Authors: Don Schmit (CIRES/CU), Adrian Daw (GSFC/NASA), Jeffrey W. Brosius (Catholic University) , Enrico Landi (University of Michigan), Doug Rabin (GSFC/NASA)

The Extreme Ultraviolet Normal Incidence Spectrograph successfully launched from White Sands Missile Range on May 18, 2021. The primary science driver for this EUNIS incarnation was to detect the faint emission from the high temperature plasma that is considered to be “smoking gun” evidence of nanoflares, and derive the emission measure of this 5-10 MK plasma in an active region. This is achieved through the use of novel multilayer optical coatings and intensified-CMOS detectors to probe the spectral regime between 92-115A, where no imaging spectrometers have ever previously observed. In this paper, we present information on the EUNIS instrument and flight campaign. The data include the He II 304A line, which is commonly observed by EUV bandpass imagers. We analyze the He II data to understand how the line profiles of this optically thick transition region line are related to intensity structures we observe in the bandpass images.