With all this talk of new NASA missions to the Moon and Mars let us reminisce about one of the oldest space craft still operational. I must admit up front, the Voyager spacecraft are definitely my favourite space mission. Launched in 1977, Voyager 1 and 2 are still in good form. Voyager 2 is 18.9 billion kilometres away from the sun, while Voyager 1 is 22.6 billion kilometres away from the Sun.

In this 43rd year after their 1977 launches, they each are much farther away from Earth and the Sun than Pluto. Voyager 1 and 2 are now in the “Heliosheath” – the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas. Voyager 1 was the first spacecraft to reach interstellar space. It is predicted that it will reach the edge of the Oort cloud in about 300 years. Both spacecraft are still sending scientific information about their surroundings through the Deep Space Network (DSN).  This includes Tidbinbilla down near Canberra, as well as the Dish at Parkes, who communicate with the spacecraft every week.

The Voyager spacecraft were built by NASA’s Jet Propulsion Laboratory in Pasadena, California, which continues to operate both.  Voyager 2 launched on August 20, 1977, from Cape Canaveral, Florida aboard a Titan-Centaur rocket. On September 5, Voyager 1 launched, also from Cape Canaveral aboard a Titan-Centaur rocket.

An artist impression of Voyager

In order to reduce power consumption, mission managers have turned off a heater on part of NASA’s Voyager 1 spacecraft, dropping the temperature of its ultraviolet spectrometer instrument more than 23 degrees Celsius. It is now operating at a temperature below minus 79 degrees Celsius, the coldest temperature that the instrument has ever endured. This heater shut-off is a step in the careful management of the diminishing electrical power so that the Voyager spacecraft can continue to collect and transmit data through 2025.

At the moment, the spectrometer continues to collect and return data. It was originally designed to operate at temperatures as low as minus 35 degrees Celsius, but it has continued to operate in even colder temperatures as heaters around it have been turned off over the last 17 years. It was not known if the spectrometer would continue working, but since 2005, it has been operating at minus 56 degrees Celsius.  So engineers are encouraged that the instrument has continued to operate, even after the nearby heater was turned off in December.

The instruments of Voyager

The primary mission was the exploration of Jupiter and Saturn. Voyager 1 discovered a thin ring around Jupiter and two new Jovian moons: Thebe and Metis and as it passed Saturn, it found five new moons and a new ring called the G-ring.

Jupiter’s Red Spot from Voyager

After making a string of discoveries there — such as active volcanoes on Jupiter’s moon Io and intricacies of Saturn’s rings — the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets.

Their current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun’s domain. And beyond.

After putting plaques on Pioneer 10 & 11 – NASA put a more ambitious message aboard Voyager 1 and 2 that is intended to communicate a story of our world to extraterrestrials. The Voyager message is carried by a phonograph record, a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth.

The Golden Record cover shown with its extraterrestrial instructions. Credit: NASA/JPL