update ast 8.6.3

1 files changed, 262 insertions, 0 deletions

diff --git a/ast/erfa/refco.c b/ast/erfa/refco.c
new file mode 100644
index 0000000..918d990
--- /dev/null
+++ b/ast/erfa/refco.c
@@ -0,0 +1,262 @@
+#include "erfa.h"
+
+void eraRefco(double phpa, double tc, double rh, double wl,
+              double *refa, double *refb)
+/*
+**  - - - - - - - - -
+**   e r a R e 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:
+**    phpa   double    pressure at the observer (hPa = millibar)
+**    tc     double    ambient temperature at the observer (deg C)
+**    rh     double    relative humidity at the observer (range 0-1)
+**    wl     double    wavelength (micrometers)
+**
+**  Returned:
+**    refa   double*   tan Z coefficient (radians)
+**    refb   double*   tan^3 Z coefficient (radians)
+**
+**  Notes:
+**
+**  1) The model balances speed and accuracy to give good results in
+**     applications where performance at low altitudes is not paramount.
+**     Performance is maintained across a range of conditions, and
+**     applies to both optical/IR and radio.
+**
+**  2) The model omits the effects of (i) height above sea level (apart
+**     from the reduced pressure itself), (ii) latitude (i.e. the
+**     flattening of the Earth), (iii) variations in tropospheric lapse
+**     rate and (iv) dispersive effects in the radio.
+**
+**     The model was tested using the following range of conditions:
+**
+**       lapse rates 0.0055, 0.0065, 0.0075 deg/meter
+**       latitudes 0, 25, 50, 75 degrees
+**       heights 0, 2500, 5000 meters ASL
+**       pressures mean for height -10% to +5% in steps of 5%
+**       temperatures -10 deg to +20 deg with respect to 280 deg at SL
+**       relative humidity 0, 0.5, 1
+**       wavelengths 0.4, 0.6, ... 2 micron, + radio
+**       zenith distances 15, 45, 75 degrees
+**
+**     The accuracy with respect to raytracing through a model
+**     atmosphere was as follows:
+**
+**                            worst         RMS
+**
+**       optical/IR           62 mas       8 mas
+**       radio               319 mas      49 mas
+**
+**     For this particular set of conditions:
+**
+**       lapse rate 0.0065 K/meter
+**       latitude 50 degrees
+**       sea level
+**       pressure 1005 mb
+**       temperature 280.15 K
+**       humidity 80%
+**       wavelength 5740 Angstroms
+**
+**     the results were as follows:
+**
+**       ZD       raytrace     eraRefco   Saastamoinen
+**
+**       10         10.27        10.27        10.27
+**       20         21.19        21.20        21.19
+**       30         33.61        33.61        33.60
+**       40         48.82        48.83        48.81
+**       45         58.16        58.18        58.16
+**       50         69.28        69.30        69.27
+**       55         82.97        82.99        82.95
+**       60        100.51       100.54       100.50
+**       65        124.23       124.26       124.20
+**       70        158.63       158.68       158.61
+**       72        177.32       177.37       177.31
+**       74        200.35       200.38       200.32
+**       76        229.45       229.43       229.42
+**       78        267.44       267.29       267.41
+**       80        319.13       318.55       319.10
+**
+**      deg        arcsec       arcsec       arcsec
+**
+**     The values for Saastamoinen's formula (which includes terms
+**     up to tan^5) are taken from Hohenkerk and Sinclair (1985).
+**
+**  3) A wl value in the range 0-100 selects the optical/IR case and is
+**     wavelength in micrometers.  Any value outside this range selects
+**     the radio case.
+**
+**  4) Outlandish input parameters are silently limited to
+**     mathematically safe values.  Zero pressure is permissible, and
+**     causes zeroes to be returned.
+**
+**  5) The algorithm draws on several sources, as follows:
+**
+**     a) The formula for the saturation vapour pressure of water as
+**        a function of temperature and temperature is taken from
+**        Equations (A4.5-A4.7) of Gill (1982).
+**
+**     b) The formula for the water vapour pressure, given the
+**        saturation pressure and the relative humidity, is from
+**        Crane (1976), Equation (2.5.5).
+**
+**     c) The refractivity of air is a function of temperature,
+**        total pressure, water-vapour pressure and, in the case
+**        of optical/IR, wavelength.  The formulae for the two cases are
+**        developed from Hohenkerk & Sinclair (1985) and Rueger (2002).
+**
+**     d) The formula for beta, the ratio of the scale height of the
+**        atmosphere to the geocentric distance of the observer, is
+**        an adaption of Equation (9) from Stone (1996).  The
+**        adaptations, arrived at empirically, consist of (i) a small
+**        adjustment to the coefficient and (ii) a humidity term for the
+**        radio case only.
+**
+**     e) The formulae for the refraction constants as a function of
+**        n-1 and beta are from Green (1987), Equation (4.31).
+**
+**  References:
+**
+**     Crane, R.K., Meeks, M.L. (ed), "Refraction Effects in the Neutral
+**     Atmosphere", Methods of Experimental Physics: Astrophysics 12B,
+**     Academic Press, 1976.
