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Philae Found

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Re: Philae Found

#61

Post by dredmorbius »

ygra wrote: post #39
tqkxzugoaupvwqr wrote: post #35

Earlier quoted context omitted.

Finding the lander made a difference. Now they can put the the data into context (“[...] we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context [...].”). ESA is lucky it had a high-resolution camera to distinguish the lander from the terrain. If you only have low-res cameras, it might be useful to have a visually distinguished lander so you find it despite…

But then you probably have a camera that has exactly one use – finding the lander – which doesn't necessarily yield the same quality of scientific results than having a camera that is more useful to the actual goals of the mission. Yes, finding Philae is nice, but not finding it wouldn't have been that bad, and the camera surely generated worthwhile data even without finding Philae.

s/camera/filter or sensor/

You could probably have any number of multi-purposed systems for that task.

Re: Philae Found

#62

Post by tgb »

jonknee wrote: post #41
tqkxzugoaupvwqr wrote: post #35

Earlier quoted context omitted.

Finding the lander made a difference. Now they can put the the data into context (“[...] we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context [...].”). ESA is lucky it had a high-resolution camera to distinguish the lander from the terrain. If you only have low-res cameras, it might be useful to have a visually distinguished lander so you find it despite…

If they didn't have a high res camera and could only identify the lander as a brightly colored speck it would not provide any "context" for their data other than it did not vanish into space.

The suggestion, I think, is to have both, under the assumption that one extra low-res single-purpose camera would be relatively easy to add. Once you find it with one camera, you can find it with the other.

Re: Philae Found

#63

Post by dredmorbius »

baq wrote: post #38
andreygrehov wrote: post #33

Off-topic, but why do they usually shoot black and white? Is it something to do with the file size?

it's not worth it scientifically to use a bayer filter. if there's a color shot, it's usually false color or three successive shots with a R/G/B filter separately. this spacecraft may not have such filters available as the comet is expected to be about as colorful as a lump of coal.

Anular velocity might also be too high to get a suitable impression. Three separate scans would be shifted leaving a rainbow-blurred image. Still lifes are easier (e.g., geostationary shots of Earth, Mars rover shots).

Re: Philae Found

#64

Post by qume »

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…

If they were to commit resources to this situation, a simple, tiny, low power radio beacon would be an option.

Rather than search for it, let it tell Rosetta where it is.

The problem with this is that even though the beacon could be only a few grams and use micro-watts (1 milliwatt transmission 1/1000th of the time?) of energy, Rosetta would need a receiver capable of picking it up.

I assume Rosetta has something like software defined radio but due to when it was designed, not sure if this is the case. In any case Rosetta is loaded with really sophisticated radio gear probably it could be build such that there is no weight or energy penalty for this.

Wish more NASA folk would read hacker news and could chime in

Re: Philae Found

#65

Post by chakalakasp »

NASA and ESA's recent push to land things on comets and asteroids makes me pause and wonder if they have in the last decade or so calculated the orbit of an object that concerns them.

Re: Philae Found

#66

Post by hcrisp »

Coding_Cat wrote: post #57
spuz wrote: post #53

Earlier quoted context omitted.

I'm surprised at how rugged the surface looks in these high-res images. Especially compared to the imagined flat landing areas we were used to seeing in the run up to the landing [1]. Just shows how difficult a task it was to land and keep the craft the right way up. [1] https://en.wikipedia.org/wiki/Philae_(spacecraft)#/media/Fil...

There is no atmosphere and thus no wind (let alone flowing water), so no natural forces to smooth it out. On a related note, moon dust is apparently incredibly sharp for the same reason.

And very low gravity to cause landslides and even the terrain out.

Re: Philae Found

#67

Post by lucb1e »

I didn't get why this was important and the article didn't reveal it upon skimming. Since it seems to get people very enthusiastic I gave it a proper read. After 11 paragraphs, the actual news is revealed:

> “This [...] means that we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context, now that we know where that ground actually is!”

Re: Philae Found

#68

Post by AstroJetson »

scoot wrote: post #31
AstroJetson wrote: post #13

Earlier quoted context omitted.

Me too, it's good to know that Philae hadn't bounced off into space.

RTFA. It was already known it had landed, just not exactly where.

Yes, they knew it landed, they got data back and then other than the last burst, never heard from it again. That's from the article and other news sources.

Nice to know that it was still there after the last burst, that it hadn't been swept into space. And from the pictures it's going to be on there for awhile.

Re: Philae Found

#69

Post by gokhan »

masklinn wrote: post #23
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 surf…

Maybe they should put it into a very very close orbit and wait for the micro gravity doing it's work. Maybe large harpoons tangling on sticks every side. It's easy for me to talk at this point, but it's their job to expect that surface. I don't think other comets passing closer by have better surfaces.

I'm following this mission almost from the beginning, amazed by the success despite Philae's short lived life on comet, and think the science aspect of it all is unbelievably great. But that landing moment made all the difference, and it failed to fix it on the surface, hence the criticism.

Would we consider Curiosity mission success if landing put it upside down?

Re: Philae Found

#70

Post by Yhippa »

thr0waway1239 wrote: post #28
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.

That comic actually helped me understand much better why the OP article was so important.
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