The detailed explanations and behind the scenes looks are really interesting, meeting such tiny piece of rock 400M km away is just crazy.
Sometimes it's also funny (one of the scientists was showing a slow mo video with seemingly nothing happening "well, you got time, right? WE had to wait for 10 years")
What makes this even more crazy is that the space craft cruised 31 months powered down, from Mars to beyond the orbit of Jupiter and then back. The precision required to accomplish this is tiny!
The mission controllers must have had a pretty good confidence before giving the ok to power down.
Huge accomplishment and magnificent engineering. Hats off to the guys in ESOC and other ESA facilities.
It's a big blow to the flight dynamics team that the copyright arrangement for the pictures from some of the onboard scientific cameras makes it impossible for the FD team to use them. Sponsors of the instruments keep denying the permission to guarantee that no competing science and publications can be made before they publish.
A very bad side effect of scientists only caring about published results, not acquiring the raw data needed for those published results.
No, they're not close at all. The comet is three by five kilometers across, and the mass is around 3.14 * 10^12 kg. The orbiter at launch weighs in at 2900 kg and the lander is 100 kg.
The mission gets even more ambitious in November when, after moving Rosetta closer to 67P, mission controllers will attempt to put the Philae lander on the surface.
The lander will use harpoons to anchor itself and will carry out a series of experiments, including drilling into the material that makes up the comet.
The mission aims to add to knowledge of comets and their role in ferrying the building blocks of life around the early Solar System.
Harpoons. Very, very cool. I can't wait to find out more about this comet!
The head of the mission mentioned about boulder like structures on the comet, origins of which is not knows. The comet also has vast plain areas, suitable for landing a probe. It will be by November when we get detailed results of the chemical composition of the comet.
I find that pretty amazing! That's a lot of water coming off one comet just being sprayed everywhere.
Wow I am starting to understand why they are so interested in that propellant-free drive.
Does the comet actually have enough gravity to make an orbit happen or is the orbit completely artificial?
Yes it does.
Rosetta is now at 100 km distance while they are trying to figure out the mass and the mass distribution of the comet (unknown at this time!), and will eventually settle in a 20 km orbit, finally 10 km, around the comet.
This isn't going to be easy, see elsewhere ITT for some detailed discussion.
It will still have to use thrusters because orbiting an small irregular blob of melting ice and rock isn't going to work without precise maneuvering.
Of course, how you get that water to the target is another matter - getting it to a space station could be hard, but maybe you could pull chunks off the comet and send them crashing into, say, Mars. This might be a way of 'terraforming', to get water into the atmosphere, maybe even allow some of it to collect into small lakes, then you send some probes over with plants to start growing, bootstrap your way up.
What more it'll take to create an artificial intelligent life which can sustain herself almost everywhere?
If you are ever stuck trying to name a variable, fire up your browser, look at Rosetta's trajectory and let the fact that it's a flawlessly-executed ten-year billion-kilometer plan to catch up with a fleck of rock in space sink in. Then go back to your coding :)
The past contests and their entries are quite interesting, ranging from mapping the whole surface of the Galilean moons of Jupiter (Io, Ganymede, Callisto, Europa) or doing an asteroid hopping mission in the main asteroid belt.
I might participate in the next one.
...where you imagine that you actually are working on trajectories - at Gattaca Aerospace .
(Great movie, one of my favorites.)
It's the hardest thing in programming, and the fact that we do it in foreign language doesn't help.
How could I possibly?
"Rosetta will, follow, at least for now, a three-legged triangular orbit that requires a small thruster burn at each apex. The legs are about 100 km long and it will take Rosetta between three and four days to complete each one."
When the mass and mass distribution has been established, the spacecraft will eventually settle in an orbit about 20 kilometers from the comet and finally down to 10 kilometers.
Yes, exactly. But since the comet is highly irregular in shape and mass distribution (both are still unknown at this point!), the orbit won't be a perfect ellipse, not even close.
For example, the perturbations from Earth's equatorial bulge causes the perigee of an orbit to shift eastwards (see: Molniya orbit). The Moon's gravity field is very irregular and orbiting the Moon at low altitude is just black magic.
That approximation can describe an orbit for a while, but after time the position will differ from the predicted orbit, until at some point you have very little idea of where it will be.
The time it takes for this to happen is called the Lyapunov time. For example, the Solar System is chaotic that way in the ~100 MY time scale. See http://en.wikipedia.org/wiki/Stability_of_the_Solar_System .
A Rosetta goal now is to figure out the comet's mass distribution, so that the orbital predictions can be better. The orbit won't be "stable" but it will be more "predictable."
Even then, we expect Rosetta to release gas, dust, and water vapor which affects the orbit. I expect there will be orbital corrections over the next few years.
One definition for the "stability" of an orbit is that if you give the orbiter a small nudge, it will not radically change its orbit. Lagrangian points L4 and L5 are not stable (with this definition) while L1, L2 and L3 are (only in theory, though, in practice perturbations matter a lot).
Since the mass distribution is unknown, we can't quite predict if the orbit will be stable or not. The mass distribution may be very uneven and there may be spikes in the distribution (due to shape and porosity of the comet) that could cause the orbit to be unstable. The comet also rotates and makes things more difficult.
Now the goal of the crew is to find an orbit that is reasonably stable and predictable given the knowledge of mass distribution they have. Nevertheless, the space craft will probably have to do thrust maneuvers to stay in orbit around the comet.
And once the comet comes close enough to the sun and starts to lose mass to the vapor trail, all bets are off. That almost certainly implies some kind of unstability due to mass changes as well as the drag from the vapor trail. The comet may even break down to several pieces when it comes close to the sun.
When orbiting a uniformly-dense sphere in an otherwise empty universe, this holds. When orbiting a body that approximates a uniform sphere in a universe where all other large bodies are relatively far away, this mostly holds. But significant deviations from a spherical shape can easily make most orbits unstable.
Little known fact: the Earth's Moon deviates enough from a uniform sphere to make long-term orbits tricky. Wikipedia article:
Nice bit about a small satellite released by Apollo 16:
"Instead, something bizarre happened. The orbit of PFS-2 rapidly changed shape and distance from the Moon. In 2-1/2 weeks the satellite was swooping to within a hair-raising 6 miles (9.7 km) of the lunar surface at closest approach. As the orbit kept changing, PFS-2 backed off again, until it seemed to be a safe 30 miles away. But not for long: inexorably, the subsatellite's orbit carried it back toward the Moon. And on May 29, 1972—only 35 days and 425 orbits after its release"—PFS-2 crashed into the Lunar surface.
And this is all without any of the additional trickery coming from outgassing.
My understanding is that it's unlikely that they would ever recombine into a solid object since the gravity between them is so weak.
We're not talking about propellant residue, that was very well planned ahead.
The spacecraft carried about 1.5 tons of propellant at launch. That gives the spacecraft a delta-v budget that is several kilometers per second.
The next thruster burns (on the triangular "hyperbolic orbits") will be tiny, in the order of centimeters per second.
No, not quite. Remember, we're talking about a three body problem here so any intuition from two body dynamics doesn't really hold.
The spacecraft travels 100km closer to the sun than the comet, but that's a very small fraction of the total distance. When you factor in the small acceleration from the comet body, we can no longer think of the orbit as being a slightly smaller orbit with a shorter period (and thus overtaking the comet).
My best understanding is that the triangular "orbit" is to measure the mass and gravitational properties of the comet in order to orbit as well as scientific goals.