21

Technology

Technology is the foundation of scientific exploration. Two Voyager spacecraft were launched over four decades ago, now far beyond any human made object, and are still returning valuable scientific data about the interstellar medium. This achievement was enabled by new technologies such as the radioisotope thermoelectric generators, instruments, and high reliability electronics. The term “technology” has many meanings in current literature, but for the purposes of this decadal survey, technology means “the systematic application of scientific or other organized knowledge to practical tasks” (Galbraith 1978) In this way, technology applies to everything it takes to develop and deliver science missions into the solar system to perform science investigations. Today, our current technological capabilities are considered “state of the art.” However, there are state of the art technologies that exist today (e.g., flight processors) that have not yet been adopted to improve the science return of planetary missions. As we progress, we are constantly developing new or improved technologies (any set of productive techniques which offer a significant improvement in terms of higher resolution, unique techniques, survival in extreme environments, reliability, or lower costs over the state of the art) to answer science questions that were previously out of reach.

New science findings create new questions. Answering these questions has made science investigations more demanding, requiring the advancement of technology at a pace challenging our experience. Planetary science presents unique challenges in terms of instrumentation, power generation, mass control, miniaturization, propulsion, precision landing, hazard avoidance, communication, and extreme environments to name a few. Enabling planetary science missions requires early and substantial technology investments.

The Vision and Voyages for Planetary Science in the Decade 2013–2022 (V&V) decadal survey recommended that “a substantial program of planetary exploration technology development should be reconstituted” and “consistently funded at approximately 6 to 8 percent of the total NASA Planetary Science Division (PSD) budget” (NRC 2011). The NASA PSD has been generally successful in implementing these recommendations and has made good strides in developing technologies for this coming decade. Terrain Relative Navigation (TRN), precision landing, organics detection, sample collection and preservation, imaging and target characterization, hazard detection and avoidance (HD&A), are perfect examples.

This decadal survey offers observations about the progress made in technology management and development over the past decade, and identifies areas where improvements can further enable the exciting science missions identified in this decade and those that follow. Just as the science landscape changes, so does the technology landscape. Technological advances are being made both within NASA as well as in other government, academia,

and industry. Such advances can be better leveraged if the technology roadmaps are assessed and adjusted to take advantage of them as they emerge. A technology development program that holistically oversees this work can ensure the highest return on investment.

TECHNOLOGY DEVELOPMENT IN NASA

The approach to technology development within NASA has changed multiple times through the decades from centralized control, to distributed management, to the present-day hybrid approach. At the beginning of the V&V decadal survey, technology development within SMD was uncoordinated and lacked focus, and the V&V decadal survey recommended that the PSD reestablish a cohesive technology program. At that time the Agency also did not have a focused mission directorate for technology. During the V&V period, PSD implemented the V&V recommendations and established several new programs, while NASA established the Space Technology Mission Directorate (STMD). The V&V midterm review found that NASA had made substantial progress in meeting the technology goals of V&V (NASEM 2018).

As V&V was being developed, NASA had taken steps to improve the way it approached technology development across the full scope of work in the mission directorates. In the fiscal year 2011 budget request, NASA requested separate funding for space technology, and its budget has grown considerably since then. STMD develops crosscutting, pioneering new technologies and capabilities necessary for NASA to achieve current and future missions. These high-payoff, revolutionary technologies are rapidly developed, demonstrated, and integrated through collaborative partnerships. STMD invests in and matures broadly applicable, disruptive technology not currently available in industry, to meet the needs of future NASA missions in science and exploration, as well as to lower the cost for other government agencies and commercial space initiatives. Today, STMD is largely focused on advancing technologies and testing new capabilities at the Moon that will be critical for crewed missions to Mars: The Moon is essentially serving as a technology testbed and proving ground for Mars.

In 2017 PSD established the Planetary Exploration Science Technology Office (PESTO) at Glenn Research Center (GRC) to (1) manage planetary technology investments that are not yet specific to a mission in development; (2) coordinate planetary-relevant technology investments across PSD and other NASA organizations; and (3) meet the goal of maximizing infusion into specific missions. This office recommends annual technology investment strategies (considering investments being made by STMD and other NASA and government organizations) and updates the roadmap to achieve the strategic goals, based primarily on future mission needs. PESTO manages the development of technologies that have not yet been adopted by missions (except nuclear systems) and fosters a coordinated technology investment portfolio across NASA by collating and tracking existing investments across the Agency to communicate needs, identify gaps and promote cross-directorate collaboration. Last, PESTO promotes technology infusion by communicating technology development results to mission planners, facilitating technical exchanges between mission engineers and technologists throughout the development life cycle, hosting technology reviews, and tracking infusion success stories.

To assess the efficacy of NASA’s technology efforts, the committee researched best practices for technology strategies and approaches and developed a flow diagram, Figure 21-1, to use in assessing how well NASA’s technology efforts reflect best practices. In addition, best practices in technology development programs reflect principles (see Box 21-1) that guide the program’s execution and facilitate the assessment.

A comparison of NASA’s technology efforts with best practices revealed areas where NASA can improve. These are shown as red and blue text in Figure 21-1 and are described in findings and recommendations below. The technology principles in Box 21-1 provide additional clarity on these best practices in managing an effective technology development portfolio that will enable additional and more advanced science investigations in the future.

Planetary Science Division Technology Development

Whereas the V&V midterm review (NASEM 2018) found that NASA’s PSD efforts over the first half of the decade had generally met V&V technology goals, NASA has not been able to financially sustain the same percentage of funding over the past 5 years of the decade. During the second half of the decade, based on

NASA data, the level of funding fell short of the recommended 6–8 percent level with it declining to about 4 percent. The V&V recommended that it was critical that technology funding not be used to cover overrun costs of missions stating, “Reallocating technology funds to cover tactical exigencies is tantamount to “eating the seed corn.” The National Academy of Sciences, National Academy of Engineering, and Institute of Medicine report Rising Above the Gathering Storm: Energizing and Employing America for a Brighter Economic Future stated: “At least 8 percent of the budgets of federal research agencies should be set aside for discretionary funding managed by technical program managers in those agencies to catalyze high-risk, high-payoff research” (NAS et al. 2007). This finding supports a similar level of PSD funding for the significant technology advancements that will be needed to accomplish strategic research and missions prioritized in this report (see Chapter 22).

Finding: NASA has not sustained the recommended level of planetary technology funding, 6–8 percent of the PSD budget, with the level declining to about 4 percent over the past 5 years. This is now significantly below the level of investment recommended in V&V.

Recommendation: NASA PSD should strive to consistently fund technology advancement at an average of 6 to 8 percent of the PSD budget.

Technology funding within PSD is distributed across numerous programs including competed programs within R&A (e.g., PICASSO, MatISSE, and DALI; see Table 17-1), as well as for example, the Mars Exploration Program, the Lunar Discovery and Exploration Program, and the icy satellites surface technology program. As a result, the recommendations in this report for 10 percent of the PSD budget to be devoted to R&A (Chapter 17) and 6–8 percent to be invested in technology development contain significant overlap.

Progress toward the recommended funding level is difficult owing to the lack of a centralized accounting of technology funding throughout PSD. Currently, there is no single focal point in PSD that oversees and approves all technology development activities. The establishment of PESTO as a lead organization has been a good first step, but PESTO does not have responsibility for coordination of all technology work in PSD. The committee was unable to identify who in PSD has the authority to make technology investment decisions. This approach has led to a technology program that is piecemeal; that is, it is managed at individual technology program level as opposed to one with an integrated strategy for the advancement of planetary and astrobiology science. In fact, the committee learned that there was no technology plan in PSD that described, for example, how technology was managed, who was involved, how those organizations worked together, and who made decisions. As a result, there appears to be no way for PSD to effectively consider how the various technology efforts can be integrated holistically such that the combination of certain technologies would provide even higher returns on investment. In addition, there appears to be no document with STMD that describes how PSD and STMD work together to coordinate and exercise their respective roles and responsibilities. This lack of documented agreement, particularly between PSD and STMD, inhibits the execution of a cohesive technology development program that ensures technology investments improve the ability of all missions, regardless of destinations, to meet their science goals with improved capabilities.

The lack of documented structure and agreements also inhibits the science community and supporting communities from understanding the technology development strategy for planetary and astrobiology future endeavors. A transparent approach, with all program level documentation available to all interested parties, would help the technology program to take advantage of the breadth and depth of creativity available in the science and supporting communities, particularly because the proposal selection rates are so low. As it stands, creativity is stymied by a piecemeal solicitation approach, and new ideas are difficult to bring forward. Coupled with this, there appears to be no obvious source for understanding the status of important technology developments. PESTO does publish some information on its website, but it does not appear to be complete.

Last, the relationship between the science community and the NASA technology program could be strengthened if the technology program regularly reported progress at both major conferences and the discipline analysis/assessment groups (e.g., Mercury, Venus, Lunar, Mars, Small Bodies, and Outer Planets). Reporting of technology progress metrics, such as the return on investment (RoI) metric, suggested below,

would contribute substantially to a transparent organizational approach, which valued the input and feedback of its stakeholders.

Finding: The committee found it difficult to uncover what technology activities were currently active and how much funding was being allocated to technology development, an issue that was also identified in the V&V midterm review (NASEM 2018). Transparency is important to the science community as they plan for and develop approaches to accomplishing the next set of science objectives so that their implementation approaches can take advantage of the technology work being pursued by PSD and STMD.

Finding: The charter for PESTO includes the responsibility to “Work with partnering organizations to develop partnership agreements and approaches,” but the committee could not find any evidence that there were documented agreements with its major partner, STMD, where STMD committed to provide PSD with its fair share of the STMD resources and how those resources were to be expended in pursuit of PSD technology needs. At present, PSD is dependent on STMD to provide technology flight opportunities for those technologies important to the pursuit of planetary science and astrobiology. However, STMD’s current focus is on enabling the human exploration of the Moon, and there is no mechanism or agreement with PSD that ensures STMD resources are allocated to PSD’s needs consistent with PSD’s percentage of the agency’s budget.

Finding: The committee could not find evidence that PSD or PESTO had documented how the PSD technology program is managed and executed, with the only evidence being the PESTO charter and many individual technology efforts documented in solicitations like ROSES. As a result, the science community and the supporting organizations, such as industry, other government agencies, and so on have only limited visibility into PSD’s technology program, mostly through personal connections and advertisements for technology efforts (e.g., ROSES) thus making this program less than fully transparent.

Finding: As the single focal point for technology program management within PSD, PESTO needs to be cognizant of all technology efforts important to accomplishing the science priorities in the decadal survey. Based on the charter, it appears that several important technology areas are missing from their purview, such as planetary defense and planetary protection.

Recommendation: The PSD technology program should create a PSD Technology Program Plan that provides the details on what the program goals are, how the program operates, who is involved, and how the science community and supporting organizations can play a role. This plan should include how plans, funding levels, solicitation approaches, including selection rates, and results are communicated to the community at large. This plan should be prominent on the PSD PESTO website and updated annually. Based on PESTO’s charter, this office should be cognizant of all technology efforts related to planetary science, astrobiology and planetary defense and could serve as the single organization responsible for all technology development or as a minimum for integrating all technology development.

Recommendation: PSD should establish a standard mechanism for the science community and other relevant organizations to provide input into PSD on technology needs, including new and creative approaches to technology, similar to how the science community provides input through the various science analysis/assessment groups (AGs). Two possible examples could be a PSD Technology AG, similar to the science AGs, or a collaboration among existing AG technology leads. A mechanism of this sort would be an effective way to increase transparency in the technology program.

Technologies in development typically fall into 3 categories:

• Enabling—those technologies that currently do not exist but are necessary to accomplish the science priorities;
• Enhancing—those technologies which can improve the science RoI by reducing resources required or improving performance so that more science can be accomplished for the same amount of dollars; and
• Dormant—those technologies that may be sufficiently advanced to use in missions but are not yet accepted by the implementers of science missions.

Enabling technologies, by their nature, are the highest priority for investment but the remaining technologies, enhancing and dormant, reduce future costs and increase future mission performance. However, there does not currently appear to be a way to know how significant these technologies could be from a science return on investment. This lack of information impairs PSD’s ability to increase the amount of science that is ultimately pursued.

Recommendation: PSD should develop a set of return on investment metrics that guide the investment and encourage incorporation of technologies. These metrics should be transparent to the planetary science and astrobiology community.

The maturation of technologies in the aerospace community from the early concept through actual use in a space mission have been defined in nine technology readiness levels (TRLs). NASA requires that any new technologies be at TRL level 6 before a mission’s preliminary design review to ensure the successful incorporation of that technology. V&V identified the transition of technologies from TRL-4 to TRL-6 as a “valley of death,” where there was no mechanism to bring these technologies to a level of maturity needed for insertion in flight projects. PSD embraced this recommendation and created the MatISSE program to help solve this obstacle for instrumentation and worked with STMD to include planetary technologies in their flight project technology lines. These changes have been very beneficial. Now, NASA’s technology development efforts are geared to bringing new technologies to TRL-6 with the expectation that flight projects will bring those technologies from TRL-6 to flight readiness status (TRL-8) and fly them. While this strategy works for many technology developments, in some cases, when a TRL-6 technology is evaluated for insertion by a flight project during its early phases (e.g., pre-Phase A), the technology might be deemed too programmatically and/or technically risky to be included in the mission. There are several reasons that might lead to this situation. Among the most important are (1) despite NASA best efforts, TRL definitions still have a certain degree of ambiguity that might result in a premature conclusion of a technology development task, leaving too much scope for a flight project to accomplish within its resources; and (2) not all technologies at TRL-6 are created equal. Some take more resources and risks to mature them than flight projects can afford. This has created a second obstacle where technologies judged to be insertable at TRL-6 are not being used (e.g., aerocapture).

PSD and SMD have established some specific programs, such as the Mars Exploration Program, that can and do consider integration of important technologies into flight projects, and these programs have been successful in incorporating the technologies. Mars 2020 is a good example; however, other science missions without a parent program do not have these opportunities. NASA has instituted a process in its competed mission lines, where some technologies can be added to the mission without penalty by stipulating in the Announcement of Opportunity (AO) specific technologies. A great example is the Psyche Discovery mission, which is flying an optical communication experiment as part of its payload to bring that technology to a TRL of 9. This approach is creative, and the committee encourages NASA to continue this approach and even consider expanding it. Unfortunately, the list of technologies to be included has been limited, leaving many technologies without a mechanism for integration in flight projects.

Finding: There are several important technologies that could improve PSD’s science return on investment that are not being integrated into flight projects because they are deemed too risky by the flight projects.

Recommendation: This second obstacle (technology at TRL-6 deemed too risky) should be addressed by PSD, and a solution implemented that considers the long-term return on investment of all technologies under development.

Solutions could include:

• Directing some technologies to be used or providing incentives for using technologies in this category, such as increasing the number of technologies offered in AOs; allowing technology demonstration mission in SIMPLEx AOs; or similar approaches in any new programs;

• Allowing missions to include technologies with high RoI for future missions by allocating additional reserves over and above any cost caps to cover unknowns;
• Creating a separate technology line similar to the former New Millennium Program where multiple technologies could be demonstrated in small flight missions; and
• Adopting a systematic way of bounding the risks, the cost, and the schedule of technologies at TRL-6 by requiring additional information at TRL-6 such as defining work required to complete the space qualification of all components necessary to achieve flight status and documenting the attendant list of technical and programmatic risks.

Space Technology Mission Directorate Technology Development

Collaboration between SMD and STMD has enabled technology development for several significant planetary spaceflight exploration technologies. As an example, STMD-supported space technologies used for Mars 2020 include Mars Environmental Dynamics Analyzer (MEDA), Mars Oxygen In Situ Resource Utilization Experiment (MOXIE), Mars Entry, Descent and Landing Instrument 2 (MEDLI2), and Terrain Relative Navigation (TRN). STMD further supports technology development for launch and landing systems and thrusters, some of which aim for future lunar explorations, among others.

An analysis of STMD spending over the past 5 years shows that it has invested approximately 10.6 percent of its budget on planetary science technologies. Given that STMD is chartered to support all NASA efforts, a budget allocation to PSD similar to its share of the Agency budget is appropriate. SMD’s budget is about 30 percent of the NASA budget, with PSD representing about 11 percent of the Agency’s budget, so STMD’s investment has been about right. However, over the past several years, STMD’s priorities seem to have been shifted to more commercial and human exploration technology developments putting some pressure on plans for robotic technologies needed for future PSD science missions. As noted earlier, there does not seem to be a documented agreement between STMD and PSD that ensures STMD’s continued investment in planetary and astrobiology technologies.

Finding: During the past decade, SMD/PSD and STMD have worked together on developing high risk technologies important to the future of planetary science and astrobiology missions.

Finding: STMD investment in PSD technology needs can be reprioritized by other parts of the Agency when other Agency needs are deemed greater.

Recommendation: STMD should ensure that its level of investment in SMD mission technologies is balanced at approximately 30 percent of its overall budget with the PSD portion at no less than 10 percent.

