System engineering approach applied to Galileo system

Developing a localization system, with more precise performances than GPS that guarantees Europe autonomy is a complex challenge that ESA and a large number of European economical actors of space industry were decided to meet. To design and manage such a huge system would have been impossible without applying System Engineering best practices, thanks to fundamental activities, multidisciplinary teams and dedicated tools. This paper gives an overview of the System Engineering approach applied to design and develop Galileo, the European Satellite Radio-Navigation System. Galileo system scope is so wide that we have decided to focus on some particular steps of the System Engineering processes that are: Requirements Engineering and Architec-ture. All along this paper, examples are given to illustrate the additional difficulties that have made Systems Engineering more and more complex

Panorama of ideas on structure and materials for the design of a multi-modular space station at EML2.

The goal of the article will be to come up with an optimized solution that can answer the question of how to build a space station (named THOR, Trans-lunar Human explORation): fit for Deep Space Habitat. The spacecraft’s structure examined here is based around seven cylindrical habitable modules, each one fulfilling a specific function - leisure and daily life, experiments, Extra Vehicular Activity, Space Medical Center - and two extra spherical sections, used both for daily life activities and docking tasks. Taking the challenges and constraints of deep-space environment into account and adding up the effects of solar winds in deep space environment, each module has been put through an accurate analysis to then be optimized during the conceptual design of the spacecraft. Some ideas for the propulsive system layout and overall configuration for the docking system have also been proposed. To make the study at hand as thorough as possible, the research project focus on and examines a wide array of materials used to build spacecraft and stations: metal alloys, composite materials, sandwich honeycomb core, inflatable anti-solar-radiation (at the option of water storage inside), and see-through glass-like materials. Eventually, a conclusive part then try to sum up both structural concepts and material analysis for the final internal and external design of the spacecraft. During the study, many questions about possible innovative solutions arose, and the final chapter summarize them all

STR: a student developed star tracker for the ESA-LED ESMO moon mission

In the frame of their engineering degree, ISAE’s students are developing a Star Tracker, with the aim of being the core attitude estimation equipment of the European Moon Student Orbiter. This development goes on since several years and is currently in phase B. We intend to start building an integrated breadboard for the end of the academic year. The STR is composed of several sub-systems: the optical and detection sub-system, the electronics, the mechanics and the software. The optical detection part is based on an in-house developed new generation of APS detectors. The optical train is made of several lenses enclosed in a titanium tube. The electronics includes a FPGA for the pre-processing of the image and a microcontroller in order to manage the high level functions of the instrument. The mechanical part includes the electronics box, as well as the sensor baffle. The design is optimized to minimize the thermo-elastic noise of the assembly. Embedded on ESMO platform, this Star Tracker will be able to compute the satellite‘s attitude, taking into account the specific requirements linked to a Moon mission (illumination, radiation requirements and baffle adaptation to lunar orbit). In order to validate the design, software end-to-end simulation will include a complete simulation of the STR in its lunar dynamic environment. Therefore, we are developing a simple orbital model for the mission (including potential dazzling by celestial bodies)

Rendez vous optimization with an inhabited space station at eml2

In the context of future human space exploration missions in solar system and according to the roadmap proposed by ISECG (International Space Exploration Coordination Group), a new step could be to maintain as an outpost, at one of the libration points of the Earth-Moon system, a space station that would ease access to far destinations as Moon, Mars and asteroids and would allow to test some innovative technologies, before employing them for far distant human missions. One of the main challenges will be to maintain permanently and ensure on board crew survival. Then the main problem to solve is to manage the station servitude, during deployment (modules integration) and operational phase. The main challenges of this project lie in the design of the operational scenarios and, particularly, in trajectories selection, so as to minimize velocity increments (energy consumption) and transportation duration (crew safety). Transfer trajectories have already been deeply studied, since the 1950s. The work presented in this paper focuses on the feasibility of rendezvous in the vicinity of Earth-Moon Lagrangian Point n°2 (EML2) by comparing several rendezvous strategies and by providing quantitative results for a cargo or a human spacecraft (chaser) with the space station (target)

Operational scenarios optimization for resupply of crew and cargo of an International gateway Station located near the Earth-Moon-Lagrangian point-2

