Radioisotope Power Systems

NASA RPS Missions

The U.S. Navy launched the first radioisotope power system in 1961. A total of 24 NASA missions have successfully flown with an RPS since 1969. One new mission — NASA's Dragonfly quadcopter — is in development.

Active & Future Missions

Past Missions

Missions by Destination

Missions by Type

NASA RPS Missions Table

Active & Future Missions

Dragonfly

Future Mission

Power for this proposed quadcopter mission to Saturn's Moon Titan would be supplied by a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) mounted in a cylinder on the back of the drone.
Proposed Launch: July 2028

Artist’s concept of Dragonfly soaring over the dunes of Saturn’s moon Titan.

NASA/Johns Hopkins APL/Steve Gribben

Mars Perseverance Rover

Active Mission

The Perseverance rover is powered and warmed by a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). The rover continues to collect samples on the surface of Mars.
Launch: July 30, 2020 | 11:50 UTC
Mars Landing: Feb. 8, 2021 | 20:55 UTC

NASA’s Perseverance Mars rover took this selfie, made up of 62 individual images, on July 23. A rock nicknamed “Cheyava Falls,” which has features that may bear on the question of whether the Red Planet was long ago home to microscopic life, is to the left of the rover near the center of the image.

NASA/JPL-Caltech/MSSS

Mars Curiosity Rover

Active Mission

The Curiosity rover is powered and warmed by a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). The rover has been exploring the surface of Mars since landing in 2012.
Launch: Nov. 26, 2011 | 15:02 UTC
Mars Landing: Aug. 6, 2012 | 05:32 UTC

A rover sits on the hilly, orange Martian surface beneath a flat grey sky, surrounded by chunks of rock.

NASA's Curiosity rover at the base of Mt. Sharp

NASA/JPL-Caltech/MSSS

New Horizons

Active Mission

New Horizons is powered by a single radioisotope thermoelectric generator (RTG). The compact, rugged General Purpose Heat Source (GPHS)-RTG aboard New Horizons carries approximately 24 pounds (11 kilograms) of plutonium oxide fuel.
Launch: Jan. 19, 2006 | 19:00 UTC
Pluto Flyby: July 14, 2015 | 11:48:45 UTC
Arrokoth Flyby: Jan. 1, 2019 | O:533 UTC

Two men work on a grand piano-sized spacecraft wrapped in a gold insulating blanket. A large cylinder, a radioisotope thermoelectric generator, sticks out of the side.

New Horizons carries seven scientific instruments and a radioisotope thermoelectric generator. The spacecraft weighs 1,060 pounds.

NASA/JHUAPL

Voyager 1

Active Mission

Voyager 1 is powered by Multi-Hundred Watt Radioisotope Thermoelectric Generators (MHW-RTGs) and warmed by nine radioisotope heater units (RHUs). The MHW-RTGs produced about 158 Watts each at launch in 1977. Voyager power was in stable operation at 225 We in November 2023.
Launch: Sept. 5, 1977 | 12:56:01 UTC
Jupiter Flyby: Mar. 5, 1979
Saturn Flyby: Nov. 12, 1980
Entered Interstellar Space: Aug. 25, 2012

A Voyager spacecraft against a background of stars.

Artist's concept of a Voyager spacecraft in deep space.

NASA/JPL-Caltech

Voyager 2

Active Mission

Voyager 2 is powered by Multi-Hundred Watt Radioisotope Thermoelectric Generators (MHW-RTGs) and warmed by nine radioisotope heater units (RHUs). The MHW-RTGs produced about 158 Watts each at launch in 1977. Voyager 2's power was in stable operation at 225 We in April 2024.
Launch: Aug. 20, 1977 | 14:29:44 UTC
Jupiter Flyby: July 9, 1979
Saturn Flyby: Aug. 26, 1981
Uranus Flyby: Jan. 24, 1986
Neptune Flyby: Aug. 25, 1989
Entered Interstellar Space: Nov. 5, 2018

A Voyager spacecraft is shown in deep space among distant stars and gases.

