Architecture definition process and the annual cycle

Summary. NASA does not fix the Moon to Mars Architecture once. ESDMD runs an annual "strategic analysis cycle" of studies and trades, which ends at the annual Architecture Concept Review (ACR). Each review produces a new revision of the ADD; Rev C is the product of the 2025 review. The cycle is how new technologies, partners and elements enter the architecture. Within it, "definition tasks" settle open questions, in an order set by "architecture roadmapping" that starts from "Why?". NASA also tracks how well the architecture meets its objectives from one review to the next. This page covers ADD Section 1.3.4 (pp. 18–19) and Sections 3 and 3.1.1–3.1.2 (pp. 71–74). It also covers the "Architecture Definition" white paper (Dec 2025) on roadmapping, and the 2025 Architecture Update's page on performance and effectiveness. The decisions themselves are on Key definition tasks; Appendix C's account of roadmapping (pp. 186–188) is below. How the 2023 strategy document planned the cycle is below, and how the 2023 and 2024 executive overviews describe it, with what each cycle set out to do, is after that.

The annual cycle

• "NASA updates and improves this document through its annual Architecture Concept Review, which solicits input from across the agency's mission directorates, centers, and technical authorities. The annual Architecture Concept Review cycle creates opportunities to continually incorporate cutting-edge technologies and new partnerships with industry, other U.S. government organizations, international entities, and academia" (ADD Rev C, p. 11).
• "NASA's ESDMD manages this process through the annual strategic analysis cycle. These cycles prioritize architecture work and studies needed to address open questions, identify architectural drivers to buy down mission risk, coordinate with partners, identify gaps in the architecture, and resolve them. The cycles conclude with study findings and/or updates to the Architecture Definition Document and supporting architecture products, which are reviewed at the annual Architecture Concept Review meeting" (p. 18).
• "These iterative cycles enable definition of new elements or systems and modifications to the architecture as existing elements and programs mature. NASA also assesses how emerging technologies and new solutions can address architecture needs during the strategic analysis cycle. The analysis process reflects a variety of viewpoints, perspectives, and ideas from stakeholders and partners" (p. 19).
• "Strategic analysis cycle trade studies also consider technology advancements, alternative solutions, and different concepts to identify efficiencies or development priorities in future segments. As program execution matures and NASA conducts exploration missions, the architecture accounts for realized system performance and new scientific discoveries. These efforts inform how NASA adds future systems and elements into the architecture" (p. 19).

The Executive Summary puts it briefly: "NASA updates the document annually to reflect the maturation of the architecture and progress toward exploration objectives" (p. 9).

The figure on p. 19

The figure "Evolutionary Architecture Process" (ADD Rev C, p. 19, read from the PDF; the text layer drops it) is a row of chevrons running left to right towards a globe labeled "Moon to Mars Objectives":

1. "Objective Decomposition" and "Architecture Definition Document"
2. "Architecture Concept Review"
3. "Architecture Studies", "Element Definition" and "Architecture Refinement"
4. "Architecture Concept Review"
5. "Architecture Studies", "Element Definition" and "Architecture Refinement"
6. "Architecture Concept Review", then "…"

Arrows below the row label each review-to-review loop "Annual Cycle". An arrow across the top, labeled "Objective Decomposition", runs from the objectives back to the start of the row.

The 2023 strategy document's plan

The 2023 Strategy and Objectives Development document describes this process in the future tense (Section 6.0, "What's Ahead", Strategy and Objectives Development, PDF pp. 34–35):

• Strategic analysis cycles. "The Exploration Systems Development Mission Directorate will conduct strategic, iterative review of the blueprint architecture through Strategic Analysis Cycles (SAC), which will occur annually with the goal of prioritizing the work and studies needed to address open questions, coordinate with industry and international partners, and identify and resolve gaps in the architecture to achieve progress" (PDF p. 34).
• The ADD. "Documentation produced during these cycles includes the Architecture Definition Document (ADD), which will capture the most current objectives decomposition and the architecture implementation that supports it. This product will identify how the architectural elements (and their systems, subsystems, etc.) map to the characteristics and needs. The ADD also identifies gaps in the ability to satisfy blueprint objectives. Gaps can be assessed both internally by NASA and externally by stakeholders for opportunities to address in subsequent blueprint architecture and documentation iterations." White papers "will capture results of the assessments (and their rationale)" (PDF p. 34).
• Architecture Concept Reviews. "The cornerstone activity of the yearly blueprint architecture process is NASA's internal ACR." "ACRs will be scheduled to support the yearly budget planning process by enabling analysis and understanding of architectural updates and changes in advance. Following ACR events, results will be reviewed with agency leadership and shared externally through updated ADD publication and associated supplemental products" (PDF p. 35).
• Federated Board targeted reviews. The Federated Board, "in coordination with auxiliary members from NASA Centers, Tech Authorities, and other key offices – conducts targeted reviews, deep dives, and periodic gap analyses of the Moon to Mars architecture", and "provides a high-level coordination path to address concerns prior to elevation at the Executive Council for approval" (PDF p. 35).

Its figure (PDF p. 35, read from the PDF), captioned "The architectural wireframe must be constantly reviewed to ensure prioritization, address open questions, coordinate with partners, and identify and resolve gaps in the blueprint architecture to achieve progress." Chevrons from left to right:

1. "Moon to Mars Objectives"
2. "ACR Product Review", "Architecture Definition Document", "Revised Architecture"
3. "Architecture Concept Review"
4. "Architecture Confirmation (Federated Board, Stakeholder Targeted Reviews)"
5. "ACR Product Development/Review", "Architecture Definition Document Expansion", "Refined/Expanded Architecture"
6. "Architecture Concept Review"

An arrow runs back along the bottom from the last review, labeled "Annual Cycle to Mature Architecture".

