Mission: Hayabusa 2 Options

[Paolo]

it's not the actual sampling operation, yet. it's the first rehearsal:
http://www.hayabusa2.jaxa.jp/en/topics/20180911e/

[Hungry4info]

We're about 1 km away now (if not less). The most recent image as of this post has a major data drop-out, but here's the most recent good image from UTC 2018-09-12 02:32.
Edit: A new image from UTC 2018-09-12 02:51. I'm pretty sure we can now see the spacecraft's shadow on the asteroid -- a dark smudge centered in the opposition surge that appears to be visible in both of the images in this post.

Attached thumbnail(s)

 

[Explorer1]

Good eye! I don't think it was visible in previous images, was it?

[Hungry4info]

Indeed. As far as I can tell, the two images in that post are the only two images where it is clearly visible, and I've not seen it in any previous image.
The site is giving me 404 errors right now, unfortunately.

Edit:
From https://twitter.com/haya2e_jaxa/status/1039723761728217089

[TD1-R1] Currently, our real time navigation image gallery has halted. Please wait as we work on the problem. Operation of the spacecraft is continuing normally.

[Therion]

According to update in japanese Hayabusa2 descended to 600 m above sufrace and then autonomous system stopped the descent and began to rise, probably due to unabillity to measure distance by LIDAR because Ryugu's surface have very low reflectivity.

As for the spacecraft's shadow - it's clearly visible in several frames:


/how can i reduce the size of inserted image?

[pandaneko]

The reason for unexpected rise during H2 descent is as follows. My translation of the relevant description in Japanese.

We have been conducting a rehearsal for the first touch down since 10 September. The spacecraft started descending on 11 September.

Today (12 September) H2 was going down to the lowest height intended, but its autonomous system ordered H2 to to rise and
H2 started rising back to its HP.

It is thought that the reason for this is LIDAR could not cope with the low reflectivity of Ryugu and could not measure the seperation
distance well enough.

H２ is now back at its HP ad is healthy. We will be looking again at the constants that had been given to H2 and also looking at
possibility of improved sequence.

P

[Roman Tkachenko]

3D Visualization of Asteroid Ryugu

https://www.youtube.com/watch?v=DDTBBggihiw

[vikingmars]

3D Visualization of Asteroid Ryugu
https://www.youtube.com/watch?v=DDTBBggihiw

CONGRATULATIONS Roman

[Paolo]

The spacecraft shadow and opposition effect
http://www.hayabusa2.jaxa.jp/en/topics/20180915e/

[Hungry4info]

A couple interesting tweets from their twitter feed. One about landing site imagery acquisition during the recent rehearsal attempt, and another about MINERVA-II1 rover deployment schedule.

Although TD1-R1 was interrupted, we were able to see the response of Hayabusa2 at low altitude and gain a valuable image of the landing candidate area at high resolution. The Project Team feels that we are narrowing down the unexplored areas step by step.

This week we will deploy the MINERVA-II1 rovers! Tomorrow (Sept 19) is the preparatory operation prior to the descent and on the 20th, the spacecraft will start descending towards Ryugu. The separation of MINERVA-II1 is scheduled for the 21st.

[Guest_mcmcmc_*]

3D Visualization of Asteroid Ryugu

https://www.youtube.com/watch?v=DDTBBggihiw

Cool.... but very uncomfortable, I feel like being driving (flying?) in reverse! Wouldn't it be better a rotation downwards? Or even better, from right to left, which probably gives a better 3d effect?

[pandaneko]

Something has been bothering me a lot. It is as follows.

If an asteroid is made of hard metal and somewhow it is covered with sands and pebbles and rocks and if someting collides with it very
hard resulting schock wave must be cataclysmic to shake them beyond escape velocity, leaving nothing but the metal asteroid.

Craters on Ryugu seem to suggest that Ryugu is like a metal, soft metal, soft enough to leave crater holes but hard enough not to break
up on impact. So, why are there regolith and boulders still left on Ryugu? Where did those boulders come from in the first place?

I am trying to persuade myself that those shaken off Ryugu travelled into deep space and came back to where they started from after
billions of years in the solar system. Am I going mad?

P

[Explorer1]

There's probably no metal at all in Ryugu, it's more of a 'rubble pile', of low density rocks (just like Itokawa), with many voids and empty spaces inside. I'd guess the inside is as broken and fractured as the surface the cameras can show us.
The craters we see are all very soft, with rounded edges, and every impact just breaks off more pieces, which either don't have enough velocity to escape and come back as boulders (I'd guess the enormous one at the pole is one), or, if they have enough velocity, fly off as separate bodies, permanently. The ones we see now were all probably part of the original body when it first broke off in turn from its parent body eons ago, and have just been broken up and reformed, probably many times since.

The impact projectile Hayabusa 2 is carrying is the perfect experiment to demonstrate this when they fire it at Ryugu. It should replicate the natural process on a smaller scale.

[wildespace]

There's probably no metal at all in Ryugu, it's more of a 'rubble pile', of low density rocks (just like Itokawa), with many voids and empty spaces inside. I'd guess the inside is as broken and fractured as the surface the cameras can show us.
The craters we see are all very soft, with rounded edges, and every impact just breaks off more pieces, which either don't have enough velocity to escape and come back as boulders (I'd guess the enormous one at the pole is one), or, if they have enough velocity, fly off as separate bodies, permanently. The ones we see now were all probably part of the original body when it first broke off in turn from its parent body eons ago, and have just been broken up and reformed, probably many times since.

The impact projectile Hayabusa 2 is carrying is the perfect experiment to demonstrate this when they fire it at Ryugu. It should replicate the natural process on a smaller scale.

Ryugu's extremely low gravity probably corresponds to it being a rocky rubble pile. If it were a solid metal asteroid, it would have a much stronger density and gravity, right?

[OrbitrapInSpace]

If an asteroid is made of hard metal and somewhow it is covered with sands and pebbles and rocks and if someting collides with it very
hard resulting schock wave must be cataclysmic to shake them beyond escape velocity, leaving nothing but the metal asteroid.

the collision will result in huge fragmentation, generating a kind of cloud of material, which will collide each other and dissipate the energy, to the point their relative speed is reduced and accretion starts again.

close observation of Ryugu and its reaction to the impactor is hence part of the evaluation of the theoretical descriptions.

Patrick Michel is part of the Hayabusa scientific team, and he is an expert in simulation of such processes,

movies illustrating the various mechanisms here : simulations of asteroid collisions