Onboard Spacecraft Research Articles

Framework for Data‒Driven Fault Diagnosis of Numerical Spacecraft Propulsion Systems

The increasing complexity of deep space missions introduces significant challenges in maintaining spacecraft health, particularly in the propulsion systems, due to the inherent communication delays with Earth. This research proposes a novel framework for the autonomous, data-driven fault diagnosis of spacecraft propulsion systems. Leveraging data generated from a spacecraft propulsion system simulation model. The study addresses the limitations imposed by computational resources and sensor installation constraints through Sequential Forward Selection (SFS) for optimized sensor placement and feature selection. The framework's effectiveness is demonstrated through implementation on a microcomputer, showing promising results in terms of diagnostic accuracy and processing speed, thus highlighting its potential for onboard spacecraft application. This study not only advances the autonomous capabilities of spacecraft in deep space but also contributes to the broader field of Prognostics and Health Management (PHM) by providing a scalable, efficient approach to fault diagnosis in critical spacecraft systems. The proposed framework demonstrates a promising approach to optimizing diagnostic tasks for spacecraft systems. However, the trade-offs observed necessitate a careful consideration of task-specific requirements and the potential need for adjustments to maintain a high level of accuracy alongside computational efficiency.

STUDY OF TECHNOLOGY FOR THE RELIABILITY AND SURVIVABILITY MODELLING OF ONBOARD CONTROL SYSTEM OF SMALL SPACECRAFT OPERATING IN COMPLEX MODES

The technology of system modeling of reliability and survivability of the onboard control system (OCS) of the spacecraft is presented in the study of various options for the activation of operating modes. The technology of spacecraft functioning based on the concept of digital twins currently takes a leading position. That’s concept allows you to create realistic virtual copies of spacecraft, to simulate not only the objects themselves, but also the processes of their design and operation in various conditions of a priori uncertainty. Such conditions, first of all, should include the destructive effects of an aggressive external environment (outer space) and the multi-mode nature (sequence and intensity of the modes involved) of the functioning of onboard spacecraft systems. The implementation of the requirements of multi-purpose and multi-mode control in these conditions is closely related to the study of the reliability and survivability of such objects from the standpoint of considering their structural construction. The proposed article discusses an approach to assessing the reliability and survivability of onboard systems of small spacecraft (SS), which is based on the concept of a parametric genome structure, taking into account the multi-mode operation in an aggregated form.

A Spacecraft Onboard Autonomous Task Scheduling Method Based on Hierarchical Task Network-Timeline

To address the inherent challenges of deep space exploration, such as communication delays and the unpredictability of spacecraft environments, this study focuses on enhancing spacecraft adaptability and autonomy, which are essential for Autonomous Space Scientific Exploration. A pivotal aspect of this endeavor is the advancement of spacecraft task scheduling, which is integral to increasing spacecraft autonomy. Current research in this domain predominantly revolves around mission timing planning and is primarily executed from ground stations. However, these plans often lack the granularity required for direct implementation by spacecraft. In response, our study proposes an innovative approach to augment spacecraft autonomy, introducing a method that articulately describes mission objectives and resource information. We designed a novel hierarchical task network-timeline (HTN-T) algorithm, an amalgamation of the HTN scheduling method and the distinctive elements of existing research. This algorithm addresses time constraints through horizontal and vertical expansions, building upon the resolution of logical constraints found in conventional planning methods. Furthermore, it introduces a priority-based strategy for resolving resource conflicts in spacecraft tasks. This algorithm is substantiated through validation, including proof-of-principle demonstrations and assessments within a Space–ground Collaborative Management and Control System encompassing both ground and spacecraft operations. The findings indicate that our proposed algorithm achieves high rates of scheduling success and operational efficiency within a feasible timeframe, thus effectively navigating the complexities of autonomous spacecraft task scheduling.

