7 ms·
I find it truly amazing that New Horizons was able to take photos of a 20 mile object whilst flying past at ~8 miles/sec - that’s an incredibly small space and
by mbrundle 8y ago
I find it truly amazing that New Horizons was able to take photos of a 20 mile object whilst flying past at ~8 miles/sec - that’s an incredibly small space and time window within which to capture the images. Does anyone know how NASA manages to pilot spacecraft with this level of precision? What kind of engineering processes do you need to enable this?
- deleted 8y ago[deleted]
- jameskilton 8y agoActually doing the fly-by is less impressive (the fly-by was planned and programmed a while ago) than the fact that we were able to line up Horizons to an object like this at all! https://twitter.com/Alex_Parker/status/1077986070128668674 https://twitter.com/Alex_Parker/status/1077986070128668674
- weavie 8y agoI find it more impressive and awe inspiring that stuff in space is so predictable that we can actually program the fly by such a long time in advance and get such a high degree of accuracy.
- dnautics 8y agohave you ever done course corrections in KSP? A tiny nudge early on is enough to make a huge difference farther out!
- TeMPOraL 8y agoYup. And if you've ever done maneuvers manually in KSP, you know that a tiny error in your nudge early on - e.g. hamfisting the throttle, or being a little too late in mid-maneuver staging - leads to a huge difference farther out, which you then have to correct, wasting precious ∆v :). I'm very much impressed by the control precision of real-life space probes.
- dnautics 8y agoah yes, you are commenting on the precision not on the magnitude of the displacement!
- brianpgordon 8y agoCheck out the crazy journey Rosetta took on the way to 67P/Churyumov–Gerasimenko: https://commons.wikimedia.org/wiki/File:Animation_of_Rosetta_trajectory.gif https://commons.wikimedia.org/wiki/File:Animation_of_Rosetta...
- theon144 8y agoWow, I actually had no idea; how is this all pre-planned, does somebody at NASA just put "67-P/Churyumov" into a "Orbital Maneuver Planner" and let some computers crunch the possible paths out? Or does someone actually sit down and come up with the possible sequence of orbital assits (to later verify with a computer) with a pencil and paper?
- ironcan 8y agoJust a correction, but it's a project of the European Space Agency, not NASA.
- lokedhs 8y agoIt's a combination of both. They have tools that help worth the trajectory calculations, but they have to manually decide on the basic layout of the path to take. There is a very interesting interview with Pablo Munoz from the Bepi Colombo team about flight dynamics on the Omega Tau podcast that explains this: http://omegataupodcast.net/295-bepicolombo/ http://omegataupodcast.net/295-bepicolombo/ The other interviews on the same episode are also worth listening to. In fact, the entire podcast is great.
- michelpp 8y agoCommon orbits are solutions to the two body problem, but Shane Ross has a few videos on youtube about chaotic solutions to the three body problem, allowing objects to move in very complex orbits with very little fuel. This has been used for a few missions as I understand it, the math is WAY above my head, but the video is still quite watchable with lots of cool orbit animations: https://www.youtube.com/watch?v=FwHDEB1VS_0 https://www.youtube.com/watch?v=FwHDEB1VS_0
- joaomacp 8y agoI think everyone with an interest in spaceflight should play Kerbal Space Program. It gives you a sense of scale, both of space and time (luckily you can fast-forward to 100.000x), and also teaches you the basics of making orbital trajectories and correcting them, landing on planets/moons with different gravity... I'm really glad to have played it!
- aurailious 8y agoMy understanding was that the exact position was known within a few hundred miles of precision using both Hubble and the NH's cameras.
- kamaal 8y agoEven more so given that how do you navigate these things in space, I mean its position. Given how large space is, and there is no map etc. It's just insane. I guess every press of button needs to be planned years in advance.
- mpweiher 8y agoI also find this somewhere between impressive and amazing. However... ...after watching the Dragon/ISS docking manoeuvre for quite a bit longer than I probably should have, I think I now understand this precision better. When we think of "flying" including flying in space, we automatically have an image of something that's a bit unstable, always being buffeted a little, because that's how all the flying we are familiar with is. Actually seeing that docking manoeuvre, you get a feel for just how stable things are in space. When the Dragon is parked in its relative position (10m?) it is just there, rock solid, as if attached with steel beams. No, better, as if both parts are part of a single piece of granite. No quivering, nothing. Of course this is intellectually clear/obvious, but seeing it in practice is something different. https://www.youtube.com/watch?v=ysyK-J0tkEk https://www.youtube.com/watch?v=ysyK-J0tkEk
- hcrisp 8y agoI searched for "New Horizons GNC" and this link came up [1]. "The AOCS/GNC (Attitude and Orbital Control System / Guidance Navigation and Control) subsystem takes care that a spacecraft points to a specific point in space, determines the s/c attitude, and does trajectory corrections." [1] https://space.stackexchange.com/questions/9556/how-does-new-horizons-control-its-attitude https://space.stackexchange.com/questions/9556/how-does-new-...
