Ideally you want to have a large collecting area (aperture) for radar to get good resolution. But it isn't practical to put a big radar dish in space. So they u

Ideally you want to have a large collecting area (aperture) for radar to get good resolution. But it isn't practical to put a big radar dish in space. So they use a small aperture and simulate a larger one by sweeping out an area over time and using some clever maths. Hence 'synthetic aperture radar'.