Published: Sept. 15, 2017

CU Aerospace Cassini Memories

Bobby Braun  Bobby Braun, Smead Aerospace Professor and Dean of the College of Engineering and Applied Science: “Years ago, I was involved in a JPL-led review of the European Space Agency Huygens probe entry, descent and landing flight system and mission design to Titan.”

Matt Rhode Matt Rhode, Lab Coordinator, Smead Aerospace: “I built the infrared spectrometer housing when I was a student employee here in 1996, working in what at the time was the electrical engineering machine shop, now in use by Bioserve.”

Dylan Boone (Smead Scholar/Aerospace alumnus): Navigation Engineer, JPL: “I’ve worked on Cassini for 4 years now as an Orbit Determination Analyst on the Navigation Team. We fly the spacecraft, determining where it is, where it is going, and performing maneuvers to hit flyby targets and achieve science goals of the mission.

"(My) responsibilities include processing spacecraft tracking data from NASA’s Deep Space Network to compute orbit solutions, predicting the spacecraft’s future location, and reconstructing past trajectories. During my time on Cassini, the Navigation Team has supported the following activities: science observation of the icy plumes of Enceladus through occultation, discovery of tiny moonlets in Saturn’s rings, the final flyby of Saturn’s largest moon, Titan, and five low periapses traveling in the space between Saturn’s rings and cloud tops. At 5:55am MDT on Friday morning, Cassini will transition from spacecraft to fireball in the space of one minute."

CU Boulder Professor Larry Esposito has been eying the fabulous rings of Saturn for much of his career, beginning as a team scientist on NASA’s Pioneer 11 mission when he discovered the planet’s faint F ring in 1979.

He followed that up with observations of Jupiter’s and Saturn’s rings from the Voyager and Galileo spacecraft, which carried instruments designed and built at CU Boulder. Now, as the principal investigator on CU Boulder’s $12 million Ultraviolet Imaging Spectrograph (UVIS) on the Cassini-Huygens mission to Saturn, Esposito and his Cassini colleagues are feeling a bit somber: The spacecraft has run out of fuel and was intentionally disintegrated in Saturn’s dense atmosphere early on the morning of Sept. 15.

“We are still making discoveries about the Saturn system studying the Cassini data, and we expect to be making them for some time,” said Esposito of CU Boulder’s Laboratory for Atmospheric and Space Physics (LASP). “But it is a bittersweet ending to a mission that has fascinated us as scientists and enthralled the public with images and new findings for many years.”

Discoveries galore

The UVIS instrument suite, a set of telescopes used to measure ultraviolet light from the Saturn system, has been used to study the structure and evolution of Saturn's rings; the chemistry, clouds and energy balance of Saturn and Titan; and the surfaces and atmospheres of some of Saturn's 62 known moons, said Esposito.

Launched in 1997 and pulling up at Saturn in 2004 for the first of hundreds of orbits through the planet’s system, the mission has fostered scores of dazzling discoveries. These include in-depth studies that date and even weigh the astonishing rings, the discovery of methane lakes on the icy moon Titan, water plumes found squirting from the moon Enceladus and close-up views of the bright auroras at the planet's poles.

One of Esposito’s favorite discoveries using UVIS was the detection of a huge cloud of neutral oxygen atoms in the Saturn system on approach in 2003, which puzzled scientists for years. Subsequent research by the Cassini team indicated the oxygen atoms were coming from a salty, subterranean ocean on Enceladus, which scientists think may have conditions favorable for primitive life.

How old are Saturn’s rings?

Many discoveries by Esposito and his UVIS team involve Saturn’s rings—made up of ice, rocks and moonlets as large as Mount Everest—the age of which have been debated for decades. Esposito, who used observations from the Voyager mission to compare the rings of Saturn, Jupiter and Neptune, believes Saturn’s rings may be as old as the solar system, which is believed to have formed some 4.6 billion years ago.

“When the two Voyager spacecraft passed by Saturn in 1980 and 1981, we thought the rings were relatively young,” Esposito said. “But data from Cassini are consistent with the picture that Saturn has had rings throughout its history.

“We see extensive, rapid recycling of ring material in which moons are continually shattered into ring particles, which then gather and reform moons.”

Other UVIS team members from CU Boulder include Ian Stewart, George Lawrence, William McClintock, Alain Jouchoux, Greg Holsclaw, Emilie Royer, Anya Portyankina and Michael Aye.

Esposito likened the ever-changing rings at Saturn to construction in Beijing, China, where marble from structures erected during the Ming Dynasty (1368–1644) is being recycled to build new structures today.

“The same sort of thing is happening with Saturn’s rings,” Esposito said. “They are renewed continually, so the rings themselves can be ancient, but the structures we see today are just part of their current manifestation. We have even watched the rings changing over the course of this mission.”

Cassini’s grand finale

The UVIS instrument was turned on during Cassini’s final dive into Saturn’s atmosphere and routed data to Earth until its final moments.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

CU Boulder is the only university in the world to have designed and built instruments that have visited every planet in the solar system, plus Pluto. LASP students control four NASA satellites from campus, and about 120 undergraduate and graduate students working are there on different aspects of flight projects, ranging from engineering and spacecraft operations to data management and science analysis.