Publications (16)7.17 Total impact
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Article: Near-infrared thermal emissivity from ground based atmospheric dust measurements at ORM
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ABSTRACT: We present an analysis of the atmospheric content of aerosols measured at Observatorio del Roque de los Muchachos (ORM; Canary Islands). Using a laser diode particle counter located at the Telescopio Nazionale Galileo (TNG) we have detected particles of 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 um size. The seasonal behavior of the dust content in the atmosphere is calculated. The Spring has been found to be dustier than the Summer, but dusty conditions may also occur in Winter. A method to estimate the contribution of the aerosols emissivity to the sky brightness in the near-infrared (NIR) is presented. The contribution of dust emission to the sky background in the NIR has been found to be negligible comparable to the airglow, with a maximum contribution of about 8-10% in the Ks band in the dusty days.07/2011; -
Article: El Roque de Los Muchachos Site Characteristics. III. Analysis of Atmospheric Dust and Aerosol Extinction
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ABSTRACT: Canary Islands are normally interested by dominant North-East winds that, in some meteorological conditions, can transport sand at high altitude from the Sahara desert. The dust may affect the efficiency of the telescopes and decreases the transparency of the sky. In order to maximize the scientific return of the telescopes located at the ORM, we present an analysis of the atmospheric dust content and its effects on astronomical observations. B, V and I dust aerosol astronomical extinction are derived. Using a 5 years series database of data taken from the four channel TNG dust monitor, we compute a mean hourly and daily values of the dust content. We have detected particles having size 0.3, 0.5, 1.0 and 5.0 um. Using a power law we have derived the content of 10.0 um particles. We found a typical local dust concentration ranging from 3x10^6 particles per cubic meter at 0.3 um, to 10^3 at 5.0 um and 10 at 10.0 um, increasing up to 3 order of magnitudes during the dust storms, with a relative higher increase of 1.0, 5.0 and 10.0 um particles. The number of local dust storm events is the same in winter- and summertime, but, the average background and storm-related increases in the dust concentration in summer are significantly higher than in winter. In a uniform approximation, during the dust storms, an average height of the dust layer of 2.5 km above the telescope is inferred. During the sand storms La Palma Island is affected by an almost uniform layer extending up to 5 km above the sea level, down, at least the height of the telescope. The visible extinction is dominated by particles at 1.0, 5.0 and 10.0 um. In agreement with the results from Carlsberg Automatic Meridian Circle (CAMC) we find a typical extinction during dust storms of about 0.2 mag/airmass. Comment: Accepted for publication in A&A. 9 pages, 11 figures. This work is the continuation of a series of papers concerning a detailed study of the Astroclimatology at ORM. The two previous papers (both Lombardi et al.) have reference PASP.2006.118.1198-1204 and PASP.2007.119.292-30202/2008; -
Chapter: PIGS - A New Wavefront Sensor Concept for ELTs
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ABSTRACT: Adaptive Optics Systems for Extremely Large Telescopes (ELT) will need new wavefront sensing concepts to deploy their full capabilities. In this paper we exemplify the necessity of new wavefront sensing ideas by discussing briefly some major problems and present as a possible solution the pseudo infinite guide star sensor (PIGS). A prototype of a PIGS sensor was already built in the laboratory, which could demonstrate its feasibility.12/2005: pages 31-34; -
Article: Speckle interferometry observations of main belt asteroids at TNG
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ABSTRACT: Speckle interferometry observations of eight main belt asteroids (3 Juno, 12 Victoria, 16 Psyche, 30 Urania, 88 Thisbe, 135 Hertha, 230 Athamantis, and 324 Bamberga) were obtained at the Telescopio Nazionale Galileo in La Palma (Canary Islands, Spain). Average sizes and apparent shapes were measured, and were found to fit reasonably the predictions of indirect techniques for size and shape determination (radiometry and photometry). No new binary objects were discovered.10/2002; 500:497-500. -
Article: Speckle interferometry measurements of the asteroids 10-Hygiea and 15-Eunomia
