Earth Return & Sample Science Options

[nprev]

Now that the 'boop' has been completed (with spectacular success!), we'll move the discussion to here for subsequent mission events.

[walfy]

Boosted the shadows to reveal what I assume are the rocks wedged in the mylar flap. Looks like our little robot gorged like a T-REx!


The third image in the sequence was the most over exposed, so the rocks hiding in the shadows are the least grainy when revealed:

[dsmillman]

The audio of the 10/23/2020 teleconference can be accessed for 30 days at:

1-866-373-4996

[Tom Tamlyn]

Thanks to for that link.

It was a great press conference. Even though Brian's helpful summary covered most of the the major points, it made fascinating listening, with detailed, clear, and fluent presentations and answers from Dante Lauretta and Thomas Zurbuchen, and sharp, business-like questions from well-informed reporters.

The stow operation is currently expected to begin on Tuesday. As Brian mentioned, the mission is seeking substantial extra DSN coverage in order to do something unusual for robotic spacecraft: conduct an operation interactively with "the ground in the loop." The revised stow plan will have a number of check points, at which the operation will pause while images are downloaded and analyzed to determine whether to proceed with the plan or try something different. As a result the stow operation is expected to last three days, instead of several hours as originally planned.

The previously scheduled activity of spinning the spacecraft with the arm extended to obtain a moment of inertia measurement has been cancelled, and Lauretta pretty much ruled out any other possibility for measuring the sample mass (as opposed to estimating the mass from images) prior to landing. However, he did seem to acknowledge that there had not been any occasion to think about a different way such a measurement could be taken during the return trip. I suppose it's possible they might come up with a way to tease some sample mass information out of trajectory telemetry during the return voyage.

[JRehling]

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.

[marsbug]

It's a nice problem to have in a way... but it's still a problem . Still it sounds like the team have it in hand.

[Explorer1]

However, he did seem to acknowledge that there had not been any occasion to think about a different way such a measurement could be taken during the return trip. I suppose it's possible they might come up with a way to tease some sample mass information out of trajectory telemetry during the return voyage.

Assuming the mass without the sample (including fuel and subtracting the nitrogen gas used) is known precisely enough, there should be a slight difference in how it 'handles' during maneuvers like the Earth return burn and any TCMs.

[dtolman]

So they cancelled the spin because visual inspection confirmed an abundance of material?

[Marcin600]

So they cancelled the spin because visual inspection confirmed an abundance of material?

"...To preserve the remaining material..."
"...Any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss..."
"...The loss of mass is of concern to me, so I’m strongly encouraging the team to stow this precious sample as quickly as possible - said Dante Lauretta..."
["some of sample particles appeared to be escaping slowly from the TAGSAM head - passing through small gaps where a mylar flap is slightly wedged open by larger rocks"]
(here)

I think that with very gentle and careful moving the TAGSAM head while enclosing it in the return capsule, and doing it without undue delay, the final loss of the collected mass (they collected about 400 g - much more than planned 60 g) will be insignificant. We have to keep our fingers crossed for this

[Reed]

The audio of the 10/23/2020 teleconference can be accessed for 30 days at:

FWIW, also on youtube (starts at ~13 minutes) https://www.youtube.com/watch?v=n274YX4xk_0 - just audio except for showing the gif from the press release for a while

[rlorenz]

Assuming the mass without the sample (including fuel and subtracting the nitrogen gas used) is known precisely enough, there should be a slight difference in how it 'handles' during maneuvers like the Earth return burn and any TCMs.

In theory, yes (I think I remember reading a scifi story where a stowaway on a spacecraft is discovered this way). But in practice, this is a very small signal to look for (if you want to measure a 400g sample to 10%, as part of a 400kg spacecraft, that's a 0.01% precision)

I think thruster performance is probably not more consistent than 1%, maybe worse.

