Michael Geyer

TerraSAR-X Mission Planning System: Automated Command Generation for Spacecraft Operations

On June 15, 2007, TerraSAR-X was successfully launched from Baikonur, Kazakhstan. On board TerraSAR-X, a high-resolution X-band synthetic aperture radar (SAR) instrument is being operated as the primary payload. The user community requesting SAR products is composed of commercial and scientific partners as documented in a public-private-partnership agreement. The operations of the TerraSAR-X bus as well as payload operations are performed by the Mission Operations Segment (MOS). The Mission Planning System (MPS), which is a part of the MOS, has been designed to handle complex payload and standard bus operations in an automated manner. The purpose of this paper is to describe the concepts and the TerraSAR-X realization of the MPS.

The joint TerraSAR-X / TanDEM-X mission planning system

This paper recalls the essential system requirements and elements for the joint TerraSAR-X / TanDEM-X mission planning system. Its commissioning approach, tests and results are described in detail.

TerraSAR-X/TanDEM-X Mission Planning Handling Satellites in Close Formation

This paper presents mission planning aspects of the future TanDEM-X mission scheduled for launch in 2010. In 2007 the TerraSAR-X satellite was successfully launched. Its payload consists of an earth observing Synthetic Aperture Radar, which supplies high resolution radar images. The primary goal of the TerraSAR-X mission is to supply the commercial and scientific users with radar image data on request. The TanDEM-X satellite is a nearly identical copy of the TerraSAR-X satellite. The two satellites will be orbiting the Earth in a close formation with distances from 250m to 500m. The radar instruments on both satellites may be used synchronously in a bi-static mode: One or both satellites actively transmit radar pulses; the echo is received by both satellites. This configuration gives a stereoscopic view such that information comprising all three dimensions can be retrieved from the data. The TanDEM-X mission goal is to generate a digital elevation model covering the whole Earth’s surface. In addition, the radar instruments on both the TerraSAR-X and the TanDEM-X satellites will still be operated in the TerraSAR-X mono-static mode and therefore both satellites may support the TerraSARX mission goals. The combined TerraSAR-X / TanDEM-X mission planning system will handle the two satellites as well as two completely different missions with their different mission goals. As a consequence, the new combined TerraSAR-X / TanDEM-X mission planning system not only has to support two satellites with their mutual constraints, but also will handle two different missions at the same time: the long-term mapping approach of the TanDEM-X mission and the short-term on-demand approach of the TerraSAR-X mission. There are two critical issues regarding the operational safety of the formation flight: the close distance of the two satellites implies a significant collision risk in case of anomalies. Next, illuminating the other satellite with radar pulses can cause severe damage to the illuminated satellite.

GECCOS – the new Monitoring and Control System at DLR-GSOC for Space Operations, based on SCOS-2000

At DLR-GSOC, the German Space Operations Center, the Satellite Monitoring and Control System (MCS) originating from ESA-SCOS-2000 was adapted for the first time for the mission CHAMP, beginning from the year 2000. Since then a custom GSOC branch of this MCS is in active development, both with respect to mission-specific adaptations as well as multi-mission related , ultimately leading to GSOC’s own MCS called “GECCOS” – the GSOC Enhanced Commandand Control System for Operating Spacecrafts. GECCOS, based on SCOS-2000 Release 3.1, represents a generic MCS and supports a broad set of scientific and commercial satellite platforms: CHAMP, GRACE, TSX (TerraSAR-X, TanDEM-X, PAZ), EnMAP, TET, SmallGEO (HAG-1, EDRS-C, H2Sat), Spacebus 3000 (COMSATBw 1&2), Eurostar 3000 (EDRSA) and in future SWARM Bus (GRACE-FO). Additionally, GECCOS has the capability to act as MCS as well as Central Check-out System (CCS) so it is capable of supporting S/C projects from AIT phase until mission operations phases. This has been demonstrated in the context of the missions TerraSAR-X, TanDEM-X, PAZ, TET and BIROS. That approach offers significant advantages regarding inherent validation of the future S/C operational MCS, being compatible with the S/C database (in SCOS2000 terms Mission Information Base, MIB) as well as with flight control procedures (FCP), already within early AIT and S/C checkout phases. This is a key driver for the use of GECCOS within SmallGEO platform based S/C operations as their CCS is also based on SCOS-2000 Release 3.1. kernel. The combination of CCS and MCS data handling kernels is an important paradigm which is also one of the key drivers for future MCS/CCS projects like the European Ground Systems Common-Core (EGSCC), a project led by ESA. In this contribution we present the main adaptations and advantages GECCOS offers when compared to classical MCS like ESA SCOS-2000 and point out how it can fulfill the MCS requirements for upcoming Missions operated at modern control centers.

