Impact & Benefits

Timeline

Radioisotope Power Systems (RPS) have powered some of the most ambitious and long-lived missions in the rich history of planetary exploration.

1960s

1970s

1960s

The astronaut is standing on the Moon next to the landing module. He is extracting a round cylinder from a storage compartment on the side.

Apollo 12 astronaut Alan Bean extracts the fuel element of a Radioisotope Thermoelectric Generator (RTG) from storage on the lunar module on the Moon. The RTG was used to power the Apollo Surface Experiment Package (ALSEP).

NASA

1961: The U.S. Navy launches Transit IV-A, a test the first-of-its kind radioisotope power supply in space.

1969: NASA launches its first Radioisotope Thermoelectric Generator (RTG) aboard the Nimbus III weather satellite.

1969: Apollo 11 carries the first radioisotope power system to the Moon. All six Apollo lunar missions carry special long-term, radioisotope-powered science experiments called Apollo Lunar Surface Experiment Packages (ALSEPs).

1969: Nimbus III helps scientists track deadly Hurricane Camille.

1970s

A rocky plain on Mars is visible over the top of the Viking 1 lander. Part of the top deck of the lander, including a large antenna dish, are visible in the foreground.

Viking 1 Lander image of Chryse Planitia looking over the lander. The large white object at lower left and center, with the American flag on the side, is the Radioisotope Thermoelectric Generator (RTG) cover. The high-gain S-band antenna is at upper right. The view, from 22 N, 50 W, is to the northwest. Chryse Planitia is a wide, low plain covered with large rocks and loose sand and dust. The image was taken on Aug. 30, 1976, a little over a month after landing.

NASA

1972: NASA retires the Nimbus III orbiter after a successful mission.

1976: NASA's Viking 1 and Viking 2 landers – powered by SNAP-19 RTGS – send back the first images and data from the surface of Mars.

1977: Taking advantage of a rare planetary alignment, NASA's twin Voyagers launch for the outer solar system. Their long voyages are powered by the Multi-Hundred Watt RTGs.

1977: Designed for a life of one year (Apollo 17 was designed for two), the Apollo Lunar Surface Experiments are powered down. Most of the knowledge of the lunar interior at the time came from ALSEPs.

1980s

Blue Neptune and its storms as seen from a spacecraft.

This photograph of Neptune was reconstructed from two images taken by Voyager 2's narrow-angle camera, through the green and clear filters. The image shows three of the features that Voyager 2 has been photographing during recent weeks. At the north (top) is the Great Dark Spot, accompanied by bright, white clouds that undergo rapid changes in appearance. To the south of the Great Dark Spot is the bright feature that Voyager scientists have nicknamed "Scooter." Still farther south is the feature called "Dark Spot 2," which has a bright core. Each feature moves eastward at a different velocity, so it is only occasionally that they appear close to each other, such as at the time this picture was taken.

NASA/JPL-Caltech

1986: Voyager 2 becomes the first – and still the only – spacecraft to fly past Uranus.

1989: Voyager 2 becomes the first – and still the only – spacecraft to fly past Neptune.

1989: The Galileo orbiter – powered and heated by two General Purpose Heat Source RTGs (GPHS-RTGs) and 120 Radioisotope Heater Units (RHUs) – launches for Jupiter from the Space Shuttle Atlantis.

1990s

Engineers in cleanroom suits insert a cylindrical device into a spacecraft.

Workers install one of three Radioisotope Thermoelectric Generators (RTGs) on the Cassini spacecraft. More ›

1990: NASA and ESA team up to launch the Ulysses orbiter on the first mission to study the heliosphere—the region of space influenced by the Sun and its magnetic field—from a unique solar polar orbit. The spacecraft is powered by a GPHS-RTG, which enabled the long, looping orbits required to explore the poles the Sun.

1994: Ulysses makes history as it makes the first pass by the poles of the Sun.

1996: Ulysses collects bonus science as it passes through the tail of comet Hyakutake. The spacecraft revealed comet tails are far longer than expected.

2000s

This self-portrait of NASA's Mars Exploration Rover Opportunity comes courtesy of the Sun and the rover's front hazard-avoidance camera. The dramatic snapshot of Opportunity's shadow was taken as the rover moved into Endurance crater. The image was taken on sol 180 (July 26, 2004), a date that marked double the rover's primary 90-sol mission.

