The June 2012 transit of Venus. Framework for interpretation of observations

Ground based observers have on 5/6th June 2012 the last opportunity of the century to watch the passage of Venus across the solar disk from Earth. Venus transits have traditionally provided unique insight into the Venus atmosphere through the refraction halo that appears at the planet outer terminator near ingress/egress. Much more recently, Venus transits have attracted renewed interest because the technique of transits is being successfully applied to the characterization of extrasolar planet atmospheres. The current work investigates theoretically the interaction of sunlight and the Venus atmosphere through the full range of transit phases, as observed from Earth and from a remote distance. Our model predictions quantify the relevant atmospheric phenomena, thereby assisting the observers of the event in the interpretation of measurements and the extrapolation to the exoplanet case. Our approach relies on the numerical integration of the radiative transfer equation, and includes refraction, multiple scattering, atmospheric extinction and solar limb darkening, as well as an up to date description of the Venus atmosphere. We produce synthetic images of the planet terminator during ingress/egress that demonstrate the evolving shape, brightness and chromaticity of the halo. Guidelines are offered for the investigation of the planet upper haze from vertically-unresolved photometric measurements. In this respect, the comparison with measurements from the 2004 transit appears encouraging. We also show integrated lightcurves of the Venus/Sun system at various phases during transit and calculate the respective Venus-Sun integrated transmission spectra. The comparison of the model predictions to those for a Venus-like planet free of haze and clouds (and therefore a closer terrestrial analogue) complements the discussion and sets the conclusions into a broader perspective.Comment: 14 pages; 14 figures; Submitted on 02/06/2012; A&A, accepted for publication on 30/08/201

Flatness of the setting Sun

Atmospheric refraction is responsible for the bending of light-rays in the atmosphere. It is a result of the continuous decrease in the refractive index of the air as a function of altitude. A well-known consequence of this phenomenon is the apparently elliptic shape of the setting or rising Sun (or full-Moon). In the present paper we systematically investigate this phenomenon in a standard atmosphere. Theoretical and numerical calculations are compared with experimental data. The asymmetric rim of the Sun is computed as a function of its inclination angle, observational height and meteorological conditions characterized by pressure, temperature and lapse-rate. We reveal and illustrate some extreme and highly unusual situations.Comment: RevTex, 10 pages, 14 Figures. A web-page is accompanying this study: http://www.fi.uib.no/~neda/sunset/index.htm

Lorentz-transformation and Galileo-transformation Windows

We define Lorentz-transformation windows as windows that change the direction of transmitted light rays like a Lorentz transformation. Similarly, Galileo-transformation windows change the direction of transmitted light rays like a Galileo transformation. This light-ray-direction change distorts the scene seen through such a window in the same way in which the scene would be distorted in a photo taken with a camera moving through the scene. Lorentz-transformation windows can also undo the distortion of the scene when moving at relativistic velocity relative to it. For small angles between the direction of the light rays and the direction of the velocity, Galileo-transformation windows can be realised with relatively simple telescope windows, which consist of arrays of identical micro-telescopes

Global monitoring of ionospheric weather by GIRO and GNSS data fusion

Prompt and accurate imaging of the ionosphere is essential to space weather services, given a broad spectrum of applications that rely on ionospherically propagating radio signals. As the 3D spatial extent of the ionosphere is vast and covered only fragmentarily, data fusion is a strong candidate for solving imaging tasks. Data fusion has been used to blend models and observations for the integrated and consistent views of geosystems. In space weather scenarios, low latency of the sensor data availability is one of the strongest requirements that limits the selection of potential datasets for fusion. Since remote plasma sensing instrumentation for ionospheric weather is complex, scarce, and prone to unavoidable data noise, conventional 3D-var assimilative schemas are not optimal. We describe a novel substantially 4D data fusion service based on near-real-time data feeds from Global Ionosphere Radio Observatory (GIRO) and Global Navigation Satellite System (GNSS) called GAMBIT (Global Assimilative Model of the Bottomside Ionosphere with Topside estimate). GAMBIT operates with a few-minute latency, and it releases, among other data products, the anomaly maps of the effective slab thickness (EST) obtained by fusing GIRO and GNSS data. The anomaly EST mapping aids understanding of the vertical plasma restructuring during disturbed conditionsPeer ReviewedPostprint (published version

Flow structure and optical beam propagation in high-Reynolds-number gas-phase shear layers and jets

