When a radio signal traverses the atmosphere it will be delayed by not only thedistance between transmitter and receiver, but also the atmosphere. Given knowl-edge of the characteristics of the sent signal the effect of the atmosphere can beobtained from the received signal. This concept is called radio occultation. Radiooccultation can provide high accuracy profiles of temperature, pressure and watervapour troughout the atmosphere.This report aims to present the work and results from a thesis performed atRUAG Space in Göteborg. The purpose of the thesis was to implement a simulatorwhich with high accuracy could generate a signal as it would have been receivedhad it propagated through the atmosphere.We will show that the generated signal passes the requirements that have beenset. / När en radiovåg passerar genom atmosfären kommer den att fördröjas, inte bara avavståndet mellan sändare och mottagare utan också av atmosfären. Givet kunskapom karaktäristiken hos den sända signalen kan atmosfärens effekt erhållas från denmottagna signalen. Detta koncept kallas för radio-ockultation. Radio-ockultationkan med hög noggrannhet ge profiler för temperatur, tryck och vattenånga genomatmosfären.Denna rapport ämnar presentera det jobb och de resultat som uppnåtts genomett examensarbete genomfört på RUAG Space i Göteborg. Examensarbetets syftevar att implementera en simulator som med hög noggrannhet kan generera ensignal så som den hade sett ut då den propagerat genom atmosfären.Vi kommer att visa att den genererade signalen uppnår de krav som ställts.

Texte remanié de: Thèse de doctorat--Lettres--Université de Lausanne, 2002. / Bibliogr. p. 395-436.

My dissertation details the work I have done related to remote sensing of thermal activityon Io and thermal remote sensing used in the search for oases on Mars. At Io, I studiedtwo volcanoes, Tvashtar and Prometheus and their thermal activity. At Mars, I investigatedsuggestions of a possible oasis in one of the youngest volcanic regions, Cerberus Fossaeand nearby areas of SE Elysium.Tvashtar was the site of the first high-spatial-resolution observation of an extraterrestriallava curtain. The Tvashtar complex was also the site of a large, confined eruption a fewmonths after the fissure eruption. I discuss the work involved in estimating the brightnesstemperatures and power output of both eruptions as seen by the Galileo SSI. I also discusscooling and eruption-style models and their application to Tvashtar. In every geometricallycorrect observation of Prometheus, we have seen a 100 km tall SO2 gas and dust plumeabove its flow field. This plume and field migrated ~80 km between the Voyager and Galileo eras. I describe the work I performed in modeling the plume's creation as lava-volatileinteractions at the flow fronts.My Mars research entailed the search for thermal systems and constraints on nearsurfacewater ice in an equatorial region that contains some of the youngest lava flows onMars. This region, SE Elysium, also shows evidence of contemporaneous water and lava. Life as we know it requires a source of energy and liquid water, so a geologically youngregion containing both water and energy is an obvious place to study. I show, however, thatthe recent suggestions of extant near-surface water ice and possible endogenic energy escapeare not necessary, and that the thermal imaging of the region requires rock rather thanwater ice near the surface. I also show that the current instruments at Mars are insufficientfor the remote discovery of thermal reservoirs and then discuss some possible remedies.

Galileo was first a student of medicine and philosophy at the University of Pisa. After two years of study, at the age of nineteen, he met a certain Ostillio Ricci, professer or mathematics. From that time onwards, "leaving everything else aside, he abandoned himself to the study of mathematics". [...]

Magisterarbeit.

