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Robo Reagan posted:wait a government project was way over budget and way past due? A thing to know is that a small part of why it cost so much is because congress didn't give it enough funding. It went over budget, and then rather than increasing the funding -- as they'd do for something important like a fighter jet that catches on fire randomly -- they made cuts to NASA's budget instead. NASA has spent 10s of millions just on storage costs. Parts have needed to be replaced due to sitting around too long. Congress literally took lessons from the Zaurg School of Finance and made minimum payments on a layaway telescope.
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Dec 25, 2021 15:03
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PIZZA.BAT posted:the expected operation is 4 years which is how much time it will need to get all the most important photos taken. its expected lifetime is about 8 years because that's how much propellant it has on board to keep it oriented correctly / in L2. unfortunately because it depends on actual propellant to stay in its orbit there's no real room for the stellar nasa engineering to keep it operational for way longer than expected quote:Webb's mission lifetime after launch is designed to be at least 5-1/2 years, and could last longer than 10 years. The lifetime is limited by the amount of fuel used for maintaining the orbit, and by the possibility that Webb’s components will degrade over time in the harsh environment of space. The fuel part is so uncertain because 1) The place they're putting it is unstable and very hard to simulate, so long-term predictions of how much fuel it needs over time are difficult. 2) Different things that the JWST could be taking pictures of will change how quickly it uses fuel. Every new thing it points at represents a tiny amount of fuel used. Nearby things like exoplanets or proto-stars or whatever are faster pictures to take, while looking at the farthest oldest stars is a really long exposure. If we end up taking more pics of close stuff it'll use up the fuel faster, but we still get the same total number of pictures.
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Dec 25, 2021 16:12
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That Dang Lizard posted:I believe they added a docking ring so in theory they could refuel it, it would just be very complicated and expensive to do so. They were going to at one point, but apparently quietly dropped the idea. There's no docking ring anywhere on the photos of doing launch integration. According to Famous Goon Scott Manley, it would probably be a bad idea anyways, because without the shuttle manipulator arm doing any manned service mission would just be pretty impossible. The sunshade material is unbelievably delicate. OTOH that doesn't mean a refuel is impossible: various companies have been working on mini-satellites that can "refuel" another one by attaching like a limpet, and move the big one around that way. Northrup Grumman has done this twice now. They don't even need a docking ring, it just does some robot  and shoves a clamp into the target sat's main engine.So I think that if a JWST extension were to happen it would go like that. A new, moderately inexpensive robot that flies out and attaches to JWST, and NASA sends up new software to make the two work together.
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Dec 25, 2021 19:13
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Pennywise the Frown posted:edit: wait, is this thing being set up WAY beyond the distance of the moon? I haven't read too much into it. Just stuff about the launch. Yup. They can't put the thing in earth's orbit like the Hubble because even the earth radiates too much heat for it to work. So like you'd need the giant sun-shield and also a giant "earth-shield", and that's just too complicated. There's this cool thing called a Lagrange Point, where the gravity of the earth and sun balance up and you can have a thing "stay put" relative to the earth. It's way out there. Normally if an object was orbiting the Sun an extra 1.5 million KM further out than the earth, it wouldn't have the same orbit time as the earth. We'd go around the sun in 1 year, and the other thing would take like 1 year and 5 days. (Mars is 50% further out from the sun than Earth an it has a 686 day orbit.) That would mean that it would get out of sync with Earth and we'd drift further and further apart. But the Lagrange Point allows it to follow Earth's 1 year orbit so we stay together. Chris Pistols posted:What are they pointing it at first? Surely they've got a list of top 3 things to have a look at straight away. just a guess but I'd imagine the first few things will be "boring" well-observed objects that we already have lots of data on -- to calibrate it and make sure the instruments do what they expect Klyith fucked around with this message at 20:24 on Jan 8, 2022 |
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Jan 8, 2022 20:22
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Ramrod Hotshot posted:Will Webb be looking at extrasolar planets or just cosmology type stuff, ie quasars and big bang remnants? yeah it will do extrasolar planet stuff it's got a really neat spectrograph that will be able to tell the composition of planet's atmospheres (for those planets that pass in front of their parent star and eclipse it) and one of the more exciting things is that it will be good at seeing through dust, so I think they'll be looking at stars that still have dust discs where maybe planets are still forming. that's a cool one because "how is babby planet formed" is still a topic with lots of questions. edit: But the cosmology & deep time stuff is the primary mission, and the thing that only JWST can do. We needed a bigass telescope, bigger than hubble, to see that far. And it had to be a space telescope to see that deep in infrared. Thus JWST. So the future "menu" will depend a lot on what they see the first year or two. Maybe the universe 14 billion years was super uniform, and after looking for a while they'll be like, huh guess we can stop taking pictures of ancient galaxies that are all pretty much the same. OTOH maybe they keep finding new stuff about the shortly-post-big-bang universe and JWST ends up doing mostly that for its whole life. Klyith fucked around with this message at 01:33 on Jan 9, 2022 |
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Jan 9, 2022 01:15
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SAY YOHO posted:Not sure I am also dumb, my best understanding is that, in the rubber sheet analogy, the Lagrange points are relatively flat areas in the two body problem, meaning you don't have to use a lot of fuel to stay there. This is how they're described in pretty much every scifi novel, especially the ones where the FTL drive only works in those spots. It's not the worst handwave description for them, but it's not true. Reality is both more complicated and much more mundane. Lagrange points aren't flat areas of gravity. If the "rubber sheet" was flat that would mean no gravity at all, and stuff would just fly away. If I could use a device on you that flattened gravity, you'd be flung off the earth. That's not what happens to stuff at Lagrange points. Two basic principles of orbital mechanics: 1. The lower / tighter your orbit, the faster you move. The ISS is in low earth orbit, 420km above us. It's moving 7.66 kilometers per second and goes around the Earth once every 90 minutes. The Moon is about 380,000 km up. It moves at just over 1km/second and takes 28 days to do an orbit. Higher orbit = slower. 2. The bigger (more massive) the thing you're orbiting, the faster your orbit velocity. The Earth is orbiting the Sun at almost 30km/s, despite the fact that we're a long way from the Sun. That's because the Sun is stonkin' huge. The Parker Solar Probe is the fastest object built by man -- it dives so close to the Sun that it enters the outer layers of the solar corona. It goes over 190km/second at its fastest. So, the JWST is in orbit around the Sun, just like Earth. But it's 1.5 million km further out. This means that by principle #1, it should be going slower than the Earth, and taking longer to orbit. If that were the case it would start "falling behind", getting further and further away. That would be annoying, it would need bigger radios to communicate. And eventually it would be 180° out of sync, on the opposite side of the Sun to us. You can't radio through the Sun, so we'd be out of contact for a while. Then we'd start "catching up" and getting closer. But now you want to think about fact #2. The Lagrange point L2 is on the line from the Sun through the Earth. Along that line you are adding the Earth's gravity to the Sun's. In effect, it's as if the Sun is a little bit heavier. The specific L2 point along that line is where that Earth+Sun equals an orbit velocity that's the same as Earth. tl;dr the Earth has JWST on a string and is pulling it along saying "keep up, don't fall behind!"
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Feb 15, 2022 20:16
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Good Sphere posted:Does the James Webb go up and down in a circle because of constant corrections, or does it mostly naturally do that? I can kinda see it being able to orbit vertically like that because it's the Sun's gravity pulling it in one direction, and then the Earth's gravity pulling it in another direction. It naturally oscillates around the center. Doing that is actually more stable, and so needs fewer correcting burns, than sitting right exactly at the center of the L point. If you look at the main image for the wikipedia article about L points, you can see that while the centers might be "flat", they're flat like the very top of a hill or center of a saddle is flat. As soon as something drifts a tiny bit off the center they'd start "rolling downhill" and get pushed even more off center. But that effect can also produce a kinda orbit around the center. It's constantly drifting away and being pushed back at the same time.
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Feb 16, 2022 00:10
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Butterwagon posted:I feel dumb because I thought the L2 point was unstable, but JWST is able to "orbit" it? Wouldn't any deviation from L2 make it drift further away if it's unstable? If it was standing still relative to the L2 point, yes, a deviation away from the center would be a compounding problem. But this halo orbit thing makes the deviations work against each other. When it's up, it gets pushed down; when it's left, it gets pushed right. It's still not stable over the long term. Webb will need to make little corrections to stay in place, and when it runs out of fuel it'll drift off. But "unstable" is a relative thing. Other Lagrangian points are permanently stable: L4 & L5. Those are the ones that Jupiter has collections of asteroids in. We could put something in the Earth's L4 or L5 point and it would stay there for-almost-ever. But they are very far away: as far away from Earth as the Earth is from the Sun. So you need an even bigger rocket to put something out there. And all that distance is sucky for high-bandwidth radio communication when you're sending lots of high-res telescope pictures. There's been proposals to put a satellite out there watching the Sun to be an "early-warning" alarm for bad solar flare events. But TBQH if there was a giant solar flare I'm not sure what we'd really do about it even with an early warning. "Hey everybody we need to shut down the entire world power grid today to protect it against this solar flare." "End the blackout! No shutdown! No masks! Arr freedums!" Butterwagon posted:So why is it "orbit" and not "stay as close to L2 as possible at all times"? Stay as close to L2 at all times = balance a pen upright on your palm. Very hard because if you're a fraction off the pen starts falling over, and that means it tips over harder. Try it! (Use a pen, not a pencil with a sharp point. A pencil stabbed through your hand is cheating, that stays upright easily.) "Orbit" around the L2 = balance a moving bicycle. It's still not stable, a bicycle falls over without someone to help it. But there are some forces helping you out. note: neither of these are exact analogies edit: Butterwagon posted:An orbit is stable. There are several moons of planets that are eventually gonna impact or break up around their planet, ex Mars's moon Phobos and a tiny inner moons of Jupiter, or get flung out into space. Klyith fucked around with this message at 05:52 on Feb 16, 2022 |
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Feb 16, 2022 05:41
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Butterwagon posted:Huh. I understand the metaphor but I don't know what the forces would be. I guess being too far ahead or above would get pulled back/down by the combined line of action of the earth and sun and vise versa? I think that makes sense. Yeah. Gravity, plus centripetal forces of moving on a curved path in the "real" orbit around the Sun. It's really hard to intuitively understand, rotating reference frames are like that. And the math for this stuff is so difficult that it wasn't possible to solve until the 70s and 80s with computer simulation. I loving hated anything to do with rotational forces back when I was in college, never quite got it. Playing Kerbal Space Program literally helped me understand this stuff in ways that a college course didn't. Butterwagon posted:I still don't get why that's more stable in the inwards/outwards direction. edit: I misread. How does the orbit correct for the inwards/outwards deviation? Ok, it's like this, when you're in an orbit, a force will produce orbital motion 90° off of where the force is pointing. A force that adds speed makes you move out. One that pushes out makes you move backwards. Slowing down takes you in, and in makes you go forwards. So there's a natural cycle to that. JWST moves through each of these areas of force for just the right amount of time to change the true orbit around the Sun in ways that make a complete circle. The halo orbit is very squashed in the in/out direction, and much wider in the x/y plane as seen from Earth. The in/out force is much steeper than the other two. kazr posted:Love reading this poo poo tell me more, also your avatar is incredible lol An additional thing that makes all this harder for JWST: it can't back up. Normally on a spacecraft you'd put little mini thrusters on all six sides. That way it can make corrections in any direction up/down, left/right, and forward/backward. The JWST has them on its boxy control module below the sunshield. But that's a problem -- if they had thrusters firing forwards they'd fire straight into the insanely delicate sunshield and tear it up. And they can't put them above the shield because the totally exposed mirror is up there. So it can only thrust in 5 directions! That means that every maneuver they do, they're always aiming to be just a tiny bit short in that outwards direction. It's like they're kicking a ball up a hill and never want to kick hard enough that it goes all the way over the hill and starts rolling down the other side, then you'd lose your ball. (I like my av too, but it does have the residual shame of being purchased to support the Lowtax Spine Scam.) Klyith fucked around with this message at 17:05 on Feb 16, 2022 |
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Feb 16, 2022 16:24
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Seth Pecksniff posted:I think the light from the big bang is far beyond our observable universe at this point The big bang happened everywhere, so it's not really about being far. The big bang happened where you are sitting, and where the most distant thing the JWST sees. Everything was all in one place then. The answer is kinda yes and no: the Cosmic Microwave Background is in many ways the light of the big bang. It's the oldest light in the universe, the first light that was possible to travel any distance. Before that the universe was too dense and hot for light to move without instantly hitting anything. It had to expand and cool down to become transparent. But that happened 370,000 years after the actual instant of the big bang, so it's also not exactly like seeing the big bang itself. But it's the oldest thing it is possible to see.
