def make_vis_data(name, sky0, ra_deg, dec_deg, max_radius_deg, length_sec,
num_time_steps, num_channels):
"""Generates visibility data."""
settings_dict = {
'simulator': {
'max_sources_per_chunk': '2000'
},
'observation': {
'length': str(length_sec),
'num_time_steps': str(num_time_steps),
'start_frequency_hz': '140e6',
'frequency_inc_hz': '1e6',
'num_channels': str(num_channels),
'phase_centre_ra_deg': str(ra_deg),
'phase_centre_dec_deg': str(dec_deg)
},
'telescope': {
'input_directory': 'SKA1-LOW_SKO-0000422_Rev3_38m.tm',
'pol_mode': 'Scalar'
},
'interferometer': {
'channel_bandwidth_hz': '100e3',
'time_average_sec': '1.0',
'max_time_samples_per_block': '4',
'ms_filename': 'sim_' + name + '.ms',
'oskar_vis_filename': 'sim_' + name + '.vis'
}
}
settings = oskar.SettingsTree('oskar_sim_interferometer')
settings.from_dict(settings_dict)
settings['observation/start_time_utc'] = get_start_time(ra_deg, length_sec)
sky = make_sky_model(sky0, settings, max_radius_deg)
sky.save('sky_' + name + '.txt')
sim = oskar.Interferometer(settings=settings)
sim.set_sky_model(sky)
sim.run()
16,
5,
precision=precision)
sky.append_sources(phase_centre_ra_deg, phase_centre_dec_deg, 1.0)
# Set up the telescope model.
tel = oskar.Telescope(precision)
tel.set_channel_bandwidth(100e3)
tel.set_time_average(10.0)
tel.set_pol_mode('Scalar')
tel.load('SKA1-LOW_v5_single_random.tm')
# Set station properties after stations have been defined.
tel.set_phase_centre(phase_centre_ra_deg, phase_centre_dec_deg)
tel.set_station_type('Isotropic')
# Set up the basic simulator and run simulation.
simulator = oskar.Interferometer(precision)
simulator.set_settings_path(os.path.abspath(__file__))
simulator.set_max_sources_per_chunk(sky.num_sources + 1)
simulator.set_sky_model(sky)
simulator.set_telescope_model(tel)
simulator.set_observation_frequency(frequency_hz)
simulator.set_observation_time(start_time_mjd_utc=51544.375,
length_sec=10800.0,
num_time_steps=180)
simulator.set_output_measurement_set(filename)
start = time.time()
simulator.run()
print('Simulation for %05.1f MHz completed after %.3f seconds.' %
(frequency_hz / 1e6, time.time() - start))
settings.from_dict(params)
# Set the numerical precision to use.
precision = 'single'
if precision == 'single':
settings['simulator/double_precision'] = 'false'
# Create a sky model containing three sources from a numpy array.
sky_data = numpy.array(
[[20.0, -30.0, 1, 0, 0, 0, 100.0e6, -0.7, 0.0, 0, 0, 0],
[20.0, -30.5, 3, 2, 2, 0, 100.0e6, -0.7, 0.0, 600, 50, 45],
[20.5, -30.5, 3, 0, 0, 2, 100.0e6, -0.7, 0.0, 700, 10, -10]])
sky = oskar.Sky.from_array(sky_data, precision) # Pass precision here.
# Set the sky model and run the simulation.
sim = oskar.Interferometer(settings=settings)
sim.set_sky_model(sky)
sim.run()
# Make an image 4 degrees across and return it to Python.
# (It will also be saved with the filename 'example_I.fits'.)
imager = oskar.Imager(precision)
imager.set(fov_deg=4, image_size=512)
imager.set(input_file='example.vis', output_root='example')
output = imager.run(return_images=1)
image = output['images'][0]
# Render the image using matplotlib and save it as a PNG file.
im = plt.imshow(image, cmap='jet')
plt.gca().invert_yaxis()
plt.colorbar(im)