Post processing of multiple GPS receivers to enhance baseline accuracy

Inexpensive, commercial available off-the-shelf (COTS) Global Positioning Receivers (GPS) have typical accuracy of ±3 meters when augmented by the Wide Areas Augmentation System (WAAS). There exist applications that require position measurements between two moving targets. The focus of this work is to explore the viability of using clusters of COTS GPS receivers for relative position measurements to improve their accuracy. An experimental study was performed using two clusters, each with five GPS receivers, with a fixed distance of 4.5 m between the clusters. Although the relative position was fixed, the entire system of ten GPS receivers was on a mobile platform. Data was recorded while moving the system over a rectangular track with a perimeter distance of 7564 m. The data was post processed and yielded approximately 1 meter accuracy for the relative position vector between the two clusters.

Precise Orbit Determination of Low Earth Satellites at AIUB using GPS and SLR data

An ever increasing number of low Earth orbiting (LEO) satellites is, or will be, equipped with retro-reflectors for Satellite Laser Ranging (SLR) and on-board receivers to collect observations from Global Navigation Satellite Systems (GNSS) such as the Global Positioning Sys- tem (GPS) and the Russian GLONASS and the European Galileo systems in the future. At the Astronomical Insti- tute of the University of Bern (AIUB) LEO precise or- bit determination (POD) using either GPS or SLR data is performed for a wide range of applications for satellites at different altitudes. For this purpose the classical numeri- cal integration techniques, as also used for dynamic orbit determination of satellites at high altitudes, are extended by pseudo-stochastic orbit modeling techniques to effi- ciently cope with potential force model deficiencies for satellites at low altitudes. Accuracies of better than 2 cm may be achieved by pseudo-stochastic orbit modeling for satellites at very low altitudes such as for the GPS-based POD of the Gravity field and steady-state Ocean Circula- tion Explorer (GOCE).

Sideband characterization and atmospheric observations with various 340 GHz heterodyne receivers

This paper describes sideband response measurements and atmospheric observations with a double sideband and two Single Sideband (SSB) receiver prototypes developed for the multi-beam limb sounder instrument stratosphere-troposphere exchange and climate monitor radiometer. We first show an advanced Fourier-Transform Spectroscopy (FTS) method for sideband response and spurious signal characterization. We then present sideband response measurements of the different prototype receivers and we compare the results of the SSB receivers with sideband measurements by injecting a continuous wave signal into the upper and lower sidebands. The receivers were integrated into a total-power radiometer and atmospheric observations were carried out. The observed spectra were compared to forward model spectra to conclude on the sideband characteristics of the different receivers. The two sideband characterization methods show a high degree of agreement for both SSB receivers with various local oscillator settings. The measured sideband response was used to correct the forward model simulations. This improves the agreement with the atmospheric observations and explains spectral features caused by an unbalanced sideband response. The FTS method also allows to quantify the influence of spurious harmonic responses of the receiver.

Tintenfass und Teleskop. Galileo Galilei im Schnittpunkt wissenschaftlicher, literarischer und visueller Kulturen im 17. Jahrhundert

Die Figur Galileo Galilei ist für die europäische Wissenschaftsgeschichte, für die Kulturwissenschaften und für eine wissensgeschichtlich orientierte Literatur- und Kunstwissenschaft von großem Interesse. In diesem Band werden die Überschneidungen, Wechselwirkungen und Transferprozesse zwischen den wissenschaftlichen und kulturellen Dimensionen untersucht, die für Galileis Profilierung als frühneuzeitlicher Wissenschaftler ebenso wichtig sind wie für die im weiteren Sinn kulturelle Wahrnehmung seiner Entdeckungen und seiner Schriften – vor allem in Literatur und Kunst. Der Band ist interdisziplinär konzipiert, um die fachlichen Einzelperspektiven von Literatur-, Kunst- und Kulturwissenschaftlern sowie Wissenschaftshistorikern zusammenzuführen. Analysiert werden Formen und Funktionen der Produktion, Konzeptualisierung und Repräsentation von Wissen sowie Aspekte der Diskussion und Diffusion von Galileis Wissensansprüchen im Kontext der Frühen Neuzeit. Mit dieser Fokussierung auf die im Schnittbereich verschiedener kultureller Formationen angesiedelte Etablierung Galileis liefert der Band somit einen Beitrag zur interdisziplinären Erforschung von Galileis Rolle und Rezeption in der europäischen Kultur- und Wissensgeschichte des 17. Jahrhunderts. Sprachen: Deutsch, Englisch, Italienisch

Galileo Orbit and Clock Quality of the IGS Multi-GNSS Experiment

The Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS) aims at the data collection and analysis of all available satellite navigation systems. In particular the new global and regional satellite navigation systems are of interest, i.e., the European Galileo, the Chinese BeiDou, the Japanese QZSS as well as satellite based augmentation systems. This article analyzes the orbit and clock quality of the Galileo products of four MGEX analysis centers for a common time period of 20 weeks. Orbit comparisons of the individual analysis centers have a consistency at the 5–30 cm level. Day boundary discontinuities range from 4 to 28 cm whereas 2-day orbit fit RMS values vary between 1 and 7 cm. The accuracy evaluated by satellite laser ranging residuals is on the one decimeter level with a systematic bias of about −5 cm for all analysis centers. In addition, systematic errors on the decimeter level related to solar radiation pressure mismodeling are present in all orbit products. Due to the correlation of radial orbit errors with the clock parameters, these errors are also visible as a bump in the Allan deviation of the Galileo satellite clocks at the orbital frequency.

Galileo Galilei : Zusammenstellung der Forschungen und Entdeckungen Galilei's auf dem Gebiete der Naturwissenschaft : als Beitrag zur Geschichte der neueren Physik

von R. Caspar

Galileo Galilei, Brustbild

Signatur des Originals: S 36/G00870

Koyré y la libertad de Galileo

El presente artículo toma como base los estudios del historiador de la ciencia Alexandre Koyré, a propósito del nacimiento de la fisica con Galileo Galilei. A partir de allí pretendemos inferir que el desconocimiento de una ciencia materialista de las sociedades llevó a Koyré a un obstáculo que contradice sus propios puntos teóricos de partida. Es decir que ese obstáculo teórico lo condujo, a nuestro parecer, a un desvío espiritualista a la hora de preguntarse: ¿por qué Galileo? En tal sentido pretendemos mostrar la utilidad de una sociología crítica de la ciencia a fin de releer los estudios del sabio ruso-francés.