Picture it: Our solar system, August 25, 1989. NASA’s Voyager 2 spacecraft makes a close flyby of Neptune, giving humanity its first close-up look at the solar system’s eighth planet.
This event would mark the end of the Voyager mission’s Grand Tour of the four gas giants—Jupiter, Saturn, Uranus, and Neptune. Since that time, no other spacecraft have visited Neptune.
Wrapped in clouds of teal and cobalt colors, Neptune looks much like a blue-hued sibling of Jupiter and Saturn. Though the blue coloring indicates the presence of methane in the atmosphere, a massive slate-colored storm, dubbed the “Great Dark Spot” is similar to Jupiter’s own Great Red Spot.
During the Voyager 2 flyby, six new moons and four rings were also discovered. However, these discoveries and images weren’t an easy feat to accomplish.
At about 30 times farther from the Sun than the Earth is, this icy giant only receives 0.001 times the amount of sunlight as compared to Earth.
With such poor lighting conditions, Voyager 2’s camera would need longer exposure times to get quality images of the planet. However, reaching a maximum speed of roughly 60,000 mph (90,000 kph) would make the images blurry—much like taking a picture of a roadside sign from the window of a speeding car.
This meant that the team would need to improvise. They programmed Voyager 2’s thrusters to fire gently in order to rotate the spacecraft so the camera would stay focused on its target. This allowed clear pictures to be taken without interruption to the craft’s overall speed and direction.
Because the probe’s distance from Earth also meant radio signals from Voyager 2 would be weaker than those of other flybys, the Deep Space Network (DSN) was utilized to assist. This network uses radio antennas at sites in Madrid, Spain; Canberra, Australia; and Goldstone, California.
In order to boost the signal from the DSN during the Neptune encounter, non-DSN antennas were used to collect data. These included a 210 ft (64 meter) dish in Parkes, Australia, and multiple 82 ft (25 meter) antennas at the Very Large Array (VLA) in Socorro, New Mexico.
This effort ensured that the engineers could hear Voyager 2 loud and clear, and increased the amount of data that could be sent to Earth during any given period, allowing the spacecraft to send back more pictures from the flyby.
“One of the things that made the Voyager planetary encounters different from missions today is that there was no internet that would have allowed the whole team and the whole world to see the pictures at the same time,” said Ed Stone, Voyager’s project scientist since 1975. “The images were available in real time at a limited number of locations.”
This didn’t stop the team from being committed to giving the public updates as quickly as possible.
From August 21st to August 29th, they shared their discoveries with the world during daily press conferences. In fact, starting at 4am CST on August 24th, a program called “Voyager All Night” broadcast regular updates from the probe’s closest approach to the planet. The morning after this televised event, Vice President Dan Quayle commended the Voyager team during his visit to the Lab.
Later that same evening, Chuck Berry, whose song “Johnny B. Goode” was included on the Golden Record that flew with both Voyager spacecraft, played at JPL’s celebration of this feat.
“The Voyager planetary program really was an opportunity to show the public what science is all about,” said Stone. “Everyday we learned something new.”
As we all know, this wasn’t the end of the Voyagers’ achievements. Their discoveries extend well beyond that historic week three decades ago.
Voyager data complements other missions, including NASA’s Interstellar Boundary Explorer (IBEX). And NASA is preparing the Interstellar Mapping and Acceleration Probe (IMAP) which is due to launch in 2024.
This mission will capitalize on Voyager observations.
With both probes now in interstellar space, they are reporting back information on space “weather” and conditions from the region outside the Heliosphere—a protective bubble around the planets created by high-speed particles and magnetic fields from our Sun—that is filled with debris from stars that exploded elsewhere in our galaxy.
Indeed, the Voyager craft have taken humanity’s first tenuous step into the cosmic ocean where no probe has gone before.