Jingye Yan

Imaging Analysis and First Results of the Geostationary Interferometric Microwave Sounder Demonstrator

The Geostationary Interferometric Microwave Sounder (GIMS) is a new concept of atmospheric microwave sounder for Chinas future geostationary Earth orbit meteorological satellite (FY-4). It is a microwave interferometric radiometer (MIR) using aperture synthesis and working in rotating time-sharing mode with a circular antenna array. A GIMS proof-of-concept demonstrator operating in the temperature sounding bands of 50-56 GHz has been successfully developed. The instrument uses a circular array with 28 elements (including one in the center of the array). It is capable of imaging a scene with an angular resolution of about 0.08° and a radiometric resolution of less than 1 K with 5-m integration time within a 5° field of view (FOV). Some theoretical aspects of the imaging characteristics of GIMS are discussed, such as the alias-free FOV, angular resolution, radiometric resolution, and imaging algorithm. Some early tests and preliminary imaging experiments of the GIMS demonstrator are also presented.

The Geostationary Interferometric Microwave Sounder (GIMS): Instrument overview and recent progress

The concept of Geostationary Interferometric Microwave Sounder (GIMS) has been proposed based on the rotating circular thinned array, aiming for Chinas next generation geostationary meteorological satellite (FY-4M). The spaceborne system design has been investigated. The tradeoff analysis between the system performance and system complexity has been studied. A full-scale ground-based 50∼56GHz GIMS demonstrator with 28 elements has been defined and developed. Preliminary test results of the demonstrator will also be presented in this paper.

The CAS airborne X-band synthetic aperture radiometer: system configuration and experimental results

Using interferometric synthetic aperture radiometer to measure the brightness temperature distribution of the Earth is a relative new technique for the microwave earth observation. Steady progresses of this technology have been achieved in both one-dimensional and two-dimensional cases since 1990s. The typical instruments are ESTAR and MIRAS. The CAS airborne X-band synthetic aperture radiometer is a thinned array microwave imaging radiometer, developed by National Microwave Remote Sensing Laboratory (NMRS Lab), Center for Space Science and Applied Research (CSSAR) and Chinese Academy of Sciences (CAS). The system integration of the instrument was accomplished in the Jan, 2004, and the first flying experiment was held in Apr, 2004. In this paper, both the system configuration and the experimental results of the instrument are described in detail

Conceptual design and breadboarding activities of Geostationary Interferometric Microwave Sounder (GIMS)

In this paper, the authors will report some basic considerations on the synthetic aperture imaging radiometer for mm-wave sounding from GEO, especially for the Chinas next generation geostationary meteorological satellite (FY-4M).

Clock scan of imaging interferometric radiometer and its applications

High spatial resolution image of passive microwave brightness temperature can be taken by so called synthetic aperture radiometer or imaging interferometric radiometer. However the future application of this new technology is limited by its large number of element antennas and receiving channels. To overcome this difficulty, a novel time shared scan scheme is presented using the concept of clock arms. Potential applications of this new scan scheme are also presented in this paper.

A combined L-band synthetic aperture radiometer and fan-beam scatterometer for soil moisture and Ocean salinity measurement

The concept of a new type combined L-band active and passive sensor for soil moisture and ocean salinity measurement has been proposed in this paper. The passive part of this combined system is a one-dimensional synthetic aperture radiometer, while the active part is a digital beam forming scatterometer. Preliminary considerations for space-borne system design and performance evaluation has also been introduced in this paper. A ground-based demonstrator is defined and under development.

Microstructures and strengthening mechanisms of Cu/Ni/W nanolayered composites

Cu/Ni/W nanolayered composites with individual layer thickness ranging from 5 nm to 300 nm were prepared by a magnetron sputtering system. Microstructures and strength of the nanolayered composites were investigated by using the nanoindentation method combined with theoretical analysis. Microstructure characterization revealed that the Cu/Ni/W composite consists of a typical Cu/Ni coherent interface and Cu/W and Ni/W incoherent interfaces. Cu/Ni/W composites have an ultrahigh strength and a large strengthening ability compared with bi-constituent Cu–X (X = Ni, W, Au, Ag, Cr, Nb, etc.) nanolayered composites. Summarizing the present results and those reported in the literature, we systematically analyze the origin of the ultrahigh strength and its length scale dependence by taking into account the constituent layer properties, layer scales and heterogeneous layer/layer interface characteristics, including lattice and modulus mismatch as well as interface structure.

System study and development of an L-band 1-D synthetic aperture radiometer for ocean salinity measurement

System study and development of an L-band one-dimensional synthetic aperture radiometer, or microwave interferometric radiometer (MIR), has been introduced in this paper. This radiometer is the passive part of a combined active/passive instrument for space-based ocean salinity observation. Recent progresses on radiometer hardware development and system simulation have been introduced.

Study on sensitivity of interferometric radiometer

Since the late 80s when interferometric radiometry started to be applied to Earth observation, much literature has addressed the question of radiometric sensitivity of the instrument, but all references are based on a relatively simple system model, where only incident target noise and receiver noise are taken into account. After Corbella presented his more complex equation of the visibilities to include antenna pattern characterization and antenna coupling, a review of the general expression of sensitivity is also necessary to include the impacts of antenna coupling and other system imperfections. This paper concerns about the sensitivity of a microwave imaging interferometric radiometer. By defining a general signal model of the total output of the receiver, the sensitivity is discussed in both redundancy and non-redundancy cases.

Discovering the sky at the Longest Wavelengths (DSL)

The radio sky at frequencies below ~30 MHz is virtually unobservable from Earth due to ionospheric disturbances and the opaqueness of the ionosphere below ~10MHz, and also due to strong terrestrial radio interference. Deploying a radio observatory in space would open up this largely unexplored frequency band for science in astronomy, cosmology, geophysics, and space science. A Chinese-European team is proposing an ultra long wavelength (ULW) radio interferometer mission DSL (Discovering the Sky at the Longest Wavelengths). The proposed radio interferometer will be deployed in low-altitude lunar orbit, exploiting the radio quietness of the lunar far side. DSL will consist of a mother-spacecraft for data transport and control, plus eight small micro-satellites each equipped with three orthogonal dipoles. These satellites form a virtual distributed observatory with adjustable baselines, allowing different scientific observation strategies. The satellites are configured in a flexible quasi-linear array in nearly identical orbits, guaranteeing low relative drift rates. Short orbital periods and orbit precession ensure quick filling of the interferometric spatial frequency (u, v, w) space, enabling high quality imaging. The science themes considered for the DSL mission include pioneering studies of the unknown and exploratory science such as the search for signatures of the cosmological Dark Ages, complementing current (e.g. LOFAR) and future SKA telescope searches; full-sky continuum survey of discrete sources, including ultra-steep spectrum extragalactic sources, pulsars, and transients (galactic and extragalactic); full-sky map of continuum diffuse emission; solar-terrestrial physics, planetary sciences, and cosmic ray physics. The main frequency band covered is 1-30 MHz extending down to 0.1 MHz, and up to about 50 MHz for cross-referencing with ground-based instruments. DSL will support a variety of observational modes, including broad-band spectral analysis for Dark Ages, radio interferometric cross-correlations for imaging, and flexible raw data downlink capability. Data processing will be performed at radio astronomy science data centres in Europe and China.