Rigorous software design for nano and micro satellites using BIP framework

The CubETH satellite mission, a cooperative Swiss CubeSat mission involving ETH Zurich, EPF Lausanne, several universities of applied sciences, and Swiss companies, will allow technology demonstrations and proof-of-concepts concerning GNSS-based navigation information by carrying five patch antennas, each connected to two independent u-blox NEO-7N receivers. These very small, commercially available low-cost receivers are able to track single-frequency code and phase data of all the major GNSS, i.e. GPS, GLONASS, QZSS, Galileo and Beidou. The main science objective for the CubETH mission is to investigate precise orbit determination strategies using COTS hardware. The mission shall also demonstrate new technologies, applicable in the field of small satellites. In this work, we focus mostly on development of robust flight software for small and nano satellites. During the Swisscube project there were numerous problems with validation and verification of the flight software code. The software has to be adapted to the hardware architecture selected for every new satellite mission. While commercial tools exist to help with the issue, subject of robust software development was not addressed by the cubesat community, mostly due to lack of resources. Some projects simply structure their code in C/C++ and then extensively test it, maybe using some analysis tools such as "Lint" [5]. This is an helpful tool to find some design errors, but it does not guarantee that the software behavior is the desired one. Others use SysML/UML tools to describe the system as a whole and then check some properties such as energy consumption. SysML can be a valid tool for system engineering as a whole, but it is not rigorous enough to allow automatic software behavior verification and validation. In this project the “Behavior Interaction Priority” BIP framework will be used to design the software running in the control and data management subsystem (CDMS) of CubETH. The BIP framework has been developed by the Verimag laboratory in Grenoble university and is currently used in the EPFL by the "Rigorous System Design Laboratory" (RISD). We have designed and modeled a full software architecture using this framework to formally verify our software. We will present lessons learned and problems that were encountered during the development.

A simple & [and] accessible front-end satellite receiver for communications and e-learning in emerging countries

Olivier Videme Bossou

For the universities of the emergent countries, and those of Cameroon in particular, the fight to reach a durable development requires to know the needed scientific and technical information for their development, how to get it and to spread it out among partners in the country. Obviously, the complete answer to these preoccupations lies well beyond the framework of this project, but a projection, partial but highly significant, can nevertheless be obtained if one concentrates one's efforts on a specific technological field : in the present study, we shall treat of antennas for telecommunications systems. This subject is highly suitable as example and potential incubator for future achievements. The ultimate goal is to design and carry out the fabrication of a system of satellite communications adapted to the financial resources and to the development needs of the universities of the South. First of all, we will review the state of the art in satellite communication systems, both for already operating ones and also for new systems, still under development. Then we will determine which system of satellite telecommunications has a receiver and communication fees with affordable costs : our choice will be made on Worldspace satellite system, which was actually designed for developing countries. We will also review the status of planar antenna and low noise amplifier technology, and then explicit the basic challenge involved in our thesis project. One of the aims of this project is to use local wood as dielectric in SSFIP type antennas. Before using a material as dielectric in an antenna design, it must be characterized. Before carrying the characterization of local wood species, we will begin by reviewing some commonly used dielectric measurement techniques. Then we will carry out a series of measurements to characterize the species of wood growing in the Cameroonian forest. At the end of the series of measurements and according to the dielectric losses observed, we will select the species of wood best suited to make a good substrate for a microstrip antenna. Next, we will design, manufacture and test low cost antennas. These antennas must satisfy not only technical criteria compatible with those of the telecommunications system chosen but, even most importantly, it must meet socioeconomic criteria : the antennas must be manufactured with low cost and locally available materials, making use of simple technological processes. Once we have found the wood species that exhibits the lowest dielectric losses, we will simulate, and then manufacture the SSFIP type antenna with wood as substrate and aluminium as conducting element. Then we will measure its characteristics and check whether they are compatible with those of a Worldspace receiver. The signal received from the satellite by the antenna is very weak. It will be important to strengthen the received signal with a low noise amplifier (LNA) before connecting the antenna to the receiver. Thus the antenna and the LNA constitute an active antenna and form what we call here the radiofrequency (RF) front-end. We will design, manufacture and measure the LNA characteristics. A simple manufacturing process must be used to realize these antennas, because later on they must be manufactured locally in Cameroon : this is a determining challenge to ensure the economic independence, which is essential in our thesis project. Afterwards we will join the LNA to the planar antenna and connect the active antenna obtained in this manner to a commercial Worldspace receiver. Finally, we will perform receiving tests of the Worldspace radio station with the system designed. In parallel, our project includes a second goal, which presents an equivalent significance. We will use existing Matlab codes to develop an online course to teach antenna theory. In addition, at the end of the project and when the Cameroonian local manufacture would have started, we will put all algorithms used for the antenna design on the web site in a multi-media applet, together with a complete documentation of all the manufacturing technologies used. The courses that already exist in Lausanne and Yaounde, relating to the description of other types of antennas will be added, thus leading to a complete teachware that would ensure the durability and the dissemination of the results obtained, and would provide an invaluable tool for teaching and training.

