Cassini, the NASA spacecraft which has been orbiting the planet Saturn since 2004, is about to end its mission. Launched in 1997, Cassini has greatly increased scientists’ knowledge of the giant ringed planet, sending both information and breathtaking photographs which have won the robotic space traveler many fans. On September 15, 2017, Cassini will end its mission. The 5,000 pound school bus-sized craft will burn up as it makes a final plunge towards Saturn’s surface.
While Cassini’s fans are thankful for the astronomical knowledge it has provided, many are sad about losing the spacecraft. On September 6, on the social media website Twitter, NASA posted a photo of Cassini with the message, “The main engine cover has been closed for the last time.”
“Good bye, friend!” said one comment. “Made me cry,” read a post by one commenter while another wrote, “So sad the end is near.”
The Final Mission
In the final days of its mission, Cassini still has important work to do. Starting in November 2016, Cassini began a phase of its mission NASA scientists call its Grand Finale. First, it approached a narrow ring called the F Ring, which is located on the outer edge of Saturn’s main rings. Next, it began a series of 22 final orbits around the planet. Each orbit takes less than a week in Earth time. Its last orbit begins September 9.
During its final plunge towards Saturn’s surface, Cassini will continue to collect data which it will send back to Earth. As it falls, it will measure Saturn’s magnetic and gravitational fields, determine the mass of the rings, take samples of the planet’s atmosphere, and provide a final view of Saturn’s moon, Enceladus. Through it all, it will continue to capture images, which will give even more detailed views of the planet.
On September 15, the scientists who have worked on the mission will meet at NASA’s Jet Propulsion Laboratory in Pasadena, California. They will stand by as Cassini points its instruments towards Saturn. The spacecraft will send data and images about what it sees back to Earth. Three hours later, Cassini will reach Saturn’s atmosphere. It will begin plunging through the thick gas clouds that surround the planet. At that point, it will lose its ability to send messages back to Earth. Since it takes transmissions 83 minutes to travel from Saturn to Earth, by the time NASA receives Cassini’s last transmission around 5 a.m, it will have already burned up in Saturn’s atmosphere.
The Cassini mission has been a joint project including NASA, the European Space Agency (ESA), and the Italian space agency, Agenzia Spaziale Italiana (ASI). The Cassini mission has been extremely successful. With the data it has captured, scientists learned more about the formation and behavior of Saturn’s famous system of rings. For example, they learned that the rings were thicker than they first believed.
“We thought the plane of the rings was no taller than two stories of a modern-day building and instead we’ve come across walls more than 2 miles [3 kilometers] high,” says Carolyn Porco, who leads Cassini imaging team based at the Space Science Institute in Boulder, Colorado. “Isn’t that the most outrageous thing you could imagine? It truly is like something out of science fiction.”
In January 2005, a space probe called Huygens carried onboard Cassini parachuted to the surface of Titan, Saturn’s largest moon. Huygens was able to transmit back to NASA for about 90 minutes after making a perfect landing.
During nearly 300 orbits of Saturn, Cassini has been able to collect over 600 gigabytes worth of data. Although this amount of data can fit easily on many modern computers, it has led to a lot of science–so far, about 4,000 different scientific papers have been written with the information Cassini has collected!
Learn more about the history of the Cassini program at NASA.
Watch a video about how the Huygens probe landed on the surface of Titan at the European Space Agency.
Images and Sources
Saturn surface photo: NASA/JPL-Caltech/Space Science Institute
Enceladus photo: NASA/JPL-Caltech/Space Science Institute
Saturn rings as waves photo: NASA/JPL-Caltech/Space Science Institute
Titan photo: NASA/JPL-Caltech/Space Science Institute
All photos public domain