Search NASA⌕ Search

SEARCH · Search NASA

Results for “GROUND BASED”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Evidence for beaming of Jupiter's decametric radiation - Simultaneous observations from Voyagers and ground-based observatories

The paper presents incontrovertible evidence for the beaming of the Jovian decametric radiation, based on simultaneous observations at about 22 MHz from one or both of the Voyager spacecraft and one or the other of two ground-based observatories. The data are used to test the hollow-cone beaming models that have been proposed to account both for the long-term statistics of the ground-based observations and for the arc structures discovered in the dynamic spectral plots of Voyager data. It is concluded that occurrences of non-Io-related Source A events are determined by the corotation with the inner Jovian magnetosphere of curved-sheet beams, and those of Io-related Source B storms by a similar type of beam that moves with the northern foot of the Io flux tube. Both types of beam can be approximated by hollow-cone beam sectors. Rough measurements of the observed portions of some of the beams have been made.

Maeda, Koitiro↗
NASA NTRS1987

Ground-based 1- to 32-microns observations of ARP 220: Evidence for a dust-embedded AGN?

New observations of the 10 and 20 micron size of the emission region in Arp 220 are presented. Also given are ground based photometry from 1 to 32 micron including measurements of the strength of the silicate feature at 10 micron. The results show that the 20 micron size of Arp is smaller than 1.5 arcsec (500 pc); comparison of IRAS and ground based observations show that IRAS 12 micron flux measured with a large arcmin beam is the same as that seen from the ground with a 3 arcsec aperture. At 10 micron a deep silicate absorption feature is seen that corresponds to a visual extinction of about 50 mag. These results suggest that a very significant portion of the 10 to the 12th power L sub 0 infrared luminosity from Arp 220 comes from a region less than or of the order of 500 pc in diameter. When these results are combined with recent measurement of a broad Brackett alpha line by DePoy and an unresolved 2.2 micron source by Neugebauer, Matthews and Scoville, a very attractive possibility for the primary luminosity source Arp 220 is a dust embedded compact Seyfert type nucleus.

Becklin, E. E.↗
NASA NTRS1982

Merits of supplemental ground-based measurements of lightning electric fields in the interpretation of airborne measurements

Calculations are presented which indicate that airborne recordings of the electric fields from lightning will be difficult to interpret without correlated continuous broadband electric field measurements at a ground-based station. Furthermore, through application of the results in Master et al. (1981), field measurements made at altitudes above ground may be calibrated by comparison with ground-based measurements of the same discharge. The requirements of the electric-field recording systems sufficient for identification, characterization, and calibration of airborne field measurements are discussed.

Beasley, W. H.↗
NASA NTRS1986

Networking ground-based images of Comet Halley during the Giotto encounter

During the period immediately before and after the European, Russian, and Japanese spacecraft encounters with Comet Halley in early March 1986, sequences of ground-based electronic images of the comet, obtained at Table Mountain Observatory (TMO), CA, were transmitted via the Space Physics Analysis Network (SPAN) to the European Space Operations Centre (ESOC), and to University College London (UCL). During the 48-h period when the European Space Agency spacecraft Giotto was within the extended coma of Comet Halley, the ground-based images revealed that the comet displayed several spectacular near-nuclear and large-scale features. The TMO images provided a format for the interpretation of the unique in situ results obtained during the closest of the five spacecraft encounters with Comet Halley.

Rees, David↗
NASA NTRS1984

Recent Ground-based Observations of the Global Properties of the Sun

Ground based observations have achieved sufficient sensitivity and duration to scrutinize many global properties of the Sun. Variations in the properties of granular and supergranular convection are measured. The surface rotation measurements continue to present contradictory results. A spectrum of torsional motions are detected. A variety of oscillation measurements now are available for nearly direct probing of the solar interior.

Labonte, B. J.↗
NASA NTRS1985

Ground-based observations of near ecliptic zodiacal light brightness

Ground-based observation of the evening zodiacal light taken by Weinberg and Mann (1967) from Mt. Halaekala, Hawaii, during March 1966 are used to derive a table of zodiacal light brightnesses at high spatial resolution (as little as 0.5 deg in differential ecliptic longitude, DEL and 1.0 deg in ecliptic latitude beta) over the DEL region 29.5-56 deg, beta = -30 to +30 deg. Significant differences are found in the brightness distributions above and below the ecliptic plane.

