Atmospheric optical-turbulence at Roque de los Muchachos Observatory: database and recalibration of the generalized-SCIDAR data

We present the largest database so far of atmospheric optical-turbulence profiles (197035 individual CN2(h)) for an astronomical site, the Roque de los Muchachos Observatory (La Palma, Spain). This C2 (h) database was obtained through generalized-SCIDAR observations at the 1 meter Jacobus Kapteyn telescope from Febrary 2004 to August 2009, obtaining useful data for 211 nights. The overestimation of the turbulence strength induced during the generalized SCIDAR data processing has been analyzed for the different observational configurations. All the individual C2 (h) have been recalibrated to compensate the introduced errors during data treatment following (Avila & Cuevas 2009). Comparing results from profiles before and after the recalibration, we analyze its impact on the calculation of relevant parameters for adaptive optics.Comment: 8 pages, 3 figures, MNRAS accepte

Astronomical Site Ranking Based on Tropospheric Wind Statistics

We present comprehensive and reliable statistics of high altitude wind speeds and the tropospheric flows at the location of five important astronomical observatories. Statistical analysis exclusively of high altitude winds point to La Palma as the most suitable site for adaptive optics, with a mean value of 22.13 m/s at the 200 mbar pressure level. La Silla is at the bottom of the ranking, with the largest average value 200 mbar wind speed(33.35 m/s). We have found a clear annual periodicity of high altitude winds for the five sites in study. We have also explored the connection of high to low altitude atmospheric winds as a first approach of the linear relationship between the average velocity of the turbulence and high altitude winds (Sarazin & Tokovinin 2001). We may conclude that high and low altitude winds show good linear relationships at the five selected sites. The highest correlation coefficients correspond to Paranal and San Pedro Martir, while La Palma and La Silla show similar high to low altitude wind connection. Mauna Kea shows the smallest degree of correlation, which suggests a weaker linear relationship. Our results support the idea of high altitude winds as a parameter for rank astronomical sites in terms of their suitability for adaptive optics, although we have no evidence for adopting the same linear coefficient at different sites. The final value of this linear coefficient at a particular site could drastically change the interpretation of high altitude wind speeds as a direct parameter for site characterization.Comment: 18 pages, 5 figures. Accepted in MNRA

Optical Turbulence Measurements and Models for Mount John University Observatory

Site measurements were collected at Mount John University Observatory in 2005 and 2007 using a purpose-built scintillation detection and ranging system. $C_n^2(h)$ profiling indicates a weak layer located at 12 - 14 km above sea level and strong low altitude turbulence extending up to 5 km. During calm weather conditions, an additional layer was detected at 6 - 8 km above sea level. $V(h)$ profiling suggests that tropopause layer velocities are nominally 12 - 30 m/s, and near-ground velocities range between 2 -- 20 m/s, dependent on weather. Little seasonal variation was detected in either $C_n^2(h)$ and $V(h)$ profiles. The average coherence length, $r_0$, was found to be $7 \pm 1$ cm for the full profile at a wavelength of 589 nm. The average isoplanatic angle, $\theta_0$, was $1.0 \pm 0.1$ arcsec. The mean turbulence altitude, $\bar{h_0}$, was found to be $2.0\pm0.7$ km above sea level. No average in the Greenwood frequency, $f_G$, could be established due to the gaps present in the \vw\s profiles obtained. A modified Hufnagel-Valley model was developed to describe the $C_n^2(h)$ profiles at Mount John, which estimates $r_0$ at 6 cm and $\theta_0$ at 0.9 arcsec. A series of $V(h)$ models were developed, based on the Greenwood wind model with an additional peak located at low altitudes. Using the $C_n^2(h)$ model and the suggested $V(h)$ model for moderate ground wind speeds, $f_G$ is estimated at 79 Hz.Comment: 14 pages; accepted for publication in PAS

The best skies for astronomy

Seminario impartido por Casiana Muñoz-Tuñón (IAC) el 15 de noviembre de 2016 en las Oficinas del CIAI en Santa Cruz de Tenerife

Re-calibrated Generalized-Scidar measurements at Cerro Paranal (VLT's site)

Generalized Scidar (GS) measurements taken at the Paranal Observatory in November/December 2007 in the context of a site qualification for the future European Extremely Large Telescope E-ELT are re-calibrated to overcome the bias induced on the CN2 profiles by a not correct normalization of the autocorrelation of the scintillation maps that has been recently identified in the GS technique. A complete analysis of the GS corrected measurements as well as of the corrected errors is performed statistically as well as on individual nights and for each time during all nights. The relative errors of the CN2 profiles can reach up to 60% in some narrow temporal windows and some vertical slabs, the total seeing up to 12% and the total integrated turbulence J up to 21%. However, the statistic analysis tells us that the absolute errors of the median values of the total seeing is 0.06 arcsec (relative error 5.6%), for the boundary seeing 0.05 arcsec (relative error 5.6%) and for the seeing in the free atmosphere 0.04 arcsec (relative error 9%). We find that, in spite of the fact that the relative error increases with the height, the boundary and the free atmosphere seeing contribute in an equivalent way to the error on the total seeing in absolute terms. Besides, we find that there are no correlations between the relative errors and the value of the correspondent seeing. The absolute error of the median value of the isoplanatic angle is 0.13 arcsec (relative error 6.9%).Comment: 22 figures, MNRAS accepte

