The all-sky imager at ALO uses a fisheye lens and a cooled CCD detector to record wide-field images of the nighttime upper atmosphere. The instrument captures airglow — faint light emitted by atoms and molecules at specific altitude layers in the mesosphere and thermosphere — through low-pass near-infrared or narrow-band interference filters tuned to individual emission lines.
Airglow images reveal horizontal structures driven by atmospheric dynamics: gravity waves appear as rippling bands of alternating brightness sweeping across the full sky, and larger-scale patterns reflect tidal and planetary-wave activity. Time-lapse movies constructed from successive images make these wave structures visible, while keograms — north–south or east–west brightness slices through the image stack — provide a compact record of how emission intensity evolves through the night.
The imager operates during clear, moonless nights each month, co-located at ALO with the CONDOR meteor radar and the Na Lidar. Simultaneous multi-instrument observations allow wind and temperature fields to be combined with wave patterns seen in the airglow images to fully characterize the dynamics in this region.
See also: CONDOR meteor radar · Na Lidar — co-located instruments at ALO