reflectance

sbpy.units.reflectance(wfb, cross_section=None, reflectance=None, **kwargs)

Reflectance related equivalencies.

Supports conversion from/to reflectance and scattering cross-section to/from total flux or magnitude at 1 au for both heliocentric and observer distances. Uses sbpy’s photometric calibration system: solar_spectrum and solar_fluxd.

Spectral flux density equivalencies for Vega are automatically used, if possible. Dimensionless logarithmic units are also supported if the corresponding solar value is set by set.

Parameters:

wfbastropy.units.Quantity, synphot.SpectralElement, string

Wavelength, frequency, or a bandpass corresponding to the flux density being converted.

cross_sectionastropy.units.Qauntity, optional

Total scattering cross-section. One of cross_section or reflectance is required.

reflectanceastropy.units.Quantity, optional

Average reflectance. One of cross_section or reflectance is required.

**kwargs

Keyword arguments for observe().

Returns:

equivlist

List of equivalencies

Examples

Convertion between scattering cross-section and reflectance >>> import numpy as np >>> from astropy import units as u >>> from sbpy.units import reflectance, VEGAmag, spectral_density_vega >>> from sbpy.calib import solar_fluxd, vega_fluxd >>> >>> solar_fluxd.set({‘V’: -26.77471503 * VEGAmag}) … # doctest: +IGNORE_OUTPUT >>> vega_fluxd.set({‘V’: 3.5885e-08 * u.Unit(‘W / (m2 um)’)}) … # doctest: +IGNORE_OUTPUT >>> mag = 3.4 * VEGAmag >>> cross_sec = np.pi * (460 * u.km)**2 >>> ref = mag.to(‘1/sr’, reflectance(‘V’, cross_section=cross_sec)) >>> print(‘{0:.4f}’.format(ref)) 0.0287 1 / sr >>> mag1 = ref.to(VEGAmag, reflectance(‘V’, cross_section=cross_sec)) >>> print(‘{0:.2f}’.format(mag1)) 3.40 mag(VEGA)

>>> # Convertion between magnitude and scattering cross-section
>>> ref = 0.0287 / u.sr
>>> cross_sec = mag.to('km2', reflectance('V', reflectance=ref))
>>> radius = np.sqrt(cross_sec/np.pi)
>>> print('{0:.2f}'.format(radius))
459.69 km
>>> mag2 = cross_sec.to(VEGAmag, reflectance('V', reflectance=ref))
>>> print('{0:.2f}'.format(mag2))
3.40 mag(VEGA)