Measuring spin rates, and changes therein is something that can be done with exquisite precision, but more particularly putting the sample mass out on the TAGSAM arm gives a large moment arm, so the sample mass 'signal' component of the vehicle's moment of inertia. So having a viable retrieval of sample mass from this spin exercise does not mean you can do it with useful precision in a translation manoeuvre....

[mcaplinger]

In theory, yes (I think I remember reading a scifi story where a stowaway on a spacecraft is discovered this way). But in practice, this is a very small signal to look for (if you want to measure a 400g sample to 10%, as part of a 400kg spacecraft, that's a 0.01% precision)... I think thruster performance is probably not more consistent than 1%, maybe worse.

Agreed, I don't think thruster firing is going to tell you anything.

But the other small forces on the spacecraft (e.g., radiation pressure) might be well enough characterized. Time will tell.

The story is of course https://en.wikipedia.org/wiki/The_Cold_Equations

[JRehling]

Apollo 13 had a bit of a concern regarding sample mass, but it was an issue of many kg, not g:

http://www.collectspace.com/news/news-0416..._souvenirs.html

[stevesliva]

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?

Any word on this? I wonder in the context of an extended mission (proposal? idea?).

[jccwrt]

If Bennu regolith is anywhere near as sticky as lunar regolith, that whole part of the spacecraft is probably filthy from the compressed nitrogen burst.

[Explorer1]

Expedited stow begins tomorrow. Images will be returned at each step. https://www.nasa.gov/press-release/nasa-s-o...asteroid-sample

[Marcin600]

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...”

[HSchirmer]

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.

[HSchirmer]

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

[pbanholzer]

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/

[Hungry4info]

OSIRIS-REx in the Midst of Stow
https://www.asteroidmission.org/?latest-new...e-midst-of-stow

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]

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)

[Marcin600]

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]

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.

[Marcin600]

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

[Marcin600]

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

[Marcin600]

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 "


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."

[mcaplinger]

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?]

[Hungry4info]

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]

A little lightened. Could it be a crater? (dug by one of the return engines)

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[Marcin600]

Animated gif

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[FOV]

I agree Hungry4info. Spectacular. My messing about with filters and such.

[Marcin600]

a little earlier - and closer

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[Marcin600]

edge of the hole ?

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[Marcin600]

first stages

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[Explorer1]

Wow! dusting off the old swear jar! The liquid metaphor from the telecon is a great description, it really looks like its seething. Spaceflight image of the year!

Too bad about not returning to Bennu to see the wider view, but a bird in the hand (or SRC) is worth two in the bush, as they say.

[Marcin600]

the second stage

I wonder if all these thin, elongated shadows (almost black, thick lines) are the silhouettes of flat grains of regolith right next to the camera?

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[Brian Swift]

Before and After. Frames 274 and 469 from NavCam2_TAG_single_loop_complete_small_gif.gif.
"After" frame has been brightened by 2.5x to better match "before".
The rocks(boulders?) along the right and bottom edge of "after" image can be matched to "before" image which covers a somewhat wider area.

[Marcin600]

Before and After. Frames 274 and 469 from NavCam2_TAG_single_loop_complete_small_gif.gif.
"After" frame has been brightened by 2.5x to better match "before".
The rocks(boulders?) along the right and bottom edge of "after" image can be matched to "before" image which covers a somewhat wider area.

Looking at this brilliant before-after compilation, it now seems to me that all these dark areas and other things are happening on or above the surface, and that it is not a crater or a depression after all.
PS Of course except the pre-existing shallow crater (the target of the operation). These black areas can be hanging clouds or spots of very fine, dark debris (?)

[Greenish]

Agree that these are fantastic images, most inspiring to get engaged with for me since some of the early Curiosity stuff.

Dusting off some of my tool from then (like StereoPhotoMaker, which has improved!) here's some quick pseudo-3D views from nearby frames at the end of the sequence. Contrast stretched.

Cross-eye view

"Rotating illusion" gif (click to animate)... this one I turned 90 deg because it was easier for me to visually process.

