Atacama Pathfinder EXperiment APEX
APEX-1 (230 GHz)
MPIfR Bonn   ESO   Onsala Space Observatory

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APEX-1 (230 GHz) Calibration Plan

On these pages we present the results and analysis of the APEX-1 calibration plan observations.

Intensity calibration stability

By observing strong (non-masing) spectral lines in several sources over the whole frequency range accessible by our receivers, we provide a intensity reference for scientific observations. These measurements are performed in regular intervals, at least once per observing block. This way we are able to monitor the calibration stability as a function of time and frequency.

Frequency stability

For narrow-line sources the regular observations can also be used to determine the centre velocity and line width of selected spectral lines. In this way we are able to monitor the stability of our complete LO system, from Doppler shift calculation to backend properties. Through the line-width monitoring we can detect any extra broadening, e.g. because of LO frequency fluctuations.

For the source WB947 we monitor the 12CO(2-1) line (in USB and LSB) For each date the peak velocity and line width are estimated by a Gaussian fit.

Other properties