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Old 26th September 2022, 01:04 AM   #1
Mike Helland
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Live Feed from NASA’s DART Spacecraft on Approach to Asteroid Dimorphos

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

12.5 hours from now

Description:

NASA’s Double Asteroid Redirection Test (DART) has one single instrument onboard – the Didymos Reconnaissance and Asteroid Camera for Optical Navigation, aka the DRACO camera. DRACO serves as the spacecraft’s eye and will guide DART to its final destination: impact with asteroid Dimorphos.
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Old 26th September 2022, 12:18 PM   #2
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Yep I'll be watching, but it's the results that will be interesting.
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Old 26th September 2022, 12:23 PM   #3
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"Roll skill check."
...

"Critical failure. You have directed the asteroid towards earth."
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Old 26th September 2022, 03:18 PM   #4
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Originally Posted by Mike Helland View Post
https://www.youtube.com/watch?v=-6Z1E0mW2ag

12.5 hours from now

Description:

NASA’s Double Asteroid Redirection Test (DART) has one single instrument onboard – the Didymos Reconnaissance and Asteroid Camera for Optical Navigation, aka the DRACO camera. DRACO serves as the spacecraft’s eye and will guide DART to its final destination: impact with asteroid Dimorphos.
Not much to see on that feed. Just a black screen with a white dot.

Here is more of an event, with NASA staff.

https://www.youtube.com/watch?v=4RA8Tfa6Sck
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Old 26th September 2022, 03:25 PM   #5
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Less than 50 minutes to go! I think we'll not see much new for a while and then things will happen fast. AT best, I think all will see is a Wile E. Coyote **paf!** from the remote camera.

Both my NASA HD and Standard Def stations are offline (cable TV)! Fortunately it's showing on The Science Channel. I can also see it on the computer but the TV picture is better.

(update)
I-minus 44 minutes -- On the full-screen view I can see the main asteroid, and a single dot where the impact asteroid is orbiting it. Kind of surreal.

(update)
I-30 minutes -- I pulled up one of the feeds on YouTube. I was kind of hoping to check out the chat but it's scrolling by so fast (and filled with so much noise) that I can't see it would be of any use to anyone. (I can't see having to go back and review for historical purposes, either.)
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Last edited by alfaniner; 26th September 2022 at 03:46 PM.
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Old 26th September 2022, 04:17 PM   #6
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Stunning
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Old 26th September 2022, 04:17 PM   #7
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Impact!
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Old 26th September 2022, 04:21 PM   #8
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This Twitter account updates you every time JWST starts looking at something new. It was watching:

https://twitter.com/JWSTObservation/...36368814018576
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Old 26th September 2022, 04:22 PM   #9
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That looked like a lot of blood at the end, the whole screen went red.
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Old 26th September 2022, 04:39 PM   #10
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That. Was. Amazing.

In the last minutes my mind was flooded with all sorts of crazy science-fiction ideas -- "Wouldn't it be cool if...?" One thing I'm sure will generate some speculation is that ridge sticking out of the end, which with some imagination looks like an engine flare. I'm pretty sure it was just a ridge that happened to be right at the terminator, but it was so perfectly placed it was... itneresting.
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Old 26th September 2022, 08:19 PM   #11
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Originally Posted by Ryan O'Dine View Post
That looked like a lot of blood at the end, the whole screen went red.
The thing was a living creature and full of blood! And we Terrans killed it. Expect retribution soon.
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Old 26th September 2022, 08:27 PM   #12
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Originally Posted by Gord_in_Toronto View Post
The thing was a living creature and full of blood! And we Terrans killed it. Expect retribution soon.
There was a parody account of DART the Asteroid Slayer, live tweeting its supposed adventure.

The second to last tweet before impact is gold.

"THIS ONE IS FOR THE DINOSAURS!"

https://twitter.com/DARTprobe/status...38291449237505
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Old 26th September 2022, 09:54 PM   #13
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I watched the Punch An Asteroid Show live.
It was satisfying.
But now I'm waiting to find out if it made any difference.
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Old 27th September 2022, 03:45 AM   #14
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The lead scientist clearly has a sense of humour!