[Greenish]

And here are two more, from adjacent frames (no shadow appearing suddenly and the disparity is less exaggerated). Also rotated so the motion is ~horizontal to align with eye separation.
crosseye:
gif:

... seems to me that all these dark areas and other things are happening on or above the surface, and that it is not a crater or a depression after all.
PS Of course except the pre-existing shallow crater (the target of the operation). These black areas can be hanging clouds or spots of very fine, dark debris (?)

From these shots it appears to me that the dark areas are shadowed by the curtain of suspended material. What look like streaks of light under the "sheet" of particles are really cool, and there does appear to be a depression. Edit: The center of the impact zone is at about at the edge of the frame by this part of the sequence.

[Marcin600]

My attempt to make "before-and-after" animation (frames: 279 and 476):

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[Marcin600]

Now it looks to me as if a cloud of debris was coming from the top of the photo (from the sampling site) and was being pushed from the bottom left corner (by the engine blast?). A black veil is created where the cloud thickens (on the border of the interaction of these two forces). This thickened veil also seems to cast a shadow towards the left and bottom of the photo...
This is just my speculation.

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[Greenish]

Animated movie of the 'blast,' starting from where ground becomes visible again.



Full-res all frames here: https://imgur.com/a/Wp8swJD... had to make it pretty small, and use every other frame, to upload here as a GIF.

(I did NOT think this would work. All the hard part done by those who implemented the SIFT-based stack alignment tools in ImageJ! It is quite possible there are some distortions, but I'm learning as I go.)

[monty python]

Wow Greenish! Emptied my wallet into the swear jar.

[Guillermo Abrams...]

Animated movie of the 'blast,' starting from where ground becomes visible again.

Oh, this is the one that convinced me. Thanks!
Guillermo

[Marcin600]

Animated movie of the 'blast,' starting from where ground becomes visible again.



Full-res all frames here: https://imgur.com/a/Wp8swJD... had to make it pretty small, and use every other frame, to upload here as a GIF.

(I did NOT think this would work. All the hard part done by those who implemented the SIFT-based stack alignment tools in ImageJ! It is quite possible there are some distortions, but I'm learning as I go.)

I just can't stop looking at this movie. Outstanding compilation!!!

Although the movement of the cloud relative to the surface is probably slightly exaggerated (?) by the movement of the camera and the associated change in the angle of view, you can still see the huge dynamics of the debris! And this amazing creep of shadows on the surface! It looks a bit like a version of a dust storm with large stones in it. Very unique and informative shots!

I would love to see what's in the black area at the top and outside of the pictures, in the place where TAGSAM "touched" the surface. I wonder if we will see such pictures from a distance?

[Marcin600]

My rough attempt to put the post sampling picture in the context of Nightingale, including scale and orientation of the picture.
I used this Nightingale mosaic and frames 279 and 476 of the NavCam 2 TAG animation.
As the shots from NavCam 2 were taken slightly obliquely to the Bennu surface, there is a shortening of the perspective compared to the mosaic and some view distortion.

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[Marcin600]

And also an attempt to superimpose a post sampling picture on the Nightingale mosaic

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[Marcin600]

SamCam and NavCam 2 Imaging Footprint During TAG - now "officially" on the OSIRIS-REx website

[Marcin600]

I added my own interpretation of the TAGSAM head touch point location to my previously posted OSIRIS-REx photo compilations (based on newly released Imaging Footprint During TAG)

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[Marcin600]

Considerations on the extended OSIRIS-REx mission to Apophis:

https://www.space.com/osiris-rex-asteroid-p...it-apophis-2029 :

„...scientists behind NASA's OSIRIS-REx asteroid sample-return mission are contemplating sending the spacecraft to study a second asteroid in 2029, this time the infamous Apophis. If that appointment comes to be, the spacecraft will arrive at Apophis in April 2029...
The OSIRIS-REx team plans to propose an extended mission to NASA in the summer of 2022, Lauretta said. Visiting Apophis is one option for what that extended mission could look like, but so far, it's the only target that engineers have found the spacecraft could visit long-term...”