+**
+**     Gill, Adrian E., "Atmosphere-Ocean Dynamics", Academic Press,
+**     1982.
+**
+**     Green, R.M., "Spherical Astronomy", Cambridge University Press,
+**     1987.
+**
+**     Hohenkerk, C.Y., & Sinclair, A.T., NAO Technical Note No. 63,
+**     1985.
+**
+**     Rueger, J.M., "Refractive Index Formulae for Electronic Distance
+**     Measurement with Radio and Millimetre Waves", in Unisurv Report
+**     S-68, School of Surveying and Spatial Information Systems,
+**     University of New South Wales, Sydney, Australia, 2002.
+**
+**     Stone, Ronald C., P.A.S.P. 108, 1051-1058, 1996.
+**
+**  Copyright (C) 2013-2016, NumFOCUS Foundation.
+**  Derived, with permission, from the SOFA library.  See notes at end of file.
+*/
+{
+   int optic;
+   double p, t, r, w, ps, pw, tk, wlsq, gamma, beta;
+
+
+/* Decide whether optical/IR or radio case:  switch at 100 microns. */
+   optic = ( wl <= 100.0 );
+
+/* Restrict parameters to safe values. */
+   t = ERFA_GMAX ( tc, -150.0 );
+   t = ERFA_GMIN ( t, 200.0 );
+   p = ERFA_GMAX ( phpa, 0.0 );
+   p = ERFA_GMIN ( p, 10000.0 );
+   r = ERFA_GMAX ( rh, 0.0 );
+   r = ERFA_GMIN ( r, 1.0 );
+   w = ERFA_GMAX ( wl, 0.1 );
+   w = ERFA_GMIN ( w, 1e6 );
+
+/* Water vapour pressure at the observer. */
+   if ( p > 0.0 ) {
+      ps = pow ( 10.0, ( 0.7859 + 0.03477*t ) /
+                          ( 1.0 + 0.00412*t ) ) *
+                 ( 1.0 + p * ( 4.5e-6 + 6e-10*t*t )  );
+      pw = r * ps / ( 1.0 - (1.0-r)*ps/p );
+   } else {
+      pw = 0.0;
+   }
+
+/* Refractive index minus 1 at the observer. */
+   tk = t + 273.15;
+   if ( optic ) {
+      wlsq = w * w;
+      gamma = ( ( 77.53484e-6 +
+                 ( 4.39108e-7 + 3.666e-9/wlsq ) / wlsq ) * p
+                    - 11.2684e-6*pw ) / tk;
+   } else {
+      gamma = ( 77.6890e-6*p - ( 6.3938e-6 - 0.375463/tk ) * pw ) / tk;
+   }
+
+/* Formula for beta from Stone, with empirical adjustments. */
+   beta = 4.4474e-6 * tk;
+   if ( ! optic ) beta -= 0.0074 * pw * beta;
+
+/* Refraction constants from Green. */
+   *refa = gamma * ( 1.0 - beta );
+   *refb = - gamma * ( beta - gamma / 2.0 );
+
+/* Finished. */
+
+}
+/*----------------------------------------------------------------------
+**  
+**  
+**  Copyright (C) 2013-2016, NumFOCUS Foundation.
+**  All rights reserved.
+**  
+**  This library is derived, with permission, from the International
+**  Astronomical Union's "Standards of Fundamental Astronomy" library,
+**  available from http://www.iausofa.org.
+**  
+**  The ERFA version is intended to retain identical functionality to
+**  the SOFA library, but made distinct through different function and
+**  file names, as set out in the SOFA license conditions.  The SOFA
+**  original has a role as a reference standard for the IAU and IERS,
+**  and consequently redistribution is permitted only in its unaltered
+**  state.  The ERFA version is not subject to this restriction and
+**  therefore can be included in distributions which do not support the
+**  concept of "read only" software.
+**  
+**  Although the intent is to replicate the SOFA API (other than
+**  replacement of prefix names) and results (with the exception of
+**  bugs;  any that are discovered will be fixed), SOFA is not
+**  responsible for any errors found in this version of the library.
+**  
+**  If you wish to acknowledge the SOFA heritage, please acknowledge
+**  that you are using a library derived from SOFA, rather than SOFA
+**  itself.
+**  
+**  
+**  TERMS AND CONDITIONS
+**  
+**  Redistribution and use in source and binary forms, with or without
+**  modification, are permitted provided that the following conditions
+**  are met:
+**  
+**  1 Redistributions of source code must retain the above copyright
+**    notice, this list of conditions and the following disclaimer.
+**  
+**  2 Redistributions in binary form must reproduce the above copyright
+**    notice, this list of conditions and the following disclaimer in
+**    the documentation and/or other materials provided with the
+**    distribution.
+**  
+**  3 Neither the name of the Standards Of Fundamental Astronomy Board,
+**    the International Astronomical Union nor the names of its
+**    contributors may be used to endorse or promote products derived
+**    from this software without specific prior written permission.
+**  
+**  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+**  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+**  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+**  FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+**  COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+**  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+**  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+**  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+**  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+**  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+**  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+**  POSSIBILITY OF SUCH DAMAGE.
+**  
+*/