Decorrelation of L-band and C-band interferometry to volcanic risk prevention

NASA Astrophysics Data System (ADS)

Malinverni, E. S.; Sandwell, D.; Tassetti, A. N.; Cappelletti, L.

2013-10-01

SAR has several strong key features: fine spatial resolution/precision and high temporal pass frequency. Moreover, the InSAR technique allows the accurate detection of ground deformations. This high potential technology can be invaluable to study volcanoes: it provides important information on pre-eruption surface deformation, improving the understanding of volcanic processes and the ability to predict eruptions. As a downside, SAR measurements are influenced by artifacts such as atmospheric effects or bad topographic data. Correlation gives a measure of these interferences, quantifying the similarity of the phase of two SAR images. Different approaches exists to reduce these errors but the main concern remain the possibility to correlate images with different acquisition times: snow-covered or heavily-vegetated areas produce seasonal changes on the surface. Minimizing the time between passes partly limits decorrelation. Though, images with a short temporal baseline aren't always available and some artifacts affecting correlation are timeindependent. This work studies correlation of pairs of SAR images focusing on the influence of surface and climate conditions, especially snow coverage and temperature. Furthermore, the effects of the acquisition band on correlation are taken into account, comparing L-band and C-band images. All the chosen images cover most of the Yellowstone caldera (USA) over a span of 4 years, sampling all the seasons. Interferograms and correlation maps are generated. To isolate temporal decorrelation, pairs of images with the shortest baseline are chosen. Correlation maps are analyzed in relation to snow depth and temperature. Results obtained with ENVISAT and ERS satellites (C-band) are compared with the ones from ALOS (L-band). Results show a good performance during winter and a bad attitude towards wet snow (spring and fall). During summer both L-band and C-band maintain a good coherence with L-band performing better over vegetation.

Study of bidirectional broadband passive optical network (BPON) using EDFA

NASA Astrophysics Data System (ADS)

Almalaq, Yasser

Optical line terminals (OLTs) and number of optical network units (ONUs) are two main parts of passive optical network (PON). OLT is placed at the central office of the service providers, the ONUs are located near to the end subscribers. When compared with point-to-point design, a PON decreases the number of fiber used and central office components required. Broadband PON (BPON), which is one type of PON, can support high-speed voice, data and video services to subscribers' residential homes and small businesses. In this research, by using erbium doped fiber amplifier (EDFA), the performance of bi-directional BPON is experimented and tested for both downstream and upstream traffic directions. Ethernet PON (E-PON) and gigabit PON (G-PON) are the two other kinds of passive optical network besides BPON. The most beneficial factor of using BPON is it's reduced cost. The cost of the maintenance between the central office and the users' side is suitable because of the use of passive components, such as a splitter in the BPON architecture. In this work, a bidirectional BPON has been analyzed for both downstream and upstream cases by using bit error rate analyzer (BER). BER analyzers test three factors that are the maximum Q factor, minimum bit error rate, and eye height. In other words, parameters such as maximum Q factor, minimum bit error rate, and eye height can be analyzed utilized a BER tester. Passive optical components such as a splitter, optical circulator, and filters have been used in modeling and simulations. A 12th edition Optiwave simulator has been used in order to analyze the bidirectional BPON system. The system has been tested under several conditions such as changing the fiber length, extinction ratio, dispersion, and coding technique. When a long optical fiber above 40km was used, an EDFA was used in order to improve the quality of the signal.

Impact of the ionosphere on an L-band space based radar

NASA Technical Reports Server (NTRS)

Chapin, Elaine; Chan, Samuel F.; Chapman, Bruce D.; Chen, Curtis W.; Martin, Jan M.; Michel, Thierry R.; Muellerschoen, Ronald J.; Pi, Xiaoqing; Rosen, Paul A.

2006-01-01

We have quantified the impact that the ionosphere would have on a L-band interferometric Synthetic Aperture Radar (SAR) mission using a combination of simulation, modeling, Global Positioning System (GPS) data collected during the last solar maximum, and existing spaceborne SAR data.

L Band Service Compatibility Part I: Optimum OOBE Compatibility

DOT National Transportation Integrated Search

2014-12-04

Discussion: -- Two Parts - Today we focus on optimum L Band ABC Out of Band Emission into GPS L1, OOBE. - Next ABC meeting will examine GPS-side mitigation of Adjacent Band Interference, ABI. -- Greater Compatibility: OOBE and ABI are distinct but pa...

Coastal flood inundation monitoring with Satellite C-band and L-band Synthetic Aperture Radar data

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, Amina; Bannister, Terri

2013-01-01

Satellite Synthetic Aperture Radar (SAR) was evaluated as a method to operationally monitor the occurrence and distribution of storm- and tidal-related flooding of spatially extensive coastal marshes within the north-central Gulf of Mexico. Maps representing the occurrence of marsh surface inundation were created from available Advanced Land Observation Satellite (ALOS) Phased Array type L-Band SAR (PALSAR) (L-band) (21 scenes with HH polarizations in Wide Beam [100 m]) data and Environmental Satellite (ENVISAT) Advanced SAR (ASAR) (C-band) data (24 scenes with VV and HH polarizations in Wide Swath [150 m]) during 2006-2009 covering 500 km of the Louisiana coastal zone. Mapping was primarily based on a decrease in backscatter between reference and target scenes, and as an extension of previous studies, the flood inundation mapping performance was assessed by the degree of correspondence between inundation mapping and inland water levels. Both PALSAR- and ASAR-based mapping at times were based on suboptimal reference scenes; however, ASAR performance seemed more sensitive to reference-scene quality and other types of scene variability. Related to water depth, PALSAR and ASAR mapping accuracies tended to be lower when water depths were shallow and increased as water levels decreased below or increased above the ground surface, but this pattern was more pronounced with ASAR. Overall, PALSAR-based inundation accuracies averaged 84% (n = 160), while ASAR-based mapping accuracies averaged 62% (n = 245).

Reconfigurable L-Band Radar

NASA Technical Reports Server (NTRS)

Rincon, Rafael F.

2008-01-01

The reconfigurable L-Band radar is an ongoing development at NASA/GSFC that exploits the capability inherently in phased array radar systems with a state-of-the-art data acquisition and real-time processor in order to enable multi-mode measurement techniques in a single radar architecture. The development leverages on the L-Band Imaging Scatterometer, a radar system designed for the development and testing of new radar techniques; and the custom-built DBSAR processor, a highly reconfigurable, high speed data acquisition and processing system. The radar modes currently implemented include scatterometer, synthetic aperture radar, and altimetry; and plans to add new modes such as radiometry and bi-static GNSS signals are being formulated. This development is aimed at enhancing the radar remote sensing capabilities for airborne and spaceborne applications in support of Earth Science and planetary exploration This paper describes the design of the radar and processor systems, explains the operational modes, and discusses preliminary measurements and future plans.

Earth Studies Using L-band Synthetic Aperture Radar

NASA Technical Reports Server (NTRS)

Rosen, Paul A.

1999-01-01

L-band SAR has played an important role in studies of the Earth by revealing the nature of the larger-scale (decimeter) surface features. JERS-1, by supplying multi-seasonal coverage of the much of the earth, has demonstrated the importance of L-band SARs. Future L-band SARs such as ALOS and LightSAR will pave the way for science missions that use SAR instruments. As technology develops to enable lower cost SAR instruments, missions will evolve to each have a unique science focus. International coordination of multi-parameter constellations and campaigns will maximize science return.

Satellite Based Soil Moisture Product Validation Using NOAA-CREST Ground and L-Band Observations

NASA Astrophysics Data System (ADS)

Norouzi, H.; Campo, C.; Temimi, M.; Lakhankar, T.; Khanbilvardi, R.

2015-12-01

Soil moisture content is among most important physical parameters in hydrology, climate, and environmental studies. Many microwave-based satellite observations have been utilized to estimate this parameter. The Advanced Microwave Scanning Radiometer 2 (AMSR2) is one of many remotely sensors that collects daily information of land surface soil moisture. However, many factors such as ancillary data and vegetation scattering can affect the signal and the estimation. Therefore, this information needs to be validated against some "ground-truth" observations. NOAA - Cooperative Remote Sensing and Technology (CREST) center at the City University of New York has a site located at Millbrook, NY with several insitu soil moisture probes and an L-Band radiometer similar to Soil Moisture Passive and Active (SMAP) one. This site is among SMAP Cal/Val sites. Soil moisture information was measured at seven different locations from 2012 to 2015. Hydra probes are used to measure six of these locations. This study utilizes the observations from insitu data and the L-Band radiometer close to ground (at 3 meters height) to validate and to compare soil moisture estimates from AMSR2. Analysis of the measurements and AMSR2 indicated a weak correlation with the hydra probes and a moderate correlation with Cosmic-ray Soil Moisture Observing System (COSMOS probes). Several differences including the differences between pixel size and point measurements can cause these discrepancies. Some interpolation techniques are used to expand point measurements from 6 locations to AMSR2 footprint. Finally, the effect of penetration depth in microwave signal and inconsistencies with other ancillary data such as skin temperature is investigated to provide a better understanding in the analysis. The results show that the retrieval algorithm of AMSR2 is appropriate under certain circumstances. This validation algorithm and similar study will be conducted for SMAP mission. Keywords: Remote Sensing, Soil

Passive Microwave Measurements Over Conifer Forests at L-Band and C-Band

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lang, R.; Chauhan, N.; Kim, E.; Bidwell, S.; Goodberlet, M.; Haken, M.; deMatthaeis, P.

2000-01-01

Measurements have been made at L-band and C-band over conifer forests in Virginia to study the response of passive microwave instruments to biomass and soil moisture. A series of aircraft measurements were made in July, August and November, 1999 over relatively homogenous conifer forests of varying biomass. Three radiometers participated in these measurements. These were: 1) the L-band radiometer ESTAR, a horizontally polarized synthetic aperture radiometer which has been used extensively in past measurements of soil moisture; 2) the L-band radiometer SLFMR, a vertically polarized cross-track scanner which has been used successfully in the past for mapping sea surface salinity; and 3) The ACMR, a new C-band radiometer which operates at V- and H-polarization and in the configuration for these experiments did not scan. All three radiometers were flown on the NASA P-3 aircraft based at the Goddard Space Flight Center's Wallops Flight Facility. The ESTAR and SLFMR were mounted in the bomb bay of the P-3 and imaged across track whereas the ACMR was mounted to look aft at 54 degrees up from nadir. Data was collected at altitudes of 915 meters and 457 meters. The forests consisted of relatively homogeneous "managed" stands of conifer located near Waverly, Virginia. This is a relatively flat area about 30 miles southeast of Richmond, VA with numerous stands of trees being grown for the forestry industry. The stands selected for study consisted of areas of regrowth and mature stands of pine. In addition, a small stand of very large trees was observed. Soil moisture sampling was done in each stand during the aircraft over flights. Data was collected on July 7, August 27, November 15 and November 30, 1999. Measurements were made with ESTAR on all days. The ACMR flew on the summer missions and the SLFMR was present only on the August 27 flight. Soil moisture varied from quite dry on July 7 to quite moist on November 30 (which was shortly after a period of rain). The microwave

Design of dual band FSS by using quadruple L-slot technique

NASA Astrophysics Data System (ADS)

Fauzi, Noor Azamiah Md; Aziz, Mohamad Zoinol Abidin Abd.; Said, Maizatul Alice Meor; Othman, Mohd Azlishah; Ahmad, Badrul Hisham; Malek, Mohd Fareq Abd

2015-05-01

This paper presents a new design of dual band frequency selective surface (FSS) for band pass microwave transmission application. FSS can be used on energy saving glass to improve the transmission of wireless communication signals through the glass. The microwave signal will be attenuate when propagate throughout the different structure such as building. Therefore, some of the wireless communication system cannot be used in the optimum performance. The aim of this paper is designed, simulated and analyzed the new dual band FSS structure for microwave transmission. This design is based on a quadruple L slot combined with cross slot to produce pass band at 900 MHz and 2.4 GHz. The vertical of pair inverse L slot is used as the band pass for the frequency of 2.4GHz. While, the horizontal of pair inverse L slot is used as the band pass at frequency 900MHz. This design is simulated and analyzed by using Computer Simulation Technology (CST) Microwave Studio (MWS) software. The characteristics of the transmission (S21) and reflection (S11) of the dual band FSS were simulater and analyzed. The bandwidth of the first band is 118.91MHz which covered the frequency range from 833.4MHz until 952.31MHz. Meanwhile, the bandwidth for the second band is 358.84MHz which covered the frequency range from 2.1475GHz until 2.5063GHz. The resonance/center frequency of this design is obtained at 900MHz with a 26.902dB return loss and 2.37GHz with 28.506dB a return loss. This FSS is suitable as microwave filter for GSM900 and WLAN 2.4GHz application.

Impact of the Ionosphere on an L-band Space Based Radar

NASA Technical Reports Server (NTRS)

Chapin, Elaine; Chan, Samuel F.; Chapman, Bruce D.; Chen, Curtis W.; Martin, Jan M.; Michel, Thierry R.; Muellerschoen, Ronald J.; Pi, Xiaoqing; Rosen, Paul A.

2006-01-01

We have quantified the impact that the ionosphere would have on a L-band interferometric Synthetic Aperture Radar (SAR) mission using a combination of simulation, modeling, Global Positioning System (GPS) data collected during the last solar maximum, and existing spaceborne SAR data. We conclude that, except for high latitude scintillation related effects, the ionosphere will not significantly impact the performance of an L-band InSAR mission in an appropriate orbit. We evaluated the strength of the ionospheric irregularities using GPS scintillation data collected at Fairbanks, Alaska and modeled the impact of these irregularities on azimuth resolution, azimuth displacement, peak sidelobe ratio (PSLR), and integrated sidelobe ratio (ISLR). Although we predict that less than 5% of auroral zone data would show scintillation related artifacts, certain sites imaged near the equinoxes could be effected up to 25% of the time because the frequency of occurrence of scintillation is a strong function of season and local time of day. Our examination of ionospheric artifacts observed in InSAR data has revealed that the artifacts occur primarily in the polar cap data, not auroral zone data as was previously thought.

ELBARA II, an L-band radiometer system for soil moisture research.

PubMed

Schwank, Mike; Wiesmann, Andreas; Werner, Charles; Mätzler, Christian; Weber, Daniel; Murk, Axel; Völksch, Ingo; Wegmüller, Urs

2010-01-01

L-band (1-2 GHz) microwave radiometry is a remote sensing technique that can be used to monitor soil moisture, and is deployed in the Soil Moisture and Ocean Salinity (SMOS) Mission of the European Space Agency (ESA). Performing ground-based radiometer campaigns before launch, during the commissioning phase and during the operative SMOS mission is important for validating the satellite data and for the further improvement of the radiative transfer models used in the soil-moisture retrieval algorithms. To address these needs, three identical L-band radiometer systems were ordered by ESA. They rely on the proven architecture of the ETH L-Band radiometer for soil moisture research (ELBARA) with major improvements in the microwave electronics, the internal calibration sources, the data acquisition, the user interface, and the mechanics. The purpose of this paper is to describe the design of the instruments and the main characteristics that are relevant for the user.

ELBARA II, an L-Band Radiometer System for Soil Moisture Research

PubMed Central

Schwank, Mike; Wiesmann, Andreas; Werner, Charles; Mätzler, Christian; Weber, Daniel; Murk, Axel; Völksch, Ingo; Wegmüller, Urs

2010-01-01

L-band (1–2 GHz) microwave radiometry is a remote sensing technique that can be used to monitor soil moisture, and is deployed in the Soil Moisture and Ocean Salinity (SMOS) Mission of the European Space Agency (ESA). Performing ground-based radiometer campaigns before launch, during the commissioning phase and during the operative SMOS mission is important for validating the satellite data and for the further improvement of the radiative transfer models used in the soil-moisture retrieval algorithms. To address these needs, three identical L-band radiometer systems were ordered by ESA. They rely on the proven architecture of the ETH L-Band radiometer for soil moisture research (ELBARA) with major improvements in the microwave electronics, the internal calibration sources, the data acquisition, the user interface, and the mechanics. The purpose of this paper is to describe the design of the instruments and the main characteristics that are relevant for the user. PMID:22315556

L-Band System Engineering - Concepts of Use, Systems Performance Requirements, and Architecture

NASA Technical Reports Server (NTRS)

Henriksen, Stephen; Zelkin, Natalie

2011-01-01

This document is being provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-band and L-band Communications Standard Development. Task 7 was motivated by the five year technology assessment performed for the Federal Aviation Administration (FAA) under the joint FAA-EUROCONTROL cooperative research Action Plan (AP-17), also known as the Future Communications Study (FCS). It was based on direction provided by the FAA project-level agreement (PLA FY09_G1M.02-02v1) for "New ATM Requirements-Future Communications." Task 7 was separated into two distinct subtasks, each aligned with specific work elements and deliverable items. Subtask 7-1 addressed C-band airport surface data communications standards development, systems engineering, test bed development, and tests/demonstrations to establish operational capability for what is now referred to as the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2, which is the subject of this report, focused on preliminary systems engineering and support of joint FAA/EUROCONTROL development and evaluation of a future L-band (960 to 1164 MHz) air/ground (A/G) communication system known as the L-band digital aeronautical communications system (L-DACS), which was defined during the FCS. The proposed L-DACS will be capable of providing ATM services in continental airspace in the 2020+ timeframe. Subtask 7-2 was performed in two phases. Phase I featured development of Concepts of Use, high level functional analyses, performance of initial L-band system safety and security risk assessments, and development of high level requirements and architectures. It also included the aforementioned support of joint L-DACS development and evaluation, including inputs to L-DACS design specifications. Phase II provided a refinement of the systems engineering activities performed during Phase I, along

Large Scale Assessment of Radio Frequency Interference Signatures in L-band SAR Data

NASA Astrophysics Data System (ADS)

Meyer, F. J.; Nicoll, J.

2011-12-01

Imagery of L-band Synthetic Aperture Radar (SAR) systems such as the PALSAR sensor on board the Advanced Land Observing Satellite (ALOS) has proven to be a valuable tool for observing environmental changes around the globe. Besides offering 24/7 operability, the L-band frequency provides improved interferometric coherence, and L-band polarimetric data has shown great potential for vegetation monitoring, sea ice classification, and the observation of glaciers and ice sheets. To maximize the benefit of missions such as ALOS PALSAR for environmental monitoring, data consistency and calibration are vital. Unfortunately, radio frequency interference (RFI) signatures from ground-based radar systems regularly impair L-band SAR data quality and consistency. With this study we present a large-scale analysis of typical RFI signatures that are regularly observed in L-band SAR data over the Americas. Through a study of the vast archive of L-band SAR data in the US Government Research Consortium (USGRC) data pool at the Alaska Satellite Facility (ASF) we were able to address the following research goals: 1. Assessment of RFI Signatures in L-band SAR data and their Effects on SAR Data Quality: An analysis of time-frequency properties of RFI signatures in L-band SAR data of the USGRC data pool is presented. It is shown that RFI-filtering algorithms implemented in the operational ALOS PALSAR processor are not sufficient to remove all RFI-related artifacts. In examples, the deleterious effects of RFI on SAR image quality, polarimetric signature, SAR phase, and interferometric coherence are presented. 2. Large-Scale Assessment of Severity, Spatial Distribution, and Temporal Variation of RFI Signatures in L-band SAR data: L-band SAR data in the USGRC data pool were screened for RFI using a custom algorithm. Per SAR frame, the algorithm creates geocoded frame bounding boxes that are color-coded according to RFI intensity and converted to KML files for analysis in Google Earth. From

EMI survey for maritime satellite, L-band, shipboard terminal

NASA Technical Reports Server (NTRS)

Taylor, R. E.; Brandel, D. L.; Hill, J. S.

1975-01-01

The paper presents results of an onboard EMI survey of an L-band shipboard terminal for operation with two geostationary maritime satellites. Significant EMC results include: (1) antenna noise temperature measurements indicate a maximum of 70 K steady background component at 1.6 GHz at sea for elevation angles of 5 degrees and higher; (2) field intensity measurements from 1-10 GHz show that a L-band terminal can operate simultaneously with onboard S-band and X-band navigation radar; (3) radar transmitter case emissions, below deck, in-band from 1535-1660 MHz, at 1 m distance from the cabinet, are equivalent, or greater than above-deck emissions in the same frequency range; and (4) conducted-emission tests of a ship's power lines to both radars show both narrow band and broad band emissions are 15 dB to 50 dB higher than equivalent U.S. commercial power lines from 150 kHz to 32 MHz.

A Passive Microwave L-Band Boreal Forest Freeze/Thaw and Vegetation Phenology Study

NASA Astrophysics Data System (ADS)

Roy, A.; Sonnentag, O.; Pappas, C.; Mavrovic, A.; Royer, A.; Berg, A. A.; Rowlandson, T. L.; Lemay, J.; Helgason, W.; Barr, A.; Black, T. A.; Derksen, C.; Toose, P.

2016-12-01

The boreal forest is the second largest land biome in the world and thus plays a major role in the global and regional climate systems. The extent, timing and duration of seasonal freeze/thaw (F/T) state influences vegetation developmental stages (phenology) and, consequently, constitute an important control on how boreal forest ecosystems exchange carbon, water and energy with the atmosphere. The effective retrieval of seasonal F/T state from L-Band radiometry was demonstrated using satellite mission. However, disentangling the seasonally differing contributions from forest overstory and understory vegetation, and the soil surface to the satellite signal remains challenging. Here we present initial results from a radiometer field campaign to improve our understanding of the L-Band derived boreal forest F/T signal and vegetation phenology. Two L-Band surface-based radiometers (SBR) are installed on a micrometeorological tower at the Southern Old Black Spruce site in central Saskatchewan over the 2016-2017 F/T season. One radiometer unit is installed on the flux tower so it views forest including all overstory and understory vegetation and the moss-covered ground surface. A second radiometer unit is installed within the boreal forest overstory, viewing the understory and the ground surface. The objectives of our study are (i) to disentangle the L-Band F/T signal contribution of boreal forest overstory from the understory and ground surface, (ii) to link the L-Band F/T signal to related boreal forest structural and functional characteristics, and (iii) to investigate the use of the L-Band signal to characterize boreal forest carbon, water and energy fluxes. The SBR observations above and within the forest canopy are used to retrieve the transmissivity (γ) and the scattering albedo (ω), two parameters that describe the emission of the forest canopy though the F/T season. These two forest parameters are compared with boreal forest structural and functional

Combined observations of Arctic sea ice with near-coincident colocated X-band, C-band, and L-band SAR satellite remote sensing and helicopter-borne measurements

NASA Astrophysics Data System (ADS)

Johansson, A. M.; King, J. A.; Doulgeris, A. P.; Gerland, S.; Singha, S.; Spreen, G.; Busche, T.

2017-01-01

In this study, we compare colocated near-coincident X-, C-, and L-band fully polarimetry SAR satellite images with helicopter-borne ice thickness measurements acquired during the Norwegian Young sea ICE 2015 (N-ICE2015) expedition in the region of the Arctic Ocean north of Svalbard in April 2015. The air-borne surveys provide near-coincident snow plus ice thickness, surface roughness data, and photographs. This unique data set allows us to investigate how the different frequencies can complement one another for sea ice studies, but also to raise awareness of limitations. X-band and L-band satellite scenes were shown to be a useful complement to the standard SAR frequency for sea ice monitoring (C-band) for lead ice and newly formed sea ice identification. This may be in part be due to the frequency but also the high spatial resolution of these sensors. We found a relatively low correlation between snow plus ice thickness and surface roughness. Therefore, in our dataset ice thickness cannot directly be observed by SAR which has important implications for operational ice charting based on automatic segmentation.

Microwave time delays for the dual L-C-band feed system

NASA Technical Reports Server (NTRS)

Chen, J.

1989-01-01

A new dual-frequency feed system at Goldstone is designed to receive the Phobos spacecraft signal at L-band (1668 + or - 40 MHz) and transmit to the spacecraft at C-band (5008.75 + or - 5.00 MHz) simultaneously. Hence, calculations of the time delay from the C-band range calibration coupler to the phase center of the L-C dual feed and back to the L-band range calibration coupler are required to correct the range measurements. Time delays of the elements in the dual-frequency feed system are obtained mostly from computer calculations and partly from experimental measurements. The method used and results obtained are described.

Inferring Land Surface Model Parameters for the Assimilation of Satellite-Based L-Band Brightness Temperature Observations into a Soil Moisture Analysis System

NASA Technical Reports Server (NTRS)

Reichle, Rolf H.; De Lannoy, Gabrielle J. M.

2012-01-01

The Soil Moisture and Ocean Salinity (SMOS) satellite mission provides global measurements of L-band brightness temperatures at horizontal and vertical polarization and a variety of incidence angles that are sensitive to moisture and temperature conditions in the top few centimeters of the soil. These L-band observations can therefore be assimilated into a land surface model to obtain surface and root zone soil moisture estimates. As part of the observation operator, such an assimilation system requires a radiative transfer model (RTM) that converts geophysical fields (including soil moisture and soil temperature) into modeled L-band brightness temperatures. At the global scale, the RTM parameters and the climatological soil moisture conditions are still poorly known. Using look-up tables from the literature to estimate the RTM parameters usually results in modeled L-band brightness temperatures that are strongly biased against the SMOS observations, with biases varying regionally and seasonally. Such biases must be addressed within the land data assimilation system. In this presentation, the estimation of the RTM parameters is discussed for the NASA GEOS-5 land data assimilation system, which is based on the ensemble Kalman filter (EnKF) and the Catchment land surface model. In the GEOS-5 land data assimilation system, soil moisture and brightness temperature biases are addressed in three stages. First, the global soil properties and soil hydraulic parameters that are used in the Catchment model were revised to minimize the bias in the modeled soil moisture, as verified against available in situ soil moisture measurements. Second, key parameters of the "tau-omega" RTM were calibrated prior to data assimilation using an objective function that minimizes the climatological differences between the modeled L-band brightness temperatures and the corresponding SMOS observations. Calibrated parameters include soil roughness parameters, vegetation structure parameters

A ground based L-band radiometer for the monitoring of soil moisture in the region of Millbrook, New York, USA

USDA-ARS?s Scientific Manuscript database

A field experiment was performed in grassland near Millbrook, New York, using a NOAA Microwave Observation Facility, which comprises a network for in situ observation of soil moisture and a mobile dual polarized L band radiometer. During the field campaign, intensive measurements of L band brightnes...

Low threshold L-band mode-locked ultrafast fiber laser assisted by microfiber-based carbon nanotube saturable absorber

NASA Astrophysics Data System (ADS)

Lau, K. Y.; Ng, E. K.; Abu Bakar, M. H.; Abas, A. F.; Alresheedi, M. T.; Yusoff, Z.; Mahdi, M. A.

2018-04-01

We demonstrate a passively mode-locked erbium-doped fiber laser in L-band wavelength region with low mode-locking threshold employing a 1425 nm pump wavelength. The mode-locking regime is generated by microfiber-based saturable absorber using carbon nanotube-polymer composite in a ring cavity. This carbon nanotube saturable absorber shows saturation intensity of 9 MW/cm2. In this work, mode-locking laser threshold is observed at 36.4 mW pump power. At the maximum pump power of 107.6 mW, we obtain pulse duration at full-width half-maximum point of 490 fs and time bandwidth product of 0.33, which corresponds to 3-dB spectral bandwidth of 5.8 nm. The pulse repetition rate remains constant throughout the experiment at 5.8 MHz due to fixed cavity length of 35.5 m. Average output power and pulse energy of 10.8 mW and 1.92 nJ are attained respectively through a 30% laser output extracted from the mode-locked cavity. This work highlights the feasibility of attaining a low threshold mode-locked laser source to be employed as seed laser in L-band wavelength region.

Effective Tree Scattering and Opacity at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Joseph, Alicia T.; Cosh, Michael H.; Jackson, Thomas J.

2011-01-01

This paper investigates vegetation effects at L-band by using a first-order radiative transfer (RT) model and truck-based microwave measurements over natural conifer stands to assess the applicability of the tau-omega) model over trees. The tau-omega model is a zero-order RT solution that accounts for vegetation effects with effective vegetation parameters (vegetation opacity and single-scattering albedo), which represent the canopy as a whole. This approach inherently ignores multiple-scattering effects and, therefore, has a limited validity depending on the level of scattering within the canopy. The fact that the scattering from large forest components such as branches and trunks is significant at L-band requires that zero-order vegetation parameters be evaluated (compared) along with their theoretical definitions to provide a better understanding of these parameters in the retrieval algorithms as applied to trees. This paper compares the effective vegetation opacities, computed from multi-angular pine tree brightness temperature data, against the results of two independent approaches that provide theoretical and measured optical depths. These two techniques are based on forward scattering theory and radar corner reflector measurements, respectively. The results indicate that the effective vegetation opacity values are smaller than but of similar magnitude to both radar and theoretical estimates. The effective opacity of the zero-order model is thus set equal to the theoretical opacity and an explicit expression for the effective albedo is then obtained from the zero- and first- order RT model comparison. The resultant albedo is found to have a similar magnitude as the effective albedo value obtained from brightness temperature measurements. However, it is less than half of that estimated using the theoretical calculations (0.5 - 0.6 for tree canopies at L-band). This lower observed albedo balances the scattering darkening effect of the large theoretical albedo

Wideband and flat-gain amplifier based on high concentration erbium-doped fibres in parallel double-pass configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamida, B A; Cheng, X S; Harun, S W

A wideband and flat gain erbium-doped fibre amplifier (EDFA) is demonstrated using a hybrid gain medium of a zirconiabased erbium-doped fibre (Zr-EDF) and a high concentration erbium-doped fibre (EDF). The amplifier has two stages comprising a 2-m-long ZEDF and 9-m-long EDF optimised for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fibre Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achievedmore » with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.« less

Slant path L- and S-Band tree shadowing measurements

NASA Technical Reports Server (NTRS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.

1994-01-01

This contribution presents selected results from simultaneous L- and S-Band slant-path fade measurements through a pecan, a cottonwood, and a pine tree employing a tower-mounted transmitter and dual-frequency receiver. A single, circularly-polarized antenna was used at each end of the link. The objective was to provide information for personal communications satellite design on the correlation of tree shadowing between frequencies near 1620 and 2500 MHz. Fades were measured along 10 m lateral distance with 5 cm spacing. Instantaneous fade differences between L- and S-Band exhibited normal distribution with means usually near 0 dB and standard deviations from 5.2 to 7.5 dB. The cottonwood tree was an exception, with 5.4 dB higher average fading at S- than at L-Band. The spatial autocorrelation reduced to near zero with lags of about 10 lambda. The fade slope in dB/MHz is normally distributed with zero mean and standard deviation increasing with fade level.

Slant path L- and S-Band tree shadowing measurements

NASA Astrophysics Data System (ADS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.

1994-08-01

This contribution presents selected results from simultaneous L- and S-Band slant-path fade measurements through a pecan, a cottonwood, and a pine tree employing a tower-mounted transmitter and dual-frequency receiver. A single, circularly-polarized antenna was used at each end of the link. The objective was to provide information for personal communications satellite design on the correlation of tree shadowing between frequencies near 1620 and 2500 MHz. Fades were measured along 10 m lateral distance with 5 cm spacing. Instantaneous fade differences between L- and S-Band exhibited normal distribution with means usually near 0 dB and standard deviations from 5.2 to 7.5 dB. The cottonwood tree was an exception, with 5.4 dB higher average fading at S- than at L-Band. The spatial autocorrelation reduced to near zero with lags of about 10 lambda. The fade slope in dB/MHz is normally distributed with zero mean and standard deviation increasing with fade level.

Parameterization of L-, C- and X-band Radiometer-based Soil Moisture Retrieval Algorithm Using In-situ Validation Sites

NASA Astrophysics Data System (ADS)

Gao, Y.; Colliander, A.; Burgin, M. S.; Walker, J. P.; Chae, C. S.; Dinnat, E.; Cosh, M. H.; Caldwell, T. G.

2017-12-01

Passive microwave remote sensing has become an important technique for global soil moisture estimation over the past three decades. A number of missions carrying sensors at different frequencies that are capable for soil moisture retrieval have been launched. Among them, there are Japan Aerospace Exploration Agency's (JAXA's) Advanced Microwave Scanning Radiometer-EOS (AMSR-E) launched in May 2002 on the National Aeronautics and Space Administration (NASA) Aqua satellite (ceased operation in October 2011), European Space Agency's (ESA's) Soil Moisture and Ocean Salinity (SMOS) mission launched in November 2009, JAXA's Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the GCOM-W satellite launched in May 2012, and NASA's Soil Moisture Active Passive (SMAP) mission launched in January 2015. Therefore, there is an opportunity to develop a consistent inter-calibrated long-term soil moisture data record based on the availability of these four missions. This study focuses on the parametrization of the tau-omega model at L-, C- and X-band using the brightness temperature (TB) observations from the four missions and the in-situ soil moisture and soil temperature data from core validation sites across various landcover types. The same ancillary data sets as the SMAP baseline algorithm are applied for retrieval at different frequencies. Preliminary comparison of SMAP and AMSR2 TB observations against forward-simulated TB at the Yanco site in Australia showed a generally good agreement with each other and higher correlation for the vertical polarization (R=0.96 for L-band and 0.93 for C- and X-band). Simultaneous calibrations of the vegetation parameter b and roughness parameter h at both horizontal and vertical polarizations are also performed. Finally, a set of model parameters for successfully retrieving soil moisture at different validation sites at L-, C- and X-band respectively are presented. The research described in this paper is supported by the Jet Propulsion

In-harbor and at-sea electromagnetic compatibility survey for maritime satellite L-band shipboard terminal

NASA Technical Reports Server (NTRS)

1974-01-01

Geostationary maritime satellites, one over the Pacific and one over the Atlantic Ocean, are planned to make available high-speed communications and navigation (position determination) services to ships at sea. A shipboard satellite terminal, operating within the authorized maritime L-band, 1636.5 to 1645.0 MHz, will allow ships to pass voice, teletype, facsimile, and data messages to shore communication facilities with a high degree of reliability. The shore-to-ship link will also operate in the maritime L-band from 1535.0 to 1543.5 MHz. A significant number or maritime/commercial ships are expected to be equipped with an L-band satellite terminal by the year 1980, and so consequently, there is an interest in determining electromagnetic compatibility between the proposed L-band shipboard terminal and existing, on-board, shipboard communications/electronics and electrical systems, as well as determining the influence of shore-based interference sources. The shipboard electromagnetic interference survey described was conducted on-board the United States Line's American Leader class (15,690 tons) commercial container ship, the "American Alliance" from June 16 to 20, 1974. Details of the test plan and measurements are given.

Mapping Greenland's Firn Aquifer using L-band Microwave Radiometry

NASA Astrophysics Data System (ADS)

Miller, J.; Bringer, A.; Jezek, K. C.; Johnson, J. T.; Scambos, T. A.; Long, D. G.

2016-12-01

Greenland's recently discovered firn aquifer is one of the most interesting, yet still mysterious, components of the ice sheet system. Many open questions remain regarding timescales of refreezing and/or englacial drainage of liquid meltwater, and the connections of firn aquifers to the subglacial hydrological system. If liquid meltwater production at the surface of the Greenland ice sheet continues to increase, subsequent increases in the volume of mobile liquid meltwater retained within Greenland's firn aquifer may increase the possibility of crevasse-deepening via hydrofracture. Hydrofracture is an important component of supraglacial lake drainage leading to at least temporary accelerated flow velocities and ice sheet mass balance changes. Firn aquifers may also support hydrofracture-induced drainage and thus are potentially capable of significantly influencing ice sheet mass balance and sea level rise. Spaceborne L-band microwave radiometers provide an innovative tool for ice-sheet wide mapping of the spatiotemporal variability of Greenland's firn aquifer. Both refreezing and englacial drainage may be observable given the sensitivity of the microwave response to the upper surface of liquid meltwater retained within snow and firn pore space as well as the ability of L band instruments to probe the ice sheet from the surface to the firn-ice transition at pore close-off depth. Here we combine L-band (1.4 GHz) brightness temperature observations from multiple sources to demonstrate the potential of mapping firn aquifers on ice sheets using L-band microwave radiometry. Data sources include the interferometric MIRAS instrument aboard ESA's Soil Moisture and Ocean Salinity (SMOS) satellite mission and the radiometer aboard NASA's Soil Moisture Active Passive (SMAP) satellite mission. We will also present mulit-frequency L-band brightness temperature data (0.5-2 GHz) that will be collected over several firn aquifer areas on the Greenland ice sheet by the Ohio State

High performance architecture design for large scale fibre-optic sensor arrays using distributed EDFAs and hybrid TDM/DWDM

NASA Astrophysics Data System (ADS)

Liao, Yi; Austin, Ed; Nash, Philip J.; Kingsley, Stuart A.; Richardson, David J.

2013-09-01

A distributed amplified dense wavelength division multiplexing (DWDM) array architecture is presented for interferometric fibre-optic sensor array systems. This architecture employs a distributed erbium-doped fibre amplifier (EDFA) scheme to decrease the array insertion loss, and employs time division multiplexing (TDM) at each wavelength to increase the number of sensors that can be supported. The first experimental demonstration of this system is reported including results which show the potential for multiplexing and interrogating up to 4096 sensors using a single telemetry fibre pair with good system performance. The number can be increased to 8192 by using dual pump sources.

L-band InSAR Penetration Depth Experiment, North Slope Alaska

NASA Astrophysics Data System (ADS)

Muskett, Reginald

2017-04-01

Since the first spacecraft-based synthetic aperture radar (SAR) mission NASA's SEASAT in 1978 radars have been flown in Low Earth Orbit (LEO) by other national space agencies including the Canadian Space Agency, European Space Agency, India Space Research Organization and the Japanese Aerospace Exploration Agency. Improvements in electronics, miniaturization and production have allowed for the deployment of SAR systems on aircraft for usage in agriculture, hazards assessment, land-use management and planning, meteorology, oceanography and surveillance. LEO SAR systems still provide a range of needful and timely information on large and small-scale weather conditions like those found across the Arctic where ground-base weather radars currently provide limited coverage. For investigators of solid-earth deformation attention must be given to the atmosphere on Interferometric SAR (InSAR) by aircraft and spacecraft multi-pass operations. Because radar has the capability to penetrate earth materials at frequencies from the P- to X-band attention must be given to the frequency dependent penetration depth and volume scattering. This is the focus of our new research project: to test the penetration depth of L-band SAR/InSAR by aircraft and spacecraft systems at a test site in Arctic Alaska using multi-frequency analysis and progressive burial of radar mesh-reflectors at measured depths below tundra while monitoring environmental conditions. Knowledge of the L-band penetration depth on lowland Arctic tundra is necessary to constrain analysis of carbon mass balance and hazardous conditions arising form permafrost degradation and thaw, surface heave and subsidence and thermokarst formation at local and regional scales.

Impact of fiber ring laser configuration on detection capabilities in FBG based sensor systems

NASA Astrophysics Data System (ADS)

Osuch, Tomasz; Kossek, Tomasz; Markowski, Konrad

2014-11-01

In this paper fiber ring lasers (FRL) as interrogation units for distributed fiber Bragg grating (FBG) based sensor networks are studied. In particular, two configurations of the fiber laser with erbium-doped fiber amplifier (EDFA) and semiconductor optical amplifier (SOA) as gain medium were analyzed. In the case of EDFA-based fiber interrogation systems, CW as well as active-mode locking operation were taken into account. The influence of spectral overlapping of FBGs spectra on detection capabilities of examined FRLs are presented. Experimental results show that the SOA-based fiber laser interrogation unit can operate as a multi-parametric sensing system. In turn, using an actively mode-locked fiber ring laser with an EDFA, an electronically switchable FBG based sensing system can be realized.

U.S. Aeronautical L-Band Satellite Technology Test Program : Interim Tests Results

DOT National Transportation Integrated Search

1975-06-01

The U.S. Aeronautical L-Band satellite test program was performed between September 1974 and April 1975 as part of an international ATS-6 L-Band satellite test program. The U.S. program consisted of both technology and ATC communications demonstratio...

Discrimination of coastal wetland environments in the Amazon region based on multi-polarized L-band airborne Synthetic Aperture Radar imagery

NASA Astrophysics Data System (ADS)

Souza-Filho, Pedro Walfir M.; Paradella, Waldir R.; Rodrigues, Suzan W. P.; Costa, Francisco R.; Mura, José C.; Gonçalves, Fabrício D.

2011-11-01

This study assessed the use of multi-polarized L-band images for the identification of coastal wetland environments in the Amazon coast region of northern Brazil. Data were acquired with a SAR R99B sensor from the Amazon Surveillance System (SIVAM) on board a Brazilian Air Force jet. Flights took place in the framework of the 2005 MAPSAR simulation campaign, a German-Brazilian feasibility study focusing on a L-band SAR satellite. Information retrieval was based on the recognition of the interaction between a radar signal and shallow-water morphology in intertidal areas, coastal dunes, mangroves, marshes and the coastal plateau. Regarding the performance of polarizations, VV was superior for recognizing intertidal area morphology under low spring tide conditions; HH for mapping coastal environments covered with forest and scrub vegetation such as mangrove and vegetated dunes, and HV was suitable for distinguishing transition zones between mangroves and coastal plateau. The statistical results for the classification maps expressed by kappa index and general accuracy were 83.3% and 0.734 for the multi-polarized color composition (R-HH, G-HV, B-VV), 80.7% and 0.694% for HH, 79.7% and 0.673% for VV, and 77.9% and 0.645% for HV amplitude image. The results indicate that use of multi-polarized L-band SAR is a valuable source of information aiming at the identification and discrimination of distinct geomorphic targets in tropical wetlands.

High sensitivity cascaded preamplifier with an optical bridge structure in Brillouin distributed fiber sensing system

NASA Astrophysics Data System (ADS)

Bi, Weihong; Lin, Hang; Fu, Xinghu; Fu, Guangwei

2013-12-01

Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission system and have been an important element for enabling the development of optical communication system. EDFA amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain, broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW pump power.

L-band InSAR Penetration Depth Experiment, North Slope Alaska

NASA Astrophysics Data System (ADS)

Muskett, R. R.

2017-12-01

Since the first spacecraft-based synthetic aperture radar (SAR) mission NASA's SEASAT in 1978 radars have been flown in Low Earth Orbit (LEO) by other national space agencies including the Canadian Space Agency, European Space Agency, India Space Research Organization and the Japanese Aerospace Exploration Agency. Improvements in electronics, miniaturization and production have allowed for the deployment of SAR systems on aircraft for usage in agriculture, hazards assessment, land-use management and planning, meteorology, oceanography and surveillance. LEO SAR systems still provide a range of needful and timely information on large and small-scale weather conditions like those found across the Arctic where ground-base weather radars currently provide limited coverage. For investigators of solid-earth deformation attention must be given to the atmosphere on Interferometric SAR (InSAR) by aircraft and spacecraft multi-pass operations. Because radar has the capability to penetrate earth materials at frequencies from the P- to X-band attention must be given to the frequency dependent penetration depth and volume scattering. This is the focus of our new research project: to test the penetration depth of L-band SAR/InSAR by aircraft and spacecraft systems at a test site in Arctic Alaska using multi-frequency analysis and progressive burial of radar mesh-reflectors at measured depths below tundra while monitoring environmental conditions. Knowledge of the L-band penetration depth on lowland Arctic tundra is necessary to constrain analysis of carbon mass balance and hazardous conditions arising form permafrost degradation and thaw, surface heave and subsidence and thermokarst formation at local and regional scales. Ref.: Geoscience and Environment Protection, vol. 5, no. 3, p. 14-30, 2017. DOI: 10.4236/gep.2017.53002.

Effect of Forest Canopy on Remote Sensing Soil Moisture at L-band

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lang, R. H.; Jackson, T. J.; Haken, M.

2005-01-01

Global maps of soil moisture are needed to improve understanding and prediction of the global water and energy cycles. Accuracy requirements imply the use of lower frequencies (L-band) to achieve adequate penetration into the soil and to minimize attenuation by the vegetation canopy and effects of surface roughness. Success has been demonstrated over agricultural areas, but canopies with high biomass (e.g. forests) still present a challenge. Examples from recent measurements over forests with the L-band radiometer, 2D-STAR, and its predecessor, ESTAR, will be presented to illustrate the problem. ESTAR and 2D-STAR are aircraft-based synthetic aperture radiometers developed to help resolve both the engineering and algorithm issues associated with future remote sensing of soil moisture. ESTAR, which does imaging across track, was developed to demonstrate the viability of aperture synthesis for remote sensing. The instrument has participated several soil moisture experiments (e.g. at the Little Washita Watershed in 1992 and the Southern Great Plains experiments in 1997 and 1999). In addition, measurements have been made at a forest site near Waverly, VA which contains conifer forests with a variety of biomass. These data have demonstrated the success of retrieving soil moisture at L-band over agricultural areas and the response of passive observations at L-band to biomass over forests. 2D-STAR is a second generation instrument that does aperture synthesis in two dimensions (along track and cross track) and is dual polarized. This instrument has the potential to provide measurements at L-band that simulate the measurements that will be made by the two L-band sensors currently being developed for future remote sensing of soil moisture from space: Hydros (conical scan and real aperture) and SMOS (multiple incidence angle and synthetic aperture). 2D-STAR participated in the SMEX-03 soil moisture experiment, providing images from the NASA P-3 aircraft. Preliminary results

Polarimetric and Structural Properties of a Boreal Forest at P-Band and L-Band

NASA Astrophysics Data System (ADS)

Tebaldini, S.; Rocca, F.

2010-12-01

With this paper we investigate the structural and polarimetric of the boreal forest within the Krycklan river catchment, Northern Sweden, basing on multi-polarimetric and multi-baseline SAR surveys at P-Band and L-Band collected in the framework of the ESA campaign BioSAR 2008. The analysis has been carried out by applying the Algebraic Synthesis (AS) technique, recently introduced in literature, which provides a theoretical framework for the decomposition of the backscattered signal into ground-only and volume-only contributions, basing on both baseline and polarization diversity. The availability of multiple baselines allows the formation of a synthetic aperture not only along the azimuth direction but also in elevation. Accordingly, the backscattered echoes can be focused not only in the slant range, azimuth plane, but in the whole 3D space. This is the rationale of the SAR Tomography (T-SAR) concept, which has been widely considered in the literature of the last years. It follows that, as long as the penetration in the scattering volume is guaranteed, the vertical profile of the vegetation layer is retrieved by separating backscatter contributions along the vertical direction, which is the main reason for the exploitation of Tomographic techniques at longer wavelengths. Still, the capabilities of T-SAR are limited to imaging the global vertical structure of the electromagnetic scattering in a certain polarization. It then becomes important to develop methodologies for the investigation of the vertical structure of different Scattering Mechanisms (SMs), such as ground and volume scattering, in such a way as to derive information that can be delivered also outside the field of Radar processing. This is an issue that may become relevant at longer wavelengths, such as P-Band, where the presence of multiple scattering arising from the interaction with terrain could hinder the correct reconstruction of the forest structure. The availability of multiple polarizations

C- and L-band space-borne SAR incidence angle normalization for efficient Arctic sea ice monitoring

NASA Astrophysics Data System (ADS)

Mahmud, M. S.; Geldsetzer, T.; Howell, S.; Yackel, J.; Nandan, V.

2017-12-01

C-band Synthetic Aperture Radar (SAR) has been widely used effectively for operational sea ice monitoring, owing to its greater seperability between snow-covered first-year (FYI) and multi-year (MYI) ice types, during winter. However, during the melt season, C-band SAR backscatter contrast reduces between FYI and MYI. To overcome the limitations of C-band, several studies have recommended utlizing L-band SAR, as it has the potential to significantly improve sea ice classification. Given its longer wavelength, L-band can efficiently separate FYI and MYI types, especially during melt season. Therefore, the combination of C- and L-band SAR is an optimal solution for efficient seasonal sea ice monitoring. As SAR acquires images over a range of incidence angles from near-range to far-range, SAR backscatter varies substantially. To compensate this variation in SAR backscatter, incidence angle dependency of C- and L-band SAR backscatter for different FYI and MYI types is crucial to quantify, which is the objective of this study. Time-series SAR imagery from C-band RADARSAT-2 and L-band ALOS PALSAR during winter months of 2010 across 60 sites over the Canadian Arctic was acquired. Utilizing 15 images for each sites during February-March for both C- and L-band SAR, incidence angle dependency was calculated. Our study reveals that L- and C-band backscatter from FYI and MYI decreases with increasing incidence angle. The mean incidence angle dependency for FYI and MYI were estimated to be -0.21 dB/1° and -0.30 dB/1° respectively from L-band SAR, and -0.22 dB/1° and -0.16 dB/1° from C-band SAR, respectively. While the incidence angle dependency for FYI was found to be similar in both frequencies, it doubled in case of MYI from L-band, compared to C-band. After applying the incidence angle normalization method to both C- and L-band SAR images, preliminary results indicate improved sea ice type seperability between FYI and MYI types, with substantially lower number of mixed

Color composite C-band and L-band image of Kilauea volcanoe on Hawaii

NASA Technical Reports Server (NTRS)

1994-01-01

This color composite C-band and L-band image of the Kilauea volcano on the Big Island of Hawaii was acuired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperature Radar (SIR-C/X-SAR) flying on the Space Shuttle Endeavour. The city of Hilo can be seen at the top. The image shows the different types of lava flows around the crater Pu'u O'o. Ash deposits which erupted in 1790 from the summit of Kilauea volcano show up as dark in this image, and fine details associated with lava flows which erupted in 1919 and 1974 can be seen to the south of the summit in an area called the Ka'u Desert. Other historic lava flows can also be seen. Highway 11 is the linear feature running from Hilo to the Kilauea volcano. The Jet Propulsion Laboratory alternative photo number is P-43918.

Examples L-Band Interference will be Presented and Discussed, as well as the Importance of L-Band Soil Moisture Observations

NASA Technical Reports Server (NTRS)

Kim, Edward

2010-01-01

Examples of L-band interference will be presented and discussed, as well as the importance of L-band soil moisture observations, as part of this one-day GEOSS workshop XXXVII on "Data Quality and Radio Spectrum Allocation Impact on Earth Observations" will address the broad challenges of data quality and the impact of generating reliable information for decision makers who are Earth data users but not necessarily experts in the Earth observation field. GEO has initiated a data quality assessment task (DA-09-01a) and workshop users will review and debate the directions and challenges of this effort. Radio spectrum allocation is an element of data availability and data quality, and is also associated with a GEO task (AR-06-11). A recent U.S. National Research Council report on spectrum management will be addressed as part of the workshop. Key representatives from industry, academia, and government will provide invited talks on these and related issues that impact GEOSS implementation.

Soil Moisture Limitations on Monitoring Boreal Forest Regrowth Using Spaceborne L-Band SAR Data

NASA Technical Reports Server (NTRS)

Kasischke, Eric S.; Tanase, Mihai A.; Bourgeau-Chavez, Laura L.; Borr, Matthew

2011-01-01

A study was carried out to investigate the utility of L-band SAR data for estimating aboveground biomass in sites with low levels of vegetation regrowth. Data to estimate biomass were collected from 59 sites located in fire-disturbed black spruce forests in interior Alaska. PALSAR L-band data (HH and HV polarizations) collected on two dates in the summer/fall of 2007 and one date in the summer of 2009 were used. Significant linear correlations were found between the log of aboveground biomass (range of 0.02 to 22.2 t ha-1) and (L-HH) and (L-HV) for the data collected on each of the three dates, with the highest correlation found using the LHV data collected when soil moisture was highest. Soil moisture, however, did change the correlations between L-band and aboveground biomass, and the analyses suggest that the influence of soil moisture is biomass dependent. The results indicate that to use L-band SAR data for mapping aboveground biomass and monitoring forest regrowth will require development of approaches to account for the influence that variations in soil moisture have on L-band microwave backscatter, which can be particularly strong when low levels of aboveground biomass occur

Studying Notable Debris Disks In L-band with the Vortex Coronagraph

NASA Astrophysics Data System (ADS)

Patel, Rahul; Beichman, Charles; Choquet, Elodie; Mawet, Dimitri; Meshkat, Tiffany; ygouf, marie

2018-01-01

Resolved images of circumstellar disks are integral to our understanding of planetary systems, as the micron sized dust grains that comprise the disk are born from the collisional grinding of planetesimals by larger planets in the system. Resolved images are essential to determining grain properties that might otherwise be degenerate from analyzing the star’s spectral energy distribution. Though the majority of scattered light images of disks are obtained at optical and near-IR wavelengths, only a few have been imaged in the thermal IR at L-band. Probing the spatial features of disks at L-band opens up the possibility of constraining additional grain properties, such as water/ice features.Here, we present the results of our effort to image the disks of a few notable systems at L-band using the NIRC2 imager at Keck, in conjunction with the newly commissioned vector vortex coronagraph. The vortex, along with the QACITS fine guiding program installed at Keck, enables us to probe the small ~lambda/D angular separations of these systems, and reach contrasts of 1/100,000. We will discuss the systems that have been imaged, and lessons learned while imaging in L-band. Our analysis of these disks reveal features previously unseen, and will lay the foundation for followup studies by missions such as JWST at similar wavelengths from space.

L-band radiometry for sea ice applications

NASA Astrophysics Data System (ADS)

Heygster, G.; Hedricks, S.; Mills, P.; Kaleschke, L.; Stammer, D.; Tonboe, R.

2009-04-01

Although sea ice remote sensing has reached the level of operational exploitation with well established retrieval methods, several important tasks are still unsolved. In particular during freezing and melting periods with mixed ice and water surfaces, estimates of ice concentration with passive and active microwave sensors remain challenging. Newly formed thin ice is also hard to distinguish from open water with radiometers for frequencies above 8 GHz. The SMOS configuration (planned launch 2009) with a radiometer at 1.4 GHz is a promising technique to complement observations at higher microwave frequencies. ESA has initiated a project to investigate the possibilities for an additional Level-2 sea ice data product based on SMOS. In detail, the project objectives are (1) to model the L band emission of sea ice, and to assess the potential (2) to retrieve sea ice parameters, especially concentration and thickness, and (3) to use cold water regions for an external calibration of SMOS. Modelling of L band emission: Several models have are investigated. All of them work on the same basic principles and have a vertically-layered, plane-parallel geometry. They are comprised of three basic components: (1) effective permittivities are calculated for each layer based on ice bulk and micro-structural properties; (2) these are integrated across the total depth to derive emitted brightness temperature; (3) scattering terms can also be added because of the granular structure of ice and snow. MEMLS (Microwave Emission Model of Layered Snowpacks (Wiesmann and Matzler 1999)) is one such model that contains all three elements in a single Matlab program. In the absence of knowledge about the internal structure of the sea ice, three-layer (air, ice and water) dielectric slab models which take as input a single effective permittivity for the ice layer are appropriate. By ignoring scattering effects one can derive a simple analytic expression for a dielectric slab as shown by Apinis and

Alcohol sensing over O+E+S+C+L+U transmission band based on porous cored octagonal photonic crystal fiber

NASA Astrophysics Data System (ADS)

Paul, Bikash Kumar; Islam, Md. Shadidul; Ahmed, Kawsar; Asaduzzaman, Sayed

2017-06-01

A micro structure porous cored octagonal photonic crystal fiber (P-OPCF) has been proposed to sense aqueous analysts (alcohol series) over a wavelength range of 0.80 μm to 2.0 μm. By implementing a full vectorial finite element method (FEM), the numerical simulation on the proposed O-PCF has been analyzed. Numerical investigation shows that high sensitivity can be gained by changing the structural parameters. The obtained result shows the sensitivities of 66.78%, 67.66%, 68.34%, 68.72%, and 69.09%, and the confinement losses of 2.42×10-10 dB/m, 3.28×10-11 dB/m, 1.21×10-6 dB/m, 4.79×10-10 dB/m, and 4.99×10-9 dB/m at the 1.33 μm wavelength for methanol, ethanol, propanol, butanol, and pentanol, respectively can satisfy the condition of much legibility to install an optical system. The effects of the varying core and cladding diameters, pitch distance, operating wavelength, and effective refractive index are also reported here. It reflects that a significant sensitivity and low confinement loss can be achieved by the proposed P-OPCF. The proposed P-OPCF also covers the wavelength band (O+E+S+C+L+U). The investigation also exhibits that the sensitivity increases when the wavelength increases like S O-band< S E-band < S S-band < S C-band < S L-band < S U-band. This research observation has much pellucidity which has remarkable impact on the field of optical fiber sensor.

Modeling Periodic Adiabatic Shear Bands Evolution in a 304L Stainless Steel Thick-Walled Cylinder

NASA Astrophysics Data System (ADS)

Liu, Mingtao; Hu, Haibo; Fan, Cheng; Tang, Tiegang

2015-06-01

The self-organization of multiple shear bands in a 304L stainless steel thick-walled cylinder (TWC) was numerically studied. The microstructures of material lead to the non-uniform distribution of local yield stress, which plays a key role in the formation of spontaneous shear localization. We introduced a probability factor satisfied Gauss distribution into the macroscopic constitutive relationship to describe the non-uniformity of local yield stress. Using the probability factor, the initiation and propagation of multiple shear bands in TWC were numerically replicated in our 2D FEM simulation. Experimental results in the literature indicate that the machined surface at the internal boundary of a 304L stainless steel cylinder provides a work-hardened layer (about 20 μm) which has significantly different microstructures from base material. The work-hardened layer leads to the phenomenon that most shear bands are in clockwise or counterclockwise direction. In our simulation, periodic oriented perturbations were applied to describe the grain orientation in the work-hardened layer, and the spiral pattern of shear bands was successfully replicated.

Hypervelocity impact testing of L-band truss cable meteoroid shielding on Skylab

NASA Technical Reports Server (NTRS)

Jex, D. W.

1973-01-01

A series of tests was performed to determine the protection provided by the L-band truss cable meteoroid shielding installed on Skylab space station at space environment temperatures of minus 180 F. The damage sustained when three test specimens were impacted by spherical projectiles at hypersonic speed was investigated. It is concluded that the L-band truss cable meteoroid shielding provides adequate protection at the indicated temperature.

Precisely determined the surface displacement by the ionospheric mitigation using the L-band SAR Interferometry over Mt.Baekdu

NASA Astrophysics Data System (ADS)

Lee, Won-Jin; Jung, Hyung-Sup; Park, Sun-Cheon; Lee, Duk Kee

2016-04-01

Mt. Baekdu (Changbaishan in Chinese) is located on the border between China and North Korea. It has recently attracted the attention of volcanic unrest during 2002-2005. Many researchers have applied geophysical approaches to detect magma system of beneath Mt.Baekdu such as leveling, Global Positioning System (GPS), gases analysis, seismic analysis, etc. Among them, deformation measuring instruments are important tool to evaluate for volcanism. In contrast to GPS or other deformation measuring instruments, Synthetic Aperture Radar Interferometry (InSAR) has provided high resolution of 2-D surface displacement from remote sensed data. However, Mt. Baekdu area has disturbed by decorrelation on interferogram because of wide vegetation coverage. To overcome this limitation, L-band system of long wavelength is more effective to detect surface deformation. In spite of this advantage, L-band can surfer from more severe ionospheric phase distortions than X- or C- band system because ionospheric phase distortions are inverse proportion to the radar frequency. Recently, Multiple Aperture Interferometry (MAI) based ionospheric phase distortions mitigation method have proposed and investigated. We have applied this technique to the Mt.Baekdu area to measure surface deformation precisely using L-band Advanced Land Observing Satellite-1(ALOS-1) Phased Array type L-band Synthetic Aperture Radar(PALSAR) data acquiring from 2006 to 2011.

Bandwidth-Tunable Fiber Bragg Gratings Based on UV Glue Technique

NASA Astrophysics Data System (ADS)

Fu, Ming-Yue; Liu, Wen-Feng; Chen, Hsin-Tsang; Chuang, Chia-Wei; Bor, Sheau-Shong; Tien, Chuen-Lin

2007-07-01

In this study, we have demonstrated that a uniform fiber Bragg grating (FBG) can be transformed into a chirped fiber grating by a simple UV glue adhesive technique without shifting the reflection band with respect to the center wavelength of the FBG. The technique is based on the induced strain of an FBG due to the UV glue adhesive force on the fiber surface that causes a grating period variation and an effective index change. This technique can provide a fast and simple method of obtaining the required chirp value of a grating for applications in the dispersion compensators, gain flattening in erbium-doped fiber amplifiers (EDFAs) or optical filters.

Comparison of Measured Galactic Background Radiation at L-Band with Model

NASA Technical Reports Server (NTRS)

LeVine, David M.; Abraham, Saji; Kerr, Yann H.; Wilson, William J.; Skou, Niels; Sobjaerg, Sten

2004-01-01

Radiation from the celestial sky in the spectral window at 1.413 GHz is strong and an accurate accounting of this background radiation is needed for calibration and retrieval algorithms. Modern radio astronomy measurements in this window have been converted into a brightness temperature map of the celestial sky at L-band suitable for such applications. This paper presents a comparison of the background predicted by this map with the measurements of several modern L-band remote sensing radiometer Keywords-Galactic background, microwave radiometry; remote sensing;

Aquarius Active-Passive RFI Environment at L-Band

NASA Technical Reports Server (NTRS)

Le Vine, David M.; De Matthaeis, Paolo

2014-01-01

Active/Passive instrument combinations (i.e., radiometer and radar) are being developed at L-band for remote sensing of sea surface salinity and soil moisture. Aquarius is already in orbit and SMAP is planned for launch in the Fall of 2014. Aquarius has provided for the first time a simultaneous look at the Radio Frequency Interference (RFI) environment from space for both active and passive instruments. The RFI environment for the radiometer observations is now reasonably well known and examples from Aquarius are presented in this manuscript that show that RFI is an important consideration for the scatterometer as well. In particular, extensive areas of the USA, Europe and Asia exhibit strong RFI in both the radiometer band at 1.41 GHz and in the band at 1.26 GHz employed by the Aquarius scatterometer. Furthermore, in areas such as the USA, where RFI at 1.4 GHz is relatively well controlled, RFI in the scatterometer band maybe the limiting consideration for the operation of combination active/passive instruments.

All-optical gain-clamped wideband serial EDFA with ring-shaped laser

NASA Astrophysics Data System (ADS)

Lu, Yung-Hsin; Chi, Sien

2004-01-01

We experimentally investigate the static and dynamic properties of all-optical gain-clamped wideband (1530-1600 nm) serial erbium-doped fiber amplifier with a single ring-shaped laser, which consists of a circulator and a fiber Bragg grating at the output end. The lasing light passing through the second stage is intentionally blocked at the output end by a C/L-band wavelength division multiplexer owning the huge insertion loss, and thus, the copropagating ring-laser light is formed by the first stage. This design can simultaneously clamp the gains of 1547 and 1584 nm probes near 14 dB and shows the same dynamic range of input power up to -4 dBm for conventional band and long-wavelength band. Furthermore, the transient responses of 1551 and 1596 nm surviving channels exhibit small power excursions (<0.54 dB) as the total saturating tone with -2 dBm is modulated on and off at 270 Hz.

Impact of Co-Site Interference on L/C-Band Spectrum for UAS Control and Non-Payload Communications

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Bishop, William D.; Hoder, Douglas J.; Shalkhauser, Kurt A.; Wilson, Jeffrey D.

2015-01-01

In order to provide for the safe integration of unmanned aircraft systems into the National Airspace System, the control and non-payload communications (CNPC) link connecting the ground-based pilot with the unmanned aircraft must be highly reliable. A specific requirement is that it must operate using aviation safety radiofrequency spectrum. The 2012 World Radiocommunication Conference (WRC-12) provided a potentially suitable allocation for LOS CNPC spectrum in C-Band at 5030-5091 MHz band which, when combined with a previous allocation in L-Band (960-1164 MHz) may satisfy the LOS spectrum requirement and provide for high reliability through dual-band redundancy. However, the LBand spectrum hosts a number of aeronautical navigation systems which require high-power transmitters on-board the aircraft. These high-power transmitters co-located with sensitive CNPC receivers operating in the same frequency band have the potential to create co-site interference, reducing the performance of the CNPC receivers and ultimately reducing the usability of the L-Band for CNPC. This paper examines the potential for co-site interference, as highlighted in recent flight tests, and discusses the impact on the UAS CNPC spectrum availability and requirements for further testing and analysis.

Obituary: David L. Band (1957-2009)

NASA Astrophysics Data System (ADS)

Cominsky, Lynn

2011-12-01

David L. Band, of Potomac Maryland, died on March 16, 2009 succumbing to a long battle with spinal cord cancer. His death at the age of 52 came as a shock to his many friends and colleagues in the physics and astronomy community. Band showed an early interest and exceptional aptitude for physics, leading to his acceptance at the Massachusetts Institute of Technology as an undergraduate student in 1975. After graduating from MIT with an undergraduate degree in Physics, Band continued as a graduate student in Physics at Harvard University. His emerging interest in Astrophysics led him to the Astronomy Department at the Harvard Smithsonian Center for Astrophysics (CfA), where he did his dissertation work with Jonathan Grindlay. His dissertation (1985) entitled "Non-thermal Radiation Mechanisms and Processes in SS433 and Active Galactic Nuclei" was "pioneering work on the physics of jets arising from black holes and models for their emission, including self-absorption, which previewed much to come, and even David's own later work on Gamma-ray Bursts," according to Grindlay who remained a personal friend and colleague of Band's. Following graduate school, Band held postdoctoral positions at the Lawrence Livermore Laboratory, the University of California at Berkeley and the Center for Astronomy and Space Sciences at the University of California San Diego where he worked on the BATSE experiment that was part of the Compton Gamma Ray Observatory (CGRO), launched in 1991. BATSE had as its main objective the study of cosmic gamma-ray bursts (GRBs) and made significant advances in this area of research. Band became a world-renowned figure in the emerging field of GRB studies. He is best known for his widely-used analytic form of gamma-ray burst spectra known as the "Band Function." After the CGRO mission ended, Band moved to the Los Alamos National Laboratory where he worked mainly on classified research but continued to work on GRB energetics and spectra. When NASA planned

L-Band Orthogonal-Mode Crossed-Slot Antenna and VHF Crossed-Loop Antenna

DOT National Transportation Integrated Search

1972-01-01

A low-gain, circularly polarized, L-ban antenna; a low-gain, lineraly polarized, L-band antenna; and a low-gain, lineraly polarized, L-ban antenna; and a low-gain, circularly polarized, upper hemisphere, VHF satellite communications antenna intended ...

Midlatitude Measurements of L-Band Ionospheric Scintillation with the ATS-5 Spacecraft

DOT National Transportation Integrated Search

1975-09-01

The report presents some results of L-band signal level measurements taken from the ATS-5 spacecraft operating in the narrow-band frequency translation mode. The uplink signal was sent from the DOT/TSC/Westford Propagation Facility in Westford, Massa...

Simplex-method based transmission performance optimization for 100G PDM-QPSK systems with non-identical spans

NASA Astrophysics Data System (ADS)

Li, Yuanyuan; Gao, Guanjun; Zhang, Jie; Zhang, Kai; Chen, Sai; Yu, Xiaosong; Gu, Wanyi

2015-06-01

A simplex-method based optimizing (SMO) strategy is proposed to improve the transmission performance for dispersion uncompensated (DU) coherent optical systems with non-identical spans. Through analytical expression of quality of transmission (QoT), this strategy improves the Q factors effectively, while minimizing the number of erbium-doped optical fiber amplifier (EDFA) that needs to be optimized. Numerical simulations are performed for 100 Gb/s polarization-division multiplexed quadrature phase shift keying (PDM-QPSK) channels over 10-span standard single mode fiber (SSMF) with randomly distributed span-lengths. Compared to the EDFA configurations with complete span loss compensation, the Q factor of the SMO strategy is improved by approximately 1 dB at the optimal transmitter launch power. Moreover, instead of adjusting the gains of all the EDFAs to their optimal value, the number of EDFA that needs to be adjusted for SMO is reduced from 8 to 2, showing much less tuning costs and almost negligible performance degradation.

Characterization and Modeling of Dual Stage Quadruple Pass Configurations

NASA Astrophysics Data System (ADS)

Sellami, M.; Sellami, A.; Berrah, S.

In this paper, the proposed system achieves a gain of 62dBs. It employs a dual-stage (DS) to enhance the amplification and a tunable band-pass filter (TBF) to filter out the backward amplified spontaneous emission (ASE) that degrades the signal amplification at the input end of the EDFA. The technique there by reduces the effect of ASE self-saturation [1]. This configuration is also useful in reducing the sensitivity of the EDFA to extra strenuous reflections caused by imperfections of the splices and other optical components [2]. as well as improving noise figure and gain. The experimental work will build up by using the active component Silica based EDF (Si-EDF) in Dual Stage Quadruple Pass (DSQP) configuration. By using Tunable Band pass Filter (TBF) in DSQP between the port 1 and port 2 of circulators (CRT2, CRT3) to filter out the unwanted ASE.

Dual-band frequency selective surface with large band separation and stable performance

NASA Astrophysics Data System (ADS)

Zhou, Hang; Qu, Shao-Bo; Peng, Wei-Dong; Lin, Bao-Qin; Wang, Jia-Fu; Ma, Hua; Zhang, Jie-Qiu; Bai, Peng; Wang, Xu-Hua; Xu, Zhuo

2012-05-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations.

Survey of L Band Tower and Airborne Sensor Systems Relevant to Upcoming Soil Moisture Missions

USDA-ARS?s Scientific Manuscript database

Basic research on the physics of microwave remote sensing of soil moisture has been conducted for almost thirty years using ground-based (tower- or truck-mounted) microwave instruments at L band frequencies. Early small point-scale studies were aimed at improved understanding and verification of mi...

UAV-based L-band SAR with precision flight path control

NASA Astrophysics Data System (ADS)

Madsen, Soren N.; Hensley, Scott; Wheeler, Kevin; Sadowy, Gregory A.; Miller, Tim; Muellerschoen, Ron; Lou, Yunling; Rosen, Paul A.

2005-01-01

NASA's Jet Propulsion Laboratory is currently implementing a reconfigurable polarimetric L-band synthetic aperture radar (SAR), specifically designed to acquire airborne repeat track interferometric (RTI) SAR data, also know as differential interferometric measurements. Differential interferometry can provide key displacement measurements, important for the scientific studies of Earthquakes and volcanoes1. Using precision real-time GPS and a sensor controlled flight management system, the system will be able to fly predefined paths with great precision. The radar will be designed to operate on a UAV (Unmanned Arial Vehicle) but will initially be demonstrated on a minimally piloted vehicle (MPV), such as the Proteus build by Scaled Composites. The application requires control of the flight path to within a 10 m tube to support repeat track and formation flying measurements. The design is fully polarimetric with an 80 MHz bandwidth (2 m range resolution) and 16 km range swath. The antenna is an electronically steered array to assure that the actual antenna pointing can be controlled independent of the wind direction and speed. The system will nominally operate at 45,000 ft. The program started out as a Instrument Incubator Project (IIP) funded by NASA Earth Science and Technology Office (ESTO).

UAV-Based L-Band SAR with Precision Flight Path Control

NASA Technical Reports Server (NTRS)

Madsen, Soren N.; Hensley, Scott; Wheeler, Kevin; Sadowy, Greg; Miller, Tim; Muellerschoen, Ron; Lou, Yunling; Rosen, Paul

2004-01-01

NASA's Jet Propulsion Laboratory is currently implementing a reconfigurable polarimetric L-band synthetic aperture radar (SAR), specifically designed to acquire airborne repeat track interferometric (RTI) SAR data, also know as differential interferometric measurements. Differential interferometry can provide key displacement measurements, important for the scientific studies of Earthquakes and volcanoes. Using precision real-time GPS and a sensor controlled flight management system, the system will be able to fly predefined paths with great precision. The radar will be designed to operate on a UAV (Unmanned Arial Vehicle) but will initially be demonstrated on a minimally piloted vehicle (MPV), such as the Proteus build by Scaled Composites. The application requires control of the flight path to within a 10 meter tube to support repeat track and formation flying measurements. The design is fully polarimetric with an 80 MHz bandwidth (2 meter range resolution) and 16 kilometer range swath. The antenna is an electronically steered array to assure that the actual antenna pointing can be controlled independent of the wind direction and speed. The system will nominally operate at 45,000 ft. The program started out as a Instrument Incubator Project (IIP) funded by NASA Earth Science and Technology Office (ESTO).

Comparison of Model Prediction with Measurements of Galactic Background Noise at L-Band

NASA Technical Reports Server (NTRS)

LeVine, David M.; Abraham, Saji; Kerr, Yann H.; Wilson, Willam J.; Skou, Niels; Sobjaerg, S.

2004-01-01

The spectral window at L-band (1.413 GHz) is important for passive remote sensing of surface parameters such as soil moisture and sea surface salinity that are needed to understand the hydrological cycle and ocean circulation. Radiation from celestial (mostly galactic) sources is strong in this window and an accurate accounting for this background radiation is often needed for calibration. Modem radio astronomy measurements in this spectral window have been converted into a brightness temperature map of the celestial sky at L-band suitable for use in correcting passive measurements. This paper presents a comparison of the background radiation predicted by this map with measurements made with several modem L-band remote sensing radiometers. The agreement validates the map and the procedure for locating the source of down-welling radiation.

Deep L'- and M-band Imaging for Planets around Vega and epsilon Eridani

NASA Astrophysics Data System (ADS)

Heinze, A. N.; Hinz, Philip M.; Kenworthy, Matthew; Miller, Douglas; Sivanandam, Suresh

2008-11-01

We have obtained deep adaptive optics (AO) images of Vega and epsilon Eri to search for planetary mass companions. We observed at the MMT in the L' (3.8 μm) and M (4.8 μm) bands using Clio, a recently commissioned imager optimized for these wavelengths. Observing at these long wavelengths represents a departure from the H band (1.65 μm) more commonly used for AO imaging searches for extrasolar planets. The long wavelengths offer better predicted planet/star flux ratios and cleaner (higher Strehl) AO images at the cost of lower diffraction-limited resolution and higher sky background. We have not detected any planets or planet candidates around Vega or epsilon Eri. We report the sensitivities obtained around both stars, which correspond to upper limits on any planetary companions which may exist. The sensitivities of our L'- and M-band observations are comparable to those of the best H-regime observations of these stars. For epsilon Eri, our M-band observations deliver considerably better sensitivity to close-in planets than any previously published results, and we show that the M band is by far the best wavelength choice for attempts at ground-based AO imaging of the known planet epsilon Eri b. The Clio camera itself, with MMTAO, may be capable of detecting epsilon Eri b at its 2010 apastron, given a multinight observing campaign. Clio appears to be the only currently existing AO imager that has a realistic possibility of detecting epsilon Eri b. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.

Design of an Airborne L-Band Cross-Track Scanning Scatterometer

NASA Technical Reports Server (NTRS)

Hilliard, Lawrence M. (Technical Monitor)

2002-01-01

In this report, we describe the design of an airborne L-band cross-track scanning scatterometer suitable for airborne operation aboard the NASA P-3 aircraft. The scatterometer is being designed for joint operation with existing L-band radiometers developed by NASA for soil moisture and ocean salinity remote sensing. In addition, design tradeoffs for a space-based radar system have been considered, with particular attention given to antenna architectures suitable for sharing the antenna between the radar and radiometer. During this study, we investigated a number of imaging techniques, including the use of real and synthetic aperture processing in both the along track and cross-track dimensions. The architecture selected will permit a variety of beamforming algorithms to be implemented, although real aperture processing, with hardware beamforming, provides better sidelobe suppression than synthetic array processing and superior signal-to-noise performance. In our discussions with the staff of NASA GSFC, we arrived at an architecture that employs complete transmit/receive modules for each subarray. Amplitude and phase control at each of the transmit modules will allow a low-sidelobe transmit pattern to be generated over scan angles of +/- 50 degrees. Each receiver module will include all electronics necessary to downconvert the received signal to an IF offset of 30 MHz where it will be digitized for further processing.

Fpga based L-band pulse doppler radar design and implementation

NASA Astrophysics Data System (ADS)

Savci, Kubilay

As its name implies RADAR (Radio Detection and Ranging) is an electromagnetic sensor used for detection and locating targets from their return signals. Radar systems propagate electromagnetic energy, from the antenna which is in part intercepted by an object. Objects reradiate a portion of energy which is captured by the radar receiver. The received signal is then processed for information extraction. Radar systems are widely used for surveillance, air security, navigation, weather hazard detection, as well as remote sensing applications. In this work, an FPGA based L-band Pulse Doppler radar prototype, which is used for target detection, localization and velocity calculation has been built and a general-purpose Pulse Doppler radar processor has been developed. This radar is a ground based stationary monopulse radar, which transmits a short pulse with a certain pulse repetition frequency (PRF). Return signals from the target are processed and information about their location and velocity is extracted. Discrete components are used for the transmitter and receiver chain. The hardware solution is based on Xilinx Virtex-6 ML605 FPGA board, responsible for the control of the radar system and the digital signal processing of the received signal, which involves Constant False Alarm Rate (CFAR) detection and Pulse Doppler processing. The algorithm is implemented in MATLAB/SIMULINK using the Xilinx System Generator for DSP tool. The field programmable gate arrays (FPGA) implementation of the radar system provides the flexibility of changing parameters such as the PRF and pulse length therefore it can be used with different radar configurations as well. A VHDL design has been developed for 1Gbit Ethernet connection to transfer digitized return signal and detection results to PC. An A-Scope software has been developed with C# programming language to display time domain radar signals and detection results on PC. Data are processed both in FPGA chip and on PC. FPGA uses fixed

Miniature L-Band Radar Transceiver

NASA Technical Reports Server (NTRS)

McWatters, Dalia; Price, Douglas; Edelstein, Wendy

2007-01-01

A miniature L-band transceiver that operates at a carrier frequency of 1.25 GHz has been developed as part of a generic radar electronics module (REM) that would constitute one unit in an array of many identical units in a very-large-aperture phased-array antenna. NASA and the Department of Defense are considering the deployment of such antennas in outer space; the underlying principles of operation, and some of those of design, also are applicable on Earth. The large dimensions of the antennas make it advantageous to distribute radio-frequency electronic circuitry into elements of the arrays. The design of the REM is intended to implement the distribution. The design also reflects a requirement to minimize the size and weight of the circuitry in order to minimize the weight of any such antenna. Other requirements include making the transceiver robust and radiation-hard and minimizing power demand. Figure 1 depicts the functional blocks of the REM, including the L-band transceiver. The key functions of the REM include signal generation, frequency translation, amplification, detection, handling of data, and radar control and timing. An arbitrary-waveform generator that includes logic circuitry and a digital-to-analog converter (DAC) generates a linear-frequency-modulation chirp waveform. A frequency synthesizer produces local-oscillator signals used for frequency conversion and clock signals for the arbitrary-waveform generator, for a digitizer [that is, an analog-to-digital converter (ADC)], and for a control and timing unit. Digital functions include command, timing, telemetry, filtering, and high-rate framing and serialization of data for a high-speed scientific-data interface. The aforementioned digital implementation of filtering is a key feature of the REM architecture. Digital filters, in contradistinction to analog ones, provide consistent and temperature-independent performance, which is particularly important when REMs are distributed throughout a large

False-color L-band image of Manaus region of Brazil

NASA Image and Video Library

1994-04-13

STS059-S-068 (13 April 1994) --- This false-color L-Band image of the Manaus region of Brazil was acquired by the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the Space Shuttle Endeavour on orbit 46 of the mission. The area shown is approximately 8 kilometers by 40 kilometers (5 by 25 miles). At the top of the image are the Solimoes and Rio Negro Rivers just before they combine at Manaus to form the Amazon River. The image is centered at about 3 degrees south latitude, and 61 degrees west longitude. The false colors are created by displaying three L-Band polarization channels; red areas correspond to high backscatter at HH polarization, while green areas exhibit high backscatter at HV polarization. Blue areas show low returns at VV polarization; hence the bright blue colors of the smooth river surfaces. Using this color scheme, green areas in the image are heavily forested, while blue areas are either cleared forest or open water. The yellow and red areas are flooded forest. Between Rio Solimoes and Rio Negro a road can be seen running from some cleared areas (visible as blue rectangles north of Rio Solimoes) north towards a tributary of Rio Negro. SIR-C/X-SAR is part of NASA's Mission to Planet Earth (MTPE). SIR-C/X-SAR radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-Band (24 cm), C-Band (6 cm), and X-Band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory (JPL). X-SAR was developed by the Dornire and Alenia Spazio Companies

Challenges for continuity of L-Band observations over land

USDA-ARS?s Scientific Manuscript database

Over land, L-band observations are primarily used for the detection of soil freeze/thaw events and the quantification of surface soil moisture content. Both products have important science, climate and decision support applications and would benefit from longer historical data records derived from s...

Design and Performance of a Miniature Radar L-Band Transceiver

NASA Technical Reports Server (NTRS)

McWatters, D.; Price, D.; Edelstein, W.

2004-01-01

Radar electronics developed for past JPL space missions historically had been custom designed and as such, given budgetary, time, and risk constraints, had not been optimized for maximum flexibility or miniaturization. To help reduce cost and risk of future radar missions, a generic radar module was conceived. The module includes a 1.25-GHz (L-band) transceiver and incorporates miniature high-density packaging of integrated circuits in die/chip form. The technology challenges include overcoming the effect of miniaturization and high packaging density to achieve the performance, reliability, and environmental ruggedness required for space missions. The module was chosen to have representative (generic) functionality most likely required from an L-band radar. For very large aperture phased-array spaceborne radar missions, the large dimensions of the array suggest the benefit of distributing the radar electronics into the antenna array. For such applications, this technology is essential in order to bring down the cost, mass, and power of the radar electronics module replicated in each panel of the array. For smaller sized arrays, a single module can be combined with the central radar controller and still provide the bene.ts of configuration .exibility, low power, and low mass. We present the design approach for the radar electronics module and the test results for its radio frequency (RF) portion: a miniature, low-power, radiation-hard L-band transceiver.

Conduction-band valley spin splitting in single-layer H-T l2O

NASA Astrophysics Data System (ADS)

Ma, Yandong; Kou, Liangzhi; Du, Aijun; Huang, Baibiao; Dai, Ying; Heine, Thomas

2018-02-01

Despite numerous studies, coupled spin and valley physics is currently limited to two-dimensional (2D) transition-metal dichalcogenides (TMDCs). Here, we predict an exceptional 2D valleytronic material associated with the spin-valley coupling phenomena beyond 2D TMDCs—single-layer (SL) H-T l2O . It displays large valley spin splitting (VSS), significantly larger than that of 2D TMDCs, and a finite band gap, which are both critically attractive for the integration of valleytronics and spintronics. More importantly, in sharp contrast to all the experimentally confirmed 2D valleytronic materials, where the strong valence-band VSS (0.15-0.46 eV) supports the spin-valley coupling, the VSS in SL H-T l2O is pronounced in its conduction band (0.61 eV), but negligibly small in its valence band (21 meV), thus opening a way for manipulating the coupled spin and valley physics. Moreover, SL H-T l2O possesses extremely high carrier mobility, as large as 9.8 ×103c m2V-1s-1 .

The application of airborne imaging radars (L and X-band) to earth resources problems

NASA Technical Reports Server (NTRS)

Drake, B.; Shuchman, R. A.; Bryan, M. L.; Larson, R. W.; Liskow, C. L.; Rendleman, R. A.

1974-01-01

A multiplexed synthetic aperture Side-Looking Airborne Radar (SLAR) that simultaneously images the terrain with X-band (3.2 cm) and L-band (23.0 cm) radar wavelengths was developed. The Feasibility of using multiplexed SLAR to obtain useful information for earth resources purposes. The SLAR imagery, aerial photographs, and infrared imagery are examined to determine the qualitative tone and texture of many rural land-use features imaged. The results show that: (1) Neither X- nor L-band SLAR at moderate and low depression angles can directly or indirectly detect pools of water under standing vegetation. (2) Many of the urban and rural land-use categories present in the test areas can be identified and mapped on the multiplexed SLAR imagery. (3) Water resources management can be done using multiplexed SLAR. (4) Drainage patterns can be determined on both the X- and L-band imagery.

Tropical forest tree stands characterization with L-band polarimetric radar

NASA Technical Reports Server (NTRS)

Wu, Shih-Tseng

1990-01-01

The effectiveness of using L-band polarimetric data to determine tropical tree-stand parameters is discussed with specific attention given to the correction of the radar data. Tree-parameter data from ground studies is compared to L-band polarimetric data (in both uncorrected and topographically corrected forms) for two test areas. The test sites are at two different elevations but both include 81 test plots with topographic data and tree-characteristic data given. Synthetic-aperture radar (SAR) data are found to be related to bole volume and tree volume, and the topographically corrected data show results similar to the uncorrected data. Similar r-values are given for both data sets because the data with incidence-angle values below 35 and above 55 are removed. Topographical correction is important when local incidence angles exceed the limits.

Wavelength tunable L Band polarization-locked vector soliton fiber laser based on SWCNT-SA and CFBG

NASA Astrophysics Data System (ADS)

Yan, Yaxi; Wang, Jiaqi; Wang, Liang; Cheng, Zhenzhou

2018-04-01

Wavelength tunable L-Band polarization-locked vector soliton fiber laser based on single-walled carbon nanotube saturable absorber (SWCNT-SA) and chirped fiber Bragg grating (CFBG) is presented for the first time. By inserting the SWCNT-SA into an all-fiber laser cavity, polarization-locked vector solitons (PLVS) are obtained. The CFBG glued on a plastic cantilever is used for wavelength tuning. By mechanically bending the cantilever, the center wavelength of the PLVS pulses can be continuously tuned from 1606.8 nm to 1614 nm, while the polarization-locked state is kept stable. The properties and dynamics of PLVSs are experimentally investigated and stable PLVS operation including high-order PLVSs is demonstrated. The pulse width and repetition rate are 7.06 ps and 11.9 MHz at a wavelength of 1611 nm, respectively. This work demonstrates the feasibility of using polarization-insensitive CFBG to realize wavelength tuning in PLVS fiber laser.

Color composite C-band and L-band image of Kilauea volcanoe on Hawaii

NASA Image and Video Library

1994-04-15

STS059-S-074 (15 April 1994) --- This color composite C-Band and L-Band image of the Kilauea volcano on the big island of Hawaii was acquired by the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) flying on the Space Shuttle Endeavour. The city of Hilo can be seen at the top. The image shows the different types of lava flows around the crater Pu'u O'o. Ash deposits which erupted in 1790 from the summit of Kilauea volcano show up as dark in this image, and fine details associated with lava flows which erupted in 1919 and 1974 can be seen to the south of the summit in an area called the Ka'u Desert. In addition, the other historic lava flows created in 1881 and 1984 from Mauna Loa volcano (out of view to the left of this image) can easily be seen despite the fact that the surrounding area is covered by forest. Such information will be used to map the extent of such flows, which can pose a hazard to the subdivisions of Hilo. Highway 11 is the linear feature running from Hilo to the Kilauea volcano. The Kilauea volcano has been almost continuously active for more than the last 11 years. Field teams that were on the ground specifically to support these radar observations report that there was vigorous surface activity about 400 meters (one-quarter mile) inland from the coast. A moving lava flow about 200 meters (660 feet) in length was observed at the time of the Shuttle over flight, raising the possibility that subsequent images taken during this mission will show changes in the landscape. SIR-C/X-SAR is part of NASA's Mission to Planet Earth (MTPE). SIR-C/X-SAR radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-Band (24 cm), C-Band (6 cm), and X-Band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR

Soil moisture limitations on monitoring boreal forest regrowth using spaceborne L-band SAR data

Treesearch

Eric S. Kasischke; Mihai A. Tanase; Laura L. Bourgeau-Chavez; Matthew Borr

2011-01-01

A study was carried out to investigate the utility of L-band SAR data for estimating aboveground biomass in sites with low levels of vegetation regrowth. Data to estimate biomass were collected from 59 sites located in fire-disturbed black spruce forests in interior Alaska. PALSAR L-band data (HH and HV polarizations) collected on two dates in the summer/fall of 2007...

An L Band Spectrum of the Coldest Brown Dwarf

NASA Astrophysics Data System (ADS)

Morley, Caroline V.; Skemer, Andrew J.; Allers, Katelyn N.; Marley, Mark. S.; Faherty, Jacqueline K.; Visscher, Channon; Beiler, Samuel A.; Miles, Brittany E.; Lupu, Roxana; Freedman, Richard S.; Fortney, Jonathan J.; Geballe, Thomas R.; Bjoraker, Gordon L.

2018-05-01

The coldest brown dwarf, WISE 0855, is the closest known planetary-mass, free-floating object and has a temperature nearly as cold as the solar system gas giants. Like Jupiter, it is predicted to have an atmosphere rich in methane, water, and ammonia, with clouds of volatile ices. WISE 0855 is faint at near-infrared wavelengths and emits almost all its energy in the mid-infrared. Skemer et al. presented a spectrum of WISE 0855 from 4.5–5.1 μm (M band), revealing water vapor features. Here, we present a spectrum of WISE 0855 in the L band, from 3.4–4.14 μm. We present a set of atmosphere models that include a range of compositions (metallicities and C/O ratios) and water ice clouds. Methane absorption is clearly present in the spectrum. The mid-infrared color can be better matched with a methane abundance that is depleted relative to solar abundance. We find that there is evidence for water ice clouds in the M band spectrum, and we find a lack of phosphine spectral features in both the L and M band spectra. We suggest that a deep continuum opacity source may be obscuring the near-infrared flux, possibly a deep phosphorous-bearing cloud, ammonium dihyrogen phosphate. Observations of WISE 0855 provide critical constraints for cold planetary atmospheres, bridging the temperature range between the long-studied solar system planets and accessible exoplanets. The James Webb Space Telescope will soon revolutionize our understanding of cold brown dwarfs with high-precision spectroscopy across the infrared, allowing us to study their compositions and cloud properties, and to infer their atmospheric dynamics and formation processes.

The modification of X and L band radar signals by monomolecular sea slicks

NASA Technical Reports Server (NTRS)

Huehnerfuss, H.; Alpers, W.; Cross, A.; Garrett, W. D.; Keller, W. C.; Plant, W. J.; Schuler, D. L.; Lange, P. A.; Schlude, F.

1983-01-01

One methyl oleate and two oleyl alcohol surface films were produced on the surface of the North Sea under comparable oceanographic and meteorological conditions in order to investigate their influence on X and L band radar backscatter. Signals are backscattered in these bands primarily by surface waves with lengths of about 2 and 12 cm, respectively, and backscattered power levels in both bands were reduced by the slicks. The reduction was larger at X band than at L band, however, indicating that shorter waves are more intensely damped by the surface films. The oleyl alcohol film caused greater attenuation of short gravity waves than the film of methyl oleate, thus demonstrating the importance of the physicochemical properties of films on the damping of wind-generated gravity capillary waves. Finally, these experiments indicate a distinct dependence of the degree of damping on the angle between wind and waves. Wind-generated waves traveling in the wind direction are more intensely damped by surface films than are waves traveling at large angles to the wind.

Integrated cladding-pumped multicore few-mode erbium-doped fibre amplifier for space-division-multiplexed communications

NASA Astrophysics Data System (ADS)

Chen, H.; Jin, C.; Huang, B.; Fontaine, N. K.; Ryf, R.; Shang, K.; Grégoire, N.; Morency, S.; Essiambre, R.-J.; Li, G.; Messaddeq, Y.; Larochelle, S.

2016-08-01

Space-division multiplexing (SDM), whereby multiple spatial channels in multimode and multicore optical fibres are used to increase the total transmission capacity per fibre, is being investigated to avert a data capacity crunch and reduce the cost per transmitted bit. With the number of channels employed in SDM transmission experiments continuing to rise, there is a requirement for integrated SDM components that are scalable. Here, we demonstrate a cladding-pumped SDM erbium-doped fibre amplifier (EDFA) that consists of six uncoupled multimode erbium-doped cores. Each core supports three spatial modes, which enables the EDFA to amplify a total of 18 spatial channels (six cores × three modes) simultaneously with a single pump diode and a complexity similar to a single-mode EDFA. The amplifier delivers >20 dBm total output power per core and <7 dB noise figure over the C-band. This cladding-pumped EDFA enables combined space-division and wavelength-division multiplexed transmission over multiple multimode fibre spans.

Simultaneous measurements of L- and S-band tree shadowing for space-Earth communications

NASA Technical Reports Server (NTRS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.; Lin, Hsin P.

1995-01-01

We present results from simultaneous L- and S-Band slant-path fade measurements through trees. One circularly-polarized antenna was used at each end of the dual-frequency link to provide information on the correlation of tree shadowing at 1620 and 2500 MHz. Fades were measured laterally in the shadow region with 5 cm spacing. Fade differences between L- and S-Band had a normal distribution with low means and standard deviations from 5.2 to 7.5 dB. Spatial variations occurred with periods larger than 1-2 wavelengths. Swept measurements over 160 MHz spans showed that the stdv. of power as function of frequency increased from approximately 1-6 dB at locations with mean fades of 4 and 20 dB, respectively. At a 5 dB fade, the central 90% of fade slopes were within a range of 0.7 (1.9) dB/MHz at L-(S-) Band.

Nondestructive detection of pork quality based on dual-band VIS/NIR spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Wenxiu; Peng, Yankun; Li, Yongyu; Tang, Xiuying; Liu, Yuanyuan

2015-05-01

With the continuous development of living standards and the relative change of dietary structure, consumers' rising and persistent demand for better quality of meat is emphasized. Colour, pH value, and cooking loss are important quality attributes when evaluating meat. To realize nondestructive detection of multi-parameter of meat quality simultaneously is popular in production and processing of meat and meat products. The objectives of this research were to compare the effectiveness of two bands for rapid nondestructive and simultaneous detection of pork quality attributes. Reflectance spectra of 60 chilled pork samples were collected from a dual-band visible/near-infrared spectroscopy system which covered 350-1100 nm and 1000-2600 nm. Then colour, pH value and cooking loss were determined by standard methods as reference values. Standard normal variables transform (SNVT) was employed to eliminate the spectral noise. A spectrum connection method was put forward for effective integration of the dual-band spectrum to make full use of the whole efficient information. Partial least squares regression (PLSR) and Principal component analysis (PCA) were applied to establish prediction models using based on single-band spectrum and dual-band spectrum, respectively. The experimental results showed that the PLSR model based on dual-band spectral information was superior to the models based on single band spectral information with lower root means quare error (RMSE) and higher accuracy. The PLSR model based on dual-band (use the overlapping part of first band) yielded the best prediction result with correlation coefficient of validation (Rv) of 0.9469, 0.9495, 0.9180, 0.9054 and 0.8789 for L*, a*, b*, pH value and cooking loss, respectively. This mainly because dual-band spectrum can provide sufficient and comprehensive information which reflected the quality attributes. Data fusion from dual-band spectrum could significantly improve pork quality parameters prediction

Ground-Based Passive Microwave Remote Sensing Observations of Soil Moisture at S and L Band with Insight into Measurement Accuracy

NASA Technical Reports Server (NTRS)

Laymon, Charles A.; Crosson, William L.; Jackson, Thomas J.; Manu, Andrew; Tsegaye, Teferi D.; Soman, V.; Arnold, James E. (Technical Monitor)

2001-01-01

Accurate estimates of spatially heterogeneous algorithm variables and parameters are required in determining the spatial distribution of soil moisture using radiometer data from aircraft and satellites. A ground-based experiment in passive microwave remote sensing of soil moisture was conducted in Huntsville, Alabama from July 1-14, 1996 to study retrieval algorithms and their sensitivity to variable and parameter specification. With high temporal frequency observations at S and L band, we were able to observe large scale moisture changes following irrigation and rainfall events, as well as diurnal behavior of surface moisture among three plots, one bare, one covered with short grass and another covered with alfalfa. The L band emitting depth was determined to be on the order of 0-3 or 0-5 cm below 0.30 cubic centimeter/cubic centimeter with an indication of a shallower emitting depth at higher moisture values. Surface moisture behavior was less apparent on the vegetated plots than it was on the bare plot because there was less moisture gradient and because of difficulty in determining vegetation water content and estimating the vegetation b parameter. Discrepancies between remotely sensed and gravimetric, soil moisture estimates on the vegetated plots point to an incomplete understanding of the requirements needed to correct for the effects of vegetation attenuation. Quantifying the uncertainty in moisture estimates is vital if applications are to utilize remotely-sensed soil moisture data. Computations based only on the real part of the complex dielectric constant and/or an alternative dielectric mixing model contribute a relatively insignificant amount of uncertainty to estimates of soil moisture. Rather, the retrieval algorithm is much more sensitive to soil properties, surface roughness and biomass.

Estimation of Soil Moisture with L-band Multi-polarization Radar

NASA Technical Reports Server (NTRS)

Shi, J.; Chen, K. S.; Kim, Chung-Li Y.; Van Zyl, J. J.; Njoku, E.; Sun, G.; O'Neill, P.; Jackson, T.; Entekhabi, D.

2004-01-01

Through analyses of the model simulated data-base, we developed a technique to estimate surface soil moisture under HYDROS radar sensor (L-band multi-polarizations and 40deg incidence) configuration. This technique includes two steps. First, it decomposes the total backscattering signals into two components - the surface scattering components (the bare surface backscattering signals attenuated by the overlaying vegetation layer) and the sum of the direct volume scattering components and surface-volume interaction components at different polarizations. From the model simulated data-base, our decomposition technique works quit well in estimation of the surface scattering components with RMSEs of 0.12,0.25, and 0.55 dB for VV, HH, and VH polarizations, respectively. Then, we use the decomposed surface backscattering signals to estimate the soil moisture and the combined surface roughness and vegetation attenuation correction factors with all three polarizations.

Simulation of L-band and HH microwave backscattering from coniferous forest stands - A comparison with SIR-B data

NASA Technical Reports Server (NTRS)

Sun, Guo-Qing; Simonett, David S.

1988-01-01

SIR-B images of the Mt. Shasta region of northern California are used to evaluate a composite L-band HH backscattering model of coniferous forest stands. It is found that both SIR-B and simulated backscattering coefficients for eight stands studied have similar trends and relations to average tree height and average number of trees per pixel. Also, the dispersion and distribution of simulated backscattering coefficients from each stand broadly match SIR-B data from the same stand. Although the limited quality and quantity of experimental data makes it difficult to draw any strong conclusions, the comparisons indicate that a stand-based L-band HH composite model seems promising for explaining backscattering features.

Landcover Based Optimal Deconvolution of PALS L-band Microwave Brightness Temperature

NASA Technical Reports Server (NTRS)

Limaye, Ashutosh S.; Crosson, William L.; Laymon, Charles A.; Njoku, Eni G.

2004-01-01

An optimal de-convolution (ODC) technique has been developed to estimate microwave brightness temperatures of agricultural fields using microwave radiometer observations. The technique is applied to airborne measurements taken by the Passive and Active L and S band (PALS) sensor in Iowa during Soil Moisture Experiments in 2002 (SMEX02). Agricultural fields in the study area were predominantly soybeans and corn. The brightness temperatures of corn and soybeans were observed to be significantly different because of large differences in vegetation biomass. PALS observations have significant over-sampling; observations were made about 100 m apart and the sensor footprint extends to about 400 m. Conventionally, observations of this type are averaged to produce smooth spatial data fields of brightness temperatures. However, the conventional approach is in contrast to reality in which the brightness temperatures are in fact strongly dependent on landcover, which is characterized by sharp boundaries. In this study, we mathematically de-convolve the observations into brightness temperature at the field scale (500-800m) using the sensor antenna response function. The result is more accurate spatial representation of field-scale brightness temperatures, which may in turn lead to more accurate soil moisture retrieval.

Evaluation of Airborne l- Band Multi-Baseline Pol-Insar for dem Extraction Beneath Forest Canopy

NASA Astrophysics Data System (ADS)

Li, W. M.; Chen, E. X.; Li, Z. Y.; Jiang, C.; Jia, Y.

2018-04-01

DEM beneath forest canopy is difficult to extract with optical stereo pairs, InSAR and Pol-InSAR techniques. Tomographic SAR (TomoSAR) based on different penetration and view angles could reflect vertical structure and ground structure. This paper aims at evaluating the possibility of TomoSAR for underlying DEM extraction. Airborne L-band repeat-pass Pol-InSAR collected in BioSAR 2008 campaign was applied to reconstruct the 3D structure of forest. And sum of kronecker product and algebraic synthesis algorithm were used to extract ground structure, and phase linking algorithm was applied to estimate ground phase. Then Goldstein cut-branch approach was used to unwrap the phases and then estimated underlying DEM. The average difference between the extracted underlying DEM and Lidar DEM is about 3.39 m in our test site. And the result indicates that it is possible for underlying DEM estimation with airborne L-band repeat-pass TomoSAR technique.

ATS-5 ranging receiver and L-band experiment. Volume 2: Data reduction and analysis

NASA Technical Reports Server (NTRS)

1971-01-01

The results of ranging and position location experiments performed at the NASA Application Technology Satellite ground station at Mojave California are presented. The experiments are simultaneous C-band and L-band ranging to ATS-5, simultaneous C-band and VHF ranging, simultaneous 24-hour ranging and position location using ATS-1, ATS-3, and ATS-5. The data handling and processing technique is also described.

Soil Moisture Active/Passive (SMAP) L-band microwave radiometer post-launch calibration

USDA-ARS?s Scientific Manuscript database

The SMAP microwave radiometer is a fully-polarimetric L-band radiometer flown on the SMAP satellite in a 6 AM / 6 PM sun-synchronous orbit at 685-km altitude. Since April 2015, the radiometer has been under calibration and validation to assess the quality of the radiometer L1B data product. Calibrat...

Towards an improved soil moisture retrieval for organic-rich soils from SMOS passive microwave L-band observations

NASA Astrophysics Data System (ADS)

Bircher, Simone; Richaume, Philippe; Mahmoodi, Ali; Mialon, Arnaud; Fernandez-Moran, Roberto; Wigneron, Jean-Pierre; Demontoux, François; Jonard, François; Weihermüller, Lutz; Andreasen, Mie; Rautiainen, Kimmo; Ikonen, Jaakko; Schwank, Mike; Drusch, Mattias; Kerr, Yann H.

2017-04-01

From the passive L-band microwave radiometer onboard the Soil Moisture and Ocean Salinity (SMOS) space mission global surface soil moisture data is retrieved every 2 - 3 days. Thus far, the empirical L-band Microwave Emission of the Biosphere (L-MEB) radiative transfer model applied in the SMOS soil moisture retrieval algorithm is exclusively calibrated over test sites in dry and temperate climate zones. Furthermore, the included dielectric mixing model relating soil moisture to relative permittivity accounts only for mineral soils. However, soil moisture monitoring over the higher Northern latitudes is crucial since these regions are especially sensitive to climate change. A considerable positive feedback is expected if thawing of these extremely organic soils supports carbon decomposition and release to the atmosphere. Due to differing structural characteristics and thus varying bound water fractions, the relative permittivity of organic material is lower than that of the most mineral soils at a given water content. This assumption was verified by means of L-band relative permittivity laboratory measurements of organic and mineral substrates from various sites in Denmark, Finland, Scotland and Siberia using a resonant cavity. Based on these data, a simple empirical dielectric model for organic soils was derived and implemented in the SMOS Soil Moisture Level 2 Prototype Processor (SML2PP). Unfortunately, the current SMOS retrieved soil moisture product seems to show unrealistically low values compared to in situ soil moisture data collected from organic surface layers in North America, Europe and the Tibetan Plateau so that the impact of the dielectric model for organic soils cannot really be tested. A simplified SMOS processing scheme yielding higher soil moisture levels has recently been proposed and is presently under investigation. Furthermore, recalibration of the model parameters accounting for vegetation and roughness effects that were thus far only

Evaluation of Spaceborne L-band Radiometer Measurements for Terrestrial Freeze/Thaw Retrievals in Canada

NASA Technical Reports Server (NTRS)

Roy, A.; Royer, A.; Derksen, C.; Brucker, L.; Langlois, A.; Mailon, A.; Kerr, Y.

2015-01-01

The landscape freeze/thaw (FT) state has an important impact on the surface energy balance, carbon fluxes, and hydrologic processes; the timing of spring melt is linked to active layer dynamics in permafrost areas. L-band (1.4 GHz) microwave emission could allow the monitoring of surface state dynamics due to its sensitivity to the pronounced permittivity difference between frozen and thawed soil. The aim of this paper is to evaluate the performance of both Aquarius and Soil Moisture and Ocean Salinity (SMOS) L-band passive microwave measurements using a polarization ratio-based algorithm for landscape FT monitoring. Weekly L-band satellite observations are compared with a large set of reference data at 48 sites across Canada spanning three environments: tundra, boreal forest, and prairies. The reference data include in situ measurements of soil temperature (Tsoil) and air temperature (Tair), and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) and snow cover area (SCA) products. Results show generally good agreement between Lband FT detection and the surface state estimated from four reference datasets. The best apparent accuracies for all seasons are obtained using Tair as the reference. Aquarius radiometer 2 (incidence angle of 39.6) data gives the best accuracies (90.8), while for SMOS the best results (87.8 of accuracy) are obtained at higher incidence angles (55- 60). The FT algorithm identifies both freeze onset and end with a delay of about one week in tundra and two weeks in forest and prairies, when compared to Tair. The analysis shows a stronger FT signal at tundra sites due to the typically clean transitions between consistently frozen and thawed conditions (and vice versa) and the absence of surface vegetation. Results in the prairies were poorer because of the influence of vegetation growth in summer (which decreases the polarization ratio) and the high frequency of ephemeral thaw events during winter. Freeze onset

Improved Band-to-Band Registration Characterization for VIIRS Reflective Solar Bands Based on Lunar Observations

NASA Technical Reports Server (NTRS)

Wang, Zhipeng; Xiong, Xiaoxiong; Li, Yonghong

2015-01-01

Spectral bands of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrumentaboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite are spatially co-registered.The accuracy of the band-to-band registration (BBR) is one of the key spatial parameters that must becharacterized. Unlike its predecessor, the Moderate Resolution Imaging Spectroradiometer (MODIS), VIIRS has no on-board calibrator specifically designed to perform on-orbit BBR characterization.To circumvent this problem, a BBR characterization method for VIIRS reflective solar bands (RSB) based on regularly-acquired lunar images has been developed. While its results can satisfactorily demonstrate that the long-term stability of the BBR is well within +/- 0.1 moderate resolution bandpixels, undesired seasonal oscillations have been observed in the trending. The oscillations are most obvious between the visiblenear-infrared bands and short-middle wave infrared bands. This paper investigates the oscillations and identifies their cause as the band spectral dependence of the centroid position and the seasonal rotation of the lunar images over calibration events. Accordingly, an improved algorithm is proposed to quantify the rotation and compensate for its impact. After the correction, the seasonal oscillation in the resulting BBR is reduced from up to 0.05 moderate resolution band pixels to around 0.01 moderate resolution band pixels. After removing this spurious seasonal oscillation, the BBR, as well as its long-term drift are well determined.

Omni-directional L-band antenna for mobile communications

NASA Technical Reports Server (NTRS)

Kim, C. S.; Moldovan, N.; Kijesky, J.

1988-01-01

The principle and design of an L-band omni-directional mobile communication antenna are discussed. The antenna is a circular wave guide aperture with hybrid circuits attached to higher order mode excitation. It produces polarized and symmetric two split beams in elevation. The circular waveguide is fed by eight probes with a 90 degree phase shift between their inputs. Radiation pattern characteristics are controlled by adjusting the aperture diameter and mode excitation. This antenna satisfies gain requirements as well as withstanding the harsh environment.

L-band ultrafast fiber laser mode locked by carbon nanotubes

NASA Astrophysics Data System (ADS)

Sun, Z.; Rozhin, A. G.; Wang, F.; Scardaci, V.; Milne, W. I.; White, I. H.; Hennrich, F.; Ferrari, A. C.

2008-08-01

We fabricate a nanotube-polyvinyl alcohol saturable absorber with a broad absorption at 1.6 μm. We demonstrate a pulsed fiber laser working in the telecommunication L band by using this composite as a mode locker. This gives ˜498±16 fs pulses at 1601 nm with a 26.7 MHz repetition rate.

An L-band SAR for repeat pass deformation measurements on a UAV platform

NASA Technical Reports Server (NTRS)

Hensley, Scott; Lou, Yunling; Rosen, Paul; Wheeler, Kevin; Zebker, Howard; Madsen, Soren; Miller, Tim; Hoffman, Jim; Farra, Don

2003-01-01

We are proposing to develop a miniaturized polarimetric L-band synthetic aperture radar (SAR) for repeat-pass differential interferometric measurements of deformation for rapidly deforming surfaces of geophysical interest such as volcanoes or earthquakes that is to be flown on a unmanned aerial vehicle (UAV) or minimally piloted vehicle (MPV). Upon surveying the capabilities and availabilities of such aircraft, the Proteus aircraft and the ALTAIR UAV appear to meet our criteria in terms of payload capabilities, flying altitude, and endurance. To support the repeat pass deformation capability it is necessary to control flight track capability of the aircraft to be within a specified 10 m tube with a goal of 1 m. This requires real-time GPS control of the autopilot to achieve these objectives that has not been demonstrated on these aircraft. Based on the Proteus and ALTAIR's altitude of 13.7 km (45,000 ft), we are designing a fully polarimetric L-band radar with 80 MHz bandwidth and a 16 km range swath. The radar will have an active electronic beam steering antenna to achieve a Doppler centroid stability that is necessary for repeat-pass interferometry. This paper presents some of the trade studies for the platform, instrument and the expected science.

Broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface

NASA Astrophysics Data System (ADS)

Mao, Chenyang; Yang, Yang; He, Xiaoxiang; Zheng, Jingming; Zhou, Chun

2017-12-01

In this paper, a broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface is proposed. The proposed metasurface can effectively convert linear-polarized (TE/TM) incident wave into the reflected wave with three different polarizations within the frequency bands of 5.5-22.75 GHz. Based on the electric and magnetic resonant features of the double-L-shaped structure, the proposed metasurface can convert linearly polarized waves into cross-polarized waves at three resonant frequency bands. Furthermore, the incident linearly polarized waves can be effectively converted into left/right handed circular-polarized (LHCP and RHCP) waves at other four non-resonance frequency bands. Thus, the proposed metasurface can be regarded as a seven-band multi-polarization converter. The prototype of the proposed polarization converter is analyzed and measured. Both simulated and measured results show the 3-dB axis ratio bandwidth of circular polarization bands and the high polarization conversion efficiency of cross-polarization bands when the incident wave changes from 0° to 30° at both TE and TM modes.

Sea Surface Salinity and Wind Retrieval Algorithm Using Combined Passive-Active L-Band Microwave Data

NASA Technical Reports Server (NTRS)

Yueh, Simon H.; Chaubell, Mario J.

2011-01-01

Aquarius is a combined passive/active L-band microwave instrument developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, the global water cycle, and climate. The primary science objective of this mission is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean with a spatial resolution of 150 kilometers and a retrieval accuracy of 0.2 practical salinity units globally on a monthly basis. The measurement principle is based on the response of the L-band (1.413 gigahertz) sea surface brightness temperatures (T (sub B)) to sea surface salinity. To achieve the required 0.2 practical salinity units accuracy, the impact of sea surface roughness (e.g. wind-generated ripples and waves) along with several factors on the observed brightness temperature has to be corrected to better than a few tenths of a degree Kelvin. To the end, Aquarius includes a scatterometer to help correct for this surface roughness effect.

On the retrieval of sea ice thickness and snow depth using concurrent laser altimetry and L-band remote sensing data

NASA Astrophysics Data System (ADS)

Zhou, Lu; Xu, Shiming; Liu, Jiping; Wang, Bin

2018-03-01

The accurate knowledge of sea ice parameters, including sea ice thickness and snow depth over the sea ice cover, is key to both climate studies and data assimilation in operational forecasts. Large-scale active and passive remote sensing is the basis for the estimation of these parameters. In traditional altimetry or the retrieval of snow depth with passive microwave remote sensing, although the sea ice thickness and the snow depth are closely related, the retrieval of one parameter is usually carried out under assumptions over the other. For example, climatological snow depth data or as derived from reanalyses contain large or unconstrained uncertainty, which result in large uncertainty in the derived sea ice thickness and volume. In this study, we explore the potential of combined retrieval of both sea ice thickness and snow depth using the concurrent active altimetry and passive microwave remote sensing of the sea ice cover. Specifically, laser altimetry and L-band passive remote sensing data are combined using two forward models: the L-band radiation model and the isostatic relationship based on buoyancy model. Since the laser altimetry usually features much higher spatial resolution than L-band data from the Soil Moisture Ocean Salinity (SMOS) satellite, there is potentially covariability between the observed snow freeboard by altimetry and the retrieval target of snow depth on the spatial scale of altimetry samples. Statistically significant correlation is discovered based on high-resolution observations from Operation IceBridge (OIB), and with a nonlinear fitting the covariability is incorporated in the retrieval algorithm. By using fitting parameters derived from large-scale surveys, the retrievability is greatly improved compared with the retrieval that assumes flat snow cover (i.e., no covariability). Verifications with OIB data show good match between the observed and the retrieved parameters, including both sea ice thickness and snow depth. With

Side-polished fiber based gain-flattening filter for erbium doped fiber amplifiers

NASA Astrophysics Data System (ADS)

Varshney, R. K.; Singh, A.; Pande, K.; Pal, B. P.

2007-03-01

A simple and accurate novel normal mode analysis has been developed to take into account the effect of the non-uniform depth of polishing in the study of the transmission characteristics of optical waveguide devices based on loading of a side-polished fiber half-coupler with a multimode planar waveguide. We apply the same to design and fabricate a gain-flattening filter suitable for fiber amplifiers. The wavelength dependent filtering action of the overall device could demonstrate flattening of an EDFA gain spectrum within ±0.7 dB over a bandwidth of 30 nm in the C-band. Results obtained by the present analysis agree very well with our experimental results. This present analysis should be very useful in the accurate design and analysis of any SPF-MMOW device/component including side-polished fiber based sensors.

High-efficiency L-band T/R Module: Development Results

NASA Technical Reports Server (NTRS)

Edelstein, Wendy N.; Andricos, Constantine; Wang, Feiyu; Rutled, David B.

2005-01-01

Future interferometric synthetic aperture radar (InSAR) systems require electronically scanned phased-array antennas, where the transmit/receive (T/R) module is a key component. The T/R module efficiency is a critical figure of merit and has direct implications on the power dissipation and power generation requirements of the system. Significant improvements in the efficiency of the T/R module will make SAR missions more feasible and affordable. The results of two high-efficiency T/R modules are presented, each based on different power amplifier technologies. One module uses a 30W GaAs Class-AlB power amplifier and the second module uses a 70W LD-MOS Class-ElF power amplifier, where both modules use a common low power section. Each module operates over an 80MHz bandwidth at L-band (1.2GHz) with an overall module efficiency greater than 58%. We will present the results of these two T/R modules that have been designed, built and tested.

The Breakthrough Listen Search for Intelligent Life: L-Band Data Recovery and Analysis

NASA Astrophysics Data System (ADS)

Lifset, Noah

2018-01-01

Breakthrough Listen is a next generation SETI project conducted under the leadership of UC Berkeley. In January 2016, it began collecting data with the Green Bank Telescope in West Virginia. It started a targeted campaign of stars within 50 pc with the L-band receiver (1.1-1.9 GHz). Enriquez et al. (2017) analyzed two thirds of this data comprising an homogeneous sample. The remaining one third of the L-band data taken since then is incomplete in some way, and thus required a different analysis. This project identified all possible issues with this data, and classified it based on its ability to be analyzed. Seven issues were found, and six are able to be accounted for with adapted analysis techniques. The data set consisted of observations of 366 stars within 50 pc, with 297 able to be analyzed and 69 needing to be re-observed. The Breakthrough Listen observation strategy uses 6 five minute observations per target star alternating between ON-target and OFF-target in the form ABACAD, which allows for easier radio-frequency interference identification. The analysis techniques, called turboSETI, search for a narrowband signal with a drifting doppler shift. For this data, a maximum drift rate of 4 Hz/s was chosen, which corresponds to an ET emitter on a planet three times the size of earth rotating three times as fast. An SNR threshold for signal detection of 15 was chosen, which allows for detection of signals with an EIRP (Equivalent Isotropic Radiated Power) of 9.72 x109 W for an emitter at a distance of 10 Ly. A total of 10 candidates signals were found, which were all determined to be either a satellite or another type of RFI. We can infer an upper limit of ~ 5 x108 stars in the milky way transmitting continuously towards earth in the L-band with a EIRP of 1012 W or greater.

A Dual Polarization, Active, Microstrip Antenna for an Orbital Imaging Radar System Operating at L-Band

NASA Technical Reports Server (NTRS)

Kelly, Kenneth C.; Huang, John

1999-01-01

A highly successful Earth orbiting synthetic antenna aperture radar (SAR) system, known as the SIR-C mission, was carried into orbit in 1994 on a U.S. Shuttle (Space Transportation System) mission. The radar system was mounted in the cargo bay with no need to fold, or in any other way reduce the size of the antennas for launch. Weight and size were not limited for the L-Band, C-Band, and X-Band radar systems of the SIR-C radar imaging mission; the set of antennas weighed 10,500 kg, the L-Band antenna having the major share of the weight. This paper treats designing an L-Band antenna functionally similar to that used for SIR-C, but at a fraction of the cost and at a weight in the order of 250 kg. Further, the antenna must be folded to fit into the small payload shroud of low cost booster rocket systems. Over 31 square meters of antenna area is required. This low weight, foldable, electronic scanning antenna is for the proposed LightSAR radar system which is to be placed in Earth orbit on a small, dedicated space craft at the lowest possible cost for an efficient L-Band radar imaging system. This LightSAR spacecraft radar is to be continuously available for at least five operational years, and have the ability to map or repeat-map any area on earth within a few days of any request. A microstrip patch array, with microstrip transmission lines heavily employed in the aperture and in the corporate feed network, was chosen as the low cost approach for this active dual-polarization, 80 MHz (6.4%) bandwidth antenna design.

A Dual Polarization, Active, Microstrip Antenna for an Orbital Imaging Radar System Operating at L-Band

NASA Technical Reports Server (NTRS)

Kelly, Kenneth C.; Huang, John

2000-01-01

A highly successful Earth orbiting synthetic antenna aperture radar (SAR) system, known as the SIR-C mission, was carried into orbit in 1994 on a U.S. Shuttle (Space Transportation System) mission. The radar system was mounted in the cargo bay with no need to fold, or in any other way reduce the size of the antennas for launch. Weight and size were not limited for the L-Band, C-Band, and X-Band radar systems of the SIR-C radar imaging mission; the set of antennas weighed 10,500 kg, the L-Band antenna having the major share of the weight. This paper treats designing an L-Band antenna functionally similar to that used for SIR-C, but at a fraction of the cost and at a weight in the order of 250 kg. Further, the antenna must be folded to fit into the small payload shroud of low cost booster rocket systems. Over 31 square meters of antenna area is required. This low weight, foldable, electronic scanning antenna is for the proposed LightSAR radar system which is to be placed in Earth orbit on a small, dedicated space craft at the lowest possible cost for an efficient L- Band radar imaging system. This LightSAR spacecraft radar is to be continuously available for at least five operational years, and have the ability to map or repeat-map any area on earth within a few days of any request. A microstrip patch array, with microstrip transmission lines heavily employed in the aperture and in the corporate feed network, was chosen as the low cost approach for this active dual-polarization, 80 MHz (6.4%) bandwidth antenna design.

Investigation of L-band shipboard antennas for maritime satellite applications

NASA Technical Reports Server (NTRS)

Heckert, G. P.

1972-01-01

A basic conceptual investigation of low cost L-band antenna subsystems for shipboard use was conducted by identifying the various pertinent design trade-offs and related performance characteristics peculiar to the civilian maritime application, and by comparing alternate approaches for their simplicity and general suitability. The study was not directed at a single specific proposal, but was intended to be parametric in nature. Antenna system concepts were to be investigated for a range of gain of 3 to 18 dB, with a value of about 10 dB considered as a baseline reference. As the primary source of potential complexity in shipboard antennas, which have beamwidths less than hemispherical as the beam pointing or selecting mechanism, major emphasis was directed at this aspect. Three categories of antenna system concepts were identified: (1) mechanically pointed, single-beam antennas; (2) fixed antennas with switched-beams; and (3) electronically-steered phased arrays. It is recommended that an L-band short backfire antenna subsystem, including a two-axis motor driven gimbal mount, and necessary single channel monopulse tracking receiver portions be developed for demonstration of performance and subsystem simplicity.

Active-passive synergy for interpreting ocean L-band emissivity: Results from the CAROLS airborne campaigns

NASA Astrophysics Data System (ADS)

Martin, A. C. H.; Boutin, J.; Hauser, D.; Dinnat, E. P.

2014-08-01

The impact of the ocean surface roughness on the ocean L-band emissivity is investigated using simultaneous airborne measurements from an L-band radiometer (CAROLS) and from a C-band scatterometer (STORM) acquired in the Gulf of Biscay (off-the French Atlantic coasts) in November 2010. Two synergetic approaches are used to investigate the impact of surface roughness on the L-band brightness temperature (Tb). First, wind derived from the scatterometer measurements is used to analyze the roughness contribution to Tb as a function of wind and compare it with the one simulated by SMOS and Aquarius roughness models. Then residuals from this mean relationship are analyzed in terms of mean square slope derived from the STORM instrument. We show improvement of new radiometric roughness models derived from SMOS and Aquarius satellite measurements in comparison with prelaunch models. Influence of wind azimuth on Tb could not be evidenced from our data set. However, we point out the importance of taking into account large roughness scales (>20 cm) in addition to small roughness scale (5 cm) rapidly affected by wind to interpret radiometric measurements far from nadir. This was made possible thanks to simultaneous estimates of large and small roughness scales using STORM at small (7-16°) and large (30°) incidence angles.

L-Band Digital Aeronautical Communications System Engineering - Initial Safety and Security Risk Assessment and Mitigation

NASA Technical Reports Server (NTRS)

Zelkin, Natalie; Henriksen, Stephen

2011-01-01

This document is being provided as part of ITT's NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: "New ATM Requirements--Future Communications, C-Band and L-Band Communications Standard Development." ITT has completed a safety hazard analysis providing a preliminary safety assessment for the proposed L-band (960 to 1164 MHz) terrestrial en route communications system. The assessment was performed following the guidelines outlined in the Federal Aviation Administration Safety Risk Management Guidance for System Acquisitions document. The safety analysis did not identify any hazards with an unacceptable risk, though a number of hazards with a medium risk were documented. This effort represents a preliminary safety hazard analysis and notes the triggers for risk reassessment. A detailed safety hazards analysis is recommended as a follow-on activity to assess particular components of the L-band communication system after the technology is chosen and system rollout timing is determined. The security risk analysis resulted in identifying main security threats to the proposed system as well as noting additional threats recommended for a future security analysis conducted at a later stage in the system development process. The document discusses various security controls, including those suggested in the COCR Version 2.0.

Simulated Biomass Retrieval from the Spaceborne Tomographic SAOCOM-CS Mission at L-Band

NASA Astrophysics Data System (ADS)

Blomberg, Erik; Soja, Maciej J.; Ferro-Famil, Laurent; Ulander, Lars M. H.; Tebaldini, Stefano

2016-08-01

This paper presents an evaluation of above-ground biomass (ABG) retrieval in boreal forests using simulated tomographic synthetic-aperture radar (SAR) data corresponding to the future SAOCOM-CS (L-band 1.275 GHz) mission. Using forest and radar data from the BioSAR 2008 campaign at the Krycklan test site in northern Sweden the expected performance of SAOCOM-CS is evaluated and compared with the E-SAR airborne L- band SAR (1.300 GHz). It is found that SAOCOM-CS data produce retrievals on par with those obtained with E-SAR, with retrievals having a relative RMSE of 30% or less. This holds true even if the acquisitions are limited to a single polarization, with HH results shown as an example.

Simultaneous retrieval of sea ice thickness and snow depth using concurrent active altimetry and passive L-band remote sensing data

NASA Astrophysics Data System (ADS)

Zhou, L.; Xu, S.; Liu, J.

2017-12-01

The retrieval of sea ice thickness mainly relies on satellite altimetry, and the freeboard measurements are converted to sea ice thickness (hi) under certain assumptions over snow loading. The uncertain in snow depth (hs) is a major source of uncertainty in the retrieved sea ice thickness and total volume for both radar and laser altimetry. In this study, novel algorithms for the simultaneous retrieval of hi and hs are proposed for the data synergy of L-band (1.4 GHz) passive remote sensing and both types of active altimetry: (1) L-band (1.4GHz) brightness temperature (TB) from Soil Moisture Ocean Salinity (SMOS) satellite and sea ice freeboard (FBice) from radar altimetry, (2) L-band TB data and snow freeboard (FBsnow) from laser altimetry. Two physical models serve as the forward models for the retrieval: L-band radiation model, and the hydrostatic equilibrium model. Verification with SMOS and Operational IceBridge (OIB) data is carried out, showing overall good retrieval accuracy for both sea ice parameters. Specifically, we show that the covariability between hs and FBsnow is crucial for the synergy between TB and FBsnow. Comparison with existing algorithms shows lower uncertainty in both sea ice parameters, and that the uncertainty in the retrieved sea ice thickness as caused by that of snow depth is spatially uncorrelated, with the potential reduction of the volume uncertainty through spatial sampling. The proposed algorithms can be applied to the retrieval of sea ice parameters at basin-scale, using concurrent active and passive remote sensing data based on satellites.

Soil Moisture Active Passive (SMAP) L-Band Microwave Radiometer Post-Launch Calibration

NASA Technical Reports Server (NTRS)

Peng, Jinzheng; Piepmeier, Jeffrey R.; Misra, Sidharth; Dinnat, Emmanuel P.; Hudson, Derek; Le Vine, David M.; De Amici, Giovanni; Mohammed, Priscilla N.; Yueh, Simon H.; Meissner, Thomas

2016-01-01

The SMAP microwave radiometer is a fully-polarimetric L-band radiometer flown on the SMAP satellite in a 6 AM/ 6 PM sun-synchronous orbit at 685 km altitude. Since April, 2015, the radiometer is under calibration and validation to assess the quality of the radiometer L1B data product. Calibration methods including the SMAP L1B TA2TB (from Antenna Temperature (TA) to the Earth's surface Brightness Temperature (TB)) algorithm and TA forward models are outlined, and validation approaches to calibration stability/quality are described in this paper including future work. Results show that the current radiometer L1B data satisfies its requirements.

Soil Moisture ActivePassive (SMAP) L-Band Microwave Radiometer Post-Launch Calibration

NASA Technical Reports Server (NTRS)

Peng, Jinzheng; Piepmeier, Jeffrey R.; Misra, Sidharth; Dinnat, Emmanuel P.; Hudson, Derek; Le Vine, David M.; De Amici, Giovanni; Mohammed, Priscilla N.; Yueh, Simon H.; Meissner, Thomas

2016-01-01

The SMAP microwave radiometer is a fully-polarimetric L-band radiometer flown on the SMAP satellite in a 6 AM/ 6 PM sun-synchronous orbit at 685 km altitude. Since April, 2015, the radiometer is under calibration and validation to assess the quality of the radiometer L1B data product. Calibration methods including the SMAP L1B TA2TB (from Antenna Temperature (TA) to the Earth’s surface Brightness Temperature (TB)) algorithm and TA forward models are outlined, and validation approaches to calibration stability/quality are described in this paper including future work. Results show that the current radiometer L1B data satisfies its requirements.

Relation between L-band soil emittance and soil water content

NASA Technical Reports Server (NTRS)

Stroosnijder, L.; Lascano, R. J.; Van Bavel, C. H. M.; Newton, R. W.

1986-01-01

An experimental relation between soil emittance (E) at L-band and soil surface moisture content (M) is compared with a theoretical one. The latter depends on the soil dielectric constant, which is a function of both soil moisture content and of soil texture. It appears that a difference of 10 percent in the surface clay content causes a change in the estimate of M on the order of 0.02 cu m/cu m. This is based on calculations with a model that simulates the flow of water and energy, in combination with a radiative transfer model. It is concluded that an experimental determination of the E-M relation for each soil type is not required, and that a rough estimate of the soil texture will lead to a sufficiently accurate estimate of soil moisture from a general, theoretical relationship obtained by numerical simulation.

UAVSAR: Airborne L-band Radar for Repeat Pass Interferometry

NASA Technical Reports Server (NTRS)

Moes, Timothy R.

2009-01-01

The primary objectives of the UAVSAR Project were to: a) develop a miniaturized polarimetric L-band synthetic aperture radar (SAR) for use on an unmanned aerial vehicle (UAV) or piloted vehicle. b) develop the associated processing algorithms for repeat-pass differential interferometric measurements using a single antenna. c) conduct measurements of geophysical interest, particularly changes of rapidly deforming surfaces such as volcanoes or earthquakes. Two complete systems were developed. Operational Science Missions began on February 18, 2009 ... concurrent development and testing of the radar system continues.

A search for J-band variability from late-L and T brown dwarfs

NASA Astrophysics Data System (ADS)

Clarke, F. J.; Hodgkin, S. T.; Oppenheimer, B. R.; Robertson, J.; Haubois, X.

2008-06-01

We present J-band photometric observations of eight late-L and T type brown dwarfs designed to search for variability. We detect small amplitude periodic variability from three of the objects on time-scales of several hours, probably indicating the rotation period of the objects. The other targets do not show any variability down to the level of 0.5-5 per cent This work is based on observations obtained at the European Southern Observatory, La Silla, Chile (ESO Programme 72.C-0006). E-mail: fclarke@astro.ox.ac.uk (FJC); sth@ast.cam.ac.uk (STH); bro@amnh.org (BRO); xavier.haubois@obspm.fr (XH)

BorealScat: A Tower Experiment for Understanding Temporal Changes in P- and L-Band Backscattering from a Boreal Forest

NASA Astrophysics Data System (ADS)

Ulander, Lars M. H.; Soja, Maciej J.; Monteith, Albert R.; Eriksson, Leif E. B.; Fransson, Johan E. S.; Persson, Henrik, J.

2016-08-01

This paper describes the tower-based radar BorealScat, which is being developed for polarimetric, tomographic and Doppler measurements at the hemi-boreal forest test site in Remningstorp, Sweden. The facility consists of a 50-m high tower equipped with an antenna array at the top of the tower, a 20-port vector network analyser (VNA), 20 low-loss cables for interconnection, and a calibration loop with a switching network. The first version of BorealScat will perform the full set of measurements in the frequency range 0.4 - 1.4 GHz, i.e. P-band and L-band. The tower is currently under construction at a forest stand dominated by Norway spruce (Picea abies (L.) Karst.). The mature stand has an above-ground dry biomass of 300 tons/ha. Data collections are planned to commence in autumn 2016.

The Tor Vergata Scattering Model Applied to L Band Backscatter During the Corn Growth Cycle

NASA Astrophysics Data System (ADS)

Joseph, A. T.; van der Velde, R.; Ferrazzoli, P.; Lang, R. H.; Gish, T.

2013-12-01

At the USDA's Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) experimental site in Beltsville (Maryland, USA) a field campaign took place throughout the 2002 corn growth cycle from May 10th (emergence of corn crops) to October 2nd (harvest). One of the microwave instruments deployed was the multi-frequency (X-, C- and L-band) quad-polarized (HH, HV, VV, VH) NASA GSFC / George Washington University (GWU) truck mounted radar. During the field campaign, this radar system provided once a week fully polarized C- and L-band (4.75 and 1.6 GHz) backscatter measurements from incidence angle of 15, 35, and 55 degrees. In support of these microwave observations, an extensive ground characterization took place, which included measurements of surface roughness, soil moisture, vegetation biomass and morphology. The field conditions during the campaign are characterized by several dry downs with a period of drought in the month of August. Peak biomass of the corn canopies was reached at July 24, 2002 with a total biomass of approximately 6.5 kg m-2. This dynamic range in both soil moisture and vegetation conditions within the data set is ideal for the validation of discrete medium vegetation scattering models. In this study, we compare the L band backscatter measurements with simulations by the Tor Vergata model (Bracaglia et al., 1995). The measured soil moisture, vegetation biomass and most reliably measured vegetation morphological parameters (e.g. number of leaves, number of stems and stem height) were used as input for the Tor Vergata model. The more uncertain model parameters (e.g. surface roughness, leaf thickness) and the stem diameter were optimized using a parameter estimation routine based on the Levenberg-Marquardt algorithm. As cost function for this optimization, the HH and VV polarized backscatter measured and simulated by the Tor Vergata model for incidence angle of 15, 35 and 55 degrees were used (6 measurements in total). The

Localized landslide risk assessment with multi pass L band DInSAR analysis

NASA Astrophysics Data System (ADS)

Yun, HyeWon; Rack Kim, Jung; Lin, Shih-Yuan; Choi, YunSoo

2014-05-01

In terms of data availability and error correction, landslide forecasting by Differential Interferometric SAR (DInSAR) analysis is not easy task. Especially, the landslides by the anthropogenic construction activities frequently occurred in the localized cutting side of mountainous area. In such circumstances, it is difficult to attain sufficient enough accuracy because of the external factors inducing the error component in electromagnetic wave propagation. For instance, the local climate characteristics such as orographic effect and the proximity to water source can produce the significant anomalies in the water vapor distribution and consequently result in the error components of InSAR phase angle measurements. Moreover the high altitude parts of target area cause the stratified tropospheric delay error in DInSAR measurement. The other obstacle in DInSAR observation over the potential landside site is the vegetation canopy which causes the decorrelation of InSAR phase. Thus rather than C band sensor such as ENVISAT, ERS and RADARSAT, DInSAR analysis with L band ALOS PLASAR is more recommendable. Together with the introduction of L band DInSAR analysis, the improved DInSAR technique to cope all above obstacles is necessary. Thus we employed two approaches i.e. StaMPS/MTI (Stanford Method for Persistent Scatterers/Multi-Temporal InSAR, Hopper et al., 2007) which was newly developed for extracting the reliable deformation values through time series analysis and two pass DInSAR with the error term compensation based on the external weather information in this study. Since the water vapor observation from spaceborne radiometer is not feasible by the temporal gap in this case, the quantities from weather Research Forecasting (WRF) with 1 km spatial resolution was used to address the atmospheric phase error in two pass DInSAR analysis. Also it was observed that base DEM offset with time dependent perpendicular baselines of InSAR time series produce a significant error

Modelling of the L-band brightness temperatures measured with ELBARA III radiometer on Bubnow wetland

NASA Astrophysics Data System (ADS)

Gluba, Lukasz; Sagan, Joanna; Lukowski, Mateusz; Szlazak, Radoslaw; Usowicz, Boguslaw

2017-04-01

Microwave radiometry has become the main tool for investigating soil moisture (SM) with remote sensing methods. ESA - SMOS (Soil Moisture and Ocean Salinity) satellite operating at L-band provides global distribution of soil moisture. An integral part of SMOS mission are calibration and validation activities involving measurements with ELBARA III which is an L-band microwave passive radiometer. It is done in order to improve soil moisture retrievals - make them more time-effective and accurate. The instrument is located at Bubnow test-site, on the border of cultivated field, fallow, meadow and natural wetland being a part of Polesie National Park (Poland). We obtain both temporal and spatial dependences of brightness temperatures for varied types of land covers with the ELBARA III directed at different azimuths. Soil moisture is retrieved from brightness temperature using L-band Microwave Emission of the Biosphere (L-MEB) model, the same as currently used radiative transfer model for SMOS. Parametrization of L-MEB, as well as input values are still under debate. We discuss the results of SM retrievals basing on data obtained during first year of the radiometer's operation. We analyze temporal dependences of retrieved SM for one-parameter (SM), two-parameter (SM, τ - optical depth) and three-parameter (SM, τ, Hr - roughness parameter) retrievals, as well as spatial dependences for specific dates. Special case of Simplified Roughness Parametrization, combining the roughness parameter and optical depth, is considered. L-MEB processing is supported by the continuous measurements of soil moisture and temperature obtained from nearby agrometeorological station, as well as studies on the soil granulometric composition of the Bubnow test-site area. Furthermore, for better estimation of optical depth, the satellite-derived Normalized Difference Vegetation Index (NDVI) was employed, supported by measured in situ vegetation parameters (such as Leaf Area Index and Vegetation

PALS (Passive Active L-band System) Radiometer-Based Soil Moisture Retrieval for the SMAP Validation Experiment 2012 (SMAPVEX12)

NASA Astrophysics Data System (ADS)

Colliander, A.; Jackson, T. J.; Chan, S.; Bindlish, R.; O'Neill, P. E.; Chazanoff, S. L.; McNairn, H.; Bullock, P.; Powers, J.; Wiseman, G.; Berg, A. A.; Magagi, R.; Njoku, E. G.

2014-12-01

NASA's (National Aeronautics and Space Administration) Soil Moisture Active Passive (SMAP) mission is scheduled for launch in early January 2015. For pre-launch soil moisture algorithm development and validation, the SMAP project and NASA coordinated a SMAP Validation Experiment 2012 (SMAPVEX12) together with Agriculture and Agri-Food Canada in the vicinity of Winnipeg, Canada in June 7-July 19, 2012. Coincident active and passive airborne L-band data were acquired using the Passive Active L-band System (PALS) on 17 days during the experiment. Simultaneously with the PALS measurements, soil moisture ground truth data were collected manually. The vegetation and surface roughness were sampled on non-flight days. The SMAP mission will produce surface (top 5 cm) soil moisture products a) using a combination of its L-band radiometer and SAR (Synthetic Aperture Radar) measurements, b) using the radiometer measurement only, and c) using the SAR measurements only. The SMAPVEX12 data are being utilized for the development and testing of the algorithms applied for generating these soil moisture products. This talk will focus on presenting results of retrieving surface soil moisture using the PALS radiometer. The issues that this retrieval faces are very similar to those faced by the global algorithm using the SMAP radiometer. However, the different spatial resolution of the two observations has to be accounted for in the analysis. The PALS 3 dB footprint in the experiment was on the order of 1 km, whereas the SMAP radiometer has a footprint of about 40 km. In this talk forward modeled brightness temperature over the manually sampled fields and the retrieved soil moisture over the entire experiment domain are presented and discussed. In order to provide a retrieval product similar to that of the SMAP passive algorithm, various ancillary information had to be obtained for the SMAPVEX12 domain. In many cases there are multiple options on how to choose and reprocess these data

Inter-comparison of SMAP, Aquarius and SMOS L-band brightness temperature observations

USDA-ARS?s Scientific Manuscript database

Soil Moisture Active Passive (SMAP) mission is scheduled for launch on January 29, 2015. SMAP will make observations with an L-band radar and radiometer using a shared 6 m rotating reflector antenna. SMAP is a fully polarimetric radiometer with the center frequency of 1.41 GHz. The target accuracy o...

Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR)

PubMed Central

Kittell, Aaron W.; Hustedt, Eric J.; Hyde, James S.

2014-01-01

Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8 to 80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible [1]. Two different systems are presented and distances of 18–30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER. PMID:22750251

Oil spill analysis by means of full polarimetric UAVSAR (L-band) and Radarsat-2 (C-band) products acquired during Deepwater Horizon Disaster

NASA Astrophysics Data System (ADS)

Latini, Daniele; Del Frate, Fabio; Jones, Cathleen E.

2014-10-01

SAR instruments with polarimetric capabilities, high resolution and short revisit time can provide powerful support in oil spill monitoring and different techniques of analysis have been developed for this purpose [1][2]. An oil film on the sea surface results in darker areas in SAR images, but careful interpretation is required because dark spots can also be caused by natural phenomena. In view of the very low backscatter from slicks, the Noise Equivalent Sigma Zero (NESZ) is a primary sensor parameter to be considered when using a sensor for slick analysis. Among the existing full polarimetric sensors, the high resolution and very low NESZ values of UAVSAR (L-band) and RADARSAT-2 (C-band) make them preferable for oil spill analysis compared to the last generation SAR instruments. The Deepwater Horizon disaster that occurred in the Gulf of Mexico in 2010 represents a unique and extensive test site where large amounts of SAR imagery and ground validation data are available. By applying the Cloude-Pottier decomposition method to full polarimetric UAVSAR (L-band) and RADARSAT-2 (C-band), it is possible to extract parameters that describe the scattering mechanism of the target. By comparing quasi-simultaneous acquisitions and exploiting the different penetration capabilities of the sensors, we investigate the potential of full polarimetric SAR to discriminate oil on the sea surface from look-alike phenomena covering the full range of backscattering values down to those at the instrument noise floor.

Use of C-band Sentinel-1 and L-band UAVSAR data for flood extent mapping during Hurricane Harvey

NASA Astrophysics Data System (ADS)

Lakshmi, V.; Kundu, S.; Torres, R.

2017-12-01

Hurricane Harvey was one of the most destructive storms that struck the Houston area in August 2017 causing loss of life and property. In this study, an estimation of flooding extent is done using two sets of microwave remote sensing data, Unmanned Aerial Vehicle Synthetic Aperture Radar (UAVSAR) and Sentinel-1. UAVSAR is an L-band SAR (Synthetic Aperture Radar) data which is an airborne repeat-pass interferometric observation system and has 16 km swath. Sentinel-1 is the C band microwave data developed by European Space Agency covering a large area (250 km). Data are analyzed to examine the flood extent over Houston during Harvey. Flood extent mapping is carried out using the Sentinel-1 data and UAVSAR using backscatter signatures which displays the extent of changes and destruction during the flood. Keywords: Harvey, UAVSAR, Sentinel-1, flood extent

Empirical Soil Moisture Estimation with Spaceborne L-band Polarimetric Radars: Aquarius, SMAP, and PALSAR-2

NASA Astrophysics Data System (ADS)

Burgin, M. S.; van Zyl, J. J.

2017-12-01

Traditionally, substantial ancillary data is needed to parametrize complex electromagnetic models to estimate soil moisture from polarimetric radar data. The Soil Moisture Active Passive (SMAP) baseline radar soil moisture retrieval algorithm uses a data cube approach, where a cube of radar backscatter values is calculated using sophisticated models. In this work, we utilize the empirical approach by Kim and van Zyl (2009) which is an optional SMAP radar soil moisture retrieval algorithm; it expresses radar backscatter of a vegetated scene as a linear function of soil moisture, hence eliminating the need for ancillary data. We use 2.5 years of L-band Aquarius radar and radiometer derived soil moisture data to determine two coefficients of a linear model function on a global scale. These coefficients are used to estimate soil moisture with 2.5 months of L-band SMAP and L-band PALSAR-2 data. The estimated soil moisture is compared with the SMAP Level 2 radiometer-only soil moisture product; the global unbiased RMSE of the SMAP derived soil moisture corresponds to 0.06-0.07 cm3/cm3. In this study, we leverage the three diverse L-band radar data sets to investigate the impact of pixel size and pixel heterogeneity on soil moisture estimation performance. Pixel sizes range from 100 km for Aquarius, over 3, 9, 36 km for SMAP, to 10m for PALSAR-2. Furthermore, we observe seasonal variation in the radar sensitivity to soil moisture which allows the identification and quantification of seasonally changing vegetation. Utilizing this information, we further improve the estimation performance. The research described in this paper is supported by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2017. All rights reserved.

Soil moisture observations using L-, C-, and X-band microwave radiometers

NASA Astrophysics Data System (ADS)

Bolten, John Dennis

The purpose of this thesis is to further the current understanding of soil moisture remote sensing under varying conditions using L-, C-, and X-band. Aircraft and satellite instruments are used to investigate the effects of frequency and spatial resolution on soil moisture sensitivity. The specific objectives of the research are to examine multi-scale observed and modeled microwave radiobrightness, evaluate new EOS Aqua Advanced Microwave Scanning Radiometer (AMSR-E) brightness temperature and soil moisture retrievals, and examine future satellite-based technologies for soil moisture sensing. The cycling of Earth's water, energy and carbon is vital to understanding global climate. Over land, these processes are largely dependent on the amount of moisture within the top few centimeters of the soil. However, there are currently no methods available that can accurately characterize Earth's soil moisture layer at the spatial scales or temporal resolutions appropriate for climate modeling. The current work uses ground truth, satellite and aircraft remote sensing data from three large-scale field experiments having different land surface, topographic and climate conditions. A physically-based radiative transfer model is used to simulate the observed aircraft and satellite measurements using spatially and temporally co-located surface parameters. A robust analysis of surface heterogeneity and scaling is possible due to the combination of multiple datasets from a range of microwave frequencies and field conditions. Accurate characterization of spatial and temporal variability of soil moisture during the three field experiments is achieved through sensor calibration and algorithm validation. Comparisons of satellite observations and resampled aircraft observations are made using soil moisture from a Numerical Weather Prediction (NWP) model in order to further demonstrate a soil moisture correlation where point data was unavailable. The influence of vegetation, spatial

False-color L-band image of Manaus region of Brazil

NASA Technical Reports Server (NTRS)

1994-01-01

This false-color L-band image of the Manaus region of Brazil was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperature Radar (SIR-C/X-SAR) flying on the Space Shuttle Endeavour on its 46th orbit. The area shown is approximately 8 kilometers by 40 kilometers (5 by 25 miles). At the top of the image are the Solimoes and Rio Negro River. The image is centered at about 3 degrees south latitude, and 61 degrees west longitude. Blue areas show low returns at VV poloarization; hence the bright blue colors of the smooth river surfaces. Green areas in the image are heavily forested, while blue areas are either cleared forest or open water. The yellow and red areas are flooded forest. Between Rio Solimoes and Rio Negro, a road can be seen running from some cleared areas (visible as blue rectangles north of Rio Solimoes) north toward a tributary or Rio Negro. The Jet Propulsion Laboratory alternative photo number is P-43895.

Suppressing multiples using an adaptive multichannel filter based on L1-norm

NASA Astrophysics Data System (ADS)

Shi, Ying; Jing, Hongliang; Zhang, Wenwu; Ning, Dezhi

2017-08-01

Adaptive subtraction is an important link for removing surface-related multiples in the wave equation-based method. In this paper, we propose an adaptive multichannel subtraction method based on the L1-norm. We achieve enhanced compensation for the mismatch between the input seismogram and the predicted multiples in terms of the amplitude, phase, frequency band, and travel time. Unlike the conventional L2-norm, the proposed method does not rely on the assumption that the primary and the multiples are orthogonal, and also takes advantage of the fact that the L1-norm is more robust when dealing with outliers. In addition, we propose a frequency band extension via modulation to reconstruct the high frequencies to compensate for the frequency misalignment. We present a parallel computing scheme to accelerate the subtraction algorithm on graphic processing units (GPUs), which significantly reduces the computational cost. The synthetic and field seismic data tests show that the proposed method effectively suppresses the multiples.

M-band imaging of the HR 8799 planetary system using an innovative LOCI-based background subtraction technique

DOE PAGES

Galicher, Raphael; Marois, Christian; Macintosh, Bruce; ...

2011-09-02

Multi-wavelength observations/spectroscopy of exoplanetary atmospheres are the basis of the emerging exciting field of comparative exoplanetology. The HR 8799 planetary system is an ideal laboratory to study our current knowledge gap between massive field brown dwarfs and the cold 5 Gyr old solar system planets. The HR 8799 planets have so far been imaged at J- to L-band, with only upper limits available at M-band. We present here deep high-contrast Keck II adaptive optics M-band observations that show the imaging detection of three of the four currently known HR 8799 planets. Such detections were made possible due to the developmentmore » of an innovative LOCI-based background subtraction scheme that is three times more efficient than a classical median background subtraction for Keck II AO data, representing a gain in telescope time of up to a factor of nine. These M-band detections extend the broadband photometric coverage out to ~5 μm and provide access to the strong CO fundamental absorption band at 4.5 μm. The new M-band photometry shows that the HR 8799 planets are located near the L/T-type dwarf transition, similar to what was found by other studies. Finally, we also confirm that the best atmospheric fits are consistent with low surface gravity, dusty, and non-equilibrium CO/CH 4 chemistry models.« less

Independent polarization and multi-band THz absorber base on Jerusalem cross

NASA Astrophysics Data System (ADS)

Arezoomand, Afsaneh Saee; Zarrabi, Ferdows B.; Heydari, Samaneh; Gandji, Navid P.

2015-10-01

In this paper, we present the design and simulation of a single and multi-band perfect metamaterial absorber (MA) in the THz region base on Jerusalem cross (JC) and metamaterial load in unit cells. The structures consist of dual metallic layers for allowing near-perfect absorption with absorption peak of more than 99%. In this novel design, four-different shape of Jerusalem cross is presented and by adding L, U and W shape loaded to first structure, we tried to achieve a dual-band absorber. In addition, by good implementation of these loaded, we are able to control the absorption resonance at second resonance at 0.9, 0.7 and 0.85 THz respectively. In the other hand, we achieved a semi stable designing at first resonance between 0.53 and 0.58 THz. The proposed absorber has broadband polarization angle. The surface current modeled and proved the broadband polarization angle at prototype MA. The LC resonance of the metamaterial for Jerusalem cross and modified structures are extracting from equivalent circuit. As a result, proposed MA is useful for THz medical imaging and communication systems and the dual-band absorber has applications in many scientific and technological areas.

Effects of the equatorial ionosphere on L-band Earth-space transmissions

NASA Technical Reports Server (NTRS)

Smith, Ernest K.; Flock, Warren L.

1993-01-01

Ionosphere scintillation can effect satellite telecommunication up to Ku-band. Nighttime scintillation can be attributed to large-scale inhomogeneity in the F-region of the ionosphere predominantly between heights of 200 and 600 km. Daytime scintillation has been attributed to sporadic E. It can be thought of as occurring in three belts: equatorial, high-latitude, and mid-latitude, in order of severity. Equatorial scintillation occurs between magnetic latitudes +/- 25 degrees, peaking near +/- 10 degrees. It commonly starts abruptly near 2000 local time and dies out shortly after midnight. There is a strong solar cycle dependence and a seasonal preference for the equinoxes, particularly the vernal one. Equatorial scintillation occurs more frequently on magnetically quiet than on magnetically disturbed days in most longitudes. At the peak of the sunspot cycle scintillation depths as great as 20 dB were observed at L-band.

An L-band SAR for repeat pass deformation measurements on a UAV platform

NASA Technical Reports Server (NTRS)

Wheeler, Kevin; Hensley, Scott; Lou, Yunling

2004-01-01

We are proposing to develop a miniaturized polarimetric L-band synthetic aperture radar (SAR) for repeatpass differential interferometric measurements of deformation for rapidly deforming surfaces of geophysical interest such as volcanoes or earthquakes that is to be flown on a unmanned aerial vehicle (UAV or minimally piloted vehicle (MPV).

An L-band transit-time oscillator with mechanical frequency tunability

NASA Astrophysics Data System (ADS)

Song, Lili; He, Juntao; Ling, Junpu; Cao, Yibing

2017-02-01

An L-band coaxial Transit-time Oscillator (TTO) with mechanical frequency tunability is introduced in this paper. Particle-in-cell simulations have been done. The output power efficiency has been improved at least 20% under a 10.2 GW input power and with a tunable range from 1.57 GHz to 1.90 GHz by modulating the outer conductor. It is worth to note that the efficiency can reach as high as 41% at 1.75 GHz. The mechanical engineering method is also detailed in this work. The frequency tuning range of the coaxial TTO is 22.6% of the central frequency. On the other hand, the frequency can be tuned from 1.6 GHz to 1.85 GHz by modulating the inner conductor. The author highlights a hollow structure of the L-band coaxial TTO which can work from 1.03 GHz to 1.31 GHz via modulating the outer conductor in the rest of the article. The frequency tuning range of the hollow TTO is 21.4% of the central frequency. More importantly, the hollow TTO can be easily achieved after the inner conductor is removed from the coaxial TTO. The electric field distributions of the coaxial and hollow TTOs are analyzed, resulting in that the longitudinal and transverse working modes are TM01 and π mode, respectively. The same working mode from these two structures implies the stability of the TTOs mentioned above.

Aquarius L-Band Radiometers Calibration Using Cold Sky Observations

NASA Technical Reports Server (NTRS)

Dinnat, Emmanuel P.; Le Vine, David M.; Piepmeier, Jeffrey R.; Brown, Shannon T.; Hong, Liang

2015-01-01

An important element in the calibration plan for the Aquarius radiometers is to look at the cold sky. This involves rotating the satellite 180 degrees from its nominal Earth viewing configuration to point the main beams at the celestial sky. At L-band, the cold sky provides a stable, well-characterized scene to be used as a calibration reference. This paper describes the cold sky calibration for Aquarius and how it is used as part of the absolute calibration. Cold sky observations helped establish the radiometer bias, by correcting for an error in the spillover lobe of the antenna pattern, and monitor the long-term radiometer drift.

Multiwavelength L-band fiber laser with bismuth-oxide EDF and photonic crystal fiber

NASA Astrophysics Data System (ADS)

Ramzia Salem, A. M.; Al-Mansoori, M. H.; Hizam, H.; Mohd Noor, S. B.; Abu Bakar, M. H.; Mahdi, M. A.

2011-05-01

A multiwavelength laser comb using a bismuth-based erbium-doped fiber and 50 m photonic crystal fiber is demonstrated in a ring cavity configuration. The fiber laser is solely pumped by a single 1455 nm Raman pump laser to exploit its higher power delivery compared to that of a single-mode laser diode pump. At 264 mW Raman pump power and 1 mW Brillouin pump power, 38 output channels in the L-band have been realized with an optical signal-to-noise ratio above 15 dB and a Stokes line spacing of 0.08 nm. The laser exhibits a tuning range of 12 nm and produces stable Stokes lines across the tuning range between Brillouin pump wavelengths of 1603 nm and 1615 nm.

Radar measurement of L-band signal fluctuations caused by propagation through trees

NASA Technical Reports Server (NTRS)

Durden, Stephen L.; Klein, Jeffrey D.; Zebker, Howard A.

1991-01-01

Fluctuations of an L-band, horizontally polarized signal that was transmitted from the ground through a coniferous forest canopy to an airborne radar are examined. The azimuth synthetic aperture radar (SAR) impulse response in the presence of the measured magnitude fluctuations shows increased sidelobes over the case with no trees. Statistics of the observed fluctuations are similar to other observations.

Wide-band fanned-out supercontinuum source covering O-, E-, S-, C-, L- and U-bands

NASA Astrophysics Data System (ADS)

Ahmad, H.; Latif, A. A.; Awang, N. A.; Zulkifli, M. Z.; Thambiratnam, K.; Ghani, Z. A.; Harun, S. W.

2012-10-01

A wide-band supercontinuum source generated by mode-locked pulses injected into a Highly Non-Linear Fiber (HNLF) is proposed and demonstrated. A 49 cm long Bismuth-Erbium Doped Fiber (Bi-EDF) pumped by two 1480 nm laser diodes acts as the active gain medium for a ring fiber laser, from which mode-locked pulses are obtained using the Non-Polarization Rotation (NPR) technique. The mode-locked pulses are then injected into a 100 m long HLNF with a dispersion of 0.15 ps/nm km at 1550 nm to generate a supercontinuum spectrum spanning from 1340 nm to more than 1680 nm with a pulse width of 0.08 ps and an average power of -17 dBm. The supercontinuum spectrum is sliced using a 24 channel Arrayed Waveguide Grating (AWG) with a channel spacing of 100 GHz to obtain a fanned-out laser output covering the O-, E-, S-, C-, L- and U-bands. The lasing wavelengths obtained have an average pulse width of 9 ps with only minor fluctuations and a mode-locked repetition rate of 40 MHz, and is sufficiently stable to be used in a variety of sensing and communication applications, most notably as cost-effective sources for Fiber-to-the-Home (FTTH) networks.

Random forest wetland classification using ALOS-2 L-band, RADARSAT-2 C-band, and TerraSAR-X imagery

NASA Astrophysics Data System (ADS)

Mahdianpari, Masoud; Salehi, Bahram; Mohammadimanesh, Fariba; Motagh, Mahdi

2017-08-01

Wetlands are important ecosystems around the world, although they are degraded due both to anthropogenic and natural process. Newfoundland is among the richest Canadian province in terms of different wetland classes. Herbaceous wetlands cover extensive areas of the Avalon Peninsula, which are the habitat of a number of animal and plant species. In this study, a novel hierarchical object-based Random Forest (RF) classification approach is proposed for discriminating between different wetland classes in a sub-region located in the north eastern portion of the Avalon Peninsula. Particularly, multi-polarization and multi-frequency SAR data, including X-band TerraSAR-X single polarized (HH), L-band ALOS-2 dual polarized (HH/HV), and C-band RADARSAT-2 fully polarized images, were applied in different classification levels. First, a SAR backscatter analysis of different land cover types was performed by training data and used in Level-I classification to separate water from non-water classes. This was followed by Level-II classification, wherein the water class was further divided into shallow- and deep-water classes, and the non-water class was partitioned into herbaceous and non-herbaceous classes. In Level-III classification, the herbaceous class was further divided into bog, fen, and marsh classes, while the non-herbaceous class was subsequently partitioned into urban, upland, and swamp classes. In Level-II and -III classifications, different polarimetric decomposition approaches, including Cloude-Pottier, Freeman-Durden, Yamaguchi decompositions, and Kennaugh matrix elements were extracted to aid the RF classifier. The overall accuracy and kappa coefficient were determined in each classification level for evaluating the classification results. The importance of input features was also determined using the variable importance obtained by RF. It was found that the Kennaugh matrix elements, Yamaguchi, and Freeman-Durden decompositions were the most important parameters

Use of IRI to Model the Effect of Ionosphere Emission on Earth Remote Sensing at L-Band

NASA Technical Reports Server (NTRS)

Abraham, Saji; LeVine, David M.

2004-01-01

Microwave remote sensing in the window at 1.413 GHz (L-band) set aside for passive use only is important for monitoring sea surface salinity and soil moisture. These parameters are important for understanding ocean dynamics and energy exchange between the surface and atmosphere, and both NASA and ESA plan to launch satellite sensors to monitor these parameters at L-band (Aquarius, Hydros and SMOS). The ionosphere is an important source of error for passive remote sensing at this frequency. In addition to Faraday rotation, emission from the ionosphere is also a potential source of error at L-band. As an aid for correcting for emission, a regression model is presented that relates ionosphere emission to the integrated electron density (TEC). The goal is to use TEC from sources such as TOPEX, JASON or GPS to obtain estimates of emission over the oceans where the electron density profiles needed to compute emission are not available. In addition, data will also be presented to evaluate the use of the IRI for computing emission over the ocean.

Measurement and Analysis of L-Band (1535-1660 MHz) Electromagnetic (EM) Noise on Ships

DOT National Transportation Integrated Search

1974-12-01

A program of L-band (1535-1660 MHz) electromagnetic (EM) noise measurements conducted on ships is described. The magnitude and duration of EM noise on ships is of particular significance in terms of potential radio frequency interference (RFI) to fut...

Systems implications of L-band fade data statistics for LEO mobile systems

NASA Astrophysics Data System (ADS)

Devieux, Carrie L.

This paper examines and analyzes research data on the role of foliage attenuation in signal fading between a satellite transmitter and a terrestrial vehicle-mounted receiver. The frequency band of measurement, called L-Band, includes the region 1610.0 to 1626.5 MHz. Data from tests involving various combinations of foliage and vehicle movement conditions clearly show evidence of fast fading (in excess of 0.5 dB per millisecond) and fade depths as great or greater than 16 dB. As a result, the design of a communications link power control that provides the level of accuracy necessary for power sensitive systems could be significantly impacted. Specific examples of this include the communications links that employ Code Division Multiple Access (CDMA) as a modulation technique.

Systems implications of L-band fade data statistics for LEO mobile systems

NASA Technical Reports Server (NTRS)

Devieux, Carrie L.

1993-01-01

This paper examines and analyzes research data on the role of foliage attenuation in signal fading between a satellite transmitter and a terrestrial vehicle-mounted receiver. The frequency band of measurement, called L-Band, includes the region 1610.0 to 1626.5 MHz. Data from tests involving various combinations of foliage and vehicle movement conditions clearly show evidence of fast fading (in excess of 0.5 dB per millisecond) and fade depths as great or greater than 16 dB. As a result, the design of a communications link power control that provides the level of accuracy necessary for power sensitive systems could be significantly impacted. Specific examples of this include the communications links that employ Code Division Multiple Access (CDMA) as a modulation technique.

Theoretical performance analysis of doped optical fibers based on pseudo parameters

NASA Astrophysics Data System (ADS)

Karimi, Maryam; Seraji, Faramarz E.

2010-09-01

Characterization of doped optical fibers (DOFs) is an essential primary stage for design of DOF-based devices. This paper presents design of novel measurement techniques to determine DOFs parameters using mono-beam propagation in a low-loss medium by generating pseudo parameters for the DOFs. The designed techniques are able to characterize simultaneously the absorption, emission cross-sections (ACS and ECS), and dopant concentration of DOFs. In both the proposed techniques, we assume pseudo parameters for the DOFs instead of their actual values and show that the choice of these pseudo parameters values for design of DOF-based devices, such as erbium-doped fiber amplifier (EDFA), are appropriate and the resulting error is quite negligible when compared with the actual parameters values.Utilization of pseudo ACS and ECS values in design procedure of EDFAs does not require the measurement of background loss coefficient (BLC) and makes the rate equation of the DOFs simple. It is shown that by using the pseudo parameters values obtained by the proposed techniques, the error in the gain of a designed EDFA with a BLC of about 1 dB/km, are about 0.08 dB. It is further indicated that the same scenario holds good for BLC lower than 5 dB/m and higher than 12 dB/m. The proposed characterization techniques have simple procedures and are low cost that can have an advantageous use in manufacturing of the DOFs.

L band brightness temperature observations over a corn canopy during the entire growth cycle

USDA-ARS?s Scientific Manuscript database

During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (T¬B) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive characte...

40  Gb/s DWDM Structure with Optical Phase Configuration for Long-Haul Transmission System

NASA Astrophysics Data System (ADS)

Lin, Hsiu-Sheng; Lai, Po-Chou

2017-06-01

We propose the experimental transport of 48 channels with 40 Gbit/s dense wavelength-division multiplexing (DWDM) system that uses single-mode fiber (SMF) in combination with dispersion compensation fiber (DCF) which is a dispersion compensation device, in C and L band wavelength range to solve the dispersion program. The DWDM system scheme employing single Mach-Zehnder modulation (MZM) return-to-zero differential phase-shift keying (RZ-DPSK) modulation format with hybrid Raman/EDFA (Erbium-doped fiber amplifier) configuration to improve transmission signal, and employing an optical phase conjugation (OPC) configuration in the middle line. That can compensate for dispersion impairment and improve nonlinear effects to investigate transmission distance performances.

Airborne Active and Passive L-Band Observations in Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12)

NASA Astrophysics Data System (ADS)

Colliander, A.; Yueh, S. H.; Chazanoff, S.; Jackson, T. J.; McNairn, H.; Bullock, P.; Wiseman, G.; Berg, A. A.; Magagi, R.; Njoku, E. G.

2012-12-01

NASA's (National Aeronautics and Space Administration) Soil Moisture Active Passive (SMAP) Mission is scheduled for launch in October 2014. The objective of the mission is global mapping of soil moisture and freeze/thaw state. Merging of active and passive L-band observations of the mission will enable unprecedented combination of accuracy, resolution, coverage and revisit-time for soil moisture and freeze/thaw state retrieval. For pre-launch algorithm development and validation the SMAP project and NASA coordinated a field campaign named as SMAPVEX12 (Soil Moisture Active Passive Validation Experiment 2012) together with Agriculture and Agri-Food Canada in the vicinity of Winnipeg, Canada in June-July, 2012. The main objective of SMAPVEX12 was acquisition of data record that features long-time series with varying soil moisture and vegetation conditions (for testing the application of time-series approach) over aerial domain of multiple parallel lines (for spatial disaggregation studies). The coincident active and passive L-band data were acquired using the Passive Active L-band System (PALS), which is an airborne radiometer and radar developed for testing L-band retrieval algorithms. For SMAPVEX12 PALS was installed on a Twin Otter aircraft. The flight plan included flights at two altitudes. The higher altitude was used to map the whole experiment domain and the lower altitude was used to obtain measurements over a specific set of field sites. The spatial resolution (and swath) of the radar and radiometer from low altitude was about 600 m and from high altitude about 1500 m. The PALS acquisitions were complemented with high resolution (~10 m) L-band SAR measurements carried out by UAVSAR instrument on-board G-III aircraft. The campaign ran from June 7 until July 19. The PALS instrument conducted 17 brightness temperature and backscatter measurement flights and the UAVSAR conducted 14 backscatter measurement flights. The airborne data acquisition was supported by

The Marvels of Electromagnetic Band Gap (EBG) Structures

DTIC Science & Technology

2003-11-01

terminology of "Electromagnetic conference papers and journal articles dealing with Band- gaps (EBG)". Recently, many researchers the characterizations...Band Gap (EBG) Structures 9 utilized to reduce the mutual coupling between Structures: An FDTD/Prony Technique elements of antenna arrays. based on the...Band- Gap of several patents. He has had pioneering research contributions in diverse areas of electromagnetics,Snteructure", Dymposiget o l 21 IE 48

Space-Based Telemetry and Range Safety Project Ku-Band and Ka-Band Phased Array Antenna

NASA Technical Reports Server (NTRS)

Whiteman, Donald E.; Valencia, Lisa M.; Birr, Richard B.

2005-01-01

The National Aeronautics and Space Administration Space-Based Telemetry and Range Safety study is a multiphase project to increase data rates and flexibility and decrease costs by using space-based communications assets for telemetry during launches and landings. Phase 1 used standard S-band antennas with the Tracking and Data Relay Satellite System to obtain a baseline performance. The selection process and available resources for Phase 2 resulted in a Ku-band phased array antenna system. Several development efforts are under way for a Ka-band phased array antenna system for Phase 3. Each phase includes test flights to demonstrate performance and capabilities. Successful completion of this project will result in a set of communications requirements for the next generation of launch vehicles.

Band-edges and band-gap in few-layered transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Bhunia, Hrishikesh; Pal, Amlan J.

2018-05-01

We have considered liquid-exfoliated transition metal dichalcogenides (WS2, WSe2, MoS2, and MoSe2) and studied their band-edges and band-gap through scanning tunneling spectroscopy (STS) and density of states. A monolayer, bilayer (2L), and trilayer (3L) of each of the layered materials were characterized to derive the energies. Upon an increase in the number of layers, both the band-edges were found to shift towards the Fermi energy. The results from the exfoliated nanosheets have been compared with reported STS studies of MoS2 and WSe2 formed through chemical vapor deposition or molecular beam epitaxy methods; an uncontrolled lattice strain existed in such 2L and 3L nanoflakes due to mismatch in stacking-patterns between the monolayers affecting their energies. In the present work, the layers formed through the liquid-exfoliation process retained their interlayer coupling or stacking-sequence prevalent to the bulk and hence allowed determination of band-energies in these strain-free two-dimensional materials.

Pass-Band Characteristics of an L-Shaped Waveguide in a Diamond Structure Photonic Crystal

NASA Astrophysics Data System (ADS)

Chen, Shibin; Ma, Jingcun; Yao, Yunshi; Liu, Xin; Lin, Ping

2018-06-01

The conduction characteristics of a L-shaped waveguide in a diamond structure photonic crystal is investigated in this paper. The waveguides were fabricated with titanium dioxide ceramic via 3-D printing and sintering. The effects of the position and size of line defects on the transmission characteristics are first simulated using a finite-difference time-domain method. The simulated results show that, when the length of the rectangular defect equals the lattice constant, multiple extended modes are generated. When the centers of the single unit cell of the diamond structure and the line defect waveguide coincide, higher transmission efficiency in the line defect can be achieved. In addition, the corner of the L-shaped waveguide was optimized to reduce reflection loss at the turning point using the arc transition of the large diameter. Our experimental results indicate that L-shaped waveguides with an optimized photonic band gap structure and high-K materials can produce a pass-band between 13.8 GHz and 14.4 GHz and increase transmission efficiency. The computed results agree with the experimental results. Our results may help the integration of microwave devices in the future and possibly enable new applications of photonic crystals.

Recalibration and Validation of the SMAP L-Band Radiometer

NASA Technical Reports Server (NTRS)

Peng, Jinzheng; Piepmeier, Jeffrey; Le Vine, David M.; Dinnat, Emmanuel; Bindlish, Rajat; De amici, Giovanni; Mohammed, Priscilla; Misra, Sidharth; Yueh, Simon; Meissner, Thomas

2017-01-01

SMAP mission was launched on 31st January 2015 in a 6 AM 6 PM sun-synchronous orbit at 685 km altitude to measure soil moisture and freethaw globally. The passive instrument of SMAP is a fully polarimetric L-band radiometer (1.4GHz) operating with a bandwidth of 24MHz. The radiometer L1B data product version 3 has been released for public science activities. Post-launch calibration and validation activities are described in [4,5]. Validation results show that SMAP antenna temperature (TA) is 2.6 K warmer over galactic Cold Sky (CS), and land TB is 2.6 K colder comparing to SMOS land TB (compared at the top of the atmosphere) after the update of the reflectors thermal model. Due to the biases, the SMAP radiometer is under re-calibration for next data release in 2018.We present the updated calibration approaches for the SMAP radiometer product. We will discuss the various radiometer calibration parameters and part of the validation process and result.

High power passive mode-locked L-band fiber laser based on microfiber topological insulator saturable absorber

NASA Astrophysics Data System (ADS)

Semaan, Georges; Meng, Yichang; Salhi, Mohamed; Niang, Alioune; Guesmi, Khmaies; Luo, Zhi-Chao; Sanchez, Francois

2016-04-01

In this communication, we demonstrate a passive mode-locked Er:Yb co-doped double-clad fiber laser using a tapered microfiber topological insulator (Bi2Se3) saturable absorber (TISA). The topological insulator is drop-casted onto the tapered fiber and optically deposited by optical tweezer effect. We use a ring laser setup including the fabricated TISA. By carefully optimizing the cavity losses and output coupling ratio, the mode-locked laser can operate in L-band with a high average output power. At a maximum pump power of 5 W, we obtain the 91st harmonic mode-locking of soliton bunches with a 3dB spectral bandwidth of 1.06nm, a repetition rate of 640.9 MHz and an average output power of 308mW. As far as we know, this is the highest output power yet reported of a mode-locked fiber laser operating with a TISA.

L band InSAR sudy on the Ganos section of the North Anatolian Fault Zone (NAFZ)

NASA Astrophysics Data System (ADS)

de Michele, Marcello

2016-04-01

The North Anatolian Fault (NAF), with a total length of about 1500 km, is one of the most active right-lateral strike-slip faults in the world. It defines the tectonic boundary between the Anatolian Plate and the Eurasian Plate in northern Turkey, accommodating ~14-30 mm/yr of relative plate motion between the two plates (fig. 1). The Gazikoy-Saros segment (the Ganos fault, GF) is the onshore segment of the northern strand of the NAF between the Marmara Sea and the Gulf of Saros. It was last ruptured in 1912 with a Ms=7.4 earthquake that broke the entire inland segment of the fault, a length of about 50 km, and produced a right-lateral strike-slip component of at least 3 m. Other large historical earthquakes that have been attributed to the Ganos fault occurred in A.D. 824, 1343, 1509 and 1766 (e. g. Reilinger et al., 2000; Meade et al., 2002; Motagh et al., 2007; Janssen et al., 2009; Megraoui et al., 2012 ; Ersen Aksoy et al., 2010). The GF forms a 45 km long linear fault system and represents the link between the northern strand of the NAFZ in the Sea of Marmara and the North Aegean Trough where slip partitioning results in branching of the fault zone. The present study aims at showing the results retrieved from L band Interferometric Syntethic Aperture Radar (InSAR) measurements for the monitoring of Crustal Deformation in the Anatolian Fault Zone in the frame of the MARMARA SUPERSITE PROJECT "MARSITE" on the Ganos section of the North Anatolian fault zone. We processed SAR data made available through the CAT-1 ESA (European Space Agency) archives, acquired by the L-band radar sensor ALOS PALSAR between 2007 and 2011. The aim of this exercise is to test L-band capabilities to map the spatial and temporal evolution of the present-day crustal deformation phenomena affecting the Ganos section of the NAFZ with high level of spatial details. The goal of this task is to assess whether InSAR L-Band data can be useful to evaluate the long-term behavior of active faults

On the use of L-band microwave and multi-mission EO data for high resolution soil moisture

NASA Astrophysics Data System (ADS)

Bitar, Ahmad Al; Merlin, Olivier; Malbeteau, Yoann; Molero-Rodenas, Beatriz; Zribi, Mehrez; Sekhar, Muddu; Tomer, Sat Kumar; José Escorihuela, Maria; Stefan, Vivien; Suere, Christophe; Mialon, Arnaud; Kerr, Yann

2017-04-01

Sub-kilometric soil moisture maps have been increasingly mentioned as a need in the scientific community for many applications ranging from agronomical and hydrological (Wood et al. 2011). For example, this type of dataset will become essential to support the current evolution of the land surface and hydrologic modelling communities towards high resolution global modelling. But the ability of the different sensors to monitor soil moisture is different. The L-Band microwave EO provides, at a coarse resolution, the most sensitive information to surface soil moisture when compared to C-Band microwave, optical or C-band SAR. On the other hand the optical and radar sensors provide the spatial distribution of associated variables like surface soil moisture,surface temperature or vegetation leaf area index. This paper describes two complementary fusion approaches to obtain such data from optical or SAR in combination to microwave EO, and more precisely L-Band microwave from the SMOS mission. The first approach, called MAPSM, is based on the use of high resolution soil moisture from SAR and microwave. The two types of sensors have all weather capabilities. The approach uses the new concept of water change capacity (Tomer et al. 2015, 2016). It has been applied to the Berambadi watershed in South-India which is characterised by high cloud coverage. The second approach, called Dispatch, is based on the use of optical sensors in a physical disaggregation approach. It is a well-established approach (Merlin et al. 2012, Malbeteau et al. 2015) that has been implemented operationally in the CATDS (Centre Aval de Traitement des Données SMOS) processing centre (Molero et al. 2016). An analysis on the complementarity of the approaches is discussed. The results show the performances of the methods when compared to existing soil moisture monitoring networks in arid, sub-tropical and humid environments. They emphasis on the need for large inter-comparison studied for the qualification

21-nm-range wavelength-tunable L-band Er-doped fiber linear-cavity laser

NASA Astrophysics Data System (ADS)

Yang, Shiquan; Zhao, Chunliu; Li, Zhaohui; Ding, Lei; Yuan, Shuzhong; Dong, Xiaoyi

2001-10-01

A novel method, which utilizes amplified spontaneous emission (ASE) as a secondary pump source, is presented for implanting a linear cavity erbium-doped fiber laser operating in L-Band. The output wavelength tuned from 1566 nm to 1587 nm, about 21 nm tuning range, was obtained in the experiment and the stability of the laser is very good.

Proposal of a gigawatt-class L/Ku dual-band magnetically insulated transmission line oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ju, J.-C., E-mail: jujinchuan@126.com; Fan, Y.-W.; Shu, T.

2014-10-15

We present a gigawatt (GW)-class magnetically insulated transmission line oscillator (MILO) which is capable of generating dual-band high power microwaves (HPMs). The proposed device, deriving from previously studied complex MILO and dual-frequency MILO, is designed to produce two HPMs in L-band and Ku-band, respectively. It is found in particle-in-cell (PIC) simulation that when the diode voltage is 610 kV, HPMs with frequencies of 1.72 GHz and 14.6 GHz can be achieved with powers of 3.3 GW and 2.4 GW, respectively. The corresponding total power conversion efficiency is approximately 12.8%. Power difference of the two generated HPMs is approximately 1.4 dB, and frequency difference of themmore » reaches a level as high as ∼10 dB.« less

L-Band RFI in Japan

NASA Technical Reports Server (NTRS)

Soldo, Yan; de Matthaeis, Paolo; Le Vine, David M.

2016-01-01

In recent years, three instruments have been launched into orbit with the aim of producing global maps of sea surface salinity and soil moisture using the 1400-1427 MHz band: SMOS, Aquarius and SMAP. Although this frequency band is allocated to passive measurements only, RFI (Radio-Frequency Interference) is present in the data of all three missions. On a global scale, the three sensors have observed approximately the same distribution of RFI. Japan is an important exception that has implications for the design of RFI detection algorithms. RFI in Japan is caused by a large number of emitters belonging to the same system (TV receivers) and for this reason some traditional RFI detection strategies detect little to no RFI over Japan. The study of this case has led to an improvement of the approach to detect RFI in Aquarius data.

Application of the Tor Vergata Scattering Model to L Band Backscatter During the Corn Growth Cycle

NASA Astrophysics Data System (ADS)

Joseph, A. T.; van der Velde, R.; Choudhury, B. J.; Ferrazzoli, P.; O'Neill, P. E.; Kim, E. J.; Lang, R. H.; Gish, T.

2010-12-01

At the USDA’s Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) experimental site in Beltsville (Maryland, USA) a field campaign took place throughout the 2002 corn growth cycle from May 10th (emergence of corn crops) to October 2nd (harvest). One of the microwave instruments deployed was the multi-frequency (X-, C- and L-band) quad-polarized (HH, HV, VV, VH) NASA GSFC / George Washington University (GWU) truck mounted radar. During the field campaign, this radar system provided once a week fully polarized C- and L-band (4.75 and 1.6 GHz) backscatter measurements from incidence angle of 15, 35, and 55 degrees. In support of these microwave observations, an extensive ground characterization took place, which included measurements of surface roughness, soil moisture, vegetation biomass and morphology. The field conditions during the campaign are characterized by several dry downs with a period of drought in the month of August. Peak biomass of the corn canopies was reached at July 24th with a total biomass of approximately 6.5 kg m-2. This dynamic range in both soil moisture and vegetation conditions within the data set is ideal for the validation of discrete medium vegetation scattering models. In this study, we compare the L band backscatter measurements with simulations by the Tor Vergata model (Ferrazzoli and Guerriero 1996). The measured soil moisture, vegetation biomass and most reliably measured vegetation morphological parameters (e.g. number of leaves, number of stems and stem height) were used as input for the Tor Vergata model. The more uncertain model parameters (e.g. surface roughness, leaf thickness) and the stem diameter were optimized using a parameter estimation routine based on the Levenberg-Marquardt algorithm. As cost function for this optimization, the HH and VV polarized backscatter measured and simulated by the Tor Vergata model for incidence angle of 15, 35 and 55 degrees were used (6 measurements in total). The

Application of the Tor Vergata Scattering Model to L Band Backscatter During the Corn Growth Cycle

NASA Technical Reports Server (NTRS)

Joseph, A. T.; vanderVelde, R.; ONeill, P. E.; Lang, R.; Gish, T.

2010-01-01

At the USDA's Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) experimental site in Beltsville, Maryland, USA) a field campaign took place throughout the 2002 corn growth cycle from May 10th (emergence of corn crops) to October 2nd (harvest). One of the microwave instruments deployed was the multi-frequency (X-, C- and L-band) quad-polarized (HH, HV, VV, VH) NASA GSFC/George Washington University (GWU) truck mounted radar. During the field campaign, this radar system provided once a week fully polarized C- and L-band (4.75 and 1.6 GHz) backscatter measurements from incidence angle of 15, 35, and 55 degrees. In support of microwave observations, an extensive ground characterization took place, which included measurements of surface roughness, soil moisture, vegetation biomass and morphology. The field conditions during the campaign are characterized by several dry downs with a period of drought in the month of August. Peak biomass the corn canopies was reached on July 24th with a total biomass of approximately 6.5 kg/sq m. This dynamic range in both soil moisture and vegetation conditions within the data set is ideal for the validation of discrete medium vegetation scattering models. In this study, we compare the L band backscatter measurements with simulations by the Tor Vergata model (ferrazzoli and Guerriero 1996). The measured soil moisture, vegetation biomass and most reliably measured vegetation morphological parameters (e.g. number of leaves, number of stems and stem height) were used as input for the Tor Vergata model. The more uncertain model parameters (e.g. surface roughness, leaf thickness) and the stem diameter were optimized using a parameter estimation routine based on the Levenberg-Marquardt algorithm. As cost function for this optimization, the HH and VV polarized backscatter measured and stimulated by the TOR Vergata model for incidence angle of 15, 35, and 55 degrees were used (6 measurements in total). The calibrated

Multipolarization P-, L-, and C-band radar for coastal zone mapping - The Louisiana example

NASA Technical Reports Server (NTRS)

Wu, Shih-Tseng

1989-01-01

Multipolarization P-, L-, and C-band airborne SAR data sets were acquired over a coastal zone and a forested wetland of southern Louisiana. The data sets were used with field-collected surface-parameter data in order to determine the value of SAR systems in assessing and mapping coastal-zone surface features. The coastal-zone surface features in this study are sediments, sediment distribution, and the formation of new isles and banks. Results of the data analysis indicate that the P-band radar with 68-cm wavelength is capable of detecting the submerged sediment if the area is very shallow (i.e., a water depth of less than one meter). The penetration capability of P-band radar is also demonstrated in the forested wetland area. The composition and condition of the ground surface can be detected, as well as the standing water beneath dense tree leaves.

Multi-Band Received Signal Strength Fingerprinting Based Indoor Location System

NASA Astrophysics Data System (ADS)

Sertthin, Chinnapat; Fujii, Takeo; Ohtsuki, Tomoaki; Nakagawa, Masao

This paper proposes a new multi-band received signal strength (MRSS) fingerprinting based indoor location system, which employs the frequency diversity on the conventional single-band received signal strength (RSS) fingerprinting based indoor location system. In the proposed system, the impacts of frequency diversity on the enhancements of positioning accuracy are analyzed. Effectiveness of the proposed system is proved by experimental approach, which was conducted in non line-of-sight (NLOS) environment under the area of 103m2 at Yagami Campus, Keio University. WLAN access points, which simultaneously transmit dual-band signal of 2.4 and 5.2GHz, are utilized as transmitters. Likewise, a dual-band WLAN receiver is utilized as a receiver. Signal distances calculated by both Manhattan and Euclidean were classified by K-Nearest Neighbor (KNN) classifier to illustrate the performance of the proposed system. The results confirmed that Frequency diversity attributions of multi-band signal provide accuracy improvement over 50% of the conventional single-band.

The DSS-14 C-band exciter

NASA Technical Reports Server (NTRS)

Rowan, D. R.

1989-01-01

The development and implementation of a C-band exciter for use with the Block IV Receiver-Exciter Subsystem at Deep Space Station 14 (DSS-14) has been completed. The exciter supplements the standard capabilities of the Block IV system by providing a drive signal for the C-band transmitter while generating coherent translation frequencies for C-band (5-GHz) to S-band (2.2- to 2.3-GHz) Doppler extraction, C-band to L-band (1.6-GHz) zero delay measurements, and a level calibrated L-band test signal. Exciter functions are described, and a general explanation and description of the C-band uplink controller is presented.

Spatial Mutual Information Based Hyperspectral Band Selection for Classification

PubMed Central

2015-01-01

The amount of information involved in hyperspectral imaging is large. Hyperspectral band selection is a popular method for reducing dimensionality. Several information based measures such as mutual information have been proposed to reduce information redundancy among spectral bands. Unfortunately, mutual information does not take into account the spatial dependency between adjacent pixels in images thus reducing its robustness as a similarity measure. In this paper, we propose a new band selection method based on spatial mutual information. As validation criteria, a supervised classification method using support vector machine (SVM) is used. Experimental results of the classification of hyperspectral datasets show that the proposed method can achieve more accurate results. PMID:25918742

Unusual large-pitch banding in poly(L-lactic acid): Effects of composition and geometry confinement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woo, Eamor M.; Lugito, Graecia; Hsieh, Ya-Ting

2014-02-24

Lamellar patterns and orientations in blends of two crystalline polymers: poly(ethylene oxide) (PEO) and low-molecular-weight poly(L-lactic acid) (PLLA) were investigated using polarizing light optical microscopy (POM), and atomic and scanning electron microscopy (AFM, SEM). Specific etching off of PEO was used to reveal the complex earlier-grown PLLA lamellae patterns with various PEO content in blends. Banding of extremely long pitch (50 μm) in crystallized PLLA spherulites was induced by two kinetic factors: geometry confinement by top cover and introduction of diluent such as PEO. The mechanisms and correlation among the lamellar assembly, ring bands, and cracks are exemplified. Lamellar patternsmore » and ring-band types in blends were found to vary with respect to not only blend compositions, but also confinement of top-cover.« less

Commissioning and first light results of an L'-band vortex coronagraph with the Keck II adaptive optics NIRC2 science instrument

NASA Astrophysics Data System (ADS)

Femenía Castellá, Bruno; Serabyn, Eugene; Mawet, Dimitri; Absil, Olivier; Wizinowich, Peter; Matthews, Keith; Huby, Elsa; Bottom, Michael; Campbell, Randy; Chan, Dwight; Carlomagno, Brunella; Cetre, Sylvain; Defrère, Denis; Delacroix, Christian; Gomez Gonzalez, Carlos; Jolivet, Aïssa; Karlsson, Mikael; Lanclos, Kyle; Lilley, Scott; Milner, Steven; Ngo, Henry; Reggiani, Maddalena; Simmons, Julia; Tran, Hien; Vargas Catalan, Ernesto; Wertz, Olivier

2016-07-01

On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7μm. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B.

25 Tb/s transmission over 5,530 km using 16QAM at 5.2 b/s/Hz spectral efficiency.

PubMed

Cai, J-X; Batshon, H G; Zhang, H; Davidson, C R; Sun, Y; Mazurczyk, M; Foursa, D G; Sinkin, O; Pilipetskii, A; Mohs, G; Bergano, Neal S

2013-01-28

We transmit 250x100G PDM RZ-16QAM channels with 5.2 b/s/Hz spectral efficiency over 5,530 km using single-stage C-band EDFAs equalized to 40 nm. We use single parity check coded modulation and all channels are decoded with no errors after iterative decoding between a MAP decoder and an LDPC based FEC algorithm. We also observe that the optimum power spectral density is nearly independent of SE, signal baud rate or modulation format in a dispersion uncompensated system.

Coherent model of L-band radar scattering by soybean plants: model development, validation and retrieval

USDA-ARS?s Scientific Manuscript database

An improved coherent branching model for L-band radar remote sensing of soybean is proposed by taking into account the correlated scattering among scatterers. The novel feature of the analytic coherent model consists of conditional probability functions to eliminate the overlapping effects of branc...

Weekly Gridded Aquarius L-band Radiometer-Scatterometer Observations and Salinity Retrievals over the Polar Regions - Part 2: Initial Product Analysis

NASA Technical Reports Server (NTRS)

Brucker, L.; Dinnat, E. P.; Koenig, L. S.

2014-01-01

Following the development and availability of Aquarius weekly polar-gridded products, this study presents the spatial and temporal radiometer and scatterometer observations at L band (frequency1.4 GHz) over the cryosphere including the Greenland and Antarctic ice sheets, sea ice in both hemispheres, and over sub-Arctic land for monitoring the soil freeze-thaw state. We provide multiple examples of scientific applications for the L-band data over the cryosphere. For example, we show that over the Greenland Ice Sheet, the unusual 2012 melt event lead to an L-band brightness temperature (TB) sustained decrease of 5 K at horizontal polarization. Over the Antarctic ice sheet, normalized radar cross section (NRCS) observations recorded during ascending and descending orbits are significantly different, highlighting the anisotropy of the ice cover. Over sub-Arctic land, both passive and active observations show distinct values depending on the soil physical state (freeze-thaw). Aquarius sea surface salinity (SSS) retrievals in the polar waters are also presented. SSS variations could serve as an indicator of fresh water input to the ocean from the cryosphere, however the presence of sea ice often contaminates the SSS retrievals, hindering the analysis. The weekly grided Aquarius L-band products used a redistributed by the US Snow and Ice Data Center at http:nsidc.orgdataaquariusindex.html, and show potential for cryospheric studies.

The design of a linear L-band high power amplifier for mobile communication satellites

NASA Technical Reports Server (NTRS)

Whittaker, N.; Brassard, G.; Li, E.; Goux, P.

1990-01-01

A linear L-band solid state high power amplifier designed for the space segment of the Mobile Satellite (MSAT) mobile communication system is described. The amplifier is capable of producing 35 watts of RF power with multitone signal at an efficiency of 25 percent and with intermodulation products better than 16 dB below carrier.

Dual band metamaterial perfect absorber based on artificial dielectric "molecules".

PubMed

Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

2016-07-13

Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence.

Station to instrumented aircraft L-band telemetry system and RF signal controller for spacecraft simulations and station calibration

NASA Technical Reports Server (NTRS)

Scaffidi, C. A.; Stocklin, F. J.; Feldman, M. B.

1971-01-01

An L-band telemetry system designed to provide the capability of near-real-time processing of calibration data is described. The system also provides the capability of performing computerized spacecraft simulations, with the aircraft as a data source, and evaluating the network response. The salient characteristics of a telemetry analysis and simulation program (TASP) are discussed, together with the results of TASP testing. The results of the L-band system testing have successfully demonstrated the capability of near-real-time processing of telemetry test data, the control of the ground-received signal to within + or - 0.5 db, and the computer generation of test signals.

Accurate Measurements of the Dielectric Constant of Seawater at L Band

NASA Technical Reports Server (NTRS)

Lang, Roger H.; Utku, Cuneyt; Tarkocin, Yalcin; LeVine, David M.

2010-01-01

This report describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz that is at the center of the L-Sand radiometric protected frequency spectrum. Aquarius will be sensing the sea surface salinity from space in this band. The objective of the project is to refine the model function for the dielectric constant as a function of salinity and temperature so that remote sensing measurements can be made with the accuracy needed to meet the measurement goals (0.2 psu) of the Aquarius mission. The measurements were made, using a microwave cavity operated in the transmission configuration. The cavity's temperature was accurately regulated to 0.02 C by immersing it in a temperature controlled bath of distilled water and ethanol glycol. Seawater had been purchased from Ocean Scientific International Limited (OS1L) at salinities of 30, 35 and 38 psu. Measurements of these seawater samples were then made over a range of temperatures, from l0 C to 35 C in 5 C intervals. Repeated measurements were made at each temperature and salinity, Mean values and standard deviations were then computed. Total error budgets indicated that the real and imaginary parts of the dielectric constant had a relative accuracy of about l%.

Integrated optics prototype beam combiner for long baseline interferometry in the L and M bands

NASA Astrophysics Data System (ADS)

Tepper, J.; Labadie, L.; Diener, R.; Minardi, S.; Pott, J.-U.; Thomson, R.; Nolte, S.

2017-06-01

Context. Optical long baseline interferometry is a unique way to study astronomical objects at milli-arcsecond resolutions not attainable with current single-dish telescopes. Yet, the significance of its scientfic return strongly depends on a dense coverage of the uv-plane and a highly stable transfer function of the interferometric instrument. In the last few years, integrated optics (IO) beam combiners have facilitated the emergence of 4-telescope interferometers such as PIONIER or GRAVITY, boosting the imaging capabilities of the VLTI. However, the spectral range beyond 2.2 μm is not ideally covered by the conventional silica based IO. Here, we consider new laser-written IO prototypes made of gallium lanthanum sulfide (GLS) glass, a material that permits access to the mid-infrared spectral regime. Aims: Our goal is to conduct a full characterization of our mid-IR IO two-telescope coupler in order to measure the performance levels directly relevant for long-baseline interferometry. We focus in particular on the exploitation of the L and M astronomical bands. Methods: We use a dedicated Michelson-interferometer setup to perform Fourier transform spectroscopy on the coupler and measure its broadband interferometric performance. We also analyze the polarization properties of the coupler, the differential dispersion and phase degradation, as well as the modal behavior and the total throughput. Results: We measure broadband interferometric contrasts of 94.9% and 92.1% for unpolarized light in the L and M bands. Spectrally integrated splitting ratios are close to 50%, but show chromatic dependence over the considered bandwidths. Additionally, the phase variation due to the combiner is measured and does not exceed 0.04 rad and 0.07 rad across the L and M band, respectively. The total throughput of the coupler including Fresnel and injection losses from free-space is 25.4%. Furthermore, differential birefringence is low (<0.2 rad), in line with the high contrasts

Drought index driven by L-band microwave soil moisture data

NASA Astrophysics Data System (ADS)

Bitar, Ahmad Al; Kerr, Yann; Merlin, Olivier; Cabot, François; Choné, Audrey; Wigneron, Jean-Pierre

2014-05-01

Drought is considered in many areas across the globe as one of the major extreme events. Studies do not all agree on the increase of the frequency of drought events over the past 60 years [1], but they all agree that the impact of droughts has increased and the need for efficient global monitoring tools has become most than ever urgent. Droughts are monitored through drought indexes, many of which are based on precipitation (Palmer index(s), PDI…), on vegetation status (VDI) or on surface temperatures. They can also be derived from climate prediction models outputs. The GMO has selected the (SPI) Standardized Precipitation Index as the reference index for the monitoring of drought at global scale. The drawback of this index is that it is directly dependent on global precipitation products that are not accurate over global scale. On the other hand, Vegetation based indexes show the a posteriori effect of drought, since they are based on NDVI. In this study, we choose to combine the surface soil moisture from microwave sensor with climate data to access a drought index. The microwave data are considered from the SMOS (Soil Moisture and Ocean Salinity) mission at L-Band (1.4 Ghz) interferometric radiometer from ESA (European Space Agency) [2]. Global surface soil moisture maps with 3 days coverage for ascending 6AM and descending 6PM orbits SMOS have been delivered since January 2010 at a 40 km nominal resolution. We use in this study the daily L3 global soil moisture maps from CATDS (Centre Aval de Traitement des Données SMOS) [3,4]. We present a drought index computed by a double bucket hydrological model driven by operational remote sensing data and ancillary datasets. The SPI is also compared to other drought indicators like vegetation indexes and Palmer drought index. Comparison of drought index to vegetation indexes from AVHRR and MODIS over continental United States show that the drought index can be used as an early warning system for drought monitoring as

Modelling the Passive Microwave Signature from Land Surfaces: A Review of Recent Results and Application to the L-Band SMOS SMAP Soil Moisture Retrieval Algorithms

NASA Technical Reports Server (NTRS)

Wigneron, J.-P.; Jackson, T. J.; O'Neill, P.; De Lannoy, G.; De Rosnay, P.; Walker, J. P.; Ferrazzoli, P.; Mironov, V.; Bircher, S.; Grant, J. P.;

Erbium-doped fiber amplifier elements for structural analysis sensors

NASA Technical Reports Server (NTRS)

Hanna-Hawver, P.; Kamdar, K. D.; Mehta, S.; Nagarajan, S.; Nasta, M. H.; Claus, R. O.

1992-01-01

The use of erbium-doped fiber amplifiers (EDFA's) in optical fiber sensor systems for structural analysis is described. EDFA's were developed for primary applications as periodic regenerator amplifiers in long-distance fiber-based communication systems. Their in-line amplification performance also makes them attractive for optical fiber sensor systems which require long effective lengths or the synthesis of special length-dependent signal processing functions. Sensor geometries incorporating EDFA's in recirculating and multiple loop sensors are discussed. Noise and polarization birefringence are also considered, and the experimental development of system components is discussed.

Weekly gridded Aquarius L-band radiometer/scatterometer observations and salinity retrievals over the polar regions - Part 2: Initial product analysis

NASA Astrophysics Data System (ADS)

Brucker, L.; Dinnat, E. P.; Koenig, L. S.

2014-05-01

Following the development and availability of Aquarius weekly polar-gridded products, this study presents the spatial and temporal radiometer and scatterometer observations at L band (frequency ~1.4 GHz) over the cryosphere including the Greenland and Antarctic ice sheets, sea ice in both hemispheres, and over sub-Arctic land for monitoring the soil freeze/thaw state. We provide multiple examples of scientific applications for the L-band data over the cryosphere. For example, we show that over the Greenland Ice Sheet, the unusual 2012 melt event lead to an L-band brightness temperature (TB) sustained decrease of ~5 K at horizontal polarization. Over the Antarctic ice sheet, normalized radar cross section (NRCS) observations recorded during ascending and descending orbits are significantly different, highlighting the anisotropy of the ice cover. Over sub-Arctic land, both passive and active observations show distinct values depending on the soil physical state (freeze/thaw). Aquarius sea surface salinity (SSS) retrievals in the polar waters are also presented. SSS variations could serve as an indicator of fresh water input to the ocean from the cryosphere, however the presence of sea ice often contaminates the SSS retrievals, hindering the analysis. The weekly grided Aquarius L-band products used are distributed by the US Snow and Ice Data Center at http://nsidc.org/data/aquarius/index.html , and show potential for cryospheric studies.

Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

NASA Technical Reports Server (NTRS)

Yueh, Simon H.; Chaubell, Mario J.

2012-01-01

Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed

Wave-function-based approach to quasiparticle bands: Insight into the electronic structure of c-ZnS

NASA Astrophysics Data System (ADS)

Stoyanova, A.; Hozoi, L.; Fulde, P.; Stoll, H.

2011-05-01

Ab initio wave-function-based methods are employed for the study of quasiparticle energy bands of zinc-blende ZnS, with focus on the Zn 3d “semicore” states. The relative energies of these states with respect to the top of the S 3p valence bands appear to be poorly described as compared to experimental values not only within the local density approximation (LDA), but also when many-body corrections within the GW approximation are applied to the LDA or LDA + U mean-field solutions [T. Miyake, P. Zhang, M. L. Cohen, and S. G. Louie, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.74.245213 74, 245213 (2006)]. In the present study, we show that for the accurate description of the Zn 3d states a correlation treatment based on wave-function methods is needed. Our study rests on a local Hamiltonian approach which rigorously describes the short-range polarization and charge redistribution effects around an extra hole or electron placed into the valence respective conduction bands of semiconductors and insulators. The method also facilitates the computation of electron correlation effects beyond relaxation and polarization. The electron correlation treatment is performed on finite clusters cut off the infinite system. The formalism makes use of localized Wannier functions and embedding potentials derived explicitly from prior periodic Hartree-Fock calculations. The on-site and nearest-neighbor charge relaxation lead to corrections of several eV to the Hartree-Fock band energies and gap. Corrections due to long-range polarization are of the order of 1.0 eV. The dispersion of the Hartree-Fock bands is only slightly affected by electron correlations. We find the Zn 3d “semicore” states to lie ~9.0 eV below the top of the S 3p valence bands, in very good agreement with values from valence-band x-ray photoemission.

Analysis of single band and dual band graphene based patch antenna for terahertz region

NASA Astrophysics Data System (ADS)

George, Jemima Nissiyah; Madhan, M. Ganesh

2017-10-01

A microstrip patch antenna is designed using a very thin layer of graphene as the radiating patch, which is fed by a microstrip transmission line. The graphene based patch is designed on a silicon substrate having a dielectric constant of 11.9, to radiate at a single frequency of 2.6 THz. Further, this antenna is made to resonate at dual frequencies of 2.48 THz and 3.35 THz, by changing the substrate height, which is reported for the first time. Various antenna parameters such as return loss, VSWR, gain, efficiency and bandwidth are also determined for the single and dual band operation. For the single band operation, a bandwidth of 145.4 GHz and an efficiency of 92% was achieved. For dual band operation, a maximum bandwidth of 140.5 GHz was obtained at 3.35 THz and an efficiency of 87.3% was obtained at the first resonant frequency of 2.48 THz. The absorption cross section of the antenna is also analysed for various substrate heights and has maximum peaks at the corresponding resonating frequencies. The simulation has been carried out by using a full wave electromagnetic simulator based on FDTD method.

Design analysis and simulation study of an efficiency enhanced L-band MILO

NASA Astrophysics Data System (ADS)

Dixit, Gargi; Kumar, Arjun; Jain, P. K.

2017-01-01

In this article, an experimental L-band compact magnetically insulated transmission line oscillator (MILO) has been simulated using the 3D PIC simulation code "Particle Studio," and an improvement in the device efficiency has been obtained. The detailed interaction and operating mechanism describing the role of sub-assemblies have been explained. The performance of the device was found to be the function of the distance between the end-surface of the cathode and the beam-dump disk. During simulation, a high power microwave of the TM01 mode is generated with the peak RF-power of 6 GW and the power conversion efficiency of 19.2%, at the operating voltage of ˜600 kV and at the current of 52 kA. For better impedance matching or maximum power transfer, four stubs have been placed at the λg/4 distance from the extractor cavity, which results in the stable RF power output. In this work, an improved L-band MILO along with a new type beam-dump disk is selected for performance improvement with typical design parameters and beam parameters. The total peak power of improved MILO is 7 GW, and the maximum power conversion efficiency is 22.4%. This improvement is achieved due to the formation of the virtual cathode at the load side, which helps in modulating the energy of electrons owing to maximum reflection of electrons from the mesh or foil.

A time-series approach to estimating soil moisture from vegetated surfaces using L-band radar backscatter

USDA-ARS?s Scientific Manuscript database

Many previous studies have shown the sensitivity of radar backscatter to surface soil moisture content, particularly at L-band. Moreover, the estimation of soil moisture from radar for bare soil surfaces is well-documented, but estimation underneath a vegetation canopy remains unsolved. Vegetation s...

CHARACTERIZATION OF THE INNER DISK AROUND HD 141569 A FROM KECK/NIRC2 L-BAND VORTEX CORONAGRAPHY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mawet, Dimitri; Bottom, Michael; Matthews, Keith

HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a new image of the third inner disk component of HD 141569 A made in the L ′ band (3.8 μ m) during the commissioning of the vector vortex coronagraph that has recently been installed in the near-infrared imager and spectrograph NIRC2 behind the W.M. Keck Observatory Keck II adaptive optics system. We used reference point-spread function subtraction, which reveals the innermost disk component from the innermore » working distance of ≃23 au and up to ≃70 au. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q , N , and 8.6 μ m PAH emission reported earlier. We also see an outward progression in dust location from the L ′ band to the H band (Very Large Telescope/SPHERE image) to the visible ( Hubble Space Telescope ( HST )/STIS image), which is likely indicative of dust blowout. The warm disk component is nested deep inside the two outer belts imaged by HST-NICMOS in 1999 (at 406 and 245 au, respectively). We fit our new L ′-band image and spectral energy distribution of HD 141569 A with the radiative transfer code MCFOST. Our best-fit models favor pure olivine grains and are consistent with the composition of the outer belts. While our image shows a putative very faint point-like clump or source embedded in the inner disk, we did not detect any true companion within the gap between the inner disk and the first outer ring, at a sensitivity of a few Jupiter masses.« less

Simulation of radar backscattering from snowpack at X-band and Ku-band

NASA Astrophysics Data System (ADS)

Gay, Michel; Phan, Xuan-Vu; Ferro-Famil, Laurent

2016-04-01

This paper presents a multilayer snowpack electromagnetic backscattering model, based on Dense Media Radiative Transfer (DMRT). This model is capable of simulating the interaction of electromagnetic wave (EMW) at X-band and Ku-band frequencies with multilayer snowpack. The air-snow interface and snow-ground backscattering components are calculated using the Integral Equation Model (IEM) by [1], whereas the volume backscattering component is calculated based on the solution of Vector Radiative Transfer (VRT) equation at order 1. Case study has been carried out using measurement data from NoSREx project [2], which include SnowScat data in X-band and Ku-band, TerraSAR-X acquisitions and snowpack stratigraphic in-situ measurements. The results of model simulations show good agreement with the radar observations, and therefore allow the DMRT model to be used in various applications, such as data assimilation [3]. [1] A.K. Fung and K.S. Chen, "An update on the iem surface backscattering model," Geoscience and Remote Sensing Letters, IEEE, vol. 1, no. 2, pp. 75 - 77, april 2004. [2] J. Lemmetyinen, A. Kontu, J. Pulliainen, A. Wiesmann, C. Werner, T. Nagler, H. Rott, and M. Heidinger, "Technical assistance for the deployment of an x- to ku-band scatterometer during the nosrex ii experiment," Final Report, ESA ESTEC Contract No. 22671/09/NL/JA., 2011. [3] X. V. Phan, L. Ferro-Famil, M. Gay, Y. Durand, M. Dumont, S. Morin, S. Allain, G. D'Urso, and A. Girard, "3d-var multilayer assimilation of x-band sar data into a detailed snowpack model," The Cryosphere Discussions, vol. 7, no. 5, pp. 4881-4912, 2013.

High-Resolution Soil Moisture Retrieval using SMAP-L Band Radiometer and RISAT-C band Radar Data for the Indian Subcontinent

NASA Astrophysics Data System (ADS)

Singh, G.; Das, N. N.; Panda, R. K.; Mohanty, B.; Entekhabi, D.; Bhattacharya, B. K.

2016-12-01

Soil moisture status at high resolution (1-10 km) is vital for hydrological, agricultural and hydro-metrological applications. The NASA Soil Moisture Active Passive (SMAP) mission had potential to provide reliable soil moisture estimate at finer spatial resolutions (3 km and 9 km) at the global extent, but suffered a malfunction of its radar, consequently making the SMAP mission observations only from radiometer that are of coarse spatial resolution. At present, the availability of high-resolution soil moisture product is limited, especially in developing countries like India, which greatly depends on agriculture for sustaining a huge population. Therefore, an attempt has been made in the reported study to combine the C-band synthetic aperture radar (SAR) data from Radar Imaging Satellite (RISAT) of the Indian Space Research Organization (ISRO) with the SMAP mission L-band radiometer data to obtain high-resolution (1 km and 3 km) soil moisture estimates. In this study, a downscaling approach (Active-Passive Algorithm) implemented for the SMAP mission was used to disaggregate the SMAP radiometer brightness temperature (Tb) using the fine resolution SAR backscatter (σ0) from RISAT. The downscaled high-resolution Tb was then subjected to tau-omega model in conjunction with high-resolution ancillary data to retrieve soil moisture at 1 and 3 km scale. The retrieved high-resolution soil moisture estimates were then validated with ground based soil moisture measurement under different hydro-climatic regions of India. Initial results show tremendous potential and reasonable accuracy for the retrieved soil moisture at 1 km and 3 km. It is expected that ISRO will implement this approach to produce high-resolution soil moisture estimates for the Indian subcontinent.

Monitoring Everglades freshwater marsh water level using L-band synthetic aperture radar backscatter

USGS Publications Warehouse

Kim, Jin-Woo; Lu, Zhong; Jones, John W.; Shum, C.K.; Lee, Hyongki; Jia, Yuanyuan

2014-01-01

The Florida Everglades plays a significant role in controlling floods, improving water quality, supporting ecosystems, and maintaining biodiversity in south Florida. Adaptive restoration and management of the Everglades requires the best information possible regarding wetland hydrology. We developed a new and innovative approach to quantify spatial and temporal variations in wetland water levels within the Everglades, Florida. We observed high correlations between water level measured at in situ gages and L-band SAR backscatter coefficients in the freshwater marsh, though C-band SAR backscatter has no close relationship with water level. Here we illustrate the complementarity of SAR backscatter coefficient differencing and interferometry (InSAR) for improved estimation of high spatial resolution water level variations in the Everglades. This technique has a certain limitation in applying to swamp forests with dense vegetation cover, but we conclude that this new method is promising in future applications to wetland hydrology research.

Dispersive Phase in the L-band InSAR Image Associated with Heavy Rain Episodes

NASA Astrophysics Data System (ADS)

Furuya, M.; Kinoshita, Y.

2017-12-01

Interferometric synthetic aperture radar (InSAR) is a powerful geodetic technique that allows us to detect ground displacements with unprecedented spatial resolution, and has been used to detect displacements due to earthquakes, volcanic eruptions, and glacier motion. In the meantime, due to the microwave propagation through ionosphere and troposphere, we often encounter non-negligible phase anomaly in InSAR data. Correcting for the ionsphere and troposphere is therefore a long-standing issue for high-precision geodetic measurements. However, if ground displacements are negligible, InSAR image can tell us the details of the atmosphere.Kinoshita and Furuya (2017, SOLA) detected phase anomaly in ALOS/PALSAR InSAR data associated with heavy rain over Niigata area, Japan, and performed numerical weathr model simulation to reproduce the anomaly; ALOS/PALSAR is a satellite-based L-band SAR sensor launched by JAXA in 2006 and terminated in 2011. The phase anomaly could be largely reproduced, using the output data from the weather model. However, we should note that numerical weather model outputs can only account for the non-dispersive effect in the phase anomaly. In case of severe weather event, we may expect dispersive effect that could be caused by the presence of free-electrons.In Global Navigation Satellite System (GNSS) positioning, dual frequency measurements allow us to separate the ionospheric dispersive component from tropospheric non-dispersive components. In contrast, SAR imaging is based on a single carrier frequency, and thus no operational ionospheric corrections have been performed in InSAR data analyses. Recently, Gomba et al (2016) detailed the processing strategy of split spectrum method (SSM) for InSAR, which splits the finite bandwidth of the range spectrum and virtually allows for dual-frequency measurements.We apply the L-band InSAR SSM to the heavy rain episodes, in which more than 50 mm/hour precipitations were reported. We report the presence of

Auditory risk assessment of college music students in jazz band-based instructional activity.

PubMed

Gopal, Kamakshi V; Chesky, Kris; Beschoner, Elizabeth A; Nelson, Paul D; Stewart, Bradley J

2013-01-01

It is well-known that musicians are at risk for music-induced hearing loss, however, systematic evaluation of music exposure and its effects on the auditory system are still difficult to assess. The purpose of the study was to determine if college students in jazz band-based instructional activity are exposed to loud classroom noise and consequently exhibit acute but significant changes in basic auditory measures compared to non-music students in regular classroom sessions. For this we (1) measured and compared personal exposure levels of college students (n = 14) participating in a routine 50 min jazz ensemble-based instructional activity (experimental) to personal exposure levels of non-music students (n = 11) participating in a 50-min regular classroom activity (control), and (2) measured and compared pre- to post-auditory changes associated with these two types of classroom exposures. Results showed that the L eq (equivalent continuous noise level) generated during the 50 min jazz ensemble-based instructional activity ranged from 95 dBA to 105.8 dBA with a mean of 99.5 ± 2.5 dBA. In the regular classroom, the L eq ranged from 46.4 dBA to 67.4 dBA with a mean of 49.9 ± 10.6 dBA. Additionally, significant differences were observed in pre to post-auditory measures between the two groups. The experimental group showed a significant temporary threshold shift bilaterally at 4000 Hz (P < 0.05), and a significant decrease in the amplitude of transient-evoked otoacoustic emission response in both ears (P < 0.05) after exposure to the jazz ensemble-based instructional activity. No significant changes were found in the control group between pre- and post-exposure measures. This study quantified the noise exposure in jazz band-based practice sessions and its effects on basic auditory measures. Temporary, yet significant, auditory changes seen in music students place them at risk for hearing loss compared to their non-music cohorts.

Strain gradient drives shear banding in metallic glasses

NASA Astrophysics Data System (ADS)

Tian, Zhi-Li; Wang, Yun-Jiang; Chen, Yan; Dai, Lan-Hong

2017-09-01

Shear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective of MGs as a hard particle-reinforced material based on atomic-scale structural heterogeneity. The local stable structures indicated by a high level of local fivefold symmetry (L5FS) act as hard "particles" which are embedded in the relatively soft matrix. We demonstrate this concept by performing atomistic simulations of shear banding in CuZr MG. A shear band is prone to form in a sample with a high degree of L5FS which is slowly quenched from the liquid. An atomic-scale analysis on strain and the structural evolution reveals that it is the strain gradient effect that has originated from structural heterogeneity that facilitates shear transformation zones (STZs) to mature shear bands. An artificial composite model with a high degree of strain gradient, generated by inserting hard MG strips into a soft MG matrix, demonstrates a great propensity for shear banding. It therefore confirms the critical role strain gradient plays in shear banding. The strain gradient effect on shear banding is further quantified with a continuum model and a mechanical instability analysis. These physical insights might highlight the strain gradient as the hidden driving force in transforming STZs into shear bands in MGs.

Complete theory of symmetry-based indicators of band topology.

PubMed

Po, Hoi Chun; Vishwanath, Ashvin; Watanabe, Haruki

2017-06-30

The interplay between symmetry and topology leads to a rich variety of electronic topological phases, protecting states such as the topological insulators and Dirac semimetals. Previous results, like the Fu-Kane parity criterion for inversion-symmetric topological insulators, demonstrate that symmetry labels can sometimes unambiguously indicate underlying band topology. Here we develop a systematic approach to expose all such symmetry-based indicators of band topology in all the 230 space groups. This is achieved by first developing an efficient way to represent band structures in terms of elementary basis states, and then isolating the topological ones by removing the subset of atomic insulators, defined by the existence of localized symmetric Wannier functions. Aside from encompassing all earlier results on such indicators, including in particular the notion of filling-enforced quantum band insulators, our theory identifies symmetry settings with previously hidden forms of band topology, and can be applied to the search for topological materials.Understanding the role of topology in determining electronic structure can lead to the discovery, or appreciation, of materials with exotic properties such as protected surface states. Here, the authors present a framework for identifying topologically distinct band-structures for all 3D space groups.

Foliar spray banding characteristics

Treesearch

A.R. Womac; C.W. Smith; Joseph E. Mulrooney

2004-01-01

Foliar spray banding was explored as a means of reducing peticide use compared to broadcast applications. Barious geometric spray patterns and delivery angles of foliar spray bands were investigated to increase spray deposits in a crop row at a constant spray rate of 94 L/ha. Wind-free laboratory results indicated that a banded application using three 65° hollow-cone...

L Band EPR Tooth Dosimetry for Heavy Ion Irradiation

PubMed Central

Yamaguchi, Ichiro; Sato, Hitoshi; Kawamura, Hiraku; Hamano, Tsuyoshi; Yoshii, Hiroshi; Suda, Mitsuru; Miyake, Minoru; Kunugita, Naoki

2016-01-01

Electron Paramagnetic Resonance (EPR) tooth dosimetry is being developed as a device to rapidly assess large populations that were potentially exposed to radiation during a major radiation accident or terrorist event. While most exposures are likely to be due to fallout and therefore involve low linear energy transfer (LET) radiation, there is also a potential for exposures to high LET radiation, for which the effect on teeth has been less well characterized by EPR. Therefore, the aim of this paper is to acquire fundamental response curves for high LET radiation in tooth dosimetry using L band EPR. For this purpose, we exposed human teeth to high energy carbon ions using the heavy ion medical accelerator in Chiba at the National Institute of Radiological Sciences. The primary findings were that EPR signals for carbon ion irradiation were about one-tenth the amplitude of the response to the same dose of 150 kVp X-rays. PMID:27542817

Validation of Forested Inundation Extent Revealed by L-Band Polarimetric and Interferometric SAR Data

NASA Technical Reports Server (NTRS)

Chapman, Bruce; Celi, Jorge; Hamilton, Steve; McDonald, Kyle

2013-01-01

UAVSAR, NASA's airborne Synthetic Aperture Radar (SAR), conducted an extended observational campaign in Central and South America in March 2013, primarily related to volcanic deformations along the Andean Mountain Range but also including a large number of flights studying other scientific phenomena. During this campaign, the L-Band SAR collected data over the Napo River in Ecuador. The objectives of this experiment were to acquire polarimetric and interferometric L-Band SAR data over an inundated tropical forest in Ecuador simultaneously with on-the-ground field work ascertaining the extent of inundation, and to then derive from this data a quantitative estimate for the error in the SAR-derived inundation extent. In this paper, we will first describe the processing and preliminary analysis of the SAR data. The polarimetric SAR data will be classified by land cover and inundation state. The interferometric SAR data will be used to identify those areas where change in inundation extent occurred, and to measure the change in water level between two observations separated by a week. Second, we will describe the collection of the field estimates of inundation, and have preliminary comparisons of inundation extent measured in the field field versus that estimated from the SAR data.

L-Band Brightness Temperature Variations at Dome C and Snow Metamorphism at the Surface

NASA Technical Reports Server (NTRS)

Brucker, Ludovic; Dinnat, Emmanuel; Picard, Ghislain; Champollion, Nicolas

2014-01-01

The Antarctic Plateau is a promising site to monitor microwave radiometers' drift, and to inter-calibrate microwave radiometers, especially 1.4 GigaHertz (L-band) radiometers on board the Soil Moisture and Ocean Salinity (SMOS), and AquariusSAC-D missions. The Plateau is a thick ice cover, thermally stable in depth, with large dimensions, and relatively low heterogeneities. In addition, its high latitude location in the Southern Hemisphere enables frequent observations by polar-orbiting satellites, and no contaminations by radio frequency interference. At Dome C (75S, 123E), on the Antarctic Plateau, the substantial amount of in-situ snow measurements available allows us to interpret variations in space-borne microwave brightness temperature (TB) (e.g. Macelloni et al., 2007, 2013, Brucker et al., 2011, Champollion et al., 2013). However, to analyze the observations from the Aquarius radiometers, whose sensitivity is 0.15 K, the stability of the snow layers near the surface that are most susceptible to rapidly change needs to be precisely assessed. This study focuses on the spatial and temporal variations of the Aquarius TB over the Antarctic Plateau, and at Dome C in particular, to highlight the impact of snow surface metamorphism on the TB observations at L-band.

Transfer-matrices for series-type microwave antenna circuits. [L-band radiometer

NASA Technical Reports Server (NTRS)

Schmidt, R. F.

1981-01-01

Transfer matrices are developed which permit analysis and computer evaluation of certain series type microwave antenna circuits associated with an L-Band microwave radiometer (LBMR) under investigation at Goddard Space Flight Center. This radiometer is one of several diverse instrument designs to be used for the determination of soil moisture, sea state, salinity, and temperature data. Four port matrix notation is used throughout for the evaluation of LBMR circuits with mismatched couplers and lossy transmission lines. Matrix parameters in examples are predicted on an impedance analysis and an assumption of an array aperture distribution. The notation presented is easily adapted to longer and more varied chains of matrices, and to matrices of larger dimension.

A particle swarm optimized kernel-based clustering method for crop mapping from multi-temporal polarimetric L-band SAR observations

NASA Astrophysics Data System (ADS)

Tamiminia, Haifa; Homayouni, Saeid; McNairn, Heather; Safari, Abdoreza

2017-06-01

Polarimetric Synthetic Aperture Radar (PolSAR) data, thanks to their specific characteristics such as high resolution, weather and daylight independence, have become a valuable source of information for environment monitoring and management. The discrimination capability of observations acquired by these sensors can be used for land cover classification and mapping. The aim of this paper is to propose an optimized kernel-based C-means clustering algorithm for agriculture crop mapping from multi-temporal PolSAR data. Firstly, several polarimetric features are extracted from preprocessed data. These features are linear polarization intensities, and several statistical and physical based decompositions such as Cloude-Pottier, Freeman-Durden and Yamaguchi techniques. Then, the kernelized version of hard and fuzzy C-means clustering algorithms are applied to these polarimetric features in order to identify crop types. The kernel function, unlike the conventional partitioning clustering algorithms, simplifies the non-spherical and non-linearly patterns of data structure, to be clustered easily. In addition, in order to enhance the results, Particle Swarm Optimization (PSO) algorithm is used to tune the kernel parameters, cluster centers and to optimize features selection. The efficiency of this method was evaluated by using multi-temporal UAVSAR L-band images acquired over an agricultural area near Winnipeg, Manitoba, Canada, during June and July in 2012. The results demonstrate more accurate crop maps using the proposed method when compared to the classical approaches, (e.g. 12% improvement in general). In addition, when the optimization technique is used, greater improvement is observed in crop classification, e.g. 5% in overall. Furthermore, a strong relationship between Freeman-Durden volume scattering component, which is related to canopy structure, and phenological growth stages is observed.

Characterizing the temporal variability of L-band backscatter using dense UAVSAR time-series in preparation for the NISAR mission

NASA Astrophysics Data System (ADS)

Lavalle, M.; Lee, A.; Shiroma, G. X. H.; Rosen, P. A.

2017-12-01

The NASA-ISRO SAR (NISAR) mission will deliver unprecedented global maps of L-band HH/HV backscatter every 12 days with resolution ranging from a few to tens of meters in support of ecosystem, solid Earth and cryosphere science and applications. Understanding and modeling the temporal variability of L-band backscatter over temporal scales of years, months and days is critical for developing retrieval algorithms that can robustly extract the biophysical variables of interest (e.g., forest biomass, soil moisture, etc.) from NISAR time series. In this talk, we will focus on the 5-year time series of 60 JPL/UAVSAR polarimetric images collected near the Sacramento Delta to characterize the inter-annual, seasonal and short-scale variability of the L-band polarimetric backscatter for a broad range of land cover types. Our preliminary analysis reveals that backscatter from man-made structures is very stable over time, whereas backscatter from bare soil and herbaceous vegetation fluctuates over time with standard deviation of 2.3 dB. Land-cover classes with larger biomass such as trees and tall vegetation show about 1.5 dB standard deviation in temporal backscatter variability. Closer examination of high-spatial resolution UAVSAR imagery reveal also that vegetation structure, speckle noise and horizontal forest heterogeneity in the Sacramento Delta area can significantly affect the point-wise backscatter value. In our talk, we will illustrate the long UAVSAR time series, describe our data analysis strategy, show the results of polarimetric variability for different land cover classes and number of looks, and discuss the implications for the development of NISAR L2/L3 retrieval algorithms of ecosystem science.

Interpretation of recent alpine landscape system evolution using geomorphic mapping and L-band InSAR analyses

NASA Astrophysics Data System (ADS)

Imaizumi, Fumitoshi; Nishiguchi, Takaki; Matsuoka, Norikazu; Trappmann, Daniel; Stoffel, Markus

2018-06-01

Alpine landscapes are typically characterized by inherited features of past glaciations and, for the more recent past, by the interplay of a multitude of types of geomorphic processes, including permafrost creep, rockfalls, debris flows, and landslides. These different processes usually exhibit large spatial and temporal variations in activity and velocity. The understanding of these processes in a wide alpine area is often hindered by difficulties in their surveying. In this study, we attempt to disentangle recent changes in an alpine landscape system using geomorphic mapping and L-band DInSAR analyses (ALOS-PALSAR) in the Zermatt Valley, Swiss Alps. Geomorphic mapping points to a preferential distribution of rock glaciers on north-facing slopes, whereas talus slopes are concentrated on south-facing slopes. Field-based interpretation of ground deformation in rock glaciers and movements in talus slopes correlates well with the ratio of InSAR images showing potential ground deformation. Moraines formed during the Little Ice Age, rock glaciers, and talus slopes on north-facing slopes are more active than landforms on south-facing slopes, implying that the presence of permafrost facilitates the deformation of these geomorphic units. Such deformations of geomorphic units prevail also at the elevation of glacier termini. For rock cliffs, the ratio of images indicating retreat is affected by slope orientation and elevation. Linkages between sediment supply from rock cliffs and sediment transport in torrents are different among tributaries, affected by relative locations between sediment supply areas and the channel network. We conclude that the combined use of field surveys and L-band DInSAR analyses can substantially improve process understanding in steep, high-mountain terrain.

Mangrove vegetation structure in Southeast Brazil from phased array L-band synthetic aperture radar data

NASA Astrophysics Data System (ADS)

de Souza Pereira, Francisca Rocha; Kampel, Milton; Cunha-Lignon, Marilia

2016-07-01

The potential use of phased array type L-band synthetic aperture radar (PALSAR) data for discriminating distinct physiographic mangrove types with different forest structure developments in a subtropical mangrove forest located in Cananéia on the Southern coast of São Paulo, Brazil, is investigated. The basin and fringe physiographic types and the structural development of mangrove vegetation were identified with the application of the Kruskal-Wallis statistical test to the SAR backscatter values of 10 incoherent attributes. The best results to separate basin to fringe types were obtained using copolarized HH, cross-polarized HV, and the biomass index (BMI). Mangrove structural parameters were also estimated using multiple linear regressions. BMI and canopy structure index were used as explanatory variables for canopy height, mean height, and mean diameter at breast height regression models, with significant R2=0.69, 0.73, and 0.67, respectively. The current study indicates that SAR L-band images can be used as a tool to discriminate physiographic types and to characterize mangrove forests. The results are relevant considering the crescent availability of freely distributed SAR images that can be more utilized for analysis, monitoring, and conservation of the mangrove ecosystem.

Total Electron Content Retrieved From L-Band Radiometers and Potential Improvements to the IGS Model

NASA Astrophysics Data System (ADS)

Soldo, Yan; Hong, Liang; El-Nimri, Salem; Le Vine, David M.

2018-04-01

In recent years, several L-band microwave instruments have been launched into Earth's orbit to measure soil moisture and ocean salinity (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active/Passive [SMAP]). As the microwave signal travels through the ionosphere, the polarization vector rotates (Faraday rotation) and it is possible to estimate the total electron content (TEC) along the path by measuring this change. A comparison is presented of the TEC retrieved from Aquarius and SMAP over the ocean with the values provided by the IGS (International Global Navigation Satellite System Service (GNSS)). The TEC retrieved from Aquarius and SMAP measurements show good agreement with each other and, on a global scale, are in agreement with the TEC provided by the IGS. However, there are cases in which the TEC from the two satellite sensors are in good agreement with each other but differ significantly from the IGS TEC. The comparison suggests that the L-band instruments are a reliable source of TEC over the ocean and could be a valuable supplementary source of TEC values that could be assimilated in the IGS models, especially over the ocean, where GNSS ground stations are sparse.

Liquid-crystal WDM power equalizer

NASA Astrophysics Data System (ADS)

Chiao, Jung-Chih; Huang, Tizhi

2002-06-01

In this work, we demonstrated a liquid-crystal WDM (wavelength-division-multiplexing) power equalizer. It provides functionality of optical power equalization and tilting using liquid-crystal modulators and harmonic synthesis approach. The demonstrations show fast gain equalization with a flatness of +/- 0.3dB for several EDFA profiles in C or L bands. The equalization for WDM discrete-channel cases also reached flatness within +/- 0.3dB. The measured polarization dependent losses are less than 0.15dB and 0.1dB for flattened and through-state profiles, respectively. The measured polarization mode dispersions are less than 0.15ps under the through, flattened and 10-dB attenuation states. The measured chromatic dispersion is less than degree(s)7ps/nm.

Reconfigurable dual-band metamaterial antenna based on liquid crystals

NASA Astrophysics Data System (ADS)

Che, Bang-Jun; Meng, Fan-Yi; Lyu, Yue-Long; Wu, Qun

2018-05-01

In this paper, a novel reconfigurable dual-band metamaterial antenna with a continuous beam that is electrically steered in backward to forward directions is first proposed by employing a liquid crystal (LC)-loaded tunable extended composite right-/left-handed (E-CRLH) transmission line (TL). The frequency-dependent property of the E-CRLH TL is analyzed and a compact unit cell based on the nematic LC is proposed to realize the tunable dual band characteristics. The phase constant of the proposed unit cell can be dynamically continuously tuned from negative to positive values in two operating bands by changing the bias voltage of the loaded LC material. A resulting dual band fixed-frequency beam steering property has been predicted by numerical simulations and experimentally verified. The measured results show that the fabricated reconfigurable antenna features an electrically controlled continuous beam steering from backward  ‑16° to forward  +13° at 7.2 GHz and backward  ‑9° to forward  +17° at 9.4 GHz, respectively. This electrically controlled beam steering range turns out to be competitive with the previously reported single band reconfigurable antennas. Besides, the measured and simulated results of the proposed reconfigurable dual-band metamaterial antenna are in good agreement.

A user's manual for the NASA/JPL synthetic aperture radar and the NASA/JPL L and C band scatterometers

NASA Technical Reports Server (NTRS)

Thompson, T. W.

1983-01-01

Airborne synthetic aperture radars and scatterometers are operated with the goals of acquiring data to support shuttle imaging radars and support ongoing basic active microwave remote sensing research. The aircraft synthetic aperture radar is an L-band system at the 25-cm wavelength and normally operates on the CV-990 research aircraft. This radar system will be upgraded to operate at both the L-band and C-band. The aircraft scatterometers are two independent radar systems that operate at 6.3-cm and 18.8-cm wavelengths. They are normally flown on the C-130 research aircraft. These radars will be operated on 10 data flights each year to provide data to NASA-approved users. Data flights will be devoted to Shuttle Imaging Radar-B (SIR-B) underflights. Standard data products for the synthetic aperture radars include both optical and digital images. Standard data products for the scatterometers include computer compatible tapes with listings of radar cross sections (sigma-nought) versus angle of incidence. An overview of these radars and their operational procedures is provided by this user's manual.

Shear-band thickness and shear-band cavities in a Zr-based metallic glass

DOE PAGES

Liu, C.; Roddatis, V.; Kenesei, P.; ...

2017-08-14

Strain localization into shear bands in metallic glasses is typically described as a mechanism that occurs at the nano-scale, leaving behind a shear defect with a thickness of 10–20 nm. Here we sample the structure of a single system-spanning shear band that has carried all plastic flow with high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and high-energy x-ray tomography (XRT). It is found that the shear-band thickness and the density change relative to the matrix sensitively depend on position along the shear band. A wide distribution of shear-band thickness (10 nm–210 nm) and density change (–1% to –12%)more » is revealed. There is no obvious correlation between shear-band thickness and density change, but larger thicknesses correspond typically to higher density changes. More than 100 micron-size shear-band cavities were identified on the shear-band plane, and their three-dimensional arrangement suggests a strongly fluctuating local curvature of the shear plane. As a result, these findings urge for a more complex view of a shear band than a simple nano-scale planar defect.« less

Shear-band thickness and shear-band cavities in a Zr-based metallic glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C.; Roddatis, V.; Kenesei, P.

Strain localization into shear bands in metallic glasses is typically described as a mechanism that occurs at the nano-scale, leaving behind a shear defect with a thickness of 10–20 nm. Here we sample the structure of a single system-spanning shear band that has carried all plastic flow with high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and high-energy x-ray tomography (XRT). It is found that the shear-band thickness and the density change relative to the matrix sensitively depend on position along the shear band. A wide distribution of shear-band thickness (10 nm–210 nm) and density change (–1% to –12%)more » is revealed. There is no obvious correlation between shear-band thickness and density change, but larger thicknesses correspond typically to higher density changes. More than 100 micron-size shear-band cavities were identified on the shear-band plane, and their three-dimensional arrangement suggests a strongly fluctuating local curvature of the shear plane. As a result, these findings urge for a more complex view of a shear band than a simple nano-scale planar defect.« less

Modeling L-band synthetic aperture radar observations through dielectric changes in soil moisture and vegetation over shrublands

USDA-ARS?s Scientific Manuscript database

L-band airborne synthetic aperture radar observations were made over California shrublands to better understand the effects by soil and vegetation parameters on backscatter. Temporal changes in radar backscattering coefficient (s0) of up to 3 dB were highly correlated to surface soil moisture but no...

Performance of horn-coupled transition edge sensors for L- and S-band optical detection on the SAFARI instrument

NASA Astrophysics Data System (ADS)

Goldie, D. J.; Glowacka, D. M.; Withington, S.; Chen, Jiajun; Ade, P. A. R.; Morozov, D.; Sudiwala, R.; Trappe, N. A.; Quaranta, O.

2016-07-01

We describe the geometry, architecture, dark- and optical performance of ultra-low-noise transition edge sensors as THz detectors for the SAFARI instrument. The TESs are fabricated from superconducting Mo/Au bilayers coupled to impedance-matched superconducting β-phase Ta thin-film absorbers. The detectors have phonon-limited dark noise equivalent powers of order 0.5 - 1.0 aW/ √ Hz and saturation powers of order 20 - 40 fW. The low temperature test configuration incorporating micro-machined backshorts is also described, and construction and typical performance characteristics for the optical load are shown. We report preliminary measurements of the optical performance of these TESs for two SAFARI bands; L-band at 110 - 210 μm and S-band 34 - 60 μm .

Relating P-band AIRSAR backscatter to forest stand parameters

NASA Technical Reports Server (NTRS)

Wang, Yong; Melack, John M.; Davis, Frank W.; Kasischke, Eric S.; Christensen, Norman L., Jr.

1993-01-01

As part of research on forest ecosystems, the Jet Propulsion Laboratory (JPL) and collaborating research teams have conducted multi-season airborne synthetic aperture radar (AIRSAR) experiments in three forest ecosystems including temperate pine forest (Duke, Forest, North Carolina), boreal forest (Bonanza Creek Experimental Forest, Alaska), and northern mixed hardwood-conifer forest (Michigan Biological Station, Michigan). The major research goals were to improve understanding of the relationships between radar backscatter and phenological variables (e.g. stand density, tree size, etc.), to improve radar backscatter models of tree canopy properties, and to develop a radar-based scheme for monitoring forest phenological changes. In September 1989, AIRSAR backscatter data were acquired over the Duke Forest. As the aboveground biomass of the loblolly pine forest stands at Duke Forest increased, the SAR backscatter at C-, L-, and P-bands increased and saturated at different biomass levels for the C-band, L-band, and P-band data. We only use the P-band backscatter data and ground measurements here to study the relationships between the backscatter and stand density, the backscatter and mean trunk dbh (diameter at breast height) of trees in the stands, and the backscatter and stand basal area.

S – C – L triple wavelength superluminescent source based on an ultra-wideband SOA and FBGs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, H; Zulkifli, M Z; Hassan, N A

2013-10-31

We propose and demonstrate a wide-band semiconductor optical amplifier (SOA) based triple-wavelength superluminescent source with the output in the S-, C- and L-band regions. The proposed systems uses an ultra-wideband SOA with an amplification range from 1440 to 1620 nm as the linear gain medium. Three fibre Bragg gratings (FBGs) with centre wavelengths of 1500, 1540 and 1580 nm are used to generate the lasing wavelengths in the S-, Cand L-bands respectively, while a variable optical attenuator is used to finely balance the optical powers of the lasing wavelengths. The ultra-wideband SOA generates an amplified spontaneous emission (ASE) spectrum withmore » a peak power of -33 dBm at the highest SOA drive current, and also demonstrates a down-shift in the centre wavelength of the generated spectrum due to the spatial distribution of the carrier densities. The S-band wavelength is the dominant wavelength at high drive currents, with an output power of -6 dBm as compared to the C- and L-bands, which only have powers of -11 and -10 dBm, respectively. All wavelengths have a high average signal-to-noise ratio more than 60 dB at the highest drive current of 390 mA, and the system also shows a high degree of stability, with power fluctuations of less than 3 dB within 70 min. The proposed system can find many applications where a wide-band and stable laser source is crucial, such as in communications and sensing. (control of laser radiation parameters)« less

Aircraft L-Band Balloon - Simulated Satellite Experiments Volume I: Experiment Description and Voice and Data Modem Test Results

DOT National Transportation Integrated Search

1975-10-01

This report details the result of an experiment performed by the Transportation Systems Center of the Department of Transportation to evaluate candidate voice and data modulation systems for use in an L-Band Air Traffic Control System. The experiment...

Transportation Systems Center/U.S. Coast Guard L-Band Maritime Satellite Test Program : Test Summary: September - November 1974

DOT National Transportation Integrated Search

1975-06-01

Several L-band satellite communications tests with the NASA ATS-6 spacecraft and the U.S. Coast Guard Cutter SHERMAN are described. The tests included 1200 bit per second digital data, voice, simultaneous data and voice, ranging, multipath and antenn...

Space-based detection of wetlands' surface water level changes from L-band SAR interferometry

USGS Publications Warehouse

Wdowinski, S.; Kim, S.-W.; Amelung, F.; Dixon, T.H.; Miralles-Wilhelm, F.; Sonenshein, R.

2008-01-01

Interferometric processing of JERS-1 L-band Synthetic Aperture Radar (SAR) data acquired over south Florida during 1993-1996 reveals detectable surface changes in the Everglades wetlands. Although our study is limited to south Florida it has implication for other large-scale wetlands, because south Florida wetlands have diverse vegetation types and both managed and natural flow environments. Our analysis reveals that interferometric coherence level is sensitive to wetland vegetation type and to the interferogram time span. Interferograms with time spans less than six months maintain phase observations for all wetland types, allowing characterization of water level changes in different wetland environments. The most noticeable changes occur between the managed and the natural flow wetlands. In the managed wetlands, fringes are organized, follow patterns related to some of the managed water control structures and have high fringe-rate. In the natural flow areas, fringes are irregular and have a low fringe-rate. The high fringe rate in managed areas reflects dynamic water topography caused by high flow rate due to gate operation. Although this organized fringe pattern is not characteristic of most large-scale wetlands, the high level of water level change enables accurate estimation of the wetland InSAR technique, which lies in the range of 5-10??cm. The irregular and low rate fringe pattern in the natural flow area reflects uninterrupted flow that diffuses water efficiently and evenly. Most of the interferograms in the natural flow area show an elongated fringe located along the transitional zone between salt- and fresh-water wetlands, reflecting water level changes due to ocean tides. ?? 2007 Elsevier Inc. All rights reserved.

Airborne active and passive L-band measurements using PALS instrument in SMAPVEX12 soil moisture field campaign

NASA Astrophysics Data System (ADS)

Colliander, Andreas; Yueh, Simon; Chazanoff, Seth; Dinardo, Steven; O'Dwyer, Ian; Jackson, Thomas; McNairn, Heather; Bullock, Paul; Wiseman, Grant; Berg, Aaron; Magagi, Ramata; Njoku, Eni

2012-10-01

NASA's (National Aeronautics and Space Administration) Soil Moisture Active Passive (SMAP) Mission is scheduled for launch in late 2014. The objective of the mission is global mapping of soil moisture and freeze/thaw state. Merging of active and passive L-band observations of the mission will enable unprecedented combination of accuracy, resolution, coverage and revisit-time for soil moisture and freeze/thaw state retrieval. For pre-launch algorithm development and validation the SMAP project and NASA coordinated a field campaign named as SMAPVEX12 (Soil Moisture Active Passive Validation Experiment 2012) together with Agriculture and Agri-Food Canada, and other Canadian and US institutions in the vicinity of Winnipeg, Canada in June-July, 2012. The main objective of SMAPVEX12 was acquisition of a data record that features long time-series with varying soil moisture and vegetation conditions over an aerial domain of multiple parallel flight lines. The coincident active and passive L-band data was acquired with the PALS (Passive Active L-band System) instrument. The measurements were conducted over the experiment domain every 2-3 days on average, over a period of 43 days. The preliminary calibration of the brightness temperatures obtained in the campaign has been performed. Daily lake calibrations were used to adjust the radiometer calibration parameters, and the obtained measurements were compared against the raw in situ soil moisture measurements. The evaluation shows that this preliminary calibration of the data produces already a consistent brightness temperature record over the campaign duration, and only secondary adjustments and cleaning of the data is need before the data can be applied to the development and validation of SMAP algorithms.

A Compact L-band Radiometer for High Resolution sUAS-based Imaging of Soil Moisture and Surface Salinity Variations

NASA Astrophysics Data System (ADS)

Gasiewski, A. J.; Stachura, M.; Dai, E.; Elston, J.; McIntyre, E.; Leuski, V.

2014-12-01

Due to the long electrical wavelengths required along with practical aperture size limitations the scaling of passive microwave remote sensing of soil moisture and salinity from spaceborne low-resolution (~10-100 km) applications to high resolution (~10-1000 m) applications requires use of low flying aerial vehicles. This presentation summarizes the status of a project to develop a commercial small Unmanned Aerial System (sUAS) hosting a microwave radiometer for mapping of soil moisture in precision agriculture and sea surface salinity studies. The project is based on the Tempest electric-powered UAS and a compact L-band (1400-1427 MHz) radiometer developed specifically for extremely small and lightweight aerial platforms or man-portable, tractor, or tower-based applications. Notable in this combination are a highly integrated sUAS/radiometer antenna design and use of both the upwelling emitted signal from the surface and downwelling cold space signal for precise calibration using a unique lobe-differencing correlating radiometer architecture. The system achieves a spatial resolution comparable to the altitude of the UAS above the surface while referencing upwelling measurements to the constant and well-known background temperature of cold space. The radiometer has been tested using analog correlation detection, although future builds will include infrared, near-infrared, and visible (red) sensors for surface temperature and vegetation biomass correction and digital sampling for radio frequency interference mitigation. This NASA-sponsored project is being developed for commercial application in cropland water management (for example, high-value shallow root-zone crops), landslide risk assessment, NASA SMAP satellite validation, and NASA Aquarius salinity stratification studies. The system will ultimately be capable of observing salinity events caused by coastal glacier and estuary fresh water outflow plumes and open ocean rainfall events.

L-Band Transmit/Receive Module for Phase-Stable Array Antennas

NASA Technical Reports Server (NTRS)

Andricos, Constantine; Edelstein, Wendy; Krimskiy, Vladimir

2008-01-01

Interferometric synthetic aperture radar (InSAR) has been shown to provide very sensitive measurements of surface deformation and displacement on the order of 1 cm. Future systematic measurements of surface deformation will require this capability over very large areas (300 km) from space. To achieve these required accuracies, these spaceborne sensors must exhibit low temporal decorrelation and be temporally stable systems. An L-band (24-cmwavelength) InSAR instrument using an electronically steerable radar antenna is suited to meet these needs. In order to achieve the 1-cm displacement accuracy, the phased array antenna requires phase-stable transmit/receive (T/R) modules. The T/R module operates at L-band (1.24 GHz) and has less than 1- deg absolute phase stability and less than 0.1-dB absolute amplitude stability over temperature. The T/R module is also high power (30 W) and power efficient (60-percent overall efficiency). The design is currently implemented using discrete components and surface mount technology. The basic T/R module architecture is augmented with a calibration loop to compensate for temperature variations, component variations, and path loss variations as a function of beam settings. The calibration circuit consists of an amplitude and phase detector, and other control circuitry, to compare the measured gain and phase to a reference signal and uses this signal to control a precision analog phase shifter and analog attenuator. An architecture was developed to allow for the module to be bidirectional, to operate in both transmit and receive mode. The architecture also includes a power detector used to maintain a transmitter power output constant within 0.1 dB. The use of a simple, stable, low-cost, and high-accuracy gain and phase detector made by Analog Devices (AD8302), combined with a very-high efficiency T/R module, is novel. While a self-calibrating T/R module capability has been sought for years, a practical and cost-effective solution has

Integrated Photonic Orbital Angular Momentum Multiplexing and Demultiplexing on Chip

DTIC Science & Technology

2014-10-31

OAM free space coherent communication link testbed. ECL: external cavity laser . EDFA: erbium-doped fiber amplifier. PC: polarization controller. ATT...wave (cw) laser centered at 1540 nm, followed by an erbium-doped fiber amplifier (EDFA), an I/Q modulator, and another EDFA. The I/Q modulator was...communication link testbed. ECL: external cavity laser . EDFA: erbium-doped fiber amplifier. PC: polarization controller. ATT: attenuator. BPF: bandpass filter

Dual-band microstrip patch antenna based on metamaterial refractive surface

NASA Astrophysics Data System (ADS)

Salhi, Ridha; Labidi, Mondher; Boujemaa, Mohamed Ali; Choubani, Fethi

2017-06-01

In this paper, we present a new design of microstrip patch antenna based on metamaterial refractive surface (MRS). By optimizing the air gap between the MRS layer and the patch antenna to be 7 mm, the band width and the gain of the proposed antenna are significantly enhanced. The proposed prototype presents a dual band antenna. The center frequency for the first band is 2.44 GHz and the generated bandwidth is 25 MHz. The second band has a center frequency of 2.8 GHz and with a bandwidth of 50 MHz. The simulation results are analyzed and discussed in terms of return loss, gain and radiation pattern using electromagnetic simulator software. Finally, the designed dual band antenna is fabricated and different measurement results are performed and compared with simulation results in order to validate its performances. The proposed antenna supports WiBro (wireless broadband), ISM, WiFi, Bluetooth, WiMAX and radars services.

Extrapolation of earth-based solar irradiance measurements to exoatmospheric levels for broad-band and selected absorption-band observations

NASA Technical Reports Server (NTRS)

Reagan, John A.; Pilewskie, Peter A.; Scott-Fleming, Ian C.; Herman, Benjamin M.; Ben-David, Avishai

1987-01-01

Techniques for extrapolating earth-based spectral band measurements of directly transmitted solar irradiance to equivalent exoatmospheric signal levels were used to aid in determining system gain settings of the Halogen Occultation Experiment (HALOE) sunsensor being developed for the NASA Upper Atmosphere Research Satellite and for the Stratospheric Aerosol and Gas (SAGE) 2 instrument on the Earth Radiation Budget Satellite. A band transmittance approach was employed for the HALOE sunsensor which has a broad-band channel determined by the spectral responsivity of a silicon detector. A modified Langley plot approach, assuming a square-root law behavior for the water vapor transmittance, was used for the SAGE-2 940 nm water vapor channel.

Ultra-wide acoustic band gaps in pillar-based phononic crystal strips

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coffy, Etienne, E-mail: etienne.coffy@femto-st.fr; Lavergne, Thomas; Addouche, Mahmoud

2015-12-07

An original approach for designing a one dimensional phononic crystal strip with an ultra-wide band gap is presented. The strip consists of periodic pillars erected on a tailored beam, enabling the generation of a band gap that is due to both Bragg scattering and local resonances. The optimized combination of both effects results in the lowering and the widening of the main band gap, ultimately leading to a gap-to-midgap ratio of 138%. The design method used to improve the band gap width is based on the flattening of phononic bands and relies on the study of the modal energy distributionmore » within the unit cell. The computed transmission through a finite number of periods corroborates the dispersion diagram. The strong attenuation, in excess of 150 dB for only five periods, highlights the interest of such ultra-wide band gap phononic crystal strips.« less

WISEP J061135.13-041024.0 AB: A J-band Flux Reversal Binary at the L/T Transition

NASA Astrophysics Data System (ADS)

Gelino, Christopher R.; Smart, R. L.; Marocco, Federico; Kirkpatrick, J. Davy; Cushing, Michael C.; Mace, Gregory; Mendez, Rene A.; Tinney, C. G.; Jones, Hugh R. A.

2014-07-01

We present Keck II laser guide star adaptive optics observations of the brown dwarf WISEP J061135.13-041024.0 showing it is a binary with a component separation of 0.''4. This system is one of the six known resolved binaries in which the magnitude differences between the components show a reversal in sign between the Y/J band and the H/K bands. Deconvolution of the composite spectrum results in a best-fit binary solution with L9 and T1.5 components. We also present a preliminary parallax placing the system at a distance of 21.2 ± 1.3 pc. Using the distance and resolved magnitudes we are able to place WISEP J061135.13-041024.0 AB on a color-absolute magnitude diagram, showing that this system contributes to the well-known "J-band bump" and the components' properties appear similar to other late-type L and early-type T dwarfs. Fitting our data to a set of cloudy atmosphere models suggests the system has an age >1 Gyr with WISE 0611-0410 A having an effective temperature (T eff) of 1275-1325 K and mass of 64-65 M Jup, and WISE 0611-0410 B having T eff = 1075-1115 K and mass 40-65 M Jup.

Investigation on the Frequency Allocation for Radio Astronomy at the L Band

NASA Astrophysics Data System (ADS)

Abidin, Z. Z.; Umar, R.; Ibrahim, Z. A.; Rosli, Z.; Asanok, K.; Gasiprong, N.

2013-09-01

In this paper, the frequency allocation reserved for radio astronomy in the L band set by the International Telecommunication Union (ITU), which is between 1400 and 1427 MHz, is reviewed. We argue that the nearby frequencies are still very important for radio astronomers on the ground by investigating radio objects (H i sources) around 1300-1500 MHz. The L-band window is separated into a group of four windows, namely 1400-1427 MHz (window A), 1380-1400 MHz (window B), 1350-1380 MHz (window C), and 1300-1350 MHz (window D). These windows are selected according to their redshifts from a rest frequency for hydrogen spectral line at 1420.4057 MHz. Radio objects up to z ≈ 0.1 or frequency down to 1300 MHz are examined. We argue that since window B has important radio objects within the four windows, this window should also be given to radio astronomy. They are galaxies, spiral galaxies, and galaxy clusters. This underlines the significance of window B for radio astronomers on the ground. By investigating the severeness of radio frequency interference (RFI) within these windows, we have determined that window B still has significant, consistent RFI. The main RFI sources in the four windows have also been identified. We also found that the Department of Civil Aviation of Malaysia is assigned a frequency range of 1215-1427 MHz, which is transmitted within the four windows and inside the protected frequency for radio astronomy. We also investigated the RFI in the four windows on proposed sites of future radio astronomy observatories in Malaysia and Thailand and found the two best sites as Universiti Pendidikan Sultan Idris (UPSI) and Ubon Ratchathani, respectively. It has also been determined that RFI in window B increases with population density.

Ultra-Thin Dual-Band Polarization-Insensitive and Wide-Angle Perfect Metamaterial Absorber Based on a Single Circular Sector Resonator Structure

NASA Astrophysics Data System (ADS)

Luo, Hao; Cheng, Yong Zhi

2018-01-01

We present a simple design for an ultra-thin dual-band polarization-insensitive and wide-angle perfect metamaterial absorber (PMMA) based on a single circular sector resonator structure (CSRS). Both simulation and experimental results reveal that two resonance peaks with average absorption above 99% can be achieved. The dual-band PMMA is ultra-thin with total thickness of 0.5 mm, which is <l/38 with respect to the operation frequencies. The surface electric field and current distributions of the unit-cell structure reveal the physical picture of the dual-band absorption. Numerical simulations demonstrate that the PMMA could retain high absorption level at large angles of polarization and incidence for both transverse electric (TE) and transverse magnetic (TM) modes. Furthermore, the absorption properties of the PMMA can be adjusted by varying the geometric parameters of the unit-cell structure.

Extrapolation of Earth-based solar irradiance measurements to exoatmospheric levels for broad-band and selected absorption-band observations

NASA Technical Reports Server (NTRS)

Reagan, J. A.; Pilewskie, P. A.; Scott-Fleming, I. C.; Hermann, B. M.

1986-01-01

Techniques for extrapolating Earth-based spectral band measurements of directly transmitted solar irradiance to equivalent exoatmospheric signal levels were used to aid in determining system gain settings of the Halogen Occultation Experiment (HALOE) sunsensor system being developed for the NASA Upper Atmosphere Research Satellite and for the Stratospheric Aerosol and Gas (SAGE) 2 instrument on the Earth Radiation Budget Satellite. A band transmittance approach was employed for the HALOE sunsensor which has a broad-band channel determined by the spectral responsivity of a silicon detector. A modified Langley plot approach, assuming a square-root law behavior for the water vapor transmittance, was used for the SAGE-2 940 nm water vapor channel.

Simultaneous dual-band radar development

NASA Technical Reports Server (NTRS)

Liskow, C. L.

1974-01-01

Efforts to design and construct an airborne imaging radar operating simultaneously at L band and X band with an all-inertial navigation system in order to form a dual-band radar system are described. The areas of development include duplex transmitters, receivers, and recorders, a control module, motion compensation for both bands, and adaptation of a commercial inertial navigation system. Installation of the system in the aircraft and flight tests are described. Circuit diagrams, performance figures, and some radar images are presented.

The Aquarius Ocean Salinity Mission High Stability L-band Radiometer

NASA Technical Reports Server (NTRS)

Pellerano, Fernando A.; Piepmeier, Jeffrey; Triesky, Michael; Horgan, Kevin; Forgione, Joshua; Caldwell, James; Wilson, William J.; Yueh, Simon; Spencer, Michael; McWatters, Dalia;

Strain-free Ge/GeSiSn Quantum Cascade Lasers Based on L-Valley Intersubband Transitions

DTIC Science & Technology

2007-01-01

found in III-V quantum cascade lasers QCLs. Various groups have obtained electroluminescence from Si-rich Si/SiGe quantum cascade structures,2–4 but...Ge/GeSiSn quantum cascade lasers based on L-valley intersubband transitions 5c. PROGRAM ELEMENT NUMBER 612305 6. AUTHOR(S) 5d. PROJECT NUMBER...ABSTRACT The authors propose a Ge/Ge0.76Si0.19Sn0.05 quantum cascade laser using intersubband transitions at L valleys of the conduction band

Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lang, R.; Wentz, F.; Messiner, T.

2012-01-01

A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.1 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest.

Simulation of amide I' band profiles of trans polyproline based on an excitonic coupling model

NASA Astrophysics Data System (ADS)

Measey, Thomas; Schweitzer-Stenner, Reinhard

2005-06-01

We measured the amide I' band profile of the IR, isotropic Raman, anisotropic Raman, and Vibrational Circular Dichroism spectrum of poly- L-proline in D 2O. The band shapes were modeled by using an algorithm that exploits the delocalized character of the excited vibrational states [R. Schweitzer-Stenner, J. Phys. Chem. B. 108 (2004) 16965]. The band shapes could be quantitatively reproduced by invoking the polyproline II or 3 1-helix conformation for all peptide residues. This corroborates the notion that the combined use of the above spectroscopies is an ideal tool to discriminate different conformations associated with the so-called random coil state of peptides.

Coherence Effects in L-Band Active and Passive Remote Sensing of Quasi-Periodic Corn Canopies

NASA Technical Reports Server (NTRS)

Utku, Cuneyt; Lang, Roger H.

2011-01-01

Due to their highly random nature, vegetation canopies can be modeled using the incoherent transport theory for active and passive remote sensing applications. Agricultural vegetation canopies however are generally more structured than natural vegetation. The inherent row structure in agricultural canopies induces coherence effects disregarded by the transport theory. The objective of this study is to demonstrate, via Monte-Carlo simulations, these coherence effects on L-band scattering and thermal emission from corn canopies consisting of only stalks.

Newly Formed Sea Ice in Arctic Leads Monitored by C- and L-Band SAR

NASA Astrophysics Data System (ADS)

Johansson, A. Malin; Brekke, Camilla; Spreen, Gunnar; King, Jennifer A.; Gerland, Sebastian

2016-08-01

We investigate the scattering entropy and co-polarization ratio for Arctic lead ice using C- and L-band synthetic aperture radar (SAR) satellite scenes. During the Norwegian Young sea ICE (N-ICE2015) cruise campaign overlapping SAR scenes, helicopter borne sea ice thickness measurements and photographs were collected. We can therefore relate the SAR signal to sea ice thickness measurements as well as photographs taken of the sea ice. We show that a combination of scattering and co-polarization ratio values can be used to distinguish young ice from open water and surrounding sea ice.

Development of NASA's Next Generation L-Band Digital Beamforming Synthetic Aperture Radar (DBSAR-2)

NASA Technical Reports Server (NTRS)

Rincon, Rafael; Fatoyinbo, Temilola; Osmanoglu, Batuhan; Lee, Seung-Kuk; Ranson, K. Jon; Marrero, Victor; Yeary, Mark

2014-01-01

NASA's Next generation Digital Beamforming SAR (DBSAR-2) is a state-of-the-art airborne L-band radar developed at the NASA Goddard Space Flight Center (GSFC). The instrument builds upon the advanced architectures in NASA's DBSAR-1 and EcoSAR instruments. The new instrument employs a 16-channel radar architecture characterized by multi-mode operation, software defined waveform generation, digital beamforming, and configurable radar parameters. The instrument has been design to support several disciplines in Earth and Planetary sciences. The instrument was recently completed, and tested and calibrated in a anechoic chamber.

Advanced Land Observing Satellite (ALOS) Phased Array Type L-Band Synthetic Aperture Radar (PALSAR) mosaic for the Kahiltna terrane, Alaska, 2007-2010

USGS Publications Warehouse

Cole, Christopher J.; Johnson, Michaela R.; Graham, Garth E.

2015-01-01

The USGS has compiled a continuous, cloud-free 12.5-meter resolution radar mosaic of SAR data of approximately 212,000 square kilometers to examine the suitability of this technology for geologic mapping. This mosaic was created from Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data collected from 2007 to 2010 spanning the Kahiltna terrane and the surrounding area. Interpretation of these data may help geologists understand past geologic processes and identify areas with potential for near-surface mineral resources for further ground-based geological and geochemical investigations.

The correlation of Skylab L-band brightness temperatures with antecedent precipitation

NASA Technical Reports Server (NTRS)

Mcfarland, M. J.

1975-01-01

The S194 L-band radiometer flown on the Skylab mission measured terrestrial radiation at the microwave wavelength of 21.4 cm. The terrain emissivity at this wavelength is strongly dependent on the soil moisture content, which can be inferred from antecedent precipitation. For the Skylab data acquisition pass from the Oklahoma panhandle to southeastern Texas on 11 June 1973, the S194 brightness temperatures are highly correlated with antecedent precipitation from the preceding eleven day period, but very little correlation was apparent for the preceding five day period. The correlation coefficient between the averaged antecedent precipitation index values and the corresponding S194 brightness temperatures between 230 K and 270 K, the region of apparent response to soil moisture in the data, was -0.97. The equation of the linear least squares line is given.

L-band Microwave Remote Sensing and Land Data Assimilation Improve the Representation of Prestorm Soil Moisture Conditions for Hydrologic Forecasting

NASA Technical Reports Server (NTRS)

Crow, W. T.; Chen, F.; Reichle, R. H.; Liu, Q.

2017-01-01

Recent advances in remote sensing and land data assimilation purport to improve the quality of antecedent soil moisture information available for operational hydrologic forecasting. We objectively validate this claim by calculating the strength of the relationship between storm-scale runoff ratio (i.e., total stream flow divided by total rainfall accumulation in depth units) and pre-storm surface soil moisture estimates from a range of surface soil moisture data products. Results demonstrate that both satellite-based, L-band microwave radiometry and the application of land data assimilation techniques have significantly improved the utility of surface soil moisture data sets for forecasting stream flow response to future rainfall events.

Effects of banding or burdizzo castration of bulls on neutrophil phagocytosis and respiratory burst, CD62-L expression, and serum interleukin-8 concentration.

PubMed

Pang, W Y; Earley, B; Sweeney, T; Pirani, S; Gath, V; Crowe, M A

2009-10-01

The objective was to investigate measures of neutrophil function in response to banding or burdizzo castration of bulls. Thirty-two Holstein-Friesian bulls (14 mo old, 505 +/- 7.8 kg of BW) were assigned to 1 of 4 treatment groups: 1) sham-handled control (CON); 2) banding castration alone (BAND); 3) burdizzo castration alone (BURD); or 4) cortisol infusion (CORT) as a further control group. For each group on d -14, 8 animals (2 animals/treatment) were tied up in tie stalls (day of treatment = d 0). At -2, 2, 6, 12, 24, 48, 72, and 144 h relative to treatment time, blood samples were collected for analyses of neutrophil phagocytosis and respiratory burst, neutrophil CD62-L expression, and serum IL-8 concentration. Leukocyte counts, phagocytosis activity, and CD62-L expression were similar (P > 0.05) among the 4 treatment groups. The BURD castrates had greater burst activity compared with BAND castrates (P = 0.048) and CON (P = 0.01) at 72 h posttreatment. The BURD castrates had a greater percentage of granulocyte positive leukocytes (Gr%; P < 0.01) at 2 h posttreatment compared with CON and CORT bulls. The BURD castrates had greater (P < 0.05) Gr% compared with BAND, CON, and CORT animals at 24, 48, and 72 h posttreatment. The BURD and BAND castrates had greater Gr% (P < 0.05) compared with CORT bulls at 144 h posttreatment. In general, BAND, BURD, and CORT did not affect serum IL-8 concentration. Banding castration, BURD, and CORT did not induce leukocytosis, whereas BURD induced a modest neutrophilia. Neutrophil functioning in terms of phagocytosis and respiratory burst and serum IL-8 concentration were not compromised by BAND, BURD, and CORT. These findings indicate nonsurgical castration is unlikely to induce a severe acute systemic inflammatory response in terms of neutrophil function.

Weekly Gridded Aquarius L-band Radiometer-scatterometer Observations and Salinity Retrievals over the Polar Regions - Part 1: Product Description

NASA Technical Reports Server (NTRS)

Brucker, Ludovic; Dinnat, Emmanuel Phillippe; Koenig, Lora S.

2014-01-01

Passive and active observations at L band (frequency (is) approximately 1.4 GHz) from the Aquarius/SAC-D mission offer new capabilities to study the polar regions. Due to the lack of polar-gridded products, however, applications over the cryosphere have been limited. We present three weekly polar-gridded products of Aquarius data to improve our understanding of L-band observations of ice sheets, sea ice, permafrost, and the polar oceans. Additionally, these products intend to facilitate access to L-band data, and can be used to assist in algorithm developments. Aquarius data at latitudes higher than 50 degrees are averaged and gridded into weekly products of brightness temperature (TB), normalized radar cross section (NRCS), and sea surface salinity (SSS). Each grid cell also contains sea ice fraction, the standard deviation of TB, NRCS, and SSS, and the number of footprint observations collected during the seven-day cycle. The largest 3 dB footprint dimensions are 97 km×156 km and 74 km×122 km (along × across track) for the radiometers and scatterometer, respectively. The data is gridded to the Equal-Area Scalable Earth version 2.0 (EASE2.0) grid, with a grid cell resolution of 36 km. The data sets start in August 2011, with the first Aquarius observations and will be updated on a monthly basis following the release schedule of the Aquarius Level 2 data sets. The weekly gridded products are distributed by the US National Snow and Ice Data Center at http://nsidc.org/data/aquarius/index.html

77 FR 76003 - Submission for OMB Review; Comment Request-Safety Standard for Omnidirectional Citizens Band Base...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-26

... Request--Safety Standard for Omnidirectional Citizens Band Base Station Antennas AGENCY: Consumer Product... antennas. DATES: Written comments on this request for extension of approval of information collection... Citizens Band Base Station Antennas establishes performance requirements for omnidirectional citizens band...

Laser a balayage spectral double-bande pour l'imagerie biomedicale multimodale

NASA Astrophysics Data System (ADS)

Goulamhoussen, Nadir

A novel swept laser providing simultaneous dual-band (780nm and 1 300 nm) wavelength scanning has been designed for use in multimodal imaging systems. The swept laser is based on two gain media : a fibered semiconductor optical amplifier (SOA) centered at 1 300nm and a free-space laser diode centered at 780 nm. Simultaneous wavelength tuning for both bands is obtained by separate wavelength filters set up around the same rotating polygonal mirror. For each band, a telescope in an infinite conjugate setup converges the wavelengths dispersed by a grating on the polygon. The polygon reflects back a narrow band of wavelengths for amplification in the gain medium. Rotating the polygon enables wavelength tuning and imaging at a rate of 6 000 to 30 000 spectral lines/s, or A-lines/s in Optical Coherence Tomography (OCT). The 780nm source has a bandwidth of 37 nm, a fibered output power of 54 mW and a coherence length of 11 mm. The 1 300nm source has a bandwidth of 75 nm, a fibered output power of 17mW and a coherence length of 7.2 mm. Three multimodal systems were designed to test the potential of the swept laser in biomedical imaging. A two color OCT which allows three-dimensional in depth imaging of biological tissues with good morphological contrast was first designed, including a novel arrangement for balanced detection in both bands. A simultaneous OCT and SECM instrument was also built in which spectrally encoded confocal microscopy (SECM) provides en face images of subcellular features with high resolution on top of the 3D high penetration image obtained by OCT. Finally, a system combining OCT with fluorescence was designed, thus adding functional imaging to structural OCT images. There are many prospective paths for these three modalities, first among them the adaptation of the systems such that they may be used with imaging probes. One potential solution would be the development of novel fiber components to combine the illumination of theses modalities while

L-Band Digital Aeronautical Communications System Engineering - Concepts of Use, Systems Performance, Requirements, and Architectures

NASA Technical Reports Server (NTRS)

Zelkin, Natalie; Henriksen, Stephen

2010-01-01

This NASA Contractor Report summarizes and documents the work performed to develop concepts of use (ConUse) and high-level system requirements and architecture for the proposed L-band (960 to 1164 MHz) terrestrial en route communications system. This work was completed as a follow-on to the technology assessment conducted by NASA Glenn Research Center and ITT for the Future Communications Study (FCS). ITT assessed air-to-ground (A/G) communications concepts of use and operations presented in relevant NAS-level, international, and NAS-system-level documents to derive the appropriate ConUse relevant to potential A/G communications applications and services for domestic continental airspace. ITT also leveraged prior concepts of use developed during the earlier phases of the FCS. A middle-out functional architecture was adopted by merging the functional system requirements identified in the bottom-up assessment of existing requirements with those derived as a result of the top-down analysis of ConUse and higher level functional requirements. Initial end-to-end system performance requirements were derived to define system capabilities based on the functional requirements and on NAS-SR-1000 and the Operational Performance Assessment conducted as part of the COCR. A high-level notional architecture of the L-DACS supporting A/G communication was derived from the functional architecture and requirements.

Sensitivity of gap symmetry to an incipient band: Application to iron based superconductors

NASA Astrophysics Data System (ADS)

Mishra, Vivek; Scalapino, Douglas; Maier, Thomas

Observation of high temperature superconductivity in iron-based superconductors with a submerged hole band has attracted wide interest. A spin fluctuation mediated pairing mechanism has been proposed as a possible explanation for the high transition temperatures observed in these systems. Here we discuss the importance of the submerged band in the context of the gap symmetry. We show that the incipient band can lead to an attractive pairing interaction and thus have significant effects on the pairing symmetry. We propose a framework to include the effect of the incipient band in the standard multi-orbital spin-fluctuation theories which are widely used for studying various iron-based superconductors. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

The Latest Results from the Focal L-Band Array for the Green Bank Telescope (FLAG), the World's (Current) Most Sensitive Phased Array Feed

NASA Astrophysics Data System (ADS)

Pingel, Nickolas; Pisano, D. J.

2018-01-01

Phased Array Feeds (PAFs) represent the next revolution in radio astronomy instrumentation. I will present results from the latest commissioning run from the Focal L-Band Array for the Green Bank telescope (FLAG), which holds the current world record for PAF sensitivity. Since we are able to operate at system temperatures comparable with the traditional GBT single pixel L-Band feed, the increase in the field-of-view provided by the beamforming capabilities of PAFs results in a dramatic (a factor of 5) increase in survey speeds. In particular, FLAG can probe similar neutral hydrogen column density regimes over a 4 sq. deg region in 24.6 minutes as opposed to 4.1 hours in an equivalent single pixel map (excluding observing overhead). In addition to comparisons between data taken with FLAG and the single-pixel L-Band feed, I will also discuss the technical aspects of the observing procedure, data reduction, and the transition path for FLAG from an instrument that is principle-investigator run to one that is general use. These FLAG results provide a very encouraging outlook on how the GBT will continue to compete with current and planned radio telescope facilities.

Impact of surface roughness on L-band emissivity of the sea ice

NASA Astrophysics Data System (ADS)

Miernecki, M.; Kaleschke, L.; Hendricks, S.; Søbjærg, S. S.

2015-12-01

In March 2014 a joint experiment IRO2/SMOSice was carried out in the Barents Sea. R/V Lance equipped with meteorological instruments, electromagnetic sea ice thickness probe and engine monitoring instruments, was performing a series of tests in different ice conditions in order to validate the ice route optimization (IRO) system, advising on his route through pack ice. In parallel cal/val activities for sea ice thickness product obtained from SMOS (Soil Moisture and Ocean Salinity mission) L-band radiometer were carried out. Apart from helicopter towing the EMbird thickness probe, Polar 5 aircraft was serving the area during the experiment with L-band radiometer EMIRAD2 and Airborne Laser Scanner (ALS) as primary instruments. Sea ice Thickness algorithm using SMOS brightness temperature developed at University of Hamburg, provides daily maps of thin sea ice (up to 0.5-1 m) in polar regions with resolution of 35-50 km. So far the retrieval method was not taking into account surface roughness, assuming that sea ice is a specular surface. Roughness is a stochastic process that can be characterized by standard deviation of surface height σ and by shape of the autocorrelation function R to estimate it's vertical and horizontal scales respectively. Interactions of electromagnetic radiation with the surface of the medium are dependent on R and σ and they scales with respect to the incident wavelength. During SMOSice the radiometer was observing sea ice surface at two incidence angles 0 and 40 degrees and simultaneously the surface elevation was scanned with ALS with ground resolution of ~ 0.25 m. This configuration allowed us to calculate σ and R from power spectral densities of surface elevation profiles and quantify the effect of surface roughness on the emissivity of the sea ice. First results indicate that Gaussian autocorrelation function is suitable for deformed ice, for other ice types exponential function is the best fit.

Efficient Band-to-Trap Tunneling Model Including Heterojunction Band Offset

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Xujiao; Huang, Andy; Kerr, Bert

In this paper, we present an efficient band-to-trap tunneling model based on the Schenk approach, in which an analytic density-of-states (DOS) model is developed based on the open boundary scattering method. The new model explicitly includes the effect of heterojunction band offset, in addition to the well-known field effect. Its analytic form enables straightforward implementation into TCAD device simulators. It is applicable to all one-dimensional potentials, which can be approximated to a good degree such that the approximated potentials lead to piecewise analytic wave functions with open boundary conditions. The model allows for simulating both the electric-field-enhanced and band-offset-enhanced carriermore » recombination due to the band-to-trap tunneling near the heterojunction in a heterojunction bipolar transistor (HBT). Simulation results of an InGaP/GaAs/GaAs NPN HBT show that the proposed model predicts significantly increased base currents, due to the hole-to-trap tunneling enhanced by the emitter-base junction band offset. Finally, the results compare favorably with experimental observation.« less

Efficient Band-to-Trap Tunneling Model Including Heterojunction Band Offset

DOE PAGES

Gao, Xujiao; Huang, Andy; Kerr, Bert

2017-10-25

In this paper, we present an efficient band-to-trap tunneling model based on the Schenk approach, in which an analytic density-of-states (DOS) model is developed based on the open boundary scattering method. The new model explicitly includes the effect of heterojunction band offset, in addition to the well-known field effect. Its analytic form enables straightforward implementation into TCAD device simulators. It is applicable to all one-dimensional potentials, which can be approximated to a good degree such that the approximated potentials lead to piecewise analytic wave functions with open boundary conditions. The model allows for simulating both the electric-field-enhanced and band-offset-enhanced carriermore » recombination due to the band-to-trap tunneling near the heterojunction in a heterojunction bipolar transistor (HBT). Simulation results of an InGaP/GaAs/GaAs NPN HBT show that the proposed model predicts significantly increased base currents, due to the hole-to-trap tunneling enhanced by the emitter-base junction band offset. Finally, the results compare favorably with experimental observation.« less

Weekly gridded Aquarius L-band radiometer/scatterometer observations and salinity retrievals over the polar regions - Part 1: Product description

NASA Astrophysics Data System (ADS)

Brucker, L.; Dinnat, E. P.; Koenig, L. S.

2014-05-01

Passive and active observations at L band (frequency ~1.4 GHz) from the Aquarius/SAC-D mission offer new capabilities to study the polar regions. Due to the lack of polar-gridded products, however, applications over the cryosphere have been limited. We present three weekly polar-gridded products of Aquarius data to improve our understanding of L-band observations of ice sheets, sea ice, permafrost, and the polar oceans. Additionally, these products intend to facilitate access to L-band data, and can be used to assist in algorithm developments. Aquarius data at latitudes higher than 50° are averaged and gridded into weekly products of brightness temperature (TB), normalized radar cross section (NRCS), and sea surface salinity (SSS). Each grid cell also contains sea ice fraction, the standard deviation of TB, NRCS, and SSS, and the number of footprint observations collected during the seven-day cycle. The largest 3 dB footprint dimensions are 97 km × 156 km and 74 km × 122 km (along × across track) for the radiometers and scatterometer, respectively. The data is gridded to the Equal-Area Scalable Earth version 2.0 (EASE2.0) grid, with a grid cell resolution of 36 km. The data sets start in August 2011, with the first Aquarius observations and will be updated on a monthly basis following the release schedule of the Aquarius Level 2 data sets. The weekly gridded products are distributed by the US National Snow and Ice Data Center at http://nsidc.org/data/aquarius/index.html .

Low-bias flat band-stop filter based on velocity modulated gaussian graphene superlattice

NASA Astrophysics Data System (ADS)

Sattari-Esfahlan, S. M.; Shojaei, S.

2018-05-01

Transport properties of biased planar Gaussian graphene superlattice (PGGSL) with Fermi velocity barrier is investigated by transfer matrix method (TMM). It is observed that enlargement of bias voltage over miniband width breaks the miniband to WSLs leads to suppressing resonant tunneling. Transmission spectrum shows flat wide stop-band property controllable by external bias voltage with stop-band width of near 200 meV. The simulations demonstrate that strong velocity barriers prevent tunneling of Dirac electrons leading to controllable enhancement of stop-band width. By increasing ratio of Fermi velocity in barriers to wells υc stop-band width increase. As wide transmission stop-band width (BWT) of filter is tunable from 40 meV to 340 meV is obtained by enhancing ratio of υc from 0.2 to 1.5, respectively. Proposed structure suggests easy tunable wide band-stop electronic filter with a modulated flat stop-band characteristic by height of electrostatic barrier and structural parameters. Robust sensitivity of band width to velocity barrier intensity in certain bias voltages and flat band feature of proposed filter may be opens novel venue in GSL based flat band low noise filters and velocity modulation devices.

HST Rotational Spectral Mapping Of Two L-Type Brown Dwarfs: Variability In And Out Of Water Bands Indicates High-Altitude Haze Layers

DOE PAGES

Yang, Hao; Apai, Dániel; Marley, Mark S.; ...

2014-12-17

We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 μm and 1.7 μm. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at othermore » wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs. We utilize the models of Saumon & Marley (2008) and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers - the driver of the variability - must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.« less

HST ROTATIONAL SPECTRAL MAPPING OF TWO L-TYPE BROWN DWARFS: VARIABILITY IN AND OUT OF WATER BANDS INDICATES HIGH-ALTITUDE HAZE LAYERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Hao; Apai, Dániel; Karalidi, Theodora

We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759–1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 μm and 1.7 μm. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at othermore » wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs. We utilize the models of Saumon and Marley and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers—the driver of the variability—must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.« less

HST Rotational Spectral Mapping Of Two L-Type Brown Dwarfs: Variability In And Out Of Water Bands Indicates High-Altitude Haze Layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Hao; Apai, Dániel; Marley, Mark S.

We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 μm and 1.7 μm. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at othermore » wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs. We utilize the models of Saumon & Marley (2008) and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers - the driver of the variability - must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.« less

Performance of a High-Concentration Erbium-Doped Fiber Amplifier with 100 nm Amplification Bandwidth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hajireza, P.; Shahabuddin, N. S.; Abbasi-Zargaleh, S.

2010-07-07

Increasing demand for higher bandwidth has driven the need for higher Wavelength Division Multiplexing (WDM) channels. One of the requirements to achieve this is a broadband amplifier. This paper reports the performance of a broadband, compact, high-concentration and silica-based erbium-doped fiber amplifier. The amplifier optimized to a 2.15 m long erbium-doped fiber with erbium ion concentration of 2000 ppm. The gain spectrum of the amplifier has a measured amplification bandwidth of 100 nm using a 980 nm laser diode with power of 150 mW. This silica-based EDFA shows lower noise figure, higher gain and wider bandwidth in shorter wavelengths comparedmore » to Bismuth-based EDFA with higher erbium ion concentration of 3250 ppm at equivalent EDF length. The silica-based EDF shows peak gain at 22 dB and amplification bandwidth between 1520 nm and 1620 nm. The lowest noise figure is 5 dB. The gain is further improved with the implementation of enhanced EDFA configurations.« less

CAROLS: a new airborne L-band radiometer for ocean surface and land observations.

PubMed

Zribi, Mehrez; Pardé, Mickael; Boutin, Jacquline; Fanise, Pascal; Hauser, Daniele; Dechambre, Monique; Kerr, Yann; Leduc-Leballeur, Marion; Reverdin, Gilles; Skou, Niels; Søbjærg, Sten; Albergel, Clement; Calvet, Jean Christophe; Wigneron, Jean Pierre; Lopez-Baeza, Ernesto; Rius, Antonio; Tenerelli, Joseph

2011-01-01

The "Cooperative Airborne Radiometer for Ocean and Land Studies" (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It is installed on board a dedicated French ATR42 research aircraft, in conjunction with other airborne instruments (C-Band scatterometer-STORM, the GOLD-RTR GPS system, the infrared CIMEL radiometer and a visible wavelength camera). Following initial laboratory qualifications, three airborne campaigns involving 21 flights were carried out over South West France, the Valencia site and the Bay of Biscay (Atlantic Ocean) in 2007, 2008 and 2009, in coordination with in situ field campaigns. In order to validate the CAROLS data, various aircraft flight patterns and maneuvers were implemented, including straight horizontal flights, circular flights, wing and nose wags over the ocean. Analysis of the first two campaigns in 2007 and 2008 leads us to improve the CAROLS radiometer regarding isolation between channels and filter bandwidth. After implementation of these improvements, results show that the instrument is conforming to specification and is a useful tool for Soil Moisture and Ocean Salinity (SMOS) satellite validation as well as for specific studies on surface soil moisture or ocean salinity.

L-band microwave remote sensing and land data assimilation improve the representation of pre-storm soil moisture conditions for hydrologic forecasting.

PubMed

Crow, W T; Chen, F; Reichle, R H; Liu, Q

2017-06-16

Recent advances in remote sensing and land data assimilation purport to improve the quality of antecedent soil moisture information available for operational hydrologic forecasting. We objectively validate this claim by calculating the strength of the relationship between storm-scale runoff ratio (i.e., total stream flow divided by total rainfall accumulation in depth units) and pre-storm surface soil moisture estimates from a range of surface soil moisture data products. Results demonstrate that both satellite-based, L-band microwave radiometry and the application of land data assimilation techniques have significantly improved the utility of surface soil moisture data sets for forecasting stream flow response to future rainfall events.

L-band microwave remote sensing and land data assimilation improve the representation of pre-storm soil moisture conditions for hydrologic forecasting

PubMed Central

Crow, W.T.; Chen, F.; Reichle, R.H.; Liu, Q.

2018-01-01

Recent advances in remote sensing and land data assimilation purport to improve the quality of antecedent soil moisture information available for operational hydrologic forecasting. We objectively validate this claim by calculating the strength of the relationship between storm-scale runoff ratio (i.e., total stream flow divided by total rainfall accumulation in depth units) and pre-storm surface soil moisture estimates from a range of surface soil moisture data products. Results demonstrate that both satellite-based, L-band microwave radiometry and the application of land data assimilation techniques have significantly improved the utility of surface soil moisture data sets for forecasting stream flow response to future rainfall events. PMID:29657342

Cell-Based Sensor System Using L6 Cells for Broad Band Continuous Pollutant Monitoring in Aquatic Environments

PubMed Central

Kubisch, Rebekka; Bohrn, Ulrich; Fleischer, Maximilian; Stütz, Evamaria

2012-01-01

Pollution of drinking water sources represents a continuously emerging problem in global environmental protection. Novel techniques for real-time monitoring of water quality, capable of the detection of unanticipated toxic and bioactive substances, are urgently needed. In this study, the applicability of a cell-based sensor system using selected eukaryotic cell lines for the detection of aquatic pollutants is shown. Readout parameters of the cells were the acidification (metabolism), oxygen consumption (respiration) and impedance (morphology) of the cells. A variety of potential cytotoxic classes of substances (heavy metals, pharmaceuticals, neurotoxins, waste water) was tested with monolayers of L6 cells (rat myoblasts). The cytotoxicity or cellular effects induced by inorganic ions (Ni2+ and Cu2+) can be detected with the metabolic parameters acidification and respiration down to 0.5 mg/L, whereas the detection limit for other substances like nicotine and acetaminophen are rather high, in the range of 0.1 mg/L and 100 mg/L. In a close to application model a real waste water sample shows detectable signals, indicating the existence of cytotoxic substances. The results support the paradigm change from single substance detection to the monitoring of overall toxicity. PMID:22737014

Cell-based sensor system using L6 cells for broad band continuous pollutant monitoring in aquatic environments.

PubMed

Kubisch, Rebekka; Bohrn, Ulrich; Fleischer, Maximilian; Stütz, Evamaria

2012-01-01

Pollution of drinking water sources represents a continuously emerging problem in global environmental protection. Novel techniques for real-time monitoring of water quality, capable of the detection of unanticipated toxic and bioactive substances, are urgently needed. In this study, the applicability of a cell-based sensor system using selected eukaryotic cell lines for the detection of aquatic pollutants is shown. Readout parameters of the cells were the acidification (metabolism), oxygen consumption (respiration) and impedance (morphology) of the cells. A variety of potential cytotoxic classes of substances (heavy metals, pharmaceuticals, neurotoxins, waste water) was tested with monolayers of L6 cells (rat myoblasts). The cytotoxicity or cellular effects induced by inorganic ions (Ni(2+) and Cu(2+)) can be detected with the metabolic parameters acidification and respiration down to 0.5 mg/L, whereas the detection limit for other substances like nicotine and acetaminophen are rather high, in the range of 0.1 mg/L and 100 mg/L. In a close to application model a real waste water sample shows detectable signals, indicating the existence of cytotoxic substances. The results support the paradigm change from single substance detection to the monitoring of overall toxicity.

Optical frequency comb based multi-band microwave frequency conversion for satellite applications.

PubMed

Yang, Xinwu; Xu, Kun; Yin, Jie; Dai, Yitang; Yin, Feifei; Li, Jianqiang; Lu, Hua; Liu, Tao; Ji, Yuefeng

2014-01-13

Based on optical frequency combs (OFC), we propose an efficient and flexible multi-band frequency conversion scheme for satellite repeater applications. The underlying principle is to mix dual coherent OFCs with one of which carrying the input signal. By optically channelizing the mixed OFCs, the converted signal in different bands can be obtained in different channels. Alternatively, the scheme can be configured to generate multi-band local oscillators (LO) for widely distribution. Moreover, the scheme realizes simultaneous inter- and intra-band frequency conversion just in a single structure and needs only three frequency-fixed microwave sources. We carry out a proof of concept experiment in which multiple LOs with 2 GHz, 10 GHz, 18 GHz, and 26 GHz are generated. A C-band signal of 6.1 GHz input to the proposed scheme is successfully converted to 4.1 GHz (C band), 3.9 GHz (C band) and 11.9 GHz (X band), etc. Compared with the back-to-back (B2B) case measured at 0 dBm input power, the proposed scheme shows a 9.3% error vector magnitude (EVM) degradation at each output channel. Furthermore, all channels satisfy the EVM limit in a very wide input power range.

Use of EO-1 Hyperion data to calculate spectral band adjustment factors (SBAF) between the L7 ETM+ and Terra MODIS sensors

USGS Publications Warehouse

Chander, Gyanesh; Mishra, N.; Helder, Dennis L.; Aaron, David; Choi, T.; Angal, A.; Xiong, X.

2010-01-01

Different applications and technology developments in Earth observations necessarily require different spectral coverage. Thus, even for the spectral bands designed to look at the same region of the electromagnetic spectrum, the relative spectral responses (RSR) of different sensors may be different. In this study, spectral band adjustment factors (SBAF) are derived using hyperspectral Earth Observing-1 (EO-1) Hyperion measurements to adjust for the spectral band differences between the Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) and the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) top-of-atmosphere (TOA) reflectance measurements from 2000 to 2009 over the pseudo-invariant Libya 4 reference standard test site.

Calculation of the X-Ray emission K and L 2,3 bands of metallic magnesium and aluminum with allowance for multielectron effects

NASA Astrophysics Data System (ADS)

Ovcharenko, R. E.; Tupitsyn, I. I.; Savinov, E. P.; Voloshina, E. N.; Dedkov, Yu. S.; Shulakov, A. S.

2014-01-01

A procedure is proposed to calculate the shape of the characteristic X-ray emission bands of metals with allowance for multielectron effects. The effects of the dynamic screening of a core vacancy by conduction electrons and the Auger effect in the valence band are taken into account. The dynamic screening of a core vacancy, which is known to be called the MND (Mahan-Nozeieres-De Dominics) effect, is taken into account by an ab initio band calculation of crystals using the PAW (projected augmented waves) method. The Auger effect is taken into account by a semiempirical method using the approximation of a quadratic dependence of the level width in the valence band on the difference between the level energy and the Fermi energy. The proposed calculation procedure is used to describe the X-ray emission K and L 2,3 bands of metallic magnesium and aluminum crystals. The calculated spectra agree well with the experimental bands both near the Fermi level and in the low-energy part of the spectra in all cases.

The correlation of Skylab L-band brightness temperatures with antecedent precipitation

NASA Technical Reports Server (NTRS)

Mcfarland, M. J.

1975-01-01

The S194 L-band radiometer flown on the Skylab mission measured terrestrial radiation at the microwave wavelength of 21.4 cm. The terrain emissivity at this wavelength is strongly dependent on the soil moisture content, which can be inferred from antecedent precipitation. For the Skylab data acquisition pass from the Oklahoma panhandle to southeastern Texas on 11 June 1973, the S194 brightness temperatures are highly correlated with antecedent precipitation from the preceding eleven day period, but very little correlation was apparent for the preceding five day period. The correlation coefficient between the averaged antecedent precipitation index values and the corresponding S194 brightness temperatures between 230 K and 270 K, the region of apparent response to soil moisture in the data, was -0.97. The equation of the linear least squares line fitted to the data was: API (cm) = 31.99 -0.114 TB (K), where API is the antecedent precipitation index and TB is the S194 brightness temperature.

Giant Pulse Phenomena in a High Gain Erbium Doped Fiber Amplifier

NASA Technical Reports Server (NTRS)

Li, Stephen X.; Merritt, Scott; Krainak, Michael A.; Yu, Anthony

2018-01-01

High gain Erbium Doped Fiber Amplifiers (EDFAs), while revolutionizing optical communications, remain vulnerable to optical damage when unseeded, e.g. due to nonlinear effects that produce random pulses with high peak power, i.e. giant pulses. Giant pulses can damage the components in a high gain EDFA or external components and systems coupled to the EDFA. We explore the conditions under which a reflective, polarization-maintaining (PM), core-pumped high gain EDFA generates giant pulses, provide details on conditions under which normal pulses evolve into giant pulses, and provide results on the transient effects of giant pulses on amplifier's fused-fiber couplers, an effect which we call Fiber Overload Induced Leakage (FOIL). While FOIL's effect on fused-fiber couplers is temporary, its damage to forward pump lasers in a high gain EDFA can be permanent.

A new technique to characterize foliage attenuation using passive radar in the L-band

NASA Astrophysics Data System (ADS)

Lesturgie, Marc; Thirion-Lefèvre, Laetitia; Saillant, Stéphane; Dorey, Philippe

2016-11-01

The goal of the experiment proposed in this paper is to give rapidly and with a limited equipment the attenuation level in the L-band for various elevation angles, between 20 and 70 degrees. The original principle is to use the L-band signal transmitted from an airport radar. The signal backscattered by a plane flying over the forest next to the airport is received on many antennas: some are over the canopy; others are on the ground under the foliage. The direct path signal transmitted by the airport radar is received by the antennas located above the forest. This signal is used to synchronize the temporal signals by detecting the waveform of the transmitting pulses. The signal backscattered by the plane is received by two H and V polar antennas located over the forest and by two other antennas placed under the foliage. The signals received by these antennas are digitized and processed to extract the plots of the opportunistic targets that approach the airport. The magnitudes of each plane echo are measured on each channel, and a comparison of the level of signal is made between the antenna above and under the forest. The ratio of magnitude between the two measurements on each polarization component gives the absorption factor of the foliage at the place of experiment. The position of the plane is given by an ADS-B receiver. For each elevation position of the antennas, the pattern of the chosen target will describe all the angles of arrival. This experiment has been deployed on two forested sites near an airport in South-East Asia. xml:lang="fr"

C-H Hot Bands in the Near-IR Emission Spectra of Leonids

NASA Technical Reports Server (NTRS)

Freund, F. T.; Scoville, J.; Holm, R.; Seelemann, R.; Freund, M. M.

2002-01-01

The reported infrared (IR) emission spectra from 1999 Leonid fireballs show a 3.4 micron C-H emission band and unidentified bands at longer wavelengths. Upon atmospheric entry, the Leonid meteorites were flash-heated to temperatures around 2400K, which would destroy any organics on the surface of the meteorite grains. We propose that the nu(sub )CH emission band in the Leonid emission spectra arises from matrix-embedded C(sub n)-H-O entities that are protected from instant pyrolysis. Our model is based on IR absorption nu(sub )CH bands, which we observed in laboratory-grown MgO and natural olivine single crystals, where they arise from C(sub n)-H-O units imbedded in the mineral matrix, indicative of aliphatic -CH2- and -CH3 organics. Instead of being pyrolyzed, the C(sub n)-H-O entities in the Leonid trails become vibrationally excited to higher levels n = 1, 2, 3 etc. During de-excitation they emit at 3.4 microns, due to the (0 => 1) transition, and at longer wavelengths, due to hot bands. As a first step toward verifying this hypothesis we measured the C-H vibrational manifold of hexane (C6H14). The calculated positions of the (2 => l ) , (3 => 2), and possibly (4 => 3) hot bands agree with the Leonid emission bands at 3.5, 3.8 and 4.l microns.

Investigation of the Band Structure of Graphene-Based Plasmonic Photonic Crystals.

PubMed

Qiu, Pingping; Qiu, Weibin; Lin, Zhili; Chen, Houbo; Tang, Yixin; Wang, Jia-Xian; Kan, Qiang; Pan, Jiao-Qing

2016-09-09

In this paper, one-dimensional (1D) and two-dimensional (2D) graphene-based plasmonic photonic crystals (PhCs) are proposed. The band structures and density of states (DOS) have been numerically investigated. Photonic band gaps (PBGs) are found in both 1D and 2D PhCs. Meanwhile, graphene-based plasmonic PhC nanocavity with resonant frequency around 175 THz, is realized by introducing point defect, where the chemical potential is from 0.085 to 0.25 eV, in a 2D PhC. Also, the bending wvaguide and the beam splitter are realized by introducing the line defect into the 2D PhC.

Thermal Conductivity Enhancement by Optical Phonon Sub-Band Engineering of Nanostructures Based on C and BN

DTIC Science & Technology

2005-09-01

Thermal Conductivity Enhancement by Optical Phonon Sub-Band Engineering of Nanostructures Based on C and BN DARPA CONTRACT MDA972-02-C-0044...AND SUBTITLE Thermal Conductivity Enhancement by Optical Phonon Sub-Band Engineering of Nanostructures Based on C and BN 5a. CONTRACT NUMBER 5b...Conductivity. Enhancement by Optical Phonon Sub-Bands Engineering in 3-D Nanostructures Based on C and BN Nanotubes" 1.3.1a. Phonon dynamics

Relative Band Oscillator Strengths for Carbon Monoxide: Alpha (1)Pi-Chi (1)Sigma(+) Transitions

NASA Technical Reports Server (NTRS)

Federman, S. R.; Menningen, K. L.; Lee, Wei; Stoll, J. B.

1997-01-01

Band oscillator strengths for CO transitions between the electronic states A (l)Pi and X(1)Sigma(+) were measured via absorption with a synchrotron radiation source. When referenced to the well-characterized (5,0) band oscillator strength, our relative values for the (7,0) to (11,0) bands are most consistent with the recent experiments of Chan et al. and the theoretical predictions of Kirby & Cooper. Since the results from various laboratory techniques and theory now agree, analyses of interstellar CO based on absorption from A-X bands are no longer hindered by uncertainties in oscillator strength.

Radio Frequency Compatibility Evaluation of S Band Navigation Signals for Future BeiDou.

PubMed

Sun, Yanbo; Xue, Rui; Zhao, Danfeng; Wang, Dun

2017-05-05

With L band frequency allocations for satellite navigation getting more crowded, S band (2483.5-2500 MHz) is already allocated for navigation services, where Globalstar broadcasts downlink communications to user terminals. The Indian Regional Navigation Satellite System (IRNSS) is transmitting navigation signals and Galileo exploits some potential signals in S band. Also, several candidate S band signals based on binary offset carrier (BOC), binary phase shift keying (BPSK), continuous phase modulation (CPM) and minimum shift keying-BOC (MSK-BOC) are suggested for BeiDou system (BDS). In quite narrow S band, mutual interference among these systems is inevitable, thus the compatibility issue is particularly significant for S band signal design. To explore desired S band signals for BDS, the paper firstly describes a comprehensive compatibility evaluation methods based on effective carrier-to-noise ratio degradation for acquisition and code tracking. Then a real simulation is established using space constellations, modulation schemes and received power. Finally, the worst mutual interference of BDS candidate signals with Galileo, IRNSS and Globalstar is calculated and compared. The results indicate that CPM signal is easier to allow peaceful coexistence of other systems with minimal mutual interference in S band compared to other BDS candidates.

Aquarius L-Band Microwave Radiometer: Three Years of Radiometric Performance and Systematic Effects

NASA Technical Reports Server (NTRS)

Piepmeier, Jeffrey R.; Hong, Liang; Pellerano, Fernando A.

2015-01-01

The Aquarius L-band microwave radiometer is a three-beam pushbroom instrument designed to measure sea surface salinity. Results are analyzed for performance and systematic effects over three years of operation. The thermal control system maintains tight temperature stability promoting good gain stability. The gain spectrum exhibits expected orbital variations with 1f noise appearing at longer time periods. The on-board detection and integration scheme coupled with the calibration algorithm produce antenna temperatures with NEDT 0.16 K for 1.44-s samples. Nonlinearity is characterized before launch and the derived correction is verified with cold-sky calibration data. Finally, long-term drift is discovered in all channels with 1-K amplitude and 100-day time constant. Nonetheless, it is adeptly corrected using an exponential model.

Low-frequency band gap of locally resonant phononic crystals with a dual-base plate.

PubMed

Zuo, Shuguang; Huang, Haidong; Wu, Xudong; Zhang, Minghai; Ni, Tianxin

2018-03-01

To achieve a wider band gap and a lower cut-on frequency, a locally resonant phononic crystal (LRPC) with a dual-base plate is investigated in this paper. Compared with the LRPC with a single plate, the band structure of the LRPC with a dual-base plate is calculated using the method of plane wave expansion and verified by the finite element method. According to the analysis of the band curves of the LRPC with a dual-base plate, the mechanisms are explained. Next, the influences of the thickness of the plates, the stiffness of the springs, the mass of resonators, and the lattice constant are also investigated. The results show that the structural asymmetry between the upper and the lower plate is conducive to reducing the cut-on frequency and broadening the band gap effectively. The results indicate a different approach for the application of LRPC in vibration and noise control.

A doubly curved reflector X-band antenna with integrated IFF array

NASA Astrophysics Data System (ADS)

Alia, F.; Barbati, S.

Primary radar antennas and Identification Friend or Foe (IFF) antennas must rotate with the same speed and synchronism, so that the target echo and IFF transponder mark will appear to the operator at the same time and at the same angular direction. A doubly-curved reflector antenna with a six-element microstrip array integrated in the reflector surface is presented to meet this requirement. The main antenna operates at X-band for low angle search radar, while the secondary antenna operates at L-band for IFF functions. The new configuration minimizes masking of the X-band radiated energy as a result of the IFF L-band elements. In fact, the only effect of the microstrip array on the X-band radiation pattern is the presence of several sidelobes in the + or - 90 deg angular region. The proposed new solution is compared to three other L-band/X-band integrated antenna configurations, and is found to be more advantageous with respect to masking, mechanical aspects, and production costs.

Multiple infrared bands absorber based on multilayer gratings

NASA Astrophysics Data System (ADS)

Liu, Xiaoyi; Gao, Jinsong; Yang, Haigui; Wang, Xiaoyi; Guo, Chengli

2018-03-01

The present study offers an Ag/Si multilayer-grating microstructure based on an Si substrate. The microstructure exhibits designable narrowband absorption in multiple infrared wavebands, especially in mid- and long-wave infrared atmospheric windows. We investigate its resonance mode mechanism, and calculate the resonance wavelengths by the Fabry-Perot and metal-insulator-metal theories for comparison with the simulation results. Furthermore, we summarize the controlling rules of the absorption peak wavelength of the microstructure to provide a new method for generating a Si-based device with multiple working bands in infrared.

Pharmacokinetics of pediatric lopinavir/ritonavir tablets in children when administered twice daily according to FDA weight bands.

PubMed

Bastiaans, Diane E T; Forcat, Silvia; Lyall, Hermione; Cressey, Tim R; Hansudewechakul, Rawiwan; Kanjanavanit, Suparat; Noguera-Julian, Antoni; Königs, Christoph; Inshaw, Jamie R J; Chalermpantmetagul, Suwalai; Saïdi, Yacine; Compagnucci, Alexandra; Harper, Lynda M; Giaquinto, Carlo; Colbers, Angela P H; Burger, David M

2014-03-01

Lopinavir/ritonavir (LPV/r) pediatric tablets (100/25 mg) are approved by the United States Food and Drug Administration (FDA) and European Medicines Agency (EMA) as part of combination antiretroviral therapy. Dosing is based on body weight bands or body surface area under FDA approval and only body surface area by the EMA. This can lead to a different recommended dose. In addition, weight band-based dosing has not been formally studied in the target population. We evaluated the pharmacokinetics (PK) of LPV/r in children, administered twice daily according to the FDA weight bands, using pediatric tablets. Fifty-three HIV-infected children were included in the PK substudy of the Paediatric European Network for the Treatment of AIDS 18 trial (KONCERT). In this study, children were randomized to receive LPV/r twice or once daily, according to FDA weight bands. A PK assessment was performed in 17, 16 and 20 children in the 15-25 kg, ≥ 25-35 kg and >35 kg weight band, respectively, while children took the tablets twice daily. Rich sampling was performed, and PK parameters were calculated by noncompartmental analysis. Given the high percentage of Asian children, it was also tested whether there was a difference in PK parameters between Asian and non-Asian children. For the total group, LPV geometric mean AUC0-12, Cmax and C12 were 106.9 h × mg/L, 12.0 mg/L and 4.9 mg/L, respectively. There were no significant differences in LPV PK parameters between the weight bands. In addition, weight was not found to be associated with variability in Cmax, C12 or AUC0-12 for the LPV PK parameters. FDA weight band-based dosing recommendations provide adequate exposure to LPV when using LPV/r pediatric tablets.

Giant Pulse Phenomena in a High Gain Erbium Doped Fiber Amplifier

NASA Technical Reports Server (NTRS)

Li, Stephen X.; Merritt, Scott; Krainak, Michael A.; Yu, Anthony

2018-01-01

High gain Erbium Doped Fiber Amplifiers (EDFAs) are vulnerable to optical damage when unseeded, e.g. due to nonlinear effects that produce random, spontaneous Q-switched (SQS) pulses with high peak power, i.e. giant pulses. Giant pulses can damage either the components within a high gain EDFA or external components and systems coupled to the EDFA. We explore the conditions under which a reflective, polarization-maintaining (PM), core-pumped high gain EDFA generates giant pulses, provide details on the evolution of normal pulses into giant pulses, and provide results on the transient effects of giant pulses on an amplifier's fused-fiber couplers, an effect which we call Fiber Overload Induced Leakage (FOIL). While FOIL's effect on fused-fiber couplers is temporary, its damage to forward pump lasers in a high gain EDFA can be permanent.

Soil moisture estimation by assimilating L-band microwave brightness temperature with geostatistics and observation localization.

PubMed

Han, Xujun; Li, Xin; Rigon, Riccardo; Jin, Rui; Endrizzi, Stefano

2015-01-01

The observation could be used to reduce the model uncertainties with data assimilation. If the observation cannot cover the whole model area due to spatial availability or instrument ability, how to do data assimilation at locations not covered by observation? Two commonly used strategies were firstly described: One is covariance localization (CL); the other is observation localization (OL). Compared with CL, OL is easy to parallelize and more efficient for large-scale analysis. This paper evaluated OL in soil moisture profile characterizations, in which the geostatistical semivariogram was used to fit the spatial correlated characteristics of synthetic L-Band microwave brightness temperature measurement. The fitted semivariogram model and the local ensemble transform Kalman filter algorithm are combined together to weight and assimilate the observations within a local region surrounding the grid cell of land surface model to be analyzed. Six scenarios were compared: 1_Obs with one nearest observation assimilated, 5_Obs with no more than five nearest local observations assimilated, and 9_Obs with no more than nine nearest local observations assimilated. The scenarios with no more than 16, 25, and 36 local observations were also compared. From the results we can conclude that more local observations involved in assimilation will improve estimations with an upper bound of 9 observations in this case. This study demonstrates the potentials of geostatistical correlation representation in OL to improve data assimilation of catchment scale soil moisture using synthetic L-band microwave brightness temperature, which cannot cover the study area fully in space due to vegetation effects.

Soil Moisture Estimation by Assimilating L-Band Microwave Brightness Temperature with Geostatistics and Observation Localization

PubMed Central

Han, Xujun; Li, Xin; Rigon, Riccardo; Jin, Rui; Endrizzi, Stefano

2015-01-01

The observation could be used to reduce the model uncertainties with data assimilation. If the observation cannot cover the whole model area due to spatial availability or instrument ability, how to do data assimilation at locations not covered by observation? Two commonly used strategies were firstly described: One is covariance localization (CL); the other is observation localization (OL). Compared with CL, OL is easy to parallelize and more efficient for large-scale analysis. This paper evaluated OL in soil moisture profile characterizations, in which the geostatistical semivariogram was used to fit the spatial correlated characteristics of synthetic L-Band microwave brightness temperature measurement. The fitted semivariogram model and the local ensemble transform Kalman filter algorithm are combined together to weight and assimilate the observations within a local region surrounding the grid cell of land surface model to be analyzed. Six scenarios were compared: 1_Obs with one nearest observation assimilated, 5_Obs with no more than five nearest local observations assimilated, and 9_Obs with no more than nine nearest local observations assimilated. The scenarios with no more than 16, 25, and 36 local observations were also compared. From the results we can conclude that more local observations involved in assimilation will improve estimations with an upper bound of 9 observations in this case. This study demonstrates the potentials of geostatistical correlation representation in OL to improve data assimilation of catchment scale soil moisture using synthetic L-band microwave brightness temperature, which cannot cover the study area fully in space due to vegetation effects. PMID:25635771

Multi-band transmission color filters for multi-color white LEDs based visible light communication

NASA Astrophysics Data System (ADS)

Wang, Qixia; Zhu, Zhendong; Gu, Huarong; Chen, Mengzhu; Tan, Qiaofeng

2017-11-01

Light-emitting diodes (LEDs) based visible light communication (VLC) can provide license-free bands, high data rates, and high security levels, which is a promising technique that will be extensively applied in future. Multi-band transmission color filters with enough peak transmittance and suitable bandwidth play a pivotal role for boosting signal-noise-ratio in VLC systems. In this paper, multi-band transmission color filters with bandwidth of dozens nanometers are designed by a simple analytical method. Experiment results of one-dimensional (1D) and two-dimensional (2D) tri-band color filters demonstrate the effectiveness of the multi-band transmission color filters and the corresponding analytical method.

Design of a dual band metamaterial absorber for Wi-Fi bands

NASA Astrophysics Data System (ADS)

Alkurt, Fatih Özkan; Baǧmancı, Mehmet; Karaaslan, Muharrem; Bakır, Mehmet; Altıntaş, Olcay; Karadaǧ, Faruk; Akgöl, Oǧuzhan; Ünal, Emin

2018-02-01

The goal of this work is to design and fabrication of a dual band metamaterial based absorber for Wireless Fidelity (Wi-Fi) bands. Wi-Fi has two different operating frequencies such as 2.45 GHz and 5 GHz. A dual band absorber is proposed and the proposed structure consists of two layered unit cells, and different sized square split ring (SSR) resonators located on each layers. Copper is used for metal layer and resonator structure, FR-4 is used as substrate layer in the proposed structure. This designed dual band metamaterial absorber is used in the wireless frequency bands which has two center frequencies such as 2.45 GHz and 5 GHz. Finite Integration Technique (FIT) based simulation software used and according to FIT based simulation results, the absorption peak in the 2.45 GHz is about 90% and the another frequency 5 GHz has absorption peak near 99%. In addition, this proposed structure has a potential for energy harvesting applications in future works.

Shallow magma system of Kilauea volcano investigated using L-band synthetic aperture radar data

NASA Astrophysics Data System (ADS)

Fukushima, Y.; Sinnett, D. K.; Segall, P.

2009-12-01

L-band synthetic aperture radar (SAR) images on Kilauea volcano have been archived by Japanese JERS-1 (1992-1998) and ALOS (2006-) satellites. L-band interferometric SAR (InSAR) can measure displacements in a broader region compared to C-band, thanks to higher phase coherence on vegetated areas. We made InSAR analyses on Kilauea using the following L-band data sets: J1) two JERS-1 images, acquired on 20 Oct. 1992 and 1 Mar. 1993 from a descending orbit (RSP path 589) with off-nadir angle of 34.3 degrees, J2) three JERS-1 images, acquired between 8 Oct. 1993 and 3 Jul. 1997 from a descending orbit (RSP path 590) with off-nadir angle of 34.3 degrees, A1) 13 ALOS images, acquired between 24 Jun. 2006 and 14 Feb. 2009 from an ascending orbit with off-nadir angle 9.9 degrees, and A2) 11 ALOS images, acquired between 21 May 2006 and 26 Feb. 2009 from a descending orbit with off-nadir angle 9.9 degrees. One-second SRTM digital elevation data were used to remove the topographic phase. The interferogram of the data set J1 contains signals of 1) a maximum of about 30 cm of range decrease resulting from a dike intrusion in the Makaopuhi crater area, 2) about 10 cm of maximum range increase in the Pu`u `O`o crater area, and 3) a few cm of range increase along the East Rift Zone (ERZ) between the summit and Pu`u `O`o craters. An interferogram (8 Oct. 1993 - 3 Jul. 1997) of the data set J2 indicates 1) range increase (maximum 7 cm/yr) in both the summit and Pu`u `O`o areas, 2) range increase (maximum 5 cm/yr) along the ERZ between the summit and Makaopuhi crater, and 3) range decrease (maximum 6cm/yr) on the southern flank near the coast that is consistent with a seaward movement of the southern flank. A small baseline subset InSAR time-series analysis was performed using all the images of the data sets A1 and A2, assuming that the data acquisitions had been made in pure vertical direction. The analysis period includes the 2007 Father's day dike intrusion. A preliminary result

Estimating net rainfall, evaporation and water storage of a bare soil from sequential L-band emissivities

NASA Technical Reports Server (NTRS)

Stroosnijder, L.; Lascano, R. J.; Newton, R. W.; Vanbavel, C. H. M.

1984-01-01

A general method to use a time series of L-band emissivities as an input to a hydrological model for continuously monitoring the net rainfall and evaporation as well as the water content over the entire soil profile is proposed. The model requires a sufficiently accurate and general relation between soil emissivity and surface moisture content. A model which requires the soil hydraulic properties as an additional input, but does not need any weather data was developed. The method is shown to be numerically consistent.

L band push broom microwave radiometer: Soil moisture verification and time series experiment Delmarva Peninsula

NASA Technical Reports Server (NTRS)

Jackson, T. J.; Shiue, J.; Oneill, P.; Wang, J.; Fuchs, J.; Owe, M.

1984-01-01

The verification of a multi-sensor aircraft system developed to study soil moisture applications is discussed. This system consisted of a three beam push broom L band microwave radiometer, a thermal infrared scanner, a multispectral scanner, video and photographic cameras and an onboard navigational instrument. Ten flights were made of agricultural sites in Maryland and Delaware with little or no vegetation cover. Comparisons of aircraft and ground measurements showed that the system was reliable and consistent. Time series analysis of microwave and evaporation data showed a strong similarity that indicates a potential direction for future research.

Monitoring of Three Case Studies of Creeping Landslides in Ecuador using L-band SAR Interferometry (InSAR)

NASA Astrophysics Data System (ADS)

Mayorga Torres, T. M.; Mohseni Aref, M.

2015-12-01

Tannia Mayorga Torres1,21 Universidad Central del Ecuador. Faculty of Geology, Mining, Oil, and Environment 2 Hubert H. Humphrey Fellowship 2015-16 IntroductionLandslides lead to human and economic losses across the country, mainly in the winter season. On the other hand, satellite radar data has cost-effective benefits due to open-source software and free availability of data. With the purpose of establishing an early warning system of landslide-related surface deformation, three case studies were designed in the Coast, Sierra (Andean), and Oriente (jungle) regions. The objective of this work was to assess the capability of L-band InSAR to get phase information. For the calculation of the interferograms in Repeat Orbit Interferometry PACkage, the displacement was detected as the error and was corrected. The coherence images (Figure 1) determined that L-band is suitable for InSAR processing. Under this frame, as a first approach, the stacking DInSAR technique [1] was applied in the case studies [2]; however, due to lush vegetation and steep topography, it is necessary to apply advanced InSAR techniques [3]. The purpose of the research is to determine a pattern of data acquisition and successful results to understand the spatial and temporal ground movements associated with landslides. The further work consists of establishing landslide inventories to combine phases of SAR images to generate maps of surface deformation in Tumba-San Francisco and Guarumales to compare the results with ground-based measurements to determine the maps' accuracy. References[1] Sandwell D., Price E. (1998). Phase gradient approach to stacking interferograms. Journal of Geophysical Research, Vol. 103, N. B12, pp. 30,183-30,204. [2] Mayorga T., Platzeck G. (2014). Using DInSAR as a tool to detect unstable terrain areas in an Andes region in Ecuador. NH3.5-Blue Poster B298, Vol. 16, EGU2014-16203. Austria. [3] Wasowski J., Bovenga F. (2014). Investigating landslides and unstable slopes with

An empirical model of L-band scintillation S4 index constructed by using FORMOSAT-3/COSMIC data

NASA Astrophysics Data System (ADS)

Chen, Shih-Ping; Bilitza, Dieter; Liu, Jann-Yenq; Caton, Ronald; Chang, Loren C.; Yeh, Wen-Hao

2017-09-01

Modern society relies heavily on the Global Navigation Satellite System (GNSS) technology for applications such as satellite communication, navigation, and positioning on the ground and/or aviation in the troposphere/stratosphere. However, ionospheric scintillations can severely impact GNSS systems and their related applications. In this study, a global empirical ionospheric scintillation model is constructed with S4-index data obtained by the FORMOSAT-3/COSMIC (F3/C) satellites during 2007-2014 (hereafter referred to as the F3CGS4 model). This model describes the S4-index as a function of local time, day of year, dip-latitude, and solar activity using the index PF10.7. The model reproduces the F3/C S4-index observations well, and yields good agreement with ground-based reception of satellite signals. This confirms that the constructed model can be used to forecast global L-band scintillations on the ground and in the near surface atmosphere.

Laser spectroscopy of the A ˜ 2 Σ + - X ˜ 2 Π i band system of l-SiC3H

NASA Astrophysics Data System (ADS)

Umeki, Hiroya; Nakajima, Masakazu; Endo, Yasuki

2015-11-01

The A ˜ 2 Σ + - X ˜ 2 Π i band system of l-SiC3H in the region 14 700-16 300 cm-1 was re-investigated by laser induced fluorescence (LIF) and fluorescence depletion spectroscopy. Rotational analyses were made for three intense bands 00 0 , 40 1 , and 60 1 70 1 by observing high-resolution LIF excitation spectra. The determined rotational constants demonstrate that SiC3H is linear in the A ˜ state, as is the case in the X ˜ state, and the observed band types are consistent with the vibrational assignments. The ν3 ″ (C1-C2 stretch) level was identified in a newly observed dispersed fluorescence spectrum from the zero-vibrational level of the A ˜ state.

A Model for Backscattering from Quasi Periodic Corn Canopies at L-Band

NASA Technical Reports Server (NTRS)

Lang, R.; Utku, C.; Zhao, Q.; O'Neill, P.