Artist's concept of a Voyager spacecraft in deep space.

NASA/JPL-Caltech

The Voyagers owe their ability to operate at such great distances from the Sun to their nuclear electric power sources, which provide the electrical power they need to function.

Dr. Edward Stone (1936-2024)

Former Voyager Project Scientist

Powered by RPS: Great Shots from Around the Solar System

26 Images

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Earth is a tiny pixel of white in a dusty sunbeam in this image of the vast emptiness of deep space.

Magestic Saturn and its rings are barely illuminated view of the entire planet.

Giant Jupiter is half illuminated by the Sun and its moon Io is a crescent in the foreground. A small glowing volcanic plume is erupting from Io.

A sweeping landscape gives way to hills on the colorized horizon in this artistic Mars composite image.

The image from NASA's Voyager 2 shows the Great Dark Spot and its companion bright smudge; on the west limb the fast moving bright feature called Scooter and the little dark spot are visible.

This false-color photograph is a composite of 15 images of the Moon taken through three color filters NASA Galileo solid-state imaging system during the spacecraft passage through the Earth-Moon system on December 8, 1992.

A color-enhanced image shows cloud patterns moving around a hexagon -shaped storm om Satirm.

In the early morning hours of July 8, 2015, mission scientists received this new view of Pluto -- the most detailed yet returned by New Horizons. The image was taken on July 7, when the NASA spacecraft was just under 5 million miles 8 million kilometers

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Past Missions

Mars Exploration Rover Opportunity

Past Mission (2003-2019)

Opportunity was a solar-powered rover that used eight radioisotope heater units (RHUs) to heat its instruments during cold Martian nights. The rover explored Mars for almost 15 years, far beyond its planned 90 day mission.
Launch: July 8, 2003 | 03:18:15 UTC
Landing: Jan. 25, 2004 | 04:54:22.7 UTC
End of Mission: Feb. 13, 2019

Computer-generated illustration shows a golf cart-sized rover on the surface of Mars.

An artist's concept of the twin Mars Exploration Rovers Spirit and Opportunity.

NASA/JPL-Caltech

Mars Exploration Rover Spirit

Past Mission (2003-2011)

Spirit was a solar-powered rover that used eight radioisotope heater units (RHUs) to heat its instruments during cold Martian nights. The rover explored Mars for more than six years, far beyond its planned 90 day mission.
Launch: July 7, 2003 | 17:58:46 UTC
Landing: Jan. 4, 2004 | 04:35 UTC
End of Mission: May 25, 2011

An artistic illustration of a golf cart-sized rover on the surface of Mars.

Artist's concept of the twin Spirit and Opportunity Mars Rovers,

NASA/JPL-Caltech

Cassini-Huygens to Saturn & Titan

Past Mission (1997-2017)

The Cassini-Huygens mission was powered and heated by three general purpose heat source radioisotope thermoelectric generators (GPHS-RTG) and 117 radioisotope heater units (RHUs). The Cassini orbiter carried the RTGs and 82 RHUs. The Huygens Titan probe carried 35 RHUs. Cassini explored for more than 20 years in space.
Launch: Oct. 15, 1997 | 08:43:00 UTC
Saturn Orbit Insertion: July 1, 2004 | 02:48 UTC
End of Mission: Sept. 15, 2017 | 11:55:46 UTC

Spacecraft heating up in Saturn's atmosphere.

As depicted in this illustration, Cassini plunges into Saturn's atmosphere on Sept. 15, 2017.

NASA/JPL-Caltech

Mars Pathfinder Sojourner Rover

Past Mission (1997)

Sojourner was a solar-powered rover that used three radioisotope heater units (RHUs) to heat its instruments during cold Martian nights. The rover explored Mars for 83 days.
Launch: July 7, 2003 | 6:58:00 UT
Landing: July 4, 1997 | 16:56:55 UTC
End of Mission: Sept. 27, 1997

Small rover sitting against a rock on the red soil of Mars

Sojourner uses its Alpha Proton X-Ray Spectrometer (APXS) instrument to study the large rock "Yogi."

