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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 NTRS1973

Mariner 9 photometric observations of Mars from November 1971 through March 1972

The large quantity of Mariner 9 television pictures taken at phase angles ranging up to twice those accessible from earth has been used to describe integrated photometric properties of Mars. Although frame-to-frame variations emphasize the shortcomings of vidicon cameras when used in a photometric mode, statistical trends have yielded data comparable with earth-based observations. Analysis of atmospheric parameters over a period of changing opacity - November 1971 through March 1972 - has provided time-varying optical depths and light-scattering information. Linear function characterization of the Mars reflectance is clearly discrepant at large incidence or emission angles and at phase angles greater than 40 deg.

Thorpe, T. E.↗
NASA NTRS2023

Impacts of Marine Surface Pressure Observations From A Spaceborne Differential Absorption Radar Investigated With an Observing System Simulation Experiment

A new instrument has been proposed for measuring surface air pressure over the marine surface with a combined active/passive scanning multi-channel differential absorption radar (DAR) to provide an estimate of the total atmospheric column oxygen content. A demonstrator instrument, the Microwave Barometric Radar and Sounder (MBARS), has been funded by the National Aeronautics and Space Administration (NASA) for airborne test missions. Here, a proof-of-concept study to evaluate the potential impact of spaceborne surface pressure data on numerical weather prediction is performed using the Goddard Modeling and Assimilation Office global observing system simulation experiment (OSSE) framework. This OSSE framework employs the Goddard Earth Observing System model and the hybrid 4D ensemble variational Gridpoint Statistical Interpolation data assimilation system. Multiple flight and scanning configurations of potential spaceborne orbits are examined. Swath width and observation spacing for the surface pressure data are varied to explore a range of sampling strategies. For wider swaths, the addition of surface pressures reduces the root mean square surface pressure analysis error by as much as 20% over some ocean regions. The forecast sensitivity observation impact tool estimates impacts on the Pacific Ocean basin boundary layer 24-hour forecast temperatures for spaceborne surface pressures on par with rawinsondes and aircraft, and greater impacts than the current network of ships and buoys. The largest forecast impacts are found in the southern hemisphere extratropics.

N.C. Privé↗
NASA NTRS1979

Four UV observations of the interstellar wind by Mariner 10 - Analysis with spherically symmetric solar radiation models

Four Mariner 10 observations of interplanetary hydrogen 1216-A and helium 584-A emissions are analyzed by using radiation models that employ spherically symmetric solar radiation fields. It is shown that the measured 584-A intensities can be represented with a statistical accuracy of about 10% by a model that assumes spherical symmetry for the 584-A solar radiation and that the 1216-A intensities can be represented to within 15% by a model based on spherically symmetric solar corpuscular and EUV radiation. An interstellar wind velocity of 22 km/s, a helium number density of 0.008 per cu cm, and an interstellar neutral-gas temperature of 1500 K near the solar system are obtained from Copernicus satellite measurements.

Ajello, J. M.↗
NASA NTRS1990

Extended time observations of California marine stratocumulus clouds from GOES for July 1983-1987

One of the goals of the First ISCCP Regional Experiment (FIRE) is to relate the relatively small scale (spatial and temporal) Intensive Field Observations (IFO) to larger time and space domains embodied in the Extended Time Observations (ETO) phase of the experiment. The data analyzed as part of the ETO are to be used to determine some climatological features of the limited area which encompasses the Marine Stratocumulus IFO which took place between 29 June and 19 July 1987 off the coast of southern California.

Minnis, Patrick↗
NASA NTRS1973

Mariner 9 ultraviolet spectrometer experiment: Afternoon terminator observations of Mars

It is possible to model the ultraviolet terminator observations of Mariner 9 either with a homogeneous atmosphere or with a scattering layer in addition to a homogeneous atmosphere. The characteristic shape of the twilight intensity variation is dependent on the latitude of observation. Observations north of 55N require a homogeneous model. Twilight measurements south of 55N indicate that a scattering layer may be a general Martian occurrence, at least in the evening. The day-to-day surveillance of the Martian terminator during the first 216 Mariner 9 revolutions indicates haze formation in the evening, and its continued presence until early morning is a daily occurrence in mid-latitudes up to 50N.

Ajello, J. M.↗
NASA NTRS1993

Observations of the marine environment from spaceborne side-looking real aperture radars

Real aperture, side looking X-band radars have been operated from the Soviet Cosmos-1500, -1602, -1766 and Ocean satellites since 1984. Wind velocities were inferred from sea surface radar scattering for speeds ranging from approximately 2 m/s to those of hurricane proportions. The wind speeds were within 10-20 percent of the measured in situ values, and the direction of the wind velocity agreed with in situ direction measurements within 20-50 deg. Various atmospheric mesoscale eddies and tropical cyclones were thus located, and their strengths were inferred from sea surface reflectivity measurements. Rain cells were observed over both land and sea with these spaceborne radars. Algorithms to retrieve rainfall rates from spaceborne radar measurements were also developed. Spaceborne radars have been used to monitor various marine hazards. For example, information derived from those radars was used to plan rescue operations of distressed ships trapped in sea ice. Icebergs have also been monitored, and oil spills were mapped. Tsunamis produced by underwater earthquakes were also observed from space by the radars on the Cosmos 1500 series of satellites. The Cosmos-1500 satellite series have provided all weather radar imagery of the earths surface to a user community in real time by means of a 137.4 MHz Automatic Picture Transmission channel. This feature enabled the radar information to be used in direct support of Soviet polar maritime activities.

