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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1993

Extensions to the CIRA reference models for middle atmosphere ozone

The recent ozone reference models generated for the new COSPAR CIRA include ozone vertical structure from 25 to 90 km as a function of month and latitude based on five satellite experiments. The new model provided here extends the ozone vertical structure climatology from 20 mb (about 25 km) to 70 mb (about 18 km) based on three years of recently reprocessed AEM-2 SAGE I (sunset) data. In addition, model refinements are made at altitudes above 25 km based on the reprocessed data. Comparisons are made between the ozone reference models and nonsatellite data sets. The model extensions to lower altitudes are in excellent agreement with in situ measurements both at mid latitudes and in the tropics. Annual mean models of ozone are also provided as a function of latitude from 100 mb (about 16 km) to 0.003 mb (about 90 km).

Keating, G. M.↗
NASA NTRS1992

Diurnal variation of overdense meteor echo duration and ozone

The diurnal variation of the median duration of overdense sporadic radar meteor echoes is examined. The meteors recorded in August, December, and January by the Ondrejov meteor radar during the period 1958-1990 were used for the analysis. A maximum median echo duration 1-3 hours after the time of local sunrise in the meteor region confirms the already known sunrise effect. Minimum echo duration occurring at the time of sunset seems to be the most important point of diurnal variation of the echo duration, when ozone is no longer dissociated by solar UV radiation. The effect of diurnal changes of the echo duration should be considered when the mass distribution of meteor showers is analyzed.

Simek, Milos↗
NASA NTRS1992

Atmospheric detectives: Atlas 2 teacher's guide with activities. For use with middle-school students

Can you imagine doing a science project in space? This is the challenging and exciting situation that researchers experience in Spacelab, the laboratory carried inside the Shuttle. Here, hundreds of kilometers above Earth's surface, the crews of the ATLAS missions scan, probe, and measure concentrations of chemicals and water vapor in Earth's protective bubble. So far, one ATLAS crew has rocketed into the atmosphere, watching many sunrises and sunsets come and go while activating delicate instruments and conducting experiments that monitor the complicated interactions between the Sun, the atmosphere, and Earth. We, the crew of ATLAS 2, will continue this important work aboard the Space Shuttle. Together, we will gather data that will be compared with information from satellites, balloons, and instruments on the ground. As part of the National Aeronautics and Space Administration's (NASA's) contribution to Mission to Planet Earth, ATLAS 2 will help develop a thorough picture of the Sun's output, its interaction with the atmosphere, and the well-being of Earth's middle atmosphere. Because the health of the atmosphere is of vital importance to all Earth's inhabitants, everyone should be part of this investigation. You can be active participants in exciting and vital activities: recycling and practicing other conservation methods and gathering information to learn more about how you can keep our atmosphere healthy now, as students, and in the future as informed citizens, scientists, technicians, and mathematicians.

Source record↗
NASA NTRS1993

Solar array thermal snap and the characteristics of its effect on UARS

The single solar array on the Upper Atmosphere Research Satellite (UARS) is subjected to a thermal distortion when the spacecraft enters and exits the Earth's shadow. The distortion results in a torque that alters the spacecraft attitude. Due to the sudden nature of the attitude discontinuity, the effect has been termed 'thermal snap'. Thermal snap has also been experienced by Landsats 4 and 5. Analyses by the spacecraft builder addressed the impact of the resultant torque on the onboard control system. This paper discusses the results of comparisons between the predicted effects of thermal snap on UARS and actual attitude solutions from UARS telemetry data. In addition, this paper describes the characteristics of the thermal snap on UARS in terms of maximum displacement, solar beta angle, and solar array drive angle. Comparisons are made between the actual times of thermal snaps and the predicted spacecraft sunrise and sunset times. The effects of the UARS thermal snap are summarized and a general comment is made relating possible effects of thermal snap on other satellites. Also, an analysis of UARS attitude solutions that span periods of thermal snap was performed to determine whether the gyro sampling time of 1/8 second is sufficient to properly model the resulting spacecraft attitude without compromising the accuracy requirements. The results of this analysis are discussed.