What changed by Rev C (the wiki's comparison):

• The cycle ran as planned. Annual reviews have produced Revisions A, B and C (below), each with white papers. Rev C describes the same "annual strategic analysis cycle" run by ESDMD (p. 18), and publishes the "gaps" as lists of technology and data gaps.
• Different labels in the figure. Rev C's p. 19 figure has "Architecture Studies", "Element Definition" and "Architecture Refinement" between reviews (above). It has no "Architecture Confirmation" step.
• No Federated Board. Rev C's text doesn't mention it (search for "Federated"). Its p. 16 figure places the architecture with the "Strategy and Architecture Office (SAO)" (Objective decomposition).
• Budget. The 2023 document ties ACRs to "the yearly budget planning process". Rev C says "The document is not a budget request" and that architecture products "do not presuppose how the agency allocates resources" (p. 13). The two statements are about different things, the review and the document, so the wiki doesn't call them a contradiction.

In the executive overviews (2023 and 2024)

Two short "executive overviews" summarize a review cycle each for a general reader: the 2023 overview, from January 2024, when Rev A and the 2023 white papers came out, and the 2024 overview, which reports Rev B as published. Both are older than Rev C. Page numbers in this section are their PDF pages.

The cadence as drawn in 2023. Figure 4, "Illustration of the annual cadence of the Architecture Concept Review process" (2023 overview, PDF p. 11, read from the PDF), is a loop of four steps:

1. "ACR Products Published", "after approval by the Executive Council", "Annually in January". Beneath it are three products: "Architecture Definition Document (ADD) Revision", "ADD Glossy Summary" and "White Papers".
2. "Architecture Workshops", "for Industry, Academia, and International Partners", "Annually in February"
3. "SAC", "Strategic Analysis Cycle"
4. "ACR", "Architecture Concept Review", "Annually in November"

The overview doesn't call itself the "ADD Glossy Summary", and the wiki doesn't either. The 2023 review met on "Nov. 14, 2023, at NASA's Kennedy Space Center in Florida", with "representatives from all of NASA's centers, leaders from all of NASA's mission directorates, various technical authorities, and other stakeholders across the agency" (PDF p. 3, photo caption).

The cycle as described in 2024 (2024 overview, PDF p. 20):

• The review. "The Architecture Concept Review cycle culminates in a meeting where leaders from across NASA's mission directorates, centers, and technical authorities to consider updates to the architecture. The architecture team polls attendees, seeking concurrence on the architecture to ensure a united vision for crewed exploration in deep space" (a verb is missing, as printed). "After completing the Architecture Concept Review, the agency releases a new revision of the Architecture Definition Document and white papers on specific technical topics."
• The strategic analysis cycle. "The Architecture Concept Review cycle begins with the kickoff of that year's strategic analysis cycle. Strategic analysis cycle tasks and trade studies help NASA to better understand the architectural needs, capability gaps, and opportunities to enhance the architecture through the addition of new elements."
• Workshops. "Each year, shortly after the release of the latest architecture products, NASA hosts workshops to gather feedback from industry, academic, and international partners. There, attendees dive into the latest updates to the architecture and discuss how partnerships can help NASA achieve its Moon to Mars Objectives." Five of the 2023 white papers were "written in response to suggestions at 2023 Moon to Mars Architecture workshops" (2023 overview, PDF pp. 8–9).
• Who. "Within the directorate, NASA's Strategy and Architecture Office leads the definition, documentation, and disposition of the architecture with buy-in from all stakeholders. They do so through the annual Architecture Concept Review process." The 2023 overview has "in consultation with stakeholders" (PDF p. 3).

What each cycle set out to do.

• For 2024 (2023 overview, "Forward Work", PDF p. 11). "During the 2024 strategic analysis cycle, NASA will begin to:

  • Address gaps in the Human Lunar Return and Foundational Exploration segments, introducing elements that provide key capabilities such as returning cargo to Earth, offloading and relocating assets on the surface of the Moon, and other important lunar logistics functions.
  • Perform strategic analysis for sub-architectures, developing strategies for services like surface communications, mobility, power, and in-situ resource utilization …
  • Conduct studies and begin to develop recommendations for the priority decisions identified for an initial campaign of crewed Mars exploration."

  "The results of these efforts will be reviewed at the next Architecture Concept Review in the fall of 2024. NASA will release revision B of the Architecture Definition Document shortly thereafter, plus a new suite of white papers". "This will be the first full-year cadence of the Architecture Concept Review cycle, normalizing the processes outlined in this document."

• What 2024 delivered, as the 2024 overview lists it ("2024 Accomplishments", PDF p. 3):

  • "Published Revision B of the Architecture Definition Document … This edition adds two new exploration elements, an updated objective decomposition, new key driving architecture decisions, and new architecture-driven technology gaps."
  • "Solicited U.S. industry proposals for innovative architecture solutions that could help the agency land and move cargo on the lunar surface."
  • "Selected nuclear fission power as the primary surface power generation technology for the initial human missions to Mars."
  • "Signed an agreement with the Japan Aerospace Exploration Agency, in collaboration with the Japanese automotive industry, formalizing partnership on the Pressurized Rover."

  The year's theme: "solidifying the process developed in 2023 through improved traceability of needs and the application to new element pre-formulation" (PDF p. 3).

• For 2025 ("2025 Look-Ahead", 2024 overview, PDF p. 26): "In 2025, NASA will continue to refine the architecture by maturing the objective decomposition for the Moon and Mars, updating the architecture-driven technology gaps, and making progress on driving architecture decisions. NASA will also engage with industry and international partners to identify innovative solutions to architecture challenges and coordinate with the science community to ensure the architecture can meet science goals."

