| The York All-Sky Airglow Camera, YASAC, is a wide field imager that was designed, built and operated to record airglow emissions originating from the upper mesosphere and middle thermosphere. Eight interference filters allow monitoring of the OI{dollar}(sp1{dollar}S) 557.7 nm Green Line, the {dollar}rm Osb2(bsp1Sigmasb{lcub}g{rcub}sp+){dollar}(0-1) 864.5 nm Atmospheric band, the OI{dollar}(sp1{dollar}D) 630.0 nm Red Line and the R branch of the OH{dollar}(sp2Pi){dollar} (7-3) band. Background measurements were made at 546.7, 572.3, 677.4 and 822.7 nm.; The camera was operated between November 1991 and May 1992 at Bear Lake, Utah (41.9{dollar}spcirc{dollar}N, 111.42{dollar}spcirc{dollar}W) to support a ground validation campaign for the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite. During this period, the imager recorded many nights where gravity wave disturbances could be viewed in the OH, O{dollar}sb2{dollar} and OI{dollar}(sp1{dollar}S) emissions. On several occasions, auroral activity was also recorded at Bear Lake.; Waves were viewed with most detail in the OI{dollar}(sp1{dollar}S) and O{dollar}sb2{dollar} emissions. Both short period {dollar}(<{dollar}10 minutes) and long period ({dollar}approx{dollar}1-4 hour) wave events were recorded. Spatial analyses of the image data provided the wavelengths and apparent periods. The vertical phase velocity could be determined through comparison of the OI{dollar}(sp1{dollar}S) and O{dollar}sb2{dollar}(0-1) emissions which originate from slightly different altitudes.; Of particular interest was an unusual event taking place on the evening of February 5th, 1992. A large packet of three wave crests, appearing in both the OI{dollar}(sp1{dollar}S) and O{dollar}sb2{dollar}(0-1) emissions traversed the entire sky. The event appears to have originated from above the mesopause.; YASAC proved to be an important tool both as a diagnostic imager and as a support instrument for collaborative investigations of the upper atmosphere. |
