Add bodeul (#389)

* Add capability to call routine bodeul

appveyor/cspice.def

@@ -10,6 +10,7 @@ EXPORTS			appndc_c
 				bodc2n_c
 				bodc2s_c
 				boddef_c
+				bodeul_
 				bodfnd_c
 				bodn2c_c
 				bods2c_c

spiceypy/spiceypy.py

@@ -413,6 +413,36 @@ def bltfrm(frmcls: int, out_cell: Optional[SpiceCell] = None) -> SpiceCell:
     return out_cell
 
 
+@spice_error_check
+def bodeul(body: int, et: float) -> Tuple[float, float, float, float]:
+    """
+    Return the Euler angles needed to compute the transformation from
+    inertial to body-fixed coordinates for any body in the kernel
+    pool.
+
+    https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/spicelib/bodeul.html
+
+    :param body: NAIF ID code of body.
+    :param et: Epoch of transformation in seconds past J2000 TDB.
+    :return:
+            Right ascension of the (IAU) north pole in radians.
+            Declination of the (IAU) north pole of the body in radians.
+            Prime meridian rotation angle in radians.
+            Angle between the prime meridian and longitude of longest axis in radians.
+    """
+    body = ctypes.c_int(body)
+    et = ctypes.c_double(et)
+    ra = ctypes.c_double()
+    dec = ctypes.c_double()
+    w = ctypes.c_double()
+    lam = ctypes.c_double()
+    libspice.bodeul_(
+        ctypes.byref(body), ctypes.byref(et),
+        ctypes.byref(ra), ctypes.byref(dec), ctypes.byref(w), ctypes.byref(lam)
+    )
+    return ra.value, dec.value, w.value, lam.value
+
+
 @spice_error_check
 @spice_found_exception_thrower
 def bodc2n(code: int, lenout: int = _default_len_out) -> Tuple[str, bool]:

spiceypy/tests/test_wrapper.py

@@ -177,6 +177,37 @@ def test_boddef():
     spice.kclear()
 
 
+def test_bodeul():
+    spice.kclear()
+    spice.furnsh(CoreKernels.testMetaKernel)
+    # define body-fixed unit vectors
+    xbf = [1.0, 0.0, 0.0]
+    ybf = [0.0, 1.0, 0.0]
+    zbf = [0.0, 0.0, 1.0]
+    # get the reference rotation matrix from pxform at et=0.0
+    ref_rotate = spice.pxform("IAU_VENUS", "J2000", 0.0)
+    # transform bf vectors to inertial coordinates
+    xin = spice.mxv(ref_rotate, xbf)
+    yin = spice.mxv(ref_rotate, ybf)
+    zin = spice.mxv(ref_rotate, zbf)
+    # obtain reference RA and DEC of north pole
+    ref_range, ref_ra, ref_dec = spice.recrad(zin)
+    # compute location of node
+    node = spice.ucrss(zbf, zin)
+    # obtain reference angle of prime meridian
+    xproj = spice.vdot(node, xin)
+    yproj = spice.vdot(node, yin)
+    ref_w = -np.arctan2(yproj, xproj)
+    ref_lam = 0
+    # hopefully obtain the same angles with call to bodeul at et=0.0
+    ra, dec, w, lam = spice.bodeul(299, 0.0)
+    npt.assert_almost_equal(ra, ref_ra, decimal=4)
+    npt.assert_almost_equal(dec, ref_dec, decimal=4)
+    npt.assert_almost_equal(w, ref_w, decimal=4)
+    npt.assert_almost_equal(lam, ref_lam, decimal=4)
+    spice.kclear()
+
+
 def test_bodfnd():
     spice.kclear()
     spice.furnsh(CoreKernels.testMetaKernel)

spiceypy/utils/libspicehelper.py

@@ -60,6 +60,7 @@
 libspice.bodc2n_c.argtypes = [c_int, c_int, c_char_p, c_int_p]
 libspice.bodc2s_c.argtypes = [c_int, c_int, c_char_p]
 libspice.boddef_c.argtypes = [c_char_p, c_int]
+libspice.bodeul_.argtypes = [c_int_p, c_double_p, c_double_p, c_double_p, c_double_p, c_double_p]
 libspice.badkpv_c.argtypes = [c_char_p, c_char_p, c_char_p, c_int, c_int, c_char]
 libspice.badkpv_c.restype = c_int
 libspice.bltfrm_c.argtypes = [c_int, s_cell_p]