Hao Liu

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.

WCOM: The science scenario and objectives of a global water cycle observation mission

Earth observation satellites play a critical role in providing information for understanding the global water cycle, which dominates the Earth-climate system. However, limitations in observations will restrict our current ability to reduce the uncertainties in the information used to make decisions regarding to water use and management. Under the support of “Strategic Priority Research Program for Space Sciences” of the Chinese Academy of Sciences, a new satellite concept of global Water Cycle Observation Mission (WCOM) is proposed, aiming to provide higher accuracy and consistent measurements of key elements of water cycle from space, including soil moisture, ocean salinity, freeze-thaw, snow water equivalent and etc. The expected more consistent and accurate datasets would be used to refine existing long-time series of satellite measurements, to constrain hydrological model projections and to detect the trends necessary for global change studies.

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

WCOM: THE MISSION CONCEPT AND PAYLOADS OF A GLOBAL WATER CYCLE OBSERVATION MISSION

WCOM, the Water Cycle Observation Mission, is proposed to improve the capability of synergetic observation of key water cycle variables. By developing innovative active-passive and multi-frequency combined sensors and retrieval models and techniques, the scientific objectives of this mission is to deepen the understanding on global water distribution, transportation and phase conversion by synergistic observations; and based on the improved model and data, to rebuilt long-term data series for revealing of the responses and feedbacks of water cycle to global changes.

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.

Research Activity on Synthetic Aperture Radiometry in CSSAR/CAS

Interferometric synthetic aperture radiometry is a relative new technique in the area of microwave earth observation to measure the brightness temperature distribution of the earth. It can enhance the spatial resolution of the passive microwave remote sensing effectively. Steady progress of this technology have been achieved in both one dimensional and two dimensional cases since 1990’s. The typical instruments are ESTAR and MIRAS, developed by NASA (and umass) and ESA respectively. Relative research has also been conducted in China, mainly by National Microwave Remote Sensing Laboratory (NMRS Lab), Center for Space Science and Applied Research (CSSAR), Chinese Academy of Sciences (CAS), since the middle of 1990’s. A C-band and an X-band instrument has been developed. In this paper, research activities on synthetic aperture radiometry in CSSAR/CAS will be reviewed and summarized, including the development of the instruments. Finally, further plans in synthetic aperture radiometry in CSSAR/CAS will also be prospected.

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.