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Wallio, H. A.

Publications and source records attributed to Wallio, H. A..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

New Remote Gas Sensor Using Rapid Electro-Optical Path Switching

Innovative gas filter correlation radiometer (GFCR) features nonmechanical switching of internal optical paths. Incoming radiation switched electro-optically, by means of polarization, between two optical paths, one of which contains correlation gas cell while other does not. Advantages include switching speed, 2 to 3 orders of magnitude faster than mechanical techniques, and high reliability. Applications include regional studies of atmospheric chemistry from either manned or unmanned aircraft as well as satellite studies of global distributions, sources and sink mechanisms for key species involved in chemistry of troposphere. Commercial applications: ability to survey many miles of natural gas pipelines rapidly from aircraft, pinpointing gas leaks by measuring methane at 2.3 micrometers.

Sachse, G. W.↗
NASA NTRS1992

Differential correction technique for removing common errors in gas filter radiometer measurements

The Measurement of Air Pollution from Satellites (MAPS) gas filter radiometer experiment was designed to measure CO mixing ratios in the earth's atmosphere. MAPS also measures N2O to provide a reference channel for the atmospheric emitting temperature and to detect the presence of clouds. In this paper we formulate equations to correct the radiometric signals based on the spatial and temporal uniformity of the N2O mixing ratio in the atmosphere. Results of an error study demonstrate that these equations reduce the error in inferred CO mixing ratios. Subsequent application of the technique to the MAPS 1984 data set decreases the error in the frequency distribution of mixing ratios and increases the number of usable data points.

Wallio, H. A.↗
NASA NTRS1990

Tropospheric sounders

The Measurement of Air Pollution Satellites (MAPS) experiment is a nadir-viewing gas correlation filter radiometer that has flow on the space shuttle in 1981 and 1984. The Tropospheric Radiometer for Atmospheric Chemistry and Environment Research (TRACER) is a proposed multi-level gas correlation filter radiometer experiment proposed for the Earth Observing System (Eos) and has received phase 1 approval. Each experiment is discussed.

Wallio, H. A.↗
NASA NTRS1986

Middle and upper tropospheric carbon monoxide mixing ratios as measured by a satellite-borne remote sensor during November 1981

Mixing ratios of tropospheric carbon monoxide measured by a gas filter radiometer carried aboard the Space Shuttle during November 1981 are reported. The data represent average mixing ratios in the middle and upper troposphere between 38 deg N and 38 deg S latitude. Approximately 10,000 individual measurements were obtained in each of the two channels of the instrument. The data are presented in the form of plots that show the individual carbon monoxide mixing ratio measurements as a function of latitude and longitude and in the form of maps that show the data averaged over 5 deg latitude by 5 deg longitude squares. The data show relatively little variation in the mixing ratio in the Southern Hemisphere; however, the data from both the tropics and the Northern Hemisphere show strong gradients with both latitude and longitude.

Reichle, H. G., Jr.↗
NASA NTRS1986

Gas filter radiometer for carbon monoxide measurements during the 1979 Summer Monsoon Experiment (MONEX)

The instrumental and data-reduction techniques used in obtaining remote measurements of carbon monoxide during the 1979 Summer Monsoon Experiment are described. The form of the signal function (the variation of signal with altitude) and the impact of variations in the vertical distribution of carbon monoxide are discussed. Estimates of the experimental accuracy are made both by assessment of error sources through the use of numerical simulations and by comparison with concurrent measurements made by means of gas chromatography. It is found that the radiometric measurements tend to be about 9 percent lower than the direct measurements and to have a precision of about 8 percent.

Reichle, H. G., Jr.↗
NASA NTRS1983

Carbon monoxide mixing ratio inference from gas filter radiometer data

A new algorithm has been developed which permits, for the first time, real time data reduction of nadir measurements taken with a gas filter correlation radiometer to determine tropospheric carbon monoxide concentrations. The algorithm significantly reduces the complexity of the equations to be solved while providing accuracy comparable to line-by-line calculations. The method is based on a regression analysis technique using a truncated power series representation of the primary instrument output signals to infer directly a weighted average of trace gas concentration. The results produced by a microcomputer-based implementation of this technique are compared with those produced by the more rigorous line-by-line methods. This algorithm has been used in the reduction of Measurement of Air Pollution from Satellites, Shuttle, and aircraft data.

Wallio, H. A.↗
NASA NTRS1982

Carbon monoxide measurements in the troposphere

Approximately 35 hours of radiometric measurements were obtained of the CO mixing ratio in the middle troposphere, upper troposphere, and lower stratosphere, by means of the Measurement of Air Pollution from Satellites (MAPS) experiment carried in the OSTA-1 payload of the second Space Shuttle flight. In view of gas filter radiometer data in the 4.67-micron band, gathered over the 38 N-38 S latitude region during both daytime and nighttime, the performance of MAPS was excellent. Significant gradients have been found in the middle tropospheric CO mixing ratio with both latitude and longitude over the North Atlantic, the Mediterranean Sea, and the Middle East.