[stevesliva]

*Orbit* Apophis. Wow.

The duration post-sample return is similar to Hayabusa2 XM's discussed starting here:
http://www.unmannedspaceflight.com/index.p...st&p=247738

... so I wonder if it's all Earth flybys, or if Venus is also in the mix.

[vjkane]

*Orbit* Apophis. Wow.

They could even poke the surface with the sampling arm to test its strength (presumably after all other studies are complete).

[Explorer1]

I've read about some other proposals for Apophis missions, arriving before the Earth encounter and escorting it to watch for changes both on the surface and from nearby (the views at closest approach would be spectacular, too!). But a spacecraft already launched has so many advantages.
Crossing fingers for approval! It's interesting that they could find no other close encounters in the next 8 years but Apophis. Something about the orbital mechanics being special?

[JRehling]

2021: Everyone's hoping that Osiris-Rex will have an Apophis encounter in 2029.

2004: Everyone's hoping that Earth won't have an Apophis encounter in 2029.

[vjkane]

I've read about some other proposals for Apophis missions, arriving before the Earth encounter and escorting it to watch for changes both on the surface and from nearby (the views at closest approach would be spectacular, too!). But a spacecraft already launched has so many advantages.
Crossing fingers for approval! It's interesting that they could find no other close encounters in the next 8 years but Apophis. Something about the orbital mechanics being special?

There would be value in closeup imaging of Apophis before its close encounter so that OSIRIS-REx can look for changes caused by the close encounter with Earth, potentially with a cubesat spacecraft.

Also, OSIRIS-REx lacks some standard remote sensing composition instruments such as a gamma-ray spectrometer. (No need for those instruments with sample being returned to Earth.)

There was a conference last year about Apophis and possible missions (including the potential OSIRIS-REx rendevous linked above). See Session 5 for the mission concepts. Conference abstracts

[Explorer1]

Yes, those are what I read, thanks for finding it! With only eight years until the encounter, the time to start solidifying any proposals is coming up.
This thread is only about O-REx though, so I won't go into those.....

[Marcin600]

It's interesting that they could find no other close encounters in the next 8 years but Apophis. Something about the orbital mechanics being special?

I guess the author meant (long-term) orbiting an asteroid, not just a close encounter. This probably significantly narrows the possibilities.
[with reduced amount of fuel, only a relatively small difference in orbital velocity between the asteroid and the spacecraft is required...]

[Explorer1]

A final Bennu flyby is planned for April to check out the sampling site (not confirmed, but "if feasible")! 3.2 km closest approach, and also an opportunity to check the instruments are working well and not too affected by dust kicked up during the TAG.

https://www.asteroidmission.org/?latest-new...eroid-departure

[Marcin600]

A final Bennu flyby is planned for April to check out the sampling site (not confirmed, but "if feasible")! 3.2 km closest approach, and also an opportunity to check the instruments are working well and not too affected by dust kicked up during the TAG.

https://www.asteroidmission.org/?latest-new...eroid-departure

It's a good news !!! I keep my fingers crossed for the OSIRIS-REx team - so that we can see this "battlefield" in April. It's now or never again !

[Marcin600]

"The International Astronomical Union (IAU) has approved more names for surface features on Bennu": https://twitter.com/OSIRISREx/status/1356300951942963200

https://www.asteroidmission.org/iau-features-3/


PS. But ... they're not officially listed yet here: https://planetarynames.wr.usgs.gov/SearchRe...ts?target=BENNU Why?

On the OSIRIS-REx website’s map I also can not see such (mentioned in the attached text) surface features, as: dorsa and fossae. Only the new names of the craters have appeared,
i.a. OSPREY is now Wuchowsen Crater; NIGHTINGALE is now Hokioi Crater etc.

