1,720,981 research outputs found
Novel extended Kalman filter + H∞ optimal output feedback control configuration for small satellites with high pointing stability requirements
Full text linkOne of the most challenging subsystems for the CubeSats is the attitude determination and control system (ADCS) because it involves hardware and software integration, advanced strategies and algorithms to determine and control the attitude that impacts on space maneuvering and well working of a large set of payload (e.g., the optical payload). Although ADCS is largely studied, it still requires further investigations and analysis in order to achieve high-performance and a reduced efforts. This paper presents an effective and reliable solution for the ADCS of CubeSats involved in Earth observation missions. The solution is based on an innovative framework that leverages the strengths of two distinct methodologies-H-infinity optimal output feedback control and the extended Kalman filter (EKF)-to significantly enhance the pointing stability of satellite systems. While H-infinity optimal output feedback control is traditionally associated with partial state knowledge, we intentionally extend its application to scenarios with complete state information. The study includes a comparative performance analysis involving three algorithm configurations: the classic combination of EKF and model predictive control (MPC), the utilization of H-infinity optimal output feedback control without EKF, and our proposed integrated approach. Performance evaluations are based on extrinsic indicators, demonstrating the advantages of our method in terms of pointing stability and overall control system performance. This research underscore the significance of combining innovative thinking with well-established methodologies, unlocking new possibilities for stability enhancement in a range of engineering applications
Analysis of the communication anomaly during E-ST@R-2 mission operations
Full text linkTo increase probability of success of future nanosatellite missions, data gathered from orbit operations are of paramount importance, especially if anomalies are observed. E-st@r-2 Cubesat was launched on April 2016 in the framework of the Fly Your Satellite! programme of the European Space Agency. Few anomalies were detected during operation, which compromised the mission either temporary or permanently. This paper describes the investigation of a major anomaly that seriously affected mission operations, i.e. low Signal-to-Noise ratio of downlink communication. In particular, no signal could be received at the main control station. Only ground stations with high gain antennas and/or proper system set up could receive and decode e-st@r-2 packets, whereas standard radio amateur station failed. For this reason, both space and ground segments were identified to be part of the problem. The analysis performed to cope with the issue covered several phases of mission lifecycle, from design to assembly, integration and test, until operations. The investigation on the anomaly has been done by means of analysis and test activity. A loss of 12 to 15 dB was estimated with respect to the link budget. A fault tree analysis was developed to identify the failure or combination of failures that resulted in the mishap. A failure modes and effects analysis of communication system was carried out, as this subsystem was identified as the major contributor to the anomaly. In parallel, testing activity was performed on the engineering model of cubesat. A thorough test campaign was planned and executed at equipment, subsystem and system level. Test results on the engineering model were compared with orbit data and results of qualification campaign on the flight unit. The investigation showed that possible causes of the anomaly could be either incomplete deployment of the antenna, or incorrect antenna connection, or loss of power in the transceiver, or a combination of these causes amplified by the tumbling motion of the CubeSat. Taking into account the extensive test campaign executed on the flight unit during development, the failures of antenna deployment and of high-power amplifier circuit are extremely unrealistic. Instead, a potential defect was detected on the coaxial cable connection to the antenna, which might have caused the final mishap under investigation. The analysis also showed that an effective ground segment helps mitigating the impact of the anomaly, thus increasing mission success to a great extent, and it is worth investing more on this mission element
Fast development and validation of a Sensing Suite system for CubeSats
No full textEducational CubeSats still remain valuable hands-on practice activity in an academic environment and provide effective and innovative solutions from technical and management points of view. Fast delivery and low cost is the paradigm driving such projects. Contemporary, the simplicity of the solutions has to match with reliability to guarantee the success of the on orbit operations. The present paper shows the entire life cycle of a Sensing Suite System suitable as scientific data collector within a CubeSat, developed in less than four months from the conceptual design to the delivery and reaching the orbit in less than six months. Technical solutions for hardware and software development and test and management good practices are provided. Circuits details to withstand and/or tolerate the space environment and data handling to maximize the number of data and measurements gathered onboard are explained. The use of breadboards and flat-sat arrangements support both the design and verification of the protoflight comprising the schedule and increasing the confidence level on the goodness of the entire solution. The reliability of the design is proven through the entire assembly, integration and verification campaign and validated by the data sent by the satellite during the operative mission