EPFL2007

Systems engineering and design of a Mars Polar Research Base with a human crew

Anton Ivanov, Claudio Leonardi, Anne-Marlene Rüede, Tatiana Volkova

Mars Polar Ice caps have been known ever since they were first observed by Cassini. Robotic exploration mis- sions, starting with Mariner 9, have confirmed that they are composed of water ice. During later missions, instruments such as Mars Global Surveyor's MOLA have established a detailed topography and have estimated their depth at about 3 km in the thickest part, while detailed internal structure has been investigated by MARSIS from Mars Express and SHARAD from the Mars Reconnaissance Orbiter. This analysis proposes to establish a base near North Polar Layered Deposits to investigate Mars' climate, hydrological processes and to test for possible traces of life. The objectives of the mission are to sustain a crew for nine months on the surface of Mars, near the North Pole, and to bring the crew back to Earth safely. During the surface mission, the crew will drill and analyze Polar Layered Deposits in ice samples. Furthermore, because the North Polar region provides an easy access to water ice, this area has the potential of sustaining a long-term human presence. The Mars Polar Research mission shall therefore prepare for long term missions, spanning over multiple crew generations. Indeed, longer duration missions and larger crews should be facilitated by this first mission. This paper describes a mission design for a Mars Polar Research base using systems engineering approach and scenario testing. The goal of the work is to establish a strategy composed of various technologies that have been selected accordingly. The requirements related to crew composition, human physiology and psychology adaptation, quality of com- munication, challenges and prospects of advancing science, as well as optimum habitat design and its usability, are derived and compiled into mass, volume, data and power consumption. A design for the base and mission scenario is also proposed. Given the identified requirements, possible technologies for life support systems, radiation protection, in-situ propellant production, thermal control, air pressure difference compensation and availability of power are discussed and solutions to focus on are recommended. Furthermore, the requirements for a long-term mission preparation are also identified and solutions to include in a first Mars mission with crew are recommended. In conclusion, approximately 110 metric tons and 160 kW are required to enable a Mars Polar mission with a human crew. A two-phase mission is recommended for enabling the testing of key in-situ resource utilization technologies allowing to minimize mass, while ensuring the security of the crew. The use of optimal payload and fairing, a Mars orbit crane system and deployable structures are recommended. Finally, in pre- paration for a long-term presence of humans on Mars, including in-situ testing of key technologies enabling the production of consumables facilitating autonomy from Earth is suggested. The consumables that have been identified as not being able to be tested before a first crew is sent to Mars are food and energy production. These developments may serve as priorities for current Mars settlement programs.

2019

Ontology-based system to support industrial system design for aircraft assembly

Jinzhi Lu, Xiaochen Zheng

The development of an aircraft industrial system is a complex process which faces the challenge of digital discontinuity in multidisciplinary engineering due to various interfaces between different digital tools, leading to extra development time and costs. This paper proposes an ontology-based system, aiming at functionality integration and design process automation, by Models for Manufacturing methodology principles. A tool-agnostic modelling, simulation and validation platform with Discrete Event Simulation and 3D simulation is enabled and demonstrated in a real case study. An ontology layer collecting the domain knowledge enables integration of the proposed system, accelerating the design process and enhancing design quality. Copyright (c) 2022 The Authors.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)