The Daily Atmospheric Ionospheric Limb Imager (DAILI) CubeSat Experiment

The Daily Atmospheric Ionospheric Limb Imager (DAILI) (Daily Atmospheric and Ionospheric Limb Imager) mission utilized a 6U CubeSat, deployed at about 410 km altitude in a 51‐degree orbit, to make simultaneous daytime limb measurements in two colors; at 630 nm to measure the OI (630 nm) redline and at 765 nm to measure the Atmospheric (0,0) band (O2A band). The ratio of the O2A band to the redline allows a retrieval of the absolute daytime density from ∼140–200 km altitude using a technique demonstrated on the Remote Atmosphere and Ionosphere Detection System (RAIDS) experiment in 2009 (Hecht et al., 2015, https://doi.org/10.1002/2014gl062355 ). Daily Atmospheric Ionospheric Limb Imager required the development of a new Earthshade that would fit into the 6U form factor and would, while observing the limb at 140 km and above, suppress scattering by a factor at or above 1 million from both the daylit Earth's surface and from clouds, and this capability is demonstrated on‐orbit. Over 7200 limb profiles were obtained, many of which were geomagnetically quiet but several of which occurred during a Kp geomagnetic storm where the NASA GUVI (Global UV Imager) instrument obtained O/ data. This allowed a determination of the extent of variations of compared to the GUVI O/ data during a large storm at altitudes below 200 km. The DAILI data for this storm are not reproduced by current models. Both the DAILI and GUVI data are consistent with significant equatorward transport of heated air from the auroral zone compared to model predictions.