Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “HoGe”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

High frequency sampling of the 1984 spring bloom within the mid-Atlantic Bight: Synoptic shipboard, aircraft, and in situ perspectives of the SEEP-I experiment

Moorings of current meters, thermistors, transmissometers, and fluorometers on the mid-Atlantic shelf, south of Long Island, suggest a cumulative seaward export of perhaps 0.35 g C/sq m/day between the 80 and 120 m isobaths during February-April 1984. Such a horizontal loss of algal carbon over the lower third of the water column would be 23 to 78% of the March-April 1984 primary production. This physical carbon loss is similar to daily grazing losses from zooplankton of 32-40% of the algal fixation of carbon. Metabolic demands of the benthos could be met by just the estimated fecal pellet flux, without direct consumption of algal carbon, while bacterioplankton needs could be served by excretory release of dissolved organic matter during photosynthesis. Sediment traps tethered 10 m off the bottom at the 120 m isobath and 50 m above the 500 m isobath caught as much as 0.16 to 0.26 g C /sq m/day during March-April 1984, in reasonable agreement with the flux estimated from the other moored instruments.

Walsh, J. J.↗
NASA NTRS1986

Active-passive airborne ocean color measurement. I - Instrumentation

The instrumentation used in a multichannel lidar fluorosensor spectrometer functioning concurrently as a passive spectroradiometer for measuring upwelling ocean color radiance is discussed. The instrument calibration techniques are addressed, including the absolute passive calibration technique, the importance of relative channel-to-channel calibration for accurate ocean color measurement, and active mode calibration techniques using passive calibration transfer methods. Ground and flight test results from the dual-mode active-passive ocean color sensor are discussed.

Hoge, F. E.↗
NASA NTRS1986

The discrimination between crude-oil spills and monomolecular sea slicks by an airborne lidar

Airborne lidar measurements were performed over a deployed monomolecular oleyl alcohol surface film ('slick'), the physicochemical characteristics of which are known to be similar to biogenic organic compounds secreted by plankton and fish, and adjacent 'clean' sea surfaces in the North Sea. In the presence of the slick, the suppression of the Raman backscatter at 381 nm and of two spectral bands indicative of water column fluorescent organic material at 414 and 482 nm were observed. This effect is explained by two possible mechanisms giving rise to a modification of the transmission or coupling of the laser beam into the water column: (1) the damping of capillary and short gravity water waves by the oleyl alcohol slick, and (2) the modification of the uppermost water layer by the oleyl alcohol film. The results obtained in the presence of a slick are compared with data measured over a Murban crude-oil spill with the same lidar system off the coast of the U.S.A. The consequences of the lidar-monomolecular film experiments with regard to the remote detection of crude-oil spills and oil-thickness measurements with an airborne laser fluorosensing system will be discussed.

Huehnerfuss, H.↗
NASA NTRS1986

Active-passive airborne ocean color measurement. II - Applications

Reported here for the first time is the use of a single airborne instrument to make concurrent measurements of oceanic chlorophyll concentration by (1) laser-induced fluorescence, (2) passive upwelling radiance, and (3) solar-induced chlorophyll fluorescence. Results from field experiments conducted with the NASA airborne oceanographic lidar (AOL) in the New York Bight demonstrate the capability of a single active-passive instrument to perform new and potentially important ocean color studies related to (1) active lidar validation of passive ocean color in-water algorithms, (2) chlorophyll a in vivo fluorescence yield variability, (3) calibration of active multichannel lidar systems, (4) effect of sea state on passive and active ocean color measurements, (5) laser/solar-induced chlorophyll fluorescence investigations, and (6) subsequent improvement of satellite-borne ocean color scanners. For validation and comparison purposes a separate passive ocean color sensor was also flown along with the new active-passive sensor during these initial field trials.

Hoge, F. E.↗
NASA NTRS1986

ERBS orbit ascent utilizing continuous low thrust maneuvers

The Earth Radiation Budget Satellite (ERBS) is a National Aeronautics and Space Administration (NASA) spacecraft whose purpose is to investigate the components of the earth's radiation budget. The ERBS was deployed in a 57 degree inclined, 352.2 kilometer altitude circular orbit by the NASA Space Transportation System (STS) on October 5, 1984. The spacecraft then ascended to its 603 kilometer, near-circular mission orbit by a series of continuous low-thrust maneuvers. The ERBS was the first free-flyer mission to rely on continuous low thrust to spiral from one circular orbit to another. Careful planning and monitoring of these maneuvers were essential to their successful execution. Errors in the prediction of the propulsion system performance or in burn duration would result in loss of contact with the spacecraft during a maneuver and could result in a premature end to the maneuver and difficulty in computing a definitive orbit.

Hoge, S. L.↗
NASA NTRS1986

Oceanographic measurement capabilities of the NASA P-3 aircraft

Instrumentation on NASA P3 aircraft available to provide ground truth for ERS-1 is described. The wave sensors include the 36 GHz Surface Contour Radar (SCR), the Ku-band Radar Ocean Wave Spectrometer (ROWS), and the Airborne Oceanographic Lidar. The other sensors include a C-band scatterometer, video camera, radiation thermometer, and AXRTs. The SCR and ROWS directional spectrum measurements are discussed. When planning for an underflight mission, the limited endurance of the aircraft (6 hr) and flight cost (2.7 K$/hr) must be considered. The advantage of the redundancy afforded by the several wave instruments is another important consideration.

Mollo-Christensen, Erik↗
NASA NTRS1986

Active-passive correlation spectroscopy - A new technique for identifying ocean color algorithm spectral regions

A new active-passive airborne data correlation technique has been developed which allows the validation of existing in-water oceoan color algorithms and the rapid search, identification, and evaluation of new sensor band locations and algorithm wavelength intervals. Thus far, applied only in conjunction with the spectral curvature algorithm (SCA), the active-passive correlation spectroscopy (APCS) technique shows that (1) the usual 490-nm (center-band) chlorophyll SCA could satisfactorily be placed anywhere within the nominal 460-510-nm interval, and (2) two other spectral regions, 645-660 and 680-695 nm, show considerable promise for chlorophyll pigment measurement. Additionally, the APCS method reveals potentially useful wavelength regions (at 600 and about 670 nm) of very low chlorophyll-in-water spectral curvature into which accessory pigment algorithms for phycoerythrin might be carefully positioned. In combination, the APCS and SCA methods strongly suggest that significant information content resides within the seemingly featureless ocean color spectrum.

Hoge, F. E.↗
NASA NTRS1986

Chlorophyll pigment concentration using spectral curvature algorithms - An evaluation of present and proposed satellite ocean color sensor bands

During the past several years symmetric three-band (460-, 490-, 520-nm) spectral curvature algorithm (SCA) has demonstrated rather accurate determination of chlorophyll pigment concentration using low-altitude airborne ocean color data. It is shown herein that the in-water asymmetric SCA, when applied to certain recently proposed OCI (NOAA-K and SPOT-3) and OCM (ERS-1) satellite ocean color bands, can adequately recover chlorophyll-like pigments. These airborne findings suggest that the proposed new ocean color sensor bands are in general satisfactorily, but not necessarily optimally, positioned to allow space evaluation of the SCA using high-precision atmospherically corrected satellite radiances. The pigment concentration recovery is not as good when existing Coastal Zone Color Scanner bands are used in the SCA. The in-water asymmetric SCA chlorophyll pigment recovery evaluations were performed using (1) airborne laser-induced chlorophyll fluorescence and (2) concurrent passive upwelled radiances. Data from a separate ocean color sensor aboard the aircraft were further used to validate the findings.

Hoge, Frank E.↗
NASA NTRS1987

Ocean color spectral variability studies using solar-induced chlorophyll fluorescence

It is suggested that chlorophyll-induced ocean color spectral variability can be studied using only a passive airborne spectroradiometer instrument, with solar-induced chlorophyll fluorescence used as the standard against which all correlations are performed. The intraspectral correlation (ISC) method is demonstrated with results obtained during an airborne mapping mission in the New York Bight. The curvature algorithm is applied to the solar-induced chlorophyll fluorescence at about 690 nm, and good agreement is found with results obtained using active-passive correlation spectroscopy. The ISC method has application to spectral variability and resulting chlorophyll concentration measurement in different environmental conditions and in different water types.

