TerraSAR-X / TanDEM-X Mission and Calibration Status with a Focus on Rainforest LTSM Time-Series Data

Abstract

After more than fifteen years of successful radar operations in space, the German twin radar satellites TerraSAR-X (TSX) and TanDEM-X (TDX) continue to deliver SAR products at their well-known excellent image quality, despite the advanced age of both instruments. This high level of data quality relies on a continuous monitoring of the instrument health based on dedicated long-term system monitoring (LTSM) data acquisitions over both natural distributed and man-made point targets. As an update to the series of previous presentations on TerraSAR-X and TanDEM-X at CEOS, in the first part of this presentation we will give an overview of the TSX/TDX mission status, discuss instrument health, the current calibration status and give an outlook on the planning of the upcoming mission phases. In support of the ongoing discussion on requirements of natural distributed targets for usage in SAR system calibration we then focus on the long-term system monitoring time series of data acquired over the Amazon rainforest for monitoring both satellite's RF frontend performance. Several sites of the Amazon rainforest have been regularly acquired for LTSM purposes over now more than 15/17 years since start of the TerraSARX mission. We analyze the potential of such a long time series for understanding variations in observed rainforest backscatter even beyond the originally specified radiometric accuracy of the TSX/TDX mission. Expanding on previous contributions we will further quantify effects observed in the LTSM dataset. At the workshop, we present an analysis of the measured backscatter variation over (i) different LTSM-sites (spatial backscatter variation over the rainforest), (ii) morning vs. evening data acquisitions and (iii) TerraSAR-X vs. TanDEM-X instruments. We will discuss the observed differences and spatiotemporal variations in terms of giving guidance in how to best utilize these sites for calibration and LSTM of current and future SAR missions, e.g., in the framework of SARCalNet.