ARNOLD AIR FORCE BASE, TENN. -- NASA Voyager 1 and 2 will reach 40 years of operation in August and September, and AEDC test teams played a part in testing the space systems for this program prior to their launch.
Voyager 2 lifted off from Launch Complex 41 at Cape Canaveral on Aug. 20, 1977, with its twin launching a couple weeks later on Sept. 5, 1977.
In 1965, NASA tasked AEDC with conducting testing of the launch system that would assist in sending the spacecraft on their journeys through space.
AEDC engineers tested the surface, solar cells and exposed components of a space vehicle, at that time called the Centaur-Voyager, a full-scale segment with a 5,000-pound retro rocket, which was mounted as it would be on the Saturn S-IVB booster. Testing simulated altitudes of up to 133,000 feet.
Forty years since their launch, Voyager 1 and 2 are now deep in space and are continuing to send information to NASA.
Of the Voyager mission, Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters, said, “I believe that few missions can ever match the achievements of the Voyager spacecraft during their four decades of exploration. They have educated us to the unknown wonders of the universe and truly inspired humanity to continue to explore our solar system and beyond.”
In 2012, Voyager 1 became the only spacecraft to have entered interstellar space, while Voyager 2 is the only spacecraft to have flown by all four outer planets: Jupiter, Saturn, Uranus and Neptune. Their planetary encounters include discovering the first active volcanoes beyond Earth, on Jupiter’s moon Io; hints of a subsurface ocean on Jupiter’s moon Europa; the most Earth-like atmosphere in the solar system, on Saturn’s moon Titan; the icy moon Miranda at Uranus; and icy-cold geysers on Neptune's moon Triton.
Voyager 1, now 13 billion miles from Earth, travels through interstellar space northward out of the plane of the planets. It has informed researchers that cosmic rays, atomic nuclei accelerated to nearly the speed of light, are as much as four times more abundant in interstellar space than in the vicinity of Earth. This means the heliosphere, the bubble-like volume containing our solar system's planets and solar wind, effectively acts as a radiation shield for the planets. Voyager 1 has also hinted that the magnetic field of the local interstellar medium is wrapped around the heliosphere.
Voyager 2, almost 11 billion miles from Earth, travels south and will be entering interstellar space in the next few years. The different locations of the two Voyagers allow scientists to compare two regions of space where the heliosphere interacts with the surrounding interstellar medium using instruments that measure charged particles, magnetic fields, low-frequency radio waves and solar wind plasma. Once Voyager 2 crosses into the interstellar medium, they will be able to sample the medium from two different locations simultaneously.
"None of us knew, when we launched 40 years ago, that anything would still be working, and continuing on this pioneering journey," said Ed Stone, Voyager project scientist based at Caltech in Pasadena, California. "The most exciting thing they find in the next five years is likely to be something that we didn't know was out there to be discovered."
The foresight of the mission designers is to be commended, leading to the longevity of the twin Voyagers. In preparing for the radiation environment at Jupiter, the harshest of the planets in the solar system, the spacecraft were well-equipped for their journeys past it.
Both are also equipped with long-lasting power supplies and redundant systems that allow them to switch to backup systems autonomously when necessary. Each carries three radioisotope thermoelectric generators, devices that use the heat energy generated from the decay of plutonium-238.
The Voyagers' power decreases by four watts per year, so engineers are learning how to operate the spacecraft under ever-tighter power constraints. To maximize their lifespans, engineers are consulting documents written decades ago describing commands and software, in addition to the expertise of former Voyager engineers.
"The technology is many generations old, and it takes someone with 1970s design experience to understand how the spacecraft operate and what updates can be made to permit them to continue operating today and into the future," said Suzanne Dodd, Voyager project manager based at NASA's Jet Propulsion Laboratory in Pasadena, California.
Team members estimate they will have to turn off the last science instrument by 2030. But even after the spacecraft no longer send information, they will continue on their trajectories at their present speed of more than 30,000 mph and complete an orbit within the Milky Way every 225 million years.
The Voyager spacecraft were built by Jet Propulsion Laboratory. The Voyager missions are part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate. For more about the Voyager spacecraft, visit: https://www.nasa.gov/voyager and https://voyager.jpl.nasa.gov.
The above was written using information provided in the NASA release “NASA’s Voyager Spacecraft Still Reaching for the Stars After 40 Years.”