AtmosphericExtinction (module)

class ExtinctionModel(lbda=None, ozoneTemplate=None, lrefAero=10000.0)

Extinction model, from:

Parameters:

• lbda – wavelength vector [AA] (default to extended optical range)
• ozoneTemplate – name of the ozone template table (see readOzoneTemplate()). By default, use the provided ozone template.
• lrefAero – aerosol reference wavelength [AA]

setParams(pars, dpars=None)

Set physical extinction parameters: pressure, ozone column density [Dobson units], aerosol optical depth at reference wavelength and aerosol angstrom exponent.

Parameters:

• pars –

  extinction parameters (pr, oi, ai, ap) where:

  • pr: surface pressure [mbar]
  • oi: ozone intensity [Dobson units]
  • ai: aerosol optical depth at reference wavelength
  • ap: aerosol angstrom exponent
• dpars – associated standard errors

The total atmospheric extinction will then be the sum of three components:

• Rayleigh extinction: pr[mbar] * HT74(1 mbar)
• Ozone extinction: oi[DU] * OzoneTemplate(1 DU)
• Aerosol extinction: ai/EXT2OPT * (lbda/lRef)**(-ap)

Note

if ndim(dpars)==2, dpars is considered as the covariance matrix of input extinction parameters. Therefore, when ndim(dpars)==1, self.extinctionErrors(pars, dpars) is equivalent to self.extinctionErrors(pars, N.diag(dpars)**2) (note the square power).

setDefaultParams(location='Mauna Kea')

Set default physical extinction parameters from predefined location.

Parameters:location – predefined location.

Parameter	Value ± Error
Mauna Kea
Pressure	616 ± 2 mbar
Ozone column	257 ± 23 DU
Aerosols optical depth @ 1 micron	0.0076 ± 0.0014
Aerosols angstrom exponent	1.26 ± 1.33

extinctionComponents()

Compute extinction individual components from extinction parameters (see setParams())

Returns:extinction components 2D-array [rayleigh,ozone,aerosols]

extinctionErrors()

Compute total extinction (diagonal) standard error from extinction parameters and associated standard errors (see setParams())

Returns:total extinction standard error

extinction(pars=None, dpars=None, components=False)

Compute total extinction (and associated standard error) from extinction parameters (and associated standard errors).

Parameters:

• pars – extinction parameters (see setParams())
• dpars – extinction parameter errors (see setParams())
• components – return individual extinction components if True

Returns:

2D-array [ext,dext,[components]]

jac()

Jacobian of total extinction with respect to extinction parameters.

Returns:jacobian 2D-array (nparam=4,nlbda)

static rayleigh_HT74(lbda, pressure)

Rayleigh extinction from Hansen & Travis (1974).

Parameters:

• lbda – wavelength vector [AA]
• pressure – effective surface pressure [mbar]

Returns:

Rayleigh extinction [mag/airmass]

write(outname, ext=None, format='txt')

Write extinction curve in output file.

Parameters:

• outname – output filename
• ext – explicit extinction curve(s) to be written out
• format – output file format (‘txt’ or ‘fits’)

plot(ext=None, ax=None, components=True, transmission=False)

Plot the atmospheric extinction/transmission and its physical components.

Parameters:

• ext – extinctions to be plotted (or None)
• ax – matplotlib Axes instance (or None)
• components – display individual components if True
• transmission – display transmission rather than extinction

Returns:

matplotlib Axes instance

readOzoneTemplate(ozoneName, lbda, colLbda='LAMBDA', colTrans='OZONE', ext=1)

Read ozone transmission template, interpolate over wavelengthes, and convert to extinction [mag/airmass].

Parameters:

• ozoneName – input FITS table, with columns colLbda (wavelength in AA) and colTrans (fractional transmission), and key ‘REFO3COL’ specifing the reference ozone column density [DU]
• lbda – output wavelengthes [AA]
• colLbda – name of the wavelength (in AA) column
• colTrans – name of the ozone transmission column
• ext – extension in which to look for wavelength and transmission columns

Returns:

ozone extinction [mag/airmass], refO3col

createTable(arrays, names, units=None, formats=None, keywords=(), extname=None)

Create a FITS-table from a set of arrays.

Parameters:

• arrays – list of input arrays (ncols,)
• names – list of column names (ncols,)
• units – list of column units (ncols,) (‘none’ by default)
• formats – list of column formats (ncols,) (‘1E’ by default)
• keywords – list of keys (key,val[,comment]) to add to table header
• extname – name of the binary table extension

Returns:

table HDU