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7.15 - Relationship Between NPR 7150.2 and NASA-STD-7009

1. Purpose

This topic discusses the relationship between the requirements and associated processes for NPR 7150.2, NASA Software Engineering Requirements,  039 and the content of NASA-STD-7009, Standard for Models and Simulation 272. Because NASA-STD-7009 is generally applicable to all types of models and simulations (which are most commonly embodied in software), it is important to understand its relevance to NPR 7150.2 and the precedence to be maintained between the two documents. Software developers can use this topic to understand the relevance and applicability of NASA-STD-7009 when developing software under NPR 7150.2.

1.1 Introduction

1.1.1 Relevant Guidance in NPR 7150.2

As discussed elsewhere, the NPR 7150.2 requirements applicability to the software being developed is determined by the contents of its Appendix D, Requirements Mapping Matrix. Requirements SWE-139 and SWE-140 implement the contents of Appendix D. The NASA-STD-7009 in turn describes how models and simulations are to be developed and verified within the bounds of the governing SWE requirements of the NPR 7150.2.

NPR 7150.2 invokes the content of NASA-STD-7009 via requirement SWE-070 in the presentation of the requirement in its section 3.4.6 and the accompanying Note:

"3.4.6 The project shall verify, validate, and accredit software models, simulations, and analysis tools required to perform qualification of flight software or flight equipment." (See SWE-070)

Note: Center processes address issues such as numerical accuracy, uncertainty analysis, and sensitivity analysis, as well as verification and validation for software implementations of models and simulations. Information regarding specific verification and validation techniques and the analysis of models and simulations can be found in the NASA standard NASA-STD-7009."

1.1.2 Applicability and Scope of NASA-STD-7009

The applicability and scope are stated in section 1.2 of NASA-STD-7009, where the acronym "M&S" denotes "models and simulations":

NASA-STD-7009 applies to M&S used by NASA and its contractors for critical decisions in design, development, manufacturing, ground operations, and flight operations. (Guidance for determining which particular M&S are in scope is provided in NASA-STD-7009, section 4.1 and Appendix A. NASA-STD-7009 also applies to use of legacy as well as commercial-off-the-shelf (COTS), government-off-the-shelf (GOTS), and modified-off-the-shelf (MOTS) M&S to support critical decisions. Generally, for such M&S, particular attention may need to be paid to defining the limits of operation and to verification, validation, and uncertainty quantification. Programs and projects are encouraged to apply this standard to M&S, if the M&S results may impact future critical decisions.

NASA-STD-7009 does not apply to M&S that are embedded in control software, emulation software, and stimulation environments. However, Center implementation plans for NPR 7150.2, NASA Software Engineering Requirements, cover embedded M&S, and address such M&S-specific issues as numerical accuracy, uncertainty analysis, sensitivity analysis, M&S verification, and M&S validation.

2. Implications for Models and Simulations

2.1 Implications for Embedded Models and Simulations

As noted in the previous section, embedded models and simulations are not in the scope of NASA-STD-7009. 272  However, the note in NPR 7150.2A 039 implies that Requirement 4.2.6 and Requirements 4.4.1-4.4.9 found in NASA-STD-7009, nevertheless be addressed for such models and simulations. Each of these requirements begins with the phrase "Shall document." None of them requires that any specific activity be performed other than the relevant documentation. As the Standard states in section 4.1: "Whatever was done is to be documented, and if nothing was done a clear statement to that effect is to be documented."

2.2 Implications for Other Models and Simulations

For all other models and simulations that are deemed by the M&S Risk Assessment to be in scope of NASA-STD-7009, there is the need to ensure that the requirements of both documents are satisfied. From the perspective of NASA-STD-7009, some of the requirements in NPR-7150.2A are not related to M&S, some are supplemental to requirements in NASA-STD-7009, and others are subsets of requirements in NASA-STD-7009.

