We describe in this study the analysis of small and large horizontal-scale gravity waves from datasets composed of images from multiple mesospheric airglow emissions as well as multistatic specular meteor radar (MSMR) winds collected in early November 2018, during the SIMONe-2018 (Spread-spectrum Interferometric Multi-static meteor radar Observing Network) campaign. These ground-based measurements are supported by temperature and neutral density profiles from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) satellite in orbits near Kühlungsborn, northern Germany (54.1.sup." N, 11.8.sup." E). The scientific goals here include the characterization of gravity waves and their interaction with the mean flow in the mesosphere and lower thermosphere and their relationship to dynamical conditions in the lower and upper atmosphere. We have obtained intrinsic parameters of small- and large-scale gravity waves and characterized their impact in the mesosphere via momentum flux (F.sub.M) and momentum flux divergence (F.sub.D) estimations. We have verified that a small percentage of the detected wave events is responsible for most of F.sub.M measured during the campaign from oscillations seen in the airglow brightness and MSMR winds taken over 45 h during four nights of clear-sky observations. From the analysis of small-scale gravity waves (Î».sub.h 725 km) seen in airglow images, we have found F.sub.M ranging from 0.04-24.74 m.sup.2 s.sup.-2 (1.62 Â± 2.70 m.sup.2 s.sup.-2 on average). However, small-scale waves with F.sub.M 3 m.sup.2 s.sup.-2 (11 % of the events) transport 50 % of the total measured F.sub.M . Likewise, wave events of F.sub.M 10 m.sup.2 s.sup.-2 (2 % of the events) transport 20 % of the total. The examination of large-scale waves (Î».sub.h 725 km) seen simultaneously in airglow keograms and MSMR winds revealed amplitudes 35 %, which translates into F.sub.M = 21.2-29.6 m.sup.2 s.sup.-2 . In terms of gravity-wave-mean-flow interactions, these large F.sub.M waves could cause decelerations of F.sub.D = 22-41 m s.sup.-1 d.sup.-1 (small-scale waves) and F.sub.D = 38-43 m s.sup.-1 d.sup.-1 (large-scale waves) if breaking or dissipating within short distances in the mesosphere and lower thermosphere region.