Like every other known planet in the solar system, Saturn was discovered and initially explored from the relative confines of our own planet, Earth. With the arrival of the Space Age in the late 1950s and early 1960s new pathways to exploration were opened by the Soviet Union and the United States. Both nations "fought" against one another to push the envelope in space exploration by reaching farther and farther into space while accomplishing feat after feat that awed the masses.

The Soviet Union and the United States were keenly fixed on reaching the Moon but each also adamantly pushed money into projects to explore the other planets including Mars and Venus; which are current targets of missions today. Saturn on the other hand; due to its vast distance from our home planet; was a totally different hurdle to jump that neither major power had the time, money, or desire to jump during the early years of the Space Age. By the time the 1970s rolled around though, this all changed as a succession of large planetary exploration spacecraft were built; mainly by the United States; to explore the outer planets and specifically Saturn.

The United States' first stab at the close exploration of Saturn billowed into the Florida sky on April 6, 1973 on a voyage that would take it over six years to reach the ringed giant and enter the history books. Pioneer 11; as it was called; safely passed through the asteroid belt in 1974 and utilized a gravity assist from Jupiter to sling-shot its way to Saturn which it reached on September 1, 1979 after traveling over two billion miles. Pioneer 11 remained in the vicinity of Saturn for ten days wherein it got within 1,240 miles of the ring plane on two separate occasions and 13,000 miles of the planet itself where it conducted numerous experiments and snapped history making photographs of the massive gas giant.[i]

More specifically Pioneer 11 utilized its complement of instruments to conduct atmospheric, temperature, heat balance, magnetic wake, and other experiments on both Saturn and its moons. It discovered that Saturn's core is the size of eighteen Earths and consists of two regions; one an iron-rich, rocky inner core and the other which encases the first that is made up of ammonia, methane, and water. Pioneer 11 was able to more accurately calculate the planet's shape and gravity than could ever be done from Earth, took pictures that allowed scientists to announce the discovery of two new rings, and even provided pictures of a new moon just beyond the edge of the ring system. The most fundamental discovery made by Pioneer 11 was that Saturn has radiation belts and a strong magnetic field and magnetosphere; proving previous scientific suspicions that couldn't be proved from Earth.[ii]

Even before Pioneer 11 reached the haloed-planet we know as Saturn, NASA had launched two more exploratory spacecraft whose trajectories would take both of them past the giant planet and answer some questions that Pioneer 11 posed during its ten day stay at the big planet but neither would make it there until almost a year after Pioneer 11 sped out of Saturn's influence into interplanetary space.

On August 20, 1977 NASA launched Voyager 2 and shortly thereafter on September 5, 1977 they launched Voyager 1; both on trajectories that would take them on a complete tour of the outer planets minus Pluto.[iii] The spacecraft were completely identical because NASA feared that the available technology meant at least one would fail during a mission where timing was critical because Jupiter, Saturn, Uranus, and Neptune align themselves for such a mission only once every 175 years.[iv] Each spacecraft was equipped with television cameras, infrared and ultraviolet sensors, magnetometers, plasma detectors, cosmic-ray sensors, and charged-particle sensors which were used in conjunction with the spacecraft radio to conduct experiments.[v]

Even though it left second, Voyager 1 took a quicker route to reach Saturn and therefore was the first of the twins to flyby the massive planet when it did so on November 12, 1980 at a distance of 40,000 miles before streaming out of the solar system. Voyager 1's twin sister arrived at Saturn on August 25, 1981 when it passed within 26,000 miles of the ringed orb of gas. Unlike Voyager 1, Voyager 2 remained in the solar system for some time as it made successful fly-bys of Uranus and Neptune prior to joining its sibling on the trail toward interstellar space.[vi]

After all the data was received by the Deep Space Network's satellites back on Earth, scientists dove in head first and began lifting the veil that Pioneer 11 had begun to do previously. Close scrutiny of images taken by the Voyager spacecraft revealed long-lived ovals and other atmospheric features on Saturn that were generally smaller than those on Jupiter. The pair also discovered unexpected structures within Saturn's rings such as spokes in the B-ring and a braided structure in the F-ring. It also discovered three new moons to include two small moons that "shepherd" the ring material around the planet as well as an auroral zone on the planet not previously seen from Earth.[vii]

Following all these amazing discoveries along with a laundry list of others, both Voyager spacecraft traveled and continue to travel out of the solar system and farther and farther away from its origin. In the twenty-fifth year after their 1977 launches, they each are much farther away from Earth and the Sun than Pluto is and is approaching the heliopause; where the Sun's dominance of the environment ends and interstellar space begins.

