Multi-Axis Doppler Direction Finder System for Relative Position and Attitude Determination

Period of Performance: 04/27/2009 - 08/31/2011


Phase 2 SBIR

Recipient Firm

Tethers Unlimited, Inc.
11711 N. Creek Pkwy S., Suite D113 Array
Bothell, WA 98011
Principal Investigator


Interest in formation and cluster-based satellite applications has grown considerably in recent years. These applications require a relative position and attitude sensor to address challenges such as station keeping, collision avoidance, and relative orientation control. Existing sensors that have been in use for years on missions requiring vehicle docking are typically not suitable for use on microsatellites due to field of view, mass and power limitations. In this Phase II effort, we propose to design and fabricate a proto-flight RF-RelNav sensor system that does not rely on external references such as stars or GPS signals, and then test the operation of multiple units integrated into representative small-spacecraft models. Sensor performance is expected to surpass ±1° angular accuracy in all three axes, ±0.1 m range resolution, and 1 Hz update rates for small numbers of spacecraft. Host impacts are expected to be only 2.5 kg of mass, 750 cm3 internal volume, and 5 W of power. The proposed effort will mature the RF-RelNav technology by verifying its operational characteristics through ground testing and by developing a qualifiable design traceable to at least Class-C hardware.