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Chiba University proposed and developed airborne and high altitude platform system (HAPS) onboard C band circularly polarized synthetic aperture radar (CP-SAR) for environment and disaster monitoring on altitude 2–20 km. This paper explains concept, system configuration, RF system and antenna, and flight test of CP-SAR in Hinotori-C2 (Firebird-C2) mission onboard CN235MPA aircraft on 14–15 March 2018 at Indonesia. The result of flight test depicts full polarimetric CP images that shows good performance of CP-SAR. The assessment of CP image analysis, and novel image classification using axial ratio (AR), ellipticity (e), and polarization ratio (p) are discussed. We plan to hold the flight test of HAPS onboard CP-SAR in 2023.

Our laboratory develops L Band circularly polarized synthetic aperture radar (SAR) sensor for microsatellite (150kg class) using 3.6m diameter of gold coated parabolic mesh antenna. This presentation explains the specification, antenna deployment system, RF system, and characteristics of parabolic mesh antenna for the developed sensor. This sensor will be employed to monitor global land deformation in the future.

Previously only linear polarization is widely used in the Synthetic Aperture Radar (SAR) system onboard spaceborne and airborne platforms. In such linearly polarized SAR (LP-SAR) systems, Faraday rotation in the ionosphere and platform posture will contribute to the system noise. Therefore to improve this situation, currently a novel Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor is developed in Microwave Remote Sensing Laboratory, Chiba University. Moreover, from this research, a new backscattering data based on circularly polarized wave in the remote sensing field can be obtained. As an early stage of the development of this CP-SAR sensor, we built an Unmanned Aerial Vehicle (UAV) platform for testing CP-SAR sensor capabilities. In this paper, we describe the novel CP-SAR sensor and the method to design CP-SAR UAV especially in estimating the requirement of data memory capacity. Also a smaller antenna is possible to be implemented since the 3-dB axial ratio on antenna characteristic becomes the main parameter in this new CP-SAR technique. Hence, a compact CP-SAR sensor onboard a small and low cost spaceborne platform yielding a high accuracy SAR image data can be realized in the near future.

The Japan Aerospace Exploration Agency (JAXA) will launch a geostationary satellite called Engineering Test Satellite-VIII (ETS-VIII) in 2005. ETS-VIII will conduct orbital experiments on mobile satellite communications at the S-band frequency, especially to support the development of a technology for the transmission and reception of multimedia information such as voice and images for land mobile systems. Various antennas have been developed for mobile satellite communications purposes, but these antennas have a complex composition. A simple satellite-tracking triangular-patch array antenna is proposed. The targeted minimum gain of the antenna is set to 6 dBic at an elevation of 48/spl deg/ in the Tokyo area for applications of a few hundred kbps. The antenna also should be designed as thin, compact, small and simple as possible, because it will be mounted on bullet train, ship or car roof.

A satellite-tracking left-handed circularly polarised triangular-patch array antenna has been developed to support the next generation of mobile satellite communications using Japanese Engineering Test Satellite VIII. The targeted minimum gain of the antenna was set to 5 dBic at an elevation of 48° in the Tokyo area, for applications of about a hundred kbit/s data transfer. The antenna is composed of three equilateral triangular patches and fed by a dual-proximity feed. The influence of the array configuration on the characteristic of this antenna is investigated using a method of moments (MoM) approach and a simple point source model. The measurement of the fabricated antenna was then performed to confirm the simulation results. The result showed that the 10 mm distance between the patch apex to the centre of the array antenna satisfies the target. The frequency characteristic of the fabricated antenna is 0.7% shifted to the higher frequency, and the maximum gain is 0.9 dB lower than the simulation results. The result also shows that the characteristic of the patch array antenna satisfies the specification at elevation angle El=48°, especially the 5 dBic gain coverage of the results covers the whole azimuth angle in a conical-cut plane at El=48°.