https://twitter.com/haya2_jaxa

I think quite a few were repeats of info from earlier.

What follows is only the gist of latest news to us in today's press release, since a lot of the press release is
based on earlier press materials.

Currnt status as of 14 June:
Distance to Ryugu is 750km. We conducted TCM-3 today (14 June) and the approach velocity as a result is
1.7 m/s. Optical/radio navigation will continue.

Light curve measurements and satellite search have been conducted, expected arrival at Ryugu is currently
27 June.

Both OCN-T and OCN-W are now being used for:
1. Optical/radio wave navigation
2. satellite search
3. Light curve measurement (self-rotation period)

At current distance with OCN-T is still about 10 pixels.

Mid infra red camera (TIR) was activated for:
1. tests
2. Light curve measurment
OCN-T is more precise and OCN-W is being used as a backup.
We have conducted 4 light curve measurements and we now know Ryugu's spin rate is about 7.6 hours,
as previously estimated. About the absolute signal strengths, we will be looking at them still further.

About NIRS3: It was powered on at the same time as RIDAR and it is working normally.

Reasons for combined optical/radio wave navigation is as follows.

It is absolutely vital to use it given the error of about 300km with previsouly used RARR (Range and Range Rate)
method. It can be reduced to a few km using DDOR (Delta Differential One-way Range) method.

900m error at Ryugu is equivalent to 6cm at 20,000km (Japan-Brasil distance).

About satellite search:

Even small ones are dangerous. We conducted our observation from a distance of 2100km. (Satellites can
exsist stably below radius of 90km). Im diamiter was the smallest possible at this distance.

(This kind of operation was also conducted with Hayabusa 1)

Date (7 June) and time of observation.
1. 08:03 － C8:09
2. 11:06－11:12
3. 14:17 － 14:23
4. 16:35 － 16:41

Exposure time was 178 seconds, 30,000 times longer than usual.

Result: Unable to find any smaller than　the detection limit of 50cm.

Therefore, we will be able to approach the stable orbit for satellites smaller than 50cm (raidus of 50km).

We will continue to minitor for smaller ones as we approach Ryugu.

About future press briefings:

27 June as we reach 20km, and thereafter on :
19 July, 2 August, and 23 August during the next two months period.

P

The start of our zoom in to Ryugu.

Phil

Click to view attachment

press release from 14 June. in English
http://www.hayabusa2.jaxa.jp/topics/press/...ss20180614e.pdf

Answer found in latest press release (june 14th):

TCM 4 was performed today between 9:30 and 10:40 Japan time (0.30 to 1.40 UTC)
delta-V: 10 cm/s (-X), 1 cm/s (+Y), 44 cm/s (+Z)
https://twitter.com/haya2_jaxa/status/1007839905752363008

Extended version of the twitter aggregator:
http://win98.altervista.org/hayabusa2/TwitterAggregator.html

first hints of surface features from 700 km
http://www.hayabusa2.jaxa.jp/topics/20180616je/index.html

Mine is the only generation to have witnessed the unveiling of the planets and their satellites by spacecraft photography. I still recall the fascination of a book on Mariner IV my brother gave me, the National Geographic map of the moon, and later Mars. Voyagers epic missions revealing all those new worlds. Seeing Hayabusa 2's fleeting glance at the first features of yet another new world still stirs the excitement in me. I can never get enough of it. Looking forward over the next 18 months for this mission, and of coarse, this New Year's day!

Added an image from the new video to my approach sequence.

Phil

Click to view attachment

Ryugu's rotation
Click to view attachment

Great movie, Roman!

What an odd-looking little beast. Markedly different from the regular 'battered potato' look of the smaller asteroids, though we're a long way still from seeing enough of them to say what's 'normal' and what's not in that regard.

I wonder if the apparent equatorial ridge is merely an effect of Ryugu spinning around the axis of maximum inertia, or if it formed from loose material pooling on the equatorial plane as in the case of asteroid Steins.
we will soon know: if the ridge is cratered the former is true, if it's smooth it's the latter. I am betting on the latter, as equatorial ridges seem to be common on small, relatively fast-spinning objects.

You just contradicted yourself...

Is that the case at Steins? It seems fairly uniformly cratered (including the equator) as far as can be seen at the limited resolution available

I think certainly the case for ring-embedded moons (e.g. Pan, Atlas and Daphnis) but for obvious reasons in their case. I'm going for the former for Ryugu.