[Marcin600]

A final flyby of Bennu (and Nightingale) on April 7 is approved !!!
https://www.asteroidmission.org/?latest-new...l-tour-of-bennu

„...The OSIRIS-REx mission team recently completed a detailed safety analysis of a trajectory to observe sample site Nightingale from a distance of approximately 2.4 miles (3.8 kilometers)...
...During this new mission phase, called the Post-TAG Observation (PTO) phase, the spacecraft will perform five separate navigation maneuvers in order to return to the asteroid and position itself for the flyby. OSIRIS-REx executed the first maneuver on Jan. 14 (...) the spacecraft is now slowly approaching the asteroid and will perform a second approach maneuver on Mar. 6 (...) OSIRIS-REx will then execute three subsequent maneuvers, which are required to place the spacecraft on a precise trajectory for the final flyby on Apr. 7 (...) OSIRIS-REx is scheduled to depart Bennu on May 10...”

[Marcin600]

„This image...was taken...on March 4, from a distance of about 186 miles (300 km)...during the mission’s Post-TAG Operations phase, as the spacecraft slowly approaches Bennu in preparation for a final observational flyby on April 7.” - https://www.asteroidmission.org/galleries/s...ennuagain/#main

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[Marcin600]

"...As of Mar. 12, the spacecraft was about 155 km from Bennu and approaching the asteroid at about 24.6 cm/s..." - https://www.asteroidmission.org/status-updates/

[alan]

Saw this on twitter:

Jason Major @JPMajor
Boulders of all sizes on the surface of the asteroid Bennu, imaged by @OSIRISREx two years ago on March 22, 2019. I inserted a Buzz Aldrin for comparative scale size.

[Marcin600]

"The OSIRIS-REx spacecraft... is currently about 30 km from the asteroid... Bennu – traveling approximately 6 cm/s..." - https://www.asteroidmission.org/?mission_update=mar-29-2020

[Marcin600]

https://www.asteroidmission.org/?latest-new...-asteroid-bennu

„...NASA’s OSIRIS-REx completed its last flyover of Bennu in around 6 am (EDT), 4am (MDT) April 7th and is now slowly drifting away from the asteroid; however, the mission team will have to wait a few more days to find out how the spacecraft changed the surface of Bennu when it grabbed a sample of the asteroid...”
„... It will take until at least April 13th for OSIRIS-REx to downlink all of the data and new pictures of Bennu’s surface recorded during the flyby. It shares the Deep Space Network Antennae with other missions like Mars Perseverance, and typically gets 4-6 hours of downlink time per day...”

[pbanholzer]

Marc - Thanks for the updates. Do you know what the pressurization of the nitrogen as released ? Oh, and fwiw I retired five years ago from 292.

[Marcin600]

I was unable to find information about the exact pressure of compressed nitrogen in 3 cylinders. The descriptions only use the terms compressed nitrogen or pressurized/high-pressure nitrogen bottles. Maybe someone has such data at hand ?

However, we must remember 3 things:
1. When we talk about gas pressure, we mean the pressure under Earth conditions (including the so-called standard temperature).
2. The pressure of the gas depends on its temperature. The colder the gas, the less pressure it has.
3. There is a vacuum on the surface of Bennu. Even gas under "normal" pressure released from the cylinder will behave as compressed gas there.

Here are some quotes found in articles on this topic and pictures of the actual 3 nitrogen cylinders on TAGSAM:

"TAGSAM is the product of Lockheed Martin. The complete TAGSAM design consists of (...) three pressurized bottles containing curation-grade nitrogen gas with a small amount of helium (to check leaks prior to launch)...
There are three independent gas bottles (which are independently released), to support up to three sampling attempts...
Gas handling is passive, operating in the simple blow-down mode...
Sample collection occurs when surface contact is sensed. At this point, a pyro valve opens to a bottle of high-purity nitrogen gas... When sample gas is released from a high-pressure bottle, the gas flows through a feedline to the head and is directed into the regolith via an annular aperture...
The majority of the gas release occurs in 5 sec ...
The gas mobilizes material underneath the head as the gas expands into the regolith. The flange seal and impedance of the soil bed cause the gas naturally to flow from the high-pressure environment underneath the head to the vacuum of space via the collection volume around the perimeter of the head. A screen around the perimeter of TAGSAM retains asteroid regolith, even as the gas escapes...

