cobi.simulation.Noise

class Noise(nside, fsky, telescope, sim='NC', atm_noise=False, nsplits=2, aso=False, verbose=True)[source]

Instrumental noise simulator for Simons Observatory telescopes.

This class generates realistic noise realizations for SO LAT and SAT observations based on the v3.1.1 noise models. Supports white noise, atmospheric/1f noise, and correlated noise between detector pairs within the same optical tube.

Parameters:

nside (int) – HEALPix resolution parameter.
fsky (float) – Sky fraction for noise power calculation (0 < fsky ≤ 1).
telescope ({'LAT', 'SAT'}) – Telescope identifier (Large Aperture or Small Aperture).
sim ({'NC', 'TOD'}, default 'NC') – Simulation type: - ‘NC’: Noise curves from SO models (analytic) - ‘TOD’: Time-ordered data based simulations (uses SO products)
atm_noise (bool, default False) – Include atmospheric and 1/f noise components.
nsplits (int, default 2) – Number of data splits (for split-based null tests).
verbose (bool, default True) – Enable logging output.
aso (bool)

nside

HEALPix resolution.

Type:: int

lmax

Maximum multipole (3*nside - 1).

Type:: int

sensitivity_mode

SO sensitivity mode (2 = baseline).

Type:: int

atm_noise

Whether atmospheric noise is included.

Type:: bool

Nell

Noise power spectra for each frequency and cross-frequency.

Type:: dict

telescope

Telescope identifier.

Type:: str

get_map(idx, freqs, fwhm, tube): Generate noise map realization for given configuration.

get_spectra(idx, freqs, fwhm, tube): Get noise power spectra for given configuration.

Examples

LAT baseline noise with atmosphere:

noise = Noise(
    nside=512,
    fsky=0.4,
    telescope='LAT',
    sim='NC',
    atm_noise=True,
    nsplits=2
)

# Generate noise for 6 LAT frequencies
freqs = np.array([27, 39, 93, 145, 225, 280])
fwhm = np.array([7.4, 5.1, 2.2, 1.4, 1.0, 0.9])
tube = np.array([0, 0, 1, 1, 2, 2])

noise_maps = noise.get_map(idx=0, freqs=freqs, fwhm=fwhm, tube=tube)

SAT white noise only:

noise_sat = Noise(
    nside=512,
    fsky=0.1,
    telescope='SAT',
    sim='NC',
    atm_noise=False
)

freqs = np.array([27, 39, 93, 145, 225, 280])
noise_maps = noise_sat.get_map(idx=0, freqs=freqs, fwhm=None, tube=None)

Notes

Uses SO v3.1.1 noise models (baseline sensitivity)
Correlated noise between frequency pairs in same tube
Supports independent realizations via idx parameter
MPI-aware for parallel generation
Output in μK_CMB units

__init__(nside, fsky, telescope, sim='NC', atm_noise=False, nsplits=2, aso=False, verbose=True)[source]

Initializes the Noise class for generating noise maps with or without atmospheric noise.

Parameters: nside (int): HEALPix resolution parameter. atm_noise (bool, optional): If True, includes atmospheric noise. Defaults to False. nhits (bool, optional): If True, includes hit count map. Defaults to False. nsplits (int, optional): Number of data splits to consider. Defaults to 2.

Parameters:

nside (int)
fsky (float)
telescope (str)
atm_noise (bool)
nsplits (int)
aso (bool)
verbose (bool)

Return type:

None

Methods

`__init__`(nside, fsky, telescope[, sim, ...])	Initializes the Noise class for generating noise maps with or without atmospheric noise.
`atm_noise_maps`(split, idx)	Generates atmospheric noise maps using Cholesky decomposition.
`atm_noise_maps_freq`(idx, freq)	Generates atmospheric noise maps using Cholesky decomposition.
`noiseQU`([idx])	Generates Q and U polarization noise maps based on the noise model.
`noiseQU_NC`(idx)	Generates Q and U polarization noise maps based on the noise model.
`noiseQU_NC_freq`(idx, freq)	Generates Q and U polarization noise maps for a specific frequency band.
`noiseQU_TOD`(idx)
`noiseQU_TOD_freq`(idx, freq)
`noiseQU_TOD_lat`(idx)
`noiseQU_TOD_lat_band`(idx, freq)
`noiseQU_TOD_sat`(idx)
`noiseQU_TOD_sat_band`(idx, freq)
`noiseQU_freq`(idx, freq)	Generates Q and U polarization noise maps for a specific frequency band.
`white_noise_maps`()
`white_noise_maps_freq`(freq)	Generates white noise maps for a specific frequency band.