Initial Pole Axis and Spin Direction Estimation of Asteroids Using Infrared Imagery

Knowing the pole axis of an asteroid is vital to autonomous asteroid exploration efforts. Ground-based initial pole estimation methods are time and data intensive and produce estimates with large uncertainties. These errors have a significant impact on proximity navigation, shape modeling, and scientific data for small body missions. In this paper, a new method of obtaining this information from onboard spacecraft imagery is presented. The proposed method estimates the pole from onboard infrared imagery using the camera-asteroid geometry. This method does not require a prior and is designed to work in a vast majority approach trajectories due to the use of infrared images. The method is applied to simulated infrared images of asteroids 101955 Bennu and 25143 Itokawa as well as real infrared images of asteroid 162173 Ryugu from the Hayabusa2 mission. The average pole errors using this method on Bennu and Itokawa images are approximately 2 and 6 deg, respectively. The pole estimate error on the Ryugu images is approximately 8 deg. The algorithm is shown to be sensitive to the percentage of spin period imaged and the spacing between the images.

Multibit Upsets of Onboard Spacecraft Electronics from a Single Cosmic Radiation Particle

Multibit Upsets of Onboard Spacecraft Electronics from a Single Cosmic Radiation Particle

Measures for attenuation of interference at the level of design of the measuring device of spacecraft

When developing temperature control interface modules used as part of spacecraft onboard equipment, it is important to correctly substantiate the set of measures to ensure their noise immunity, taken at the design levels of the measuring system, measuring device and temperature control interface module. Such a justification involves an assessment of the effectiveness of possible interference mitigation techniques at each design level. The article is devoted to the consideration of interference mitigation measures at the design level of the measuring device, which should be taken to ensure the required noise immunity of the temperature control interface module in combination with measures taken at other design levels. It is shown that in order to ensure the required noise immunity of temperature control interface modules, it is necessary at the design level of the measuring device to provide for measures to mitigate interference in the power supply module, the central instrument module and inter-module interfaces, as well as measures to eliminate gross measurement errors (misses) when processing digital data in the central instrument module. In the power supply module, it is possible to attenuate interference by introducing differential and common mode filters at the input and switching filters at the output. In the central instrument module and inter-module interfaces of the secondary power buses, noise mitigation is possible by dividing the common power bus into analog and digital buses and combining them at an equipotential point. In the central instrument module, it is possible to eliminate misses by using various statistical methods for processing digital data.

On prediction of the operating shock load level of the spacecraft onboard hardware following the mechanical dynamic test results

On prediction of the operating shock load level of the spacecraft onboard hardware following the mechanical dynamic test results

Application of double-error correction codes to protect configuration programmable logic memory against space radiation

Objectives. Programmable logic integrated circuits of the field programmable gate array (FPGA) type based on static configuration memory are widely used in the electronics of onboard spacecraft systems. Under the influence of space radiation, errors may occur in the FPGA configuration memory. The main methods of protection against such errors involve various options for reservation triggers, as well as the use of error-correcting codes in special error detection and correction circuits. The purpose of the present work is to determine which error-correcting codes are best suited to the implementation of internal scrubbing of the FPGA configuration memory taking redundancy into account.Methods. The paper analyses various methods for scrubbing FPGA configuration memory, which are used to correct errors caused by the action of space radiation. It is proposed to increase the efficiency of internal scrubbing of the FPGA configuration memory using codes that correct both single- and double-adjacent SEC-DED-DAEC errors. In this case, the need to perform external scrubbing of the configuration memory is reduced by overwriting it with a reference configuration from non-volatile radiation-resistant memory; in this way, FPGA downtime caused by the external scrubbing procedure is reduced. Due to the known SEC-DED-DAEC codes having a non-zero probability of erroneous detection and subsequent erroneous correction of a double non-adjacent error, as well as various redundancy and implementation complexities, a study was made of the most efficient code for internal scrubbing.Results. The results showed that the Datta, Neale and Hoyoon–Yongsurk codes are optimal from the indicated positions. Recommendations are given for selecting a specific code depending on the specific requirements for a particular planned space mission.Conclusions. The study confirms the effectiveness of protecting the memory of programmable logic by using two-error-correcting codes.

