After almost 20 years in space, the Cassini mission will end on September 15, 2017 at 5:07 a.m. PDT (8:07 a.m. EDT). Here's how it will happen:
In late 2016, the Cassini spacecraft will begin a completely new type of mission at Saturn. During its final months, the intrepid spacecraft's orbit will carry it high above the planet's north pole and then send it plunging between the planet and the innermost edge of its dazzling rings.
Beginning on Nov. 30, 2016, Cassini will repeatedly climb high above Saturn's north pole, then plunge to a point just outside the narrow F ring (the edge of the main rings), completing 20 such orbits. Then, on April 22, 2017, Cassini will leap over the rings to begin its final series of daring dives between the planet and the inner edge of the rings. This is the Cassini "Grand Finale." After 22 of these orbits, each taking six days to complete, the spacecraft, will plunge into the upper atmosphere of the gas giant planet, where it will burn up like a meteor, ending the epic mission to the Saturn system.
As it plunges past Saturn during the Grand Finale, Cassini will collect some incredibly rich and valuable information that the mission’s original planners might never have imagined:
- The spacecraft will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the planet is arranged on the inside, and possibly helping to solve the irksome mystery of just how fast the interior is rotating.
- It will vastly improve our knowledge of how much material is in the rings, bringing us closer to understanding their origins.
- Cassini’s particle detectors will sample icy ring particles being funneled into the atmosphere by Saturn’s magnetic field.
- Its cameras will take amazing, ultra-close images of Saturn’s rings and clouds.
No other mission has ever explored this unique region so close to the planet. What we learn from these activities will help to improve our understanding of how giant planets – and families of planets everywhere – form and evolve. And at the end of its final orbit, as it falls into Saturn’s atmosphere, Cassini completes its 20-year mission by ensuring the biologically interesting worlds Enceladus and Titan could never be contaminated by hardy microbes that might have stowed away and survived the journey intact. It’s inspiring, adventurous and romantic – a fitting end to this thrilling story of discovery.
Why End the Mission?
By 2017, Cassini will have spent 13 years in orbit around Saturn, following seven years of “cruise” on its way outward from Earth. The spacecraft is beginning to run low on rocket fuel. If left unchecked, this situation would eventually prevent mission operators from controlling the course of the spacecraft.
Two moons of Saturn, Enceladus and Titan, have captured news headlines over the past decade as Cassini data revealed the moons’ potential to contain habitable – or at least "pre-biotic” – environments.
In order to avoid the unlikely possibility of Cassini someday colliding with one of these moons and contaminating them with any hardy Earth microbes that might have survived on the spacecraft, NASA has chosen to safely dispose of the spacecraft in the atmosphere of Saturn.