Complex sentence: The Radar Imager for Mars' subsurface experiment (RIMFAX) is a ground-penetrating radar on the planned Mars 2020 Rover that uses radar waves to see geologic features under the surface.
Split into simpler sentences: The Radar Imager for Mars' subsurface experiment (RIMFAX) is a ground-penetrating radar on the planned Mars 2020 Rover. It uses radar waves to see geologic features under the surface.