The orbit of a satellite around the earth is constantly disturbed by various factors, such as variations in the gravitational field and the solar wind pressure. The drift of the satellite position can compromise the mission, and even lead to a crash or a fall in the atmosphere. The station-keeping operations therefore consist in performing an accurate measurement of the satellite trajectory and then in using its thrusters to correct the drift. The conventional solution is to measure the position with the help of a ground based radar. This solution is expensive and does not allow to have the satellite position permanently: the trajectory corrections are therefore infrequent. A positioning and autonomous navigation system using constellations of navigation satellites, called Global Navigation Satellite System (GNSS), allows a significant reduction in design and operational maintenance costs. Several studies have been conducted in this direction and the first navigation systems based on GPS receivers, are emerging. A receiver capable of processing multiple navigation systems, such as GPS and Galileo, would provide a better service availability. Indeed, Galileo is designed to be compatible with GPS, both in terms of signals and navigation data. Continuous knowledge of the position would then allow a closed loop control of the station keeping. Initially, we defined what the specifications of a multi-mission space receiver are. Indeed, the constraints on such a receiver are different from those for a receiver located on the surface of the Earth. The analysis of these constraints, and the performance required of a positioning system, is necessary to determine the specifications of the future receiver. There are few studies on the subject. Some of them are classified; others have, in our view, an analytical bias that distorts the determination of specifications. So we modeled the system: GNSS and receivers satellite orbits, radio frequency link. Some parameters of this link are not given in the specification or manufacturers documents. Moreover, the available theoretical data are not always relevant for realistic modeling. So we had to assess those parameters using the available data. The model was then used to simulate various scenarios representing future missions. After defining analysis criteria, specifications were determined from the simulation results. Calculating a position of a satellite navigation system involves three main phases. For each phase, there are several possible algorithms, with different performance characteristics, the circuit size or the computation load. The development of new applications based on navigation also drives the development of new adapted algorithms. We present the principle for determining a position, as well as GPS and Galileo navigation signals. From the signal structure, we explain the phases of the demodulation and localization. Through the use of GPS and Galileo constellations, standard algorithms achieve the performance required for space applications. However, these algorithms need to be adapted, thus some parts were specifically designed. In order to validate the choice of algorithms and parameters, we have simulated the various operating phases of the receiver using real GPS signals. Finally, impact and prospects are discussed in the conclusion.

Europe is presently building up a satellite navigation system of their own, Galileo. Unlike the American system, GPS, and the Russian system, Glonass, Galileo will be a civilian system. It will be independent from, but interoperable with both GPS and Glonass. After many delays have enough satellites been launched and placed in orbit to make it possible to start up Galileo’s initial services during December 2016. This study gives an account of the construction and development of the Galileo system. During two weeks in the spring 2016 experimental RTK measurements were made with Galileo combined with GPS where the satellite corrections were distributed from Lantmäteriet’s (the Swedish mapping, cadastral and land registration authority’s) supportsystem for satellite positioning, SWEPOS. The measurements were carried out with singlestation RTK towards a SWEPOS reference station at Mosebacke on Södermalm in Stockholm. The rover was placed over a fixed point about 1.2 km from the reference station.The purpose of the study was to determine if it was possible in the spring 2016 to make any measurements with Galileo and to see what Galileo can add to RTK measurements combined with GPS in SWEPOS. During the spring 2016 it was not possible to make any measurements with only Galileo satellites due to the fact that there were too few satellites in orbit. The results from the measurements indicate that combining Galileo and GPS could be positive for network RTK in SWEPOS. The part of achieved fixed solutions increases, the average time until fixed solution is achieved shortens and the space vehicle geometry (PDOP) gets a better value when combining GPS and Galileo. It is however too soon to say anything certain about the influence of Galileo on the position uncertainty. / Europa håller på att bygga upp ett eget satellitnavigeringssystem, Galileo. Till skillnad från det amerikanska systemet GPS är Galileo ett civilt system som kommer att vara oberoende av, men kompatibelt med, GPS och den ryska motsvarigheten Glonass. Efter stora förseningar har nu tillräckligt många satelliter placerats i omloppsbana så att det kan vara möjligt att starta upp Galileos tidiga tjänster (initial services) under december 2016. Detta arbete belyser Galileos uppbyggnad och utveckling. Under våren 2016 gjordes testmätningar med Galileo kombinerat med GPS där korrigeringsdata erhölls från Lantmäteriets stödsystem SWEPOS. Mätningarna gjordes med enkelstations-RTK mot SWEPOS referensstation Mosebacke på Södermalm i Stockholmöver en punkt belägen ca 1,2 km från Mosebacke. Syftet var att se om det under våren 2016 gick att göra mätningar mot Galileo och undersöka vad Galileo skulle tillföra RTK-mätning tillsammans med GPS i SWEPOS. Det var inte möjligt under våren 2016 att utföra mätningar mot enbart Galileo då det vid tidpunkten för mätningarna inte fanns tillräckligt många satelliter i omloppsbana. Resultaten från mätningarna i denna studie tyder på att Galileo tillför bättre satellittäckning vid RTK-mätning tillsammans med GPS, andelen fixlösningar ökar, tiden till att fixlösning erhålles blir kortare och satellitgeometrin blir bättre. Det ärdäremot för tidigt att med säkerhet uttala sig om Galileos påverkan på positionsosäkerheten, både i plan och höjd.

