...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.
I'm very much impressed by the control precision of real-life space probes.
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/
The other interviews on the same episode are also worth listening to. In fact, the entire podcast is great.
And this is one of the many reasons why these machines are horrendously expensive - they are incredibly precise.
It's just insane. I guess every press of button needs to be planned years in advance.
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.
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, 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.
The good thing is that, for such a thing to be really useful, we'd have to invent better propulsion systems which would, in turn, make the network much cheaper to build.
Especially when you consider how far away the "beacons" are.
for some state-of-the-art research on this topic.
> I know these things because I used to work at JPL
Ok, I don't. What are the three DoFs and how do they relate to 6DoFs or six Keplerian elements? Some background-fixing?
How do we get to work with these teams, if even possible?
(Though it should be impossible for me(given I'm an Indian), still how do someone who could work there go about joining them)
(BTW, in this day and age if you can't figure out the answer to a question like that on your own, you're not ready.)
Well, no, but they do have to deal with an atmosphere that has, until they get to it, only been theorized about, never observed - which is not the case for the atmosphere above New York.
There have been precisely four spacecraft that have gone anywhere near so far out as New Horizons, and they are between them the source for the majority of data we have about the atmosphere in the outer solar system. One of them discovered an anomalous acceleration effect that confused scientists for decades (and which, while it turns out not to have been externally caused, certainly left scientists wondering for a while whether their model for the solar wind was accurate). Of those that we believe have passed through the termination shock of the solar atmosphere, none have yet returned much accurate information, so we actually don't know much about the conditions there. I don't mean to say that these effects have meaningfully impacted navigation for deep space probes, but more these are genuine voyages of discovery - where they're going is predictable but until they get there we really don't necessarily know whether our predictions will be accurate.
Implicit in this statement: the camera was pointing close to the direction of travel and the target wasn't moving much within the field of view. Hugely easier than trying to image from the side at closest approach, which at best would have given a smeared image and at worst a complete miss.
It's still impressive and awesome. But always try to skew the odds of success in your favor when dealing with stuff like this. You have one pass and then the opportunity is gone.
True that. AFAIK the closest-approach images have not yet been downloaded.
As long you have navigation(GPS) and fuel(to make adjustments), that shouldn't be a problem?
But of course you don't have a map in space, so how do you navigate, and course correct etc, is another big puzzle in itself.
The book Digital Apollo touches on a wide range of issues associated with building systems that can do this.
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.
“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
> 0.1 * 0.1
I don't know about you, but I don't trust myself to get this right, much less developers who often don't understand the issues involved.
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.
It's a neat picture, but I fear that any subsequent pictures will have less impact on the public, as many laymen will say "Meh, saw that the other day on <insert_news_site>. Old news".
I'm really looking forward to the spectacular shots we will get from the close-in imager. New Horizons will be MUCH closer to this object than it was Pluto, so it should really get some fantastic shots of the surface features.
For comparison, just check out the wikipedia pages. They show a pretty solid contrast of the capabilities/uses of the two devices:
Welded together by gravity, i'm really in awe seeing the, by far, weakest power so lovely at work.
This object(s) seem statistically unlikely to me. I'm not saying it's artificial. That would be even more unlikely, by orders of magnitude. Just saying "Wow!".
Another is the "YORP Effect". Sunlight falling on an asteroid produces a slight thermal radiation pressure (push). If, due to asymmetries in asteroid shape/albedo, the net radiation pressure force is not aligned with the asteroid's center of mass, it will produce a torquing force which will cause the asteroid to spin faster (or slower) over time. Applying the idea of YORP Effect to binary asteroids yields the "BYORP [Binary YORP] Effect", by which the orbital dynamics of the binary system are modified by this asymmetric radiation pressure over time, in a way that either pushes them together into a contact binary or apart into two unbound asteroids.
It's even hypothesized that some asteroids may be in a binary/contact-binary cycle on long timescales! There are solutions to the above in which the BYORP effect causes a loss of angular momentum in a binary pair, causing them to merge into a contact binary - but the contact binary may settle into a state where the YORP Effect actually causes the newly merged asteroid to spin faster, eventually flinging them apart due to centripetal forces... back into a binary state where the BYORP Effect may again cause them to merge someday.
Recommended reading: https://arxiv.org/abs/1010.2676
At this mass these bodies are at, they aren't going to crush together from gravity to form a single round body.
