Streamlining the testing for the PLATO Instrument Control Unit startup of the Application Software post-boot execution

PLAnetary Transits and Oscillations of Stars (PLATO), the third medium-class mission of the European Space Agency’s (ESA) Cosmic Vision program, is foreseen for launch in 2026 and stands out with its distinctive approach to exoplanet exploration [1]. The core of PLATO’s On-Board Data Processing System (DPS) is a crafted architecture that encompasses various components, including an Instrument Control Unit (ICU) and 12+2 Digital Processing Units (DPUs). These elements are interconnected through a SpaceWire network, which includes 6 routers. This network serves as a backbone for seamless communication among the different components of the Payload. The Application Software (ASW) of the Instrument Control Unit (ICU) plays a crucial role in the PLATO system’s operations. It takes over once the system has booted, the ASW is integral to overseeing critical functions essential for mission success. Its primary responsibilities encompass executing the day-to-day operations of the satellite. This includes managing data transmission, which involves both the collection and processing of data. The software adeptly handles ongoing tasks, adapts to different modes, and facilitates communication with ground control stations. Additionally, the ASW is responsible for configuring parameters for the Data Processing Unit (DPU), monitoring the Failure Detection, Isolation, and Recovery (FDIR) process and SW, conducting image stacking, and efficiently managing hardware compression. Remarkably, the ASW demonstrates its effectiveness by efficiently managing a daily data volume of 435 Gb on ground. On the other hand, the PLATO Boot Software (BSW) holds paramount importance in the mission, distinguished by its low complexity. The BSW ensures the integrity of the system startup process. It plays a fundamental role in the startup and maintenance operations of the ICU, engaging in essential tasks like board diagnostics and the initiation of the ASW. Its significance extends to crucial responsibilities such as systems and hardware initialization, including SpW communication, ensuring SDRAM integrity through systematic checks, generating comprehensive boot reports, maintaining a consistent heartbeat, managing housekeeping duties, and facilitating event generation. Its responsibilities also extend to overseeing the nominal boot sequence and executing telecommands. Together, the PLATO’s ICU BSW and ASW contribute to the satellite’s overall functionality. While the BSW focuses on the startup and initialization phase, the ASW oversees the continuous, mission-specific operations throughout the satellite’s time in space. The seamless transition from BSW phase to ASW phase is vital for the successful initialization and configuration of PLATO payload, enabling the satellite to fulfill its designated functions. This comprehensive transition phase ensures that the satellite will operate reliably and efficiently in its operational environment. Prior to initiating the ASW application, the BSW conducts a verification process to ensure that the ASW does not load into the section of SDRAM already utilized by the BSW. This process includes integrity checks where the BSW verifies the integrity of the compressed ASW image stored in NVM (Non-Volatile Memory) before decompressing it into SDRAM. Additionally, integrity checks are conducted on the ASW after it has been decompressed in SDRAM. Of particular significance is the TCL test verification and validation process, essential for ensuring the accuracy and reliability of the PLATO ASW startup post-boot. Rigorous testing and verification procedures, including software regression tests using a reprogrammed TCL script, are employed to validate PLATO ASW functionality. These tests, conducted on setup-configured images stored in MRAM memory, play a vital role in minimizing errors and ensuring PLATO mission success. This paper thoroughly explores the pivotal role played by the PLATO ICU BSW in the startup process. It emphasizes testing and verifying functionality to ensure the accurate startup of the ASW post-boot. The attainment of this goal involves launching setup-configured images stored in MRAM memory, executed through a reprogrammed TCL script designed for software regression tests. In conclusion, the seamless transition from BSW to ASW phase, supported by comprehensive TCL test verification and validation, is paramount for PLATO’s payload operational efficiency and success in fulfilling its scientific objectives.