What changed by Rev C (the wiki's comparison):

• The plans and the revision notes line up. Rev B's revision note lists the two elements, the expanded decomposition, "architecture decisions" and the technology gaps (ADD Rev C, p. 3). Rev C's lists an updated decomposition with Mars use cases and functions for four science goals, refined technology gaps and refined definition tasks (p. 4), and dates three completed Mars tasks to the 2025 review (Key definition tasks). The fission selection is MD-07, dated to the 2024 review.
• Products now come out in December, not January. The 2023 figure has products published "Annually in January", as Rev A was (01/22/2024). Rev B and Rev C were released on 12/13/2024 and 12/12/2025 (p. 3; below). No source read says the schedule changed.
• No Executive Council in the cycle. Rev C doesn't mention the Executive Council (search of the text), as it doesn't mention the Federated Board (above).
• No polling. Rev C says the review "solicits input from across the agency's mission directorates, centers, and technical authorities" (p. 11). It doesn't describe polling or concurrence (search for "concurrence" and "poll").

Revisions produced so far

Each major ADD revision is labeled with the review that produced it (ADD Rev C, pp. 3–4):

Review	ADD revision	Released
—	Initial	04/18/2023
2023 Architecture Concept Review	Revision A	01/22/2024
2024 Architecture Concept Review	Revision B	12/13/2024
2025 Architecture Concept Review	Revision C	12/12/2025

Two minor corrections, A.1 and B.1, were issued as management directives in between. The full table is on the source page. The white papers among the wiki's sources carry "ACR24" and "ACR25" in their file names (for example the ACR25 data-gaps white paper). Rev A came with 13 white papers and Rev B with 12, by the executive overviews' lists; none of the 2023 papers is among the wiki's sources, and all twelve 2024 ones are (2023 overview, PDF p. 9; 2024 overview, PDF pp. 8–9).

What else a review produces. The 2025 review also produced the 2025 Architecture Update, a 20-page summary "released alongside" Rev C, and six white papers "for awareness where more detailed rationale is available for key findings or decisions" (Update, p. 3; the six are listed on its source page). The Update adds a caveat: "While conversations continue about potential changes in implementation, the products represent the contracted baseline and will be updated and responsive to changes if and when they occur" (Update, p. 3). Its focus areas for the 2026 cycle are "lunar logistics capabilities, refining NASA's lunar power strategy, and examining the communications and navigation needs of crewed Mars missions" (Update, p. 18).

NASA's shelf of products, by review. NASA's Architecture Definition Documents page lists every review's products: for 2022, the first ADD (on NTRS), an executive overview and an objectives mapping table; for 2023 and 2024, an ADD revision, an executive overview and mapping tables; for 2025, Rev C, the Update, the two decomposition workbooks and the two gap spreadsheets. The Moon Base Users Guide sits apart, under "2026 Ignition | Phased Moon Base Implementation". The wiki holds Rev C but not Revisions A and B or the 2022 ADD; the full table, with what is held, is on the page's source page. NASA's White Papers page lists 35 papers (2022: 5; 2023: 12; 2024: 12; 2025: 6). Its 2023 list is one short of the overview's 13: it leaves out "Key Mars Architecture Decisions", which the 2025 "Architecture Definition" paper supersedes (White Papers page). In February 2025 NASA's own slide still listed both superseded papers, 31 in all for 2022–2024 (6, 13, 12), each marked Moon-focused, Mars-focused or cross-cutting (Architecture 101, slide 19).

Rev B by its briefing. Revision B added "50+ pages of new content including the two new appendices and the two new exploration elements", and its appendices had other letters than Rev C's: B for the key decisions, C for the technology gaps, D for definitions. Rev C's are C, D and F, with the data gaps as a new Appendix E (the wiki's matching by subject; Architecture Updates deck, February 2025). So in material that cites Rev B (December 2024 to late 2025), "Appendix C" means the technology gap list; in Rev C and its December 2025 companions it is architecture definition.

"Architecture definition", formerly "architecture decisions"

Rev C "Updated 'architecture decisions' terminology to 'architecture definition' to better capture the process and outcomes of these activities" and "Refined architecture definition tasks" (ADD Rev C, p. 4). Rev B had "Added and expanded architecture decisions" (p. 3), so documents from 2024 and earlier use the older term.

Where the details are (contents, pp. 5–7):

• Section 3.1 "Architecture Definition" (pp. 72–76): unique considerations by destination and the roadmapping approach are below; the summary of key definition tasks is on Key definition tasks.
• Section 3.4 "Element Definition and Pre-Formulation" (p. 82). Rev C "Added content on element definition and pre-formulation methodology" (p. 4). See Elements.
• Appendix C "Architecture Definition" (pp. 186–197): roadmapping (below), legacy lunar architecture decisions, completed key definition tasks and open key definition tasks (Key definition tasks)

The tech-gap spreadsheet traces gaps to definition tasks, some marked ✓. The ADD's gap tables say "“✓” indicates completed definition task" (ADD Rev C, p. 204); see Key definition tasks.

