sirius.simulation

simulation(point_source_flux, point_source_ra_dec, pointing_ra_dec, phase_center_ra_dec, phase_center_names, beam_parms, beam_models, beam_model_map, uvw_parms, tel_xds, time_xda, chan_xda, pol, noise_parms, save_parms)

Creates a dask graph that computes a simulated measurement set and triggers a compute and saves the ms to disk.

Parameters

• point_source_flux (float np.array, [n_point_sources,n_time, n_chan, n_pol], (singleton: n_time, n_chan), Janskys) – The flux of the point sources.

• point_source_ra_dec (float np.array, [n_time, n_point_sources, 2], (singleton: n_time), radians) – The position of the point sources.

• pointing_ra_dec (float np.array, [n_time, n_ant, 2], (singleton: n_time, n_ant), radians) – Pointings of antennas, if they are different from the phase center. Set to None if no pointing offsets are required.

• phase_center_ra_dec (float np.array, [n_time, 2], (singleton: n_time), radians) – Phase center of array.

• phase_center_names (str np.array, [n_time], (singleton: n_time)) – Strings that are used to label phase centers.

• beam_parms (dict) –

• beam_parms['mueller_selection'] (int np.array, default=np.array([ 0, 5, 10, 15])) – The elements in the 4x4 beam Mueller matrix to use. The elements are numbered row wise. For example [ 0, 5, 10, 15] are the diagonal elements.

• beam_parms['pa_radius'] (float, default=0.2, radians) – The change in parallactic angle that will trigger the calculation of a new beam when using Zernike polynomial aperture models.

• beam_parms['image_size'] (int np.array, default=np.array([1000,1000])) – Size of the beam image generated from the Zernike polynomial coefficients.

• beam_parms['fov_scaling'] (int, default=15) – Used to scale the size of the beam image which is given fov_scaling*(1.22 *c/(dish_diam*frequency)).

• beam_parms['zernike_freq_interp'] (str, default='nearest', options=['linear', 'nearest', 'zero', 'slinear', 'quadratic', 'cubic']) – What interpolation method to use for Zernike polynomial coefficients.

• beam_models (list) – List of beam models to use. Beam models can be any combination of function parameter dictionaries, image xr.Datasets or Zernike polynomial coefficient xr.Datasets.

• beam_model_map (int np.array, [n_ant]) – Each element in beam_model_map is an index into beam_models.

• uvw_parms (dict) –

• uvw_parms['calc_method'] (str, default='astropy', options=['astropy','casa']) – Astropy coordinates or CASA tool measures can be used to calculate uvw coordinates.

• uvw_parms['auto_corr'] (bool, default=False) – If True autocorrelations are also calculated.

• tel_xds (xr.Dataset) – An xarray dataset of the radio telescope array layout (see zarr files in sirius_data/telescope_layout/data/ for examples).

• time_xda (xr.DataArray) – Time series xarray array.

• chan_xda (xr.DataArray) – Channel frequencies xarray array.

• pol (int np.array) – Must be a subset of [‘RR’,’RL’,’LR’,’LL’] => [5,6,7,8] or [‘XX’,’XY’,’YX’,’YY’] => [9,10,11,12].

• noise_parms (dict) – Set various system parameters from which the thermal (ie, random additive) noise level will be calculated. See https://casadocs.readthedocs.io/en/stable/api/tt/casatools.simulator.html#casatools.simulator.simulator.setnoise.

• noise_parms['mode'] (str, default='tsys-manuel', options=['simplenoise','tsys-manuel','tsys-atm']) – Currently only ‘tsys-manuel’ is implemented.

• noise_parms['t_atmos'] (, float, default = 250.0, Kelvin) – Temperature of atmosphere (mode=’tsys-manual’)

• noise_parms['tau'] (float, default = 0.1) – Zenith Atmospheric Opacity (if tsys-manual). Currently the effect of Zenith Atmospheric Opacity (Tau) is not included in the noise modeling.

• noise_parms['ant_efficiency'] (float, default=0.8) – Antenna efficiency

• noise_parms['spill_efficiency'] (float, default=0.85) – Forward spillover efficiency.

• noise_parms['corr_efficiency'] (float, default=0.88) – Correlation efficiency.

• noise_parms['t_receiver'] (float, default=50.0, Kelvin) – Receiver temp (ie, all non-atmospheric Tsys contributions).

• noise_parms['t_ground'] (float, default=270.0, Kelvin) – Temperature of ground/spill.

• noise_parms['t_cmb'] (float, default=2.725, Kelvin) – Cosmic microwave background temperature.

• save_parms (dict) –

• save_parms['mode'] (str, default='dask_ms_and_sim_tool', options=['lazy','zarr','dask_ms_and_sim_tool','zarr_convert_ms','dask_ms','cngi']) –

• save_parms['DAG_name_vis_uvw_gen'] (str, default=False) – Creates a DAG diagram png, named save_parms[‘DAG_name_write’], of how the visibilities and uvw coordinates are calculated.

• save_parms['DAG_name_write'] (str, default=False) – Creates a DAG diagram png, named save_parms[‘DAG_name_write’], of how the ms is created with name.

• save_parms['ms_name'] (str, default='sirius_sim.ms') – If save_parms[‘mode’]=’zarr’ the name sirius_sim.vis.zarr will be used.

