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#20
by
plutogno
on 16 Jun, 2018 14:47
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Looks curiously diamond shaped.
I quote from by book "Robotic Exploration of the Solar System - Part 4" on the diamond shape of Steins, an asteroid visited by Rosetta:
The diamond shape was attributed to material sliding toward its equator as its rotation was spun up by the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, involving different radiation pressures over the night and day sides. If this is what really happened, this means Steins is a porous ‘rubble pile’ body like Itokawa. The spin-up and slippage of material would have obliterated the previously existing craters, thereby ‘rejuvenating’ the surface of the asteroid.
we will soon see if the same interpretation is true for Ryugu
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#21
by
theinternetftw
on 16 Jun, 2018 16:34
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In the press conference that was held a few days ago, a prediction of asteroid shape was included.
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#22
by
Star One
on 16 Jun, 2018 16:57
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Looks curiously diamond shaped.
I think we'll find there are large craters that make it appear diamond shaped at this distance.
We are only a week away now. Can we get a discussion thread going to keep the update thread quiet (or change the title of this thread to include discussions)? Yes, I know I added to the noise....
I second the need for a discussion thread as I was reluctant to post a discursive comment in what is clearly an update thread.
edit/gongora: Discussion thread ->
https://forum.nasaspaceflight.com/index.php?topic=45855.0
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#23
by
Bubbinski
on 16 Jun, 2018 22:08
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When I did my research for the article I found that Ryugu was designated a C-type asteroid believed to be ancient and have primordial water & minerals. Will be VERY interesting to find out if the water at Ryugu (in hydrous minerals, not liquid) has the same exact ratios as the water on Earth, which would indicate asteroids brought water to the infant Earth. I read that the water found on comet Churyumov - Gerasimenko by Rosetta/Philae was slightly different, which meant that comets like it could not have brought water to Earth.
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#24
by
hop
on 16 Jun, 2018 22:30
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Pre-encounter review of Ryugu
Asteroid Ryugu Before the Hayabusa2 EncounterAsteroid (162173) Ryugu is the target object of Hayabusa2, an asteroid exploration and sample return mission led by Japan Aerospace Exploration Agency (JAXA). Ground-based observations indicate that Ryugu is a C-type near-Earth asteroid with a diameter of less than 1 km, but the knowledge of its detailed properties is still very limited. This paper summarizes our best understanding of the physical and dynamical properties of Ryugu based on remote sensing and theoretical modeling. This information is used to construct a design reference model of the asteroid that is used for formulation of mission operations plans in advance of asteroid arrival. Particular attention is given to the surface properties of Ryugu that are relevant to sample acquisition. This reference model helps readers to appropriately interpret the data that will be directly obtained by Hayabusa2 and promotes scientific studies not only for Ryugu itself and other small bodies but also for the Solar System evolution that small bodies shed light on.
More on the spectral classification and origin of Bennu and Ryugu
Expected spectral characteristics of (101955) Bennu and (162173) Ryugu, targets of the OSIRIS-REx and Hayabusa2 missionsNASA's OSIRIS-REx and JAXA's Hayabusa2 sample-return missions are currently on their way to encounter primitive near-Earth asteroids (101955) Bennu and (162173) Ryugu, respectively. Spectral and dynamical evidence indicates that these near-Earth asteroids originated in the inner part of the main belt. There are several primitive collisional families in this region, and both these asteroids are most likely to have originated in the Polana-Eulalia family complex. We present the expected spectral characteristics of both targets based on our studies of our primitive collisional families in the inner belt: Polana-Eulalia, Erigone, Sulamitis, and Clarissa. Observations were obtained in the framework of our PRIMitive Asteroids Spectroscopic Survey (PRIMASS). Our results are especially relevant to the planning and interpretation of in-situ images and spectra to be obtained by the two spacecraft during the encounters with their targets.
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#25
by
Apollo-phill
on 17 Jun, 2018 16:29
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I understand that it carries three Minerva "rovers".