NASA/JPL-Caltech

Ulysses

Past Mission (1990-2009)

The international Ulysses mission used a general purpose heat source radioisotope thermoelectric generator (GPHS-RTGs) to power its long orbits from Jupiter to the poles of the Sun. The spacecraft explored the Sun and our solar system for more than 18 years.
Launch: Oct. 6, 1990 | 11:47:16 UTC
First Solar Polar Pass (Southern): June-Nov. 1994
First Solar Polar Pass (Northern): June-Sept. 1995
Closest approach to Sun (124 million miles or 200 million km): Mar. 12, 1995
End of Mission: June 30, 2009

An artist's concept of the joint ESA-NASA Ulysses spacecraft.

NASA/ESA

Galileo

Past Mission (1989-2003)

Galileo was powered and warmed by two general purpose heat source radioisotope thermoelectric generators (GPHS-RTGs) and 120 radioisotope heater units (RHUs). The orbiter included 103 RHUs while its atmospheric probe carried 17. Galileo's mission ended after 14 years in space.
Launch: Oct. 18, 1989 | 16:53:40 UTC
Jupiter Orbit Insertion: Dec. 8, 1995
End of Mission: Sept. 21, 2003 | 19:43:14 UTC

An illustration showing the a spacecraft flying in front of Jupiter.

Artist's concept of Galileo orbiter arrival at Jupiter. Note: This illustration shows the Galileo orbiter's antenna in its true deployment.

NASA/JPL-Caltech

Viking 1

Past Mission (1976-1982)

The Viking 1 lander was powered by two SNAP-19 radioisotope thermoelectric generators (RTGs). SNAP stands for Systems for Nuclear Auxilliary Power. Viking 1 operated on the surface of Mars for more than six years.
Launch: Aug. 20, 1975 | 21:22:00 UTC
Mars Orbit Insertion: June 19, 1976
Landing: July 20, 1976 | 11:53:06 UTC
End of Orbiter Mission: Aug. 7, 1980
End of Lander Mission: Nov. 11, 1982

A retro handpainted illustration of a Viking lander extending its robotic arm on the surface of Mars.

NASA/JPL-Caltech

Viking 2

Past Mission (1976-1980)

The Viking 2 lander was powered by two SNAP-19 radioisotope thermoelectric generators (RTGs). SNAP stands for Systems for Nuclear Auxilliary Power. Viking 2 operated on the surface of Mars for almost four years.
Launch: Sept. 9, 1975 | 18:39:00 UTC
Mars Orbit Insertion: Aug. 7, 1976
Mars Landing: Sept. 3, 1976 | 22:58:20 UT
End of Orbiter Mission: July 24, 1978
End of Lander Mission: April 12, 1980

Rover’s-eye view of an orange-brown, barren landscape covered in boulders of many sizes. In the near foreground, part of the rover is captured in its own camera’s field of view.

A view from the Viking 2 lander.

NASA/JPL/Caltech

Pioneer 11

Past Mission (1973-1995)

Pioneer 11 was powered and heated by four SNAP-19 radioisotope thermoelectric generators (RTGs), with heat from twelve radioisotope heater units (RHUs). First to fly past Saturn, the spacecraft transmitted data back to Earth for 22 years.
Launch: April 6, 1973 | 02:11:00 UTC
Jupiter Flyby: Dec. 3, 1974
Saturn Flyby: Sept. 1, 1979
End of Mission: Nov. 24, 1995

A spacecraft travels through the darkness of deep space with the faint glow of the Milky Way in the background.

An artist's concept of the Pioneer 10 or 11 spacecraft in deep space.

