
Hayabusa-2: Japan's rovers send pictures from asteroid - ColinWright
https://www.bbc.co.uk/news/science-environment-45598156
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gene-h
Another interesting thing about these rovers is that they are fully
autonomous. They decide on where to explore the asteroid on their own using
stereocameras, photodiodes, accelerometers, gyroscope, and temperature
sensors.[0][1] In the last Minerva rover much of the autonomy consisted of
hopping randomly, hopping in a human specified direction where direction is
estimated from solar position by the photo diodes, and survival hopping[2].
One interesting issue they have to contend with is the low albedo(0.05) of
Ryugu. The low albedo(0.05)[3] makes portions of the asteroid surface a rather
warm 100°C[4], which is not good for long term operation of the electronics.
And of course really cold temperatures are not good for the rover either. In
the last Minerva rover survivals hops were to have been performed to keep
temeperatures as moderate as possible. For example, hopping away from the sun
during the 'morning' and towards the sun in the 'evening.' Presumably there
are also some behaviors to get out of dark ruts like the Philae probe got
stuck in.

[0][https://www.dlr.de/pf/Portaldata/6/Resources/lcpm/abstracts/...](https://www.dlr.de/pf/Portaldata/6/Resources/lcpm/abstracts/Abstract_Yoshimitsu_T.pdf)
[1][http://www.hayabusa2.jaxa.jp/en/topics/20180919e/](http://www.hayabusa2.jaxa.jp/en/topics/20180919e/)
[2][https://ieeexplore.ieee.org/abstract/document/1307442/](https://ieeexplore.ieee.org/abstract/document/1307442/)
[3][https://en.wikipedia.org/wiki/162173_Ryugu](https://en.wikipedia.org/wiki/162173_Ryugu)
[4][http://www.hayabusa2.jaxa.jp/en/topics/20180907e/](http://www.hayabusa2.jaxa.jp/en/topics/20180907e/)

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fludlight
Direct source:
[http://www.hayabusa2.jaxa.jp/en/topics/20180922e/](http://www.hayabusa2.jaxa.jp/en/topics/20180922e/)

More detail:

[http://global.jaxa.jp/projects/sat/hayabusa2/](http://global.jaxa.jp/projects/sat/hayabusa2/)

[http://www.hayabusa2.jaxa.jp/en/](http://www.hayabusa2.jaxa.jp/en/)

[http://www.hayabusa2.jaxa.jp/en/galleries/](http://www.hayabusa2.jaxa.jp/en/galleries/)

[http://global.jaxa.jp/projects/sat/hayabusa2/pdf/20180905_ha...](http://global.jaxa.jp/projects/sat/hayabusa2/pdf/20180905_hayabusa2_e.pdf)

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saagarjha
Are those pictures true-color?

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desireco42
This is Japanese mission, I would expect cameras to be really good.

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modzu
maybe its got an xtrans!

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cheeko1234
Hayabusa2 carries multiple science payloads for remote sensing, sampling, and
four small rovers that will investigate the asteroid surface by hopping and
then on top of all that it will bring back samples in 2020!

All of that for less than $150 million!

~~~
maxxxxx
How does that compare with european or US missions?

~~~
alpha_squared
The most recent, somewhat comparable (though not really), would be the ESA's
Rosetta mission to comet P67. That cost around $1.8 billion[0].

[0]
[https://en.wikipedia.org/wiki/Rosetta_(spacecraft)#Design_an...](https://en.wikipedia.org/wiki/Rosetta_\(spacecraft\)#Design_and_construction)

~~~
maxxxxx
Are they similar in complexity? If Japan can do it that cheaply then others
should take a long, hard look at their own cost. It's not like Japan is a low
wage country.

~~~
adventured
NASA, for example, spends immense amounts of money on trying to ensure that
their projects have a high success rate.

They'd rather spend $2b to get a 97% likelihood of a positive outcome, than
$1b with an 80% likelihood.

Time is a big deal when you're going to spend a decade on a project. NASA will
have a ~$250b budget for the next decade. The people that they have access to
to work on projects, are finite however. Their lifespans are finite, how much
time they're willing to spend on one thing is often very restricted, and just
nailing them down for a given project can be difficult. There are a lot of
other things they can be doing with their time. You want to get things right
the first time and not spend five years doing it all over again (and more
likely, the project is simply cancelled). NASA's budget being sizable, gives
them some flexibility on spending more to increase positive outcome chances.

It's better to spend $10b on James Webb (if necessary), than $3b with a
meaningfully higher chance of failure. If it fails at the lower budget, they
still won't do it all over again, it'll just be dead. It'd be a massive loss
of time and potential.

~~~
glandium
> They'd rather spend $2b to get a 97% likelihood of a positive outcome, than
> $1b with an 80% likelihood.

I don't know if you picked your numbers out of a hat, but napkin statistical
analysis (if I'm not mistaken) is that two attempts with an 80% likelihood
would have a 96% likelihood of at least one success. That's not quite exactly
97%, but if your numbers are not their actual assessment, it's worth wondering
if their bets are the good ones.

The thing that skews their monetary needs towards the expensive option with a
better likelihood, as I understand it, is that they can't afford the bad PR
that comes from failure.

But in pure, statistical terms, they might, actually be better off betting
less money on projects with less likelihood of success. They would fail more
often, but overall, would spend less money for the same amount of success.

~~~
ridgeguy
NASA tried "faster, better, cheaper". It didn't work out so well.

Mars Climate Orbiter, Mars Polar Lander were two missions executed under the
FBC regime. They failed, arguably due to underfunding that elevated risks.
It's hard to say, because the statics are sparse.

