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Historical RTG performance data through 2020


Whiting, Christofer; Woerner, David (2022), Historical RTG performance data through 2020, Dryad, Dataset,


Radioisotope thermoelectric generators (RTG) are the only technology capable of providing 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 45 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 early 2020. 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).


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. 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, SNAP-19 (Nimbus III, Viking 1, and Viking 2), SNAP-27, 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. (courtesey 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), GPHS-RTG (Galileo and Cassini), and MMRTG were obtained directly from the mission control at the Jet Propulsion Laboratory.

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

GPHS-RTG (New Horizons) was obtained directly from the mission control at the Applied Physics Laboratory.

Usage Notes

Data is tabulated in a standard Excel spreadsheet with standard formatting. Some important contextual information is also provided in the table, but complete context and appreciation for the data require 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 data set.

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.

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