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REAL FUNCTION slRVER (PHI, RA, DA, ST)
*+
* - - - - - - -
* R V E R
* - - - - - - -
*
* Velocity component in a given direction due to Earth rotation
* (single precision)
*
* Given:
* PHI real latitude of observing station (geodetic)
* RA,DA real apparent RA,DEC
* ST real local apparent sidereal time
*
* PHI, RA, DEC and ST are all in radians.
*
* Result:
* Component of Earth rotation in direction RA,DA (km/s)
*
* Sign convention:
* The result is +ve when the observatory is receding from the
* given point on the sky.
*
* Accuracy:
* The simple algorithm used assumes a spherical Earth, of
* a radius chosen to give results accurate to about 0.0005 km/s
* for observing stations at typical latitudes and heights. For
* applications requiring greater precision, use the routine
* slPVOB.
*
* P.T.Wallace Starlink 20 July 1994
*
* Copyright (C) 1995 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
REAL PHI,RA,DA,ST
* Nominal mean sidereal speed of Earth equator in km/s (the actual
* value is about 0.4651)
REAL ESPEED
PARAMETER (ESPEED=0.4655)
slRVER=ESPEED*COS(PHI)*SIN(ST-RA)*COS(DA)
END
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