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

Period of Performance: 11/08/2007 - 07/31/2008


Phase 1 SBIR

Recipient Firm

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


The interest in formation and cluster-based satellite applications has grown considerably in recent years, especially as launch costs have dropped and the availability of secondary rides have increased. Unfortunately, the realization of these applications has proven difficult because of challenges such as station keeping and collision avoidance. In this proposed Phase I effort, TUI will demonstrate the performance of a relative attitude and position sensor that uses a unique combination of omni-directional antennas, Doppler direction finding techniques, and a deeply integrated ranging channel. Previous experiments done by TUI indicate that angular accuracy will easily exceed +/- 0.5 degrees while ranging measurements are expected to be at least +/- 10 cm. Because of the short distances typically used in formation-based micro-satellite applications, the power requirements and hence the mass and volume requirements will be relatively small. The performance-to-cost ratio of the proposed sensor is also expected to be quite high due to the use of readily available, low power RF components and high-speed digital logic. This will allow easy integration of the sensor into nano and micro-satellite platforms, facilitating the development of clustered spacecraft systems such as formation flying synthetic apertures and fractionated spacecraft architectures.