This illustration shows NASAs Cassini spacecraft above Saturn's northern hemisphere prior to one of its 22 grand finale dives. Credits: NASA/JPL-Caltech

After almost 20 years in space, NASAs Cassini spacecraft, controlled from the Space Flight Operations Facility at the Jet Propulsion Laboratory in Pasadena, will enter the final chapter of its remarkable story of exploration: its Grand Finale.of 22

The Grand Finale actually began in April when the spacecraft began a series weekly dives into the space between Saturn and its icy rings. Cassini began its five final orbits around Saturn on Sunday, August 13. This will end with a final plunge into Saturns atmosphere on September 15. During this time, its instruments send back to Earth new and unique information about what will be its closest encounter with the planet, before it finally burns up like a meteor in Saturns dense atmosphere and becomes part of the planet itself.

As it makes these five dips into Saturn, followed by its final plunge, Cassini will become the first Saturn atmospheric probe, said Linda Spilker, Cassini project scientist at JPL. Its long been a goal in planetary exploration to send a dedicated probe into the atmosphere of Saturn, and were laying the groundwork for future exploration with this first foray.

On these final dives, the spacecraft is expected to encounter an atmosphere dense enough to require the use of its small rocket thrusters to maintain stability conditions similar to what it encountered during many of its close flybys of Saturns moon Titan, which has its own dense atmosphere.

Cassinis Titan flybys prepared us for these rapid passes through Saturns upper atmosphere, said Earl Maize, Cassini project manager. Thanks to our past experience, the team is confident that we understand how the spacecraft will behave at the atmospheric densities our models predict.

No other mission has ever explored this unique region in the planets surroundings. Scientists at JPL say what can be learned from these final orbits will help to improve mans understanding of how giant planets and planetary systems everywhere form and evolve.

On September 11, a distant encounter with the moon Titan will slow Cassinis orbit around Saturn and bend its path slightly to send the spacecraft toward its September 15 plunge into the planet.

During the half-orbit plunge, the plan is to have seven Cassini science instruments, including the ion and neutral mass spectrometer (INMS) turned on and reporting measurements in near real-time. With these, the spacecraft will be able collect some incredibly rich and valuable information that was too risky to obtain earlier in the mission.

The spacecraft will make detailed maps of Saturns 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 also vastly improve mans knowledge of how much material is in the rings and how they were formed.

Cassinis particle detectors will also sample icy ring particles being funneled into the atmosphere by Saturns magnetic field.

Its cameras will take amazing, ultra-close images of Saturns rings and clouds and send those back to earth, almost in real-time. Other instruments will make detailed, high-resolution observations of Saturns auroras, temperature, and the vortexes at the planets poles. Its radar will peer deep into the atmosphere to reveal small-scale features that the spacecraft could not observe prior to the Grand Finale.

At this final plunge, the spacecraft is expected to reach an altitude where atmospheric density is about twice what it encountered during its final five passes. Once Cassini reaches that point, its thrusters will no longer be able to work against the push of Saturns atmosphere to keep the spacecrafts antenna pointed toward Earth, and contact will permanently be lost. The spacecraft will break up like a meteor moments later, ending its long and rewarding journey.

While its always sad when a mission comes to an end, Cassinis finale plunge is a truly spectacular end for one of the most scientifically rich voyages yet undertaken in the solar system. From its launch in 1997 to the unique Grand Finale science of 2017, the Cassini-Huygens mission (Huygens is the European probe that the spacecraft launched in 2005 into the moon Titan) has racked up a remarkable list of achievements.

This Grand Finale is still a controlled dive until its final seconds when it burns up and loses contact. After spending 13 years in orbit around Saturn following a seven-year journey from Earth, the spacecraft is running low on fuel, and mission operators are afraid the situation will prevent them from controlling Cassinis course.

To avoid the remote possibility of Cassini colliding with the moons Titan and Enceladus and contaminating them, NASA has chosen to safely dispose of the spacecraft in the atmosphere of Saturn, thereby ensuring future missions could still continue studying the habitability and potential life scientists have observed for years on those moons, courtesy of Cassini.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL manages the mission for NASAs Science Mission Directorate in Washington. JPL also designed, developed and assembled the Cassini orbiter.

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JPL's Space Flight Operations Facility Prepares for Cassini Mission's 'Grand Finale' - Pasadena Now