Abstract
A sun photometer which operates at five wavelengths in the near infrared between 1.0 and 4.0 μm has been developed. The instrument is a manually operated, fitter wheel design and has principal applications for atmospheric aerosol studies. The wavelength filters were selected at bands with minimal gaseous absorption. A modified Langley analysis which accounts for residual gaseous absorption is employed for the instrument calibration. Calibration and stability results for the instrument are presented.