All About Circuits has been reporting on the scientific instruments aboard the Voyager Spacecraft over the last 10 weeks. Today is the 40th anniversary of the Voyager 2 launch. In this article, series coordinator Mark Hughes provides a look back at four decades of accomplishments with links to reader resources.

### The Voyage Out of the Solar System

The USSR's 86 kg Sputnik 1 satellite launched in October of 1957 and orbited for three months. The only sensors aboard were thermometers for measuring the internal and external temperature of the satellite.

120 days later, the United States of America’s 13.4 kg Explorer 1 launched and carried cosmic-ray detectors, five temperature sensors, acoustic impact detectors, and wire grid micrometeorite impact detectors. The final transmission of Explorer 1 came 105 days later, and it eventually burned up in the Earth’s atmosphere some 12 years later. These advancements were major milestones in the space race and gave us GPS technology along the way.

Scientists from the two countries continued to loft men and satellites with increasingly complex sensors into the skies above.

##### Image of the Voyager 2 launch. Image courtesy of NASA.

Rocket engineers developed propulsion systems capable of generating the thrust needed to lift heavy payloads and learned how to reach the speeds necessary to escape Earth permanently. Giving an object the speed necessary to escape the solar system $$6.5\times 10^6 \tfrac{\text{m}}{\text{s}}$$ is a Herculean task, and engineers used carefully planned gravitational slingshot techniques coupled with carefully calculated course corrections to steal momentum from the outer planets.

But to create a probe that can leave our lonely Earth and then our solar system to visit what lies beyond, while still collecting and transmitting useful scientific data, is a task worthy of Zeus himself. But this feat wasn’t accomplished by mythical gods—it was accomplished by scientists and engineers who set out to solve a problem, and solved it brilliantly.

##### Image of scientists testing Voyager 2. Image courtesy of NASA.

The two Voyager spacecraft launched twenty years after the very first satellites. Each spacecraft had a launch mass of 825.5 kg (1820 lbs) and carried a variety of scientific instruments that allowed them to unlock the secrets of the planets and moons in our solar system. By studying the space in between the planets, they also hoped to unlock the secrets of our sun. The Voyager mission taught us that there are active volcanoes on Jupiter’s moon Io and gave us a baseline to determine that Jupiter’s giant red spot is slowly shrinking away. We learned that Jupiter’s moon Europa is an icy planet that might contain life. We learned about the composition of Saturn’s rings.

They accomplished all of this without microprocessors and with only 68 kilobytes of memory.

But four decades is far too long to operate on battery power and the two spacecraft are too far away from the sun for solar panels, so diminishing Radioisotope Thermoelectric Generators provide the available power.

The Voyager missions also challenged some of the brightest minds to create a cohesive representation of our planet and species in the Golden Record.

##### Image of Voyager test model. Image courtesy of NASA.

All About Circuits has been featuring different Voyager scientific instruments each Sunday of these past ten weeks in celebration of the Voyager missions 40th anniversary. Today, we invite you to take a look back at our previous articles and learn a bit more about the missions that amazed humankind all those years ago.

### Voyager Articles at All About Circuits

Below, you will find the Voyager series here on All About Circuits. Explore the sensors, experiments, and engineering that have made this feat of space exploration possible and meaningful.

### Going Further

The Voyager Spacecraft will continue to transmit scientific data until 2025, and we can track their position for an additional 10 years after that. If you would like to know more about the Voyager spacecraft, here are some resources that we used while writing these articles.

The Voyager Backgrounder document provides an overview of the spacecraft, its mission, and the various scientific experiments aboard the spacecraft.

The Design and Performance Summary Series (DESCANSO) provided by the Deep Space Communications and Navigation Center of Excellence, provides thoroughly detailed information about communication with deep space spacecraft.

##### Image of scientist inspecting Voyager 2 antenna. Image courtesy of NASA.

The Jet Propulsion Laboratory's Photojournal provides images and animations of spacecraft and the solar system.

The Scientific and Technical Information Program is a collection of scientific and technical papers about all of NASA's missions.

### Conclusion

We hope that you have enjoyed this series and that it'll inspire you to take a moment to think about all of the incredibly hard work that went into making the Voyager spacecraft possible.

The spacecraft designers meticulously designed every aspect of the spacecraft and devoted 11,000 man-years to take the spacecraft from inception to Neptune.

Happy 40 years in space, Voyager!