| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * pal1Atmt
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| 5 |
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| 6 | * Purpose:
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| 7 | * Calculate troposphere parameters
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| 8 |
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| 9 | * Language:
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| 10 | * Starlink ANSI C
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| 11 |
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| 12 | * Type of Module:
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| 13 | * Library routine
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| 14 |
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| 15 | * Invocation:
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| 16 | * void pal1Atmt ( double r0, double t0, double alpha, double gamm2,
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| 17 | * double delm2, double c1, double c2, double c3,
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| 18 | * double c4, double c5, double c6, double r,
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| 19 | * double *t, double *dn, double *rdndr );
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| 20 |
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| 21 | * Arguments:
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| 22 | * r0 = double (Given)
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| 23 | * Height of observer from centre of the Earth (metre)
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| 24 | * t0 = double (Given)
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| 25 | * Temperature of the observer (K)
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| 26 | * alpha = double (Given)
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| 27 | * Alpha (see HMNAO paper)
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| 28 | * gamm2 = double (Given)
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| 29 | * Gamma minus 2 (see HMNAO paper)
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| 30 | * delm2 = double (Given)
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| 31 | * Delta minus 2 (see HMNAO paper)
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| 32 | * c1 = double (Given)
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| 33 | * Useful term (see palRefro source)
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| 34 | * c2 = double (Given)
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| 35 | * Useful term (see palRefro source)
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| 36 | * c3 = double (Given)
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| 37 | * Useful term (see palRefro source)
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| 38 | * c4 = double (Given)
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| 39 | * Useful term (see palRefro source)
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| 40 | * c5 = double (Given)
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| 41 | * Useful term (see palRefro source)
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| 42 | * c6 = double (Given)
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| 43 | * Useful term (see palRefro source)
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| 44 | * r = double (Given)
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| 45 | * Current distance from the centre of the Earth (metre)
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| 46 | * t = double * (Returned)
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| 47 | * Temperature at r (K)
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| 48 | * dn = double * (Returned)
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| 49 | * Refractive index at r.
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| 50 | * rdndr = double * (Returned)
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| 51 | * r * rate the refractive index is changing at r.
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| 52 |
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| 53 | * Description:
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| 54 | * Refractive index and derivative with respect to height for
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| 55 | * the troposphere.
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| 56 |
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| 57 | * Authors:
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| 58 | * TIMJ: Tim Jenness (JAC, Hawaii)
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| 59 | * PTW: Patrick T. Wallace
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| 60 | * {enter_new_authors_here}
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| 61 |
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| 62 | * Notes:
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| 63 | * - Internal routine used by palRefro
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| 64 | * - Note that in the optical case c5 and c6 are zero.
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| 65 |
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| 66 | * History:
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| 67 | * 2012-08-24 (TIMJ):
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| 68 | * Initial version, copied from Fortran SLA source.
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| 69 | * Adapted with permission from the Fortran SLALIB library.
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| 70 | * {enter_further_changes_here}
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| 71 |
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| 72 | * Copyright:
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| 73 | * Copyright (C) 2004 Patrick T. Wallace
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| 74 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 75 | * All Rights Reserved.
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| 76 |
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| 77 | * Licence:
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| 78 | * This program is free software; you can redistribute it and/or
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| 79 | * modify it under the terms of the GNU General Public License as
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| 80 | * published by the Free Software Foundation; either version 3 of
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| 81 | * the License, or (at your option) any later version.
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| 82 | *
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| 83 | * This program is distributed in the hope that it will be
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| 84 | * useful, but WITHOUT ANY WARRANTY; without even the implied
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| 85 | * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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| 86 | * PURPOSE. See the GNU General Public License for more details.
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| 87 | *
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| 88 | * You should have received a copy of the GNU General Public License
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| 89 | * along with this program; if not, write to the Free Software
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| 90 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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| 91 | * MA 02110-1301, USA.
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| 92 |
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| 93 | * Bugs:
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| 94 | * {note_any_bugs_here}
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| 95 | *-
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| 96 | */
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| 97 |
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| 98 | #include <math.h>
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| 99 |
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| 100 | #include "palmac.h"
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| 101 | #include "pal1.h"
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| 102 |
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| 103 | void pal1Atmt ( double r0, double t0, double alpha, double gamm2,
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| 104 | double delm2, double c1, double c2, double c3, double c4,
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| 105 | double c5, double c6, double r,
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| 106 | double *t, double *dn, double *rdndr ) {
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| 107 |
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| 108 | double tt0;
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| 109 | double tt0gm2;
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| 110 | double tt0dm2;
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| 111 |
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| 112 | *t = DMAX( DMIN( t0 - alpha*(r-r0), 320.0), 100.0 );
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| 113 | tt0 = *t / t0;
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| 114 | tt0gm2 = pow( tt0, gamm2 );
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| 115 | tt0dm2 = pow( tt0, delm2 );
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| 116 | *dn = 1.0 + ( c1 * tt0gm2 - ( c2 - c5 / *t ) * tt0dm2 ) * tt0;
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| 117 | *rdndr = r * ( -c3 * tt0gm2 + ( c4 - c6 / tt0 ) * tt0dm2 );
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| 118 |
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| 119 | }
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