How the architecture evolves (Section 3)

Section 3 opens: "Section 2 captures the existing components of the architecture … However, the architecture is far from 'complete' — it evolves continuously. When NASA needs to update and improve the architecture — including defining future segments, identifying new technology needs, and adding new elements — it follows the processes outlined below" (ADD Rev C, p. 71). The processes, and where the wiki covers them:

ADD section	Process	Wiki page
3.1 (pp. 72–76)	Architecture definition: definition tasks and roadmapping	this page; Key definition tasks
3.2 (pp. 77–79)	Identifying and prioritizing architecture-driven technology gaps	Gaps index
3.3 (pp. 80–81)	Identifying architecture-driven data gaps	Data gaps index
3.4 (p. 82)	Element definition and pre-formulation	Elements
3.5 (pp. 83–103)	Recurring tenet assessments	Recurring tenets

Unique considerations by destination

Section 3.1.1 (pp. 72–73) sets out why the lunar and Mars architectures need more than past experience:

• "Although NASA landed humans on the Moon with Apollo, the current lunar architecture represents a significantly more complex endeavor with many unique considerations. The Moon to Mars Architecture must maintain flexibility to incrementally build functionality" (p. 72).
• Aborts take longer. "While aborts back to Earth can be initiated relatively quickly, aborts or rescue operations for missions to the lunar South Pole or NRHO are more complex and would take days (versus hours from the International Space Station)" (p. 72).
• The South Pole. Its "unique lighting, terrain, and other environmental conditions present unique strategic planning challenges", which the architecture "will need to address … with capabilities like power sharing; mobility; communications and positioning, navigation, and timing; and others" (p. 72).
• Gravity transitions. Crews will move "between microgravity and partial gravity environments, including eventually doing so after extended durations in microgravity", without the ground support ISS crews have. "Testing concepts of operations for surface exploration with deconditioned crew members on the Moon is also a crucial Mars-forward activity" (p. 72).
• Mars. Missions there "represent significant increases in complexity across many dimensions, including distance traveled, communications delays, Earth-independent operations, time crew members spend in the deep space environment, and total mission duration … Lunar missions create opportunities to develop systems and concepts of operations to address some of these challenges, but Mars missions still represent an orders-of-magnitude increase in difficulty" (pp. 72–73).

Architecture roadmapping

Section 3.1.2 (pp. 73–74):

• Guiding questions. "An exploration architecture must answer a set of guiding questions: Where do we go? Why do we go? Where do we go? How do we get there and back? What do we do there? Who is involved?" (p. 73, quoted as printed: "Where do we go?" appears twice and "When?" is missing, though the figures include it; open question 21).
• Order matters. "NASA establishes a recommended sequence for answering these architecture questions via key definition tasks in the architecture roadmapping process … The sequence also affects the remaining architecture trade space" (p. 73).
• Why first, not when. "Beginning with the question of 'When?' for example, creates flow-down implications and constraints for other questions". "Beginning with 'Why?,' however, foregrounds NASA's Moon to Mars Objectives and the agency's pillars of exploration. This flow ensures that all of the questions that follow from 'Why?' address the agency's exploration objectives, rather than targeting a specific constraint, like a mission deadline" (p. 73).
• What roadmapping does. "NASA uses architecture roadmapping to identify, catalog, and sequence key definition tasks. Roadmapping ensures NASA conducts definition tasks in an effective order, prioritizing those with many flow-down impacts and minimizing re-work. This roadmapping approach also ensures NASA coordinates across internal stakeholders" (p. 74).
• More detail. "For more information about the flow of guiding questions and architecture roadmapping, refer to the 'Architecture Definition' white paper" (p. 74, footnote 22). Its content is below.

The two figures (pp. 73–74, read from the PDF; the text layer drops them) show the same six questions in two orders. Each question has an "…the architecture optimizes for:" or "…which influences …" line and three example drivers:

	"Prioritizing 'When'" (p. 73): "If the first decision is when to go…"	"Prioritizing 'Why'" (p. 74): "If the first decision is why we go…"
1	WHEN We Go: optimizes for Target Date, Development Timeline, Mission Duration	WHY We Go: optimizes for National Posture, Science, Inspiration
2	HOW We Go: Development Timeline, Utilization Options, Mission Duration	WHERE We Go: Landing and Ascent, Utilization Options, Mission Duration
3	WHAT We Do There: Landing and Ascent, Surface Stay Duration, Utiliation Options (as printed, PDF checked)	WHO Is Involved: Number of Crew, Areas of Expertise, Utilization Options
4	WHO Is Involved: Number of Crew, Areas of Expertise, Utilization Options	WHAT We Do There: Landing and Ascent, Surface Stay Duration, Utilization Options
5	WHERE We Go: Landing and Ascent, Utilization Options, Mission Duration	WHEN We Go: Target Date, Development Timeline, Mission Duration
6	WHY We Go: To Beat a Deadline, To Employ Existing Tech, To Claim a Milestone	HOW We Go: Development Timeline, Utilization Options, Mission Duration

The point of the pair: put "When" first, and "Why" is left to answers such as "To Beat a Deadline"; put "Why" first, and the architecture optimizes for national posture, science and inspiration. The p. 74 order runs Why, Where, Who, What, When, How. The 2025 Architecture Update describes the "Architecture Definition" white paper as summarizing "the six major questions that make up an exploration architecture" (2025 Architecture Update, p. 17).

In ADD Appendix C.1

Appendix C, "Architecture Definition", opens with C.1 "Architecture Roadmapping" (pp. 186–188), the process behind the lists on Key definition tasks. Page numbers here are ADD Rev C. Much of it repeats the "Architecture Definition" white paper (below) in nearly the same words; the comparison is the wiki's.

What it is. "NASA's architecture roadmapping process, rooted in systems engineering principles, establishes a recommended sequence for answering the many questions that make up the architecture." It "also incorporates 'legacy decisions' that predate the Moon to Mars Architecture approach but still influence lunar exploration" (p. 186). C.1 has its own table of "key roadmapping terms" (architecture definition task, definition outcome, trade space, key and priority key definition task, legacy decision). Its definitions differ in places from Appendix F's and the white paper's, most of all for "trade space" (Glossary).