NASA

Apollo 17 ALSEP

Past Mission (1972-1977)

The crew of Apollo 17 set up the last Apollo Lunar Surface Experiments Package (ALSEP) on the Moon. It was powered by one SNAP-27 radioisotope thermoelectric generator (RTG). The experiment concluded in 1977.
Launch: Dec. 7, 1972 | 05:33:00 UTC
Landing: Dec. 11, 1972 | 19:54:58 UTC
End of Mission: Dec. 19, 1972
End of ALSEP Experiments: 1977

An experiment collects data on the surface of the Moon.

Apollo 17 ALSEP

NASA

Apollo 16 ALSEP

Past Mission (1971-1977)

The crew of Apollo 16 set up an Apollo Lunar Surface Experiments Package (ALSEP) on the Moon. It was powered by one SNAP-27 radioisotope thermoelectric generator (RTG). The experiment concluded in 1977.
Launch: April 16, 1972 | 17:54:00 UTC
Landing: April 21, 1972 | 02:23:35 UTC
End of Mission: April 27, 1972
End of ALSEP Experiments: 1977

Apollo 16 ALSEP

NASA

Pioneer 10

Past Mission (1973-2003)

Pioneer 10 was powered and heated by four SNAP-19 RTGs, with heat from twelve Radioisotope Heater Units (RHUs). First to fly past Jupiter, the spacecraft transmitted back to Earth for more than 30 years.
Launch: Mar, 2, 1972 | 01:49:04 UTC
First Through Main Asteroid Belt: July 1872
First to Jupiter (Flyby): Dec. 4, 1973
End of Mission: Jan. 23, 2003

An illustration of Pioneer 10 at Jupiter.

Apollo 15 ALSEP

Past Mission (1971-1977)

The crew of Apollo 15 set up an Apollo Lunar Surface Experiments Package (ALSEP) on the Moon. It was powered by one SNAP-27 radioisotope thermoelectric generator (RTG). The experiment concluded in 1977.
Launch: July 26, 1971 | 13:34:00.6 UTC
Landing: July 30, 1971 | 22:16:29 UTC
End of Mission: Aug. 7, 1971
End of ALSEP Experiments: 1977

An astronaut in a spacesuit leans over to install an experiment on the Moon.

Apollo 15 ALSEP site.

NASA

Apollo 14 ALSEP

Past Mission (1971-1977)

The crew of Apollo 14 set up an Apollo Lunar Surface Experiments Package (ALSEP) on the Moon. It was powered by one SNAP-27 radioisotope thermoelectric generator (RTG). The experiment concluded in 1977.
Launch: Jan. 31, 1971 | 21:03:02 UTC
Landing: Feb. 5, 1971 | 09:18:11 UTC
End of Mission: Feb. 9, 1971
End of ALSEP Experiments: 1977

The RTG of Apollo 14's ALSEP.

NASA

Apollo 13 ALSEP

Past Mission (1970)

Apollo 13 returned to Earth with its SNAP-27 radioisotope thermoelectric generator (RTG) in the Lunar Excursion Module (LEM). Following the astronauts' safe return, the lunar module carrying the RTG fell into deep water in Pacific Ocean.
Launch: April 11, 1970 | 18:07:41 UTC
Landing: N/A
End of Mission: April 17, 1970
End of ALSEP Experiment: N/A

A trio of smiling astronauts step off a helicopter onto the deck of an aircraft carrier in the ocean.

The crewmembers of the Apollo 13 mission, step aboard the USS Iwo Jima following splashdown and recovery operations in the South Pacific Ocean. Exiting the helicopter from left are astronauts Fred W. Haise Jr., lunar module pilot; James A. Lovell Jr., commander; and John L. Swigert Jr., command module pilot.