Lambertson, M.↗
NASA NTRS1993

Analysis of selected nitric oxide observations in the lower thermosphere by HALOE on UARS

Measurements of nitric oxide mixing ratios have been made by the Halogen Occultation Experiment on the Upper Atmosphere Research Satellite over an altitude range extending from 15 to 130 km on every spacecraft sunrise and sunset event with the exception of about 8 percent downtime. Selected NO profiles from the first few months of observations were examined with emphasis on the relation between geomagnetic disturbances and enhanced NO in the lower thermosphere. During a large geomagnetic storm on November 8-9, 1991, HALOE obtained 15 NO sunrise profiles along about the 50 deg N latitude circle. A factor of three increase in NO mixing ratio above about 115 km at this latitude and a one to two day decay time were observed. The measured NO longitude/altitude cross section on this day shows a longitudinal asymmetry in the NO distribution with a maximum near the geomagnetic pole. From approximately one month's data, a latitude/altitude cross section of zonal mean NO mixing ratio was calculated. An example of such cross sections demonstrates a strong positive correlation between geomagnetic activity and thermospheric NO globally. This auroral forcing has a larger effect on increasing NO at high latitude than at low latitude.

Luo, Mingzhao↗
NASA NTRS1993

Far-IR Fabry-Perot spectrometer for OH measurements

The Far Infrared Limb Observing Spectrometer (FILOS) is an instrument designed to measure chemical species in the upper atmosphere using limb emission in the FIR region of the spectrum. FILOS uses three Fabry-Perot etalons in series to obtain a resolution of 0.0017/cm near 100/cm (100 microns). It is compact and has low power and low data rate requirements so that it may be flown as an auxiliary balloon payload with larger instruments. FILOS has two 0.05/cm bandwidth channels which are currently tuned to a HCl line at 104.2/cm and a pair of OH lines at 101.3/cm. The instrument is described in further detail and results are presented from two recent balloon flights in which OH was measured as a function of time on one hour centers from sunrise to sunset.

Pickett, Herbert M.↗
NASA NTRS1993

The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment - The ATLAS-1 mission

ATMOS is an investigation of the chemistry and composition of the middle atmosphere using a modified Michelson interferometer designed to be carried on board the Space Shuttle. During orbital sunsets and sunrises it obtains high resolution infrared solar spectra every 2 seconds. The instrument was first flown on the Spacelab 3 mission in April, 1985, and is being reflown as part of the ATLAS series of payloads which started with the ATLAS-1 flight in March 1992. A summary of the results from the Spacelab 3 mission will be presented. These results included several first detections of critical atmospheric species in addition to the thirty or more constituents for which profiles were derived at altitudes between 10 and 150 km. Preliminary results from the ATLAS-1 mission will be described as part of an update to the status of this long term effort.

Gunson, Michael R.↗
NASA NTRS1993

Effects of levitated dust on astronomical observations from the lunar surface

It is believed that a substantial population of levitated dust is present in the terminator region of the moon. Stray light scattered by this dust layer may contaminate astronomical observations made from the lunar surface using infrared, visible, and ultraviolet light. The evidence for dust levitation stems from: Surveyor vidicon images of horizon glow; anomalous brightness in photographs of the solar corona taken by Apollo astronauts while the spacecraft was just inside the moon's shadow; and observations by Apollo astronauts of streamers just prior to lunar orbital sunrise or just after lunar orbital sunset. It has been proposed that the differential charging of the lunar surface in the terminator region due to photoemission and the consequent strong local electric fields comprise the mechanism responsible for this levitation. Although quantitative data on the levitated lunar dust distribution are meager, it is possible to estimate column densities and sizes. In this paper we summarize the estimates of particulate sizes and number densities of previous authors, and construct a nominal terminator dust distribution, as a function of particulate radius and altitude above the lunar surface. Using the model we estimate the brightness of scattered sunshine for three wavelength bands. For the results in the visible wavelengths, we compare the estimated brightness with the known brightness of selected astronomical objects and discuss the implications for lunar-based astronomy.

