Saturn eclipsing the sun, seen from behind by the Cassini orbiter. Earth can be seen as a small dot between the rings on the upper, left-hand side. Image Credit: NASA/JPL/Space Science Institute
The NASA Cassini mission is winding down, quite literally. On April 26, the Cassini spacecraft became the first to dive between Saturn and its ring system. This begins the spacecraft’s “grand finale” in which it will make 22 amazing orbits and, on September 15, enter Saturn’s atmosphere and burn up. The spacecraft will be useful until the very last moment–it will be sending back data continuously, including measurements of the composition of Saturn’s atmosphere, rotation rate and interior structure.
Until that time, the instrument teams have several new observations to make. These include understanding a Saturn radiation belt, discovered inside the rings in 2004, and taking close-up pictures of the rings and other features.
Read the 2004 Article: New Radiation Belt
Read the NASA PDF Resource on the Mission (published 1997)
Originally called Cassini-Huygens, the mission involves ESA, NASA and the Italian Space Agency. The idea of the mission began in 1982, when the European Science Foundation and the American National Academy of Sciences formed a working group to investigate future cooperative missions. Two European scientists suggested a paired Saturn Orbiter and Titan Probe as a possible joint mission. In 1983, NASA's Solar System Exploration Committee recommended the same Orbiter and Probe pair as a core NASA project. NASA and the European Space Agency (ESA) performed a joint study of the potential mission from 1984 to 1985. ESA continued with its own study in 1986, while American astronaut Sally Ride, in her 1987 report, also examined and approved of the Cassini mission.
In 1988, NASA Associate Administrator for Space Science and Applications Len Fisk wrote to his counterpart at ESA, Roger Bonnet, strongly suggesting that ESA choose the Cassini mission from the three candidates at hand and promising that NASA would commit to the mission when ESA did.
Read About the Spacecraft
The mission arrived at Saturn on July 1, 2004. The mission was originally planned for four years. But Cassini-Huygens was so successful that the mission multiple times, eventually to 2017. It has flown past seven of the larger satellites, including giant Titan – which is larger than the planet Mercury. The orbiter passed Titan more than 70 times. Flying within 880 km of the moon, it studied Titan’s orange clouds and nitrogen-rich atmosphere. It also mapped its surface with an imaging radar.
On Christmas Day 2004, Huygens separated from Cassini. Three weeks later, it entered Titan’s thick atmosphere, becoming the first probe to land on the surface of a planetary satellite (other than Earth’s moon). Protected by a heat shield, the probe slowed from 18,000 to 1,400 km per hour in just three minutes. Soon after, a large parachute opened. At a height of about 160 km, the probe began to take pictures and study the atmosphere. For more than two hours, data from Huygens were received and stored on Cassini as it flew overhead.
To learn more about Cassini, Huygens, Saturn, Titan, the rest of the Saturn system, and the Grande Finale, check out these links.
Read About the Mission
See the Mission Timeline
Read the FAQ for Cassini – The Grand Finale
Read the 2017 Article: Bittersweet feeling as Cassini mission embarks on its ‘grand finale’ ahead of death plunge
Read the 2014 Article: Cassini 10 Years at Saturn Top 10 Discoveries
Read the 2017 April Article: Cassini Completes Final -- and Fateful -- Titan Flyby