A spectroradiometer for the measurement of direct and scattered solar irradiance from on‐board the NASA ER‐2 high‐altitude research aircraft

Abstract

A compact, diode‐array spectrophotometer has been designed to make measurements of the downward spectral flux on a horizontal surface, the limb brightness and the apparent brightness in the nadir direction from on‐board the NASA ER‐2 research aircraft. The instrument was included as part of the photochemical payload used for the Stratospheric Photochemistry, Aerosol and Dynamics Expedition (SPADE) of the NASA High‐Speed Research Program. The spectrophotometer is based on a 1024‐element, randomly‐addressable Reticon photodiode array and makes measurements covering the 300 to 775 nm spectral region at a resolution of about 1 nm. Some aspects of the design and the performance of the instrument during SPADE will be presented. The direct‐beam, spectral measurements are in good agreement with modelled data (MODTRAN).