Why NASA does it ("Value Proposition", pp. 186–187). Roadmapping "provides value in three main ways":

• "Minimizing later rework or disruption: Architecture roadmapping prioritizes high-impact definition tasks that influence every aspect of the architecture early in the overall architecting process, minimizing implementation delays, rework, or re-litigation."
• "Defining inter-organizational critical paths: … responsibility for conducting definition tasks crosses multiple organizations. One task may be in the critical path of a seemingly unrelated task." Roadmapping "ensures programs, projects, and technical authorities are aware of how their activities and outcomes affect other authorities."
• "Informing investment strategies: Down-selects are necessary when multiple investments could meet objectives, but budget and schedule demands preclude multiple developments. Making these down-selects too early or too late can cause unwanted costs, delays, or architectural limitations."

The process ("Roadmapping Process", pp. 187–188; the sub-sections are numbered C.1.2.1, then C.1.1.1 to C.1.1.3, as printed):

1. Identify and define. "Definition tasks include the question to be answered (i.e., the type of outcome needed), potential options, the NASA authority for the definition task (if known), relevant stakeholders, and architecture context." Two methods: "First, a bottom-up analysis drew initial input from decades of heritage studies; then, an ongoing top-down assessment has identified candidate key definition tasks from the objective decomposition." A new candidate is matured "and then brings it forward for approval at the annual Architecture Concept Review" (p. 187).
2. Map the flow-downs. "Each candidate key definition task has dependencies on and for other key definition tasks; the dependencies are called 'flow-downs.'" They are kept in "a digital, SysML-based definition space model" that can "generate definition sequences, and trace the impact of definition outcomes" (p. 187).
3. Sequence. "The initial analysis is based directly on the flow-downs and is designed to minimize violations of those flow-downs. However, this is an optimization problem in which many solutions are possible." The other considerations are the white paper's list (resources, technology investment needs, impact on the remaining trade space). "Priority key definition tasks are approved at the Architecture Concept Review each year to be included in the sequence and to be addressed in the near term" (p. 187).
4. Document the outcome. "The actual process for conducting each key definition task will vary depending on the relevant authority". After analysis and recommendations "in coordination with stakeholders, the relevant authority selects a definition outcome." "Definition outcomes appear in annual revisions of the Architecture Definition Document … Resulting impacts to the architecture are reported at subsequent Architecture Concept Reviews" (p. 188).

The figure on p. 188, "Notional Depiction of Categorizing the Key Definition Tasks Based on Time Criticality" (read from the PDF), is the white paper's Figure Four, "Notional Definition Flow" (below): the same title inside the image, the same "Priority Definition" and "Later Definition" panels, the same arrow and color key. The ADD's text: "Separating priority key definition tasks from the later key definition tasks allows stakeholders to prioritize their resources. The sequence represents the optimal order, but it is not strictly serial; multiple definition tasks can proceed in parallel. The sequence may evolve as priorities shift and NASA resolves feedback loops between key definition tasks" (p. 188).

What the "Architecture Definition" white paper adds

Page numbers in this subsection are the white paper's (Dec 2025). It "supersedes two previous Moon to Mars Architecture white papers: Systems Analysis of Architecture Drivers (2022) and Key Mars Architecture Decisions (2023)" (p. 1). Neither is among the wiki's sources.

The six questions, each once. "An exploration architecture, such as NASA's Moon to Mars Architecture, must answer a set of guiding questions: Why we go? Who is involved? Where we go? What we do there? When do we go? How we go?" (p. 1). Unlike the ADD's list (p. 73), this one has every question once. Its Key Takeaways list five, "Who, What, When, Why, and How?", without "Where" (p. 6; open question 21). Figure One (p. 1, read from the PDF) sets the six in a ring around the words "Answers to six driving questions help NASA tell a compelling architecture story".

Trade space. "NASA's answers to those questions shape the trade space, the range of options for exploration missions. There are numerous more specific questions or trades beneath each of the six guiding questions, and many of the trades are interrelated such that the answer to one will impact the next, which will impact the next, and so on" (p. 1). "Through key definition tasks, NASA converts its Moon to Mars Objectives into elements and assets that can achieve those objectives" (p. 1). "Selecting one option within the architecture trade space can preclude or require other options in ways both expected and unexpected … It also enables the agency to respond to technological advances and industry developments — as technologies emerge or mature, they can open up new architectural capabilities. Roadmapping empowers NASA leaders to make the right decisions at the right time" (p. 1).

The Apollo example. "Apollo famously responded to the mandate of 'landing a man on the Moon and returning him safely to the Earth' before the end of the decade, establishing 'When' as the priority. NASA successfully achieved that goal, but because the resulting architecture was optimized to meet a tight implementation schedule, it was not a particularly extensible architecture, which had profound implications for the sustainability of human exploration of deep space" (p. 2). For Mars, putting "When" first "might dictate reliance on heritage systems rather than new technologies that take time to develop; it could favor Mars stay durations that can be achieved faster, rather than stay durations that achieve more of NASA's exploration objectives" (p. 2). Starting from "Why?", "architectural trades (e.g., transportation technology) aren't limited by timeline, enabling NASA to send the right people to the right destinations at the right time, rather than constraining the trade space" (pp. 2–3). The paper's Figures Two and Three are the two ADD figures tabled above, with the same labels (both PDFs checked).

Iterative, not linear. "in practice, developing the architecture is iterative, not linear, with NASA addressing many questions and trades simultaneously. A flexible, sustainable architecture that addresses these questions holistically reduces cost by minimizing disruption, re-work, and cost and schedule changes. The answer to any one of these questions is less important than whether all six answers complement each another. When they do, NASA can establish an achievable, affordable, and adaptable architecture" (p. 3; "each another" as printed).