Table 1 indicates the specific relationship of each requirement in NPR 7150.2A to NASA-STD-7009. The key to the remarks in the fourth column is

  • Not Related: The NPR requirement is not germane to M&S per se. It may, for example, be a requirement on the NASA Centers (cf. SWE-003: "Each Center shall establish, document, execute, and maintain software processes").
  • Supplemental: The NPR requirement is relevant to software for M&S, but it is over and above any requirement in NASA-STD-7009. For example, SWE-014 ("The project shall implement, maintain, and execute the software plan(s)") has no counterpart in NASA-STD-7009, which requires in Requirement 4.1.4 just that there be a plan (albeit for the M&S as a whole and not just the software), but has no requirement that this plan be implemented, maintained or executed.
  • Subset of Requirement X: The NPR requirement is only a part of a requirement in NASA-STD-7009: Requirement 4.1.4 requires that there be a plan for the M&S that includes such software aspects as verification and configuration management, but has additional requirements on M&S-specific aspects that have no counterpart in the NPR.

3. Table 1. NPR 7150.2A vs. NASA-STD-7009

Section of NPR 7150.2A 039

Requirement Descriptor

SWE #

NASA-STD-7009 272 Relationship

Preface

Effective date

1

Scope statement implicitly includes M&S implemented in software

Organizational Capability

Agency software initiative

2

Not Related

 

Center plan

3

Not Related

 

Benchmark

4

Not Related

 

Software processes

5

The Note in 3.4.6 of NPR 7150.2A means that the topics in the Note are to be addressed in Center processes

 

List of agency's programs & projects containing software

6

Not Related

SW Life Cycle Planning

Software plans

13

Subset of Rqmt. 4.1.4

 

Execute planning

14

Supplemental

 

Cost estimation

15

Supplemental

 

Schedule

16

Supplemental

 

Training

17

Supplemental to Rqmt. 4.6.2(a)

 

Reviews

18

Supplemental

 

Software development life cycle or model

19

Supplemental

 

Software classification

20

Supplemental

 

Software classification changes

21

Supplemental

 

Software assurance

22

Supplemental

 

Software safety

23

Supplemental

 

Plan tracking

24

Supplemental

 

Corrective action

25

Supplemental

 

Changes

26

Supplemental

Off The Shelf (OTS) SW

COTS, GOTS, MOTS, etc.

27

Supplemental

Verification & Validation

Verification planning

28

Subset of Rqmt. 4.1.3(e)

 

Validation planning

29

Subset of Rqmt. 4.1.3(e)

 

Verification results

30

Subset of Rqmts. 4.4.1 – 4.4.3

 

Validation results

31

Subset of Rqmts. 4.4.4 – 4.4.6

Project Formulation

CMMI levels for class A, B and C software

32

Supplemental

 

Acquisition Assessment

33

Supplemental

 

Acceptance criteria

34

Subset of Rqmt. 4.1.3(a)

 

Supplier selection

35

Subset of Rqmt. 4.1.4

 

Software processes

36

Supplemental

 

Milestone

37

Supplemental

 

Acquisition planning

38

Supplemental

Government Insight

Insight into software activities

39

Supplemental

 

Access to software products

40

Supplemental

 

Open source notification

41

Supplemental

 

Electronic access to source code

42

Supplemental

Supplier Monitoring

Track change request

43

Supplemental

 

Software measurement data

44

Supplemental

 

Joint audits

45

Supplemental

 

Software schedule

46

Supplemental

 

Traceability data

47

Supplemental

 

Solicitation

48

Supplemental

Software Requirements Development

Document

49

Subset of Rqmt. 4.1.3

 

Software requirements

50

Supplemental

 

Flow-down & derived requirements

51

Supplemental

 

Bi-directional traceability

52

Supplemental

Software Requirements Management

Manage requirements change

53

Supplemental

 

Corrective action

54

Supplemental

 

Requirements validation

55

Supplemental

Software Design

Document design

56

Supplemental

 

Software architecture

57

Supplemental

 

