HG12

class sbpy.photometry.HG12(H=8, G12=0.3, **kwargs)

Bases: HG12BaseClass

HG12 photometric phase model (Muinonen et al. 2010)

This system is adopted by IAU as the “standard” model for disk-integrated phase functions of planetary objects. Note that there is a discontinuity in the derivative for parameter G12, sometimes making the model fitting difficult. Penttil”a et al. (2016, Planet. Space Sci. 123, 117-125) revised the H, G12 system such that the G12 parameter has a continuous derivative. The revised model is implemented in class G12_Pen16.

Examples

>>> # Define the phase function for Themis with
>>> # H = 7.121, G12 = 0.68
>>>
>>> import astropy.units as u
>>> from sbpy.calib import solar_fluxd
>>> from sbpy.photometry import HG12
>>> themis = HG12(7.121 * u.mag, 0.68, radius = 100 * u.km, wfb = 'V')
>>> with solar_fluxd.set({'V': -26.77 * u.mag}):
...     print('geometric albedo = {0:.4f}'.format(themis.geomalb))
...     print('phase integral = {0:.4f}'.format(themis.phaseint))
geometric albedo = 0.0622
phase integral = 0.3949

Initialize DiskIntegratedPhaseFunc

Parameters:

radiusastropy.units.Quantity, optional

Radius of object. Required if conversion between magnitude and reflectance is involved.

wfbQuantity, SpectralElement, string

Wavelengths, frequencies, or bandpasses. Bandpasses may be a filter name (string). Required if conversion between magnitude and reflectance is involved.

**kwargsoptional parameters accepted by

astropy.modeling.Model.__init__()

Attributes Summary

G12
H
param_names	Names of the parameters that describe models of this type.

Methods Summary

evaluate(ph, h, g12)	Evaluate the model on some input variables.
fit_deriv(ph, h, g12)

Attributes Documentation

G12 = Parameter('G12', value=0.3, bounds=[-0.0818919, 0.909714])

H = Parameter('H', value=8.0)

param_names = ('H', 'G12')

Names of the parameters that describe models of this type.

The parameters in this tuple are in the same order they should be passed in when initializing a model of a specific type. Some types of models, such as polynomial models, have a different number of parameters depending on some other property of the model, such as the degree.

When defining a custom model class the value of this attribute is automatically set by the Parameter attributes defined in the class body.

Methods Documentation

static evaluate(ph, h, g12)

Evaluate the model on some input variables.

static fit_deriv(ph, h, g12)