In the years 2010-2014 the satellites TSX and TDX collected all the Synthetic Aperture Radar (SAR) data necessary to fulfill the primary TanDEM-X mission objective: the generation of a global digital elevation model with unprecedented accuracy. In September 2014, when the necessary data set was almost complete, a transition to the so-called science phase took place. Its focus was the implementation of the TanDEM-X secondary mission objectives. TSX and TDX fly in close formation in low Earth orbit in order to form a SAR interferometer in space with adjustable interferometric baselines. Due to the diversity of scientific applications, the science phase was marked by several baseline and hence formation changes and, in addition, by unusual formation geometries. Modifications to the proven operational handling of SAR payloads and the data downlink became necessary as well as the adaptation of existing safety concepts. Furthermore, the transition from one baseline setting to the other had to be managed operationally safe and in such a way that downtimes were minimal. Nomenclature SAR= Synthetic Aperture Radar TanDEM-X Mission =
The German Space Operations Center currently operates five low Earth orbit satellites in routine phase. The supported missions are the GRACE-mission (two satellites with an along track separation of 200km), the TerraSAR-X/TanDEM-X mission (two satellites in close formation flight at few hundred meters distance) and the Firebird mission with an infra-red camera on the spacecraft TET-1. The Firebird mission will be extended by a second spacecraft BIROS in near future. Effort has been spent to exploit synergy potentials in operations of these spacecraft. Since 2014 they are controlled in a multi-mission control room to facilitate combined operations for the multi-mission flight support team. The concept of the multi-mission layout of the control room will be described in this paper. Control room activities of low Earth orbiting satellites are driven by ground stations passes. Maximal synergies are possible whenever the ground station passes of the different missions are homogenously distributed over the day. In this case a minimum of multi-mission flight personnel is able to support the different missions sequentially. However, the timing of the ground station passes may not be chosen freely as the visibility times of ground stations are given by the combination of orbit and the geolocation of the available ground stations. In order to avoid conflicts with support times of other satellites a choice between different visibilities in sub sequential orbits is, in some cases, compliant with the mission's operations concept and requirements. Another option might be the selection of alternative ground stations in different parts of the world. The operational integration of new ground stations in the mission's network with an appropriate connection line is a precondition. The missions TerraSAR-X/TanDEM-X and GRACE comprise two spacecraft each. In both cases the spacecraft orbit fly in close spatial proximity and both missions use ground stations of the German Aerospace Center (DLR) in Germany, namely Weilheim in southern part, and Neustrelitz in northern part. One ground station supports the first satellite of the mission, the other ground station the second satellite of the same mission. As a consequence the support times in the control room for the two spacecraft are practically identical. In order to open-up the possibility to support parallel passes with a minimum of staff the operational task during passes needs to be reduced and simplified. This is done by assistance of automatic processes taking care of certain pass preparation functions, commanding and post pass activities or by the restriction of active interaction to one satellite only. The concept ideas are described in the paper. A further complication exists by the fact that the satellites of the GRACE mission do not have a sun synchronous orbit. The passes of the Grace satellites move in daytime in contrast to the ones of the TanDEM-X/TerraSAR-X mission and the TET-1 spacecraft. As a consequence the overall support pattern changes from day to day. An extreme ...
S2TEP-1 is the first in a series of satellites using the Small Satellite Technology Platform, in short S2TEP. It is developed by the Institute of Space Systems of the German Aerospace Center (DLR) and it will be operated by the German Space Operations Center (GSOC) in Oberpfaffenhofen, Germany. In order to accommodate to the overall low mission costs and high mission risk, a lightweight approach based on a flexible and (partly) autonomous Ground Segment (G/S) has been foreseen. Synergies with other satellite missions at GSOC or with the Central Checkout System (CCS) will be used wherever applicable and productive. A high degree of automation shall be assured. As the desired degree of external interaction from the customer exceeds that of any mission operated by GSOC so far, a Remote Control Center (RCC) has to be established, from where anomaly recovery operations and special payload campaigns can be performed. The focus of our approach lies on cost effectiveness, a shorter development time, user-friendliness and reusability. A high level of security is not required by the project, nevertheless an adequate level of reliability and security is provided. Three designs that meet these requirements are described and discussed in this paper, together with the constraints that arise from implementing them within the current network infrastructure at GSOC. The chosen design for the Central Checkout and Mission Control and Data System is presented: the final approach results in a system built in a nearly traditional way integrated in the multi-mission environment of GSOC.
Eu:CROPIS (Euglena and Combined Regenerative Organic-Food Production in Space)is a biological life support mission scheduled for launch in 2017 on-board a Falcon 9 rocket. The spin stabilized satellite will be operated under different levels of acceleration to investigate the growth of tomatoes under simulated Mars and Moon gravity. It comprises two pressurized greenhouses, which are rotated around the spacecraft longitudinal axis, a radiation detector and a secondary payload from NASA AMES research center. Each greenhouse compartment will be operated for 6 months at different rotational speed in order to simulate different gravitational forces. Special care has to be taken in the design and the operations of Eu:CROPIS because biological processes may not be disturbed during spacecraft anomalies, and stable thermal conditions and lighting cycles must be assured.The 250 kg satellite is built by the DLR Institute for Space Systems and will be operated by the German Space Operations Center (GSOC) -another DLR institution. This allows an exceptionally close cooperation between the operations team and the spacecraft manufacturer. Decisions can be made together on whether a technical solution is to be implemented within the space segment or the ground segment. This approach minimizes the overall mission costs and maximizes the scientific output. Operational benefits arise from the on-board data handling, which permits the re-use of existing mission planning systems and minimizes adjustments to the mission control and data system. Additionally, an experimental but more powerful downlink mode may be used operationally after successful checkout, which could reduce the downlink time and related costs. This paper gives an overview of the operations concept including LEOP and routine operations, data dissemination and the interfaces to the user segment. It will also describe the technical innovations that have been made in the ground segment to avoid additional effort on the space segment. A new application was developed and added to the Central Checkout System, and is being used for Assembly, Integration and Test (AIT) as well as for the development of flight control procedures.
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