Detailed design

58

Supplemental

 

Bidirectional traceability

59

Supplemental

Software Implementation

Design into code

60

Supplemental

 

Coding standards

61

Supplemental

 

Unit test

62

Supplemental

 

Version description

63

Subset of Rqmt. 4.2.9

 

Bidirectional traceability

64

Supplemental

Software Testing

Plan, procedures, reports

65

Supplemental

 

Perform testing

66

Supplemental

 

Verify implementation

67

Supplemental

 

Evaluate test results

68

Subset of Rqmts. 4.4.1 – 4.4.6

 

Document defects & track

69

Supplemental

 

Models, simulations, tools

70

Supplemental

 

Update plans & procedures

71

Supplemental

 

Bidirectional traceability

72

Supplemental

 

Platform or hi-fidelity simulations

73

Not Related to M&S in Scope

Software Operations, Maintenance, and Retirement

Document maintenance plans

74

Subset of Rqmt. 4.1.4

 

Plan operations, maintenance & retirement

75

Subset of Rqmt. 4.1.4

 

Implement plans

76

Supplemental

 

Deliver software products

77

Supplemental

 

As-built documentation

78

Supplemental

Software Configuration Management

Develop configuration management plan

79

Supplemental

 

Track & evaluate changes

80

Supplemental

Software Configuration Management

Identify software configuration items

81

Supplemental

 

Authorizing changes

82

Supplemental

 

Maintain records

83

Supplemental

 

Configuration audits

84

Supplemental

 

Implement procedures

85

Supplemental

Risk Management

Continuous risk management

86

Supplemental

Peer Reviews/ Inspections

Requirements, test plans, design & code

87

Supplemental

 

Checklist, criteria & tracking

88

Supplemental

 

Basic measurements

89

Supplemental

Software Measurement

Objectives

90

Supplemental

 

Software measurement areas

91

Supplemental

 

Collection & storage

92

Supplemental

 

Analyze data

93

Supplemental

 

Report analysis

94

Supplemental

Software Measurement

Software measurement system

95

Not Related

 

Objectives & procedures

96

Not Related

Best Practices

Agency process asset library

98

Not Related

 

Identify applicable practices

99

Not Related

Training

Software engineering training

100

Not Related

 

Software training plan

101

Not Related

Software Documentation Requirements

Software development/management plan

102

Supplemental

 

Software configuration management plan

103

Supplemental

 

Software test plan

104

Supplemental

 

Software maintenance plan

105

Supplemental

 

Software assurance plan

106

Supplemental

 

Center software training plan

107

Not Related

 

Center software engineering improvement

108

Not Related

 

Software requirements specification

109

Supplemental

 

Software data dictionary

110

Not Related to M&S in Scope

 

Software design description

111

Supplemental

 

Interface design description

112

Not Related to M&S in Scope

 

Software change request/ problem report

113

Supplemental

 

Software test procedures

114

Supplemental

 

Software users manual

115

Supplemental

 

Software version description

116

Supplemental

 

Software metrics report

117

Supplemental

 

Software test report

118

Supplemental

 

Software inspection/ peer review/ inspections

119

Supplemental

Tailoring of Requirements

Submit generic waiver request

120

Supplemental

 

Document approved alternate requirements

121

Supplemental

Designation of Engineering Technical Authority

Center level Engineering Technical Authority approval

122

Not Related

Compliance

Direction for Technical Authority

124

Not Related

 

Compliance matrix

125

Supplemental

 

Considerations for waivers

126

Not Related

 

Review of "P(Center)"

127

Not Related

Compliance

Compliance records

128

Not Related

 

Check compliance

129

Not Related

Software Life Cycle Planning

Software safety plan

130

Supplemental

 

IV&V Plan

131

Supplemental

 

Classification assessment

132

Not Related

 

Software safety determination

133

Supplemental

 

Safety-critical software requirements

134

Supplemental

Software Implementation

Static analysis

135

Supplemental

 

