# Ten Years of Experience with Scientific TerraSAR-X Data Utilization
## 3 Results
### Analysis of the Scientific TerraSAR-X Acquisitions  
The predominant share of the acquisitions (59 percent) throughout the entire operational phase of the TerraSAR-X mission was ordered in the three to five meter resolution StripMap mode. Only 14 percent were acquired in ScanSAR mode, benefitting from the coverage of larger areas. The highest spatial resolution is offered by the different Spotlight modes and 28 percent are allotted to these modes. This report does not distinguish between the different polarizations. Single, dual and quad-polarized data are jointly considered. The trends and the share of the different modes over time are presented in Figure 10.  
The interest in the different modes was quite uniform at the beginning of the mission. In the following years the demand varied but has been stable since 2012. Approximately two-thirds of all acquisitions are performed in StripMap mode, 30 percent require the high spatial resolution of the Spotlight modes and the remaining 5 percent are interested in a larger coverage and order ScanSAR products. Figure 11 provides more detail about the utilization of the Spotlight modes.  
Figure 11: Proportion (in percent) of TerraSAR-X Spotlight modes on an annual basis from 1 st January 2008 to 30 th June 2017: The highest resolution Staring Spotlight mode displayed on top, the high-resolution HR-Spotlight mode in the middle and the standard resolution Spotlight mode at the bottom.  
Figure 10: Proportion (in percent) of TerraSAR-X modes on an annual basis from 1 January 2008 to 30 June 2017: High-resolution Spotlight mode displayed on top, the medium resolution StripMap mode in the middle and the coarser resolution ScanSAR mode at the bottom.  
The interest in the highest resolution modes was the highest at the beginning of the mission. Almost 40 percent of all acquisitions were performed in the Spotlight modes. This demand dropped until 2011, but then increased again to a relatively constant level of 30 percent. In 2013, the Staring Spotlight mode was introduced. Remarkably, the very high-resolution potential is well accepted but did not lead to a systematic increase of the percentage of Spotlight orders in relation to the other modes.  
The proportion of single and dual polarized acquisitions has been relatively constant throughout the mission's operating phase. However, an increase in the request of dual polarized data since 2016 is noticeable. On average, 79 percent of all scientific data takes were acquired in either HH or VV polarization. 21 percent requested dual polarization (HH/VV, HH/HV, VV/VH) and a few experimental data sets acquired in full polarization (0.4 percent). In 2017, the proportion changed to 60 percent of the acquisitions in single and 40 percent in dual polarization.  
Figure 12 shows the geographic and quantitative distribution of the 100,711 scientific acquisitions of the TerraSAR-X mission. Note that the number of acquired scenes and not the number of individual PIs was taken into account for this map. Hence, areas where more scenes were acquired for scientific studies are represented to a higher extent. The number of scenes available in the archive per \(1^{\circ}\times 1^{\circ}\) tile decreases from red (representing intensively observed areas) via orange, yellow and green to blue.  
The research sites are globally distributed, with a large concentration on central Europe. However, other sites are regularly monitored whenever the system is not fully utilized. TerraSAR-X data are provided in the frame of several internationally coordinated activities as well, including the GEOHazard initiative [187], which monitors volcanos and earthquake-threatened areas, the Global Forest Observations Initiative (GFOI) [188] and the Polar Space Task Group [189]. In these cases, TerraSAR-X provides high-resolution SAR data of hot spots for local analyses.