Key terms from the white paper

The "Key Terms" table (p. 2, as printed):

Term	Definition
Guiding Questions	"Questions that determine the purpose and scope of an exploration architecture (i.e., Who, What, Where, When, Why, and How?)"
Trade Space	"A range of possible options for implementation for a particular area of the architecture."
Trade Studies	"Analyses that examine sets of options to better understand the impacts and benefits of individual options. Colloquially referred to as 'trades.'"
Architecture Definition Task	"An examination of a question within the architecture, typically to shape or reduce the trade space (e.g., trade studies in ser-vice to Moon to Mars Architecture definition)."
Roadmapping	"The process of ordering definition tasks in a manner that maximizes opportunities and minimizes risk."
Definition Outcome	"The result of an architecture definition task, which could include a decision, down-select, ground rule, methodology, or other narrowing of the trade space."

What makes a task "key", with the paper's examples (crew number against habitat windows), is on Key definition tasks.

The roadmapping process

• Three steps. "NASA uses a systems engineering–driven process to: 1. identify key architecture definition tasks, 2. determine relationships between these tasks (including dependencies and flow-down impacts), 3. and develop a recommended logical order in which to conduct these key definition tasks" (p. 3).
• A digital model. "NASA maintains a digital modeling environment to manage this complex web of information. The model tracks the possible options that NASA is studying through definition tasks (i.e., the definition trade space) and the flow-down relationships between them" (p. 4).
• What sets the order. "The flow-down relationships are used as a key input in creating recommendations for the sequence in which the definition tasks should be conducted — this is the roadmapping. Several other considerations influence the sequence, including the level of resources that constrain how many definition tasks the agency could conduct in a given year, needs that inform technology development investments, the impact of a given definition outcome on the remaining trade space, and more" (p. 4).
• A partial sequence that grows. "NASA established a partial roadmapping sequence and adds to it each year. This is represented by the 'priority' key definition tasks, which should be made early in the architecting process" (p. 4).
• Priority definitions. "From the overall list of definition tasks, NASA has identified priority areas with many flow-down impacts. The agency brings these definition tasks to the annual Architecture Concept Review for concurrence from agency stakeholders. Once approved, the agency prioritizes resources for these definitions." They "do not follow a linear order. NASA addresses multiple tasks in parallel" (p. 4). The current Mars list is on Key definition tasks.

How the Mars catalog was built

"To develop the catalog of Mars architecture definition tasks, NASA subject matter experts conducted a bottom-up review of heritage Mars architecture studies. Analyzing decades of documents, these experts identified the most influential factors in designing the initial human exploration campaign for Mars. Next, they decomposed the agency's blueprint objectives for exploration using a top-down approach. This produced use cases and functions that must be performed by yet-undefined elements and assets, which revealed needed definition tasks. The resulting analysis — which is still ongoing — identified nearly 100 candidate definition tasks for the Mars architecture. NASA has since further refined this list, examined the possible definition outcomes for each, and identified flow-down relationships (i.e., dependencies) between the possible outcomes" (p. 4). Compare Objective decomposition, where the ADD describes use cases and functions; the paper doesn't name that section.

Figure Four: notional definition flow

Figure Four (p. 4, read from the PDF) "visualizes this order". Titled "Notional Definition Flow", it draws each "Definition Task" as a map pin. Pins are colored by the guiding question they serve, following a "Definition Color Key" of WHY, WHERE, WHO, WHAT, WHEN and HOW. Lines link the pins from left to right above an arrow labeled "Timeline to Exploration Destination". The left panel, "Priority Definition", has solid lines; the right panel, "Later Definition", dashed ones. A legend shows how "Completed Definition Tasks" are drawn. The figure is notional: it names no tasks, and the wiki doesn't count its pins. ADD Appendix C prints the same figure under another caption (above). At the January 2026 workshop it was shown again under the heading "Architecture Maturation Strategy", with the same panels, arrow, legend and color key (the wiki's comparison; 2026 industry and academia workshop, slide 37).

Decision roadmapping on NASA's web page

NASA's "Architecting from the Right" page has a section, "Architecture Decision Roadmapping", that is a shorter version of the 2024 overview's feature of the same name (PDF pp. 14–15), in other words. What it adds is below: the "logical order", its example and the "delaying — or accelerating" sentence are not in the overview's text (searched). Undated; it uses the pre-Rev C word "decisions" where Rev C says definition tasks (source page):

• "Each decision has precedent relationships with many other decisions. Although there is no 'right' order in which to make these decisions, there is a logical order."
• Its example: "a decision about the number of astronauts to send to Mars orbit limits the number of astronauts an architecture can send to the Martian surface, so it makes sense to decide how many crew are needed on the surface to achieve mission objectives before limiting the Mars transportation system's crew complement." That is the order of MD-05 (crew to the surface, decided) and MD-06 (crew to Mars vicinity, open) (the wiki's pairing; Key definition tasks).
• "decisions with major flow-down impacts on other subsequent decisions are categorized as priority decisions"; NASA tracks them "using digital engineering tools", and "The value of the digital decision roadmapping tool is that it allows NASA to quickly assess the impacts of delaying — or accelerating — these important architecture decisions."

The workshops: NASA's web page

NASA's Architecture Workshops page records the outside workshops since 2023 (source page):

• May 2023: a one-hour webinar for U.S. industry and academia.
• June 2023: workshops, with presentations of six 2022 white papers.
• February 2024: workshops, with briefings on eight 2023 white papers and Mars trajectory and abort animations for "2039 mission opportunity".
• February 2025: separate workshops for international partners and for industry and academia, each with "Foundational Exploration Gaps" and briefings on 2024 white papers.
• 2026: industry and academia in "Washington, DC, on January 21 and 22 at the National Academy of Sciences"; international partners in Rome "on February 24 and 25", co-hosted by the Italian Space Agency, with posters from eight partner agencies.

