EO-ALERT: A Satellite Architecture for Autonomous Maritime Monitoring in Almost-Real-Time

This paper presents an overview of the maritime monitoring satellite architecture and results achieved by the EO-ALERT H2020 project. EO-ALERT proposes the definition and development of the next-generation Earth Observation (EO) data processing chain, based on a novel flight segment architecture that moves EO data processing elements from the ground segment to on-board the satellite, with the aim of delivering the EO products directly to the end user with very low latency; in almost-real-time, e.g. within 1 minute. This paper presents the EO-ALERT architecture, its performance and hardware, with a focus on its application to maritime scenarios. Performances are presented for multiple reference user scenarios; autonomous ship detection, for a service similar to the EMSA VDS, and extreme weather monitoring, for wind and wave. The ground test results using EO data show that the proposed architecture can deliver maritime EO products to the end user with latency lower than one-point-five minutes, for both SAR and Optical Very High Resolution (VHR) missions, demonstrating the viability of the architecture for almost-real-time maritime monitoring

Advanced Data Chain Technologies for the Next Generation of Earth Observation Satellites Supporting On-Board Processing for Rapid Civil Alerts

The growing number of planned Earth Observation (EO) satellites, together with the increase in payload resolution and swath, brings to the fore the generation of unprecedented volumes of data that needs to be downloaded, processed and distributed with low latency. This creates a severe bottleneck problem, which overloads ground infrastructure, communications to ground, and hampers the provision of EO products to the End User with the required performances. The European H2020 EO-ALERT project (http://eo-alert-h2020.eu/), proposes the definition of next-generation EO missions by developing an on-board high speed EO data processing chain, based on a novel flight segment architecture that moves optimised key EO data processing elements from the ground segment to on-board the satellite. EO-ALERT achieves, globally, latencies below five minutes for EO products delivery, reaching latencies below 1 minute in some scenarios. The proposed architecture solves the above challenges through a combination of innovations in the on-board elements of the data chain and the communications link. Namely, the architecture introduces innovative technological solutions, including on-board reconfigurable data handling, on-board image generation and processing for generation of alerts (EO products) using Artificial Intelligence (AI), high-speed on-board avionics, on-board data compression and encryption using AI and reconfigurable high data rate communication links to ground including a separate chain for alerts with minimum latency and global coverage. Those key technologies have been studied, developed, implemented in software/hardware (SW/HW) and verified against previously established technologies requirements to meet the identified user needs. The paper presents an overview of the development of the innovative solutions defined during the project for each of the above mentioned technological areas and the results of the testing campaign of the individual SW/HW implementations within the context of two operational scenarios: ship detection and extreme weather observation (nowcasting), both requiring a high responsiveness to events to reduce the response time to few hours, or even to minutes, after an emergency situation arises. The technologies have been experimentally evaluated during the project using relevant EO historical sensor data. The results demonstrate the maturity of the technologies, having now reached TRL 4-5. Generally, the results show that, when implemented using COTS components and available communication links, the proposed architecture can generate and delivery globally EO products/alerts with a latency lower than five minutes, which demonstrates the viability of the EO-ALERT concept. The paper also discusses the implementation on an Avionic Test Bench (ATB) for the validation of the integrated technologies chain

A Novel Architecture for the Next Generation of Earth Observation Satellites Supporting Rapid Civil Alert

The EO-ALERT European Commission H2020 project proposes the definition, development, and verification and validation through ground hardware testing, of a next-generation Earth Observation (EO) data processing chain. The proposed data processing chain is based on a novel flight segment architecture that moves EO data processing elements traditionally executed in the ground segment to on-board the satellite, with the aim of delivering EO products to the end user with very low latency. EO-ALERT achieves, globally, latencies below five minutes for EO products delivery, and below one minute in realistic scenarios. The proposed EO-ALERT architecture is enabled by on-board processing, recent improvements in processing hardware using Commercial Off-The-Shelf (COTS) components, and persistent space-to-ground communications links. EO-ALERT combines innovations in the on-board elements of the data chain and the communications, namely: on-board reconfigurable data handling, on-board image generation and processing for the generation of alerts (EO products) using Machine Learning (ML) and Artificial Intelligence (AI), on-board AI-based compression and encryption, high-speed on-board avionics, and reconfigurable high data rate communication links to ground, including a separate chain for alerts with minimum latency and global coverage. This paper presents the proposed architecture, its hardware realization for the ground testing in a representative environment and its performance. The architecture’s performance is evaluated considering two different user scenarios where very low latency (almost-real-time) EO product delivery is required: ship detection and extreme weather monitoring/nowcasting. The hardware testing results show that, when implemented using COTS components and available communication links, the proposed architecture can deliver alerts to the end user with a latency below five minutes, for both SAR and Optical missions, demonstrating the viability of the EO-ALERT architecture. In particular, in several test scenarios, for both the TerraSAR-X SAR and DEIMOS-2 Optical Very High Resolution (VHR) missions, hardware testing of the proposed architecture has shown it can deliver EO products and alerts to the end user globally, with latency lower than one-point-five minutes