Returns

ms_xds

Return type

xr.Dataset

simulation_chunk(point_source_flux, point_source_ra_dec, pointing_ra_dec, phase_center_ra_dec, beam_parms, beam_models, beam_model_map, uvw_parms, tel_xds, time_chunk, chan_chunk, pol, noise_parms, uvw_precompute=None)

Simulates uvw coordinates, interferometric visibilities and adds noise. This function does not produce a measurement set.

Parameters

• point_source_flux (float np.array, [n_point_sources,n_time, n_chan, n_pol], (singleton: n_time, n_chan), Janskys) – The flux of the point sources.

• point_source_ra_dec (float np.array, [n_time, n_point_sources, 2], (singleton: n_time), radians) – The position of the point sources.

• pointing_ra_dec (float np.array, [n_time, n_ant, 2], (singleton: n_time, n_ant), radians) – Pointings of antennas, if they are different from the phase center. Set to None if no pointing offsets are required.

• phase_center_ra_dec (float np.array, [n_time, 2], (singleton: n_time), radians) – Phase center of array.

• beam_parms (dict) –

• beam_parms['mueller_selection'] (int np.array, default=np.array([ 0, 5, 10, 15])) – The elements in the 4x4 beam Mueller matrix to use. The elements are numbered row wise. For example [ 0, 5, 10, 15] are the diagonal elements.

• beam_parms['pa_radius'] (float, default=0.2, radians) – The change in parallactic angle that will trigger the calculation of a new beam when using Zernike polynomial aperture models.

• beam_parms['image_size'] (int np.array, default=np.array([1000,1000])) – Size of the beam image generated from the Zernike polynomial coefficients.

• beam_parms['fov_scaling'] (int, default=15) – Used to scale the size of the beam image, which is given by fov_scaling*(1.22 *c/(dish_diam*frequency)).

• beam_parms['zernike_freq_interp'] (str, default='nearest', options=['linear', 'nearest', 'zero', 'slinear', 'quadratic', 'cubic']) – What interpolation method to use for Zernike polynomial coefficients.

• beam_models (list) – List of beam models to use. Beam models can be any combination of function parameter dictionaries, image xr.Datasets or Zernike polynomial coefficient xr.Datasets.

• beam_model_map (int np.array, [n_ant]) – Each element in beam_model_map is an index into beam_models.

• uvw_parms (dict) –

• uvw_parms['calc_method'] (str, default='astropy', options=['astropy','casa']) – Astropy coordinates or CASA tool measures can be used to calculate uvw coordinates.

• uvw_parms['auto_corr'] (bool, default=False) – If True autocorrelations are also calculated.

• tel_xds (xr.Dataset) – An xarray dataset of the radio telescope array layout (see zarr files in sirius_data/telescope_layout/data/ for examples).

• time_chunk (str np.array, [n_time], 'YYYY-MM-DDTHH:MM:SS.SSS') – Time series. Example ‘2019-10-03T19:00:00.000’.

• chan_chunk (float np.array, [n_chan], Hz) – Channel frequencies.

• pol (int np.array) – Must be a subset of [‘RR’,’RL’,’LR’,’LL’] => [5,6,7,8] or [‘XX’,’XY’,’YX’,’YY’] => [9,10,11,12].

• noise_parms (dict) – Set various system parameters from which the thermal (ie, random additive) noise level will be calculated. See https://casadocs.readthedocs.io/en/stable/api/tt/casatools.simulator.html#casatools.simulator.simulator.setnoise.

• noise_parms['mode'] (str, default='tsys-manuel', options=['simplenoise','tsys-manuel','tsys-atm']) – Currently only ‘tsys-manuel’ is implemented.

• noise_parms['t_atmos'] (, float, default = 250.0, Kelvin) – Temperature of atmosphere (mode=’tsys-manual’)

• noise_parms['tau'] (float, default = 0.1) – Zenith Atmospheric Opacity (if tsys-manual). Currently the effect of Zenith Atmospheric Opacity (Tau) is not included in the noise modeling.

• noise_parms['ant_efficiency'] (float, default=0.8) – Antenna efficiency

• noise_parms['spill_efficiency'] (float, default=0.85) – Forward spillover efficiency.

• noise_parms['corr_efficiency'] (float, default=0.88) – Correlation efficiency.

• noise_parms['t_receiver'] (float, default=50.0, Kelvin) – Receiver temp (ie, all non-atmospheric Tsys contributions).

• noise_parms['t_ground'] (float, default=270.0, Kelvin) – Temperature of ground/spill.

• noise_parms['t_cmb'] (float, default=2.725, Kelvin) – Cosmic microwave background temperature.

Returns

• vis (complex np.array, [n_time,n_baseline,n_chan,n_pol]) – Visibility data.

• uvw (float np.array, [n_time,n_baseline,3]) – Spatial frequency coordinates.

• weight (complex np.array, [n_time,n_baseline,n_pol]) – Data weights.

• sigma (complex np.array, [n_time,n_baseline,n_pol]) – RMS noise of data.

• t_arr (float np.array, [4]) – Timing infromation: calculate uvw, evaluate_beam_models, calculate visibilities, calculate additive noise.