Laboratory and Flight-Test Analysis of Rubidium Frequency Reference Performance Under Dynamics

Frank van Graas, Samantha Craig, Wouter Pelgrum

Abstract:	Incorporation of a stable frequency reference, such as a Rubidium oscillator, into a pseudoranging system has several advantages. For example, a calibrated frequency reference provides an additional observable with favorable geometry compared to an additional satellite. The clock solution enables vertical stabilization in GNSS systems, and allows for 3D position and velocity coasting using only 3 satellites. The additional clock observable can also be used to improve the integrity assessment of the position, velocity and time (PVT) solution. The performance of Rubidium frequency standards is well-documented for stationary operation. In dynamic environments that include changes in orientation, acceleration, temperature, pressure and magnetic field, the performance of frequency references for PVT applications is not well characterized in the literature. This paper includes results from laboratory and flight test experiments. Laboratory tests were conducted to characterize oscillator performance under varying gravity and magnetic field conditions. Three Rubidium oscillators were flown on Ohio University´s DC-3 research aircraft. The oscillators were mounted in three different locations in different ways, including vibration isolation and hard mounting to the floor of the aircraft. Each of the oscillators was connected to a GPS receiver for error characterization. The frequency stability performance is profiled against the flight dynamics based on a navigation-grade inertial navigation system. The goal of the paper is to characterize the in-flight performance of Rb oscillators and to determine the feasibility of deriving frequency error corrections based on aircraft orientation and dynamics.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2950 - 2958
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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