The Example Aeolus

The Horizon Simulation Framework was created alongside with it’s test case—Aeolus. While the built in subsystem models and accompanying targets are specific to Aelous, small modifications can be made to model similar missions, and with an understanding of HSF, any model and mission can be synthesized and simulated. The Aeolus mission is a simple one: image as many targets as possible and downlink the data when needed in one orbit of 6307 seconds. Aeolus is a two satellite constellation with both satellites starting on opposite ends of the globe from each other and with opposite velocity vectors. The subsystems that make up each satellite includes the Attitude, Determination and Control (ADCS), Communication (COMM), Earth Observing Sensor (EO Sensor), Solid State Data Recorder (SSDR) and Power. These subsystems were modeled as described in Chapter 3. In order to create a system from subsystems, HSF provides the basic infrastructure to define constraints on the performance of the system and inter-dependencies between subsystem, as well as maintain state data. A constraint is a limitation placed on a subsystem that dictates the functional bounds of the model. For example, the power subsystem may have a constraint that the battery depth of discharge is not allowed to surpass 70%. A dependency is an interface used to communicate data between subsystems, so that a subsystem with a dependency may calculate its state from its dependent subsystem. An example of this is that the power subsystem must know how much power the ADCS required to complete the current task. Lastly, the state is maintained at a system level with each subsystem propagating its own state. The details of these fundamental elements will be discussed in the chapters that follow.