Attributes

`cholesky_matrix_elements`	Computes the Cholesky matrix elements for the noise model.
`rand_alm`	Generates random spherical harmonic coefficients (alm) with a specified power spectrum.

__init__(nside, fsky, telescope, sim='NC', atm_noise=False, nsplits=2, aso=False, verbose=True)[source]

Initializes the Noise class for generating noise maps with or without atmospheric noise.

Parameters: nside (int): HEALPix resolution parameter. atm_noise (bool, optional): If True, includes atmospheric noise. Defaults to False. nhits (bool, optional): If True, includes hit count map. Defaults to False. nsplits (int, optional): Number of data splits to consider. Defaults to 2.

Parameters:

nside (int)
fsky (float)
telescope (str)
atm_noise (bool)
nsplits (int)
aso (bool)
verbose (bool)

Return type:

None

property rand_alm: numpy.ndarray

Generates random spherical harmonic coefficients (alm) with a specified power spectrum.

Returns: np.ndarray: A complex array of spherical harmonic coefficients.

property cholesky_matrix_elements: Tuple[numpy.ndarray, numpy.ndarray, numpy.ndarray, numpy.ndarray, numpy.ndarray, numpy.ndarray, numpy.ndarray, numpy.ndarray, numpy.ndarray]

Computes the Cholesky matrix elements for the noise model.

Returns: Tuple of nine np.ndarray elements representing the Cholesky matrix components.

white_noise_maps()[source]

Return type:: numpy.ndarray

white_noise_maps_freq(freq)[source]

Generates white noise maps for a specific frequency band.

Returns: np.ndarray: An array of white noise maps for the specified frequency band.

Parameters:: freq (str)
Return type:: numpy.ndarray

atm_noise_maps_freq(idx, freq)[source]

Generates atmospheric noise maps using Cholesky decomposition.

Returns: np.ndarray: An array of atmospheric noise maps for different frequency bands.

Parameters:

idx (int)
freq (str)

Return type:

numpy.ndarray

atm_noise_maps(split, idx)[source]

Generates atmospheric noise maps using Cholesky decomposition.

Returns: np.ndarray: An array of atmospheric noise maps for different frequency bands.

Return type:: numpy.ndarray

noiseQU_NC(idx)[source]

Generates Q and U polarization noise maps based on the noise model.

Returns: np.ndarray: An array of Q and U noise maps.

Return type:: numpy.ndarray

noiseQU_NC_freq(idx, freq)[source]

Generates Q and U polarization noise maps for a specific frequency band.

Returns: np.ndarray: An array of Q and U noise maps for the specified frequency band.

Parameters:

idx (int)
freq (str)

Return type:

numpy.ndarray

noiseQU_TOD_sat(idx)[source]

Parameters:: idx (int)
Return type:: numpy.ndarray

noiseQU_TOD_lat(idx)[source]

Parameters:: idx (int)
Return type:: numpy.ndarray

noiseQU_TOD_sat_band(idx, freq)[source]

Parameters:

idx (int)
freq (str)

Return type:

numpy.ndarray

noiseQU_TOD_lat_band(idx, freq)[source]

Parameters:

idx (int)
freq (str)

Return type:

numpy.ndarray

noiseQU_TOD(idx)[source]

Parameters:: idx (int)
Return type:: numpy.ndarray

noiseQU_TOD_freq(idx, freq)[source]

Parameters:

idx (int)
freq (str)

Return type:

numpy.ndarray

noiseQU(idx=None)[source]

Generates Q and U polarization noise maps based on the noise model.

Returns: np.ndarray: An array of Q and U noise maps.

Parameters:: idx (int | None)
Return type:: numpy.ndarray

noiseQU_freq(idx, freq)[source]

Generates Q and U polarization noise maps for a specific frequency band.

Returns: np.ndarray: An array of Q and U noise maps for the specified frequency band.

Parameters:

idx (int)
freq (str)

Return type:

numpy.ndarray