Qualification of onboard software for cryogenic stages

The software which resides in onboard computers of ISRO’s satellite launch vehicles is mission critical. Onboard software needs to perform its functional requirements under various operational conditions that may be encountered during the operation of a launch vehicle. Any error in such software may lead to catastrophic failures, which is not acceptable in a mission critical application like launch vehicle onboard software. Of the various launch vehicle onboard software elements, control software for cryogenic stages is the most complex due to stringent timing requirements and hardware interface requirements. A software is developed in adherence to process laid down in ISRO software process document.

As part of qualifying the software for cryogenic stages, the software is subjected to meticulous and a series of well-defined quality assurance (QA) and independent verification and validation (IV&V) processes. The typical IV&V activities span through the entire life cycle commencing from requirements, design, implementation and testing and includes requirements and design review, static analysis, code inspection, software tests and closed-loop simulations.

In addition to the IV&V activities, Quality Audits are carried out to ensure end-to-end traceability of requirements and compliance to established development processes and review recommendations. This paper examines the QA & IV&V techniques followed for qualification of onboard software for cryogenic stages, highlighting typical observations and improvements done thereafter.