Feasibility of observing dayside aurora using NIR camera onboard high‐altitude balloons

Abstract

This letter reports a feasibility study on dayside auroral observation using a near‐infrared (NIR) InGaAs camera from high‐altitude, long‐duration balloons. This effort is motivated by science interest in the dayside aurora. Model predictions indicate daytime observations are possible because the sky brightness significantly decreases towards longer wavelengths at certain altitude in the upper atmosphere, and the NIR ambient sky brightness substantially decreases with increasing altitude. To address the question whether aurora can indeed be detected in the upper atmosphere, auroral test observations were conducted at the Poker Flat Research Range from March 22 to April 26, 2005. The InGaAs camera used in this test covers a waveband from 900 to 1700 nm with a 320 × 256 focal plane array, 30 × 30 μm pixels, and a 9° field of view. For one evening event, we estimate the NIR sky brightness using the MODTRAN atmospheric radiance model and compare it with the expected sky brightness at 30–50 km altitudes. The comparison indicates that the N2+ Meinel emission at ∼1100 nm should be seen at 35–40 km altitudes and above, and therefore, confirms that such dayside auroral observations are feasible. Auroral studies using this method include, e.g., studies of interplanetary shock and pressure pulse induced auroras as well as conjugate auroras.