TECHNOLOGIES FOR THIS DECADE AND BEYOND

Many of the strategic research (SR) objectives in each of the science chapters of this survey require new and improved technologies to accomplish them. The science missions pursuing these SRs or planetary defense (PD) also require new or improved capabilities to reach their destination, operate there, and accomplish the necessary measurements. Seventeen technology areas were identified for this decade and beyond that need advancement based on an assessment of the SR objectives, priority missions, and the current technological state of the art. Besides benefiting these critical science investigations, technology advancements can benefit all classes of missions, large and small, and potentially enable missions in higher cost categories to be accomplished in the next class below. Lucy and Psyche both use solar arrays for power, at distances from the Sun that were not feasible in the early days of the Discovery Program.

Table 21-1 summarizes the technology priorities for the coming decadal, the key science questions that benefit from these technologies, the destinations where the strategic research activities associated with particular key questions would be conducted, and gives a summary of the rationale for the technology improvements. Each technology area in Table 21-1 is described in more detail in the following sections.

TABLE 21-1 Technologies Identified to Be Advanced in This Decade and Beyond

INSTRUMENTATION

General In Situ Instruments

Instruments to perform in situ measurements need to continue to be advanced by technology developments to improve sensitivity and dynamic range, mitigate noise sources, and reduce mass, power and volume requirements. Many of these developments are enabling for the strategic research objectives within this survey, including for priority missions. For example, the continued maturation of in situ geochronology techniques will enable direct measurement of the timing of key geologic events on terrestrial planet surfaces, now only possible by sample return. Similarly, improvements in the range, resolution, and size of mass spectrometers have broad applicability, from improved measurement precision of noble gas isotopes in atmospheres, to improved discrimination of both organic and inorganic samples on planetary surfaces. Current instrument development programs such as PICASSO (TRL 1–4), MatISSE (TRL 4–6), ICEE (TRL 5–6), and targeted programs for extreme environments (i.e., HOTTech, COLDTech) can continue to make advancements. Future flight instrument development can also take advantage of terrestrial field environments for demonstration (i.e., via PSTAR). This approach fills the gap between in situ instruments and advanced laboratory equipment.

General Remote Sensing Instruments

Instruments for electro-optical remote sensing also benefit from continued technology developments to improve sensitivity and dynamic range, wavelength coverage, spectral and/or spatial resolution, and the constant push to reduce mass, power, and volume. Active instruments in particular provide new measurement capabilities for priority missions: improved radar and EM sounding of planetary subsurfaces and interiors, lidar techniques for interrogation of composition, wind and dust profiles, as well as measurement of surface seismic motion, and sub-millimeter sounding of atmospheres. Operation in extreme environments also defines a set of technology needs, such as sensors for the surfaces of Europa or Venus (also see Challenging Environments). Beyond this decade, sensing techniques such as muon tomography and ultra-precise gravimetry offer exciting new capabilities to interrogate planetary interiors remotely. Last, improvements in both space- and ground-based telescopic instruments will enable remote characterization, including biosignature searches, of exoplanet atmospheres (NASEM 2019a); also covered in Chapter 20, Infrastructure.

Instruments to Search for Evidence of Life

The sensitivity of in situ instruments focused on the search for life continues to improve, driving down limits of detection. Current detectors capable of meeting or exceeding mission measurement requirements already exist, as evidenced by the maturation of several mission concepts to search for evidence of life on Europa and Enceladus. However, more work is needed. For example, development of new technologies for microscale and nanoscale analysis (e.g., optical microscopy, Raman and infrared spectroscopy, and laser-induced breakdown spectroscopy) and implementation of commercial compact, low-power RNA and DNA sequencing devices could add robustness to the life detection technology portfolio (NASEM 2019a). The performance of these and other detectors can be further improved with front-end sample handling and sample preparation systems (including chromatography and other separation techniques to distinguish biomolecules from a complex abiotic organic background), as well as careful mitigation of contamination sources. Current instrument development programs need to continue; the ICEE-2 program, for example, is supporting development of a range of organic analyzers as well as instruments for vibrational spectrometry and microscopy. For astrobiology instruments and other payloads that would benefit from integrated instrument techniques/suites with multiple independent biosignature tests, candidate subsystem solutions for life detection (e.g., sampling tools, sample processing tools, and sensitive detectors) could then be selected for integration under targeted programs such as COLDTech.

Finding: Instrument development (in situ and remote sensing) continues through existing programs such as PICASSO, MatISSE, and targeted programs such as COLDTech and HOTTech. Instruments, in particular those focused on the search for biosignatures, would benefit from early integration (with other instruments as well as sample acquisition, handling, and preprocessing systems) to enable multiple analytical techniques to be applied to the same collected sample.

In Situ Sample Acquisition, Handling, and Preprocessing

Planetary missions featuring in situ sample analysis need to meet requirements for sample acquisition, handling, and processing. Significant technological development has already been achieved for active and passive sample acquisition. Successful examples of active acquisition include the scoops used on the Viking and Phoenix missions to Mars, the TAGSAM system on the OSIRIS-REx mission, and the MSL drill and sample processing system. Regarding passive sample acquisition systems, the Cassini mission successfully sampled gas and icy materials from the Enceladus plume, the Stardust mission collected dust samples from the comet Wild 2, and a large funnel system is in development for a future Enceladus plume flythrough mission under the COLDTech Program. However, more work is needed for specific sample acquisition cases (e.g., high velocity >10 km/s plume sampling at Triton), and future missions will place increasingly challenging requirements on the handling and preprocessing of acquired samples, particularly for sensitive life detection and geochemical isotopic measurements. These requirements arise both from advanced measurement capabilities of one or more instruments that depend on precise, intensive sample preparation (NASEM 2019b), and from the need to control potential forward contamination from Earth (McKay et al. 2020) (more in Planetary Protection and Contamination Control). It is critical that science requirements drive sample handling technologies, including nondestructive acquisition and preparation, rather than off-the-shelf engineering solutions or ease of implementation (NASEM 2019b).

Sample handling encompasses the mostly physical manipulation of an acquired sample to prepare it for subsequent analysis steps. Examples may include ingestion of material (in any physical state), metering, shaping (powdering, leveling, sectioning), physical subsampling/separation, and fine positioning. Ingestion may include containment of the acquired sample or downstream steps such as preparation of a liquid sample for injection into a MEMS-scale processor. Some preliminary measurements, such as verification sensors, mass determination, or inspection imaging, may be folded into the handling steps.

Sample preprocessing encompasses the mostly chemical treatment and modification of an acquired sample to prepare it for analysis. Examples may include controlled mixing with reagents and labels, filtering, concentration, extraction, derivatization, with some preliminary verification measurements potentially folded in, prior to analysis by one, or ideally multiple, analytical techniques.

Sample handling and preprocessing can enable measurements of chemical or morphological biosignatures that are at trace concentration (e.g., nanomolar levels and below), are isolated to certain minor phases of a heterogeneous sample or are otherwise difficult to detect owing to analytical interferences that occur in a particular technique. These benefits also apply to high-priority geochemical objectives, such as precision isotopic analysis (e.g., oxygen isotope systematics) in individual minerals or compounds, for which sample preparation is needed to improve quantitative capability and lower potential ambiguity of results. Focused development in sample handling and preprocessing additionally would enable multiple instruments to share a common front-end, which can lead not only to savings of mass and complexity, but also to improved science return owing to alignment of analyses to a common sample.

Finding: Sample acquisition has benefited from significant technology development, although work is still needed for specific cases. Sample analysis requires significant handling and preprocessing of acquired samples prior to sensor analysis. Sample handling and preprocessing technology need urgent attention to extract target materials accurately and efficiently from acquired samples, and these implementations need to be science-requirements-driven.

GENERAL TECHNOLOGY AREAS

Autonomy

The development of more capable and robust autonomous mission and spacecraft systems is a strongly growing need in planetary science, astrobiology, and planetary defense. Autonomy is implemented as a set of computer algorithms that permit missions and spacecraft to operate and achieve their objectives with some degree of independence from human decision makers. As such, autonomy can provide truly mission-enabling functionality through rapid response to spacecraft conditions including anomalies, processing and evaluation of large

raw data sets (e.g., optical imaging), and eventually achievement of science objectives through goal-seeking and optimization processes. Autonomy is primarily associated with onboard decision making, and thereby bounded by computing resources on a spacecraft. It can apply as well to algorithms implemented in a ground segment (e.g., “autonomous mission control”) to increase the efficiency and effectiveness of Earth-based decision-making procedures under interplanetary communication time constraints.

Onboard autonomy development has been driven by the need for real-time planetary spacecraft control and management, including fault detection and recovery; navigation, orbit insertion, and landing; and in situ mobility (e.g., autonomous roving) subsystems. Based on a record of success to date, these applications can be developed further and implemented more broadly, with increasing degrees of independence, on priority missions in the coming decade. Future missions, particularly those under severe communications or environmental constraints (e.g., ocean world missions such as the Europa Lander concept, Venus surface, and others), will depend additionally on autonomy realized at the system level, to include evaluation of multiple, complex data inputs to make balanced decisions based on higher-level mission priorities, even when the precise conditions and inputs may be unpredictable a priori (Amini et al. 2020). This leads to the need for greater application of artificial intelligence, particularly utilizing machine learning tools that can be developed and tested to a high standard of robustness (NASEM 2019a). Selected topics that highlight particularly urgent areas of autonomy development in the coming decade follow here.

