Tandem-L is a proposal for a SAR mission with two L-band satellites which aims to observe globally dynamic processes of the Earth's surface. The mission will provide, on the one hand, 12 higher-level products addressing the problematics of, for example 3D forest structure measurements or large scale deformation monitoring. On the other hand, it will deliver focused SAR data to generate other products, which will contribute to the understanding of e.g. ice or ocean dynamics. This paper presents the current systematic generation concepts of these products as outlined during the first part of the phase B1.

Tandem-L is a proposal for an innovative L-band SAR mission for the systematic observation of dynamic processes on the Earth's surface. The mission concept is based on two SAR satellites flying in close formation featuring latest digital beamforming techniques in combination with a large deployable reflector for increasing the swath width and imaging resolution. This enables innovative operation modes such as polarimetric SAR tomography for determining the vertical structure of vegetation and ice. With novel imaging and processing techniques and the vast recording capacity of up to 8 Terabyte/day, it will provide vital information for solving pressing scientific questions in the biosphere, geosphere, cryosphere, and hydrosphere and will make an essential contribution for a better understanding of the Earth system and its dynamics This paper gives an overview of the Tandem-L mission project which has successfully passed the intermediate system requirements review of Phase B1.

In the past years we have exploited the TanDEM-X elevation model for impact crater research. This is the first high-resolution global DEM which permits accessing all confirmed impact structures. We demonstrate that the high horizontal and vertical accuracies, coupled with the dense pixel grid, allow studying the morphologies of simple and complex craters over a wide diameter range.

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.

The satellite of the TerraSAR-X mission, called TSX, was launched on 15 June 2007 and its identically constructed twin satellite TDX, which is required by the mission TanDEM-X, launched on 21 June 2010. Together they supply high-quality radar data in order to serve two mission goals: Scientific observation of Earth and the provisioning of remote sensing data for the commercial market (TerraSAR-X mission) and the generation of a global digital elevation model (DEM) of Earth’s surface (TanDEM-X mission). On the occasion of the 10th anniversary of the mission, the focus will be on the development of the TerraSAR-X system during this period, including the extension of the ground segment, the evolution of the product portfolio, dedicated mission campaigns, radar experiments, refinement of the satellite operations and orbit control, and the results of the performance monitoring. Despite numerous interventions in the overall system, we managed to incorporate new scientific and commercial requirements and to improve and enhance the overall system in order to fulfill the increasing demand for Earth observation data without noticeable interruptions to ongoing operations.

The history of the TerraSAR-X and TanDEM-X mission planning system is briefly presented. In addition to the not trivial demands of the first years, special attention is given to the challenges of recent years. Here the TanDEM-X science phase, conducted between 2014 and 2016, is the most prominent feature. It is shown how agile software engineering methods can help to keep the already achieved system robustness, and how further enhancements can easily be incorporated.

Currently, about 190 geological structures are identified to be of impact origin. About 120 of these can be traced in the terrestrial surface topography. The rest is hidden from direct view by sedimentation, erosion or submersion. In the past three years we have exploited the TanDEM-X elevation model for impact crater research. The TanDEM-X DEM is the first high-resolution global DEM which permits accessing all confirmed impact structures. Of particular interest was how the TanDEM-X DEM compares with other global elevation models. Our work illustrates the potential of the TanDEM-X DEM for remote sensing studies of impact craters and even permit to estimate how the TanDEM-X elevation data may be used to find new impact crater candidates by autonomous search methods.

This paper reports on the current status and recent extensions of the TerraSAR-X ground segment in its ninth year of operation.

In the past two decades space-borne sensors have provided us with high-quality elevation data of the solid surfaces of several large bodies of the solar system. For Earth, the German TanDEM-X mission delivers a new digital elevation model (DEM) with unprecedented accuracy. From December 2010 to March 2015 the two X-band radar satellites TerraSAR-X and TanDEM-X have been operated in close formation as a single-pass SAR interferometer. The data acquired in bistatic mode are processed to yield a global DEM with an independent pixel spacing of 12 m and an absolute height error of < 10 m. It covers all land surfaces between 90° S and 90° N latitude.

Since 2007, the TerraSAR-X mission provides high-resolution SAR data with high quality and an unprecedented geometric accuracy to both commercial and science users. The first satellite TSX was supplemented by a second, mostly identical, satellite TDX in 2010 for the generation of a global Digital Elevation Model (DEM) in the frame of the TanDEM-X (TerraSAR-X Add-On For Digital Elevation Measurements) mission. Since then the two missions share a joint space segment consisting of both TSX and TDX and a common ground segment which was first developed for TerraSAR-X and had been later extended for TanDEM-X. While TanDEM-X uses both satellites (nominally one in receive-only mode) for an acquisition, TerraSAR-X data are acquired by either one of the two satellites. It is this sharing of one ground segment which necessitated on-going updates of the TerraSAR-X ground segment in accordance with the TanDEM-X mission constraints. Furthermore, both satellites show a good health and resources, specifically the TSX which has considerably exceeded its nominal life time of 5.5 years by now, and thus justify on-going improvements to even better support user needs. This presentation summarizes the current SAR imaging modes and product portfolio and describes the recent ground segment system updates. Among these are the following: After having completed the global DEM data acquisition, the TanDEM-X mission currently focuses on the provision of radar data products for a number of new science technology related applications based not only on a bistatic, but also on a pursuit mono-static flight configuration. This pursuit mono-static flight configuration with its time lag of about 10 seconds between the two satellites allowed the processing of TanDEM-X acquisitions into TerraSAR-X product pairs which are offered to both the TerraSAR-X and the TanDEM-X science community. This includes fully polarimetric and along-track interferometry data acquired in the dual-receive antenna configuration. Receiving stations may be combined in a so-called TerraSAR-X ground station pool. Data takes ordered for such a station pool (instead of a single receiving station) are then planned for downlink to one or even several stations (in case of a partial downlink) by the mission planning leading to a much better exploitation of the limited downlink resources. Originally, the TerraSAR-X mission was not designed for near-real time (NRT) applications. Thus, the NRT functionality had to be included “as best as possible” within given constraints. Due to a growing demand for TerraSAR-X NRT products, the NRT capability was extended considerably over the last years. The TerraSAR-X product portfolio now supports maritime applications like ship and oil detection, wind and wave products are currently under integration. An improved mission planning and the downlink station pool concept leads to reduced product latencies.