Análisis estadístico del viento a 200 milibares en los Observatorios de Canarias

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna)El viento a 200 milibares (V200) ha sido propuesto recientemente como un parámetro importante para la selección y calidad de observatorios astronómicos. En esta contribución presentamos la estadística y análisis detallados de V200 sobre las Islas Canarias en el periodo 1980-2001 basado en medidas obtenidas de los archivos del Centro de Diagnóstico Climatológico (NCEPINCAR) y del Centro Territorial de Canarias Occidental del Instituto Nacional de Meteorología. La alta correlación de /os resultados para La Palma y Tenerife ratifica la estabilidad del cielo de Canarias, proporcionando una confirmación independiente de la homogeneidad del cielo en islas oceánicas como Canarias. El análisis de frecuencias y variabilidad de V200 en un periodo de 22 años sugiere una periodicidad estacional de este parámetro en nuestras islas, con valores que muestran la excelente calidad de los cielos canarios para observaciones astronómicas. Como complemento, presentamos una comparación de valores promedios de V200 en diferentes observatorios astronómicos del mundo

Active Trigger Points Are Associated With Anxiety and Widespread Pressure Pain Sensitivity in Women, but not Men, With Tension Type Headache

BACKGROUND: A better understanding of gender differences can assist clinicians in further developing therapeutic programs in tension type headache (TTH). OBJECTIVE: To evaluate gender differences in the presence of trigger points (TrPs) in the head, neck, and shoulder muscles and their relationship with headache features, pressure pain sensitivity, and anxiety in people with TTH. METHODS: Two hundred and ten (59 men, 151 women) patients with TTH participated. TrPs were bilaterally explored in the temporalis, masseter, suboccipital, upper trapezius, splenius capitis, and sternocleidomastoid muscles. Headache features were collected using a 4-week headache diary. Trait and state anxiety levels were assessed using the State-Trait Anxiety Inventory. Pressure pain thresholds (PPTs) over the temporalis, C5/C6 joint, second metacarpal, and tibialis anterior were assessed. RESULTS: Women with TTH exhibited a significantly higher number of total (P = 0.027) and active (P = 0.030), but similar number of latent (P = 0.461), TrPs than men with TTH. Active TrPs in the temporalis, suboccipital, and splenius capitis muscles were the most prevalent in both men and women with TTH. The number of active TrPs was associated with anxiety levels (r = 0.217; P = 0.045) in women, but not in men (P = 0.453): the higher the number of active TrPs, the more the trait levels of anxiety. Women exhibited lower PPTs than men (all, P < 0.001). In men, the number of active, but not latent, TrPs was negatively associated with localized PPTs (all, P < 0.05), whereas in women, the number of active and latent TrPs was negatively associated with PPTs in all points (all, P < 0.01): the higher the number of TrPs, the lower the widespread PPTs. CONCLUSIONS: This study described gender differences in the presence of TrPs in TTH. Women with TTH showed lower PPTs than men. The association between TrPs, anxiety levels, and pressure pain hyperalgesia seems to be more pronounced in women than in men with TTH

Optical turbulence vertical distribution with standard and high resolution at Mt. Graham

A characterization of the optical turbulence vertical distribution (Cn2 profiles) and all the main integrated astroclimatic parameters derived from the Cn2 and the wind speed profiles above the site of the Large Binocular Telescope (Mt. Graham, Arizona, US) is presented. The statistic includes measurements related to 43 nights done with a Generalized Scidar (GS) used in standard configuration with a vertical resolution Delta(H)~1 km on the whole 20 km and with the new technique (HVR-GS) in the first kilometer. The latter achieves a resolution Delta(H)~20-30 m in this region of the atmosphere. Measurements done in different periods of the year permit us to provide a seasonal variation analysis of the Cn2. A discretized distribution of Cn2 useful for the Ground Layer Adaptive Optics (GLAO) simulations is provided and a specific analysis for the LBT Laser Guide Star system ARGOS (running in GLAO configuration) case is done including the calculation of the 'gray zones' for J, H and K bands. Mt. Graham confirms to be an excellent site with median values of the seeing without dome contribution epsilon = 0.72", the isoplanatic angle theta0 = 2.5" and the wavefront coherence time tau0= 4.8 msec. We find that the optical turbulence vertical distribution decreases in a much sharper way than what has been believed so far in proximity of the ground above astronomical sites. We find that 50% of the whole turbulence develops in the first 80+/-15 m from the ground. We finally prove that the error in the normalization of the scintillation that has been recently put in evidence in the principle of the GS technique, affects these measurements with an absolutely negligible quantity (0.04").Comment: 11 figures. MNRAS, accepte

Astronomical site selection: On the use of satellite data for aerosol content monitoring

The main goal of this work is the analysis of new approaches to the study of the properties of astronomical sites. In particular, satellite data measuring aerosols have recently been proposed as a useful technique for site characterization and searching for new sites to host future very large telescopes. Nevertheless, these data need to be critically considered and interpreted in accordance with the spatial resolution and spectroscopic channels used. In this paper we have explored and retrieved measurements from satellites with high spatial and temporal resolutions and concentrated on channels of astronomical interest. The selected datasets are OMI on board the NASA Aura satellite and MODIS on board the NASA Terra and Aqua satellites. A comparison of remote sensing and in situ techniques is discussed. As a result, we find that aerosol data provided by satellites up to now are not reliable enough for aerosol site characterization, and in situ data are required.Comment: LaTeX2e MN v2.2, 16 pages with 13 figures. Accepted for Mon. Not. R. Astron. Soc.(2008