FIGS322-Processes a FIGS data cube down to an image

Description:

FIGS321 takes a FIGS data cube, as produced by the FIGS data acquisition system, and reduces it to a single image, subtracting off the various beamswitch and chopping backgrounds.

Parameters:

CUBE

The name of a data cube produced by the FIGS data acquisition system. That is is should have the dimensions (wavelength steps,8,beamswitch cycles).

IMAGE

The name of the resulting single image produced by collapsing down the FIGS data cube.

ADD

Disables the subtraction of the background beamswitch and chopping data. This is unusual (ADD=NO is the default) and is generally only required for test data.

BACK

Returns the background spectrum only, rather than the background subtracted source data.

Source comments:

 F I G S 3 2 2 ,   F I G S 3 2 1

 Given a FIGS data cube as produced by the FIGS data acquisition
 system, processes it to produce either an image of wavelength
 against cycle number (FIGS322) or a single spectrum (FIGS321).

 Command parameters -

 'CUBE'     The name of the cube from which the planes
            are to be taken.  This should be a raw FIGS data
            cube.
 'IMAGE'    The name of the resulting image (FIGS322)
 'SPECTRUM' The name of the resulting spectrum (FIGS321)
 'CUTOFF'   The level (in sigma) at which a point will
            be ignored (FIGS321 only)

 Command keywords -

 'ADD'      Add the data together rather than subtracting the
            beamswitch and chop backgrounds

 'BACK'     Return the background spectrum only

 'NORM'     Normalize data to mean level of each cycle.
            (FIGS321 only.)

 Input data -

 This routine assumes that the first axis of the cube data
 represents wavelength, that the second represents spectral
 scans in the order A1a,A1b,B1a,B1b,B2a,B2b,A2a,A2b, where
 A1,A2,B1,B2 represent the parts of the beamswitch ABBA cycle
 and a and b represent the signal and background chop positions
 respectively.  In grating mode 2, there are no chop positions,
 and the second axis is just A1,B1,A2,B2. Grating mode 3 data
 is modified by the on-line acquisition software so that it
 has the same format as grating mode 1 data.  This means that the
 second dimension of the cube has to be either 4 or 8.  The
 cube third axis represents beamswitch cycle number.
 The data is sorted into wavelength order using the various
 grating parameters read from the .FITS sub-structure of CUBE.
 The data is normalized to give a figure in detected photons
 per second.

 Output data -

 IMAGE is created with the same structure as CUBE
 except that main data array will only have 1 or 2 dimensions, and any
 AXIS sub-structures that CUBE has will be deleted/renamed
 as appropriate. If a spectrum is produced the errors (derived from
 the cycle to cycle statistics) are generated.

                                 KS / AAO 8th June 1985