High resolution 2-D ISAR image collection and processing

This paper goes into the practical and theoretical foundations of 2-D ISAR (inverse synthetic aperture radar) image collection and processing. Its application to validate high definition aircraft geometry models is also discussed. The ISAR data is collected by a Ground-to-Air Measurement System (GTAMS) at Tyndall Air Force Base, Florida. The GTAMS System consists of a ultra high range resolution (UHRR) radar system to collect all aspect radar signatures. The GTAMS facility ties into an ACMI system (aircraft combat maneuvering instrumentation system) that provides real-time aircraft position, attitude, and velocity parameters each time the GTAMS system collects a radar target signature. This paper details the methodology of collecting ISAR images at the GTAMS facility as well as their processing into focused 2-D ISAR images. The use of ACMI aircraft position information to derive the image focusing parameters is also discussed. The raw data required to form an ISAR image consist of 512 pulses of UHRR radar I/Q video data collected during the dwell, or “look” at the aircraft. The ACMI tracking data are also collected and include position, velocity, and attitude information. These data are converted into an ISAR image in a multistep process including range and Doppler focusing, weighting for sidelobe reduction, and 2-dimensional Fourier transformation. Examples of the results of these various processing steps are shown