Transmission data reduction by coding data acquired at satellites flying in close formation

摘要

並走する二衛星に合成開口レーダを搭載して地表面の移動目標検出を行なう際には，二衛星の大量な@@ 観測データを地上に伝送することが必要であり，広帯域な無線回線が必要となる課題がある.本稿では，この課題@@ を解決するために，並走衛星から撮像する同一地表面の画像情報が強い相関を持つことに着目し，複数信号源のデ@@ ータの冗長性を取り除き，差分情報を伝送することにより，全体としてのデータ伝送量を削减する方式を提案する.%The Synthetic Aperture Radar obtains the information of moving target on the earth surface using MTI (Moving Target Indication) technique, which is a differentiation of the earth surface image data acquired successively, either at two antennas mounted on one, satellite, or at two satellites flying in close formation. In the latter case, the differentiation operation is normally applied in the ground station, and each satellite needs to transmit the acquired voluminous data to the ground station independently, consuming broad downlink bandwidths. The earth surface image data acquired at the two satellites have a strong correlation since the static background image data other than the moving targets are essentially the same except for the noise factors. We focus on this fact and claim that the transmission data should be reduced by taking off the redundancy of the two data and sending the differential parts only. In this paper, we first explain the coding theory discussion related to this redundancy suppression. We discuss source, channel and network coding, and also the Slepian-Wolf theorem for two correlated sources. Then, we propose a coding and compressing scheme for a simplified model. Next, we generalize it to apply to a more realistic model and present a procedure of the proposed scheme.