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Earth Return & Sample Science
Explorer1
post Oct 26 2020, 08:41 PM
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Expedited stow begins tomorrow. Images will be returned at each step. https://www.nasa.gov/press-release/nasa-s-o...asteroid-sample
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Marcin600
post Oct 26 2020, 09:42 PM
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An excerpt from Dante Lauretta speech about the dust on the camera - from the quoted audioconference [44:50 - 45:35]:

„...We have seen that there is dust loading on our other optical elements, the navigation camera... and the sam cam which used to document the interaction with the asteroid surface. So we do need to know the state of that camera. And the dust loading isn’t a problem, it just changes the exposure times. I like to think about, you know, when you’re wearing glasses and the glasses are pretty dirty, you don’t really notice it until you take the glasses away and look and clean them, but not as much light as passing through those lenses, so you just need to stare integrate the camera time longer for that activity. So that is one reason and one thing we plan on doing on monday, is checking out the camera. So we’re hoping to begin the stow activities on tuesday...”
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HSchirmer
post Oct 27 2020, 12:20 AM
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QUOTE (JRehling @ Oct 24 2020, 07:24 PM) *
Looking at the apparent fragility of those "rocks" I wonder what is going to happen during the high g forces during entry. None of it will vanish, but it might lose some of the original structure.
First, more interesting will be whether there are clathrates and volatiles that decompose on the return, or during reentry.
More worrisome is whether they will be lost in a "burp" when the sample return container is opened.

Second, (I haven't read the sample return protocol, so excuse the presumptions, BUT) I'm hoping they're going to amend the sample retrieval process to include dropping the sample return capsule in mylar-kevlar and then dunking the entire sample return into liquid nitrogen to prevent any further decomposition of clathrates or loss of volatiles.

Third, this sounds like a WONDERFUL opportunity to seek funding for a "WildFire" sample analysis module on the ISS. Something where you could keep samples in a micro-gravity environment, at cryogenic temperatures, while "decanting" them from probes.
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HSchirmer
post Oct 27 2020, 12:23 AM
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QUOTE (rlorenz @ Oct 25 2020, 10:16 PM) *
In theory, yes (I think I remember reading a scifi story where a stowaway on a spacecraft is discovered this way).

"The Cold Equations" https://docs.google.com/viewer?a=v&pid=...MmU1OTQ2YWViOWY
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pbanholzer
post Oct 27 2020, 01:10 AM
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Here's an article on contamination control for the SRC. Capturing/identifying sample outgassing is addressed in section 7.2 (and maybe other places I didn't catch).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6350808/
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Hungry4info
post Oct 28 2020, 10:47 PM
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OSIRIS-REx in the Midst of Stow
https://www.asteroidmission.org/?latest-new...e-midst-of-stow

QUOTE
Today, after the head was seated into the SRC’s capture ring, the spacecraft performed a "backout check," which commanded the TAGSAM arm to back out of the capsule. This maneuver is designed to tug on the collector head and ensure that the latches – which keep the collector head in place – are well secured. Following the test, the mission team received telemetry confirming that the head is properly secured in the SRC.

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Marcin600
post Oct 29 2020, 05:05 PM
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NASA will host a media teleconference at 4 p.m. EDT (8 p.m. = 20:00 UTC) today, Thursday, Oct. 29 - stream live at: http://www.nasa.gov/live

"During the teleconference, OSIRIS-REx team members will discuss how the stowage process has gone so far, what else they have learned about the sample, and what the next steps are for the mission to return the sample to Earth." (here)
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Marcin600
post Oct 29 2020, 08:52 PM
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From teleconference: 400 g was visible in the camera, but they calculate that in reality there is currently maybe even well over 1 kg of samples in the TAGSAM head !!!

Most of the visible rocks (in the photos - flying around the TAGSAM head) are very flat - like corn flakes



The parcel is now packed and ready to ship to Utah:
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Explorer1
post Oct 29 2020, 09:03 PM
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Dante just said that the navcam was taking images (not yet released) that will show some of the surface effects from the thrusters and direct contact. So even if there's no return to Bennu's proximity, there should be some neat before/after images to look forward to.
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Marcin600
post Oct 29 2020, 09:25 PM
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From teleconference (+/-): "...The fact that TAGSAM has penetrated about 48 cm into regolith shows that the cohesive forces in regolith are very, very weak. There is almost no force between the crumbs that hold them together. The TAGSAM head sank in the regolith like in fluid...The same would happen with astronauts who would try to walk on an asteroid - they would sink into regolith to a depth depending on whether they were standing on loose soil, on a boulder or on some bedrock..."