Murphy, D. L.↗
NASA NTRS1993

Cloud, dust, and ozone vertical profiles from solar occultation measurements: Implications for dynamics

An instrument was designed for solar occultation measurements of the martian atmosphere from the Phobos spacecraft. It was composed of three different dispersive systems working in the ultraviolet (UV: 0.22-0.32 microns) for the measurement of O3 and aerosols, in the near infrared (NIR: 0.76 microns, 0.94 microns) for the detection of O2 and H2O, and in the infrared (IR: 1.9 microns, 3.7 microns) where CO2 and H2O were measured. A detailed description of the instrument may be found in the special issue of Nature. Its principle objective is to measure from the Phobos orbit the spectrum of the Sun, modified by atmospheric extinction, during sunset. The UV-NIR spot has an angular diameter of 1 arcmin, or approximately 3 km vertical resolution, and is located near the center of the solar disk. The IR field is about twice as large and its line of sight is shifted by 8.5 arcmin, or approximately 20 km, relative to the previous one. It is therefore located near the edge of the solar disk. Sampling times are generally 0.5, 1, and 2 s for IR, UV, and NIR channels respectively, corresponding to vertical excursions of the line of sight of 1, 2, and 4 km respectively under nominal conditions. The instrument operated from February 8 to March 26 (the martian equinox occurred on February 17). The latitude of the intersection of the Sun-spacecraft axis with the surface of Mars varied from -11 to +20, the seasonal date L(sub s) being in the range 0 - 20. All measurements were therefore made near northern spring equinox in equatorial regions. Due to an error in the pointing system, only partial results were obtained, the region below approximately equals 30 km altitude being never sounded by the UV-NIR spectrometer. On the contrary, nine complete occultations were obtained in the IR channels, whose line of sight was fortunately approximately equals 20 km below the UV-NIR axis.

Chassefiere, E.↗
NASA NTRS1994

Four years of ground-based total ozone measurements by visible spectrometry in Antarctica

Visible spectrometers SAOZ have been developed at Service d'Aeronomie for permanent ground-based ozone monitoring at all latitudes up to the polar circle in winter. Observations are made by looking at the sunlight scattered at zenith in the visible range, twice a day, at sunrise and sunset. Compared to ozone observations in the UV generally in use, visible observations in the small Chappuis bands at twilight have the advantages of being independent of stratospheric temperature, little contaminated by tropospheric ozone and multiple scattering, and of permitting observations even in winter at the polar circle. SAOZ instruments have been installed since 1988 at several stations in the Antarctic and the Arctic. More than four years data at Dumont d'Urville in Terre Adelie (67 deg S) are now available. The station is generally located at the edge of the vortex in spring and therefore the ozone hole is seen there only occasionally. The lowest values (140 DU) were reported in early October 1991. According to these first regular observations throughout the whole winter ozone seems to increase in late autumn and winter. Its decay does not start before the end of August. Although of smaller amplitude than with the previous version five data, the ratio between the groundbased and satellite/TOMS measurements displays a systematic seasonal variation correlated partly to the sun zenith angle of observations from orbit and partly to the temperature of the stratosphere. Since ground-based measurements are always made at 90 deg SZA, the SZA dependence must come from the satellite data interpretation (TOMS observations are between 43 to 88 deg SZA). The temperature dependence could be partly due to variations of ozone absorption cross-sections in the ultraviolet used by the satellite spectrometer, and partly to a systematic seasonal cycle of the air mass factor use in the interpretation of the ground based observations. However, the last contribution appears to be too small to compensate the ozone increase in winter reported by SAOZ, which is then real.

Goutail, F.↗
NASA NTRS1994

UV-B radiation amplification factor determined based on the simultaneous observation of total ozone and global spectral irradiance

The Japan Meteorological Agency started the spectral observation of solar ultraviolet (UV) irradiance on 1 January 1990 at Tateno, Aerological Observatory in Tsukuba (35 deg N, 140 deg E). The observation has been carried out using the Brewer spectrophotometer for the wavelengths from 290 to 325 nm with a 0.5 nm interval every hour from 30 minutes before sunrise to 30 minutes after sunset throughout a year. Because of remarkable similarity within observed spectra, an observed spectrum can be expressed by a simple combination of a reference spectrum and two parameters expressing the deformation of the observed spectrum from the reference. By use of the relation between one of the deformation parameters and the total ozone simultaneously observed with the Dobson spectrophotometer, the possible increase of UV irradiance due to ozone depletion is estimated. For damaging UV, the irradiance possibly increases about 19 percent with the ozone depletion of 10 percent at noon throughout the year in the northern midlatitudes. DUV at noon on the summer solstice possibly increases about 5.6 percent with the ozone depletion of 10 m atm-cm for all latitudes in the Northern Hemisphere.

Ito, T.↗
NASA NTRS1994

The determination of HNO3 column amounts from tunable diode laser heterodyne spectrometer spectra taken at Jungfruajoch, Switzerland

In May of 1991 a tunable diode laser heterodyne spectrometer built by the National Physical Laboratory was operated at the International Scientific Station of the Jungfraujoch (46.5 deg N, 8.0 deg E, altitude 3.56 km). Nitric acid spectra in the region of 868 wavenumbers were recorded at sunset and sunrise on two separate days at a resolution of 0.0013 wavenumbers with a signal-to-noise ratio of approximately 130:1. A vertical column amount of HNO3 of 1.61 x 10(exp 16) molecules/sq cm was determined using an atmospheric transmission model developed at the University of Denver. The mean of a number of mid-latitude, northern hemisphere profiles was used as the initial profile for the inversion. A comparison of different initial profiles provides information on the sensitivity of the retrieved column amount of 1.61 x 10(exp 16) molecules/sq cm lies within the range of values published in the World Meteorological Organization Report no. 16 (1986), but is considerably larger than the value of (0.99 - 1.29) x 10(exp 16) reported by Rinsland et al. (1991) for June during the period 1986 to 1990.

Fogal, P. F.↗
NASA NTRS1994

Total solar eclipse of 1995 October 24

A total eclipse of the sun will be visible from Asia and the Pacific Ocean on 24 Oct. 1995. The path of the moon's shadow begins in the Middle East and sweeps across India, Southeast Asia, and the waters of the Indonesian archipelago before ending at sunset in the Pacific. Detailed predictions for this event are presented and include besselian elements, geographic coordinates of the path of totality, physical ephemeris of the umbra, topocentric limb profile corrections, local circumstances for 400 cities, maps of the eclipse path, weather prospects, the lunar limb profile, and the sky during totality.

Espenak, Fred↗
NASA NTRS1995

Total Solar Eclipse of 1997 March 9

A total eclipse of the Sun will be visible from Asia and the Pacific Ocean on 1997 March 9. The path of the Moon's umbral shadow begins in eastern Kazakhstan and travels through Mongolia and eastern Siberia, where it swings northward to end at sunset in the Arctic Ocean. A partial eclipse will be seen within the much broader path of the Moon's penumbral shadow, which includes eastern Asia, the northern Pacific, and the northwest corner of North America. Detailed predictions for this event are presented and include besselian elements, geographic coordinates of the path of totality, physical ephemeris of the umbra, topocentric limb profile corrections, local circumstances for 280 cities, maps of the eclipse path, weather prospects, the lunar limb profile, and the sky during totality. Tips and suggestions are also given on how to safely view and photograph the eclipse.

Espenak, Fred↗
NASA NTRS1994

Equatorial heating and hemispheric decoupling effects on inner magnetospheric core plasma evolution

We have extended our previous semikinetic study of early stage plasmasphere refilling with perpendicular ion heating by removing the restriction that the northern and southern boundaries are identical and incorporating a generalized transport description for the electrons. This allows investigation of the effects of electron heating and a more realistic calculation of electric fields produced by ion and electron temperature anisotropies. The combination of perpendicular ion heating and parallel electron heating leads to an equatorial electrostatic potential peak, which tends to shield and decouple ion flows in the northern and southern hemispheres. Unequal ionospheric upflows in the northern and southern hemispheres lead to the development of distinctly asymmetric densities and other bulk parameters. At t = 5 hour after the initiation of refiling with different source densities (N(sub north) = 100 cu/cm, N(sub south) = 50 cu/cm), the maximum potential drops of the northern and southern hemispheres are 0.6 and 1.3 V, respectively. At this time the minimum ion densities are 11 and 7 cu/cm for the northern and southern hemispheres. DE 1 observations of asymmetric density profiles by Olsen may be consistent with these predictions. Termination of particle heating causes the reduction of equatorial potential and allows interhemispheric coupling. When the inflows from the ionospheres are reduced (as may occur after sunset), decreases in plasma density near the ionospheric regions are observed while the heated trapped ion population at the equator persists.

