I believe they all do.

Plenty of cameras.

MINERVA-II:
http://mineta-lab.yz.yamagata-u.ac.jp/HAYABUSA2.html
http://www.dlr.de/pf/Portaldata/6/Resource...oshimitsu_T.pdf
http://www.astro.mech.tohoku.ac.jp/~nagaok...iras_knaga1.pdf

MASCOT:
https://www.colorado.edu/event/ippw2018/sit...ot_ippw2018.pdf
https://elib.dlr.de/86421/1/reill_2824197.pdf

I watched through this one hour+ press question time video. There was not much we do not know
from other earlier information.

One thing catched my ears. It is about polar regions and naturally there were questions from
the press, including a few questions about the big boulder like thing at the north pole, if H2
will be exploring polar regions.

Prof Yoshikawa's answer was positive, but it seemed to me from the tone of his voice that JAXA
will be very uncomfortable to move H2 from the 20km parking position unless there are
scientifically good reasons.

If I remember correctly, H2 will have to move up in order to look at polar regions. If they go up
then they will have to inch back down to the parking height again, that sort of thing...

Another thing that was new to me, even if it should not be, was that H2's descent is actually still
part of catching up with Ryugu from behind. Once H2 reaches the parking position behind Ryugu
Ryugu will be rotating retrograde in front of H2, with its panells behind H2 facing the sun.

JAXA apparently want to keep that position as long as they can afford it. I think it is a kind of
vantage position with full energy supply from behind and Ryugu right in front.

P

Wouldn't it be much easier landing on a static pole rather than on a moving equator?
Although linear speed of the surface of a 450-meters radius body fully rotating in 7.5 hours should be just 10 cm/s, why trying to sync H2 speed to surface speed and to avoid incoming rocks? A little rocks hitting the sampler at a few cm/s would apply a torque which would make H2 start rotating on its horizontal axis.
A big rock hitting H2 at 20 cm/2 would "pass" to H2 enough speed to cross escape velocity?!?


My math:
Frequency = F = 1 round in 7.5h = 1 round in 27000 s
Radius = R = 450m
Linear speed = V = W * R
W = 2*pi*F

V = 2 *pi * 1/27000 * 450 = 0,10 m/s

I now remember something else from this YT movie. A woman reporter asked about landing sites.

Prof said that they would choose areas free from boulders with size 1 meter or larger across
because sampler horn is one meter long and even suggested landing in a crater to avoid boulders.

P

Two very strong eroded crater candidates centre and just above the equator:

Click to view attachment

(image enhanced by me to show features better)

P.S. any chance to make a 3D model based on rotation images providing a stereo view?

I was thinking about these two. Plus a possible darker area near the limb at 4 o'clock.

I was watching the final approach of H2 one or two minutes before arriving at the parking position.

H2 was doing something strange as shown below just before arrival at a velocity of 4cm/s, but the velocity
was 3cm/s even after arrival.

P

Well it says 0.00 now.

A new image
Click to view attachment

Wow! It really does look a bit brighter at the pole. Press conference soon (stereo image here: https://brianmay.com/brian/brianssb/brianssbjun18.html#29 )

Isn't the boulder shining at the top pole (apparently, south pole) a rare mineral, not the same kind making
up the rest of Ryugu?. I mean, something hard and slicky on surface, like diamond?

P

As Phil said earlier in the thread when it first became visible, it might only be reflecting more sunlight, and not actually be any different in composition from the rest of the surface. But with more pixels, it does seem like it's not the only spot that seems slightly brighter. Itokawa was a lot more uniform from what I can recall.
Might be an intriguing target for one of the landers, or maybe even the impactor....

Ongoing press conference in japanese on youtube:
https://www.youtube.com/watch?v=Zmya363w010

Japanese press release is online:
http://fanfun.jaxa.jp/jaxatv/files/20180627_hayabusa2.pdf

They announced they will also release English version.

Facts sheet too:
http://fanfun.jaxa.jp/countdown/hayabusa2/...sat33_fs_22.pdf



3d pictures:
http://win98.altervista.org/hayabusa2/3d.html

Interesting detail on page 91 of fact sheet about next approaching phase: for whole path from 20 km to 0 km it will be used ONC-W1 camera, but from 20km to 30m there will be the contribution from LIDAR (1 single laser beam), and from 50m to 0 the contribution of LRF (4 laser beams). Last 30 meters will have also contribution from light-reflection from target-marker-balls, reflecting lite from onboard LEDs.
They will also use a 3d digital model ("Ryuguoid"?).

Further details on p.94
Align to surface linear speed at 100m.
Switch from LIDAR to LRF at 40m (previous slide shows overlapping).
Target balls released at 30m.
Switch to autonomous mode and target-markers tracking at 15 meters.
Free fall starting from 5-10 m, landing close to the ball.

After shooting SCI bullet, precise landing into the crater will be allowed by using multiple target markers.

Schedule:
End of July - Medium altitude observation 1 (altitude 5 km)
Late August - gravity measurement descent (altitude 1 km)
Late August - scheduled landing site
September - October - Touchdown operation slot 1
September - October - Rover Drop Operation Slot 1 (which one of 4 rovers?)


March-april 2019: shooting of SCI
July 2019: rover Drop Operation Slot 2 (which one of 4 rovers?!?)

The first picture, the cross eyed version, is inverted. The asteroid looks inside-out.

because it is not cross-eyes but parallal-eyes.

You would think so, but Dante Lauretta explained to me why not. It has to do with the challenges of navigating in the gravity field around the object. If you fly in from the top toward a pole, small imprecision in your understanding of the gravity field gets greatly amplified into where your spacecraft flies. Whereas if you are orbiting and you match velocities as you descend to the surface, it's a much easier situation to describe, physically, and the effect of small errors is much less. (Not sure if this makes sense.) OSIRIS-REx will also be selecting a landing site away from the poles.

That makes some sense, very interesting. I’m guessing if you’re approaching from above a pole, the gravitational effects are circling beneath you, whereas matching velocities in an equatorial descent the gravitational effects are “stationary.” And then there are the gravitational changes dependent on elevation, which would have to be dealt with in both scenarios during descent. So a matched-velocity equatorial descent eliminates circular motion of the gravitational effects of the poles, and leaves only elevational effects to contend with. Looking forward to being corrected.

If that were the problem, couldn't you just rotate the spacecraft to match the asteroid's rotation rate?
The way I interpreted it, and likewise I'm very much looking forward to being corrected if this is the case, is that for an equatorial descent, your trajectory covers a longer distance in the reference frame of the asteroid, the uncertainties in the gravity field get averaged out over a longer path length (because the asteroid's rotating) than if you hovered over the pole and descended.

How do you keep the antenna pointed at Earth (which is vital for receiving telemetry during sampling operations) while spinning about?
On the other hand, perhaps Hayabusa 2's target markers assist enough in navigation to attempt something? If the bright pole turns out to be really interesting after closer inspection, maybe one of the landers can be deployed to the area first. There are quite a few onboard!

The sampling operations will of course be conducted autonomously. Too far for real-time even if Ryugu wasn't rotating, so there would be no value added in maintaining a continuous Earth lock anyhow. The spacecraft will still have inertial reference even while on the surface, and once it breaks away it can get a stellar attitude reference to update that & then re-point the antenna to send the telemetry.

It would probably be more worrisome if the spacecraft spent the night on the surface since that would be about 3.5 hrs without solar power at the equator. However, willing to bet that they have more than enough margin for that in the batteries, plus I don't think that the sampling runs will take that long; appears to be a touch & go kind of thing.

The JAXA publicity girl rang me today about the question I put to them. It is good news, and bad in a way.

Putting it in a nutshell what we see in ONC-W1 window of Haya2 web page is real. She explained the history and
the reason for the current caption just above the window.

Since the window will show the position (direction seen from H2) and the size of Ryugu JAXA apparently think that
it is appropriate to call it "Navigation camera simplified diagram". I have my comments here, but ...

