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+#include "erfa.h"
+
+void eraHfk5z(double rh, double dh, double date1, double date2,
+ double *r5, double *d5, double *dr5, double *dd5)
+/*
+** - - - - - - - - -
+** e r a H f k 5 z
+** - - - - - - - - -
+**
+** Transform a Hipparcos star position into FK5 J2000.0, assuming
+** zero Hipparcos proper motion.
+**
+** Given:
+** rh double Hipparcos RA (radians)
+** dh double Hipparcos Dec (radians)
+** date1,date2 double TDB date (Note 1)
+**
+** Returned (all FK5, equinox J2000.0, date date1+date2):
+** r5 double RA (radians)
+** d5 double Dec (radians)
+** dr5 double FK5 RA proper motion (rad/year, Note 4)
+** dd5 double Dec proper motion (rad/year, Note 4)
+**
+** Notes:
+**
+** 1) The TT date date1+date2 is a Julian Date, apportioned in any
+** convenient way between the two arguments. For example,
+** JD(TT)=2450123.7 could be expressed in any of these ways,
+** among others:
+**
+** date1 date2
+**
+** 2450123.7 0.0 (JD method)
+** 2451545.0 -1421.3 (J2000 method)
+** 2400000.5 50123.2 (MJD method)
+** 2450123.5 0.2 (date & time method)
+**
+** The JD method is the most natural and convenient to use in
+** cases where the loss of several decimal digits of resolution
+** is acceptable. The J2000 method is best matched to the way
+** the argument is handled internally and will deliver the
+** optimum resolution. The MJD method and the date & time methods
+** are both good compromises between resolution and convenience.
+**
+** 2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
+**
+** 3) The FK5 to Hipparcos transformation is modeled as a pure rotation
+** and spin; zonal errors in the FK5 catalogue are not taken into
+** account.
+**
+** 4) It was the intention that Hipparcos should be a close
+** approximation to an inertial frame, so that distant objects have
+** zero proper motion; such objects have (in general) non-zero
+** proper motion in FK5, and this function returns those fictitious
+** proper motions.
+**
+** 5) The position returned by this function is in the FK5 J2000.0
+** reference system but at date date1+date2.
+**
+** 6) See also eraFk52h, eraH2fk5, eraFk5zhz.
+**
+** Called:
+** eraS2c spherical coordinates to unit vector
+** eraFk5hip FK5 to Hipparcos rotation and spin
+** eraRxp product of r-matrix and p-vector
+** eraSxp multiply p-vector by scalar
+** eraRxr product of two r-matrices
+** eraTrxp product of transpose of r-matrix and p-vector
+** eraPxp vector product of two p-vectors
+** eraPv2s pv-vector to spherical
+** eraAnp normalize angle into range 0 to 2pi
+**
+** Reference:
+**
+** F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739.
+**
+** Copyright (C) 2013-2016, NumFOCUS Foundation.
+** Derived, with permission, from the SOFA library. See notes at end of file.
+*/
+{
+ double t, ph[3], r5h[3][3], s5h[3], sh[3], vst[3],
+ rst[3][3], r5ht[3][3], pv5e[2][3], vv[3],
+ w, r, v;
+
+
+/* Time interval from fundamental epoch J2000.0 to given date (JY). */
+ t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJY;
+
+/* Hipparcos barycentric position vector (normalized). */
+ eraS2c(rh, dh, ph);
+
+/* FK5 to Hipparcos orientation matrix and spin vector. */
+ eraFk5hip(r5h, s5h);
+
+/* Rotate the spin into the Hipparcos system. */
+ eraRxp(r5h, s5h, sh);
+
+/* Accumulated Hipparcos wrt FK5 spin over that interval. */
+ eraSxp(t, s5h, vst);
+
+/* Express the accumulated spin as a rotation matrix. */
+ eraRv2m(vst, rst);
+
+/* Rotation matrix: accumulated spin, then FK5 to Hipparcos. */
+ eraRxr(r5h, rst, r5ht);
+
+/* De-orient & de-spin the Hipparcos position into FK5 J2000.0. */
+ eraTrxp(r5ht, ph, pv5e[0]);
+
+/* Apply spin to the position giving a space motion. */
+ eraPxp(sh, ph, vv);
+
+/* De-orient & de-spin the Hipparcos space motion into FK5 J2000.0. */
+ eraTrxp(r5ht, vv, pv5e[1]);
+
+/* FK5 position/velocity pv-vector to spherical. */
+ eraPv2s(pv5e, &w, d5, &r, dr5, dd5, &v);
+ *r5 = eraAnp(w);
+
+ return;
+
+}
+/*----------------------------------------------------------------------
+**
+**
+** 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.
+**
+*/