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NPR 8705.4
Effective Date: June 14, 2004
Expiration Date: December 14, 2020
Printable Format (PDF)

(NASA Only)

Subject: Risk Classification for NASA Payloads (Updated w/change 3)

Responsible Office: Office of Safety and Mission Assurance

| TOC | ChangeLog | Preface | Chapter1 | Chapter2 | AppendixA | AppendixB | AppendixC | ALL |

Appendix B - Classification Considerations for NASA Class A-D Payloads

Four risk levels or classifications have been characterized in Appendix A. The classification considerations in this appendix provide a structured approach for defining a hierarchy of risk combinations for NASA payloads by considering such factors as criticality to the Agency Strategic Plan, national significance, availability of alternative research opportunities or reflight opportunities, success criteria, magnitude of investment, and other relevant factors. Additional or alternate classification considerations may be applied to a specific payload or payload element. The importance weighting assigned to each consideration is at the discretion of the responsible Mission Directorate.

Characterization Class A Class B Class C Class D
Priority (Criticality to Agency Strategic Plan) High priority High priority Medium priority Low priority
National significance Very high High Medium Low to medium
Complexity Very high to high High to medium Medium to low Medium to low
Mission Lifetime (Primary Baseline Mission) Long, > 5 years Medium, 2-5 years Short, < 2 years Short, < 2 years
Cost High High to medium Medium to low Low
Launch Constraints Critical Medium Few Few to none
In-Flight Maintenance N/A Not feasible or difficult Maybe feasible May be feasible and planned
Alternative Research Opportunities or Re-flight Opportunities No alternative or re-flight opportunities Few or no alternative or re-flight opportunities Some or few alternative or re-flight opportunities Significant alternative or re-flight opportunities
Examples HST, Cassini, JIMO, JWST MER, MRO, Discovery payloads, ISS Facility Class Payloads, Attached ISS payloads ESSP, Explorer Payloads, MIDEX, ISS complex subrack payloads SPARTAN, GAS Can, technology demonstrators, simple ISS, express middeck and subrack payloads, SMEX


1. Mission impact; i.e., loss of function effect on other payloads or ISS operations may also be a characterization factor. For example, loss of the function of freezers and centrifuges may impact other payloads and increase the overall level of risk.

2. The safety risk to crew inherent in the operation of a human-crewed vehicle may be a factor in payload classification determinations. Class C and D payloads that may have a significant risk of not achieving mission success may be considered unsuitable for launch on a crewed vehicle, unless they are secondary payloads making use of available launch capacity that would otherwise go unused.

3. Other situation-dependent payload classification considerations may include human-rating environment, logistics support, and interoperability interfaces.

| TOC | ChangeLog | Preface | Chapter1 | Chapter2 | AppendixA | AppendixB | AppendixC | ALL |
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