Development and infusion of system-level autonomy: Whereas component- or subsystem-level autonomy addresses decision making within a specific domain, such as instrument target detection/prioritization or mobility planning, its application on future missions may ultimately be limited by the need for repeated human interaction to resolve competing drivers at the mission level (e.g., optimizing target selection and mobility planning together). System-level autonomy targets the entire system to harmonize every system component and reduce redundancy and incompatibility between subsystems. Traditionally development and infusion of significant system-level autonomous systems have been limited by factors related to the distributed “ownership” of system-level autonomy requirements and to the perception of risk associated with removal of humans from decision-making loops (Amini et al. 2020). In the past, such advancements may have often been seen as enhancements to mission capability, but not necessarily critical to core mission objectives. Going forward, missions highlighted by this survey and beyond, particularly those to remote planetary environments and generating vastly greater volumes of raw data (Theiling et al. 2020), system-level autonomy, enabled by new advancements in artificial intelligence and machine learning, will be seen as a critical, mission-enabling technology.

Finding: Autonomy needs to evolve at a systems level to integrate and harmonize subsystems to make decisions and execute planned operations on remote yet complex planetary science and astrobiology missions. Machine learning/artificial intelligence can support the implementation of autonomy in such environments.

Extended in situ mobility: Surface rovers, aerial vehicles, or other mobile elements continue to be high-priority systems for autonomy. Autonomy enables long-traverse rover missions for this decade, combining multiple sensor fusion for real-time hazard detection and path optimization to yield order-of-magnitude increases in range and operational efficiency (Amini et al. 2020; Matthies et al. 2020). For a lunar rover, autonomous driving is critical in darkness, and even strongly enhancing during sunlit traverses, where even slight communication delays can limit traverse speed. On more distant bodies, autonomous mobility similarly enables more efficient access to more terrain or riskier yet high-priority terrain, such as caves or ravines, by minimizing ground-in-the-loop control.

Finding: Long-traverse rover and other extended mobility missions are enabled by higher-speed, hazard-avoiding autonomous mobility over longer durations, particularly where human interactions are limited or impossible. Future remote missions with, for example, rovers and aerial vehicles, will increasingly rely on mobility autonomy to access a greater range of surface regions and features.

Science acquisition and analysis: Achieving autonomous science analysis (including target selection/sample acquisition, instrument operation, data analysis/interpretation, and follow up by optimization or redirection) has the potential to vastly increase the effectiveness and reduce the cost of planetary missions. Large

data volumes generated by modern, high-resolution instruments are not efficiently transmitted from remote environments and analyzed on Earth within reasonable timeframes to address complex scientific analyses (Theiling et al. 2020). Furthermore, some complex science objectives, such as life detection or identification of surface features from orbit, are not amenable to prescriptive algorithms, necessitating iterative analyses and synthesis of data from multiple instruments. Such requirements imply that future missions with severe resource limitations are critically enabled by science autonomy, again at a system level guiding activities and instruments to achieve broad goals.

Finding: Autonomy applied to all science acquisition and analysis activities can greatly benefit science return from remote missions. Where science objectives require onboard data prioritization and iterative analysis, science autonomy will be critically enabling.

Challenging Environments

Extreme environment: Technologies for resisting extreme temperatures have advanced in the past decade. Solar power generation in extremely high/low temperatures has been demonstrated both near the Sun (at 0.046 AU by the Parker Solar Probe) and far from it (5 AU by the Juno mission). Advances have been made in silicon carbide (SiC) integrated circuit (IC) electronics through the Long-Lived In Situ Solar System Explorer (LLISSE) that bring the technology to the level of 1970–1980 silicon-based electronics used in Viking and Voyager (Hunter et al. 2020). While identifying progress in the past decade, technologies for protecting spacecraft from extreme environments continue to remain enabling as strategic research expands to new and more hostile environments. Future missions under consideration plan to explore Mercury’s surface, Venus’s atmosphere and surface, lunar polar regions, Mars’s polar regions, and ocean worlds. Extremely cold/high temperatures impact hardware, constraining mission operational periods, and high pressure, such as on Venus or ocean world interiors, is another strong constraint on mission operations. Some targets, such as Venus and potentially Europa, host corrosive chemicals such as sulfuric acid. Systems and materials isolating and resisting extreme conditions enable longer mission durations in extreme environments. Technologies necessary to be advanced include power storage and generation systems, materials, mechanical actuators, and electronics, including memory, among others.

Finding: Protecting spacecraft from extreme environments (e.g., temperature/pressure/chemical corrosion) needs to be advanced to enable in situ priority missions. Technologies needing further advances include power generation and storage, materials, actuators, and electronics, including memory, among others.

Dust mitigation: The mission of NASA’s Opportunity rover ended in mid-2018 because of the lack of solar power generation caused by dust covering owing to a dust storm. NASA’s InSight lander also suffered from dust covering its solar panels, and attempted to remove the dust by using the spacecraft’s arm had limited success. Similar issues can happen on other planets and moons. Therefore, effective dust removal/mitigation methods for spacecraft systems are considered an enabling technology for in situ priority missions planning long-term operations in dusty environments. Unfortunately, while various approaches such as mechanical, fluid, and electric methods have been proposed, current technology does not offer effective dust mitigation processes.

Finding: Dust deposition may not be considered extreme but may be fatal to missions under some circumstances. Proper mitigation technologies warrant further advances to enable in situ long-term priority missions to rocky bodies.

Radiation: Radiation continues to be a major risk to spacecraft that requires extensive testing, analysis, and parts screening to prevent failures of avionics that can cause the premature termination of science missions. New approaches and technologies to mitigating or eliminating radiation damage have the potential to reduce costs and increase spacecraft capabilities by reducing the parts processes and/or eliminating the extensive shielding required for such destinations as Jupiter. Ultimately, advances in radiation protection could enable the use of commercial grade products (see Game-changing Trends). In addition, higher specific energy primary batteries based on lithium carbon monofluoride will play key roles in future lander missions to icy moons, but they are susceptible to significant capacity loss when exposed to high radiation. While studies have shown initial tests to

quantify radiation effects on the batteries, further technologies for protecting batteries from radiation are essential to enhance such missions.

Finding: Approaches and technologies to protecting spacecraft electronics and power storage systems from radiation have been developed, but further technical advances will enhance future missions targeting icy moons around giant planets. Such advances will also reduce costs and increase capabilities of future spacecraft, potentially enabling the use of commercial grade parts.

Cold/Cryogenic Sample Return

Cold/cryogenic sample return is a key technology area that enables returning cold/cryogenic volatile samples from planetary bodies to curation and laboratory facilities on Earth without compromising sample integrity, and as such, requires significant development for upcoming mission opportunities in the next decade.

This technology area has been identified as crucial for addressing several strategic research activities that can only be accomplished by future sample return missions. In contrast to traditional sample return technologies that only deal with uncooled materials, cold/cryogenic sample return technologies require systems that acquire, contain, and preserve volatile samples in cold/cryogenic environments under ambient conditions. Volatile sampling, handling, and containment technologies require strict temperature and pressure controls to avoid phase changes and chemical alterations over a long-term period (Milam et al. 2020). Spacecraft systems and instruments required for sample acquisition and handling have to be thermally isolated and kept at cryogenic conditions during sampling operations. Cryocoolers need to be maintained at constant cryogenic temperatures and pressures during potentially long Earth-return cruise phases requiring increased thermal containment capability and reliability. One of the most challenging operational phases occurs during reentry and recovery, when return capsules contact and interact with Earth’s atmosphere, exposing the sample containment systems to adverse conditions (e.g., high heat). All of these enabling technologies have to be capable of maintaining the samples’ integrity throughout every mission phase so that they can be successfully delivered to planetary sample curation and laboratory analysis facilities (Milam et al. 2020).

Finding: Cold/cryogenic sample return requires significant development of technologies to enable the acquisition, containment, and preservation of cold/cryogenic volatile materials at ambient sampling conditions. Such technologies are needed to be employed during all phases of the mission in order to preserve and maintain the scientific integrity of the samples.

