Eberhard Gill

Eberhard Gill
Delft University of Technology | TU · Department of Space Engineering (SpE)

PhD, MSc Space Engineering

About

344
Publications
96,812
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4,912
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Introduction
Eberhard Gill is Chairholder and Section Head Space Sytems Engineering (SSE) at the Faculty of Aerospace Engineering of the Delft University of Technology. He is Scientific Director the TU Delft Space Institute. Eberhard does research in Space Systems Engineering, Navigation, Distributed Space Systems and Miniaturized spacecraft.

Publications

Publications (344)
Article
Full-text available
The estimation of the relative pose of an inactive spacecraft by an active servicer spacecraft is a critical task for close-proximity operations, such as In-Orbit Servicing and Active Debris Removal. Among all the challenges, the lack of available space images of the inactive satellite makes the on-ground validation of current monocular camera-base...
Article
The objective of this paper is to investigate which approach would lead to more reliable CubeSats: full subsystem redundancy or improved testing. Based on data from surveys, the reliability of satellites and subsystems is estimated using a Kaplan–Meier estimator. Subsequently, a variety of reliability models is defined and their maximum likelihood...
Article
Piezoelectric actuators are a very attractive technology for active optics mechanisms in space applications due to their very high precision and reliability. However, self-heating of these actuators may be limit their use in space or under high loads, due to the limited ability to evacuate heat. Test procedures that reproduce the operational condit...
Article
Full-text available
The use of deep neural networks (DNNs) in terrestrial applications went from niche to widespread in a few years, thanks to relatively inexpensive hardware for both training and inference, and large datasets available. The applicability of this paradigm to space systems, where both large datasets and inexpensive hardware are not readily available, i...
Article
Full-text available
The relative pose estimation of an inactive spacecraft by an active servicer spacecraft is a critical task in the design of current and planned space missions, due to its relevance for close-proximity operations, such as In-Orbit Servicing and Active Debris Removal. This paper introduces a novel framework to enable robust monocular pose estimation...
Conference Paper
Full-text available
The estimation of the relative pose of an inactive spacecraft by an active servicer spacecraft is a critical task for close-proximity operations, such as In-Orbit Servicing and Active Debris Removal. Among all the challenges, the lack of available space images of the inactive satellite makes the on-ground validation of current monocu-lar camera-bas...
Preprint
Full-text available
This paper proposes a model-based framework to automatically and efficiently design understandable and verifiable behaviors for swarms of robots. The framework is based on the automatic extraction of two distinct models: 1) a neural network model trained to estimate the relationship between the robots' sensor readings and the global performance of...
Article
Full-text available
Small satellites with increased capabilities in terms of power and propulsion are being demanded for future missions. This paper addresses an alternative bi-modal solution which consists of a solar thermal propulsion system coupled with a micro-Organic Rankine Cycle system, to co-generate thrust and electrical power. Current literature on bi-modal...
Article
Full-text available
The purpose of this work is to present a novel CubeSat architecture, aimed to explore Near Earth Asteroids. The fast growth in small satellite commercial-off-the-shelf technologies, which characterized the last decade of space industry, is exploited to design a 3U CubeSat able to provide a basic scientific return sufficient to improve the target as...
Article
Full-text available
This paper discusses principles and techniques to evaluate processors for dependable computing in space applications. The focus is on soft errors, which dominate the failure rate of processors in space. Error, failure and propagation models from literature are selected and employed to estimate the failure rate due to soft errors in typical processo...
Article
This paper introduces a strategy for an autonomous reconfiguration of a fractionated synthetic aperture radar (SAR) spacecraft system. The radar antenna is distributed on a small-satellite formation that can be reconfigured on orbit depending on the mission requirements. Once the acquisition geometry is specified in terms of formation type and the...
Article
Full-text available
Small satellites are receiving increased recognition in the space domain due to their reduced associated launch costs and shorter lead time when compared to larger satellites. However, this advantage is often at the expense of mission capabilities, such as available electrical power and propulsion. A possible solution is to shift from the conventio...
Conference Paper
Small satellites with increased capabilities in terms of power and propulsion are being demanded for future missions. This paper proposes a possible solution which is the design of a novel integrated solar thermal system that co-generates propulsion and power on-board mini satellites. The system consists of a solar thermal propulsion system (STP) c...
Conference Paper
Employing a satellite swarm for radio astronomy has been continuously addressed in the Orbiting Low Frequency ARray (OLFAR) project. A 100 km diameter of aperture array constructed by distributed satellites will be able to provide sky maps of better than 1 arc-minute spatial resolution at 10 MHz. However, an orbit design strategy for the swarm sate...
