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The Beginning and the Ending of the Cassini-Huygens Mission to Saturn

Launch and Journey to Saturn

Before Cassini-Huygens blasted into outer space, only three other probes had visited Saturn. Pioneer 10 was the first in 1979, beaming back only pictures. In the 1980s, Voyagers 1 and 2 also went by Saturn, taking limited measurements as they continued their mission to the outer planets and eventually to interstellar space (Gutrel 38). Named after Christiaan Huygens (who discovered Titan, a moon of Saturn) and Giovanni Cassini (who took many detailed observations of Saturn), the Cassini-Huygens probe was launched almost 20 years after the Voyager probes in October of 1997 (41-2). The combined probe is 22 feet in length, cost $3.3 billion, and weighs in at 12,600 pounds. It is so heavy that the probe needed gravity assists from Venus, Earth, and Jupiter just to get enough energy to arrive at Saturn, taking a total of 2.2 billion miles to make it (38). During this trip, Cassini-Huygens passed by the Moon in summer of 1999 and six months later went by Masursky, a 10-miles wide asteroid which, as discovered by the probe, differs chemically from the other asteroids in its region. In late 2000, the probe went by Jupiter and took measurements of its powerful magnetic field as well as photographing the planet (39). Finally, in June of 2004, the probe arrived at Saturn (42), and in early 2005 Huygens separated from Cassini and descended into the atmosphere of Titan.

The Cassini-Huygens probe being prepped for launch.

The Cassini-Huygens probe being prepped for launch.

Instruments

During its mission, Cassini implemented powerful tools to help unravel the mysteries of Saturn. These tools were powered by 3 generators containing a total of 72 pounds of plutonium that have an output of 750 watts total (38, 42). The Cosmic Dust Analyzer “measures the size, speed and direction of dust grains. Some of these bits may originate from other planetary systems.” The Composite Infrared Spectrometer “analyzes the structure of Saturn’s atmosphere and the composition of its satellites and rings” by looking at the emission/absorption spectrums, particularly in the infrared band. The Imaging Science Subsystem is what is used to capture images of Saturn; it has UV to infrared capabilities. The Radar bounces radio waves to the object, and then waits for the return bounce to measure terrain. The Ion and Neutral Mass Spectrometer looks at the atoms/subatomic particles coming from the planetary system. Finally, the Radio Science Subsystem looks at radio waves from Earth and how they change through Saturn’s atmosphere and rings (40).

These are but a small portion of what Cassini is capable of. Though originally designed for only 76 orbits, 1 GB of data per day, and 750,000 photographs (38), Cassini has seen its mission extended until 2017. Huygens has returned valuable data about Titan, which looks more like a primitive Earth every day. Cassini also has increased our knowledge of Saturn and the moons surrounding it.

Saturn's north pole on April 26, 2017 in real color.

Saturn's north pole on April 26, 2017 in real color.

The Grand Finale

On April 21, 2017, Cassini initiated the end of its life as made its final close approach to Titan, getting to within 608 miles to gather radar data and used a gravitational slingshot to push the probe into its Grand Finale flybys around Saturn, with 22 orbits.During the first dive, scientists were surprised to find that the area between the rings and Saturn is...empty. A void, with very little to no dust in the 1,200 mile area the probe passed through. The RPWS instrument only found a few pieces less than 1 micron in length. Maybe gravitational forces are at play here, clearing the area out (Kiefert "Cassini Encounters," Kiefert "Cassini Concludes").

The final dive.

The final dive.

Where's the plasma?

Where's the plasma?

Also detected by RPWS was a drop in plamsa between the A and B rings, otherwise known as the Cassini Division, indicating that the ionosphere of Saturn gets impeded as UV light is blocked from hitting the surface of Saturn, generating the plasma in the first place. But another mechanism may be making the ionosphere, for plasma changes were still seen despite the blockage. Scientists theorize that the D-ring may be creating ionized ice particles that are moving around, generating plasma. Differences in particle count seen as the orbit went on indicated that this particle flow (consisting of methane, CO2, CO+N, H2O, and other various organics) can cause differences in this plasma (Parks, Klesman "Saturns ring").

As the final orbits continued, more data was gathered. Closer and closer did Cassini get to Saturn, and on August 13, 2017 it completed its closest approach at the time at 1,000 miles above the atmosphere. This helped position Cassini for a final flyby of Titan on September 11 and for the death dive into Saturn on September 15 (Klesman "Cassini").

Image from Sept. 13, 2017.

Image from Sept. 13, 2017.

The final image from Cassini.

The final image from Cassini.

Cassini fell into Saturn's gravity well and transmitted data in real-time for as long as possible until the last signal arrived at 6:55 am central time on September 15, 2017. The total time of travel in Saturn's atmosphere was about 1 minute, during which time all the instruments were busy recording and sending data. After the ability to transmit was compromised, the craft likely took another minute to break up and become part of the place it called home (Wenz "Cassini Meets."

Of course, Cassini hadn't just examined Saturn alone. The many wonderful moons of the gas giant were also examinwed in earnest and one in particular especially: Titan. Alas, those are stories for different articles...

Works Cited

Guterl, Fred. "Saturn Spectacular." Discover Aug. 2004: 36-43. Print.

Kiefert, Nicole. "Cassini Encounters the 'Big Empty' During Its First Dive." Astronomy.com. Kalmbach Publishing Co., 03 May. 2017. Web. 07 Nov. 2017.

Klesman, Alison. "Cassini Prepares for Mission's End." Astronomy.com. Kalmbach Publishing Co., 16 Aug. 2017. Web. 27 Nov. 2017.

---. "Saturns ring rain is a downpour, not a drizzle." Astronomy.com. Kalmbach Publishing Co., 04 Oct. 2018. Web. 16 Nov. 2018.

---. "Saturns Rings Are a Recent Addition." Astronomy, Apr. 2018. Print. 19.

Parks, Jake. "Shadows and rain from Saturn's Rings Alter the Planet's Ionosphere." Astronomy.com. Kalmbach Publishing Co., 12 Dec. 2017. Web. 08 Mar. 2018.

Wenz, John. "Cassini Meets Its End." Astronomy.com. Kalmbach Publishing Co., 15 Sept. 2017. Web. 01 Dec. 2017.

© 2012 Leonard Kelley

Comments

Leonard Kelley (author) on December 14, 2012:

Thanks Reynold! It is definitely worth the effort to look up the Voyager probes, and even Pioneer. They are incredible machines.

Reynold Jay from Saginaw, Michigan on December 14, 2012:

This shows what little I know!!! OTher probes??? First I heard of it. SHame on me. Thanks for bringing me up to date. Well done and awesome.