NASA

Apollo 12 ALSEP

Past Mission (1969-1977)

The crew of Apollo 12 set up the first Apollo Lunar Surface Experiments Package (ALSEP) on the Moon. It was powered by one SNAP-27 radioisotope thermoelectric generator (RTG). The experiment concluded in 1977.
Launch: Nov. 14, 1969 | 16:22:00 UTC
Landing: Nov. 19, 1969 | 06:54:35 UTC
End of Mission: Nov. 24, 1969
End of ALSEP Experiments: 1977

An astronaut in a spacesuit removes a cylinder from the side of a lunar lander on the Moon.

Astronaut Alan L. Bean, Lunar Module LM pilot, unloads the Apollo Lunar Surface Experiment Package ALSEP Radioisotope Thermoelectric Generator RTG fuel cask from the lunar module

NASA

Apollo 11 EASEP

Past Mission (1969)

The crew of Apollo 11 set up the prototype Early Apollo Surface Experiment Package (EASEP) package on the Moon. It was heated by two radioisotope heater units (RHUs).
Launch: July 16, 1969 | 13:32:00 UTC
Landing: July 20, 1969 | 20:17:40 UTC
End of Mission: July 24, 1969
End of EASEP Experiment: Aug. 27, 1969

An astronaut in a spacesuit installs an experiment on the surface of the Moon. The lunar landing module is visible in the background.

Apollo 11 astronaut Edwin "Buzz" Aldrin installs the Apollo 11 EASEP experiment on the Moon.

NASA

Nimbus III

Past Mission (1969-1972)

Weather satellite Nimbus III was powered by 10,500 solar cells and two SNAP-19B3 radioisotope thermoelectric generators (RTGs).
Launch: April 14, 1969 | 07:54:03 UTC
End of Mission: Jan. 22, 1972

An artist's concept of the Nimbus II spacecraft in orbit above Earth.

Artist's concept of a Nimbus spacecraft in orbit above Earth.

NASA

Nimbus B-1

Past Mission (1968)

The failure of the Nimbus B-1 launch vehicle forced its destruction by a range safety officer. The spacecraft and and upper stage sank in Santa Barbara Channel. Its SNAP-19B radioisotope thermoelectric generators (RTG)s were recovered and its fuel was reused for Nimbus III.
Launch: May 18, 1968 | 08:23:00 UTC
End of Mission: May 18, 1968

Artist's concept of a Nimbus spacecraft in orbit above Earth.

NASA

RPS Missions by Destination

RPS-powered spacecraft have explored every planet in our solar system from Venus outward— including the weather systems of Earth—and the polar regions of the Sun, as well as Pluto and the Kuiper Belt.

NASA

RPS-enabled missions have contributed to scientific knowledge across the solar system — and beyond.

Sun	Ulysses (1990-2009 orbit)
Venus	Cassini (2000 flyby) Galileo (1990 flyby)
Earth	Cassini (1998 flyby ) Galileo (1990 and 1992 flybys ) Nimbus III (1969-1972)
Earth's Moon	Apollo 11-17 (Apollo Lunar Surface Experiment Package (1969-1977)
Mars	Perseverance Rover (2020 - Present) Curiosity Rover (2012 - Present) +Opportunity Rover (2004-2018) +Spirit Rover (2004-2011) +Sojourner Rover (1997) Viking 2 Lander (1976-1982) Viking 1 Lander (1976-1980)
Asteroids	Galileo (1991 and 1993 flybys)
Jupiter and its Moons	New Horizons (2007 Flyby) Galileo (1995-2003 orbit) \| +Galileo atmospheric probe (1995 descent) Ulysses (1991 flyby, 2004 flyby) Cassini (2000 Flyby) Voyager 1 (1979 flyby) Voyager 2 (1979 flyby)
Saturn and its Moons	Cassini-Huygens (2004-2017) \| +Huygens Titan probe (2005) Voyager 1 (1980) Voyager 2 (1980) Pioneer 11 (1973)
Uranus and its Moons	Voyager 2 (1986 flyby)
Neptune and its Moons	Voyager 2 (1989 flyby)
Pluto and its Moons	New Horizons (2015 flyby)
Kuiper Belt	New Horizons (2019 flyby)
Comets	Galileo (1994 observation)
Interstellar Space	Voyager 1 (2012-Present) Voyager 2 (2018-Present) Note: Pioneers 10 and 11 and New Horizons also are on interstellar trajectories.

