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Spacecraft to Fly Through Geyser Plumes On Saturn Moon
Riding with Robots writes "Today the robotic Saturn probe Cassini will make its closest buzz ever over the surface of the enigmatic ice moon Enceladus, whose surprising giant water geysers hint at a hidden ocean of liquid water. The spacecraft will fly right through the tops of the geyser plumes in order to sample the material that originated beneath the surface. NASA is offering a video, interactive guide and image gallery in advance of the event."
I should add that although the closest approach to Enceladus is happening as I type this, Cassini won't have a chance to turn its antenna toward Earth until later this evening (U.S. time). The downlink will take several hours, so the first pictures probably won't be publicly available until tomorrow.
Saddle up: Riding with Robots
I already sampled the water from the geysers on Enceladus back in '78 at a Greatful Dead concert.
Tasted kind of sweet with a hint of mint.
NASA needs to get with the times. They've got 30 years of catching up to do.
The probe was going to be flying around the rings of Saturn, so they added the Cosmic Dust Analyzer, which can analyze dust particles. For the type of thing they are doing here, they can treat water as a dust particle as it will freeze. It is particulate matter.
Well, the initial plans called for wipers, but that would have required another .4 kg of expensive plutonium pellets in the RTG, and the added mass of the motor, intermittent-wipe controller, and the mechanism for changing spare wiper blades would have meant that the hermetically sealed capsule containing the Blob (frozen by Steve McQueen in the 1950s) would have been bumped to another deep-space probe.
The spacecraft is flying 200 km from the south pole of Enceladus. The plume extends *thousands* of kilometers into space. We're not passing through the top of the plume by any means. We're getting right into it.
You all keep using that word. I do not think it means what you think it means.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Yes, it has thrusters. Midcourse corrections happen every now and then.
It's not so much that orbital mechanics is hard; a lot of it is just brute-force computation. The hard part is getting reliable data to base said computation on.
The meek may inherit the earth, but the strong shall take the stars.
Getting good data is hard, but good course planning is also hard. It's easy to find an orbit that will work; push an object sideways around a mass at any of a wide range of velocities, and voila, it's in an orbit.
What's hard -- and really as much an art as a science -- is taking the laws of orbital mechanics, the very restricted maneuvering-fuel budget, and several thousand science goals (often mutually excusive), and turning them into an efficient mission plan.
Then add to that dealing with the unexpected. The Cassini team had a whole orbital tour worked out before launch, then discovered while the probe was already en route to Saturn that they needed to completely change the orbital geometry for the Huygens probe's Titan descent to compensate for a radio design snafu. They succeeded in not only rejiggering nearly all the planned science to fit into a new orbital tour, but also in grabbing a few resulting new opportunities for observations along the changed route.
The best analogy I can think of is to the difference between generating a set of legal chess moves, and a set of good chess moves.
When all you have is a hammer, everything looks like a skull.
It should be noted, it also has a mass spectrometer. While this can't identify whether a given particle is dust or ice, I believe it can determine the ratio, so while measuring density on the cosmic dust analyzer, they can make a good guess how much of it is water and how much is dust based on the results from the spectrometer.
And furthermore, Cassini will fly a mere 32 miles over the surface of Enceladeus. Considering the detail visible from 2600+ miles away on a pass several years ago, there should be a couple really great images result from this pass.
It's rather amazing to think that NASA can successfully fly this spacecraft within 32 miles of an object 300 miles in diameter, while moving at 32,000 mph in an elliptical orbit that carries it over 1 million miles away from Saturn at the extreme, with very limited manuevering fuel. Go Cassini!