APEX, the Atacama Pathfinder Experiment, is a collaboration between Max Planck Institut für Radioastronomie (MPIfR) at 55%, Onsala Space Observatory (OSO) at 13%, and the European Southern Observatory (ESO) at 32% to construct and operate a modified ALMA prototype antenna as a single dish on the high altitude site of Llano Chajnantor. The telescope was manufactured by VERTEX Antennentechnik in Duisburg, Germany.

Observing with APEX allows us to study cold dust and gas in our own Milky Way and in distant galaxies. Tracing the thermal continuum emission and analyzing high frequency spectral lines improve our understanding of the structure and chemistry of planetary atmospheres, dying stars, regions of star formation as well as distant starburst galaxies. We can address issues from the vast scales of the structure of the Universe down to the physics and chemistry of comets.

Because of the COVID-19 contingency, as of March 25th the Observatory works in Survival mode, with many systems and instruments in standy by. For more details and the latest status, please check the ESO announcement.

Observations	Site Information and Logistics
The telescope	About Sequitor base
Atmosphere	About Chajnantor site
Instrumentation	APEX telephone list
Observing with APEX	Safety
Preparing an observing run	Emergency contacts
APEX data archiving	Safety documents
The APEX project	Miscellaneous Information
The APEX staff	Picture gallery
APEX news	Chajnantor camera image (Refresh each five minutes)
APEX Internal resources (Password protected)	Weather monitor Radiometer data online!