def test_jones_set_interp(cst_beam, hera_loc):
# check setting the interpolation method
array_location = hera_loc
beam = cst_beam.copy()
beam.freq_interp_kind = None
beam.interpolation_function = 'az_za_simple'
beam_list = pyuvsim.BeamList([beam])
antenna1 = pyuvsim.Antenna('ant1', 1, np.array([0, 10, 0]), 0)
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
source_altaz = np.array([[0.0], [np.pi / 4.]])
freq = 123e6 * units.Hz
with pytest.raises(ValueError, match='freq_interp_kind must be set'):
antenna1.get_beam_jones(array, source_altaz, freq)
jones = antenna1.get_beam_jones(array,
source_altaz,
freq,
freq_interp_kind='cubic')
assert beam.freq_interp_kind == 'cubic'
jones0 = antenna1.get_beam_jones(array, source_altaz, freq)
jones1 = antenna1.get_beam_jones(array,
source_altaz,
freq,
freq_interp_kind='linear')
assert beam.freq_interp_kind == 'linear'
jones2 = antenna1.get_beam_jones(array, source_altaz, freq)
assert (np.all(jones2 == jones0) and np.all(jones1 == jones)
and np.all(jones1 == jones0))
def test_jones_set_spline(cst_beam, hera_loc):
# Run get_beam_jones with spline options.
array_location = hera_loc
beam0 = cst_beam.copy()
beam0.freq_interp_kind = 'cubic'
telescope_config_name = os.path.join(SIM_DATA_PATH, 'mwa128_config.yaml')
with open(telescope_config_name, 'r') as yf:
telconfig = yaml.safe_load(yf)
telconfig['spline_interp_opts'] = {'kx': 1, 'ky': 1}
beam_list = pyuvsim.simsetup._construct_beam_list(np.arange(1), telconfig)
beam_list.set_obj_mode()
beam_list.append(beam0)
assert beam0 is beam_list[-1]
# Make antenna that uses beam #1
antenna = pyuvsim.Antenna('ant1', 1, np.array([0, 10, 0]), 1)
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
altaz = [[0.0134], [1.0]]
alts = np.linspace(0, np.pi / 4, 50)
azs = np.linspace(0, 2 * np.pi, 50)
alts, azs = np.meshgrid(alts, azs)
altaz = np.zeros((50**2, 3))
altaz[:, 0] = alts.flatten()
altaz[:, 1] = azs.flatten()
array.beam_list.spline_interp_opts = None
antenna.get_beam_jones(array, altaz, 150e6)
def test_gaussbeam_values():
"""
Make the long-line point sources up to 10 degrees from zenith.
Obtain visibilities
Confirm that the values match the expected beam values at those zenith angles.
"""
sigma = 0.05
hera_uv = UVData()
hera_uv.read_uvfits(EW_uvfits_file)
array_location = EarthLocation.from_geocentric(
hera_uv.telescope_location[0],
hera_uv.telescope_location[1],
hera_uv.telescope_location[2],
unit='m')
freq = hera_uv.freq_array[0, 0] * units.Hz
time = Time(hera_uv.time_array[0], scale='utc', format='jd')
catalog, mock_keywords = pyuvsim.create_mock_catalog(
time=time,
arrangement='long-line',
Nsrcs=41,
max_za=10.,
array_location=array_location)
beam = pyuvsim.AnalyticBeam('gaussian', sigma=sigma)
array = pyuvsim.Telescope('telescope_name', array_location, [beam])
# Need a dummy baseline for this test.
antenna1 = pyuvsim.Antenna('ant1', 1, np.array([0, 0, 0]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array([107, 0, 0]), 0)
baseline = pyuvsim.Baseline(antenna1, antenna2)
coherencies = []
zenith_angles = []
for src in catalog:
task = pyuvsim.UVTask(src, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
engine.apply_beam()
# task.source.az_za_calc(time, array_location)
zenith_angles.append(task.source.az_za[1]) # In radians.
