Coherent data alignment and baseline calibration for improved two-pass interferometric synthetic aperture radar

Abstract

Currently, two principal operation modes are utilized by interferometric synthetic aperture radar (IFSAR) systems for data collection. The first mode is a one-antenna, two-pass IFSAR operation mode, where the aircraft platform possesses a single antenna and flies by the scene of interest twice collecting data. The two-antenna, one-pass IFSAR operation mode is the second mode, in which the aircraft platform possesses two antennas and flies by the scene of interest once while collecting data. Each one of these IFSAR operation modes possesses certain strengths and weaknesses. The one-antenna, two-pass mode allows for large baselines but suffers from imprecise knowledge of the baseline length, and consequently does not possess accurate target height scaling. Alternatively, the two-antenna, one-pass mode allows for precise knowledge of baseline length, but often at the expense of a limited baseline length, and consequently suffers from increased height noise. We describe an innovative IFSAR operation mode for overcoming these weaknesses by combining the two current IFSAR operation modes into a new two-antenna, two-pass IFSAR operation mode. By accurately estimating the antenna baseline between the two flight passes from the data itself, target height scaling accuracies are improved to the equivalent of a two-antenna, one-pass IFSAR system with the height-noise performance commensurate with the larger baseline. This, in turn, allows for more accurate information about target ground position locations and heights.