Upper-atmospheric and ionospheric parameters exhibit variability on global spatial scales with periods from several hours to several days, characteristic of lower-atmospheric planetary waves and tides. To study the origins, vertical propagation, and possible effects of these planetary-scale perturbations on the coupled thermosphere-ionosphere system, a new “whole atmosphere” GCM is being developed under a NASA sponsored collaborative project between the University of Colorado and National Weather Service's (NWS) Environmental Modeling and Space Environment Centers (EMC and SEC). IDEA's neutral atmosphere is a 150-layer GCM based on NWS's operational weather prediction Global Forecast System (GFS) model extended from its nominal top altitude of about 60 km to well over 600 km. It incorporates all physical processes relevant in the extended domain and ranging from the hydrological cycle and atmosphere-surface exchanges in the troposphere, to solar and Joule heating and mutual diffusion of major species in the thermosphere. The neutral atmosphere module is interactively coupled to the Global Ionosphere-Plasmasphere (GIP) model extending to altitudes over 10000 km. The GIP model solves for the transport of major ionized species along geomagnetic field lines and includes the photochemistry and transport of minor species. The IDEA-GCM will be ideally suited for forecasting terrestrial weather impacts on the near-Earth space environment. Other possible applications will likely include global change studies further bridging climate and weather in the whole Earth system environment.