coherencies.append(
np.real(engine.apparent_coherency[0, 0]).astype(
float)) # All four components should be identical
coherencies = np.array(coherencies)
zenith_angles = np.array(zenith_angles)
# Confirm the coherency values (ie., brightnesses) match the beam values.
beam_values = np.exp(-(zenith_angles)**2 / (2 * beam.sigma**2))
nt.assert_true(np.all(beam_values**2 == coherencies))
def test_gaussbeam_values():
"""
Make the long-line point sources up to 10 degrees from zenith.
Confirm that the coherencies match the expected beam values at those zenith angles.
"""
sigma = 0.05
hera_uv = UVData()
hera_uv.read_uvfits(EW_uvfits_file)
array_location = EarthLocation.from_geocentric(*hera_uv.telescope_location,
unit='m')
freq = hera_uv.freq_array[0, 0] * units.Hz
time = Time(hera_uv.time_array[0], scale='utc', format='jd')
catalog, mock_keywords = pyuvsim.create_mock_catalog(
time=time,
arrangement='long-line',
Nsrcs=41,
min_alt=80.,
array_location=array_location)
catalog.update_positions(time, array_location)
beam = pyuvsim.AnalyticBeam('gaussian', sigma=sigma)
array = pyuvsim.Telescope('telescope_name', array_location, [beam])
# Need a dummy baseline for this test.
antenna1 = pyuvsim.Antenna('ant1', 1, np.array([0, 0, 0]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array([107, 0, 0]), 0)
baseline = pyuvsim.Baseline(antenna1, antenna2)
task = pyuvsim.UVTask(catalog, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
engine.apply_beam()
altitudes = task.sources.alt_az[0] # In radians.
# All four components should be identical
if isinstance(engine.apparent_coherency, units.Quantity):
coherency_use = engine.apparent_coherency.to_value("Jy")
else:
coherency_use = engine.apparent_coherency
coherencies = np.real(coherency_use[0, 0] +
coherency_use[1, 1]).astype(float)
zenith_angles, _ = simutils.altaz_to_zenithangle_azimuth(
altitudes, np.zeros_like(np.array(altitudes)))
# Confirm the coherency values (ie., brightnesses) match the beam values.
beam_values = np.exp(-(zenith_angles)**2 / (2 * beam.sigma**2))
assert np.all(beam_values**2 == coherencies)
def test_beamlist_errors(beam_objs):
newbeams = copy.deepcopy(beam_objs)
beamlist = pyuvsim.BeamList(newbeams)
# Try to make a BeamList with a mixture of strings and objects.
newlist = copy.deepcopy(beamlist._obj_beam_list)
newlist[2] = beamlist._obj_to_str(newlist[2])
with pytest.raises(ValueError, match='Invalid beam list:'):
pyuvsim.BeamList(newlist)
# Try to append an invalid beam path while in object mode.
beam_path = 'invalid_file.uvbeam'
with pytest.raises(ValueError, match='Invalid file path'):
beamlist.append(beam_path)
# Compare Telescopes with beamlists of different lengths
del newbeams[0]
array_location = EarthLocation(lat='-30d43m17.5s',
lon='21d25m41.9s',
height=1073.)
tel0 = pyuvsim.Telescope('tel0', array_location, newbeams)
tel1 = pyuvsim.Telescope('tel1', array_location, beam_objs)
assert tel0 != tel1
def test_single_zenith_source_uvdata():
"""Test single zenith source using test uvdata file."""
