Atmospheric correction method for interferometric synthetic array radar systems operating at long range

A method for use with an interferometric synthetic aperture radar system having two antennas separated by a predetermined separation distance which generates data comprising complex image pairs representative of an image scene, and wherein the method computes and corrects phase errors due to atmospheric turbulence, said method comprising the steps of:

• generating a first pair of images having a short baseline using the synthetic aperture radar system;
• generating a second pair of images having a long baseline using the synthetic aperture radar system;
• combining the respective first and second pairs of images to produce first and second summed complex interferograms;
• processing the first complex interferogram sum to unwrap its phase, wherein the phase of each complex pixel is computed and the absolute phase is reconstructed, up to a single additive constant and to produce an unwrapped phase image;
• processing the real-valued unwrapped phase image and a scalar value given by the ratio of the grazing angle differences between the long baseline images and that of the short baseline images to scale the unwrapped phase image by the baseline ratio;
• processing the scaled reference phase image and the second complex interferogram sum to remove the phase reference from the second complex interferogram sum to produce a complex image whose phase is that of the second complex interferogram sum minus the reference phase image;
• processing the complex image using a complex Wiener filter to produce a low-pass filtered complex interferogram;
• processing the complex image and the low-pass filtered complex interferogram to remove the phase of the Wiener-filtered interferogram from the complex image and provide an atmospherically corrected complex image whose phase is the phase of the complex image minus the phase of the low-pass filtered complex image, which complex image;
• processing the atmospherically corrected complex image to produce a real-valued atmospherically corrected image having unwrapped phase;
• and
• adding the real-valued atmospherically corrected image and the real-valued reference phase image provided by the baseline ratio scaling function to produce an image that is proportional to terrain elevation.