Real Time Calibration of Antenna Phase Errors for Ultra Short Baseline Attitude Systems

where he has been on the faculty for 26 years. His research deals with land, air and space vehicle navigation and control. He is the co-author of two control system textbooks. ABSTRACT Ultra short baseline attitude systems with base-lines under 0.5 meters are desirable for any application which requires a high level of integrity. The higher level of integrity is a direct result of the limited number of integer ambiguities for shorter baselines. However, for ultra-short baseline attitude systems, phase errors translate into larger angular errors than they do in long baseline systems [1-8]. Many of the phase error sources such as carrier tracking loop noise and thermal noise can be filtered using inexpensive inertial sensors, however, other factors such as line bias variations and differences in antenna phase delay patterns generate slowly varying phase errors. Antenna phase errors are a function of line-of-sight to the satellites and vary at rates based on satellite movement and platform angular rate. Line bias errors are a function of temperature. These rates are generally too slow for inexpensive inertial sensors to provide any filtering. Several methods for calibrating out these errors are presented.