Figure 11. ESIM simulation applicat

Figure 11. ESIM simulation application layers.The Java Astrodynamics Library at APL (JALA) is built on top of the Orekit framework and is used to configure specific sensor-target scenarios. ESIM allows for the configuration of several different sensor types: optical, radar, and passive RF (in progress). For each sensor type, appropriate detection models (e.g., elevation masks, signal-to-noise ratio, sun/moon exclusions) are used to provide realism to synthetic measurement generation. Visualizations are accomplished via the custom Tactic Globe Visualizer (TGV); Fig. 12 shows an example scenario, from a space-based perspective, of two terrestrial sensors each tracking a specific target over time.ESIM follows a simplified closed-loop approach for simulation data flow (see Fig. 13). The basic ESIM construction contains three essential modules: ESIM Simulator, Tracker/Scheduler, and the Spacecraft Sensor. The ESIM Simulator is the main program that controls the execution of the configurable modules, such as the Tracker/Scheduler and the Spacecraft Sensor. This modular setup gives the user compartmentalized control over the processing thread composition and runtime flow, allowing them to test different combinations of various options in a single integrated environment.