Mission: Hayabusa 2 Options

[MahFL]

https://twitter.com/haya2_jaxa

[MahFL]

Last time I spent hours in copying each slide in google and translating... then the day after they issued the english version.
So I'll wait. :-)

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

[pandaneko]

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

[Phil Stooke]

The start of our zoom in to Ryugu.

Phil

[Paolo]

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

[Guest_mcmcmc_*]

Why is it that flight path segments are not straight?

P

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

This zigzag path increases the stereo vision effect to increase the accuracy of the approach

[Paolo]

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

[Guest_mcmcmc_*]

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

[Paolo]

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

[Steve G]

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!

[Phil Stooke]

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

Phil

[Roman Tkachenko]

Ryugu's rotation

[nprev]

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.

[Paolo]

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.

[MahFL]

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.

You just contradicted yourself...