def test_phase_rotation_identity(self):
self.vis = create_visibility(
self.lowcore,
self.times,
self.frequency,
channel_bandwidth=self.channel_bandwidth,
phasecentre=self.phasecentre,
weight=1.0,
polarisation_frame=PolarisationFrame("stokesIQUV"))
self.vismodel = predict_skycomponent_visibility(self.vis, self.comp)
newphasecenters = [
SkyCoord(182, -35, unit=u.deg),
SkyCoord(182, -30, unit=u.deg),
SkyCoord(177, -30, unit=u.deg),
SkyCoord(176, -35, unit=u.deg),
SkyCoord(216, -35, unit=u.deg),
SkyCoord(180, -70, unit=u.deg)
]
for newphasecentre in newphasecenters:
# Phase rotating back should not make a difference
original_vis = self.vismodel.vis
original_uvw = self.vismodel.uvw
rotatedvis = phaserotate_visibility(phaserotate_visibility(
self.vismodel, newphasecentre, tangent=False),
self.phasecentre,
tangent=False)
assert_allclose(rotatedvis.uvw, original_uvw, rtol=1e-7)
assert_allclose(rotatedvis.vis, original_vis, rtol=1e-7)
def test_phase_rotation_inverse(self):
self.vis = create_visibility(self.lowcore, self.times, self.frequency,
channel_bandwidth=self.channel_bandwidth,
phasecentre=self.phasecentre, weight=1.0,
polarisation_frame=PolarisationFrame("stokesIQUV"))
self.vismodel = predict_skycomponent_visibility(self.vis, self.comp)
there = SkyCoord(ra=+250.0 * u.deg, dec=-60.0 * u.deg, frame='icrs', equinox='J2000')
# Phase rotating back should not make a difference
original_vis = self.vismodel.vis
original_uvw = self.vismodel.uvw
rotatedvis = phaserotate_visibility(phaserotate_visibility(self.vismodel, there, tangent=False,
inverse=True),
self.phasecentre, tangent=False, inverse=True)
assert_allclose(rotatedvis.uvw, original_uvw, rtol=1e-7)
assert_allclose(rotatedvis.vis, original_vis, rtol=1e-7)
def shift_vis_to_image(vis: Visibility, im: Image, tangent: bool = True, inverse: bool = False) -> Visibility:
"""Shift visibility to the FFT phase centre of the image in place
:param vis: Visibility data
:param im: Image model used to determine phase centre
:param tangent: Is the shift purely on the tangent plane True|False
:param inverse: Do the inverse operation True|False
:return: visibility with phase shift applied and phasecentre updated
"""
assert isinstance(vis, Visibility), "vis is not a Visibility: %r" % vis
nchan, npol, ny, nx = im.data.shape
# Convert the FFT definition of the phase center to world coordinates (1 relative)
# This is the only place in ARL where the relationship between the image and visibility
# frames is defined.
image_phasecentre = pixel_to_skycoord(nx // 2 + 1, ny // 2 + 1, im.wcs, origin=1)
if vis.phasecentre.separation(image_phasecentre).rad > 1e-15:
if inverse:
log.debug("shift_vis_from_image: shifting phasecentre from image phase centre %s to visibility phasecentre "
"%s" % (image_phasecentre, vis.phasecentre))
else:
log.debug("shift_vis_from_image: shifting phasecentre from vis phasecentre %s to image phasecentre %s" %
(vis.phasecentre, image_phasecentre))
vis = phaserotate_visibility(vis, image_phasecentre, tangent=tangent, inverse=inverse)
vis.phasecentre = im.phasecentre
assert isinstance(vis, Visibility), "after phase_rotation, vis is not a Visibility"
return vis
def test_phase_rotation(self):
self.vis = create_visibility(
self.lowcore,
self.times,
self.frequency,
channel_bandwidth=self.channel_bandwidth,
phasecentre=self.phasecentre,
weight=1.0,
polarisation_frame=PolarisationFrame("stokesIQUV"))
self.vismodel = predict_skycomponent_visibility(self.vis, self.comp)
# Predict visibilities with new phase centre independently
ha_diff = -(self.compabsdirection.ra - self.phasecentre.ra).to(
u.rad).value
vispred = create_visibility(
self.lowcore,
self.times + ha_diff,
self.frequency,
channel_bandwidth=self.channel_bandwidth,
phasecentre=self.compabsdirection,
weight=1.0,
polarisation_frame=PolarisationFrame("stokesIQUV"))
vismodel2 = predict_skycomponent_visibility(vispred, self.comp)
# Should yield the same results as rotation
rotatedvis = phaserotate_visibility(
self.vismodel, newphasecentre=self.compabsdirection, tangent=False)
assert_allclose(rotatedvis.vis, vismodel2.vis, rtol=1e-7)
assert_allclose(rotatedvis.uvw, vismodel2.uvw, rtol=1e-7)