I understand that what they will do is lower Hayabusa-2 to the surface and deploy (release) the first Minerva "rover". Then return to an altitude above Ryugu.
At later dates, they do similar for the other two Minerva's .
How does each "rover" traverse ? Or are they actually "static" ? Diagram in press kit shows "hopping" . So has each Minerva a mechanism to cause hopping ? Spring/s ? Small thruster ? Other mechanism ?
Any detail welcomed
Phill
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#26
by
Hungry4info3
on 17 Jun, 2018 18:00
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This document describes the mobility mechanism for the MINERVA rover(s), and the design is the same for MASCOT as well. Basically, an imbalanced mass is rotated inside the "rover" with a motor. Newton's laws take effect, and the rover hops off the asteroid's surface.
http://spaceflight101.com/spacecraft/hayabusa-2/MINERVA can hop from one location to another using two DC motors – the first serving as a torquer, rotating an internal mass that leads to a resulting force, sufficient to make the rover hop for several meters. The second motor rotates the table on which the torquer is placed in order to control the direction of the hop. The rover reaches a top speed of 9 centimeters per second, allowing it to hop a considerable distance. Communications with the Hayabusa spacecraft are accomplished at data rates of up to 9,600 bits per second.
At about 4:25 in this video, the mechanism is shown being used in MASCOT.
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#27
by
ThereIWas3
on 17 Jun, 2018 18:05
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The little rovers are cube-shaped, so making them suddenly "flip" over causes them to jump up into the air and a bit to the side. It is not exactly a precise form of navigation, but can get it to a few random locations within a small area. Presumably the other sensors can deal with whichever side ends up on the top and bottom.
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#28
by
Apollo-phill
on 17 Jun, 2018 18:26
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Thank out to Hungry4info and ThereIwas3 for details of Hayabusa2 rover mechanisms
Phill
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#29
by
mcgyver
on 17 Jun, 2018 18:58
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#30
by
mcgyver
on 17 Jun, 2018 19:02
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#31
by
ThereIWas3
on 17 Jun, 2018 19:55
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The temperature-difference powered bi-metal actuator? When the sun shines on it it pops from one position to the other.
MINERAVA is a 15cm cube (about 6 inches) and weighs 900g (2lb)
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#32
by
CuddlyRocket
on 17 Jun, 2018 23:30
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I read that the water found on comet Churyumov - Gerasimenko by Rosetta/Philae was slightly different, which meant that comets like it could not have brought water to Earth.
More precisely, they couldn't have brought
all the water to Earth. If there had been another source of water, it would likely be different thereby resulting in the mixture being different.
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#33
by
mcgyver
on 18 Jun, 2018 06:14
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The temperature-difference powered bi-metal actuator? When the sun shines on it it pops from one position to the other.
MINERAVA is a 15cm cube (about 6 inches) and weighs 900g (2lb)
links and discussion moved to new thread:
https://forum.nasaspaceflight.com/index.php?topic=45855.0This one is now only for updates.
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#34
by
mcgyver
on 18 Jun, 2018 06:31
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Some references to attempt searching for stuff about MINERVA rovers (MIcro-Nano Experimental Robot Vehicle for the Asteroid):
Hayabusa 1 = MINERVA-I (just "MINERVA"), one sigle rover
Hayabusa 2 = MINERVA-II, three different rovers
MINERVA-II:
Rovers named "1A" and "1B":
ISYS / JAXA, Aizu University, 2 rovers
Tetsuo YOSHIMITSU, Takashi KUBOTA, and Atsushi TOMIKI (Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency)
Rover named "2"
Tohoku University, Tokyo Denki University [/size], Osaka University, Yamagata University[/size]
[/size]
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#35
by
mcgyver
on 18 Jun, 2018 07:06
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#36
by
mcgyver
on 18 Jun, 2018 12:10
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#37
by
mcgyver
on 18 Jun, 2018 12:46
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#38
by
mcgyver
on 18 Jun, 2018 16:57
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#39
by
mcgyver
on 18 Jun, 2018 18:39
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Could anybody please add a link to update thread in first post?