Each of these last 22 orbits takes about six and a half days to complete. They begin April 22 and end Sept. 15. When Cassini is nearest to Saturn during each orbit, the spacecraft’s speed ranges between 75,000 and 78,000 miles per hour (121,000 and 126,000 kilometers per hour), depending on the orbit. The Grand Finale orbits are so named because they not only carry Cassini to its end, but because they are truly grand. The spacecraft flies through an unexplored region of the Saturnian system, producing unique images and attempting to solve longtime mysteries, such as the mass of Saturn’s rings and the planet’s rotation rate — the length of a Saturn day. And then during Cassini’s last five orbits, the spacecraft dips down to directly sample Saturn’s upper atmosphere.
The summaries posted on this page for each Grand Finale orbit include only a few highlights of the many unparalleled science investigations that Cassini performs during these unprecedented orbits. Also, because Saturn is a gas giant, Cassini can’t be described as being a certain distance from the planet’s “surface.” So, to convey Cassini’s distance from Saturn, each summary also includes the spacecraft’s closest approach to Saturn’s 1-bar level for that orbit. A bar is the atmospheric pressure you experience on Earth at sea level.
The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado. For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org . Cassini’s Grand Finale orbits — the final orbits of its nearly 20-year mission — the spacecraft travels in an elliptical path that sends it diving at tens of thousands of miles per hour through space between the rings and the planet where no spacecraft has ventured before on September 15, 2017.