Misconi, N. Y.↗
NASA NTRS1991

Ground based preparation for microgravity growth of alloy semiconductors

Ground-based research conducted in order to prepare a microgravity space flight experiment is presented. The thermophysical properties of a PbSnTe alloy used for semiconductors are investigated, and furnace calibration and fluid-flow measurements are performed. The alloy has a zero energy crossing at approximately 40 percent SnTe in its band-gap vs composition diagram, which facilitates the design of long-wavelength IR detectors and lasers. The uniformity of devices made from this material depends on the ratio of PbTe and SnTe and requires the composition of the crystal growth to be closely controlled. The main obstacle to such control is the fact that liquid of this material is always solutally or thermally unstable, and, in a high-temperature gradient, the double convective instability cannot be made stable by balancing thermal and solutal expansion. In order to extend the science of crystal growth, the limits of suppression of convection have to be tested in low earth orbit.

Fripp, Archibald L.↗
NASA NTRS1996

Ground Based Studies of Thermocapillary Flows in Levitated Drops

Ground-based experiments together with analytical studies are presently being conducted for levitated drops. Both acoustic and electrostatic techniques are being employed to achieve levitation of drops in a gaseous environment. The scientific effort is principally on the thermal and the fluid phenomena associated with the local heating of levitated drops, both at 1-g and at low-g. In particular, the thermocapillary flow associated with local spot heating is being studied. Fairly stable acoustic levitation of drops has been achieved with some exceptions when random rotational motion of the drop persists. The flow visualization has been carried out by light scattering from smoke particles for the exterior flow and fluorescent tracer particles in the drop. The results indicate a lack of axial symmetry in the internal flow even though the apparatus and the heating are symmetric. The theoretical studies for the past year have included fundamental analyses of acoustically levitated spherical drops. The flow associated with a particle near the velocity antinode is being investigated by the singular perturbation technique. As a first step towards understanding the effect of the particle displacement from the antinode, the flow field about the node has been calculated for the first time. The effect of the acoustic field on the interior of a liquid drop has also been investigated. The results predict that the internal flow field is very weak.

Sadhal, Satwindar Singh↗
NASA NTRS2012

Measuring Gap Fraction, Element Clumping Index and LAI in Sierra Forest Stands Using a Full-Waveform Ground-Based Lidar

The Echidna Validation Instrument (EVI), a ground-based, near-infrared (1064 nm) scanning lidar, provides gap fraction measurements, element clumping index measurements, effective leaf area index (LAIe) and leaf area index (LAI) measurements that are statistically similar to those from hemispherical photos. In this research, a new method integrating the range dimension is presented for retrieving element clumping index using a unique series of images of gap probability (Pgap) with range from EVI. From these images, we identified connected gap components and found the approximate physical, rather than angular, size of connected gap component. We conducted trials at 30 plots within six conifer stands of varying height and stocking densities in the Sierra National Forest, CA, in August 2008. The element clumping index measurements retrieved from EVI Pgap image series for the hinge angle region are highly consistent (R2=0.866) with those of hemispherical photos. Furthermore, the information contained in connected gap component size profiles does account for the difference between our method and gap-size distribution theory based method, suggesting a new perspective to measure element clumping index with EVI Pgap image series and also a potential advantage of three dimensional Lidar data for element clumping index retrieval. Therefore further exploration is required for better characterization of clumped condition from EVI Pgap image series.

Zhao, Feng↗
NASA NTRSDate not supplied

P52D-1583 - Further Improvements to Constraints on Titan’s Atmospheric n-Butane, via Ground-Based Observations

We have acquired high spectral resolution ground-based observations of Titan in the mid-infrared from NASA Infrared Telescope Facility’s Texas Echelon Cross Echelle Spectrograph instrument , designed to constrain the abundances of new molecules within Titan’s atmosphere. The target molecule for this work, n-butane (n-C H ), though predicted by photochemical models of Titan’s atmosphere , has never been detected. Using the NEMESIS radiative transfer code , we retrieved a disk-averaged temperature profile for Titan by modeling CH emission in the 1248 cm region. Using this temperature profile, we then retrieved disk-averaged profiles of ethene (C H ), propane (C H ), and propene (C H ) in the 956 and 965 cm regions, which are also home to the strong and vibrational features of n-butane. We used an n-butane pseudoline list from JPL in order to systematically introduce a range of n-butane mixing ratios into the model, to constrain the molecule’s abundance based on the model’s changing fit to the data. We derive 3-confidence upper limits at an altitude of 150 km of 48 and 31 ppb for n-butane, via the and bands in the 956 and 965 cm regions, respectively. These are significantly tighter upper limits when compared to the ~300 ppb upper limit found in our recent work which used the same methodology but on much lower resolution limb data collected by the Cassini spacecraft. Upper limits on gas abundances are important for continued improvement of photochemical models of Titan’s atmosphere, which is understood to be an important analog for the prebiotic Earth atmosphere . They are also important for understanding the composition of Titan’s lakes and seas, which are likely to contain these larger hydrocarbons . Finally, as larger molecules like C ’s are thought to be able to serve as formation sites for building haze particles, constraining their abundances is important for understanding the process of haze formation at Titan and at Earth Ref: [1] J. H. Lacy, et al., PASP, 2002. [2] Y.L. Yung, et al., ApJS, 1984. [3] M. Dobrijevic, et al., Icarus, 2021. [4] P. G. J. Irwin et al., JQSRT, 2008. [5] K. Sung, et al., JQSRT, 2020. [6] B. L. Steffens, et al., PSJ, 2022. [7] Clarke & Ferris, Origins Life Evol. Biosphere, 1997. [8] D. Cordier, et al., ApJ, 2008. [9] D. B. Curtis, et al., JPCA, 2005.

Brendan Steffens↗
NASA NTRS2018

A Large Ground-Based Observing Campaign of the Disintegrating Planet K2-22b

We present 45 ground-based photometric observations of the K2-22 system collected between 2016 December and 2017 May, which we use to investigate the evolution of the transit of the disintegrating planet K2-22b. Last observed in early 2015, in these new observations we recover the transit at multiple epochs and measure a typical depth of <1.5%. We find that the distribution of our measured transit depths is comparable to the range of depths measured in observations from 2014 and 2015. These new observations also support ongoing variability in the K2-22b transit shape and time, although the overall shallowness of the transit makes a detailed analysis of these transit parameters difficult. We find no strong evidence of wavelength-dependent transit depths for epochs where we have simultaneous coverage at multiple wavelengths, although our stacked Las Cumbres Observatory data collected over days-to-months timescales are suggestive of a deeper transit at blue wavelengths. We encourage continued high-precision photometric and spectroscopic monitoring of this system in order to further constrain the evolution timescale and to aid comparative studies with the other few known disintegrating planets.

K2-22↗
NASA NTRSDate not supplied

The Multiplatform Precipitation Feature (MPF) Database: Synthesizing Satellite and Ground-Based Precipitation and Lightning Datasets for Convective Studies

NASA’s Lightning Imaging Sensor (LIS) and the Global Precipitation Measurement (GPM) mission have contributed a wealth of data toward global lightning and precipitation studies, respectively. Combining lightning and precipitation datasets leverages their unique insights into deep convective processes that inform about characteristics of convection and its intensity. Recent efforts to synthesize the LIS and GPM datasets prepare the opportunity for unprecedented large-scale, value-added multiplatform analyses of convection. This data synthesis proof-of-concept study elaborates on the creation of a database of reflectivity-based multiplatform precipitation features (MPFs) that capture a combination of information extracted from spatiotemporally coincident lightning and precipitation data within individual storm features. The space-based GPM Dual-frequency Precipitation Radar (DPR) provides a record of precipitation data, while the GPM Validation Network (VN) additionally incorporates ground-based polarimetric Doppler radar data to provide microphysical and kinematic context to DPR data. The LIS instrument onboard the International Space Station has contributed lightning observations since 2017. MPFs encapsulating information from these datasets are created from isolated regions of filtered, smoothed DPR reflectivity data to which ellipses are fit. Each MPF includes feature location, size, and eccentricity information as well as summary reflectivity characteristics. They also include summaries of precipitation microphysics and derived three-dimensional wind available from ground-based radar data. LIS data provides standard lightning characteristics such as flash count and density to each MPF as well as other informative metrics such as flash area and radiance. Each MPF file includes information about the original data from which the MPF and its characteristics were determined, allowing end-user reconstruction of the ellipse and deeper “level I” analysis of captured data. This database of VN-LIS MPFs enables broad statistical analysis of the relationships between the microphysical, kinematic, and electrical properties of convection. Preliminary results from a demonstration of the database will be described as well as ongoing efforts and avenues for future work.

Lightning↗
NASA NTRS1985

Infrared Measurements of Atmospheric Ethane (C2H6) From Aircraft and Ground-Based Solar Absorption Spectra in the 3000/ cm Region

A number or prominent Q-branches or the upsilon(sub 7) band or C2H6 have been identified near 3000/ cm in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The, ground-based spectra yield a column of 9.0 x 10(exp 15) molecules/sq cm above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv.

