A Synthetic Aperture Radar is a side-looking radar system that utilizes the platform’s flight path to simulate an extremely large antenna or aperture electronically and generates high-resolution remote sensing imagery. SAR is used to create two-dimensional images or three-dimensional reconstructions of objects using the radar antenna’s motion over a target region to provide finer spatial resolution than conventional beam-scanning radars. SAR works similarly to a phased array, but contrary to several parallel antenna elements of a phased array, SAR uses one antenna in time-multiplex. The distance the SAR device travels over a target in the time taken for the radar pulses to return to the antenna creates the large synthetic antenna aperture. Typically, the larger the aperture, the higher the image resolution will be, regardless of whether the aperture is physical (a large antenna) or synthetic (a moving antenna) – this allows SAR to create high-resolution images with comparatively small physical antennas. Additionally, SAR has the property of having larger apertures for more distant objects, allowing consistent spatial resolution over a range of viewing distances. Contrary to FLIR optical imaging systems, the SAR/GMTI Radar System can operate day and night in all weather conditions because it uses the reflections of RF signals generated by its own antenna, not the reflection of sunlight. Unlike FLIR systems, which allow very detailed surveillance in an area of about 150m x 150m during day and night (200m x 200m with AselFLIR-300T used in GÖZCÜ-I/Heron and ANKA Block-A/B UAVs and 130m x 130m with AN/AAS-52 used in MQ-1 Predator UAV), the SAR/GMTI System allows the user to view a larger area at high resolution even in adverse weather conditions (Since the field of view is very limited, using a FLIR is defined as ‘looking through a straw or finding a needle in a haystack’). While optical systems (FLIR) can produce images in sub-seconds (about 24 frames per second) at vertical viewing angles such as 0-20 degrees, the SAR/GMTI Radar System can generate images in seconds (can take 1 minute in some cases) at more horizontal angles such as 20-85 degrees (which gives the user a stand-off range advantage), depending on the speed and viewing range of the carrier platform. While numerous images can be obtained in an ever-increasing number with optical systems, only a single image can be generated with SAR/GMTI Systems. 

We can summarize the main advantages of radar imaging compared to optical imaging as follows: