Abstract
While there is no rigorous framework to develop nanosatellites flight software, this manuscript aimed to explore and establish processes to design a reliable and reusable flight software architecture for cost-efficient student Cubesat missions such as Masat-1. Masat-1 is a 1Unit CubeSat, developed using a systems engineering approach, off-the-shelf components and open-source software tools. It was our aim to use it as a test-bed platform and as an initial reference for Cubesat flight software development in Morocco. The command and data handling system chosen for Masat-1 is a system-on-module-embedded computer running freeRTOS. A real-time operating system was used in order to simplify the real-time onboard management. To ensure software design reliability, modularity, reusability and extensibility, our solution follows a layered service oriented architectural pattern, and it is based on a finite state machine in the application layer to execute the mission functionalities in a deterministic manner. Moreover, a client-server model was elected to ensure the inter-process communication and resources access while using uniform APIs to enhance cross-platform data exchange. A hierarchical fault tolerance architecture was also implemented after a systematic assessment of the Masat-1 mission risks using reliability block diagrams (RBDs) and functional failure mode, effect and criticality analysis (FMECA).
Highlights
In order for a satellite to be operational, every system needs to operate correctly and in unison with the rest of the spacecraft main bus subsystems
It is worth mentioning that combinations of failures are not considered, and each single item failure is assumed to be the only failure in the system [5]; Step 3 Define the overall mission critical items list (CIL): an item is critical if its failure mode severity is classified as catastrophic, or if a failure mode criticality number (CN) is greater or equal to 6 in conformance with the criticality matrix (Table 3); Step 4 Define corrective/preventive solutions necessary to eliminate the failure or to mitigate/control the risk
The FMECA analysis enabled the identification of all potential failure modes, their potential causes and their impact on the system/mission
Summary
In order for a satellite to be operational, every system needs to operate correctly and in unison with the rest of the spacecraft main bus subsystems. Masat-1 is a 1Unit nanosatellite with the dimensions of 10 × 10 × 10 cm and a maximum weight of 1.33 kg It is a standardized format of nanosatellites known as Cubesats. This standard was established to expedite the aerospace mission design life cycle and decrease development costs while providing the same scientific capabilities as bigger aerospace programs. Since their creation in 1999, more than 400 nanosatellites have been launched by universities, industries and military. As it is illustrated, the Cubesat market is growing. Thereby, it is our intention to use the Masat-1 mission as an initiative to join the aerospace
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