多時期のHICO画像を使用した太陽非同期軌道の画像の特性の把握

抄録

Sun-synchronous sub-recurrent orbit is a combination of sun-synchronous orbit and sub-recurrent orbit and is the most suitable orbit for Earth observation satellites. A satellite on this orbit regularly passes over the same location on Earth at the same local time. Therefore, the satellite can observe the Earth under the same conditions each time. However, this orbit has a weakness in that the observation frequency is relatively low for high- or medium-spatial-resolution satellites. To overcome this shortcoming, many commercial satellites have a pointing function. In recent years, mini-satellite constellations have attracted attention for their high observation frequency and low launch cost. Novel satellite constellations in non-sun-synchronous orbit have emerged. It is expected that current satellites on sun-synchronous orbit will be constellated with such mini-satellites on non-sun-synchronous orbit. Because non-sun-synchronous orbit has a small inclination, it has disadvantages in that the latitude ranges to be observed are limited and the local observing time at the same observed location varies. However, it has the advantage of making multiple observations on the same day at the same place. It is important to understand the differences in the properties between satellite images captured by satellites on sun-synchronous and non-sun-synchronous orbit in order to develop future applications using both kinds of images. In this research, we conducted a comparison analysis of the radiance spectra of typical objects using multi-temporal images from the Hyperspectral Imager for the Coastal Ocean (HICO) (non-sun-synchronous) and Landsat-8 OLI (sun-synchronous) images. We found that the spectral patterns of the HICO images matched up with those of the Landsat-8 OLI images after the effects caused by different atmospheric conditions and solar and viewing zenith angles were removed. We concluded that there are relatively small differences between satellite images captured by satellites in non-sun-synchronous and sun-synchronous orbit, and that it is important to correct the radiometric effects caused by various solar zenith angles when performing multi-temporal analysis. In the future, it will be necessary to assess the effects due to Bi-Directional Reflectance Distribution Function (BRDF) in different orbits.