Article
Full-text available
PocketQubes are a form factor of highly miniaturized satellites with a body of one or more cubic units of 5 cm. In this paper, the characteristics of PocketQubes in terms of their constraints and their (potential) utility are treated. To avoid space debris and limit collision risk, the orbits of PocketQubes need to be constraint. An analysis of orb...
Article
This paper presents a new approach for autonomous reconfiguration of distributed space systems, which ensures safe guidance of spacecraft formations towards the desired patterns while optimizing the total propellant consumption. The orbital transfer is reduced to the form of a convex optimization problem to guarantee rapid computation of control la...
Conference Paper
Full-text available
This paper introduces a novel framework which combines a Convolutional Neural Network (CNN) for feature detection with a Covariant Efficient Procrustes Perspective-n-Points (CEPPnP) solver and an Extended Kalman Filter (EKF) to enable robust monocular pose estimation for close-proximity operations around an uncooperative spacecraft. The relative po...
Article
Full-text available
This work proposes PageRank as a tool to evaluate and optimize the global performance of a swarm based on the analysis of the local behavior of a single robot. PageRank is a graph centrality measure that assesses the importance of nodes based on how likely they are to be reached when traversing a graph. We relate this, using a microscopic model, to...
Article
Operational spacecraft are facing a risk of collision with space debris objects. The net capturing method has been proposed to mitigate this risk on spacecraft. The mass-spring model is usually applied for net modeling by discretizing a cable into one or several mass-spring-damper elements in simulation. The absolute nodal coordinates formulation (...
Article
This paper presents innovative approaches for guidance of spacecraft formations during reconfiguration, developed under the paradigms of cluster autonomy and safe maneuverability. A task-assignment algorithm identifies those satellites that need to be rearranged in order to minimize the total propellant consumption. The decision process relies on c...
Article
Induction-based reaction spheres have been presented in many references and their performances are normally investigated through experiments or numerical simulations which are time-consuming. Here, an analytical way is presented and it enables researchers to evaluate a new design quickly. The presented performance analysis is conducted through the...
Conference Paper
This paper analyzes the contribution of caches to failures at processor level due to soft errors. In order to do this, approximated methodologies to estimate the percentage of the total Sensitive Area (SA) of a processor for each unit during early design exploration are proposed. Then, to identify the most vulnerable units, a metric called Relative...
Preprint
The past two decades saw a renewed interest in low frequency radio astronomy, with a particular focus on frequencies above 30 MHz. However, at frequencies below 30 MHz, Earth-based observations are limited due to a combination of severe ionospheric distortions, almost full reflection of radio waves below 10 MHz, solar eruptions and human-made radio...
Article
Bus saturation is deemed as one of the primary causes of delays in the data propagation between spacecraft components. However, the conditions under which bus congestion can affect measurements variability were not well characterized before. This work presents a bus saturation model and a set of experiments to characterize the bus performance of sa...
Article
The past two decades have witnessed a renewed interest in low frequency radio astronomy, with a particular focus on frequencies above 30 MHz e.g., LOFAR (LOw Frequency ARray) in the Netherlands and its European extension ILT, the International LOFAR Telescope. However, at frequencies below 30 MHz, Earth-based observations are limited due to a combi...
Conference Paper
Small satellites are receiving increased recognition in the space domain due to their reduced associated launch costs and their shorter lead time when compared to larger satellites. However, this advantage is often at the expense of mission capability, such as available electrical power. A possible solution is to change from the conventional solar...
Article
Full-text available
This paper proposes a roadmap to address present and future needs in space systems with RISC-V processors. RISC-V is an open and modular Instruction Set Architecture (ISA) which is rapidly growing in popularity in terrestrial applications. In order to satisfy different applications with contrasting requirements in satellite data systems, four diffe...
Conference Paper
Full-text available
This paper reports on a comparative assessment of Image Processing (IP) techniques for the relative pose estimation of uncooperative spacecraft with a monocular camera. Currently, keypoints-based algorithms suffer from partial occlusion of the target, as well as from the different illumination conditions between the required offline database and th...
Article
Full-text available
The relative pose estimation of an inactive target by an active servicer spacecraft is a critical task in the design of current and planned space missions, due to its relevance for close-proximity operations, i.e. the rendezvous with a space debris and/or in-orbit servicing. Pose estimation systems based solely on a monocular camera are recently be...
Article
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-...
Article
This paper presents an innovative approach combining a fuzzy controller and a control allocation method applied to the control problem of allocating actuators’ efforts in an over-actuated system. The controller is applied to a space debris removal mission using a deployable net on-board a 3U CubeSat. The controller calculates the necessary effort o...