hera_uv = UVData()
hera_uv.read_uvfits(EW_uvfits_file)
time = Time(hera_uv.time_array[0], scale='utc', format='jd')
array_location = EarthLocation.from_geocentric(
hera_uv.telescope_location[0],
hera_uv.telescope_location[1],
hera_uv.telescope_location[2],
unit='m')
freq = hera_uv.freq_array[0, 0] * units.Hz
# get antennas positions into ENU
antpos = hera_uv.antenna_positions[0:2, :] + hera_uv.telescope_location
antpos = uvutils.ENU_from_ECEF(antpos.T,
*hera_uv.telescope_location_lat_lon_alt).T
antenna1 = pyuvsim.Antenna('ant1', 1, np.array(antpos[0, :]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array(antpos[1, :]), 0)
# setup the things that don't come from pyuvdata:
# make a source at zenith
time.location = array_location
source = create_zenith_source(time, 'zensrc')
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[100e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
baseline = pyuvsim.Baseline(antenna1, antenna2)
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
task = pyuvsim.UVTask(source, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
visibility = engine.make_visibility()
nt.assert_true(np.allclose(visibility, np.array([.5, .5, 0, 0]),
atol=5e-3))
def test_single_zenith_source():
"""Test single zenith source."""
time = Time('2018-03-01 00:00:00', scale='utc')
array_location = EarthLocation(lat='-30d43m17.5s',
lon='21d25m41.9s',
height=1073.)
time.location = array_location
freq = (150e6 * units.Hz)
source = create_zenith_source(time, 'zensrc')
antenna1 = pyuvsim.Antenna('ant1', 1, np.array([0, 0, 0]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array([107, 0, 0]), 0)
baseline = pyuvsim.Baseline(antenna1, antenna2)
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[150e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
task = pyuvsim.UVTask(source, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
visibility = engine.make_visibility()
nt.assert_true(np.allclose(visibility, np.array([.5, .5, 0, 0]),
atol=5e-3))
def test_file_to_tasks():
hera_uv = UVData()
hera_uv.read_uvfits(EW_uvfits_file)
time = Time(hera_uv.time_array[0], scale='utc', format='jd')
sources = np.array([create_zenith_source(time, 'zensrc')])
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[150e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
uvtask_list = pyuvsim.uvdata_to_task_list(hera_uv, sources, beam_list)
tel_loc = EarthLocation.from_geocentric(*hera_uv.telescope_location,
unit='m')
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[150e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
telescope = pyuvsim.Telescope(hera_uv.telescope_name, tel_loc, beam_list)
ant_pos = hera_uv.antenna_positions + hera_uv.telescope_location
ant_pos_enu = uvutils.ENU_from_ECEF(
ant_pos.T, *hera_uv.telescope_location_lat_lon_alt).T
expected_task_list = []
antenna_names = hera_uv.antenna_names
antennas = []
for num, antname in enumerate(antenna_names):
beam_id = 0
antennas.append(
pyuvsim.Antenna(antname, num, ant_pos_enu[num], beam_id))
antennas1 = []
for antnum in hera_uv.ant_1_array:
index = np.where(hera_uv.antenna_numbers == antnum)[0][0]
antennas1.append(antennas[index])
antennas2 = []
for antnum in hera_uv.ant_2_array:
index = np.where(hera_uv.antenna_numbers == antnum)[0][0]
antennas2.append(antennas[index])
for idx, antenna1 in enumerate(antennas1):
antenna2 = antennas2[idx]
baseline = pyuvsim.Baseline(antenna1, antenna2)
task = pyuvsim.UVTask(sources[0], time.jd, hera_uv.freq_array[0, 0],
baseline, telescope)
task.uvdata_index = (idx, 0, 0)
expected_task_list.append(task)
for idx, task in enumerate(uvtask_list):
exp_task = expected_task_list[idx]
nt.assert_equal(task, exp_task)
def test_single_offzenith_source_miriad():
"""Test single off-zenith source using test uvdata file."""