The success of the Voyagers at Saturn and the other outer planets have led to two mission extensions including the newest one which led to a new mission title of the Voyager Interstellar Mission where the Deep Space Network will continue to receive signals from the far-flung spacecraft as long as they can and we humans can learn about what is going on outside of our solar system in the greater Milky Way.[viii]

The direct descendent of the Voyager twins was created through a team effort between the ESA, NASA, and Italy's Agenzia Spaziale Italiana and was given the name Cassini and it carried a probe named Huygens for a combined mission name of Cassini-Huygens. This three-axis stabilized, radioisotope thermonuclear generator (RTG) powered spacecraft was the largest interplanetary spacecraft ever constructed by NASA and was launched on October 15, 1997 on its way to the Saturn system. In order to get there Cassini would use a Venus-Venus-Earth-Jupiter Gravity Assist trajectory to reach the planet where it would be inserted into orbit around the planet for a planned mission of 76 orbits over the span of four years.[ix]

Cassini's mission consisted of delivering the Huygens probe to Titan and then to remain in Saturn's orbit and conduct around-the-clock experiments that would be beamed back to Earth for analysis. The main objectives of the Cassini mission were to determine the three-dimensional structure and dynamical behavior of Saturn's rings, determine the composition and geological history of Saturn's moons, determine the nature and origin of the dark material on Lapetus' leading hemisphere, measure the three-dimensional structure and dynamical behavior of Saturn's magnetosphere, study the atmosphere at cloud level, and do detailed studies of Titan for future space missions.

It took Cassini about six and a half years to reach its target system but on that June 30th day in 2004, the future looked impressive. The very first orbit Cassini took around its giant target would be the closest of all its encounters with Saturn when it was approximately 37,500 miles away. During its initial four year mission, Cassini successfully jettisoned its Huygens probe into Titan, discovered new information on storms and radiation belts on the planet, passed through the rings multiple times, and so much more.

The data received from Cassini is still being processed and new things are being learned every day which has led NASA to extend the Cassini mission until September 2010 as the Cassini Equinox Mission to further explore the planet. With major budget cuts coming in the foreseeable future and the lack of public support to build new spacecraft, Cassini's lease on life should be extended at least another four to five years as NASA attempts to continue to explore Saturn but at a reduced cost of having to develop new spacecraft and facilities to support it.[x]

[i] William E. Burrows, This New Ocean: The Story of the First Space Age (New York: Modern Library, 1998), 488.

[ii] William E. Burrows, This New Ocean: The Story of the First Space Age (New York: Modern Library, 1998), 488-489.

[iii] Andrae Angrum, site manager, "Voyager: The Interstellar Mission" (NASA, Jet Propulsion Laboratory, California Institute of Technology, 2009), http://voyager.jpl.nasa.gov (accessed October 27, 2009).

[iv] Douglas H. Kirkpatrick, ed. Understanding Space: An Introduction to Astronautics (New York: McGraw-Hill, 2005), 27.

[v] National Aeronautics and Space Administration, NASA Facts: Voyager to the Outer Planets (Pasadena, CA: Jet Propulsion Laboratory, California Institute of Technology, 2007), 2.

[vi] National Aeronautics and Space Administration, NASA Facts: Voyager to the Outer Planets (Pasadena, CA: Jet Propulsion Laboratory, California Institute of Technology, 2007), 3.

[vii] National Aeronautics and Space Administration, NASA Facts: Voyager to the Outer Planets (Pasadena, CA: Jet Propulsion Laboratory, California Institute of Technology, 2007), 3.

[viii] Andrae Angrum, site manager, "Voyager: The Interstellar Mission" (NASA, Jet Propulsion Laboratory, California Institute of Technology, 2009), http://voyager.jpl.nasa.gov (accessed October 27, 2009).

[ix] Dr. David R. Williams, "Planetary Missions," National Space Science Data Center, Goddard Space Flight Center (National Aeronautics and Space Administration, 2008), http://nssdc.gsfc.nasa.gov/pla netary/projects.html (accessed October 28, 2009).

[x] Dr. David R. Williams, "Planetary Missions," National Space Science Data Center, Goddard Space Flight Center (National Aeronautics and Space Administration, 2008), http://nssdc.gsfc.nasa.gov/pla netary/projects.html (accessed October 28, 2009).

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