- ilkkao 8y agoIn the press conference they said that the spacecraft tried to take one megapixel image of Ultima Thule one hour after this image. Interesting to see it in couple months.
- tabtab 8y agoIt will be a giant blurry thumb, just like my vacation photos. Except maybe green and glowing this time.
- gibolt 8y agoFor a more detailed summary of the amazing collaborations necessary and challenges faced, Scott Manley: https://youtu.be/ymJRlUQfPfQ https://youtu.be/ymJRlUQfPfQ
- macleginn 8y agoThey actually managed to predict the bi-lobed shape by keeping track of when the shadow of the object swept different points on the Earth’s surface. Amazing.
- scrumbledober 8y agoI watched that video and when the pictures finally came out i was completely floored by how accurately they were able to predict the shape. An incredible problem solving strategy that seems very simple in hindsight.
- dekhn 8y agothe development of double precision floating point, and the kalman algorithm, were two major improvements. Basically there is a computer at JPL that, given a location in the solar system and a current location of a ship, will give you instructions on when to burn. After you burn fuel to move, you update based on visual locations of known stars, fit a model, and do incremental burns until convergence. The book Digital Apollo touches on a wide range of issues associated with building systems that can do this.
- karmakaze 8y ago> the development of double precision floating point So refreshing to hear that a double is good enough for JPL when repeatedly told it's not good enough for mere dollars and cents.
- perl4ever 8y agoNew Horizons is a mere few billion miles/km away, while financial matters these days sometimes involve trillions. Plus extra digits for cents and fractions thereof, of course. “There are 10^11 stars in the galaxy. That used to be a huge number. But it’s only a hundred billion. It’s less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers.” - Richard Feynman
- dekhn 8y agoi know you're joking but it's really the precision at large numbers that makes doubles so valuable. Typically when somebody is steering a spacecraft to a remote location, the large distance as well as the fine precision needs to be represented. I am not aware of people working with very large sums of money who also need penny-level precision (and even then, floats aren't the right solution).
- planteen 8y agoJPL also has PhD applied mathematicians on staff to ensure numerical stability of their algorithms at double precision. Most developers do not have the ability to do that sort of non-trivial analysis. They are not just blindly saying "a double is good enough."
- lisper 8y ago> photos of a 20 mile object whilst flying past at ~8 miles/sec Not to detract at all from the astonishing technical achievement, but that's the wrong comparison. You can see the ISS with your naked eye, and it's a <1 mile object flying past at 4.8 miles/sec. The right comparison is with the distance at which this photo was taken: 18,000 miles, or about half an hour from closest approach. Actually, the right comparison is of the closest approach distance (~2000 miles) with the distance from earth (4,000,000,000 miles). That's like launching a missile from Los Angeles to New York and hitting your target to within a meter.
- jdmichal 8y agoTo be fair, while that's an accurate representation of the distances, it's not accurate of the difficulty. They don't have to deal with unpredictable atmosphere. There's reasons laser-guided missiles are about 1-2 meters-ish of accuracy with constant guidance, while we can basically fire-and-forget spacecraft to 4 billion miles away.
- Retric 8y agoSpacecraft also do some corse corrections. You can also measure where your going very accurately averaging over a few hours.
- dwaltrip 8y agoThey do have to deal with accurately determining the target destination, especially so in this case.
- lisper 8y agoNo, that's actually not true. Hitting Ultima-Thule is much harder. For starters, just figuring out where U-T actually is is very difficult. The observations we have only constrain two of its three degrees of orbital freedom. The third has to be inferred via orbital mechanics. Likewise, figuring out where the spacecraft is is also non-trivial. By way of contrast, figuring out where you are relative to New York to within a meter of accuracy is, nowadays, a simple matter of switching on your GPS receiver. (Even without GPS, all you need is inertial guidance that is stable for half an hour or so. That's much easier to achieve.) Finally, there are unpredictable orbital disturbances. N-H uses thrusters for attitude control, whose effect on the trajectory is not entirely predictable. (c.f. https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly, which was only detectable because, although Pioneer had thrusters, they were turned off for long periods of time). I know these things because I used to work at JPL. There are entire teams dedicated to spacecraft navigation. The stuff they do will blow your mind.
- tabtab 8y agoRe: able to take photos of a 20 mile object whilst flying past at ~8 miles/sec...Does anyone know how NASA manages to pilot spacecraft with this level of precision? I cannot speak for this probe, but other probes have made the probe itself or camera boom move slightly to compensate for the target moving relative to the probe. It's kind of like moving your head back and forth to follow a tennis match if your eyes alone have difficulty tracking. The object looks like BB-8. We'll get even better pics in the coming weeks.
- ohiovr 8y agoNot to mention seeing it in practically pitch black darkness
- deleted 8y ago[deleted]