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Mission: Hayabusa 2
jasedm
post Jun 17 2018, 10:32 AM
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QUOTE (Paolo @ Jun 17 2018, 09:49 AM) *
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.


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 smile.gif

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....
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Paolo
post Jun 17 2018, 11:33 AM
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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)

QUOTE
Steins is not solid rock but a rubble pile and has a conical appearance that is probably the result of reshaping due to Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) spin-up. The OSIRIS images constitute direct evidence for the YORP effect on a main-belt asteroid.
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Phil Stooke
post Jun 17 2018, 04:39 PM
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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


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... because the Solar System ain't gonna map itself.
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Explorer1
post Yesterday, 01:47 PM
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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.
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mcmcmc
post Yesterday, 05:57 PM
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QUOTE (Explorer1 @ Jun 18 2018, 01:47 PM) *
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:
QUOTE
Our 5th Trajectory Control Manoeuvre (TMC05) for optical navigation was made on June 18, 2018 from ~11:00-12:10 JST. Thrusters gave a velocity change of about 8cm/s (-x), 1cm/s (+y) & 61 cm/s (+z). Hayabusa2 was ~220km from Ryugu and the relative velocity after TCM05 was ~0.7m/s.


https://twitter.com/haya2e_jaxa/status/1008716414541225985
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mcmcmc
post Yesterday, 05:59 PM
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Raw tracjectory data updated:
http://www.hayabusa2.jaxa.jp/hy2sc2/data/hy2_trj.txt


Now file reflects estimated arrival date of june 27th.
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Floyd
post Yesterday, 08:06 PM
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Is another image set expected to be released soon? At less than 200 KM the rotational movie would be quite detailed.


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MahFL
post Today, 04:00 AM
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QUOTE (Floyd @ Jun 18 2018, 08:06 PM) *
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.
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