Se toma en cuenta que en la investigación de la naturaleza se supone el postulado denominado “realismo ontológico” que define el enfoque de la investigación fundamentalmente como realista. Se muestra que en las investigaciones de la naturaleza realizadas por Galileo subyace de hecho el postulado del realismo ontológico; por ello y por el hecho de que tal postulado, por sus raíces presocráticas, presenta un carácter materialista, el enfoque de la actividad científica galileana fue de hecho realista materialista. El postulado del realismo ontológico materialista, o mecanicista en sentido lato, señala que hay un mundo exterior que existe independientemente del sujeto cognoscente y que es material. Este postulado supone a su vez un concepto general de objetividad ontológica mecanicista según el cual la objetividad es una condición de la materia en sí misma y no lo pone el sujeto cognoscente. Pero, para hacer frente al racionalismo esencialista que identifica propiedades primarias con entes, se distingue dos sentidos o dimensiones diferentes de objetividad ontológica: dimensión propia y dimensión derivada. Esta distinción es paralela a dos niveles de realidad con estatus ontológico distinto: elemental (primario) y compuesto (secundario). En dimensión propia la objetividad se aplica en el dominio de los elementos a los que se reduce la materia corpórea en última instancia y algunos de cuyos rasgos básicos, en la versión final galileana, son: indivisibles y no extensos, tal vez sin consistencia alguna, análogos a puntos geométricos, plenos, no vacíos. De elementos con tales condiciones se dice, entonces, que son objetivos en sentido ontológico propio. La dimensión derivada del concepto de objetividad ontológica se aplica en el dominio de las propiedades de objetos materiales, entre las que Galileo considera la forma, cantidad de materia y movimiento mecánico fundamentalmente; de tales propiedades se dice que son objetivas en sentido ontológico derivado. En ninguna de las dos dimensiones se ha encontrado que Galileo haya salido del esquema mecanicista. Cuando tuvo la necesidad de fundamentar la matematización de la naturaleza (posibilidad de la física matemática) estimó que no era necesario salir del marco ontológico mecanicista, sino que consideró suficiente una concepción realista de las teorías de tipo semántico. En tal intención, postuló la existencia de “propiedades matemáticas” en los cuerpos (propiedades mecánicas o primarias) y consideró un puente semántico entre estas propiedades materiales (no conceptuales) con estatuto ontológico derivado y los conceptos e ideas de la ciencia matemática, estos últimos son así objetos conceptuales con significado fáctico. De modo que no fue necesario postular en la naturaleza material la existencia de entidades ideales (objetos matemáticos) con estatus ontológico primario. Se complementa este estudio con una breve consideración semántica intuitiva orientada a enfatizar el carácter complejo y sistémico del concepto de objetividad ontológica. / Tesis

The goal of this thesis is to analyze current requirements of navigation system RNP RNAV. Particularly is behaving about estimation current ways and description of future improving GNSS performance. In submitted thesis is describes present evolution of area navigation and required navigation performance RNP. The next part deals with the common access how to raise the performance parameters, their estimation and also description how it'll be solve in future systems.

No description available.