Forward scatter

In telecommunication and astronomy, forward scatter is the deflection—by diffraction, nonhomogeneous refraction, or nonspecular reflection by particulate matter of dimensions that are large with respect to the wavelength in question but small with respect to the beam diameter—of a portion of an incident electromagnetic wave, in such a manner that the energy so deflected propagates in a direction that is within 90° of the direction of propagation of the incident wave (i.e., the phase angle is greater than 90°).
The scattering process may be polarization-sensitive, i.e., incident waves that are identical in every respect but their polarization may be scattered differently.
Comets
Forward scattering can make a back-lit comet appear significantly brighter because the dust and ice crystals are reflecting and enhancing the apparent brightness of the comet by scattering that light towards the observer. Comets studied forward-scattering in visible-thermal...