The GAFE Simulator is a time domain simulator, which supports the approach of FDIR design and validation as described in the GAFE Methodology. It provides the following main features:

• Fits outcome of Structural Analysis in form of functional behaviour and terminology
• Fully data-driven configuration, including
  • FDIR, OPS, System, AOCS Algorithms configuration
  • Equipment instantiation (number of units and their individual parametrisation)
• Provides libraries for
  • AOCS Algorithmic Components
  • Equipment (Actuators, Sensors, Non-AOCS devices)
• Programmers interface for new AOCS Algorithmic Components and new Equipment
• Full observability and logging of all relevant information
• Logging data preconditioning and visualisation
• Monte-Carlo capability

The breakdown into Modules and their main tasks in the frame of FDIR gives a good overview about the included functionality:

• System
  • System Configuration Manager
    • manages current system configuration (system state, processor module, avionic chain) from a list of possible (user defined) system configurations
    • distribution to Equipment Manager, AOCS Mode Manager, AOCS Algorithms, FDIR/OPS
    • models reboot delay of the on-board computer
    • defines AOCS mode and Equipment power cycle at wake-up
    • defines source and usage of context information
    • enables/disables FDIR
  • Equipment Manager
    • selection and activation/deactivation of AOCS units currently required
    • keeps unit's health status
    • informs about overall status of equipment required for current and desired AOCS mode
  • AOCS Mode Manager
    • manages AOCS main modes and submodes
    • gets inputs from OPS PUS Services (monitoring positive AOCS Algorithms flags) and from ground (TCs)
    • distributes to Equipment Manager, FDIR/OPS and AOCS Algorithms
• FDIR/OPS PUS Services
  • provides parameter monitoring and functional monitoring with the same parameterization and behaviour as PUS Services 12 and 142 (private)
  • applied for FDIR purposes
  • slightly enhanced to be also used for OPS (!) purposes (e.g. for switching AOCS modes)
• AOCS Algorithms
  • gets HK inputs from Equipment
  • is subdivided into AOCS Algorithmic Components which defines modularity
  • follows standardized interface and design rules for Components
    • provides standard validity flags from one Component to the next to allow clear functional chains and blocks propagation of “problems”
    • each Component delivers its specific status information about invalidities, checks and positive events (used by FDIR/OPS)
    • clean and simple way to declare and set states
  • generates overall AOCS Algorithms automatically based on user parametric configuration of Components handling
    • Components activation/deactivation for specified modes
    • Components handling of sample rates and offset, outputs and states hold and reset
    • Overall states handling to allow context information usage driven by System
  • provides this preset of AOCS Algorithmic Components
    • Measurement processing for: Magnetometer, Earth Sensor, Sun Sensor, Startracker, GNSR, Lidar, Camera, Clock, Reaction Wheels
    • Determination functions for: Satellite attitude and rate, Earth direction, Sun direction, Magnetic field and rate, Orbit (OOP), Earth ephemeris, Relative position and orbital elements (to target), Reaction Wheel friction estimation, etc.
    • Controller for: Rate Damping, Attitude Acquisition and Safe Mode, Nominal Mode, ...
    • Actuator Commanding for: Magnetorquers, Reaction Wheels, Reaction Control Systems (Thrusters)
• Equipment Models subdivided into
  • Generic model part common to all equipment
    • Mini-State-Machine (on, off, full performance, degraded performance)
    • Error injection (Stale data, drift, noise increase, bias)
  • Specific part, belonging to this type of Equipment:
    • with the specific algorithm for the main functionality of this equipment
    • Sensors available: Magnetometer, Earth Sensor, Sun Sensor, Startracker, GNSR, Lidar, Camera, Accelerometer, Clock
    • Actuators available: Magnetorquer, Reaction Wheels, Reaction Control System (Thrusters)
    • Additional: Solar Array Drive Mechanism (SADM), Antenna Pointing Mechanism
• Classical Environment simulation with
  • Position and Attitude Integrators
  • Earth rotation, Equation of equinoxes and time, Nutation, Precession
  • Gravity and Magnetic field model of higher order
  • Different atmospheric models, Solar pressure, Gravity disturbance of Sun and Moon, Gravity gradient, Residual magnetic moment
  • Satellite modelling as point or as sphere or with faces
  • Using Terrestrial time (TT) and UTC

See below the top-level architecture in which the Modules described above are implemented

After running simulations whether single or in batch, the logging data is available for the user either for further post-processing or for simple data visualization and inspection.

The picture below visualizes a typical session for visualization and inspection: