Well, the European Space Agency has done it! The Philae lander has successfully touched down on Comet 67P.
It’s pretty incredible. We’ve landed robotic payloads on the Moon, Mars, Venus, and Titan, but we knew about those bodies before attempting those landings. We didn’t have that luxury with the Rosetta mission. The spacecraft and lander were built over a decade ago for a landing environment we didn’t know all that much about. Rosetta only got the chance to survey Comet 67P and look for a suitable landing site once it was in orbit around it and committed to landing on that comet’s surface.
That was one big part of this mission that could have gone wrong this morning. Comet 67P is an irregularly shaped moving target, and while scientists picked the nominal “landing site J” weeks ago there was no guarantee that the Philae lander would make it to that spot. It could have come down on a really uneven spot or a cliff face, something that would have been unsurvivable for the lander. And of course, the landing was totally autonomous. It takes about a half-hour for a signal to travel between Rosetta and Earth so there was no chance for any real-time course corrections.
Close-up of the region containing Philae’s primary landing site J.
But Philae went in for a landing this morning and nailed it. About six minutes after 8am PST, ESA started getting telemetry from the spacecraft, confirming that it was on the comet’s surface safe and sound.
But that telemetry isn’t telling the whole story just yet. We don’t know exactly where the lander has touched or how everything went. Data says the lander’s legs buckled only about an inch and a half, suggesting that the landing was pretty soft. But there’s one piece of data that’s missing that’s a little worrying — the lander’s harpoons have not anchored it to the comet.
Comet 67P isn’t big, which means the pull of its gravity isn’t very strong. That’s why the Philae lander has harpoons. Without those anchors firmly in place, Philae’s landing might be a little on the tenuous side.
But still, the lander is down and we can add comet to the list of celestial objects we’ve visited. And as more data comes back from the lander we can get into the really fun stuff: the science! Because that’s the crux of space exploration. It’s not about flash, it’s about knowledge. As CEO of UK Space Agency Dr. David Parker said this morning, “Hollywood is good but Rosetta is better!”
Featured image — the Philae lander after separation with its legs splayed out — via ESA