In the 1970s and 1980s, Charley Kohlhase led the mission design team at the Jet Propulsion Laboratory that selected the best flight paths for Voyagers 1 and 2 and chose the aiming points at each outer planet to return the best science. He also created, with Jim Blinn, the first computer-graphic flyby animations for each encounter. Kohlhase, who spent 40 years at NASA and received the agency’s Distinguished Service Medal, also found time to write the JPL “Travel Guides” given to the press before the Uranus and Neptune encounters, and has an asteroid (13801 Kohlhase) named in his honor. An exhibited photographer, digital artist, published author, and environmentalist, Kohlhase still oversees studies and design activities for several space missions. He lives in Pasadena, California, and has two daughters and three grandchildren. Air & Space asked him to recall a few of his favorite Voyager images. See the gallery above for his selection.
Pictured above: Kohlhase has always dreamed about the future, whether reading science fiction or designing missions for NASA. So it comes as no surprise to find him using 3D software and his artistic talents to create pictures of future journeys to other worlds. In this scene titled “Outpost,” rendered on his computer at home in Pasadena, an advanced manned spaceship is shown approaching a remote facility on a distant water world.
Voyager 1: Io and Europa
Kohlhase comments: “When Voyager 1 returned this photo in late February 1979 of the two inner Galilean moons Io and Europa, I was struck with the sudden awareness and excitement that every day we would see more and more of these planet-sized worlds as the spacecraft neared Jupiter. They were beautiful and happily unlike Earth’s dull gray, cratered moon. I could hardly wait for the close-up photos of their unusual surfaces.”
Voyager 2: Europa
“In this Voyager 2 image of Europa, I was immediately struck by the network of cracks on its frozen surface, and again pleased to see no craters. The scientists were already talking about a vast ocean beneath this crust, with tidally-induced crustal movement leading to the long fissures. Some believed the brighter centers inside the darker adjacent crack edges may have indicated warmer water rising up to fill the cracks and then freezing. Life in this deep ocean was probably unlikely, but I realized that scientists would lobby for future missions to penetrate the thick crust and probe the Europan ocean for bio-signatures.”
“After [NASA astronomer] Linda Morabito had discovered Io’s volcano Pele in an optical navigation image, I never dreamed that it would be so huge, with sulfur and sulfur-dioxide products erupting to heights 30 times that of Mount Everest, and falling onto the surface over an area the size of France. I realized that tidal forces from Io’s slightly elliptical orbit about Jupiter were responsible for the interior heating to drive Pele, but never dreamed that hundreds of smaller volcanoes would be detected on Io in the years following Voyager.”
Iapetus, Saturn's Moon
“Having been a fan of Arthur C. Clarke and his 2001: A Space Odyssey, I had always wondered why the book’s journey was to the 'eye of Iapetus,' while the movie chose Jupiter as its destination. Saturn’s moon Iapetus could always be seen by early astronomers when going away from their telescopes, only to disappear when emerging from behind Saturn. The answer was clear: its leading hemisphere was as dark as tar, its trailing hemisphere as bright as snow. This Voyager 2 image taken on August 22, 1981 provided clear proof.”
Saturn's B Ring
“In this Voyager 2 image taken on August 22, 1981 from 1.5 million miles, we were all dazzled by the dark spokes which formed rapidly in the B ring of Saturn, then dissipated over several rotations of the ring particles orbiting faster near Saturn and slower farther away. We had already been awed by the thousands of ringlets and gaplets produced by the gravitational effects of the moons outside of the rings, but this new phenomenon ‘took the cake.’ Some suggested that impacts with ring bergs knocked loose charged particles, which were then magnetically propelled out along radial lines, only to settle down and dissipate with their orbital speed differences across the great expanse of the B ring.”
Voyager 1: Saturn
“I will never forget this beautiful Voyager 1 image of Saturn taken four hours after closest approach on November 12, 1980. I was sad that we would be leaving this great ringed world to escape from the solar system, but also hopeful that Voyager 2 would continue to dazzle us when it flew past this majestic gas giant of moons and rings just over nine months later. As Voyager 1 had successfully captured the Titan flyby objectives, this freed Voyager 2 to choose a target point at Saturn that would sling-shot it on to Uranus as part of its Grand Tour, but we mission designers already had great plans in mind for its sequence of observations within the Saturn kingdom.”
Uranus' Innermost Moon
“This amazing image of the innermost of Uranus’ five large moons reveals a jumbled and chaotic surface which some believed could only have resulted from a great collision that shattered Miranda eons ago, only to have it slowly reassemble in orbit to yield these widely varying types of terrain. Scientists would have chosen one of the larger moons for close passage, but the aiming point for continuing to Neptune only permitted a close pass of Miranda. But no one was disappointed. It seemed that the moons of the outer planets were all far more interesting than Earth’s moon.”
Triton, Neptune's Moon
“Many of us doubted whether the cold kingdom of Neptune with its long-known moons Triton and Nereid could ever compete with the delights of the warmer planetary realms closer to the sun. We were therefore totally surprised to see the amazing surface of the large moon Triton, which orbits Neptune in a retrograde direction. This Voyager 2 image taken on August 25, 1989 revealed geyser-like eruptions of nitrogen gas and darker particles which were carried by faint winds downrange to deposit dark streaks on the surface below. Indeed, our distant robot had done its job yet again, using its array of sensors to feed our minds with more questions to inspire young scientists for years to come.”
The Golden Record
In this pre-launch photo, Kohlhase holds the Voyager "Golden Record" that carries samples of Earth's culture to the stars.