Atmospheric Monitoring at a Cosmic Ray Observatory ‒a long-lasting endeavour

The Pierre Auger Observatory for detecting ultra-high energy cosmic rays has been founded in 1999. After a
main planning and construction phase of about five years, the regular data taking started in 2004, but it took
another four years until the full surface detector array was deployed. In parallel to the main detectors of the
Observatory, a comprehensive set of instruments for monitoring the atmospheric conditions above the array
was developed and installed as varying atmospheric conditions influence the development and detection of
extensive air showers.
The multitude of atmospheric monitoring installations at the Pierre Auger Observatory will be presented as
well as the challenges and efforts to run such instruments for several decades.