DART & HERA, NASA/ESA Asteroid Redirection Missions Options

[nprev]

Surprised we didn't already have a thread. DART launched successfully at 0621 UTC today (23 Nov 21). Mission page here, encounter (as in collision) with small satellite of 65803 Didymos in late Sep/early Oct 2022.

[Antdoghalo]

Yay! We get to map two new objects for the price of one mission next September then try to blow one up as a cool experiment!

[Explorer1]

I remember watching Deep Impact live; what an experience, and finally to be replicated!
And of course, Hera will come after to survey the damage. It would have been nice for AIM to be funded and be there already as originally planned, but it's just as well, we really don't know how much debris will be produced, do we?

[JRehling]

I had the thrilling good fortune to watch this launch from a (considerable) distance. It's quite an interesting mission… not really space "exploration" per se, at least in its primary intent.

[nprev]

True, but we will get some science nevertheless, at least in terms of imagery.

[stevesliva]

I had the thrilling good fortune to watch this launch from a (considerable) distance. It's quite an interesting mission… not really space "exploration" per se, at least in its primary intent.

Reminds me a lot of DS-1 when I read the list of tech demonstrations on it at the JHUAPL site.

DS1 was more than 20 years ago...

[Marcin600]

From NASA Twitter: 55 minutes into its flight, the DART Mission spacecraft has separated from the SpaceX Falcon 9 second stage, and will soon begin to orient itself toward the Sun. - https://twitter.com/NASA/status/1463407550087503875 (nice video and goodbye to this spaceship forever)

Attached thumbnail(s)

 

[JohnVV]

dose anyone have any news on any SPICE kernels for it's trajectory

we have ones for Lucy but what about DART

[Tom Tamlyn]

And of course, Hera will come after to survey the damage.

I hadn't heard about Hera. It's an ESA mission to send a spacecraft to 65803 Didymos, the asteroid that Dart will crash into, and survey the damage. https://www.esa.int/Safety_Security/Hera

There's no thread for Hera on UMSF, but there are a few posts in the Unmanned Exploration Of Comets & Asteroids topic. http://www.unmannedspaceflight.com/index.p...ic=1951&hl=

NASA has an unrelated mission with the same name that doesn't involve robotic space exploration.

[TrappistPlanets]

I hadn't heard about Hera. It's an ESA mission to send a spacecraft to 65803 Didymos, the asteroid that Dart will crash into, and survey the damage. https://www.esa.int/Safety_Security/Hera

There's no thread for Hera on UMSF, but there are a few posts in the Unmanned Exploration Of Comets & Asteroids topic. http://www.unmannedspaceflight.com/index.p...ic=1951&hl=

NASA has an unrelated mission with the same name that doesn't involve robotic space exploration.

could we just also use this thread for Hera sense DART and Hera is going to the same double asteroid system? (question mainly for nprev)

[nprev]

Good idea, since they are indeed closely related to each other. Thread title changed.

[monty python]

So much international effort almost serendipitously focused on this asteroid makes me so happy.

I love it when a plan comes together!

[Explorer1]

I recall that Hera (originally called AIM) and DART had their orders reversed, but the lack of funding on the former by ESA for several years (until restoration and renaming to HERA) meant that DART will now be the initial scouting mission. Seems a bit of a reversal (shouldn't one characterize the Didymos system fully with a scientific mission before trying to alter it with a technology demonstration?) But this approach has its advantages; DART's onboard targeting will still allow it to catch Didymos, and there is no need to shelter an expensive scientific craft from a debris plume of unknown size. LICIACube will take plenty of spectacular images, I am sure!

[TrappistPlanets]

what would be the highest resolution image possible of the asteroids?

