Update – Sept. 11, 2017: This feature (originally published on April 25, 2017) has been updated to reflect Cassini's current mission status, as well as new lessons and activities.


In the News

After almost 20 years in space, NASA's Cassini spacecraft has begun the final chapter of its remarkable story of exploration. This last phase of the mission has delivered unprecedented views of Saturn and taken Cassini where no spacecraft has been before – all the way between the planet and its rings. On Friday, Sept. 15 Cassini will perform its Grand Finale: a farewell dive into Saturn’s atmosphere to protect the environments of Saturn’s moons, including the potentially habitable Enceladus.

Animation of Cassini Pi in the Sky 4 math problem

Lessons All About Saturn

Explore our collection of standards-aligned lessons about NASA's Cassini mission.

How It Works

On April 22, Cassini flew within 608 miles (979 km) of Saturn’s giant moon Titan, using the moon’s gravity to place the spacecraft on its path for the ring-gap orbits. Without this gravity assist from Titan, the daring, science-rich mission ending would not be possible.

Cassini is almost out of the propellant that fuels its main engine, which is used to make large course adjustments. A course adjustment requires energy. Because the spacecraft does not have enough rocket fuel on board, Cassini engineers have used an external energy source to set the spacecraft on its new trajectory: the gravity of Saturn’s moon Titan. (The engineers have often used Titan to make major shifts in Cassini’s flight plan.)

Titan is a massive moon and thus has a significant amount of gravity. As Cassini comes near Titan, the spacecraft is affected by this gravity – and can use it to its advantage. Often referred to as a “slingshot maneuver,” a gravity assist is a powerful tool, which uses the gravity of another body to speed up, slow down or otherwise alter the orbital path of a spacecraft.

In this installment of the "Crazy Engineering" video series from NASA's Jet Propulsion Laboratory, host Mike Meacham talks to a Cassini engineer about astrodynamics and how it was used to design the Saturn mission's Grand Finale.

When Cassini passed close by Titan on April 22, the moon’s gravity pulled strongly on the spacecraft. The flyby gave Cassini a change in velocity of about 1,800 mph (800 meters per second) that sent the spacecraft into its first of the ring-gap orbits on April 23. On April 26, Cassini made its first of 22 daring plunges between the planet and its mighty rings.

Cassini final orbits petal plot

This graphic illustrates Cassini's trajectory, or flight path, during the final two phases of its mission. The 20 Ring-Grazing Orbits that Cassini made between November and April 2017 are shown in gray; the 22 Grand Finale Orbits are shown in blue. The final partial orbit is colored orange. + Enlarge image

Up-close image of Saturn's clouds from Cassini

Clouds on Saturn take on the appearance of strokes from a cosmic brush thanks to the wavy way that fluids interact in Saturn's atmosphere. This images used in this false-color view were taken with the Cassini spacecraft narrow-angle camera on May 18, 2017. Image credit: NASA-JPL/Caltech/SSI | › Full image and caption

Animated image of Saturn's moon Enceladus from Cassini

This animated image of Saturn's moon Enceladus is a composite of six images taken by the Cassini spacecraft on Aug. 1, 2017. Image credit: NASA-JPL/Caltech/SSI | › Full image and caption

Up-close image of Saturn's rings from Cassini

These are the highest-resolution color images of any part of Saturn's rings, to date, showing a portion of the inner-central part of the planet's B Ring. The view is a mosaic of two images that show a region that lies between 61,300 and 65,600 miles (98,600 and 105,500 kilometers) from Saturn's center. Image credit: NASA-JPL/Caltech/SSI | › Full image and caption

As Kepler’s third law indicates, Cassini traveled faster than ever before during these final smaller orbits. Cassini's orbit continued to cross the orbit of Titan during these ring-gap orbits. And every couple of orbits, Titan passed near enough to give the spacecraft a nudge. One last nudge occured on September 11, placing the spacecraft on its final, half-orbit, impact trajectory toward Saturn.

