GOLD will fly an ultraviolet (UV) imaging spectrograph on a geostationary satellite to measure densities and temperatures in Earth’s thermosphere and ionosphere. The goal of the investigation is to address an overarching question in heliophysics science: What is the global-scale response of the thermosphere and ionosphere to forcing in the integrated Sun-Earth system? Measurements from GOLD will be used, in conjunction with sophisticated models of the terrestrial thermosphere and ionosphere, to revolutionize our understanding of the space environment. More information can be found at the GOLD website at GOLD.