Pointing Alignment Estimation for Precision Pointing Determination: Modeling, Estimation Method, and Calibration

The improved accuracy of attitude sensors has revealed that change and estimation error of pointing alignment became a dominant factor in pointing determination for highresolution Earth observation. The Advanced Land Observing Satellite (ALOS), which was launched on January 24, 2006, introduced a new approach to pixel geolocation determination and enabled fast and uniformly-precise geometric correction without ground control points. In this process, the pointing alignment has been a major source of error and has required continued calibration. This paper proposes modeling and an estimation algorithm for the pointing alignment change. The modeling assumes that the change consists of a bias term, orbit periodic terms, and a long-term drift, and the estimation applies weighted least-square optimization to this model. The paper also reports its operational calibration results based on flight data.