Mission: Hayabusa 2 Options

[pandaneko]

Than you, mcmcmc, but I am not that busy and I feel my translations could be useful. Let me continue with pages
whic seem new on 19 July briefing materials.

Page 2: Today's contents
We will be talking about
・Mission status
・Sciences（remote sensing, sampling, TIR）
・Mission scheduling

Page 3: Contents outline

０．Mission flow outline
１．Project status and overall scheduling
２．Sciences expected
３．Expectations for sample analysis
４．Outcome of initial observation by NIRS3 camera
５．Mission scheduling
６．Steps to be taken in near future

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[pandaneko]

Page 14

Scanning made on 11 July led to acquisition of geographical data of whole Ryugu
(Top picture)

Distribution of observation points on the map.

Colours reflect the angles which laser pointing makes with repect to imaginary line from the centre of the asteroid
(zero degree when pointed vertically down) and the geographical data was estimated from the shape models.

(Right hand picture)

Shape of Ryugu estimated from LIDAR data, almost in agreenment with shape models

[pandaneko]

Page 15

2.7 Sciences expected

★ （ONC）and (NIRS3）reflection spectra: dark and flat

– Ryugu's reflection spectra are different from other asteroids'
– on the other hand there are similarities to other asteroids and meteorites

– very dark suface : high possibility of carbon compounds
– asteroid is almost uniform, but also shows local variations and we hope future precision analysis will provie
clarification

[pandaneko]

Apologies, here is the rest of page 15.

★ re-assembly scenario
– very large blocks of rock seem to suggest mother astronomical body fractures might have re-assembled
– pinpoint identification of sampling locations（LSS）

★ safety first, then scientific evaluation, sampling records, understanding of geological contexts
– sample analysis on return and comparision with OSIRIS-REx samples

I feel that I should upload page by page so that viewers can concentrate on single pages before moving on to the
next page.

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[pandaneko]

Page 16

３．Expectations for sample analysis

1. Firing of 5g tantalum (atomic number 73) bullet
2. Hopefully a minimum of 100mg samples from three locations to be returned to earth in 2020

Page 21

４．Initial data from TIR

TIR operations to date are as follows:

6 June/ TIR function checking
7 June/
Ryugu light curve observation（１）＠2000km
，diam.～ 0.5 pixel
18 June/
Ryugu light curve observation（２）＠200km，diam.～5 pixels

9 to 22 June/
Ryugu photographed once almost everyday
27 June / arrival at home position
29 June/ Darkness checking by looking into deep space
30 June/
Observation of whole Ryugu （１）＠20km，dia.. ～50 pixels
2 July/ Image deformation checking started
3 July/ TIR observation programme renewed/updated

So far, light curves have been made available to viewers. Today, we provide:
Thermography data
and

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Larger Ryugu picture

[pandaneko]

Page 23 TIR thermography

Image acquisition： 07:02 to 14:45 on 30 June 2018 (UTC)，every 8 minutes for one complete revolution
at home position (20km height)，approx. 20m／pixel

Page 24
4. Initial observation by mid infrared cameras

★ main features
・obtained characteristic geological features such as whole shape, huge craters and blocks of rock
・north-south temp. difference (due to inclined spin axis contributing to summer and winter and seasonal
changes
・temp. cycle from morning through noon to evening
・absolute temperature (now being investigated）

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[pandaneko]

Page 27

4. Initial observation by mid infrared cameras
TIR images contributing to selection of landing spots（LSS）

★ Scientific purposes: To find out scientifically significant features of the asteroid
 geological features of the surface estimated from above（bed rock, gravels and sands etc）
 understanding from spectral data（removing the effects of grain size, gaps and spaces between and
thermal radiation）
 sample composition and amount expected（by sampling at varied spots）
★ Mission purposes：safe return and steady operation of H2
 increased amount of samples（by sampling at best places for the purpose）
 Temperature forecasts（too hot places to be avoided for landing）
 evading obstacles（go for less dangerous spots for landing）
We are looking at :

TIR images/ thermal inertia/ temp. dostribution/grain size/
gaps and spaces/rock block density/ temp. forecasts/ collision possibility/ sample amounts/spectral analysis/
surface structure/ max. temp.

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[pandaneko]

Page 28

4. Initial observation by mid infrared cameras

TIR observation summerised as follows:

• ＴＩＲ imaging of whole asteroid surface achieved (except polar regions) at 10μm band in 2D space
• seasonal changes detected and discovery of huge craters and rock blocks and S-N temp. difference
• thermo-physical features have been measutred of rock blocks, leading, hopefully, to future better and
more precise understanding of, such as evolution/formation of asteroid and history of its inside evolution
• landing spots selection and scientific and mission related information such as grain size, temp. environment
and collision avoidance etc etc


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[pandaneko]

Page 33

Middle height lowering operation outline
(This is a matrix. There are 4 columns from left to right. P)

Top row from left to right shows: Operation Number/ phase/ operation outline/ H2 height

Number１ / descending from home position/ same as touch down operation using GCP-NAV, NIRS3 is ON/
20〜7 km


Number ２ / imaging of the spot immediately below H2 (while descending)/ starting ONC-T and TIR observation/
7〜5 km

Number３ / imaging of the spot immediately below H2 (while hovering/ image right below while maintaining
the same 5km height/ 5 km

Number ４/imaging of the spot immediately below H2 (while ascending)/ accelerate to go up and imaging
continues while doing so until H2 reaches the height of 7km/ 5〜7 km

Number ５ / return to home position/ downlink of data starts while going up/7〜20 km


※ for details of GCP-NAV refer to next page

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[pandaneko]

Page 34

Comparison of middle height lowering operation and BOX-C operation
(Here again, it is a three column matrix. I will translate row by row from top to bottom. P)


Captions from left to right are: Phase /middle height lowering operation(MHL operation)/ BOX-C operation


Row 1: Duration of descending operation

MHL: about half a day
BOX-C: about a few days


Row 2: position control while descending

MHL: by GCP-NAV
BOX-C: by HPNAV

Row 3: Position control while imaging

MH: by hovering with GCP-NAV HPNAV
BOX-C: free motion through a pre-determined ΔV (delta V)

Row 4: Observation duration

MH: 8 hours
BOX-C: about 10 hours

Row 5: Imaging attitude

MH: +Z direction
BOX-C: by scanning

Row 6: operation concepts

MH: Image the same target spot from different angles by lowering H2 height (same as precision landing control/

BOX-C: go down while maintaining hovering operation（extention of the same hovering, but done roughly)

NB：GCP-NAV (Ground Control Point Navigation)
Method for determining the position and speed of H2 by looking at specific land marks

HPNAV (Home Position Navigation)

Method for determining the position and speed of H2 by attitude data and also by looking into the centre of the
asteroid image

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[pandaneko]

Page 35

Gravity measurement descent operation outline

(Here, diagram does not need translation)

This completes my translation of 19th July press briefing materials by JAXA.

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[Paolo]

thank you Pandaneko! you are really an asset to this forum!

[Adam Hurcewicz]

And here it is - from 6 km
http://www.hayabusa2.jaxa.jp/topics/20180725je/index_e.html

[charborob]

If I understand correctly what is explained in the link in the preceding post, Hayabusa 2 is not orbiting Ryugu but somehow hovering a certain distance from it, and maneuvering around this position. Is that possible? Doesn't it have to counteract the gravitational attraction from Ryugu? Or is the gravitational force negligible at 20 km?

[Paolo]

yes. like Hayabusa at Itokawa, Hayabusa 2 remains in solar orbit and sort of flies in formation with Ryugu, remaining on its Sun-facing side