Optical-Turbulence and Wind Profiles at San Pedro Mártir (original) (raw)
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Optical-Turbulence and Wind Profiles at San Pedro Mártir with G-SCIDAR
Revista Mexicana De Astronomia Y Astrofisica, 2007
Se presentan resultados del monitoreo de perfiles de turbulenciaóptica en San Pedro Mártir, México, durante 11 noches en abril-mayo 1997 y 16 noches en mayo 2000. La velocidad de las capas turbulentas también se monitoreo, pero sólo durante la temporada del 2000. 6414 perfiles de turbulencia y 3016 perfiles de velocidad fueron medidos y analizados estadísticamente. Los resultados referentes a los perfiles de turbulencia son: (i) el seeing) producido en los primeros 1.2 km, sin incluir la turbulencia de cúpula, en los telescopios de 1.5 y 2.1 m tiene medianas de 0. 63 y 0. 44. (ii) La turbulencia por encima de 1.2 km y en la atmósfera completa produce seeing con valores medianos de 0. 38 y 0. 71. (iii) Elángulo de isoplanatismo para corrección total enóptica adaptativa tiene una valor mediano de 1. 87. (iv) La correlación temporal de la intensidad de la turbulencia cae a 50% en períodos de tiempo de 2 y 0.5 horas, aproximadamente, para alturas mayores y menores que 16 km sobre el nivel del mar, respectivamente. (v) El tiempo de decorrelación delángulo de isoplanatismo tiene un valor estimado de 2 horas. Los resultados referentes a los perfiles de viento son: (vi) No se encuentra correlación significativa entre la intensidad de turbulencia (C 2 N) y la velocidad de las capas turbulentas. (vii) Las capas por debajo de 5 km y por arriba de 16 km, sobre el nivel del mar, son similarmente lentas, con velocidades medianas de 8.6 y 9.6 m s −1. (viii) Entre 9 y 16 km, donde algunas noches tiene lugar la corriente de chorro, la velocidad del viento mediana es de 26.0 m s −1. (ix) De las medidas simultáneas de C 2 N (h) y V (h), calculamos el tiempo de coherencia de la turbulencia, capa por capa. Los resultados obtenidos sitúan a San Pedro Mártir entre los sitios más adecuados para la instalación de telescopiosópticos de la próxima generación.
3D optical turbulence characterization at San Pedro Mártir
Muchos instrumentos son capaces de proporcionar estimaciones locales (en espacio y tiempo) de todos los parámetros astroclimáticos que dependen de la turbulenciaóptica. Actualmente, la técnica numérica es eĺ unico método que puede proporcionar una caracterización en 3D de la turbulenciaóptica. Desde hace algunos años, grandes esfuerzos han sido dedicados a incrementar la confiabilidad del modelo atmosférico de meso-escala llamado Meso-Nh para simular perfiles de C 2 N arriba de sitios astronómicos. Los resultados más recientes y más prometedores han sido obtenidos en el sitio de San Pedro Mártir. En este artículo, se presenta un resumen de dichos resultados.
Turbulence Profiles with Generalized Scidar at San Pedro Mártir Observatory and Isoplanatism Studies
Publications of the Astronomical Society of the Pacific, 1998
The results obtained from 3398 vertical pro les of atmospheric turbulence measured during 11 nights at the Observatorio Astron omico Nacional in San Pedro M artir (Baja California, M exico) are presented. The observations were carried out with the generalized scidar (GS) installed at the 1.5 m and the 2.1 m telescopes of that site, in March and April 1997. The open air seeing was measured with a di erential image motion monitor (DIMM). The GS can detect turbulence pro les along the whole optical path, unlike the classical scidar which is insensitive to low altitude turbulence. For the rst time, to our knowledge, pro les including turbulence near the ground are monitored and statistically analyzed. Isoplanatic angles for speckle interferometry and adaptive optics (AO) in either full or partial compensation are deduced, as well as the focus anisoplanatism parameter for sodium laser guide stars. The advantage of minimizing the distance between the turbulent layers and the conjugated plane of the deformable mirror of an AO system is studied. The comparison of GS pro les obtained at both telescopes, together with DIMM measurements, show that the turbulence near the ground is more strongly dominant at the 1.5 m telescope than at the 2.1 m telescope, where the median values of the seeing near the ground, in the free atmosphere and in the whole optical path are 0.56, 0.44 and 0.77 arcsec, respectively. These values are comparable to or better than those of the major astronomical observatories, although a larger data sample is needed for a de nitive comparison.
