  We aim to interpret future photometric and spectral measurements from these
instruments, in terms of physical parameters of the planets, with an
atmospheric model using a minimal number of assumptions and parameters.
  We developed Exoplanet Radiative-convective Equilibrium Model (Exo-REM) to
analyze the photometric and spectro- scopic data of directly imaged planets.
The input parameters are a planet's surface gravity (g), effective temperature
(Teff ), and elemental composition. The model predicts the equilibrium
temperature profile and mixing ratio profiles of the most important gases.
Opacity sources include the H2-He collision-induced absorption and molecular
lines from eight compounds (including CH4 updated with the Exomol line list).
Absorption by iron and silicate cloud particles is added above the expected
condensation levels with a fixed scale height and a given optical depth at some
reference wavelength. Scattering was not included at this stage.
  We applied Exo-REM to photometric and spectral observations of the planet
beta Pictoris b obtained in a series of near-IR filters. We derived Teff = 1550
+- 150 K, log(g) = 3.5 +- 1, and radius R = 1.76 +- 0.24 RJup (2-{\sigma} error
bars from photometric measurements). These values are comparable to those found
in the literature, although with more conservative error bars, consistent with
the model accuracy. We were able to reproduce, within error bars, the J- and
H-band spectra of beta Pictoris b. We finally investigated the precision to
which the above parameter
