2. Rationale

The crew and ground control will likely have access to more data than an automated abort system. Therefore, both the crew and ground control have the capability to initiate the abort when necessary for crew survival.

3. Guidance

The crew and ground control will likely have access to more data than an automated abort system. Therefore, both the crew and ground control can initiate the abort when necessary for crew survival.

See Topic 7.24 - Human Rated Software Requirements for other Software Requirements related to Human Rated Software, specifically HR-715 - Interface With Range Safety Destruct System. 

3.1 Software Tasks for Ground Initiated Aborts

To ensure that the space system provides the capability for ground control to initiate the Earth ascent abort sequence, the following software tasks should be implemented:

1. Abort Sequence Control Systems: Develop and implement a robust control system that allows ground control to manually initiate the abort sequence. This system should be designed to function effectively and safely under all operational conditions.
2. Human-Machine Interface (HMI): Design and implement an intuitive and user-friendly HMI that enables ground control to easily and effectively initiate the abort sequence. The interface should provide clear indications and feedback to the operators regarding the status of the abort sequence. The HMI design should take into consideration the Display Standards in Appendix F of NASA Spaceflight Human-System Standard, Volume 2: Human Factors, Habitability, And Environmental Health (NASA-STD-3001, Vol 2, Rev D). ⁴⁹⁸ 
3. Safety Analysis for Abort Systems: Perform comprehensive safety analyses, including 8.07 - Software Fault Tree Analysis and 8.05 - Software Failure Modes and Effects Analysis, to identify and mitigate potential hazards associated with the manual initiation of the abort sequence. Ensure that the abort systems will not compromise safety during these operations.
4. Redundancy and Fault Tolerance: Design and implement abort initiation systems that have redundancy and fault tolerance to allow ground control to initiate an ascent abort even in the presence of faults or failures. This includes implementing backup controls and redundant computing systems.
5. Real-time Monitoring and Alerts: Design and implement real-time monitoring systems that provide ground control with up-to-date information on the spacecraft's status and performance. This includes alerts for any conditions that may require the initiation of the abort sequence.
6. Independent Verification and Validation (IV&V): Conduct independent verification and validation to ensure that the abort initiation systems meet specified requirements and function correctly under all operational scenarios. IV&V activities should include rigorous testing and analysis of these systems.
   1. IV&V Analysis Results: Assure that the capability for ground control to initiate an Earth ascent abort sequence has been implemented in the software and independently verified and validated to meet safety and mission requirements.
   2. IV&V Participation: Involve the IV&V provider in reviews, inspections, and technical interchange meetings to provide real-time feedback and ensure thorough assessment.
   3. IV&V Management and Technical Measurements: Track and evaluate the performance and results of IV&V activities to ensure continuous improvement and risk management.
7. Simulation and Testing: Perform extensive simulations and testing to verify that the abort initiation systems can handle all nominal and off-nominal scenarios without compromising safety. This includes testing for unexpected conditions, boundary conditions, and the full range of potential failure modes. The flight operations team should participate in these simulations to thoroughly test the various conditions and scenarios.
   1. Code Coverage with MC/DC Criterion: Develop, implement, and execute test cases for all identified safety-critical software components to ensure that there is 100% code test coverage. This includes normal operations, failure modes, fault detection, isolation, and recovery procedures. Use the Modified Condition/Decision Coverage (MC/DC) criterion.
8. Configuration Management: Maintain strict configuration management to ensure that the correct software versions and configurations are used. This reduces the risk of errors due to incorrect or inconsistent configurations that could affect abort initiation capabilities.
9. Error Handling and Recovery Mechanisms: Implement robust error handling and recovery mechanisms to address errors detected during the initiation of the abort sequence. Ensure that error handling is adequate and that the system can recover from errors without leading to hazardous or catastrophic events.
10. Training and Documentation: Provide comprehensive training and documentation for the ground control team on how to use the abort initiation systems. This includes detailed procedures, troubleshooting guides, and emergency protocols to ensure the team is well-prepared to handle any situation. This is best done by providing a User Manual with instructions and applicable information about each error/fault and how to initiate aborts.
    
    

By implementing these tasks, the space system can be designed to effectively provide the capability for ground control to initiate the Earth ascent abort sequence, ensuring mission success and safety.

3.2 Additional Guidance

Additional guidance related to this requirement may be found in the following materials in this Handbook:

3.3 Center Process Asset Libraries

See the following link(s) in SPAN for process assets from contributing Centers (NASA Only). 

