TAILIEUCHUNG - Geoscience and Remote Sensing New Achievements_2

Tham khảo sách 'geoscience and remote sensing new achievements_2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 13 C-band Scatterometers and Their Applications Vahid Naeimi and Wolfgang Wagner Vienna University of Technology Austria 1. Introduction Scatterometers are non-imaging active sensors used to measure the intensity of microwave backscatter while scanning the surface of the earth from an aircraft or a satellite. Active microwave sensors are radars providing their own illumination and do not depend upon ambient radiation like passive microwave sensors. They transmit microwave electromagnetic pulses toward the surface and measure how much of that signals return after interacting with the target. Scatterometer is a form of radar that is used to investigate different geophysical properties of the surface and few centimeters beneath. Spaceborne scatterometers have the advantage of providing global coverage on a continuous basis which cannot be achieved through airborne or ground measurements. They have the capability of providing day and night time measurements unaffected by cloud cover. Scatterometers were originally designed to study ocean winds but have been also used to study of cryosphere vegetation and soil surface properties. A number of scatterometers have been flown on space missions since the early 1970s. The first scatterometer in space was a Ku-band instrument on Skylab mission. Investigations on the potential use of scatterometers in geosciences achieved a major technical milestone with the launch of Seasat carrying a Ku-band scatterometer SASS in 1978. Other missions have followed SASS C-band scatterometers onboard the European Space Agency s ESA Earth Remote Sensing ERS 1 ERS-2 satellites in 1991 and 1995 the NASA s Ku-band scatterometer NsCAT in 1996 SeaWinds on QuikSCAT in 1999 SeaWinds on ADEOS-II in 2002 and Advanced Scatterometer ASCAT onboard Metop-A launched in 2006. In this study we focus on spaceborne C-band scatterometers and present an overview of their applications in geoscience. 2. C-band Scatterometers SCAT onboard ERS satellites The first

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