<title>Development of an onboard spectro-polarimeter for Earth observation at NAL</title>

Abstract

Various methods, techniques and sensors for Earth observation are being developed worldwide as the necessity of protecting the Earth's environment increases. In particular, polarimetric analysis of solar rays reflected from the Earth's surface is expected to play an important role in future Earth environment observation. A new type of spectro-polarimeter based on a liquid crystal tunable filter (LCTF) has been developed at NAL for such analysis. Efforts are now under way to put this sensor to practical use in airborne or satellite-based remote sensing of the Earth's environment by developing a sensor package and onboard observation system based around it. This paper first presents the operational principle and construction of the LCTF spectro-polarimeter, which captures images in the 400 - 720 nm wavelength band. Next, an outline of an onboard observation system incorporating the spectro-polarimeter is described and its applicability to airborne remote sensing discussed. The performance of the observation system is then shown based on experimental results. Other possible applications of the sensor are presented, and finally, the results of the evaluation of the observation system, e.g. hyper-spectral resolution of less than 10 nm, are summarized in the conclusion.