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ABSTRACT: Speckle interferometry measurements of the asteroids 10-Hygiea and 15-Eunomia have been obtained with the speckle facility aboard the AdOpt@TNG module, permanently mounted on the 3.58m TNG telescope in Canary Islands. Direct angular diameter measurements and estimates of the apparent ellipticity are given allowing to derive the density of these asteroids, combining our data with published results. Our data for 15-Eunomia, moreover, are compatible with both an egg-shaped and a double, in contact, asteroid model. A brief discussion of both models is here presented.Astronomy and Astrophysics 01/2000; 354:315-320. · 4.59 Impact Factor -
Article: Telescopio Nazionale Galileo
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ABSTRACT: By imaging the edge of the Moon we have tested a seeing monitor able to evaluate the isokinetic patch size. These measurements have a relevant interest because of several Laser Guide Star (LGS) tilt recovery schemes that have been proposed. In our approach the edge of the Moon mimics a LGS as seen far from the laser projector. The conceptual design of the instrument, the data reduction techniques and the preliminary results obtained at the Asiago Astronomical Observatory are given. Because, as a by product, the instrument is able to evaluate r 0 , a comparison with seeing data collected at the 1.82 m telescope of Cima Ekar during the three nights test of the described instrument is also given. 1 Introduction The isokinetic patch size can be defined as the characteristic angular size where the tilt induced by atmospherical perturbation becomes decorrelated. In order to obtain an optimal correction with an Adaptive Optics system it is necessary to have a bright reference source within...04/1999; -
Article: Telescopio Nazionale Galileo
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ABSTRACT: The atmospheric image motion control loop for the 3.6m Telescopio Nazionale Galileo (TNG) has been tested and characterized in lab using a turbulence generator. The tip-tilt sensor is based on four Avalanche Photodiodes and the tilt corrector is a voice coil actuated flat mirror. The feedback network is implemented using a a DSP-based system. We have used the same focal ratios of the beam as it will be experienced by the system at the foci of the TNG telescope. The collected data are time--series useful to perform a Fourier analysis aimed to estimate the effectiveness of the correction. These data can be compared with: theoretical and measured tilt spectra obtained at the telescope site, in order to predict the degree of correction that can be achieved by such a system; measured data on single components, like the transfer function of the tip-tilt mirror, the latency of the DSP calculation and the characterization of the APDs tip-tilt sensor unit. The collected data are also suitable t...04/1999; -
Article: Minimum diameter of a laser projector for some perspective-based laser guide-star tilt retrieval schemes.
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ABSTRACT: Because of the finite speed of light, a laser guide Star that is seen from the side is not exactly a straight line. When such a laser guide star is used to sense tip-tilt with some of the perspective-based techniques that are used to retrieve an absolute tip-tilt laser, such nonstraightness introduces an error. We estimate this effect for various diameters of a laser projector, assuming a Kolmogorov turbulence spectrum and figuring the maximum achievable Strehl ratio. We found that under poor seeing conditions the effect is not negligible and that laser projectors larger than those currently used are required.Applied Optics 08/1998; 37(21):4645-8. · 1.41 Impact Factor -
Article: Optimum configurations for two off-axis parabolae used to make an optical relay
Journal of Modern Optics 07/1997; 44(7):1259-1267. · 1.17 Impact Factor -
Conference Proceeding: Laboratory characterization of an APD-based tip-tilt corrector
Adaptive Optics and Applications; 01/1997 -
Article: PIGS - a new wavefront sensor conceopt for ELTs
Brandner, W., Kasper, M. E.: Science with Adaptive Optics, Springer, 31-34 (2005). -
Article: Isokinetic patch measurements on the edge of the Moon
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ABSTRACT: By imaging the edge of the Moon we have tested a seeing monitor able to evaluate the isokinetic patch size. These measurements have a relevant interest because of several Laser Guide Star (LGS) tilt recovery schemes that have been proposed. In our approach the edge of the Moon mimics a LGS as seen far from the laser projector. The conceptual design of the instrument, the data reduction techniques and the preliminary results obtained at the Asiago Astronomical Observatory are given. Because, as a by product, the instrument is able to evaluate $r_0$, a comparison with seeing data collected at the 1.82 m telescope of Cima Ekar during the three nights test of the described instrument is also given.http://dx.doi.org/10.1051/aas:1998244. -
