Earth) or last quarter (270$^{\circ}$ from superior conjunction, also not seen from Earth) by a factor of $\sim$3[@dyudina]. Note that the phase dependence of an EGP’s light curve in the mid-infrared will depend on the degree to which heat can be efficiently redistributed over its entire face. This will depend on 3-dimensional GCM effects that have not been worked out. For the close-in EGPs, due to expected day/night temperature differences[@GuillotShowman02; @ShowmanGuillot02], it is likely that there will be phase variations at all wavelengths. In particular, phase variations at thermal wavelengths are likely to shed light on the atmospheric dynamics and longitudinal temperature distribution of an EGP.

Since its orbit and orientation play such an important role in an EGP’s flux at the Earth and in its interpretation, we summarize the basic formulae and concepts. We restrict ourselves to the optical, for which the concept of an albedo has a clear meaning, but note that the approach we summarize has general applicability.

The planet/star flux ratio ($f$) is given by: $$f = p ({\rm R}_{\rm p}/R)^2 \Phi(\alpha),
\label{falpha}$$ where $R$ is the planet/star distance, $p$ is the geometric albedo, $\Phi(\alpha)$ is the phase function, and $\alpha$ is the star-EGP-Earth angle. $\Phi(\alpha)$ 