def set_pointing(self):
"""Set the antenna beam to point at (az, alt). """
az, alt, twist = np.radians(self.pointing)
lat = np.pi/2 - self.zenith[0]
lon = self.zenith[1]
saz, caz = np.sin(az), np.cos(az)
salt, calt = np.sin(alt), np.cos(alt)
slat, clat = np.sin(lat), np.cos(lat)
slon, clon = np.sin(lon), np.cos(lon)
# matrix to convert vector in topocentric coordinate to equatorial coordinate (x starts from the vernal equinox)
top2eq_m = np.array([[-slon, -slat*clon, clat*clon],
[ clon, -slat*slon, clat*slon],
[ 0, clat, slat]])
p_top = np.array([saz*calt, caz*calt, salt]) # point_direction in topocentric coord
p_eq = np.dot(top2eq_m, p_top) # point_direction in equatorial coord
self._point_direction = coord.cart_to_sph(p_eq)[-2:]
def set_pointing(self):
"""Set the antenna beam to point at (az, alt). """
az, alt, twist = np.radians(self.pointing)
lat = np.pi/2 - self.zenith[0]
lon = self.zenith[1]
saz, caz = np.sin(az), np.cos(az)
salt, calt = np.sin(alt), np.cos(alt)
slat, clat = np.sin(lat), np.cos(lat)
slon, clon = np.sin(lon), np.cos(lon)
# matrix to convert vector in topocentric coordinate to equatorial coordinate (x starts from the vernal equinox)
top2eq_m = np.array([[-slon, -slat*clon, clat*clon],
[ clon, -slat*slon, clat*slon],
[ 0, clat, slat]])
p_top = np.array([saz*calt, caz*calt, salt]) # point_direction in topocentric coord
p_eq = np.dot(top2eq_m, p_top) # point_direction in equatorial coord
self._point_direction = coord.cart_to_sph(p_eq)[-2:]
def response(self, xyz):
"""Beam response across active band for specified topocentric coordinates.
This uses the beam model implemented in driftscan package.
Parameters
----------
xyz : array like, of shape (3, ...)
Unit direction vector in topocentric coordinates (x=E, y=N, z=UP).
`xyz` may be arrays of multiple coordinates.
Returns
-------
Returns 'x' linear polarization (rotate pi/2 for 'y') of shape (nfreq, ...).
"""
xyz = np.array(xyz)
lat = np.radians(44.15268333) # exact value not important
lon = np.radians(91.80686667) # exact value not important
zenith = np.array([0.5*np.pi - lat, lon])
m = top2eq_m(lat, lon) # conversion matrix
shp = xyz.shape
p_eq = np.dot(m, xyz.reshape(3, -1)).reshape(shp) # point_direction in equatorial coord
p_eq = coord.cart_to_sph(p_eq.T) # to theta, phi
# cylinder width in wavelength
width = self.width / (const.c / (1.0e9 * self.freqs))
nfreq = len(self.freqs)
resp = np.zeros((nfreq,)+xyz.shape[1:])
for fi in xrange( nfreq):
resp[fi] = cylbeam.beam_amp(p_eq, zenith, width[fi], self.fwhm_h, self.fwhm_h)
# resp[fi] = cylbeam.beam_amp(p_eq, zenith, width[fi], self.fwhm_e, self.fwhm_h) # for X dipole
# resp[fi] = cylbeam.beam_amp(p_eq, zenith, width[fi], self.fwhm_h, self.fwhm_e) # for Y dipole
return resp
