GEST

Abstract

Galactic Exoplanet Survey Telescope (GEST) was proposed for a discovery mission to search for microlensing terrestrial planets toward the Galactic bulge and also Kuiper Belt Objects (KBOs) that are believed to hold vital information of the early history of the solar system. Microlensing planet search method is hinged on photometric singular behavior of lensing (refraction) that is due to discontinuities in the distribution of photon paths whose phenomenon is better known in total reflection. The singularities (caustics) directly translate into potentially large planetary signals but the small size of the caustics imposes four essential requirements for earth mass planet searches: massive survey, angular resolution, temporal resolution, and continuous monitoring capability in a statistically stable observing condition. A 1–2m scale wide FOV space telescope with a large focal plane such as the GEST meets the needs. Habitability of earth mass planets in the habitable (liquid water) zone is suspected to depend crucially on a giant planet near the snowline. The large mass of the giant planets makes the planetary caustics larger and easier to detect them in abundance. In microlensing, one needs not wait 12 years to detect a jupiter at the Jupiter orbit (5 AU) unlike in other planet search methods (doppler, astrometry, transit) because the planetary microlensing events will complete their courses within 50 days or so −70 times shorter! Close-in giant planets of the bulge stars will be registered as transits in the microlensing data base and will form a valuable platform for comparison studies of the planets from different detection methods and different environments. When the Galactic bulge is behind the sun, the GEST will be ideal for high resolution mapping of the large scale structures which will include weak lensing by dark matter, quasar lensing and host galaxies, strong lensing by clusters, and a large volume of galaxies, which with selective follow-up measurements of whose redshifts and IR images will shed light on the dark stuff (matter, energy, essence, extra dimensions, topological defects, …).