Hayabusa 2 rovers send new images from Ryugu surface | Hacker News Reader

Hayabusa 2 rovers send new images from Ryugu surface

bbc.co.uk

278 pointsDanBC58 comments

"Gravity on the surface of Ryugu is very weak, so a rover propelled by normal wheels or crawlers would float upwards as soon as it started to move," officials with the Japan Aerospace Exploration Agency (JAXA) wrote in a description of MINERVA-II1A and MINERVA-II1B.

So, the robots — each of which measures 7 inches wide by 2.8 inches tall (18 by 7 centimeters) and weighs 2.4 lbs. (1.1 kilograms) — hop instead. They do this by moving a "torquer" in their interior, which rests atop a disk-shaped turntable.

By rotating the torquer, a reaction force against the asteroid surface makes the rover hop with a significant horizontal velocity," a team of researchers led by JAXA's Tetsuo Yoshimitsu wrote in a 2012 study outlining the concept. "After hopp[ing] into the free space, it moves ballistically. With this mechanism, by changing the magnitude of torque, the hopping speed can be altered, so as not to exceed … the escape velocity from the asteroid surface.

Src: https://www.space.com/41941-hayabusa2-asteroid-rovers-hoppin...

You don't happen to know of an animation showing the system in action, do you?

https://youtu.be/b9fITBmQt1Y?t=4m25s

I recommend watching the whole video.

That was perfect. Thank you!

Wonder if they could use some sort of rather slow mechanical deformation to provide movement with pump mechanisms. I guess that still would rely on significant gravity or other anchoring ti avoid slippage.

Problem with that is you're relying on the surface properties of the material you're pushing against. If it's too soft, you get no motion. If it's too hard you get too much. The nice thing about using internal reaction wheels is that the torque you get is entirely independent of the surface you're resting on.

Oh those are very observations. Thanks for pointung them out.

Movement along the surface via friction (wheels, crawling, snaking etc) is not considered feasible. The surface is probably too loose to provide much traction, but more importantly the low gravity means the vehicle will certainly become caked in dust very quickly. Hopping means you don't disturb the surface, and if you do you probably fly clear of the resulting dust cloud.

Makes sense. Now that yoo bring up dust, how does erosion occur in space, or how would dust form other than perhaps through temperature fluctuations?

I am not an expert but I suppose it gets bombarded by a lot small particles all the time. Over a few million/billion years that adds up.

Dirty snowball + heat = dirt. Small bits once locked in ice are now dust.

I love that they opted for color cameras. Not much color to be seen, but the flares, together with the motion blur (while falling and hopping!) make the pictures look really dynamic. :)

I'm not entirely sure that's motion blur. The images shown in the article make it look like it's just lens distortion. It's probably a fairly wide angle lens, and that's why things look stretched out the further from the center of the image they are. (I think.)

Some of it definitely is, they even mention it here: http://www.hayabusa2.jaxa.jp/en/topics/20180922e/

Wonder if it's because they were planning on taking pictures while hopping? The usual one-picture-per-color-filter method that they usually use on space probes probably wouldn't work well while in relatively fast motion.

They did, see my other post. I don't know about the filters though, I'm not deep in the material, I also only know what they posted on twitter :P

i wish they had better cameras though

This was my question - they are the size of like 6 iPhones stacked together. Seems like they should look at least as good as the selfie cameras in your average smartphone.

Reading this sub-thread, it makes me wonder how a consumer level smartphone camera would perform in space... I was under the assumption that they might have a limited operating temperature range, and that they might have issues in the extreme cold?

すごいよ Sugoiyo! Super! Cool! Wow! Awesome achievement Japan.

I really admire that its means of propulsion doesn’t involve wheels (since the gravity is so low)

Just came back from Europe. Everyone knows about this and all media reported on it. Surprisingly so little is said in American media. Its not new that Americans do not like other nations succeed in space! If these were US-based rovers, each network will give it 10 minutes cover. Same sad story about Chinese Moon landing. Most American friends laughed at me when I told them China landed rover on moon. Some even question Wiki article as conspiracy theory.

Consider literal competitions--it was similarly appalling to watch recent Olympics in the US. 95% or more of the coverage was of Americans winning. If a particular day had fewer wins, they would replay earlier footage rather than dare show any other country succeeding at non-American dominant areas. One saving grace is that the NBC app had all the footage they didn't deem worthy of broadcasting.

