Asteroid approach, Science operations begin! |
Asteroid approach, Science operations begin! |
Nov 30 2018, 05:17 PM
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#31
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
I guess the best word I can think of here is "ironic".
Hayabusa 2 was planned with three sample acquisitions in mind, with the idea of getting diverse samples. But Ryugu turned out to appear fairly homogeneous so now they are only planning one sample (what about the sub surface sampling though? But I digress... ). Then you have OSIRIS-REx only planning one single sample grab from Bennu. I know they haven't reported anything yet about any of Bennu's compositional differences but, well... just look at it. Technically, they could make three tries at sampling, provided the canister didn't fill up on the first try, so I wonder if they might rethink things. Also, I'm a little worried at this point. OSIRIS-REx seems to be counting on there being dust and small pebbles for its sampling. It is still too far from Bennu to tell, but if the surface turns out to be like Ryugu with nothing but larger pebbles and rocks available, I wonder how they will deal with that. |
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Nov 30 2018, 07:08 PM
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#32
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Member Group: Members Posts: 214 Joined: 30-December 05 Member No.: 628 |
That's a nice side-by side comparison of the three bodies, and it is consistent with the unexpectedly rocky surface of Ryuku and likely Bennu too.
Isn't that how panning for gold works? If you put heterogeneous gravel in a pan and agitate it, the smaller particles will settle to the bottom and the larger chunks will "float" to the top, even if they are intrinsically denser, because their irregular shapes prevent them from packing together as tightly. So in a rubble pile asteroid, the finer material will tend to migrate to the center. Itokawa probably had a bit more structural rigidity than the other two, at least enough to prevent this sorting process from proceeding quite so far. The similar slightly oblate shapes of Ryugu and Bennu seem to reflect a balance between centrifugal force and their minimal gravity which may prove to be the norm for very loosely accreted piles of variously-sized junk. If so, it may well complicate the sample collection process as Holder suggests. |
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Dec 2 2018, 01:05 PM
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#33
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Member Group: Members Posts: 102 Joined: 29-January 10 From: Poland Member No.: 5205 |
OSIRIS-REx Arrival to Bennu (3-18 Dec 2018)
https://www.youtube.com/watch?v=Yrc4jR3Gy5M I use SPICE (bsp,bc,tsc,tpc,tf) files from NAIF/NASA Model of OREX is from NASA 3D models converted to cmod. Soft is Celestia 1.7 64bit More info apout arrival : https://www.asteroidmission.org/asteroid-operations/ -------------------- Adam Hurcewicz from Poland
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Dec 3 2018, 11:30 AM
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#34
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Member Group: Members Posts: 120 Joined: 26-May 15 From: Rome - Italy Member No.: 7482 |
I allowed myself to revisit Emily's comparison (Itokawa + Ryugu) and add asteroid Bennu:
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Dec 3 2018, 05:55 PM
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#35
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Junior Member Group: Members Posts: 71 Joined: 12-December 16 Member No.: 8089 |
This is what I'm assuming to be new, higher-resolution MapCam imagery. This GIF is featured on the mission's front page and the "spacecraft imagery" page, but clicking on the link (https://www.asteroidmission.org/?attachment_id=12095#main) leads to a 404... Anyways, many congratulations to the OSIRIS-REx team for completing the long journey to Bennu! I wish nothing but the very best for the mission ahead! |
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Dec 3 2018, 07:08 PM
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#36
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
At the OSIRIS-REx website, the caption for the above image sequence reads as follows:
QUOTE This series of images taken by the OSIRIS-REx spacecraft shows Bennu in one full rotation from a distance of around 50 miles (80 km). The spacecraft’s PolyCam camera obtained the thirty-six 2.2-millisecond frames over a period of four hours and 18 minutes. Date Taken: Nov. 25, 2018 Instrument Used: OCAMS (PolyCam) Credits: NASA's Goddard Space Flight Center/University of Arizona Congratulations to the spacecraft team for a successful arrival today! |
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Dec 3 2018, 08:31 PM
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#37
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Member Group: Members Posts: 715 Joined: 22-April 05 Member No.: 351 |
I suspect it may take a lot of careful planning to find a safe touchdown surface on that asteroid.
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Dec 3 2018, 08:54 PM
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#38
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
The first thing that stands out is how unusually sharp and angular the surface debris appears.
-------------------- If Occam had heard my theory, things would be very different now.
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Dec 4 2018, 02:33 AM
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#39
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Junior Member Group: Members Posts: 40 Joined: 28-July 07 Member No.: 2984 |
The animation makes it look like boulders should be flying off of it left and right.
It'd be interesting to run a "Project Crowbar" to lever off one of the bigger boulders and drag/toss it into orbit for a full grapple and analysis. |
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Dec 4 2018, 06:17 AM
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#40
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
I pride myself on being able to discern solar system worlds, but if it were not for Ryugu's special polar boulder and Bennu's "pimple" boulder I would not be able to tell the two apart without consulting reference images.
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 5 2018, 12:33 AM
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#41
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Senior Member Group: Members Posts: 1452 Joined: 26-July 08 Member No.: 4270 |
One thing that will help will be that the camera views aren't going to be constantly at full phase.
Here's Bennu at half phase from MapCam. https://www.asteroidmission.org/20181203_mapcam/ -------------------- -- Hungry4info (Sirius_Alpha)
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Dec 5 2018, 03:13 AM
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#42
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Sure is a jagged little beast. Makes me wonder if the regolith is relatively fresh with less thermal & micrometeoritic weathering than we've seen on other comparable bodies.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Dec 5 2018, 04:03 AM
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#43
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
... Isn't that how panning for gold works? If you put heterogeneous gravel in a pan and agitate it, the smaller particles will settle to the bottom and the larger chunks will "float" to the top, even if they are intrinsically denser, because their irregular shapes prevent them from packing together as tightly. Actually, what you're describing is "the Brasil Nut Effect" and there's even a paper on this "The spherical Brazil Nut Effect and its significance to asteroids" https://academic.oup.com/mnras/article-pdf/...556/stu1388.pdf Panning for gold is kinda the opposite, based on bulk density rather than grain size. Since gold is denser than stone, it is retained in the pan, or settles out into the grooves of a sluice, or if you're really old-school, settles out in the wool of a sheepskin... |
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Dec 5 2018, 05:47 PM
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#44
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
High Phase Angle Picture taken seven hours before arrival by MapCam (click on link).
There will be a press conference December 10th to discuss the initial scientific results from approach, along with presentations at the AGU (American Geophysical Union) meeting on the 11th and 12th. Press Conference Page QUOTE Get ready for some asteroid science. Now that OSIRIS-REx has arrived at Bennu, the mission team will be presenting the initial results of their scientific studies of the asteroid during the spacecraft’s Approach Phase. The highlights will be discussed at a press conference on Dec. 10 at the American Geophysical Union’s fall meeting in Washington, DC. For conference attendees, three special scientific sessions in collaboration with JAXA’s Hayabusa2 mission will explore the early results from both missions in more detail on Dec. 11 and 12
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Guest_Steve5304_* |
Dec 7 2018, 01:05 PM
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#45
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Guests |
High Phase Angle Picture taken seven hours before arrival by MapCam (click on link). The thing on the bottom left looks like a flat curled up sheet Its probably an optical illusion but man this thing has definitely collected a lot of rocky stuff over the years. Much different than Ryugu Full Rotation https://www.asteroidmission.org/?attachment_id=12182#main |
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