### EXTINCTION

Extinction correct SCUBA-2 data

#### Description:

This application can be used to extinction correct data in a number of ways.

#### Parameters:

Group of files to be used as bad bolometer masks. Each data file specified with the IN parameter will be masked. The corresponding previous mask for a subarray will be used. If there is no previous mask the closest following will be used. It is not an error for no mask to match. A NULL parameter indicates no mask files to be supplied. [!]
Value of the 225 GHz zenith optical depth. Only used if TAUSRC equals ‘CSOTAU’ or ’ AUTO’ . If a NULL (!) value is given, the task will use the appropriate value from the FITS header of each file. Note that if a value is entered by the user, that value is used for all input files. In AUTO mode the value might not be used.
Value of the zenith optical depth for the current wavelength. Only used if TAUSRC equals ‘FILTERTAU’ . Note that no check is made to ensure that all the input files share the same filter.
Method to use to calculate the flatfield solution. Options are POLYNOMIAL and TABLE. Polynomial fits a polynomial to the measured signal. Table uses an interpolation scheme between the measurements to determine the power. [POLYNOMIAL]
The order of polynomial to use when choosing POLYNOMIAL method. [1]
Signal-to-noise ratio threshold to use when filtering the responsivity data to determine valid bolometers for the flatfield. [3.0]
If true the previous and following flatfield will be used to determine the overall flatfield to apply to a sequence. If false only the previous flatfield will be used. A null default will use both flatfields for data when we did not heater track at the end, and will use a single flatfield when we did heater track. The parameter value is not sticky and will revert to the default unless explicitly over-ridden. [!]
Indicate that the data have been sky removed even if the fact can not be verified. This is useful for the case where the sky background has been removed using an application other than SMURF REMSKY. [FALSE]
Input file(s). The input data must have had the sky signal removed
Method to use for airmass calculation. Options are:
• ADAPTIVE - Determine whether to use QUICK or FULL based on the elevation of the source and the opacity.

• FULL - Calculate the airmass of each bolometer.

• QUICK - Use a single airmass for each time slice.

Control the verbosity of the application. Values can be NONE (no messages), QUIET (minimal messages), NORMAL, VERBOSE, DEBUG or ALL. [NORMAL]
Output file(s)
##### OUTFILES = LITERAL (Write)
The name of text file to create, in which to put the names of all the output NDFs created by this application (one per line). If a null (!) value is supplied no file is created. [!]
A group expression containing the resistor settings for each bolometer. Usually specified as a text file using " ^" syntax. An example can be found in $STARLINK_DIR/share/smurf/resist.cfg [$STARLINK_DIR/share/smurf/resist.cfg]
If true, responsivity data will be used to mask bolometer data when calculating the flatfield. [TRUE]
Specifies values to be used for scaling the 225 GHz tau to the specific filter. These values will only be used if CSOTAU or WVMRAW methods are used to determine the tau. The group should have the form:

ext.taurelation.$<$FILT$>$ = (a,b,c)

where $<$FILT$>$ is the filter name and " a" , " b" and " c" are the coefficients for a relationship of the form

tau_filt = a ( tau_cso $+$ b $+$ c sqrt(tau_cso) )

A null value will use the default relations. [!]

Source of optical depth data. Options are:
• WVMRAW - use the Water Vapour Monitor time series data

• WVMFIT - use a fit to the Water Vapor Monitor data

• CSOFIT - use a fit to the CSO 225 GHz tau data

• CSOTAU - use a single 225 GHz tau value

• FILTERTAU - use a single tau value for this wavelength

• AUTO - Use WVM if available and reliable, else a WVM or CSO fit.

[AUTO]

##### WVMLOG = FILENAME (Write)
Name of a text file into which to write raw WVM data with columns for each stage of processing. Multiple blocks of data may be written to the file if the WVM data are processed in chunks. New data are appended to the file if it already exists. If a null (!) value is supplied, no file is written. [!]

#### Notes:

• The iterative map-maker will extinction correct the data itself and this command will not be necessary.

• QLMAKEMAP automatically applies an extinction correction.

#### Related Applications

SMURF: REMSKY, MAKEMAP; SURF: EXTINCTION