Active Microwave Instrument
|Within Vocab||SeaVoX Device Catalogue|
|Definition||An active microwave instrument consisting of a synthetic aperture radar (SAR) and a wind scatterometer (SCAT), the former designed to capture imagery of ocean, land and ice at high resolution and independently of weather conditions, and the latter utilised to measure horizontal wind speed and wind vector over the surface, as well as soil moisture and sea-ice type. The SAR radar operates by obtaining strips of imagery in two modes: the imaging mode, and the wave mode. In imaging mode, SAR provides two-dimensional images between (6 - 30)m along-track at a spatial resolution of 26m. In wave mode, imagettes of 5 km by 5 km in size are captured at regular intervals of 200 km along track; the imagettes are then processed within the swath to obtain the wave spectra, as changes in radar reflectivity on the sea surface are proxies for length and direction of surface waves. SCAT is composed by three sideways-looking antennae which generate radar beams at 45, 90 and 135 degrees azimuth across a swath 500 km wide situated 200 km to the right of the sub-satellite track. The radar backscatter is then measured for overlapping cells of 50 km resolution, using a grid spacing of 25 km. This technique permits three different viewing directions almost simultaneously, facilitating the determination of surface wind vectors. SAR and SCAT can be operated together, unless SAR is in imaging mode. The wave direction detected range is (0 - 180) degrees, at an accuracy of +/- 20 degrees; the detected wavelength range is (100 - 1000)m, with an accuracy of +/- 25%. AMI-SAR operates at the C-band frequency of 5.3 GHz with a bandwidth of 15.5 MHz, using vertically polarised antennas. The spatial resolution achieved is 30 m over a 100 km swath, located 250 km to the right of the sub-satellite track; the look angle is 23 degrees. Wind direction detected range is (0 - 360) degrees, at an accuracy of +/- 20 degrees; wind speed detected range is (4 - 24) m/s, at an accuracy of 2 m/s and spatial resolution of 50 km. AMI-SCAT operates at the C-band frequency of 5.3 GHz +/- 200 kHz. Flown on ERS-1, ERS-2. http://www.wmo-sat.info/oscar/instruments/view/23; https://www.wmo-sat.info/oscar/instruments/view/24|
|Is Version Of||TOOL1064|
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