py21cmsense.observation.Observation¶
-
class
py21cmsense.observation.Observation(*, observatory, hours_per_day=6, obs_duration=NOTHING, integration_time=60, n_channels=82, bandwidth=8, n_days=180, bl_min=0, bl_max=inf, redundancy_tol=1, coherent=True, spectral_index=2.6, tsky_amplitude=260000, tsky_ref_freq=150, uv_cov=None)[source]¶ A class defining an interferometric Observation.
- Parameters
observatory (
Observatory) – An object defining attributes of the observatory itself (its location etc.)hours_per_day (float or Quantity, optional) – The number of good observing hours per day. This corresponds to the size of a low-foreground region in right ascension for a drift scanning instrument. The total observing time is n_days*hours_per_day. Default is 6. If simulating a tracked scan, hours_per_day should be a multiple of the length of the track (i.e. for two three-hour tracks per day, hours_per_day should be 6).
obs_duration (float or Quantity, optional) – The time assigned to a single LST bin, by default the time it takes for a source to travel through the beam’s FWHM. If a float, assumed to be in minutes.
integration_time (float or Quantity, optional) – The amount of time integrated into a single visibility, by default a minute. If a float, assumed to be in seconds.
n_channels (int, optional) – Number of channels used in the observation. Defaults to 82, which is equivalent to 1024 channels over 100 MHz of bandwidth. Sets maximum k_parallel that can be probed, but little to no overall effect on sensitivity.
bandwidth (float or Quantity, optional) – The bandwidth used for the observation, assumed to be in MHz. Note this is not the total instrument bandwidth, but the redshift range that can be considered co-eval.
n_days (int, optional) – The number of days observed (for the same set of LSTs). The default is 180, which is the maximum a particular R.A. can be observed in one year if one only observes at night. The total observing time is n_days*hours_per_day.
bl_min (float, optional) – Set the minimum baseline (in meters) to include in the uv plane.
bl_max (float, optional) – Set the maximum baseline (in meters) to include in the uv plane.
redundancy_tol (int, optional) – The number of decimal places to which baseline vectors must match (in all dimensions) to be considered redundant.
coherent (bool, optional) – Whether to add different baselines coherently if they are not instantaneously redundant.
spectral_index (float, optional) – The spectral index of the foreground model. The foreground model is approximated as a spatially-independent power-law, and used only for generating sky noise temperature. The default is 2.6, based on Mozdzen et al. 2017: 2017MNRAS.464.4995M, figure 8, with Galaxy down (see also tsky_amplitude and tsky_ref_freq).
tsky_amplitude (float or Quantity, optional) – The temperature of foregrounds at tsky_ref_freq. See spectral_index. Default assumed to be in mK.
tsky_ref_freq (float or Quantity) – Frequency at which the foreground model is equal to tsky_amplitude. See spectral_index. Default assumed to be in MHz.
Methods
__init__(self, \*, observatory[, …])Initialize self.
clone(self, \*\*kwargs)Create a new instance of this instance, but with arbitrary changes to parameters.
from_yaml(yaml_file)Attributes
The effective radiometric noise temperature per UV bin (i.e.
Temperature of the sky at the default frequency
System temperature (i.e.
A dictionary of redundant baseline groups.
Frequency of the observation
1D array of kparallel values, defined by the bandwidth and number of channels.
Number of LST bins in the complete observation.
Central redshift of the observation
The total (effective) integration time over UV bins for a particular LST bin.
Centres of the linear grid which defines a side of the UV grid corresponding to
uv_coverage()and its derivative quantities.A 2D array specifying the effective number of baselines in a grid of UV, after earth rotation synthesis for a particular LST bin.