  In anticipation of future flagship missions focused on the goal of achieving
direct imaging of rocky exoplanets, we have developed a database of models to
help the community examine the potential spectral characteristics of a broad
range of rocky planet atmospheres. Using the publicly available Planetary
Spectrum Generator (PSG), we have computed a grid of 141,600 rocky exoplanet
geometric albedo spectra across a 7-dimensional parameter space. Using this
grid, we have performed a color-color analysis seeking to identify the most
useful near-ultraviolet and red or near-infrared photometric followup channels
to combine with a green-optical (discovery) spectral channel. We found that a
combination of filters at 0.4 um, 0.58 um, and (approx) 0.8um were able to
distinguish between atmospheres with moderate-to-high concentrations of four
different dominant absorbing constituents, given at least 10 hours of
observation on a star at 10 parsec with a 15-meter-class space telescope;
however, more moderate abundances similar to those of Solar System rocky bodies
would be more challenging to detect. We recommend that future missions seeking
to characterize directly imaged rocky exoplanets by colors alone further
consider multi-band photometry as a first discriminator for planetary
characteristics.
