The twin Voyager spacecraft are celebrating 40 years of space travel as they continue to send data to NASA from the far-flung reaches of local space.

NASA reports that the Voyager craft communicates with ground control on a daily basis, despite being the longest-lived and furthest-travelling spacecraft ever launched.

The two space probes, Voyager 1 and Voyager 2, each carry a copy of a Golden Record of images, sounds and messages from Earth. The recordings could endure for billions of years, carrying a record of human civilization deep into the galaxy.

Voyager 1 became the first spacecraft to enter interstellar space when it passed beyond the outer reaches of the solar system. Voyager 2 is the only spacecraft to conduct a flyby of all the gas giants Jupiter, Saturn, Uranus, and Neptune. The Voyager craft was the first to self-diagnose and address technical problems autonomously.

I believe that few missions can ever match the achievements of the Voyager spacecraft during their four decades of exploration, Thomas Zurbuchen of NASA said. They have educated us to the unknown wonders of the universe and truly inspired humanity to continue to explore our solar system and beyond.

Voyager 1, which launched on Sept. 5, 1977, is now nearly 13 billion miles from Earth. The probe has determined that cosmic rays are about four times more powerful in interstellar space than near Earth, suggesting that our solar systems heliosphere serves as a shield against outside radiation.

Voyager 2, launched on Aug. 20, 1977, is about 11 billion miles from Earth and should enter interstellar space within a few years. The probes are heading in opposite directions, allowing scientists to compare data collected from two sides of the solar systems neighborhood.

None of us knew, when we launched 40 years ago, that anything would still be working, and be continuing on this pioneering journey, Ed Stone of Caltech in Pasadena said. The most exciting thing they find in the next five years is likely to be something that we didnt know was out there to be discovered.

In honor of the occasion, NASA will beam an uplifting message from humanity into interstellar space on the 40th anniversary of Voyager 1s launch. The agency is holding a contest via social media to select the message. Contestants are encouraged to tag a short message #MessageToVoyager by August 15.

Kathy Fey is a freelance writer with a creative writing degree from Mount Holyoke College. She is an active blogger and erstwhile facilitator of science and engineering programs for children.

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Voyager celebrates 40 years of space exploration - The Space Reporter