Tailoring the TerraSAR-X Mission Planning System to PPP Needs

The TerraSAR-X earth-observing radar mission, scheduled for launch in October 2006, has been set up as a public private partnership (PPP) to serve both scientific and commercial needs. The TerraSAR-X ground segment has to deal with the scientific community on the one hand and a commercial exploiter on the other hand. The mission planning system has been designed to satisfy the scientific and commercial partners, having own structures and motivations and sometimes-diverging interests, in the frame of a common mission. Both partners are interested in a schedule that is stable with respect to the time. Also the commercial exploiter has the strong interest to provide his final customers with reliable information. For a stable schedule, order behaviour is crucial: the more orders are known in advance, the more steady the execution timeline will behave in time. On the science side, the science coordinator will guide the individual scientists and their orders in a review process. As a result, the typical science order will be set up and fed into the system well in advance of the envisaged execution time. On the other side, the nature of the commercial market will lead to orders that come in just-i n-time and have to be scheduled and produced as fast as possible. In addition, there will be short-time high-priority orders from both sides as well as the need to schedule data-takes in respond to emergency tasks. As a consequence, the task of establishing an optimising planning process is demanding: The high-priority orders, with execution times in the very near future, will conflict with the already established schedule. Even during the design and implementation phase, the mission planning system had to be adapted to the changing needs of the commercial market leading to new requirements. On such a basis, the optimisation criteria for the planning process are hard to quantify. As a solution, the TerraSAR-X planning system implements a priority concept, agreed by the science and commercial part. A quota concept wi ll make sure that both sides will get, on time average, a fair share of the satellite resources. Periodical strategic planning meetings, with members from the science and commercial side as well as from mission management, will be supported by experienced mission planning engineers with statistical information regarding the past mission as well as the order situation in the future. The paper will outline the experiences as by shortly before the launch. It will describe how initial concepts had to be modified and where add-ons emerging from the starting commercialisation affected the system design.

Rethinking Ground Systems: Supporting New Mission Types through Modularity and Standardization

We begin to see an increase in the diversity of todays space missions: Small student-designed satellites, unique scientific missions and fleets of commercial spacecraft are just a few of those mission types. In order to cater for new demands on the ground system and to offer customer-tailored solutions we started to rethink the foundations of the German Space Operations Center (GSOC) ground system in terms of a service-oriented architecture approach using standardized technology, mainly CCSDS Mission Operations services. We show how we modularize our ground system, identify and clearly name the mission functions present in the current system complete with timing information and data size requirements. We illustrate this process by employing a concrete prototypical mission with involvement across all departments from antenna control, data processing to mission planning and flight dynamics, and hint at the challenges encountered along the way. The chosen technical solution is motivated and explained, and aspects of deployment, performance, and security are discussed.

Towards a Modular And Flexible New Ground System

At GSOC, we start developing a concept for a modular and flexible ground system. Applying a service oriented architecture and using standardized interfaces, such a system will help to support upcoming missions of all kinds, especially in the context of the increasing amount of small satellites. Such a system will offer complete new ways to organize space operations in form of distributed operations. Also dedicated setups for special mission phases will become much easier as the system is designed to be dynamically deployed or changed. Providing the opportunity to access the system not only from within the control center allows using the experts wherever they are located and reduces the need to double such resources.