The propagation of the gas through the regolith likely occurs at hypervelocity speeds for much or all of its expansion. The initial peak speed of the gas while exiting TAGSAM is around 800 m/s. Because the porosity in Bennu's regolith is occupied by a vacuum rather than an atmosphere, the expansion of the gas through the interstitial spaces of the regolith will be a choked flow. In the case of choked flow, the expansion speed of the gas is its sound speed, which depends on gas temperature...

The TAGSAM gas reaches equilibrium with the environment as it expands unto the subsurface. Thus, the temperature of the gas is controlled by the ambient temperature...

The dynamics of the sample gas, and the response of regolith, will be different in Earth-atmospheric and gravity conditions versus those on Bennu...

In the gravity regime, the speed of the nitrogen gas through the regolith spans from the peak speed of release from TAGSAM, ~800 m/s, to the “steady state” expansion of the gas through the subsurface, around 325 m/s for 255 K.

Ground-based Earth testing has an ever-present gravitational acceleration of 9.8 m/s2, which is about 100000 larger than the gravitational environment at Bennu...
On the Earth’s surface, the weight of a cm-sized particle is a larger force than the aerodynamic lifting force of flowing gas unless the wind speeds are high (fortunately, most windy days on Earth do not loft cm-sized gravel into the air). In contrast, the weight of a 1-cm particle on Bennu is roughly 100000 less than on Earth because Bennu’s surface gravity is 10000 less than Earth’s surface gravity, yet the gas-driven forces remain the same...

Although there was thermal control on the gas delivery system, the hot case corresponds to an increased bottle pressure over the cold case, and as a result the hot case had higher bottle pressures compared with the cold case..."


A lot of details are e.g. here:
https://link.springer.com/content/pdf/10.10...-018-0521-6.pdf
https://www.sciencedirect.com/science/artic...20304826#bb0085
https://arxiv.org/ftp/arxiv/papers/1702/1702.06981.pdf

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[pbanholzer]

Thanks so much for all of this. More than I expected! I was curious about the force imparted to the sample - visually, it was obviously very strong and was designed for a different surface. I'll take some time to read the articles. I'm annoyed that I didn't use Tagsam as a keyword in my searches . :-)

[Explorer1]

Images released:
https://www.nasa.gov/feature/goddard/2021/n...-asteroid-bennu

Video here:
https://www.youtube.com/watch?v=J8ylW0SVplM

[Explorer1]

Press conference and new images to be released Monday, together with the Earth return burn:
https://www.nasa.gov/press-release/nasa-inv...eturn-to-earth/

[Marcin600]

Jun 04, 2021: "NASA’s OSIRIS-REx spacecraft is 328,000 miles, or 528,000 kilometers, away from the asteroid Bennu (...) The May 10 departure maneuver was calculated and executed so precisely, the mission team decided not to do a clean-up maneuver last week. The next possible maneuver adjustment could occur in 2022." - https://www.asteroidmission.org/?mission_update=jun-3-2021

[vjkane]

NASA has put out its call for proposals for extended missions (the regular senior reviews) https://www.lpi.usra.edu/NASA-academies-res...2PMSR-FINAL.pdf. For the OSIRIS-REx mission, it has specific guidance, "The OREx mission will be reviewed at this PMSR, ahead of its nominal schedule, in order to evaluate opportunities for spacecraft operations after the Sample Return Capsule has been released from the spacecraft. OREx should submit a proposal which describes an encounter with the asteroid Apophis in 2029-2031. The proposal should cover the time period FY23-FY31, including cruise, encounter, and closeout."

