Enrico Stoll

On-orbit servicing

Space robots were the topic of this paper. While on earth, nobody would follow such advice; in space, there are few other options than to replace a malfunctioning spacecraft. There are no repair shops and gas stations in the Earth orbit. Because of the lack of so-called on-orbit servicing (OOS) opportunities, some malfunctioning spacecraft continue operational work with reduced or hardly any performance. The only general modification, which can currently be undertaken to an arbitrary spacecraft in orbit, is a software update. In this paper, exploration and manipulation capabilities of space robots were discussed. Teleprescence through a data relay satellite and teleoperation capabilities were mentioned and discussed.

SPHERES interact—Human–machine interaction aboard the International Space Station

The deployment of space robots for servicing and maintenance operations that are teleoperated from the ground is a valuable addition to existing autonomous systems, because it will provide flexibility and robustness in mission operations. In this connection, not only robotic manipulators are of great use, but also free-flying inspector satellites supporting the operations through additional feedback to the ground operator. The manual control of such an inspector satellite at a remote location is challenging, because navigation in three-dimensional space is unfamiliar and large time delays can occur in the communication channel. This paper shows a series of robotic experiments, in which free flyers are controlled by astronauts aboard the International Space Station (ISS). The Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES) were utilized to study several aspects of a remotely controlled inspector satellite. The focus in this case study is investigating different approaches to human–spacecraft interaction with varying levels of autonomy under zero-gravity conditions.

The RapidEye constellation and its data products

RapidEye is a commercial remote sensing mission delivering geospatial information. Five identical satellites in a sun-synchronous orbit image more than four million square kilometers per day. RapidEye features the unique ability to revisit any area on Earth daily. Within three years of operation, the constellation mastered a number of complex challenges, which led to an evolved mission concept. RapidEye started commercial operations in February 2009 and utilizes its own dedicated spacecraft control center and a full ground segment designed to plan, acquire, and process several millions of square kilometers of imagery every day. In order to keep up with evolving market demands, RapidEye has continually worked at advancing the mission concept beyond its original vision and capabilities, extending the mission concept to include data sales, emergency response, and direct downlink capabilities. As a result RapidEye can reliably and predictably supply the most current, cost-effective, and high quality information about features on the Earths surface. This paper describes the challenges that have to be met for adapting to an evolving geospatial information market. It shows the possibilities and limitations of the satellite constellation and the engineering efforts that have to be undertaken to provide highly reliable data products.

Operational collision avoidance of small satellite missions

Collision avoidance is a topic of increasing importance. The number of satellites in Earth orbit is steadily growing and with the high amount of space debris, either crossing through or resident in orbit, collision probabilities between two such objects can become critical. Small satellite missions usually operate with limited capabilities when it comes to locating potential collision occurrences and deriving the associated collision probability. Accordingly, they have to rely on external organizations, such as the Joint Space Operation Center (JSpOC) and their information system to plan for contingency operations. This paper reviews the benefits of using such an external service for a small satellite constellation. It analyses the relevant data for use in daily operations and shows collision avoidance approaches based on the available data. Conjunction summaries for the RapidEye satellite constellation are evaluated and their influence on the planning of collision avoidance maneuvers is shown.

Construction and Realization of a Low-Cost Satellite Attitude Simulator Concept

In this paper we present the realization of a test environment to test preflight highfidelity inter-satellite communication links on gro und. The basic requirements are given by the research project “Telepresence for Space Missio ns” as part of a collaborative research centre (SFB 453) funded by the German Research Community (DFG). The intention of this project is establishing a communication link from Low Earth Orbit (LEO) to a geostationary relay satellite in order to control robotic applica tions on LEO satellites. While about 0.6 seconds. To establish an Inter Satellite Link (ISL) a tracking mechanism for a steerable antenna is needed. To verify the functionality of the tracking mechani sm, a test bed has been developed at the Institute of Astronautics using an existing concept of a test bed for an attitude simulation system. This test bed for attitude simulations is b ased on an antenna turntable which is part of the S-band ground station at the Institute of As tronautics. Using this antenna turntable with 2 degrees of freedom (azimuth, elevation) the simulator design envisages another degree in order to demonstrate possible satellite attitude s. A key point in the design is the easy and fast reconfiguration of the antenna turntable into the attitude test bed. In this paper the constraints for the construction and final realization of this attitude simulator test bed is depicted. It describes all mo difications needed to reconfigure the antenna turntable into an attitude simulator system test bed and visa versa. Eventually, the test setup will be illustrated which will be used f or the addressed verification.

Concept of an algorithm to determine the signal delay time for telepresence space applications

The vision of a space robot as an extended arm of the human operator on ground is a key component for on-orbit robotic service missions. This concept of telepresence requires a high-quality sensor feedback from the space environment to the operator including stereo video and force-feedback. For the force feedback channel the knowledge of the signal delay time during operation is an important factor to increase the immersiveness of the system. In case of radio contact to space segments which are not in GEO, the signal delay time varies according to the distance between the spacecraft and the ground station. This paper proposes a method for deriving the required signal delay from the Doppler frequency shift alone which is readily available from the receiver since the actual signal delay is an input value for the control loop in the haptic channel

