Cassini to make a double play

December 12, 2011 By Jia-Rui C. Cook
A quartet of Saturn's moons, from tiny to huge, surround and are embedded within the planet's rings in this Cassini composition. Credit: NASA/JPL-Caltech/Space Science Institute

( -- In an action-packed day and a half, NASA's Cassini spacecraft will be making its closest swoop over the surface of Saturn's moon Dione and scrutinizing the atmosphere of Titan, Saturn's largest moon.

The closest approach to Dione, about 61 miles (99 kilometers) above the surface, will take place at about 1:39 a.m. PST (4:39 a.m. EST) on Dec. 12. One of the questions Cassini scientists will be asking during this flyby is whether Dione's surface shows any signs of activity. Understanding Dione's internal structure will help address that question, so Cassini's radio will learn how highly structured the moon's interior is by measuring variations in the moon's on the spacecraft. The composite infrared spectrometer instrument will also look for heat emissions along fractures on the moon's surface.

Cassini will also be probing whether Dione, like another Saturnian moon, Rhea, has a tenuous atmosphere. Scientists expect a Dionean atmosphere - if there is one - to be much more ethereal than even Rhea's. Research published in journal and led by Sven Simon, a Cassini magnetometer team member at the University of Cologne, Germany, found magnetic field disturbances around Dione, hinting at a tenuous atmosphere. But scientists hope to get stronger confirmation by "tasting" the space around the moon with Cassini's ion and neutral mass spectrometer.

On Cassini's journey out from Dione toward Titan, the imaging science subsystem will turn back to look at Dione's distinctive, wispy fractures and a ridge called Janiculum Dorsa.

Cassini will approach within about 2,200 milles (3,600 kilometers) of the Titan surface, at about 12:11 p.m. PST (3:11 PM EST) on Dec. 13. At Titan, the will be making measurements to understand how the seasonal transition from spring to summer affects in the atmosphere near Titan's north pole. It will also search for mist.

The visual and infrared mapping spectrometer and imaging science subsystem will be observing the same equatorial deserts where the imaging science subsystem saw sudden and dramatic surface changes last year, when Titan was experiencing early northern spring.  One possibly theory is that rainstorms caused these changes. As Cassini recedes from , the imaging cameras will also continue to observe the moon for another day to monitor any new weather systems.

Explore further: Cassini Doubleheader: Flying By Titan and Dione

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1.3 / 5 (6) Dec 12, 2011
What's the chances that the observers will be very surprised at what they find?
1 / 5 (10) Dec 12, 2011
Gotta do something to justify the cost of this thing.

Guys at NASA and JPL have to at least LOOK busy to justify their salary.

He had to at least ACT like they discovered anything worthwhile, so he could keep that salary.

Face it, most of the space exploration we've done is a complete waste of money until somebody produces scalable FUSION or COLD FUSION reactors OR some other exotic, unknown nuclear or quantum energy source.

The resources out there are worthless without the energy to use them.

The science is pretty mundane, and nothing revolutionary since at least 20 years ago.
1.8 / 5 (4) Dec 12, 2011
I continue to wonder why, when spending the money and effort to send a probe away from the Earth-Moon system, the probe goes by with what, to me, is minimal instrumentation and a frightfully short period of time spent collecting data at the various "stops". Why not equip such probes with a bevy of microsatellites, each of which could be launched and left in permanent orbit around the various destination moons and planets? Considering how long the Voyagers have continued functioning, wouldn't the space exploration money be better spent sending up fewer probes that last as long on duty as the Voyagers, rather than sending many probes that are supposed to stop working after just a few weeks or months on task?
1 / 5 (50) Dec 12, 2011
Because those micro satellites need fuel to decelerate; therefore, the mothership needs 1)more fuel to get them there, 2)more fuel to get their fuel there.

It's not as simple as just dropping packages off on the way. Those packages are also going the same speed as the mothership.

To put it simply, we just don't have the technology or more importantly the funding to accomplish such missions.

wouldn't the space exploration money be better spent sending up fewer probes that last as long on duty as the Voyagers

The voyagers were not tasked with turning around. This is the sticking point you aren't aware of.

Also I'm pretty sure every probe we've built that has solar escape velocity has a voyager-type endgame assuming they last long enough. New Horizons (the Pluto probe) will have an end mission much like that of the Voyagers.

And Cassini is quite the wrong project for you to wage your criticisms against because it contained an orbiter. That's where these pictures are from.

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