Cassini prepares for ‘grand finale’

This artist’s rendering shows NASA’s Cassini spacecraft above Saturn’s northern hemisphere, heading toward its first dive between Saturn and its rings on April 26, 2017. Image & Caption Credit: NASA/JPL-Caltech

On Wednesday, April 26, 2017, NASA’s Cassini spacecraft will conduct the first in a series of 22 dives between Saturn’s atmosphere and the gas giant’s rings as a part of the mission’s “grand finale”. It will conclude a mission that has spent almost 13 years exploring the Saturnian system.

Cassini’s flight team is making preparations to begin the spacecraft’s final chapter in its 13-year history orbiting Saturn. The mission will end on Sept. 15, 2017, when Cassini enters the ringed planet’s atmosphere, which will, in turn, destroy the storied vehicle, as visualized in a new video released by NASA.

An illustration of the final orbits of the Cassini spacecraft shows the robotic explorer diving between the rings and the planet. The blue lines represent the 22 close flybys while the orange shows the final plunge into Saturn’s atmosphere. Image Credit: NASA

“No spacecraft has ever gone through the unique region that we’ll attempt to boldly cross 22 times,” said Thomas Zurbuchen, the associate administrator for NASA’s Science Mission Directorate, in a news release. “What we learn from Cassini’s daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve. This is truly discovery in action to the very end.”

The dives represent the closest that Cassini has traveled to Saturn since arriving at the ringed planet in 2004. By exploring the region of space between the atmosphere and the rings, it aims to gain a new understanding of how gas giant planets and their associated ring systems form and evolve through time. The flight plan, which has been under development since a 2010 NASA decision to end the mission this year, uses expertise that has been gained over the course of the mission.

The plan to send Cassini into Saturn’s atmosphere was devised over concerns that, once the spacecraft runs out of fuel, it could hit one of the potentially habitable moons orbiting the planet, including Enceladus.

Designing the flight plan to pass between Saturn’s atmosphere and rings will allow Cassini to refine its orbit over the coming months while also maximizing the scientific return of its final maneuver.

“This planned conclusion for Cassini’s journey was far and away the preferred choice for the mission’s scientists,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “Cassini will make some of its most extraordinary observations at the end of its long life.”

During the final months, the mission team hopes to gain insight into Saturn’s internal structure, the origin of its rings, obtain the first-ever sampling of the planet’s atmosphere and ring particles, and capture close-up views of the gas giant’s clouds and innermost rings.

The mission team is doing a final check of commands to be sent to the probe on April 11, which will direct Cassini to begin its final orbits following its final close pass of Titan on April 22. The gravity of Titan will bend Cassini’s flight path and shrink its orbit toward Saturn with the first close flyby of the grand finale.

“Based on our best models, we expect the gap to be clear of particles large enough to damage the spacecraft,” said Earl Maize, Cassini’s project manager at JPL. “But we’re also being cautious by using our large antenna as a shield on the first pass, as we determine whether it’s safe to expose the science instruments to that environment on future passes. Certainly, there are some unknowns, but that’s one of the reasons we’re doing this kind of daring exploration at the end of the mission.”

Following a distant flyby of Titan in mid-September, Cassini’s flight path will be bent further to dive into Saturn’s atmosphere.

As Cassini enters the atmosphere, its thrusters will its the remaining fuel to keep its antenna pointed toward Earth for as long as possible, transmitting data from several instruments to provide data until the signal is lost.

“Cassini’s grand finale is so much more than a final plunge,” said Spilker. “It’s a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the mission.”

Video courtesy of JPL

Tagged: Cassini Grand Finale Jet Propulsion Laboratory Lead Stories NASA Saturn

Paul Knightly

Paul is currently a graduate student in Space and Planetary Sciences at the University of Akransas in Fayetteville. He grew up in the Kansas City area and developed an interest in space at a young age at the start of the twin Mars Exploration Rover missions in 2003. He began his studies in aerospace engineering before switching over to geology at Wichita State University where he earned a Bachelor of Science in 2013. After working as an environmental geologist for a civil engineering firm, he began his graduate studies in 2016 and is actively working towards a PhD that will focus on the surficial processes of Mars. He also participated in a 2-week simluation at The Mars Society's Mars Desert Research Station in 2014 and remains involved in analogue mission studies today. Paul has been interested in science outreach and communication over the years which in the past included maintaining a personal blog on space exploration from high school through his undergraduate career and in recent years he has given talks at schools and other organizations over the topics of geology and space. He is excited to bring his experience as a geologist and scientist to the Spaceflight Insider team writing primarily on space science topics.