def phaserotate_visibility(vis: Visibility, newphasecentre: SkyCoord, tangent=True, inverse=False) -> Visibility:
"""
Phase rotate from the current phase centre to a new phase centre
If tangent is False the uvw are recomputed and the visibility phasecentre is updated.
Otherwise only the visibility phases are adjusted
:param vis: Visibility to be rotated
:param newphasecentre:
:param tangent: Stay on the same tangent plane? (True)
:param inverse: Actually do the opposite
:return: Visibility
"""
assert isinstance(vis, Visibility), "vis is not a Visibility: %r" % vis
l, m, n = skycoord_to_lmn(newphasecentre, vis.phasecentre)
# No significant change?
if numpy.abs(n) > 1e-15:
# Make a new copy
newvis = copy_visibility(vis)
phasor = simulate_point(newvis.uvw, l, m)
nvis, npol = vis.vis.shape
# TODO: Speed up (broadcast rules not obvious to me)
if inverse:
for i in range(nvis):
for pol in range(npol):
newvis.data['vis'][i, pol] *= phasor[i]
else:
for i in range(nvis):
for pol in range(npol):
newvis.data['vis'][i, pol] *= numpy.conj(phasor[i])
# To rotate UVW, rotate into the global XYZ coordinate system and back. We have the option of
# staying on the tangent plane or not. If we stay on the tangent then the raster will
# join smoothly at the edges. If we change the tangent then we will have to reproject to get
# the results on the same image, in which case overlaps or gaps are difficult to deal with.
if not tangent:
if inverse:
xyz = uvw_to_xyz(vis.data['uvw'], ha=-newvis.phasecentre.ra.rad, dec=newvis.phasecentre.dec.rad)
newvis.data['uvw'][...] = \
xyz_to_uvw(xyz, ha=-newphasecentre.ra.rad, dec=newphasecentre.dec.rad)[...]
else:
# This is the original (non-inverse) code
xyz = uvw_to_xyz(newvis.data['uvw'], ha=-newvis.phasecentre.ra.rad, dec=newvis.phasecentre.dec.rad)
newvis.data['uvw'][...] = xyz_to_uvw(xyz, ha=-newphasecentre.ra.rad, dec=newphasecentre.dec.rad)[
...]
newvis.phasecentre = newphasecentre
return newvis
else:
return vis
def test_phase_rotate(self):
uvw = numpy.array([(1, 0, 0), (0, 1, 0), (0, 0, 1)])
pos = [
SkyCoord(17, 35, unit=u.deg),
SkyCoord(17, 30, unit=u.deg),
SkyCoord(12, 30, unit=u.deg),
SkyCoord(11, 35, unit=u.deg),
SkyCoord(51, 35, unit=u.deg),
SkyCoord(15, 70, unit=u.deg)
]
# Sky coordinates to reproject to
for phasecentre in pos:
for newphasecentre in pos:
# Rotate UVW
xyz = uvw_to_xyz(uvw, -phasecentre.ra.rad, phasecentre.dec.rad)
uvw_rotated = xyz_to_uvw(xyz, -newphasecentre.ra.rad,
newphasecentre.dec.rad)
# Determine phasor
l_p, m_p, n_p = skycoord_to_lmn(phasecentre, newphasecentre)
phasor = simulate_point(uvw_rotated, l_p, m_p)
for sourcepos in pos:
# Simulate visibility at old and new phase centre
l, m, _ = skycoord_to_lmn(sourcepos, phasecentre)
vis = simulate_point(uvw, l, m)
l_r, m_r, _ = skycoord_to_lmn(sourcepos, newphasecentre)
vis_rotated = simulate_point(uvw_rotated, l_r, m_r)
# Difference should be given by phasor
assert_allclose(vis * phasor, vis_rotated, atol=1e-10)
def transform(x, y, z, ha, dec):
"""
:param x:
:param y:
:param z:
:param ha:
:param dec:
:return:
"""
res = xyz_to_uvw(numpy.array([x, y, z]), numpy.radians(ha), numpy.radians(dec))
assert_allclose(numpy.linalg.norm(res), numpy.linalg.norm([x, y, z]))
assert_allclose(uvw_to_xyz(res, numpy.radians(ha), numpy.radians(dec)), [x, y, z])
return res
def create_visibility(config: Configuration,
times: numpy.array,
frequency: numpy.array,
channel_bandwidth,
phasecentre: SkyCoord,
weight: float,
polarisation_frame=PolarisationFrame('stokesI'),
integration_time=1.0) -> Visibility:
""" Create a Visibility from Configuration, hour angles, and direction of source
Note that we keep track of the integration time for BDA purposes
:param config: Configuration of antennas
:param times: hour angles in radians
:param frequency: frequencies (Hz] [nchan]
:param weight: weight of a single sample
:param phasecentre: phasecentre of observation
:param channel_bandwidth: channel bandwidths: (Hz] [nchan]
:param integration_time: Integration time ('auto' or value in s)
:param polarisation_frame: PolarisationFrame('stokesI')
:return: Visibility
"""
assert phasecentre is not None, "Must specify phase centre"
if polarisation_frame is None:
polarisation_frame = correlate_polarisation(config.receptor_frame)