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Jul 8, 2022 16:16
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listen guys Joe Biden has a stutter, it's not polite to make fun of it
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Jul 11, 2022 23:19
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Log082 posted:that feeling when you realize all the little spirally things are full on galaxies lmao I'm pretty sure that everything you see in that picture is a galaxy. like even the really bright star-lookin' things are just foreground galaxies. they're not a fuzzy blob because they're too bright and have blown out exposure. and if there had been a star in our own galaxy in the way, we wouldn't be able to see any of that stuff (I don't know 100%, but that was the case with hubble ultra-deep field pics)
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Jul 11, 2022 23:33
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Seth Pecksniff posted:There's gotta be like aliens doing the exact same thing we are right? Like they're looking at the Milky Way as it was millions of years ago I dunno, this is a single grain of sand in the whole sky. There could be countless alien astronomers looking through countless telescopes, and they'd still never happen to look at the Milky Way. Because there are just so many galaxies to look at. Far more than even countless astronomers could observe.
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Jul 11, 2022 23:45
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Seth Pecksniff posted:
Some of galaxies in that image are so old that they probably can't have had anything living in them at the time! Because the earliest stars in the universe didn't have any heavy elements to make planets from. It took like a billion years for stars to form, die, and explode stuff besides hydrogen and helium into the universe. One of the goals of the JWST is to take pics of the earliest stars that formed in the universe. Negostrike posted:Nothing in that pic is a star in Milky Way, right? I'm pretty sure, yes. Negostrike posted:Everything in there is far as balls, like from around 13 gya? Many of the galaxies are closer / younger than that. Like all the big yellow-white fuzzy ones in the center, those are a big heavy cluster of galaxies that's somewhere between us and the furthest ones. Real far away but not stupid far. The oldest ones are the things that are all smeared out and circular distorted. They're super loving crazy far and the gravitational lensing from the big cluster is how we can see them at all. Otherwise they'd be one of the tiny little background dots that's too small to see anything, even for JWST.
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Jul 11, 2022 23:59
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that being is likely long dead, but we might have captured it as it was doing that millions of billions of years ago!
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Roumba posted:On https://webbtelescope.org/contents/media/images/2022/038/01G7JGTH21B5GN9VCYAHBXKSD1, NASA's/Webb Telescope's official website image description pdf says: whoops I was wrong about the stars thing!
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Jul 12, 2022 00:23
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Wilkins Micawber posted:A question to the dorks: do they expect its quality or capabilities to evolve/expand over time? Kind of like the last mars Rover, how the pics it sent back were kinda "meh" and then they hit the turbo button and it was spitting out hi-rez porn gifs or w/e. Yeah, these are all just the quick pics. For pretty much all astronomy pictures, whether telescope or robot rover or voyager probe, you get the best results by combining photos together to enhance them. The Hubble Ultra Deep Field was made by combining hundreds of exposures made over the course of months, with a total exposure time of 11.5 days. The SMACS picture (the super-distant galaxies) by Webb was made in 12.5 hours of exposure. And it makes Hubble look like the lovely one with a thumb partly over the lens.
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Jul 13, 2022 00:20
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Vampire Panties posted:does it have the fidelity to see another planet down to land features or oceans? Could it see moons in other planetary systems? Could it find a neutron star? no, no, and "yes but" Finding neutron stars isn't that hard, we know lots of them. They're tiny, and the good telescopes to see them with are the opposite of JWST: x-ray and gamma ray telescopes. So JWST could find a neutron star by seeing the hot ashes of a supernova explosion that produced a neutron star. Lawman 0 posted:I'll be real and suggest that there is probably bacteria, algae and lichen equivalents basically everywhere they can get a foothold and if enough time has passed. Animals and like trees though? Dunno if they show up everytime. Yeah here's how I look at it: the oldest rocks we know where it's possible to find signs of life, we see life. And in even older stuff where you can only see hints and maybes, we see hints. It appears that as soon as earth could host life, life was here. So that maybe seems optimistic about the possibility of life elsewhere: if it was so easy on earth that we didn't have to wait around for lightning to strike, that kinda argues that life isn't that hard to make. OTOH, here's the pessimistic part: after we got life, we waited 2 billion years for anything multicellular. 2 billions years is a long time. Nothing more interesting than stromatolites and algae that whole time. Not even lichen. This argues that complex life is a lightning strike event. It was something freakishly rare, way more rare than kist single-cell organisms working closely together. However it happened on Earth, if that one chance had gone wrong, might it take another 2 billion years before it happened again? That would mean we'd still be waiting today. So intelligent life might be really rare mainly due to the simple life -> complex life filter.