Некоторые выводы по результатам применения конструкторско-технологического анализа надежности для изделий ракетно-космического назначения. Часть 2

The paper generalizes results of introducing procedures of reliability design and technological analysis (RDTA) in the one-time actuation mechanisms of the spacecraft rotary structures (hereinafter referred to as the mechanisms). It provides principles of the mechanisms design and examples of establishing the design documentation requirements in their design process. The differences between processes of the mechanism design and construction are presented, and examples of design and technological factors that could lead to potential failures of such mechanisms are given. Principles of substantiating the spacecraft onboard equipment performance and reliability are considered. Commonality and differences in substantiating performance and reliability of mechanisms and of other onboard equipment of spacecraft are provided. As a result of the RDTA introduction, it was revealed that methods were missing in substantiating performance and reliability of the products for various purposes that were different in form. Only the content of engineering tasks that ensured fulfillment of their service purpose was varying. Moreover, solutions to such problems could be verified using the formalized procedures in reliability design and technological analysis.

Двукратно резервированный твердотельный усилитель СВЧ-мощности для бортовой аппаратуры космических аппаратов

The paper considers a block diagram, known constructions, and proposed design of a twofold reserved solid-state microwave power amplifier (RSSPA) for space-craft onboard equipment. Modern requirements of the RSSPA to a thermostatically controlled plate (TCP) used to remove heat from only one amplifier of the RSSPA are stated. The advantages and disadvantages of “two-storey” constructions and design with vertical positioning of power amplifier boards with respect to the TCP are shown. The paper proposes the RSSPA, in which its components with a high heat dissipation and the components directly connected with them are placed on the base of the RSSPA case mounted on the TCP via a thermally conductive pad, and all other components are placed on the side walls of the case. Its design is simpler and lighter. The proposed RSSPA is perspective for spacecraft onboard equipment including command and measurement systems.

A high-precision synchronization system based on custom benchmarks

In order to meet the requirements of high synchronization of information flow for the cooperation among subsystems of spacecraft and of autonomous operation and management of spacecraft, this article proposes a synchronization system design based on a custom synchronization benchmark. This plan provides a custom synchronization benchmark design method and design constraints and proposes synchronization strategies for different system requirements. On this basis, a high-precision synchronization system design scheme is proposed. By conducting tests, the synchronization error compliance of the synchronization system is verified based on custom benchmarks. This design does not rely on the availability of GPS signals, and the synchronization system design is triggered by the requirement for synchronization accuracy. This method can be applied to spacecraft onboard systems and ground testing systems with extensive application value.

Deep reinforcement learning spacecraft guidance with state uncertainty for autonomous shape reconstruction of uncooperative target

In recent years, space research has shifted heavily its focus towards enhanced autonomy on-board spacecrafts for on-orbit servicing activities (OOS). OOS and proximity operations include a variety of activities: the focal point of this work is the autonomous guidance of a chaser spacecraft for the shape reconstruction of an artificial uncooperative object. Adaptive guidance depends on the ability of the system to build a map of the uncertain environment, figuring out its location inside of it and accordingly determining the control law. Thus, autonomous navigation is framed as an active Simultaneous Localization and Mapping (SLAM) problem and modeled as a Partially Observable Markov Decision Process (POMDP). A state-of-the-art Deep Reinforcement Learning (DRL) method, Proximal Policy Optimization (PPO), is investigated to develop an agent capable of cleverly planning the shape reconstruction of the target. Starting from previous research on the topic, this work develops further proposing a continuous action space, such that the agent is no more forced to choose between a predefined set of possible discrete actions, fixed both in magnitude and direction. In this way any combination of the three-dimensional thrust vector components is available. The chaser spacecraft is a small satellite mounting an electric propulsion engine defining the action space range, in linearized eccentric relative motion with the selected uncooperative object. Through a rendered triangular mesh, the agent capabilities of geometry reconstruction and mapping are evaluated, considering the number of quality pictures made for each face. Extensive training tests are performed with random initial conditions to verify the generalizing capability of the DRL agent. The results are then validated in a comprehensive testing campaign, whose primary focus is the introduction of noisy measurements coming from navigation, affecting pose estimation. The sensitivity of the proposed method to this condition is analyzed and the efficiency of a retraining procedure is examined. The applicability of DRL methods and neural networks to support autonomous guidance in a close proximity scenario is corroborated and the technique employed is vastly tested and verified.

