Engineering topics

Skinner, Wilbert R.

Publications and source records attributed to Skinner, Wilbert R..

7 records

NASA NTRS1994

Incorporation of multiple cloud layers for ultraviolet radiation modeling studies

Cloud data sets compiled from surface observations were used to develop an algorithm for incorporating multiple cloud layers into a multiple-scattering radiative transfer model. Aerosol extinction and ozone data sets were also incorporated to estimate the seasonally averaged ultraviolet (UV) flux reaching the surface of the Earth in the Detroit, Michigan, region for the years 1979-1991, corresponding to Total Ozone Mapping Spectrometer (TOMS) version 6 ozone observations. The calculated UV spectrum was convolved with an erythema action spectrum to estimate the effective biological exposure for erythema. Calculations show that decreasing the total column density of ozone by 1% leads to an increase in erythemal exposure by approximately 1.1-1.3%, in good agreement with previous studies. A comparison of the UV radiation budget at the surface between a single cloud layer method and a multiple cloud layer method presented here is discussed, along with limitations of each technique. With improved parameterization of cloud properties, and as knowledge of biological effects of UV exposure increase, inclusion of multiple cloud layers may be important in accurately determining the biologically effective UV budget at the surface of the Earth.

Charache, Darryl H.↗

NASA NTRS1993

The high-resolution Doppler imager on the Upper Atmosphere Research Satellite

The high-resolution Doppler imager (HRDI) on the Upper Atmosphere Research Satellite is a triple-etalon Fabry-Perot interferometer designed to measure winds in the stratosphere, mesosphere, and lower thermosphere. Winds are determined by measuring the Doppler shifts of rotational lines of the O2 atmospheric band, which are observed in emission in the mesosphere and lower thermosphere and in absorption in the stratosphere. The interferometer has high resolution (0.05/cm), good offhand rejection, aud excellent stability. This paper provides details of the design and capabilities of the HRDI instrument.

Hays, Paul B.↗

NASA NTRS1992

Extraction of Aerosol and Rayleigh Components from Doppler Lidar Return Signal

One of the most significant problems which limits the applicability of lidar systems for pressure and density profile measurements below 30 km altitude is the presence of atmospheric aerosols which contaminate the molecular or Rayleigh return signal. A new technique is described which allows for the separation of the return signal into aerosol and molecular scattered components. The technique was applied to data from the University of Michigan's High Resolution Doppler Lidar (HRDL).

Barnes, John E.↗

NASA NTRS1992

Tropospheric and stratospheric wind profiling with a direct detection Doppler lidar

The Space Physics Research Laboratory at the University of Michigan has been operating a direct detection, high resolution Doppler Lidar (HRDL) to measure winds in the boundary layer, free troposphere and lower stratosphere. A direct detection Doppler lidar measures the Doppler shift of the aerosol or Rayleigh backscattered signal, from which the wind velocity vector can be retrieved (Benedetti-Michelangeli et al, 1972, 1974; Chanin et al., 1989; Abreu et al., 1992). The system components are shown. The transmitting system is a Continuum NY-60 Nd:YAG laser frequency doubled to a wavelength of 532 nm. The laser is injection seeded for single line mode operation yielding a linewidth of 0.0045 cm(exp -1) (135 MHz) with excellent shot-to-shot frequency stability. The laser produces 60 mJ pulses and operates at a 50 Hz repetition rate for an effective output power of 3.0 W. A description of the University of Michigan's Doppler lidar is given with examples of wind profiles for the boundary layer, free troposphere, and for the lower stratosphere. The system provides a reliable method of remotely measuring the wind. The wind error is smallest in regions of high aerosols. The system also produces aerosol extinction profiles versus altitude which can be determined by the shape of the spectra. The system has been installed in a trailor so that measurements can be made for field campaigns. Winds and aerosol data are available immediately at the site for use in forecasting.

Abreu, Vincent J.↗

NASA NTRS1987

Optimization of a triple etalon interferometer

The High Resolution Doppler Image (HRDI) is a triple etalon Fabry-Perot interferometer designed to measure Doppler shifts of rotational lines in the O2 atmospheric system from the Upper Atmosphere Research Satellite. These shifts are used to determine wind vectors in the stratosphere and mesosphere. This paper presents the techniques used to determine the gap thicknesses and reflectivities of the three etalons of the HRDI instrument. The spacings are found to be 1.000, 0.186, and 0.025 cm. These spacings are independent of the reflectivity of the etalons. The reflectivities of the three etalons should be nearly equal to minimize the errors in the wind measurement caused by mistuning of the etalons. The choice of the reflectivity does not strongly influence the statistical error in the wind error when the values are less than about 0.90.

Skinner, Wilbert R.↗

NASA NTRS1987

Use of gamma ray radiation to parallel the plates of a Fabry-Perot interferometer

The use of gamma radiation to parallel the plates of a Fabry-Perot etalon is examined. The method for determining the etalon parallelism, and the procedure for irradiating the posts are described. Changes in effective gap for the etalon over the surface are utilized to measure the parallelism of the Fabry-Perot etalon. An example in which this technique is applied to an etalon of fused silica plates, which are 132 mm in diameter and coded with zinc sulfide and cryolite, with Zerodur spaces 2 cm in length. The effect of the irradiation of the posts on the thermal performance of the etalon is investigated.

Skinner, Wilbert R.↗

NASA NTRS1986

Observation of molecular rotational bands with a single Fabry-Perot interferometer

A method is described for using a single Fabry-Perot interferometer to study the emissions from an entire molecular rotation band, not just a single line to determine atmospheric temperature. It is shown that if the effective line spacing of the band to free spectral range is nearly a rational number, the resulting signal is highly temperature sensitive, particularly at low temperatures. It is shown that the finesse of the instrument is not extremely important but that the instrument function must be known very precisely. The method is illustrated with the O2 atmospheric band and an interferometer flown on the Dynamics Explorer 2 satellite.

Skinner, Wilbert R.↗