In the context of future human space exploration missions in the solar system (with an horizon of 2025) and according to the roadmap proposed by ISECG (International Space Exploration Coordination Group) [1], a new step could be to maintain as an outpost, at one of the libration points of the Earth-Moon system, a space station. This would ease access to far destinations as Moon, Mars and asteroids and would allow testing some innovative technologies, before employing them for far distant human missions. One of the main challenges will be to maintain permanently, and ensure on board crew health thanks to an autonomous space medical center docked to the proposed space station, as a Space haven. Then the main problem to solve is to manage the station servitude, during deployment (modules integration) and operational phase. Challenges lie, on a global point of view, in the design of the operational scenarios and, on a local point of view, in trajectories selection, so as to minimize velocity increments (energy consumption) and transportation duration (crew safety). Which recommendations could be found out as far as trajectories optimization is concerned, that would fulfill energy consumption, transportation duration and safety criterion? What would technological hurdles be to rise for the building of such Space haven? What would be performances to aim at for critical sub-systems? Expected results of this study could point out research and development perspectives for human spaceflight missions and above all, in transportation field for long lasting missions. Thus, the thesis project, presented here, aims starting from global system life-cycle decomposition, to identify by phase operational scenario and optimize resupply vehicle mission. The main steps of this project consist of: - Bibliographical survey, that covers all involved disciplines like mission analysis (Astrodynamics, Orbital mechanics, Orbitography, N-Body Problem, Rendezvous…), Applied Mathematics, Optimization, Systems Engineering…. - Entire system life-cycle analysis, so as to establish the entire set of scenarios for deployment and operations (nominal cases, degraded cases, contingencies…) and for all trajectories legs (Low Earth Orbit, Transfer, Rendezvous, re-entry…) - Trade-off analysis for Space Station architecture - Modeling of the mission legs trajectories - Trajectories optimization Three main scenarios have been selected from the results of the preliminary design of the Space Station, named THOR: the Space Station deployment, the resupply cargo missions and the crew transportation. The deep analysis of those three main steps pointed out the criticality of the rendezvous strategies in the vicinity of Lagrangian points. A special effort has been set on those approach maneuvers. The optimization of those rendezvous trajectories led to consolidate performances (in term of energy and duration) of the global transfer from the Earth to the Lagrangian point neighborhood and return. Finally, recommendations have been deduced that support the Lagrangian points importance for next steps of Human Spaceflight exploration of the Solar system

Application of the Systems Engineering methodology to the design of the AOCS of an Earth Observation satellite

This document describes the application of enhanced functional flow block diagrams (eFFBD) on the attitude and orbital control system (AOCS) of an Earth Observation satellite. First requirements and constraints of the satellite and its mission have been identified. Afterwards, these requirements and constraints were used to design the eFFBD of the AOCS

Scenarios optimization for a servicing inhabited space station at Earth-Moon Lagrangian point (EML2)

Human Space exploration is nowadays at a turning point of its history. Space agencies collaborate in order to determine next steps in this context, through for example, the International Space Exploration Coordination Group (ISECG). Agreement has been reached to identify that human beings will be sent in the upcoming decades to Mars, Moon or asteroids surface. Among all the selected scenarios, locating a deep-space habitat in the vicinity of the Earth Moon Lagrangian (EML) points has been designated as being a cornerstone of the human space exploration strategy. This paper examines how to design a low cost mission, using the natural dynamics for station integration, crew rotations, cargo delivery and disposal. Moreover, it focuses on the impacts of the station architecture on the global optimization (in term of duration and delta-v) of the trajectories from LEO (Low Earth Orbit) departure to rendezvous in EML and return. Several scenarios have been studied to compare transfer strategies (direct, indirect, lunar flyby, weak stability boundaries) and modeling types (four-body problem, restricted circular three-body problem, ephemeris). Actually, optimization criteria strongly depend on the mission phase. When crew transit is considered, mission duration has mainly to be minimized, while cargo transportation will minimize the global delta-v. The main contribution of this paper lies in the rendezvous dimensioning encompassing both the architectural point of view and the dynamics point of view. This is the first time a study optimizes mission duration and delta-v over all phases of the journey for Human exploration

