Hayabusa-2: Japan's rovers send pictures from asteroid | Hacker News Reader

Hayabusa-2: Japan's rovers send pictures from asteroid

bbc.co.uk

251 pointsColinWright42 comments

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/... [1]http://www.hayabusa2.jaxa.jp/en/topics/20180919e/ [2]https://ieeexplore.ieee.org/abstract/document/1307442/ [3]https://en.wikipedia.org/wiki/162173_Ryugu [4]http://www.hayabusa2.jaxa.jp/en/topics/20180907e/

Direct source: http://www.hayabusa2.jaxa.jp/en/topics/20180922e/

More detail:

http://global.jaxa.jp/projects/sat/hayabusa2/

http://www.hayabusa2.jaxa.jp/en/

http://www.hayabusa2.jaxa.jp/en/galleries/

http://global.jaxa.jp/projects/sat/hayabusa2/pdf/20180905_ha...

Are those pictures true-color?

I believe these are color cameras, yes.

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

maybe its got an xtrans!

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!

Is that the actual cost? I know there were estimates from 2010 for ~146 million USD, but I kinda doubt that the mission is actually that cheap (considering the launch probably cost $80 million by itself)

How does that compare with european or US missions?

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...

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.

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.

I for one like the fact that different national space agencies are going with completely different approaches. I doubt that the skycrane used for the NASA's Martian Science Lab mission could be accomplished on a shoestring JAXA budget. On the other hand, an asteroid sample return mission would've cost billions and taken decades if NASA had done it.

At the end of the day, we all take different paths but ultimately get to the same place. Humanity wins.

> 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.

"as I understand it, is that they can't afford the bad PR that comes from failure."

I think that's the real problem.

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).

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.

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.

The James Webb scares me. They now have put so much money and time into it that a failure would just be unimaginable. I am sure they have run the numbers but personally I am not sure if they wouldn't be better off with iterating faster and cheaper while accepting some level of risk.

Maybe a failure of the James Webb would be a good motivator for a manned mission to the Lagrange point :)

There are also some ESA part on hayabusa 2 (Mascot descender)

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

It's truly amazing, isn't it.

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=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.

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.

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

And Pioneer was heading out into the solar system.

https://www.nasa.gov/centers/ames/missions/archive/pioneer.h...

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

https://en.wikipedia.org/wiki/Venera

I'd love humanity to be visiting another solar system by now, but even starting a few decades ago we'd probably would have had to violate a few important laws of physics in order to reach another star.

Space is big

Hopefully soon we'll have the privilege of walking on the surface of planets ( other than earth of course ), comets and asteroids.

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

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

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.

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.

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!

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

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

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

I doesn’t, It jumps.

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!

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

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?

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

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

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?

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