Analysis of docking manoeuvres for 12U Cubesat with a collaborative mothercraft
No full textThe use of CubeSats as drones for inspecting the collaborative mothercraft is one of the most interesting in-orbit service missions for this kind of small spacecraft. The most challenging operation in this context is the retrieval of the CubeSat by the mothercraft after the inspection phase especially because any violation of safety constraints must be avoided. A well-established docking strategy in nominal and off-nominal conditions is fundamental already during the preliminary design phases. The present paper shows drivers and requirements that identify a set of design parameters on the state boundaries of the CubeSat, its main features, and the uncertainties due to the space environment and the system uncertainties. After the choices of the guidance, navigation, and control strategies and architectures, simulation sessions lead to an assessment of the robust performance in nominal conditions. Then, the off-nominal conditions are deduced and new simulation sessions confirm the capability of the system to react against discrepancies between actual state and desired state and system failures. The proposed solution is applied to a 12U CubeSat mission that will be released and, in case, retrieved by a mothercraft for observation purposes. The paper highlights the solution’s effectiveness in nominal conditions, and when an error occurs in the approach velocity and failures affect the propulsion system, as an example of the entire analysis
Safe approach of a small satellite with a large spacecraft. Analysis of nominal and off-nominal solutions
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PASSIVE ATTITUDE STABILIZATION STRATEGY FOR A 3U STUDENT CUBESAT
No full textCubeSats are increasingly being used for various space missions due to their low cost and fast delivery. While active attitude control systems, based on reaction wheels, are a valuable solution when precise pointing is required, they can be energy-intensive for a spacecraft with body-mounted solar panels and expensive for educational and fast-delivered missions. On the contrary, passive attitude control systems offer an attractive alternative that can reduce costs and improve reliability. This is particularly true when a reduced set of data should be sent to ground and the communication system can include low-directive antennas. This study addresses the challenge of passive attitude control for a 3U CubeSat in a communication mission, mostly designed and developed by students of Politecnico di Torino, emphasizing the importance of simplicity and lightness in the design process. To this end, we propose a passive attitude control system that leverages hysteresis rods made of a magnetic alloy with a low resistance to magnetization that allows an easy induction in the magnetic material enabling angular velocity damping. Additionally, a magnet is utilized to generate a magnetic dipole of 0.11 Am2 that aligns the satellite's long axis with the local magnetic field vector, simplifying the control system. The hysteresis rods and the magnet can be easily integrated into the satellite's structure, making the system highly robust and reliable. The proposed system is rigorously validated via simulations conducted using MATLAB and Simulink, with the aim of comparing the results obtained with data from an Inertial Measurement Unit (IMU) integrated within the satellite. The simulations demonstrate that the proposed passive attitude control system can maintain the satellite's orientation within a few degrees of the desired position, even in the presence of external disturbances. Along the orbit, the attitude is stabilized with a misalignment of the body axis with respect to Earth's Magnetic Field of 10 deg. Lastly, the simulations highlight that the released energy is dumped in less than 10 days. The proposed ACS configuration is mounted on board a 3U CubeSat planned to be launched in June 2023. It is expected to have results for the orbits to verify our solutions by the end of August 2023
CubeSats development at Politecnico di Torino: The e-st@r program