miriad_uv = UVData()
miriad_uv.read_miriad(os.path.join(DATA_PATH, 'hera_testfile'),
ant_str='9_10')
miriad_uv.select(times=miriad_uv.time_array[0])
src_az = Angle('90.0d')
src_alt = Angle('85.0d')
src_za = Angle('90.0d') - src_alt
src_l = np.sin(src_az.rad) * np.sin(src_za.rad)
src_m = np.cos(src_az.rad) * np.sin(src_za.rad)
src_n = np.cos(src_za.rad)
time = Time(miriad_uv.time_array[0], scale='utc', format='jd')
array_location = EarthLocation.from_geocentric(
miriad_uv.telescope_location[0],
miriad_uv.telescope_location[1],
miriad_uv.telescope_location[2],
unit='m')
freq = miriad_uv.freq_array[0, 0] * units.Hz
# get antennas positions into ENU
antpos = miriad_uv.antenna_positions[0:2, :] + miriad_uv.telescope_location
antpos = uvutils.ENU_from_ECEF(antpos.T,
*miriad_uv.telescope_location_lat_lon_alt).T
antenna1 = pyuvsim.Antenna('ant1', 1, np.array(antpos[0, :]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array(antpos[1, :]), 0)
# setup the things that don't come from pyuvdata:
# make a source off zenith
time.location = array_location
source = create_offzenith_source(time, 'offzensrc', az=src_az, alt=src_alt)
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[100e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
baseline = pyuvsim.Baseline(antenna1, antenna2)
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
task = pyuvsim.UVTask(source, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
visibility = engine.make_visibility()
# analytically calculate visibility
beam.peak_normalize()
beam.interpolation_function = 'az_za_simple'
interpolated_beam, interp_basis_vector = beam.interp(
az_array=np.array([src_az.rad]),
za_array=np.array([src_za.rad]),
freq_array=np.array([freq.to('Hz').value]))
jones = np.zeros((2, 2), dtype=np.complex64)
jones[0, 0] = interpolated_beam[1, 0, 0, 0, 0]
jones[1, 1] = interpolated_beam[0, 0, 1, 0, 0]
jones[1, 0] = interpolated_beam[1, 0, 1, 0, 0]
jones[0, 1] = interpolated_beam[0, 0, 0, 0, 0]
uvw_wavelength_array = hera_uv.uvw_array * units.m / const.c * freq.to(
'1/s')
vis_analytic = 0.5 * np.dot(
jones,
np.conj(jones).T) * np.exp(
-2j * np.pi *
(uvw_wavelength_array[0, 0] * src_l + uvw_wavelength_array[0, 1] *
src_m + uvw_wavelength_array[0, 2] * src_n))
vis_analytic = np.array([
vis_analytic[0, 0], vis_analytic[1, 1], vis_analytic[1, 0],
vis_analytic[0, 1]
])
print('Analytic visibility', vis_analytic)
print('Calculated visibility', visibility)
nt.assert_true(np.allclose(visibility, vis_analytic, atol=5e-3))
def test_offzenith_source_multibl_uvfits():
"""Test single off-zenith source using test uvdata file.
Calculate visibilities for a baseline triangle.