Validation of software development tools

136

Supplemental

Software Peer Reviews/ Inspections

Peer Review/ Inspections of Software plans

137

Supplemental

Software Documentation Requirements

Software safety plan contents

138

Supplemental

Compliance

"Shall: statements in this NPR

139

Supplemental

 

"P (Center)"

140

Supplemental

4. Rationale for STD-7009

The NASA Standard for Models and Simulations (NASA-STD-7009) 272 had its genesis in the Space Shuttle Columbia Accident Investigation (2003).  Generally, its purpose is to improve the "development, documentation, and operation of models and simulations" (Diaz Report) 144 and "include a standard method to assess the credibility of the models and simulations" (Office of the Chief Engineer (OCE) Memo 376) .  After an approximately three-year development period, the NASA Standard for Models and Simulations, NASA-STD-7009 was approved by NASA's Engineering Review Board on July 11, 2008 for voluntary use.

NASA-STD-7009  holds a unique place in the world of modeling and simulation in that it is, by direction, generally applicable to all types of models and simulations (M&S) and in all phases of development, though it is primarily focused on the results of an M&S-based analysis.  All standards and recommended practices for M&S to date have either been focused on a single type of M&S (e.g., structures, fluids, electrical controls, etc.) or a particular phase of M&S development (e.g., verification, validation, etc.).  NASA management is confronted with numerous types of analyses that may be involved in making critical decisions. Depending on the situation at hand, a common framework for understanding the results and assessing the credibility of that analysis may seem intuitive.  However, this is complicated by the vast differences in engineering systems, and, thus, the adoption of a standard like this has been slow.

After formal approval in July 2008, the NASA-STD-7009  was largely left to the individual program, project, or M&S practitioner to adopt as they wished.  While already existing programs and projects were not required to adopt it, new programs and projects were to adopt it, depending on their needs, desires, and criticality of the M&S-based analysis at hand.

5. Guidance for NASA-STD-7009

Guidance for use and application of NASA-STD-7009 272 can be found in the NASA-STD-7009 Guidebook located at the following link: https://standards.nasa.gov.  This is a comprehensive instruction set on the use and application of NASA-STD-7009 as it relates to Verification and Validation of Models and Simulations.  Pay particular attention to the use and application of the Credibility Assessment Scale (CAS) 414.

6. Resources

6.1 Tools

Tools relative to this Topic may be found in the table below. You may wish to reference the Tools Table in this handbook for an evolving list of these and other tools in use at NASA. Note that this table should not be considered all-inclusive, nor is it an endorsement of any particular tool. Check with your Center to see what tools are available to facilitate compliance with this requirement.

No tools have been currently identified for this Topic. If you wish to suggest a tool, please leave a comment below.

7. Lessons Learned

The requirements for a NASA Standard have matured from the Columbia Accident Investigation Board (CAIB) Report.  The CAIB Report found problems pertaining to "ineffective and inconsistent application of M&S tools, along with cases of misuse."  It called on NASA to "develop, validate, and maintain physics-based computer models to evaluate Thermal Protection System damage from debris impacts. These tools should provide realistic and timely estimates of any impact damage from possible debris from any source that may ultimately impact the Orbiter." NASA was to establish impact damage thresholds that trigger responsive corrective action, such as on-orbit inspection and repair, when indicated.

Lessons Learned and their applicability to the need to perform verification and validation are well documented in the above identified resources.  These should be reviewed and retained by any program or project utilizing Modeling and Simulation products throughout the Software development life cycle.

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

Performance Decrease due to Propulsion Thruster Plume Impingement on the Voyager Spacecraft, Lesson Number: 0377:

"A 21% shortfall in Voyager's velocity change was suspected to be due to exhaust plume impingement. Due to the complexity of spacecraft/thruster configurations, additional care must be taken in the development and utilization of spacecraft and plume models. Analysis should be conducted on early and final designs." 582


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