Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 (2022)

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20 Infrastructure for Planetary Science and Exploration Planetary science is highly dependent on infrastructure—i.e., the equipment, instrumentation, and facilities that enable advanced study of planetary bodies, through simulations, experiments, remote observations, and spacecraft exploration. 1 In response to the survey’s statement of task for the development of a comprehensive research strategy, this chapter provides background, findings, and recommendations on key infrastructure elements that support the priority activities in planetary science and astrobiology identified in other parts of the report. Infrastructure, as defined here, includes the facilities, services, and organizational relationships needed to advance the mission of NASA’s Planetary Science Division that are not directly supported by individual program elements. The critical infrastructure of our discipline is housed at NASA, NSF, and other government facilities, but also in individual institutions throughout the world. Due to the sheer volume of facilities, the committee necessarily describes only a subset here. This discussion is not an exhaustive and complete list of every possible facility, but instead provides an overview of key facility types, noting specific needs and areas of concern when applicable. Any omissions are unintentional and are not meant to imply that a specific facility is unimportant. Development and improvement of infrastructure are long-term investments and need to be viewed with a longer time horizon than a decade; thus, recommendations made that would result in investments in the coming decade need to consider needs beyond that period of time. NASA INFRASTRUCTURE NASA directly funds many facilities relevant to planetary science and planetary missions, ranging from telescopes to spacecraft communication to test facilities. Not all of these facilities fall solely under the aegis of the Planetary Science Division, but a subset of those of critical importance to our community is included. NASA Test and Environmental Simulation Facilities NASA’s Field Centers are home to many test facilities used for technology, instrument, or spacecraft integration and testing. The Centers have ISO 9001-certified cleanrooms, vibration, acoustic, and electromagnetic interference test capabilities, and thermal vacuum chambers; several have limited radiation testing facilities, as well. These facilities are available for use by the community through partnership agreements and the committee supports this effort. In addition, NASA Centers host a variety of facilities capable of replicating other planetary environments, including high pressure planetary interiors, very low-pressure atmospheres, extremely hot surface temperatures, and atmospheres and surfaces so cold that methane and other organic compounds form condensates and ices. These facilities permit instrument and technology development and testing, but also enable scientific experiments to be performed under conditions like those encountered on other 1 A glossary of acronyms and technical terms can be found in Appendix F. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-1 

planetary bodies. The size and capabilities of the different simulation facilities vary, and this variety is needed to accommodate the different needs of the planetary science community. One example is the NASA Glenn Extreme Environments Rig (GEER), which can simulate many different extreme environments, but has thus far focused much of its effort on replicating conditions at the surface of Venus (Lukco et al. 2018). Another example is the Planetary Aeolian Laboratory (PAL) at the NASA Ames Research Center (ARC), which over the past few decades has been used to study aeolian processes at pressures representative of the surface of Venus, Mars, and Titan (e.g., Greeley and Iversen 1985; Burr et al. 2015; Swann et al. 2020). Environmental simulations may also be needed to understand instrument measurements at extreme conditions. For example, the high surface temperatures on Venus have been shown to affect mineral spectra in the visible and NIR wavelengths, and this type of spectroscopy is one of the only available tools for examining variations in surface composition from orbit (Helbert et al. 2021). It is thus critical to have laboratory facilities capable of replicating extreme environments to develop spectral libraries for interpretation of mission measurements, or calibration of mission instruments. Scientific experiments cover many areas of research, including material properties, chemistry (of geologic materials, gases, organic/prebiotic), aeolian processes, the microphysics of nucleation, condensation, and ice formation, and physicochemical properties of planetary materials. However, NASA Centers are not immune from management, staffing, and funding issues. A review of SMD planetary facilities in 2015 (Mackwell 2016) noted that a lack of on-site personnel with an active interest in using and improving the NASA ARC PAL wind tunnels, coupled with a lack of engagement of management in facility operation or experiments, had likely resulted in limited community use of the PAL facility and a growing need for modernization of equipment. This is despite PAL’s Mars Surface Wind Tunnel (MARSWIT) being the only facility in the United States capable of simulating Mars surface pressures over a 13-m active wind tunnel into which sand and dust may be introduced. Finding: NASA’s diverse planetary environment experimental facilities would benefit from regular review by an External Review Board to determine if their capabilities and operations are meeting community needs. For those that are underutilized, an evaluation of both their technological and administrative aspects, including a feasibility study and cost-benefit analysis of whether refurbishment, rebuilding, or retirement is appropriate. Retained facilities need adequate funding for both on-site management and staff, as well as future modernization and expansion. These facilities could also be more effectively utilized by the planetary science community by increasing their discoverability via a database of available systems and their capabilities. NASA Telescope Facilities Observatories (on the ground and in space) provide both unique discoveries and essential support for planetary missions as well as the continuing search for and characterization of exoplanets by providing spatial, temporal, and spectral context for observations from spacecraft. Both ground and space-based facilities support the major subsets of the survey’s 12 key science questions by providing essential monitoring of dynamic or unique solar system phenomena, including atmospheres (Q7, Chapter 10), comets (Q1, Q2, and Q3, Chapters 4-6), cryovolcanic/plume activity (Q5, Q6, and Q8, Chapters 8-9 and 11), occultations (Q4, Chapter 7), and many more, all varying on timescales of hours to multiple decades. Changes over long timescales are challenging for a visiting spacecraft, so telescope observations fill the gaps between missions. There are excellent synergies between planetary missions and ground/space-based observatories, such as Earth-based support campaigns, which encompass both professional facilities (multi- spectral from radio to X-ray) and amateur observers (in visible and near-infrared). Ground-based facilities have the benefit of longevity, and their capabilities can increase over time as science instruments can be upgraded, repaired, or replaced. These instruments have relaxed mass and size constraints compared to spacecraft instrumentation, delivering capabilities such as high spectral resolution, spectral multiplexing, and the strong light-gathering power of large apertures. Currently, NASA/IRTF PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-2 

