# Ten Years of Experience with Scientific TerraSAR-X Data Utilization
###### Abstract  
This paper presents the first comprehensive review on the scientific utilization of earth observation data provided by the German TerraSAR-X mission. It considers the different application fields and technical capabilities to identify the key applications and the preferred technical capabilities of this high-resolution SAR satellite system from a scientific point of view. The TerraSAR-X mission is conducted in a close cooperation with industry. Over the past decade, scientists have gained access to data through a proposal submission and evaluation process. For this review, we have considered 1636 data utilization proposals and analyzed 2850 publications. In general, TerraSAR-X data is used in a wide range of geoscientific research areas comprising anthroposphere, biosphere, cryosphere, geosphere, and hydrosphere. Methodological and technical research is a cross-cutting issue that supports all geoscientific fields. Most of the proposals address research questions concerning the geosphere, whereas the majority of the publications focused on research regarding \"methods and techniques\". All geoscientific fields involve systematic observations for the establishment of time series in support of monitoring activities. High-resolution SAR data are mainly used for the determination and investigation of surface movements, where SAR interferometry in its different variants is the predominant technology. However, feature tracking techniques also benefit from the high spatial resolution. Researchers make use of polarimetric SAR capabilities, although they are not a key feature of the TerraSAR-X system. The StripMap mode with three meter spatial resolution is the preferred SAR imaging mode, accounting for 60 percent of all scientific data acquisitions. The Spotlight modes with the highest spatial resolution of less than one meter are requested by only approximately 30 percent of the newly acquired TerraSAR-X data. TerraSAR-X; synthetic aperture radar (SAR), radar mission; remote sensing 201810.1170.3390/rs100811700103390/rs100811700103390/rs100811700390/rs1008117  
SAR can be operated in Spotlight, StripMap and ScanSAR mode providing different spatial resolutions and areal coverages with two polarizations in various combinations. The TerraSAR-X mission pursues two main goals. The first is the provision of high-quality, multimode X-band SAR-data for scientific research and applications. The second goal is to support the establishment of a commercial earth observation (EO) market and to develop a sustainable EO-service business, based on derived information products. This paper reviews the TerraSAR-X mission solely from the perspective of scientific data utilization. It considers technical and operational issues and provides a resume of the mission's utilization and a background for future EO mission designs. In general, earth observation data are an invaluable source of information for geoscientific research which, in turn, has resulted in a growing body of associated publications. NASA's Seasat was the first successful civilian SAR project in space, operating for 100 days in 1978 [2]. The SIR-C/X-SAR mission provided the unique capability for investigating the suitability of different frequencies and polarizations for applications in ecology, geology, hydrology, and oceanography [3]. Europe, in particular the European Space Agency, Canada and Japan have run SAR missions since the early 1990s. In this regard, these SAR missions [4; 5; 6; 7], their objectives [8; 9] and design, the sensors and other technical aspects were of interest [1; 2; 9; 10; 11; 12; 13; 14]. Also the summary of a research call [15] and the potential for specific geoscientific applications are presented [16; 17; 18; 19; 20]. To date however, a comprehensive review of a high-resolution SAR system such as TerraSAR-X considering the technical capabilities, individual user needs in the relevant application fields and the system utilization associated with it has not been published in the peer-reviewed literature yet.