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

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)

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

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

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)

Dynamics in the centre manifold around equilibrium points in periodically perturbed three-body problems

A new application of the parameterization method is pre- sented to compute invariant manifolds about the equilib- rium points of Periodically Perturbed Three-Body Problems ( PPTBP ). These techniques are applied to obtain high-order semi-numerical approximations of the center manifolds abo ut the points L 1 , 2 of the Sun-perturbed Earth-Moon Quasi- Bicicular Problem ( QBCP ), which is a particular case of PPTBP . The quality of these approximations is compared with results obtained using equivalents of previous normal form procedures. Then, the parameterization is used to ini- tialize the computation of Poincaré maps, which allow to get a qualitative description of the periodically-perturb ed dynamics near the equilibrium pointsPostprint (published version

Optimization of star research algorithm for esmo star tracker

This paper explains in detail the design and the development of a software research star algorithm, embedded on a star tracker, by the ISAE/SUPAERO team. This research algorithm is inspired by musical techniques. This work will be carried out as part of the ESMO (European Student Moon Orbiter) project by different teams of students and professors from ISAE/SUPAERO (Institut Supe ́rieur de l’Ae ́ronautique et de l’Espace). Till today, the system engineering studies have been completed and the work that will be presented will concern the algorithmic and the embedded software development. The physical architecture of the sensor relies on APS 750 developed by the CIMI laboratory of ISAE/SUPAERO. First, a star research algorithm based on the image acquired in lost-in-space mode (one of the star tracker opera- tional modes) will be presented; it is inspired by techniques of musical recognition with the help of the correlation of digital signature (hash) with those stored in databases. The musical recognition principle is based on finger- printing, i.e. the extraction of points of interest in the studied signal. In the musical context, the signal spectrogram is used to identify these points. Applying this technique in image processing domain requires an equivalent tool to spectrogram. Those points of interest create a hash and are used to efficiently search within the database pre- viously sorted in order to be compared. The main goals of this research algorithm are to minimise the number of steps in the computations in order to deliver information at a higher frequency and to increase the computation robustness against the different possible disturbances

JUMPSAT: Qualifying three equipments in one Cubesat mission

We work on a student 3U Cubesat mission, called JUMPSAT, expected for 2017. This is a collaborative project involving both institutions (CNES, ONERA) and schools (ISAE, TELECOM Bretagne). The different equipments to qualify are the Supaero Star Tracker, which measures stars’ luminosity to infer the satellite’s attitude, a detector for particles trapped in the Earth magnetic field designed by the ONERA, and the AOCS. Uplink and Downlink communications will be provided during the mission by the HETE Primary Ground Stations. JUMPSAT is the first Cubesat which needs a three axis attitude control, which involves an innovative mission analysis, to overcome all these constraints. The mission analysis deals with the orbit’s determination, the Cubesat’s structure, the power strategy, and the visibility balance. The particles detector is the only constraint for the altitude of the satellite: we can get meaningful data only at altitudes higher than 700 km. Moreover, the most interesting zones are South Atlantic and poles. But a circular orbit with this altitude does not respect the LOS (French space act).The structure of the Cubesat is also hard to define. To get information from the satellite, we need an antenna, and an attitude and orbital control system to point the antenna at the ground station and the Star Tracker at the stars. Solar Panels cannot be opened out because of the micro elements that could be settled on the particles detector. However, fixed solar panels are not very efficient to recharge batteries. The power balance shows critical problems: both attitude control system and the Star Tracker consume a lot, and cannot work at the same time during the whole orbit. However, all the components are linked: the Star Tracker is not efficient if the satellite attitude is not stabilized; the antenna functioning must be synchronized with visibilities by the ground station. Anyway, the visibility balance stresses the point that a ground station at Toulouse would be particularly welcome. We need also to take into account phenomena of eclipse and satellite drift. To conclude, our mission analysis is deeply constrained by the equipments we want to qualify. Our task is to find the optimal orbit, suggest a power strategy considering the orbital constraints and components’ physical parameters, and to study the visibility balance. It is a real challenge in terms of power consumption, architecture, orbital strategy for such a small satellite

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