Tatsuharu Kobayashi

CRL/NASDA airborne dual-frequency polarimetric interferometric SAR system

An airborne X and L-band Synthetic Aperture Radar system was developed by the joint project of Communication Research Laboratory and National Space Development Agency of Japan from 1993 to 1996. It is installed on the airplane, Gulfstream II. The resolution is 1.5 m/3.0 m (for X/L-band) in both azimuth and range direction. The both SAR are operated with polarimeter capability. The X-band SAR has cross-track interferometry function. In this report we describe our SAR system, ground processing system and the performance of our system. Furthermore we will discuss motion compensation and interferogram quality.

Development of X-band airborne polarimetric and interferometric SAR with sub-meter spatial resolution

These days, the space-borne SAR becomes one of the powerful instruments to observe the earth surface. On the other hand, a airborne SAR is also important for development of SAR system and analysis technique. Moreover, airborne SAR is able to make immediate observation of disaster area. The National Institute of Information and Communications Technology (NICT) has been developing the new airborne synthetic aperture radar: PÍ-SAR2 since 2006. The PÍ-SAR2 is an airborne X-band polarimetric and cross-track inter-ferometric SAR with sub-meter spatial resolution. The spatial resolution is measured less than 0.5m using some corner reflectors. The PÍ-SAR2 system were completed and began the operation in autumn 2008.

CRL/NASDA airborne SAR (Pi-SAR) observations of sea ice in the Sea of Okhotsk

Abstract Multi-frequency, multi-polarization airborne synthetic aperture radar (SAR) observations of sea ice in the southern Sea of Okhotsk were carried out in February 1999 in conjunction with RADARSAT SAR observations. The final goal of this study is to clarify the backscattering characteristics and to understand the scattering mechanisms of sea ice in the Sea of Okhotsk by using microwave multiparametric SAR. The airborne SAR (Pi-SAR) has two frequencies (X- and L-band) and multi-polarization (HH, VV, HV, VH) with 1.5 m (X-band) and 3.0 m (L-band) resolution. It was developed by the Communications Research Laboratory (X-band) and the National Space Development Agency of Japan (L-band). We show the frequency dependence and polarization properties of radar backscattering from sea ice. We find that it is possible to distinguish ice types by comparing backscattering from sea ice in the X- and L-bands. Investigation of the polarization characteristics at X-band was very useful for detecting the thin-ice area (e.g. nilas and gray ice).

High-resolution dual-bands interferometric and polarimetric airborne SAR (Pi-SAR) and its applications

X-and L-band airborne SAR developed by CRL and NASDA has the capability of high resolution, polarimetry and cross-track interferometry. The radar has been operated since 1995 in the domestic area of Japan aiming at technical capability and validating for various applications. In this paper, we pick up the examples of the volcanic events to show the ability of the Pi-SAR.

Calibration of the high performance airborne SAR system (Pi-SAR2)

NICT (National Institute of Information and Communications Technology, Japan) have developed a high performance airborne SAR system (Pi-SAR2) since 2006, as a successor to the Pi-SAR (X-band). Pi-SAR2 has polarimetric and interferometric functions with high spatial resolution of 0.3–0.6 m in along track (azimuth) direction and 0.3–0.5 m in cross track (slant-range) direction at X-band. In this paper we report the ground based calibration experiment using active radar calibrators (ARC) and corner reflectors (CR) in conjunction with the Pi-SAR2 test flight.

Observation of artificial slicks with SIR-C/X-SAR around Japan

In order to determine suitable parameters for surveillance of oil pollution with imaging radar from space and to investigate the damping mechanism of surface waves by slicks, the experiments to observe controlled slick areas were made around Japan during each of the SIR-C/X-SAR first and second flight missions in April and October 1994, respectively. The artificial slick areas were produced by a small ship with oleyl alcohol. The small ship measured the sea surface conditions including surface wind vector, etc. The dependencies of the damping ratio of NRCS on radar frequencies and polarizations are compared for wind speed and directions, and other surface conditions. The preliminary results of the analysis are shown.

Calibration experiments of advanced X-band airborne SAR system, Pi-SAR2

In the National Institute of Information and Communications Technology, Japan (NICT), we have developed an advanced X-band airborne synthetic aperture radar (SAR) system, Pi-SAR2, since 2006, to succeed the X-band polarimetirc and interferometric airborne SAR, Pi-SAR. The Pi-SAR2 has a higher spatial resolution of 0.3–0.6 m in the azimuth direction and 0.3–0.5 m in the range direction, as well as polarimetric and interferometric observation functions. The calibration experiments of the Pi-SAR2 were carried out as a part its test flights in December 2008 and February 2010. Calibration targets were deployed on a runway of the Taiki Aerospace Experiment Field in Hokkaido, Japan, to be observed.

Performance evaluation on cross-track interferometric SAR function of the airborne SAR system (PI-SAR2) OF NICT

The National Institute of Information and Communications Technology (NICT) developed an airborne X-band SAR system (Pi-SAR2: polarimetric and interferometric SAR 2) to monitor the earths environment and disasters [1]. Pi-SAR2 has polarimetric and interferometric functions with high spatial resolution of 0.3m [2]. In this paper we describe the single-pass interferometric function of Pi-SAR2 and show the performance evaluation on the interferometric function of Pi-SAR2 by using corner reflectors. Moreover we describe the volcanic monitoring by using interferometric SAR.

A backscattering model for bubbles in lake ice and comparisons with satellite and airborne SAR data

The observations using an airborne SAR have been carried out in conjunction with RADARSAT SAR observations of the lake ice in the northeastern part of Hokkaido, Japan, and of the sea ice in the Sea of Okhotsk, in February 1998 and 1999. In situ observations have also been performed on the lakes in order to understand the radar backscattering mechanism. The strong SAR backscattering from the lake ice has been modeled in terms of the angle-dependent Mie scattering from sphere bubbles in the ice. The incidence angle dependence of the calculated backscattering coefficient was derived with frequency and polarization as parameters. The backscattering coefficients obtained by the model calculations were consistent with the SAR data.

Development of the onboard processor for Pi-SAR2

The synthetic aperture radar (SAR) has been utilized for monitoring natural disaster areas because the SAR observation can be performed irrespective of the daylight and weather conditions. To reduce the time from observation to distributing SAR images to the headquarters for disaster control and disaster area, we have developed an onboard processor which is capable of doing a full-spec processing for the airborne SAR called as the polarimetric and interferometric SAR (Pi-SAR2) since 2009. We demonstrated that the developed onboard processor is effective to reduce the time from observation to distribution and the SAR image can be transferred to the ground within 15 min after observation via the communication satellite called as the engineering test satellite VIII (ETS-VIII) in the experiments on March 2011.