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Thesis
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Contributions to the simulation and automatic control of the attitude for the satellites
Mihail, Gabriel-Marian
2009-05-24
Abstract: Contributii la simularea si comanda automata a starii orbitale a satelitilor Datele cu privire la starea orbitala a satelitilor sunt prin natura lor tridimensionale. In consecinta cea mai buna imagine de ansamblu asupra orientarii unui satelit in spatiu se poate realiza prin constructia unor proiectii tridimensionale si nu prin reprezentarea fiecarui unghi de orientare in functie de timp. Mai mult, tendinta continua de crestere a puterii computerelor, favorizeaza reprezentarea tridimensionala practic in timp real a acestor date, chiar daca viteza lor de evolutie este mare. In mod firesc, o evolutie naturala in operatiunile de control al starii orbitale este dezvoltarea de programe de vizualizare si analiza pe orbita, care pot fi conectate la fluxul de telemetrie al satelitilor. Marea majoritate a simulatoarelor de sateliti pot fi catalogate in trei grupuri in functie de folosinta: dezvoltare-proiectare, integrare si verificare si nu il ultimul rand operare. Cerintele din domeniul operatiunilor spatiale sunt de cele mai multe ori speciffice si acest lucru face dificila includerea lor in specificatiile initiale ale unui pachet software mai ales ca ele evolueaza pe masura ce satelitul insusi trece de la o faza operationala la alta. De aceea in cele mai multe cazuri este necesara o solutie adaptata la particularitatile misiunii. Aceasta teza prezinta o solutie de analiza a misiunii spatiale Bird care zboara coordonata de Centrul German de Operatiuni Spatiale- un instrument software care poate fi folosit de ingineri si manageri pentru investigatia si evaluarea operatiunilor spatiale. Cel de al doilea modul StarSim prezentat in aceasta teza a fost adaugat ulterior proiectului, pe masura ce studiile autorului au migrat spre domeniul senzorilor stelari si posibilitatii de emulare a lor. Dispozitivele de determinare a starii orbitale a satelitilor sunt extreme de importante. Exista mai multe metode de a face acest lucru dar printre cele mai folosite sunt camerele stelare. Nici o alta metoda nu reuseste sa le egaleze in precizie (de ordinul secundelor de arc) si de aceea acestea se folosesc de obicei complementar. Senzorii stelari identifica stelele observate in campul vizual al instrumentului prin compararea lor cu informatia stocata in prealabil si din aceasta identificare se poate masura orientarea satelitului in spatiu (in termeni aproape inertiali daca se presupune ca stelele au o pozitie fixa in spatiu). Contributions to the simulation and automatic control of the attitude for the satellites Attitude data are per nature three-dimensional. As a consequence, the best way to get the whole picture about the orientation of a satellite is not plotting each orientation angle versus time, or even projecting the data on a plane but implying a true three-dimensional display. Nowadays, the power of computers is such that a real-time display of fast changing data in three dimensions is not a problem anymore. Consequently, a natural evolution in operations of attitude control system shall involve the development of attitude visualization and analysis software, which can be coupled with the telemetry stream of the satellite. The vast majority of the satellite simulators may be divided into three groups according to their usage: development, integration and verification, and finally operations. The need for spacecraft operations are most of the time mission specific and this is difficult to be comprised in the initial specifications of a software package because the specifications itself are evolving from the initial stages of a mission to the operational phase. Therefore a customized solution should be implemented. This thesis is presenting a mission analysis solution developed for the Bird satellite flying at German Space Operation Centre- a software tool that can be used by engineers or managers to analyze and evaluate satellite operations and to answer the questions about the project. The other package presented in this thesis- the StarSim module has been later added to the project as the author’s studies migrated to the star identification hardware (star trackers) and possibilities to emulate them. A very important device on any spacecraft is the one which determines the spacecraft’s attitude. There are many different methods by which the attitude of a satellite can be determined, but one of the mostly widely used is the star tracker. Other methods for determining attitude exist, but none can reach the precision of a star tracker (arc-seconds accuracy) most of the time being just complementary of it. The star trackers are functioning by identifying the stars within the field of view (from the comparison with previous stored information) and based on this the attitude of the star tracker can be determined, which then can be transformed to the attitude of the spacecraft itself (in almost inertial term if we consider the stars are fixed on the sky).
Keyword(s): Sateliţi artificiali -- Simulare pe calculator -- Teză de doctorat ; Sateliţi artificiali -- Comandă automată -- Teză de doctorat
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Record created 2016-07-12, last modified 2016-07-12
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