Communication Systems

As planetary science and astrobiology missions become more complex and the science data volume continues to increase, maintaining high-data-rate communication is essential to return the science data collected. While this technology area has constantly been advancing to meet the mission requirements in the past decade, it needs to keep evolving to achieve higher data communication rates over the limitations of radio frequency (RF) communications, including bandwidth, spectrum, and overall size of frequency packages and power used. The priority mission concepts considered by this decadal all used these current, state of the art data communication techniques and equipment. However, a review of the science strategic research objectives recognized that current capabilities will be inadequate in the future and that the emerging optical communication capabilities will be capable of meeting future communication demands.

NASA is developing the Laser Communications Relay Demonstration (LCRD), which was launched in late 2021. LCRD will be NASA’s first two-way optical communications relay satellite that will demonstrate the benefits of optical technologies, such as higher data transmission and less size, weight, and power requirements. Two other demonstrations are planned in 2022 including the Deep Space Optical Communications demonstration on the Psyche spacecraft. Despite the significant improvements in data rates, optical communication will require improvements in antenna/spacecraft pointing for missions beyond 5 AU.

Finding: Despite the continuing advances in radio frequency communications, future science missions will have data volumes that surpass the technology’s capabilities. Optical communication technologies currently in development within NASA will be able to achieve much higher-data-rate communication. Continued investment in this technology is necessary to achieve the required capabilities.

In the meantime, the following technology advances can continue improve data transfer efficiency: higher radio frequencies and channel coding and modulations can avoid spectrum congestion while using limited power and spectrum; better compression processes can reduce data sizes, leading to efficient communication; and large, deployable mesh reflectors dramatically improve communication rates (Hamkins 2020).

Finding: Further advances in higher frequency transponders and antennas, efficient data processing, and large, deployable reflectors can enhance the communication capability.

Entry/Deorbit, Descent and Landing Systems

Several missions under consideration involve scientific exploration with landed platforms at several destinations (e.g., Mars, Europa, and Venus). While some of these destinations have been previously visited and are well surveyed, other destinations are much less explored and information about their environment and surface characteristics is lacking. That information is needed to design landing systems that deliver the science payload to the surface with acceptable risk. Even for those places that have been visited before, there is a need to access ever more challenging landing sites driven by the desire to maximize science value. To respond to these challenges, continued development of enabling landing technologies is required.

NASA has been investing heavily in TRN and HD&A technologies as part of its Mars Exploration Program, its Safe and Precise Landing Integrated Capabilities Evolution (SPLICE) project and predecessors (ALHAT), and its Europa Lander mission concept technology investments. These investments led to the highly successful development and use of TRN by the Perseverance rover on Mars, which allowed the project to land in Jezero Crater, a site of great scientific value but with unprecedented landing risk: a great example of how proper technology investments can lead to superior science investigations.

As we look into the future, more TRN technology developments are required to improve its robustness to landing in poor illumination conditions, including the development of active techniques (e.g., LIDAR), which can have great benefit for landing on places like the poorly illuminated Moon’s south pole or to relax the stringent landing site selection constraints in hard to access destinations such as Europa’s surface. These advances in TRN and HD&A will require high performance computing to perform the complex computations needed. In addition to TRN and HD&A, soft landing requires robust sensing of the lander’s altitude and velocity with respect to the landing surface. Past soft landers used heavy, bulky, and costly radio frequency sensors tailor made for each mission, which are difficult, or in some cases impossible, to afford for smaller landers and nonflagship missions. NASA, through its SPLICE project, has been addressing this problem with the development of the Navigation Doppler LIDAR landing sensor but despite many years of development, landing missions still struggle to find landing altimeters and velocimeters that can be afforded in developing time/cost and spacecraft resources.

Finding: As more difficult terrains are envisioned for future missions, continued technology investments in TRN/HD&A can enable spacecraft to safely land in ever more challenging and constrained landing situations.

Missions contacting the surface of small bodies require interactions with the body’s surface—e.g., sampling and drilling—that involve reaction forces that can overcome the spacecraft gravitational forces. Missions like NASA’s OSIRIS-REx side-stepped this problem by using the Touch and Go (TAG) sampling technique, which sampled surface regolith, but generally could not reach the deeper depths for more primordial or unmodified material. Potential solutions to this include the use of anchoring devices or propulsive reaction forces.

Finding: Efforts have been limited to develop technologies to enable landers to acquire deep samples; for example, 10s of cm to 1m, or other interactions that require large reactive forces in low-gravity regimes. Investment in such technologies would enable access to primordial/unmodified subsurface materials of small bodies.

NASA has invested considerable resources in the development of thermal protection systems (TPS) like the Heatshield for Extreme Entry Environment Technology (HEEET), and the Phenolic-Impregnated Carbon Ablator (PICA). These TPS technologies are currently capable of operating over a wide range of entry conditions and are

crucial for the landing of larger payloads on Mars and for enabling atmospheric probes on Venus, Saturn, Titan, Uranus, and Neptune. HEEET (currently at TRL-6 for certain conditions) was developed in the past decade, as the heritage carbon phenolic used for the Galileo entry probe is no longer available (Ellerby et al. 2020).

Finding: NASA’s investments on TPS technologies have enabled several landing missions and atmospheric probes in the past and, together with current developments like HEEET, stand to enable many future missions to multiple destinations.

In addition to these enabling technologies, there are also enhancing technologies and engineering developments that can also benefit from investments prior to a project start.

NASA has invested considerable resources in the development of deployable aero-decelerators (e.g., HIAD, SIAD, and ADEPT) that have the potential to dramatically increase landed mass on future missions. These technologies, however, seem to fall into the “second valley of death”—that is, are too risky—and do not yet seem to be under consideration for future missions.

Finding: NASA and the science community would benefit from studying how the maturing aero-decelerator technologies can be integrated into future missions to increase science value.

An area where NASA technology development has fallen short is in the redevelopment of high specific impulse (ISP) throttleable descent engines to enable the landing of heavier payloads with higher lander precision. The Mars Sample Retrieval Lander (SRL), currently under development, requires a pinpoint landing capability that demands large and fuel-consuming position corrections during powered flight, meaning that the low efficiency throttleable mono-prop engines developed first by Viking and later resurrected for Curiosity and Perseverance are insufficient.

Finding: The Mars SRL as well as current and future missions to the Moon and other destinations could benefit greatly from the availability and use of high ISP (~300 sec) bi-prop throttleable engines.

In Situ Mobility (Aerial/Surface)

Aerial mobility: As in Earth aviation, aerial mobility can provide a vantage for rapid, precise surface analysis over regional scales, in situ studies of atmospheric properties, and unique access to hazardous terrain (Bapst et al. 2020; Cutts et al. 2020; Mittelholz et al. 2020). This capability comes in many forms, such as rotorcraft, balloons, and airplanes, among others. Rotorcraft such as the Mars Ingenuity technology demonstration and the Dragonfly mission have provided and are expected to provide important measurements over multiple terrain types. Balloon platform technology can address SR objectives but needs advances this decade to meet the requirements of in situ atmospheric explorations on Venus and other planetary atmospheres. This technology requires the capability to inflate after storage in the parent spacecraft while remaining ultralight and resisting damage during deployment and controlling altitude during long-term operations. (Cutts et al. 2020; Matthies et al. 2020).

Finding: Balloon platform technology has not yet achieved the maturity of rotorcraft and airplanes and is enabling for rapid, precise surface analysis and in situ studies of atmospheric properties on Venus and other planetary atmospheres. The technology requires the capability of inflation, given ultralight materials and structures, without damage and for controlling altitude during science operations.

Surface mobility: A number of long duration, long-traverse rover missions were identified as necessary to address SRs at the Moon this decade. Rover technology has made major strides over the past decades. NASA’s Perseverance rover is currently demonstrating advanced surface mobility capabilities, following the earlier Mars rover missions. However, priority missions are now planning traverse operations as far as 2,000 km, far longer than ever completed previously. Autonomous mobility capabilities of traversing over rough and steep terrains can optimize the path selection process. Autonomy required for these rover capabilities are covered in the Autonomy section, but other technology advances are also required. At present, the titanium-based shape memory alloy tire, developed by NASA Glenn Research Center, is one example of a technological advance that improves a rover’s performance, compared

to Apollo’s LRV tires. Also, onboard actuators consume electric power to warm up and keep their performance. NASA has currently made efforts in heatless mobility actuators that can reduce electric power consumption.

Finding: Rover surface mobility on terrestrial bodies has evolved over decades. Now long-traverse surface mobility is identified as an enabling technology that allows smooth traversing regardless of large rocks and steep slopes at traverse rates much greater than current technology. Such capabilities need to mature this decade.

Some locations identified to be scientifically valuable, such as deep pits, caves, crevasses, and rough terrains, prohibit access by regular rover-type vehicles having wheels. To access these regions, different technology capabilities, such as crawling, hopping, and flying, can enable challenging in situ investigations, including remote sensing and sample acquisition. For example, robotic probes detachable from their parent rovers or landers that can crawl over steep slopes can enable accessing the bottom of cliffs, fractured terrains, or crevasses where high-priority astrobiology targets (e.g., permanently shadowed regions and plume sources) may be located. Such technologies (e.g., JPL’s Axel) are currently under development, although further work is essential.

