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Cassini at Saturn: Halftime Highlights
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Narrator: Cassini scientists flip over Saturn. I'm Jane Platt and you're listening to a podcast from JPL -- NASA's Jet Propulsion Laboratory in Pasadena, California. The Cassini spacecraft is two years into its four-year planned mission. So does that mean it's halfway done? Or halfway started? Actually, it's a bit of both. There've already been incredible discoveries during the first couple of years. For the next two years, scientists have a new game plan for Cassini. Starting in late July, they're movin' on. Movin' up and over.

Cuzzi: What we'll do is we'll flip the orbit of the spacecraft, we'll flip it almost up and over the planet, down the other side. So it's like flipping the orbit of the spacecraft pretty much 180 degrees over.

Narrator: To the other side.

Cuzzi: To the other side.

Narrator: Cassini scientist Dr. Jeff Cuzzi, joining us from NASA Ames Research Center specializes in Saturn's rings. He says this flipping-over-Saturn process will take about a year. He'll recap some first-two-year highlights for us, and we'll hear some sounds from the journey. But first, let's find out. Like the proverbial chicken crossing the road -- why does Cassini need to get to the other side?

Cuzzi: A lot of these orbits will be looking almost down on the pole of the planet, both from the north pole, which is unlit now, and from the south pole, which is lit. So we'll see the rings from the lit side and the unlit side.

Narrator: And how will Cassini get that new view of the other side of Saturn? Jerry Jones of JPL knows. He's the Chief Navigator for Cassini. Hint: Think Saturn's largest moon, Titan.

Jones: Primarily we use the gravity pull of Titan to change the trajectory of the spacecraft. So as we go by Titan, Titan changes the velocity direction and we're off in a new orbit. So as navigators our primary job is to get to the right place at Titan so we can get the right change. So Titan's doing all the work. We're just fine-tuning the orbit to get to the right place.

Narrator: Here on Earth, we can go online to map out how to drive from point A to point B. But it's more challenging for Cassini navigators.

Jones: We start off with a fairly rough map. We now have a very fine map of where everything is. So in that sense, we're a lot like Mapquest. We know where all the "towns" are. We know what the paths are to get from any one place to another. So we've really been building up our own Mapquest kind of a capability. And so if we want to take a different path, we could do that, how much propellant is it going to take, how long is it going to take?

Narrator: For Jones and his team, one of the biggest challenges of maneuvering Cassini from afar came in January 2005. They had to guide the European Space Agency's Huygens probe -- which was riding piggyback on Cassini -- down through the hazy atmosphere of Titan.

Jones: It was quite a challenge to put the probe down in the right place, get it there on time, a very tight corridor to go through. And you don't get to practice ahead of time. We had done a lot of simulations, but real life is always different from practice. So that was really the high point -- getting it down.

Narrator: But get it down they did. And a microphone on the probe recorded that descent. Here's what it might have sounded like if you could have been on a ride-along -- dropping through Titan's atmosphere.

Natsound of probe descent (roaring noise)

Narrator: And observations from the Huygens probe, and from all of Cassini's instruments, tell tantalizing tales of Titan. Jeff Cuzzi.

Cuzzi: And it's got weather, and it's got storms and it's got clouds and its got mountains and rivers and sand dunes and all kinds of very interesting things, and we didn't really know that before. From the probe we saw mountains with these rivers running down into actual delta systems like the Nile delta or the Mississippi river delta. We see these things right there on Titan and they come right down to some flat area, which is not a sea, we don't know what it is. It's very fascinating to speculate.

Narrator: The next two years will bring nearly three dozen flybys of Saturn's moons, including 30 more of Titan. One Titan flyby coming up in July will feature the radar instrument, which has homed in on lots of those intriguing Titan surface details. Other Cassini discoveries so far -- new moons of Saturn and dramatic evidence of geysers spewing water ice crystals from beneath the surface of the moon Enceladus. So if all assumptions are correct --

Cuzzi: So we know that Enceladus has this molten body of water right underneath the surface down at the south pole. It's just an amazing, amazing thing to contemplate what might be in that water.

Narrator: As for Saturn itself -- Cassini has unveiled new sights and sounds of monster storms.

Cuzzi: We've seen them bubble up from below the atmosphere in the cameras and watch how they boil and change. We've heard the lightning from these storms with the radio antennas on Cassini. These storms, these storms are very violent, amazingly large storms that come and go.

Narrator: In fact, earlier this year, scientists converted those radio emissions from Saturnian lightning into something we can hear.

Natsound of lightning on Saturn (crackling sounds)

Narrator: Storms, clouds, mountains, rivers, sand dunes, geysers. Who knew what the Saturnian system would reveal during Cassini's first two years? And who knows what's ahead for the second half of the journey? More Cassini information and images is online at http://www.nasa.gov/cassini or http://saturn.jpl.nasa.gov . Thanks for joining us for this podcast from NASA's Jet Propulsion Laboratory.

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