RADARSAT-1 is Canada's first commercial Earth observation satellite. It was launched on November 4, 1995 into a sun-synchronous (dawn-dusk) orbit above the Earth with an altitude of 798 kilometerss and inclination of 98.6 degrees. Developed under the management of the Canadian Space Agency (CSA) in cooperation with Canadian provincial governments and the private sector, it provides images of the Earth for both scientific and commercial applications. RADARSAT-1's images are useful in many fields including agriculture, cartography, hydrology, forestry, oceanography, geology, ice and ocean monitoring, arctic surveillance, and detecting ocean oil slicks.
RADARSAT-1 uses a Synthetic Aperture Radar (SAR) sensor to image the Earth at a single microwave frequency of 5.3 GHz, also known as C-Band (wavelength of 5.6 cm). Unlike optical satellites that depend on reflected sunlight to illuminate the Earth's surface, SAR systems transmit microwave energy towards the surface and record the signals reflected back. Thus, RADARSAT-1 can image the Earth, day or night, in any atmospheric condition, such as cloud cover, rain, snow, dust or haze.
The resolution of RADARSAT-1's images depends on the beam mode used, of which RADARSAT-1 has seven. The beam modes range from Fine mode, which covers an area of 50 kmē with a resolution of 10 meters to ScanSAR wide, which covers a 500 square kilometer area with a resolution of 100 meters. The Standard beam mode covers an area of 100 square kilometer and has a resolution of 30 meters. In addition to several beam modes, RADARSAT-1 also has the unique ability to direct its beam at different incidence angles.
With an orbital period of 100.7 minutes, RADARSAT-1 circles the Earth 14 times a day. The orbit path repeats every 24 days, this means that the satellite is in exactly the same location and can take the same image (same beam mode and beam position) every 24 days. This is useful for interferometry and detecting changes at that location that took place during the 24 days. Using different beam positions, a particular location of interest can also be imaged over a shorter timeframe of a few days.
RADARSAT-1 is a right looking satellite, meaning that microwave beam transmits and receives on the right side of the satellite relative to its orbital path. As it descends in its orbit from the North Pole it faces west and when it ascends from the South Pole it faces east. Locations on the Earth can therefore be imaged from opposite sides. This fact, combined with the different beam modes and positions, provide users with many possible perspectives from which to image a location.
National Aeronautics and Space Administration (NASA) provided the Delta II rocket to launch RADARSAT-1 in exchange for access to its data. Estimates are that the total cost of the project, excluding launch, was $620 million (Canadian). The Canadian federal government contributed about $500 million, the four participating provinces (Quebec, Ontario, Saskatchewan and British Columbia) about $57 million, and the private sector about $63 million.
RADARSAT International, Inc. (RSI), a Canadian private company, was created in 1989 to process, market and distribute RADARSAT-1 data.
RADARSAT-1 continues to operate to this day, well beyond its planned five-year lifetime. RADARSAT-2 is under development and is scheduled for launch in 2004.
