We’ve enjoyed the benefits of having NASA’s Cassini spacecraft in orbit of Saturn for years. It’s almost like it’s always been there, looking down on one of the most awe-inspiring sights in the solar system. It only seems like forever because Cassini has sent back so much amazing stuff. Cassini began its observation of Saturn in 2004, and now it’s time for the probe’s final act as it runs low on fuel. Later this month, the spacecraft will begin a downward spiral that eventually sends it into Saturn’s crushing atmosphere. It’ll see some amazing things on the way, though.
Cassini was launched in October of 1997, taking almost seven years to reach Saturn. It arrived carrying the Huygens lander, which was successfully deployed on the surface of Saturn’s moon Titan in 2005. It was the first, and as far only landing to take place in the outer solar system. After deploying Huygens, Cassini continued its orbital observation of Saturn and its moons, but it did so from a distance. NASA didn’t want to risk damage to the probe from Saturn’s icy ring material, but they’ll be much more daring in the coming months. This mission made a number of discoveries, including the presence of hydrocarbon lakes on Titan and the water plumes on Enceladus.
Mission managers at NASA’s Jet Propulsion Laboratory (JPL) call Cassini’s final maneuvers the “Grand Finale.” Beginning on April 22nd, Cassini will expend some of its dwindling fuel to execute a close flyby of Titan, which is pretty massive as far as moons go. Titan’s gravity will slingshot Cassini toward Saturn where it will (hopefully) pass between Saturn’s upper atmosphere and the innermost D-ring. That gap is just 1,200 miles (1,930 kilometers) wide, and it’s not completely empty. Cassini is expected to be pelted by small particles, which can pack a punch as the probe is rocketing past as more than 76,000 mph (122,000 kph). NASA will orient the probe to shield the antenna from direct impacts.
Cassini will be closer to Saturn than ever before during the Grand Finale, and NASA plans to use that opportunity to the fullest. The probe will use its mass spectrometer to analyze the gases in Saturn’s upper atmosphere, sending back the most detailed data ever on the composition of a gas giant.
This slingshot maneuver is not the end of the Grand Finale — Cassini is expected to complete 22 of these extremely close orbits before it’s finally pulled down into Saturn’s atmosphere. Cassini will hit Saturn’s atmosphere on September 15th, beginning its final 3-minute dive into oblivion. NASA plans to use the last of Cassini’s fuel to keep the antenna pointed toward Earth so it can transmit data for as long as possible.