It successfully soft landed, but they don't have confirmation anchors deployed to keep the probe stable and on the surface. Which is a retraction from an original statement the anchors did deploy and sink into the surface.
It successfully soft landed, but they don't have confirmation anchors deployed to keep the probe stable and on the surface. Which is a retraction from an original statement the anchors did deploy and sink into the surface.
If the lander did not successfully pin itself to the surface it would probably rebound and fly back in more or less the direction of it's approach - it depends how flat the landing area would be with respect to the contact surfaces of the lander. It must have some primary or secondary capture mechanism to stop it drifting off the surface. The comet's gravitational field is miniscule. The futher away from it's centre of mass, the more tenuous the pull towards it would be. I have no idea if there is a contingency built into the reaction control propellant system to allow for the possibility of a second attempt to latch back onto the comet should the need arise. How long do they want the lander to remain operational? It would be really neat so see what happens from the surface when the comet gets close enough to the Sun for it to spout geysers. Giotto was travelling at high relative velocity on it's encounter with Halley. It's really weird that stars and comets continually shrink in size - a bit like a boiled sweet you can suck that gets smaller and smaller as it is eroded until it is eventually sucked dry.
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@ Grecchus- I believe the probe has harpoons/anchors underneath the craft and screws on the landers feet which are supposed immediately screw into the surface on touch down. So I guess it's possible the feet are screwed in by the anchors did not deploy.
Yes, Solium, I did pick up on that crucial piece of info. If you think about it, the two harpoons needed to react immediately and with instant effect the moment the lander made contact. I understand Philae did have a slow relative speed of approach, however, unless it was able to attach within a fraction of a second of physical contact occurring I can't see how it could do anything other than glance off. The leg screws won't work at the extremeties of the reach of the legs unless the more centrally located harpoons struck first to, as you say, firmly anchor it to the surface. Hopefully, the engineers put together some kind of damping gear to absorb the shock of 'touchdown.' The question of the moment is . . . why didn't those harpoons fire as they were supposed to?
They are now unsure wether the probe has landed on its landing gear or upside down (it appears there's a chance it could have bounced after first impact). I wonder if the telemetry received will be upside down as well.
This 'bounce' business is a little bit worrysome. The probe wouldn't bounce, it would rebound. The only thing that could stop it from flying continuously away from the comet's surface after intitial contact would be a fully controllable thrust vectoring system with enough fuel onboard for contingencies. It looks to me as if Rosetta pushed Philae away from itself without the benefit of a thrust control system. In other words, it took aim at the designated landing spot on the cometary surface and let basic physics and the sort of deflection shot judgement the Red Baron would have used to shoot down an opponent to get to it's spot. Bearing in mind the lander was to set down on a large tumbling mass it's not too hard to see that if it couldn't anchor itself pronto it more than likely would get flung off. It's the same thing when you have a spinning top and you fire a pea at it. The pea doesn't just bounce off. The rotational energy of the spinning top actually flings the pea off and at an acute angle so that it is repulsed with greater force than it had before it made contact with the spinning object. Or, when you were a kid and you took small chances of injuring yourself by spinning up a roundabout to fast speeds, then used mental arithmetic to judge when best to jump on or jump off the device. Remember that hefty yank when you jumped on and held fast, or when you jumped off and had to synchronise moving feet and legs against the ground. Does that make sense?
They did say it had a very soft landing. So I don't see it bouncing or rebounding. Seems to me because the anchors didn't work it kinda shifted about on the surface. (and hopefully settled in.) I know there isn't much gravity, but we are talking about a tiny object on a 2.5 mile rock. I wouldn't think it would fling off. Totally nonscientific babbling on my part.
I certainly hope it has managed to cling to the surface. The Daily Mail have a very detailed article. Apparently, a thruster was supposed to fire to push the probe down against the comet surface and to help counter the reaction forces generated as the harpoons fired to lock it down. Neither the thrusters, nor the harpoons worked. They're saying Philae has settled onto the surface but that it's hanging on by fingernails. We shall see definitively what actually happened when the dust clears. Sleep tight!
Apparently, a thruster was supposed to fire to push the probe down against the comet surface and to help counter the reaction forces generated as the harpoons fired to lock it down
I was wondering about that! If the harpoons did fire but hit solid rock it would certainly create a recoil effect. Odd that both components failed, but the fact they did probably saved the craft.
The best comment about the whole thing on Twitter surely came from Tammin Sursok (Pretty Little Liars): "We are talking about "someone's" butt more than the fact that a SPACESHIP LANDED ON A COMET! That my friends is the beginning of the end..."
They did say it had a very soft landing. So I don't see it bouncing or rebounding.
now they're saying it bounced away almost a kilometer but somehow landed again in a rejected site. The 90 minute daily window of sunlight for recharging is too short for longterm survival. http://www.bbc.com/news/science-environment-30034060
They did say it had a very soft landing. So I don't see it bouncing or rebounding.
now they're saying it bounced away almost a kilometer but somehow landed again in a rejected site. The 90 minute daily window of sunlight for recharging is too short for longterm survival. http://www.bbc.com/news/science-environment-30034060
Yes, unfortunate news. They say it bounced up to three times before settling back down. It's stuck in a spot that is mostly in shadow. A huge cliff, rock or crater wall is in the way. They also said one of its legs is not on the ground but sticking out into space. I'm kinda shocked how they got everything wrong in the initial report. I would expect that kind of clumsiness from Russia or China not Europe. At the end of the day, it is on the comet and operational for the time being. So it was still a great accomplishment.