[Floyd]

I assume you mean images from the LICIACube. Google is your friend--good to develop the skill to answer your own questions. Lots of information on this satellite including the two cameras Leia and Luke. The most detailed information I've come across in in this PDF

"LICIACube is equipped with two optical cameras (narrow and wide FoV) that allow acquiring significant images and evidence of the DART mission fulfillment. The primary instrument, named LEIA (Liciacube Explorer Imaging for Asteroid), is a catadioptric camera composed of two reflective elements and three refractive elements with a FoV of ± 2.06° on the sensor diagonal. The optic is designed to work in focus between 25 km and infinity and the detector is a monochromatic CMOS sensor with 2048x2048 pixel. The latter is equipped with a Panchromatic filters centered at 650nm±250nm. The primary camera will acquire pictures from a high distance providing high level of details of the frame field.

The secondary instrument, named LUKE (Liciacube Unit Key Explorer), is the Gecko imager from SCS space, a camera with an RGB Bayer pattern filter, designed to work in focus between 400 m to infinity. The sensor unit is designed to contain the image sensor interfacing with a NanoCU, while the optics consists of a ruggedized, mission configurable aperture, lens and required spectral filters. Moreover, the hardware is capable of directly integrating the image data to the integrated mass storage."

I'll let you do the math to find the resolution.

[TrappistPlanets]

I assume you mean images from the LICIACube. Google is your friend--good to develop the skill to answer your own questions. Lots of information on this satellite including the two cameras Leia and Luke. The most detailed information I've come across in in this PDF

"LICIACube is equipped with two optical cameras (narrow and wide FoV) that allow acquiring significant images and evidence of the DART mission fulfillment. The primary instrument, named LEIA (Liciacube Explorer Imaging for Asteroid), is a catadioptric camera composed of two reflective elements and three refractive elements with a FoV of ± 2.06° on the sensor diagonal. The optic is designed to work in focus between 25 km and infinity and the detector is a monochromatic CMOS sensor with 2048x2048 pixel. The latter is equipped with a Panchromatic filters centered at 650nm±250nm. The primary camera will acquire pictures from a high distance providing high level of details of the frame field.

The secondary instrument, named LUKE (Liciacube Unit Key Explorer), is the Gecko imager from SCS space, a camera with an RGB Bayer pattern filter, designed to work in focus between 400 m to infinity. The sensor unit is designed to contain the image sensor interfacing with a NanoCU, while the optics consists of a ruggedized, mission configurable aperture, lens and required spectral filters. Moreover, the hardware is capable of directly integrating the image data to the integrated mass storage."

I'll let you do the math to find the resolution.

we could easily get a 4k or 8k texture map from those images

hopefully someone creates a shape model from the imagery (as radar meshes tend to not be fully correct, good example of this is toutatis), so i am able to properly reproject the stuff

[bobik]

Nice overview paper on ESA's Hera expedition.

[Explorer1]

Didymos ahead in DRACO!
Not much given they were from from late July, but new observations were taken in August as well (not released yet).
Two and a half weeks left, where did the time go?

[Explorer1]

LICIACube has been released.

[Phil Stooke]

https://twitter.com/JHUAPL/status/1572409029640716288

Jupiter!

Phil

[jasedm]

Fascinated to see the results from this mission - 4 days to impact!

[Explorer1]

This brings me big memories of Deep Impact that summer of 2005, and watching the early webcasts (how quaint they were).
One of the press releases mentions LICIACube will take a few days to relay the plume images back, so it won't be quite the same in terms of immediate feedback, but still looking forward to it!

[jasedm]

5 hours to go......

https://www.youtube.com/watch?v=vxImS5CYHwM

[Marcin600]

Live Feed from NASA's DART Spacecraft on Approach to Asteroid Dimorphos - in 17 minutes:

https://www.youtube.com/watch?v=-6Z1E0mW2ag

https://dart.jhuapl.edu/

[Marcin600]

live

Attached thumbnail(s)

 

[Explorer1]

Can't see the binary distinguished yet... but soon! Quite a bit of 'bouncing' for now.

[Marcin600]

still tiny

Attached thumbnail(s)

 

[Marcin600]

only artifacts?

Attached thumbnail(s)

 

[Hungry4info]

On the stream they just mentioned that they're seeing Dimorphos now. So that might be real.

[fredk]

Looks pretty convincing:

400% zoom with gamma tweak.

[Marcin600]

yes

Attached thumbnail(s)

 

[Explorer1]

Target lock!

Didymos is already looking irregular now....

[Marcin600]

things are speeding up

Attached thumbnail(s)

 

[Hungry4info]

Didymos is now resolved.

Attached thumbnail(s)

 

[Marcin600]

bigger

Attached thumbnail(s)

 

[Phil Stooke]

Beginning to see possible structure on the terminator.

Phil

[Marcin600]

interesting shape, with a clearly protruding part at the bottom

Attached thumbnail(s)

 

[nprev]

Precision lock achieved!!!

[Marcin600]

two craters (?) and a "constriction" (?)

Attached thumbnail(s)

 

[Phil Stooke]

A bit more detail. The protrusion will probably resolve into a big boulder.

Phil

[Phil Stooke]

Getting clearer...

Phil

[Marcin600]

craters (?)

Attached thumbnail(s)

 

[Marcin600]

more craters (?)

Attached thumbnail(s)

 

[Phil Stooke]

.....!

Phil

[nprev]

IMPACT.

Absolutely incredible terminal images.

[fredk]

The final full frame:

[nprev]

[Explorer1]

Wow! Takes me back to 14 years old....

And that thin streak on the lower left (top of an enormous boulder, just barely in the Sun?)

Now we wait for LICIACube (and Hera, eventually)

[Marcin600]

Congratulations on a beautiful whack! :-)
It was great!

Attached thumbnail(s)

 

[fredk]

The final partial frame:

and it's approximate location in the previous frame:

[Tom O'Reilly]

What is that light "bar" on the lower left side of Dimorphos? Present in multiple images, doesn't seem to be a camera artifact. Another object behind Dimorphos?

Attached thumbnail(s)

 

[CryptoEngineer]

Wow! Takes me back to 14 years old....

Strong vibes of 7 year old me watching Ranger 7 send photos as it crashed into the Moon in 1964.

[Marcin600]

group portrait

Attached thumbnail(s)

 

[Explorer1]

Top of a huge boulder, mostly in shadow?
Press conference in about 15 minutes.

[Marcin600]

What is that light "bar" on the lower left side of Dimorphos? Present in multiple images, doesn't seem to be a camera artifact. Another object behind Dimorphos?

The illuminated rim of a relatively large crater (or some other depression).
For example like here:

Attached thumbnail(s)

 

[StargazeInWonder]

This comparison has to be noted:

Attached thumbnail(s)

 

[Hungry4info]

Imaging of the DART impact plume from an Earth-based telescope.

Attached thumbnail(s)

 

[Explorer1]

Fascinating fact from the presser: looks like the ion engine would have been used in the case of a miss to hit Didymos 2 years from now for a second attempt!

[Marcin600]

It seems to me that fragments of Didymos's surface are a bit like Helene's surface - I see there a kind of fragmentary "surface crust" (???)

Attached thumbnail(s)

 

[Hungry4info]

Dimorphos mosaic (credit: zelario4)

Attached thumbnail(s)

 

[Tom O'Reilly]

The illuminated rim of a relatively large crater (or some other depression).
For example like here:

Yes! That illustration is very clarifying.

[Phil Stooke]

Nice view of the impact:

https://twitter.com/fallingstarIfA/status/1...583529731670021


Phil

[djellison]

This is the best stack of images I could wrangle from the video at https://www.nasa.gov/feature/dart-s-final-i...prior-to-impact

[Phil Stooke]

Since there are no other craters, I don't think the isolated bright object is a crater rim. More likely, I think, is a large rock sticking up into the sunlight. There was a very prominent rock on Itokawa like that. Explorer1 already suggested the same thing.

I hope we will be getting better versions of the primary asteroid images as well. It looks a bit like Itokawa with rough and smooth areas.

Phil

[monty python]

Strong vibes of 7 year old me watching Ranger 7 send photos as it crashed into the Moon in 1964.

Same here. Back then, hitting the moon with a working spacecraft was hard. We have come so far since then!

[Phil Stooke]

I think Ranger 9 was the only one people actually got to watch.

https://sservi.nasa.gov/articles/live-video-from-ranger-9/

(the video link doesn't work on that site but it is on Youtube)

Phil

[Brian Swift]

PNGs of a few images and downloadable 1080p video from pre-impact available from JHUAPL DART site
https://dart.jhuapl.edu/News-and-Resources/...php?id=20220926
Don't know why there is horizontal flip between video and still images.

[xflare]

That impact debris/plume sequence is extraordinary. Is that about what we expected to see? I wonder is Dimorphos is still in one piece

[Marcin600]

Since there are no other craters, I don't think the isolated bright object is a crater rim. More likely, I think, is a large rock sticking up into the sunlight. There was a very prominent rock on Itokawa like that. Explorer1 already suggested the same thing.

I hope we will be getting better versions of the primary asteroid images as well. It looks a bit like Itokawa with rough and smooth areas.

Phil

After looking at the enlarged fragment on the djellison's mosaic, now I also think it is an illuminated very large boulder on the surface - as Explorer1 suggested (you can see the texture of the rock)

[Marcin600]

https://www.nasa.gov/feature/dart-s-final-i...prior-to-impact

So it looks like the view from the impact video and all the frames pasted here are mirror-inverted

[john_s]

I notice that the final partial frame appears somewhat out of focus. This makes sense because the frame width is apparently 16 meters and the telescope aperture is 0.21 meters, so the frame is only about 80 apertures wide. For a camera focused at infinity, the size of the focus spot should be equivalent to the aperture.

John

[Explorer1]

ASI Conference for LICIACube results is here

[tolis]

Pictures!

[Explorer1]

Wow, those streamers, it looks quite catastrophic! Much more violent than the SCI on Ryugu, as expected!

[Marcin600]

pictures are for example here:
https://www.asi.it/2022/09/liciacube-confer...prime-immagini/

conference recording (on LICIACube results) - here:
https://asitv.it/contenuti/download/live/1e...163abba25/files

and here is video from the ATLAS telescopes:
https://www.youtube.com/watch?v=gaSXHVGCYZ8

Attached thumbnail(s)

 

[marsbug]

I notice that the final partial frame appears somewhat out of focus. This makes sense because the frame width is apparently 16 meters and the telescope aperture is 0.21 meters, so the frame is only about 80 apertures wide. For a camera focused at infinity, the size of the focus spot should be equivalent to the aperture.

John

Ah, I did wonder about that, thank you.

[vikingmars]

Wow, those streamers, it looks quite catastrophic! Much more violent than the SCI on Ryugu, as expected!

Wow ! Yes: Dimorphos must be made of very loose material and may have been partially destroyed, if not entirely. We will see...

[mcaplinger]

Dimorphos must be made of very loose material and may have been partially destroyed, if not entirely.

Regardless of what the images look like, that seems very unlikely, at least if you believe "Spacecraft Geometry Effects on Kinetic Impactor Missions", Owen et al, https://iopscience.iop.org/article/10.3847/PSJ/ac8932/pdf

However, they did a ton of work and then at the end

It seems likely, based on observations
during the surface sampling in the OSIRIS-REx mission... that the weak material limit is
the most likely case. In fact, if Dimorphos’ surface is as weak
as that observed during the SCI experiment, it could be significantly
weaker than even the weak limit presented here.

I haven't read the paper in enough detail to know if their modeling is truly appropriate or just detailed but in an unrealistic way. But the spacecraft only had a mass of about 500 kg and Dimorphos is of order 10**7 more massive and DART wasn't going that fast.

On the other hand, I was thinking of this:

Han Solo: That's what I'm trying to tell you, kid; it ain't there... It's been totally blown away.

[marsbug]

Wow ! Yes: Dimorphos must be made of very loose material and may have been partially destroyed, if not entirely. We will see...

Looking at this picture: https://www.asi.it/wp-content/uploads/2022/09/6.png
The asteroid regolith is fairly dark material, but Didymos is quite over exposed. At the same time the streamers and debris, while widespread, are still barely visible, with no really bright spots except the one where the mini-moon itself is located. So the streamers are not dense, and don't have any larger chunks in (unless Dimorphos has a pure carbon interior), but the point where the mini moon sits is still bright - which suggests the moon itself is still dense and reflective compared to the streamers, and likely most of it is still in one place.

[Explorer1]

I think it's fair to say, however, there has been a not-insignificant loss of mass; a portion of the debris is on an escape trajectory, another portion will remain in orbit around Didymos, eventually impacting either body or escaping later on, and a portion will have settled back down or not been moved at all. I know there will be more LICIACube images to come (such as seeing the other side system!), but otherwise we will have to wait for HERA to figure out the ground truth of what 'We' just did, and the ratio of these portions, more exactly.

[Marcin600]

By the way, I added the scale indicators to this image: https://www.nasa.gov/sites/default/files/th...049_43695_0.png
(based on the NASA description - width of the image is 31 m - to better visualize the size of what we see on the last full frame of Dimorphos):

these stones are really big ...
(difficult terrain for any eventual lander, rover or human explorer)

Attached thumbnail(s)

 

[vikingmars]

Regardless of what the images look like, that seems very unlikely, at least if you believe "Spacecraft Geometry Effects on Kinetic Impactor Missions", Owen et al, https://iopscience.iop.org/article/10.3847/PSJ/ac8932/pdf

However, they did a ton of work and then at the end



I haven't read the paper in enough detail to know if their modeling is truly appropriate or just detailed but in an unrealistic way. But the spacecraft only had a mass of about 500 kg and Dimorphos is of order 10**7 more massive and DART wasn't going that fast.

On the other hand, I was thinking of this:

Han Solo: That's what I'm trying to tell you, kid; it ain't there... It's been totally blown away.

Thank you very much for the paper : I went through it and, now, I'm convinced that Dimorphos has survived the impact and remains quite in good shape. The crater would be very visible and, maybe we will see some secondary impacts not only on Dimorphos, but also on Didymos as well. When the ESA spacecraft will reach the system in December 2026, there will be a lot of impressive images to be seen. Maybe some rocks were also thrown in orbit around Didymos by the impact, building some kind of 'secondary moons', making the system even more interesting to visit

[Explorer1]

When the ESA spacecraft will reach the system in December 2026, there will be a lot of impressive images to be seen. Maybe some rocks were also thrown in orbit around Didymos by the impact, building some kind of 'secondary moons', making the system even more interesting to visit

Hopefully they won't be too big! OSIRIS-Rex sized pebbles are just fine, but big chunks are not a good idea! Though I am sure HERA will be well-prepared.
However, I think the gap in time is large enough for the area to clear naturally; Stardust certainly had no issues revisiting Tempel 1 after 6 years.

[fredk]

Regardless of what the images look like, that seems very unlikely

My guess was also that it was extremely unlikely that Dimorphos could be destroyed. Then I did a spherical-cow/back-of-the-envelope calculation:

For mass 535 kg at 6.65 km/s, DART had kinetic energy of around 10^10 J.

For a radius of 80 m and density of around 1.86 g/cm^3 (as assumed in Owen etal), the gravitational binding energy of Dimorphos is -3/5 GM^2/R ~ -10^7 J.

So DART had ~1000 times as much kinetic energy as would be needed to completely disperse Dimorphos (ie to "rest at infinity"), ignoring any mechanical cohesion in the moon.

That was surprizingly high to me - I guess the point is gravity is weak and Dimorphos is small. Still, in reality that huge kinetic energy has to overcome mechanical cohesion and much of it will also go into heat, rather than overcoming gravitational potential energy. And of course much of the ejecta will greatly exceed escape velocity, so you're "overdispersing" a small amount of ejecta at the expense of "underdispersing" (or not dispersing at all) the rest.

So in the end the destruction (or not) of the moon is determined by the mechanical and thermal details, which presumably Owen etal have modeled sufficiently.

[mcaplinger]

I guess the point is gravity is weak and Dimorphos is small.