The page puts the review "Each fall" and the workshops after publication; the industry page says "Workshops are typically held in February of each year" (Industry Engagement page). The charts and posters it links for February 2024 to 2026 are among the sources; the 2023 charts, the webinar recording and the animations are not (sources/manifest.csv). One file it lists as a February 2024 briefing, "White Paper Briefing: Lunar Site Selection", is the 2023 paper itself, so the wiki holds that one 2023 white paper; its content is on Lunar site selection (source page; open question 92). The workshops' slides rank below ADD Rev C: they brief the products, they don't replace them.

The paragraphs below take what NASA said the workshops changed (January 2026), then each year's workshops in order: February 2024, February 2025, February 2026.

What the workshops changed, as NASA briefed it in January 2026. The industry and academia deck opens with "Workshops in Action": they "Spurred additional communication on topics including Logistics, Mobility, Power, and Comm & Nav, etc"; led to "Adapting engagement to enable more industry studies in priority areas" and "Changes to solicitation, procurement, and study approaches"; and "Informed development of NASA's architecture-driven technology gaps and data gaps" (slide 4). A slide headed "Incorporating Your Feedback: Product Revitalization" shows eight kinds of ADD Rev C page (segments, sub-architectures, element one-pagers, tech gaps, unallocated functions, functional mappings, element icons, data gaps), without saying which are new (slide 6). Sessions are not recorded and no press is invited, but "NASA will take notes in all sessions to ensure we capture your feedback", and the presentations are posted afterwards (slide 17) (2026 industry and academia workshop).

February 2024. The opening briefing reported ACR23's products (Rev A, the executive overview, "13 White Papers"), Rev A's decomposition changes in numbers, the 2023 elements and the first seven Mars decisions, and set the 2024 strategic analysis cycle (SAC24) three tasks: Human Lunar Return and Foundational Exploration "segment gaps, including lunar logistics, large cargo return, conceptual reference missions, and cargo offloading/relocation"; "strategic analysis for segment sub-architectures, including surface communication, large-scale mobility, power systems, in-situ resource utilization (ISRU), and ingress/egress strategies"; and "decision packages for initial seven Mars exploration decisions". Its process figure, "An Evolutionary Architecture Process", runs from the objectives through product review, the review, "ARCHITECTURE CONFIRMATION" and "ARCHITECTURE DEFINITION DOCUMENT EXPANSION" to the next review, with an "ANNUAL CYCLE TO MATURE ARCHITECTURE" (Overview and Updates, slides 8–14). ESDMD's panel slide listed what the 2022 workshops had asked for and what changed: decomposition syntax "leveled across objective areas", plainer words or glossary entries for terms that "don't translate from English easily", "Four additional sub-architectures", and white papers up "from 6 … in ACR22 to an additional 13 … for ACR23" (Mission Directorate Panel, slide 2). STMD said it was "Participating in virtually all SAC24 tasks" and "Working gap prioritization processes across the architecture" (slide 13).

A year later, February 2025. The opening briefing at both workshops counted "almost 200 registrants" from "nearly 100 organizations" in industry and academia, and "over 70 registrants" from "over 20 space agencies" among partners. It listed the 2024 workshops' feedback: industry wanted "more clarity on the agency's investment priorities" and to be "involved earlier in the gap definition process"; partners wanted "clear paths through preformulation to element initiation", and emerging agencies "more clarity on where they can engage". "What's Different this Year?": workshops "retooled … to promote more engagement", "non-NASA panelists", and a focus on "finding avenues to collaborate that close architecture and technology gaps" (Architecture Updates deck, slides 2, 8, 19; industry copy, slide 2). The "Architecture 101" roundtable closed on prompts such as "How can NASA help industry forecast where gaps exist and when they need to come on-line?" (Architecture 101, slide 18). The industry and academia panels deck has 13 session cards, among them two listening sessions, "What Are We Missing?", and sessions on architecture products, interoperability, logistics and mobility, power and communications, science, the human system, the Moon as "a Proving Ground for Mars", the cislunar economy and the national interest, with speakers from NASA, companies and laboratories; the partners' deck has 6, in a "Moon Room" and a "Mars Room", with agency speakers (MBRSC, KASA, ASA, CNES; then JAXA, ESA, CSA, ASI) on two sessions where the industry programme had companies. The Paths to Partnership panel and the Architecture 101 roundtable are on their own decks' last slides (panels, industry and academia; panels, international). One briefing ties a NASA office's yearly planning to this cycle: the Mars Campaign Office's new-start process begins each November–February when "SAO holds Architecture Concept Review and releases annual Architecture Definition Document revision", and reports progress back "for ESDMD architecture gap updates" (Gaps index).

The international partners heard the same charts in Rome on 24–25 February 2026, with two "fireside chats" added, "Your Feedback Matters: How Partners Shape the Architecture" and "Moon to Mars Program Office Update: What's New? What's Next?", and a slide headed "Incorporating Your Feedback: ADD Before and After" that sets a Rev B page on the Orion spacecraft beside Rev C's one-pager (slides 20, 21, 44; 2026 international partners workshop deck).

Measuring the architecture: performance and effectiveness

ADD Rev C doesn't describe how NASA scores the architecture as a whole: a search of its text finds no "measures of performance" or "measures of effectiveness". The 2025 Architecture Update does, briefly, under "Arch Performance & Effectiveness" (p. 16). Page numbers in this section are the Update's.

