Phoenix-XNS - A Miniature Real-Time Navigation System for LEO Satellites

The paper describes the development of a miniature GPS receiver with integrated real-time navigation system for orbit determination of satellites in low Earth orbit (LEO). The Phoenix-XNS receiver is based on a commercial-off-the-shelf (COTS) single-frequency GPS receiver board that has been qualified for use in a moderate space environment. Its firmware is specifically designed for space applications and accounts for the high signal dynamics in the acquisition and tracking process. The supplementary eXtended Navigation System (XNS) employs an elaborate force model and a 24-state Kalman filter to provide a smooth and continuous reduced-dynamics navigation solution even in case of restricted GPS availability. Through the use of the GRAPHIC code-carrier combination, ionospheric path delays can be fully eliminated in the filter, which overcomes the main limitation of conventional single-frequency receivers. Tests conducted in a signal simulator test bed have demonstrated a filtered navigation solution accuracy of better than 1 m (3D rms)

An Interferometric SAR Satellite Mission

The paper provides a critical review of the achievements in SAR interferometry from the ERS mission as well as from the Shuttle Radar Topography Mission SRTM. It describes the development from the original idea of the Interferometric Cartwheel to the concept of a formation flight of identical and active SAR satellites. From the experience gained from ERS and SRTM interferometric data processing as well as from the analysis of the Cartwheel concept a list of mission requirements has been set up. The most demanding one is the autonomous configuration flight of a tight x-band constellation, where the satellites fly as close as up to 30 m with a dead-band of +/- 10 m. The guidance, navigation and control considerations come to the conclusion that such a mission is feasible

Student perceptions on a collaborative engineering design course

To adequately prepare engineering students for their professional career, educational institutions offer projects in which students collaboratively solve engineering design problems. It is known from research these projects can lead to a variety of learning outcomes and student experiences. However, studies that provide insights in the influence of different features of an educational design are rare. In the current study we use Cultural Historical Activity Theory (CHAT) as analytical framework to understand how different elements of an educational design affect students’ experience. Additionally, we use the notion of contradictions to identify opportunities for structural course improvement. Focus groups were conducted with 12 Master students in Aerospace Engineering, that participated in a collaborative engineering design course. During the course, students applied Systems Engineering (SE) and Concurrent Engineering (CE) and worked in the Collaborative Design Laboratory (CDL), which is a state-of-the-art facility that holds a variety of industry relevant tools. It was found that students valued the guidance of their coach and experts, co-located collaboration and the freedom to structure their own process. However, they perceived challenges with regard to adoption of tools in the CDL, sharing their progress with their supervisor, coordination of collaborative efforts and scheduling issues. An analysis using CHAT revealed what contradictions caused these challenges. Finally, recommendations are given on how course structure can be structurally improved

An Embodied Cognition Approach To Collaborative Engineering Design Activities

Higher educational institutions have broadly adopted Collaborative Engineering Design (CED) activities to prepare students for complex problem-solving in multidisciplinary settings. These activities are non-linear and mediated by various social practices and tools. Therefore educators might struggle in facilitating the achievement of specific learning goals. Embodied cognition is an approach that explains non-linear behaviour through orgamism-environment interactions and might therefore provide educators with insights on how to prompt students towards desired actions in CED activities. According to embodied cognition, we learn through actions that emerge as a response to a problem (task) and environmental constraints. Educators can guide students’ behaviour by proposing tasks and adapting the environmental constraints of a learning situation, thus creating a field of promoted action. In this paper, we outline the progress of a design-based research in which insights from embodied cognition are implemented to promote desired student behaviour in CED activities. We report on the results of our problem-exploration phase. A systematic literature review and focus groups with students revealed that students are often hesitant to adopt new practices and tools that could potentially improve their collaborative design process. Next, we propose three theory-based design principles in which the task and environmental constraints are leveraged to foster the adoption of practices and tools and apply them to CED activities. Finally, we will share preliminary observations of the learning processes triggered by the designed activities and outline the directions for future research

Towards the Use of Commercial-off-the-Shelf Small-Satellite Components for Deep-Space CubeSats: a Feasibility and Performance Analysis

The aim of this paper is to assess the feasibility of using currently available commercial-off-the-shelf (COTS) small-satellites components in deep-space scenarios, studying their applicability and performance. To evaluate the performances, an asteroid fly-by mission is briefly introduced, but several of the selection criteria and ideas can be extended to other deep space mission concepts. This particular mission scenario requires to follow three main trends: miniaturization, standardization and automation. For this reason the mission represents a good test bench scenario to analyze the products of the current small-satellites industry. Once the reference mission has been defined, the preliminary ΔV is computed and the micro-propulsion system is selected. Afterwards, for several satellite subsystems the requirements are compared with the expected performance of a set of small-satellite components currently available on the market. Once the most promising hardware solutions are identified, mass and volume budgets are defined. Subsequently, drawbacks and limits of using COTS components for deep-space exploration are highlighted, focusing on the readiness level of each subsystem. Finally, recommendations are given on what methods and hardware are needed in the near future to overcome the limiting factors and to allow deep-space exploration using low-cost CubeSats

Three-dimensional modeling and time-delay stability analysis for robotics docking simulation

Hardware-in-the-loop simulations of two interacting bodies are often accompanied by a time delay. The time delay, however small, may lead to instability in the hardware-in-the-loop system. The present work investigates the source of instability in a two spacecraft system model with a time-delayed contact force feedback. A generic compliance-device based contact force model is proposed with elastic, viscous, and Coulomb friction effects in three dimensions. A 3D nonlinear system model with time delay is simulated, and the effect of variations in contact force model parameters is studied. The system is then linearized about a nominal state to determine the stability regions in terms of parameters of the spring-dashpot contact force model by the pole placement method. Furthermore, the stability analysis is validated for the nonlinear system by energy observation for both the stable and unstable cases

Miniaturized Radio Tranceiver for PocketQubes, Exceeding Performance of CubeSat Solutions

In this paper, a detailed design is presented of a communications module that is designed to fit tight PocketQube design budgets but still offer performance at least comparable to commercial off-the-shelf CubeSat solutions. The communications module features extremely efficient power usage, less than 2 Watt DC for 1 Watt RF output while fitting in an extremely small volume, (42 x 42 x 8mm, approximately a quarter of the volume of CubeSat solutions). Our system also features a new communication scheme based on Short Block LPDC codes that provides a very high code gain (approximately 6dB for hard-decision and 9dB for soft-decision) using a high code rate. A ground modem implementation based on GNURadio is also presented, taking advantage of a new implementation for low-latency asynchronous data transmission

A Pico-Satellite Design to Demonstrate Trajectory and Science Applications

This paper presents the design, integration and testing of a pico satellite, Delfi-PQ, a 3P PocketQube developed by Delft University of Technology, expected to be launched at the end of 2020. The main goal of this project is creating a miniaturized platform for future space missions with performances comparable to CubeSats, taking advantage of the miniaturization of electronic components and their integration. Education of aerospace engineering students is a second key goal of the project, where students involved in the project as part of their curricular activities