PRESENCE OF TERRESTRIAL ATMOSPHERIC GAS-ABSORPTION BANDS IN STANDARD EXTRATERRESTRIAL SOLAR IRRADIANCE CURVES IN THE NEAR-INFRARED SPECTRALREGION

The solar irradiance curves compiled by Wehrli [Physikalisch-Meteorolo gisches Observatorium Publ. 615 (World Radiation Center, Davosdorf, Sw itzerland, 1985)] and by Neckel and Labs [Sol. Phys. 90, 205 (1984)] a re widely used. These curves were obtained based on measurements of so lar radiation from the ground and from aircraft platforms. Contaminati ons in these curves by atmospheric gaseous absorptions were inevitable . A technique for deriving the transmittance spectrum of the Sun's atm osphere from high-resolution (0.01 cm(-1)) solar occultation spectra m easured above the Earth's atmosphere by the use of atmospheric trace m olecule spectroscopy (ATMOS) aboard the space shuttle is described. Th e comparisons of the derived ATMOS solar transmittance spectrum with t he two solar irradiance curves show that the curve derived by Wehrli c ontains many absorption features in the 2.0-2.5-mu m region that are n ot of solar origin, whereas the curve obtained by Neckel and Labs is c ompletely devoid of weak solar absorption features that should be ther e. An Earth atmospheric oxygen band at 1.268 mu m and a water-vapor ba nd near 0.94 mu m are likely present in the curve obtained by Wehrli. It is shown that the solar irradiance measurement errors in some narro w spectral intervals can be as large as 20%. An improved solar irradia nce spectrum is formed by the incorporation of the solar transmittance spectrum derived from the ATMOS data into the solar irradiance spectr um from Neckel and Labs. The availability of a new solar spectrum from 50 to 50000 cm(-1) from the U.S. Air Force Phillips Laboratory is als o discussed. (C) 1995 Optical Society of America.