"""
hera_uv = UVData()
hera_uv.read_uvfits(
longbl_uvfits_file, ant_str='cross'
) # consists of a right triangle of baselines with w term
hera_uv.unphase_to_drift()
src_az = Angle('90.0d')
src_alt = Angle('85.0d')
src_za = Angle('90.0d') - src_alt
src_l = np.sin(src_az.rad) * np.sin(src_za.rad)
src_m = np.cos(src_az.rad) * np.sin(src_za.rad)
src_n = np.cos(src_za.rad)
time = Time(hera_uv.time_array[0], scale='utc', format='jd')
array_location = EarthLocation.from_geocentric(
hera_uv.telescope_location[0],
hera_uv.telescope_location[1],
hera_uv.telescope_location[2],
unit='m')
freq = hera_uv.freq_array[0, 0] * units.Hz
# get antennas positions into ENU
antpos, ants = hera_uv.get_ENU_antpos()
antenna1 = pyuvsim.Antenna('ant1', ants[0], np.array(antpos[0, :]), 0)
antenna2 = pyuvsim.Antenna('ant2', ants[1], np.array(antpos[1, :]), 0)
antenna3 = pyuvsim.Antenna('ant3', ants[2], np.array(antpos[2, :]), 0)
# setup the things that don't come from pyuvdata:
# make a source off zenith
time.location = array_location
source = create_offzenith_source(time, 'offzensrc', az=src_az, alt=src_alt)
# beam = UVBeam()
# beam.read_cst_beam(beam_files, beam_type='efield', frequency=[100e6, 123e6],
# telescope_name='HERA',
# feed_name='PAPER', feed_version='0.1', feed_pol=['x'],
# model_name='E-field pattern - Rigging height 4.9m',
# model_version='1.0')
beam = pyuvsim.AnalyticBeam('tophat')
beam_list = [beam]
baselines = [
pyuvsim.Baseline(antenna2, antenna1),
pyuvsim.Baseline(antenna3, antenna1),
pyuvsim.Baseline(antenna3, antenna2)
]
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
tasks = [pyuvsim.UVTask(source, time, freq, bl, array) for bl in baselines]
visibilities = []
uvws = []
for t in tasks:
engine = pyuvsim.UVEngine(t)
visibilities.append(engine.make_visibility())
uvws.append(t.baseline.uvw)
uvws = np.array(uvws)
# analytically calculate visibilities
beam.peak_normalize()
beam.interpolation_function = 'az_za_simple'
interpolated_beam, interp_basis_vector = beam.interp(
az_array=np.array([src_az.rad]),
za_array=np.array([src_za.rad]),
freq_array=np.array([freq.to('Hz').value]))
jones = np.zeros((2, 2), dtype=np.complex64)
jones[0, 0] = interpolated_beam[1, 0, 0, 0, 0]
jones[1, 1] = interpolated_beam[0, 0, 1, 0, 0]
jones[1, 0] = interpolated_beam[1, 0, 1, 0, 0]
jones[0, 1] = interpolated_beam[0, 0, 0, 0, 0]
uvw_wavelength_array = hera_uv.uvw_array[
0:hera_uv.Nbls] * units.m / const.c * freq.to('1/s')
visibilities_analytic = []
for u, v, w in uvw_wavelength_array:
vis = 0.5 * np.dot(
jones,
np.conj(jones).T) * np.exp(2j * np.pi *
(u * src_l + v * src_m + w * src_n))
visibilities_analytic.append(
np.array([vis[0, 0], vis[1, 1], vis[1, 0], vis[0, 1]]))
print('pyuvsim uvws: ', np.around(uvws))
print('file uvws: ', np.around(hera_uv.uvw_array[0:hera_uv.Nbls]))
print('Difference: ', uvws - hera_uv.uvw_array[0:hera_uv.Nbls])
# the file used different phasing code than the test uses -- increase the tolerance
nt.assert_true(
np.allclose(uvws, hera_uv.uvw_array[0:hera_uv.Nbls], atol=1e-4))
print('Analytic visibility', visibilities_analytic)
print('Calculated visibility', visibilities)
print(np.array(visibilities) - np.array(visibilities_analytic))
# the file used different phasing code than the test uses -- increase the tolerance
nt.assert_true(np.allclose(visibilities, visibilities_analytic, atol=1e-4))
def test_redundant_baselines():
"""Check that two perfectly redundant baselines are truly redundant. """
hera_uv = UVData()
