
Philae Found - de_dave
http://www.esa.int/Our_Activities/Space_Science/Rosetta/Philae_found
======
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/](http://www.pbs.org/program/catch-comet/)

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

~~~
kordless
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.

~~~
dfox
With our current understanding of physics, chemical rockets have one giant
engineering advantage: the same mass that is consumed for energy production is
also the reaction mass. So anything better for imparting large delta-Vs has to
be non-newtonian and our current understanding of physics does not allow
existence of any such thing.

~~~
johncolanduoni
That's a big oversimplification. Project Orion-style propulsion is certainly
not ruled out by our current understanding of physics. There's no non-
Newtonian mechanics involved, just the substitution of a nuclear reaction
instead of a chemical one. Not to mention that we have lots of evidence of
non-Newtonian mechanics (e.g. Special and general relativity), even if whether
GR can assist in space travel is an open question.

------
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!”

~~~
edge17
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.

~~~
wolf550e
The SpaceX comparison is bad because they don't do science missions. SpaceX do
commercial launches for paying customers. Mission success is defined by
whether the payload gets to its intended orbit, unharmed. Even if SpaceX learn
a lot from a mission, if the payload is lost then the mission failed. While
one can learn from failures, when the mission is not a test, learning is not
enough for the mission to be called a success.

~~~
edge17
SpaceX has done quite a few missions to develop their rockets before getting
contracts from NASA, etc. Some of those also included payloads.

~~~
wolf550e
SpaceX did three kinds of flights:

1\. Launch contracts for paying customers where mission success was defined as
"unharmed payload to correct orbit".

2\. Test/demo missions with mass simulator instead of payload where mission
success was defined as "unharmed payload to correct orbit" (two missions:
Falcon 1 Flight 4 [0] and Falcon 9 Flight 1 [1]).

3\. Rocket landing development flights with Grasshopper where mission success
was defined as advancing the ability to land the booster.

SpaceX did R&D on all flights (for example they unsuccessfully tried parachute
recovery), but for all flights of Falcon 1 and Falcon 9 (not Grasshopper),
they always stated that mission success is to get the customer's payload
unharmed to the correct orbit, or to demonstrate the ability to get the
customer's payload unharmed to the correct orbit. If they defined mission
success as anything else, a potential customer might think SpaceX would
sacrifice the payload to advance SpaceX's own goals (like recoverability R&D),
and this customer would not fly with SpaceX.

0 -
[https://en.wikipedia.org/wiki/Ratsat](https://en.wikipedia.org/wiki/Ratsat)

1 -
[https://en.wikipedia.org/wiki/Dragon_Spacecraft_Qualificatio...](https://en.wikipedia.org/wiki/Dragon_Spacecraft_Qualification_Unit)

------
infodroid
The hi-res image shows how just how unlucky a landing spot this was.

[http://www.esa.int/spaceinimages/Images/2016/09/OSIRIS_narro...](http://www.esa.int/spaceinimages/Images/2016/09/OSIRIS_narrow-
angle_camera_image_with_Philae_2_September)

~~~
spuz
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...](https://en.wikipedia.org/wiki/Philae_\(spacecraft\)#/media/File:Rosetta%27s_Philae_on_Comet_67P_Churyumov-
Gerasimenko.jpg)

~~~
wcoenen
It was aimed at a flat spot, but when it failed to attach to the surface it
bounced and floated for almost 2 hours, hitting the surface again 1 km
away[1][2]. Its speed of 38 cm/s during that time was below escape velocity
but not by much.

[1]
[https://www.youtube.com/watch?v=rJ2eqH3Bz4c](https://www.youtube.com/watch?v=rJ2eqH3Bz4c)

[2] [http://blogs.esa.int/rosetta/2014/11/14/three-touchdowns-
for...](http://blogs.esa.int/rosetta/2014/11/14/three-touchdowns-for-
rosettas_lander/)

~~~
pavel_lishin
> _it failed to attach to the surface it bounced and floated for almost 2
> hours, hitting the surface again 1 km away[1][2]. Its speed of 38 cm /s
> during that time was below escape velocity but not by much._

These numbers sound completely ridiculous, unless you've played Kerbal Space
Program, and know the visceral pain of bouncing above Minmus with a pixel of
monopropellant left in the tanks.

------
usaphp
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]

[1]:
[https://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasime...](https://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimenko)

------
thr0waway1239
"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?

[1]
[https://www.youtube.com/watch?v=4eJhcxfYR4I&t=16m35s](https://www.youtube.com/watch?v=4eJhcxfYR4I&t=16m35s)

~~~
whamlastxmas
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.

~~~
dredmorbius
A dye bomb is used for aerial crash/rescue. That would contaminate a surface,
but also provide a possible visual marker. Maybe several launched away from
the lander, but which could be used to triangulate it, in the rare case that
might actually be of interest.

