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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.

Chiba University proposed and developed airborne C band circularly polarized synthetic aperture radar (CP-SAR) for environment and disaster monitoring. 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 (ρ) are discussed.

Forest fire in Indonesia occurred mostly in peatland area when the peatland areas were dried with groundwater table more than 40 cm. This peatland condition has become degradation areas with high potentials to fire. Some previous research utilized optics data remote sensing to detect the potential combustible peatland area while others concerned on backseat-tering information of synthetic aperture radar data compared with Forest Fire Danger Rating System (FDRS) data to identify a peat fire risk area. Peatland is prone to fire, usually associated with land that is open, close to the road, and dry conditions. In this research, polarimetric decomposition and interferometric SAR techniques have been used to determine the potential of combustible peatland area. Polarimetric Decomposition is easier to use to recognize open peatland areas. Besides that, it can also be used to identify roads and canals in peatland areas. Based on the research carried out this time, by implementing the Yamaguchi three-component model-based decomposition, we easily distinct areas that are exposed to peatlands. The dominant surface scattering marks open spaces. By using interferometric SAR technique, we also easily map areas experiencing subsidence. Regions that experience subsidence in peatland areas are usually dry areas with low groundwater conditions. Based on the results of interferometric synthetic aperture radar by using ALOS-2 PALSAR-2 data, subsidence conditions have been found in this area of peatland. SAR ALOS-2 PALSAR-2 image acquired on May 9, 2015, is used as master image and image received on March 25, 2017, is used as a slave image. Phase interferogram generated with multi-looking 5 × 5 pixels, Goldstein filtering 5 × 5 pixels, and normal baseline -43 m, and H-ambiguity 1049.4. Annual subsidence rate average was 2.8 cm/year, minimum 2.5 cm/year, and a maximum of 3.5 cm/year. The subsidence rate then converted to groundwater level information based on Woosten model and validated by using groundwater table measurement from the field. The simulation of groundwater table in average is 69.4 cm, with minimum value 63 cm and maximum value 87 cm. Based on validation and compared to the field data with correlation 0.85, and the area confirmed as high potential of combustible peatland area.

This paper outlines the development work of a new Field Programmable Gate Array (FPGA) based chirp generator from which the new chirp generator is capable of synthesizing 4 pairs of I & Q chirp signals. The paper first proposes a multi-channel Direct Digital Synthesis (DDS) based reconfigurable chirp generator architecture whereby the chirp signal properties for each channel are independently reconfigurable in real-time. In addition, a reconfigurable Timing and Control Unit (TCU) is embedded into the system to generate the important timing synchronization signals which are essential for SAR hardware system. The proposed chirp generator is implemented on a custom-designed FPGA-based hardware platform with 8 on-board independent channels of Digital-to-Analog Converter (DAC). In future, the system will be used in Josaphat Microwave Remote Sensing Laboratory (JMRSL) airborne and spaceborne dual-band (C/X) full polarimetric Circularly Polarized Synthetic Aperture Radar (CP-SAR) system.

This paper presents the development work of a PC-based airborne SAR baseband system that integrates commercial off-the-shelf Arbitrary Waveform Generator (AWG) and highspeed digitizer, and a custom-designed Timing and Control Unit (TCU). The proposed system is general purpose, in which the critical operating parameters such as waveform modulation format, baseband bandwidth, pulse width, pulse repetition frequency, and all the relevant timing and control signals are re-configurable in real-time. As a brief functional summary of the system, it can, i) generates 2-channel (I & Q) of 1.2 GHz (maximum) bandwidth chirp signal with its pulse width ranged from 0.5 us to $100\ \mu\mathrm{s}$ , ii) able to digitize 2-channel (I & Q) of 1 GHz (maximum) bandwidth chirp echoes with on-board 4 G-Samples of recording buffer, and iii) generate accurate and precise timing and control signals with timing resolution of 10 ns. The system is currently deployed as the baseband and control system for Josaphat Microwave Remote Sensing Laboratory (JMRSL) C band airborne full polarimetric Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor built for Earth surface, environmental, and disaster monitoring.

We developed a novel concept for X-band (center frequency 9.4 GHz, HH polarization) airborne SAR, the Wide Area Long Range Synthetic Aperture Radar (WALR-SAR) onboard a Boeing 737–200 aircraft for simultaneous air and terrestrial disaster monitoring. This paper explains the configuration of our WALR-SAR system and slotted array antenna installed on the Boeing 737–200. Ground measurements of the slotted array antenna were realized to measure the characteristics of antenna and its results are discussed in this paper. Flight test of WALR-SAR onboard Boeing 737–200 in Hinotori-X1 (Firebird-X1) mission was performed during the period of 2 to 10 August 2017 at Pare-Pare and Makassar, Indonesia. Results show good performance of the WALR-SAR system and its image acquisition that covers the depression angle 0.5 to 42.0 degrees.

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.

We are developing L-band Circularly Polarized Synthetic Aperture Radar(CP-SAR) for Unmanned Aerial Vehicle (UAV) and microsatellite. Our SAR base-band processor consists of FPGA and PC block. Base-band processor is basically common part which is adaptable to any type of SAR. Hence the pulse specification must be configured to match any platform and observation situation, and in addition, autonomous pulse variability is required to get more precise SAR image. We developed base-band Tx, Rx part and some post processor by using FPGA and PC. In the future, all functions will migrate from PC to FPGA, and complete low cost SAR system consist of only FPGA and Telecommunication devices.

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.