devotes 50 percent of its time to solar system studies, but all other facilities rely on competitive proposals each semester, with limited NASA/ESA guidance on priorities for spacecraft mission science support. Observatories may also consider offering the possibility of long-term status for monitoring programs, extending over multiple cycles with mutually agreed renewal procedures. Extremely large telescopes coming online late in the next decade (see NSF section below) will deliver advanced capabilities with angular resolution comparable to Voyager approach data (Wong et al. 2021). NASA investment in these observatories would enable new capabilities for spacecraft mission support, potentially even affecting mission payload decisions if designed to operate in conjunction with dedicated support programs. Finding: Planetary science at NASA-funded observatory facilities benefits from a proposal mechanism for spacecraft mission support, for example, the Keck 2022A call for mission support proposals, as well as multi-cycle programs. pace-based facilities can access spectral regions invisible from the ground and are not subject to blurring due to atmospheric turbulence at visible wavelengths, or high sky backgrounds at infrared wavelengths. Suborbital and airborne telescopes partially escape these atmospheric effects without the high cost of spacecraft development and launch. Specific spectral ranges are only accessible from space-based facilities including X-ray, the ultraviolet, and atmosphere-opaque regions of the infrared. Observing and instrument conditions (e.g., thermal and photometric, etc.) can also be stabilized on space platforms, enabling high- precision measurements and long time series. Thus, it is important that astrophysical instruments and observatory capabilities are designed with planetary observations in mind. An excellent approach for enabling solar system observations is the purposeful inclusion of solar system scientists on science working groups, development teams, and instrument and operations staff which has proven to be highly successful for JWST (Hammel and Milam 2021). It is also desirable to allow flexible scheduling for unanticipated phenomena, through mechanisms such as director’s discretionary programs, and a variety of observation cadences, from short-term to long-term monitoring of objects, potentially over multiple years with long term programs. Finding: To enable planetary observations, Astrophysical telescope assets need to continue to include tracking non-sidereal rapidly moving objects, with dynamic range accommodations for both bright and faint targets. The Deep Space Network The Deep Space Network (DSN) is a critical element of NASA’s solar system exploration program. It is the only asset available for communications with deep space missions. The DSN is currently composed of three stations located in Goldstone, California, Madrid, Spain, and Canberra, Australia, along with operations control and other services in the United States. Each station has one 70-meter antenna, with three 34-meter Beam WaveGuide antennas at Goldstone and Canberra and four at Madrid. NASA has plans to add at least one more 34-meter antenna at each complex in the near future (Lazio et al. 2020). These antennas support more than three dozen missions with downlink and uplink capabilities in S-, X-, and Ka- band (limited). Collectively, these stations provide nearly continuous full-sky coverage. The 70-meter dishes are in high demand, particularly during critical events, because of their downlink capability, sensitivity, and ability to satisfy other mission requirements. As such, they are heavily oversubscribed, and current deep-space missions are limited mostly by downlink rather than onboard storage capacity (Johnston 2020). The DSN also contends with aging infrastructure, particularly the 70-m antennas that were constructed in the 1960s; a 2020 NASA OIG audit (IG-20-023) raised concerns about the inability to properly maintain these systems. Nonetheless, the DSN continues to perform extraordinarily well, returning data with a very low drop- out rate and achieving command and telemetry availability of better than 95 percent to most operating PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-3 

missions. In the coming decade, with the launch of JWST and expansion of human exploration, demands for DSN support will increase dramatically, projected at another factor of 10 by the early 2030s, Figure 20.1. Future capabilities afforded by optical communication, transponder advances, advanced onboard compression and data processing software, and other means may provide future increases in returned data volumes and will be important to meeting mission demands (Lichten 2021), but the DSN infrastructure needs to keep pace. Due to differences in atmospheric opacity, planetary missions require downlink capability in multiple frequency bands. For example, three-band telemetry during outer planet atmospheric occultations allows sounding of different pressure depths within the atmosphere. In addition, S-band capacity is required for communications from Venus during probe, balloon, lander, and orbit insertion operations because communications in other bands cannot penetrate the atmosphere. X-band capability is required for communication through the atmosphere of Titan, and also for emergency spacecraft communications. Although Ka-band downlink has a clear capacity advantage, there is a need to maintain multiple-band downlink capability, because Ka-band imposes additional power and pointing demands on spacecraft with limited resources that may be difficult to meet, especially in the event of spacecraft safe mode entry. Finally, the DSN is crucial for precision spacecraft ranging and navigation, and this capability needs to be maintained. Finding: S-, Ka-, and X-bands are critical to planetary mission communication, requiring careful management of these key frequencies. X-band also remains crucial for science data downlink, recognizing that Ka-band pointing and spacecraft stability requirements pose challenges for resource- limited missions, particularly in safe mode conditions. Outer solar system exploration also requires either 70-meter antennas or equivalent arrays to achieve the data rates needed for distant missions, such as to Uranus, Neptune, and the Kuiper belt. In order to support multiple missions, the DSN needs to be able to receive data from more than one mission at one station simultaneously. If new arrays can only mimic the ability of one 70-meter station and nothing more, missions will remain downlink-constrained and will have to compete against one another for limited downlink resources. Recommendation: NASA should expand uplink and downlink capacities as necessary to meet the navigation and communication requirements of the missions recommended by this decadal survey, with adequate margins, while also balancing the demands from other projects, including JWST, Roman Space Telescope, Artemis, and others. The Goldstone Solar System Radar (GSSR) is a key facility for ground-based planetary radar observations, specifically, the 70-m DSS-14 and 34-m DSS-13 elements of the DSN. GSSR is a fully steerable radar facility that can transmit at X-band (8560 MHz, 3.5 cm) at a continuous power of 500 kW from DSS-14; the 80 kW, C-band (7190 MHz, 4.2 cm) DSS-13 is primarily used for asteroid and lunar studies. After the loss of the Arecibo Observatory in December 2020, which at the time was the largest, most sensitive, and most powerful planetary radar facility, GSSR is now the primary facility for radar observations of near-Earth objects (NEOs) and other planetary bodies. Radar mapping of the Venusian surface is most feasible at L- and S-band; the current GSSR infrastructure is unable to support radar observations of the Venusian surface. Additionally, GSSR is some 15 times less sensitive than Arecibo was, which results in limited observing capabilities in monostatic configuration. Finding: GSSR is the remaining key facility for ground-based planetary radar observations and can provide critical planetary defense and other planetary science observations. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-4 

FIGURE 20.1. Past and predicted loading of the DSN for 2010 to 2045 based on a past notional mission manifest (Abraham et al. 2018). Although the planned missions have changed, the challenge remains that a factor of 10 increase in data downlink is expected by 2030 due to mission complexity and instrument advances. Planetary Sample Curation and Associated Laboratory Facilities Just as geological samples from Earth record the natural history of our planet, astromaterials hold the natural history of the solar system and beyond. Astromaterials include samples of extra-terrestrial origin collected on Earth (e.g., meteorites and cosmic dust) and samples returned from space as part of a sample return mission (e.g., Apollo, Stardust, Genesis). With a large increase in sample return missions (e.g., Hayabusa, Hayabusa-2, OSIRIS-REx, and Mars Sample Return), curation facilities are at a critical juncture; these samples are stored in curation facilities designed to maintain the integrity of the samples, and these facilities represent a key infrastructure that supports planetary sample science. Moreover, the curatorial facilities are managed by a workforce of curators that have the knowledge to responsibly conserve the samples to maximize their science value in perpetuity. Additionally, they are responsible for allocating astromaterials samples to the scientific community. NASA’s astromaterials represent an invaluable resource for the planetary science community, and NASA allocates >1000 samples to scientists across the globe each year. Sample analysis work is supported by numerous NASA R&A programs. Finding: Continued funding is needed to support and maintain the curatorial facilities that host NASA’s astromaterials collections for past, present, and future sample return efforts. The Mars Sample Return Facility costs should fall within the existing budget for MSR (see Chapter 22) The Mars Sample Receiving Facility (SRF) is a critical part of the Mars Sample Return (MSR) Program. The SRF will conduct, under strict containment, preliminary examination and analysis of unsterilized samples collected and returned to Earth. The SRF will be required to implement planetary protection PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-5 

Category V (Restricted Earth Return) requirements and contamination control requirements. Evaluation of martian samples in the SRF requires an ISO-certified positive-pressure cleanroom and biosafety Level-4 (BSL-4) negative-pressure containment in a cabinet or suit laboratory; existing BSL-4 laboratories are not designed to host cleanrooms, and there are many approvals needed for certifying the BSL-4 status of a new facility. For Class V restricted missions, public health officials and other regulatory agencies need to be involved in planning and implementation. Current MSR schedules suggest that the SRF will need to be ready in about 10 years (early 2030s), which is approximately equal to the amount of time it would take to build and commission a new BSL-4 lab, if this is the implementation approach needed. Furthermore, the SRF will need to have a clear workflow toward release of samples to long-term curation and to the community for planned analyses that take advantage of leading geochemical and microanalytical facilities around the world (Carrier et al. 2021; see also Chapter 22). Development of a plan for the design and construction of the SRF is still in early stages and may already be behind schedule for sample return in the early 2030s timeframe. Recommendation: NASA, in partnership with ESA and community stakeholders, should develop the plan for the end-to-end processing of samples returned from Mars. This plan should include the definition, design, and construction of the Mars Sample Receiving Facility to ensure that it is ready to receive the samples by 2031. The plan should also outline the approach for expeditiously distributing the samples to the scientific community for analysis and to a long-term curation facility. In addition to sample return missions, astromaterials collected on Earth as meteorites and cosmic dust represent a critical feedstock for planetary sample science. Many sample collection efforts are supported by federal funding and rely on infrastructure. For example, cosmic dust is captured in collectors mounted on high-altitude aircraft such as WB-57 (Ellington Airfield at Johnson Space Center) and ER-2 (Armstrong Flight Research Center), which are both maintained and supported by NASA. The United States also supports the Antarctic Search for Meteorites (ANSMET) through a three-agency agreement between NASA, NSF, and the Smithsonian. Nearly half of all astromaterials sample requests made to NASA each year request samples from the U.S. Antarctic Meteorite collection. Furthermore, this collection is composed of samples from the Moon, Mars, undifferentiated and differentiated asteroids, further highlighting the breadth of the sample science community that uses the U.S. Antarctic Meteorite collection as a critical resource. Finding: Continued efforts are needed to support and maintain the infrastructure that enables the collection of astromaterials on Earth, including Antarctic meteorites and cosmic dust. As technological advancements and new ideas expand the variety and scope of scientific questions that can be asked with astromaterials samples, so expands the need for better storage, processing, and sample handling capabilities of curation laboratories that house and process astromaterials samples. Over the coming decade, we will need to improve our ability to curate and process under “cold” conditions. The ever-expanding plans for the return of samples from volatile-rich solar system targets and/or targets of astrobiological significance (e.g., volatile-rich samples from the lunar poles, comet nucleus samples, future ocean world samples of biological importance) necessitate the development of curation at temperatures below that of typical curation facilities (20 °C). Temperature requirements depend primarily on which volatiles are expected within the returned sample, which in turn relate to the conditions under which the material formed and has since been preserved. The curatorial temperatures for terrestrial materials, including tissue samples and ice cores, include: ≤ -20 °C (the temperature of typical walk-in freezers in which physical processing and documentation takes place); ≤ -40 °C for archival storage (e.g., of ice cores); and -80 to -196 °C (liquid nitrogen) for biological samples (e.g., Anchordoquy and Molina 2007; Rissanen et al. 2010). Thus, except for biological tissue storage, the field of Earth materials curation has not yet entered the realm of cryogenics, although cold curation and processing of astromaterials are in development PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-6 

