Short description: Suite of satellite simulators
Satellite simulators at ESOC are built on top of the SIMULUS infrastructure, composed of a run-time framework (SIMSAT), software emulators, a set of reusable generic models and a set of ground station equipment models.
Recent simulator developments are also based on a Reference Architecture (REFA), which has been introduced in order to identify, define, develop and integrate a reference operational spacecraft simulator architecture.
REFA allows achieving shorter and more cost-efficient simulator development cycles by means of heavy reuse while producing higher quality results. All simulators based on REFA are compliant with the Simulation Model Portability version 2 (SMP2) standard that provides standardized interfaces between the simulation models and the simulation runtime environment for common simulation services, as well as a number of mechanisms to support intermodal communication.
A key element inside an operational simulator is the On-Board Software (OBSW) emulation. The concept is to utilize the real mission’s OBSW in the core simulation while other parts of the spacecraft are being modelled in a functional manner. This enhances the overall realism of the simulation, and moreover enables further verification and validation of the OBSW. The execution of the actual mission’s OBSW is supported by a microprocessor software emulator; the emulation mechanism is the most computational and intensive one within the simulation environment.
SIMULUS provides a suite of pure software instruction level emulators (EMU) for space qualified 32-bit SPARC V7/ V8 RISC on-board microprocessors: the ERC32 (including TSC695F, TSC695FL and TSC691E); the LEON 2 (including AT697E and AT697F) and the LEON 3 (including UT699, with optional extra cores to provide functionality required for system-on-chip). While provided within SIMULUS, the emulator suite can be dealt with independently as it is completely decoupled from the other infrastructure components.
All simulation models, including the emulator, are executed by the SIMSAT simulation environment.
SIMSAT is composed of several modules providing all kernel functionalities required to support runtime simulation. The kernel includes a scheduling and execution engine that is based on a typical discrete event simulation concept. Events are generated inside the execution of simulation models and are stamped with specific simulation times.
Events are linked with function call-backs that correspond to simulation models’ functionalities. In turn, these may schedule new events, and so on. The simulation’s kernel scheduler serializes all event execution and records the timing of the overall execution using a global clock mechanism.
SIMULUS contains aligned and compatible versions of SIMSAT, GNDM, GENM, REFA, EMU, UMF, SLE API and EUD. It is available on GNU/Linux and validated on SUSE Linux Enterprise Server (SLES).