As a postdoc, I've been involved with the Differential Speckle Survey Instrument (DSSI; PIs Steve Howell and Elliot Horch) team, taking observations at Gemini North (and soon South). DSSI is designed to characterize exoplanet host star multiplicity; it has already helped validate dozens of exoplanet candidates. Speckle observations consist of very short exposure “snapshots” (60 millisec) that negate smearing effects of the rapidly changing atmosphere. A dichroic splits the light entering DSSI into two beams that each pass through different wavelength filters to separate EMCCDs; having two filters allows us to better characterize detected companions. Images with resolutions better than 0.1 arsec and contrast sensitivities of Δmagnitude=6-10 are needed to search for real or co-aligned stellar companions and assess the validity of Kepler’s terrestrial planet candidates. Only Gemini+DSSI provide the necessary resolution to “see” planets or stars orbiting within 4 Astronomical Units (AU) and the delta magnitude to distinguish between true and line-of-sight companions. We are the only speckle imaging group performing Kepler-related follow-up on large telescopes, with a focus on small planet host stars. DSSI is open to any NOAO proposers, so we also observe known multiple star systems to better characterize their colors, orbits, and formation mechanisms; search for companions to nearby stars on solar system scales; and observe pre-main sequence low-mass stars to measure dynamical masses and spectral types.
You can check out the paper I wrote comparing speckle observations to spectral observations on my research page.
Above: Blurry photo of me working in Gemini's dome to assemble and mount DSSI in July 2014. Below: DSSI Team (with David participating remotely) during our July 2015 observing run at Gemini North.