Loading data into Miriad: ATLOD

ATCA millimetre observations are loaded into Miriad in the same fashion as centimetre data: task atlod is used.

At 12mm, the opacity of the atmosphere can be significant: in mediocre conditions, the signal loss is can be a 20% at low elevations. With 12-mm data, an opacity correction should be applied to the data during the atlod step. To apply this correction, atlod uses a model of the atmosphere (using meteorological data contained within the dataset) to compute a model opacity. Note that this is just that - a model - and so has its limitation. To apply atmospheric opacity correction, use options=opcorr.

ATLOD
options=opcorr,birdie,reweight,xycorr	Options for typical 12-mm
	continuum observation, or
options=opcorr,hanning,compress	possible options for spectral
	line observations.

Please note the following:

• ATCA observations made before October 2003 failed to contain the meteorological data, and so options=opcorr cannot be used.
• At 12mm, no self-generated RFI at multiples of 128 MHz is seen. Task atlod's birdie option for continuum data is used to discard edge channels and every second channel (as noted earlier, successive channels are not independent, and so there is no sensitivity penalty in discarding every second channel).