Remote sensing of lower-middle thermosphere temperatures using the N₂ Lyman-Birge-Hopfield (LBH) bands

Abstract. The scientific and societal importance of short-term changes in the thermosphere-ionosphere (T-I) system has highlighted the need to advance our understanding of short-term changes in the lower-middle thermosphere. This need has become increasingly important with the rapid increase in the number of low-earth-orbiting satellites. Geomagnetic activity can dramatically increase thermospheric temperatures and, almost equivalently, thermospheric densities and satellite drag. However, specification of drag during quiet periods may also be problematic when the number of satellites is large. While temperatures and densities at higher altitudes (>~250 km) have been extensively studied and modeled, there is a knowledge gap for densities at lower-middle thermosphere altitudes (< ~200 km). At these lower altitudes the primary sources of thermospheric density data, in situ and drag data from satellites, are rarely available. Remote sensing of temperatures and composition by NASA’s Global-scale Observations of the Limb and Disk (GOLD) mission can help fill this gap The GOLD mission produces disk images of neutral temperature, which is key parameter for understanding neutral density in the lower-middle thermosphere. However, since disk images of the temperature have become available only since the launch of GOLD, some researchers may be unfamiliar with the current observational capability that is relevant to the data interpretation. Also, other temperature retrieval techniques than GOLD’s have been published. Comparisons indicate that GOLD’s technique gives the most consistent results and yields the lowest uncertainties. This paper discusses both temperature retrieval techniques and issues in interpreting GOLD’s images of temperatures.