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Historical RTG performance data through 2023

Cite this dataset

Whiting, Christofer; Woerner, David (2024). Historical RTG performance data through 2023 [Dataset]. Dryad. https://doi.org/10.5061/dryad.1zcrjdfw2

Abstract

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).

README: Historical RTG Performance Data - 2023 Update


Usage Clause - 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 directly, or indirectly, uses any values from this dataset reference the book where this data is presented in a copyrighted graphical format. We also ask that any uses of post-2020 performance data cite this updated dataset as described on the dataset's webpage.

Please Reference: 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)

Whiting, Christofer; Woerner, David (2023). Historical RTG Performance Data - 2023 Update [Dataset]. Dryad. https://doi.org/10.5061/dryad.1zcrjdfw2


Brief Description:
This dataset contains all of the available power and performance data for RTGs that have been flown in space through mid-to-late 2023. Power values for RTG performance were collected from reputable and authoritative sources and organized into a tabular format of time versus normalized electrical power. Normalized electrical power is the power at a given time, divided by the power at the beginning-of-mission (BOM). BOM power and date for each mission are also provided. Individual RTG performance data are provided when available. For example, Cassini was powered by 3 GPHS-RTGs and individual performance data from each of these RTGs are presented. Some important pieces of context for each RTG mission are also provided above the table.


Description of the data and file structure:
Data are organized into an Excel spreadsheet that contains several tables of RTG performance. Each major RTG design has its own table. Each table is presented in a separate tab. One tab also collates all of the tables and presents them in a single tab. Data in the individual tabs and the collated tab are identical.

Within each table, performance data for each RTG mission are presented as time versus normalized electrical power. Normalized electrical 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. Due to the fact that RTGs can take days to weeks to fully equilibrate with a new environment, BOM power is defined as the highest power level reached by the RTGs within 30 days of the BOM date.


Usage Context:
Performance data for RTGs are highly dependent on the RTG design and specific mission characteristics. It is not possible to completely outline all of the important context needed to fully appreciate this data in a simple dataset. Therefore, the user is highly encouraged to access the book cited at the beginning of this document. This book provides all the context necessary to make full use of, and understand, this dataset.


Pedigree of the data:
RTGs have a very long and storied history (60+ years), but the entities in charge of monitoring and managing the power data from RTGs has not been consistent. Sometimes, the Department of Energy (or its predecessor, the Atomic Energy Commission) was in charge of maintaining RTG power data. Sometimes, NASA was in charge of maintaining the data. Sometimes, the various mission control centers were in charge of maintaining the data. This has created a lot of confusion regarding the ownership and quality of power data for many RTGs. In many cases, some of the data was never published at all (e.g. Galileo after 8 years and Pioneer after 18 years). It is therefore important that the pedigree of this data is described in detail, especially the data that has never been published previously.

SNAP-9A (Transit 5BN-1 and Transit 5BN-2), SNAP-19B (Nimbus III), and 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 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 goes to August 2021.

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

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

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

Methods

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.

Usage notes

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

Funding