Article
The increasing number of satellites for specific space missions is hindering efficient control from the ground stations. In addition, the risk of failing or deteriorating elements in a multi-satellite system (MSS) leads to the uncertainty in its operating environment which challenges traditional centralized planning algorithms. Centralized algorith...
Article
Full-text available
In this work, we explore emergent behaviors by swarms of anonymous, homogeneous, non-communicating, reactive robots that do not know their global position and have limited relative sensing. We introduce a novel method that enables such severely limited robots to autonomously arrange in a desired pattern and maintain it. The method includes an autom...
Article
Full-text available
In recent years, satellite design has extended towards miniaturisation to reduce associated cost with launching and conducting space missions. Small satellites provide low-cost platforms for space missions. However, this lower cost comes at the expense of the removal of key sub-systems, such as the propulsion system, due to the small available onbo...
Article
In recent years, the increasing need in small satellite solutions triggers the miniaturization of attitude control systems. Reaction spheres were proposed as promising replacements of conventional reaction wheels for their 4π rotations. Since the generated control torques could be about any desired axes, a single reaction sphere is sufficient for t...
Conference Paper
Full-text available
Spacecraft buses using distributed software architectures have been adopted in space missions design due to their increased performance and reliability. However, to achieve reliability in highly distributed systems, fault-tolerant mechanisms must be implemented to mitigate the anomalous behavior of components and software processes. One of the most...
Conference Paper
Full-text available
This paper investigates the performance of miniaturized reaction spheres. Currently, a majority of existing reaction spheres are at a technology readiness level of 3 to 4 and prototypes are developed for 50 kg-class spacecraft. Since the motivation of replacing reaction wheels with reaction spheres stems from the limited volume and power budgets of...
Conference Paper
Full-text available
This paper presents innovative approaches for guidance of spacecraft formations during reconfiguration. The proposed strategies are developed under the paradigms of cluster autonomy and safe maneuverability. To that end, a task-assignment algorithm identifies the satellites that need to be rearranged in order to minimize the total propellant consum...
Conference Paper
Full-text available
The problem of pure magnetic detumbling of a fast-tumbling picosatellite is considered. A new weighted B-dot control algorithm is proposed. The algorithm enables power reduction while not sacrificing detumbling performance. Analytical expressions relating the maximal expected rotational rate to the minimum sampling time required are presented. Simu...
Article
This brief presents a comprehensive approach for the modeling of micropropulsion systems based on the vaporization of a liquid. The model combines the analytical and empirical relations derived from extensive experimental analysis and fundamental physical laws. This allows modeling of key parameters, such as mass flow rate, for the entire system co...
Article
There is a clear trend towards the developments of micro-propulsion system to enhance the capabilities of nano- and pico-satellites. A promising propulsion option to meet the strict requirements of these small satellites is the Low-Pressure Micro-Resistojet (LPM) which works under rarefied gas dynamic regime. To simplify the engineering design of t...
Article
Full-text available
In this work the extent to which orbit and attitude sensors may cross-support each other in a joint processing to reduce estimation errors of the relative orbital and attitude dynamics is investigated. In order to do this, an engineering dynamic model taking into account the coupling effects between orbit and attitude dynamics is exploited for esti...
Conference Paper
This paper introduces a strategy for an autonomous reconfiguration of a fractionated Synthetic Aperture Radar (SAR). The component antenna is distributed on a small-satellite formation that can be reconfigured on orbit depending on the mission requirements. Once the acquisition geometry is specified in terms of formation type and the desired requir...
Conference Paper
Vaporizing Liquid Microthrusters (VLM) have recently received attention as promising propulsion technology for highly miniaturized spacecraft due to its high thrust levels and low power consumption. This paper presents the results of numerical optimization of the parameters for the design of the heating chamber of VLMs that use water as the propell...
Conference Paper
A Low-Pressure Micro-Resistojet (LPM) is under development at TU Delft with the intention to provide future nano- and pico-satellites with the necessary capability to execute formation flying maneuvers, orbit change maneuvers, and station keeping. In this particular type of electro-thermal thruster, water is a green propellant of excellent performa...
Article
The purpose of this paper is to seek the suitable local objectives for each satellite to optimal the global mission allocation strategy with a global utility function. This paper uses a game-theoretical formulation for a multi-satellite system in which the satellites are viewed as a unique unit with their self-interests. To solve the problem, the f...