+Solar- or battery-powered missions enabled by Radioisotope Heater Units (RHUs)

NASA RPS Missions by Type

A radial hub with the Sun at the center shows the science destinations of Radioisotope Power System missions. There have been five flyby missions, four orbiters, three rovers and three landers.

Radioisotope Power Systems (RPS) have provided the power to explore, discover, and understand our solar system and beyond. This graphic shows the type and destinations of RPS missions where science was performed.

NASA/JPL-Caltech

NASA RPS Missions List

Mission	Power Source	RHUs	Type	Launch Date	Outcome
Nimbus-B-1	SNAP-19 B2		Meteorology (Earth)	5/18/1968	Unsuccessful
Nimbus-III	SNAP-19 B3		Meteorology (Earth)	4/14/1969	Successful
Apollo 11 ALSEP	Solar	2	Lunar Experiment	7/16/1969	Successful
Apollo 12 ALSEP	SNAP-27		Lunar Experiment	11/14/1969	Successful
Apollo 13 ALSEP	SNAP-27		Lunar Experiment	4/11/1970	Unsuccessful
Apollo 14 ALSEP	SNAP-27		Lunar Experiment	1/31/1971	Successful
Apollo 15 ALSEP	SNAP-27		Lunar Experiment	7/26/1971	Successful
Pioneer 10	SNAP-19	12	Jupiter Flyby	3/2/1972	Successful
Apollo 16 ALSEP	SNAP-27		Lunar Experiment	4/16/1972	Successful
Apollo 17 ALSEP	SNAP-27		Lunar Experiment	12/7/1972	Successful
Pioneer 11	SNAP-19	12	Jupiter Flyby Saturn Flyby	4/5/1973	Successful
Viking 1	SNAP-19		Mars Landing	8/20/1975	Successful
Viking 2	SNAP-19		Mars Landing	9/9/1975	Successful
Voyager 2	MHW-RTG	9	Jupiter Flyby Saturn Flyby Uranus Flyby Neptune Flyby Interstellar Space	8/20/1977	In Flight
Voyager 1	MHW-RTG	9	Jupiter Flyby Saturn Flyby Interstellar Space	9/5/1977	In Flight
Galileo	GPHS-RTG	120	Jupiter Orbiter	10/18/1989	Successful
Ulysses	GPHS-RTG		Jupiter Flybys Solar Orbiter	10/6/1990	Successful
Mars Pathfinder Sojourner Rover	Solar	3	Mars Rover	12/4/1996	Successful
Cassini-Huygens	GPHS-RTG	117	Saturn Orbiter	10/15/1997	Successful
Mars Spirit	Solar	8	Mars Rover	6/10/2003	Successful
Mars Opportunity	Solar	8	Mars Rover	7/7/2003	Successful
New Horizons	GPHS-RTG		Pluto Flyby KBO Flyby	1/19/2006	In Flight
Mars Curiosity	MMRTG		Mars Rover	11/26/2011	Exploring Martian Surface
Mars Perseverance	MMRTG		Mars Rover	7/30/2020	Exploring Martian Surface
Dragonfly	MMRTG		Titan Moon Rover (Saturn)	~2028	Future Mission

Missions in bold are currently operating.

Keep Exploring

More on Radioisotope Power Systems

About Radioisotope Power Systems

The rover is upside down in this straight from the back view. The image is centered on a cylinder with fins, the spacecraft's Radioisotope Thermoelectric Generator.

About Plutonium-238

Close up of two pencil-eraser sized glowing cylinders, radiating heat.

Radioisotope Power Systems Safety and Reliability

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.

Radioisotope Power Systems FAQ