DOI: 10.1594/wdcrsat.r4oar50i
title: Five minute means of OH(3-1) airglow rotational temperatures from the mesopause region obtained with GRIPS 14 located at the German Remote Sensing Data Center, Oberpfaffenhofen

description: Temperatures are derived from the rotational vibrational transition of the OH molecule originating from a thin layer in approximately 87km centroid height. The spectra have been obtained with the GRound-based Infrared P-branch Spectrometer (GRIPS 14) located at the German Remote Sensing Data Center of the German Aerospace Center (DLR-DFD) at Oberpfaffenhofen (OPN: 48.09°N, 11.28°E) – a measurement station of the international Network of Mesospheric Change (NDMC).
During routine operation one spectrum is obtained every 15 s, originating from a field of view of approximately 15.5° x 15.5° which corresponds to ca. 24 x 24 km2 in zenith direction at 87 km height. The covered wavelength range allows the observation of the OH(3-1) Q- and P-branches as well as of the OH(4-2) R- and Q-branches. Rotational temperatures are calculated using OH(3-1) P-branch emissions between 1520 nm and 1550 nm. In addition to the field of view (FoV) in zenith direction, the instrument is successively pointed into three more directions at 30° zenith angle: 90°(E), 210°(SSW), 330°(NNW) azimuth angles, increasing the effective FoV in these directions to approximately 880 km².
Regular observations with the scanning GRIPS 14 were performed at Oberpfaffenhofen from 17 July 2015 until 10 November 2015 and with the identical setup again from 13 April 2016 until 19 April 2018. 
Since data are recorded for each FoV successively, the initial data are not directly comparable, therefore a five minute mean value is derived for each FoV, if there are two or more high precision temperature values available within the respective interval of −150 s and +149.999 s around a UTC full five minute time stamp. The corresponding precision of the five minute mean value follows from Gaussian error propagation and typically lies between ±2.5 K and ±8 K.
description: GRIPS 14 is equipped with a Czerny-Turner spectrograph and a thermoelectrically cooled InGaAs array. Only the P1(2), P1(3) and P1(4) rotational lines of the (3-1) vibrational transition are used for the derivation of temperatures. Intensities are only read out at the line centers of the smoothed spectra due to residual overlapping of the lines at their wings. Important physical constants applied during the processing are taken from Mies (1974) (Einstein coefficients) and Krassovsky et al. (1962) (rotational term values). Further details concerning the derivation of rotational temperatures are presented in Schmidt, C., Höppner, K. and Bittner, M. (2013): A ground-based spectrometer equipped with an InGaAs array for routine observations of OH(3-1) rotational temperatures in the mesopause region. Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) 102 (2013) 125–139. https://dx.doi.org/10.1016/j.jastp.2013.05.001. Details concerning specifically the observations with the scanning setup are included in Thomas Offenwanger’s master thesis (German) written at the University of Augsburg in June 2016 (Faculty of Applied Computer Science, Institute of Geography): “Räumliche Charakteristik atmosphärischer Wellen in OH*-Airglowdaten: Anwendung eines neuen Messverfahrens basierend auf IR-Spektrometern”.