Anyway, right now, if you take a look at the window you will see a tiny dot in the upper left corner of the window.
That is real. That is what the wide angle camera can see given H2's current orientation as at 14:08 JST 28 June.

One consolation may be that if it keeps being there (likely) then we will be seeing closer-ups as H2 goes down in
July/August.

Anyway, that is one mystery evaporated.

P

What I heard in the 2 hour+ press conference video after arrival at the parking position may help part answer this
question above.

There was a question from the press about descending sequence and one of the profs said that descent is
fully autnomous and that was the case also with Hayabusa. However, in the case of Hayabusa they had to send
telemetry signals from here, simply because Hayabusa was mulfunctioning already at the time of descent.

With H2 desceding operation will be also autonomous, no telemetry from the ground, but from what height down
I do not know.

I took some notes while watching this 2 hour conference video and I will put them up very shortly, but nothing
much new to us, frequent watchers.

P

Thanks, now I get it.

I extrapolated some japanese words from PDFs, just in case somebody wants to attempt searching in japanese sites and documentation...
タッチダウン = touchdown
降下する = to descend
降下 = descent
はやぶさ2 = Hayabusa 2

For better understanding:
Telecommands are from ground to probe.
Telemetries (= probe status data) are from probe to ground.

I tried obtaining a 3d model from the currently available images using 3DF Zephyr with no luck.
Let's see if/when they will release more detailed images, possibly obtained by moving around Ryugu rather than waiting for it to rotate.

Better I could do was getting a couple of "flipping gif" (same point of view, but flipping centered on poles or equator):




http://win98.altervista.org/hayabusa2/3d.html

I took out my notes about the 2+ hour video of yesterday's press briefing at ISAS. All of them are very
uninteresting and not new, except perhaps one. That is the comparison of Ryugu and the Earth in terms of
colour.

The video carries both in the same picture frame, and adjusted for whatever you need for true comparison.
I did not understand the terms they used. That video sequence is around 41 munutes into the video.

Anyway, what they were saying is that Ryugu is dark and that it is because of carbon. Diamond is also carbon,
but not that dark as far as I know.

That polar cap is icing on the cake, in English?

P

http://www.spaceflightfans.cn/33868.html#more-33868

I can't see this anywhere else so I am linking to spaceflightfans.cn, a chinese space interest site. Ryugu in color. Spoiler: it's black!

Phil

Plus, have there been studies on how the shape of a 'rubble pile' would be altered depending on its size/mass and rotation rate? The striking overall symmetry and equatorial ridge seem to indicate this.

"a graben-like feature"

Or we could say a channel-like feature, or a rolling boulder track-like feature, or even a chain of subdued craters. But until we know more about it, it's probably better to use generic terms like 'valley' or 'trough' which don't imply a particular mode of origin. A graben is a depressed area between two parallel fractures where the surface has dropped down, and that seems unlikely here if the asteroid is what it appears to be, a mass of unconsolidated rubble.

This is really just following the mapping work by Gene Shoemaker, Don Wilhelms and others at USGS who pioneered lunar and planetary geological mapping in the 1960s, it's not my idea.

EDIT: here's an alternative interpretation to make that point graphically.

Click to view attachment

Phil

I remember reading something on this subject. it must have been from radar observations. it seems most smallish, rubble pile fast rotators are roundish and have equatorial ridges.
fast rotating rubble piles also seem to be the reason why a large percentage of near Earth asteroids have satellites of their own.

Ryugu could have been fast rotator with its own moon in the past. But when that moon escaped, it took away lot of momentum from the system, which slowed down Ryugu to it's current 7,6 h rotation..

Or what else could shaped Ryugu like this except the fast rotation?

A glancing blow from some other object could explain both the fast rotation as well as the fact that it is rotating backwards. Maybe something similar to why Uranus has such a wierd axial tilt. Perhaps that impact left more stuff around the equiator. Somebody could do some math modelling of spinning rubble piles to see if they can assume a shape like this..