Integrating Advanced Calibration Techniques into Routine Spacecraft Operations

RapidEye AG is a commercial provider of geo-spatial information products derived from Earth observation image data. The source of this data is the RapidEye constellation of five low-Earth orbiting imaging satellites. The payload is a Multi-Spectral Imager, which does not contain an onboard calibration subsystem. A preliminary in-orbit vicarious calibration campaign was performed after launch to confirm pre-launch calibration results by assessing the spatial response non-uniformity of each sensor. In an effort to improve the relative spatial calibration of the push broom imager and demonstrate the feasibility of an independent spatial calibration methodology, a side slither maneuver approach was developed for the RapidEye constellation. Upgrades made to the RapidEye system to integrate the side slither calibration technique into routine spacecraft operations is presented in this paper along with some in-orbit data to highlight attitude stability results and power generation constraints. This paper also presents sample imagery that contained noticeable spatial artifacts, which were then improved using side slither derived detector correction parameters. A significant improvement in image quality was achieved when compared to our standard correction parameters derived using previous methods. I. Introduction UNDAMNETAL to the success of mission operations is the ability to adapt to ever-changing mission needs and enhance the operational system to meet customer requirements. Image data from satellite electro-optical sensors often contains spatial artifacts such as banding and streaking that are caused by detector response variations, factors related to image formation, and the space environment. In order to reduce the negative impact of image artifacts on product quality, the Calibration and Validation Team at RapidEye adopted the Side Slither calibration technique for relative radiometric calibration of the sensor and correction of the imagery. This paper describes the upgrades made to the RapidEye system, in terms of acquisition planning and engineering enhancements, to integrate the side slither imaging campaign into routine spacecraft operations. RapidEye is a complete end-to-end commercial Earth observation system 1 The MSI does not contain an on-board calibration subsystem. A preliminary in-orbit vicarious calibration campaign was performed after launch to confirm pre-launch calibration results by assessing the spatial response non-uniformity of each sensor. Over time, detector sensitivity changes require new gain and offset values to correct the banding and striping artifacts in the image data. In an effort to improve the relative spatial calibration of the Push Broom MSI and demonstrate the feasibility of an independent spatial calibration methodology, a side slither maneuver (SSM) was performed with the RapidEye constellation. During SSM, the spacecraft is oriented in a 90° yaw configuration while confining the roll and pitch angle to 0°. The detector array runs parallel to the direction of comprising a constellation of five microsatellites, a dedicated Spacecraft Control Center (SCC), a data downlink ground station service, and a full ground segment designed to plan, acquire, and process millions of square kilometers of imagery every day to generate unique land information products. The major fields of geospatial applications and services are: agriculture, forestry, infrastructure, security, and emergency monitoring. The design and manufacturing of the spacecraft were based upon the SSTL 150 platform developed by Surrey Satellite Technology Ltd. (SSTL). Jena-Optronik GmbH provided the Multi-Spectral Imager (MSI) payload.

Multimodal Human Spacecraft Interaction in Remote Environments

Most malfunctioning spacecraft require only a minor maintenance operation, but have to be retired due to the lack of so-called On-Orbit Servicing (OOS) opportunities. There is no maintenance and repair infrastructure for space systems. Occasionally, space shuttle based servicing missions are launched, but there are no routine procedures foreseen for the individual spacecraft. The unmanned approach is to utilize the explorative possibilities of robots to dock a servicer spacecraft onto a malfunctioning target spacecraft and execute complex OOS operations, controlled from ground. Most OOS demonstration missions aim at equipping the servicing spacecraft with a high degree of autonomy. However, not all spacecraft can be serviced autonomously. Equipping the human operator on ground with the possibility of instantaneous interaction with the servicer satellite is a very beneficial capability that complements autonomous operations. This work focuses on such teleoperated space systems with a strong emphasis on multimodal feedback, i.e. human spacecraft interaction is considered, which utilizes multiple human senses through which the operator can receive output from a technical device. This work proposes a new concept for free flyer control and shows the development of an according test environment.

The control of inspector satellites via relay satellites

There are various robotic On-Orbit Servicing concepts existing, which aim at utilizing inspector satellites for obtaining high-fidelity video feedback from the remote environment. Most of these inspection tasks, which involve proximity operations, can be done autonomously by the spacecraft. However, there are cases such as sensor malfunctions or undefined spacecraft states, in which it seems advantageous to have the possibility of human interaction with the inspector satellite. An operator on ground with the capability of real-time control can complement autonomous operations and add robustness to mission operations. The SPHERES Interact program at the MIT Space Systems Laboratory currently develops concepts for efficient human spacecraft interaction. Using three experimental satellites aboard the International Space Station, a series of tests were executed, which evaluated different approaches and methods. Additionally, using another three of these experimental satellites on the air bearing table at the Space Systems Laboratory, advanced concepts can already be developed and verified on ground. This paper shows experiments, in which the SPHERES at MIT were controlled via a geostationary relay satellite of the European Space Agency (ESA), using a ground station in Germany. It emphasizes the benefits of real-time human spacecraft interaction and describes the design of the associated test environment.

The concurrend configuration of a TMTC software during the Satellite Life Cycle

The design of satellite systems with the aspects of reducing costs and development time has become more and more popular. The breakthrough of high performance processing allows new development strategies. Special simulation programs used for different satellite development phases shall bring the expected success. The usage of such simulation programs opens the way for an extended employment of the commercial of the self (COTS) Monitoring and Control (M&C) tool “FRAMTEC - Framework for Advanced Monitoring, Telemetry and Control”. This software tool is a generic M&C tool and can be used for (nearly) every M&C application. Processing TeleMetrie and TeleCommand (TMTC) data of a satellite during the mission operation phase is a typical field of employment of this tool. The configuration and test of such typical TMTC software tools is always connected with high costs and time. This paper shows how to reduce cost und configuration time by using FRAMTEC as a Monitoring and Control tool in mission operation phase as used in the satellite project “BayernSat” of the Institute of Astronautics / Technische Universitat Munchen. The employment of Framtec as a M&C tool for the whole Electrical Ground Support Equipment – EGSE allows the continuous configuration over during the development phases of a satellite. This integration of the software tool FRAMTEC in the development process and phases and its benefit in cost- and time-efficient is described. Finally, an outlook in realizing this approach is discussed.