reflectance

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

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 bretween 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)