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

5.1 References

5.2 Tools

6. Lessons Learned

6.1 NASA Lessons Learned

No Lessons Learned have currently been identified for this requirement.

6.2 Other Lessons Learned

No other Lessons Learned have currently been identified for this requirement.

7. Software Assurance

7.1 Tasking for Software Assurance

1. Ensure the development, implementation, and testing of robust control algorithms that are capable of ground control initiating the Earth ascent abort sequence. These algorithms must undergo thorough testing to guarantee their reliability and safety in all operational scenarios.
2. Ensure redundancy and fault tolerance are included in the design to ensure that critical functions can continue to operate autonomously when ground control initiates an ascent abort, even in the presence of faults or failures. This includes implementing backup systems and failover mechanisms.
3. Ensure that Integrated real-time monitoring and diagnostic tools are used to continuously assess the health and status of critical systems and subsystems. These tools should detect anomalies and trigger autonomous responses to mitigate potential catastrophic events and alert ground control of the potential need for intervention.
4. Employ safety analysis techniques such as 8.07 - Software Fault Tree Analysis and 8.05 - Software Failure Modes and Effects Analysis to identify potential hazards and failure modes. This helps in designing controls and mitigations for the autonomous operation of critical functions.
5. Ensure extensive simulations and testing are conducted to verify that ground control can initiate the Earth ascent abort sequence and that the control systems can handle all nominal and off-nominal scenarios. This includes testing for unexpected situations and boundary conditions.
6. Ensure strict configuration management to ensure that the correct software versions and configurations are used. This reduces the risk of errors due to incorrect or inconsistent configurations that could impact ascent abort operations.
7. Ensure robust error handling and recovery mechanisms are implemented to address errors stemming from detected faults. This ensures that error handling is adequate and that the system can autonomously recover from errors without leading to hazardous or catastrophic events.
8. Perform safety reviews on all software changes and software defects.
9. Confirm that 100% code test coverage is addressed for all identified safety-critical software components or that software developers provide a technically acceptable rationale or a risk assessment explaining why the test coverage is not possible or why the risk does not justify the cost of increasing coverage for the safety-critical code component.
10. Analyze that the software test plans and software test procedures cover the software requirements and provide adequate verification of hazard controls, specifically that ground control can initiate the Earth ascent abort sequence under various conditions, including nominal and off-nominal scenarios. (See SWE-071 - Update Test Plans and Procedures tasks). Ensure that the project has developed and executed test cases to test the software system’s recovery from faults during abort operations.
11. Analyze the software test procedures for the following:
    1. Coverage of the software requirements.
    2. Acceptance or pass/fail criteria,
    3. The inclusion of operational and off-nominal conditions, including boundary conditions,
    4. Requirements coverage and hazards per SWE-066 - Perform Testing and SWE-192 - Software Hazardous Requirements, respectively.
12. Perform test witnessing for safety-critical software to ensure that ground control can initiate the Earth ascent abort sequence under various conditions, including nominal and off-nominal scenarios.
13. Confirm that test results are sufficient verification artifacts for the hazard reports.
14. Ensure comprehensive training and documentation for operators is available.

7.2 Software Assurance Products

1. 8.52 - Software Assurance Status Reports
2. 8.54 - Software Requirements Analysis
3. 8.55 - Software Design Analysis
4. 8.56 - Source Code Quality Analysis
5. 8.57 - Testing Analysis 
6. 8.58 - Software Safety and Hazard Analysis 
7. 8.59 - Audit Reports
8. Test Witnessing Signatures (See SWE-066 - Perform Testing)

7.3 Metrics

The list does not specifically list software assurance metrics tailored for the requirement that the space system shall provide the capability for the ground control to initiate the Earth ascent abort sequence. However, general software assurance and safety metrics from NASA standards can be applied to ensure that this requirement is met effectively and safely. These metrics include:

