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authorWilliam Joye <wjoye@cfa.harvard.edu>2018-01-09 19:28:07 (GMT)
committerWilliam Joye <wjoye@cfa.harvard.edu>2018-01-09 19:28:07 (GMT)
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+#include "erfa.h"
+
+int eraAtio13(double ri, double di,
+ double utc1, double utc2, double dut1,
+ double elong, double phi, double hm, double xp, double yp,
+ double phpa, double tc, double rh, double wl,
+ double *aob, double *zob, double *hob,
+ double *dob, double *rob)
+/*
+** - - - - - - - - - -
+** e r a A t i o 1 3
+** - - - - - - - - - -
+**
+** CIRS RA,Dec to observed place. The caller supplies UTC, site
+** coordinates, ambient air conditions and observing wavelength.
+**
+** Given:
+** ri double CIRS right ascension (CIO-based, radians)
+** di double CIRS declination (radians)
+** utc1 double UTC as a 2-part...
+** utc2 double ...quasi Julian Date (Notes 1,2)
+** dut1 double UT1-UTC (seconds, Note 3)
+** elong double longitude (radians, east +ve, Note 4)
+** phi double geodetic latitude (radians, Note 4)
+** hm double height above ellipsoid (m, geodetic Notes 4,6)
+** xp,yp double polar motion coordinates (radians, Note 5)
+** phpa double pressure at the observer (hPa = mB, Note 6)
+** tc double ambient temperature at the observer (deg C)
+** rh double relative humidity at the observer (range 0-1)
+** wl double wavelength (micrometers, Note 7)
+**
+** Returned:
+** aob double* observed azimuth (radians: N=0,E=90)
+** zob double* observed zenith distance (radians)
+** hob double* observed hour angle (radians)
+** dob double* observed declination (radians)
+** rob double* observed right ascension (CIO-based, radians)
+**
+** Returned (function value):
+** int status: +1 = dubious year (Note 2)
+** 0 = OK
+** -1 = unacceptable date
+**
+** Notes:
+**
+** 1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
+** convenient way between the two arguments, for example where utc1
+** is the Julian Day Number and utc2 is the fraction of a day.
+**
+** However, JD cannot unambiguously represent UTC during a leap
+** second unless special measures are taken. The convention in the
+** present function is that the JD day represents UTC days whether
+** the length is 86399, 86400 or 86401 SI seconds.
+**
+** Applications should use the function eraDtf2d to convert from
+** calendar date and time of day into 2-part quasi Julian Date, as
+** it implements the leap-second-ambiguity convention just
+** described.
+**
+** 2) The warning status "dubious year" flags UTCs that predate the
+** introduction of the time scale or that are too far in the
+** future to be trusted. See eraDat for further details.
+**
+** 3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
+** one second at the end of each positive UTC leap second,
+** introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
+** practice is under review, and in the future UT1-UTC may grow
+** essentially without limit.
+**
+** 4) The geographical coordinates are with respect to the ERFA_WGS84
+** reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
+** longitude required by the present function is east-positive
+** (i.e. right-handed), in accordance with geographical convention.
+**
+** 5) The polar motion xp,yp can be obtained from IERS bulletins. The
+** values are the coordinates (in radians) of the Celestial
+** Intermediate Pole with respect to the International Terrestrial
+** Reference System (see IERS Conventions 2003), measured along the
+** meridians 0 and 90 deg west respectively. For many
+** applications, xp and yp can be set to zero.
+**
+** 6) If hm, the height above the ellipsoid of the observing station
+** in meters, is not known but phpa, the pressure in hPa (=mB), is
+** available, an adequate estimate of hm can be obtained from the
+** expression
+**
+** hm = -29.3 * tsl * log ( phpa / 1013.25 );
+**
+** where tsl is the approximate sea-level air temperature in K
+** (See Astrophysical Quantities, C.W.Allen, 3rd edition, section
+** 52). Similarly, if the pressure phpa is not known, it can be
+** estimated from the height of the observing station, hm, as
+** follows:
+**
+** phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
+**
+** Note, however, that the refraction is nearly proportional to
+** the pressure and that an accurate phpa value is important for
+** precise work.
+**
+** 7) The argument wl specifies the observing wavelength in
+** micrometers. The transition from optical to radio is assumed to
+** occur at 100 micrometers (about 3000 GHz).
+**
+** 8) "Observed" Az,ZD means the position that would be seen by a
+** perfect geodetically aligned theodolite. (Zenith distance is
+** used rather than altitude in order to reflect the fact that no
+** allowance is made for depression of the horizon.) This is
+** related to the observed HA,Dec via the standard rotation, using
+** the geodetic latitude (corrected for polar motion), while the
+** observed HA and RA are related simply through the Earth rotation
+** angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
+** means the position that would be seen by a perfect equatorial
+** with its polar axis aligned to the Earth's axis of rotation.
+**
+** 9) The accuracy of the result is limited by the corrections for
+** refraction, which use a simple A*tan(z) + B*tan^3(z) model.
+** Providing the meteorological parameters are known accurately and
+** there are no gross local effects, the predicted astrometric
+** coordinates should be within 0.05 arcsec (optical) or 1 arcsec
+** (radio) for a zenith distance of less than 70 degrees, better
+** than 30 arcsec (optical or radio) at 85 degrees and better
+** than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
+**
+** 10) The complementary functions eraAtio13 and eraAtoi13 are self-
+** consistent to better than 1 microarcsecond all over the
+** celestial sphere.
+**
+** 11) It is advisable to take great care with units, as even unlikely
+** values of the input parameters are accepted and processed in
+** accordance with the models used.
+**
+** Called:
+** eraApio13 astrometry parameters, CIRS-observed, 2013
+** eraAtioq quick CIRS to observed
+**
+** Copyright (C) 2013-2016, NumFOCUS Foundation.
+** Derived, with permission, from the SOFA library. See notes at end of file.
+*/
+{
+ int j;
+ eraASTROM astrom;
+
+
+/* Star-independent astrometry parameters for CIRS->observed. */
+ j = eraApio13(utc1, utc2, dut1, elong, phi, hm, xp, yp,
+ phpa, tc, rh, wl, &astrom);
+
+/* Abort if bad UTC. */
+ if ( j < 0 ) return j;
+
+/* Transform CIRS to observed. */
+ eraAtioq(ri, di, &astrom, aob, zob, hob, dob, rob);
+
+/* Return OK/warning status. */
+ return j;
+
+/* 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.
+**
+*/