Spaceborne synthetic aperture radar (SAR) motion compensation using autofocus

Document Type : Original Article

Authors

1 Avionics Department, Military Technical College

2 National Authority for Remote Sensing and Space

Abstract

A common tool for remote sensing is Synthetic Aperture Radar (SAR).
It is a very confident compared to other forms of remote sensing since it
has the advantages of operating with high efficiency in all weather and
throughout the day. In ideal circumstances, the SAR platform travels
along a straight path at constant height and velocity. However, the
eccentric orbit of satellites does not support this idea leading to decrease
the quality of the focused image. This paper suggests a Phase Gradient
Autofocus (PGA) solution to be applied to Sentinel-1 data addressing
the SAR image-focus problem where space-variant motion defects could
not be disregarded, taking the biggest advantages of using satellite SAR
having access to actual data, such as Sentinel 1 level-0 and level-1 real
data obtained from the European Space Agency Copernicus website,
a free access hub for level-0 and level-1 data types. Furthermore, two
distinct measures are employed in the endorsement process. First,
measuring the contrast and entropy of the formatted image. Second,
four high power reflecting points in the scene area has been visually
inspected moreover assessing their amplitude response.The suggested
approach that employs PGA optimizes the image quality by attaining
improved entropy and contrast when compared to the original Sentinel-1
images.

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