(Herd et al. 2016). Most importantly, the infrastructure requirements for cold curation vary substantially depending on the temperature requirements for the samples. For example, without specific temperature requirements for Artemis samples, detailed planning for an Artemis cold curation facility cannot proceed. Even after a decision is made about sample temperature requirements, R&D work will be needed to optimize infrastructure requirements for the curation and processing of geological materials under cold conditions. Finding: Further work is needed to define the sample temperature requirements for curating and processing future cold or volatile samples and for developing the appropriate facilities. Analytical laboratories also are a critical piece of infrastructure for planetary science and astrobiology, providing a key role in the analysis and understanding of returned samples, meteorites, and mission data. As stated in the last decadal survey, “The most important instruments for any sample return mission are the ones in the laboratories on Earth” (NASEM 2011). Maintenance of sample analysis capability is critical for planned sample return efforts, as is development of new techniques and instrumentation. As an example, the ANGSA program has demonstrated the usefulness of the technique of X-ray Computed Tomography for documenting materials in previously unopened lunar samples from Apollo missions without disturbing the sample (Zeigler et al. 2020). Along with returned samples, instrument capability is critical for analysis of meteorites and laboratory experimental products. Additionally, sample return efforts are being sent to worlds with the potential of returning materials beyond typical geologic materials (e.g., ice, organic molecules, gases) that require special care while analyzing or entirely new techniques to measure. NASA provides funding critical support, maintain, and expand the analytical and experimental capabilities of U.S. based laboratory facilities to conduct planetary science and astrobiology; this includes equipment investment, as well as adequate technical support staff. Long-term support of PI-led laboratories is essential for maintaining national leadership in specialized microanalytical capabilities crucial to planetary sample analysis (e.g., metal isotopes, age dating work with less common isotope systems, zircon analysis, FIB and TEM work). DOE and NSF support synchrotron capabilities play a key role in nanometer-scale ancient earth fossil analysis and will be important to the next decade’s astrobiological samples. The committee endorses the finding of the National Academies’ report Strategic Investments in Instrumentation and Facilities for Extraterrestrial Sample Curation and Analysis (NASEM 2019) that longer-term funding support for technical staff is desirable to ensure labs maintain this expertise and capability better than current short term soft money funding programs allow. Plutonium-238 Production Radioisotope Power Systems (RPS) are essential to the exploration of the solar system. The Visions & Voyages (V&V) decadal survey recognized that plutonium-238 (238Pu) fuel is essential for comprehensive exploration of the solar system and made a recommendation to restart production with a goal of producing 1.5 kg/year. NASA’s RPS Program Office and the Department of Energy (DoE) has begun such a program and are now successfully producing fuel (Sutliff et al. 2021), on track to accomplish a production rate of 1.5 kg/year in 2026 (Zakrajsek 2021, Dudzinksi 2021). Spacecraft power systems use 238Pu formed into fuel pellets of 0.15 kg of PuO2 each and then encased in an iridium clad. Depending on the RPS system required, the number of clads per system vary from 32 (4.8 kg of 238Pu) for one MMRTG system to 72 (10.8 kg) for one GPHS RPS system. The RPS Program Office (with DoE) has supported a one-time production of up to 22 clads in one year to support Mars 2020, but the currently planned production rates are 10 to 15 clads/year. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-7 

FIGURE 20.2. Example illustrating the need to increase production of 238PuO2 above 1.5 kg/year. With the cadence assumed here (Dragonfly with 1 MMRTG, NF opportunities with 1 Next Gen Mod 1 RTG each, and a Flagship with 3 Next Gen Mod 1 RTGs), a steady 1.5 kg/year production is insufficient for even a modest program of missions. The transformation of source material into 238PuO2 pellets, and subsequent fabrication of clads, requires significant infrastructure to develop and represents a major investment by NASA. The current remaining inventory from the DOE stockpile is ~30 kg of PuO2, which can be mixed with newly produced material to meet the power specification required for RPS units. Production is expected to increase to 1.5 kg/year by 2026. With a rate of 238PuO2 production of 1.5 kg/year, clads can be manufactured steadily at 10 clads/year; clad production can be increased by depleting the stockpile of older 238PuO2. The committee commends the NASA/DOE approach to steadily produce 238PuO2 clads independent of mission new starts or selections. However, the currently planned production rate remains a significant limiting factor in NASA’s ability to develop new deep space missions. Based on the Planetary Mission Concept Studies, as well as the studies commissioned by this decadal survey, RPS demand far outweighs availability in the upcoming decade. With a regular cadence of New Frontiers and Flagship missions launched, and assuming the use of Next Gen Mod 1 RTGs (requiring 64 238PuO2 clads) (Zakrajsek 2021), the committee derives an example scenario in Figure 20.2; this modest power scenario ignores any demands from the Discovery, Lunar, or Mars programs, human exploration needs or other NASA programmatic needs, and assumes 20 kg of 238Pu is available now. Even with a steady 1.5 kg/year production, the type and number of missions that can be flown will be constrained by the number of available clads, far less than the desired program of missions, until the current PuO2 inventory is exhausted. After that point, production of 238Pu will be the rate-limiting step. Recommendation: NASA should evaluate plutonium-238 production capacity against the mission portfolio recommended in this report and against other NASA and national needs, and increase PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-8 