Hoge, Frank E.↗
NASA NTRS1987

Multiplatform sampling (ship, aircraft, and satellite) of a Gulf Stream warm core ring

The purpose of this paper is to demonstrate the ability to meet the need to measure distributions of physical and biological properties of the ocean over large areas synoptically and over long time periods by means of remote sensing utilizing contemporaneous buoy, ship, aircraft, and satellite (i.e., multiplatform) sampling strategies. A mapping of sea surface temperature and chlorophyll fields in a Gulf Stream warm core ring using the multiplatform approach is described. Sampling capabilities of each sensing system are discussed as background for the data collected by means of these three dissimilar methods. Commensurate space/time sample sets from each sensing system are compared, and their relative accuracies in space and time are determined. The three-dimensional composite maps derived from the data set provide a synoptic perspective unobtainable from single platforms alone.

Smith, Raymond C.↗
NASA NTRS1987

Radiance-ratio algorithm wavelengths for remote oceanic chlorophyll determination

Two-band radiance-ratio in-water algorithms in the visible spectrum have been evaluated for remote oceanic chlorophyll determination. Airborne active-passive (laser-solar) data from coastal, shelf-slope, and blue-water regions were used to generate two-dimensional chlorophyll-fluorescence and radiance-ratio statistical correlation matrices containing all possible two-band ratio combinations from the thirty-two available contiguous 11.25-nm passive bands. The principal finding was that closely spaced radiance-ratio bands yield chlorophyll estimates which are highly correlated with laser-induced chlorophyll fluorescence within several distinct regions of the ocean color spectrum. Band combinations in the yellow, orange-red, spectral regions showed considerable promise for satisfactory chlorophyll pigment estimation in near-coastal Case II waters. Pigment recovery in Case I waters was best accomplished using blue-green radiance ratios in the 490/500-nm region.

Hoge, Frank E.↗
NASA NTRS1988

The effects of geopotential resonance on orbit determination for Landsat-4

Analysis is presented demonstrating improved performance for Landsat-4 orbit determination using the Goddard Trajectory Determination System with an adjusted Goddard Earth Model-9 (GEM-9) for geopotential coefficients of the 15th degree and order. The orbital state is estimated along with the sine and cosine coefficients of degree and order 15, (C, S) sub 15,15. The estimates are made for two 5-day intervals of range and doppler data, primarily from the Tracking and Data Relay Satellite, during a period of low solar activity in January 1987. The average values of the estimated coefficients (C, S) sub 15,15 are used to modify the GEM-9 model, and orbit determination performance is tested on 17 consecutive 34-hour operational tracking data arcs in January 1987. Significant reductions in the mean values and standard deviations of the along-track position difference and the drag model scaling parameter from solution to solution are observed. The approach is guided by the shallow resonance theory of geopotential orbit perturbations.

Hoge, S. L.↗
NASA NTRS1988

Oceanographic applications of laser technology

Oceanographic activities with the Airborne Oceanographic Lidar (AOL) for the past several years have primarily been focussed on using active (laser induced pigment fluorescence) and concurrent passive ocean color spectra to improve existing ocean color algorithms for estimating primary production in the world's oceans. The most significant results were the development of a technique for selecting optimal passive wavelengths for recovering phytoplankton photopigment concentration and the application of this technique, termed active-passive correlation spectroscopy (APCS), to various forms of passive ocean color algorithms. Included in this activity is use of airborne laser and passive ocean color for development of advanced satellite ocean color sensors. Promising on-wavelength subsurface scattering layer measurements were recently obtained. A partial summary of these results are shown.

