Take-home points from today’s ESA media briefing

Here’s what you need to take home from today’s media briefing by ESA on the Rosetta mission, following yesterday’s landing on the comet.

  • Rosetta
Philae descending towards 67P as seen from Rosetta.

Philae descending towards 67P as seen from Rosetta.

Rosetta is fine and in stable orbit around 67P. After separation yesterday morning, it took the following image of Philae on its slow descent (around 3.5km/h) towards the surface of 67P. You can clearly see the details of the lander with its legs unfolded and its solar panels and antenna. The descent lasted 7h due to 67P’s extremely fain gravity (which is due to its low mass), slowly pulling the lander towards its surface. The first touchdown occurred at 16:03 UTC, just 3min after the scheduled time, which is incredible precision!

Philae (red circle) on its descent towards 67P, taken from Rosetta.

Philae (red circle) on its descent towards 67P, taken from Rosetta.

Rosetta also took the amazing following image, showing Philae and 67P on the same image, and you can really notice for the first time the size of the lander compared to the size of the comet. It’s an amazing image taken by a man-made object some 500 million kilometres from Earth of another man-made object in a controlled descent towards the surface of an unexplored comet.

  • Philae

The lander’s thruster supposed to keep it on the surface and the harpoons supposed to anchor it did not work. As a consequence, the lander landed, then because the surface seems to be harder than the scientists had planned, it bounced back off to an altitude of about 1km at a speed of around 30cm/s before landing again (a 2h bounce due to 67P’s low gravity!), and doing a second smaller bounce of a few minutes at 3cm/s. It finally landed and the instruments onboard indicate it has stopped moving.

Philae's Initial landing site (red square) and estimated position now (blue diamond) on 67P.

Philae’s Initial landing site (red square) and estimated position now (blue diamond) on 67P.

So Where’s Philae? That’s the million dollar question. Here’s an image showing the initial landing site (red square) just next to a 1km large crater, and the zone in which Philae seems to be now (blue diamond). The team is working hard to try and identify exactly where the lander is in that area and the Osiris camera onboard Rosetta will be taking some more images to try and find Philae.

From the images taken by Philae of its surroundings, it seems it might have ended up on the ridge of the crater, next to a cliff, which puts it in a precarious position and partly in shadow. Its solar panels are therefore not getting enough sunlight and the lander is working on batteries, which limit the lander to a few days of operations. The team is cautious about using any mechanical instrument at the moment as it could dislodge the lander and possibly eject it from the surface of 67P.

Nevertheless, as the team pointed out, the mission is still ongoing and Philae’s precarious position does not take away anything from the fact that this team has managed, for the first time in human history, to successfully land a probe on a speeding comet after a 10-year journey through space and billions of kilometres, and that this probe is successfully transmitting images back to us. As the ESA flight director emotionally put it at today’s media briefing:

These guys are indeed the best, and we can trust they’re working incredibly hard to figure out the best way forward for Philae. In any case, rest assured this is only the beginning of the adventure to study 67P for the next two years as it travels through the inner solar system.

The world's first ever image from the surface of a comet.

The world’s first ever image from the surface of a comet.

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