Experimental assessment of an asymmetric steel–concrete frame under a column loss scenario

Several noteworthy accidents clearly pointed out the risk of disproportioned collapse of framed structures. Design codes recently recognized it by adding a new requirement: the structural robustness. Among the different approaches to check robustness, the most popular is associated with the column loss scenario: the analysis should verify that, in case of a column loss, an alternative load path does exist, limiting the portion of structure affected by collapse. Consequently, numerous experimental and numerical studies of 2D and 3D structures were carried out in recent years to identify the mechanism of load transfer from the damaged to the undamaged part of the structure. This knowledge becomes an essential and fundamental key for assuring adequate resistance against progressive collapse by the development of catenary action in the beams and membrane action in the floor slab. Studies of reinforced concrete systems and of bare steel sub-assemblies are numerous. More recent is the focus on the response of steel–concrete composite structures subjected to accidental events. Furthermore, most of these studies focused on the characterization of 2D sub-assemblies or 3D in-scale framed structures. This paper presents an experimental assessment of the structural response of a 3D full-scale steel and concrete composite frame under the column loss scenario. The results are finally compared with the response of a frame with the same overall geometry but different columns’ layout, tested by the Authors within the same research programme

S4Pro Application and Mission Scenrios

This document represents deliverable D1.1 prepared in the frame of Task 1.1 of Work Package 1 of S4Pro project H2020 Grant agreement number 822014. This deliverable contains the description of S4Pro relevant to: - candidate Earth observation applications, specifically optics applications, SAR applications, and GNSS applications; - state of the art analysis for key-enabling technologies relevant to such applications; - payload data processing and communicatio

Fault Tolerant Control of a Variable Pitch Quadrotor

In this paper, we solve the fault tolerant tracking problem for a variable pitch quadrotor. Following the Disturbance Observer Based Control design paradigm, we face the observation problem for the blade pitch, and consequently the related fault and failure diagnosis problems. The control allocation algorithm solves the optimal redistribution problem of the control effort among the propellers in case of actuation failure. The optimization problem takes into account the energy consumption, the health condition of the actuators and the presence of input constraints, such as saturation and rate of change limits. In particular, we face the specific problem of lock-in-place servo failures, which reduce the number of the control actions in the system. Indeed, together with a fault detection and isolation module, lock-in-place servo failures can be managed in the control allocation algorithm while keeping the tracking capabilities. The proposed optimal fault tolerant accommodation algorithm can be coupled with most of the nonlinear control laws commonly applied to conventional multirotor systems. Numerical simulations with noise and constraints show the capability of the scheme to handle this class of failures

Fault Tolerant Control for Remotely Operated Vehicles with Thruster Faults using Nonlinear Disturbance Observers

In this paper, a disturbance observer based control strategy is developed to provide fault tolerance to thruster faults for a remotely operated vehicle. The scheme relies on the vehicle’s position, orientation and velocity information only, without the need for additional measurements from the thrusters such as voltage, current, and rotation speed. Because the system is over-actuated, a bank of observers is designed for purposes of fault detection and isolation. A nonlinear disturbance observer is designed to restructure itself, according to the fault isolation outcome, to estimate the fault magnitude. The fault estimation is finally exploited by the control law using an active fault tolerant control strategy. The solution is designed for the cases where at most one faulty thruster is expected. The fault tolerant control strategy is tested in simulation, where a severe thruster fault is injected