Mission: Hayabusa 2 Options

[Therion]

What bothers me about JAXA's latest findings is the dryness of Ryugu.

JAXA were constantly saying, before arrival, that Ryugu had been chosen because it appears to be a water rich(?)
asteroid. The reason must be remote spectroscopy unless it was just their wishfull thinking and unlss there are
other means of guessing properties of asteroid surface.

So, my guess is that remote spectroscopy across billion km is not at all reliable. Is that right?

P

There was some "suspected transient sublimation activity" as well. Curiously, the signature was observed when Ryugu was at aphelion.

New candidates for active asteroids: main-belt (145) Adeona, (704) Interamnia, (779) Nina, (1474) Beira, and near-Earth (162173) Ryugu
Possible sublimation and dust activity on primitive NEAs: Example of (162173) Ryugu

[vjkane]

pandaneko and Roman Tkachenko - thank you for your work and posts here!

[pandaneko]

What follows is from the witter section of the main Hayabusa 2 web page, two bits in one go.

Status of hayabusa2 （week starting on 6 August 2018）

We conducted a free fall experiment during 5 to 7 August. This was the same operation as landing and meant
it was the second near landing for H2.

Height reached was 851m and we were able to obtain a large number of close up photos. Right now, people are
flowing into ISAS in droves from within Japan and overseas and they are happily discussing new findings.
(13 August 2018)

(we do not seem to be viewing them, not in large numbers...., P)

[Phil Stooke]

"What bothers me about JAXA's latest findings is the dryness of Ryugu.

JAXA were constantly saying, before arrival, that Ryugu had been chosen because it appears to be a water rich(?)
asteroid. The reason must be remote spectroscopy unless it was just their wishfull thinking and unlss there are
other means of guessing properties of asteroid surface.

So, my guess is that remote spectroscopy across billion km is not at all reliable. Is that right?"


I was under the impression that it was chosen for being carbon-rich. Any thoughts about water would be an assumption, not based on direct evidence. Even so, it may contain water below a surface which has been dried by heating. Spectroscopy only tells us about the uppermost surface layer. So I would suggest waiting for later results.

Phil

[Explorer1]

Article on DLR's plans for the MASCOT landing: https://www.dlr.de/dlr/en/desktopdefault.as...#/gallery/31672

[Roman Tkachenko]

10 possible landing sites for MASCOT lander

[Roman Tkachenko]

10 possible landing sites for MASCOT lander (3D visualization)

[rlorenz]

So, my guess is that remote spectroscopy across billion km is not at all reliable. Is that right?"

I'm fond of saying 'If you laid all the near-infrared spectroscopists end-to-end, they'd reach across an ocean, but wouldn't reach a conclusion'.

The history of planetary science is full of claims and counterclaims on the interpretation of near-IR spectra, more so than any other type of data, I think, except perhaps geomorphology.
There are of course counterexamples where such spectra have been decisive and important.

[pandaneko]

Thank you, Roman, this rotating movie looks pretty good, and my guess is MA-4 for MASCOT landing. It is a crater rim and may have
something interesting. I really, really want to see photos from MASCOT!!!

P

[pandaneko]

There was an interesting article in today's local national newspaper. I will carry my translation in
two bits. Here goes the first bit.


Hayabusa 2, in addition to sampling operations, has 4 landers. Hayabusa-1 failed (lost its lander)
to land its only lander called Minerva and JAXA team is determined to make it a success this time.

These landers will be be seperated from H2 from September on.

H 1 had only one lander called Minerva, but this time H2 has 3 Japanese landers (3 of Minerva -2)
and one European lander called MASCOT jointly developped by DLR and CNES.

They will be seperated from H2 and gravitationally land on Ryugu. They are classified as
autonomous robots.

Naming of 3 Japanese landers is complicated. They are simply called, Minerva-1　and Minerva-2
and Minerva-1 consists of two landers.

Minerva-2 is a direct successor to the failed Minerva carried by Hayabusa which landed on Itokawa. Minerva-1 was newly and jointly developped by a group of 5 Japanese universities. JAXA developped two of Minerva-2 and they are called Minerva-2-1 and Minerva-2-2.

These names are complicated, so JAXA will name them properly if and when they managed to land
on Ryugu. Right now, they are simply,2-1 and 2-2.

Two of the 2-1 are very similar to the Minerva carried by Hayabusa 1(one). They are cylindrical
with a diam. of 17 cm and height 7cm, weighing 1 kg, only slightly larger than 12cm x 10cm x
600gm Minerva. They will be released at the same time.