We report on the structure of the scalar index-of-refraction field generated by turbulent, gas-phase, incompressible and compressible shear layers and incompressible jets, and on associated beam-propagation aero-optical phenomena. Using simultaneous imaging of the optical-beam distortion and the turbulent-flow index-of-refraction field, wavefront-phase functions were computed for optical beams emerging from the turbulent region in these free-shear flows, in an aero-optical regime producing weak wavefront distortions. Spatial wavefront-phase behaviour is found to be dominated by the large-scale structure of these flows. A simple level-set representation of the index-of-refraction field in high-Reynolds-number, incompressible shear layers is found to provide a good representation of observed wavefront-phase behaviour, indicating that the structure of the unsteady outer boundaries of the turbulent region provides the dominant contributions

Atmospheric propagation effects relevant to optical communications

A number of atmospheric phenomena affect the propagation of light. The effects of clear air turbulence are reviewed as well as atmospheric turbidity on optical communications. Among the phenomena considered are astronomical and random refraction, scintillation, beam broadening, spatial coherence, angle of arrival, aperture averaging, absorption and scattering, and the effect of opaque clouds. An extensive reference list is also provided for further study. Useful information on the atmospheric propagation of light in relation to optical deep space communications to an earth based receiving station is available, however, further data must be generated before such a link can be designed with committed performance

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 183

This bibliography lists 273 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1978

Retrieval and molecule sensitivity studies for the global ozone monitoring experiment and the scanning imaging absorption spectrometer for atmospheric chartography

The Global Ozone Monitoring Experiment (GOME) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) are diode based spectrometers that will make atmospheric constituent and aerosol measurements from European satellite platforms beginning in the mid 1990's. GOME measures the atmosphere in the UV and visible in nadir scanning, while SCIAMACHY performs a combination of nadir, limb, and occultation measurements in the UV, visible, and infrared. A summary is presented of the sensitivity studies that were performed for SCIAMACHY measurements. As the GOME measurement capability is a subset of the SCIAMACHY measurement capability, the nadir, UV, and visible portion of the studies is shown to apply to GOME as well

Desenvolupament d'un programari per a l'anàlisi i avaluació de l'efecte de la turbulència atmosfèrica en la propagació òptica

Atmospheric turbulence is the number one enemy of amateurs and not so amateurs in astronomical observation. The tinkling of images when viewing celestial bodies in our solar system, or the impossibility of accurately glimpsing galaxies in the deep sky is due to atmospheric "seeing", among other things. Moreover, it is not only those interested in observing that are affected by this phenomenon, but in the near future, where optical communications will be responsible for linking ground stations and satellites, they will also be penalised by atmospheric turbulence. This is the reason for the emergence of this project, for the study in simulation of atmospheric "Seeing". How it affects telescopes, analysing optical aberrations and their correction by means of Zernike Polynomials and, on the other hand, how to calculate the attenuation introduced by the atmosphere in the communications channel with satellites. Addressing basic principles in optics, the aim is to simulate all the necessary factors for the interest of two research groups within SENER Aerospace, S.A. and the Telecommunications Technology Centre of Catalonia (CTTC), and to conclude this project in two applications developed in MATLAB® programming software and its App Designer design tool, for future interested parties to receive in advance the simulated situation of the turbulence conditions at the study site. This project has been taken to different congresses, online and in person, in order to teach the knowledge acquired in the development of this year's project, such as the International OSA Network of Students (IONS), the National Optics Meeting (RNO), the 4th Symposium on Space Education Activities (SSEA) and The European Society for Engineering Education (SEFI)

Měření vlivu kapek pro optický bezvlaknový spoj a matematické modelování vícefázového proudění

Free space optics will emerge alongside major communications technologies as an important player in the field of wireless communications. This technology, like other technologies, has to face the challenges caused by unstable and unfavorable atmospheric conditions that determine the resulting quality of the transmitted signal. The paper is intended to determine the extent of a deterioration of the transmitted signal during rainfall. The precipitation is simulated in laboratory conditions, and the resulting knowledge of the droplet formation is transferred to a mathematical model that helps simulate multiphase flow under given conditions.Optické bezvláknové spoje se v budoucnosti vyskytnou po boku majoritních komunikačních technologií jako důležitý hráč na poli bezdrátových komunikací. Tato technologie, stejně jako jiné technologie, musí čelit výzvám pramenícím z nestálých a nepříznivých atmosférických podmínek, které rozhodují o výsledné kvalitě přenášeného signálu. Tato práce má za úkol zjistit míru zhoršení přenášeného signálu během dešťových srážek. Srážkový úhrn je simulován v laboratorních podmínkách a výsledné poznatky o tvorbě dešťových kapek jsou přeneseny do matematického modelu, který napomáhá simulování vícefázového proudění v daných podmínkách.440 - Katedra telekomunikační technikyvýborn