The main focus of the Satellite Systems Engineering Group is the lead of analyses and simulations for satellite missions and satellite systems to support in house and external satellite projects activities as well as the support of customers regarding technical controlling aspects. The group activities are organized in 4 main sections and include classical systems engineering, system simulations, development of simulators and customer support services.
This section is performing analyses for the end-to-end chain of spaceborne systems including satellites or general platforms, payloads and launch vehicles. Considering the user and mission constraints the platform subsystems and their interactions on system level are analyzed in order to verify if they fulfill the regarding requirements. Payload on platform and platform in launch vehicle accommodation analyses are made by state of the art CAD/CAM systems using self developed 3D databases containing common platforms and launch vehicles. Figure 1 shows a typical spacecraft configuration and the satellite in a launch vehicle accommodation analysis.
|Figure 1: Accommodation analyses|
The simulation activities cover the design, engineering and verification phases of space projects. Space or airborne systems are simulated regarding coverage, revisit-time, repeat cycles, etc. to investigate if the proposed solutions fulfill the mission objectives and the user requirements. As an example for a simulation result Figure 2 shows the access pattern of a target for different satellite systems.
|Figure 2: Access pattern of a target for different satellite systems|
Orbit selections are analyzed and optimized to obtain the best coverage and revisit cycles for specific areas of interest. Mission simulations using realistic user scenarios are performed to receive information about imaging capacity and system limitations under operational conditions considering manoeuvres and service intervals, power and data storage constraints. As part of mission design Figure 3 illustrates the analysis for a satellite attitude control system.
|Figure 3: Attitude control system analysis|
Many of the activities described in Chapter 2.1 and 2.2 are supported by the mission planning tool which is developed by the Satellite Systems Engineering Group and used for scenario design, general analysis, visualization, report generation and mission planning. The self developed modules for high-end coverage analysis, mission planning and –optimization, mission analyisis and satellite simulation are connected and integrated and built up in the Multi Satellite Mission Planner (MSMP). It has interfaces with COTS products to ensure the compatibility with industry. The mission simulator allows the simulation of any mission scenario based on satellites or other objects (drones, jets, ships, land vehicles) and its interaction. User driven scenarios including imaging or interactivities between the described objects can be simulated and optimized. The results can be used for system design purposes as well as for system verifications during the real operation. All simulations can be visualized in 3D for presentations or movie generation. The Satellite Simulator allows in the current version the simulation of the satellite's Orbit Control subsystem and Power subsystem and delivers information for satellite manoeuvring and power conditions into the Mission Simulator. Figure 4 shows the modular architecture of the Mission Planning Tools, Figure 5 the schematic concept for the simulation of user scenarios optimizing imaging schedules with tasks of multiple priorities.
|Figure 4: Shell model of mission planning tool|
|Figure 5: Schematic concept of mission planning|
All the described activities performed in the Satellite Systems Engineering Group are used to support DLR internal and external project or programme activities. The strong cooperation to the other groups of the Department Reconnaissance and Security allows technical and scientific services on system level beginning with the evaluation and design phase up to the operational phase for platforms, SAR payloads and user centres. The Satellite Systems Engineering Group is involved in Security Relevant Earth Observation projects. Furthermore, the DLR MAPSAR study and TerraSAR-X were supported by the Group.