GRIPS-HI, a novel spectral imager for ground based measurements of mesopause temperatures

Abstract

Abstract The NDMC (Network for the Detection of Mesospheric Change) is a global network of measurement sites dedicated to the surveillance of the mesopause region. One main objective of the network is the early identification of climate signals. A key parameter is the mesopause temperature which can be derived from the emission spectrum of a layer of vibrationally excited hydroxyl (OH) at an altitude of approximately 87 km87\\hspace{0.1667em}\\text{km}. Foremost, emission lines in the SWIR regime between 1520 nm1520\\hspace{0.1667em}\\text{nm} and 1550 nm1550\\hspace{0.1667em}\\text{nm} are of interest for remote temperature sensing. This report deals with the development of a new generation of GRIPS instruments, which are commonly employed for the observation of mesopause temperatures. The new prototype demonstrates how the application of so called Spatial Heterodyne Interferometers (SHI) can overcome the limitations of currently used grating spectrometers, in terms of spectral resolution and optical throughput. The presented prototype proposes improvements in optical throughput and spectral resolution of about one order of magnitude, significantly reducing the uncertainties of the measured mesopause temperatures. Furthermore, an SHI can be built in monolithic configurations which are aligned and characterized once during assembly without the need of realignment at the measurement site. This makes SHI based instruments ideal for mobile applications.