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.
I tried to find the full version of the PBS "To catch a comet" about the Rosette/Philae mission but came up empty handed. Searching google, I was able to find a talk by Mark McCaughrean (ESA) called "Rosetta: to Catch a Comet". Been watching it for about 30 minutes and it's awesome. So, for anyone else looking for something to watch, this worked out great. Pretty amazing talk!
There's also the argument for doing things a better way. Our propulsion systems suck, which is why we're having to send robots to comets instead of humans. Humans don't get stuck in cracks. Robots get stuck in cracks because they have no clue how to measure things they've never seen before.
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!”
Also, the third paragraph shows why it was relevant:
> The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on 12 November 2014.
Mostly the curiosity of the public and more importantly the scientists who worked so hard on the project only to have their lander not land properly.
Otherwise the fact that Philae was lost almost immediately upon landing has been a huge story line this past year. I believe the blog assumed the readers would know this. A CNN article would typically provide back story but this is original source from ESA.
There were a couple of mechanisms intended to hook it upright to the surface upon landing. Instead it bounced 2 or 3 times and landed tilted in some rocks. The battery was only sufficient for a few hours of pictures and other experiments. If it had landed upright and charged by solar panels it could have operated a long time, perhaps until now. The hope was that some of the solar panels were exposed it might revive after a couple of weeks. There was a hint it called the orbitor at least once, but no more data.
It is scientifically useful, but mostly people are just pleasantly surprised that the proverbial needle in the haystack was actually found before the mission of Rosetta itself ends, and happy to get closure for the story of the little probe that went MIA. It's an emotional response first and foremost, just being human.
Scientifically speaking, a successful mission is one where you've gathered all the data for analysis and can work with it long after the mission is over.
It's like, if SpaceX launches a rocket and it explodes - a real failure would be if they captured no telemetry and had no idea what happened vs knowing everything that happened and being able to replay the mission after the fact. Often times the data is far more important than the outcome.
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.
From Wikipedia about the comet: "One of the most outstanding discoveries of the mission so far is the detection of large amounts of free molecular oxygen (O
2) gas surrounding the comet. Current solar system models suggest the molecular oxygen should have disappeared by the time 67P was created, about 4.6 billion years ago in a violent and hot process that would have caused the oxygen to react with hydrogen and form water. Molecular oxygen has never before been detected in cometary comas. In situ measurements indicate that the O
2/H
2O ratio is isotropic in the coma and does not change systematically with heliocentric distance, suggesting that primordial O
2 was incorporated into the nucleus during the comet's formation. Detection of molecular nitrogen (N
2) in the comet suggests that its cometary grains formed in low-temperature conditions below 30 K (−243.2 °C; −405.7 °F)." [1]
"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.
Andrew Ng gave a talk recently where he talks about designing the autonomous cars not for aesthetics, but predictability (via visual distinctiveness). [1] In the same spirit, shouldn't there be efforts to make these spacecraft modules more visually distinctive?
"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.
My entirely uneducated guess is that a layer of paint would impede the cooling of electronics that depend on the housing to dissipate heat.Paint would also absorb more solar heat than plain metal.
> 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.
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
At some point in the future, someone is going to fly to that comet, land, get out of their vessel and walk over to Philae and smile, give it a pat on the head, and then take it home; someone in the future is going to be lucky enough to experience that task and become a part of its history.
And it might still work. One of the neat things about Philae is that it's rated to withstand temperatures down to −60 °C. Most other space probes(and electronics in general) are not rated for such low temperatures and will experience solder joint failures if such temperatures are reached. Most space probes stay above their failure temperature with heaters, if said heaters fail, the space probe dies and won't function even if it warms back up. This happened to the Mars Exploration Rover Spirit.
We don't know just how low Philae can go, however, there is a good chance it's electronics won't break below the rated temperature.
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.
Not sure how accurate it is, but an article found via cursory Googling[0] makes it seem like a true-color photo doesn't have as much scientific value as other spectrum recording photography - different filters over the monochrome camera can make it easier to see heat, minerals, radiation, etc.
Goes on to mention producing a true-color photo is kind of a pain in the ass for these probes.
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.
Also the picture may not be "black" and "white", it's just captured at a single frequency [or a small spectrum], and readings are for that particular frequency.
Combine multiple spectrum and you get a color image.(Though comets don't have too much change across the spectrum.)
Some decisions are made about what is going to be observed. For example, if the objective is to study the methane atmosphere (as it's being done on Jupiter), you calibrate your camera and filters for that. Then photo is taken, with whiter points indicating more emission or reflection on that wavelength. Black and white is how we see "more / less emissions"
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.
Why did it take so many months for the orbiter to get a photo?
Compared to the rest of the achievements of this mission, it seems like this should have been relatively easy: 67P is all of like 2.5 miles wide and the orbit is at like 10 miles. You'd think that a few high res photos in a single orbit would capture nearly every inch of the entire rock.
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.
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.
There were three aspects to fixing the landing, to my understanding.
Legs keep it oriented, give a stable platform, and cushion the initial landing.
Top thruster pushes it into the surface, damping any bounce back from the impact.
Harpoons attach to the surface, affixing it permanently.
The top thruster was reported to not work at all, and the harpoons were unable to work by themselves. It's not clear if they would have worked if the top thruster was working as well.
I am assuming you don't want to know why the whole mission is important (that should be obvious), and that instead you want to know why taking a photo of Philae is important.
It is important because Philae did made measurements and sent the data to us, but we didn't knew what the measurements measured, now we know.
It would be like throwing a ball that can tell about how much a place is wet in a random direction, and conclude that some place is 90% wet... Then, what place it was? A lake? A swamp? A beach? And then you find a picture of it in a bog, and conclude the bog was 90% wet.
