Keywords: pako

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### CALIBRATE

In a standard calibration for heterodyne receivers, we observe 3 subscans, ``SAC'': on a Sky position, an Ambient temperature load (a.k.a., ``hot'' load), and a ``Cold'' load. Calibrations are always and automatically done in TOTAL POWER.

A calibration needs to be done for any heterodyne observation in order to get data with a calibrated intensity scale. It is normally done before the target observations. It must always be done after changing receiver and/or backend setups. It should also be done when changing sources and often enough to follow any variation of the athmosphere, about every 15 minutes.

After you enter a calibrate setup manually, we recommend to ``save'' it, optionally to a named file:

`SAVE CALIBRATE [/FILE calibrate-1]`

It can then at any later time be reloaded with `@ calibrate[-1]`, see `HELP SAVE`.

The special calibration subscans are done by switching the beam optics so that the receivers see a special calibration unit in the receiver cabin.

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