Nobuyoshi Fugono

Airborne microwave rain-scatterometer /radiometer

Abstract An airborne microwave rain-scatterometer/radiometer system operated at 10 and 34-45 GHz was developed for the remote sensing of precipitation, especially rain, from an aeroplane. Airborne rain-scatterometers were developed as a first step for the development of the future spaceborne rain-scatterometer. Flight experiments of more than 30 hours were performed in co-operation with the ground-based C-band weather radar. The sensor system of the airborne microwave rain-scatterometer/radiometer, flight experiment in June 1981 cooperating with the ground-based weather radar, and results of data analyses are described.

SIR-B Experiments in Japan: Sensor Calibration and Oil Pollution Detection Over Ocean

Preliminary results of the SIR-B experiments conducted in Japan are reported mainly on the sensor calibration and the oil pollution experiments. No significant result was obtained for the rice crop experiment which was carried out at the same time, mainly due to the late flight of SIR-B. The sensor calibration experiment was eventually reduced to only the evaluation of the imaging characteristics of SIR-B. However, a reasonable relation between the image count and RCS is found, and the resolution analysis by using the corner reflector images gives satisfactory results. A possible cause leading to what are rather overestimates of the resolution is pointed out to be the background clutter. A simulated oil slick area over sea was clearly detected on the SIR-B image, although the incident angle was not so appropriate for the purpose. This result demonstrates the capability of a space-borne synthetic aperture radar for effective surveillance of oil spills over high seas.

Quantitative Measurements of Path-Integrated Rain Rate by an Airborne Microwave Radiometer over the Ocean

Abstract Data on the airborne microwave radiometer, which is one of the sensors of the airborne microwave rain-scatterometer/radiometer (AMRS) system, are analyzed to infer path-integrated rain rate measured from topside. The equation of radiative transfer is used to relate quantitatively the antenna temperature to the rain rate profile inferred by the scatterometer. The influence of the ocean surface temperature on the radiometer measurements of rain is evaluated by a model computation. The theoretical prediction agrees excellently with the measurements. The effect of nonuniform rain along the propagation path is also evaluated by using the experimental data. It is shown that the excess antenna temperature (difference between the antenna temperature under raining and no-rain conditions) in the 10 GHz band is proportional to the path-integrated rain rate, and a method for determining the reference temperature (antenna temperature under a no-rain condition) is suggested.

Summary of millimeter wave propagation experiments using Japan’s first geostationary satellite «Kiku-2»

A one year millimeter wave propagation experiment with a satellite-to-earth link was performed using Japan’s first geostationary satellite «Kiku-2». The satellite carries a beacon transmitter with three coherent frequencies, 1.7, 11.5 and 34.5 GHz. A coherent receiving system with a 10 m diameter antenna was employed. Other instrumentation included a C band rain radar. The experiment was carried out on 24 h-a-day basis and achieved nearly eight thousand hours of test time. The results show that a 20 dB rain margin is necessary for a millimeter wave satellite communication link with 99.9 % reliability. This paper describes the experiment and the results in outline.AnalyseUne expérience sur la propagation des ondes millimétriques a été conduite pendant une année en employant «Kiku-2», le premier satellite géostationnaire du Japon. Ce satellite comporte une balise émettrice cohérente à trois fréquences : 1,7, 11,5 et 34,5 GHz. En outre, un radar météorologique en bande C était disponible. L’expérience fonctionnait 24 h par jour, et la durée totale de mesure a atteint presque 8 000 h. Les résultats montrent qu’une marge de 20 dB est nécessaire pour garantir une liaison satellite — terre en ondes millimétriques contre la pluie avec une fiabilité de 99,9 %. On résume ici les grandes lignes de l’expérience et les résultats.

Propagation experiment with Japanese satellite, ETS-II (KIKU-2)

Abstract The first Japanese geostationary satellite, Engineering Test Satellite Type II [Kiku-2], has been successfully placed at 130°E at the beginning of March 1977. Using beacon transmitters at three coherent frequencies of 1.7, 11.5 and 34.5 GHz which are installed in ETS-II, the Radio Research Laboratories (RRL) of the Ministry of Posts and Telecommunications (MOPT) conduct propagation experiments to obtain preliminary information for the Experimental Communication Satellite (ECS) experiment. The experimental system for propagation experiment with ETS-II is composed of a main receiving station, a rain radar, a radio-meter, meteorological instruments and data handling computers. The receiving data, including signal levels of co- and cross-polarization in these frequencies and phase differences between each of these frequencies and polarization, are sampled every 200 msec. The satellite-to-Earth propagation experiment at the highest frequency has been satisfactorily started on 11 March 1977.

SIR-B image calibration by a corner reflector array

Abstract SIR-B image data taken over a corner reflector array are analysed to calibrate the image and to estimate the 3dB resolution. Square trihedral corner reflectors having different radar cross-sections (RCSs) are successfully used to relate an image data number to RCS. RCS of the background surface is estimated and its effect is also included in the above relation. The 3dB resolutions are estimated by two independent techniques. The results obtained from the two techniques agree with each other within their relative difference by 5·6 per cent except for one case. The estimated resolutions are larger than those predicted by the Jet Propulsion Laboratory. The estimates should be regarded as the image resolutions and do not represent the sensor characteristics.

System design and examination of spaceborne microwave rain-scatterometer☆

Abstract The remote sensing of precipitation, especially rain by the spaceborne weather radar is an important subject which has not been realized. The system design and examination of the spaceborne weather radar which is called as the spaceborne microwave rain-scatterometer are performed by considering users requirements to observe rain, the restrictions derived from the interface with satellite and the state of the art and the possibility of spaceborne microwave technology. Characteristic parameters for spaceborne microwave rain-scatterometer are determined based on the users requirements for the system. Functions and performances of each subsystem (antenna, transmitters, receivers and data transmission processor) with the detailed block diagram of the total system of spaceborne microwave rain-scatterometer are shown. All of the critical items of hardware in the development of spaceborne microwave rain-scatterometer are also discussed.

Propagation characteristics for millimeter and quasi-millimeter waves by using three Japanese geostationary satellites

Abstract Propagation experiments using the following geostationary satellites, Engineering Test Satellite-II (ETS-II), Medium-Capacity Communication Satellite for Experimental Purposes (CS), Medium-Scale Broadcasting Satellite for Experimental Purposes (BSE) and Experimental Communication Satellite (ECS), are being conducted by Radio Research Laboratories (RRL) with the co-operation of National Space Development Agency of Japan (NASDA), Nippon Telegraph and Telephone Public Corporations (NNT) and Japan Broadcasting Corporations (NHK). The Experimental Communication Satellite (ECS) will be launched into the geostationary orbit in February 1980. This satellite will then be used for further propagation experiments. The various and numerous propagation data obtained by using these satellites is being collected from many places all over Japan. The summary of the propagation experiments conducted at the main station is as follows. 1. (a) Experimental periods covered in this paper are about 1 year for ETS-II and CS, and six months for BSE. 2. (b) The percentages of time in which measured attenuation exceed 5, 10 and 15 dB are 0.7, 0.3 and 0.15% respectively at 34.5 GHz (ETS-II), 0.08, 0.016 and 0.008% respectively at 19.45 GHz (CS), 0.025, 0.0025 and 0.0009% respectively at 11.7125 GHz (BSE), and 0.02, 0.0023 and 0.001% respectively at 11.5 GHz (ETS-II). 3. (c) Duration of attenuation exceeding 30 dB at 34.5 GHz is less than 50 min with the occurrence probability of 0.013% for a one year period. Attenuation exceeding 6 dB at 11.5 GHz and the one exceeding 10 dB at 19.45 GHz are 0.0025% (8 min in a year) and 0.015% (10 min in three months). 4. (d) In the cumulative distributions of XPD (Cross Polarization Discrimination), values of XPD exceeding the percentages of time, 0.3, 0.1, 0.03 and 0.01% are 25, 22, 19 and 17 dB respectively at 34.5 GHz, 28, 23, 20 and 16.5 dB respectively at 19.45 GHz and 33, 29, 26 and 24 dB respectively at 11.5 GHz. This paper presents an outline of the propagation experiments carried out by using ETS-II, CS, BS and ECS, and propagation characteristics of radio waves mainly above 10 GHz at the main station (Kashima Branch, RRL).