NASA's Galileo: The First Dive into Jupiter and its Moons

Like the famed astronomer for whom it was named, the RTG-powered Galileo spacecraft logged quite a few firsts during its 14-year mission to Jupiter, including finding evidence for liquid water oceans under the moon Europa's icy surface. MORE on GALILEO ›

slide 2 - Saturn and its beautiful rings

Remembering a Class Act: 1997-2017

After 13 glorious years in Saturn’s orbit, the Cassini-Huygens mission ended on Sept. 15, 2017 when the aging spacecraft entered Saturn’s atmosphere. The RTG-powered spacecraft rewrote the textbook on Saturn and Titan, and transformed our view of the solar system. MORE ›

43 Years After Launch, Voyager 1 Continues to Set Records

Powered by three RTGs, NASA’s Voyager 1 is the farthest human-made object from Earth. The spacecraft entered interstellar space in 2012, and it continues to explore the boundary between the Sun's influence and interstellar space. It takes almost 21 hours for a signal from Earth to reach Voyager 1. MORE ›

Galileo's Close Encounter with Ida

On Oct. 28, 1993, as the RTG-powered Galileo spacecraft was approaching Jupiter, it snapped images of the asteroid Ida. While analyzing the images five months later, scientists noticed a small moon orbiting the asteroid, the first observation of an asteroid with a satellite. MORE ›

Voyager 2's Stunning Neptune Portrait Turns 31

Thirty-one years ago, on Aug. 25, 1989, NASA's Voyager 2 spacecraft made a close flyby of Neptune, giving humanity its first close-up of our solar system's eighth planet. No other spacecraft has visited Neptune since. The RTG-powered Voyager 2 is now 11.5 billion miles from Earth. MORE ›

NASA's Galileo: The First Dive into Jupiter and its Moons

Remembering a Class Act: 1997-2017

43 Years After Launch, Voyager 1 Continues to Set Records

Galileo's Close Encounter with Ida

Voyager 2's Stunning Neptune Portrait Turns 31

Voyager 1

Voyager 2

New Horizons: Mission Elapsed Time

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For more than five decades, radioisotope power systems have played a critical role in the exploration of space, enabling missions of scientific discovery to destinations across the solar system. › More

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