Ammonia fuelled space electric propulsion systems using C12A7:e- electride as electron emitter

Given the significant changes taking place in the geopolitical global situation, and the derived supply chain issues for some traditional electric propulsion propellants like xenon, alternative propellants issue is perceived as a strategic topic to tackle, and ammonia (NH3) is becoming one serious candidate. Ammonia is increasingly being investigated to extend green hydrogen use by overcoming the storage and transportation issues of hydrogen. Ammonia characteristics like its superior energy density and low temperature and/or pressure needs for storage (10 bar at 20°C for liquid ammonia), make it very valuable for simplified unexpensive energy storage and transportation, and these characteristics makes it also especially suitable for on-board spacecrafts electric propulsion purposes. Based on our research activities on ammonia generation and dissociation processes with C12A7:e- electride as catalyst, this work will describe the most relevant characteristics and properties associated to the advantages of using the cheap and abundant ammonia, and will also present and discuss the results of the first successful tests performed with ammonia as fuel for a C12A7:e- electride based neutralizer, including relevant endurance tests in operation conditions. Additionally, the dual application as propellant and on-board energy generation system of ammonia will also be discussed.

The Concept of Constructing a Stand to Test the SpaceWire Onboard Equipment with Possibility of Software and Hardware Simulation of Reconfigurable Topology of the Spacecraft Onboard Network

The Concept of Constructing a Stand to Test the SpaceWire Onboard Equipment with Possibility of Software and Hardware Simulation of Reconfigurable Topology of the Spacecraft Onboard Network

An architecture for a visual-based PNT alternative

This paper treats the problem of positioning and navigation in the absence of GNSS. Given recently raised vulnerabilities for GNSS both on Earth and in space, the work revisits the old problem of the sextant in new light. The combination of stars and planetary horizons was the popular tool for autonomous navigation on-board spacecraft, but given the rise of GNSS receivers, this solution has been largely disregarded. New spacecraft missions beyond Earth have made new progress in visual-based navigation. The work utilises these new methodologies in the scenario that RF-derived positioning is unavailable, achieving a performance below 100 m.An additional important consideration is the development of new navigation infrastructure in LEO and the Moon. Current methods seek to use GNSS and RF-derived sources for orbit determination, however, to be seen as ‘redundancy infrastructure’ for critical Earth and beyond applications, these signals cannot be the primary and only source of navigation reference. This paper utilises derived performances for visual-based methods and applies them to the ranging service problem. Most user scenarios in maritime, aviation and lunar domains are satisfied.This work illustrates implementation using the simple architecture of a star tracker camera. Known as CROSS, the technology is a new navigation tool in development by the University of Sydney. As a star tracker is common device to many spacecraft platform, it simplifies implementation, given that redundant systems are always not a priority to the manufacturer.

The Radiation Resistance of Microelectronic Devices under the Combined Influence of Destabilizing Factors of Space at the Design Stage

An estimation of the joint action of destabilizing factors of space on typical microelectronic components in the design of onboard spacecraft equipment is presented, and an estimation of the characteristics of microelectronic components under radiation exposure is shown.

Calibrating beam fluxes of a low-energy neutral atom beam facility.

Scientific detection and imaging instruments for low-energetic neutral atoms (ENA) onboard spacecraft require thorough pre-flight laboratory calibration against a well-characterized neutral atom beam source. To achieve this requirement, a dedicated test facility is available at the University of Bern, which is equipped with a powerful plasma ion source and an ion beam neutralization stage. Using surface neutralization, low-energy neutral atom beams of any desired gas species can be produced in the energy range from 3keV down as low as 10eV. As the efficiency of the neutralization stage is species and energy dependent, the neutralizer itself needs to be calibrated against an independent reference. We report on the calibration and characterization of this neutral atom beam source using our recently developed Absolute Beam Monitor (ABM) as a primary calibration standard. The ABM measures the absolute ENA flux independent of neutral species in the energy range from 10eV to 3keV. We obtain calibration factors of a few 100cm-2s-1 pA-1, depending on species at beam energies above about 100eV, and a power-law decrease for energies below 100eV. Furthermore, the energy loss of neutralized ions in the surface neutralizer is estimated from time-of-flight measurements using the ABM. The relative energy loss increases with ENA energy from low levels near zero up to 20%-35% at 3keV, depending on atomic species. Having calibrated our neutral beam source allows for accurate calibration of ENA space instruments.