However, if you've got two bodies in very similar orbits around the Sun, in close proximity, it doesn't seem incredible to me that they might eventually collide and stick.
What I mean is, your argument doesn't make any sense. Just because the universe is big, doesn't make unlikely events more likely to be stumbled upon.
Your post implied that the existence of such objects is unlikely, not the observation.
To which the other poster replied that (unlikely event) x (vastness of space) = likely occurance.
Once they are orbiting each other then it’s just a matter of time for the orbits to decay. In the final, they would be spinning very very fast but would be inching towards each other until they touch.
I don't know if this is how it actually happens, but it gives a mechanism for this being fairly common. The only information I could find was a short wikipedia article:
Similarly for Ultima Thule. They may have been able to find a different target, but it was very difficult to find any target at all in the first place (lots of Kuiper belt objects are known; the difficulty was finding one that could be reached by New Horizons). See this Twitter thread that was linked elsewhere: https://twitter.com/Alex_Parker/status/1077986070128668674
Bigger objects have greater gravity than smaller objects, therefore are more spheroid.
As we get better at observing, we'll see more objects that are less spheroid.
Pluto may be a KBO also. Further, it's possible some moons of the gas-giant planets are captured KBO's.
The unusual thing about Ultima Thule is that it's in a nearly circular and "flat" orbit, which many experts interpret to mean it's mostly undisturbed from its point of origin. It's a prime "fossil".
Pluto has a "disturbed" orbit such that its origin is currently unknown. Same for gas-giant moons. Pluto has also been turned inside-out, perhaps multiple times, by a still unidentified force. Ultima Thule is probably mostly as-is since formation.
Given lack of fast erosion from liquid water or significant wind (in a very thin atmosphere), whatever geologic process is smoothing out Pluto is happening quickly compared to other points of reference we have.
I use the example of Earth's geologic plates, but that's only one possible explanation. There's also speculation about freeze/thaw cycles of the planetary material and atmosphere (since it has an irregular orbit), movement of water-ice mountains, cryovolcanos, and other theories.
substantive content: new horizons uses a modified MIPS R3000 CPU (ok, not the PSX's GPU, and not used for everything on NH, but) https://www.theverge.com/2015/1/15/7551365/playstation-cpu-p...
I think the images are the first thing that get downloaded, so it should not take more than a week to get all high res images.
1 - https://en.wikipedia.org/wiki/New_Horizons#Telecommunication...
Image of the occultation profile vs actual shape:
Each line is the same star viewed from a different point on Earth. They arranged for telescopes in a long line North to South to all observe UT at the same time, just as it was predicted to pass in front of the star. Then they precisely timed the apparent blinks of the star. The North-South offset meant the star bisected UT across different sections for each telescope.
Then they just worked out the parallax difference and mapped out the blink times on a chart to see the silhouette.
This is what an occultation looks like: https://www.youtube.com/watch?v=7Y_qc8Ifhso
Crazy they are able to map a few of those together so precisely to get this data.
Then I get sad because things just take so incredibly long on a stellar scale, and a human life is so short.
Just one thing: it would be great if NASA dropped imperial units as main units in such articles.
As seen in the combined image.
The 21st century world of asteroid and Kuiper belt colonization is going to be far fluffier and squishier than we thought it would be in 80's Sci-fi!
Wednesdays news conference speculated UT shape is primordial, while the others may have been carved through four billion years of planetary evolution.
Are these common in the asteroid belt or as smaller moons of the outer planets?
Mimas (and Iaepetus too) really looks like the Death Star and now this thing looks like BB-8.
Ultima Thule-BB-8 comparison: https://pbs.twimg.com/media/Dv7psG3VYAA8jqa.jpg
Mimas-Death Star comparison: https://cdn-images-1.medium.com/max/575/1*nUxm5MD_2xO5Y9Lorr...
Iaepetus-Death Star comparison: https://cdn.images.express.co.uk/img/dynamic/80/750x445/8290...
I remember reading they were going to aim for 2000 miles from Ultima Thule, was the closest approach revised to 18,000 miles?
But the asymmetry of Ultima Thule means that its gravitational field would be weird. Not like a sphere at all. So the acceleration of gravity and escape velocity would vary a lot from place to place.
And just for fun, I also worked out a best guess for the force between the two "lobes": 1.5 x 10^13 N (assuming Ultima Thule is the same density as our Moon), which is about equal to the (Earth) weight of all the ships in the world.