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Asteroid approach, Science operations begin!
Bagelvoid
post Oct 22 2020, 06:33 PM
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QUOTE (abalone @ Oct 22 2020, 04:34 AM) *
Good spray of material with the nitrogen blast. This is what they were looking for to indicate a good potential for a sample

https://youtu.be/LJBv4reH9IU


Thank you for making the retimed video. Really like it touchdown on the rocky equivalent of styrofoam or cheese puff.
The rocks are "just" hold" together. Nitrogen pressure might have been overkill.
Hope they got a good sample.

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JRehling
post Oct 22 2020, 06:45 PM
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Wow, the expectation was that these rocks would be unlike anything in our meteorite collections because they couldn't survive entering the Earth's atmosphere. That turns out to be a profound understatement. These samples really could represent something we've never seen before.
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walfy
post Oct 22 2020, 08:28 PM
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QUOTE (john_s @ Oct 22 2020, 06:56 AM) *
I'm having a little trouble understanding the dark background, starting the instant the gas is released and debris starts flying. Is the debris cloud so dense that it instantaneously blocks almost all sunlight from reaching the ground below? I guess that's the case, but it seems surprising. And then why is there such a well-defined edge to the shadow in the final frames? Why does the debris cloud have sharp enough edge to cast a shadow like that?

John


I was wondering exactly the same thing. Very perplexing. Neo56's excellent sequence (click here for it) makes me think it's a crater and not a shadow, but then again, the edge of the "crater" seems to shift, like it's a dust shadow.

Or perhaps the edge of the crater is settling and shifting slowly. Considering that the astroid is active, popping up little parts of itself that slowly settle back on the surface, played out over billions of years the surface might be somewhat like a children's ball bit with light plastic balls to easily sink into.
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HSchirmer
post Oct 22 2020, 11:28 PM
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It reacts like a frozen clump of sand or gravel.
Not unlike the lumps you get in a salt shaker near the ocean -

Random video- https://www.facebook.com/watch/?v=10155535292172786
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Holder of the Tw...
post Oct 23 2020, 03:22 PM
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QUOTE (JRehling @ Oct 22 2020, 12:45 PM) *
... these rocks would be unlike anything in our meteorite collections because they couldn't survive entering the Earth's atmosphere.


Maybe a possible reason why we never found any large samples - only possible dust microsamples - from the Tunguska event?
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john_s
post Oct 23 2020, 04:33 PM
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QUOTE (walfy @ Oct 22 2020, 01:28 PM) *
Neo56's excellent sequence (click here for it) makes me think it's a crater and not a shadow, but then again, the edge of the "crater" seems to shift, like it's a dust shadow.

Or perhaps the edge of the crater is settling and shifting slowly. Considering that the astroid is active, popping up little parts of itself that slowly settle back on the surface, played out over billions of years the surface might be somewhat like a children's ball bit with light plastic balls to easily sink into.


Thanks- Neo56's sequence makes things clearer. It does look like the gas release rapidly excavated a surprisingly large crater, which is responsible for most of the shadowing. In that sequence the crater shape appears to be relatively stable (because the shadow edge is relatively stable) but the stuff inside it is still churning around in the microgravity. I hope there are frames later in the sequence that we haven't seen yet, which show the view from a greater distance.

Hopefully the surface put up enough resistance to provide the back-pressure necessary to propel material upward into the sample chamber.

John
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Decepticon
post Oct 23 2020, 09:20 PM
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Is there a minimum weight requirement in the sample to be considered a successful sample return?
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mcaplinger
post Oct 23 2020, 09:28 PM
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QUOTE (Decepticon @ Oct 23 2020, 01:20 PM) *
Is there a minimum weight requirement in the sample to be considered a successful sample return?

Yes, 60 grams. https://www.asteroidmission.org/?latest-new...-asteroid-bennu


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Guillermo Abrams...
post Oct 23 2020, 09:58 PM
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So much sample was collected that some of it is actually slowly escaping the sampling head. Sample mass measuremente has been cancelled to protect the sample, and they will store it as it is. smile.gif

https://twitter.com/OSIRISREx/status/1319750746741612546


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Guillermo Abramson
Leťs espaŮol? VisitŠ mi blog!
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Marcin600
post Oct 23 2020, 10:54 PM
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"...Analysis by the OSIRIS-REx team suggests that bits of material are passing through small gaps where the head’s mylar flap is slightly wedged open. The mylar flap (the black bulge on the left inside the ring) is designed to keep the collected material locked inside, and these unsealed areas appear to be caused by larger rocks that didn’t fully pass through the flap..."

"All data so far suggest that the collector head is holding much more than 2 ounces of regolith" (here)

I wonder if these escaping pieces of rocks will not cause a problem with the tight closure of the sampler head in the return capsule unsure.gif
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Explorer1
post Oct 23 2020, 11:09 PM
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Wow, it is literally chock-full of sample! A nice problem to have....I almost expected that given the enormous cloud, but good to know for sure!
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Brian Swift
post Oct 23 2020, 11:14 PM
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QUOTE (Marcin600 @ Oct 23 2020, 03:54 PM) *
"All data so far suggest that the collector head is holding much more than 2 ounces of regolith" (from here)

From the audio teleconference:
  • Estimating 400g collection
  • Proceeded 24-48cm into regolith with gas being expelled
  • Continued to move forward for an additional 3 seconds after gas release while backoff thrusters were firing before moving away
  • 90-95% of TAGSAM screen blocked with material
  • Didnít test deep penetration on ground
  • Didnít plan on material coming out of TAGSAM during stow
  • Trying to get DSN time for continuous coverage during stow for "ground in the loop" operations
  • Moving away from Bennu at 40cm/s. Cancled breaking burn to minimize imparting forces on samples
  • Canít do sample mass measurement after stow
  • Minimizing exposure to sun to prevent overheating sample. So wonít be able to have camera on it while "parked" before stow
  • Can have up to 5mm particle on TAGSAM face for stow, currently largest is 4mm
  • Only one of several latches required for earth re-entry

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Marcin600
post Oct 23 2020, 11:36 PM
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"...Continued to move forward for an additional 3 seconds after gas release while backoff thrusters were firing before moving away..."

Could the gases from the backoff thrusters "contaminate" the samples?
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Tom Tamlyn
post Oct 23 2020, 11:55 PM
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QUOTE (Brian Swift @ Oct 23 2020, 06:14 PM) *
From the audio teleconference:


Is the audio teleconference available online?
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mcaplinger
post Oct 23 2020, 11:56 PM
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One thing that surprised me was Dante talking about "dust loading" (I think he said) on Navcam and SamCam. I wonder how dirty the nadir panel of the spacecraft is now?


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