Engineering topics

Doda, D. D.

Publications and source records attributed to Doda, D. D..

4 records

NASA NTRS1981

Surface reflectance measurements in the ultraviolet from an airborne platform. II

The spectral and broadband reflectance of naturally occurring desert sand, black lava, gypsum sand, and snow cover is measured from a twin engine Cessna 402-series aircraft. The measurement system is computer controlled and electrically isolated from the aircraft. It consists of upward and downward looking hemispheric diffusers, filters, a rotating 90 degree mirror, a focusing lens, and a double monochromator/PMT or a UV enhanced photodiode. Measurements are made at several altitudes enabling the empirical determination of the backscatter and attenuation effects on the reflectance. These reflectance results along with those reported earlier for a pine forest, green farmland, the open ocean, and brown farmland are represented analytically.

Doda, D. D.↗

NASA NTRS1980

Surface reflectance measurements in the UV from an airborne platform. I

The reflectance of naturally occurring surfaces is measured from a twin engine Cessna 402B aircraft both spectrally (0.29-0.40 micron) with a compact double monochromator and broadband (0.29-1.2 micron) with a UV enhanced photodiode. The measurement system, which is computer controlled and electrically isolated from the aircraft, consists of upward and downward looking hemispheric diffusers, filters, a rotating 90 deg mirror, a focusing lens, and a double monochromator/PMT or the UV photodiode. Measurements are taken at several altitudes enabling the empirical determination of backscatter and attenuation effects on the reflectance. The results are presented for pine forest canopy, green farmland, open ocean, and brown farmland as a function of wavelength and altitude.

Doda, D. D.↗

NASA NTRS1979

Total ozone determination by spectroradiometry in the middle ultraviolet

A method has been developed to determine total ozone from multispectral measurements of the direct solar irradiance. The total ozone is determined by a least squares fit to the spectrum between 290 nm and 380 nm. The aerosol extinction is accounted for by expanding it in a power series in wavelength; use of the linear term proved adequate. A mobile laboratory incorporating a sky scanner has been developed and used to obtain data to verify the method. Sun tracking, wavelength setting of the double monochromator, and data acquisition are under control of a minicomputer. Results obtained at Wallops Island, Virginia, and Palestine, Texas, agree well with simultaneous Dobson and Canterbury spectrometer and balloon ECC ozonesonde values. The wavelength calibration of the monochromator and the values for the normalized ozone absorption are the most important factors in an accurate determination of total ozone.

Garrison, L. M.↗

NASA NTRS1978

Diffuse-direct ultraviolet ratios with a compact double monochromator

An improved system has been implemented for measuring the ratio of the diffuse skylight to the direct sunlight in the biologically active region of the UV near the atmospheric limit. It combines a double monochromator employing holographic gratings for reduction of stray light with a cooled photomultiplier tube to provide a greatly improved SNR below 300 nm. Data may be obtained in either a scan mode or a narrowband photometry mode; in the latter mode accurate ratios have been obtained near 290 nm. Representative data are discussed along with a theoretical model of the ratio. The system is compact enough for use in a mobile monitoring system.

Garrison, L. M.↗