Lijie Niu

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.

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).

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.

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.

MICAP (Microwave imager combined active and passive): A new instrument for Chinese ocean salinity satellite

Sea surface salinity (SSS) plays an important role in global water cycle. In recent years, satellite based remote sensing has proven to be a promising approach for global SSS observation. A new payload concept, named MICAP (microwave imager combined active and passive), has been introduced in this paper. MICAP is a suit of active/passive instrument package, which includes L/C/K band one-dimensional MIR (microwave interferometric radiometer) and L-band DBF (digital beamforming) scatterometer, sharing a parabolic cylinder reflector. MICAP has been selected to be a candidate payload for future Chinese ocean salinity mission. In this paper, the MICAP instrument concept, specification and preliminary system design will be introduced.

Analysis and experimental study of high stability microwave radiometer

A new ocean salinity mission concept has been proposed and a ground-based prototype is being developed in MIRSlab, CAS. The passive part of the combined instrument is a one-dimension synthetic aperture radiometer. A critical technical challenge is that the radiometer needs to have very high sensitivity and high calibration stability. In this paper, theoretical analysis is given to high stability radiometer, and a high stability L-band radiometer has been developed to demonstrate its performance.

IMI (Interferometric Microwave Imager): A L/S/C tri-frequency radiometer for Water Cycle Observation Mission(WCOM)

Water Cycle Observation Mission (WCOM) is an earth science mission proposed and focused on the research of water cycle under global change. With its three dedicated designed main payloads, WCOM can achieve synchronized observation on a group of global water cycle key parameters, including soil moisture, ocean salinity, snow water equivalent, soil freeze-thaw, atmospheric water vapor, precipitation and other associated parameters. One of the three WCOM main payloads names IMI (Interferometric Microwave Imager), which is a newly designed L/S/C tri-frequency radiometer aiming to provide advanced measurement capability on soil moisture and ocean salinity. In this paper, the instrument concept and preliminary system design of WCOM/IMI will be introduced. Recent progresses on the filed experiments of an L-band demonstrator will also be introduced.

Interelement Phase Calibration for the Geostationary Interferometric Microwave Sounder (GIMS)

The Geostationary Interferometric Microwave Sounder (GIMS) is a new concept of atmospheric microwave sounder for Chinas future geostationary Earth orbit meteorological satellite (FY-4). A novel self-calibration method for interferometric radiometers with a rotating thinned array, particularly for GIMS, has been proposed in this letter. Compared with the traditional relative phase calibration approach, neither dedicated hardware nor dedicated calibration working model is needed to achieve the relative phase calibration in this novel interelement phase calibration. The self-calibration approach is inherently merged with the nominal observation working model of GIMS, owing to the continuous array rotating of the GIMS instrument. A running average scheme has been introduced into the self-calibration approach to enhance the signal-to-noise ratio of the calibration data, which is normally very low with the natural earth scene. The method is demonstrated by both simulation and field imaging experiment.

Development of a three-element interferometer at 50∼56 GHz for Geostationary Interferometric Microwave Sounder (GIMS)

The Geostationary Interferometric Microwave Sounder (GIMS) is a new concept imaging radiometer proposed by CSSAR, aiming for Chinas next generation geostationary meteorological satellite (FY-4M). The concept of GIMS is based on aperture synthesis with a rotating circular thinned array. A three-element interferometer has been developed and tested to investigate the feasibility of the GIMS system design. A full-scale ground-based demonstrator with 27 elements is also under development, which is defined as a minimum system intended to fulfill the threshold application requirements. In this paper, the preliminary results of these activities will be reported.