ESA GNC Conference Papers Repository

CGS S.p.A. has developed its AOCS verification and test cycle currently in use through different programs, including the MITA (launched in 2000) and AGILE (2007) satellites, two Italian Space Agency missions. The cycle of work adopts models and simulators at different levels and it is based on four main steps. The first step consists in the setting of the AOCS Simulator of the plant, which is the satellite with its dynamics, equipments and environment. Then, after the design and the development of the AOCS algorithms, according to a Model- Based Design (MBD) method, the AOCS Simulator is used to simulate the behaviour and interaction of all the elements of the control loop, in order to send the Input Data to the AOCS algorithms implementing the GNC functions. Thank to this Rapid Prototyping approach it is possible to perform lots of simulations at an early stage of the project to support and verify the design. For the second step the AOCS algorithms models are isolated and the code is automatically generated by an automatic code generator, that transforms the models to an ANSI C code optimized for speed, memory usage, and simplicity, with great save of times and a lower possibility of error with respect to an human coding. The code is compiled to run on the On Board Data Handling (OBDH) emulator. During this step, before the availability of the real OBDH, it is checked that the ANSI C code represents faithfully the AOCS algorithms, through providing the same Input Data to both OBDH emulator and the AOCS Simulator. Then there is the comparison between the Output Data obtained that must be the same if the ANSI C code is generated correctly. The third step is the AOCS EGSE, where the sensors and actuators, the AOCS algorithms running on the OBDH EM/FM and the software simulation of any other AOCS equipment, the dynamics and the space environment are combined together (Hardware In the Loop verification method). At this level real time runs are performed and the Output Data stored through the I/O Data Recorder. Then all the Output Data are compared together with the ones of the previous steps in order to check the congruency of the results. At this level it is verified the correct execution of the AOCS algorithms once implemented on a representative hardware. The last step is the in orbit validation of the results; during the commissioning phase, the House Keeping are analyzed in order to verify the design and the performance of the AOCS and to detect possible anomalies, that can be corrected with a SW update.