Sampling design and imaging method of clock scanning interferometric radiometer for GEO earth observation

摘要

Synthetic aperture interferometric radiometry is a promising technique for microwave earth observation. Recently, with the increasing demands of GEO (Geostationary earth orbit)high resolution earth observation, the clock scanning interferometric radiometer is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application. It can effectively solve the trade-off problem of system complexity and time resolution. Consequently, it can greatly simplify the system hardware. Clock scan has two scanning mode: the step rotation scan and continuous rotation scan. Their basic rules and designing methods are explored in this paper. The scanning trajectories and the associated sampling grid are the prime designing matters, which determine the measured visibilities and affect the final imaging reconstruction. Continuous uniform clock scan is the prime option for future GEO application. Because of its spiral sampling grid, conventional FFT based methods can not be directly used. The Gridding method is introduced to deal with this uneven sampling case, which is a kind of convolution resampling technique used to transform the uneven scattered data to regular Cartesian grid. At last, the potential applications of geostationary earth observation are explored with numerical simulations to validate the significance of this new imaging configuration and also the feasibility of the associated sampling design and imaging method.