he data collected by the photopolarimeter helped scientists estimate the weight and age of Saturn's rings and piece together the intricate structure of Saturn's F ring, which appears to be made up of braided ringlets.
"When the books are written about this mission, this (instrument) will be the highlight of Voyager 2," Hord told the Daily Camera in 1981 after the spacecraft visited Saturn.
The CU photopolarimeter also offered researchers insights into the structure of Jupiter's Great Red Spot and into the makeup of the doughnut-shaped ring around Jupiter, known as the Io torus, which scientists now know is formed by volcanic eruptions on the surface of Io, one of Jupiter's moons.
Tracking lightning
The second CU instrument riding on the two Voyagers was designed to listen.
The two planetary radio astronomy instruments picked up radio emissions from all four of the giant planets as the spacecraft passed by, as well as emissions from the sun and Earth.
"What we have is essentially a very sophisticated radio receiver mounted onboard both spacecraft," said James Warwick, CU's principal investigator for the radio astronomy instrument. "The remarkable thing about these receivers is they operate at very low frequencies from the point of view of radio astronomy."
Radio astronomy has a long history in the Boulder area that stretches back decades before Voyager was launched. Scientists built ground-based receivers at a site north of Boulder and, later, at another site near Nederland.
"We had been observing radio signals from Jupiter and the sun and various radio sources sprinkled over the sky since 1954," said Warwick, who is now retired and living in California.
The Voyager mission gave Boulder scientists the chance to observe those radio signals closer to the source. As the radio astronomy instruments made their way through the solar system onboard Voyager 1 and 2, they sent back information that allowed scientists to learn about the strength of the giant planets' magnetic fields and, because those fields are tied to the way the planets spin, about their rotation as well.
"Charged particles spiral around the (magnetic) field lines, and as they do, they generate radio emissions," said Joe Romig, a former doctoral student of Warwick's who worked on the project. "Because the magnetic fields are inclined to the axis of rotation, as the planet rotates, the radio emission is modulated. From that, we can determine the rotation of the deep interior of the planet."
The two radio astronomy instruments showed scientists that Uranus and Neptune had weaker magnetic fields than Jupiter and Saturn, but those magnetic fields were tilted -- 40 degrees to 60 degrees -- relative to the rotation of the planets.
But the discovery that both Romig and Warwick recall as being among the most interesting was going on in the planets' atmospheres.
"One of the remarkable things we discovered, I believe, at Saturn was we found we had radio emissions that were very similar to what is produced by terrestrial lightning," Warwick said.
After the discovery on Saturn, researchers went back to comb through the data from Jupiter, where they also found evidence of electrostatic discharges, Romig said.
And again, when the radio astronomy instrument on Voyager 2 made it to Neptune and Uranus, more lightning-like phenomena were recorded.
"We picked up lightning," Romig said. "We got lightning from those giant planets."
Just won't quit
Nearly 35 years after launching, both Voyagers still are heading out to explore the unknown and both are still talking to Earth long beyond their expected life spans. In part, that's thanks to the increased ability of scientists on Earth to still pick up messages from the spacecraft.
"As we improve our facilities on the ground, our sphere of communication is expanding faster than Voyager is flying away," CU's Esposito said.
But no matter how good the ground facilities are, the two Voyager spacecraft -- launched during an era when personal computers were just beginning to hit the market -- have to be in good shape to continue communicating with Earth.
"The handheld calculator that I was using (in 1979) had more memory and more sophistication than the computers onboard Voyager," said Simmons, the experiment manager for the photopolarimeter. "And yet, with a very simply engineered computer technology, that spacecraft has been able to do all kinds of things, and the engineers who programmed it have been so creative in figuring out how to do something so sophisticated with such a basic computer system."
The working photopolarimeter on Voyager 2 was flipped off in 1992, since it was designed to look at larger objects such as planets, but the CU-designed radio astronomy instrument is still able to send back information, and it may continue to help researchers learn about the heliopause and what lies beyond.
The radio astronomy instrument, built by Colorado-based Martin Marietta, has spent most of its days living in empty space, but it still functions beautifully, Warwick said.
"We're getting out of it everything we hoped to get out of it in the first place -- and so much more besides -- because the doggone thing just won't quit," Warwick said.
by Camera Staff Writer Laura Snider dailycamera.com.