Engineering topics

Clancy, R. Todd

Publications and source records attributed to Clancy, R. Todd.

26 records · Page 2

NASA NTRS1992

Observations of Mars using Hubble Space Telescope

The lack of a continuous record of Martian meteorology or of volatile cycles on Mars for extended periods of several Martian years seriously hinders efforts to understand the physics of the Martian atmosphere and surface system. The spacecraft observations are limited to only a few isolated time periods, and the Earth based record is limited by the relatively short periods surrounding oppositions when telescopic observations can yield useful data. To remedy this situation, the authors have embarked on a three year program of Mars observations using the Hubble Space Telescope (HST). Several scientific investigations are being carried out using the images, including: a study of the albedo variations; unit mapping of spectral reflectances; determination of optical depths due to aerosols and condensates; a study of the properties of condensate clouds and hoods; comparison of surface and atmospheric features; observation of size and shape of the polar caps; and investigation of surface atmospheric phenomena.

James, Philip B.↗

NASA NTRS1991

Planetary atmospheres: Microwave spectroscopic studies of planetary atmospheres

Ground-based spectroscopic observations of isotopes of CO in the atmospheres of Mars, Venus, and Titan have been collected over the 1982-1990 period. These observations have been analyzed to obtain information on the photochemistry, dynamics, and thermal profiles of these planetary atmospheres. In the cases of the mesosphere (80-100 km altitude) of Venus and the lower atmosphere (0-70 km altitude) of Mars, the primary conclusion of this research is that significant interannual variations in the global thermal and compositional structures of these atmospheres occur over 10 year periods. The Titan studies have focussed on pinning down the true atmospheric CO abundance. A more detailed summary of the results for each of these planetary atmospheres is provided.

Clancy, R. Todd↗

NASA NTRS1990

Global changes in the 0-70 km thermal structure of the Mars atmosphere derived from 1975 to 1989 microwave CO spectra

J = 1 - 2 (C-12)O (230 GHz) and (C-13)O (220 GHz) spectra of Mars obtained during the particularly favorable opposition of Mars in 1988 are analyzed. A CO mixing ratio is derived for November 1988 which agrees with a determination from 1967 observations. It is demonstrated that if the mixing ratio of CO was not drastically different in early 1980 and early 1982, the low- to midlatitude average thermal structure of the Mars atmosphere at these times was consistent with clear-air radiative-convective equilibrium conditions. Mars atmospheric temperature profiles derived from (C-12)O spectra are also presented.

Clancy, R. Todd↗

NASA NTRS1990

Corrections regarding the Lellouch et al. (1989) analysis of Mars atmospheric C-12O and C-13O spectra

Lellouch et al. (1989) obtained atmospheric CO mixing ratios from Martian C-12O and C-13O microwave spectra that were 3-5 times greater than the Kaplan et al. (1969) IR measurememts; they also inferred a factor-of-2 increase in atmospheric CO abundance between September, 1986 and January, 1987. A reanalysis has been conducted of the Lellouch material, and more detailed treatment of the radiative transfer analysis indicates that its observations are consistent with the Kaplan CO volume mixing ratio determination. It is also ascertained that the Lellouch atmospheric temperature profiles are in error, with no evidence being found for the extreme temperature inversions inferred for the lowest 5 km of the Martian atmosphere.

Clancy, R. Todd↗

NASA NTRS1990

Planetary atmospheres: Microwave spectroscopic and space physics

Ground-based spectroscopic observations of isotopes of CO in the atmosphere of Mars, Venus, and Titan were collected over the 1982-1990 period. These observations were analyzed to obtain information on the photochemistry, dynamics, and thermal profiles of these planetary atmospheres. In the cases of the mesosphere (80-100 km altitude) of Venus and the lower atmosphere (0-70 km altitude) of Mars, the primary conclusion of this research is that significant interannual variation in the global, thermal, and compositional structures of these atmospheres occur over 10 year periods. The Titan studies have focussed on pinning down the true atmosphere CO abundance. A more detailed summary of the results for each of these planetary atmospheres is provided.

Clancy, R. Todd↗

NASA NTRS1989

Climatology and trends of mesospheric (58-90) temperatures based upon 1982-1986 SME limb scattering profiles

Atmospheric temperature profiles for the altitude range 58-90 km were calculated using data on global UV limb radiances from the SME satellite. The major elements of this climatology include a high vertical resolution (about 4 km) and the coverage of the 70-90 km altitude region. The analysis of this extensive data set provides a global definition of mesospheric-lower thermospheric temperature trends over the 1982-1986 period. The observations suggest a pattern of 1-2 K/year decreases in temperatures at 80-90-km altitudes accompanied by 0.5-1.5 K/year increases in temperatures at 65-80-km altitudes.

Clancy, R. Todd↗

NASA NTRS1988

Stratospheric NO2 over Antarctica as measured by the Solar Mesosphere Explorer during austral spring, 1986

This paper presents the results of polar NO2 measurements carried out by the SME satellite during the fall and spring of 1985 and 1986 and compares the results with observations at the north pole and the results of model calculations. During the austral spring, a polar low was observed in stratospheric NO2 densities measured between 24 and 40 km, consistent with the predictions of standard photochemical theory. The geographic extent of the area of low NO2 densities was found to decrease as the hours of sunlight increased, in marked contrast to the behavior of the Antarctic ozone hole during the same period. A comparison of measurements with model calculations for NO2 imply that much of the odd nitrogen is converted to HNO3 during the polar night. Data also suggest no evidence that changes in high-altitude odd nitrogen are influencing the ozone below, or that the 'ozone hole' penetrates above 24 km to affect odd nitrogen there.

Thomas, Ronald J.↗

NASA NTRS1988

Solar Mesosphere Explorer observations of stratospheric and mesospheric water vapor

It is noted that while the SME (Solar Mesosphere Explorer) data is consistent with the earlier LIMS (Limb Infrared Monitor of the Stratosphere) results, its interpretation is complicated by aerosol contamination, particularly at altitudes below 35 km. This contamination arose from several volcanic eruptions, including that of El Chichon. Analyses are reported of a subset of data from the SME satellite, concentrating primarily on the period January through March 1982 so as to avoid contamination from the El Chichon volcanic aerosol. The SME observations of water vapor between 20 and 60 km were inverted for the first three months of 1982 as well as for selected additional periods. Reasonable results are obtained at locations where no contamination by aerosol is suspected.

Jakosky, Bruce M.↗