TanDEM-X Mission Status, Products and Perspectives

TanDEM-X is an innovative single-pass interferometric radar mission, which is comprised of two formation flying satellites. The TerraSAR-X (TSX) satellite was launched on June 15th 2007, and its almost identically constructed twin satellite TanDEM-X (TDX) was launched on 21st of June 2010. Together they supply high-quality radar data in order to serve two main mission goals: Scientific observation of the Earth and provision of remote sensing data for the commercial market (TerraSAR-X mission), and the generation of a global digital elevation model (DEM) of the Earth's surface (TanDEM-X mission). Between December 2010 and early 2015, radar data of all land surfaces has been acquired and as of September 2016 the final TanDEM-X DEM dataset has been available. This paper provides a final quality assessment of the TanDEM-X global DEM products with respect to the relative and absolute height accuracy and data coverage both at the global and geocell level. In addition, an overview on current mission status is given and new DEM products, which are currently in the scope of the TanDEM-X mission, are described

TanDEM-X DEM 2020: What is new?

In the last years, the TanDEM-X mission systematically acquired data to create another global DEM, the so-called 'TanDEM-X DEM 2020', mainly between September 2017 and mid-2020. This contribution describes the status of the generation of this second global TanDEM-X DEM with special focus on procedural and algorithmic modifications compared to the first global TanDEM-X DEM

TanDEM-X Acquisition Planning and DEM Performance in the Third Year of Operation

TanDEM-X is a spaceborne SAR mission with the goal to derive a global Digital Elevation Model (DEM). The two incorporated satellites fly in a close formation with distances of around 500 m. These small baselines form a single pass bistatic interferometer for accurate DEM acquisitions. The final DEM product will enter a new level of detail and accuracy on a global scale. The absolute height error shall be less than 10 m in a 90% confidence interval at a pixel spacing of 12 m. The vertical height specification for the TanDEM-X mission foresees a 90% point-to-point error of 2 m (4 m) for areas with predominant terrain slopes smaller than 20% (greater than 20%) for a 1° by 1° cell. This presentation gives an overview about the planning and the actual status of the global DEM acquisition. This includes the acquisition plan after the first two years of operation, i. e. two global coverages, including the acquisitions of the Antarctica and difficult terrain. Also, the actual performance status in terms of absolute and relative height error and the narrow relation between the DEM acquisition planning and the performance evaluation is presented

GSOCs Planning Library: History, Generic Features and Lessons Learnt

Mission Planning at GSOC started, in cooperation with other agencies, with manually triggered processes. Within the mission D-2, first experiences have been gathered with the Experiment Scheduling Program of the Marshall Space Flight Center. For succeeding missions, the interactive planning application Pinta has been developed, together with additional tools which support event calculation and automated planning using simple heuristics. A major step forward was the implementation of a fully automated planning system for TerraSAR-X, where it was in charge of the whole mission, including payload and bus. Soon this Mission Planning system had been extended to also include a second satellite and additional mission goals for the TanDEM-X mission. In preparation of a successor mission, desires of internal and external users and operators of the TerraSAR-X/TanDEM-X missions have been analyzed. Even though no successor mission for TerraSAR-X has been selected yet, the Mission Planning team evolved its planning libraries according to the outcome of this analysis and to respond to further lessons learnt, which had been gathered in different other missions throughout the years, such as FireBird, EDRS, Galileo and several LEOPs. This paper describes how GSOCs planning libraries evolved, presents the current status, and presents the current status. It discusses what generic features have proven beneficial, which features were less helpful, and describes obstacles which need to be considered in different missions. The paper concludes with an outlook on how the GSOC Mission Planning team prepares its systems for the future

The TerraSAR-X Mission and System Design

This paper describes the TerraSAR-X Mission Concept within the context of a public-private-partnership (PPP) agreement between the German Aerospace Center DLR and industry. It briefly describes the PPP-concept as well as the overall project organization. The paper then gives an overview of the satellite design, the corresponding Ground Segment as well as the main mission parameters. After a short introduction to the scientific and commercial exploitation scheme, the paper finally focuses on the mission accomplishments achieved so far during the ongoing mission

Flight Dynamics Operations of the TanDEM-X Formation

Since end of 2010 the German TerraSAR-X and TanDEM-X satellites are routinely operated as the first configurable single-pass Synthetic Aperture Radar interferometer in space. The two 1340 kg satellites fly in a 514 km sun-synchronous orbit. In order to collect sufficient measurements for the generation of a global digital elevation model and to demonstrate new interferometric SAR techniques and applications, more than three years of formation flying are foreseen with flexible baselines ranging from 150 m to few kilometers. As a prerequisite for the close formation flight an extensive flight dynamics system was established at DLR/GSOC, which comprises of GPS-based absolute and relative navigation and impulsive orbit and formation control. Daily formation maintenance maneuvers are performed by TanDEM-X to counterbalance natural and artificial disturbances. The paper elaborates on the routine flight dynamics operations and its interactions with mission planning and ground-station network. The navigation and formation control concepts and the achieved control accuracy are briefly outlined. Furthermore, the paper addresses non-routine operations experienced during formation acquisition, frequent formation reconfiguration, formation maintenance problems and space debris collision avoidance, which is even more challenging than for single-satellite operations. In particular two close approaches of debris are presented, which were experienced in March 2011 and April 2012. Finally, a formation break-up procedure is discussed which could be executed in case of severe onboard failures

W42 - a scalable spatial database system for holding Digital Elevation Models

The design of a scalable system for holding spatial data in general and digital elevation models (DEMs) in specific has to account for the characteristics of data from various application fields. The data can be heterogeneous in coverage, as well as in resolution, information content and quality. A database aiming at the representation of world-wide DEMs has to consider these differences in the design of the system with respect to the structure and the algorithms. The database system W42, which is presented in the work at hand, is a scalable spatial database system capable of holding, extracting, mosaicking, and fusing spatial data represented in raster- as well as in vector-format. Design aspects for this task can be specified as holding spatial data in unique data structures and providing unique access functions to the data. These are subject of this work as well as first experiences gained from the implementation of part of the extensions made for the TanDEM-X mission

High speed research system study. Advanced flight deck configuration effects

In mid-1991 NASA contracted with industry to study the high-speed civil transport (HSCT) flight deck challenges and assess the benefits, prior to initiating their High Speed Research Program (HSRP) Phase 2 efforts, then scheduled for FY-93. The results of this nine-month effort are presented, and a number of the most significant findings for the specified advanced concepts are highlighted: (1) a no nose-droop configuration; (2) a far forward cockpit location; and (3) advanced crew monitoring and control of complex systems. The results indicate that the no nose-droop configuration is critically dependent upon the design and development of a safe, reliable, and certifiable Synthetic Vision System (SVS). The droop-nose configuration would cause significant weight, performance, and cost penalties. The far forward cockpit location, with the conventional side-by-side seating provides little economic advantage; however, a configuration with a tandem seating arrangement provides a substantial increase in either additional payload (i.e., passengers) or potential downsizing of the vehicle with resulting increases in performance efficiencies and associated reductions in emissions. Without a droop nose, forward external visibility is negated and takeoff/landing guidance and control must rely on the use of the SVS. The technologies enabling such capabilities, which de facto provides for Category 3 all-weather operations on every flight independent of weather, represent a dramatic benefits multiplier in a 2005 global ATM network: both in terms of enhanced economic viability and environmental acceptability