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Mission Assurance Requirements

Scope and Description

This topic covers the design of mission assurance requirements for a smallsat project. Mission Assurance is a full life-cycle engineering process to identify and mitigate design, production, test, and field support deficiencies threatening mission success. This includes design margins, testing tolerances, analyses, reviews, documentation, and reporting. Smallsat missions are often constrained by budget and schedule. In addition, smallsat teams are unlikely to be flowed these requirements. Proper focus and effort invested in this task should ensure that a mission leverages the smallsat paradigm for efficiency and innovation while achieving a satisfactory level of mission confidence.

Resources under this topic area primarily include government standards that provide baseline process requirements and book chapters and articles that provide smallsat-specific guidance on developing low-cost missions. The content in this section provides high-level guidance, but content from many other Knowledge Base topics could inform specific decisions that are part of this task.

Best Practices and Lessons Learned

  • Avoid omitting traditional analysis and testing processes designed to improve mission confidence. Instead, save schedule and budget by making them more informal and focused. This can mean only analyzing high risk or mission critical elements of the design and not requiring a formal report, but only a results spreadsheet and slide package for informal peer review.
  • Even if you are not flowed a complete set of requirements, make sure to establish them yourself. It is important from a mission confidence and cost/schedule efficiency perspective to establish consistent requirements for your own team and for flowing to vendors/subcontractors. This reduces the chances that your smallsat includes a subsystem that either (1) has a significantly increased chance of failure relative to the rest of your system or (2) is unnecessarily expensive and high-reliability given the overall reliability level of your entire spacecraft. These requirements can and should be flexible or allow for waivers.
  • While it is important to baseline processes and requirements, avoid taking these definitions to the most granular level of detail. As much as possible, leave detailed, low-level decisions up to your engineers and technicians.
  • Always consider the strong links to cost and schedule when establishing mission assurance requirements.

Resources

Software Tool
NASA

This interactive online software tool offers a step-by-step guide for determining radiation risks that ... apply given a set of simple input from the user. Smallsat teams can develop dose depth curves and single event effects (SEE) plots based on the orbit and other input parameters. In addition, R-GENTIC provides advice on electronics and software/firmware design for radiation tolerance in the specified environment.

This document defines engineering design and environmental test requirements and guidelines for NASA ... Class C and D space flight systems. This section is titled "Flight System Design" and covers both requirements and guidance. This is an excellent reference for setting baseline requirements and design margins on each element of a smallsat design. Margins are given at various key lifecycle milestones. The information is concise, practical, and references several other NASA and DoD documents in case additional detail is needed on a particular requirement or piece of guidance.

Article
David Petrick

This slide package provides an update from NASA GSFC on Class D mission assurance. Class D is the highest ... risk posture classification for missions governed by NASA's traditional process and program managements requirements. Class D is introduced and slides 9 and 10 provide valuable high-level guidance on mission assurance for high-risk missions. A number of figures and tables in the main body of the presentation and in the backup slides are a good references regarding mission assurance for high-risk space missions, including related processes, concepts, and guidance.

Book
George Sebestyen et al.

This chapter describes “procedures and program management techniques that lead to reduced spacecraft ... cost.” Note that what is presented here is one experienced leader's approach to low-cost spacecraft development. Other approaches exist, but this is a valuable and concisely presented example. Some of the recommended practices in this chapter can lead to well-reasoned removal or de-scoping of design reviews.

Website
Defense Acquisition University

This web page provides a concise, high-level overview of requirements management. Note that the content ... presented here is not specific to space systems, but it nonetheless provides potentially valuable information for smallsat developers. In addition to its own content, this web page includes links to relevant training courses, documents, and other web pages on the DAU website.

These sections provide background and introductory information on traditional space mission risk classifications ... and present a "process to identify risk posture and contract requirements". It presents a very traditional and involved process; however, it includes valuable information that can be applied to tailoring process requirements for smallsat missions.

This document defines engineering design and environmental test requirements and guidelines for NASA ... Class C and D space flight systems. This section is titled "Integration and Environmental Test" and covers both requirements and guidance. This is an excellent reference for setting baseline processes and test requirements on each element of a smallsat design. Test equipment tolerance requirements, environmental test parameters, recommended documentation, testing flow, and useful definitions of key terms are all included. The information is concise, practical, and references a number of other NASA and DoD documents in case additional detail is needed on a particular requirement or piece of guidance.

White Paper
Aerospace Corporation

This report describes and presents some of the results and conclusions of a survey to review baseline ... Class C and Class D mission planning and execution. See pages 34 to 42 for useful summary considerations, conclusions, and notable insights from this effort. The survey responses provided in Appendix B provide a diverse set of opinions on balancing risk and efficiency on Class D projects. Many of these approaches are relevant to smallsat missions.

This doctoral thesis provides a comprehensive review of engineering project lifecycles from a wide range ... of organizations. It then presents a smallsat-specific mission lifecycle and demonstrates the application of that smallsat lifecycle to a university cubesat. Section 3 presents this smallsat lifecycle, including a detailed description of each phase and design review. The review in Section 2 is a valuable resource for understanding and comparing the various traditional systems engineering processes and associated design reviews.

Article
Jared Clements et al.

This conference paper presents a "scaled systems engineering approach to cubesat missions implemented ... on a programmatically constrained mission." The authors present the concept of "constraint-driven design" and describe how this is different from the traditional top-down, requirements-driven space mission design process. Subsections address systems engineering, technical management, technical process, and operations.

White Paper
NASA

This page in the NASA Public Lessons Learned System describes the importance of establishing a "mandatory ... closed-loop system for detailed, independent, and timely technical reviews of all analyses performed in support of the reliability/design process." These reviews are important for detecting design defects.

Software Tool
Vanderbilt University

SEAM is a web application for modeling assurance cases integrated with system models. SEAM supports the ... Goal Structuring Notation (GSN) standard and a subset of the SysML system modeling standard. Documentation and video tutorials are provided.

Article
Jeff Juranek

This conference presentation includes "key recommendations" on how to improve the efficiency of space ... hardware assembly, integration, and test. The recommendations are supported by examples and data.

White Paper
Aerospace Corporation

This report presents a checklist for procurement organizations and producers of aerospace hardware, software, ... and systems to ensure that test like you fly (TLYF) principles are followed.

This document describes "the Launch Services Program (LSP) program level and technical requirements placed ... on containerized CubeSat dispenser and Picosatellite (CubeSats) satellites for integration on NASA LSP ELV mission."

White Paper
Aerospace Corporation

These sections provide comprehensive background information on traditional space mission assurance classes. ... While most small satellites do not fit into any of these traditional classes, the high-level guidelines and background information in these sections can inform and provide a framework for the establishment of process requirements for any smallsat mission.

This standard "describes a technical basis for promoting and implementing Reliability and Maintainability ... (R&M) concepts on all new NASA programs and projects." It presents a comprehensive set of processes that impact spacecraft reliability and an objectives-based approach to selecting which processes to include in a given mission lifecycle.

White Paper
NASA

This paper describes NASA's Class-D approach for missions that are low cost, have short development/operations ... lifecycles, and are higher risk-posture. This is a concise document that provides "tailoring/streamlining principles" and "minimum expected practices" that can be used by any smallsat team to guide the establishment of effective and efficient processes.

White Paper
NASA

This handbook "provides guidance for laying out a mission success approach for cubesat missions." This ... includes a clear and concise presentation of environmental test recommendations in the appendix. This document can be useful for NASA cubesat developers, their vendors, and any team developing mission assurance requirements for a smallsat mission.

This handbook provides guidelines for prioritizing mission success activities for "highly constrained" ... spaceflight projects like smallsat missions. This document is a very practical tool for determining mission assurance requirements. It does not prescribe a set of requirements, but instead encourages and informs critical thinking about how to maximize the probability of mission success with limited resources.

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