Cassini began its journey towards Saturn after receiving gravitational boosts from Venus (twice), Earth, and Jupiter. It entered Saturn’s orbit on June 30, 2004 and released Huygens for landing on Titan on January 1st 2005.
Scientists used Cassini’s radioisotope thermoelectric generator to observe and learn more about Saturn and its moons, and will eventually crash it into its atmosphere around 2017’s northern summer solstice to end the mission.
The Cassini Mission
Cassini spent over two decades orbiting Saturn and its moons, gathering data that will aid scientists in understanding gaseous planets such as our own. But it also entertained, comforted and inspired countless civilians with beautiful pictures showing an Earth that seems faraway yet close at hand.
Cassini used remote sensing instruments for long distance measurements while its fields and particles instruments made “in situ” direct sensing measurements of particles, magnetic fields, atoms and radio waves directly. Cassini utilized reaction wheels and thrusters to point its instruments as well as an enhanced communication antenna – this provided redundancy as it took between 68 to 84 minutes for signals from Earth to reach Cassini and back again, according to engineer Kim Steadman from JPL.
The Cassini-Huygens mission, named after astronomers Giovanni Cassini and Christiaan Huygens, was an international collaboration among three organizations: National Aeronautics and Space Administration’s Jet Propulsion Laboratory; European Space Agency and Agenzia Spaziale Italiana of Italy. Sixteen nations collaborated in creating both its spacecraft and instrument payload.
The Grand Finale
Engineers on the Cassini mission had to design their spacecraft with redundancy in mind, knowing that one or more components could fail and prevent it from collecting data or communicating with Earth, but also keep its path clear from Saturn’s atmosphere if encountering danger.
Engineers designed the spacecraft so it could perform 22 life-threatening dives between Saturn and its rings from April to September 2017: so-called ring dives.
Scientists conducted extensive “dives” into Saturn to study its moons and rings, such as Titan’s dense atmosphere and oceans. Furthermore, using radio occultation techniques they examined particle distribution within Saturn’s rings; this allowed them to better comprehend what makes their shape, structure and dynamics tick – information vital in pinpointing future targets for spacecraft rendezvouses.
Enceladus
After Enceladus’ unexpected geologic activity was identified shortly after Cassini arrived at Saturn, Cassini quickly altered its mission plan to include more close flybys of this fascinating moon. These flybys have provided important clues regarding what may be occurring beneath Enceladus’ ice shell and the size of its secret ocean.
Scientists have recently made the startling discovery that Enceladus’ fractured surface produces water rich with complex organic molecules like methane – precursors to life on Earth. If life does exist on Enceladus, it likely exists around hydrothermal vents in its ocean depths.
Enceladus’ active geology is driven by tidal forces as its orbit passes around Saturn and pulls and pushes it around in response to gravity, creating friction heat at its ocean bottom, which releases silica particles carried on currents to its surface, where they vaporize into methane-rich plumes that then escape through cracks on Enceladus’ icy surface and form its methane-rich plumes.
Titan
Cassini provided tantalizing glimpses into Titan, Saturn’s largest moon, during 127 flybys of Saturn. Its Huygens probe made key atmospheric measurements that fueled scientific speculation on life on this mysterious world; including evidence for complex carbon molecules in its dense atmosphere as well as evidence of liquid methane and ammonia ocean beneath its surface.
The orbiter also conducted an array of other experiments. It made detailed maps of Saturn’s rings, measured its gravitational and magnetic fields with exquisite precision, surveyed its magnetosphere, and captured stunning close-up images.
In January 2005, one of the highlights of this mission occurred when Titan was visited by its probe. Scientists used its design to explore whether it would enter mountain ranges, plains or oceans upon its landing and sent back data to assist with interpretation of results from its descent; during its descent it transmitted back data via electronic tracks called probe support equipment (PSE), which tracked it, recovered data from instruments attached to its body and transmitted it back up until final separation on 25 December 2004.