No full textThe paper describes into the details the e-st@r (Educational SaTellite @ politecnico di toRino) program, which is an educational project under development at the Department of Aerospace Engineering of Politecnico di Torino. The program has been funded by the Italian Ministry of University and Research and by the Politecnico di Torino. E-st@r is a cubesat, developed by students under the guide of researchers and professors, and it has been accepted by the European Space Agency (ESA) to be launched by the Vega LV during its maiden flight. The CubeSat has been developed taking into account some driving requirements and constraints. As a matter of fact, the use of Commercial-Off-The-Shelf (COTS) components, the adoption of simple technique and technologies as well as the constraints imposed by the available launcher (the mission orbit, as an example), stem directly from the consideration of the e-st@r program as an educational project. Notwithstanding the necessity of keeping things simple, e-st@r has also scientific objectives, which reflect real interests of the scientific, educational and industrial communities. The main scientific objective of e-st@r is the development and test of an active Attitude Determination and Control Subsystem (ADCS) based on magnetic actuators. The secondary objective is the testing of commercial components and materials into space. The active ADCS has been chosen as the main payload for the e-st@r mission because it represents a challenging experiment. The capability of actively control the attitude of a pico-satellite could give a boost to the proliferation of a so simple and low-cost technology, which can result in a great advance for the general target of reducing drastically cost to access and exploit space. Moreover, in the basic operative mode the satellite does not need high pointing accuracy to communicate with the ground stations, so the failure of the ADCS shall not affect the mission success. E-st@r verification campaign is being completed in these days and the delivery to ESA/ESTEC is scheduled for Autumn 2010. Many students have been and are now involved in the program for their final Master thesis, but the e-st@r project is also being very successful among undergraduate students and lot of them are working on it with enthusiasm during class works in regular courses. PhD students also participate in the development of the satellite, for special investigations. The paper will illustrate the educational approach to the development and main achievements of the program. Copyright ©2010 by the International Astronautical Federation. All rights reserved
On orbit inspection with CubeSats: State of the art and future perspective
No full textThe current Space Agencies exploration programme encompasses the analysis and development of gap-filling activities towards future reliable missions. Within this context, examples of these activities could be found in orbit debris management, reusable Space Transportation Systems and orbital stations based on the heritage of the ISS. For all of these, a system performing on orbit inspection could represent an opportunity to increase both mission reliability and safety, while reducing the need of Astronauts Extra Vehicular Activity. Indeed, a constant monitoring of the external conditions of a target could: 1) track down damages and geometry of components 2) support maintenance activities 3) identify and characterize dynamics and materials. Since the introduction of the CubeSat standard in the early 2000s, there has been a proliferation of nanosatellites in Low Earth Orbit with more than 100-200 launched annually, pushing towards interplanetary applications. It has been verified that CubeSats can efficiently support a wide range of space missions: several studies have been already conducted and are ongoing. For example, the CubISSat mission to inspect the International Space Station has been developed within SysNova ESA framework with interesting results. Other examples are the e-Inspector CDF study, a mission targeted at gathering data about Envisat to prepare the removal mission and the ESA SROC study, a mission targeted at the observation of the new-born Space Rider. The paper presents design solutions for CubeSats equipped with stereoscopic vision system and hyperspectral camera payloads, involved in the visual inspection of specific target. Different mission concepts and CubeSat configurations are evaluated and compared. For each solution, advantages and challenges that impact both on payload performances and system requirements are identified and discussed. A preliminary study is presented on the quality of the multispectral information in relation to the changes in distance from the target, spectral bands involved, relative velocity and spectral resolution. Similarly, stereoscopic system performances are analysed with respect to spatial resolution of the camera, field of view, image size and complexity of the algorithms for data processing. All these parameters impose constraints on the CubeSat design and assembly in terms of features such as pointing accuracy and stability, precise attitude control and navigation, data storage capability, processor throughput and data rate. Thanks to the analysis of general case studies, a baseline feasibility analysis of an inspection mission is then traced, taking into account the most promising COTS CubeSat-based technology but facing the state of the art towards more effective future missions. As a result, a technology development roadmap is suggested, highlighting critical accomplishments to fulfil in order to improve reliability and performances of inspection missions. Giving an overview of current and future capabilities of CubeSats for inspection missions, this paper aims to put the basics for future CubeSat applications development, assisting the human vision of space exploration
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