Because a few hardy microbes from Earth might have survived onboard Cassini all these years, NASA has chosen to safely dispose of the spacecraft in the atmosphere of Saturn to avoid the possibility of Cassini someday colliding with and contaminating moons such as Enceladus and Titan that may hold the potential for life. Cassini will continue to send back science measurements as long as it is able to transmit during its final dive into Saturn.

Why It’s Important

Flying closer than ever before to Saturn and its rings has provided an unprecedented opportunity for science. During these orbits, Cassini’s cameras have captured ultra-close images of the planet’s clouds and the mysterious north polar hexagon, helping us to learn more about Saturn’s atmosphere and turbulent storms.

The cameras have been taking high-resolution images of the rings, and to improve our knowledge of how much material is in the rings, Cassini has also been conducting gravitational measurements. Cassini's particle detectors have sampled icy ring particles being funneled into the atmosphere by Saturn's magnetic field. Data and images from these observations are helping bring us closer to understanding the origins of Saturn’s massive ring system.

Cassini has also been making detailed maps of Saturn's gravity and magnetic fields to reveal how the planet is structured internally, which could help solve the great mystery of just how fast Saturn is rotating.

On its first pass through the unexplored 1,500-mile-wide (2,400-kilometer) space between the rings and the planet, Cassini was oriented so that its high-gain antenna faced forward, shielding the delicate scientific instruments from potential impacts by ring particles. After this first ring crossing informed scientists about the low number of particles at that particular point in the gap, the spacecraft was oriented differently for the next four orbits, providing the science instruments unique observing angles. For ring crossings 6, 7 and 12, the spacecraft was again oriented so that its high-gain antenna faced forward.

Fittingly, Cassini's final moments will be spent doing what it does best, returning data on never-before-observed regions of the Saturnian system. On September 15, just hours before Cassini enters Saturn's atmosphere for its Grand Finale dive, it will collect and transmit its final images back to Earth. During its fateful dive, Cassini will be sending home new data in real time informing us about Saturn’s atmospheric composition. It's our last chance to gather intimate data about Saturn and its rings – until another spacecraft journeys to this distant planet.

Explore the many discoveries made by Cassini and the story of the mission on the Cassini website.

Teach It

Use these standards-aligned lessons to get your students excited about the science we have learned and have yet to learn about the Saturnian system.

Explore More

TAGS: Saturn, Titan, Cassini, Grand Finale, Teachable Moments, Kepler's Laws, K-12, Lessons,

  • Ota Lutz
READ MORE

When the offer letter arrived from NASA’s Jet Propulsion Laboratory, Kiana Williams could hardly believe it. Thousands of science and engineering students apply each year for internships at the lab known for its dare-anything missions to the planets and beyond. Williams never expected it would be her first internship.

“It actually took me about a week to accept that it was a real offer and that I’d actually be coming to intern at NASA/JPL,” she said.

Kiana Williams at NASA's Jet Propulsion Laboratory

Mechanical engineering student Kiana Williams grew up near JPL in Southern California, but she never thought to apply for an internship until JPL's Education Office visited her university in Alabama. Now, a first-time intern, she says she realizes, "Oh, I can do this." Image credit: NASA/JPL-Caltech

This summer, Williams is joining more than 700 undergraduate, graduate and doctoral students for internships at JPL in Pasadena, California. Over 10 weeks, they will design new ways to study stars, investigate icy moons thought to be hospitable to life, and even help choose a landing spot for the next Mars rover.

“I get the opportunity to design an entire space telescope from top to bottom,” said Williams, a senior mechanical engineering student at Tuskegee University in Alabama. “It’s kind of a big task, but at the same time it’s fun, so it makes my day go really quickly.”

One of 10 NASA field centers, JPL is the birthplace of spacecraft and instruments that have explored every planet in the solar system, studied our home planet and looked beyond to discover new worlds. It doesn’t just design and build spacecraft, it also operates them, and collects and studies the science they return.

“It’s the only place in the world where everyone needed to conceive of, design, build, launch and land spacecraft, get the science data and write the papers about that science data are all in one place,” said Matt Golombek, a JPL scientist whose interns over the years have helped choose the landing sites for all five Mars rovers and landers since Pathfinder in 1997.

