Planetary spectra for anisotropic scattering
Abstract
We examine here some of the effects on planetary spectra that would be produced by departures from isotropic scattering. The phase function ∼gw(1 + a cosθ) is the simplest departure to handle analytically and the only phase function, other than the isotropic one, that can be incorporated into a Chandrasekhar first approximation. This approach has the advantage of illustrating effects resulting from anisotropies while retaining the simplicity that yields analytic solutions. The curve of growth is the sine qua non of planetary spectroscopy. Our discussion emphasizes the difficulties and importance of ascertaining curves of growth as functions of observing geometry. A plea is made to observers to analyze their empirical curves of growth, whenever it seems feasible, in terms of coefficients of (1 ∼gw) ^{1/2} and (1 ∼gw) , which are the leading terms in radiativetransfer analysis. An algebraic solution to the two sets of anisotropic H functions is developed in the appendix. It is readily adaptable to programmable desk calculators and gives emergent intensities accurate to 0.3%, which is sufficient even for spectroscopic analysis.
 Publication:

Planetary and Space Science
 Pub Date:
 October 1976
 DOI:
 10.1016/00320633(76)900088
 Bibcode:
 1976P&SS...24..967C
 Keywords:

 Absorption Spectra;
 Astronomical Spectroscopy;
 Electromagnetic Scattering;
 Planetary Radiation;
 Chandrasekhar Equation;
 Continuous Radiation;
 Forward Scattering;
 Radiative Transfer;
 Lunar and Planetary Exploration