Article: El Roque de Los Muchachos site characteristics
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ABSTRACT: Context. It is known that the Canary Islands are normally affected by dominant winds flowing from north-northeast, that in some meteorological conditions, can transport sand from the Sahara desert at high altitude. The dust may affect the efficiency of the telescopes and decrease the transparency of the sky.Aims. To maximize the scientific return of the telescopes located at the Observatorio del Roque de Los Muchachos (ORM), we present an analysis of the atmospheric dust content and its effects on astronomical observations. Than $B$, $V$ and $I$ dust aerosol astronomical extinction are derived.Methods. Using a 5-year series database of data taken from a dust monitor located inside the Telescopio Nazionale Galileo (TNG) dome, we computed mean hourly and daily values of the dust content as measured with a four-channel dust monitor.Results. We detected particles of 0.3, 0.5, 1.0, and 5.0 $\mu$m. Furthermore, using a power law we derived the content of 10.0 $\mu$m particles. We found a typical local dust concentration ranging from 3 $\times$ 10$^6$ particles per cubic metre at 0.3 $\mu$m, to 10$^3$ at 5.0 $\mu$m and 10 at 10.0 $\mu$m, increasing up to 3 orders of magnitudes during the dust storms, with a relatively higher increase of 1.0, 5.0, and 10.0 $\mu$m particles. The number of local dust storm events is the same in the local winter and summer, but the average background and storm-related increases in the dust concentration in summer are significantly higher than in winter. In a uniform approximation, during the dust storms, an average height of the dust layer of 2.5 km above the telescope is inferred.Conclusions. During the sand storms, La Palma Island is affected by an almost uniform layer extending up to 5 km above the sea level. The visible extinction is dominated by particles at 1.0, 5.0 and 10.0 $\mu$m. In agreement with the results from Carlsberg Automatic Meridian Circle (CAMC), we find a typical extinction of about 0.2 mag airmass$^{-1}$ during dust storms.http://dx.doi.org/10.1051/0004-6361:20078372. -
Article: Speckle interferometry observations of asteroids at tng
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ABSTRACT: The Speckle camera of the 3.5 m Telescopio Nazionale Galileo (TNG) has been used to measure apparent sizes and shapes of a number of main belt asteroids. The average size measurements are in a generally good agreement with the results of indirect IRAS-based radiometric techniques. The measured shapes are compared with predictions based on previously derived spin axis directions and lightcurve photometry of some of the observed objects. Also in this case the agreement is reasonable and the speckle observations allow us to discriminate in some cases between the two pole solutions usually found for each object. No clear evidence of binaries was found. The results show that the TNG speckle camera can be a powerful tool to resolve relatively large main belt asteroids and to calibrate the results of the IRAS survey.Icarus. -
Article: Status progress of AdOpt@TNG and offer to the international astronomical community
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ABSTRACT: The Adaptive Optics Module of the Telescopio Nazionale Galileo (AdOpt@TNG) has enjoyed a huge refurbishment. A new WaveFront Sensing CCD (EEV39 80x80pixels by SciMeasure) has been mounted, allowing for up to 1KHz frame rate. Thanks to the versatility of the pyramid wavefront sensor, the fast changing of the 4x4 and 8x8 pupil sampling has been easily and successfully implemented. A dual pentium processor PC with Real-Time Linux has substituted the old VME as Real Time Computer. The implementation of the new Deformable Mirror by Xinetics will be also discussed. A new Graphical User Interface has been built to allow for user-friendly utilization of the module by astronomers. On-sky observations will be presented in terms of FWHM and Strehl Ratio for different values of guiding star magnitudes and seeing conditions. The encouraging on-sky results and overall system stability pushed to offer AdOpt@TNG to the international astronomical community.Ellerbroek, Brent L. ; Bonaccini Calia, Domenico: Advances in Adaptive Optics II, SPIE, 62722G (2006). -
Article: Multi Scintillation Layer-Oriented Seeing Monitor
266:588.
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Institutions
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1997
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University-Hospital of Padova
Padova, Veneto, Italy
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