Atacama Pathfinder EXperiment APEX
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The atmosphere above Llano de Chajnantor

At the APEX site on Llano de Chajnantor the amount of perceptible water vapour (PWV) is typically 1.0 mm and falls below 0.5 mm up to 25% of the time. The image below shows the atmospheric transmission between 200 GHz and 1.6 THz for different PWV values.

In order to prepare the observations and make time estimates for different atmospheric conditions the following atmospheric transmission calculator can be used. It is based on the ATM model written by Juan Pardo. The calculator covers the frequency range 200 to 1600 GHz.

New 2017 atmospheric transmission calculator beta version

To estimate the atmospheric transmission directly for LABOCA, SABOCA and Z-SPEC about the pwv use the following calculator

This plot shows the PWV as function of month as measured by the ALMA radiometer.

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