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At least 325 records · Page 18

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NASA NTRS1971

Determination of stratospheric temperature and height gradients from nimbus 3 radiation data

To improve the specification of stratospheric horizontal temperature and geopotential height fields from satellite radiation data, needed for high flying aircraft, a technique was derived to estimate data between satellite tracks using interpolated IRIS 15-micron data from Nimbus III. The interpolation is based on the observed gradients of the MRIR 15-micron radiances between subsatellite tracks. The technique was verified with radiosonde data taken within 6 hours of the satellite data. The sample varied from 1126 pairs at low levels to 383 pairs at 10 mb using northern hemisphere data for June 15 to July 20, 1969. The data were separated into five latitude bands. The Rms temperature differences were generally from 2 to 5 C for all levels above 300 mb. From 500 to 300 mb RMS differences vary from 4 to 9C except at high latitudes which show values near 3C. The RMS differences between radiosonde heights and those calculated hydrostatically from the surface were from 30 to 280 meters increasing from the surface to 10 mb. Integration starting at 100 mb reduced the RMS difference in the stratosphere to 20 to 120 meters from 70 to 10 mb. From a comparison with actual operational maps at 50 and 10 mb, it appears the techniques developed produce analyses in general agreement with those from radiosonde data. In addition, they are able to indicate details over areas of sparse data not shown by conventional techniques.

Nicholas, G. W.↗

NASA NTRS1971

Development and testing of the infrared interferometer spectrometer for the Mariner Mars 1971 spacecraft

The design, development and testing of the infrared interferometer spectrometer is reported with emphasis on the unique features of the Mariner instrument as compared to previous IRIS instruments flown on the Nimbus meteorological research satellites. The interferometer functions in the spectral range from 50 microns to 6.3 microns. A noise equivalent radiance of 0.5 X 10 to the -7th power W/sq cm/ster/cm has been achieved. Major improvements that were implemented included the cesium iodide beamsplitter and electronic features to suppress the effect of vibration on the Michelson mirror motion and digital filtering through the summation of increased sampling of the infrared signal. A bit error detection and correction scheme was also implemented in order to recover the science data with a higher level of confidence over the telecommunication link.

Hanel, R. H.↗

NASA NTRS1972

Rocket/Nimbus Sounder Comparison (RNSC)

The experimental results for radiance and temperature differences in the Wallops Island comparisons indicate that the differences between satellite and rocket systems are of the same order of magnitude as the differences among the various satellite and rocket sounders. The Arcasondes produced usable data to about 50 km, while the Datasondes require design modification. The SIRS and IRIS soundings provided usable data to 30 mb; extension of these soundings was also investigated.

Source record↗

NASA NTRS1971

Interhemispheric comparison of atmospheric circulation features as evaluated from NIMBUS satellite data

Findings are presented for IRIS data from NIMBUS 3 in mapping the global ozone distribution. The seasonal and regional variations of ozone, especially in the Southern Hemisphere, reveal features that were not evident from the sparse ground-based ozone observation network in this hemisphere. A regression analysis was undertaken for temperature and height fields on radiance data. Spectrum analyses of upper wind data from the North American section and Australia were completed.

Reiter, E. R.↗

NASA NTRS1972

Atmospheric wind fields derived from Nimbus ozone measurements

The global ozone measurements made by the Nimbus 3 IRIS were used to trace the circulation in the upper troposphere. This was possible because the atmospheric ozone content is closely related to the geopotential heights in the upper troposphere. There is a linear relationship between 200 mbar geopotential heights and the total ozone measured by Nimbus 3. With the help of the geostrophic law, atmospheric winds can be derived from the horizontal gradient of the geopotential heights. Utilizing the linear relationship shown, winds can be deduced from satellite measurements of total ozone.

Prabhakara, C.↗

NASA NTRS1973

A composite study of cloud, ozone and other data from recent satellite experiments

Pictorial data from the Image Dissector Camera System (IDCS) and Temperature-Humidity Infrared Radiometer (THIR) experiments on Nimbus 4 satellite are analyzed along with: (a) global total ozone maps prepared from Infrared Interferometer Spectrometer (IRIS) data and (b) total ozone and its vertical distribution as derived from Backscatter Ultraviolet (BUV) spectrometer data. A close relationship is generally observed between centers of high ozone and vortices in the IDCS and THIR montages. This is also confirmed by low centers in the 200 mb Northern Hemisphere charts. The vertical distribution of ozone indicates that the enhancement in ozone in these cases occurs in the lower stratosphere (and possibly to a minor extent in the troposphere) rather than in the upper stratosphere and mesosphere.

Rao, M. S. V.↗

NASA NTRS1973

Mechanisms for Mars dust storms.

Characteristics of the Mars global dust storm are reviewed. At the Mariner 9 encounter, the dust consisted of highly absorbing particles distributed rather uniformly up to great height (about 50 km). These observations together with temperature distributions inferred from the Mariner 9 IRIS by Hanel et al. (1972) are used to estimate global wind systems during the dust storm. The global distribution and direction of light surface streaks indicate that the axisymmetric circulation was a dominant part of flow during the dust storm. The axisymmetric winds may become strong enough to raise dust over wide areas of Mars' tropics under unusual conditions: the incoming solar radiation must be near its seasonal maximum, the static stability must be low, and the atmosphere must be able to absorb and re-emit a sizeable fraction of the incoming radiation. Strong winds around the periphery of the retreating south polar cap would be driven by the temperature gradient at the cap edge and by the mass outflow due to subliming CO2. These polar winds could generate local dust storms, raising the general level of dustiness, and providing the conditions necessary for onset of a global dust storm.

Leovy, C. B.↗

NASA NTRS1974

Mariner Jupiter/Saturn 1977 infrared interferometer spectrometer (MJS' 77) design study

A design study of the Infrared Interferometer Spectrometer and Radiometer (IRIS) instrument for the Mariner Jupiter/Saturn 1977 mission was conducted. The objective of the study was to investigate a number a potential problem areas identified in previous studies and to develop the instrument system designs along the lines providing for the optimum performance obtainable with the allowable budgets. The considerations for the optical design, mechanical design, and electronic design are examined.

Source record↗

NASA NTRS1974

Mariner-9 based simulation of radiative convective temperature changes in the Martian dust-laden atmosphere-soil system

A numerical simulation of radiative, conductive, and convective heat transfer of the Martian dust-laden atmosphere-soil system is presented with particular emphasis given to heating/cooling in regions of sharp variation in temperature or absorption and its resultant impact on outgoing planetary spectral radiance, as measured by the Mariner 9 IRIS. Thermal coupling between the ground and atmospheric subsystems is modeled by the total heat flux balance at the interface. In the simulation procedure, local thermodynamic equilibrium (LTE) is assumed, and a combined strong-weak line transmission function permits short- and long-range exchanges of energy from the surface toward space. Direct absorption of insolation in the near-IR bands by both silicate dust and CO2 is incorporated.

Dannevik, W. P.↗

NASA NTRS1974

Techniques for carrying out radiative transfer calculations for the Martian atmospheric dust

A description is given of the modification of a theory on the reflectance of particulate media so as to apply it to analysis of the infrared spectra obtained by the IRIS instrument on Mariner 9. With the aid of this theory and the optical constants of muscovite mica, quartz, andesite, anorthosite, diopside pyroxenite, and dunite, modeling calculations were made to refine previous estimates of the mineralogical composition of the Martian dust particles. These calculations suggest that a feldspar rich mixture is a very likely composition for the dust particles. The optical constants used for anorthosite and diopside pyroxenite were derived during this program from reflectance measurements. Those for the mica were derived from literature reflectance data. Finally, a computer program was written to invert the measured radiance data so as to obtain the absorption coefficient spectrum which should then be independent of the temperature profile and gaseous component effects.

Aronson, J. R.↗

NASA NTRS1975

A simple method to incorporate water vapor absorption in the 15 microns remote temperature sounding

The water vapor absorption in the 15 micron CO2 band, which can affect the remotely sensed temperatures near the surface, are estimated with the help of an empirical method. This method is based on the differential absorption properties of the water vapor in the 11-13 micron window region and does not require a detailed knowledge of the water vapor profile. With this approach Nimbus 4 IRIS radiance measurements are inverted to obtain temperature profiles. These calculated profiles agree with radiosonde data within about 2 C.

