Hydra® is a modular autonomous rendezvous and docking (AR&D) sensor system for use on orbit. It uses multiple
sensor heads that feed data to a single processing module, allowing the system to be configured according to mission
needs. The modularity also decreases the required amount of external real estate, since the processing electronics can be
internal to spacecraft. Advanced Optical Systems has built an initial Hydra® prototype that includes an Advanced Video
Guidance Sensor (AVGS) and ULTOR® sensor head. The AVGS sensor head provides laser-based active measurement
of distance and orientation, while the ULTOR® sensor head provides passive measurement of the same. We have tested
the Hydra® prototype in the Marshall Space Flight Center's Flight Robotics Laboratory. In this paper we describe the
Hydra® prototype and present the results of ground testing the sensor system.