I suspect there's a lot of re-thinking of how to land on a comet going on as
well.

~~~
TaylorAlexander
Certainly I started thinking about better ways once this image made it clear
what we (humans) are dealing with here.

I can imagine a cage-like outer shell where the robot inside is able to rotate
on two axes under power. Let it tumble any which way and then use sensors to
determine the correct orientation and right itself.

NASA has a concept for this: [https://ti.arc.nasa.gov/tech/asr/intelligent-
robotics/tenseg...](https://ti.arc.nasa.gov/tech/asr/intelligent-
robotics/tensegrity/superballbot/)

~~~
david-given
That's pretty much what Spirit and Opportunity's airbag landing system was,
although a lot simpler --- it was set up so that no matter what way up it was
after it came to a rest (after bouncing and rolling!), when the bags deflated
it would automatically roll the right way up so that when the deployment
mechanism finally opened, the rover could just drive out.

I've tried to find a video showing it happening, but while there's lots of
animations of bouncing, rolling, and the final opening up, they all miss the
critical moment. Also, car safety videos are _really_ badly poisoning the
search results...

~~~
figgis
[https://youtu.be/-_9BYSDtwRc?t=197](https://youtu.be/-_9BYSDtwRc?t=197)

Here you go. Really enjoyed watching that.

------
movedx
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.

~~~
gene-h
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.

~~~
widforss
Worth mentioning is that objects keep their thermal energy for much longer in
a vacuum since there is nothing that can conduct the heat away, so the heaters
does not have to output that much energy.

------
proactivesvcs
I found ESA's "Rosetta and Philae Cartoons" videos strangely touching:
[https://www.youtube.com/playlist?list=PLgx5PMpgonqUD1aO3g0bZ...](https://www.youtube.com/playlist?list=PLgx5PMpgonqUD1aO3g0bZ_a7VKg8VGTeS)

I hope they finish the series!

------
luso_brazilian
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/](https://xkcd.com/1446/)

[2]
[https://www.explainxkcd.com/wiki/index.php/1446:_Landing/All...](https://www.explainxkcd.com/wiki/index.php/1446:_Landing/All_pictures)

~~~
thr0waway1239
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.

~~~
sundarurfriend
Wow. I had only mild interest in the news and was about to close this tab
after I learned what the hell Philae _is_ (without opening TFA), but this
comic series made me excited about the project and made me check out the
article. Good job, Randall, and thanks!

------
cJ0th
Rosetta also tweeted an update ;)

[https://twitter.com/ESA_Rosetta/status/772818246059823104](https://twitter.com/ESA_Rosetta/status/772818246059823104)

------
huhtenberg
Is there a map that shows its original landing site and the final resting
place?

~~~
simonh
Here you go:
[http://static.keptelenseg.hu/p/ba7a0e382320f9656ef892707c673...](http://static.keptelenseg.hu/p/ba7a0e382320f9656ef892707c673df8.jpg)

~~~
huhtenberg
Good find, thanks!

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

~~~
hbosch
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.

0\. [http://www.straightdope.com/columns/read/3088/why-are-
images...](http://www.straightdope.com/columns/read/3088/why-are-images-from-
space-probes-always-in-black-and-white)

~~~
ygra
Cameras often have wavelength filters to allow recording only certain wave
lengths, that can be switched. So taking a colour photo requires three
different exposures. Depending on how long you can take a single picture and
how much changes in between you may not really get a useful result. A Bayer
filter like in common digital cameras these days would also reduce resolution
and restrict you at the sensor level to colour photos.

About the only use for colour photos in space is PR with non-scientists
anyway. That was one major obstacle the Hubble Space Telescope had to face.
It's a useful component, to be sure, but not one to justify adding much more
weight or cost to a planned mission in all cases.

In case of Rosetta/Philae the probe was _very_ weight-restricted, taking even
a very long course towards the comet to save fuel since it didn't have much.

~~~
dajohnson89
PR for non scientists is extremely important. Non scientists fund the
missions.

------
netgusto
This made me smile. Nice news !

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

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

~~~
AstroJetson
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.

~~~
scoot
Then RYFC: _" it's good to know that Philae hadn't bounced off into space."_
does not correlate with someone who had bother to read the article before
commenting. You can't "bounce" from a stationary position, but glad to see
you've now caught up.

------
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.

~~~
mturmon
Finding near earth objects is done in the open:
[http://neo.jpl.nasa.gov/ca/](http://neo.jpl.nasa.gov/ca/)

The succession of missions (going back 20 years now) is here:
[http://neo.jpl.nasa.gov/faq/#spacecraft](http://neo.jpl.nasa.gov/faq/#spacecraft)

------
fuhrysteve
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.

------
DrNuke
This is even more incredible than the already unbelievable amaze generated by
this mission as a whole. Hat off.

------
b1gtuna
Haha itsy bitsy little space craft hiding behind a rock!

------
bjd2385
What's that rather straight `rod`-like protrusion to the lower-left? Looks
like some kind of antenna.

~~~
proactivesvcs
Half way down [http://www.bbc.co.uk/news/science-
environment-37276221](http://www.bbc.co.uk/news/science-environment-37276221)
is an overlay describing the parts. It sitting on its side, so I think you're
referring to one of its three legs jutting out.

------
zygomega
Does anyone know why communication is being shut down? Can they leave it on so
we can get telemetry?

------
gokhan
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.

~~~
masklinn
> 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.

~~~
gokhan
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?

------
sqldba
Poor little thing. God speed.

------
dandare
Nice, but why is this information so "all-important"? How is it going to
advance our knowledge of ... anything?

~~~
speeder
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.