• What is measured. "As NASA refines and expands the Moon to Mars Architecture, it also measures how well the architecture is meeting the agency's Moon to Mars Objectives. Measures of performance and measures of effectiveness assess what objectives the architecture is meeting and how well it is meeting them, respectively. These might include, for example, the architecture's ability to provide mobility services on the lunar surface, the actual distance it can support, and how that capability compares with the agency's stated objectives" (p. 16).
• Year over year. "These year-over-year changes capture significant growth in key exploration capabilities. For example, the addition of the Pressurized Rover in 2023 significantly increased mobility opportunities, while the addition of the lunar surface fission system this year significantly increases the power that the architecture can provide." NASA "tracks these measurements year-to-year to demonstrate how initiating new elements, building utilization capabilities, and further defining the Moon to Mars Architecture bring the agency closer to meeting all of its exploration goals" (p. 16).

The chart (p. 16, read from the PDF; the text layer drops it) is a radar chart that "provides a simplified look at how the architecture's performance has evolved over past Architecture Concept Review (ACR) cycles". It has one line per year: 2022, 2023, 2024 and 2025. Around it are six labels, each followed by "Opportunity": Communications, Habitation, Cargo, Crew Time, Mobility and Power. It has eleven axes:

Axes, as printed
Crew Opportunity Days Per Year · Pressurized Floor Area · Total Cargo Delivery Per Year · Minimum Utilization Cargo Delivery per Year · EVA Opportunities Per Year · Micro to Partial Gravity Transitions · Uncrewed Mobility Range Per Year · Crewed Mobility Range Per Year · Maximum Repositioning Capability on Surface · Distributable Power · Peak Surface Transmission Rate

The chart has no scale, units or values, and it draws no boundaries between the six labels, so the wiki doesn't assign axes to them or read values off it. A chart with the same eleven axis labels, six labels and four years, titled "Measuring Architecture Performance Over Time", was shown at the January 2026 workshop for industry and academia (the wiki's comparison; the lines were not compared) (2026 industry and academia workshop, slide 14). One reading from the figure, which fits the text: on "Distributable Power", only the 2025 line reaches far from the center. The measures, their targets and the method are not given.

The Pressurized Rover is a Rev A element (2023 review), and the fission system a Rev C one (Elements; Pressurized Rover; Lunar Nuclear Fission System).

Changes since Rev C: the May 2026 realignment

ADD Rev C is a publication of the "Exploration Systems Development Mission Directorate (ESDMD) Strategy and Architecture Office (SAO)" (ADD Rev C source page). Five months after it, NASA reorganized:

• ESDMD is merged. "With human spaceflight operational to both low Earth orbit and the Moon, the Exploration Systems Development Mission Directorate and Space Operations Mission Directorate will unify as HSMD", the Human Spaceflight Mission Directorate. ARMD and STMD become the Research and Technology Mission Directorate (RTMD) (realignment release, 22 May 2026). HSMD "provides unified leadership for the agency's systems, operations, and architectures" (HSMD page, updated 11 September 2026).
• "Moon to Mars" becomes "Artemis". HSMD's divisions are Low Earth Orbit, Moon Base, and "Artemis, Jeremy Parsons as Program Manager (renamed from Moon to Mars)" (Administrator's workforce note, 22 May 2026).
• The Moon Base Program holds the lunar work outside Artemis. Directive 6 consolidates "all lunar programs outside of the Artemis program" into a Moon Base Program within HSMD, "responsible for integrating exploration architecture, surface mobility, science payloads, cargo landers, habitability systems, logistics, observation, communication, navigation and other technical demonstrations into a coherent end-to-end campaign". It is to "Develop an integrated lunar architecture and operations plan that identifies the critical path, long lead items, supply chain vulnerabilities, international, interagency, and commercial partnerships" (workforce note, Directive 6). The Moon Base Program Manager says that after the post-Ignition RFI "our architecture team is evaluating what's needed, matching up to technology gaps", as reported (podcast, August 2026).
• Nuclear and SCaN move to RTMD. The Space Reactor Office (SR-1, LR-1) and SCaN are RTMD divisions; all space nuclear funding goes to the Space Reactor Office (workforce note, Directive 7). Directive 6 still gives the Moon Base Program authority "across all lunar missions, including SCaN".
• HSMD solicits against "Moon Base architecture gaps". Its NextSTEP-3 Appendix B (June 2026) asks industry for "concept demonstrations, risk reduction opportunities, and studies that address Moon Base architecture gaps", without naming a gap or saying where the gaps are listed (NextSTEP-3 B page; RT-2).

None of these sources mentions the Strategy and Architecture Office, the Architecture Definition Document, the Architecture Concept Review or a next revision, and the HSMD page's leadership list names no architecture office. The NextSTEP-3 pages don't either. The wiki records that as silence, not as a change to the process described above.

Related pages

Objective decomposition · Architecture framework · Key definition tasks · Recurring tenets · Gaps index · Elements · Why Moon to Mars · ADD Rev C source page · "Architecture Definition" white paper · NASA's Feature Stories page (dated articles, April 2023 to February 2025)

Sources

ADD Rev C, pp. 3–7, 9, 11, 13, 16, 18–19, 71–74, 186–188, 204 · "Architecture Definition" white paper, pp. 1–6 · 2025 Architecture Update, pp. 3, 16–18 · Strategy and Objectives Development (2023), PDF pp. 34–35 · 2023 executive overview, PDF pp. 3, 8–9, 11 · 2024 executive overview, PDF pp. 3, 8–9, 20, 26 · NASA web pages: Architecture Definition Documents, White Papers, Architecting from the Right, Architecture Workshops, Architecture Concept Review · 2026 industry and academia workshop, slides 4, 6, 14, 17 · May 2026 realignment: release, Administrator's workforce note, HSMD page, Moon Base podcast