The Infrared Astronomical Characteristics of Roque de los Muchachos Observatory: precipitable water vapor statistics

TL;DR

This study assesses the atmospheric water vapor at Roque de los Muchachos Observatory using GPS and radiometer data, highlighting its suitability for infrared astronomy with seasonal variations and variability analysis.

Contribution

It provides the first detailed statistical analysis of precipitable water vapor at ORM using GPS, comparing it with radiometer data, and evaluates its implications for infrared observations.

Findings

Median PWV of 3.8 mm indicates good IR observing conditions.

Over 60% of nighttime PWV is below 3 mm in peak months.

PWV exhibits clear seasonal patterns with winter and spring being optimal.

Abstract

The atmospheric water vapor content above the Roque de los Muchachos Observatory (ORM) obtained from Global Positioning Systems (GPS) is presented. GPS measurements have been evaluated by comparison with 940nm-radiometer observations. Statistical analysis of GPS measurements points to ORM as an observing site with suitable conditions for infrared (IR) observations, with a median column of precipitable water vapor (PWV) of 3.8 mm. PWV presents a clear seasonal behavior, being Winter and Spring the best seasons for IR observations. The percentage of nighttime showing PWV values smaller than 3 mm is over 60% in February, March and April. We have also estimated the temporal variability of water vapor content at the ORM. A summary of PWV statistical results at different astronomical sites is presented, recalling that these values are not directly comparable as a result of the differences in the techniques used to recorded the data.