Between December 2010 and early 2015 the German Aerospace Center (DLR) operated the X-band radar satellites TerraSAR-X and TanDEM-X in close formation as a single-pass SAR interferometer. Data from Earth’s entire land surface acquired in bistatic mode permitted generation of a global high quality digital elevation model (DEM). Its accuracy, both in resolution and height, exceeds similar existing datasets from spaceborne mission. Because of its excellent quality and global coverage, the TanDEM-X DEM will be a very useful data source in support of impact crater studies. We report on the status of the TanDEM-X DEM generation and present results for about 90 impact structures, covering the entire spectrum of crater types, i.e. from small and simple to large, complex and eroded.

Between December 2010 and early 2015 the German Aerospace Center (DLR) operated the X-band radar satellites TerraSAR-X and TanDEM-X in close formation as a single-pass SAR interferometer. Data from Earth’s entire land surface acquired in bistatic mode permitted generation of a global high quality digital elevation model (DEM). Its accuracy, both in resolution and height, exceeds similar existing datasets from spaceborne mission. Because of its excellent quality and global coverage, the TanDEM-X DEM will be a very useful data source in support of impact crater studies. We report on the status of the TanDEM-X DEM generation and present results for about 90 impact structures, covering the entire spectrum of crater types, i.e. from small and simple to large, complex and eroded.

TSX, an advanced synthetic aperture radar satellite, launched on June 15 th 2007 and the almost identically rebuild TDX satellite, launched on June 21 th 2010 serve two challenging radar missions. First: The TerraSAR-X mission, providing high quality SAR data for scientific and commercial purposes, covering a large variation of SAR modes from a high resolution staring spotlight mode with 1 m resolution to large area wide ScanSAR mode offering up to 260 km swath width. Second: The TanDEM-X mission, generating a global digital elevation model (DEM). This paper focuses on the TerraSAR-X mission after 8 years in space, the status of the both spacecraft, as well as the ground segment activities.

Since 2007, the TerraSAR-X mission provides high-resolution SAR data with high quality and an unprecedented geometric accuracy to both commercial and science users. The first satellite TSX was supplemented by a second, mostly identical, satellite TDX in 2010 for the generation of a global Digital Elevation Model (DEM) in the frame of the TanDEM-X (TerraSAR-X Add-On For Digital Elevation Measurements) mission. Since then the two missions share a joint space segment consisting of both TSX and TDX and a common ground segment which was first developed for TerraSAR-X and had been later extended for TanDEM-X. While TanDEM-X uses both satellites (nominally one in receive-only mode) for an acquisition, TerraSAR-X data are acquired by either one of the two satellites. It is this sharing of one ground segment which necessitated on-going updates of the TerraSAR-X ground segment in accordance with the TanDEM-X mission constraints. Furthermore, both satellites show a good health and resources, specifically the TSX which has considerably exceeded its nominal life time of 5.5 years by now, and thus justify on-going improvements to even better support user needs. This presentation summarizes the current SAR imaging modes and product portfolio and describes the recent ground segment system updates. Among these are the following: After having completed the global DEM data acquisition, the TanDEM-X mission currently focuses on the provision of radar data products for a number of new science technology related applications based not only on a bistatic, but also on a pursuit mono-static flight configuration. This pursuit mono-static flight configuration with its time lag of about 10 seconds between the two satellites allowed the processing of TanDEM-X acquisitions into TerraSAR-X product pairs which are offered to both the TerraSAR-X and the TanDEM-X science community. This includes fully polarimetric and along-track interferometry data acquired in the dual-receive antenna configuration. Receiving stations may be combined in a so-called TerraSAR-X ground station pool. Data takes ordered for such a station pool (instead of a single receiving station) are then planned for downlink to one or even several stations (in case of a partial downlink) by the mission planning leading to a much better exploitation of the limited downlink resources. Originally, the TerraSAR-X mission was not designed for near-real time (NRT) applications. Thus, the NRT functionality had to be included “as best as possible” within given constraints. Due to a growing demand for TerraSAR-X NRT products, the NRT capability was extended considerably over the last years. The TerraSAR-X product portfolio now supports maritime applications like ship and oil detection, wind and wave products are currently under integration. An improved mission planning and the downlink station pool concept leads to reduced product latencies.

We use the global digital elevation model (DEM) generated in the TanDEM-X mission for mapping further confirmed terrestrial impact craters. This DEM provides the most accurate spaceborne global elevation data. It permits detailed studies of the topography of the sites of simple and complex structures with unprecedented accuracy.

The TanDEM-X mission generates a global digital elevation model (DEM) with unprecedented properties. We use it for mapping confirmed terrestrial impact craters as listed in the Earth Impact Database. Both for simple and complex craters detailed investigations of the morphology of the particular structure and of the surrounding terrain can be performed.