No abstract
The micro-satellite TET-1 carries several technology experiments. It is the first in a series offering the possibility of in-orbit verification of new equipment made in Germany by the industrial and scientific aerospace community. TET-1 was launched 22nd July 2012 and is operated by the German Space Operations Center. Attitude and attitude control is influenced by several of the experiments. Special attitude control modes are required for a number of experiments in order to point the satellite in a prescribed direction or to a specific location on Earth. These comprise an experiment with three infra-red cameras, a pico thruster and finally a new type S-band transponder. The Li Polymer battery was not expected to have any effect on attitude control. However, it was discovered that charging and discharging the battery disturbs the magnetic field sensors, thus a different approach to attitude control is required when it is in use. Implementation of and special demands on the attitude control system for these experiments will be presented. The mission is experimental with high demands on the attitude control system. The envisaged duration was one year only with a possible prolongation of a further year. Components were therefore not chosen for longevity. However, the actual amount of disruptions due to sensor and/or actuator outages and due to idiosyncrasies in the spacecrafts thermal budget was higher than expected. The ensuing challenges for the attitude control system will be discussed. A software upload in May 2013 mitigated several of the issues addressed above. The improvements in the software and autonomous on-board reactions will be presented in the final Section together with some recommendations for the follow-on missions TET-2 and BIROS.
Compact and inexpensive Earth observation satellites in low Earth orbit are now routinely developed by universities, "New Space" businesses, and space agencies. They enable new opportunities for fast turnaround times of imaging data takes, which is e. g. particularly important for disaster response. For this kind of satellites and the missions enabled by them a ground system exhibiting the same characteristics, namely being compact and mobile, yet inexpensive and flexible, is desired.We present DLR's approach for the provisioning of a ground segment fit for the kind of missions outlined above. The objective of this project consists of the engineering, delivery, and demonstration of a compact and yet complete Mission Operations System, runnable on commodity mobile hardware, enabling fully automated workflow-driven operations of alike missions from anywhere in the world with access to a ground station or ground station network.Just as disasters strike suddenly, the ground segment needs to be set up and spun up in a timely manner. This leads to the requirement of being able to quickly roll out the system on new hardware, possibly even several of these systems in parallel. Our paper provides insight on how we perform the automatic deployment and provisioning.Because the system is supposed to be decentralized and used in the field, particular challenges need to be overcome resulting from the lack of all of the infrastructure typically present in conventional control centers, such as network connectivity. An embedded Flight Dynamics system is taking care of automated orbit determination and related event generation to support the mission needs and maneuver capabilities. Special effort is made to cope with auxiliary data that may not be updated on a regular basis in a closed mission environment.The feasibility of the concept is demonstrated by a first system deployment as drop-in replacement for the existing conventional Mission Operations System for DLR's BIROS satellite at the GSOC control center. A second demonstration campaign is performed from a remote location without access to control center infrastructure.
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.
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