SURFLIB_2DFT_CHOP - Calculate the FT of the 2D chop throw

Description:

Given the chop parameters calculate the FT of the chop. The dual beam chop is treated as two delta functions of opposite sign separated by the chop throw and centred at the middle of the data array. The Fourier transform of this function is a sine wave in the direction of the chop (zero at the middle beam) with wavelength related to the spatial frequency of the array (pixel spacing).

Invocation:

CALL SURFLIB_2DFT_CHOP (CHOP_THROW, CHOP_PA, PIXSIZE, NX, NY, FT_DATA, FT_VARIANCE, WT_DATA, WT_VARIANCE, STATUS)

Arguments:

CHOP_THROW = REAL (Given)

chop throw in arcsec

CHOP_PA = REAL (Given)

position angle of chop. Positive is anti-clockwise from North. This angle is in degrees.

PIXSIZE = REAL (Given)

pixel size in arcsec

NX = INTEGER (Given)

Number of pixels in X

NY = INTEGER (Given)

Number of pixels in Y

FT_DATA (IDIMS(1), IDIMS(2)) = REAL (Returned)

data array containing F.T. of chop

FT_VARIANCE (IDIMS(1), IDIMS(2)) = REAL (Returned)

variance on DATA; set to 0

WT_DATA (IDIMS(1), IDIMS(2)) = REAL (Returned)

data array containing weight of chop

WT_VARIANCE (IDIMS(1), IDIMS(2)) = REAL (Returned)

variance on DATA; set to 0

STATUS = INTEGER (Given and returned)

global status

Copyright

Copyright ©1995,1996,1997,1998,1999 Particle Physics and Astronomy Research Council. All Rights Reserved.