1. Verification and Validation Metrics:
   • Test Coverage: Ensuring that all scenarios, including the initiation of the Earth ascent abort sequence by ground control, are covered by tests.
   • Defect Density: Tracking the number of defects found during testing per thousand lines of code to ensure software reliability.
   • Requirements Traceability: Ensuring that each requirement, including the abort sequence initiation, is traced to its implementation and corresponding test cases.
2. Safety Metrics:
   • Hazard Analysis: Identifying and evaluating potential hazards related to the ground-initiated abort sequence, and ensuring adequate mitigation strategies are in place.
   • Safety-critical Requirements Compliance: Verifying that all safety-critical requirements are followed and adequately tested to prevent any failure during the abort sequence initiation.
3. Quality Metrics:
   • Code Quality: Metrics such as cyclomatic complexity and static analysis results to ensure that the code is maintainable and less prone to errors.
   • Code Churn: Measuring changes in the codebase to monitor stability and identify areas of frequent modification that may need more rigorous testing.
4. Performance Metrics:
   • Response Time: Measuring the time taken for the system to initiate the abort sequence after receiving the command from ground control to ensure timely execution.
   • System Uptime: Ensuring that the system is available and operational when needed, especially during critical mission phases.
5. Configuration Management Metrics:
   • Version Control: Ensuring proper version control for all software components involved in the abort sequence to track changes and maintain consistency.
   • Change Requests: Monitoring the number of change requests and their impact on the system's reliability and safety.
6. Training Metrics:
   • Personnel Training Completion: Ensuring that all personnel involved in the development, testing, and operation of the abort sequence capability have completed the necessary training.
7. Independent Verification and Validation (IV&V) Metrics
   • IV&V Analysis Results: Provide assurance that the capability for ground control to initiate the Earth ascent abort sequence has been independently verified and validated to meet safety and mission requirements.
   • IV&V Participation: Involving the IV&V provider in reviews, inspections, and technical interchange meetings to provide real-time feedback and ensure thorough assessment.
   • IV&V Management and Technical Measurements: Tracking and evaluating the performance and results of IV&V activities to ensure continuous improvement and risk management.

Examples of potential SA metrics are: 

• # of potential hazards that could lead to catastrophic events  
• # of Non-Conformances identified during each testing phase (Open, Closed, Severity)  
• Code coverage data: % of code that has been executed during testing  
• % of traceability completed for all hazards to software requirements and test procedures  
• # of hazards with completed test procedures/cases vs. total # of hazards over time  
• # of Non-Conformances identified while confirming hazard controls are verified through test plans/procedures/cases  
• # of Hazards containing software that has been tested vs. total # of Hazards containing software  
• # of safety-related Non-Conformances  
• # of Safety Critical tests executed vs. # of Safety Critical tests witnessed by SA  
• Software code/test coverage percentages for all identified safety-critical components (e.g., # of paths tested vs. total # of possible paths)   
• # of safety-critical requirement verifications vs. total # of safety-critical requirement verifications completed  
• Test coverage data for all identified safety-critical software components  
• # of Software Requirements that do not trace to a parent requirement  
• % of traceability completed in each area: System Level requirements to Software requirements; Software Requirements to Design; Design to Code; Software Requirements to Test Procedures
• % of traceability completed for all hazards to software requirements and test procedures
• Defect trends for trace quality (# of circular traces, orphans, widows, etc.)
• #  of Configuration Management Audits conducted by the project – Planned vs. Actual

These metrics ensure that the software supporting ground control’s capabilities to initiate the Earth ascent abort sequence is reliable, safe, and meets the specified requirements. For detailed guidance, referring to the Software Assurance and Software Safety Standard (NASA-STD-8739.8) and the NASA Procedural Requirements (NPR 7150.2) would provide a comprehensive framework.

See also Topic 8.18 - SA Suggested Metrics

7.4 Guidance

To ensure ground control can initiate the Earth ascent abort sequence, the following software assurance and safety tasks should be implemented:

