py21cmsense.observatory.Observatory.grid_baselines

Observatory.grid_baselines(coherent: bool, frequency: Quantity, PhysicalType('frequency')] | None=None, integration_time: Quantity, PhysicalType('time')]=<Quantity 60. s>, observation_duration: Quantity, PhysicalType('time')] | None=None, phase_center_dec: Quantity, PhysicalType('angle')] | None=None, max_chunk_mem_gb: float = 1.0) → ndarray[source]

Grid baselines onto a pre-determined uvgrid, accounting for earth rotation.

Parameters:

  • coherent – Whether to coherently sum baselines within each uv cell, or incoherently sum them.

  • frequency – The frequency at which to grid the baselines. If not given, grids the baselines in bins of distance in meters.

  • integration_time (float or Quantity, optional) – The amount of time integrated into a snapshot visibility.

  • observation_duration (float or Quantity, optional) – Amount of time in a single (coherent) LST bin, assumed to be in minutes.

  • ndecimals (int, optional) – Number of decimals to which baselines must match to be considered redundant.

Returns:

array – Shape [n_baseline_groups, Nuv, Nuv]. The coherent sum of baselines within grid cells given by ugrid. One can treat different baseline groups independently, or sum over them.

Notes

The grid can either be in units of distance (meters) or in units of wavelengths, depending on the value of frequency. If frequency is None, the grid is in meters, which will yield the _same_ grid for all frequencies. If frequency is given, the grid is in units of wavelengths, and will be different for different frequencies (i.e. the grid will be constant in units of wavelengths, while the baselines themselves will change in units of wavelengths).

For calculating the power spectrum sensitivity in 21cmSense, it is sufficient to use the same grid in units of meters for all frequencies. In general this should only cause very slight differences in the results, and it has the advantage of being much faster to compute over many frequencies/redshifts.

If the Observatory object is being used to generate noise realizations for other purposes, it may be important to use a grid in units of wavelengths.

See also

grid_baselines_coherent

Coherent sum over baseline groups of the output of this method.

grid_baseline_incoherent

Incoherent sum over baseline groups of the output of this method.