hera_uv.read_uvfits(EW_uvfits_file, ant_str='cross')
hera_uv.unphase_to_drift()
src_az = Angle('90.0d')
src_alt = Angle('85.0d')
src_za = Angle('90.0d') - src_alt
src_l = np.sin(src_az.rad) * np.sin(src_za.rad)
src_m = np.cos(src_az.rad) * np.sin(src_za.rad)
src_n = np.cos(src_za.rad)
time = Time(hera_uv.time_array[0], scale='utc', format='jd')
array_location = EarthLocation.from_geocentric(
hera_uv.telescope_location[0],
hera_uv.telescope_location[1],
hera_uv.telescope_location[2],
unit='m')
freq = hera_uv.freq_array[0, 0] * units.Hz
# get antennas positions into ENU
antpos, _ = hera_uv.get_ENU_antpos()
en_shift = [5., 5., 0]
antenna1 = pyuvsim.Antenna('ant1', 1, np.array(antpos[0, :]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array(antpos[1, :]), 0)
antenna3 = pyuvsim.Antenna('ant3', 3, np.array(antpos[0, :]) + en_shift, 0)
antenna4 = pyuvsim.Antenna('ant4', 4, np.array(antpos[1, :]) + en_shift, 0)
# setup the things that don't come from pyuvdata:
# make a source off zenith
time.location = array_location
source = create_offzenith_source(time, 'offzensrc', az=src_az, alt=src_alt)
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[100e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
baseline1 = pyuvsim.Baseline(antenna1, antenna2)
baseline2 = pyuvsim.Baseline(antenna3, antenna4)
print('Baseline1 uvw: ', baseline1.uvw)
print('Baseline2 uvw: ', baseline2.uvw)
print('Baseline1 enus: ', baseline1.antenna1.pos_enu,
baseline1.antenna2.pos_enu)
print('Baseline2 enus: ', baseline2.antenna1.pos_enu,
baseline2.antenna2.pos_enu)
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
task1 = pyuvsim.UVTask(source, time, freq, baseline1, array)
engine = pyuvsim.UVEngine(task1)
visibility1 = engine.make_visibility()
task2 = pyuvsim.UVTask(source, time, freq, baseline2, array)
engine = pyuvsim.UVEngine(task2)
visibility2 = engine.make_visibility()
nt.assert_true(np.allclose(visibility1, visibility2))
def test_source_below_horizon():
time = Time('2018-03-01 00:00:00', scale='utc')
array_location = EarthLocation(lat='-30d43m17.5s',
lon='21d25m41.9s',
height=1073.)
time.location = array_location
freq = (150e6 * units.Hz)
source = create_offzenith_source(time,
'src_down',
az=Angle('0d'),
alt=Angle('-40d'))
antenna1 = pyuvsim.Antenna('ant1', 1, np.array([0, 0, 0]), 0)
antenna2 = pyuvsim.Antenna('ant2', 2, np.array([107, 0, 0]), 0)
baseline = pyuvsim.Baseline(antenna1, antenna2)
beam = UVBeam()
beam.read_cst_beam(beam_files,
beam_type='efield',
frequency=[150e6, 123e6],
telescope_name='HERA',
feed_name='PAPER',
feed_version='0.1',
feed_pol=['x'],
model_name='E-field pattern - Rigging height 4.9m',
model_version='1.0')
beam_list = [beam]
array = pyuvsim.Telescope('telescope_name', array_location, beam_list)
task = pyuvsim.UVTask(source, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
visibility = engine.make_visibility()
nt.assert_true(np.allclose(visibility, np.array([0, 0, 0, 0])))
# redo with RA/Dec defined source
time = Time(2458098.27471265, format='jd')
time.location = array_location
source_coord = SkyCoord(ra=Angle('13h20m'),
dec=Angle('-30d43m17.5s'),
obstime=time,
frame='icrs',
location=array_location)
source = pyuvsim.Source('src_down', source_coord.ra, source_coord.dec,
freq, [1.0, 0, 0, 0])
task = pyuvsim.UVTask(source, time, freq, baseline, array)
engine = pyuvsim.UVEngine(task)
visibility = engine.make_visibility()
nt.assert_true(np.allclose(visibility, np.array([0, 0, 0, 0])))