILAE.

As the ROSETTA mission enters its twilight phase, with just three weeks to go until the lander hits the comet and goes silent forever, they found PHILAE.

Here’s a link to the official announcement on the ESA ROSETTA page.

Make no mistake about it, this is an amazing technical achievement by ESA. PHILAE was basically the proverbial needle in the haystack, except a) this particular haystack was constantly turning and spinning and wobbling, b) the needle ESA was looking for was the Gold Medal winner in the Olympics “Hide and Seek” competition, and c) the camera itself was moving. It’s also hugely important scientifically too, because locating PHILAE means the scientists who worked on it, and got results from it, now have the most important thing they could hope for: context.

What do I mean? Well, now they know exactly where PHILAE finally came to rest those scientists will be able to make a lot more sense out of the readings it took and the measurements it made before it fell asleep, because they can now see the bigger picture – the terrain and features around the landing site, the type of ground it is on, how much dust there is around it, what processes are going on around it, etc. In geology – on any world, or body – context is king.

So, we now have “closure” (awful word I know, sorry!) of a sort. We know where PHILAE “landed” after it decided its planned landing site was too boring and it took off like an inquisitive, restless hobbit in search of somewhere more interesting and exciting. That turned out to be a crevice or a cave in a mountainside, starved of sunlight, about as bad a choice of landing site for a fragile, solar-powered lander as it was possible to find. And rather than landing elegantly on its feet, like a cat jumping off a sofa, PHILAE landed on its side, lying up against the rock, with its slim legs sticking out and no hope of righting itself.

And that’s where it will stay.

But maybe not forever..?

Maybe one day, in the far future, astronauts will reach Comet CG and land on it, on a daring science mission inspired by ROSETTA’s. It would make sense to choose CG as a target for such a mission, which is surely inevitable; ROSETTA’s cameras have photographed CG in such astonishing detail that future explorers would be able to take maps of its surface with them, guiding them to the most interesting features and places. And once they’re there, surely those explorers would feel moved to go to PHILAE’s cave and pay their respects, photographing it for the sake of history, just as future lunar explorers will no doubt travel to the Apollo landing sites and pay their respects there.

And who knows, maybe they won’t stop there. Perhaps their mission will have another objective – to bring PHILAE home.

Imagine… it’s 2069… Halley’s Comet is returning to the inner solar system, and to mark its return it is decided to send people to CG, to follow-up ROSETTA’s studies and bring PHILAE back to Earth, to study how it has been affected by all its years on the comet before cleaning it and putting it on display. Imagine watching live footage from the astronauts’ cameras as they make their way down that slope, weaving through that field of boulders, towards the cave… suddenly, there, up ahead, a glint of metallic silvery light shining in the darkness beneath a huge boulder… they walk on, getting closer, and closer, until their prize comes into view: PHILAE, now covered with a mixture of dust and ice, but still recognisable from the way its spindly legs stick out from its side…  walking up to the lander the explorers slowly sweep their cameras across it, showing the millions watching back on Earth what they have travelled so far to see… one of the explorers reaches out with a shaking, gloved hand and gently wipes some of the dust away, revealing the shining blue solar panels beneath… Then, a long pause for photographs, the lander imaged from every possible angle, for context, before the explorers position themselves around it – and lift it, so, so carefully, off its side and set it back on its feet, as it should have been in the first place at a landing site so, so far away over the horizon… more photos as the lander is brushed and dusted clean, and then the watching millions see it lifted up from the ground and carried away from the cave which has been its grave for so many years… PHILAE is coming home…

A ridiculously sentimental and unrealistic idea, I know! But wouldn’t that be amazing? Wouldn’t that be a wonderfully inspiring thing to do, and watch?

Whatever happens in the future, whatever PHILAE’s eventual fate is, at least we know where it is now. And when the ROSETTA orbiter sets down on the comet in three weeks’ time it will be reunited with its partner in exploration.

I can’t wait to see the “reunion” animation ESA’s brilliant Outreach team creates to mark the end of the mission.

And I’ve already got my hankies ready.



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