  The hot Jupiter HD 189733b is probably the best studied of the known
extrasolar planets, with published transit and eclipse spectra covering the
near UV to mid-IR range. Recent work on the transmission spectrum has shown
clear evidence for the presence of clouds in its atmosphere, which
significantly increases the model atmosphere parameter space that must be
explored in order to fully characterise this planet. In this work, we apply the
NEMESIS atmospheric retrieval code to the recently published HST/STIS
reflection spectrum, and also to the dayside thermal emission spectrum in the
light of new Spitzer/IRAC measurements, as well as our own re-analysis of the
HST/NICMOS data. We first use the STIS data to place some constraints on the
nature of the cloud on HD189733b, and explore solution degeneracy between
different cloud properties and the abundance of Na in the atmosphere; as
already noted in previous work, absorption due to Na plays a significant role
in determining the shape of the reflection spectrum. We then perform a new
retrieval of the temperature profile and abundances of H2O, CO2, CO and CH4
from the dayside thermal emission spectrum. Finally, we investigate the effect
of including cloud in the model on this retrieval process. We find that the
current quality of data does not warrant the extra complexity introduced by
including cloud in the model; however, future data are likely to be of
sufficient resolution and signal-to-noise that a more complete model, including
scattering particles, will be required.