1. Abort Sequence Control Systems: Ensure a reliable control system for ground control to manually initiate the abort sequence safely is developed and implemented.
2. Human-Machine Interface (HMI): Ensure a user-friendly HMI that allows ground control to quickly and effectively initiate the abort sequence with clear status feedback is designed and implemented. The HMI design should take into consideration the Display Standards in Appendix F of NASA Spaceflight Human-System Standard, Volume 2: Human Factors, Habitability, And Environmental Health (NASA-STD-3001, Vol 2, Rev D). ⁴⁹⁸ 
3. Software Safety and Hazard Analysis: Develop and maintain a Software Safety Analysis throughout the software development life cycle. Assess that the Hazard Analyses (including hazard reports) identify the software components associated with the system hazards per the criteria defined in NASA-STD- 8739.8, Appendix A. (See SWE-205 - Determination of Safety-Critical Software tasks.) Perform these on all new requirements, requirement changes, and software defects to determine their impact on the software system's reliability and safety. Confirm that all safety-critical requirements related to ground control initiating the Earth ascent abort sequence have been implemented and adequately tested to prevent catastrophic events during mission-critical operations. It may be necessary to discuss these findings during the Safety Review so the reviewers can weigh the impact of implementing the changes. (See Topic 8.58 – Software Safety and Hazard Analysis.)
   1. Hazard Analysis/Hazard Reports: Confirm that a comprehensive hazard analysis was conducted to identify potential hazards that could result from critical software behavior. This analysis should include evaluating existing and potential hazards and recommending mitigation strategies for identified hazards. The Hazard Reports should contain the results of the analyses and proposed mitigations (See Topic 5.24 - Hazard Report Minimum Content.)
   2. Software Safety Analysis: To develop this analysis, utilize safety analysis techniques, including 8.07 - Software Fault Tree Analysis and 8.05 - Software Failure Modes and Effects Analysis to identify and mitigate hazards in the abort process. When generating this SA product, see Topic 8.09 - Software Safety Analysis for additional guidance.
4. Redundancy and Fault Tolerance: Ensure abort initiation systems have redundancy and fault tolerance to maintain functionality during faults or failures.
5. Real-time Monitoring and Alerts: Ensure real-time monitoring systems to keep ground control informed of the spacecraft's status, with alerts for conditions requiring abort initiation, are designed and implemented.
6. Safety Reviews: Perform safety reviews on all software changes and defects to verify that ground control can initiate the Earth ascent abort sequence, under various conditions, including nominal and off-nominal scenarios, that could result in a catastrophic event. This ensures that each fault has a fault detection mechanism and the modifications do not introduce new vulnerabilities or increase the risk of failure due to the fault.
7. Peer Reviews: Participate in peer reviews on all software changes and software defects affecting safety-critical software and hazardous functionality to verify that ground control can initiate the Earth ascent abort sequence, under various conditions, including nominal and off-nominal scenarios. (See SWE-134 - Safety-Critical Software Design Requirements tasks.) 
   1. Change Requests: Monitor the number of software change requests and software defects and their impact on the system's reliability and safety. Increases in the number of changes may be indicative of requirements issues or code quality issues resulting in potential schedule slips. (See SWE-053 - Manage Requirements Changes, SWE-080 - Track and Evaluate Changes.) 
8. Test Witnessing: Perform test witnessing for safety-critical software to verify that ground control can initiate the Earth ascent abort sequence, under various conditions, including nominal and off-nominal scenarios. (See SWE-066 - Perform Testing.) This includes witnessing tests to:
   1. Confirm that ground control can initiate the Earth ascent abort sequence under various conditions without resulting in catastrophic consequences. This could include:
      1. Measuring the time taken for the system to detect and report faults to ground control so they can implement mitigation procedures in timely and accurate manner. A prolonged period could cause catastrophic consequences.
      2. Ensuring the system is available and operational when needed, especially during critical mission phases.
   2. Uncover unrecorded software defects and confirm they get documented and recorded.
   3. Confirm robust error handling and recovery mechanisms to address errors detected during the initiation of the abort sequence are implemented without compromising safety. This includes ensuring that error handling is adequate and that the system can recover from errors without leading to hazardous or catastrophic events
9. Simulation and Testing: Ensure extensive simulations and testing are performed to confirm the systems can handle both nominal and off-nominal scenarios without compromising safety.
10. Configuration Management: Ensure strict configuration management is maintained to ensure only the correct software versions and configurations are used. (See SWE-187 - Control of Software Items for more information.) This proactive measure will significantly reduce the risk of errors due to incorrect or inconsistent configurations that could compromise monitoring and control capabilities. This also includes performing the SWE-187 tasking.
    1. Assess that the software safety-critical items, including the hazard reports and safety analysis, are configuration-managed (See SWE-081 - Identify Software CM Items tasking.)
11. Code Coverage: Confirm that 100% code test coverage is addressed for all identified safety-critical software components or ensure that software developers provide a risk assessment explaining why the test coverage is impossible or why the risk does not justify the cost of increasing coverage for the safety-critical code component. This includes normal operations, failure modes, fault detection, isolation, and recovery procedures. (See SWE-189 - Code Coverage Measurements, SWE-219 - Code Coverage for Safety Critical Software.)
12. Training and Documentation: Ensure comprehensive training and documentation are available for the ground control team on using abort initiation systems, including procedures and emergency protocols.

By implementing these tasks, we will ensure that ground control can effectively initiate the Earth ascent abort sequence, maximizing mission safety and success.

For additional information, also see HR-715 - Interface With Range Safety Destruct System.  

7.5 Additional Guidance

Additional guidance related to this requirement may be found in the following materials in this Handbook: