1. Requirements

3.5.3 The project manager, in conjunction with the Safety and Mission Assurance organization,  shall determine the software safety criticality in accordance with NASA-STD-8719.13. 

1.1 Notes

Software Safety Critical Assessment Tool, in NASA-HDBK-2203, can be used to determine the software safety criticality.  Engineering and software assurance must reach agreement on safety-critical determination of the software.  Disagreements are elevated via both the Engineering Technical Authority and Safety and Mission Assurance Technical Authority chains.

1.2 Applicability Across Classes

2. Rationale

Each project, with the responsible Software Assurance organization, evaluates the project software to determine if the software is safety-critical.  If the software is determined to be safety critical, the software safety requirements within NPR 7150.2, NASA Software Engineering Requirements, and NASA-STD-8719.13, NASA Software Safety Standard

3. Guidance

The project can use NASA-STD-8739.8

NASA-STD-8719.13

The software safety criticality assessment process and the location of the assessment results are documented within the Software Safety Plan (or equivalent). Most projects document the software safety criticality with the software classification. The project's system safety documentation also addresses it.

A best practice is to document the software safety criticality assessment results with the software classification assessment, with local S&MA and the Engineering TA both approving the results.  An example form is provided in NASA-STD-8719.13

4. Small Projects

No additional guidance is available for small projects. The community of practice is encouraged to submit guidance candidates for this paragraph.

5. Resources

6. Lessons Learned

A documented lesson from the NASA Lessons Learned database notes the following: 

• Mars Global Surveyor (MGS) Spacecraft Loss of Contact. Lesson Number 1805:  "Contact was lost with the Mars Global Surveyor (MGS) spacecraft in November 2006 during its 4th extended mission. A routine memory load command sent to an incorrect address 5 months earlier corrupted positioning parameters, and their subsequent activation placed MGS in an attitude that fatally overheated a battery and depleted spacecraft power. The report by the independent MGS Operations Review Board listed 10 key recommendations to strengthen operational procedures and processes, correct spacecraft design weaknesses, and assure that economies implemented late in the course of long-lived missions do not impose excessive risks." 

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