Just a guess though

Edit: Have just been reading about the 'YORP' effect, as regards the shaping of asteroids over time - I'm surprised this can be inferred for Steins' shape bearing in mind the resolution of available imagery during the Rosetta flyby though....

quoting from the abstract for "E-Type Asteroid (2867) Steins as Imaged by OSIRIS on Board Rosetta" (the full article is beyond the paywall, I have a pdf of it somewhere)

That should be regarded as an opinion, not an established fact. It may be true but the images only suggest it, they don't prove it.

Phil

According to the counter at http://www.hayabusa2.jaxa.jp/ , less than a meter per second (walking speed!) for the final 200 km. Looks like another manouevre was completed.

Yes, TCM05:


https://twitter.com/haya2e_jaxa/status/1008716414541225985

Raw tracjectory data updated:
http://www.hayabusa2.jaxa.jp/hy2sc2/data/hy2_trj.txt


Now file reflects estimated arrival date of june 27th.

Is another image set expected to be released soon? At less than 200 KM the rotational movie would be quite detailed.

A chart in the Jun 14th press release seems to indicate June 20th for a 110 pixel image. Then June 25th for a 400 pixel image.

File updated on june 18th (but same link); orbital parameters still the same.




I didn't interpret it as a plan for new images releases, but just as an overview of resolution evolution.

But at least the press release provides a schedule for next maneuvers (p.27):
20/6: TCM06
22/6: TCM07
24/6: TCM08
26/6: TCM09
27/6: Arrival maneuvre

There is also aschedule for next press releases:
27/6 (arrival at 20 km)
19/7 (5 km)
2/8 (1 km)
23/8

Boom, there we have it! I see some equatorial craters as well as polar craters.
Rotational bulge is very distinctive and equatorial ridge seems to be quite pronounced as well.

Axis of rotation is almost perpendicular to ecliptic plane, but rotation is retrograde.
Advantage is, that we'll gonna see whole Ryugu's surface, althogh landing spots may be limited to equator only.. (according to press release in japanese)

"C" and "D" should allow creating a 3d anaglyph.

There is a substantial amount of informative comments in Japanese from project members and I will translate
these and put them on within the next 20 minutes.

P

My translations will be based on the URL which carries comments in Japanese and the text right here here is
the comments before the first set of photos on that web page.

Ryugu seen from a distance of 240km to 330 km

What follows are the photos taken around 15:00 (330km) on 17 June and 06:00(240km) on 18 June using
ONC-T (time stumps are JST).

The following photos are before averaging and corrected only for different distances so that they become about
the same size. The order of photos is not in the order of the time of taking them, but in the order of
self-rotation.

P

More translated comments after the first set of photos will follow.

We now know that an English version is available. Great help as our team in the world cup is to start
any moment now!

P

Ryugu looks like this fish to me.

P

Congratulation!

The shape at this point reminds me more of Balok's warning buoy...

Click to view attachment

Click to view attachment

Amazing, the diversity that we see in small bodies.

This is what granular NaCl (table salt) looks like under a microscope.

We're now less than 100 km from the asteroid, and the asteroid's size should be about 100 pixels in Hayabusa 2's camera.

The approach speed has slowed a lot to 0.28ms, which of course is sensible.

I had an interesting experience today. As usual, I accessed the main web page of Hayabusa 2 and the speed was
something like 53m/s, very slow as somebody remarked, at walking pace, and then I doubted my vision.

The number in the speed of 53m/s seemed to have changed in a very short while my eyes were off the display
unit. I was not sure if the number that I was seeing was the number that I had seen, so I kept watching and
within a few seconds I realised that the number was indeed changing in front of my eye balls.

In fact, the speed kept going down over the next 30 or 40 seconds. It kept going down, and down, until it
reached 28m/s and it is staying there.

This episode was around PM12:38 or 12:39 local JST today (20 June 2018).

My current hope is that since the home height is 20km, and the remaining distance shown is as far as to that
home position we may start seeing something on the Haya2 control panell display window for OCN-W1 at around
30,40km height, no?

There is also something else I now understand about the speed. The speed shown on the main web page is the
absolute value of the vector quantity and the actual speed of approaching Ryugu is the projetion, hence
can be slower (usually).

At this rate of going, though, we may be having a clear view of Ryugu within the next 24 hours?

P

I guess you forgot a dot: 0.53 m/s ; it's now moving very slow, just 53 cm/s, or 2 km/h (just a walk)



I think they are not realtime data, but simulated data got from here:
http://www.hayabusa2.jaxa.jp/hy2sc2/data/hy2_trj.txt

But they periodically update these data, so probably data "before today" are actual recorded data, data "after today" are "scheduled operations".


