Gravity Observation Based Alignment Transfer

This paper presents a new alignment transfer method which uses only accelerometer measurements in the gravitational field. The TRIAD (Three-Axis Attitude Determination) algorithm is reformulated to use two pairs of gravitational measurements instead of star observations to achieve three-axis attitude determination. A major benefit of the method is the freedom to choose missile Inertial Measurement Unit (IMU) gyms based solely on in-flight considerations. An additional benefit is the ability to update the alignment transfer by simply making new measurements of gravity and reprocessing the measurements taken before erection. This new alignment transfer method eliminates 'Time to Complete Alignment Transfer' from the major contributors of the alignment error. Algorithm development, error analysis and laboratory results are provided.