Cassini Spacecraft’s long tour comes to an end

For 30 years, David Atkinson has had a recurring thought: the Cassini Spacecraft.

Now it is all coming to an end. At 4:55 a.m. Friday, the spacecraft’s final message will reach Earth.

Then, it will disintegrate in Saturn’s atmosphere.

“Seeing Cassini end is a very sentimental and difficult time. I’m 61 years old, and I have thought about Cassini for 30 years,” said Atkinson, a researcher at NASA’s Jet Propulsion Laboratory in Pasadena, California. “It’s a part of my life and family, and in a few days it’s going away. It’s going to be a very sad day.”

An alumnus of Washington State University and professor emeritus at the University of Idaho, Atkinson began his work with Cassini in 1987. He led a team that developed a probe to measure wind speed and direction on Titan, one of Saturn’s moons.

The Cassini Spacecraft has been orbiting and photographing Saturn for the past 13 years, and it will end its mission by plummeting into Saturn’s atmosphere. Cassini has made numerous discoveries, including a global ocean with hydrothermal activity on one moon, and liquid methane seas on another, according to NASA. By burning up in Saturn’s atmosphere, Cassini will ensure the moons remain pristine and free of bacteria potentially carried by the spacecraft.

Cassini launched from Earth in 1997 and its probe reached Titan – a giant moon orbiting Saturn – on Jan. 14, 2005.

“This was one of the greatest days of my professional career,” Atkinson said.

The probe landed safely on Titan, and an experiment for which Atkinson had waited 18 years was about to begin. However, as Atkinson waited to receive data from Cassini, a red message on his computer screen indicated a problem with a receiver. This receiver was supposed to transmit data from the probe back to Earth.

“My greatest day quickly turned into one of my most difficult days in my professional career,” Atkinson said. “While everyone around me was celebrating, my team and I sat in shock and disbelief.”

It was a simple mistake that briefly devastated the researcher.

“I have talked about this experience to students all over the country, and everybody is fascinated by the feelings I had that day,” Atkinson said. “Students try to relate to my situation. Some have had something go wrong with one of their works that took them weeks or months to complete. But to have 18 years of your life almost taken away by a simple forgotten command, it’s difficult to describe.”

As Atkinson wrestled with the problem, he remembered something a team member said. Using telescopes from Earth, Atkinson and his team were able to pick up the radio signals and retrieve some data from the probe.

With the data they retrieved, Atkinson’s team found that winds on Titan were not what they expected. They expected to find high wind speeds close to the atmosphere and a gradual decrease in speeds closer to the surface. However, they found that as the probe went down 27 miles from the atmosphere, wind speeds dropped to nearly zero, before picking up speed, and then dropping again near the surface.

“This story really shows the robustness in these missions,” Atkinson said.

Today, Atkinson is a member of a team trying to send a probe back to Saturn, as well as two different teams trying to reach Venus.

“Venus, Earth and Mars are sister planets. We have studied Mars for years and years, but Venus is more similar to Earth,” Atkinson said. “We want to know why Venus doesn’t have plate tectonics. We want to know why Venus’ atmosphere has incredibly strong winds, how Venus formed and evolved, and why Venus doesn’t have a magnetic field. Basically, the planets form a laboratory that we can use to better understand the Earth.”