ESO Telescopes Successfully Face Worst Weather in a Decade

Over a five day period starting on 4 July 2011 the northern part of Chile, including the Chilean Atacama Desert — normally one of the driest places on Earth — was hit by one of the most intense weather fronts to pass through the region in more than 10 years. ESO’s Paranal Observatory was in the path of this extremely rare storm, but the safety procedures that were in place worked very well. No one was injured and there was no damage to the telescopes. Only minor damage to the site infrastructure was recorded, demonstrating that all installations at Paranal are well prepared for the rare adverse weather conditions that can occur on a high mountain in the Atacama Desert.

This weather system was the worst experienced by the observatory since the beginning of operations in 1998. There was very high humidity, strong winds over 30 metres/second, large amounts of dust, torrential rain, and sub-zero temperatures.

The Residencia hotel building was particularly affected by the heavy rain and there was some localised flooding. Fortunately, timely precautions prevented any damage. During the very rare event of rain the telescopes and instruments are protected by special covers to prevent damage.

Andreas Kaufer, director of the observatory, reports “Three observing nights were lost due to the bad weather conditions. This was an unusual loss of observing time, but we were prepared for such rare events to happen during winter periods. Even with this unusual weather we expect about 340 clear nights per year at Paranal. Today the site has been cleaned up and the minor damage to infrastructure is already mostly repaired”.

The La Silla Observatory, located about 500 km south of Paranal, was not affected by these bad weather conditions.

The 5000-metre-high Chajnantor plateau where the APEX telescopes and ALMA is situated also faced unusually heavy snowfall and storm-like conditions. No damage has been reported at APEX. At ALMA, the observatory systems are being carefully inspected, and while no damage has been reported the buildup of snow is causing difficulties.

Courtesy of European Southern Observatory

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