ASTRA-HyRAX

ASTRA-HyRAX [Auburn University]

ASTRA-HyRAX (Auburn Satellite Testbed for Retrodirective Array – Hybrid Retrodirective Array in X-band) is a technology demonstration 3U CubeSat developed by Auburn University in the United States under the Auburn University Small Satellite Program (AUSSP). The mission is funded by the U.S. Army Space and Missile Defense Command (SMDC).

The mission is intended to demonstrate and characterize a hybrid retrodirective array (HRA) operating in X-band for determining the direction of arrival of radio-frequency signals from targets of opportunity. A secondary objective is to flight-test a custom-designed X-band radio developed in-house at Auburn, intended for reuse on future missions such as TRYAD. The satellite will conduct controlled experiments with known ground transmitters to validate system performance in orbit.

The spacecraft platform and structural bus are provided by EnduroSat. The primary payload, HyRAX, is a scalable hybrid retrodirective array based on phased-array technology and developed at Auburn. It determines signal direction by measuring phase differences across multiple antenna elements. The flight configuration consists of a compact 2×2 array to validate functionality and performance in the space environment. A larger ground-based HRA system will operate alongside Auburn’s RF tracking ground station to provide calibration data and additional experiment opportunities. The onboard X-band radio supports high-frequency downlink testing and serves as a prototype for future missions.

The payload receives RF signals, computes their direction vectors, and associates each measurement with precise GPS-derived position and timing data. The system can store this data or use it for retrodirective transmission back toward the signal source. During operations, the satellite slews to align the array toward expected targets, activates the payload during passes, records signal vectors, and downlinks telemetry via the X-band radio during ground station passes. The experiment cycle includes target acquisition, signal processing, data tagging, and post-pass data transmission.