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66 lines
2.0 KiB
Fortran
66 lines
2.0 KiB
Fortran
REAL FUNCTION sla_RVEROT (PHI, RA, DA, ST)
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*+
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* - - - - - - -
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* R V E R O T
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* - - - - - - -
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*
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* Velocity component in a given direction due to Earth rotation
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* (single precision)
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*
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* Given:
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* PHI real latitude of observing station (geodetic)
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* RA,DA real apparent RA,DEC
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* ST real local apparent sidereal time
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*
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* PHI, RA, DEC and ST are all in radians.
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*
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* Result:
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* Component of Earth rotation in direction RA,DA (km/s)
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*
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* Sign convention:
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* The result is +ve when the observatory is receding from the
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* given point on the sky.
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*
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* Accuracy:
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* The simple algorithm used assumes a spherical Earth, of
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* a radius chosen to give results accurate to about 0.0005 km/s
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* for observing stations at typical latitudes and heights. For
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* applications requiring greater precision, use the routine
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* sla_PVOBS.
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*
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* P.T.Wallace Starlink 20 July 1994
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*
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* Copyright (C) 1995 Rutherford Appleton Laboratory
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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REAL PHI,RA,DA,ST
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* Nominal mean sidereal speed of Earth equator in km/s (the actual
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* value is about 0.4651)
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REAL ESPEED
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PARAMETER (ESPEED=0.4655)
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sla_RVEROT=ESPEED*COS(PHI)*SIN(ST-RA)*COS(DA)
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END
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