Synthetic aperture interferometric technique has wide applications in optics,radio astronomy and mi-crowave remote sensing areas.With the increasing demands of high resolution imaging observation,a new time-sharing sampling scheme of asynchronous rotation scan is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application.This configuration is basically composed by two asynchronously and concentrically ro-tating antenna groups,whose revolving radii and speeds are different.The synthetic aperture system with asynchronous rotation scanning scheme can effectively solve the trade-off problem of system complexity,and greatly simplify the system hardware at the cost of sacrificing a certain time resolution.The basic rules and design methods of asynchronous rotation scan are investigated The Gridding method is introduced to inverse the spiral sampling data for image reconstruction.The potential ap-plications of geostationary orbit(GEO)earth observation and solar polar orbit(SPO)plasma cloud observation are explored with numerical simulations to validate the significance and feasibility of this new imaging configuration.
Space Very Long Baseline Interferometry(S-VLBI) is an aperture synthesis technique utilizing an array of radio telescopes including ground telescopes and space orbiting telescopes.It can achieve much higher spatial resolution than that from the ground-only VLBI.In this paper,a new concept of twin spacecraft S-VLBI has been proposed,which utilizes the space-space baselines formed by two satellites to obtain larger and uniform uv coverage without atmospheric influence and hence achieve high quality images with higher angular resolution.The orbit selections of the two satellites are investigated.The imaging performance and actual launch conditions are all taken into account in orbit designing of the twin spacecraft S-VLBI.Three schemes of orbit design using traditional elliptical orbits and circular orbits are presented.These design results can be used for different scientific goals.Furthermore,these designing ideas can provide useful references for the future Chinese millimeter-wave S-VLBI mission.
With the benefits of digital IC technology development, the synthetic aperture interferometric radiometer (SAIR) technique is growing fast and expanding to more and more application areas. The near field imaging detection is a potential application which has received increasing demand recently. Because the Fourier imaging theory of the traditional SAIR is based on far-field approximation, it will be invalid for near-field condition. This paper is devoted to establishing a new accurate imaging algorithm for near-field SAIR imaging. Firstly, the visibility function in near field is deduced and the relationship of which to far-field visibility function is analyzed. Then, a numerical method based on pseudo inverse and focal plane approximation is developed. The effectivity of this method is tested with imaging simulation of point source and extended source, and the superiority is also demonstrated by comparing with the existing phase-modified Fourier transform method. At last, the field experiment with one-dimensional SAIR instrument is performed to validate the practical feasibility of this method.
