First optical validation of a Schwarzschild Couder telescope: the ASTRI SST-2M Cherenkov telescope

The Cherenkov Telescope Array (CTA) represents the most advanced facility designed for Cherenkov Astronomy. ASTRI SST-2M has been developed as a demonstrator for the Small Size Telescope in the context of the upcoming CTA. Its main innovation consists in the optical layout which implements the Schwarzschild-Couder configuration and is fully validated for the first time. The ASTRI SST-2M optical system represents the first qualified example for two mirrors telescope for Cherenkov Astronomy. This configuration permits to (i) maintain a high optical quality across a large FoV (ii) de-magnify the plate scale, (iii) exploit new technological solutions for focal plane sensors. The goal of the paper is to present the optical qualification of the ASTRI SST-2M telescope. The qualification has been obtained measuring the PSF sizes generated in the focal plane at various distance from the optical axis. These values have been compared with the performances expected by design. After an introduction on the Gamma Astronomy from the ground, the optical design and how it has been implemented for ASTRI SST-2M is discussed. Moreover the description of the setup used to qualify the telescope over the full field of view is shown. We report the results of the first--light optical qualification. The required specification of a flat PSF of $\sim 10$ arcmin in a large field of view ~10 deg has been demonstrated. These results validate the design specifications, opening a new scenario for Cherenkov Gamma ray Astronomy and, in particular, for the detection of high energy (5 - 300 TeV) gamma rays and wide-field observations with CTA.Comment: 6 pages, 5 figure

Methodological proposal for assessing peripheral lands to the Lavalle irrigated oasis, Mendoza (Argentina)

La factibilidad de obtener productos agrícolas de calidad, irrigados con agua salina, hace necesario evaluar áreas periféricas al oasis irrigado para determinar su aptitud para el cultivo. El objetivo es articular diversas metodologías para cartografiar y evaluar unidades ecológicamente homogéneas en tierras marginales de Mendoza utilizando las comunidades vegetales como indicador. Se relevó un área piloto mediante procesamiento de imagen LANDSAT/TM y se analizó la vegetación, suelo y freática. Las unidades evaluadas y sus respectivos rangos de salinidad, en dS m-1, hasta 50 cm fueron: estepa de Heterostachys ritteriana, 91-83; matorral de Allenrolfea vaginata con H. ritteriana, 83-48; matorral abierto de A.vaginata con Prosopis strombulifera, 62-55; estepa abierta de Suaeda divaricata con Atriplex argentina, 52-83; matorral de S. divaricata con Lycium tenuispinosum, 40-43; bosquecillo abierto de Prosopis flexuosa, 37-26; matorral denso de Prosopis alpataco, 7-6. La concentración de sales solubles sobrepasa los niveles críticos tolerados por las plantas cultivadas. No se detectaron niveles freáticos en los primeros 15 m de profundidad. Se considera que los suelos tienen buen drenaje interno, por lo que pueden ser recuperados sin inversiones elevadas. Este enfoque metodológico mostró una buena correspondencia entre las comunidades vegetales, su expresión espectral y las condiciones de salinidad y drenaje del suelo.The feasibility to obtain quality agricul tural products, irrigated with saline water, makes it necessary to assess areas peripheral to the irrigated oasis in order to determine their suitability for cropping. The goal is to combine diverse methodologies for mapping and assessing ecologically homogeneous units in marginal lands of Mendoza, using plant communities as an indicator of these units. A pilot area was surveyed using LANDSAT/TM image processing, and vegetation, soil and water table were analysed. Assessed vegetation units and their respective salinity ranges (dS m-1), up to 50 cm depth, were: steppe of Heterostachys ritteriana, 91-83; shrubland of Allenrolfea vaginata with H. ritteriana, 83-48; open shrubland of A.vaginata con Prosopis strombulifera, 62-55; open steppe of Suaeda divaricata with Atriplex argentina, 52-83; shrubland of S. divaricata con Lycium tenuispinosum, 40-43; open woodland of Prosopis flexuosa, 37-26; dense shrubland of Prosopis alpataco, 7-6. The concentration of soluble salts exceeds the critical levels tolerated by cultivated plants. No water tables were detected within 15 m from the surface. It is considered that soils have good drainage conditions, so they can be recovered without high investment. This methodological approach showed good correspondence among plant communities, their spectral expression, and soil salinity and drainage conditions.Fil: González Loyarte, María Margarita.Fil: Gaviola, Silvia. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ingeniería AgrícolaFil: Buk, Enrique. Instituto Argentino de Nivología, Glaciología y Ciencias AmbientalesFil: Rodeghiero, Alfio G.. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias BiológicasFil: Menenti, Massimo

Assessing the ecological vulnerability of the shallow steppe Lake Neusiedl (Austria-Hungary) to climate-driven hydrological changes using a palaeolimnological approach

