Search results for "Satellite navigation"

Sachs-Wolfe at second order: the CMB bispectrum on large angular scales

2009

We calculate the Cosmic Microwave Background anisotropy bispectrum on large angular scales in the absence of primordial non-Gaussianities, assuming exact matter dominance and extending at second order the classic Sachs-Wolfe result delta T/T = Phi/3. The calculation is done in Poisson gauge. Besides intrinsic contributions calculated at last scattering, one must consider integrated effects. These are associated to lensing, and to the time dependence of the potentials (Rees-Sciama) and of the vector and tensor components of the metric generated at second order. The bispectrum is explicitly computed in the flat-sky approximation. It scales as l(-4) in the scale invariant limit and the shape d…

Galileo, God and Mathematics

2005

This chapter explores the relationship between God and the mathematics of Galileo. In the early modern era, the mathematical sciences began to produce potential instruments of power and to supply technically and socially valuable knowledge—for use in engineering, administration, and social control. This ability to produce useful knowledge and potential instruments of power became the critical basis for the existence of the mathematical sciences. In discussing Galileo's thoughts about mathematics and the mathematical sciences, it is necessary to keep in mind that he did not codify them and that he worked—as did many early modern scholars—with conflicting epistemologies. Furthermore, there is…

Performance assessment of PPP surveys with open source software using the GNSS GPS-GLONASS-Galileo constellations

2020

In this work, the performance of the multi-GNSS (Global Navigation Satellite System) Precise Point Positioning (PPP) technique, in static mode, is analyzed. Specifically, GPS (Global Positioning System), GLONASS, and Galileo systems are considered, and quantifying the Galileo contribution is one of the main objectives. The open source software RTKLib is adopted to process the data, with precise satellite orbits and clocks from CNES (Centre National d&rsquo

Space-borne frequency comb metrology

2016

Precision time references in space are of major importance to satellite-based fundamental science, global satellite navigation, earth observation, and satellite formation flying. Here we report on the operation of a compact, rugged, and automated optical frequency comb setup on a sounding rocket in space under microgravity. The experiment compared two clocks, one based on the optical D2 transition in Rb, and another on hyperfine splitting in Cs. This represents the first frequency comb based optical clock operation in space, which is an important milestone for future satellite-based precision metrology. Based on the approach demonstrated here, future space-based precision metrology can be i…

Global Navigation Satellite Systems And Services

2008

This chapter introduces the concept of Satellite Navigation in the context of space infrastructures and technologies that can contribute for improvement of life on Earth. It includes a review of the motivations for developing a satellite navigation system, and the applications and services these systems have in daily life. Furthermore, currently existing Global Navigation Satellite Systems (GPS and GLONASS) and other GNSS systems under development (GALILEO) are described from different perspectives: from the technical and architectural aspects to the ways chosen to finance their development and operations. To round up this chapter, an analysis of the expected trends in GNSS systems is prese…

In the Service of the Reich: Aspects of Copernicus and Galileo in Nazi Germany’s Historiographical and Political Discourse

2001

ArgumentFocus of this paper is on the historiographical fate of Nicholas Copernicus and Galileo Galilei in Nazi Germany. Both played interesting roles in Nazi propaganda and the legitimization of Nazi political goals. In the “Third Reich,” efforts to claim Copernicus as a German astronomer were closely linked to revisionist policies in Eastern Europe culminating in the war-time expansion. The example of Galileo’s condemnation by the Catholic Church in 1633 became a symbol of its unjustified opposition to new “scientific” results, namely Nazi racial theory. After Catholic opposition against Nazi racial theory had reached a peak in 1937, the Galileo affair was turned into an instrument of Naz…

AsYouLikeHim: Images ofGalileoSince the17thCentury

2003

The Uses of Analogies in Seventeenth and Eighteenth Century Science

2011

The object of this paper is to look at the extent and nature of the uses of analogy during the first century following the so-called scientific revolution.Using the research tool provided by JSTOR we systematically analyze the uses of “analog” and its cognates (analogies, analogous, etc.) in the Philosophical Transactions of the Royal Society of London for the period 1665–1780. In addition to giving the possibility of evaluating quantitatively the proportion of papers explicitly using analogies, this approach makes it possible to go beyond the maybe idiosyncratic cases of Descartes, Kepler, Galileo, and other much studied giants of the so-called Scientific Revolution. As a result a classifi…