These two has internal motors and jump as the original Minerva was intended to do. They do not
have wheels as it is feared that if they did they might fly out into deep space and also because
rokcs on asteroid surface will make it difficult for them to move about freely.

Indtead, two hooks, one above the robot body and one below will kick Ryugu surface, like in a
kicking motion, to move to next positions.

Each carries a couple of cameras and two of them are used to take photos of the same object
at the same time so that they can measure size of very small grains. In addition, they have light
direction, temp. and jump rotation sensors.

According to JAXA, they were made into a twin because they did not know the spin direction nor
surface temp. of Ryugu and they thought that one of them should not completely covered by
a solar panell so that heat will not accumulate too much inside the robot.

Also, two will have a better chance of success than a single robot.

Contrary to 2-2, 2-1 is more self propelling. 2-1 is powered by solar energy it will go into vacation
mode when night falls on Ryugu. When internal temp. exeeds 80 degrees it will go into
a siesta mode and stops its activities.

There are many shades on Ryugu and if 2-1 happend to enter shaded areas it will go into
"if it is dark-mode" and immediately jumps back to its earlier lighted position.

Its cameras will record, at pe-determined intervals, only meaningful objects and delete dark space
etc. before sending data to Hayabusa 2.

It will also be taught about the minimum and maximum jumping limit given by the now available
Ryugu's gravitational constant so that it will not shoot out into deep space.

Their life time is about a few days. Mierva-2, in particular, will have a difficult life as it is solar
powered and if solar panel surface is affected by sands etc.it will meet a premature death.

2-2 was jointly developped by a group of 5 universities and is meant to serve as an engineering
test robot (15cm. diam x 16cm height x 1kg weight) and carries 4 different types of moving
mechanisms for evaluation.　

P

[Phil Stooke]

Thank you for doing this. It is very useful and interesting.

Phil

[galileo]

August 2 press conference, PDF in english.
http://global.jaxa.jp/projects/sat/hayabus...ss20180719e.pdf

[pandaneko]

What follows is the second part of the newspaper story about Ryugu landers.

MASCOT is much larger at 10kg, 30cmx30cmx20cm.

It was originally designed for a joint ESA/JAXA Marco Polo project. Marco Polo was not chosen and it was instead placed on Hayabusa 2.
It can make, limited to once only, a very big jump (200m maximum).

With autonomous robots of this kind it is a big advantage if asteroid surface can be examined to millimeter level and acuracy by moving
to different locations.

JAXA think that Minerva 2 technology will be useful in future explorations of planets. Larger landers will take time to develop and cost
a lot of money and cannot take the risk of landing in tricky places.

However, smaller ones typically up to 10kg can take these risky chances and a few of them can be placed in areas of interest without
sacrificing too much resources.

JAXA hope to use these small robots with their MMX project (Phobos sample return, 2024) and SLIM project (small moon lander, 2021).

Lessons learnt from Minerva 1 (one) with Hayabusa 1 (one)

Hayabusa seperated its Minerva lander in Novmber 2005, but it failed to land. The reason was as follows.

Hayabusa started to go up with its chemical thrusters before the command from the ground station for seperating Minerva reached it.

Consequently, Minerva could not approach Itokawa and the only result was the photo of Hayabusa solar panell.
　
It was XXX of JAXA who sent this seperation command to Hayabusa. His thought at that time was that the command from the earth
will be more reliable than Hayabusa's autonomous judgment about separation timing.

In reality , Hayabusa started its chemical thrusters earlier than expected. His thought when this happned was "OMG, we had it!"

From this lesson Minerva 2 seperation will be done completely autonomously by giving prior commands to Hayabusa 2 such as
seperation height and speed.

JAXA are now determined never ever to send further commands about Minerva seperation.

P

[wildespace]

The latest press conference PDF contains slides in English along with Japanese: http://fanfun.jaxa.jp/jaxatv/files/20180823_hayabusa2.pdf
All focused on the touchdown planning.

[pandaneko]

The latest press conference PDF contains slides in English along with Japanese: http://fanfun.jaxa.jp/jaxatv/files/20180823_hayabusa2.pdf
All focused on the touchdown planning.

Thank you, Wildespace, for this. There was an article in a local newspaper today. It mentions something not stated in this document.
The height during rehearsal is between 20m and 30m.

P