NASA/JPL-Caltech

2003: Mars Exploration Rovers Spirit and Opportunity launch for the Red Planet. Both rovers are solar powered, but carried Radioisotope Heater Units (RHUs) to keep science instruments warm on the cold surface of Mars.

2004: Cassini becomes the first spacecraft to orbit Saturn. Three RTGs and 117 RHUs provide power and heat to the spacecraft.

2009: Ulysses ends its successful exploration of the polar regions of the Sun.

The breadth of science addressed by Ulysses is truly astonishing.The data acquired during the long lifetime of this mission have provided an unprecedented view of the solar activity cycle and its consequences and will continue to keep scientists busy for many years to come.

ed Smith

Ulysses Project Scientist

May 25, 2011: "Spirit" Rover Completes Mission on Mars

Spirit last communicated on March 22, 2010, as Martian winter approached and the rover's solar-energy supply declined. The rover operated for more than six years after landing in January 2004 for what was planned as a three-month mission. NASA checked frequently in recent months for possible reawakening of Spirit as solar energy available to the rover increased during Martian spring. A series of additional re-contact attempts ended today, designed for various possible combinations of recoverable conditions.

"Our job was to wear these rovers out exploring, to leave no unutilized capability on the surface of Mars, and for Spirit, we have done that," said Mars Exploration Rover Project Manager John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

2010s

Arrokoth looks like two reddish pancakes that merged into a peanut shape.

This composite image of the primordial contact binary Kuiper Belt Object 2014 MU69 (officially named Arrokoth) was compiled from data obtained by NASA's New Horizons spacecraft as it flew by the object on Jan. 1, 2019. - Full image and caption

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko

November 26, 2011: Curiosity Lifts Off

NASA began a historic voyage to Mars with the launch of the Mars Science Laboratory, which carries a car-sized rover named Curiosity. Liftoff from Cape Canaveral Air Force Station aboard an Atlas V rocket occurred at 10:02 a.m. EST (7:02 a.m. PST). The mission will pioneer precision landing technology and a sky-crane touchdown to place Curiosity near the foot of a mountain inside Gale Crater on Aug. 6, 2012.

August 5, 2012: Curiosity Lands on Mars

NASA's Mars Science Laboratory—the rover Curiosity—lands in Gale Crater. Its energy is provided by a radioisotope power system.

July 14, 2015: New Horizons Passes Pluto

NASA's New Horizons spacecraft becomes the first visitor from Earth to the Pluto system. Its long journey is made possible by an RTG power source.

September 15, 2017: Cassini's Grand Finale

NASA's Cassini spacecraft makes a fateful plunge into the atmosphere of Saturn, ending its 13-year tour of the ringed planet. Both Cassini and the Huygens probe were enabled by radioisotope heater units.

June 10, 2018: Opportunity's End of Mission

Designed to last just 90 Martian days and travel 1,100 yards (1,000 meters), Opportunity vastly surpassed all expectations in its endurance, scientific value and longevity. In addition to exceeding its life expectancy by 60 times, the rover traveled more than 28 miles (45 kilometers) by the time it reached its most appropriate final resting spot on Mars — Perseverance Valley.

January 1, 2019: New Horizons Passes Arrokoth

Arrokoth is located in the Kuiper Belt, beyond the orbit of Neptune. New Horizons flew just 2,200 miles (3,500 kilometers) from the object's surface, when it was about 4 billion miles (6.6 billion kilometers) from the Sun -- the most distant planetary flyby in history and the first close-up look at a solar system object of this type.

2020s

A small helicopter sits on the surface of Mars near the much larger Perseverance rover.

The Mars Perseverance rover poses for a selfie with its travel buddy, the Ingenuity helicopter.

NASA/JPL-Caltech/MSSS

July 30, 2020: Mars Perseverance Rover Launches

Based on the same platform as the Curiosity Mars Rover, Perseverance will be looking for more evidence of past water on Mars.

February 18, 2021: Mars Perseverance Rover Lands on Mars

Perseverance, the Mars 2020 rover, landed in Jezero Crater to analyze and collect samples of Martian soil and rock.

2027: Dragonfly launches to Titan

NASA's Radioisotope Power System-enabled Dragonfly spacecraft is a drone that will land on and then fly around Saturn's largest moon, Titan, looking for clues to the moon's origins and for signs of life.