Atmosphere

class specsim.atmosphere.Atmosphere(wavelength, surface_brightness_dict, extinction_coefficient, extinct_emission, condition, airmass, seeing, moon)

Bases: object

Model atmospheric surface brightness and extinction.

A simulation uses only our read-only surface_brightness and extinction attributes. Use the condition and airmass attributes to update this model. Refer to the moon model for details on updating the optional scattered moon model.

Parameters:

wavelengthastropy.units.Quantity

Array of wavelengths with units where data is tabulated.

surface_brightness_dictdict

Dictionary of tabulated sky emission surface brightness values. Each dictionary key defines a possible sky condition.

extinction_coefficientarray

Array of extinction coefficients tabulated on wavelength.

extinct_emissionbool

If set, atmospheric extinction is applied to sky emission.

conditionstr

Sky emission condition to use, which must be one of the keys of surface_brightness_dict.

seeingdict or None

Dictionary of seeing PSF parameters to use which must contain keys “fwhm_ref”, “wlen_ref” and “moffat_beta”. Seeing is used to define the atmospheric PSF, which is only used when instrument.fiberloss_method equals “galsim”.

airmassfloat

Airmass of the observation.

moonMoon or None

Model to use for scattered moonlight.

Attributes Summary

airmass	float: Observing airmass.
condition	str: Sky emission condition.
condition_names	list: The list of valid sky condition names.
extinction	numpy.ndarray: The extinction factor for the current model airmass.
moon	Moon or None: Model of scattered moonlight.
seeing_fwhm_ref	float: FWHM zenith seeing at seeing_wlen_ref.
seeing_moffat_beta	float: Beta parameter for atmospheric Moffat profile.
seeing_wlen_ref	float: Reference wavelength for seeing_fwhm_ref
surface_brightness	astropy.units.Quantity: Total sky surface brightness.

Methods Summary

get_seeing_fwhm(wavelength)	Calculate the seeing FWHM at the specified wavelength.
plot()	Plot a summary of this atmosphere model.

Attributes Documentation

airmass

float: Observing airmass.

Changes to this value automatically propagate to our scattered moon model, if there is one.

condition

str: Sky emission condition.

Must be one of the predefined names in condition_names.

condition_names

list: The list of valid sky condition names.

The valid names are keys of the atmosphere.sky.table.paths node, or “default” if only a single path is specified via a atmosphere.sky.table.path node.

extinction

numpy.ndarray: The extinction factor for the current model airmass.

Tabulated as a function of wavelength. Changes to airmass automatically update these values.

moon

Moon or None: Model of scattered moonlight.

See Moon for details on changing scattered moon simulation parameters via this attribute.

seeing_fwhm_ref

float: FWHM zenith seeing at seeing_wlen_ref.

Returns None if no seeing has been specified.

seeing_moffat_beta

float: Beta parameter for atmospheric Moffat profile.

Returns None if no seeing has been specified.

seeing_wlen_ref

float: Reference wavelength for seeing_fwhm_ref

Returns None if no seeing has been specified.

surface_brightness

astropy.units.Quantity: Total sky surface brightness.

Includes both dark sky emission and (if configured) scattered moonlight. Changes to condition or airmass are reflected here.

Methods Documentation

get_seeing_fwhm(wavelength)

Calculate the seeing FWHM at the specified wavelength.

Assumes that seeing scales with wavelength with a power -1/5, as predicted by Kolmogorov turbulence theory.

Parameters:

wavelengthastropy.units.Quantity

Wavelength in units convertible to Angstroms.

Returns:

astropy.units.Quantity

Full-width half maximum of seeing distribution at the specified wavelength, in on-sky angular units.

plot()

Plot a summary of this atmosphere model.

Requires that the matplotlib package is installed.