Synthetic Aperture Radar

What is Synthetic Aperture Radar?

A Synthetic Aperture Radar (SAR), is a airborne or spaceborne sidelooking radar system which utilizes the flight path of the platform to simulate an extremely large antenna or aperture electronically, and that generates high-resolution remote sensing imagery.

SAR uses the motion of the radar antenna over a target region to provide finer spatial resolution than conventional stationary beam-scanning radars.

The spatial resolution of radar data is directly related to the ratio of the sensor wavelength to the length of the sensor’s antenna.

Features

• SAR is a Side-looking radar system which makes a high-resolution images of the Earth’s surface.
• Continuous strips of the ground surface are “illuminated” to one side of the flight direction.
• Signal is recorded and Digital signal processing techniques in the ground are used to focus the image and obtain a higher resolution images.
• The across-track distance is called the “Range”
• The along-track distance is called the “Azimuth”.

How Does SAR Work?

A SAR is an active sensor that first transmits microwave signals and then receives back the signals that are returned, or backscattered, from the Earth’s surface.

The SAR works similar of a phased array, but contrary of a large number of the parallel antenna elements of a phased array, SAR uses one antenna in time-multiplex.

SAR Resolution

SAR has two resolutions :

1. Range Resolution- is achieved by using Pulse compression technique.
2. Azimuth Resolution- is achieved by using Synthetic aperture concept.

SAR Bands