Hoge, F. E.↗
NASA NTRS1988

Airborne Oceanographic Lidar (AOL) flight mission participation

From February 1986 to the present, the AOL participated in six interagency flight missions. (1) Shelf Edge Exchange Processes (SEEP II) (Department of Energy). The SEEP experiments are designed to assess the assimilative capacity of the Continental Shelf to absorb the energy by-products introduced into the near-shore ocean environment from coastal communities and marine activities such as energy production plants and offshore oil operations. (2) BIOWATT II (Office of Naval Research). The major objective of this study was to provide a better understanding of the relationships between ocean physics, biology, bioluminescence, and optics in oligotrophic portions of the Atlantic Ocean. (3) Fall Experiment (FLEX) (Department of Energy). The FLEX studies were designed to determine the fate of low salinity water in the coastal boundary zone that is advected south towards the Florida coast during autumn. (4) Greenland Sea and Icelandic Marine Biological Experiments (NASA). The investigations were designed to evaluate the distribution of surface layer chlorophyll in the Greeland Sea and in the coastal waters in the vicinity of Iceland. (5) Submerged Oceanic Scattering Layer Experiment (Naval Ocean Systems Center). This flight experiment demonstrated for the first time the feasibility of detecting and metrically measuring the depth to submerged layers of particulate matter in the shelf break region and in the inner coastal zone. (6) Microbial Exchanges and Coupling in Coastal Atlantic Systems (National Science Foundation). This investigation was designed to study the transportation and fate of particulates in coastal waters and in particular the Chesapeake Bay/coastal Atlantic Ocean. Shortly after the conduct of the flight experiments, airborne laser-induced chlorophyll a and phycoerythrin fluorescence data, as well as sea surface temperature and airborne expendable bathythermograph water column temperature profiles are supplied to cooperating institutions.

Hoge, F. E.↗
NASA NTRS1988

Airborne lidar detection of subsurface oceanic scattering layers

The airborne lidar detection and cross-sectional mapping of submerged oceanic scattering layers are reported. The field experiment was conducted in the Atlantic Ocean southeast of Assateague Island, VA. NASA's Airborne Oceanographic Lidar was operated in the bathymetric mode to acquire on-wavelength 532-nm depth-resolved backscatter signals from shelf/slope waters. Unwanted laser pulse reflection from the air-water interface was minimized by spatial filtering and off-nadir operation. The presence of thermal stratification over the shelf was verified by the deployment of airborne expendable bathythermographs. Optical beam transmission measurements acquired from a surface truthing vessel indicated the presence of a layer of turbid water near the sea floor over the inner portion of the shelf.

Hoge, Frank E.↗
NASA NTRS1988

Short- and long-term determination of the TDRS solar reflectivity parameter using the Goddard trajectory determination system

Two aspects of the orbit determination of the Tracking and Data Relay Satellite-East (TDRS-E) are considered. The TDRS-E solar reflectivity parameter, as it affects the accuracy of the determination and propagation of the TDRS-E geosynchronous orbit, varies seasonally due to the changing declination of the sun. Orbit solutions are carried out using varying tracking data arc lengths to ascertain the minimum arc length needed for an accurate determination of the TDRS-E orbital elements and the solar reflectivity parameter.

Bobrowsky, M.↗
NASA NTRS1988

ISEE orbital decay due to lunar third-body perturbations

The orbital decay of the International Sun-Earth Explorer (ISEE-1) and ISEE-2 spacecraft was studied. The perturbative forces due to the nonspherical components of the earth's gravitational field, atmospheric drag, solar radiation pressure, and third-body perturbations are examined. The dynamics of the earth-spacecraft-moon system is analyzed as well. Various scenarios using the perturbative forces in conjunction with propulsive energy are evaluated to determine the requirements for extending the lifetime of this type of mission.

Amenabar, J. P.↗
NASA NTRS1989

Airborne discrimination between ice and water - Application to the laser measurement of chlorophyll-in-water in a marginal ice zone

The concurrent active-passive measurement capabilities of the NASA Airborne Oceanographic Lidar have been used to (1) discriminate between ice and water in a large ice field within the Greenland Sea and (2) achieve the detection and measurement of chlorophyll-in-water by laser-induced and water-Raman-normalized pigment fluorescence. Passive upwelled radiances from sea ice are significantly stronger than those from the neighboring water, even when the optical receiver field-of-view is only partially filled with ice. Thus, weaker passive upwelled radiances, together with concurrently acquired laser-induced spectra, can rather confidently be assigned to the intervening water column. The laser-induced spectrum can then be processed using previously established methods to measure the chlorophyll-in-water concentration. Significant phytoplankton patchiness and elevated chlorophyll concentrations were found within the waters of the melting ice compared to ice-free regions just outside the ice field.

Hoge, Frank E.↗