Lin, J.↗
NASA NTRS1994

Heterogeneous conversion of N2O5 to HNO3 in the post-Mount Pinatubo eruption stratosphere

Simultaneous stratospheric volume mixing ration (VMR) profiles of dinitrogen pentoxide (N2O5) and nitric acid (HNO3) at sunrise between 25 deg N and 15 deg S latitude and profiles of HNO3 at sunset between 42 deg S and 53 deg S latitude have been derived from 0.01/cm resolution infrared solar occultation spectra recorded 9.5 months after the massive eruption of the Mount Pinatubo volcano in the Philippine Islands. The measurements were obtained by the atmospheric trace molecule spectroscopy (ATMOS) Fourier transform spectrometer during the ATLAS 1 shuttle mission (March 24 to April 2, 1992). The measured HNO3 VMRs are higher at all altitudes and latitudes than corresponding values measured by the limb infrared monitor of the stratosphere (LIMS) instrument during the same season in 1979, when the aerosol loading was near background levels. The largest relative increase in the HNO3 VMR occurred near the equator at 30-km altitude, where the ATMOS/ATLAS 1 values are about a factor of 2 higher than the LIMS measurements. Two-dimensional model calculations show that the increase in HNO3 and the ATMOS/ATLAS 1 measurement of a steep decrease in the N2O5 VMR below 30 km can be explained by the enhanced conversion of N2O5 to HNO3 on the surfaces of the Mount Pinatubo sulfate aerosols. Our profile results demonstrate the global impact of the N2O5 + H2O yields 2HNO3 heterogeneous reaction in altering the partitioning of stratospheric odd nitrogen after a major volcanic eruption.

Rinsland, C. P.↗
NASA NTRS1994

Lunar crescent visibility

We report the results of five Moonwatches, in which more than 2000 observers throughout North America attempted to sight the thin lunar crescent. For each Moonwatch we were able to determine the position of the Lunar Date Line (LDL), the line along which a normal observer has a 50% probability of spotting the Moon. The observational LDLs were then compared with predicted LDLs derived from crescent visibility prediction algorithms. We find that ancient and medieval rules are higly unreliable. More recent empirical criteria, based on the relative altitude and azimuth of the Moon at the time of sunset, have a reasonable accuracy, with the best specific formulation being due to Yallop. The modern theoretical model by Schaefer (based on the physiology of the human eye and the local observing conditions) is found to have the least systematic error, the least average error, and the least maximum error of all models tested. Analysis of the observations also provided information about atmospheric, optical and human factors that affect the observations. We show that observational lunar calendars have a natural bias to begin early.

Doggett, Leroy E.↗
NASA NTRS1994

Carbon dioxide fluxes over a raised open bog at the Kinosheo Lake tower site during the Northern Wetlands Study (NOWES)

Measurements of carbon dioxide concentration and flux were made above a raised open bog at Lake Kinosheo in the southern Hudson Bay lowlands during the Northern Wetlands Study (NOWES) experiment in 1990. The flux measurements were made using micrometeorological techniques. They provide the first nondisturbing, larger-scale CO2 flux measurements for this ecosystem and are the first to integrate the exchange over the whole 24 hours of the day. Continuous concentration measurements by infrared gas analyzers (IRGA) and spot flask samples were taken over the period July 1 to July 29. Afternoon CO2 values were only 5 to 7 parts per million by volume (ppmv) lower than measurements over the same period at Canadian background monitoring stations. This suggested that there was little draw-down by local photosynthetic sinks. CO2 fluxes were measured at 8 and 18 m by Bowen ratio and eddy correlation methods, respectively. The methods produced comparable results on averaged data but often diverged considerably on individual half-hour results. Fluxes were small. Daytime values averaged to -0.068 mg/sq m/s by eddy correlation and -0.077 mg/sq m/s by Bowen ratio over the period June 25 to July 28 (negative denotes downward flux), while at night, flux densities were +0.062 mg/sq m/s and +0.085 mg/sq m/s. Integration of the mean diurnal curve gave a net flux of -1.7 g/sq m/d. Comparable data for this type of ecosystem were not found. However, Coyne and Kelley (1975), measuring near Barrow, Alaska, over wet meadow tundra dominated by sedges and grasses, found net fluxes of -7.2 g/sq m/d. Typical net CO2 fluxes from other active temperature ecosystems have been found to be -10 to -20 g/sq m/d (Monteith, 1976). Mean half hourly fluxes were almost constant at +0.06 mg/sq m/s through the nighttime hours. About one half-hour after sunrise the flux reversed direction. Uptake peaked about 0900 eastern daylight time (EDT) and then gradually declined but remained downward until near sunset. The early peak was interpreted to signify that the many plants in the bog experienced water stress during the day as evaporative demand increased and nighttime dew was evaporated.

Neumann, H. H.↗