molecular abundances. The CHIMERA secondary eclipse code by @2013ApJ...775..137L has a statistics package with multiple Monte Carlo methods and an optimal estimation method for optimization purposes. The NEMESIS code by @2008JQSRT.109.1136I is designed for a fast and accurate analysis of planetary spectra, particularly optimized for solar system objects, including additional parameters such as limb darkening, surface temperature, and detailed cloud models. The SCARLET code by @2015arXiv150407655B emphasizes a chemical and structural model by parameterizing 3-D atmosphere properties such as the eddy diffusion constant, heat-transport, and Bond albedo. Finally, the Tau-REx code by @2015ApJ...802..107W has a complex statistical package, which includes procedurally-generated priors.

Currently, about sixty exoplanets have been observed photometrically in primary transit in multiple wavebands. Most of these objects are hot jupiters, and most of them have been observed photometrically with the [*Spitzer Space Telescope*]{}. About twenty exoplanets have been spectroscopically characterized at low resolutions of $R\sim 10-20$, mostly with [*HST*]{} between 0.3 and 1.0 $\mu m$ with STIS and/or between 1.1 and 1.7 $\mu m$ with WFC3 [@2016Natur.529...59S]. Three objects have been studied in by far the greatest detail due to the brightness of their host stars and their ease of observation: HD 189733b [@2013MNRAS.432.2917P; @2014ApJ...791...55M], HD 209458b 