> “This wonderful news 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!” says Matt Taylor, ESA’s Rosetta project scientist.
Philae did send data for three days (unless i miss-remember). Knowing where that data was taken helps put it into context. So quite important for the mission.
newscracker|9 years ago
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...
WestCoastJustin|9 years ago
https://www.youtube.com/watch?v=KOiY-OCCRjs
kilotaras|9 years ago
1. https://youtu.be/ktrtvCvZb28
Snesker|9 years ago
[deleted]
kordless|9 years ago
lucb1e|9 years ago
> “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!”
dmix|9 years ago
> The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on 12 November 2014.
Mostly the curiosity of the public and more importantly the scientists who worked so hard on the project only to have their lander not land properly.
Otherwise the fact that Philae was lost almost immediately upon landing has been a huge story line this past year. I believe the blog assumed the readers would know this. A CNN article would typically provide back story but this is original source from ESA.
peter303|9 years ago
Sharlin|9 years ago
edge17|9 years ago
It's like, if SpaceX launches a rocket and it explodes - a real failure would be if they captured no telemetry and had no idea what happened vs knowing everything that happened and being able to replay the mission after the fact. Often times the data is far more important than the outcome.
infodroid|9 years ago
http://www.esa.int/spaceinimages/Images/2016/09/OSIRIS_narro...
spuz|9 years ago
[1] https://en.wikipedia.org/wiki/Philae_(spacecraft)#/media/Fil...
achr2|9 years ago
HerpDerpLerp|9 years ago
Shame the spears could not stick it on at the first impact.
dmix|9 years ago
[changed, thanks]
usaphp|9 years ago
[1]: https://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasime...
thr0waway1239|9 years ago
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.
Andrew Ng gave a talk recently where he talks about designing the autonomous cars not for aesthetics, but predictability (via visual distinctiveness). [1] In the same spirit, shouldn't there be efforts to make these spacecraft modules more visually distinctive?
[1] https://www.youtube.com/watch?v=4eJhcxfYR4I&t=16m35s
lorenzhs|9 years ago
"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.
whamlastxmas|9 years ago
jonknee|9 years ago
If it was hot pink it would have made no difference, it ended up in a bad spot with limited solar power.
qume|9 years ago
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
matt-attack|9 years ago
movedx|9 years ago
gene-h|9 years ago
We don't know just how low Philae can go, however, there is a good chance it's electronics won't break below the rated temperature.
snowwrestler|9 years ago
fogleman|9 years ago
junke|9 years ago
proactivesvcs|9 years ago
I hope they finish the series!
luso_brazilian|9 years ago
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...
thr0waway1239|9 years ago
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.
tarr11|9 years ago
cJ0th|9 years ago
https://twitter.com/ESA_Rosetta/status/772818246059823104
huhtenberg|9 years ago
simonh|9 years ago
andreygrehov|9 years ago
hbosch|9 years ago
Goes on to mention producing a true-color photo is kind of a pain in the ass for these probes.
0. http://www.straightdope.com/columns/read/3088/why-are-images...
baq|9 years ago
anilgulecha|9 years ago
Combine multiple spectrum and you get a color image.(Though comets don't have too much change across the spectrum.)
chillydawg|9 years ago
woliveirajr|9 years ago
aw3c2|9 years ago
https://en.wikipedia.org/wiki/Pansharpened_image
NegativeLatency|9 years ago
I imagine it's easier to properly calibrate a monochrome camera, and makes it easier to image stuff outside of the visible wavelengths.
bajsejohannes|9 years ago
netgusto|9 years ago
AstroJetson|9 years ago
chakalakasp|9 years ago
mturmon|9 years ago
The succession of missions (going back 20 years now) is here: http://neo.jpl.nasa.gov/faq/#spacecraft
unknown|9 years ago
[deleted]
fuhrysteve|9 years ago
Compared to the rest of the achievements of this mission, it seems like this should have been relatively easy: 67P is all of like 2.5 miles wide and the orbit is at like 10 miles. You'd think that a few high res photos in a single orbit would capture nearly every inch of the entire rock.
DrNuke|9 years ago
b1gtuna|9 years ago
bjd2385|9 years ago
proactivesvcs|9 years ago
zygomega|9 years ago
gokhan|9 years ago
masklinn|9 years ago
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.
ragebol|9 years ago
What kind of landing gear + fixation gear would have been better?
Cogito|9 years ago
Legs keep it oriented, give a stable platform, and cushion the initial landing.
Top thruster pushes it into the surface, damping any bounce back from the impact.
Harpoons attach to the surface, affixing it permanently.
The top thruster was reported to not work at all, and the harpoons were unable to work by themselves. It's not clear if they would have worked if the top thruster was working as well.
sqldba|9 years ago
unknown|9 years ago
[deleted]
Roritharr|9 years ago
[deleted]
5xman|9 years ago
[deleted]
mardoqueo|9 years ago
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saif_2577|9 years ago
[deleted]
unknown|9 years ago
[deleted]
dandare|9 years ago
speeder|9 years ago
It is important because Philae did made measurements and sent the data to us, but we didn't knew what the measurements measured, now we know.
It would be like throwing a ball that can tell about how much a place is wet in a random direction, and conclude that some place is 90% wet... Then, what place it was? A lake? A swamp? A beach? And then you find a picture of it in a bog, and conclude the bog was 90% wet.
vog|9 years ago
> “This wonderful news 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!” says Matt Taylor, ESA’s Rosetta project scientist.
cvik|9 years ago
gokhan|9 years ago