PASADENA, California – Thirty years ago, NASA's Voyager 2 mission flew from Nettuno, capturing the first close-up images of the blue gas giant. Before this, the eighth planet in our solar system was known only as a blurred point in the distance.
And the end of the planetary tour of Voyager 2, on August 25th 1989, ended with a dazzling spectacle of Neptune and its moon, Triton. The images and scientific data returned by Voyager 2 would change our understanding of the solar system.
Voyager 2 is still the only spacecraft to visit the outer planets of Neptune and Uranus.
The Voyager probes were launched in 1977. Together they visited Saturn, Jupiter and their moons. But then, Voyager 2 had a unique opportunity.
"We had the opportunity to achieve a close overtaking with Voyager 2," said Suzanne Dodd, Voyager Project Manager. "Because of the planetary alignment when the probes were launched in 1977, the four outer giant planets were all lined up on the same side of the sun, so they could move from one close to another. It really was a Big chance."
This allowed the spacecraft to use a gravity assist device from a planet to visit the next, allowing the Voyager program to visit four planets in four years. This alignment occurs only once every 176 years.
Trina Ray was working at NASA's Jet Propulsion Laboratory for the Voyager 2 Neptune overflight. She joined the General Science Data team as her first job outside of college.
There were monitors everywhere in the Voyager operation lab at building 264 at JPL, with teams spread across several floors. Since Voyager 2 always aimed the antenna on Earth, it constantly transmitted data.
Chris Jones helped develop the flight software for the Voyager mission and helped the agency determine the best ways to manage the ever-increasing distance to communicate with the spaceship. He also helped the mission overcome the problem of decreasing light levels to return clear images of Neptune.
The images would be displayed on the monitors, line by line. In the slow approach to Neptune, the planet started out as several pixels, a blurry blue dot that grew a little bit every day.
With the approach of approach, everything has changed.
Ray would be sitting at his desk and someone would say "Wow", making everyone look at the monitors.
"This is the best image of Neptune we've ever seen," one of the scientists would say. They would return to work until someone else exclaimed, and another image would come to life.
"The incredible flow of the meeting was tremendously exciting," said Ray. "During the month leading up to the closest approach, you were really involved in what was happening. You had this feeling of acceleration. I never saw another mission profile of a spacecraft having that # 39. ; intensity of construction over the months, resulting in an incredible data set from the days around the closest approach ".
During the overflight week, Ray didn't want to sleep or even leave the monitors for a second. All the others were the same way. While the spaceship was temporarily out of communication, Ray used one of the on-site showers and took a nap. No one he knew came home.
Media from all over the world have camped in the JPL car park, presenting themselves at the daily press conference to discuss new images and scientific results.
"It's been five days of incredible science," Ray said. "And there was this intense emotion in knowing that this was the last overflight. It was the end of an era."
A new look at Neptune
The Voyager team worked together between 20 and 30 years, a working machine full of people who knew each other well and what they were capable of doing.
Ray was a new addition. Voyager would have set all her expectations on how the teams will work together for the rest of Ray's thirty-year career at NASA, which is underway. He lit a spark in her and spent the next 20 years working on the Cassini Orbit to Saturn, which was inspired by Voyager.
The science gathered during Neptune's flyby revealed that their existing models for the gas giant were too simple to show what was really happening.
They discovered that Neptune's magnetic field was tilted to one side. They found a giant point called the Great Dark Spot on the planet, similar to Jupiter's Great Red Spot. But the event was passing, because there was no more when the Hubble Space Telescope appeared four years later. It has been discovered that Neptune has some of the fastest and coldest winds in the solar system.
Four rings have been found all over the planet.
And when Voyager 2 flew near Triton, Neptune's moon, the scientists discovered he was orbiting backwards. Unlike the other moons of Neptune formed by leftovers after Neptune became a planet, Triton was a captured object that was dragged into a retrograde orbit.
During the overflight, six additional moons were discovered.
Triton was the coldest object ever seen by Voyager 2, reaching 391 degrees Fahrenheit negative. The surface from the wild aspect has proved to be geologically active, with the geysers exploding from the frozen ice of nitrogen on Triton.
Understanding the diversity of our solar system came from the Voyager flybys.
"From time to time, we found objects that did things we didn't expect," said Ed Stone, a Voyager project scientist since 1975 and a professor of physics at the California Institute of Technology. "It changed our vision of the solar system."
"It was a wonderful experience because there was so much to learn," said Stone, reflecting on his time with the Voyager mission. "We have been able to share this journey for many decades with the public. We could take people along the journey while we were discovering things in each of the flybys."
Stone believes that three aspects of Voyager have contributed to NASA's continued legacy of spacecraft: innovative engineering, transformative science and extraordinary inspiration in learning what is "out there".
What is next
Voyager 1 and 2 are the longest space vehicles in history; 42 years after their launch, both are still going strong and sending back data as they explore interstellar space. It's the farthest we've ever pushed into space. And the spacecraft were initially designed to last only five years.
Dodd started working on Voyager in 1984 and stayed on the project to see the meetings of Uranus and Neptune. Subsequently, Dodd would work on missions inspired by information gathered from Voyager data. And now, Dodd is back at the helm of Voyager again.
Dodd's 12-person team takes care of both spacecraft to make sure the probes are healthy, safe, working well and not too cold.
Jones, who has returned to help deal with the spaceship as chief engineer, calls himself a "doctor with a permanent call" for Voyager. "You never know when it might be necessary," he said.
Voyager's flybys have inspired orbiting missions like Cassini to Saturn and its moons, Galileo and Juno to Jupiter and its moons and even future planned missions.
"I describe Voyager as a grandfather of the missions that have flown since," said Dodd.
However, no mission was followed by Uranus or Neptune. If a mission was ready for launch at this time, it would take ten years to reach Neptune. But nothing is currently in the works, although Voyager's interesting scientific discoveries have given reason to return and investigate further.
"We need to develop an orbit for each of those planets," said Dodd. "At Uranus, the five main moons are very different. They have a unique geological history, so we need to understand how they were formed or captured. Uranus has a rotational pole that is tilted on one side more than the Earth, so we need an understanding of the because this happened. To Neptune, there are many features in the atmosphere similar to Jupiter and Saturn. And the moon of Neptune Triton is interesting because of the methane geysers on it. "
"When the Voyager spaceship flew from the planets of our solar system, they helped answer some questions while creating more," Ray said.
But missions on the outer planets take longer, so the teams working on them know that they will probably only work on one or two of them during their lifetime.
"We absorb into our soul the fact that we are going to launch and it will take seven years to get there," said Ray, who is now working on the Europa Clipper mission to explore the Europe of Jupiter's moon.
Those who have worked on the Voyager mission and are now assisting in the development of Europa Clipper know that they may not be able to see the mission. But they are contributing everything they have learned from Voyager and other missions to ensure it is the best it can be. And they will pass to a new generation of scientists.
For all those who are still working on Voyager, they are proud of the longest spacecraft in human history that is exploring the unexplored territory of the heliosphere.
"Send an emissary robot out of the solar system for the first time once, and this is Voyager," Ray said. "This is a milestone for humanity. Just look at these little robots and how long they've been going. Boy, he's a soldier."