Radioisotope thermoelectric generators (RTG) are the only technology currently available that can provide reliable and consistent electrical power for decades while isolated in extreme environments. RTGs have been, and will continue to be, a critical enabling component in some of humankind's most impressive feats of space exploration in the past (e.g. Cassini), present (e.g. Voyager), and future (e.g. Dragonfly). Power produced by an RTG will slowly decrease over time due to decay of the radioisotope fuel and degradation of the materials within the generator. With over 60 years of history, the technology of RTGs has evolved from producing only a few electrical watts (e.g. SNAP-3B ~3 W) to nearing a kilowatt of total mission power (e.g. Cassini beginning-of-mission 887 W). They also evolved from systems that were only designed to last a few years into systems that are now exploring interstellar space 46 years after launch. Obviously, understanding how the performance of these systems changes over their lifetime is of very high interest to anyone planning a future space exploration mission. This dataset presents all of the power and performance information that is available for all spaceborne RTGs that have been flown by NASA and the US Department of Defense through mid-to-late 2023. Some performance data that has not previously been published is also provided here, including the full lifetime for Galileo and Pioneer 11, as well as a near complete lifetime for Pioneer 10. While all of the available performance data for RTGs is presented here, it should be noted that the context of each mission and RTG design is extremely important in understanding RTG behavior. It is not possible to provide enough context to fully appreciate the behavior of all 29 RTG space missions in a dataset publication, so users are highly encouraged to find the appropriate context in Chapter 8 of the book, The Technology of Discovery: Radioisotope Thermoelectric Generators and Thermoelectric Technologies for Space Exploration (ISBN: 9781119811367).

UPDATE STATUS: Active missions (except for Voyager) have been updated through mid-to-late 2023.

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Power values were collected from reputable and authoritative sources and organized into a tabular format of time versus normalized power. Normalized power is the power at a given time, divided by the power at the beginning-of-mission (BOM). BOM power for each mission is also provided. Because RTGs can take days to weeks to fully equilibrate with their environment, BOM power is defined here as the maximum RTG power produced over the first 30 days of the mission. For many missions, this will be the first data point.  Other missions (e.g. Curiosity) will reach this maximum power level after several days.

BOM for RTG missions does not have a consistent definition. For deep space or orbital missions, BOM is launch. For missions where the RTG was installed on the surface of an extraterrestrial body, BOM is either the landing date (e.g. Martian landers or rovers) or the date the RTG was installed (e.g. Apollo lunar missions).

Some important pieces of context for each RTG mission are also provided above the table.

Pedigree of the performance data for each mission in this dataset:

SNAP-9A (Transit 5BN-1 and Tranist 5BN-2), SNAP-19B (Nimbus III), SNAP-19 (Viking 1 and Viking 2), SNAP-27 (Apollo), and Transit-RTG were obtained from graphs presented in G.L. Bennett, J.L. Lombardo, and B.L. Rock, “US Radioisotope Thermoelectric Generators in Space,” Nucl. Eng., 25(2), 49–58 (1984).

SNAP-19 (Pioneer 10 and 11) was obtained from an internal memo published by Teledyne Energy Systems, Inc. (courtesy T. Hammel). Teledyne was the design and engineering agency in charge of the SNAP-19.

MHW-RTG (LES 8 and 9) were obtained from the Cassini Final Technical Report (DOE/SF/18852-T97) published by Lockheed Martin. Lockheed was the prime contractor and system integrator for all silicon germanium RTGs (i.e. MHW-RTG and GPHS-RTG) at that time.

MHW-RTG (Voyager 1 and 2) telemetry was obtained courtesy of E. Medina of the Jet Propulsion Laboratory. Due to recent issues with the Voyager spacecraft, a public data drop of Voyager telemetry has not occurred in a while. As a result, Voyager 1 and 2 data only go to August 2021.

GPHS-RTG (Galileo) telemetry was obtained courtesy of R. Gershman of the Jet Propulsion Laboratory.

GPHS-RTG (Ulysses) was obtained courtesy of the Mission Operations Manager N. Angold.

GPHS-RTG (Cassini) performance data was obtained directly from mission control at the Jet Propulsion Laboratory.

GPHS-RTG (New Horizons) telemetry was obtained courtesy of C. Hersman of the Applied Physics Laboratory.

MMRTG (Curiosity and Perseverance) telemetry was obtained courtesy of E. Clarke and L. Rich of the Idaho National Laboratory, as well as S. Bux and S. Pinkowski of the Jet Propulsion Laboratory.

Data is tabulated in a standard Excel spreadsheet with standard formatting. Some important contextual information is provided in the table but complete context and appreciation for the data requires information that can be found in Chapter 8 of the book, The Technology of Discovery: Radioisotope Thermoelectric Generators and Thermoelectric Technologies for Space Exploration (ISBN: 9781119811367).

Pedegree of the data presented in the data set can be found in the previously cited book and in the Methods section of this dataset.

The authors collected and curated this data on their own time and are making the numerical format freely available to all (i.e. no copyright). We only ask that any publication, report, or presentation that uses any values from this data set actively reference the previously cited book. If a user wishes to also present data after 2020, please also cite this dataset as described on this webpage.

For example: C.E. Whiting and D.F. Woerner, "Chapter 8: Lifetime Performance of Spaceborne RTGs," The Technology of Discovery: Radioisotope Thermoelectric Generators and Thermoelectric Technologies for Space Exploration, D.F. Woerner, Ed., John Wiley & Sons, 2023. ISBN: 9781119811367