I can't watch the Olympics on US TV. Hours of stories about the upbringing of the US athletes interviewing moms and grandparents. Then a little actual sport if you are lucky. And certainly nothing where there isn't a US athlete/team at the front. It's unbearable.

I cannot agree more. I remember growing up it was just raw footage of events without break, and often with little or no commentary. We would sit for hours and watch the pinnicale of human physical ability. Now its 95% pomp and commentary, and you find yourself just looking up the events you wanted to watch the next day on a video hosting site. This just fits into the larger context of broadcasting digging their own grave in the glow of the internet. Even though their offerings are still often technically and artistically superior, the are bound outside like writhing beasts to their business model and it kills them by forced exposure (nessitating constant 'content'). Youtube is now doing the same by deranking channels that fail to release videos on a regular, if not frantic, schedule. Patreon is helping, but just enough to defer actually dealing with the huge problem. Its a vicious cycle.

In Maine we get the French-Language version of CBC, and they had near-constant coverage of more than just Canada. Even though I barely understand more than a few dozen words in French, it was better than watching NBC.

It's also that the PR done by NASA is about 100x as good as all the other space agencies in the world.

Really good photos and videos and web pages and TV material. Lenient sharing licenses etc.

Really good web pages? are you kidding me? lol

It's a big problem in the US that other countries only get acknowledged as in relation to the US. In a way this myopia serves the country pretty well and it's big enough to do most things themselves. But sometimes interesting things that happen in other countries get overlooked and nothing is learned.

>> Some even question Wiki article as conspiracy theory.

Is there a Wikipedia page that "some" Americans don't think is a conspiracy? Conspiracies used to be about aliens and secret research programs in bunkers. Now they are about pizza restaurants. I gave a presentation at an Airforce base where a flat-earther accused me of participating in the conspiracy. I wanted to throw him out as a dangerous or unstable person, or strap him to the underside of a plane and show him the curve in person. These days, every article, every statement, has to address the 5-10% of people who just don't believe anything anyone tells them.

I am waiting for one of the "airplanes run on compress air" conspiracy people. (It's the latest version of chemtrails.) We'll have them fill a few aircraft by hand... with buckets.

Yup, am surprised at how many people at NASA have no clue this is going on. I expected at least a retweet or a mention from NASA.

It's even worse in music, movies, and sports.

The Chinese moon CGI looked totally real.

Considering their very tiny size, I'm curious about three things... What sort of software/watchdog timer these mini rovers have set up for charging their batteries, the size and type of the batteries (in Wh, chemistry, etc), and how often they wake up and take photos and temperature measurements.

The size of the surface area exposed to the sun with high-efficiency PV cells is not very large, since they are so tiny. I'm assuming the cells are triple-junction GaAs for the greatest Wh per square cm per day.

What compression protocol is used to send images?

The pictures are thrilling! The rock looks stratified - which might imply they were created under gravity? Or is it just the camera angle...

Less gravity, more radiation/light. There is lots of water/ice involved, and the rock varies in distance from the sun. So the layered effect is probably the result of different temperatures at various depths, and the resulting sublimation (or not) of water ice. Imho it is akin to the layered effect in soil during a hard frost.

Stupid question: why does these images look so low res and over/under exposed. Sometime I feel iPhone camera tend to do much better job than those million dollar cameras on these missions. I am obviously missing some key details.

One of my personal wishes is that we covered as much surface area of asteroids and other interesting bodies in the solar system; one wonders, if we sample enough, what unexpected things we will find?

How does one "land" on an asteroid which is spinning too fast ?

Is it at all possible to match the spin of a smallish android from orbit ?

They have an open websocket to an Asteroid Landing five-layer Neural Network. The lander sends images back in real time and the earth-borne NN sends it telemetry adjustments in BSON.

Make a sturdy lander and just crash into it.

https://spaceflightnow.com/2018/06/20/asteroid-ryugu-reveale... says Ryugu only rotates once every 7.6 hours.

Sadly, no diamonds on the surface. Or gold. Would love to see how "the market" will react to that ;)

Diamonds are unlikely to be found on asteroids, because they require immense pressures to form, and the gravity on asteroids is so weak that even at the core the pressure is less than sea level air pressure on Earth.

