  Current post-processing techniques in high contrast imaging depend on some
source of diversity between the exoplanet signal and the residual star light at
that location. The two main techniques are angular differential imaging (ADI),
which makes use of parallactic sky rotation to separate planet from star light,
and spectral differential imaging (SDI), which makes use of differences in the
spectrum of planet and star light and the wavelength dependence of the point
spread function (PSF). Here we introduce our technique for exploiting another
source of diversity: orbital motion. Given repeated observations of an
exoplanetary system with sufficiently short orbital periods, the motion of the
planets allows us to discriminate them from the PSF. In addition to using
powerful PSF subtraction algorithms, such an observing strategy enables
temporal filtering. Once an orbit is determined, the planet can be
``de-orbited'' to further increase the signal-to-noise ratio. We call this
collection of techniques Orbital Differential Imaging (ODI). Here we present
the motivation for this technique, present a noise model, and present results
from simulations. We believe ODI will be an enabling technique for imaging
Earth-like planets in the habitable zones of Sun-like stars with dedicated
space missions.
