...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.
https://commons.wikimedia.org/wiki/File:Animation_of_Rosetta...
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.
https://en.wikipedia.org/wiki/BepiColombo#/media/File:Animat...
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.
https://en.m.wikipedia.org/wiki/X-ray_pulsar-based_navigatio...
Especially when you consider how far away the "beacons" are.
http://dnc.tamu.edu/drjunkins/yearwise/2000/conference/AIAA_...
https://core.ac.uk/download/pdf/9069467.pdf
for some state-of-the-art research on this topic.
Three?
> 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)
https://www.jpl.nasa.gov/opportunities/
(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
<- 0.010000000000000002
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.
[1] https://space.stackexchange.com/questions/9556/how-does-new-...
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.