Finding: Strategic research has identified scientifically valuable regions that traditional rovers and landers cannot easily access, such as caves, craters, crevasses, and other rough or fractured terrain. Technologies for accessing such challenging regions are still immature and need advancement.

Launch, Cruise, and Encounter Optimization

Several missions of interest to this decadal survey involve travel to far destinations, complex orbital tours of multiple targets, sample returns from small and distant bodies, and landers on hard-to-reach places. These mission types are characterized by long transit times that drive up Phase-E costs, large ΔVs (i.e., velocity changes) that reduce the science payload delivered to the destination, the need for large launch vehicles that drive costs beyond Discovery or New Frontiers mission class opportunities, and complex trajectories with constrained launch windows and multiple gravity assists that extend transit times and might require special spacecraft accommodations. There are potential technologies that can minimize these burdens.

Aerocapture is an orbital insertion technique which utilizes a single pass through a planetary atmosphere to dissipate enough orbital energy for planetary capture (Dutta 2020). It can deliver large orbit insertion ΔVs with minimum fuel, resulting in significant reductions in transit time, and/or increases in science payload mass. Aerocapture can also enable planet orbit insertion of smallsats, launched as secondary payloads, on targets like Venus and Mars (Austin 2020a,b). Advances in atmospheric entry guidance and control techniques, as demonstrated successfully by Curiosity and Perseverance on Mars, and advances in autonomous optical navigation, as demonstrated by the Deep Impact mission to comet Tempel 1, combined with the development of new TPS, like PICA used also by Curiosity and Perseverance and HEEET that will be used by the Mars Sample Return’s Earth Entry Vehicle, make aerocapture a technology ready for mission infusion. Because aerocapture is not being proposed for use in missions, it is considered a “dormant” technology that is perceived as high risk in a mission competitive environment.

Finding: Aerocapture is a technology that is ready for infusion and that can enhance/enable a large set of missions, but that will require special incentives by NASA to be proposed and used in a science mission.

Solar-electric propulsion (SEP) has been successfully flown in several science missions (e.g., Deep Space 1, Dawn, Hayabusa, BepiColombo) and will be flown in new missions currently under development (Psyche, Mars Sample Return Earth Return Orbiter). Continued improvements on SEP technologies can benefit a variety of future missions and destinations (Polk et al. 2020). These improvements include increases in ISP, lower power thrusters for small spacecraft, and advanced power processing units.

Finding: SEP has been successfully demonstrated in several missions and further technology improvements can enable SEP in small spacecraft and enhance a large set of science missions.

There have also been recent advances in trajectory design and optimization that combine gravity assists, low-thrust high-ISP propulsion, aero-assist, and other tools available to the trajectory and mission designer to increase delivery mass and shorten transit times for a variety of mission types (landers, orbiters, flyby). An example of these efforts is NASA’s Astrodynamics in Support of Icy Worlds Missions program that supports the maturity of astrodynamics tools in support of the exploration of icy moons orbiting gas/icy giants.

Finding: Astrodynamics and mission design tools can have a large impact on the design of innovative mission concepts that maximize science value and reduce mission costs.

New technology developments on cold propellant propulsion can result in a significant reduction on heater power needs that lead to large mass reductions on solar arrays and spacecraft mass (Casillas et al. 2020). This is of particular benefit to solar-electric powered missions to the outer planets, comets, and asteroids. NASA has been investing in this technology through the Advancement for Low-Temperature Operation in Space (TALOS) program for the Astrobotic Moon lander Peregrine, and JPL has been partnering with MSFC to extend this technology for deep space missions.

Finding: The cold propellant propulsion technology currently being developed by NASA has the potential to achieve important mass reductions in solar-electric powered missions to the outer planets, comets, and asteroids.

Planetary Defense

Planetary defense (PD) focuses on protecting Earth from devastating near-Earth asteroid and comet impacts. This technology area is organized around the stages required for effective PD implementation for this decade: near-Earth object (NEO) discovery, follow-up, and tracking; in situ characterization; and hazard mitigation.

NEO discovery, follow-up, and tracking: New survey systems coming on-line in the mid-2020s will significantly increase the number of known NEOs, which will require additional follow-up and enhanced tracking observations. Special focus on capabilities to improve the sensitivity, reliability, and range of radars are particularly useful for PD interests (e.g., phased array radar and solid-state amplifier technologies) (Lazio et al. 2020). Advancement in radar capabilities would enhance tracking and physical characterization of previously detected NEOs at further ranges, which will increase orbit refinement and provide additional physical characterization data vital for determining impact risk and aid the development of impact mitigation strategies.

Finding: Development of advanced radar technologies to improve NEO follow-up, tracking, and characterization capabilities would enhance planetary defense preparation.

In situ characterization: Spacecraft reconnaissance fly-by or rendezvous missions have been successfully demonstrated by small body missions over multiple decades. However, further advances are needed to determine key physical characteristics (e.g., mass, composition, and internal structure) of NEOs required for subsequent mitigation efforts (Abell et al. 2020). It is difficult to accurately determine these characteristics from fast flyby missions targeting small bodies of ~50 m and larger in diameter with mass being one of the most critical to measure for effective mitigation planning. Technologies that need improvement/development are terminal guidance navigation and control (GNC) algorithms and systems for targeting small NEOs during hypervelocity flybys, spacecraft systems/instruments to track such NEOs during these rapid flybys, and instruments/systems to determine the mass of NEOs during high-speed encounters (Barbee et al. 2020). Technological development of instruments that could be deployed or landed in either flyby or rendezvous missions to determine additional NEO properties (e.g., internal structure and strength) would also be useful for PD characterization objectives.

Finding: Development of technologies to obtain critical characterization information of NEOs during reconnaissance missions, particularly fast flybys, would inform planetary defense mitigation efforts.

ΔΔHazard mitigation: NEO impact scenarios vary depending on the impactor’s physical characteristics and potential warning times. Hence, there is no mitigation technique that is appropriate for every circumstance, because the NEO may need to be deflected or disrupted by impulsive means, or gradually moved off course via

slow-push methods. Impulsive techniques involve kinetic impactors or deployment of nuclear explosive devices (NEDs), whereas slow-push methods include ion beam deflection (IBD) or gravity tractor (GT) concepts. For kinetic impactors, improvement in targeting and imaging systems is required to precisely impact NEOs over a variety of encounter geometries during hypervelocity intercepts. NEDs would benefit from sensor technologies that would increase the trigger timing accuracy to ensure detonation at the optimum distance during high encounter velocities. For IBD, improvements in beam density and energy increase the effectiveness of this technique, as does decreasing the plume dispersion from the ion source or thruster. Improvements in spacecraft autonomy for long duration complex proximity operations are also needed for IBD or GT mitigation techniques (Barbee et al. 2020).

Finding: Development of multiple technologies for both impulsive and slow-push mitigation techniques is prudent given the variety of potential impact scenarios. Further demonstration of these technologies would enable planetary defense mitigation missions.

Planetary Protection and Contamination Control

Planetary protection involves protecting solar system bodies from forward contamination by terrestrial organisms and protecting Earth from possible extraterrestrial organisms that may be returned from other solar system bodies. This requires spacecraft developers to design and build spacecraft and procedures that meet both the planetary protection bioburden requirements for the particular body, for example, Mars or an ocean world like Europa or Enceladus, and the contamination control requirements necessary to ensure the science measurements are not compromised. Thus, spacecraft bioburden and the presence of specific molecular contaminants on (or outgassed from) payload surfaces need to be adequately understood, controlled, and documented.

Planetary protection and contamination control advancements involve a systemic view of both the science of microorganisms and contaminants that might overwhelm or confound measurements, and the technologies to minimize these on spacecraft surfaces. Considerable scientific work is under way to conduct more accurate and precise microbial diversity assessments in cleanrooms and on spacecraft, understand the probability of biological contamination, and develop planetary protection conventions and contamination control requirements for future missions (for, in particular, those focused on astrobiology investigations); this is outside of the scope of technology addressed here. Here the committee focuses on specific technology developments that address planetary protection and contamination control for spacecraft.

A hybrid technology that combines both culture-based and multiple next-generation sequencing methods needs to be explored as the standard methodology for spacecraft bioburden assessments. It is a high priority in the upcoming decade to mature a nucleic acid-based approach for bioburden assessments, adapting it from industry and academia approaches. This methodology needs to be tailored for key areas including, but not limited to (1) sampling and sample processing (swab to sequencing) capability from low-biomass spacecraft surfaces; (2) viable organism enumeration; (3) ability to rapidly identify PP-relevant organisms; (4) bioinformatic pipeline and database standardization; and (5) phylogenetic identification assessment of the broadest spectrum of organisms on the surface.

