JPL: Cassini Getting the Lowdown on Titan This Weekend

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JPL: Cassini Getting the Lowdown on Titan This Weekend

Post by bystander » Fri Jun 18, 2010 1:59 pm

Cassini Getting the Lowdown on Titan This Weekend
NASA JPL Cassini (2010-204) | 17 June 2010
  • [img3="Artist's concept of Cassini's flyby of Saturn's moon Titan. The spacecraft flies to within 880 kilometers (547 miles) of Titan's surface during its 71st flyby of Titan, known as "T70," the lowest in the entire mission. Image credit: NASA/JPL-Caltech"]http://www.jpl.nasa.gov/images/cassini/ ... 7-full.jpg[/img3]
NASA's Cassini spacecraft will take its lowest dip through the hazy atmosphere of Saturn's moon Titan in the early morning of June 21 UTC, which is the evening of June 20 Pacific time. This weekend's flyby, which is the 71st Titan flyby of the mission even though it is known as "T70," takes Cassini 70 kilometers (43 miles) lower than it has ever been at Titan before.

Titan's atmosphere applies torque to objects flying through it, much the same way the flow of air would wiggle your hand around if you stuck it outside a moving car window. Cassini mission planners and the NASA Engineering and Safety Center in Hampton, Va., have analyzed the torque applied by the atmosphere in detail to make sure the spacecraft can fly safely at an altitude of 880 kilometers (547 miles) above the surface.

When engineers calculated the most stable angle for the spacecraft to fly, they found it was almost the same as the angle that would enable Cassini to point its high-gain antenna to Earth. So they cocked the spacecraft a fraction of a degree, enabling them to track the spacecraft in real-time during its closest approach. Thrusters will fire throughout the flyby to maintain pointing automatically.

But why does Cassini need to get so low? Read on for the perspective of one Cassini team scientist, César Bertucci.
Cassini to Swing Low Into Titan’s Atmosphere
Insider's Cassini: 'Going Low at T-70'
NASA JPL Cassini Equinox Mission | 17 June 2010

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JPL: Cassini wraps up lowest pass through Titan atmosphere

Post by bystander » Tue Jun 22, 2010 1:39 am

Cassini wraps up its lowest pass through Titan atmosphere
NASA JPL | Cassini Equinox Mission | 21 June 2010
On Sunday evening ... NASA’s Cassini spacecraft was making its lowest swing through the atmosphere of Saturn’s moon Titan ...

Right on time, at 7:26 p.m., the Deep Space Network locked on the spacecraft downlink, a good start. I was focused on the data for spacecraft pointing. As long as we stayed within an eighth of a degree of the expected pointing, everything would be fine. At 7:45 p.m., we got the data from closest approach, a mere 880 kilometers (547 miles) in altitude. Over the vocabox, a cross between a telephone and walkie-talkie, the attitude control team reported that the thrusters were firing about twice as much as we expected. The Titan atmosphere appeared to be a little thicker than we expected, even though we had fed about 40 previous low Titan flybys by Cassini and the descent data from Huygens into our modeling.

But spacecraft control was right on the money, keeping the pointing within our predicted limits. Even with the extra thrusting, we stayed well within our safety margin.

At 7:53 p.m., the spacecraft turned away to go to the next observation. I let out a sigh of relief, happy that everything during closest approach had gone just as we planned. Five attitude control guys crowded into my office with smiles on their faces. Trina and I were marveling at what a wonderful spacecraft we have to work with. Another first for the Cassini mission!

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JPL: Cassini to Dive Low through Titan Atmosphere

Post by bystander » Tue Jul 06, 2010 8:50 pm

Cassini to Dive Low through Titan Atmosphere
NASA JPL | Cassini Equinox Mission | 06 July 2010
Titan 71 Flyby: Here Comes the Sun

As American schoolchildren head out to pools for a summer splash, NASA's Cassini spacecraft will be taking its own deep plunge through the Titan atmosphere this week.

The altitude for the upcoming Titan flyby, whose closest approach occurs in the evening of July 6, Pacific and Eastern time (or shortly after midnight on July 7, Coordinated Universal Time) will be about 125 kilometers (78 miles) higher than the super-low flyby of June 21. The altitude of this flyby - 1,005 kilometers (624 miles) -- is still considered a low dip into Titan's atmosphere. Cassini will not go lower again until May 2012.

During closest approach, Cassini's ion and neutral mass spectrometer will be sniffing out the chemical composition of Titan's atmosphere to refine estimates of the densities of nitrogen and methane there. The radar instrument will be mapping an area south of the dark region known as Senkyo and the Belet sand seas. It is an area that had not been well studied by radar until this flyby.

Because the geometry of this flyby is similar to the previous one, the magnetometer and other instruments measuring the magnetic bubble around Saturn will be conducting similar experiments. Though the magnetometer will be too high to detect any whisper of an internal magnetic field from Titan - which was the focus of the search on the last flyby -- scientists will be looking into the interaction of Titan's atmosphere with the magnetic bubble around Saturn.

This latest flyby is dubbed "T71," though planning changes early in the orbital tour have made this the 72nd targeted flyby of Titan.

More information about the Cassini-Huygens mission is at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
Titan Flyby (T-71) - July 7, 2010
T-71: Here Comes the Sun

During this Titan flyby, the ion and neutral mass spectrometer (INMS) looks at the effect of rising solar activity in southern latitudes, with closest approach on the dayside near the terminator. RADAR has a southwestern quadrant ride-along synthetic aperture radar (SAR) of a poorly covered region in the prime and extended mission, valuable for determining Titan's global shap via SAR topographic measurements. CIRS and ISS monitor Titan clouds and the evolution thereof during the day after closest approach, a so-called "caboose" period.

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