I see a speed change in simulator at 03:40, and difference between GMT and JST is exactly 9 hours, hence simulator raw data are expressed in GMT timezone:
(columns are: epoch, date PosX, PosY, PosZ, Vx, Vy, Vz)


These are the officially planned correction maneuvres:
20/6: TCM06
22/6: TCM07
24/6: TCM08
26/6: TCM09
27/6: Arrival maneuvre

In simulator :
22/6: from 0.29 to 0.09 m/s at 00:30 GMT


24/6: from 0.126 to 0.012 at 00:30 GMT:


26/6: from 0.061 to 0.002 at 01:10 GMT



27/6: from 0.026 to stop.


Please note that the probe slightly accelerates between TCMs.
Additionally, if you plot position on a chart, you can see how the horizontal position slightly changes: they declared it's done to allow enough parallax to better determining positioning of the asteroid in 3d space.

Thank you!, mcmcmc

Yes, from -0.841 to -0.275 in z direction noted. I hope, though, that we are looking at real recorded data from
the probe, not simulated data from 30km away from my house here on the ground. ISAS control room is not far
from my house.

Your data set suggests that in 2 days' time on 22 June Hayabusa 2 will reach 45km position, and 27km position
on 24th, and finally the home position with a residual Z velocity of 0.000105m/s.

My gut feeling then is that we will begin to see something on ONC-W1 after 24 hours from now, we will have to,
because even the wide angle camera must be able to see Ryugu from a distance of less than 50km!

P

I am pleased to report that the display window for OCN-W1 on the Haya 2 control panell has been switched on.

There is nothing yet to be seen, but this display area has been totally dark until now. It is now bright, as you can
see below.

P

Just in case visitors new here wonder how to get to ONC-W1 display window here follows its URL.

http://haya2now.jp/
Haya2NOW control panell

P

Simulator data just updated after TCM06:
(last column is vertical speed)


TCM06
Previously:
20/6, 03:30 GMT



Actually:
20/6 03:30 GMT


Size in ONC-T: 85
Size in ONC-W1: 8



Next TCMs:

TCM07:
Previously:
22/6 00:20 GMT


Now planned:
22/6 00:20 GMT


Size in ONC-T: 206
Size in ONC-W1: 20


TCM08:
Previously:
24/6 00:30 GMT


Now planned for:
24/6 00:20 GMT


Size in ONC-T: 343
Size in ONC-W1: 33


TCM09:
Previously:
26/6 01:00 GMT



Now planned for:
01:10 GMT[/size]


Size in ONC-T: 463
Size in ONC-W1: 44



Arrival:


Previously:
27/7 00:20 GMT


Now planned for:
27/7 00:20 GMT


Size in ONC-T: 463
Size in ONC-W1: 44




Resolution calculator:
http://win98.altervista.org/telescopio.html

Instructions say it will be just a schematic, not an image:



From 80 km, ONC-W1 still can just see 11 pixel.

Added in post 342 foreseen resolutions at each TCM

schematic, not an image, yes, it has been nagging in me.

However, this statement is no longer there and I only noticed it when I reported the power-on of the ONC-W1.
It now only says, effectively, display window will show " asteroid position and size, Hayabusa will approach
Ryugu while capturing its image in view".

This is ridiculous, because we know the position of Ryugu, it is right in the middle of the display window, and
the size, we already know and we also know that it looks like a puff fish.

Creating scehmatics should cost time and to my mind it should be a lot easier to simply place a real image
downsized to suit the window size. Oh, I would be rambling on...

We will see anyway, one way or the other very shortly.

P

It is possible that the window will show a sphere (or shape model) with a latitude-longitude grid, indicating the orientation of the asteroid in the images (rather than the position of the asteroid), or when closer in, the position of the WA image on the asteroid.

Phil

What follows is the translation of the pop-up caption of the display area, to the best of my ability, and as precisely
as possible.

"The position and the size of Ryugu as seen by the camera. In the vicinity of Ryugu Hayabusa will be
approaching it while capturing Ryugu's external appearance."

Position? , why should it matter?
Size?, we know it by now.

P

Caught!


https://twitter.com/haya2_jaxa/status/1009368813429592064

Ryugu like thing is now seen in the window we have been talking about!

P

I think this old PDF explains what is going to happen, although I can't translate it (see p.19):
http://fanfun.jaxa.jp/jaxatv/files/20180419_hayabusa2.pdf

Probably by "schematic" they mean a 3d model.

I think the box will show Hayabusa attitude w.r.t Ryugu during various operations. I whink it will look a lot like a Star Trek Enterprise screen! :-)