An abstract for the potential encounter is attached.

The other missions to be reviewed are InSight, LRO, Odyssey, MRO, MSL, MAVEN, and New Horizons.

Attached File(s)

 OSIRIS_REx_at_Apophis_2020.pdf ( 125.09K ) Number of downloads: 232

 

[Hungry4info]

The OSIRIS-REx team used an alternative method to determine the sample mass.

Alternative Sample Mass Measurement Technique for OSIRIS-REX Sample Collection Phase
https://arxiv.org/abs/2109.05561

...The alternative SMM technique utilized reaction wheel momentum data from identical TAGSAM movements prior to and following the TAG event to estimate changes in spacecraft moment of inertia. Conservation of momentum was used to isolate the sample mass from this inertia change. Using this new method, the spacecraft team was able to successfully estimate collected sample mass to be 250.37 +/- 101 g.

[vjkane]

The OSIRIS-REx team used an alternative method to determine the sample mass.

Alternative Sample Mass Measurement Technique for OSIRIS-REX Sample Collection Phase
https://arxiv.org/abs/2109.05561

That's a clever approach. They collected ~4-6 times more material than their mission success criteria! I was thinking that with the sampling head literally overflowing, it might be even more. Perhaps a lot of porosity?

Looking forward to the return of the samples.

[fredk]

They collected ~4-6 times more material than their mission success criteria!

They collected 150-350g, so 2.5 to almost 6 times the 60g requirement.

They reported (250.37 +/- 101)g - to be pedantic, that's a pretty severe example of overstated precision! (0.25 +/- 0.10)kg is more realistic.

But it is indeed a cool application of momentum conservation (as was the original plan).

[Phil Stooke]

I have updated my Bennu map to include the date of the final flyover of Nightingale, and to add the crater names approved by the IAU last year.

Phil

[JRehling]

Beautiful work, Phil. And it's fun to see a global map where objects this small and their shadows and texture show up.

[Explorer1]

A very interesting NYT article about the Apophis flyby proposal:
https://www.nytimes.com/2021/12/15/science/...osiris-rex.html

Also a link to a Korean mission proposal to rendezvous and land prior to the flyby:
https://www.cnet.com/news/scientists-plan-t...re-earth-flyby/

[StargazeInWonder]

The proposed extension to explore Apophis has been approved.

https://news.arizona.edu/story/nasa-gives-g...nother-asteroid

[Explorer1]

Summary of new results on the TAG event:
https://www.nasa.gov/feature/goddard/2022/s...astic-ball-pit/

The paper goes into granular (sorry!) detail on the interactions, as well as results from the final flyby.
https://www.science.org/doi/10.1126/sciadv.abm6229

[Marcin600]

Another two (fairly) new articles on processes on the surface of Bennu:

1. "... Bennu’s profusion of boulders acts as a shield, preventing many small meteoroids from forming craters. Instead, these impacts are more likely to break apart the boulders or chip and fracture them. Also, some impactors that do make it through the boulders make smaller craters than they would if Bennu’s surface was covered in smaller, more uniform particles, like beach sand. This activity causes the surface of Bennu to change differently than objects with fine-grained or solid surfaces. “The displacement or disruption of an individual or small group of boulders by a small impact is probably one of the most fast-acting processes on a rubble-pile asteroid’s surface. On Bennu, this contributes to making the surface appear to be many times younger than the interior..."
https://www.asteroidmission.org/?latest-new...lder-body-armor
https://www.nature.com/articles/s41561-022-00914-5 - paid