https://www.youtube.com/watch?v=8kJLM87KGgQ...eature=emb_logo (starts around 13:27)
49:00 - 50:30
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Marcin600
post Oct 29 2020, 10:16 PM
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From teleconference (+/-): "...The ship's return engines left clear marks on the surface and launched a lot of debris... The regolith deeper below the surface appears to be composed of much smaller fragments than those visible on the surface..."

https://www.youtube.com/watch?v=8kJLM87KGgQ...eature=emb_logo (starts around 13:27)
1:07:24 - 1:09:55
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Marcin600
post Oct 30 2020, 06:05 PM
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Once again Dante Lauretta statement about Bennu's regolith, this time I post an exact transcription from the recording of the teleconference on YouTube (47:17 - 51:22):


Ivan Carone (AFP): „What have you learned from Bennu’s soil thanks to this operation and, to make it simple, if someone was to walk on Bennu what do you think it would be like?”

Dante Lauretta: „(...) i’ll just go back a little bit in time here and then and I did this after the TAG event I went back to a science team meeting from 2014 where we were discussing the possible interactions of TAGSAM with the Bennu soil or the regolith during the collection event. We had multiple teams trying to model this process. It seems like it should be straightforward but it’s actually pretty chellenging because you’re in a microgravity environment and all of the literature and all the previous studies that we were looking at the gravity field is a major component in describing the soil behavior in response to various forces. So, the question we were grappling with is how does the soil beheve when you remove gravity from the equation and all the other forces start to play a role. We’re particulary interested in understanding the cohesive forces between grains and any frictional forces that could arise due to the compression. The predctions ranged from we would penetrate three meters to we would penetrate three millimeters! So, it was really not helpful for me, except that we had a kind of a range of predictions based on inferred regolith properties.

Since we penetrated, we estimate, about that 48 cm, that’s much much closer to a very low cohesion regolith model. Basically there’s almost no forces between the grains that keep them bound together. They are not sticking to each other in any way. So when you slide two grains past each other there’s no force that really seems to be measasurable that’s prohibiting that motion. So, when the TAGSAM head made contact with the regolith, it just flowed away like a fluid.

And I think that’s what would happen to an astronaut if she were to attempt to walk on the surface of the asteroid. She would sink to her knees or deeper, depending on how loose the soil was until you hit a larger boulder or some kind of bedrock.

So, that’s already I can guarantee you the team is off now that we have this ground truth calibration data set to re-evaluate models of asteroid geology, and especially soil response and soil creep, and mass wasting, and other movements on the surface of the body. So, it’s fascinating that there was so little resistance to the spacecraft from the asteroid surface. Basically it’s kind of like a ball pit at a kid’s playground right you kind of jump into it and you just sink in. And that’s what the spacecraft did. And so luckily we had those back away thrusters to reverse the direction of motion, or we might have just flown all the way through the asteroid smile.gif "


Ivan Carone (AFP): "But do you think it could go very deep, like this kind of low cohesion?"

Dante Lauretta: "Yeah, I believe the model suggested, like I said, to three meters of penetration in a completly cohesionless environment, and that seems to be the way the soil responded. We were moving at almost full velocity after we made contact, and the deceleration that we experienced before the back away thrust was primarily from the TAGSAM, recall that the TAGSAM collects material by ejecting nitrogen gas, it’s basically like a cold gas thruster. And if we hadn’t done that and we hadn’t fired the back way thrusters, there was no resistance that’s measurable coming from the actual asteroid regolith."
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mcaplinger
post Oct 30 2020, 06:40 PM
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QUOTE (Explorer1 @ Oct 29 2020, 01:03 PM) *
Dante just said that the navcam was taking images (not yet released) that will show some of the surface effects from the thrusters and direct contact.

While waiting for these (I have no idea when they will be released) one could amuse oneself figuring out what they might look like relative to the SamCam images (SamCam is 20x20 degrees and basically pointed at the TAGSAM head); Navcam1 has an FOV of 21x16 degrees and is rotated 6 degrees about Y and -70 degrees about Z. I've never seen a good visualization of this and it's pretty confusing. All of this stuff is in https://naif.jpl.nasa.gov/naif/data_comet.html [EDIT: these images were taken with what is being called Navcam 2 or NFTCam; we called it Navcam1 when we were building it, but I guess they swapped the numbers?]


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Hungry4info
post Oct 30 2020, 09:59 PM
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Absolutely spectacular video of the sampling. We see the ejecta blanket expanding away from the impact site and creating the massive shadow we saw earlier. I've uploaded one of the frames. This is amazing. Best thing I've seen since the New Horizons image of Pluto back-lit from the sun.

TAG Captured by NavCam 2
https://www.asteroidmission.org/navcam2_tag...lete_small_gif/


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Marcin600
post Oct 31 2020, 01:29 AM
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A little lightened. Could it be a crater? (dug by one of the return engines)
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