Coffey, M. T.↗
NASA NTRS2011

GLM Proxy Data Generation: Methods for Stroke/Pulse Level Inter-Comparison of Ground-Based Lightning Reference Networks

In order to produce useful proxy data for the GOES-R Geostationary Lightning Mapper (GLM) in regions not covered by VLF lightning mapping systems, we intend to employ data produced by ground-based (regional or global) VLF/LF lightning detection networks. Before using these data in GLM Risk Reduction tasks, it is necessary to have a quantitative understanding of the performance of these networks, in terms of CG flash/stroke DE, cloud flash/pulse DE, location accuracy, and CLD/CG classification error. This information is being obtained through inter-comparison with LMAs and well-quantified VLF/LF lightning networks. One of our approaches is to compare "bulk" counting statistics on the spatial scale of convective cells, in order to both quantify relative performance and observe variations in cell-based temporal trends provided by each network. In addition, we are using microsecond-level stroke/pulse time correlation to facilitate detailed inter-comparisons at a more-fundamental level. The current development status of our ground-based inter-comparison and evaluation tools will be presented, and performance metrics will be discussed through a comparison of Vaisala s Global Lightning Dataset (GLD360) with the NLDN at locations within and outside the U.S.

Cummins, Kenneth L.↗
NASA NTRS2019

Surface erythemal UV irradiance in the continental United States derived from ground-based and OMI observations: quality assessment, trend analysis and sampling issues

Surface full-sky erythemal dose rate (EDR) from the Ozone Monitoring Instrument (OMI) at both satellite overpass time and local noon time is evaluated against ground measurements at 31 sites from the US Department of Agriculture's (USDA) UV-B Monitoring and Research Program (UVMRP) over the period of 2005–2017. We find that both OMI overpass and solar noon time EDR are highly correlated with the measured counterparts (with a linear correlation coefficient of 0.90 and 0.88, respectively). Although the comparison statistics are improved with a longer time window (0.5–1.0 h) for pairing surface and OMI measurements, both OMI overpass and local noon time EDRs have 7 % overestimation that is larger than 6 % uncertainty in the ground measurements and show different levels of dependence on solar zenith angle (SZA) and to lesser extent on cloud optical depth. The ratio of EDR between local noon and OMI overpass time is often (95 % in frequency) larger than 1 with a mean of 1.18 in the OMI product; in contrast, the same ratio from surface observation is normally distributed with 22 % of the times less than 1 and a mean of 1.38. This contrast in part reflects the deficiency in the OMI surface UV algorithm that assumes constant atmospheric conditions between overpass and noon time. The probability density functions (PDFs) for both OMI and ground measurements of noontime EDR are in statistically significant agreement, showing dual peaks at ∼20 and ∼200 mW/sq. m, respectively; the latter is lower than 220 mW/ sq. m, the value at which the PDF of daily EDR from ground measurements peaks, and this difference indicates that the largest EDR value for a given day may not often occur at local noon. Lastly, statistically significant positive trends of EDR are found in the northeastern US in OMI data, but opposite trends are found within ground-based data (regardless of sampling for either noontime or daily averages). While positive trends are consistently found between OMI and surface data for EDR over the southern Great Plains (Texas and Oklahoma), their values are within the uncertainty of ground measurements. Overall, no scientifically sound trends can be found among OMI data for aerosol total and absorbing optical depth, cloud optical depth and total ozone to explain coherently the surface UV trends revealed either by OMI or ground-based estimates; these data also cannot reconcile trend differences between the two estimates (of EDR from OMI and surface observations). Future geostationary satellites with better spatiotemporal resolution data should help overcome spatiotemporal sampling issues inherent in OMI data products and therefore improve the estimates of surface UV flux and EDR from space.

Ozone Monitoring Instrument (OMI)↗
NASA NTRS1998

Combined Characterisation of GOME and TOMS Total Ozone Using Ground-Based Observations from the NDSC

Several years of total ozone measured from space by the ERS-2 GOME, the Earth Probe Total Ozone Mapping Spectrometer (TOMS), and the ADEOS TOMS, are compared with high-quality ground-based observations associated with the Network for the Detection of Stratospheric Change (NDSC), over an extended latitude range and a variety of geophysical conditions. The comparisons with each spaceborne sensor are combined altogether for investigating their respective solar zenith angle (SZA) dependence, dispersion, and difference of sensitivity. The space- and ground-based data are found to agree within a few percent on average. However, the analysis highlights for both Global Ozone Monitoring Experiment (GOME) and TOMS several sources of discrepancies, including a dependence on the SZA at high latitudes and internal inconsistencies.

Lambert, J.-C.↗
NASA NTRS2018

Preliminary Assessment of Detection Efficiency for the Geostationary Lightning Mapper Using Intercomparisons with Ground-Based Systems

As part of the calibration/validation (cal/val) effort for the Geostationary Lightning Mapper (GLM) on GOES-16, we need to assess instrument performance (detection efficiency and accuracy). One major effort is to calculate the detection efficiency of GLM by comparing to multiple ground-based systems. These comparisons will be done pair-wise between GLM and each other source. A complication in this process is that the ground-based systems sense different properties of the lightning signal than does GLM (e.g., RF vs. optical). Also, each system has a different time and space resolution and accuracy. Preliminary results indicate that GLM is performing at or above its specification.

GL↗