Ever wonder how we get amazing, nearly constantly updated satellite maps that can see through clouds and are now even finding hidden cities in heavily forested, unexplored jungles and lost cities under desert sands?
Scott Manley does an absolutely EXCELLENT job describing exactly how synthetic aperture radar (SAR) was developed over time and the principles behind it. By using polarized radar detection, you can even detect how much oil might be stored in tanks. By using subsurface scattering, you can detect features below tree cover and sand.
The part that was most amazing to me is they actually did the original image reconstruction using analog LENS technology.
Absolutely worth a listen.