Влияние неоднородной теплозащиты на характеристики излучения антенны космического аппарата

Introduction: Knowledge of the electrical characteristics of the onboard antenna on the trajectory of the descent of the spacecraft makes it possible to assess the presence or absence of radio communication. Under conditions of aerodynamic heating, the thermal protection of the onboard antenna heats up unevenly in thickness and becomes electrically inhomogeneous. Purpose of the work: Determination of the radio technical characteristics of the onboard antennas of the returning spacecraft with the effect of high-temperature heating on the thermal protection of the antenna based on calculations using the developed mathematical model of the antenna with thermal protection. Methods: Expressions for the structure of the radiation field of a rectangular waveguide under the above conditions were derived by the WKB method. Of the well-known analytical methods of solution, it is possible to use the method of integral transformations and the method of eigenfunctions. Both of these methods were used in this work. Results: The obtained theoretical results are new, they allow predicting the radio technical characteristics of the onboard antenna, taking into account uneven heating across the thickness of the thermal protection at low temperature gradients. A mathematical model of the spacecraft's onboard antenna on the descent trajectory has been developed, taking into account the inhomogeneity of thermal protection under conditions of aerodynamic heating. Practical significance: The development of a mathematical model of the main radio technical characteristics of onboard antennas, taking into account the impact of high-temperature aerodynamic heating, as well as the results of numerical calculations, can be applied in the development of recommendations for choosing thermal protection and recommendations for reducing the effect of temperature changes in the electrical parameters of thermal protection on the characteristics of onboard antennas and reducing time loss of radio communication or loss recovery.

Resource Consumption and Radiation Tolerance Assessment for Data Analysis Algorithms Onboard Spacecraft

Spacecraft operating at great distances experience limited data bandwidth and high latency for communication with Earth. Data analysis algorithms that operate onboard, the spacecraft can perform detection and discovery of events of interest without human intervention. This capability serves to increase the quality and quantity of science data collected by the mission through data summarization, downlink prioritization, and adaptive instrument mode switching. However, before such technology can be adopted for use by a mission, it is necessary to characterize the required memory and computational resources. For operation in high-radiation environments, such as in orbit around the gas giants, a characterization of radiation tolerance is also important. In this article, we propose a framework to assess the resource and radiation profiles for machine learning algorithms in a simulated spacecraft computational environment. We apply this framework to several use cases designed for the Europa Clipper spacecraft, which plans to study Jupiter’s moon Europa. This approach can also benefit other remote deployments, such as the robotic exploration of hazardous environments on Earth.

Network architecture and action space analysis for deep reinforcement learning towards spacecraft autonomous guidance

The growing ferment towards enhanced autonomy on-board spacecrafts is driving the research of leading space agencies. Concurrently, the rapid developments of Artificial Intelligence (AI) are strongly influencing the aerospace researches, regarding on-orbit servicing (OOS) activities above all. Within the wide spectrum of OOS and proximity operations, this work focuses on autonomous guidance of a chaser spacecraft for the map reconstruction of an artificial uncooperative target. Adaptive guidance is framed as an active Simultaneous Localization and Mapping (SLAM) problem and modeled as a Partially Observable Markov Decision Process (POMDP). A state-of-the-art Deep Reinforcement Learning (DRL) method, Proximal Policy Optimization (PPO), is investigated to develop an agent capable of cleverly planning the shape reconstruction of the uncooperative space object. The guidance algorithm performance are evaluated in terms of target map reconstruction, by rendering the space object with a triangular mesh and then considering the number of quality images for each face. A major differentiation in the algorithm implementation is provided by the employment of either a discrete or a continuous action space. The main differences between the two cases are critically commented and the benefits of a continuous action space are highlighted. The proposed model is trained and then extensively tested, always starting from random initial conditions, to verify the generalizing capabilities of the DRL agent, by means of the neural network architecture. On this note, a comparison analysis between a Feed-forward Neural Networks (FFNN) and a Recurrent Neural Network (RNN) is performed. The better performing model is retrieved from the aforementioned comparisons, and its robustness and sensitivity are sharply analyzed. This work confirms and develops further the applicability of DRL techniques for autonomous guidance, highlighting in a critical way its possible implementation in future close proximity scenarios.