it, as necessary, to ensure a sufficient supply to enable a robust exploration program at the recommended launch cadence. New technology investments may also help to mitigate the dearth of the 238Pu supplies in certain scenarios. For example, the RPS Program Office is developing a Dynamic RPS system. Such systems could increase the thermal to electric efficiency by a factor of ~4 over current GPHS RPS technology. Such units are not likely to be available for long duration missions endorsed by the current Decadal Study, but a demonstration of a Dynamic RPS for a mission of shorter duration could pave the way for future missions in later decades with a significantly lower demand for 238Pu. Recommendation: NASA should continue to invest in maturing higher efficiency radioisotope power system technology to best manage its supply of plutonium-238 fuel. Launch Services Launch vehicle availability and capability continue to pose a challenge to NASA’s program of planetary exploration. The workhorse Atlas V and Delta IV vehicles are expected to be retired and will no longer be available for this Decadal’s prioritized missions. The primary launch vehicles likely to be available include the existing Falcon 9 series, both Recoverable and Expendable versions, and the Vulcan Centaur; NASA will need to be agile in selecting appropriate options for planetary exploration to enable missions both small and large, near and far. The currently available vehicles can support missions to the Moon, the inner solar system, and Mars, but continued exploration of the outer solar system requires multiple gravity assists, and often long cruise durations, or high-performance propulsion systems, in-orbit assembly, or use of high- performance launch vehicles (high C3, the square of the hyperbolic excess velocity, Figure 20.3). Studies of outer solar system missions show that the use of singular Jupiter gravity assists, which enables larger spacecraft and/or shorter flight times, tightly constrains launch windows for large missions and is not an optimal solution. Commercial ride shares, emerging small launch providers, and commercial delivery services, for example the Commercial Lunar Payload Services, may also provide other opportunities for some destinations. Recommendation: NASA should develop a strategy to focus and accelerate development of high energy launch capability, or its equivalent, and in-space propulsion to enable robust exploration of all parts of the solar system. Any new systems that are developed should also build the pedigree required to permit the launch of nuclear materials. Data Archiving and Distribution In 2020, NASA convened an Independent Review Board (IRB) to examine the state of the Planetary Data Ecosystem (PDE) which includes all aspects of data collection and archiving. Rather than repeat that effort, the committee refers to key recommendations from the IRB’s report (McGrath et al. 2021) where appropriate. NASA missions and most R&A programs require a Data Management Plan (DMP) that includes the timely archiving of all raw and calibrated data, mission and instrument documentation, and calibration procedures. The production and archiving of higher-level science products have been encouraged, but these activities are often completed only after the mission ends. DMPs should ensure that ground-based datasets are archived in a manner compliant with findability, accessibility, interoperability, and reusability criteria (Wilkinson et al. 2016), in high level (reduced) formats useful for planetary researchers. This is particularly important for observations of time-variable targets, where future discoveries can generate the need to access much older data for comparison. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-9 

Finding: An index covering all planetary science, astrobiology, and field sample databases, would assist in data sharing and analysis. This index could include links to relevant spectral databases (e.g., USGS SpecLib, RELAB, GEISA, HIITRAN), other dedicated data archives (e.g., MAST, ASTROMAT), and sample archives that are available for outside users and/or collaboration. FIGURE 20.3 Performance comparison curves for launch vehicles proposed to be available during the time period covered by this decadal survey; the heavy lift options (SLS, Vulcan) are not yet ready for flight, constraining distant and/or large mission launches. The curves show how each vehicle’s payload lift mass varies with the C3 parameter, and it is necessary that the mission fit below the desired vehicle’s curve, with margin. Also shown are the required C3 values for several mission concepts studied under PMCS and as part of this decadal survey. Planetary Data System The Planetary Data System (PDS) has been a pioneering repository and archive of planetary mission data for many decades. Development of the PDS4 Information Model to handle the ever-expanding amounts of mission data, make it more user accessible, and provide advanced tools for database access and analysis should be continued. The International Planetary Data Alliance has endorsed the PDS4 standard, which is being utilized by many agencies to ensure interoperability of archives and data sets. The PDS now accepts a range of non-mission datasets, including ground-based observations and planetary analog laboratory and field measurements. PDS does offer some archiving training, including a Data Users Workshop every two years, but additional training opportunities with wide community reach would aid non-mission data providers with little archiving experience. Finding: As recommended in the IRB PDE report, “regular, accessible, and effective training programs for researchers” … is needed for… “data producers, mission specialists, and others who need to archive with the PDS.” PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-10 

