SAR - Radar with synthetic aperture

SAR was developed to avoid having to install huge antennas on every flying object. This invention is particularly useful for smaller UAS.

What exactly is that?

Synthetic aperture radar (SAR) is an imaging technique that generates 2D and 3D images from radar reflections from the ground. SAR has considerable advantages as it relies on radio instead of visible light. This allows the radar to see through difficult conditions such as haze, clouds and dense forest canopies.

The German Aerospace Center describes how SAR works on a satellite as follows. A single antenna transmits pulses at regular intervals, the echoes of which are received again. Once the echoes have been fully digitized and stored, the data is transmitted to the ground station. This in turn is treated with a complex computing process called "aperture synthesis". This involves arranging the individual virtual antennas and combining them into one large antenna. In this way, the SAR produces the same effect that would be achieved with a long antenna.

There are three different operating modes for sensors that work with X-band. The "Spotlight" mode is suitable for an area measuring 10 kilometers by 10 kilometers with a resolution of 1 to 2 meters. "Stripmap", on the other hand, is suitable for a 30-kilometer-wide strip with a zoom of 3 to 6 meters. The "ScanSAR" can capture a 100 kilometer wide strip with a resolution of 16 meters.

Who uses the SAR?

Due to its special technology, it is now standard for earth observation and remote sensing. However, it is mainly used in the military. The combat drones remotely controlled by satellites are made visible on the monitors using this technology, among other things.

However, the SAR can be used not only for military operations with large combat drones, but also for civilian drone types. Due to its small size and low weight, it can be used for many types of drones.