Reichle, H. G., Jr.↗
NASA NTRS1981

A new method for inferring carbon monoxide concentrations from gas filter radiometer data

A method for inferring carbon monoxide concentrations from gas filter radiometer data is presented. The technique can closely approximate the results of more costly line-by-line radiative transfer calculations over a wide range of altitudes, ground temperatures, and carbon monoxide concentrations. The technique can also be used over a larger range of conditions than those used for the regression analysis. Because the influence of the carbon monoxide mixing ratio requires only addition, multiplication and a minimum of logic, the method can be implemented on very small computers or microprocessors.

Wallio, H. A.↗
NASA NTRS1974

A study of the possible characteristics of a low-altitude electron layer in the Martian atmosphere

The apparent diurnal Martian surface pressure variations, as deduced from radio occultation experiments, is discussed and explained as possibly arising from the effect of a low-altitude electron layer. Possible source and loss mechanisms for the low altitude electron layer are presented and discussed. Time dependent differential equations describing the electron layer are derived, and then integrated to investigate the electron distribution resulting from several processes that might occur in the atmosphere. It is concluded that the source mechanism is the sublimation of alkali atoms from a permanent dust layer, and that the dominant loss process must involve CO2 clustering about the alkali atoms. An electron layer is developed which explains the apparent diurnal surface pressure variation.

Wallio, H. A.↗
NASA NTRS1973

The characteristics of a possible low altitude electron layer in the Martian atmosphere

The apparent diurnal Martian surface pressure variation, as deduced from radio occultation experiments, is discussed and explained as possibly arising from the effect of a low altitude electron layer. Possible source and loss mechanisms for the low altitude electron layer are presented and discussed. Time-dependent differential equations describing the electron layer are derived and then integrated to investigate the electron distribution resulting from the several processes that might occur in the atmosphere. It is concluded that the source mechanism is the sublimation of alkali atoms from a permanent dust layer (a dust layer of 0.2 micron particles of density 9/cu cm is sufficient), and that the dominant loss process must involve CO2 clustering to the alkali atoms. Using these processes, an electron layer is developed which would explain the apparent diurnal surface pressure.

Wallio, H. A.↗
NASA NTRS1972

A comparison of techniques for inversion of radio-ray phase data in presence of ray bending

Derivations are presented of the straight-line Abel transform and the seismological Herglotz-Wiechert transform (which takes ray bending into account) that are used in the reconstruction of refractivity profiles from radio-wave phase data. Profile inversion utilizing these approaches, performed in computer-simulated experiments, are compared for cases of positive, zero, and negative ray bending. For thin atmospheres and ionospheres, such as the Martian atmosphere and ionosphere, radio wave signals are shown to be inverted accurately with both methods. For dense media, such as the solar corona or the lower Venus atmosphere, the refractive recovered by the seismological Herglotz-Wiechert transform provide a significant improvement compared with the straight-line Abel transform.

Wallio, H. A.↗
NASA NTRS1972

Profile inversion in presence of ray bending

Inversion of radio occultation data for planetary atmospheres and ionospheres has been performed using the seismological Herglotz-Wiechert method, as adapted by Phinney and Anderson to the radio-occultation case. Profile reconstruction performed in computer simulated experiments with this approach have been compared with the ones obtained with the straight-ray Abel transform. For a thin atmosphere and ionosphere, like the ones encountered on Mars, microwave occultation data can be inverted accurately with both methods. For a dense ionosphere like the sun's corona, ray bending of microwaves is severe, and recovered refractivity by the Herglotz-Wiechert method provides significant improvement over the straight-ray Abel transform: the error reduces from more than 60% to less than 20% at a height of 60,000 km above the base of the corona.

Wallio, H. A.↗
NASA NTRS1972

Mars lower atmosphere - Some new implications.

Based on occultation data from the Mariner spacecraft, there are some preliminary indications of an apparent systematically higher surface pressure on the night side of Mars than on the day side. If confirmed by additional data currently becoming available, this apparent surface pressure difference could be attributed to several causes, including topography effects as has been assumed previously, an actual increase of pressure on the night side caused by diurnal effects, an apparent increase on the night side due to some mechanisms such as a dust layer, or an apparent lower pressure on the day side due to the existence of a low-lying electron layer. By calculating the effect of a low-lying electron layer on the combined neutral atmosphere and electron layer refractivity profile, it is found that the day side and night side surface pressures would be in agreement if a layer with maximum density of about 80,000 electrons per cu cm below 15 km altitude were present on the day side.

Michael, W. H., Jr.↗