9openInternationalBothLake Neusiedl, the largest steppe lake in Europe, is particularly sensitive to climate variations due to its extreme shallowness (zmax = 1.8 m) and low ratio of catchment to lake area (3.5 : 1). Changes in water budget, salinity and turbidity have key implications for the lake’s ecology and management. Here, we present a multi-proxy palaeolimnological reconstruction of the evolution of Lake Neusiedl since the end of its last complete desiccation (1865–1868), based on an undisturbed radiometrically dated core taken from the open water portion of the lake. Geochemical and biological (algal) proxies outline the succession of three major ecological stages since 1873 ± 16 yrs, with the first major changes appearing already in the 1930s as driven by climate related hydrological variability. Subfossil diatoms proved to be reliable for tracking long-term changes in the trophic conditions of Lake Neusiedl while diatom-inferred lake conductivity revealed to be unreliable due to a combination of lake environmental settings and the absence of a site-specific training set. Nonetheless, multivariate statistical analyses and comparisons with limnological data confirm a great potential of subfossil diatoms for revealing past ecological changes and tipping points of shallow lakes, as long as studies rely on a multi-proxy approach. In agreement with limnological surveys, the sediment record corroborates the high vulnerability of Lake Neusiedl, both in present and past times, towards climate-driven changes in water level and salinity, and allows the prediction, by analogy with the past, of future ecological changes in a context of global warming and increasing nutrient inputs from non-point sources.openTolotti, M.; Guella, G.; Herzig, A.; Rodeghiero, M.; Rose, N.L.; Soja, G.; Zechmeister, T.; Yang, H.; Teubner, K.Tolotti, M.; Guella, G.; Herzig, A.; Rodeghiero, M.; Rose, N.L.; Soja, G.; Zechmeister, T.; Yang, H.; Teubner, K

von Willebrand's disease in the year 2003: towards the complete identification of gene defects for correct diagnosis and treatment

Von Willebrand's disease (VWD) is an autosomally inherited bleeding disorder caused by a deficiency or abnormality of von Willebrand factor (VWF). VWF is a multimeric adhesive protein which plays an important role in primary hemostasis by promoting platelet adhesion to the subendothelium at sites of vascular injury and platelet-platelet interactions in high shear-rate conditions. It is also the carrier of factor VIII (FVIII), thus indirectly contributing to the coagulation process. VWD has a prevalence of about 1% in the general population, but the figure for clinically relevant cases is lower (about 100/million inhabitants). Bleeding manifestations are heterogeneous: mucosal bleeding is typical of all VWD cases but hemarthrosis and hematomas may also be present when FVIII levels are low. Most cases appear to have a partial quantitative deficiency of VWF (type 1 VWD) with variable bleeding tendency, whereas qualitative variants (type 2 VWD), due to a dysfunctional VWF, are clinically more homogeneous. Type 3 VWD is rare and the patients have a moderate to severe bleeding diathesis because of the virtual absence of VWF, and a recessive pattern of inheritance. The diagnosis of VWD, especially type I, may be difficult, because the laboratory phenotype is highly heterogeneous and is confounded by the fact that factors outside the VWF gene (e.g., blood group) influence VWF levels. An array of tests is usually required to characterize the VWD types of the disorder and establish the best treatment modality. The aim of treatment is to correct the dual defect of hemostasis, i.e. abnormal coagulation expressed by low levels of FVIII and abnormal platelet adhesion expressed by the prolonged bleeding time (BT). Desmopressin (DDAVP) is the treatment of choice for type 1 VWD because it corrects the FVIII/VWF levels and the prolonged BT in the majority of cases. In type 3 and in severe forms of type 1 and 2 VWD, DDAVP is not effective and for these patients plasma virally-inactivated concentrates containing FVIII and VWF are the mainstay of treatment. These concentrates are clinically effective and safe, although they do not always correct the BT

The MICADO first light imager for ELT: its astrometric performance

We report on our ongoing efforts to ensure that the MICADO NIR imager reaches differential absolute (often abbreviated: relative) astrometric performance limited by the SNR of typical observations. The exceptional 39m diameter collecting area in combination with a powerful multi-conjugate adaptive optics system (called MAORY) brings the nominal centroiding error, which scales as FWHM/SNR, down to a few 10 uas. Here we show that an exceptional effort is needed to provide a system which delivers adequate and calibrateable astrometric performance over the full field of view (up to 53 arcsec diameter).Comment: 5 pages, submitted to SPIE 2018 Astronomical Telescopes + Instrumentatio

Expected performance of the ASTRI-SST-2M telescope prototype

ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is an Italian flagship project pursued by INAF (Istituto Nazionale di Astrofisica) strictly linked to the development of the Cherenkov Telescope Array, CTA. Primary goal of the ASTRI program is the design and production of an end-to-end prototype of a Small Size Telescope for the CTA sub-array devoted to the highest gamma-ray energy region. The prototype, named ASTRI SST-2M, will be tested on field in Italy during 2014. This telescope will be the first Cherenkov telescope adopting the double reflection layout in a Schwarzschild-Couder configuration with a tessellated primary mirror and a monolithic secondary mirror. The collected light will be focused on a compact and light-weight camera based on silicon photo-multipliers covering a 9.6 deg full field of view. Detailed Monte Carlo simulations have been performed to estimate the performance of the planned telescope. The results regarding its energy threshold, sensitivity and angular resolution are shown and discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223

Qualification and Testing of a Large Hot Slumped Secondary Mirror for Schwarzschild-Couder Imaging Air Cherenkov Telescopes

Dual-mirror Schwarzschild-Couder (SC) telescopes are based on highly aspherical optics, and they represent a novel design in the world of very high energy astrophysics. This work addresses the realization and the qualification of the secondary mirror for an SC telescope, named ASTRI, developed in the context of the Cherenkov Telescope Array Observatory. The discussion surveys the overall development from the early design concept to the final acceptance optical tests