nch = len(frequency)
ants_xyz = config.data['xyz']
nants = len(config.data['names'])
nbaselines = int(nants * (nants - 1) / 2)
ntimes = len(times)
npol = polarisation_frame.npol
nrows = nbaselines * ntimes * nch
nrowsperintegration = nbaselines * nch
row = 0
rvis = numpy.zeros([nrows, npol], dtype='complex')
rweight = weight * numpy.ones([nrows, npol])
rtimes = numpy.zeros([nrows])
rfrequency = numpy.zeros([nrows])
rchannel_bandwidth = numpy.zeros([nrows])
rantenna1 = numpy.zeros([nrows], dtype='int')
rantenna2 = numpy.zeros([nrows], dtype='int')
ruvw = numpy.zeros([nrows, 3])
# Do each hour angle in turn
for iha, ha in enumerate(times):
# Calculate the positions of the antennas as seen for this hour angle
# and declination
ant_pos = xyz_to_uvw(ants_xyz, ha, phasecentre.dec.rad)
rtimes[row:row + nrowsperintegration] = ha * 43200.0 / numpy.pi
# Loop over all pairs of antennas. Note that a2>a1
for a1 in range(nants):
for a2 in range(a1 + 1, nants):
rantenna1[row:row + nch] = a1
rantenna2[row:row + nch] = a2
# Loop over all frequencies and polarisations
for ch in range(nch):
# noinspection PyUnresolvedReferences
k = frequency[ch] / constants.c.value
ruvw[row, :] = (ant_pos[a2, :] - ant_pos[a1, :]) * k
rfrequency[row] = frequency[ch]
rchannel_bandwidth[row] = channel_bandwidth[ch]
row += 1
assert row == nrows
rintegration_time = numpy.full_like(rtimes, integration_time)
vis = Visibility(uvw=ruvw,
time=rtimes,
antenna1=rantenna1,
antenna2=rantenna2,
frequency=rfrequency,
vis=rvis,
weight=rweight,
imaging_weight=rweight,
integration_time=rintegration_time,
channel_bandwidth=rchannel_bandwidth,
polarisation_frame=polarisation_frame)
vis.phasecentre = phasecentre
vis.configuration = config
log.info("create_visibility: %s" % (vis_summary(vis)))
assert isinstance(vis, Visibility), "vis is not a Visibility: %r" % vis
return vis
def create_blockvisibility(config: Configuration,
times: numpy.array,
frequency: numpy.array,
phasecentre: SkyCoord,
weight: float = 1.0,
polarisation_frame: PolarisationFrame = None,
integration_time=1.0,
channel_bandwidth=1e6,
zerow=False,
**kwargs) -> BlockVisibility:
""" Create a BlockVisibility from Configuration, hour angles, and direction of source
Note that we keep track of the integration time for BDA purposes
:param config: Configuration of antennas
:param times: hour angles in radians
:param frequency: frequencies (Hz] [nchan]
:param weight: weight of a single sample
:param phasecentre: phasecentre of observation
:param channel_bandwidth: channel bandwidths: (Hz] [nchan]
:param integration_time: Integration time ('auto' or value in s)
:param polarisation_frame:
:return: BlockVisibility
"""
assert phasecentre is not None, "Must specify phase centre"
if polarisation_frame is None:
polarisation_frame = correlate_polarisation(config.receptor_frame)
nch = len(frequency)
ants_xyz = config.data['xyz']
nants = len(config.data['names'])
ntimes = len(times)
npol = polarisation_frame.npol
visshape = [ntimes, nants, nants, nch, npol]
rvis = numpy.zeros(visshape, dtype='complex')
rweight = weight * numpy.ones(visshape)
rtimes = numpy.zeros([ntimes])
ruvw = numpy.zeros([ntimes, nants, nants, 3])
# Do each hour angle in turn
for iha, ha in enumerate(times):
# Calculate the positions of the antennas as seen for this hour angle
# and declination
ant_pos = xyz_to_uvw(ants_xyz, ha, phasecentre.dec.rad)
rtimes[iha] = ha * 43200.0 / numpy.pi
# Loop over all pairs of antennas. Note that a2>a1
for a1 in range(nants):
for a2 in range(a1 + 1, nants):
ruvw[iha, a2, a1, :] = (ant_pos[a2, :] - ant_pos[a1, :])
ruvw[iha, a1, a2, :] = (ant_pos[a1, :] - ant_pos[a2, :])
rintegration_time = numpy.full_like(rtimes, integration_time)
rchannel_bandwidth = numpy.full_like(frequency, channel_bandwidth)
if zerow:
ruvw[..., 2] = 0.0
vis = BlockVisibility(uvw=ruvw,
time=rtimes,
frequency=frequency,
vis=rvis,
weight=rweight,
integration_time=rintegration_time,
channel_bandwidth=rchannel_bandwidth,
polarisation_frame=polarisation_frame)
vis.phasecentre = phasecentre
vis.configuration = config
log.info("create_blockvisibility: %s" % (vis_summary(vis)))
assert isinstance(
vis, BlockVisibility), "vis is not a BlockVisibility: %r" % vis
return vis