RADARSAT program
The Canadian Space Agency's RADARSAT program is a series of Canadian Earth observation satellite missions. They all use an imaging technology called synthetic aperture radar (SAR).
Synthetic aperture radar
Traditional optical satellites rely on sunlight to see the areas they want to image, similar to how a camera works. SAR satellites emit microwave signals, a portion of which bounces off Earth's surface and makes its way back to the satellite's sensors.
Since microwaves are much longer than visible light waves, they're able to pass through clouds and haze, making it so that SAR satellites can image Earth, day or night, no matter the weather. SAR is also great at sensing water and angular objects – which makes it very well suited for monitoring ships, detecting oil spills, monitoring flooding, mapping sea ice and glaciers, crop and forest canopy monitoring, and detecting land subsidence from earthquakes, among many other things.
RADARSAT-1
RADARSAT-1 was Canada's first operational Earth observation satellite. It was launched on and decommissioned on .
RADARSAT-2
RADARSAT-2 is a joint project between the CSA and a commercial firm called MDA. It was launched on , and is still operated by MDA.
RADARSAT Constellation Mission
The RADARSAT Constellation Mission (RCM) is Canada's third generation of Earth observation satellites. Launched on , the three identical satellites work together to cover Canada and areas of interest in the rest of the world more frequently than ever before under the RADARSAT program. The RCM satellites are the first in the program to contain dual payloads, with both a SAR instrument as well as another for ship detection (Automatic Identification System, or AIS).