Article
This paper presents an onboard autonomous mission re-planning system for Multi-Satellites System (MSS) to perform onboard re-planing in disruptive situations. The proposed re-planning system can deal with different potential emergency situations. This paper uses Multi-Objective Hybrid Dynamic Mutation Genetic Algorithm (MO-HDM GA) combined with re-...
Article
Developers experience issues with the compatibility, connector size and robustness of electrical interface standards for CubeSats and PocketQubes. There is a need for a lean and robust electrical interface standard for these classes of satellites. The proposed interface standard comprises a linear data bus which is used for housekeeping data, inter...
Article
CubeSats have been extensively used in the past decade as scientific tools, technology demonstrators and for education. Recently, PocketQubes have emerged as an interesting and even smaller alternative to CubeSats. However, both satellite types often lack some key capabilities, such as micropropulsion, in order to further extend the range of applic...
Article
Three Low Pressure Micro-resistojets (LPM) with integrated heater and temperature measurement were designed, manufactured and characterized at Delft University of Technology. The devices were manufactured using Silicon-based Micro Electro Mechanical Systems (MEMS) technology including a heater made of Molybdenum for better operations at high temper...
Article
Contact dynamic models for active debris capturing using a net are presented and analyzed using numerical simulations. The contact dynamics are based on two methods: the penalty-based method and the impulse-based method. Both methods apply contact detection algorithms based on the Axis-Aligned Bounding Box. The impulse-based method is, for the firs...
Article
This paper presents the results of design, manufacturing and characterization of Vaporizing Liquid Microthrusters (VLM) with integrated molybdenum heaters and temperature sensing. The thrusters use water as the propellant and are designed for use in CubeSats and PocketQubes. The devices are manufactured using silicon based MEMS (Micro Electro Mecha...
Conference Paper
This paper reports on the reconstruction of key orbital elements of the Earth's orbit around the Sun from a miniaturized temperature sensor onboard the Delfi-C 3 CubeSat, a novel approach never explored before to the best of our knowledge. Delfi-C 3 is a triple-unit CubeSat, developed by Delft University of Technology, which was launched on April 2...
Article
Full-text available
In this work we investigate to what extend orbit and attitude sensors may cross-support each other in a joint processing to maximize information retrieval of the relative orbital and attitude dynamics. Its contribution clarifies to what extend the coupling effects between orbit and attitude dynamics can be advantageously exploited for estimation pu...
Article
Failure detection, isolation, and recovery is an essential requirement of any space mission design. Several spacecraft components, especially sensors, are prone to performance deviation due to intrinsic physical effects. For that reason, innovative approaches for the treatment of faults in onboard sensors are necessary. This work introduces the con...
Article
The number of launches of nano- and pico-satellites have significantly increased over the past decade. Miniaturized subsystems, such as micro-propulsion, for these classes of spacecraft are rapidly evolving and, in particular, microresistojets have shown great potential of applicability. One of the key points to address in the development of such d...
Conference Paper
Full-text available
This paper aims at analysing the current capabilities of the NORAD Space Surveillance network , in particular focusing on very small objects in LEO. Spacecraft miniaturization has been pushing the limits and capabilities of small satellites so much that spacecraft as small as 5x5x5 cm have already been launched and even smaller ones are currently e...
Article
With respect to spacecraft attitude control, reaction spheres are promising alternatives to conventional momentum exchange devices for the benefits brought by their 4π rotation. Many design concepts of reaction spheres have been proposed in the past decades, however, developments of the driving unit and the bearing, as well as their combination rem...
Article
Space missions have traditionally been controlled by operators from a mission control center. Given the increasing number of satellites for some space missions, generating a command list for multiple satellites can be time-consuming and inefficient. Developing multi-satellite, onboard mission scheduling & planning techniques is, therefore, a key re...
Article
A tethered-net is a promising method for space debris capturing. However, its deployment dynamics is complex because of the flexibility, and its dependency of the deployment parameters is insufficiently understood. To investigate the deployment dynamics of tethered-net, four critical deployment parameters, namely maximum net area, deployment time,...
Conference Paper
Full-text available
With the increasing demand for space technology, there are more and more calls for multiple satellites missions. As the number of satellite increases, generating command sequence can be a laborious procedure. It not only requires specialized knowledge from operators but also takes too much time for command list transmission from ground station to o...
Conference Paper
Full-text available
In this paper, a miniaturized reaction sphere able to rotate about arbitrary axes is presented. Compared with conventional reaction wheels, the innovative spherical actuator could enhance robustness of a spacecraft's attitude control system. For a satellite with certain targeting requirements, an assembly of three wheels is vulnerable. Non-function...