sdcal2 – ASAP SD calibration task – single dish task

Description

Task sdcal2 is an implementation of a calibration scheme like as interferometry, i.e., generate caltables and apply them. Available calibration modes are ‘ps’, ‘otf’, ‘otfraster’, and ‘tsys’. Those modes generates caltables for sky or Tsys calibration. Those caltables can be applied to the data by using calmode ‘apply’.

The above three calibration modes, ‘ps’, ‘otf’, and ‘otfraster’, generate sky calibration tables. The user should choose appropriate calibration mode depending on the data. Use case for each mode is as follows:

‘ps’: position switch (including OTF) with explicit

reference (OFF) spectra

‘otf’: non-raster OTF scan without explicit OFFs

(e.g. Lissajous, double circle, etc.) intends to calibrate fast scan data

‘otfraster’: raster OTF scan without explicit OFFs

So, if the data contains explicit reference spectra, ‘ps’ should be used. Otherwise, ‘otfraster’ and ‘otf’ are appropriate for raster OTF and non-raster OTF, respectively. In ‘otf’ and ‘otfraster’ modes, the task first try to find several integrations near edge as OFF spectra, then the data are calibrated using those OFFs. If the observing pattern is raster, you should use the ‘otfraster’ mode to calibrate data. Otherwise, the ‘otf’ mode should be used. For detail about edge marking, see inline help of sd.edgemarker module and its methods. Those modes are designed for OTF observations without explicit OFF spectra. However, these modes should work even if explicit reference spectra exist. In this case, these spectra will be ignored and spectra near edges detected by edge marker will be used as reference.

Except for how to choose OFFs, the procedure to derive calibrated spectra is common for the above three modes. Selected (or preset) OFF integrations are separated by its continuity in time domain, averaged in each segment, then interpolated to timestamps for ON integrations. Effectively, it means that OFF integrations are averaged by each OFF spectrum for ‘ps’ mode, averaged by either ends of each raster row for ‘otfraster’ mode, averaged by each temporal segments of detected edges for ‘otf’ mode. The formula for calibrated spectrum is

Tsys * (ON - OFF) / OFF.

Parameters

Title

Parameter	Default	Description
infile	''
calmode	'ps'	SD calibration mode ['ps','otf','otfraster','tsys','apply', and their possible combinations]
fraction	'10%'
noff	int(-1)
width	float(0.5)
elongated	False
tsysavg	False
tsysspw	''
applytable	''
interp	''
spwmap	*UNKNOWN*
field	''
spw	''
scan	''
pol	''
outfile	''
overwrite	False	overwrite the output file if already exists [True, False]

Parameter Explanations

infile

''

name of input SD dataset (must be in scantable format)

calmode

'ps'

SD calibration mode

fraction

'10%'

fraction of the OFF data to mark

noff

int(-1)

number of the OFF data to mark

width

float(0.5)

width of the pixel for edge detection

elongated

False

whether observed area is elongated in one direction or not

tsysavg

False

Whether Tsys is averaged in spectral axis or not

tsysspw

''

list of IF IDs (spectral windows) and their channel ranges of averaging for Tsys calibration.

applytable

''

(List of) sky and/or tsys tables

interp

''

Interpolation type in time[,freq]. Valid options are “nearest”, “linear”, “cspline”, or any numeric string that indicates an order of polynomial interpolation. You can specify interpolation type for time and frequency separately by joining two of the above options by comma (e.g., “linear,cspline”).

spwmap

*UNKNOWN*

A dictionary indicating IFNO combinations to apply Tsys calibration to target. The key should be IFNO for Tsys calibration and its associated value must be a list of science IFNOs to be applied.

field

''

select data by field IDs and names, e.g. '3C2*' ('' = all)

spw

''

select data by IF IDs (spectral windows), e.g., '3,5,7' ('' = all)

scan

''

select data by scan numbers, e.g. '21~23' (''=all)

pol

''

select data by polarization IDs, e.g, '0,1' ('' = all)

outfile

''

name of output file (See a WARNING in help)

overwrite

False

overwrite the output file if already exists