A Novel Tool for the Determination of Tropopause Heights by Using GNSS Radio Occultation Data

The tropopause is a transitional layer between the troposphere and the stratosphere. The exchange of chemical constituents of the atmosphere (namely masses of air, water vapor, trace gases etc.) and energy between the troposphere and the stratosphere occurs through this layer. We suppose that just exchanges that are taking place at the tropopause heights are strongly influenced by the Global Change forcing. For this reason it is particularly urgent to accumulate temporal data the most accurate possible and with a certain continuity series to understand comprehensively what is happening to our climate. It is well known that Radio Occultation technique applied using Global Navigations Satellite Systems (GNSS-RO) is a powerful tool to detect the tropopause heights. It can be done working on the level 2 data provided by GNSS-RO payload: i.e. atmospheric profiles of pressure and temperature. We propose to measure tropopause using GNSS-RO level 1 data;i.e. the bending angles (BA) of the GNSS signal through the atmosphere. We fit the BA profiles applying in the integral relationship of BA as refractivity profile of background the Hopfield dry model of atmosphere which depends on the fourth degree of the height above the Earth. Through the layers in which tropopause is contained, the residuals between the background model and the observed BA have an anomalous trend. The residuals in this zone form anomalous non-gaussian bumps that we have exploited just to determine the relevant parameters of the tropopause. Such bumps are due to the wrong theoretical assumption made by Hopfield for the re-construction of the dry refractivity that the temperature lapse rate of the atmosphere is constant. But we know that the definition of tropopause according the World Meteorological Organization (WMO) is just the height where a sudden change of the temperature lapse rate usually occurs. Thus in the present work we have determined tropopause heights with new algorithms which exploit the bumps occurring along the BA profiles achieved by GNSS-RO. We have used the huge amount of data provided by several space missions devoted to GNSS-RO (namely COSMIC, METOP, etc.) for tuning the algorithms, performed a validation and provided a robust statistical soundness. The same GNSS-RO observations are helpful also to reconstruct the Mapping Function commonly applied in geodetic applications. Global mapping functions built with GNSS-RO and their evolution in time can be an interesting parameter helpful for climate investigations as well.

Advanced Laser Retroreflectors for Astrophysics and Space Science

We developed advances laser retroreflectors for solar system exploration, geodesy and for precision test of General Relativity (GR) and new gravitational physics: a micro-reflector array (INRRI, Instrument for landing-Roving laser Retroreflectors Investigations), a midsize reflector array for the European Earth Observation (EO) program, Copernicus (CORA, COpernicus laser Retroreflector Array), a large, single-retroreflector (MoonLIGHT, Moon Laser Instrumentation for General relativity High accuracy Tests). These laser retroreflectors will be fully characterized at the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry Cube/microsat Characterization Facilities Laboratory), a unique and dedicated infrastructure of INFN-LNF (www.lnf.infn.it/esperimenti/etrusco/). Our research program foresees several activities: 1) Developing and characterizing the mentioned laser retroreflector devices to determine landing accuracy, rover positioning during exploration and planetary/Moon’s surface georeferencing. These devices will be passive, laser wavelength- independent, long-lived reference point. INRRI will enable the performance of full-column measurement of trace species in the Mars atmosphere by future space-borne lidars. These measurements will be complementary to highly localized measurements made by gas sampling techniques on the Rover or by laser back-scattering lidar techniques on future orbiters and/or from the surface. INRRI will also support laser and quantum communications, carried out among future Mars Orbiters and Mars Rovers. This will be possible also because the INRRI laser retroreflectors will be metal back-coated and, therefore, will not change the photon polarization. The added value of INRRI is its low mass, compact size, zero maintenance and its usefulness for any future laser altimetry, ranging, communications, atmospheric lidar capable Mars orbiter, for virtually decades after the end of the Mars surface mission, like the Apollo and Lunokhod lunar laser retroreflectors. MoonLIGHT and INRRI are proposed for landings on the Moon (two Google Lunar X Prize Missions, namely Moon Express;Russia’s Luna-27 mission, as well as others under consideration/negotia- tion, also with the help of ASI, ESA and other partnerships);2) Precision tests of GR with LLR to MoonLIGHT reflectors. Development of new fundamental gravity physics models and study of experimental constraints to these models use also laser ranging and laser reflectors throughout the solar system: extension of general relativity to include Spacetime Torsion, Non-Minimal Coupling between matter and curvature (so-called “ ” theories, or NMC gravity);3) Extension of program to: Mars, Phobos and Deimos, Jupiter and Saturn icy/rocky moons, Near Earth Asteroids.

Concentrated suspensions of Brownian beads in water: dynamic heterogeneities through a simple experimental technique

Concentrated suspensions of Brownian hard-spheres in water are an epitome for understanding the glassy dynamics of both soft materials and supercooled molecular liquids.From an experimental point of view,such systems are especially suited to perform particle tracking easily,and,therefore,are a benchmark for novel optical techniques,applicable when primary particles cannot be resolved.Differential variance analysis(DVA)is one such novel technique that simplifies significantly the characterization of structural relaxation prcKesses of soft glassy materials,since it is directly applicable to digital image sequences of the sample.DVA succeeds in monitoring not only the average dynamics,but also its spatio-temporal fluctuations,known as dynamic heterogeneities.In this work,we study the dynamics of dense suspensions of Brownian beads in water,imaged through digital video-microscopy,by using both DVA and single-particle tracking.We focus on two commonly used signatures of dynamic heterogeneities:the dynamic susceptibility,^,and the non-Gaussian parameter,a 2.By direct comparison of these two quantities,we are able to highlight similarities and differences.We do confirm th aχ4 andα2 provide qualitatively similar information,but we find quantitative discrepancies in the scalings of characteristic time and length scale on approaching the glass transition.