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Jul 13, 2022 03:45
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Handen posted:Could the imaging team not eliminate the diffraction spikes entirely with multiple exposures taken at slight rotation from each other? I.e., take one exposure, then rotate the entire craft 7.5°, take the same exposure again, and then end up with two images of the same field with diffraction spikes rotated 7.5° off-axis from the previous exposure, which can then be stacked to eliminate the differences between the two exposures, thereby eliminating BOTH sets of diffraction spikes in the process? I think this would produce a prettier picture for people to look at, but ruin it for astronomy. #1 the ever so slight imperfections in the image that happen because the main mirror isn't a platonic parabola but a bunch of hexagons, those would also get differenced. I think that would make blurring or distortion to everything away from the center of the picture. #2 The double set of spikes would still contaminate data on things that astronomers care about. So now you'd have twice as much area near the big stars that is inaccurate spectrum or whatever. And even if you could do the re-point without using fuel, it would still be wear and tear on the gyro wheels. This thing's life is gonna be primarily limited by how much it has to maneuver. Plus it would take probably 10 times longer per photo, because maneuvering a spacecraft is slooooow.
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Jul 15, 2022 13:34
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Demon Of The Fall posted:new poo poo 
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Sep 6, 2022 17:37
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Seth Pecksniff posted:What gets me is that these stars look like they're literally next doo to each other, and yet they're most likely hundreds of light-years apart. No, those guys literally are next door to each other. The star cluster R136 you're looking at is only only about 50 light years across, and that central blob where they're so close that you can't resolve individual stars is like 6. It's a starburst area: a place where a whole shitton of thick gas condensed out into a whole lot of stars, many of them super-giants that are gonna burn out and go boom super fast. Here's the tl;dr of a big star forming nebula: 1. Somehow a lot of gas gets pulled together, either by gravity and movement inside the galaxy or interactions with other galaxies (the second is much more effective, and can make a whole galaxy light up with millions of new stars). At this point it looks like a big black blob. 2. The densest region starts collapsing under its own gravity, pulling in more gas. Little knots accumulate and get big enough to collapse down into proto-stars. 3. Dozens or hundreds of stars turn on, basically all at once in astronomical time. The first thing they do is turn all that cold dense gas around them into hot expanding gas. This shuts down star formation as gas gets dispersed from the cold dense blobs. This famous picture looks like dirt being blown away in strong wind, because that's exactly what's happening. 4. If this was a big cloud, a good number of these new stars will be giant fuckers that are so bright that they light up the whole cloud complex for 100s of light years around them. This takes a couple forms (reflection where light bounces off the clouds, emission where UV and Xrays from super-giants are absorbed by gas and then that energy re-emitted as visible or IR light). <--- All the pretty pictures of cool nebula are from this step 5. The energy and solar wind from the star cluster, and the biggest stars quickly going supernova, blows away all the gas and dust. The nebula fades out. Many of the stars spread out, but a tight cluster of them may hang together a long time and still be a recognizable group for millions or billions of years. Only 10% of the gas made it into stars, the rest eventually get scooped into new clouds in the long long future.
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Sep 7, 2022 16:07
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vortmax posted:Our own local star started in a cluster like this iirc Every star starts out in some type of cluster -- the gas clouds won't start collapsing unless they've got enough mass to make dozens or hundreds of suns.
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Sep 10, 2022 03:39
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Klyith posted:This famous picture looks like dirt being blown away in strong wind, because that's exactly what's happening. Well speak of the devil! Next up on Webb's continuing tour of the Greatest Hits of modern astronomy: The Pillars of Creation.  https://www.nasa.gov/feature/goddard/2022/nasa-s-webb-takes-star-filled-portrait-of-pillars-of-creation The cool new poo poo: those bright red flares are from very young stars, which are still burping out hot gas ejections as they settle down. Webb can see into the interior of these dust clouds much better than Hubble. These "pillars" don't look nearly so solid anymore, huh?
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Oct 19, 2022 19:24
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ProperCoochie posted:NASA is doing a live stream of the OSIRIS-REx Asteroid Sample Return let's stroll down memory lane to an all-time nasa fuckup 
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Sep 24, 2023 15:44
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redshirt posted:Is that when they couldn't catch the incoming probe with the helicopter? Yes, but the stunt pilot helicopter mid-air catch wasn't even the problem! They never got a chance to grab it. The parachute didn't deploy because an accelerometer was installed backwards.
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Sep 24, 2023 20:10
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