Sharing of Software, Algorithms, and Model Output NASA DMPs increasingly require that most software, algorithms, and model output generated under NASA funding be made publicly available for wider use. The potential benefits are profound: enabling new users to work without needing to re-develop existing tools; allowing users to develop more advanced codes rather than start from scratch; enabling existing model output to be used for a whole range of new purposes. Examples include retrieval algorithms that extract temperature profiles from radiance data; or taking output generated by climate models to study weather patterns and instead using it as input to chemistry models, to assess Entry-Descent-Landing risks, or for outreach purposes. Such repurposing of existing tools and output would avoid duplication of effort and save NASA scientists, engineers, and EPO officers significant time and money. Finding: As recommended in the IRB PDE report, a plan is needed “for the preservation of models and model output, beginning with requirements for how these should be preserved and linked to other Ecosystem elements.” However, there are concerns over how to provide access to multiple iterations of software that is continuously evolving and improving, and how to preserve and distribute the huge datasets (often Terabytes in size) generated by model simulations, when new and improved simulations may render earlier datasets obsolete. Planetary research, particularly concerning time-varying phenomena or hard-to-observe bodies, continues to use data over 100 years old. By contrast, the longevity of software code may be limited by the compilers, hardware, and operating systems needed to run it, and/or superseded by more sophisticated code. Similarly, model output may be superseded by that from more sophisticated modeling systems. Finding: Community awareness of and access to the best software and model output datasets is needed, not necessarily preservation of every code, simulation, or output version indefinitely. Preserving Model Data Model input and output data generated by NASA funding is not currently accepted by the PDS. Examples of this type of data include N-body simulations, hydrocode impact simulations, atmospheric circulation modeling, and magnetosphere modeling. Such data are valuable for a diverse range of NASA- supported activities, often different from those for which the modeling was originally performed. These include assessing atmospheric and radiation risks for human exploration of Mars, testing theories of planetary formation, exploring the capabilities and requirements of proposed planetary missions or instruments, and advanced visualization. Hosting model output data in community-recognized repositories would allow them to be easily located. Making these repositories also discipline-specific, with mandated data and metadata formats, would allow them to be supplemented by generalized tools designed to enable easier access to and sampling of these often-huge datasets (Newman et al. 2021). Repositories of model output can also be designed to contain only the most recent complete outputs from a particular model, with earlier datasets simply documented for posterity. Finding: A clear plan for the preservation and sharing of planetary model input and output data, involving both the PDS and planetary modeling communities, is needed to develop a network of discipline-specific, community-recognized repositories, rather than via rigorous, costly, and often unnecessary archiving. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-11 

Sharing Software and Algorithms Descriptions of methods and simple algorithms may be documented with publications, but more complex algorithms and software require more elaborate documentation and repositories. Minimum requirements ensure results from ad hoc analysis code can be replicated or at least understood, and that specific NASA-funded software development efforts (including mission data processing pipelines) comply with NASA open-source software policies, for example using repositories such as the NASA-managed GitHub; exceptions are made for code containing proprietary or ITAR/EAR restricted material. However, software developers span a range of effort levels, from those satisfying the minimum DMP requirements to those who plan to provide training and ongoing support to all users wishing to use their codes, including regular updates to the code base, user’s guides, and tutorials. Finding: Grant programs that offer the ability to fund community-oriented software projects need to also consider code maintenance, documentation, and user support. Other Specialized Services The Navigation and Ancillary Information Facility (NAIF), which operates under the PDS, is critical for maintaining spacecraft mission SPICE kernels that contain all the ancillary information relating to how data from a particular spacecraft instrument was collected. NASA planetary missions are expected to adopt SPICE as a standard during mission planning, operations, and archiving for consistency and usability with existing tools. The committee also encourages the availability of ephemeris and visualization tools, such as JPL Horizons and the PDS Rings Node tools, for more casual use. The availability of higher-level pointing and ancillary information in the mission data itself, either in the PDS4 files, or in higher level search tools, such as PDS OPUS, PDS Imaging Atlas, and other community tools, are a valuable resource for the community. Lastly, The IAU Minor Planet Center’s (MPC) role as the worldwide repository for positional measurements of small bodies and responsibility for their initial orbit computation is crucial for planetary defense efforts to identify and track NEOs. The Center for NEO Studies (CNEOS) utilizes the MPC data to compute high-precision orbits, produces comprehensive assessments of Earth impact probabilities, and hosts the results publicly, maintenance of which are vital to inform global planetary defense efforts. Supercomputing Facilities Many research tasks require large computational resources including circulation modeling, n-body simulations of dynamical processes and solar system formation, as well as other high-resolution modelling and computations. With advances in neural net processing and machine learning techniques, a desire to run models at higher spatial and/or temporal resolution to delve deeper into processes and phenomena, as well as the collection of increasingly large quantities of data, computational resource demands are higher than ever. In addition to PI and institutional resources, NASA operates multiple advanced supercomputer clusters, some of which are available for science community use. Access to these systems is primarily granted in conjunction with R&A proposal requests, and the committee supports their use and continued modernization and expansion of capabilities in the future. SUPPORTING NSF INFRASTRUCTURE The National Science Foundation (NSF) has supported and continues to support a wide variety of current and future astronomical facilities as well as laboratory and other facilities. NASA and NSF recently reaffirmed their commitment to partnering on space research activities in a new 2020 Memorandum of PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-12 

