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Atmosphere at Chajnantor
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Home > APEX Sites > Chajnantor > Atmosphere at Chajnantor > Transmission calculator

Atmospheric transmission calculator

Plot the transmission at the signal and image bands

The calculator plots the zenith atmospheric transmission on Llano de Chajnantor, for a specified frequency and with a range that covers both image bands (LSB and USB), assuming the respective frequency separation between signal and image band, which is specific for each receiver. FLASH is a DSB receiver, and because of this, greater care has to be taken when selecting LSB or USB, since a atmospheric lines will have a negative impact on the quality of the baseline. This is to also true for SSB receivers, but they are not affected to the same extent. Common for both types of receivers it is important to avoid selecting image bands in frequency regions with in a very deep atmospheric absorption.

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

Center frequency GHz
PWV value mm


Plot the transmission as function of frequency within a specified frequency range

The calculator plots the zenith atmospheric transmission on Llano de Chajnantor, for a specified frequency range (limits 200 to 1600 GHz) for up to 6 different PWV values.

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

Lower frequency GHz
Upper frequency GHz
PWVs: