brown dwarf. Other possible exoplanets to have been directly imaged include GQ Lupi b, AB Pictoris b, and SCR 1845 b. As of March 2006, none have been confirmed as planets; instead, they might themselves be small brown dwarfs. Imaging instruments Some projects to equip telescopes with planet-imaging-capable instruments include the ground-based telescopes Gemini Planet Imager, VLT-SPHERE, the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument, Palomar Project 1640, and the space telescope WFIRST. The New Worlds Mission proposes a large occulter in space designed to block the light of nearby stars in order to observe their orbiting planets. This could be used with existing, already planned or new, purpose-built telescopes. In 2010, a team from NASA's Jet Propulsion Laboratory demonstrated that a vortex coronagraph could enable small scopes to directly image planets. They did this by imaging the previously imaged HR 8799 planets, using just a 1.5 meter-wide portion of the Hale Telescope. Another promising approach is nulling interferometry. It has also been proposed that space-telescopes that focus light using zone plates instead of mirrors would provide higher-contrast imaging, and be cheaper to launch into space due to being able to fold up the lightweight foil zone plate. Data Reduction Techniques Post-processing of observational data to enhance signal strength of off-axial bodies (i.e. exoplanets) can be accomplished in a variety of ways. Likely the earliest and most popular is the technique of Angualar Differential Imaging (ADI), where exposures are averaged, each exposure undergoes subtraction by the average, and then they are (de-)rotated to stack the feint planetary signal all in one place. Specral Differential Imaging (SDI) performs an analygous procedure, but for radial changes in brightness (as a function of spectra or wavelength) instead of angular changes. Combinations of the two are possible (ASDI, SADI, or Combined Differential Imaging "CODI"). Polarimetry Light given off by a star is un-polarized, i.e. the direction of oscillation of the light wave is random. However, when the light is reflected off the atmosphere of a planet, the light waves interact with the molecules in the atmosphere and become polarized. By analyzing the polarization in the combined light of the planet and star (about one part in a million), these measurements can in principle be made with very high sensitivity, as polarimetry is not limited by the stability of the Earth's atmosphere. Another main advantage is that polarimetry allows for determination of the composition of