'Hello Earth!' Philae calls out from space and ESA scientists spring into action

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Marco Werman: It was almost like someone emerging from a coma, and the first words when it awoke: “Hello Earth! Can you hear me?” At least that’s what scientists at the European Space Agency tweeted when they finally received a signal from their comet probe, Philae. The solar-powered probe had been silent since it crash landed six months ago on Comet 67P. Some feared it was dead. Monica Grady of the Open University is a science advisor on the Rosetta mission.


Monica Grady: I was absolutely delighted, really thrilled when I heard the news that Philae had phoned home. It was wonderful.


Werman: What about in the control room? They must have been pretty stoked.


Grady: I think so, yes. The duty officer saw the signal and the duty officer rang the mission manager, who rang the team, and they all converged in mission control, and yeah, pretty happy.


Werman: What has changed though since last November that would have allowed Philae to “awaken,” shall we say?


Grady: Well, the comet is much, much closer to the sun. Philae landed, instead of in the middle of sort of an open plain, landed at the edge, possibly under a cliff, possibly even wedged into a crevice and a huge amount of material has been removed from the surface of the comet on its travels by the heating effect of the sun. There’s now enough sunshine which is falling on Philae’s solar panels to charge up the solar batteries.


Werman: Remind us how big this Comet 67P is that Philae has landed on. You’re talking cliffs and stuff--I mean, it’s pretty huge?


Grady: Not really. It’s about the size of an airport runway, it’s about, I don’t know, five miles across or something. So...


Werman: Wow, so it is not that big. But, I mean, still this is flying through space, this is a big chunk of rock.


Grady: Yeah, huge chunk of rock and ice, yeah.


Werman: Why do we care so much about a comet?


Grady: We care so much because comets formed at the birth of the solar system and they are an accumulation of the really primitive materials, the dust and the gas and the ice that the whole of the solar system was made from, and those materials haven’t been changed. They’re a deep frozen time capsule of those early materials and we’re opening the lid on that capsule and warming up the frozenness and seeing what’s there.


Werman: So what are scientists doing this week to get, I don’t know, a conversation with Philae that would send back useful data?


Grady: Well first of all, there can only be snippets of conversation when Rosetta is in the right orientation to actually receive the signal, and that’s twice a day, because the comet is tumbling and Rosetta is orbiting. So, it’s not in any sort of geostationary orbit, for instance, like our satellites are on Earth to receive signals continuously. So, there are two periods of time when a signal can be sent and received between Philae and Rosetta. And at the moment, they don’t seem to be aligned perfectly, and so there are tweaks to Rosetta’s orbit happening at the moment, and also Rosetta is being brought a little bit more close to the nucleus of the comet so that it can communicate better. So, it’s believed that there are already some data in the can which haven’t been transmitted back to the Rosetta mothercraft yet, and it would be absolutely if some of that data were photographs, seeing what was underneath Philae and seeing the landscape around. Yeah, that would be really interesting.


Werman: Really cool.


Grady: But you've also got to remember that the Rosetta spacecraft itself is still carrying on with its mission. It’s got instruments on board, it’s doing a lot of good stuff. And so we’re learning a lot from the Rosetta spacecraft as well as from the new stuff that we’re going to learn from Philae.


Werman: Monica Grady with the Rosetta mission. Monica, glad to hear you’re back in touch with Philae.


Grady: It’s great. Thanks very much.


Werman: You’re with The World.