I'm personally ok with paying taxes to fund missions at the level of, say, New
Horizons (~$700 million over 15 years) or Cassini (>$3B).

~~~
glandium
But the point of a cheaper project that has more likelihood of failure is that
you could try again. You can even learn from the previous failure to reduce
the likelihood of failure on the second attempt. Plus, since you've done a lot
of the development for the first mission, you probably can save a lot of time
and money. But that's armchair space exploration engineering. I could be
completely wrong in my assumptions.

That being said, what is non compressible, though, is the time to get to where
we need to go (Mars, Ryugu, or whatever else in space), and having to retry is
a set back that can be counted in large number of years.

~~~
_Tev
Don't forget that every "try again" adds 80-150M to the cost for new launch
vehicle.

SpaceX is starting to change this, but most of the NASA history / planning was
done in context of high launch costs.

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rambojazz
I feel so privileged to live in a era where I can watch surface pictures of
planets, comets, and asteroids.

~~~
technocratius
It's truly amazing, isn't it.

~~~
melling
Well, to be quite honest, I thought we'd be all over the solar system by now.

As a kid 40 years ago I was excited when Viking landed on Mars... and the
Space Shuttle Enterprise was introduced.

[https://www.youtube.com/watch?v=ggjD3i7efKU](https://www.youtube.com/watch?v=ggjD3i7efKU)

[https://www.youtube.com/watch?v=i40XddxwQMs](https://www.youtube.com/watch?v=i40XddxwQMs)

What's really exciting is that people got tired of waiting for the governments
of the world and decided to invest in private space ventures.

~~~
overcast
There is only one Solar System, ours :) The rest are star systems. It's
unfortunate that it took all these years to reignite the passion in space
travel though.

~~~
melling
Yes, I was only referring to our solar system. We understood that Andromeda
was light years away back in 1976.

Forgot to mention that Skylab was still in orbit:

[https://en.wikipedia.org/wiki/Skylab](https://en.wikipedia.org/wiki/Skylab)

And Pioneer was heading out into the solar system.

[https://www.nasa.gov/centers/ames/missions/archive/pioneer.h...](https://www.nasa.gov/centers/ames/missions/archive/pioneer.html)

The Russians were sending probes to Venus during that time too:

[https://en.wikipedia.org/wiki/Venera](https://en.wikipedia.org/wiki/Venera)

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nerfhammer
It's a sample return mission! They're actually going to try to bring bits of
the asteroid back to earth

~~~
not_kurt_godel
According to Wikipedia[1], there are 2 separate sampling phases - one where it
fires a bullet into the asteroid and collects the ejecta, and another where it
will use 4.5kg of plastic explosives to blow a 2m crater in the asteroid, into
which it will descend. As a laymen, the level of complexity in this mission is
really astounding, both with respect to the sampling protocols and the 4(!)
other rovers it has.

It makes me nervous to think about how many things could potentially go
catastrophically wrong, especially after what happened with Rosetta & Philae.
I'd be curious to read an informed comparison of Hayabusa2 vs. Rosetta/Philae
and understand the rationale for Japan attempting a seemingly hugely more
complicated and risky mission.

[1]
[https://en.wikipedia.org/wiki/Hayabusa2#Sampling](https://en.wikipedia.org/wiki/Hayabusa2#Sampling)

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piyush_soni
It's super exciting what they're trying to do (especially exploding a crater,
collecting samples from that and returning with them in 2020), but I can't get
over the fact that the pictures are still worse than what a cellphone camera
would take 10 years back.

~~~
JoeAltmaier
It was designed about that long ago, so that's about right. Also even though
the light levels are pretty good (near-earth orbital radius from the sun) its
got to capture and transmit pictures using the limited power available on a
small spacecraft. The speed of transmission is limited by power and time. So
the minimum useful resolution is chosen to allow the most pictures in the
limited time available.

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supernovae
In days like this, a little bit of science and a ton of human ingenuity brings
a smile to my face. Stuff like this is what happens when we come together and
use our tech for the greater good - keep it up! Amazing that Japan has
"Crickets" hopping around on asteroid!

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darawk
Anyone have any idea why big sections are blacked out in many of these
pictures?

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space_fountain
I'm pretty sure that's just the perspective messing with us and it's just the
black of space. Keep in mind too that when the exposure is set to capture the
surface of the astroid stars won't be visible

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mc32
Given the low gravity, how does this system maintain traction?

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woofyman
I doesn’t, It jumps.

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baud147258
I remember reading about the difficulties encountered by the Hayabusa 1
mission 15 years ago. And now the JAXA has done this another time and we're
even getting pictures!

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RightMillennial
I was hoping these would be some new pictures since Saturday.

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dzink
Is there a risk that the planned explosion changes the trajectory of the 1km
wide asteroid? Odds of it swinging closer to Earth as a result?

~~~
dmurray
I haven't done the maths on how much explosive you'd need to noticeably alter
the trajectory, but it's not 4 kg. I'm not sure if 15 million kg (one
Hiroshima) would even do it.

Edit: according to Wikipedia [0], a 1967 study suggested that we could alter
the course of a 1.4km asteroid enough to avoid an Earth collision by using a
handful of Tsar-Bomba-sized nuclear weapons, each equivalent to around 6000
Hiroshimas or 25 billion of the charges proposed for the Hayabusa-2 mission.

[0]
[https://en.m.wikipedia.org/wiki/Asteroid_impact_avoidance](https://en.m.wikipedia.org/wiki/Asteroid_impact_avoidance)

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Dirlewanger
That first picture is incredibly unnerving. It's like the last picture taken
by the rover before it went suddenly offline or something.

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Hippocrates
This is fascinating. I read that MASCOT has a non-rechargeable battery that
lasts only 16 hours. Why is that?

Also, how do they test this hopping on earth?

