DOI: 10.5061/dryad.1zcrjdfw2
title: Historical RTG performance data through 2023

description: 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).
description: UPDATE STATUS: Active missions (except for Voyager) have been
 updated through mid-to-late 2023. ----------
 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.
description: 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, <em>The Technology of
 Discovery: Radioisotope Thermoelectric Generators and Thermoelectric
 Technologies for Space Exploration</em> (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
description: # 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.
 ** --- 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.