Assurance and Recertification of Safety Critical Software In Legacy Systems

1. Assurance and Recertification of Safety Critical Software In Legacy Systems Janie Hill NASA Kennedy Space Center, Florida Janice.L.Hill@nasa.gov SAS_08_Legacy_Safety_Hill

2. Agenda • Introduction • Relevance to NASA • Accomplishments • Legacy Systems Risk Database (LSRD) • Technology Readiness of the Work • Availability of Data and Case Studies • Barriers to Research • Near Term Work SAS_08_Legacy_Safety_Hill

3. Introduction • The assurance of legacy systems from a safety perspective is of particular importance when reuse of the system is considered. • A problem arises when attempting to carry out the requirements of a software safety standard on real time legacy systems with safety-critical software. • We would like to be able to “recertify” these systems for use in other programs, such as Constellation. • To do this, we propose to make a “safety case” for these legacy systems. SAS_08_Legacy_Safety_Hill

4. Introduction • This proposed research is unique because it is designed to address the reverse engineering of the process and the risk of non-performance of safety requirements, for reuse and recertification of legacy software. • The NASA Safety Standard has a specific requirement to address the safety of legacy systems with safety-critical software, however no common methodology has been found to accomplish this requirement. SAS_08_Legacy_Safety_Hill

5. Introduction • In performing the research we will apply a new methodology to multiple projects at KSC in order to retrospectively make a ‘safety case’ for real time legacy systems with safety-critical software. • The objective of this research is to test the methodology on multiple legacy systems with safety-critical software, using the NASA Software Safety standard and a component of software risk, to ‘recertify’ the software for safe reuse in a different application. • The proposed end result of the research is a tool that can be used by government and industry to apply safety standards in general to recertify with confidence the use of legacy systems with safety-critical software. SAS_08_Legacy_Safety_Hill

6. Relevance to NASA • Legacy systems with safety-critical software are abundant throughout NASA and especially prevalent at KSC. • System Assurance Analyses (SAA) of the ground systems at KSC were performed many years ago. Some, if not all, of these analyses were performed without fully analyzing the software in the context of the system. • At the time the SAA’s were performed, the NASA Software Safety Standard was either not in existence, or was not required by the contract that produced the system. • Additionally, Safety Cases were not prepared for these ground systems. • Now, some of these systems may be candidate for reuse in the Constellation Program. We need to be able to “recertify” these systems as safe, including the software, per our NASA Safety requirements. SAS_08_Legacy_Safety_Hill

7. Accomplishments January 2008 – September 2008 • Co-Authored and presented one paper on parts of the proposed methodology at the ASWEC 2008 in March 2008. • Completed the element and attribute definitions in the Software Safety Risk Taxonomy to complete the taxonomy. • Completed the questions for the Software Safety Taxonomy Based Questionnaire. • Interviewed the KCCS project manager using the TBQ • Developed risk statements based on the answers to the questions. • Analyzed the risks and bucketed the risks into risk areas. SAS_08_Legacy_Safety_Hill

8. Accomplishments • Initial Risk Data entry GUI is complete. • This functionality now allows risks to be created and input into the database during the interviews with the projects. • Traceability to the Taxonomy can now be created for each risk. • Initial Safety Requirements GUI is complete. • Safety requirements can be input into the database. • Traceability to the Safety Taxonomy can now be created for each Safety Requirement. SAS_08_Legacy_Safety_Hill

9. Risk to Taxonomy Traceability. Multiple Attributes can be selected Total number of risks, by Project. Clicking an individual row brings the “details” of the risk above LSRD – Risk Data Entry SAS_08_Legacy_Safety_Hill

10. Concept: Multiple Safety Standards will be allowed to be entered into the tool Record navigator: Move First, Next, Previous, Move Last, Add, Save, Delete functions LSRD - Safety Requirements Concept: Field locks will be used to prevent repetitive typing. Requirement rationale for each safety requirement can be captured SAS_08_Legacy_Safety_Hill

11. Parent Requirement. Child requirements are displayed and managed in the grid below Requirement to Taxonomy Traceability. Multiple Attributes can be selected LSRD – Safety Requirements SAS_08_Legacy_Safety_Hill

12. Technology Readiness of the Work Technology concept and/or application formulated Invention begins. Once basic principles are observed, practical applications can be invented. The application is speculative and there is no proof or detailed analysis to support the assumption. Examples are still limited to paper studies. • The estimate of the current TRL of this research results: Between 2 and 3. Analytical and experimental critical function and/or characteristic proof of concept. Active research and development is initiated. This includes analytical studies and laboratory studies to physically validate analytical predictions of separate elements of the technology. Examples include components that are not yet integrated or representative. SAS_08_Legacy_Safety_Hill

13. Availability of Data and Case Studies • Pilot project data collection was successful because project personnel were willing to participate and had management concurrence. • Case studies are not applicable at this point, because the methodology will create the data that is needed to study. SAS_08_Legacy_Safety_Hill

14. Near Term Work • Continue with implementation of the Legacy Systems Risk Database. • Finish the Software Safety TBQ Graphical User Interface. • Finish the Software Requirements Specification for the LSRD. • Update the design documentation for the LSRD. • Work with Donna Smith at Wallops on their projects (October) and Chuck Niles at Langley. • Work with other projects at KSC (FY 09) SAS_08_Legacy_Safety_Hill

15. Questions? SAS_08_Legacy_Safety_Hill