Quote:
Andy Rivkin, of JPL’s ’s applied physics laboratory, and Dart investigation team lead, has just been explaining the reasoning behind it:

"Conventional wisdom for planetary defense is that you don’t want to disrupt an object and blow it into a million pieces, but you want to keep it intact and just move it all as one piece.

Because if you move it all in one piece then you can keep track of it a lot easier. If you blow it into a million pieces, then some of them might still [collide with] Earth, and you don’t want to miss a thing."
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Old 27th September 2022, 04:04 AM   #15
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Can we nominate third parties for a pith award?

Dave
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Old 27th September 2022, 06:49 AM   #16
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I haven't heard anyone mention yet that Dimorphos resembles a giant Alien egg pod. And we just cracked it.

In space, no one can hear you hatch.
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Old 27th September 2022, 07:12 AM   #17
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Originally Posted by alfaniner View Post
I haven't heard anyone mention yet that Dimorphos resembles a giant Alien egg pod. And we just cracked it.

In space, no one can hear you hatch.
I think I read a science fiction short story published in Amazing from about 1936 that suggested just that. And, if I am mistaken, there should have been one.
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Old 27th September 2022, 01:08 PM   #18
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For those interested, here is Scott Manley with images and video of the impact, including some from the DART's companion spacecraft

YouTube Video This video is not hosted by the ISF. The ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
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Old 27th September 2022, 03:24 PM   #19
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Originally Posted by smartcooky View Post
For those interested, here is Scott Manley with images and video of the impact, including some from the DART's companion spacecraft

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Great stuff, thank you.
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Old 27th September 2022, 03:45 PM   #20
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Originally Posted by smartcooky View Post
For those interested, here is Scott Manley with images and video of the impact, including some from the DART's companion spacecraft

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"Thanks for proving that we can save the world from killer asteroids ..." Did I hear that right? It proved no such thing, yet.
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Old 27th September 2022, 03:51 PM   #21
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Originally Posted by GlennB View Post
"Thanks for proving that we can save the world from killer asteroids ..." Did I hear that right? It proved no such thing, yet.
You're obviously not all that familiar with Scott Manley's rather droll sense of humour!
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Old 27th September 2022, 04:41 PM   #22
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Originally Posted by smartcooky View Post
For those interested, here is Scott Manley with images and video of the impact, including some from the DART's companion spacecraft

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Looks like there will be a lot more observations and analysis required to figure out the dynamics of exactly how the collision went. It will be interesting to see how much the orbit was changed.
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Old 27th September 2022, 08:16 PM   #23
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Originally Posted by Gord_in_Toronto View Post
Looks like there will be a lot more observations and analysis required to figure out the dynamics of exactly how the collision went. It will be interesting to see how much the orbit was changed.
The mass of Dimorphos is approximately 5e+9 (5 billion) kg, while the mass of the DART impactor is around 600 kg... that is a ratio of 8.3 million to one but it struck the asteroid at 24,000 km/hr.

That doesn't sound like much, but to put it into some perspective, the asteroid that wiped out the dinosaurs has been estimated at between 5e+14 and 1.5e+15 kg. The Earth's mass is 6.05e+24 kg, so relatively speaking, an impactor of proportional size striking the Earth at that velocity would have a mass of 7.28e+17 kg... between 520 and 1560 times more massive. It would be a planet killer.

The researchers at the DART project expect the orbit of Didymos to change by about 1%... approx. 12 minutes out of its current orbital period of about 12 hours.
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Old 28th September 2022, 06:02 AM   #24
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Originally Posted by smartcooky View Post
The mass of Dimorphos is approximately 5e+9 (5 billion) kg, while the mass of the DART impactor is around 600 kg... that is a ratio of 8.3 million to one but it struck the asteroid at 24,000 km/hr.

That doesn't sound like much, but to put it into some perspective, the asteroid that wiped out the dinosaurs has been estimated at between 5e+14 and 1.5e+15 kg. The Earth's mass is 6.05e+24 kg, so relatively speaking, an impactor of proportional size striking the Earth at that velocity would have a mass of 7.28e+17 kg... between 520 and 1560 times more massive. It would be a planet killer.

The researchers at the DART project expect the orbit of Didymos to change by about 1%... approx. 12 minutes out of its current orbital period of about 12 hours.
Does all the kinetic energy of the impact get transferred to Dimorphos as a purely inelastic collision to change the orbital velocity of the asteroid or does some change the rotational period around its axis? Is some energy lost in the ejecta?
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Old 28th September 2022, 06:17 AM   #25
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Another celestial highlight --
After 20 minutes of futzing with my phone and telescope last night, this is the best picture I could get. The actual view was amazingly clear! (Jupiter and moons)
Attached Images
File Type: png Capture.PNG (81.4 KB, 12 views)
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Old 28th September 2022, 06:39 AM   #26
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Originally Posted by Gord_in_Toronto View Post
Does all the kinetic energy of the impact get transferred to Dimorphos as a purely inelastic collision to change the orbital velocity of the asteroid or does some change the rotational period around its axis? Is some energy lost in the ejecta?
I got the impression from the Scott Manley video that something weird happens and I don't think I can paraphrase what he said accurately, so just watch the video. He explains. This test should shed light on the answer. There seemed to be a huge amount of ejecta from the collision.
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Old 28th September 2022, 09:57 AM   #27
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Originally Posted by Puppycow View Post
I got the impression from the Scott Manley video that something weird happens and I don't think I can paraphrase what he said accurately, so just watch the video. He explains. This test should shed light on the answer. There seemed to be a huge amount of ejecta from the collision.
I did watch the video and some is explained but not all. What ever modelling has been done will be refined by the actual results of the experiment. And that's why scientists do such things. We await the papers.
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Old 28th September 2022, 11:11 AM   #28
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Originally Posted by Gord_in_Toronto View Post
Does all the kinetic energy of the impact get transferred to Dimorphos as a purely inelastic collision to change the orbital velocity of the asteroid or does some change the rotational period around its axis? Is some energy lost in the ejecta?
I'm not familiar with all the math involved (outside my areas of expertise and above my pay-grade), but what I can tell you is I am pretty certain if you were standing on the surface of "Didymoon", you would definitely have felt the impact!
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Old 28th September 2022, 11:21 AM   #29
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Originally Posted by smartcooky View Post
You're obviously not all that familiar with Scott Manley's rather droll sense of humour!
and film knowledge

Quote:
and you don’t want to miss a thing
https://www.youtube.com/watch?v=l8AalbfPv8I
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Old 28th September 2022, 11:56 AM   #30
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Originally Posted by Gord_in_Toronto View Post
Does all the kinetic energy of the impact get transferred to Dimorphos as a purely inelastic collision
Gonna go with "not sure" for this part of the question since it seems to be a bit malformed.

Originally Posted by Gord_in_Toronto View Post
... to change the orbital velocity of the asteroid or does some change the rotational period around its axis? Is some energy lost in the ejecta?
There are several potential sources of "lost energy" by which I mean not useful to diverting the asteroid. Heat, especially vaporization, is a potential source of loss although some of that energy will act as a rocket blast. Changing the angular momentum is a source of loss. Deforming the rocks in the asteroid is too.

Any ejecta that return to the asteroid is a waste that eventually appears as lost heat.

Ejecta that doesn't return is probably the most complicated. At one extreme if the projectile wound up passing through the object with no net effect then there is... no net effect. Same or similar thing if the result is a shock wave that passes through the object and just blows stuff off the opposite side of impact. Most desirable result at the other extreme is ejecta ejecting back along the path of the incoming projectile. That's an extra source of momentum beyond what the projectile itself brought.
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Old 28th September 2022, 12:01 PM   #31
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Originally Posted by smartcooky View Post
The mass of Dimorphos is approximately 5e+9 (5 billion) kg, while the mass of the DART impactor is around 600 kg... that is a ratio of 8.3 million to one but it struck the asteroid at 24,000 km/hr.
And I think the asteroid that it orbits is about 100 times more massive still. I'm guessing they chose a binary system like this because it will be easier and faster to observe the affect on it's orbit around the parent asteroid rather than the entire systems orbit around the sun.

I wonder if the orbit of the parent object around the Sun is known well enough to measure any impact on it.
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Old 28th September 2022, 06:01 PM   #32
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Originally Posted by RecoveringYuppy View Post
Gonna go with "not sure" for this part of the question since it seems to be a bit malformed.


There are several potential sources of "lost energy" by which I mean not useful to diverting the asteroid. Heat, especially vaporization, is a potential source of loss although some of that energy will act as a rocket blast. Changing the angular momentum is a source of loss. Deforming the rocks in the asteroid is too.

Any ejecta that return to the asteroid is a waste that eventually appears as lost heat.

Ejecta that doesn't return is probably the most complicated. At one extreme if the projectile wound up passing through the object with no net effect then there is... no net effect. Same or similar thing if the result is a shock wave that passes through the object and just blows stuff off the opposite side of impact. Most desirable result at the other extreme is ejecta ejecting back along the path of the incoming projectile. That's an extra source of momentum beyond what the projectile itself brought.
I guess you are querying my use of the phrase "inelastic collision". I was trying to say that the probe went splat rather than bouncing off. A quick Google shows that I used the wrong terminology . But I'm only asking questions from a layman's understanding.
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Old 28th September 2022, 11:47 PM   #33
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Originally Posted by RecoveringYuppy View Post
Most desirable result at the other extreme is ejecta ejecting back along the path of the incoming projectile. That's an extra source of momentum beyond what the projectile itself brought.
I thought that's what Scott Manley was saying, but it doesn't make sense to me since the energy to cause that originally comes from the momentum of the impactor. Everything should be conserved and add up to precisely the amount of energy input, shouldn't it?
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Old 29th September 2022, 06:45 AM   #34
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Yes. I wasn't implying momentum comes from nowhere. It's an efficient use of the energy of the impactor to redistribute the momentum of the asteroid/impactor.

The "basic" thing that the impactor can do is just collide and merge with the asteroid. In that case the momentum of the impactor simply adds to what the asteroid had and changes it's course. That means the energy of the impactor was wasted (as heat) because it didn't do anything further to change the momentum of the asteroid. But that energy can be used instead of wasted. It can used to create additional momentum change by creating a blast that creates ejecta that leave the asteroid. And the efficiency/effectiveness of that depends on which direction the ejecta leave the asteroid (and, of course, on how much of it there is). The more closely it leaves the asteroid in the opposite direction that the impactor arrived in, the more effective it is at increasing the momentum change.
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Old 29th September 2022, 08:01 AM   #35
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I wonder how solid this asteroid is. Is it mostly one large solid rock or a loose collection of smaller rocks of various sizes loosely held together by gravity?
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Old 29th September 2022, 08:11 AM   #36
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Pretty sure I've seen this one described as a rubble pile.

ETA: Yep. https://en.wikipedia.org/wiki/Dimorphos

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Old 29th September 2022, 09:40 AM   #37
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Pictures just released.

Webb, Hubble Capture Detailed Views of DART Impact

Quote:
“When I saw the data, I was literally speechless, stunned by the amazing detail of the ejecta that Hubble captured,” said Jian-Yang Li of the Planetary Science Institute
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Old 29th September 2022, 12:12 PM   #38
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Originally Posted by RecoveringYuppy View Post
Pretty sure I've seen this one described as a rubble pile.

ETA: Yep. https://en.wikipedia.org/wiki/Dimorphos
The close ups just before impact would tend to support this. In fact most asteroids and minor planets below about 10km have bulk densities indicating they are rubble piles - only their minute mutual gravational attraction holds them together.

Impacting a rubble pile asteroid with a heavy enough impactor at a high enough velocity, could be potentially shatter it, and it is potentially within our capability to do this.
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Old 11th October 2022, 01:46 PM   #39
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Looks like the deflection worked; orbit now 11 Hours 23 minutes from 11 Hours 55 minutes - a change of 32 minutes.

https://www.npr.org/2022/10/11/11281...roid-dimorphos
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Old 11th October 2022, 06:27 PM   #40
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Originally Posted by slyjoe View Post
Looks like the deflection worked; orbit now 11 Hours 23 minutes from 11 Hours 55 minutes - a change of 32 minutes.

https://www.npr.org/2022/10/11/11281...roid-dimorphos
Quote:
"This is a watershed moment for defense," NASA Administrator Bill Nelson said on Tuesday. "This mission shows that NASA is trying to be ready for whatever the universe throws at us."
That seems AWFULLY ambitious!
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