2. "... surface regeneration happens a lot quicker on asteroids than on Earth. (...) the Sun’s heat fractures rocks on Bennu in just 10,000 to 100,000 years. This information will help scientists estimate how long it takes boulders on asteroids like Bennu to break down into smaller particles, which may either eject into space or stay on the asteroid’s surface (...) we thought surface regeneration on asteroids took a few millions of years (...) We were surprised to learn that the aging and weathering process on asteroids happens so quickly, geologically speaking..."
https://www.asteroidmission.org/?latest-new...-sun-nasa-finds
https://www.nature.com/articles/s41561-022-...1XN-5xRyck0kRm-
paper - open

[Marcin600]

Only 6 months left until the arrival of the Bennu samples on September 24 this year - https://www.nasa.gov/feature/goddard/2023/n...ry-sept-24-2023 , https://www.asteroidmission.org/?latest-new...very-on-sept-24

"...over the next six months, the OSIRIS-REx team will practice and refine the procedures required to recover the sample in Utah and transport it to a new lab built for the material at NASA’s Johnson Space Center in Houston..."

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[Holder of the Tw...]

OSIRIS-REx has sucessfully completed is final course correction before releasing the sample capsule.

LINK: NASA Mission blog

On Sept. 17, NASA’s OSIRIS-REx engineers slightly shifted the spacecraft’s trajectory to refine the landing location of its sample capsule, which the spacecraft will deliver to Earth on Sept. 24. The spacecraft briefly fired its thrusters Sunday to change its velocity by 7 inches per minute (3 millimeters per second) relative to Earth.

This final correction maneuver moved the sample capsule’s predicted landing location east by nearly 8 miles, or 12.5 kilometers, to the center of its predetermined landing zone inside a 36-mile by 8.5-mile (58-kilometer by 14-kilometer) area on the Defense Department’s Utah Test and Training Range.

[Xerxes]

3 millimeters per second

That's surprising. What is the separation mechanism for the SRC that has precision at the order of mm/s? I dug around in the specs, but I could only find some references to a "sep/spin mechanism" and "sep nuts". In my imagination, separation occurs with precision of cm/s, but I guess that's wrong.

[stevesliva]

Release is September 24. I'd imagine that 3mm/s is about being in the right place in the gravity well when separation happens, after which the spacecraft 'diverts':
https://blogs.nasa.gov/osiris-rex/2023/09/1...s-landing-zone/

... an important diversion, because it's supposed to rendezvous and orbit Apophis in 2029-2030.

[djellison]

...In my imagination, separation occurs with precision of cm/s, but I guess that's wrong.

3 mm/sec a week out from landing is a ~1.8km change.

3 cm/sec 4 hrs from landing is less than a 500 meter change.

[Marcin600]

Sunday, Sept. 24
10 a.m. — Live coverage of NASA's OSIRIS-REx asteroid sample return
5 p.m. — Media briefing on NASA's OSIRIS-REx asteroid sample return
https://www.nasa.gov/nasalive
https://www.nasa.gov/content/live-coverage-...x-sample-return

The weather at the landing site is expected to be dry and windless, which is perfect!

[Hungry4info]

The sample return capsule has been released and OSIRIS-REx fired its engines for 20 minutes to divert it onto a new trajectory toward a rendezvous with Apophis in a few years.
https://blogs.nasa.gov/osiris-rex/2023/09/2...or-new-mission/

[kenny]

And the spacecraft bus has been officially renamed OSIRIS-REx-APEX for its new mission to asteroid Apophis.

[kenny]

NASA web site is very slow.

Same is on YouTube here:
NASA live re-direct

[Hungry4info]

Helicopters have started taking off. There are four altogether to be involved in the project.

[nprev]

Entry interface.

[Hungry4info]

Parachute deployed!

[Hungry4info]

Capsule is on the ground.

[nprev]

YES!!!! EDL is always a nail-biter!


Congratulations to the team and to NASA!

[Bjorn Jonsson]

Success! Touchdown slightly ahead of schedule (~3 minutes).

[kenny]

Great news! After all those years in deep space, everything works. Many congratulations to the team.