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Diffstat (limited to 'math/slalib/refco.f')
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diff --git a/math/slalib/refco.f b/math/slalib/refco.f new file mode 100644 index 00000000..f03a30fa --- /dev/null +++ b/math/slalib/refco.f @@ -0,0 +1,88 @@ + SUBROUTINE slRFCO ( HM, TDK, PMB, RH, WL, PHI, TLR, EPS, + : REFA, REFB ) +*+ +* - - - - - - +* R F C O +* - - - - - - +* +* Determine the constants A and B in the atmospheric refraction +* model dZ = A tan Z + B tan**3 Z. +* +* Z is the "observed" zenith distance (i.e. affected by refraction) +* and dZ is what to add to Z to give the "topocentric" (i.e. in vacuo) +* zenith distance. +* +* Given: +* HM d height of the observer above sea level (metre) +* TDK d ambient temperature at the observer (K) +* PMB d pressure at the observer (millibar) +* RH d relative humidity at the observer (range 0-1) +* WL d effective wavelength of the source (micrometre) +* PHI d latitude of the observer (radian, astronomical) +* TLR d temperature lapse rate in the troposphere (K/metre) +* EPS d precision required to terminate iteration (radian) +* +* Returned: +* REFA d tan Z coefficient (radian) +* REFB d tan**3 Z coefficient (radian) +* +* Called: slRFRO +* +* Notes: +* +* 1 Typical values for the TLR and EPS arguments might be 0.0065D0 and +* 1D-10 respectively. +* +* 2 The radio refraction is chosen by specifying WL > 100 micrometres. +* +* 3 The routine is a slower but more accurate alternative to the +* slRFCQ routine. The constants it produces give perfect +* agreement with slRFRO at zenith distances arctan(1) (45 deg) +* and arctan(4) (about 76 deg). It achieves 0.5 arcsec accuracy +* for ZD < 80 deg, 0.01 arcsec accuracy for ZD < 60 deg, and +* 0.001 arcsec accuracy for ZD < 45 deg. +* +* P.T.Wallace Starlink 22 May 2004 +* +* Copyright (C) 2004 Rutherford Appleton Laboratory +* +* License: +* This program is free software; you can redistribute it and/or modify +* it under the terms of the GNU General Public License as published by +* the Free Software Foundation; either version 2 of the License, or +* (at your option) any later version. +* +* This program is distributed in the hope that it will be useful, +* but WITHOUT ANY WARRANTY; without even the implied warranty of +* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +* GNU General Public License for more details. +* +* You should have received a copy of the GNU General Public License +* along with this program (see SLA_CONDITIONS); if not, write to the +* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, +* Boston, MA 02110-1301 USA +* +* Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. +*- + + IMPLICIT NONE + + DOUBLE PRECISION HM,TDK,PMB,RH,WL,PHI,TLR,EPS,REFA,REFB + + DOUBLE PRECISION ATN1,ATN4,R1,R2 + +* Sample zenith distances: arctan(1) and arctan(4) + PARAMETER (ATN1=0.7853981633974483D0, + : ATN4=1.325817663668033D0) + + + +* Determine refraction for the two sample zenith distances + CALL slRFRO(ATN1,HM,TDK,PMB,RH,WL,PHI,TLR,EPS,R1) + CALL slRFRO(ATN4,HM,TDK,PMB,RH,WL,PHI,TLR,EPS,R2) + +* Solve for refraction constants + REFA = (64D0*R1-R2)/60D0 + REFB = (R2-4D0*R1)/60D0 + + END |