2010-01-01

In this study, a model for backscattering at L-band from a corn canopy is proposed. The canopy consists of a quasi-periodic distribution of stalks and a random distribution of leaves. The Distorted Born Approximation (DBA) is employed to calculate the single scattered return from the corn field. The new feature of the method is that the coherence of the stalks in the row direction is incorporated in the model in a systematic fashion. Since the wavelength is on the order of the distance between corn stalks in a row, grating lobe behavior is observed at certain azimuth angles of incidence. The results are compared with experimental values measured in Huntsville, Alabama in 1998. The mean field and the effective dielectric constant of the canopy are obtained by using the Foldy approximation. The stalks are placed in the effective medium in a two dimensional lattice to simulate the row structure of a corn field. In order to mimic a real corn field, a quasi-periodic stalk distribution is assumed where the stalks are given small random perturbations about their lattice locations. Corn leaves are also embedded in the effective medium and the backscattered field from the stalks and the leaves is computed. The backscattering coefficient is calculated and averaged over successive stalk position perturbations. It is assumed that soil erosion has smoothed the soil sufficiently so that it can be assumed flat. Corn field backscatter data was collected from cornfields during the Huntsville 98 experimental campaign held at Alabama A&M University Research Station, Huntsville, Alabama in 1998 using the NASA/GW truck mounted radar. Extensive ground truth data was collected. This included soil moisture measurements and corn plant architectural data to be used in the model. In particular, the distances between the stalks in a single row have been measured. The L-band radar backscatter data was collected for both H and V polarizations and for look angles of 15o and 45o over a two week

Development of an L-, C-, and X-band radar for backscattering studies over vegetation

NASA Technical Reports Server (NTRS)

Lockhart, G. Lance

1995-01-01

With the recent surge of interest in global change, the impact of different ecosystems on the Earth's carbon budget has become the focus of many scientific studies. Studies have been launched by NASA and other agencies to address this issue. One such study is the Boreal Ecosystem-Atmosphere Study (BOREAS). BOREAS focuses on the boreal ecosystem in Northern Canada. As a part of the BOREAS study, we have developed a helicopter-borne three-band radar system for measuring the scattering coefficient of various stands within the boreal forest. During the summer of 1994 the radar was used at the southern study area (SSA) in Saskatchewan over the young jack pine (YJP), old jack pine (OJP), old black spruce (OBS) and old aspen (OA) sites. The data collected will be used to study the interaction of microwaves with forest canopy. By making use of three different frequency bands the contribution to the backscatter from each of the layers within the canopy can be determined. Using the knowledge gained from these studies, we will develop algorithms to enable more accurate interpretation of SAR images of the boreal region. This report describes in detail the development of the L-, C- and X-band radar system. The first section provides background information and explains the objectives of the boreal forest experiment. The second section describes the design and implementation of the radar system. All of the subsystems of the radar are explained in this section. Next, problems that were encountered during system testing and the summer experiments are discussed. System performance and results are then presented followed by a section on conclusions and further work.

The ν 1Band System of H-CC-CN (Cyanoacetylene)

NASA Astrophysics Data System (ADS)

Winther, F.; Klee, S.; Mellau, G.; Naı̈m, S.; Mbosei, L.; Fayt, A.

1996-02-01

The ν1band system of cyanoacetylene (H-CC-CN) has been observed with an effective resolution of 0.006 cm-1. ν1= 3327.37085(3) cm-1,B1= 0.15149762(2) cm-1,D1= 1.8065(3) × 10-8cm-1. Several hot bands from the statesv5= 1,v6= 1,v7= 1, 2 (l= 0 and 2), 3 (l= 1 and 3), and 4 (l= 0 and 2),v6=v7= 1 (l= 0 and 2), andv6= 1 andv7= 2 (l= 3) have also been observed and analyzed. Many bands show strong local perturbations due to interactions with states which are combinations of the modes 4, 5, 6, and 7. These perturbing states are also described quantitatively, and rovibrational constants are given.

Band Anticrossing in Highly Mismatched Compound Semiconductor Alloys

NASA Technical Reports Server (NTRS)

Yu, Kin Man; Wu, J.; Walukiewicz, W.; Ager, J. W.; Haller, E. E.; Miotkowski, I.; Ramdas, A.; Su, Ching-Hua; Whitaker, Ann F. (Technical Monitor)

2001-01-01

localized Se states and the conduction band. On the other hand we show that the large band gap reduction observed on the Se-rich side of the alloy system is a result of an interaction between the localized Te level and the valence bands. This interaction leads to the formation of a Te-like valence band edge that strongly interacts with the light hole valence band. Calculations based on a modified k p model account for the reduction of the band gap and the large increase of the spin-orbit splitting observed in Se-rich ZnSe(y)Te(l-y) alloys. We will also discuss the importance of these new results for understanding of the electronic structure and band offsets in other highly mismatched alloy systems.

Impact of Conifer Forest Litter on Microwave Emission at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Cosh, Michael H.; Joseph, Alicia T.; Jackson, Thomas J.

2011-01-01

This study reports on the utilization of microwave modeling, together with ground truth, and L-band (1.4-GHz) brightness temperatures to investigate the passive microwave characteristics of a conifer forest floor. The microwave data were acquired over a natural Virginia Pine forest in Maryland by a ground-based microwave active/passive instrument system in 2008/2009. Ground measurements of the tree biophysical parameters and forest floor characteristics were obtained during the field campaign. The test site consisted of medium-sized evergreen conifers with an average height of 12 m and average diameters at breast height of 12.6 cm. The site is a typical pine forest site in that there is a surface layer of loose debris/needles and an organic transition layer above the mineral soil. In an effort to characterize and model the impact of the surface litter layer, an experiment was conducted on a day with wet soil conditions, which involved removal of the surface litter layer from one half of the test site while keeping the other half undisturbed. The observations showed detectable decrease in emissivity for both polarizations after the surface litter layer was removed. A first-order radiative transfer model of the forest stands including the multilayer nature of the forest floor in conjunction with the ground truth data are used to compute forest emission. The model calculations reproduced the major features of the experimental data over the entire duration, which included the effects of surface litter and ground moisture content on overall emission. Both theory and experimental results confirm that the litter layer increases the observed canopy brightness temperature and obscure the soil emission.

Broadband tunable electromagnetically induced transparency analogue metamaterials based on graphene in terahertz band

NASA Astrophysics Data System (ADS)

Wang, Yue; Leng, Yanbing; Wang, Li; Dong, Lianhe; Liu, Shunrui; Wang, Jun; Sun, Yanjun

2018-06-01

Most of the actively controlled electromagnetically induced transparency analogue (EIT-like) metamaterials were implemented with narrowband modulations. In this paper, a broadband tunable EIT-like metamaterial based on graphene in the terahertz band is presented. It consists of a cut wire as the bright resonator and two couples of H-shaped resonators in mirror symmetry as the dark resonators. A broadband tunable property of transmission amplitude is realized by changing the Fermi level of graphene. Furthermore, the geometries of the metamaterial structure are optimized to achieve the ideal curve through the simulation. Such EIT-like metamaterials proposed here are promising candidates for designing active wide-band slow-light devices, wide-band terahertz active filters, and wide-band terahertz modulators.

Design and analysis of coplanar waveguide triple-band antenna based on defected ground structure

NASA Astrophysics Data System (ADS)

Lv, Hong; Chen, Wanli; Xia, Xinsheng; Qi, Peng; Sun, Quanling

2017-11-01

A kind of coplanar waveguide triple-band antenna based on defected ground structure is proposed, which has novel structure. Three batches with different frequency band are constructed by utilizing line combination, overlapping, and symmetry method. Stop band signals among three frequency bands are effectively suppressed by slots with different structures. More satisfactory impedance matching is realized by means of changing slot structure and improving return-loss. The presented antenna can operates simultaneously in various systems such as 3G / 4G wireless communication, Bluetooth, Worldwide Interoperability for Microwave Access, Wireless LAN. Test results show that the antenna has good radiation and gain in its working frequency band, and that it has great application potentials.

Advances in III-V based dual-band MWIR/LWIR FPAs at HRL

NASA Astrophysics Data System (ADS)

Delaunay, Pierre-Yves; Nosho, Brett Z.; Gurga, Alexander R.; Terterian, Sevag; Rajavel, Rajesh D.

2017-02-01

Recent advances in superlattice-based infrared detectors have rendered this material system a solid alternative to HgCdTe for dual-band sensing applications. In particular, superlattices are attractive from a manufacturing perspective as the epitaxial wafers can be grown with a high degree of lateral uniformity, low macroscopic defect densities (< 50 cm-2) and achieve dark current levels comparable to HgCdTe detectors. In this paper, we will describe our recent effort on the VISTA program towards producing HD-format (1280x720, 12 μm pitch) superlattice based, dual-band MWIR/LWIR FPAs. We will report results from several multi-wafer fabrication lots of 1280x720, 12 μm pitch FPAs processed over the last two years. To assess the FPA performance, noise equivalent temperature difference (NETD) measurements were conducted at 80K, f/4.21 and using a blackbody range of 22°C to 32°C. For the MWIR band, the NETD was 27.44 mK with a 3x median NETD operability of 99.40%. For the LWIR band, the median NETD was 27.62 mK with a 3x median operability of 99.09%. Over the course of the VISTA program, HRL fabricated over 30 FPAs with similar NETDs and operabilities in excess of 99% for both bands, demonstrating the manufacturability and high uniformity of III-V superlattices. We will also present additional characterization results including blinkers, spatial stability, modulation transfer function and thermal cycles reliability.

Polarimetric Decomposition Analysis of the Deepwater Horizon Oil Slick Using L-Band UAVSAR Data

NASA Technical Reports Server (NTRS)

Jones, Cathleen; Minchew, Brent; Holt, Benjamin

2011-01-01

We report here an analysis of the polarization dependence of L-band radar backscatter from the main slick of the Deepwater Horizon oil spill, with specific attention to the utility of polarimetric decomposition analysis for discrimination of oil from clean water and identification of variations in the oil characteristics. For this study we used data collected with the UAVSAR instrument from opposing look directions directly over the main oil slick. We find that both the Cloude-Pottier and Shannon entropy polarimetric decomposition methods offer promise for oil discrimination, with the Shannon entropy method yielding the same information as contained in the Cloude-Pottier entropy and averaged in tensity parameters, but with significantly less computational complexity

Can H2CCC be the Carrier of Broad Diffuse Bands?

NASA Astrophysics Data System (ADS)

Krełowski, J.; Galazutdinov, G.; Kołos, R.

2011-07-01

The recent assignment of two broad diffuse interstellar bands (DIBs) near 4882 and 5450 Å to the propadienylidene (l-C3H2) molecule is examined using a statistically meaningful sample of targets. Our spectra clearly show that the strength ratio of two broad DIBs is strongly variable, contrary to what should be observed if both features are due to l-C3H2, since the proposed transitions are lifetime broadened and start from the same level. Moreover, even in directions where the 4882 DIB and 5450 DIB are strong, the third expected l-C3H2 band, in the 5165-5185 Å region, is absent. Another puzzling characteristic of l-C3H2 as the proposed carrier of both broad diffuse bands is its column density of several 1014 cm-2, inferred from the equivalent width of the 5450 DIB. This value is one order of magnitude higher than N(CH) toward the same objects and two to three orders of magnitude higher than N(H2CCC), measured at radio frequencies in absorption, for comparable samples of the diffuse medium. We conclude that the proposed identification of broad DIBs is unjustified. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile; programs 073.C-0337(A) and 082.C-0566(A).

Cytotoxic effects of resin-modified orthodontic band adhesives. Are they safe?

PubMed

Malkoc, Siddik; Corekci, Bayram; Botsali, Hayriye Esra; Yalçin, Muhammet; Sengun, Abdülkadir

2010-09-01

To evaluate the cytotoxic effects of three different resin-modified orthodontic band adhesives. Three resin-modified orthodontic band adhesives (Bisco Ortho Band Paste LC, Multi-Cure Glass Ionomer Band Cement, and Transbond Plus Light Cure Band Adhesive) were prepared and the samples were extracted in 3 mL of Basal Medium Eagle with 10% newborn calf serum for 24 hours. The L929 cells were plated (25,000 cells/mL) in wells of 96-well dishes and maintained in a humidified incubator for 24 hours at 37 degrees C, 5% CO(2), and 95% air. After 24-hour incubation of the cells, the incubation medium was replaced by the immersed medium in which the samples were stored. Then L929 cells were incubated in contact with eluates for 24 hours. The cell mitochondrial activity was evaluated by the methyltetrazolium test. Twelve wells were used for each specimen, and methyltetrazolium tests were applied two times. The data were statistically analyzed using one-way analysis of variance and Tukey Honestly Significantly Different tests. Results with L929 fibroblasts demonstrated that all freshly prepared resin-modified orthodontic band adhesive materials reduced vital cell numbers (P > .05), in comparison to the control group. Our data demonstrate that all materials showed significant cytotoxicity compared to the control group. The results indicate that all materials showed significant cytotoxicity compared to the control group, and further studies using different test methods are needed for all resin-modified orthodontic band adhesives.

Comparisons of Aquarius Measurements over Oceans with Radiative Transfer Models at L-Band

NASA Technical Reports Server (NTRS)

Dinnat, E.; LeVine, D.; Abraham, S.; DeMattheis, P.; Utku, C.

2012-01-01

The Aquarius/SAC-D spacecraft includes three L-band (1.4 GHz) radiometers dedicated to measuring sea surface salinity. It was launched in June 2011 by NASA and CONAE (Argentine space agency). We report detailed comparisons of Aquarius measurements with radiative transfer model predictions. These comparisons are used as part of the initial assessment of Aquarius data and to estimate the radiometer calibration bias and stability. Comparisons are also being performed to assess the performance of models used in the retrieval algorithm for correcting the effect of various sources of geophysical "noise" (e.g. Faraday rotation, surface roughness). Such corrections are critical in bringing the error in retrieved salinity down to the required 0.2 practical salinity unit on monthly global maps at 150 km by 150 km resolution.

Recent progress of erbium-doped fiber amplifiers and their components

NASA Astrophysics Data System (ADS)

Fukushima, Masaru; Miura, Jutaro

2007-09-01

The Erbium-doped fiber amplifiers (EDFA) are widely available in a today's commercial market, and are deployed in various optical transmission applications from terrestrial system to undersea system. Broad gain spectrum over 9 THz enabled huge growth of bandwidth usage in 1550nm region aimed at broadband Internet, and its broad gain characteristics triggered bandwidth competition on dense wavelength division multiplex (DWDM) network these ten years. At first, we briefly review the evolutional history of EDFA with previous achievements. And we will explain the primary and important key devices which compose EDFA. We will discuss design parameters, and recent trend and achievements of the devices, which cover Erbium-doped fibers (EDF), 980-nm laser diodes (LD), and gain flattening filters (GFFs). The chip structure of 980-nm LD is explained to achieve high power and to realize high reliability. These key devices enabled EDFA to prevail in commercial area. After the discussion of key components, we will introduce recent achievements of gain controlled EDFAs which are applied in conjunction with Re-configurable Optical Add/Drop Multiplexer (ROADM). We will report the transient gain dynamics of the cascaded EDFAs with a recirculating loop experiment.

High power narrow-band fiber-based ASE source.

PubMed

Schmidt, O; Rekas, M; Wirth, C; Rothhardt, J; Rhein, S; Kliner, A; Strecker, M; Schreiber, T; Limpert, J; Eberhardt, R; Tünnermann, A

2011-02-28

In this paper we describe a high power narrow-band amplified spontaneous emission (ASE) light source at 1030 nm center wavelength generated in an Yb-doped fiber-based experimental setup. By cutting a small region out of a broadband ASE spectrum using two fiber Bragg gratings a strongly constrained bandwidth of 12±2 pm (3.5±0.6 GHz) is formed. A two-stage high power fiber amplifier system is used to boost the output power up to 697 W with a measured beam quality of M2≤1.34. In an additional experiment we demonstrate a stimulated Brillouin scattering (SBS) suppression of at least 17 dB (theoretically predicted ~20 dB), which is only limited by the dynamic range of the measurement and not by the onset of SBS when using the described light source. The presented narrow-band ASE source could be of great interest for brightness scaling applications by beam combination, where SBS is known as a limiting factor.

Clustering of Multi-Temporal Fully Polarimetric L-Band SAR Data for Agricultural Land Cover Mapping

NASA Astrophysics Data System (ADS)

Tamiminia, H.; Homayouni, S.; Safari, A.

2015-12-01

Recently, the unique capabilities of Polarimetric Synthetic Aperture Radar (PolSAR) sensors make them an important and efficient tool for natural resources and environmental applications, such as land cover and crop classification. The aim of this paper is to classify multi-temporal full polarimetric SAR data using kernel-based fuzzy C-means clustering method, over an agricultural region. This method starts with transforming input data into the higher dimensional space using kernel functions and then clustering them in the feature space. Feature space, due to its inherent properties, has the ability to take in account the nonlinear and complex nature of polarimetric data. Several SAR polarimetric features extracted using target decomposition algorithms. Features from Cloude-Pottier, Freeman-Durden and Yamaguchi algorithms used as inputs for the clustering. This method was applied to multi-temporal UAVSAR L-band images acquired over an agricultural area near Winnipeg, Canada, during June and July in 2012. The results demonstrate the efficiency of this approach with respect to the classical methods. In addition, using multi-temporal data in the clustering process helped to investigate the phenological cycle of plants and significantly improved the performance of agricultural land cover mapping.

Radio Frequency Compatibility Evaluation of S Band Navigation Signals for Future BeiDou

PubMed Central

Sun, Yanbo; Xue, Rui; Zhao, Danfeng; Wang, Dun

2017-01-01

With L band frequency allocations for satellite navigation getting more crowded, S band (2483.5–2500 MHz) is already allocated for navigation services, where Globalstar broadcasts downlink communications to user terminals. The Indian Regional Navigation Satellite System (IRNSS) is transmitting navigation signals and Galileo exploits some potential signals in S band. Also, several candidate S band signals based on binary offset carrier (BOC), binary phase shift keying (BPSK), continuous phase modulation (CPM) and minimum shift keying-BOC (MSK-BOC) are suggested for BeiDou system (BDS). In quite narrow S band, mutual interference among these systems is inevitable, thus the compatibility issue is particularly significant for S band signal design. To explore desired S band signals for BDS, the paper firstly describes a comprehensive compatibility evaluation methods based on effective carrier-to-noise ratio degradation for acquisition and code tracking. Then a real simulation is established using space constellations, modulation schemes and received power. Finally, the worst mutual interference of BDS candidate signals with Galileo, IRNSS and Globalstar is calculated and compared. The results indicate that CPM signal is easier to allow peaceful coexistence of other systems with minimal mutual interference in S band compared to other BDS candidates. PMID:28475142

Detection of the 2165 Inverse Centimeter (4.619 Micron) XCN Band in the Spectrum of L1551 IRS 5

NASA Technical Reports Server (NTRS)

Tegler, Stephen C.; Weintraub, David A.; Allamandola, Louis J.; Sandford, Scott A.; Rettig, Terrence W.; Campins, Humberto

1993-01-01

We report the detection of a broad absorption band at 2165 cm (4.619 microns) in the spectrum of L1551 IRS 5. New laboratory results over the 2200-2100 /cm wavenumber interval (4.55-4.76 microns), performed with realistic interstellar ice analogs, suggest that this feature is due to a CN-containing compound. We will refer to this compound as XCN. We also confirm the presence of frozen CO (both in nonpolar and polar matrices) through absorption bands at 2140 /cm (4.67 microns) and 2135 /cm (4.68 microns). The relative abundance of solid-state CO to frozen H2O is approx. 0.13 while the abundance of XCN seems comparable to that of frozen CO.

Wide-Band Circularly Polarized ReflectarrayUsing Graphene-Based Pancharatnam-Berry Phase Unit-Cells for Terahertz Communication.

PubMed

Deng, Li; Zhang, Yuanyuan; Zhu, Jianfeng; Zhang, Chen

2018-06-05

A wide-band and high gain circularly polarized (CP) graphene-based reflectarray operating in the THz regime is proposed and theoretically investigated in this paper. The proposed reflectarray consists of a THz CP source and several graphene-based unit-cells. Taking advantages of the Pancharatnam Berry (PB) phase principle, the graphene-based unit-cell is capable of realizing a tunable phase range of 360° in a wide-band (1.4⁻1.7 THz) by unit-cell rotating, overcoming the restriction of intrinsic narrow-band resonance in graphene. Therefore, this graphene-based unit-cell exhibits superior bandwidth and phase tunability to its previous counterparts. To demonstrate this, a wide-band (1.4⁻1.7 THz) focusing metasurface based on the proposed unit-cell that exhibits excellent focusing effect was designed. Then, according to the reversibility of the optical path, a CP reflectarray was realized by placing a wide-band CP THz source at the focal point of the metasurface. Numerical simulation demonstrates that this reflectarray can achieve a stable high gain up to 15 dBic and an axial ratio around 2.1 dB over the 1.4⁻1.7 THz band. The good radiation performance of the proposed CP reflectarray, as demonstrated, underlines its suitability for the THz communication applications. Moreover, the design principle of this graphene-based reflectarray with a full 360° phase range tunable unit-cells provides a new pathway to design high-performance CP reflectarray in the THz regime.

High resolution infrared spectroscopy of [1.1.1]propellane: The region of the ν 9 band

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maki, Arthur; Weber, Alfons; Nibler, Joseph W.

2010-11-01

The region of the infrared-active band of the ν 9 CH2 bending mode [1.1.1]propellane has been recorded at a resolution (0.0025 cm -1) sufficient to distinguish individual rovibrational lines. This region includes the partially overlapping bands ν 9 (e') = 1459 cm -1, 2ν 18 (l = 2, E') = 1430 cm -1, ν 6 + ν 12 (E') = 1489 cm-1, and ν 4 + ν 15 (A 2") = 1518 cm -1. In addition, the difference band ν 4 - ν 15 (A2") was observed in the far infrared near 295 cm -1 and analyzed to give goodmore » constants for the upper ν 4 levels. The close proximities of the four bands in the ν 9 region suggest that Coriolis and Fermi resonance couplings could be significant and theoretical band parameters obtained from Gaussian ab initio calculations were helpful in guiding the band analyses. The analyses of all four bands were accomplished, based on our earlier report of ground state constants determined from combination differences involving more than 4000 pairs of transitions from five fundamental and four combination bands. This paper presents the analyses and the determination of the upper state constants of all four bands in the region of the ν 9 band. Complications were most evident in the 2ν 18 (l = 2, E') band, which showed significant perturbations due to mixing with the nearby 2ν 18 (l = 0, A 1') and ν 4 + ν 12 (E') levels which are either infrared inactive as transitions from the ground state, or, in the latter case, too weak to observe. Finally, these complications are discussed and a comparison of all molecular constants with those available from the ab initio calculations at the anharmonic level is presented.« less

Novel Dual-Band Miniaturized Frequency Selective Surface based on Fractal Structures

NASA Astrophysics Data System (ADS)

Zhong, Tao; Zhang, Hou; Wu, Rui; Min, Xueliang

2017-01-01

A novel single-layer dual-band miniaturized frequency selective surface (FSS) based on fractal structures is proposed and analyzed in this paper. A prototype with enough dimensions is fabricated and measured in anechoic chamber, and the measured results provide good agreement with the simulated. The simulations and measurements indicate that the dual-band FSS with bandstop selectivity center at 3.95 GHz and 7.10 GHz, and the whole dimension of the proposed FSS cell is only 7×7 mm2, amount to 0.092λ0×0.092λ0, that λ0 is free space wavelength at first resonant frequency. In addition, the center frequencies have scarcely any changes for different polarizations and incidences. What's more, dual-band mechanism is analyzed clearly and it provides a new way to design novel miniaturized FSS structures.

Optimal Resonant Band Demodulation Based on an Improved Correlated Kurtosis and Its Application in Bearing Fault Diagnosis

PubMed Central

Chen, Xianglong; Zhang, Bingzhi; Feng, Fuzhou; Jiang, Pengcheng

2017-01-01

The kurtosis-based indexes are usually used to identify the optimal resonant frequency band. However, kurtosis can only describe the strength of transient impulses, which cannot differentiate impulse noises and repetitive transient impulses cyclically generated in bearing vibration signals. As a result, it may lead to inaccurate results in identifying resonant frequency bands, in demodulating fault features and hence in fault diagnosis. In view of those drawbacks, this manuscript redefines the correlated kurtosis based on kurtosis and auto-correlative function, puts forward an improved correlated kurtosis based on squared envelope spectrum of bearing vibration signals. Meanwhile, this manuscript proposes an optimal resonant band demodulation method, which can adaptively determine the optimal resonant frequency band and accurately demodulate transient fault features of rolling bearings, by combining the complex Morlet wavelet filter and the Particle Swarm Optimization algorithm. Analysis of both simulation data and experimental data reveal that the improved correlated kurtosis can effectively remedy the drawbacks of kurtosis-based indexes and the proposed optimal resonant band demodulation is more accurate in identifying the optimal central frequencies and bandwidth of resonant bands. Improved fault diagnosis results in experiment verified the validity and advantage of the proposed method over the traditional kurtosis-based indexes. PMID:28208820

Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

NASA Technical Reports Server (NTRS)

Nguyen, Hung; Simons, Rainee; Wintucky, Edwin; Freeman, Jon

2013-01-01

As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

Band selection method based on spectrum difference in targets of interest in hyperspectral imagery

NASA Astrophysics Data System (ADS)

Zhang, Xiaohan; Yang, Guang; Yang, Yongbo; Huang, Junhua

2016-10-01

While hyperspectral data shares rich spectrum information, it has numbers of bands with high correlation coefficients, causing great data redundancy. A reasonable band selection is important for subsequent processing. Bands with large amount of information and low correlation should be selected. On this basis, according to the needs of target detection applications, the spectral characteristics of the objects of interest are taken into consideration in this paper, and a new method based on spectrum difference is proposed. Firstly, according to the spectrum differences of targets of interest, a difference matrix which represents the different spectral reflectance of different targets in different bands is structured. By setting a threshold, the bands satisfying the conditions would be left, constituting a subset of bands. Then, the correlation coefficients between bands are calculated and correlation matrix is given. According to the size of the correlation coefficient, the bands can be set into several groups. At last, the conception of normalized variance is used on behalf of the information content of each band. The bands are sorted by the value of its normalized variance. Set needing number of bands, and the optimum band combination solution can be get by these three steps. This method retains the greatest degree of difference between the target of interest and is easy to achieve by computer automatically. Besides, false color image synthesis experiment is carried out using the bands selected by this method as well as other 3 methods to show the performance of method in this paper.

Validation of Aquarius Measurements Using Radiative Transfer Models at L-Band

NASA Technical Reports Server (NTRS)

Dinnat, E.; LeVine, David M.; Abraham, S.; DeMattheis, P.; Utku, C.

2012-01-01

Aquarius/SAC-D was launched in June 2011 by NASA and CONAE (Argentine space agency). Aquarius includes three L-band (1.4 GHz) radiometers dedicated to measuring sea surface salinity. We report detailed comparisons of Aquarius measurements with radiative transfer model predictions. These comparisons were used as part ofthe initial assessment of Aquarius data. In particular, they were used successfully to estimate the radiometer calibration bias and stability. Further comparisons are being performed to assess the performance of models in the retrieval algorithm for correcting the effect of sources of geophysical "noise" (e.g. the galactic background, atmospheric attenuation and reflected signal from the Sun). Such corrections are critical in bringing the error in retrieved salinity down to the required 0.2 practical salinity unit (psu) on monthly global maps at 150 km by 150 km resolution. The forward models making up the Aquarius simulator have been very useful for preparatory studies in the years leading to Aquarius' launch. The simulator includes various components to compute effects ofthe following processes on the measured signal: 1) emission from Earth surfaces (ocean, land, ice), 2) atmospheric emission and absorption, 3) emission from the Sun, Moon and celestial Sky (directly through the antenna sidelobes or after reflection/scattering at the Earth surface), 4) Faraday rotation, and 5) convolution of the scene by the antenna gain patterns. Since the Aquarius radiometers tum-on in late July 2011, the simulator has been used to perform a first order validation of the data. This included checking the order of magnitude ofthe signal over ocean, land and ice surfaces, checking the relative amplitude of signal at different polarizations, and checking the variation with incidence angle. The comparisons were also used to assess calibration bias and monitor instruments calibration drift. The simulator is also being used in the salinity retrieval. For example, initial

L-band radar sensing of soil moisture. [Kern County, California

NASA Technical Reports Server (NTRS)

Chang, A. T. C.; Atwater, S.; Salomonson, V. V.; Estes, J. E.; Simonett, D. S.; Bryan, M. L.

1980-01-01

The performance of an L-band, 25 cm wavelength imaging synthetic aperture radar was assessed for soil moisture determination, and the temporal variability of radar returns from a number of agricultural fields was studied. A series of three overflights was accomplished over an agricultural test site in Kern County, California. Soil moisture samples were collected from bare fields at nine sites at depths of 0-2, 2-5, 5-15, and 15-30 cm. These gravimetric measurements were converted to percent of field capacity for correlation to the radar return signal. The initial signal film was optically correlated and scanned to produce image data numbers. These numbers were then converted to relative return power by linear interpolation of the noise power wedge which was introduced in 5 dB steps into the original signal film before and after each data run. Results of correlations between the relative return power and percent of field capacity (FC) demonstrate that the relative return power from this imaging radar system is responsive to the amount of soil moisture in bare fields. The signal returned from dry (15% FC) and wet (130% FC) fields where furrowing is parallel to the radar beam differs by about 10 dB.

Optimized radiation-hardened erbium doped fiber amplifiers for long space missions

NASA Astrophysics Data System (ADS)

Ladaci, A.; Girard, S.; Mescia, L.; Robin, T.; Laurent, A.; Cadier, B.; Boutillier, M.; Ouerdane, Y.; Boukenter, A.

2017-04-01

In this work, we developed and exploited simulation tools to optimize the performances of rare earth doped fiber amplifiers (REDFAs) for space missions. To describe these systems, a state-of-the-art model based on the rate equations and the particle swarm optimization technique is developed in which we also consider the main radiation effect on REDFA: the radiation induced attenuation (RIA). After the validation of this tool set by confrontation between theoretical and experimental results, we investigate how the deleterious radiation effects on the amplifier performance can be mitigated following adequate strategies to conceive the REDFA architecture. The tool set was validated by comparing the calculated Erbium-doped fiber amplifier (EDFA) gain degradation under X-rays at ˜300 krad(SiO2) with the corresponding experimental results. Two versions of the same fibers were used in this work, a standard optical fiber and a radiation hardened fiber, obtained by loading the previous fiber with hydrogen gas. Based on these fibers, standard and radiation hardened EDFAs were manufactured and tested in different operating configurations, and the obtained data were compared with simulation data done considering the same EDFA structure and fiber properties. This comparison reveals a good agreement between simulated gain and experimental data (<10% as the maximum error for the highest doses). Compared to our previous results obtained on Er/Yb-amplifiers, these results reveal the importance of the photo-bleaching mechanism competing with the RIA that cannot be neglected for the modeling of the radiation-induced gain degradation of EDFAs. This implies to measure in representative conditions the RIA at the pump and signal wavelengths that are used as input parameters for the simulation. The validated numerical codes have then been used to evaluate the potential of some EDFA architecture evolutions in the amplifier performance during the space mission. Optimization of both the

Evaluation of chlorophyll-a retrieval algorithms based on MERIS bands for optically varying eutrophic inland lakes.

PubMed

Lyu, Heng; Li, Xiaojun; Wang, Yannan; Jin, Qi; Cao, Kai; Wang, Qiao; Li, Yunmei

2015-10-15

Fourteen field campaigns were conducted in five inland lakes during different seasons between 2006 and 2013, and a total of 398 water samples with varying optical characteristics were collected. The characteristics were analyzed based on remote sensing reflectance, and an automatic cluster two-step method was applied for water classification. The inland waters could be clustered into three types, which we labeled water types I, II and III. From water types I to III, the effect of the phytoplankton on the optical characteristics gradually decreased. Four chlorophyll-a retrieval algorithms for Case II water, a two-band, three-band, four-band and SCI (Synthetic Chlorophyll Index) algorithm were evaluated for three water types based on the MERIS bands. Different MERIS bands were used for the three water types in each of the four algorithms. The four algorithms had different levels of retrieval accuracy for each water type, and no single algorithm could be successfully applied to all water types. For water types I and III, the three-band algorithm performed the best, while the four-band algorithm had the highest retrieval accuracy for water type II. However, the three-band algorithm is preferable to the two-band algorithm for turbid eutrophic inland waters. The SCI algorithm is recommended for highly turbid water with a higher concentration of total suspended solids. Our research indicates that the chlorophyll-a concentration retrieval by remote sensing for optically contrasted inland water requires a specific algorithm that is based on the optical characteristics of inland water bodies to obtain higher estimation accuracy. Copyright © 2015 Elsevier B.V. All rights reserved.

Utilizing gamma band to improve mental task based brain-computer interface design.

PubMed

Palaniappan, Ramaswamy

2006-09-01

A common method for designing brain-computer Interface (BCI) is to use electroencephalogram (EEG) signals extracted during mental tasks. In these BCI designs, features from EEG such as power and asymmetry ratios from delta, theta, alpha, and beta bands have been used in classifying different mental tasks. In this paper, the performance of the mental task based BCI design is improved by using spectral power and asymmetry ratios from gamma (24-37 Hz) band in addition to the lower frequency bands. In the experimental study, EEG signals extracted during five mental tasks from four subjects were used. Elman neural network (ENN) trained by the resilient backpropagation algorithm was used to classify the power and asymmetry ratios from EEG into different combinations of two mental tasks. The results indicated that ((1) the classification performance and training time of the BCI design were improved through the use of additional gamma band features; (2) classification performances were nearly invariant to the number of ENN hidden units or feature extraction method.

Stellar-based calibration in the far infrared with application to IRAS Band 4

NASA Technical Reports Server (NTRS)

Kirby, D. J.; Rieke, G. H.; Lebofsky, L. A.

1994-01-01

Because stars emit very small portions of their outputs in the far infrared, using them as calibrators requires precise measurement and correction for filter leaks at shorter wavelengths. Therefore, it is common to base far infrared calibrations on planetary objects such as asteriods. However, asteroids are complex geological bodies whose thermal properties depend on their evolutionary histories as well as on their gross parameters such as mass and composition, making them difficult to model as calibrators. We propose a new method for measuring filter leaks that can be carried out using the end-to-end detector system and therefore allows reliable use of stellar calibrators. We illustrate this method by showing that the Infrared Astronomy Satellite (IRAS) 100 micrometers (Band 4) filters had a short wavelength leak of 14.3% +/- 3.6% on stars similar to alpha Boo, but that there is no detectable leak in the 60 micrometers (Band 3) filters. We derive a calibration for Band 4 from stellar colors in a way that is closely analogous to the calibrations of Bands 1, 2, and 3. With correction for the leak, the stellar-based calibration is virtually identical to the original calibration based on asteroids; this result requires that the spectra of the asteriods for the original calibration differ from greybody behavior between 60 and 100 micrometers by about 10%.

CPM Signals for Satellite Navigation in the S and C Bands.

PubMed

Xue, Rui; Sun, Yanbo; Zhao, Danfeng

2015-06-05

Frequency allocations in the L band suitable for global navigation satellite system (GNSS) services are getting crowded and system providers face an ever tougher job when they try to bring in new signals and services while maintaining radio frequency compatibility. With the successive opening of the S and C bands to GNSS service, the multi-band combined navigation is predicted to become a key technology for future high-precision positioning navigation systems, and a single modulation scheme satisfying the requirements in each band is a promising solution for reducing user terminal complexity. A universal modulation scheme based on the continuous phase modulation (CPM) family suitable for the above bands' demands is proposed. Moreover, this paper has put forward two specific CPM signals for the S and C bands, respectively. Then the proposed modulation schemes, together with existing candidates, are comprehensively evaluated. Simulation results show that the proposed CPM signals can not only satisfy the constraint condition of compatibility in different bands well and reduce user terminal complexity, but also provide superior performance in terms of tracking accuracy, multi-path mitigation and anti-jamming compared to other candidate modulation schemes.

Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

PubMed Central

Limaye, Mukta V.; Chen, S. C.; Lee, C. Y.; Chen, L. Y.; Singh, Shashi B.; Shao, Y. C.; Wang, Y. F.; Hsieh, S. H.; Hsueh, H. C.; Chiou, J. W.; Chen, C. H.; Jang, L. Y.; Cheng, C. L.; Pong, W. F.; Hu, Y. F.

2015-01-01

The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2− (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2− species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2−, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples. PMID:26098075

Passive L-Band H Polarized Microwave Emission During the Corn Growth Cycle

NASA Astrophysics Data System (ADS)

Joseph, A. T.; van der Velde, R.; O'Neill, P. E.; Kim, E. J.; Lang, R. H.; Gish, T. J.

2012-12-01

Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (TB's) measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These TB measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly TB's could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly TB. Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, hr, on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on TB simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent hr parameterization was responsible for the largest error reduction of TB simulations in the early growth cycle. A.T. Joseph, R. Van der Velde, P.E. O'Neill, R.H. Lang, and T. Gish, "Soil moisture retrieval during a corn growth cycle using L-band (1.6 GHz) radar observations", IEEE Transactions on Geoscience and Remote Sensing, vol. 46, DOI:10.1109/TGRS.2008.917214, Aug. 2008. M.C. Dobson, F.T. Ulaby, M

Effective Medium Ratio Obeying Wideband Left-Handed Miniaturized Meta-atoms for Multi-band Applications

NASA Astrophysics Data System (ADS)

Hossain, Mohammad Jakir; Faruque, Mohammad Rashed Iqbal; Islam, Mohammad Tariqul

2017-12-01

In this paper, a miniaturized wideband left-handed (LH) meta-atom based on planar modified multiple hexagonal split ring resonators was designed, simulated, fabricated and tested that can maintain a left-handed property. An analysis and comparison of the different array structures were performed that obtained better effective medium ratio (EMR) and wideband (5.54 GHz) for multi band operations in the microwave regime. Finite-difference time-domain (FDTD) method based Computer Simulation Technology was implemented to design the meta-atom. The meta-atom showed multi-band response in conjunction with wideband and LH property over the certain frequency bands in the microwave spectra. The EMR was considerably improved compared to previously reported meta-atoms. The measured results showed good agreement with the simulated results. The dimensions, S-parameters and EMR parameters of the proposed miniaturized LH meta-atom are appropriate for L-, S-, C-, X-, and Ku-band applications.

Effective Medium Ratio Obeying Wideband Left-Handed Miniaturized Meta-atoms for Multi-band Applications

NASA Astrophysics Data System (ADS)

Hossain, Mohammad Jakir; Faruque, Mohammad Rashed Iqbal; Islam, Mohammad Tariqul

2018-03-01

In this paper, a miniaturized wideband left-handed (LH) meta-atom based on planar modified multiple hexagonal split ring resonators was designed, simulated, fabricated and tested that can maintain a left-handed property. An analysis and comparison of the different array structures were performed that obtained better effective medium ratio (EMR) and wideband (5.54 GHz) for multi band operations in the microwave regime. Finite-difference time-domain (FDTD) method based Computer Simulation Technology was implemented to design the meta-atom. The meta-atom showed multi-band response in conjunction with wideband and LH property over the certain frequency bands in the microwave spectra. The EMR was considerably improved compared to previously reported meta-atoms. The measured results showed good agreement with the simulated results. The dimensions, S-parameters and EMR parameters of the proposed miniaturized LH meta-atom are appropriate for L-, S-, C-, X-, and Ku-band applications.

A natural-color mapping for single-band night-time image based on FPGA

NASA Astrophysics Data System (ADS)

Wang, Yilun; Qian, Yunsheng

2018-01-01

A natural-color mapping for single-band night-time image method based on FPGA can transmit the color of the reference image to single-band night-time image, which is consistent with human visual habits and can help observers identify the target. This paper introduces the processing of the natural-color mapping algorithm based on FPGA. Firstly, the image can be transformed based on histogram equalization, and the intensity features and standard deviation features of reference image are stored in SRAM. Then, the real-time digital images' intensity features and standard deviation features are calculated by FPGA. At last, FPGA completes the color mapping through matching pixels between images using the features in luminance channel.

Multitemporal L- and C-Band Synthetic Aperture Radar To Highlight Differences in Water Status Among Boreal Forest and Wetland Systems in the Yukon Flats, Interior Alaska

USGS Publications Warehouse

Balser, Andrew W.; Wylie, Bruce K.

2010-01-01

Tracking landscape-scale water status in high-latitude boreal systems is indispensible to understanding the fate of stored and sequestered carbon in a climate change scenario. Spaceborne synthetic aperture radar (SAR) imagery provides critical information for water and moisture status in Alaskan boreal environments at the landscape scale. When combined with results from optical sensor analyses, a complementary picture of vegetation, biomass, and water status emerges. Whereas L-band SAR showed better inherent capacity to map water status, C-band had much more temporal coverage in this study. Analysis through the use of L- and C-band SARs combined with Landsat Enhanced Thematic Mapper Plus (ETM+) enables landscape stratification by vegetation and by seasonal and interannual hydrology. Resultant classifications are highly relevant to biogeochemistry at the landscape scale. These results enhance our understanding of ecosystem processes relevant to carbon balance and may be scaled up to inform regional carbon flux estimates and better parameterize general circulation models (GCMs).

Do L chondrites come from the Gefion family?

NASA Astrophysics Data System (ADS)

McGraw, Allison M.; Reddy, Vishnu; Sanchez, Juan A.

2018-05-01

Ordinary chondrites (H, L, and LL chondrites) are the most common type of meteorites comprising 80 per cent of the meteorites that fall on Earth. The source region of these meteorites in the main asteroid belt has been a basis of considerable debate in the small bodies community. L chondrites have been proposed to come from the Gefion asteroid family, based on dynamical models. We present results from our observational campaign to verify a link between the Gefion asteroid family and L chondrite meteorites. Near-infrared spectra of Gefion family asteroids (1839) Ragazza, (2373) Immo, (2386) Nikonov, (2521) Heidi, and (3860) Plovdiv were obtained at the NASA Infrared Telescope Facility (IRTF). Spectral band parameters including band centres and the band area ratio were measured from each spectrum and used to constrain the composition of these asteroids. Based on our results, we found that some members of the Gefion family have surface composition similar to that of H chondrites, primitive achondrites, and basaltic achondrites. No evidence was found for L chondrites among the Gefion family members in our small sample study. The diversity of compositional types observed in the Gefion asteroid family suggests that the original parent body might be partially differentiated or that the three asteroids with non-ordinary chondrite compositions might be interlopers.

Design of tunable thermo-optic C-band filter based on coated silicon slab

NASA Astrophysics Data System (ADS)

Pinhas, Hadar; Malka, Dror; Danan, Yossef; Sinvani, Moshe; Zalevsky, Zeev

2018-03-01

Optical filters are required to have narrow band-pass filtering in the spectral C-band for applications such as signal tracking, sub-band filtering or noise suppression. These requirements lead to a variety of filters such as Mach-Zehnder interferometer inter-leaver in silica, which offer thermo-optic effect for optical switching, however, without proper thermal and optical efficiency. In this paper we propose tunable thermo-optic filtering device based on coated silicon slab resonator with increased Q-factor for the C-band optical switching. The device can be designed either for long range wavelength tuning of for short range with increased wavelength resolution. Theoretical examination of the thermal parameters affecting the filtering process is shown together with experimental results. Proper channel isolation with an extinction ratio of 20dBs is achieved with spectral bandpass width of 0.07nm.

Tunable graphene-based hyperbolic metamaterial operating in SCLU telecom bands.

PubMed

Janaszek, Bartosz; Tyszka-Zawadzka, Anna; Szczepański, Paweł

2016-10-17

The tunability of graphene-based hyperbolic metamaterial structure operating in SCLU telecom bands is investigated. For the first time it has been shown that for the proper design of a graphene/dielectric multilayer stack, the HMM Type I, Epsilon-Near-Zero and Type II regimes are possible by changing the biasing potential. Numerical results reveal the effect of structure parameters such as the thickness of the dielectric layer as well as a number of graphene sheets in a unit cell (i.e., dielectric/graphene bilayer) on the tunability range and shape of the dispersion characteristics (i.e., Type I/ENZ/Type II) in SCLU telecom bands. This kind of materials could offer a technological platform for novel devices having various applications in optical communications technology.

UAVSAR - A New Airborne L-Band Radar for Repeat Pass Interferometry

NASA Technical Reports Server (NTRS)

Mace, Thomas H.; Lou, Yunling

2009-01-01

NASA/JPL has developed a new airborne Synthetic Aperture Radar (SAR) which has become available for use by the scientific community in January, 2009. Pod mounted, the UAVSAR was designed to be portable among a variety of aircraft, including unmanned aerial systems (UAS). The instrument operates in the L-Band, has a resolution under 2m from a GPS altitude of 12Km and a swath width of approximately 20Km. UAVSAR currently flies on a modified Gulfstream-III aircraft, operated by NASA s Dryden Flight Research Center at Edwards, California. The G-III platform enables repeat-pass interferometric measurements, by using a modified autopilot and precise kinematic differential GPS to repeatedly fly the aircraft within a specified 10m tube. The antenna is electronically steered along track to assure that the antenna beam can be directed independently, regardless of speed and wind direction. The instrument can be controlled remotely, AS AN OPTION, using the Research Environment for Vehicle Embedded Analysis on Linux (REVEAL). This allows simulation of the telepresence environment necessary for flight on UAS. Potential earth science research and applications include surface deformation, volcano studies, ice sheet dynamics, and vegetation structure.

Dual Band Notched EBG Structure based UWB MIMO/Diversity Antenna with Reduced Wide Band Electromagnetic Coupling

NASA Astrophysics Data System (ADS)

Jaglan, Naveen; Kanaujia, Binod Kumar; Gupta, Samir Dev; Srivastava, Shweta

2017-10-01

A dual band-notched MIMO/Diversity antenna is proposed in this paper. The proposed antenna ensures notches in WiMAX band (3.3-3.6 GHz) besides WLAN band (5-6 GHz). Mushroom Electromagnetic Band Gap (EBG) arrangements are employed for discarding interfering frequencies. The procedure followed to attain notches is antenna shape independent with established formulas. The electromagnetic coupling among two narrowly set apart Ultra-Wide Band (UWB) monopoles is reduced by means of decoupling bands and slotted ground plane. Monopoles are 90° angularly parted with steps on the radiator. This aids to diminish mutual coupling and also adds in the direction of impedance matching by long current route. S21 or else mutual coupling of fewer than 15 dB is established over antenna operating range. Two-port envelope correlation coefficient is lower than 0.02 in UWB range of 3.1 GHz-10.6 GHz. The shifting in notch frequencies by varying variables in formulas is also reported. The suggested antenna is designed on low budget FR-4 substrate with measurements as (58 × 45 × 1.6) mm3. Simulated and measured results of fabricated antenna are found to be in close agreement.

Transparent, conducting films based on metal/dielectric photonic band gaps

NASA Astrophysics Data System (ADS)

Bloemer, Mark J.; Scalora, Michael; D'Aguanno, G.; Bowden, Charles M.; Baglio, Salvatore; Sibilia, Concita; Centini, Marco; Bertolotti, Mario

1999-07-01

A transparent conductor has been developed based on 1D metal/dielectric photonic band gap structures. Laminated metal/dielectric filters containing 100 nm of silver have been fabricated with > 50% transmittance. Applications for transparent, conducting films include antennas embedded in windshields, electrodes on flat panel displays, electromagnetic shielding, and solar window panes.

Configurations, band structures and photocurrent responses of 4-(4-oxopyridin-1(4H)-yl)phthalic acid and its metal-organic frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Xingxiu; Qiu, Xiandeng; Yan, Zhishuo

2016-05-15

4-(4-oxopyridin-1(4 H)-yl)phthalic acid (H{sub 2}L) and three H{sub 2}L-based metal-organic frameworks (MOFs) formulated as ZnL(DPE)(H{sub 2}O)·H{sub 2}O (DPE=(E)-1, 2-di(pyridine −4-yl)ethene) (1), CdL(H{sub 2}O){sub 2} (2) and CdL (3) were synthesized and structurally characterized by single-crystal X-ray diffraction. The free H{sub 2}L ligand shows an enol-form and the L{sup 2−} ligand in the three MOFs exists as the keto-form. Density functional theory (DFT) calculations indicate H{sub 2}L and the three MOFs possess different band structures. Due to the existence of the N-donor, DPE in MOF 1, the conduction band (CB) minimum and band gap of MOF 1 are much lower thanmore » those of H{sub 2}L. And MOF 1 yielded much larger photocurrent density than H{sub 2}L upon visible light illumination. Electrochemical impedance spectroscopy (EIS) shows the interfacial charge transfer impedance in the presence of MOF 1 is lower than that in the presence of H{sub 2}L. The hydrous MOF 2 and the anhydrous MOF 3 are both constructed by Cd(II) and L{sup 2−}, and they can be reversibly transformed to each other. However, MOFs 2 and 3 possess different CB minimums and VB maximums, and their band gaps are much larger than that of MOF 1. - Graphical abstract: The free ligand, 4-(4-oxopyridin-1(4H)-yl)phthalic acid (H{sub 2}L) shows different configuration from its three MOFs, and they possess different band structures. MOF 1 yielded much larger visible-light-driven photocurrent density than H{sub 2}L. The hydrous MOF 2 and the anhydrous MOF 3 can be transformed to each other, and they have larger band gaps than MOF 1.« less

The Planned Soil Moisture Active Passive (SMAP) Mission L-Band Radar/Radiometer Instrument

NASA Technical Reports Server (NTRS)

Spencer, Michael; Wheeler, Kevin; Chan, Samuel; Piepmeier, Jeffrey; Hudson, Derek; Medeiros, James

2011-01-01

The Soil Moisture Active/Passive (SMAP) mission is a NASA mission identified by the NRC 'decadal survey' to measure both soil moisture and freeze/thaw state from space. The mission will use both active radar and passive radiometer instruments at L-Band. In order to achieve a wide swath at sufficiently high resolution for both active and passive channels, an instrument architecture that uses a large rotating reflector is employed. The instrument system has completed the preliminary design review (PDR) stage, and detailed instrument design has begun. In addition to providing an overview of the instrument design, two recent design modifications are discussed: 1) The addition of active thermal control to the instrument spun side to provide a more stable, settable thermal environment for the radiometer electronics, and 2) A 'sequential transmit' strategy for the two radar polarization channels which allows a single high-power amplifier to be used.

An L-band multi-wavelength Brillouin-erbium fiber laser with switchable frequency spacing

NASA Astrophysics Data System (ADS)

Zhou, Xuefang; Hu, Kongwen; Wei, Yizhen; Bi, Meihua; Yang, Guowei

2017-01-01

In this paper, a novel L-band multi-wavelength Brillouin-erbium fiber laser consisting of two ring cavities is proposed and demonstrated. The frequency spacing can be switched, corresponding to the single and double Brillouin frequency shifts, by toggling the optical switch. Under a 980 nm pump power of 600 mw, and a Brillouin pump power of 4 mW and wavelength of 1599.4 nm, up to 16 Stokes signals with a frequency spacing of 0.089 nm and 5 Stokes signals with double spacing of 0.178 nm are generated. A wavelength tunability of 15 nm (1593 nm  -  1608 nm) is realized for both frequency spacings. The fluctuation of Stokes signals for both single and double Brillouin spacing regimes in the proposed setup is less than 1.5 dB throughout a 30 min time span.

Dutch X-band SLAR calibration

NASA Technical Reports Server (NTRS)

Groot, J. S.

1990-01-01

In August 1989 the NASA/JPL airborne P/L/C-band DC-8 SAR participated in several remote sensing campaigns in Europe. Amongst other test sites, data were obtained of the Flevopolder test site in the Netherlands on August the 16th. The Dutch X-band SLAR was flown on the same date and imaged parts of the same area as the SAR. To calibrate the two imaging radars a set of 33 calibration devices was deployed. 16 trihedrals were used to calibrate a part of the SLAR data. This short paper outlines the X-band SLAR characteristics, the experimental set-up and the calibration method used to calibrate the SLAR data. Finally some preliminary results are given.

