Hardware-in-the-Loop (HWIL) Simulation

Hardware-in-the-Loop (HWIL) simulation is a verification and validation technique where physical navigation hardware (processors, sensors, actuators) is tested against real-time simulated environments that replicate orbital dynamics, signal propagation, and sensor physics with high fidelity.

In traditional software-only simulation, navigation algorithms run on desktop computers against idealized mathematical models. HWIL closes the gap between simulation and reality by running the actual flight hardware - including the navigation processor, RF front-end, optical sensor interfaces, and power management - while injecting simulated sensor data that mimics the exact conditions the hardware will encounter in orbit.

Kepler Nav's HWIL facility generates three categories of stimuli:

RF Signal Simulation: Synthetic Starlink, OneWeb, and Iridium downlink signals with realistic power levels, Doppler profiles, multipath characteristics, and atmospheric effects. The simulator can inject controlled jamming and spoofing scenarios for EW immunity testing.

Optical Star Field Simulation: Calibrated point-light sources arranged to replicate stellar fields as seen from specific orbital positions, used to validate the star tracker's attitude determination accuracy.

X-Ray Pulsar Simulation: Timing pattern generators that replicate the periodic X-ray flux profiles of navigation-grade millisecond pulsars (PSR B1937+21, PSR J0437-4715).

The HWIL environment validates the complete navigation solution - from raw sensor measurements through the Lie Group manifold filter to final position/velocity/attitude output - under thousands of orbital scenarios including nominal operations, sensor failures, eclipse transitions, and electronic warfare attacks. This comprehensive testing is required for space mission qualification (NASA TRL-6 and above).