Global-scale observations of the limb and disk (GOLD): New observing capabilities for the ionosphere-thermosphere

The Global-scale Observations of the Limb and Disk (GOLD) mission of opportunity will greatly improve understanding of the Earth’s thermosphere and ionosphere through measurements of the global-scale response to external and internal forces. GOLD will fly an UV imager on a geostationary satellite to measure densities and temperatures across almost an entire hemisphere in this poorly understood region of the Earth’s upper atmosphere and lower space environment, at altitudes where temperatures are currently not well known. GOLD will provide the first global-scale observations of temperatures in the lower thermosphere (130–180 km), in addition to more familiar measurements such as aurora location and energy input, peak electron densities (NmF2) in the nighttime ionosphere, and atomic oxygen to molecular nitrogen column density ratios (ΣO/N2) ratios. GOLD can provide nearly continuous real-time observations of one hemisphere. In addition to measurements on the disk of the Earth, GOLD can provide coincident measurements of molecular oxygen densities and the temperature profile in the lower thermosphere (150–250 km) from stellar occultations as well as exospheric temperatures from limb profiles of molecular nitrogen emissions. GOLD has two identical channels, each capable of all the measurements described. This allows GOLD to provide coincident measurements in any desired combination, e.g., disk temperatures and ΣO/N2. Combined with the advanced models now available, measurements from GOLD will revolutionize our understanding of the global-scale response of the thermosphere and ionosphere to geomagnetic and solar forcing. The data and knowledge gained from GOLD will enhance space weather specification and forecasting capabilities.