SCULIB_ADD_CHOP - Add chop throw to apparent RA/Dec

Description:

This routine takes a chop throw and adds it on the supplied apparent RA/Dec centre position returning a new apparent RA/Dec. Works with scan map and jiggle map but does not actually know the difference itself (unless using SC chop). For EKH (SC) chopping we have to convert the scan ends to tangent plane offsets from the reference centre before calculating the angle.

Invocation:

CALL SCULIB_ADD_CHOP(BEAM, RA_REF_CENTRE, DEC_REF_CENTRE, RA_CENTRE, DEC_CENTRE, CHOP_CRD, CHOP_PA, CHOP_FUN, CHOP_THROW, LST, MJD, LAT_OBS, RA_START, RA_END, DEC_START, DEC_END, OUT_RA_CEN, OUT_DEC_CEN, STATUS)

Arguments:

BEAM = CHARACTER $*$ ($*$) (Given)

Beam name ('M','L' or 'R')

RA_REF_CENTRE = DOUBLE PRECISION (Given)

Apparent RA of the map centre. This is the centre that scan map tangent plane offsets are calculated from.

DEC_REF_CENTRE = DOUBLE PRECISION (Given)

Apparent dec of the map centre. This is the centre that scan map tangent plane offsets are calculated from.

RA_CENTRE = DOUBLE PRECISION (Given)

the apparent RA of the `centre' of the array (radians)

DEC_CENTRE = DOUBLE PRECISION (Given)

the apparent dec of the `centre' of the array (radians)

CHOP_CRD = CHARACTER $*$($*$) (Given)

Coordinate system of CHOP throw (SC,AZ,RB,RJ,GA)

CHOP_PA = REAL (Given)

Position angle of chop (in radians)

CHOP_FUN = CHARACTER $*$ ($*$) (Given)

Chop function (CENTER, SQUARE, TRIPOS)

CHOP_THROW = REAL (Given)

Chop throw in radians

LST = DOUBLE PRECISION (Given)

the local sidereal time (radians)

MJD = DOUBLE PRECISION (Given)

MJD of observation

LAT_OBS = DOUBLE PRECISION (Given)

the latitude of the observatory (radians)

RA_START = REAL (Given)

RA of start of scan (if SAMPLE_MODE=RASTER)

RA_END = REAL (Given)

RA of end of scan (if SAMPLE_MODE=RASTER)

DEC_START = REAL (Given)

DEC of start of scan (if SAMPLE_MODE=RASTER)

DEC_END = REAL (Given)

DEC of end of scan (if SAMPLE_MODE=RASTER)

OUT_RA_CEN = DOUBLE (Returned)

New position with CHOP

OUT_DEC_CEN = DOUBLE (Returned)

New DEC with CHOP

STATUS = INTEGER (Given and returned)

The global status

Notes:

It is assumed that the chop throw is divided by two prior to calling this routine for scan map mode since the chop is effectively half a chop either side of the middle. For jiggle modes the chop is effectively a full chop throw from the centre since the 3-beam chopping is done by a combination of chopping and nodding.

• This routine does not yet support TRIPOS chopping (I think)

• AZ, LO and SC chopping are supported

• The negative beam is always the 'left' beam, the $+$ve beam is the 'right'.

• The chop tracking 'droopy' beam problem should be dealt with in an earlier subroutine such that the chop is converted from LO to AZ before calling this routine

Copyright

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