Finding: The current NASA Standard Assay (NSA) is insufficient and inefficient to accurately estimate the number, diversity, and functional capabilities of spore-formers and other organisms associated with spacecraft surfaces.

Attention needs to be given to controlling the possible introduction of contaminants over and above those used for planetary protection bioburden, especially chemical species of astrobiological interest such as amino acids, nucleic acids, carboxylic acids or lipids and molecules that may confound measurements of these (e.g., isobaric species), at concentrations that might interfere with the scientific exploration of planetary bodies. Investigation of new technologies that can eliminate and/or reduce this contamination is extremely important to life detection measurements. Future life detection missions may need to use new materials that do not contain or produce these contaminants and that can withstand the cleaning and sterilization processes needed. Further technology work in this area would be extremely beneficial.

Finding: Life detection investigations are beginning in earnest, and contamination control in these planetary missions is becoming even more critical to enable the very precise and difficult astrobiology measurements that are susceptible to contamination.

Concepts for terminal sterilization—that is, the complete elimination of all biological contamination at the landing site following the completion of all scientific investigation—are in the formulation phase as part of the Europa Lander mission concept technology efforts. At bodies where the timescales of surface-subsurface transport exceed the 1,000-year period of biological exploration, missions might not require such extreme measures, providing significant cost savings. For bodies where surface-subsurface transport is less than 1,000 years, further technology development of terminal sterilization, in concert with planetary protection requirements tailored for the specific body and mission science requirements, would provide a robust strategy to minimize the risk of contamination while maximizing unambiguous science return.

Finding: Terminal sterilization has been identified as one possible technology that could prevent the possible contamination of an icy world’s ocean within the 1,000-year timeframe.

Radioisotope Power Systems

Radioisotope power systems (RPSs) convert heat generated by radioactive decay, traditionally from plutonium-238 (²³⁸Pu), into electric power. Radioisotope thermoelectric generators (RTGs), which generate an electric current across thermoelectric couples when subjected to a temperature difference, have been the workhorse power source for missions to locations with limited solar irradiance, or where the use of solar arrays is impractical. Recent and upcoming missions such as Curiosity, Perseverance, and Dragonfly are using multi-mission RTGs (MMRTGs); however, the applicability of this design is limited by an end-of-design-life (EODL, typically 17 years) power of 62 W.

Most of the priority missions for this decade and many beyond require RTGs for power, at levels several times greater than currently available, and thus would benefit from improvements in specific power (power per unit mass). In addition, this high demand for RTGs as a power source—which drives ²³⁸Pu production—motivates the need for more efficient conversion technologies (see Chapter 20). The NASA RPS Program has anticipated these needs and has been working on improved RTG designs that can provide up to EODL power of 210 W. Efforts have started with a refurbished, legacy general-purpose heat source (GPHS)-RTG expected to be available in 2024 (Overy et al. 2020). The RPS Program’s goal is to have two of these improved RTGs ready for fueling by 2026 with availability for 2030 missions. Further, the RPS Program is planning a second modification early in the next decade to further improve both conversion efficiency and power output.

Continued improvements in available power and conversion efficiency will enable future missions beyond this decade. Dynamic RPS systems, using Stirling or Brayton conversion technologies, are currently under development and could increase conversion efficiency by a factor of ~4 over the current GPHS technology. Such units are not likely to be available for missions endorsed by the current decadal study, but a flight demonstration in this decade could pave the way for infusion in later decades, resulting in a significantly lower demand for ²³⁸Pu.

Finding: It is critical that the planned development and delivery of improved RTGs with higher power output stay on schedule, as multiple missions planned for the upcoming decade depend on them as a power source. Further advancements in higher efficiency RPS technology will alleviate the demand for plutonium-238.

Solar Arrays and Energy Storage

Many future planetary science missions will require advanced solar power generation and storage technologies, often in challenging environments. While these technologies have been steadily advancing, several priority missions in this decadal point to the need for development in specific areas, usually driven by extreme environments. Inner solar system missions to Mercury and Venus push operational temperatures, for example, ~465C for the Venus surface. While missions like Parker Solar Probe and BepiColombo have demonstrated thermal management of solar arrays under high irradiance, improved array performance at higher temperatures than were experienced by MESSENGER is still needed for extended operations. In the lower Venus atmosphere, low irradiance, high temperature (LIHT) conditions and corrosive gases at high pressure present a significant challenge for solar array technology. Similarly, the Mercury surface presents sustained high irradiance, high temperature (HIHT) conditions, compromising cell performance and lifetime.

For the outer solar system, solar array performance under low irradiance, low temperature (LILT) conditions continues to improve, with Juno operating successfully at 5AU, and recent advanced array developments that make solar power at Saturn (~10 AU) competitive with RTGs (Schwartz 2020), a needed development as radioisotope power is a limited resource. Flexible blanket arrays continue to grow in area and specific power, pushing the boundaries of feasible solar powered missions.

Solar arrays for landers and rovers present unique challenges. Power needs for these flight systems are generally high enough to need large arrays that cannot be readily accommodated, so smaller arrays are used, and operations are often limited by power cycling. But improvements in the accommodation and reliability of retractable arrays can make larger arrays a viable option for future missions.

Finding: Recent NASA and industry investments in solar array technologies have resulted in improvements in photovoltaic efficiency, specific power, and array size, pushing solar as a viable power option for the outer solar system. Additional array improvements are needed for high temperature environments in the inner solar system.

Batteries are the main energy storage component of spacecraft power systems, functioning either as the primary power source, used for periods of hours or days (for applications such as atmospheric probes), or functioning as a secondary, rechargeable power source, used together with solar arrays or RTGs.

Battery technology for planetary applications has been steadily improving, as measured by specific energy (energy per unit mass) and energy density. Li-Ion is the standard chemistry for rechargeable, secondary batteries, routinely providing a specific energy of 200 Wh/kg at the battery level. However, cell-level specific energy is typically 25 percent higher; improvements in cell packaging are expected to improve this value over the next decade. In addition, new chemistries—many based on solid electrolytes with a Li anode—show promise in specific energy increases above 300 Wh/kg. Primary battery technology is also improving, driven largely by investments for targeted flight projects. For example, the Europa Lander concept has prompted the development of Li-CF_x chemistry for flight, ~2× improvement in specific energy from the conventional Li-SOCl₂ batteries, a critical improvement when battery mass is driving the system design (Bugga 2020).

In addition to specific energy, planetary missions push the need for longer battery lifetimes, particularly missions to the outer solar system with long cruise times. Improvements in calendar, operational and cycle lives are needed for outer planetary missions, as they currently limit planned mission lifetimes. In addition, improved resilience to either high temperatures on Venus and Mercury, or low temperatures on Mars and ocean worlds, is needed for future missions. These applications for specific, extreme environments often require unique electrolytes that are suited to the expected temperature conditions.

Finding: Battery capability (specific energy, energy density, lifetime) require steady improvements to keep up with future planetary mission needs. Extending the operational temperature range for extreme environments often requires special electrolytes and materials that may be a unique application.

Subsurface Access

Development of technologies enabling access to pristine/unmodified materials, ocean materials, and subsurface zones is necessary for priority future missions targeting surface/subsurface exploration on planetary bodies in the inner solar system and ocean worlds, particularly those searching for evidence of life (NASEM 2019a). Possible technologies may include drills, melt probes, tethers, submersibles, emplaced communication nodes, telemetry from the probe/drill tip, and materials capable of meeting stringent planetary protection requirements (Dachwald et al. 2020). While maturation of some of these technologies is under way through programs such as SESAME and COLDTech, significant additional work is needed. This technology area further requires rigorous validation processes at dedicated laboratory facilities for simulating surface/subsurface conditions not found on Earth, as well as extensive field testing (Howell et al. 2020; Schmidt 2020; Stone et al. 2020).

Enabling technology for missions in this decade includes developments to provide robust and pristine access to depths of at least 2 meters. Achieving a depth of 2–10 meters will provide access to samples protected from significant gamma radiation exposure (which is dependent on impact gardening erosion, and other processes), and

also allows penetration through a range of overburden/soil, sediment, and possibly seasonal ice (though again, this is body-dependent). Drilling technology capable of reaching 2 meters has been developed in Europe and will be flown on the ExoMars rover. The United States has also been developing technology for these depths but additional advancement is necessary to meet capabilities required for a priority mission in this decade. A subsequent challenge would be to deploy a multi-string sampling drill that can penetrate hard materials in the 2–10 meter range and incorporate autonomy features (to sense and react to changes in, for example, density and subsurface obstacles).

