Engineering topics

Croskey, Charles L.

Publications and source records attributed to Croskey, Charles L..

7 records

NASA NTRS1997

The CSSL (combined sporadic structures and layers) payload: In situ observations of mesospheric sodium and related parameters

The objectives, design and results of the sensor systems for the combined sporadic structures and layers (CSSL) payload are analyzed. The CSSL main objectives were to: validate current models of mesospheric sodium chemistry; explore the relationship between turbulence and Na fluctuations; and to explore the relationship between high latitude electric fields and the formation of Na anomalies.

Machuga, David W.↗

NASA NTRS1997

Charged aerosols and electrical structure of the polar summer mesopause region

The results of observations carried out in the framework of two programs, the middle atmosphere electrodynamics campaign and the noctilucent cloud (NLC) campaign, are reported. The measurements performed during overhead NLC and polar mesosphere summer echo (PMSE) conditions revealed a number of aerosol-related layering effects on the region's electrical structure. It was found that both polar components of electrical conductivity can be affected in NLC regions.

Mitchell, John D.↗

NASA NTRS1996

Middle Atmosphere Electrodynamics During a Thunderstorm

Rocket-based instrumentation investigations of middle atmospheric electrodynamics during thunderstorms were conducted in coordination with balloon-measurements at Wallops Island, Virginia. Middle atmosphere electrodynamics and energy coupling are of particular importance to associated electrical processes at lower and higher altitudes. Objectives of this research effort included: (1) investigation of thunderstorm effects on middle atmosphere electrical structure, including spatial and temporal dependence; (2) characterization of electric field transients and the associated energy deposited at various altitudes; (3) evaluation of the vertical Maxwell current density over a thunderstorm to study the coupling of energy to higher altitudes; and (4) investigation of the coupling of energy to the ionosphere and the current supplied to the 'global circuit.'

Croskey, Charles L.↗

NASA NTRS1995

Electrical structure and E-fields in the high-latitude mesosphere

A description of the electric structure as observed during a rocket sounding noctilucent cloud (NLC) observation program in the summer of 1991, is presented. Both NLC and polar mesosphere summer echo (PMSE) conditions were determined. The observable effects on ions and electrons were measured in the NLC and PMSE regions and associated electric field (E-fields) measurements indicated small alternating current vertical fields. The following findings are reported: small and large scale electron density structure is noticeable in the NLC regions; above 82 km, the occurrence of very low-mobility positive ions directly demonstrates the existence of charged aerosols, and small alternating current vertical electric fields were observed in the NLC and PMSE region.

Mitchell, John D.↗

NASA NTRS1991

Radiometric remote sensing of mesospheric and stratospheric water vapor

The remote sensing of stratospheric and mesospheric water vapor by microwave and millimeter radiometry is described. The received radiation is emitted by and interacts with all levels of the atmosphere. The pressure dependence of the linewidth for the absorption cross section of water vapor permits retrieval of vapor mixing ratios. The 183.31-GHz line of water vapor can also be used for remote sensing of the water vapor concentration in the upper atmosphere, but due to the much stronger absorption cross section for this line, ground-based observations are difficult. To date all measurements at 183 GHz have been made from platforms above the troposphere.

Croskey, Charles L.↗

NASA NTRS1991

Ground-based microwave remote sensing of water vapor in the mesosphere and stratosphere

A ground-based, portable microwave radiometer that will be used to measure water vapor in the 30-80-km altitude region, and is to operate 24 hr a day, is described. The thermally excited 22.235-GHz rotational-transition line of water vapor is employed. The emission from this region produces a signal with an apparent brightness temperature of the order 0.1 to 0.5 K. A steerable reflector is used to provide optimal viewing angles, depending on the geographic location and season. Periodic tipping curve scans by this reflector permit determination of the amount of tropospheric correction that is applied to the data. All local oscillators in the receiver are crystal-controlled so that narrow-band spectral analysis of the received line shape can be performed.

Croskey, Charles L.↗

NASA NTRS1989

Mesospheric water vapor measurements from Penn State - Monthly mean observations (1984-1987)

Mesospheric water vapor measurements obtained by ground-based microwave spectroscopy between November 1984 and July 1987 are examined. Monthly mean water vapor profiles are used to establish annual and interannual variability. The results suggest that the seasonal variation of upper mesospheric water vapor is dominated by an annual component with low mixing ratios in winter and high mixing ratios in summer. The results are compared with those reported by Bevilacqua et al. (1987).

Bevilacqua, Richard M.↗