Two campaigns to compare three turbulence profiling techniques at Las Campanas Observatory
2008
In preparation to characterize the Giant Magellan Telescope site and guide the development of its adaptive optics system, two campaigns to systematically compare the turbulence profiles obtained independently with three different instruments were conducted at Las Campanas Observatory in September, 2007 and January 2008. Slope detection and ranging (SLODAR) was used on the 2.5-m duPont telescope. SLODAR measures the C2n profile as a function of altitude through observations of double stars. The separation of the observed double star sets the maximum altitude and height resolution. Ground layer (altitudes < 1 km) and free atmosphere turbulence profiles are compared with those obtained with a lunar scintillometer (LuSci) and a multi-aperture scintillation sensor (MASS), respectively. In addition, the total atmospheric seeing was measured by both SLODAR and a differential image motion monitor (DIMM).
Generalized SCIDAR Measurements at San Pedro Mártir. II. Wind Profile Statistics
Publications of the Astronomical Society of the Pacific, 2006
We present the results of monitoring the speed of optical turbulent layers in the atmosphere above San Pedro Mártir, Mexico, during 15 nights in 2000 May. The data were obtained using the generalized scintillation detection and ranging technique (generalized SCIDAR), developed at Nice University. This paper constitutes the second in a series. The first paper presents results concerning measurements of optical turbulence strength obtained at the same site and time. The principal results of the present article are as follows: (1) The wind profiles remain stable during each night. (2) No correlation between the turbulence intensity and the speed of the turbulent 2 C N layers, V, is detected for speeds lower than ∼45 m s Ϫ1 . Above that speed, which was only exceeded in the jetstream layer on one night, the optical turbulence strength is seen to increase. (3) Layers in the first 4 km and higher than 16 km above sea level are similarly slow, with median speeds of 8.6 and 9.6 m s Ϫ1 , respectively. (4) Between 9 and 16 km, where the jet stream flows on some of the nights, the median wind speed is 26.0 m s Ϫ1 . (5) From simultaneous measurements of and , we compute the temporal coherence of the turbulence, layer by
Four Years of Optical Turbulence Monitoring at the Cerro Tololo Inter-American Observatory (CTIO)
Publications of the Astronomical Society of the Pacific, 2009
The optical turbulence conditions as measured between 2004 through the end of 2008 above Cerro Tololo, their seasonal as well as nocturnal behavior, are presented. A comparison with the MASS-DIMM system of the Thirty Meter Telescope site testing was conducted and identifies an artificially increased seeing component in the data collected by the CTIO-DIMM system under northerly winds. Evidence is shown that this increased turbulence is caused by the telescope dome. A correction for this effect is attempted and applied to the CTIO-DIMM data. The MASS data of this comparison campaign allow constraints to be set on the general assumption of uniform turbulent layers above a site.
Recalibrated turbulence profiles at San Pedro M��rtir
2011
La calibración de perfiles de turbulenciaóptica (C 2 N ) medidos con el método SCIDAR generalizado ha sido recientemente revisada y corregida por . Basándonos en ese trabajo, aquí presentamos la corrección de todos los perfiles de C 2 N medidos con el SCIDAR generalizado en el Observatorio Astronómico Nacional de San Pedro Mártir. El perfil de C 2 N mediano corregido conserva su estructura vertical general. El cociente promediado en altura de la mediana de los valores de C 2 N corregidos sobre la mediana de los valores no corregidos es igual a 0.87. La mediana del seeing corregido en el sitio es 0. ′′ 68 ± 0. ′′ 03, 4.2% menor que la mediana no corregida. Las medianas del seeing producido por turbulencia en los dos primeros kilómetros de altura sobre los telescopios de 1.5 m y 2.1 m de diámetro decrecen en un 15.8% y 13.6%, respectivamente. Elángulo isoplanático corregido tiene una mediana de 1. ′′ 96 ± 0. ′′ 04.
2013
The optical turbulence (OT) forecast is definitely mandatory for ground-based astronomy supported by AO to schedule scientific programs, instrumentation and instrumentation mode (ex: narrow or wide field) to exploit the AO potentialities and optimize the telescope management and scientific feedbacks. A status report of the on-going MOSE project aiming at assess the feasibility of the prediction of the (1) OT and (2) all the classical atmospheric parameters from which the OT depends on at the two major ESO sites for ground-based astronomy in the visible and infrared regimes (Cerro Paranal and Cerro Armazones) is presented. The study employed a wide variety of measurements obtained with different instruments running simultaneously to constrain and validate the model. Results obtained so far are very promising showing that the hydrodynamic technique is already mature for an operational implementation in present and forthcoming observatories. In this contribution we will present a summary of the most important achieved results and forthcoming plans to overcome the observed limitations. The analysis of procedures required to quantify the models score of success for the OT revealed us that an improved strategy for automatic systematic monitoring of turbulence is necessary in modern Observatories.