Advanced mesospheric temperature mapper for high-latitude airglow studies.

Over the past 60 years, ground-based remote sensing measurements of the Earth's mesospheric temperature have been performed using the nighttime hydroxyl (OH) emission, which originates at an altitude of ∼87 km. Several types of instruments have been employed to date: spectrometers, Fabry-Perot or Michelson interferometers, scanning-radiometers, and more recently temperature mappers. Most of them measure the mesospheric temperature in a few sample directions and/or with a limited temporal resolution, restricting their research capabilities to the investigation of larger-scale perturbations such as inertial waves, tides, or planetary waves. The Advanced Mesospheric Temperature Mapper (AMTM) is a novel infrared digital imaging system that measures selected emission lines in the mesospheric OH (3,1) band (at ∼1.5 µm) to create intensity and temperature maps of the mesosphere around 87 km. The data are obtained with an unprecedented spatial (∼0.5 km) and temporal (typically 30″) resolution over a large 120° field of view, allowing detailed measurements of wave propagation and dissipation at the ∼87 km level, even in the presence of strong aurora or under full moon conditions. This paper describes the AMTM characteristics, compares measured temperatures with values obtained by a collocated Na lidar instrument, and presents several examples of temperature maps and nightly keogram representations to illustrate the excellent capabilities of this new instrument.

Systematic errors in emission cross sections arising in the analysis of laboratory beam measurements.

A technique for obtaining emission cross sections in laboratory beam studies is presented, including effects on the cross section due to polarization of the emitted light. Systematic analytical errors arising from optical problems are analyzed and evaluated for a typical spectral feature. The primary sources of error are shown to arise from the particular geometry used in the optical measurements, the variation of the calibrating light source over the bandwidth of the emission feature, and the variation of the responsivity of the optical system over the bandwidth.