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.