pipecal_rratio

sofia_redux.calibration.pipecal_rratio.pipecal_rratio(za, altwv, za_ref, altwv_ref, za_coeff, altwv_coeff, pwv=False)[source]

Calculate the R ratio for a given ZA and Altitude or PWV.

The R ratio is used to correct image flux values from the observed atmospheric conditions to a reference atmospheric condition. This is required before applying calibration factors calculated at the reference atmosphere.

The procedure is:

  1. Calculate the ZA term from the polynomial coefficients and sec(ZA) - sec(ZAref).

  2. Calculate the altitude or PWV term from the polynomial coefficients and log(PWV) - log(PWVref), or ALT - ALTref.

  3. Multiply the terms together and return the result.

Parameters:
zafloat

Observed zenith angle (degrees).

altwvfloat

Observed altitude (kilo-feet) or precipitable water vapor (um).

za_reffloat

Reference ZA used to calculate response fits (degrees).

altwv_reffloat

Reference altitude (kilo-feet) or PWV (um) used to calculate response fits.

za_coefflist of float

Polynomial coefficients of response fit in ZA.

altwv_coefflist of float

Polynomial coefficients of response fit in altitude or PWV.

pwvbool, optional

If set, the water vapor response fit is used instead of the altitude fit, and altwv is treated as a water vapor value.

Returns:
rratiofloat

R ratio at observed ZA and altitude/PWV.