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Philae Found

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Re: Philae Found

#21

Post by lorenzhs »

thr0waway1239 wrote: post #14

"At 2.7 km, the resolution of the OSIRIS narrow-angle camera is about 5 cm/pixel, sufficient to reveal characteristic features of Philae’s 1 m-sized body and its legs, as seen in these definitive pictures." I looked at the pictures and the human eye can barely see the lander. Considering that the chances of losing these landers is not that low, I don't understand why they don't make them visually more distinctive. An…

"the human eye can barely see the lander" is a bit exaggerated. It's not immediately obvious where in the image the lander is (it took me a few seconds to find it), but well visible once you've got the position.

"Considering that the chances of losing these landers is not that low" - most of the time, when the mission fails, they don't make it to the surface, though. As far as I know, Beagle 2 is the only lander that was lost and later found. The Mars Polar Lander likely dropped onto the surface from some 40m up, maybe a wreckage could be found there. But other than that, I'm not aware of any landers that could be found with a camera in orbit. Debris is hard to find, even on earth - it took over 20 hours to find a crashed fighter jet in Switzerland last week, and another day to find the pilot's body.

Re: Philae Found

#22

Post by fanquake »

matt-attack wrote: post #15
thr0waway1239 wrote: post #14

"At 2.7 km, the resolution of the OSIRIS narrow-angle camera is about 5 cm/pixel, sufficient to reveal characteristic features of Philae’s 1 m-sized body and its legs, as seen in these definitive pictures." I looked at the pictures and the human eye can barely see the lander. Considering that the chances of losing these landers is not that low, I don't understand why they don't make them visually more distinctive. An…

I'm confused about the appearance of autonomous cars. When is the car observing itself? How does its own appearance come into play?

It's not observing itself, it's being observed by other autonomous vehicles.

Re: Philae Found

#23

Post by masklinn »

gokhan wrote: post #9

Unless other parts of the comet is more flat, that landing gear design seems clearly wrong. It included bolting itself to the surface, if I remember correctly, but it seems almost impossible to fixate three legs with almost no gravity on that surface.

> Unless other parts of the comet is more flat

It's pretty hard to see the details of a cometary surface from earth. And there isn't much you could do with no gravity and an all-rubble surface either way.

> It included bolting itself to the surface, if I remember correctly, but it seems almost impossible to fixate three legs with almost no gravity on that surface.

Philae had a harpoon for anchoring itself to the surface (with a thruster on the other side to compensate). The harpoon failed to fire. The legs were not intended for fixation, only to dampen the landing.

Re: Philae Found

#25

Post by aruggirello »

ragebol wrote: post #17
gokhan wrote: post #9

Unless other parts of the comet is more flat, that landing gear design seems clearly wrong. It included bolting itself to the surface, if I remember correctly, but it seems almost impossible to fixate three legs with almost no gravity on that surface.

IIRC, the designers had little idea what kind of surface the comet would have. Could be ice, could be rocks, could be dust. What kind of landing gear + fixation gear would have been better?

INANE (I Am Not A NASA Engineer), but perhaps 4 or better yet more legs arranged in a tetrahedron or analogous polyhedron would better ensure the lander did not get stuck inside a crevasse; an inner rotating body could then bring the lander into a working position. The more the legs, the higher the chance the lander could 'roll' to a lower ground when initially bouncing off the surface, but the optimal number of legs could be determined in advance by simulating the terrain (you wouldn't want it to roll all the way down a slope, ending at the bottom of a crevasse etc.).

Harpoons protruding from each leg could be fired automatically as soon as a stable enough position was detected, or manually when deemed safe; having more legs available could only improve chances of getting a safe fixation.

Re: Philae Found

#26

Post by newscracker »

I watched this documentary called "To catch a comet" about the Rosette/Philae mission to comet Churyumov–Gerasimenko. The achievement of getting to the comet and landing Philae, like many other achievements in space, is really phenomenal. So many things could've gone wrong, but the fact that the worst was Philae bouncing and getting stuck in a dark place (and not being able to perform fully) is a huge success beset by an issue of a smaller magnitude.

The description of the documentary says [1]:

> Unable to carry enough fuel owing to weight restrictions, the Rosetta scientists devised a delicate cat and mouse trajectory to reach their distant destination. In the ten years Rosetta had been in space she flew around the Earth three times, Mars once and the asteroid belt twice, to gain the momentum she needed to reach her destination. In the months before landing, the team navigated Rosetta safely to a world never before observed at such distances or accuracy. Rosetta orbited the comet before releasing Philae onto the surface.

Quoting from the article of this thread:

> “We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour.”

This brings a much better ending for the people who worked on the mission for more than 30 years. [1] We tend to anthropomorphize things like spacecrafts, landers, rovers and many other inanimate objects. I think for the team (and many others following this news), this photo would be like being able to see a dear friend one last time, say goodbye in their minds and have some kind of closure.

The Wikipedia article, and especially the section titled "Landing and surface operations" [2], is also quite interesting to read.

[1]: http://www.pbs.org/program/catch-comet/

[2]: https://en.wikipedia.org/wiki/Philae_(spacecraft)#Landing_an...

Re: Philae Found

#28

Post by thr0waway1239 »

luso_brazilian wrote: post #18

The XKCD already updated the live comic about this subject [1]. All panels are available at its sister wiki [2] In my opinion it is a beautiful work of art, pushing the limits of what the media allow the artist to do (the media in this case being comic strips in the webcomic format. [1] https://xkcd.com/1446/ [2] https://www.explainxkcd.com/wiki/index.php/1446:_Landing/All...

Thank you!

To those who didn't click on the second link, you really should. It is like a journal of the lander, except in webcomic format.

Re: Philae Found

#30

Post by jonknee »

thr0waway1239 wrote: post #14

"At 2.7 km, the resolution of the OSIRIS narrow-angle camera is about 5 cm/pixel, sufficient to reveal characteristic features of Philae’s 1 m-sized body and its legs, as seen in these definitive pictures." I looked at the pictures and the human eye can barely see the lander. Considering that the chances of losing these landers is not that low, I don't understand why they don't make them visually more distinctive. An…

> I looked at the pictures and the human eye can barely see the lander. Considering that the chances of losing these landers is not that low, I don't understand why they don't make them visually more distinctive.

If it was hot pink it would have made no difference, it ended up in a bad spot with limited solar power.

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