Scientist Matt Golombek with his summer interns at NASA's Jet Propulsion Laboratory
The self-proclaimed "landing site dude," Matt Golombek brings in a host of geology students each year to help identify landing sites on Mars. He has five students this summer helping with site selections for three upcoming missions, including Mars 2020. He says it's rewarding to see how students' JPL experience has a positive impact on their future no matter what they go on to do. (From left to right: Marshall Trautman, Matt Golombek, Rachel Hausman, Carol Hundal, Shannon Hibbard.) Image credit: NASA/JPL-Caltech

The lab’s internship programs give students studying everything from aerospace engineering to computer science and chemistry the chance to do research with NASA scientists, build spacecraft, and create new technology for future missions.

With more than 20 active spacecraft plus a to-do list that includes missions to Mars, Jupiter’s moon Europa and the asteroid belt, JPL has no shortage of projects ripe for students who are eager for careers in space exploration.

Nirmal Patel at NASA's Jet Propulsion Laboratory

Nirmal Patel says that in addition to the wow-factor of testing parts for a Mars rover, his JPL internship is a chance to meet other engineers and scientists all united in a common goal. "Here, everyone wants to explore. And when you have that common goal, it has a different atmosphere," he said. Image credit: NASA/JPL-Caltech

“It’s just amazing knowing that what we’re doing now will also be replicated on Mars in a few years,” said Nirmal Patel, a mechanical engineering student at the University of Michigan who is testing parts for the Mars 2020 rover. “It’s surreal almost. I’m still a student but I’m getting to have an impact on this project.”

David Dubois, a three-time intern who studies planetary science at the University of Versailles Saint Quentin near Paris, returned to JPL this summer to continue his research on icy moons around Saturn, Jupiter and Neptune. Using data from the Cassini mission (which will end its nearly 13-year mission at Saturn this September) he is modeling the atmosphere of Saturn’s moon Titan to better understand its chemical environment – and maybe discover if it could support life.

He says that in addition to access to one-of-a-kind data directly from spacecraft, JPL offers the opportunity to explore new fields of science and even career paths, if students are open to it.

“Being open is certainly something that I’ve learned from JPL, not being afraid of tackling different problems in different fields,” said Dubois, who is about to publish his first paper as a lead author based on his research at JPL.

David Dubois at NASA's Jet Propulsion Laboratory

When he's not doing research, David Dubois says he focuses much of his time on outreach, which is one of his other passions. This year, he traveled to India with a friend to visit schools and villages and encourage students there to pursue science. "I like to say that I think anybody is a scientist," he said, "as long as you try to provide an answer to questions around you." Image credit: NASA/JPL-Caltech

It’s precisely that exposure to its unique career offerings in science, technology, engineering and math – and a foot in the door – that JPL’s Education Office, which manages the lab’s internship programs, is working to provide to more students.

“Our students are operating right alongside the mentors and participating in the discovery process,” said Adrian Ponce, who manages JPL’s higher education group. “It’s a fantastic opportunity for them, and it’s also a great opportunity for JPL. Our internship programs are designed to bring in students from diverse backgrounds and underrepresented communities who share new ways of thinking and analyzing challenges. Many of them will become the next generation of innovators – and not just at JPL.”

For Williams, who plans to continue toward a master’s degree in design engineering after she graduates in December, her time at JPL is confirmation that she’s on the right path and has the motivation to keep going.

“It makes me feel like school is worth it,” said Williams of her internship experience so far. “All the stress I’m going through at school will be worth it because you can find places that are like JPL, that make your job fun.”

Explore JPL’s summer and year-round internship programs and apply at: https://www.jpl.nasa.gov/edu/intern

The laboratory’s STEM internship and fellowship programs are managed by the JPL Education Office. Extending the NASA Office of Education’s reach, JPL Education seeks to create the next generation of scientists, engineers, technologists and space explorers by supporting educators and bringing the excitement of NASA missions and science to learners of all ages.

TAGS: Intern, Mars 2020, Europa, Cassini, Titan, Science, Engineering, Missions

  • Kim Orr
READ MORE