On the comparison with Itokawa, my idea is that Itokawa is actually two small rubble piles stuck together, without enough total mass to collapse into a more uniform ball. Ryugu is not so much larger that it could have collapsed more, but maybe it is older? Or was not made up of multiple already-formed asteroids in the first place, so is more uniform. That fact that it has more and larger craters might suggest that it is older, using the method developed by William Hartmann to date areas of Mars. Or maybe, being more massive, it just attracted more impacts.

I would say it has more and larger craters because it's bigger rather than older. There isn't room on Itokawa for big craters.

I am more interested in seeing whether there will be smooth areas (covered with small particles instead of big rocks), as we saw on Itokawa or like the 'ponds' on Eros. So far I don't see any, but we only have one side of it at good enough resolution.

Phil

My very first intuition was that of a bipyramidal "double shatter cone", as a result of the collision of two objects of similar size.
After initial torque-free precession, rotation would have dampened down to a stable spin axis.
Anything from collisions over outgassing to YORP could have changed its angular velocity afterwards.

I popped into a local library today, just for browsing weekly magazines to catch up with goshipps and all that.

I then picked up "Newton", which is a local science for laymen sort of monthly magazine. In it was an article
about Hayabusa 2 and it contained something I did not know.

Apparently, Hayabusa2 was conceived because Hayabusa was deemed lost and dead, even before they knew
Hayabusa was limping, but alive.

I, on the other hand, have been under the impression that H2 was given a go-ahead because Hayabusa managed
to come back...No wonder they asked for donations.

P

Phil Plait - What would it be like to stand on Ryugu - http://www.syfy.com/syfywire/what-would-it...urface-of-ryugu

Very low gravity + fast rotation = strong centrifugal force, especially at the equator. Hence the equatorial bulge. Impacts with the asteroid would have dislodged a lot of material which then slipped towards equator.

BTW, here's Ryugu with colour information from that tiny colour image. Saturation increased to hopefully show colour variations in the terrain.

Click to view attachment

And with levels adjusted to reflect its dark albedo:

Click to view attachment

I doubt, that this mechanism can explain the bulge, unless you have two very unlikely synchronous impacts.
A rubble pile temprorarily acting like a liquid would approximate a Maclaurin spheroid, if rotationally symmetric to its spin axis. (Faster rotation could result in a Jacobi ellipsoid, or an according rubble-pile approximation)
The equatorial bulge is IMO too prominent for the Maclaurin scenario.
Instead, besides a possible but not very likely central collision of two almost equally-sized bodies, a merged moonlet or ring settled down along the equator would be a plausible scenario, especially considering the frequency of asteroid binaries. This is inspired by one of the scenarios considerd for the equatorial ridge on Iapetus.

Looking at the image now, might it have had to do with that large crater? It's very near the equator, and would have kicked up a lot of material. So it a) caused the reverse spin of the asteroid, and kicked up the material that settled along the equator.

Is Rugu's surface very hot? I believe average temp. is more or less the same as the temp.s anywhere on the
surface as it is spininng very fast.

P

As i understand it, 7.6 hours isn't actually considered fast rotation.
For asteroids this size it's rather slow. That's why i was proposing escaped-satellite scenario.
Here are some ryugu-shaped fast rotators:



Of those, only Bennu and 2008 EV5 have no known satellites. (And they have slowest rotation of this selection.)

Didymos | 1994 CC | 1999 KW4 | 2001 SN263 | 2004 DC

(Source of above image is Hayabusa2 press release from June 21.)

.

Trying to focus on that features
Click to view attachment

upd: for estimating detalization and certainity of my approximations (focused on center)
Click to view attachment
some boulders match

Looks like a huge boulder that had been sliced through, revealing much brighter insides.

If you look at Atlas on Saturn, you have another mechanism for equatorial bulges i.e. accretion from within a disk. The bulge in that case would be older than the rubble it captured later on.

after a few days (too many) of hiatus, here is some new images of Ryugu. A stereo rotation animation
http://www.hayabusa2.jaxa.jp/topics/20180710je/index.html

Amazing. Also looks like that rock was cleaved.