If you believe "REACTION OF DIMORPHOS' STRUCTURE TO THE DART IMPACT" https://www.hou.usra.edu/meetings/lpsc2021/pdf/2041.pdf then only 2.5e-3 of the kinetic energy isn't dissipated inelastically. That's still more than the gravitational binding energy, but I suspect the real system is a lot more complicated than any of these models. The whole concept of gravitational binding energy is somewhat abstract and ignores how the energy would be transported through the body, other sources of cohesion, etc.

TBH, I'm still not quite sure how this mission came to be or if it really tells us anything practical about how to deflect asteroids, but it was cool

[fredk]

Indeed, as I mentioned this is a job for gory-details calculations. I did find it interesting and surprizing, though, that the one energy is ~1000 times the other.

My vague understanding of the justification of this was that the models vary by factors of order unity in predictions of the delta v imparted to the moon, due to the uncertainties in the mechanical properties etc, and they wanted to pin down those factors somewhat. I'd still worry that those factors might be significantly different for different asteroids, impact geometry, etc, so indeed it isn't clear what you've learnt...

Yeah, it was cool.

[StargazeInWonder]

Given the above discussion, it may have been a missed opportunity not to have observed the other side of Dimorphos before the impact to check for effects at the antipode (or the location of any putative exit wound, if you will). If the asteroid is that loosely bound, it seems like the spacecraft drilling through the asteroid (or, still more likely, the spacecraft being embedded/destroyed and causing ejecta to leave the antipode) would be a more likely outcome than breaking the asteroid apart. But everyday intuition fails in a case like this, and the theory may not be much better.

[climber]

…..Maybe some rocks were also thrown in orbit around Didymos by the impact, building some kind of 'secondary moons', making the system even more interesting to visit

Just imagine ending up with a ring

[climber]

Very interesting hypothesis here : https://twitter.com/dr_thomasz/status/15749...uEVuWHohPUlr6YQ

[vikingmars]

Very interesting hypothesis here : https://twitter.com/dr_thomasz/status/15749...uEVuWHohPUlr6YQ

Thanks so much Climber: very interesting indeed

[Marcin600]

Here is a video compilation of 3 LICIACube pictures: https://twitter.com/i/status/1574784696311025664

[mcaplinger]

One wonders if the large overexposure of the LICIACube images was intentional or accidental.

[Marcin600]

One wonders if the large overexposure of the LICIACube images was intentional or accidental.

Rather intentional I think as the debris of the impact were expected to be faint (?)

EDIT:
According to David Avino, CEO of Argotec (in this article - https://www.repubblica.it/tecnologia/2022/0...cube-367588148/ ) LICIACube took 620 pictures that will be downloaded in the next few days.

[StargazeInWonder]

In a way, this continues the theme of Insight's failed drilling: While mechanics in space are incredibly predictable, mechanics in heterogeneous solid bodies are incredibly unpredictable.

[cIclops]

Hubble and Webb images ...

[Quetzalcoatl]

Hi,

A question arises. What is left of Dimorphos ?

[john_s]

Despite the spectacular amount of debris, I've heard rough estimates of the total volume of ejected material being equivalent to a crater ten or so meters across, so Dimorphos is probably alive and well. We'll know soon, when mutual events are detected (or not...).

John

[scalbers]

Yes this makes sense as my rule of thumb is a crater is around 20 times the diameter of the impactor.

[StargazeInWonder]

The density and structure of Dimorphos makes it hard to compare with larger bodies with known impacts. This paper

https://academic.oup.com/mnras/article/515/2/2178/6634251

estimates a density of 2.2. Chondrites have a density of about 3.5, which would make Dimorphos about one third empty space. Lunar regolith is even less dense than that, but for any significant craters, the surface soil is an insignificant fraction of the volume. In a nutshell, there's probably, in comparison to the Moon, etc., more room (literally and figuratively) for Dimorphos's regolith to compress rather than eject, which could make a crater smaller, while creating a mascon of significant size compared to the entire body of the asteroid.

[Marcin600]

Something like "mini-panoramas" of the Dimorphos surface (unfortunately not very clear) - just for fun
From this picture: https://www.nasa.gov/sites/default/files/th...splay-final.png

Attached thumbnail(s)