Halley-Marcus composite dust phase function.
The Halley-Marcus phase function was first used by Schleicher and Bair (2011), but only described in detail by Schleicher and Marcus (May 2010) online at:
“To distinguish this curve from others, we designate this as the HM phase function, for the sources of the two components: Halley and Marcus, where the Halley curve for smaller phase angles comes from our previous work (Schleicher et al. 1998) while Joe Marcus has fit a Henyey-Greenstein function to a variety of mid- and large-phase angle data sets (Marcus 2007); see here for details. Note that we do not consider our composite curve to be a definitive result, but rather appropriate for performing first-order adjustments to dust measurements for changing phase angle.”
Schleicher & Bair 2011, AJ 141, 177. Schleicher, Millis, & Birch 1998, Icarus 132, 397-417. Marcus 2007, International Comets Quarterly 29, 39-66.
>>> from sbpy.activity import phase_HalleyMarcus >>> import astropy.units as u >>> phase_HalleyMarcus(0 * u.deg) 1.0 >>> phase_HalleyMarcus(15 * u.deg) 5.8720e-01