Kalmykov, A. I.↗
NASA NTRS1973

Mariner 9 ultraviolet spectrometer experiment - Morning terminator observations of Mars

Mariner 9 ultraviolet morning terminator data indicate the presence of a high, optically thin scattering layer in the equatorial region of Mars extending to 50S. This is consistent with the afternoon terminator results, which showed the presence of a scattering layer for latitudes as far north as 50N. For both types of terminator observations, the magnitude of the reflectivity for large shadow heights and the apparent scale height of the signal are too large to be explained by a homogeneous atmosphere. The terminator observations poleward of 50S were modeled by a homogeneous atmosphere of molecular and particulate scatterers. As the lower atmosphere began to clear from the dust storm, a progressive change was noted in the magnitude of the terminator reflectivity which is attributed to a changing albedo for single scattering. The shape of the morning terminator reflectivity measured as a function of shadow height indicates larger apparent scale heights than were observed in the afternoon. The difference is attributed to an increase in thickness of the scattering layer during the night.

Ajello, J. M.↗
NASA NTRS1989

Observed reflectivities and liquid water content for marine stratocumulus

Simultaneous observations of cloud liquid water content and cloud reflectivity are used to verify their parametric relationship in a manner consistent with simple parameterizations often used in general-circulation climate models. The column amount of cloud liquid water was measured with a microwave radiometer on San Nicolas Island as described by Hogg et al., (1983). Cloud reflectivity was obtained through spatial coherence analysis of AVHRR imagery data as per Coakley and Baldwin (1984) and Coakley and Beckner (1988). The dependence of the observed reflectivity on the observed liquid water is discussed, and this empirical relationship is compared with the parameterization proposed by Stephens (1978).

Coakley, J. A., Jr.↗
NASA NTRS2012

MESSENGER and Mariner 10 Flyby Observations of Magnetotail Structure and Dynamics at Mercury

The first (M1), second (M2), and third (M3) MESSENGER flybys of Mercury traversed the planet's magnetotail from 1.25 to 3.25 RM downstream of the planet, where R(sub M) is Mercury's radius (2440 km). The encounters took place under northward, southward, and variable-polarity interplanetary magnetic field (IMF), respectively. The magnetic field strength B in Mercury's magnetotail follows a power law decrease with increasing antisunward distance ∣X∣, B approximately ∣X∣(sup G), with G varying from -5.4 for northward to -1.6 for southward IMF. Low-latitude boundary layers (LLBLs) containing strong northward magnetic field were detected at the tail flanks during two of the flybys. The observed thickness of the LLBL was 33% and 16% of the radius of the tail during M1 and M3, respectively, but the boundary layer was completely absent during M2. Clear signatures of tail reconnection are evident in the M2 and M3 magnetic field measurements. Plasmoids and traveling compression regions were observed during M2 and M3 with typical durations of approximately 1-3 s, suggesting diameters of approximately 500-1500 km. Overall, the response of Mercury's magnetotail to the steady southward IMF during M2 appeared very similar to steady magnetospheric convection events at Earth, which are believed to be driven by quasi-continuous reconnection. In contrast, the M3 measurements are dominated by tail loading and unloading events that resemble the large-scale magnetic field reconfigurations observed during magnetospheric substorms at Earth.

Magnetotail↗
NASA NTRS1973

Mariner 9 Ultraviolet Spectrometer experiment - Observations of ozone on Mars.

The Mariner 9 Ultraviolet Spectrometer has observed the 2550 A ozone spectral absorption feature on Mars. This absorption was previously detected in the south polar region by Mariner 7 in 1969. Mariner 9 did not observe ozone at any time in the equatorial region, nor at the south polar cap during its summer season. However, ozone was found in the north polar region beginning at a latitude of 45 deg N and extending northward. Ozone later appeared in the southern hemisphere southward of 50 deg S as the Mars autumnal equinox approached. The presence of ozone on Mars seems to be coupled to the water vapor content of its atmosphere.

Lane, A. L.↗
NASA NTRS1979

The Lyman-alpha observations of comet Kohoutek from Mariner 10

The paper presents the Lyman-alpha data from postperihelion observations of comet Kohoutek made with Mariner 10 UV spectrometer during the 1974 January 11-24 period when the comet distance from the sun varied from 0.521 AU to 0.860 AU. These data are analyzed to determine the hydrogen production rates. It is noted that observations against the low interplanetary background allowed a measurement of the hydrogen corona over 30 million km (or 15 minutes) as seen from the Mariner 10 spacecraft. The bulk of the observations can be fitted with a non-steady-state model assuming two velocity components (20 km/sec and 8 km/sec) of equal proportions. A 70% increase in the hydrogen production rate is found within 2 days from January 17 to 19 while the comet receded from the sun. Finally, it is noted that the postperihelion production rates from the Mariner 10 observations are comparable to the preperihelion production rates reported previously.

Kumar, S.↗