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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Nonequilibrium and equilibrium shock front radiation measurements

The intensities of the radiation emitted behind a normal shock wave in N were measured in an electric-arc driven shock tube at a shock velocity of 6.2 km/sec. Both a time-resolved broad-band radiation intensity measurement and a time-frozen spectral measurement were conducted. The rotational and vibrational temperatures are determined in both the equilibrium and the nonequilibrium regions. The results are compared with the similar data obtained by Allen et al. (1961). The measured rotational temperature seems to be in nonequilibrium, contradicting the two-temperature assumption of Park (1988), but the measured vibrational temperature agrees with Park's model.

Sharma, Surendra P.↗
NASA NTRS1984

Radiation measurements aboard Spacelab 1

The radiation environment inside Spacelab 1 was measured by a set of passive radiation detectors distributed throughout the volume inside the module, in the access tunnel, and outside on the pallet. Measurements of the low linear energy transfer (LET) component obtained from the thermoluminescence detectors ranged from 102 to 190 millirads, yielding an average low LET dose rate of 11.2 millirads/day inside the module, about twice the low LET dose rate measured on previous flights of the Space Shuttle. Because of the higher inclination of the orbit (57 versus 28.5 deg for previous Shuttle flights), substantial fluxes of highly ionizing high charge and energy galactic cosmic ray particles were observed, yielding an overall average mission dose-equivalent of about 150 millirems, more than three times higher than that measured on previous Shuttle missions.

Benton, E. V.↗
NASA NTRS1987

Determination of the scaled optical thickness of clouds from reflected solar radiation measurements

A method for determination of scaled optical thickness from reflected solar radiation measurements is described in which measurements of the reflected function are compared with asymptotic expressions for the reflection function of optically thick layers. Analytic formulas are derived which show the dependence of the reflection and transmission functions of nonabsorbing atmospheres on cloud optical thickness, ground albedo, and the asymmetry factor. An expression is derived which shows that the ground albedo produces a constant bias in the derived optical thickness, regardless of the value of the measured reflection function. Results from an analysis of high-resolution images, obtained in Oklahoma, of the reflection function of clouds shows the impact of details of the single scattering phase function on the derived optical thickness.

King, Michael D.↗
NASA NTRS1986

Determination of the optical thickness of clouds from reflected solar radiation measurements

A procedure is presented for inferring cloud optical thickness from reflected solar radiation measurements. Asymptotic expressions are defined for the reflection and transmission functions of optically thick atmospheres, noting that the reflection function sensitivity to cloud optical thickness is highest with minimal surface albedo. Attention is also given to the dependence of the optical thickness on the cloud asymmetry factor. Sample results are provided from several high altitude aircraft flights to determine the reflection function of clouds.

King, M. D.↗
NASA NTRS2000

SMART Ground-based Radiation Measurements during PRIDE

We deployed a suite of ground-based remote sensing instruments - SMART (Surface Measurements for Atmospheric Radiative Transfer), at the Roosevelt Road Naval Station in Puerto Rico during the Puerto Rico Dust Experiment (PRIDE). The instruments include several solar and infrared broadband radiometers, a sunphotometer, a shadow-band radiometer, a micro-pulse lidar, a total-sky imager, a microwave radiometer, and two solar spectrometers. These radiometers were set up on a mobile platform and a solar tracker. During 27 June - 23 July, about 25 days of data were acquired under partially cloudy sky conditions. The diurnal air temperature was fluctuating around 28.6 C to within a few degrees. Daytime average of solar irradiance reaching at the surface was ranged from about 400 W/sq m on a rainy day to about 640 W/sq m on a cloud-free day. The infrared irradiance at the surface during the measurement period was averaged about 408 W/sq m. The heights of boundary layer, dusts and clouds were captured by lidar images. Based on sunphotometer and shadow-band radiometer retrievals, the aerosol optical thickness varied from below 0.1 to over 0.6. Combining with radiative transfer modeling and other in-situ and remote sensing measurements, our ground-based measurements provide vital information on understanding the long-range transport of African dust into the Caribbean.

Tsay, Si-Chee↗
NASA NTRS2006

Atmospheric Radiation Measurements Aerosol Intensive Operating Period: Comparison of Aerosol Scattering during Coordinated Flights

