Voyager 1 and Voyager 2 launched in 1977 to explore the outer planets. Their missions continued after flybys of Jupiter and Saturn: both spacecraft went on to travel through interstellar space. They were designed to operate far from Earth, use power carefully, and receive commands remotely because people could never travel out to repair them.
The mission began with the outer planets
The twin spacecraft were designed to fly past Jupiter and Saturn. Voyager 2 later explored Uranus and Neptune as well. The alignment of the planets in the late 1970s allowed the spacecraft to use each planet’s gravity to change course toward the next destination. A planetary-flyby mission thus expanded into exploration of the heliosphere and interstellar space.
NASA says the spacecraft were initially designed for missions of about five years. Their operation beyond that period reflects durability, careful system management, and software changes sent from Earth—not a guarantee that a spacecraft would last for decades. Read the NASA Voyager Fact Sheet for mission history and objectives.
Why use RTGs instead of solar panels?
Sunlight becomes too weak to serve as the main power source as a spacecraft travels farther from the Sun. Voyager uses radioisotope thermoelectric generators (RTGs), which convert heat from plutonium decay into electricity. NASA says the RTGs provide power for the spacecraft’s instruments, computers, radio, and other systems.
The electrical power available decreases over time. Mission teams therefore shut down selected instruments to preserve communication and the measurements that can still be made. On April 17, 2026, NASA/JPL reported that it had turned off Voyager 1’s Low-energy Charged Particles instrument to conserve power. On August 4, 2026, NASA reported that operational changes had helped keep some of Voyager 2’s science instruments working longer. Instrument status can change; check NASA’s Voyager mission status page for the latest information.
How do the spacecraft handle faults and communicate with Earth?
Mission teams can send commands and new software through NASA’s Deep Space Network (DSN), but radio signals take a long time to travel to the spacecraft and for data to return. Voyager therefore has fault-protection systems that can place it in a safe state automatically when certain problems are detected. The ground team cannot respond to every event in real time as it could with equipment close to Earth.
Software updates from Earth have helped the spacecraft continue operating as their missions expanded beyond the original plan. NASA describes Voyager’s fault protection and communication constraints in Voyager: Did You Know?. Details about power and instruments are available on NASA’s Voyager instruments page.
Design lessons from a spacecraft maintained remotely
- Design for constraints: Plan for limited power, long communication delays, and systems that cannot be repaired in person.
- Include a safe mode: Allow the spacecraft to respond to some faults before the ground team receives an update.
- Allow for changes: Update software and operating priorities as mission goals evolve.
- Manage power over time: Shut down selected instruments to preserve essential functions and extend the mission.
These are lessons from Voyager’s mission; they do not mean that every system should be designed like a spacecraft. Design choices must reflect the costs, risks, and requirements of the task.
NASA and JPL references: Mission fact sheet · Voyager: Did You Know? · Voyager instruments · NASA/JPL report, April 17, 2026 · NASA report, August 4, 2026