Except if the asteroid is a piece from a bigger body that got teared apart.

Just fantastic.

I'm sure it's a very complicated problem, but I would have expected a 5 year old rover to have a better camera.

I am a bit shocked at the potatoness of it.

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! From a research data point of view, even having a color camera was overkill. Reminds me of Carl Sagan having to convince NASA to take the pale blue dot picture since it doesn’t have any significant value in the field of astronomy.

> since it doesn’t have any significant value in the field of astronomy.

PR has some value: more people will want to try and join the field and more funding could be secured.

NASA is not allowed PR as a federal agency. Imagine how far ads, sponsoring games/events, etc, would get NASA in terms of PR. Compare that to the military:

https://www.cheatsheet.com/money-career/amount-money-militar...

https://taskandpurpose.com/us-military-combat-trainer-kick-a...

Not only that, NASA's education department was as close to PR as we had and...

https://www.forbes.com/sites/startswithabang/2017/05/25/trum...

On the other hand, I visited several of the major ESA facilities across Europe, and then Kennedy Space Center, and it was a stark difference how much more commercialized KSC is. It’s a proper theme park. I don’t think any other space agency has anything so touristy.

The visitor complex is a separate entity than the KSC itself. It's run by Delaware North.

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

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

That's completely false. NASA has a very large PR (public affairs) team, 114 employees in 2016. NASA also spends about ~4 million a year with external advertising and PR agencies.

https://www.gao.gov/products/GAO-17-711?source=ra

Also, the NASA budget ended up getting a big increase, and the education budget was not cut:

https://www.sciencemag.org/news/2018/03/planetary-science-wi...

On the flip side, Brindenstine has discussed selling ad space on the sides of rockets and naming rights to missions. One concern (out of many) is ensuring that the money goes to NASA, and not just the treasury's general fund

I'm pretty sure it's not a poor camera because they couldn't afford it. It'll be because of weight considerations. If you have a higher resolution camera, everything has to be bigger and heavier - larger camera, more local storage, more processing power, bigger antenna (these have to be sent using lossless compression for science), etc. Each robot has a mass of 1.1 kg, lighter than my laptop - and it has to do other science and return a sample to earth!

I suspect that too, but am looking for data to support this. We have tiny miracles in our cell phones today, are they really any heavier than what's on that vehicle? (I understand a cell phone camera isn't Space Ready™.) Does it require, perhaps, additional hardware that wouldn't be needed otherwise with today's on-board solution? And what's up with the severe lens distortion?

Cool topic I hope to dig into a bit to get those answers.

A few factors I can think of:

The rovers launched in 2014, and they were designed well before that. I wouldn't be surprised if the camera hardware was decided on in 2010

A normal camera in space is going to have problems. I'm not any sort of camera expert, but I can imagine there's a _lot_ of electronics in one. There's the sensor. That sensor may be hooked up to an analog to digital converter, which might be hooked up to a processor that converts whatever the sensor reads into a compressed image. Someone who is familiar with how cameras work can probably think of a dozen bits I'm missing :)

All of those bits of silicon are going to get bombarded with radiation, so they need to be radiation hardened. Smaller transistors are especially susceptible to radiation, so your radiation hardened chips are going to be bigger, more power hungry, and generally not as good as more up to date ones. From looking around online, it looks like the best rad-hard cameras today are only a couple megapixels.

I'm not sure about this case, but often times cameras not a priority for a mission. They're great for generating PR and excitement, but in terms of scientific value there's lots of other instruments that may have higher priority (both in terms of the design, and in terms of available bandwidth for returning data). If the cameras are just there to make sure the rover doesn't crash into something, they're probably using a wide angle lens which helps with navigation but can cause distortions.

Also not an expert on the topic but here are some examples of space-ready cameras with pictures and specs: http://www.msss.com/space-cameras/

Obviously radiation, extreme temperatures, vibration, and vacuum are at least some of the problems. They explicitly state that lens have no moving parts, I’m not sure why that is an issue and how can they focus without moving parts - maybe they’re just permanently focused on infinity and hence close objects are blurrier?

Lens distortion might be just normal with uncorrected very wide angle lens which you want to make framing/steering easier. Otherwise you might need a separate camera just to help you aim the first one.

And the things only weigh 2 pounds. All added weight has to count on these.

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