Cassini: The Grand Finale
Almost 20 years ago,the Cassini orbiter began its 2.2 billion mile journey to Saturn with a liftoff at Cape Canaveral. It then spent 7 years in the cold vacuum of space as it journeyed through the solar system; and on Thursday, July 1, 2004 it became the first spacecraft to orbit Saturn. For over a decade Cassini observed and shared the fascinating world of Saturn, its dancing rings and its icy moons. Cassini revealed astounding details about methane rivers, liquid water, and possible ingredients that might harbor life.
Cassini’s discoveries forced scientists to revise their understanding of the giant ringed orb hanging in our sky. Now, Cassini’s grand adventure is reaching its majestic end; one last assignment. Later this month,
Cassini will end its historic expedition with 22 daring dives into the gap between Saturn and the innermost ring. To protect the worlds like Enceladus and Titan, moons with liquid water oceans under their ice crusts that might harbour conditions for life, Cassini will conclude its journey.
On September 15th 2017, Cassini will complete its last ever orbit and make a final plunge into Saturn’s atmosphere. Using the last of its fuel, Cassini will fight to keep its antenna pointing at Earth as it transmits its last data and farewell before being vaporised by the pressure in a glorious blast, in the skies of Saturn, as it becomes one with the planet.
- April 22: Titan 126 Flyby at 6:08 a.m. UTC (11:08 p.m. PDT on April 21)
- April 23: First Grand Finale Orbit Begins at 3:46 a.m. UTC (8:46 p.m. PDT on April 22)
- April 26: First Ringplane Crossing at 9 a.m. UTC (2 a.m. PDT)
- May 24: Northern Summer Solstice Begins
- Sept. 15: Cassini’s Final Entry into Saturn’s Atmosphere begins at 10:44 a.m. UTC (3:44 a.m. PDT). Spacecraft loss of signal comes one minute later at 10:45 a.m. UTC (3:45 a.m. PDT).
- Sept. 15: Final signal received on Earth at 12:08 p.m. UTC (5:08 a.m. PDT)
As Cassini plunges past Saturn, the spacecraft will collect some incredibly rich and valuable information that was too risky to obtain earlier in the mission:
- The spacecraft will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the planet is arranged internally, and possibly helping to solve the irksome mystery of just how fast Saturn is rotating.
- The final dives 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.
Discoveries to the end
Cassini’s final images will have been sent to Earth several hours before its final plunge, but even as the spacecraft makes its fateful dive into the planet’s atmosphere, it will be sending home new data in real time. Key measurements will come from its mass spectrometer, which will sample Saturn’s atmosphere, telling us about its composition until contact is lost.
While it’s always sad when a mission comes to an end, Cassini’s finale plunge is a truly spectacular end for one of the most scientifically rich voyages yet undertaken in our solar system. From its launch in 1997 to the unique Grand Finale science of 2017, the Cassini-Huygens mission has racked up a remarkable list of achievements.
Why End the Mission?
By 2017, Cassini will have spent 13 years in orbit around Saturn, following a seven-year journey from Earth. The spacecraft is running low on the rocket fuel used for adjusting its course. 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 their potential to contain habitable – or at least “prebiotic” – environments.
In order to avoid the unlikely possibility of Cassini someday colliding with one of these moons, NASA has chosen to safely dispose of the spacecraft in the atmosphere of Saturn. This will ensure that Cassini cannot contaminate any future studies of habitability and potential life on those moons.
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