Finding: While 1–2 m drill technology is maturing and planned for lunar missions, 2–10 m drill technology is critical but not mature enough to robustly sample pristine materials from subsurface layers of the widest variety of rock and ice materials on Mars, the Moon, and other bodies.

Additional key subsurface access technologies that would enable missions in future decades include:

• Deep drilling in the 10–100 m range (following decade) and km range (longer term) in rock or ice by investing in technologies such as hybrid wire-line-type drills with the potential to access subsurface reservoirs (ice on Mars or melt lenses/brine pockets on ocean worlds) and subsurface oceans.
• Alternative subsurface access probes (e.g., melt probes) for icy/ocean worlds, combining vertical access and probe mobility in solid materials, while tackling environmental stability, communication, and planetary protection/contamination control challenges.
• Submersibles for interior oceans of ocean worlds. These may include either tethered or free submersibles and would likely implement autonomy for navigation as well as sample collection and analysis.

Finding: Technology development to reach beyond 10 meters and access subsurface reservoirs and oceans would revolutionize our understanding of the interiors of terrestrial and icy/ocean worlds, and enable unprecedented astrobiology investigations in the coming decades.

Technology System Engineering and Integration

As planetary science, astrobiology and planetary defense missions have become more and more complex and sophisticated over the past five decades, the need to integrate technology advancements across multiple technology areas has become necessary to accomplish the new strategic research advocated by this decadal. In several of the following technology areas, there will be discussions where this is particularly important. As noted in earlier in the chapter, a capability to examine technology advancements from a system level is missing in the management of technology development.

Finding: Many technology areas are best advanced when integrated with other technology areas, particularly for automated landing, sampling, mobility, and surface operations.

Recommendation: NASA should initiate or continue activities that pursue the technologies identified in this decadal survey, with particular emphasis on those technologies that enable the recommended science (missions and strategic research), those enhancing technologies that will improve the overall science return on investment, and those dormant technologies that have achieved TRL-6 but are not yet deemed sufficiently mature for inclusion in flight missions.

DISRUPTIVE AND GAME-CHANGING TRENDS IN TECHNOLOGIES

Technology advancement is accelerating at an exponential pace driven by forces in the government for needs like defense and space exploration, in the commercial sector for improved products and market share, in academia through both support to government and commercial enterprises and for basic research, and by other nations seeking to improve their status on the global stage. Many of these organizations are pushing the technological boundaries and inventing new ways of thinking about difficult problems along with new techniques for how to solve them. The emergence of self-driving cars is just one example.

As these technologies become available, the aerospace community can take advantage of them to improve the way we build and operate our space missions as they continue to explore the solar system and beyond. The following technology trends have the potential to have game-changing impacts in future SMD missions. These are technology areas that are being driven mostly by forces outside NASA’s SMD, or even space exploration, but need to be monitored and explored through conferences, workshops, and other means, and invested in, with forethought to take advantage of the capabilities that they offer.

New Commercial Launch Systems

Ongoing launch vehicle developments associated with the human exploration of Moon and Mars, if successful, could result in SLS class launch vehicle capability at orders-of-magnitude lower costs. Launch system concepts like the emerging super-heavy lift launch vehicles, which involve full vehicle reusability and on-orbit refueling, have the potential to dramatically reduce launch costs and increase launch mass to the point that mass will no longer be a driver for spacecraft design. In this scenario, spacecraft miniaturization and optimization for launch mass reduction will be replaced by a brute force approach that reduces cost by using the ample mass and volume resources made available by these new launch systems. If this scenario comes to pass, NASA and the space community need to be ready to adapt its culture to make maximum use of these new launch vehicle capabilities, not only to reduce costs but to also formulate new mission concepts that are currently beyond our imagination.

Advanced Materials and Manufacturing

Significant advances in materials sciences such as carbon nanotubes and graphene have the potential for game changing improvements in spacecraft design by enabling lighter and stronger structures, higher capacity batteries, higher efficiency and lower mass solar cells, thermal management systems, electronics, and sensors. Similarly, smart structures such as origami structures and flexible structures are at a new phase of innovation to replace traditional structural designs.

New manufacturing capabilities, such as additive manufacturing (Sacco 2019), have the potential to enable the creation of new materials and parts that may one day be made in microgravity only and may only function there. This would permit a shift in the logistic and planning of space missions given this in-space construction would be a reality, ultimately allowing construction of space mission components directly in space. A recent example relevant to planetary exploration are bulk metallic glasses that allow for actuator systems that don’t require lubrication and integrated thermal management systems. Implementation of new capabilities would have the potential to lower costs and manufacture times enormously.

Quantum Computing and Artificial Intelligence/Machine Learning

While quantum computing is still in the early phases, there have already been many innovations and breakthroughs. It now appears that some of the most prominent and widely used AI and ML algorithms can be sped-up significantly if run on quantum computers, which does not mean performing a task faster, but rather taking a previously impossible task and making it possible, or even easy. As it pertains to AI/ML, there is the potential for classical and quantum machines to work together leveraging the elastic nature of the cloud and the powerful, specific problem-solving capabilities of quantum computing. Over time, both computing formats will continue to advance, but the ability to accelerate workloads on traditional graphics processing units and application-specific integrated circuits while also leveraging the power of quantum computing could be a recipe for faster, more robust computational capabilities, which we can expect to see as quantum computing becomes more widely accessible. The possibilities for space are significant with potential applications including fully autonomous science operations in challenging environments (roving, sampling, sample processing); sensor processing and interpretation; and in situ mobility with both major assets such as rovers and aircraft as well as probes. In addition, quantum sensors are also making great progress and have the potential to beat the performance of our traditional approaches. Quantum sensors have applications in a wide variety of fields including microscopy, positioning systems, communications, electric and magnetic field sensors, and seismology.

Small Fission Reactors for Power and Propulsion

Fission power systems (FPS) can offer a distinct advantage over other systems for higher power requirements and can offer new possibilities for more capable missions and access to the farthest reaches of the solar system and beyond. Nuclear-thermal propulsion and nuclear-electric propulsion (NEP), as an example, have been studied for decades but are not yet accessible because of their mass and large size. These technologies can significantly lower costs while enabling heavier science payloads, and more frequent missions (Polzin et al. 2020) and, more importantly, open exciting new science mission concepts. NEP technology, for example, can enable electric propulsion in the outer solar system where solar-electric propulsion is not feasible (Casani et al. 2020). Studies by NASA and the Department of Energy have shown that electric propulsion driven by a 10 kW space fission power reactor can enable a large number of exciting science missions to the outer solar system.

Commercial Exploration of Space

The current trend of the commercialization of the exploration of space, like the Commercial Lunar Payload Services and Human Landing System programs, has the potential of bringing new industry players with new ideas that go beyond the initial targets. The capability also expands the infrastructure of space components and services (e.g., communications, spacecraft platforms) that can be leveraged by future SMD missions to achieve great improvements in capability at lower costs.

Automotive Electronics

The past decade has seen great progress in the development of driverless car technology motivated by great advances in sensors, high performance computers, and navigation and control algorithms. It is worth noting that the electronics and software used in this application not only have to perform very complex autonomous functions that were undreamed-of a few years ago, but accomplished in the harsh demanding automotive environment while achieving the reliability demanded by the presence of human lives. All these properties are very relevant to the design and implementation of space missions. The technologies and commercial resources being developed to meet the needs of the autonomous car industry can have a profound impact in the development of future NASA’s science missions.

Pulsar Navigation

X-ray pulsar-based navigation (XNAV) is a technique that uses X-ray signals emitted by pulsars and sensed by a vehicle’s on-board X-ray sensors to determine its position in space. Its main advantage is that the spacecraft can autonomously and accurately determine its position without requiring Earth resources like the Deep Space Network. This capability could reduce our reliance on ground-based navigation capabilities and/or reduce the operations costs associated with these capabilities.

In Situ Resource Utilization

The Moon, Mars, and asteroids are key places for in situ resource utilization (ISRU) in the near-term. Human exploration of the Moon and Mars are currently driving the development of ISRU technologies. If successful, the resulting infrastructure and technology could be leveraged by robotic science missions at great benefit. Other solar system bodies such as Pluto, Charon, or other Kuiper belt objects could be further explored with a single mission to the surface. Given the possibility of ISRU, additive manufacturing and robotic assembly of spacecraft components could enable science mission extensions, such as the manufacturing of mobile probes, rovers, and aircraft, that could expand the observational capability of a single landed mission.

Finding: Emerging technologies in many different sectors offer game-changing opportunities to increase capabilities of our science investigations, while reducing the development burden and associated costs.

Recommendation: NASA should maintain cognizance of emerging new technologies and encourage the science and engineering communities to explore new ways that these technologies can enable greater science while reducing development and operations costs.

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