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 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)
def test_phase_rotation_stokesi(self):
# Define the component and give it some spectral behaviour
f = numpy.array([100.0])
self.flux = numpy.array([f, 0.8 * f, 0.6 * f])
# The phase centre is absolute and the component is specified relative (for now).
# This means that the component should end up at the position phasecentre+compredirection
self.phasecentre = SkyCoord(ra=+180.0 * u.deg, dec=-35.0 * u.deg, frame='icrs', equinox='J2000')
self.compabsdirection = SkyCoord(ra=+181.0 * u.deg, dec=-35.0 * u.deg, frame='icrs', equinox='J2000')
pcof = self.phasecentre.skyoffset_frame()
self.compreldirection = self.compabsdirection.transform_to(pcof)
self.comp = Skycomponent(direction=self.compreldirection, frequency=self.frequency, flux=self.flux,
polarisation_frame=PolarisationFrame("stokesI"))
self.vis = create_visibility(self.lowcore, self.times, self.frequency,
channel_bandwidth=self.channel_bandwidth,
phasecentre=self.phasecentre, weight=1.0,
polarisation_frame=PolarisationFrame("stokesI"))
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("stokesI"))
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=3e-6)
assert_allclose(rotatedvis.uvw, vismodel2.uvw, rtol=3e-6)
