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Specification
The ADAC subsystem states are defined based upon the computing, sensing and actuating hardware that is available. The Simulation shall model the following ADAC subsystem states:
- Quiescent - command processing, no sensor or actuator is available.
- Contingency - command processing, designated critical sensors, designated critical actuators.
- Control - command processing, full sensor complement, full actuator complement
The ADAC Sim shall extend the GMAT spacecraft model by modeling its moments of Inertia.
The ADAC Sim shall convert forces applied to the spacecraft to torques for use in Attitude Determination.
The ADAC Sim shall model attitude control thrusters.
The ADAC Sim shall model 3-Axis reaction wheel assemblies.
The ADAC Sim shall model magnetic torque rod assemblies.
The ADAC Sim shall model single-axis control moment gyros.
The ADAC Sim shall model 3-Axis accelerometer assemblies.
The ADAC Sim shall model 3-Axis gyroscope assemblies.
The ADAC Sim shall model fine and coarse sun sensors.
The ADAC Sim shall model Earth horizon sensors.
The ADAC Sim shall model star trackers.
The ADAC Sim shall model star cameras.
The ADAC Sim shall model magnetometers.
The ADAC Sim shall be created as one or more GMAT Resources using the GMAT "Create" resource command.
Simulated ADAC sensor and actuator hardware shall be created as one or more GMAT Resources using the GMAT "Create" command.
The ADAC Sim hardware models shall extend the spacecraft model by including its moments of inertia using the GMAT model language.
The ADAC Sim modes and states shall be controlled by the GMAT modeling language.
The simulation shall be available but otherwise quiescent until another mode command is executed.
The Simulation shall provide simulated commands to orient the vehicle model principal axis 90-degrees perpendicular to the sensed sun vector.
The Simulation shall provide simulated commands to rotate the vehicle model about its principal axis.
The Simulation shall model spin stabilization about the vehicle principal axis. Note that this mode may be used as a contingency state, or as part of post-launch separation with the intent that solar arrays are passively illuminated.
The Simulation shall command modeled ADAC subsystem hardware to null attitude errors derived from a commanded angle of pointing, or rotation rate.
The Simulation shall command modeled ADAC subsystem hardware to slew the spacecraft about any one axis bringing it to a commanded pointing attitude.
In order to perform an attitude hold, the Simulation shall transition between Momentum Bias and Zero Momentum modes.
The ADAC Sim shall accept Desired Attitude commands from the GMAT interface.
The ADAC Sim shall accept definition of the spacecraft moments of inertia from the GMAT interface.
The ADAC Sim shall provide the current kinematic (pointing) state to the GMAT interface on demand.
The ADAC Sim shall accept a force vector from the GMAT interface.
The ADAC Sim shall accept an epoch and ephemeris from the GMAT interface.