The Global-Scale Observations of the Limb and Disk (GOLD) Mission

TLDR

The Earth's thermosphere and ionosphere form a dynamic system that responds within hours to energy inputs from solar radiation, magnetospheric particles, and lower‑atmosphere waves, with temperature, composition, and structure varying daily. The GOLD mission aims to determine how the thermosphere‑ionosphere “weather” responds to these drivers, advancing understanding of space‑atmosphere coupling. In geostationary orbit, GOLD’s imaging spectrograph will measure 132–162 nm emissions to map thermospheric temperature and composition near 160 km on half‑hour scales, image nighttime low‑latitude ionosphere evolution, and repeatedly observe the same hemisphere to separate spatial and temporal variability over the Americas.

Abstract

The Earth's thermosphere and ionosphere constitute a dynamic system that varies daily in response to energy inputs from above and from below. This system can exhibit a significant response within an hour to changes in those inputs, as plasma and fluid processes compete to control its temperature, composition, and structure. Within this system, short wavelength solar radiation and charged particles from the magnetosphere deposit energy, and waves propagating from the lower atmosphere dissipate. Understanding the global-scale response of the thermosphere-ionosphere (T-I) system to these drivers is essential to advancing our physical understanding of coupling between the space environment and the Earth's atmosphere. Previous missions have successfully determined how the "climate" of the T-I system responds. The Global-scale Observations of the Limb and Disk (GOLD) mission will determine how the "weather" of the T-I responds, taking the next step in understanding the coupling between the space environment and the Earth's atmosphere. Operating in geostationary orbit, the GOLD imaging spectrograph will measure the Earth's emissions from 132 to 162 nm. These measurements will be used image two critical variables—thermospheric temperature and composition, near 160 km—on the dayside disk at half-hour time scales. At night they will be used to image the evolution of the low latitude ionosphere in the same regions that were observed earlier during the day. Due to the geostationary orbit being used the mission observes the same hemisphere repeatedly, allowing the unambiguous separation of spatial and temporal variability over the Americas.