In May 2003, a Twin Otter airplane, equipped with instruments for making in situ measurements of aerosol optical properties, was deployed during the Atmospheric Radiation Measurements (ARM) Program s Aerosol Intensive Operational Period in Oklahoma. Several of the Twin Otter flights were flown in formation with an instrumented light aircraft (Cessna 172XP) that makes routine in situ aerosol profile flights over the site. This paper presents comparisons of measured scattering coefficients at 467 nm, 530 nm, and 675 nm between identical commercial nephelometers aboard each aircraft. Overall, the agreement between the two nephelometers decreases with longer wavelength. During the majority of the flights, the Twin Otter flew with a diffuser inlet while the Cessna had a 1 mm impactor, allowing for an estimation of the fine mode fraction aloft. The fine mode fraction aloft was then compared to the results of a ground-based nephelometer. Comparisons are also provided in which both nephelometers operated with identical 1 mm impactors. These scattering coefficient comparisons are favorable at the longer wavelengths (i.e., 530 nm and 675 nm), yet differed by approximately 30% at 467 nm. Mie scattering calculations were performed using size distribution measurements, made during the level flight legs. Results are also presented from Cadenza, a new continuous wave cavity ring-down (CW-CRD) instrument, which compared favorably (i.e., agreed within 2%) with data from other instruments aboard the Twin Otter. With this paper, we highlight the significant implications of coarse mode (larger than 1 mm) aerosol aloft with respect to aerosol optical properties.

Hallar, A. G.↗
NASA NTRS1998

Environmental Radiation Measurements on the Mir Space Station: Internal Experiment Program - Program 1

As part of the NASA/Mir Phase 1B Science Program, the ionizing radiation environment inside and outside the Russian Mir's Space Station was monitored using a combination of Thermoluminescent Detectors (TLD) and CR-39 Plastic Nuclear Track Detectors (PNTD). Radiation measurements inside the Mir station were carried out using six Area Passive Dosimeters (APD), four located inside the Mir Base Block and two located inside the Kvant 2 module, during the NASA-2/Mir-21, NASA-3/Mir-22 and NASA-4/Mir-23 missions. The radiation environment under low shielding was measured using an External Dosimeter Array (EDA) mounted on the outer surface of the Kvant 2 module. The external radiation environment and a location inside the Kvant 2 roughly corresponding to the location of the EDA were monitored for 130 days during the NASA- 4/Mir-23 and NASA-5/Mir-24 missions. Dose rates measured by APD TLDs ranged from 271 to 407 microGy/d during the NASA-2/Mir-21 mission, from 265 to 378 microGy/d during the NASA-3/Mir-22 mission, and from 287 to 421 microGy/d during the NASA-4/Mir-23 mission. APD PNTDs have been analyzed and LET spectra have been Cenerated for the five APDs exposed on the NASA-2/Mir-21 mission and for two APD PNTDs exposed on the NASA-3/Mir-22 mission. Dose equivalent rates on the NASA-2/Mir-21 mission ranged from 513 microSv/d in the Kvant 2 module to 710 microSv/d on the floor of the Base Block. Dose as a function of shielding depth in TLDs has been measured in the thin TLD stacks including in the EDA. EDA dose range from 72.5 Gy under 0.0146 g/sq cm to 0.093 Gy under 3.25 g/sq cm of shielding. Readout and analysis of the reaming PNTDs form the NASA-3/Mir-22 mission and PNTDs from the NASA-4/Mir-23 mission (including those from the EDA) is ongoing and will be completed during the final year of this experiment. Dose equivalent rates for the NASA-3/Mir-22 and NASA-4/Mir-23 APDs will then be determined and comparisons will be made with both model calculations and with results from similar measurements.

Benton, E. V.↗
NASA NTRS1980

Simulation study of geometric shape factor approach to estimating earth emitted flux densities from wide field-of-view radiation measurements

A study was performed on the use of geometric shape factors to estimate earth-emitted flux densities from radiation measurements with wide field-of-view flat-plate radiometers on satellites. Sets of simulated irradiance measurements were computed for unrestricted and restricted field-of-view detectors. In these simulations, the earth radiation field was modeled using data from Nimbus 2 and 3. Geometric shape factors were derived and applied to these data to estimate flux densities on global and zonal scales. For measurements at a satellite altitude of 600 km, estimates of zonal flux density were in error 1.0 to 1.2%, and global flux density errors were less than 0.2%. Estimates with unrestricted field-of-view detectors were about the same for Lambertian and non-Lambertian radiation models, but were affected by satellite altitude. The opposite was found for the restricted field-of-view detectors.

Weaver, W. L.↗
NASA NTRS1979

Cloud cover models derived from satellite radiation measurements

Using daily measurement of day and night infrared and incoming and absorbed solar radiation obtained from a TIROS satellite over a period of approximately 45 months, and integrated over 2.5 degree latitude-longitude grids, the proportion of cloud cover over each grid each day was derived for the entire period. For each of four three-month periods, estimates a and b of the two parameters of the best-fit beta distribution were obtained for each grid location. The (a,b) plane was divided into a number of regions. All the geographical locations whose (a,b) estimates were in the same region in the (a,b) plane were said to have the same cloud cover type for that season. For each season, the world was thus divided into separate cloud cover types. Using estimates of mean cloud cover for each season, the world was again divided into separate cloud cover types. The process was repeated for standard deviations. Thus for each season, three separate cloud cover models were obtained using the criteria of shape of frequency distribution, mean cloud cover, and variability of cloud cover. The cloud cover statistics were derived from once-a-day, near-local-noon satellite radiation measurements.

Bean, S. J.↗