Synthetic Aperture Radar
Some solar system objects are covered by clouds or haze, making optical imaging difficult or impossible. However, these atmospheres are transparent to radio frequency waves and can be imaged using synthetic aperture radar (SAR) instruments. Sciencecraft transforms raw radar instrument data into SAR images. So, what is SAR?
An aperture is the part of the sensor's collecting area, such as the telescope or antenna diameter. A filled aperture consists of just one aperture while a synthetic aperture consists of several units placed in formation. This formation behaves as one large aperture, "synthesized" from smaller elements.
And, radar is a type of energy, similar to light. But unlike light, we can't see radar energy. It acts like sound, bouncing off surfaces and making "echoes." These echoes are "heard" by the radar antenna.
SAR instruments bounce a radar signal off the ground, then measure the strength of the signal that comes back and how long it takes. From this information, scientists can determine if the terrain high or low, wet or dry, rough or smooth. They can also tell if the surfaces are straight up and down (like walls) or slanted (like hills) and what covers the surfaces. Sciencecraft is able to create images from radar data without having to send it to the ground.