Understanding (NASA-NSF MoU 2020). This includes the use of NSF-managed stations and facilities in the Antarctic, as well as collaborative science and technology programs. Here the committee highlights several prominent facilities, but the list is not all-inclusive. Existing Ground-Based Astronomical Facilities The NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab) provides the mainstay of ground-based telescopic science for astronomy. NOIRLab has five programs, some of which had previously operated under a different management structure: The Cerro Tololo Inter-American Observatory (CTIO) in Chile, the Community Science and Data Center (CSDC), Gemini Observatory (operating in Hawaii and Chile), the Kitt Peak National Observatory (KPNO) near Tucson, Arizona, and the Vera C. Rubin Observatory which is undergoing commissioning and is expected to become operational in coming years. The NOIRLab southern assets, including telescopes at CTIO and Gemini South, provide a unique opportunity for US researchers to perform ground-breaking research in the southern hemisphere on objects out of the ecliptic plane (e.g., comets). In the coming decade, it is expected that the CSDC will provide an increasing role in supporting the future of astronomy and planetary science as the amount of astronomical data, both PI-led and public survey data, has and continues to increase tremendously. NSF support for independent PI-led investigations in big data science will be important to satisfy growing needs over the next decade for development and implementation of new workhorse methodologies and algorithms. The NSF-supported ecosystem of both 8 to 10-m class (e.g., Gemini) and 4-m class (e.g., KPNO) telescopes will continue to be important in the era of extremely large ground-based telescopes (see below). Smaller telescopes enable high-risk/high-reward experiments, proof of concept studies for programs at larger telescopes, follow up on transient discoveries, provide testbeds for new instrumentation, enable longer-term observing campaigns, and provide training opportunities for students and early career researchers (Chanover et al. 2021). Flexible access options (e.g., fast-turnaround programs at Gemini) are geared toward publishable results on short timescales. These facilities are enabling for strategic research that happens on timescales faster than the mission development cycle, such as impact monitoring (Q4, Q7, Chapters 7 and 10), small body mutual events (Q1, Q4, Chapters 4 and 7), dynamic atmospheric events (Q6, Q7, Q8, Chapters 9-11), and others. The Atacama Large (sub)Millimeter Array (ALMA) is capable of high-resolution thermal and atmospheric observations of planetary objects such as the Galilean satellites and Titan, enabling important science, particularly in combination with and/or as a complement to space mission data. For example, global and long-term perspectives of Titan provided by ALMA (and ultimately by the next-generation Very Large Array (VLA; ngVLA, see next section)) will complement local studies to be performed by Dragonfly. ALMA and ngVLA wavelength sensitivities are well-suited for detection of complex organics in atmospheres and plumes, and thermal surface/sub-surface anomalies important for understanding endogenic heat flow in outer planetary satellites. More broadly, ALMA observations of protoplanetary disks around other stars reveal important constraints on protoplanetary disk evolution and the initial stages of planet accretion (Q1 and Q12, Chapters 4 and 15) relevant to solar system studies. Future Facilities The Vera C. Rubin observatory is currently being commissioned and will revolutionize planetary astronomy with an unprecedented inventory of solar system objects as well as time-domain astronomical investigations. The NSF has invested heavily in the construction and preparation of this facility. To provide the maximum benefit to the scientific community, the NSF needs to provide the greatest possible support to this facility (while balancing with other valuable NSF outlays) including, at the earliest opportunity, funding access for both Rubin consortium guided science as well as innovative PI-led science so the PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-13 

maximum benefit of the observatory can be achieved. This ought to include ample support for software infrastructure that can benefit all researchers on a rapid timescale, as well as PI-led science, to allow for new innovations as the many discoveries by the observatory sculpt and change our view of the solar system in the next decade. The next generation of extremely large (larger than 20-m effective diameter) optical telescopes will see first light in the next decade. These include the European Extremely Large Telescope (EELT) and the Gian Magellan Telescope (GMT) in Chile, and the Thirty Meter Telescope (TMT) in the northern hemisphere. Access to TMT and GMT for the full US community will rely on the NSF’s US-ELT program. These observatories will offer unprecedented angular resolution, supported by robust adaptive optics instrumentation programs. Without NSF investment in guest observing programs at these next generation telescopes, the dramatically new science research that will be performed will only benefit from the skills, knowledge, and innovative perspectives from the subset of US researchers who are members of TMT and GMT consortia. In particular, the U.S.-ELT program could support key planetary science programs involving long-term time-domain science across all key questions, transient phenomena (Q5, Q6, Q7, Q8, Chapters 8-11), and small body characterization surveys (Q1, Q2, Q3, Q4, Chapters 4-7) (Wong et al. 2021). Finding: As stated in the Pathways to Discovery in Astronomy and Astrophysics for the 2020s decadal survey, the committee expects the ELT facilities to provide transformational planetary science, but only if the observing programs are adequately funded. Construction in the next-generation VLA (ngVLA) is planned to start in the next few years, with eventual baselines as large as almost 9000 km delivering spatial resolution at Neptune of ~130 km (de Pater et al. 2021). This facility promises advances in planetary science, particularly for the giant planets, building on prior radio science results from Juno, Cassini, the VLA, and ALMA. As with space astrophysical observatories, groundbreaking planetary research at future facilities will be aided by the purposeful inclusion of planetary astronomers within development teams and observatory staff (Hammel and Milam 2021). Recommendation: NSF-supported, ground-based telescopic observations provide critical data to address important planetary science questions. The NSF should continue (and if possible expand) funding to support existing and future observatories (e.g., NOIRLab, ALMA, TMT, GMT, ngVLA) and related PI-led and guest observer programs. Planetary astronomers should be included in future observatory plans and development in order to maximize the science return from solar system observations. Laboratory and Other Facilities (including Antarctic) The NASA and NSF MoU states their commitment to “continue working together to advance NASA and NSF—sponsored science programs…. with special emphasis on those that make use of the NSF- managed facilities, including those in the Antarctic”. A continued NASA-NSF Antarctic commitment, based on mutual understanding of needs and resources, is needed to maximize the use of facilities that can advance the scientific goals of both agencies. For example, NASA could consider having an NSF program manager or United States Antarctic Program representative participate in the review of Antarctic proposals to NASA programs. Finding: Joint NASA-NSF reviews of Antarctic research proposals and facilities would strengthen the science programs at both agencies. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-14 

Ground-Based Planetary Radar Ground-based planetary radar observations have been primarily conducted at shared-use facilities, in particular at the NSF facilities of Arecibo Observatory in Puerto Rico and Green Bank Telescope (GBT) in West Virginia. Previously, the planetary radar project at the Arecibo Observatory was supported by NASA through the Near-Earth Object Observations Program and recently through the Solar System Observations Program, tasked through the Planetary Defense Coordination Office, while the facility was NSF managed under a cooperative agreement. NASA supported all planetary radar observations at Arecibo, as well as partially supported facility maintenance and infrastructure. Although Arecibo was lost, the GBT can continue to serve as a receiving antenna for GSSR. Additionally, GBT is currently considering the addition of a radar transmitter (Bonsall et al. 2019), providing much needed complementary observations to GSSR (see Planetary Defense chapter). To date, NASA and NSF have informally cooperated at Arecibo and GBT by leveraging their grantees and contractors as intermediaries. As the remaining facilities for ground-based planetary radar observations, GSSR and GBT are critical for planetary defense and science observations. Recommendation: NASA and NSF should review the current radar infrastructure to determine how best to meet the community’s needs, including expanded capabilities at existing facilities, to replace those lost with Arecibo. INTRA-AGENCY, INTERAGENCY, AND INTERNATIONAL COLLABORATIONS Planetary science and astrobiology are multi-disciplinary, with associated fields including hydrology, geology, meteorology, microbiology, oceanography, heliophysics, astrophysics, and many more. Most of these areas of expertise have their own organizations, agencies, and research programs in every country across the world. Collaboration and sharing of infrastructure and ideas is therefore an important way to maximize efficiency and results, as recognized in NASA’s Explore: Science 2020-2024 (Vision for Science Excellence 2020). Here the committee highlights a few key infrastructure partnerships and discusses areas for future collaboration. Intra-Agency Facilities Planetary scientists currently collaborate across all of NASA Divisions, for example, with exoplanets science in both Planetary and Astrophysics, space weathering, solar wind, magnetospheres interests in both the Planetary and Heliophysics Divisions, and many others (Mandt et al. 2021). Another example is the overlap between resources used for Human Exploration and scientific uses: wind tunnels and environmental chambers may be used for spacesuit testing, as well as for instrumentation development and for scientific studies. Other examples of cross-divisional infrastructure include NASA’s ground and space-based telescope facilities, supercomputers, and other assets. Finding: The committee encourages the continued involvement of the Planetary Science Division in developing, enabling, and supporting cross-divisional facilities with input from the community on the design, capabilities, and resource allocations from these facilities. Interagency Facilities In emerging disciplines such as ocean worlds and astrobiology, as well as in more established fields such as atmospheric and geologic processes, cross-agency interactions can provide additional insights, data, tools, and facilities to advance our knowledge. As a first example, the National Oceanographic Partnership PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-15 

Program (NOPP) facilitates partnerships between 16 federal agencies (including NASA), plus academia and industry, to advance ocean science research and education. As a second example, NASA Goddard’s highly successful Heliophysics Data Portal, which facilitates the sharing and use of heliophysics data from both NASA and international missions, could serve as a template for repositories of other types of planetary output. Similarly, the Community Coordinated Modeling Center, which supports and performs space weather modeling, is a partnership between 8 agencies (including NASA, NOAA, and NSF) and numerous modeling groups across different agencies and institutions; this paradigm can provide great insight to planetary modelers aiming to set up something similar. Finding: Already established, and newly emerging, mechanisms for facility and data collaborations across other federal science agencies can serve as a good model for future NASA collaborations. Such partnerships ought to span from theoretical modelling and simulations to data ecosystems to data analysis, laboratory experiments, and field investigations across multiple entities. International Facilities In mid-2021, the European Space Agency (ESA) released its Voyage 2050 exploration themes for the period 2035-2050. One of the three large class mission themes is focused on exploration of the moons of the giant planets, in particular a goal of detecting biosignatures at an ocean world. In the medium-class mission category, recommendations included exploration of magnetospheres as a complex system, Venus geology and geophysics, as well as possible contributions to a U.S-led ice giants or solar system origins mission. Continued ESA partnerships are vital to the planetary science community, as there is a long history of successful international cooperation on mission and instrument development, testing, and operations, for example Cassini-Huygens, the Hubble Space Telescope, and the upcoming ExoMars and Mars Sample Return, among many others; some of these missions used ESA-led test facilities, launch vehicles, or ground communications. Finding: The committee encourages NASA to continue the history of successful international cooperation to advance the goals of both NASA and ESA. Further new and emerging partnerships, with JAXA, CSA, ISRO, and others, for example, are also encouraged and would enable even broader planetary science opportunities. REFERENCES Abraham, D.S., B. MacNeal, D. Heckman, Y. Chen, J. Wu, K. Tran, A. Kwok and C.-A. Lee (2018) Recommendations Emerging from an Analysis of NASA’s Deep Space Communications Capacity. AIAA 2018 Space Ops Conference. DOI: 10.2514/6.2018-2528 Anchordoquy, T.J. and M.C. Molina (2007) Preservation of DNA. Cell Preserv. Technol. 5, 180-188. Bonsall, A., G. Watts, J. Lazio, P. Taylor, E. Rivera-Valentin, E. Howell, F. Ghigo, T. Minter, H. Sizemore, S. Bhiravarasu, M. Slade, M. Busch, Ch. Dong, and J. Whitten (2019). GBT Planetary Radar System. Bulletin of the AAS, 51(7). (https://assets.pubpub.org/mwnvuyv4/31598545550747.pdf) Burr, D.M., N.T. Bridges, J.K. Smith, J.R. Marshall, B.R. White, D.A. Williams (2015). The Titan Wind Tunnel: A new tool for investigating extraterrestrial aeolian environments. Aeolian Research 18, 205 DOI: 10.1016/j.aeolia.2015.07.008 Carrier, B.L., D.W. Beaty, A. Hutzler, A.L. Smith, G. Kminek, M.A. Meyer, T Haltigin, et al., 2021. Science and Curation Considerations for the Design of a Mars Sample Return (MSR) Sample Receiving Facility (SRF). Astrobiology 21, Supplement, doi: 10.1089/ast.2021.0110. Chanover, N., C. Schmidt, and D. DeColibus (2021). The Continued Relevance of 4m Class Telescopes to Planetary Science in the 2020s. Bulletin of the AAS 53(4). DOI: 10.3847/25c2cfeb.752e4fa4 PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 20-16 

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