Dallu, G.↗

NASA NTRS1975

Automatic exposure control for space sequential camera

The final report for the automatic exposure control study for space sequential cameras, for the NASA Johnson Space Center is presented. The material is shown in the same sequence that the work was performed. The purpose of the automatic exposure control is to automatically control the lens iris as well as the camera shutter so that the subject is properly exposed on the film. A study of design approaches is presented. Analysis of the light range of the spectrum covered indicates that the practical range would be from approximately 20 to 6,000 foot-lamberts, or about nine f-stops. Observation of film available from space flights shows that optimum scene illumination is apparently not present in vehicle interior photography as well as in vehicle-to-vehicle situations. The evaluation test procedure for a breadboard, and the results, which provided information for the design of a brassboard are given.

Mcatee, G. E., Jr.↗

NASA NTRS1974

Ground-based observations of Mars and Venus water vapor during 1972 and 1973

The Venus water vapor line at 8197.71 A has been monitored at several positions on the disk of Venus and at phase angles between 22 and 91 degrees. Comparisons are made between the water vapor abundances, the presence of UV features, and the CO2 abundances determined from near simultaneous observations of CO2 bands at the same positions on the disk of Venus. Two periods of the Martian year have been monitored. The first period was during and after the great 1971 dust storm (L8 = 280 to 20 degrees or summer in the southern hemisphere). The results obtained are compared to the Mariner 9 IRIS and Mars 3 observations made during the same period. During the second period (L8 = 124 to 266 degrees) observations were made to follow the seasonal latitudinal and diurnal changes in the water vapor abundance in the Martian atmosphere. Studies of the latitudinal and diurnal water vapor distributions indicate that the location of maximum and minimum abundances for this season are positively correlated with surface temperature variations.

Barker, E. S.↗

NASA NTRS1975

The light curve of CV Serpentis, the sometimes-eclipsing Wolf-Rayet star

New photoelectric observations of the B-magnitude of CV Ser made in 1973 and 1974 show no clear evidence of an eclipse, but they establish night-to-night variability of several percent, a systematic brightness change of 0.035 mag during a portion of the single orbit observed in 1973, and irregular flaring in 1974. We made iris photometer measurements of Harvard patrol plates taken between 1905 June and 1953 July, and find no evidence of a very deep eclipse such as observed by Hjellming and Hiltner. We present several new light curves and discuss then in the light of the recent results of Cowley et al.

Schild, R.↗

NASA NTRS1975

A procedure for estimation of sea-surface temperature from remote measurements in the 10 - 13 micrometers spectral region

The feasibility is demonstrated of a procedure for the remote measurement of sea-surface temperature which inherently corrects for the effect of the intervening atmosphere without recourse to climatological data. The procedure relies upon the near-linear differential absorption properties of the infrared window region between 10 and 13 micrometers and requires radiometric measurements in a minimum of two spectral intervals within the infrared window which have a significant difference in absorption coefficient. The procedure was applied to Nimbus 4 infrared interferometer spectrometer (IRIS) data and to Skylab EREP S191 spectrometer data, and it is demonstrated that atmospheric effects on the observed brightness temperature can be reduced to less than 1.0 Kelvin.

Anding, D. C.↗

NASA NTRS1975

Composition of the Martian dust as derived by infrared spectroscopy from Mariner 9

The Martian dust spectra obtained by the infrared interferometer spectrometer (Iris) experiment on Mariner 9 have been compared with modeling computations for various minerals and rocks. The model used was based upon a recently developed theory of absorption and scattering by particulate materials. The results indicate that the composition of Martian dust is biased toward silicate structures which involve a high degree of silicate oxygen sharing. A feldspar-rich dust of approximately 1-micron particle size appears to be the best candidate, although sheet-structure silicates cannot be ruled out.

Aronson, J. R.↗

NASA NTRS1975

A method of using cluster analysis to study statistical dependence in multivariate data

A technique is presented that uses both cluster analysis and a Monte Carlo significance test of clusters to discover associations between variables in multidimensional data. The method is applied to an example of a noisy function in three-dimensional space, to a sample from a mixture of three bivariate normal distributions, and to the well-known Fisher's Iris data.

Borucki, W. J.↗

NASA NTRS1978

Properties of dust in the Martian atmosphere and its effect on temperature structure

Recent spacecraft missions to Mars have made it possible to define a number of properties of dust particles in the Mars atmosphere and to determine the influence of these particles on the vertical temperature structure. The present study draws primarily upon analyses of data from the Viking Lander imaging experiment and from the IRIS experiment of the Mariner 9 Orbiter. These data are used in a one-dimensional radiative-convective model to obtain a first-order estimate of the atmospheric temperature profile, and these predictions are compared with relevant Viking observations.

Pollack, J. B.↗