JumpSat Thermal and Mechanical Analysis

In 2017, Swiss Space Systems (S3) is planned to operate unmanned suborbital space planes for launching small satellites. Within this scenario it was supposed to be launched JumpSat, a 3-Units CubeSat developed by ISAE-SUPAERO students, in collaboration with ONERA, CNES, and TELECOM Bretagne. JumpSat mission was proposed by ISAE in 2012. Their main objectives are both in-orbit technological demonstration and scientific research [1], through an elliptical Low Earth Orbit (LEO). The students are entirely involved in this mission, beyond both technological and scientific objectives, from the early stage to the disposal. ONERA, in Toulouse, is developing Dynagrad, a radiation sensor for trapped particles in the Earth’s magnetic belts, especially in the South Atlantic Anomaly (SAA), to improve the current models of radiation and their accuracy. Space qualification for a low-cost Star Tracker is under development at ISAE-SUPAERO. It will provide enough useful knowledge about system concept and software development for future small satellites missions. Another technological demonstration will accomplish a space qualification for the three-axis attitude control sub-system (AOCS) within the JumpSat mission. The acquired knowledge will help future CubeSatsAOCS sub-systems, while other components are COTS.Moreover, a consortium with Thales Alenia Space, LAAS and ISAE-SUPAERO designed NIPMH (Nanosatellite Investigate Microwave Photonic Hardware), an experimental payload based on opto-microwave technology. It would be embedded in a 3U CubeSat for testing different components sensitivity to radiations in space, especially the optical fiber doped with erbium. Furthermore,due to the similarities among both missions, it was analyzed the possibility of the combination of both projects: NIMPH as an additional payload to JumpSat mission. It increases the mission duration up to a minimum of two years, with respect to French law for Space Operations (maximal mission duration: 25 years). This paper will focus on mechanical and thermal aspects that were completely redesigned for JumpSat to comply with all requirements of both missions. From that point comes out the idea of building the first 6U CubeSat by ISAE-SUPAERO. As those studies are present in all design phases, they have important impact on the optimal architecture design within all the subsystems. Finally, temperatures gradients are such a great problem in space that it is even more important with strong radiation doses, like for this mission. Then, thermal analysis for worst cold and hot cases is critical for analyzing the impact of the new payload within the mission

Simulating Operational Concepts for Autonomous Robotic Space Exploration Systems: A Framework for Early Design Validation

During mission design, the concept of operations (ConOps) describes how the system operates during various life cycle phases to meet stakeholder expectations. ConOps is sometimes declined in a simple evaluation of the power consumption or data generation per mode. Different operational timelines are typically developed based on expert knowledge. This approach is robust when designing an automated system or a system with a low level of autonomy. However, when studying highly autonomous systems, designers may be interested in understanding how the system would react in an operational scenario when provided with knowledge about its actions and operational environment. These considerations can help verify and validate the proposed ConOps architecture, highlight shortcomings in both physical and functional design, and help better formulate detailed requirements. Hence, this study aims to provide a framework for the simulation and validation of operational scenarios for autonomous robotic space exploration systems during the preliminary design phases. This study extends current efforts in autonomy technology for planetary systems by focusing on testing their operability and assessing their performances in different scenarios early in the design process. The framework uses Model-Based Systems Engineering (MBSE) as the knowledge base for the studied system and its operations. It then leverages a Markov Decision Process (MDP) to simulate a set of system operations in a relevant scenario. It then outputs a feasible plan with the associated variation of a set of considered resources as step functions. This method was applied to simulate the operations of a small rover exploring an unknown environment to observe and sample a set of targets

Can Uncertainty Propagation Solve The Mysterious Case of Snoopy ?

Both the number of man-made objects in space and human ambitions have been growing for the last few decades. This trend causes multiple issues, such as an increasing collision probability, or the necessity to control the space system with high precision. Thus, the need to perform an accurate estimation of the position and velocity of a spacecraft. This article aims at using Taylor Differential Algebra (TDA), an uncertainty propagation method, by implementing an ephemeris propagation tool designed to propagate long term trajectories. It will be used in the case study of Snoopy, the lost lunar module of mission Apollo 10, to explore new scenarios thanks to Monte-Carlo estimations, performed on the data gathered by this propagator