SAR Imaging

Synthetic Aperture Radar (SAR) imaging is an Earth Observation (EO) method, where a satellite sends radar pulses to the Earth and monitors it's reflections. The moving satellite forms so called synthetic aperture, which can be used for studying the signal reflections from different points on earth. The time of flight of signal provides a distance between satellite and the ground surface. Because the exact location of the satellite is known, the distance can be used for estimating Earth topography. On the other hand, the strength of the reflected signals carries information about the properties of the Earth surface.

There are many SAR satellites in the orbit, such as

• Two Sentinel 1 satellites from Copernicus program of the European Space Agency (ESA).
• ALOS PALSAR
• IceEye
• JERS
• TERRASAR-X
• TanDEM-X

Some of the SAR satellite data is available from public sources

• Data from all satellites from Copernicus program can be downloaded from SciHub, instructions for usage can be found from the Copernicus MOOC course.
• Data from many publicly open satellites can be accessed using Google Earth Engine, and it can be also used for making and running your own algorithms in the cloud. One example is the night light test application.

Some useful SAR resources

1. ESA, free EO and SAR data:
   1. ALOS, JERS, TERRASAR-X/TandDEM-X
   2. https://earth.esa.int/web/guest/pi-community/apply-for-data
   3. https://earth.esa.int/eogateway/
   4. https://earth.esa.int/web/guest/pi-community/apply-for-data/3rd-party
   5. https://earth.esa.int/eogateway/ --->    https://eocat.esa.int/sec/#data-services-area
2. The space portal of University of Vaasa
3. NASA data sources, for example NASA Earth data
4. Commercial ones, Planet, Airbus, ICEye etc. You can test and learn with the free data but it’s limited.