Hitoshi Nohmi

Relation Between L-band Microwave Penetration / Backscattering Characteristics And State Of Trees

In this paper we describe relationship between L-Band microwave penetration / backscattering characteristics and state of trees. The result of the study shows that there are a substantial correlation between quantitative condition of trees (stand density, total breast height area, total breast height area x mean height) and attenuation / backscattering cross section of L-band microwave.

Passive millimeter-wave camera with interferometric processing

A proto-type passive millimeter-wave (MMW) camera with interferometric processing has been developed and evaluated to confirm the feasibility of the interferometric MMW camera and to study the characteristics of MMW images. This proto-type camera is comprised of the minimum configuration as an interferometric imager which consists of two sets of a W-band receiver with a horn antenna, and a digital processing unit. The position of these two antennas with W-band front-end moves on the precision linear slider in horizontal and vertical axis. The coherently amplified two channel signals are digitized and processed in the hardware processor. The process is comprised of correlation of all combination of each axis data, and integration to improve the signal to noise ratio. The integrated data is processed to make an image by matched filter processing. The integration time is from 1mS to 10S depending on required integration gain. The maximum synthesized antenna aperture size is 1m for horizontal axis and 50cm for vertical axis. In this paper, the evaluation of the proto-type P-MMW camera is descried. After the evaluation, some improvement was scheduled and conducted. Also, future plan for a real-time camera using this technique is presented .

Airborne repeat-pass INSAR system

Repeat-pass interferometric SAR (INSAR) is considered an excellent tool to detect very slight Earth crustal movement caused by an earthquake, a volcano activity, and so on. The authors developed an airborne repeat-pass INSAR system which can make very precise repeat-pass flights for interferometry. A method has been devised for getting the highly precise antenna motion using the phases from corner reflectors. In this paper, an outline of their airborne repeat-pass INSAR system, the method of measuring the precise antenna motion data and the first results in a test flight to verify the possibility of airborne repeat-pass INSAR are described.

The repeat-pass interferometric SAR by Pi-SAR(L)

This paper describes the system and experiment of Pi- SAR(L) repeat pass interferometric SAR To obtain a high- quality interferometric image, it is necessary to make two flights on the same pass and observe in the same direction. We built a flight control system utilizing the preinstalled autopilot. This system measures position and altitude precisely with using a differential GPS, and controls the flight pass to be within virtual tube of 10 m diameter. The antenna rotation mechanism was also installed to control the observation direction. The repeat-pass flight has been conducted many times. The flights were stable and the deviation was within a few meters for both horizontal and vertical even in the gusty condition. The SAR data were processed in time domain based on range Doppler algorism to make the complete motion compensation. The interferometric image processed after precise phase compensation is shown.

The flight test of Pi-SAR(L) for the repeat-pass interferometric SAR

This paper describes the experiment of the repeat pass interferometric SAR using Pi-SAR(L). The air-borne repeat-pass interferometric SAR is expected as an effective method to detect landslide or predict a volcano eruption. To obtain a high-quality interferometric image, it is necessary to make two flights on the same flight pass. In addition, since the antenna of the Pi-SAR(L) is secured to the aircraft, it is necessary to fly at the same drift angle to keep the observation direction same. We built a flight control system using an auto pilot which has been installed in the airplane. This navigation system measures position and altitude precisely with using a differential GPS, and the PC Navigator outputs a difference from the desired course to the auto pilot. Since the air density is thinner and the speed is higher than the landing situation, the gain of the control system is required to be adjusted during the repeat pass flight. The observation direction could be controlled to some extent by adjusting a drift angle with using a flight speed control. The repeat-pass flight was conducted in Japan for three days in late November. The flight was stable and the deviation was within a few meters for both horizontal and vertical direction even in the gusty condition. The SAR data were processed in time domain based on range Doppler algorism to make the complete motion compensation. Thus, the interferometric image processed after precise phase compensation is shown.