Identification of Potential Sites for Astronomical Observations in Northern South-America

TL;DR

This study presents a new method using satellite and weather data to identify optimal sites for optical and infrared astronomy in northern South America, highlighting locations with high clear sky fractions.

Contribution

The paper introduces an innovative satellite-based approach to determine potential astronomical sites, validated with local weather data and applied to the Andes region.

Findings

Identified 12 suitable sites with over 30% clear sky fraction during dry seasons.

The best site in Venezuela has approximately 220 clear nights per year.

Lower quality sites are located in Sierra Nevada de Santa Marta and Serraní del Perijá.

Abstract

In this study we describe an innovative method to determine potential sites for optical and infrared astronomical observations in the Andes region of northern South America. The method computes the Clear sky fraction (CSF) from Geostationary Observational Environmental Satellite (GOES) data for the years 2008-12 through a comparison with temperatures obtained from long-term records of weather stations and atmospheric temperature profiles from radiosonde. Criteria for sky clearance were established for two infrared GOES channels in order to determine potential sites in the Andes region of northern South-America. The method was validated using the reported observed hours at Observatorio Nacional de Llano del Hato in Venezuela. Separate CSF percentages were computed for dry and rainy seasons for both, photometric and spectroscopic night qualities. Twelve sites with five year averages of CSF for spectroscopic nights larger than 30% during the dry seasons were found to be suitable for astronomical observations. The best site with (220$\pm$42) spectroscopic clear nights per year is located in the Andes of Venezuela (70$^{\circ}$28'48"W, 9$^{\circ}$5'60"N) at an altitude of 3480 meters. Lower quality regions were found in Sierra Nevada de Santamarta and Serran\'ia del Perij\'a with (126$\pm$34) and (111$\pm$27) clear nights per year, respectively. Sites over the Andes are identified in Norte de Santander with (107$\pm$23) and in the north-east part of Boyac\'a with a mean of (94$\pm$13) clear nights per year. Two sites at low latitude located in Ecuador with more than 100 clear nights per year and with similar seasonal CSF percentages were also identified. Five year evolution suggest a possible correlation be tween the lowest percentages observed during the rainy seasons of 2010 and 2011 with positive values of the Southern Oscillation Index.