Station terrienne | EPFL Graph Search

Une station terrienne ou station au sol est une installation située à la surface de la Terre qui prend en charge les communications entre la Terre et les engins spatiaux : lanceurs, satellites scientifiques ou d'application, vaisseaux spatiaux avec équipage, stations spatiales ou sondes spatiales. Définition Pour pouvoir déterminer la trajectoire d'un engin spatial (lanceur, satellite, sonde spatiale), contrôler son fonctionnement, lui envoyer des commandes et récupérer les données qu'il a collecté il est nécessaire de pouvoir échanger des informations entre celui-ci et les installations sur Terre. Ces échanges sont réalisés par ondes radio, optiques,.. Une station terrienne comprend les équipements nécessaires pour établir cette liaison par radio. Ceux-ci comprennent principalement une ou plusieurs antennes paraboliques qui sont pointées vers les engins spatiaux, des émetteurs et récepteurs radio et des équipements électroniques et informatiques chargés de contrôler, d

Lake Imaging and Monitoring Aerial Drone

David Andrew Barry, Nawaaz Sidharth Gujja Shaik, Lukas Oliver Hostettler, Karl Johannes Kangur, Jean-Luc Liardon, Ludovic Zulliger

We describe the development of a BVLOS (Beyond Visual Line-Of-Sight) model aircraft (UAV). The broad design requirements included (i) fuselage capable of accommodating an imaging package or other instrumentation, (ii) suitability for over-lake BVLOS authorization in Switzerland, (iii) capability of land or water take-offs/landing, (iv) at least 90-min flight autonomy, (v) modularity of the imaging package and (vi) real-time IR/RGB imagery. Requirement (i) was to ensure an aircraft amenable to future developments. Requirements (ii)-(iv) were driven by the goal of improving estimates of lake surface energy fluxes, since such fluxes have a major impact on long-term lake temperatures and hence ecological status. Requirement (v), in conjunction with (i), allows the UAV to be adapted to other imaging applications. The real-time imagery requirement (vi) permits modifications of on-going missions to map areas of specific interest as they are detected. The prototype UAV produced to satisfy these characteristics was built on the twin-motor My Twin Dream (MTD) aircraft, which has a 1.8-m wing span airframe and a spacious fuselage. The legal authorization necessitated, where feasible, hardware redundancy as well as installation of a parachute system. Continuous communication between the ground station and UAV is provided by the LTE cellular telephone network. The UAV communication is handled by an on-board Linux computer, which is also responsible for control of the imagery package. The avionics involved modifications of the open-source APM autopilot software and the associated ground control station. A key modification was to support a custom-built emergency recovery system, which is triggered by loss of a heartbeat signal from the autopilot. The MTD airframe was modified to accommodate the system electronics and imaging hardware. Results from test flights over Lake Geneva demonstrate the ability of the aircraft to produce imagery data.

2018

A low-cost, autonomous mobile platform for limnological investigations, supported by high-resolution mesoscale airborne imagery

David Andrew Barry, Jérôme Béguin, Beat Marcel Geissmann, Nawaaz Sidharth Gujja Shaik, Abolfazl Irani Rahaghi, Anton Ivanov, Pascal Klaus, Ulrich Lemmin, Jean-Luc Liardon, Philippe Olivier Paccaud, Stepan Tulyakov, Htet Kyi Wynn, Ludovic Zulliger

Two complementary measurement systems – built upon an autonomous floating craft and a tethered balloon – for lake research and monitoring are presented. The autonomous vehicle was assembled on a catamaran for stability, and is capable of handling a variety of instrumentation for in situ and near-surface measurements. The catamaran hulls, each equipped with a small electric motor, support rigid decks for arranging equipment. An electric generator provides full autonomy for about 8 h. The modular power supply and instrumentation data management systems are housed in two boxes, which enable rapid setup. Due to legal restrictions in Switzerland (where the craft is routinely used), the platform must be observed from an accompanying boat while in operation. Nevertheless, the control system permits fully autonomous operation, with motion controlled by speed settings and waypoints, as well as obstacle detection. On-board instrumentation is connected to a central hub for data storage, with real-time monitoring of measurements from the accompanying boat. Measurements from the floating platform are complemented by mesoscale imaging from an instrument package attached to a He-filled balloon. The aerial package records thermal and RGB imagery, and transmits it in real-time to a ground station. The balloon can be tethered to the autonomous catamaran or to the accompanying boat. Missions can be modified according to imagery and/or catamaran measurements. Illustrative results showing the surface thermal variations of Lake Geneva demonstrate the versatility of the combined floating platform/balloon imagery system setup for limnological investigations.

2019

Accuracy Prediction in Aerial Mapping

Laurent Valentin Jospin

Low cost and low weight unmanned aerial vehicle (UAV) systems with imaging capability have enjoyed a rapid development over the past years and are increasingly deployed as carriers for mapping purposes. They present a well-established tool for local-area remote sensing in the fields of agriculture, forestry, mining and hydrology as well as in scientific research. An important part of MAV mapping system is the ground station with a mission planner which serves for flight scheduling and mission execution. The traditional mission planners for MAVs are not dedicated to precise photogrammetry in complicated terrain. They allow planning and executing of autonomous flight as well as setting up of the autopilot systems. However, they lack functions for advanced flight planning, such as those motivated by achieving certain precision and reliability of the determined coordinates of features within the mapped area. The goal of this work is to create a software tool that given a planned trajectory (i.e. planned position and orientation of camera exposure), preliminary digital elevation model (DEM), assumptions on surface texture (i.e. number, distribution and accuracy of image observations) and (optionally) a certain number and distribution of ground control points (GCPs), allow to quantify the quality of the mapping.

2017

Lake Imaging and Monitoring Aerial Drone

David Andrew Barry, Nawaaz Sidharth Gujja Shaik, Lukas Oliver Hostettler, Karl Johannes Kangur, Jean-Luc Liardon, Ludovic Zulliger

2018

A low-cost, autonomous mobile platform for limnological investigations, supported by high-resolution mesoscale airborne imagery

2019