Configurations, band structures and photocurrent responses of 4-(4-oxopyridin-1(4H)-yl)phthalic acid and its metal-organic frameworks

NASA Astrophysics Data System (ADS)

Yan, Xingxiu; Qiu, Xiandeng; Yan, Zhishuo; Li, Hongjiang; Gong, Yun; Lin, Jianhua

2016-05-01

4-(4-oxopyridin-1(4 H)-yl)phthalic acid (H2L) and three H2L-based metal-organic frameworks (MOFs) formulated as ZnL(DPE)(H2O)·H2O (DPE=(E)-1, 2-di(pyridine -4-yl)ethene) (1), CdL(H2O)2 (2) and CdL (3) were synthesized and structurally characterized by single-crystal X-ray diffraction. The free H2L ligand shows an enol-form and the L2- ligand in the three MOFs exists as the keto-form. Density functional theory (DFT) calculations indicate H2L and the three MOFs possess different band structures. Due to the existence of the N-donor, DPE in MOF 1, the conduction band (CB) minimum and band gap of MOF 1 are much lower than those of H2L. And MOF 1 yielded much larger photocurrent density than H2L upon visible light illumination. Electrochemical impedance spectroscopy (EIS) shows the interfacial charge transfer impedance in the presence of MOF 1 is lower than that in the presence of H2L. The hydrous MOF 2 and the anhydrous MOF 3 are both constructed by Cd(II) and L2-, and they can be reversibly transformed to each other. However, MOFs 2 and 3 possess different CB minimums and VB maximums, and their band gaps are much larger than that of MOF 1.

Garage Band or GarageBand[R]? Remixing Musical Futures

ERIC Educational Resources Information Center

Vakeva, Lauri

2010-01-01

In this paper, I suggest that it is perhaps time to consider the pedagogy of popular music in more extensive terms than conventional rock band practices have to offer. One direction in which this might lead is the expansion of the informal pedagogy based on a "garage band" model to encompass various modes of digital artistry wherever this artistry…

Land cover classification accuracy from electro-optical, X, C, and L-band Synthetic Aperture Radar data fusion

NASA Astrophysics Data System (ADS)

Hammann, Mark Gregory

The fusion of electro-optical (EO) multi-spectral satellite imagery with Synthetic Aperture Radar (SAR) data was explored with the working hypothesis that the addition of multi-band SAR will increase the land-cover (LC) classification accuracy compared to EO alone. Three satellite sources for SAR imagery were used: X-band from TerraSAR-X, C-band from RADARSAT-2, and L-band from PALSAR. Images from the RapidEye satellites were the source of the EO imagery. Imagery from the GeoEye-1 and WorldView-2 satellites aided the selection of ground truth. Three study areas were chosen: Wad Medani, Sudan; Campinas, Brazil; and Fresno- Kings Counties, USA. EO imagery were radiometrically calibrated, atmospherically compensated, orthorectifed, co-registered, and clipped to a common area of interest (AOI). SAR imagery were radiometrically calibrated, and geometrically corrected for terrain and incidence angle by converting to ground range and Sigma Naught (?0). The original SAR HH data were included in the fused image stack after despeckling with a 3x3 Enhanced Lee filter. The variance and Gray-Level-Co-occurrence Matrix (GLCM) texture measures of contrast, entropy, and correlation were derived from the non-despeckled SAR HH bands. Data fusion was done with layer stacking and all data were resampled to a common spatial resolution. The Support Vector Machine (SVM) decision rule was used for the supervised classifications. Similar LC classes were identified and tested for each study area. For Wad Medani, nine classes were tested: low and medium intensity urban, sparse forest, water, barren ground, and four agriculture classes (fallow, bare agricultural ground, green crops, and orchards). For Campinas, Brazil, five generic classes were tested: urban, agriculture, forest, water, and barren ground. For the Fresno-Kings Counties location 11 classes were studied: three generic classes (urban, water, barren land), and eight specific crops. In all cases the addition of SAR to EO resulted

Surface deformation associated with the March 1996 earthquake swarm at Akutan Island, Alaska, revealed by C-band ERS and L-band JERS radar interferometry

USGS Publications Warehouse

Lu, Z.; Wicks, C.; Kwoun, O.; Power, J.A.; Dzurisin, D.

2005-01-01

In March 1996, an intense earthquake swarm beneath Akutan Island, Alaska, was accompanied by extensive ground cracking but no eruption of Akutan volcano. Radar interferograms produced from L-band JERS-1 and C-band ERS-1/2 images show uplift associated with the swarm by as much as 60 cm on the western part of the island. The JERS-1 interferogram has greater coherence, especially in areas with loose surface material or thick vegetation. It also shows subsidence of similar magnitude on the eastern part of the island and displacements along faults reactivated during the swarm. The axis of uplift and subsidence strikes about N70??W, which is roughly parallel to a zone of fresh cracks on the northwest flank of the volcano, to normal faults that cut the island and to the inferred maximum compressive stress direction. A common feature of models that fit the deformation is the emplacement of a shallow dike along this trend beneath the northwest flank of the volcano. Both before and after the swarm, the northwest flank was uplifted 5-20 mm/year relative to the southwest flank, probably by magma intrusion. The zone of fresh cracks subsided about 20 mm during 1996-1997 and at lesser rates thereafter, possibly because of cooling and degassing of the intrusion. ?? 2005 CASI.

Signature inversion / chiral-twin bands in odd-odd Pr nuclei?

NASA Astrophysics Data System (ADS)

Fetea, Mirela; Thompson, Sarah

2001-10-01

Over the past few years, sufficient data have been accumulated to enable a meaningful study of the systematic trends of the signature inversion (inversion point shift in spin with increasing proton and neutron numbers in a chain of isotones / isotopes as well as the magnitude of odd-even staggering). Our aim is to understand these systematic features within the framework of particle rotor model including both a residual pn interaction and a γ deformation. Signature inversion is present in the bands of odd-odd nuclei , ^120-130Cs, ^124-132La, ^126-134Pr and ^132-136Pm and having an yrast structure built on π h_11/2ν h_11/2 orbitals. Pr isotopes seem to indicate an inversion decreasing for smaller neutron numbers, trend that is opposite for the Cs nuclei(J.F. Smith et al., Phys. Lett B 406, 7 (1997)). Why? A question that remains to be answered is if there is any relation of signature inversion to chiral twin bands (two ''look alike positive parity'' bands proposed for as in ). The lower band has signature inversion all the way up. Could these effects be related to triaxiality? Can one trust an apparent conclusion suggested by L.L. Riedinger( L.L. Riedinger, talk presented at High) Spin Physics 2001, Warsaw, Poland, February, 2001, to be published in Acta Phys. Pol.: ''signature inversion in an odd-odd band of two quasiparticles pointed along different axes is always associated with the formation of chiral twin bands''?

Full-mesh T- and O-band wavelength router based on arrayed waveguide gratings.

PubMed

Idris, Nazirul A; Yoshizawa, Katsumi; Tomomatsu, Yasunori; Sudo, Makoto; Hajikano, Tadashi; Kubo, Ryogo; Zervas, Georgios; Tsuda, Hiroyuki

2016-01-11

We propose an ultra-broadband full-mesh wavelength router supporting the T- and O-bands using 3 stages of cascaded arrayed waveguide gratings (AWGs). The router architecture is based on a combination of waveband and channel routing by coarse and fine AWGs, respectively. We fabricated several T-band-specific silica-based AWGs and quantum dot semiconductor optical ampliers as part of the router, and demonstrated 10 Gbps data transmission for several wavelengths throughout a range of 7.4 THz. The power penalties were below 1 dB. Wavelength routing was also demonstrated, where tuning time within a 9.4-nm-wide waveband was below 400 ms.

Sharpending of the Vnir and SWIR Bands of the Wide Band Spectral Imager Onboard Tiangong-II Imagery Using the Selected Bands

NASA Astrophysics Data System (ADS)

Liu, Q.; Li, X.; Liu, G.; Huang, C.; Li, H.; Guan, X.

2018-04-01

The Tiangong-II space lab was launched at the Jiuquan Satellite Launch Center of China on September 15, 2016. The Wide Band Spectral Imager (WBSI) onboard the Tiangong-II has 14 visible and near-infrared (VNIR) spectral bands covering the range from 403-990 nm and two shortwave infrared (SWIR) bands covering the range from 1230-1250 nm and 1628-1652 nm respectively. In this paper the selected bands are proposed which aims at considering the closest spectral similarities between the VNIR with 100 m spatial resolution and SWIR bands with 200 m spatial resolution. The evaluation of Gram-Schmidt transform (GS) sharpening techniques embedded in ENVI software is presented based on four types of the different low resolution pan band. The experimental results indicated that the VNIR band with higher CC value with the raw SWIR Band was selected, more texture information was injected the corresponding sharpened SWIR band image, and at that time another sharpened SWIR band image preserve the similar spectral and texture characteristics to the raw SWIR band image.

Radio-frequency low-coherence interferometry.

PubMed

Fernández-Pousa, Carlos R; Mora, José; Maestre, Haroldo; Corral, Pablo

2014-06-15

A method for retrieving low-coherence interferograms, based on the use of a microwave photonics filter, is proposed and demonstrated. The method is equivalent to the double-interferometer technique, with the scanning interferometer replaced by an analog fiber-optics link and the visibility recorded as the amplitude of its radio-frequency (RF) response. As a low-coherence interferometry system, it shows a decrease of resolution induced by the fiber's third-order dispersion (β3). As a displacement sensor, it provides highly linear and slope-scalable readouts of the interferometer's optical path difference in terms of RF, even in the presence of third-order dispersion. In a proof-of-concept experiment, we demonstrate 20-μm displacement readouts using C-band EDFA sources and standard single-mode fiber.

Airborne Remote Observations of L-Band Radio Frequency Interference and Implications for Satellite Missions

NASA Technical Reports Server (NTRS)

Laymon, Charles; Srinivasan, Karthik; Limaye, Ashutosh

2011-01-01

Passive remote sensing of the Earth s surface and atmosphere from space has significant importance in operational and research environmental studies, in particular for the scientific understanding, monitoring and prediction of climate change and its impacts. Passive remote sensing requires the measurement of naturally occurring radiations, usually of very low power levels, which contain essential information on the physical process under investigation. As such, these sensed radio frequency bands are a unique natural resource enabling space borne passive sensing of the atmosphere and the Earth s surface that deserves adequate allocation to the Earth Exploration Satellite Service and absolute protection from interference. Unfortunately, radio frequency interference (RFI) is an increasing problem for Earth remote sensing, particularly for passive observations of natural emissions. Because these natural signals tend to be very weak, even low levels of interference received by a passive sensor may degrade the fidelity of scientific data. The characteristics of RFI (low-level interference and radar-pulse noise) are not well known because there has been no systematic surveillance, spectrum inventory or mapping of RFI. While conducting a flight experiment over central Tennessee in May 2010, RFI, a concern for any instrument operating in the passive L band frequency, was observed across 16 subbands between 1402-1427 MHz. Such a survey provides rare characterization data from which to further develop mitigation technologies as well as to identify bandwidths to avoid in future sensor formulation.

Single-Band and Dual-Band Infrared Detectors

NASA Technical Reports Server (NTRS)

Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor); Soibel, Alexander (Inventor); Nguyen, Jean (Inventor); Khoshakhlagh, Arezou (Inventor)

2015-01-01

Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.

Single-Band and Dual-Band Infrared Detectors

NASA Technical Reports Server (NTRS)

Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor); Soibel, Alexander (Inventor); Nguyen, Jean (Inventor); Khoshakhlagh, Arezou (Inventor)

2017-01-01

Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.

L- and K-band LMSS propagation measurements using MARECS-B, OLYMPUS, and ACTS

NASA Technical Reports Server (NTRS)

Vogel, W. J.; Torrence, G. W.; Goldhirsh, J.; Rowland, J. R.

1992-01-01

L-band measurements of land mobile satellite systems (LMSS) propagation effects were last made at the end of 1988, but some voids were left in the database, making modeling of low elevation roadside tree shadowing and multipath reflections difficult for some path geometries. Transmission of a pilot tone from MARECS-B at 55 deg West during Sep. and Dec. 1991 gave an opportunity to fill the gaps in the experimental results. Two campaigns during which fade data were obtained at elevation angles from 7 deg to 40 deg are described. Below 15 deg, specular terrain reflections in a non-shadowing, hilly environment were observed to introduce significant fading. Although the reflecting surface was at a distance of up to several km, it is shown that the reflected signals are delayed by less than 1 microsec. Mobile measurements were also attempted receiving the 20 GHz Olympus beacon, but antenna pointing problems restricted first results to straight-line driving.

Analysis of 2ν3 Band of Hto

NASA Astrophysics Data System (ADS)

Kobayashi, Kaori; Maki, Hiroki; Yamamoto, Takuya; Hara, Masanori; Hatano, Yuji; Ozeki, Hiroyuki

2014-06-01

Tritium is a radioactive isotope of hydrogen. Tritium released into natural enviroment is said to be converted into mostly HTO. The detection of HTO is important from the viewpoint of basic science as well as its radioactivity. Spectroscopy is a good tool for detection, however, high-resolution spectroscopy studies are still limited. The microwave study were carried out and the molecular constants of the ground state were determined. All fundamental ν_1, ν_2 and the ν_3 bands of HTO were reported. At 1.38 micron region, overtone and combination bands are expected. In this study, we prepared a new double wall cell for safe handling of highly concentrated tritiated water and carried out the near-infrared measurement. More than 100 transitions were observed and most of them were assigned to belong to the 2ν_3 band based on the previous quantum chemical calculations. We will report the current status of the analysis. P. Helminger, F. C. De Lucia, W. Gordy, P. A. Staats and H. W. Morgan, Phys. Rev. A, 10, 1072 (1974). S. D. Cope, D. K. Russell, H. A. Fry, L. H. Jones, and J. E. Barefield, J. Mol. Spectrosc., 127, 464 (1988). P. P. Cherrier, P. H. Beckwith, and J. Reid, J. Mol. Spectrosc., 121, 69 (1987). M. Tine, D. Kobor, I. Sakho, and L. H. Coudert, J. Mod. Phys., 3, 1945 (2012). M. J. Down, J. Tennyson, M. Hara, Y. Hatano, and K. Kobayashi, J. Mol. Spectrosc., 289, 35 (2013).

Can the Long-Term Complications of Adjustable Gastric Banding Be Overcome? Preliminary Results of Adding Gastric Plication in Patients with Impending Gastric Band Failure.

PubMed

Kim, Su Bin; Kim, Seong Min

2015-09-01

A small percentage of patients fitted with a gastric band still experience "failure." Here, the authors demonstrate the safety and feasibility of band preserving-laparoscopic gastric plication (BP-LGP), which was designed to improve weight loss and decrease gastric band adjustment frequency and thereby improve patient quality of life. All 6 patients involved in this study had a gastric band in place for more than 1 year; the median interval from gastric banding to BP-LGP was 31.7 months (range, 19.7-49.9 months). Five (83.3%) patients were female. Preoperative median body mass index (BMI) at gastric banding was 35.4 kg/m(2) (range, 31.9-43.9 kg/m(2)), median nadir BMI with the gastric band was 25.7 kg/m(2) (range, 20.9-31.0 kg/m(2)), and percentage excess BMI loss (%EBMIL) ranged from 24.3% to 123.6%. Indications for BP-LGP were as follows: chronic gastric prolapse in 2 patients (33.3%), pouch-esophageal dilatation in 3 (50.0%), and insufficient weight loss in 4 (66.6%), which included 2 patients with weight loss failure (%EBMIL of <30%). The 6 patients consecutively underwent surgery from May 2014 to January 2015. No conversion to open surgery was necessary, and no perioperative complication or mortality occurred. Mean operative time was 190 minutes. All patients showed weight loss after revision and showed resolution of troublesome signs and symptoms. Median follow-up after revision was 7.3 months (range, 5.7-10.1 months), median BMI at last follow-up was 27.6 kg/m(2) (range, 22.7-34.0 kg/m(2)), and median %EBMIL was 75.7% (range, 21.0%-103.6%). Median fill volume before revision was 6.1 mL (range, 2.7-11.0 mL), and median fill volume after revision was 0.3 mL (range, 0.0-5.3 mL). Three patients (50%) had an empty band at last follow-up. This novel method of bariatric revision (modified BP-LGP) might have a role as a salvage procedure in patients with impending gastric band failure.

Chemodosimeter-based fluorescent detection of L-cysteine after extracted by molecularly imprinted polymers.

PubMed

Cai, Xiaoqiang; Li, Jinhua; Zhang, Zhong; Wang, Gang; Song, Xingliang; You, Jinmao; Chen, Lingxin

2014-03-01

A chemodosimeter-based fluorescent detection method coupled with molecularly imprinted polymers (MIPs) extraction was developed for determination of L-cysteine (L-Cys) by combining molecular imprinting technique with fluorescent chemodosimeter. The MIPs prepared by precipitation polymerization with L-Cys as template, possessed high specific surface area of 145 m(2)/g and good thermal stability without decomposition lower than 300 °C, and were successfully applied as an adsorbent with excellent selectivity for L-Cys over other amino acids, and enantioselectivity was also demonstrated. A novel chemodosimeter, rhodamine B1, was synthesized for discriminating L-Cys from its structurally similar homocysteine and glutathione as well as various possibly co-existing biospecies in aqueous solutions with notable fluorescence enhancement when adding L-Cys. As L-Cys was added with increasing concentrations, an emission band peaked at 580 nm occurred and significantly increased in fluorescence intensity, by which the L-Cys could be sensed optically. High detectability up to 12.5 nM was obtained. An excellent linearity was found within the wide range of 0.05-50 μM (r=0.9996), and reasonable relative standard deviations ranging from 0.3% to 3.5% were attained. Such typical features as high selectivity, high sensitivity, easy operation and low cost enabled this MIPs-fluorometry to be potentially applicable for routine detection of trace L-Cys. Copyright © 2013 Elsevier B.V. All rights reserved.

Thermal Conductivity Enhancement by Optical Phonon Sub-Band Engineering of Nanostructures Based on C and BN

DTIC Science & Technology

2002-01-01

Thermal Conductivity Enhancement by Optical Phono n Sub-Band Engineering of Nanostructures Based on C and BN DARPA CONTRACT MDA972-02-C-0044... Engineering in 3-D Nanostructures Based on C an d BN Nanotubes " 1.3.1a. Phonon dynamics and thermal properties of zigzag carbon nanotubes Content I...Conductivity. Enhancement by Optical Phonon Sub-Bands Engineering in 3-D Nanostructure s Based on C and BN Nanotubes " . Here, the dynamics of the heat

Theoretical analysis on lower band cascade as a mechanism for multiband chorus in the Earth's magnetosphere

NASA Astrophysics Data System (ADS)

Gao, Xinliang; Lu, Quanming; Wang, Shaojie; Wang, Shui

2018-05-01

Whistler-mode waves play a crucial role in controlling electron dynamics in the Earth's Van Allen radiation belt, which is increasingly important for spacecraft safety. Using THEMIS waveform data, Gao et al. [X. L. Gao, Q. Lu, J. Bortnik, W. Li, L. Chen, and S. Wang, Geophys. Res. Lett., 43, 2343-2350, 2016] have reported two multiband chorus events, wherein upper-band chorus appears at harmonics of lower-band chorus. They proposed that upper-band harmonic waves are excited through the nonlinear coupling between the electromagnetic and electrostatic components of lower-band chorus, a second-order effect called "lower band cascade". However, the theoretical explanation of lower band cascade was not thoroughly explained in the earlier work. In this paper, based on a cold plasma assumption, we have obtained the explicit nonlinear driven force of lower band cascade through a full nonlinear theoretical analysis, which includes both the ponderomotive force and coupling between electrostatic and electromagnetic components of the pump whistler wave. Moreover, we discover the existence of an efficient energy-transfer (E-t) channel from lower-band to upper-band whistler-mode waves during lower band cascade for the first time, which is also confirmed by PIC simulations. For lower-band whistler-mode waves with a small wave normal angle (WNA), the E-t channel is detected when the driven upper-band wave nearly satisfies the linear dispersion relation of whistler mode. While, for lower-band waves with a large WNA, the E-t channel is found when the lower-band wave is close to its resonant frequency, and the driven upper-band wave becomes quasi-electrostatic. Through this efficient channel, the harmonic upper band of whistler waves is generated through energy cascade from the lower band, and the two-band spectral structure of whistler waves is then formed. Both two types of banded whistler-mode spectrum have also been successfully reproduced by PIC simulations.

Effective Albedo of Vegetated Terrain at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.

2011-01-01

This paper derives an explicit expression for an effective albedo of vegetated terrain from the zero- and multiple- order radiative transfer (RT) model comparison. The formulation establishes a direct physical link between the effective vegetation parameterization and the theoretical description of absorption and scattering within the canopy. The paper will present an evaluation of the derived albedo for corn canopies with data taken during an experiment at Alabama A&M Winfield A. Thomas Agricultural Research Station near Huntsville, Alabama in June, 1998. The test site consisted of two 50-m x 60-m plots - one with a bare surface and the other with grass cover - and four 30-m x 50-m plots of corn at different planting densities. One corn field was planted at a full density of 9.5 plants/sq m while the others were planted at 1/3, 1/2 and 2/3 of the full density. The fields were observed with a truck-mounted L-band radiometer at incident angle of 15 degree for the period of two weeks. Soil moisture (SM) changed daily due to irrigation and natural rainfall. Variations in gravimetric SM from 18 % to 34 % were seen during this period. Ground truth data, including careful characterization of the corn size and orientation statistics, and its dielectric, was also collected and used to simulate the effective albedo for the vegetation. The single-scattering albedo is defined as the fractional power scattered from individual vegetation constituents with respect to canopy extinction. It represents single-scattering properties of vegetation elements only, and is independent of ground properties. The values of the albedo get higher when there is dense vegetation (i.e. forest, mature corn, etc.) with scatterers, such as branches and trunks (or stalks in the case of corn), which are large with respect to the wavelength. This large albedo leads to a reduction in brightness temperature in the zero-order RT solution (known as tau-omega model). Higher-order multiple-scattering RT

Effects of Spectral Band Differences between Landsat 8 Operational Land Imager (OLI) and Sentinel 2A Multispectral Instrument (MSI)

NASA Astrophysics Data System (ADS)

Micijevic, E.; Haque, M. O.

2015-12-01

In satellite remote sensing, Landsat sensors are recognized for providing well calibrated satellite images for over four decades. This image data set provides an important contribution to detection and temporal analysis of land changes. Landsat 8 (L8), the latest satellite of the Landsat series, was designed to continue its legacy as well as to embrace advanced technology and satisfy the demand of the broader scientific community. Sentinel 2A (S2A), a European satellite launched in June 2015, is designed to keep data continuity of Landsat and SPOT like satellites. The S2A MSI sensor is equipped with spectral bands similar to L8 OLI and includes some additional ones. Compared to L8 OLI, green and near infrared MSI bands have narrower bandwidths, whereas coastal-aerosol (CA) and cirrus have larger bandwidths. The blue and red MSI bands cover higher wavelengths than the matching OLI bands. Although the spectral band differences are not large, their combination with the spectral signature of a studied target can largely affect the Top Of Atmosphere (TOA) reflectance seen by the sensors. This study investigates the effect of spectral band differences between S2A MSI and L8 OLI sensors. The differences in spectral bands between sensors can be assessed by calculating Spectral Band Adjustment Factors (SBAF). For radiometric calibration purposes, the SBAFs for the calibration test site are used to bring the two sensors to the same radiometric scale. However, the SBAFs are target dependent and different sensors calibrated to the same radiometric scale will (correctly!) measure different reflectance for the same target. Thus, when multiple sensors are used to study a given target, the sensor responses need to be adjusted using SBAFs specific to that target. Comparison of the SBAFs for S2A MSI and L8 OLI based on various vegetation spectral profiles revealed variations in radiometric responses as high as 15%. Depending on target under study, these differences could be even

Occurrence features of simultaneous H+- and He+-band EMIC emissions in the outer radiation belt

NASA Astrophysics Data System (ADS)

Fu, Song; He, Fengming; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Liu, Jiang

2018-04-01

As an important loss mechanism of radiation belt electrons, electromagnetic ion cyclotron (EMIC) waves show up as three distinct frequency bands below the hydrogen (H+), helium (He+), and oxygen (O+) ion gyrofrequencies. Compared to O+-band EMIC waves, H+- and He+-band emissions generally occur more frequently and result in more efficient scattering removal of <∼5 MeV relativistic electrons. Therefore, knowledge about the occurrence of these two bands is important for understanding the evolution of the relativistic electron population. To evaluate the occurrence pattern and wave properties of H+- and He+-band EMIC waves when they occur concurrently, we investigate 64 events of multi-band EMIC emissions identified from high quality Van Allen Probes wave data. Our quantitative results demonstrate a strong occurrence dependence of the multi-band EMIC emissions on magnetic local time (MLT) and L-shell to mainly concentrate on the dayside region of L = ∼4-6. We also find that the average magnetic field amplitude of H+-band waves is larger than that of He+-band waves only when L < 4.5 and AE∗ < 300 nT, and He+-band emissions are more intense under all other conditions. In contrast to 5 events that have average H+-band amplitude over 2 nT, 19 events exhibit >2 nT He+-band amplitude, indicating that the He+-band waves can be more easily amplified than the H+-band waves under the same circumstances. For simultaneous occurrences of the two EMIC wave bands, their frequencies vary with L-shell and geomagnetic activity: the peak wave frequency of H+-band emissions varies between 0.25 and 0.8 fcp with the average between 0.25 and 0.6 fcp, while that of He+-band emissions varies between 0.03 and 0.23 fcp with the average between 0.05 and 0.15 fcp. These newly observed occurrence features of simultaneous H+- and He+-band EMIC emissions provide improved information to quantify the overall contribution of multi-band EMIC waves to the loss processes of radiation belt electrons.

Defining Multiple Characteristic Raman Bands of α-Amino Acids as Biomarkers for Planetary Missions Using a Statistical Method

NASA Astrophysics Data System (ADS)

Rolfe, S. M.; Patel, M. R.; Gilmour, I.; Olsson-Francis, K.; Ringrose, T. J.

2016-06-01

Biomarker molecules, such as amino acids, are key to discovering whether life exists elsewhere in the Solar System. Raman spectroscopy, a technique capable of detecting biomarkers, will be on board future planetary missions including the ExoMars rover. Generally, the position of the strongest band in the spectra of amino acids is reported as the identifying band. However, for an unknown sample, it is desirable to define multiple characteristic bands for molecules to avoid any ambiguous identification. To date, there has been no definition of multiple characteristic bands for amino acids of interest to astrobiology. This study examined l-alanine, l-aspartic acid, l-cysteine, l-glutamine and glycine and defined several Raman bands per molecule for reference as characteristic identifiers. Per amino acid, 240 spectra were recorded and compared using established statistical tests including ANOVA. The number of characteristic bands defined were 10, 12, 12, 14 and 19 for l-alanine (strongest intensity band: 832 cm-1), l-aspartic acid (938 cm-1), l-cysteine (679 cm-1), l-glutamine (1090 cm-1) and glycine (875 cm-1), respectively. The intensity of bands differed by up to six times when several points on the crystal sample were rotated through 360 °; to reduce this effect when defining characteristic bands for other molecules, we find that spectra should be recorded at a statistically significant number of points per sample to remove the effect of sample rotation. It is crucial that sets of characteristic Raman bands are defined for biomarkers that are targets for future planetary missions to ensure a positive identification can be made.

Defining Multiple Characteristic Raman Bands of α-Amino Acids as Biomarkers for Planetary Missions Using a Statistical Method.

PubMed

Rolfe, S M; Patel, M R; Gilmour, I; Olsson-Francis, K; Ringrose, T J

2016-06-01

Biomarker molecules, such as amino acids, are key to discovering whether life exists elsewhere in the Solar System. Raman spectroscopy, a technique capable of detecting biomarkers, will be on board future planetary missions including the ExoMars rover. Generally, the position of the strongest band in the spectra of amino acids is reported as the identifying band. However, for an unknown sample, it is desirable to define multiple characteristic bands for molecules to avoid any ambiguous identification. To date, there has been no definition of multiple characteristic bands for amino acids of interest to astrobiology. This study examined L-alanine, L-aspartic acid, L-cysteine, L-glutamine and glycine and defined several Raman bands per molecule for reference as characteristic identifiers. Per amino acid, 240 spectra were recorded and compared using established statistical tests including ANOVA. The number of characteristic bands defined were 10, 12, 12, 14 and 19 for L-alanine (strongest intensity band: 832 cm(-1)), L-aspartic acid (938 cm(-1)), L-cysteine (679 cm(-1)), L-glutamine (1090 cm(-1)) and glycine (875 cm(-1)), respectively. The intensity of bands differed by up to six times when several points on the crystal sample were rotated through 360 °; to reduce this effect when defining characteristic bands for other molecules, we find that spectra should be recorded at a statistically significant number of points per sample to remove the effect of sample rotation. It is crucial that sets of characteristic Raman bands are defined for biomarkers that are targets for future planetary missions to ensure a positive identification can be made.

Study on general design of dual-DMD based infrared two-band scene simulation system

NASA Astrophysics Data System (ADS)

Pan, Yue; Qiao, Yang; Xu, Xi-ping

2017-02-01

Mid-wave infrared(MWIR) and long-wave infrared(LWIR) two-band scene simulation system is a kind of testing equipment that used for infrared two-band imaging seeker. Not only it would be qualified for working waveband, but also realize the essence requests that infrared radiation characteristics should correspond to the real scene. Past single-digital micromirror device (DMD) based infrared scene simulation system does not take the huge difference between targets and background radiation into account, and it cannot realize the separated modulation to two-band light beam. Consequently, single-DMD based infrared scene simulation system cannot accurately express the thermal scene model that upper-computer built, and it is not that practical. To solve the problem, we design a dual-DMD based, dual-channel, co-aperture, compact-structure infrared two-band scene simulation system. The operating principle of the system is introduced in detail, and energy transfer process of the hardware-in-the-loop simulation experiment is analyzed as well. Also, it builds the equation about the signal-to-noise ratio of infrared detector in the seeker, directing the system overall design. The general design scheme of system is given, including the creation of infrared scene model, overall control, optical-mechanical structure design and image registration. By analyzing and comparing the past designs, we discuss the arrangement of optical engine framework in the system. According to the main content of working principle and overall design, we summarize each key techniques in the system.

L-Band Microwave Experiment On Russian Investigational Satellite, First Results And Comparison With SMOS Data

NASA Astrophysics Data System (ADS)

Smirnov, M.; Khaldin, A.

2013-12-01

The main scientific objective of mission with Zond-PP on Russian investigational satellite MKA-FKI No1 is development of techniques for retrieval: sea salinity in open oceans, soil moisture in global scales, vegetation state characteristics, sea ice characteristics. At the beginning stage of space experiments the main goals were to develop and test new space microwave radiometric instrument in order to solve technical objectives: investigation of RFI in L-band all over the globe, development and testing in-flight calibration techniques and others. First obtained results of our observations are presented. Zond-PP results were compared with MIRAS. For comparison were used results of brightness temperatures measurements obtained from Zond-PP and MIRAS in the same regions with minimal time difference. Results of comparison show general accordance in the brightness temperatures levels.

SMAP L-Band Microwave Radiometer: Instrument Design and First Year on Orbit

NASA Technical Reports Server (NTRS)

Piepmeier, Jeffrey R.; Focardi, Paolo; Horgan, Kevin; Knuble, Joseph; Ehsan, Negar; Lucey, Jared; Brambora, Clifford; Brown, Paula R.; Hoffman, Pamela J.; French, Richard T.;

Improving Generalization Based on l1-Norm Regularization for EEG-Based Motor Imagery Classification

PubMed Central

Zhao, Yuwei; Han, Jiuqi; Chen, Yushu; Sun, Hongji; Chen, Jiayun; Ke, Ang; Han, Yao; Zhang, Peng; Zhang, Yi; Zhou, Jin; Wang, Changyong

2018-01-01

Multichannel electroencephalography (EEG) is widely used in typical brain-computer interface (BCI) systems. In general, a number of parameters are essential for a EEG classification algorithm due to redundant features involved in EEG signals. However, the generalization of the EEG method is often adversely affected by the model complexity, considerably coherent with its number of undetermined parameters, further leading to heavy overfitting. To decrease the complexity and improve the generalization of EEG method, we present a novel l1-norm-based approach to combine the decision value obtained from each EEG channel directly. By extracting the information from different channels on independent frequency bands (FB) with l1-norm regularization, the method proposed fits the training data with much less parameters compared to common spatial pattern (CSP) methods in order to reduce overfitting. Moreover, an effective and efficient solution to minimize the optimization object is proposed. The experimental results on dataset IVa of BCI competition III and dataset I of BCI competition IV show that, the proposed method contributes to high classification accuracy and increases generalization performance for the classification of MI EEG. As the training set ratio decreases from 80 to 20%, the average classification accuracy on the two datasets changes from 85.86 and 86.13% to 84.81 and 76.59%, respectively. The classification performance and generalization of the proposed method contribute to the practical application of MI based BCI systems. PMID:29867307

Dichroic Filter for Separating W-Band and Ka-Band

NASA Technical Reports Server (NTRS)

Epp, Larry W.; Durden, Stephen L.; Jamnejad, Vahraz; Long, Ezra M.; Sosnowski, John B.; Higuera, Raymond J.; Chen, Jacqueline C.

2012-01-01

The proposed Aerosol/Cloud/Ecosystems (ACEs) mission development would advance cloud profiling radar from that used in CloudSat by adding a 35-GHz (Ka-band) channel to the 94-GHz (W-band) channel used in CloudSat. In order to illuminate a single antenna, and use CloudSat-like quasi-optical transmission lines, a spatial diplexer is needed to add the Ka-band channel. A dichroic filter separates Ka-band from W-band by employing advances in electrical discharge machining (EDM) and mode-matching analysis techniques developed and validated for designing dichroics for the Deep Space Network (DSN), to develop a preliminary design that both met the requirements of frequency separation and mechanical strength. First, a mechanical prototype was built using an approximately 102-micron-diameter EDM process, and tolerances of the hole dimensions, wall thickness, radius, and dichroic filter thickness measured. The prototype validated the manufacturing needed to design a dichroic filter for a higher-frequency usage than previously used in the DSN. The initial design was based on a Ka-band design, but thicker walls are required for mechanical rigidity than one obtains by simply scaling the Ka-band dichroic filter. The resulting trade of hole dimensions for mechanical rigidity (wall thickness) required electrical redesign of the hole dimensions. Updates to existing codes in the linear solver decreased the analysis time using mode-matching, enabling the electrical design to be realized quickly. This work is applicable to missions and instruments that seek to extend W-band cloud profiling measurements to other frequencies. By demonstrating a dichroic filter that passes W-band, but reflects a lower frequency, this opens up the development of instruments that both compare to and enhance CloudSat.

Shear band evolution in zirconium/hafnium-based bulk metallic glasses under static and dynamic indentations

NASA Astrophysics Data System (ADS)

Zhang, Hongwen

In this thesis, a detailed investigation of thermal stability and mechanical deformation behavior of Zr/Hf-based Bulk Metallic Glasses is conducted. First, systematic studies had been implemented to understand the influence of relative compositions of Zr and Hf on thermal stability and mechanical property evolution. Second, shear band evolution under indentations were investigated experimentally and theoretically. It was found in the present work that gradually replacing Zr by Hf remarkably increases the density and improves the mechanical properties. However, a slight decrease in glass forming ability with increasing Hf content has also been identified through thermodynamic analysis although all the materials in the current study were still found to be amorphous. Many indentation studies have revealed only a few shear bands surrounding the indent on the top surface of the specimen. This small number of shear bands cannot account for the large plastic deformation beneath the indentations. Therefore, a bonded interface technique has been used to observe the slip-steps due to shear band evolution. Vickers indentations were performed along the interface of the bonded split specimen at increasing loads. At small indentation loads, the plastic deformation was primarily accommodated by semi-circular primary shear bands surrounding the indentation. At higher loads, secondary and tertiary shear bands were formed inside this plastic zone. A modified expanding cavity model was then used to predict the plastic zone size characterized by the shear bands and to identify the stress components responsible for the evolution of the various types of shear bands. The applicability of various hardness - yield-strength (H-sigma y) relationships currently available in the literature for bulk metallic glasses (BMGs) is also investigated. Experimental data generated on ZrHf-based BMGs in the current study and those available elsewhere on other BMG compositions were used to validate the

Effect of gain contouring in erbium-doped fiber amplifiers on bit error rate performance of wavelength-division multiplexing-based radio over fiber links

NASA Astrophysics Data System (ADS)

Jose, Tony; Narayanan, Vijayakumar

2018-03-01

Radio over fiber (RoF) systems use a large number of base stations (BSs) and a number of central stations (CSs), which are interlinked together to form the network. RoF systems use multiple wavelengths for communication between CSs or between CSs and BSs to facilitate the huge amount of data traffic due to the multiple services for a large number of users. When erbium-doped fiber amplifiers (EDFAs) are used as amplifiers in such wavelength-division multiplexed systems, the nonuniform gain spectrum of EDFAs causes instability to some of the channels while providing faithful amplification to other channels. To avoid this inconsistency, the gain spectrum of the amplifier needs to be uniform along the whole usable range of wavelengths. A gain contouring technique is proposed to provide uniform gain to all channels irrespective of wavelength. Optical add/drop multiplexers (OADMs) and different lengths of erbium-doped fibers are used to create such a gain contouring mechanism in the optical domain itself. The effect of a cascade of nonuniform gain amplifiers is studied, and the proposed system mitigates the adverse effects caused due to nonuniform gain-induced channel instability effectively.

[Study on the early detection of Sclerotinia of Brassica napus based on combinational-stimulated bands].

PubMed

Liu, Fei; Feng, Lei; Lou, Bing-gan; Sun, Guang-ming; Wang, Lian-ping; He, Yong

2010-07-01

The combinational-stimulated bands were used to develop linear and nonlinear calibrations for the early detection of sclerotinia of oilseed rape (Brassica napus L.). Eighty healthy and 100 Sclerotinia leaf samples were scanned, and different preprocessing methods combined with successive projections algorithm (SPA) were applied to develop partial least squares (PLS) discriminant models, multiple linear regression (MLR) and least squares-support vector machine (LS-SVM) models. The results indicated that the optimal full-spectrum PLS model was achieved by direct orthogonal signal correction (DOSC), then De-trending and Raw spectra with correct recognition ratio of 100%, 95.7% and 95.7%, respectively. When using combinational-stimulated bands, the optimal linear models were SPA-MLR (DOSC) and SPA-PLS (DOSC) with correct recognition ratio of 100%. All SPA-LSSVM models using DOSC, De-trending and Raw spectra achieved perfect results with recognition of 100%. The overall results demonstrated that it was feasible to use combinational-stimulated bands for the early detection of Sclerotinia of oilseed rape, and DOSC-SPA was a powerful way for informative wavelength selection. This method supplied a new approach to the early detection and portable monitoring instrument of sclerotinia.

Ultra-low-noise transition edge sensors for the SAFARI L-band on SPICA

NASA Astrophysics Data System (ADS)

Goldie, D. J.; Gao, J. R.; Glowacka, D. M.; Griffin, D. K.; Hijmering, R.; Khosropanah, P.; Jackson, B. D.; Mauskopf, P. D.; Morozov, D.; Murphy, J. A.; Ridder, M.; Trappe, N.; O'Sullivan, C.; Withington, S.

2012-09-01

The Far-Infrared Fourier transform spectrometer instrument SAFARI-SPICA which will operate with cooled optics in a low-background space environment requires ultra-sensitive detector arrays with high optical coupling efficiencies over extremely wide bandwidths. In earlier papers we described the design, fabrication and performance of ultra-low-noise Transition Edge Sensors (TESs) operated close to 100mk having dark Noise Equivalent Powers (NEPs) of order 4 × 10-19W/√Hz close to the phonon noise limit and an improvement of two orders of magnitude over TESs for ground-based applications. Here we describe the design, fabrication and testing of 388-element arrays of MoAu TESs integrated with far-infrared absorbers and optical coupling structures in a geometry appropriate for the SAFARI L-band (110 - 210 μm). The measured performance shows intrinsic response time τ ~ 11ms and saturation powers of order 10 fW, and a dark noise equivalent powers of order 7 × 10-19W/√Hz. The 100 × 100μm2 MoAu TESs have transition temperatures of order 110mK and are coupled to 320×320μm2 thin-film β-phase Ta absorbers to provide impedance matching to the incoming fields. We describe results of dark tests (i.e without optical power) to determine intrinsic pixel characteristics and their uniformity, and measurements of the optical performance of representative pixels operated with flat back-shorts coupled to pyramidal horn arrays. The measured and modeled optical efficiency is dominated by the 95Ω sheet resistance of the Ta absorbers, indicating a clear route to achieve the required performance in these ultra-sensitive detectors.

Based on graphene tunable dual-band terahertz metamaterial absorber with wide-angle

NASA Astrophysics Data System (ADS)

Huang, Mulin; Cheng, Yongzhi; Cheng, Zhengze; Chen, Haoran; Mao, Xuesong; Gong, Rongzhou

2018-05-01

We present a wide-angle tunable dual-band terahertz (THz) metamaterial absorber (MMA) based on square graphene patch (SGP). This MMA is a simple periodic array, consisting of a dielectric substrate sandwiched with the SGP and a continuous metallic film. The designed MMA can achieve dual-band absorption by exciting fundamental and second higher-order resonance modes on SGP. The numerical simulations indicate that the absorption spectrum of the designed MMA is tuned from 0.85 THz to 1.01 THz, and from 2.84 THz to 3.37 THz when the chemical potential of the SGP is increasing from 0.4eV to 0.8eV. Moreover, it operates well in a wide-angle of the incident waves. The presented THz MMA based on the SGP could find some potential applications in optoelectronic related devices, such as sensor, emitter and wavelength selective radiators.

Relative stability of tension band versus two-cortex screw fixation for treating fifth metatarsal base avulsion fractures.

PubMed

Husain, Z S; DeFronzo, D J

2000-01-01

This study assesses the strength of fixating avulsion fractures of the fifth metatarsal base with a 4.0-mm partially threaded cancellous screw crossing two cortices as compared to tension banding. Our data showed statistically significant fixation strength improvement over tension banding for avulsion fractures (p < 0.02) in both polystyrene foam models and fresh, nonpreserved frozen cadaveric samples. In cadavers, the screw fixations were able to withstand more than three times the load sustained by the tension band fixations. The study utilized the Instron 8500 tensiometer to apply physiologic loads to test the constructs until failure. The displacement and load data at failure show the limitations of both fixations. By increasing the load resistance while maintaining compression, the bicortical cancellous screw fixation created greater stability at the avulsion fracture of the fifth metatarsal base as compared to tension band stabilization.

Ku- and Ka-Band Phased Array Antenna for the Space-Based Telemetry and Range Safety Project

NASA Technical Reports Server (NTRS)

Whiteman, Donald E.; Valencia, Lisa M.; Birr, Richard B.

2005-01-01

The National Aeronautics and Space Administration Space-Based Telemetry and Range Safety study is a multiphase project to increase data rates and flexibility and decrease costs by using space-based communications assets for telemetry during launches and landings. Phase 1 used standard S-band antennas with the Tracking and Data Relay Satellite System to obtain a baseline performance. The selection process and available resources for Phase 2 resulted in a Ku-band phased array antenna system. Several development efforts are under way for a Ka-band phased array antenna system for Phase 3. Each phase includes test flights to demonstrate performance and capabilities. Successful completion of this project will result in a set of communications requirements for the next generation of launch vehicles.

Effective Tree Scattering at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; ONeill, Peggy E.; Lang, Roger H.; Joseph, Alicia T.; Cosh, Michael H.; Jackson, Thomas J.

2011-01-01

For routine microwave Soil Moisture (SM) retrieval through vegetation, the tau-omega [1] model [zero-order Radiative Transfer (RT) solution] is attractive due to its simplicity and eases of inversion and implementation. It is the model used in baseline retrieval algorithms for several planned microwave space missions, such as ESA's Soil Moisture Ocean Salinity (SMOS) mission (launched November 2009) and NASA's Soil Moisture Active Passive (SMAP) mission (to be launched 2014/2015) [2 and 3]. These approaches are adapted for vegetated landscapes with effective vegetation parameters tau and omega by fitting experimental data or simulation outputs of a multiple scattering model [4-7]. The model has been validated over grasslands, agricultural crops, and generally light to moderate vegetation. As the density of vegetation increases, sensitivity to the underlying SM begins to degrade significantly and errors in the retrieved SM increase accordingly. The zero-order model also loses its validity when dense vegetation (i.e. forest, mature corn, etc.) includes scatterers, such as branches and trunks (or stalks in the case of corn), which are large with respect to the wavelength. The tau-omega model (when applied over moderately to densely vegetated landscapes) will need modification (in terms of form or effective parameterization) to enable accurate characterization of vegetation parameters with respect to specific tree types, anisotropic canopy structure, presence of leaves and/or understory. More scattering terms (at least up to first-order at L-band) should be included in the RT solutions for forest canopies [8]. Although not really suitable to forests, a zero-order tau-omega model might be applied to such vegetation canopies with large scatterers, but that equivalent or effective parameters would have to be used [4]. This requires that the effective values (vegetation opacity and single scattering albedo) need to be evaluated (compared) with theoretical definitions of

Effect of conduction band non-parabolicity on the optical gain of quantum cascade lasers based on the effective two-band finite difference method

NASA Astrophysics Data System (ADS)

Cho, Gookbin; Kim, Jungho

2017-09-01

We theoretically investigate the effect of conduction band non-parabolicity (NPB) on the optical gain spectrum of quantum cascade lasers (QCLs) using the effective two-band finite difference method. Based on the effective two-band model to consider the NPB effect in the multiple quantum wells (QWs), the wave functions and confined energies of electron states are calculated in two different active-region structures, which correspond to three-QW single-phonon and four-QW double-phonon resonance designs. In addition, intersubband optical dipole moments and polar-optical-phonon scattering times are calculated and compared without and with the conduction band NPB effect. Finally, the calculation results of optical gain spectra are compared in the two QCL structures having the same peak gain wavelength of 8.55 μm. The gain peaks are greatly shifted to longer wavelengths and the overall gain magnitudes are slightly reduced when the NPB effect is considered. Compared with the three-QW active-region design, the redshift of the peak gain is more prominent in the four-QW active-region design, which makes use of higher electronic states for the lasing transition.

Optimizing spatial patterns with sparse filter bands for motor-imagery based brain-computer interface.

PubMed

Zhang, Yu; Zhou, Guoxu; Jin, Jing; Wang, Xingyu; Cichocki, Andrzej

2015-11-30

Common spatial pattern (CSP) has been most popularly applied to motor-imagery (MI) feature extraction for classification in brain-computer interface (BCI) application. Successful application of CSP depends on the filter band selection to a large degree. However, the most proper band is typically subject-specific and can hardly be determined manually. This study proposes a sparse filter band common spatial pattern (SFBCSP) for optimizing the spatial patterns. SFBCSP estimates CSP features on multiple signals that are filtered from raw EEG data at a set of overlapping bands. The filter bands that result in significant CSP features are then selected in a supervised way by exploiting sparse regression. A support vector machine (SVM) is implemented on the selected features for MI classification. Two public EEG datasets (BCI Competition III dataset IVa and BCI Competition IV IIb) are used to validate the proposed SFBCSP method. Experimental results demonstrate that SFBCSP help improve the classification performance of MI. The optimized spatial patterns by SFBCSP give overall better MI classification accuracy in comparison with several competing methods. The proposed SFBCSP is a potential method for improving the performance of MI-based BCI. Copyright © 2015 Elsevier B.V. All rights reserved.

A compact D-band monolithic APDP-based sub-harmonic mixer

NASA Astrophysics Data System (ADS)

Zhang, Shengzhou; Sun, Lingling; Wang, Xiang; Wen, Jincai; Liu, Jun

2017-11-01

The paper presents a compact D-band monolithic sub-harmonic mixer (SHM) with 3 μm planar hyperabrupt schottky-varactor diodes offered by 70 nm GaAs mHEMT technology. According to empirical equivalent-circuit models, a wide-band large signal equivalent circuit model of the diode is proposed. Based on the extracted model, the mixer is implemented and optimized with a shunt-mounted anti-parallel diode pair (APDP) to fulfill the sub-harmonic mixing mechanism. Furthermore, a modified asymmetric three-transmission-line coupler is devised to achieve high-level coupling and minimize the chip size. The measured results show that the conversion gain varies between -13.9 dB and -17.5 dB from 110 GHz to 145 GHz, with a local oscillator (LO) power level of 14 dBm and an intermediate frequency (IF) of 1 GHz. The total chip size including probe GSG pads is 0.57 × 0.68mm2. In conclusion, the mixer exhibits outstanding figure-of-merits.

Optical Tunable-Based Transmitter for Multiple Radio Frequency Bands

NASA Technical Reports Server (NTRS)

Nguyen, Hung (Inventor); Simons, Rainee N. (Inventor); Wintucky, Edwin G. (Inventor); Freeman, Jon C. (Inventor)

2016-01-01

An optical tunable transmitter is used to transmit multiple radio frequency bands on a single beam. More specifically, a tunable laser is configured to generate a plurality of optical wavelengths, and an optical tunable transmitter is configured to modulate each of the plurality of optical wavelengths with a corresponding radio frequency band. The optical tunable transmitter is also configured to encode each of the plurality of modulated optical wavelengths onto a single laser beam for transmission of a plurality of radio frequency bands using the single laser beam.

Ground-based testing of the dynamics of flexible space structures using band mechanisms

NASA Technical Reports Server (NTRS)

Yang, L. F.; Chew, Meng-Sang

1991-01-01

A suspension system based on a band mechanism is studied to provide the free-free conditions for ground based validation testing of flexible space structures. The band mechanism consists of a noncircular disk with a convex profile, preloaded by torsional springs at its center of rotation so that static equilibrium of the test structure is maintained at any vertical location; the gravitational force will be directly counteracted during dynamic testing of the space structure. This noncircular disk within the suspension system can be configured to remain unchanged for test articles with the different weights as long as the torsional spring is replaced to maintain the originally designed frequency ratio of W/k sub s. Simulations of test articles which are modeled as lumped parameter as well as continuous parameter systems, are also presented.

A first generation cytogenetic ideogram for the Florida manatee (Trichechus manatus latirostris) based on multiple chromosome banding techniques

USGS Publications Warehouse

Gray, B.A.; Zori, Roberto T.; McGuire, P.M.; Bonde, R.K.

2002-01-01

Detailed chromosome studies were conducted for the Florida manatee (Trichechus manatus latirostris) utilizing primary chromosome banding techniques (G- and Q-banding). Digital microscopic imaging methods were employed and a standard G-banded karyotype was constructed for both sexes. Based on chromosome banding patterns and measurements obtained in these studies, a standard karyotype and ideogram are proposed. Characterization of additional cytogenetic features of this species by supplemental chromosome banding techniques, C-banding (constitutive heterochromatin), Ag-NOR staining (nucleolar organizer regions), and DA/DAPI staining, was also performed. These studies provide detailed cytogenetic data for T. manatus latirostris, which could enhance future genetic mapping projects and interspecific and intraspecific genomic comparisons by techniques such as zoo-FISH.

Surface soil moisture retrieval using the L-band synthetic aperture radar onboard the Soil Moisture Active Passive satellite and evaluation at core validation sites

USDA-ARS?s Scientific Manuscript database

This paper evaluates the retrieval of soil moisture in the top 5-cm layer at 3-km spatial resolution using L-band dual-copolarized Soil Moisture Active Passive (SMAP) synthetic aperture radar (SAR) data that mapped the globe every three days from mid-April to early July, 2015. Surface soil moisture ...

Measurement accuracies in band-limited extrapolation

NASA Technical Reports Server (NTRS)

Kritikos, H. N.

1982-01-01

The problem of numerical instability associated with extrapolation algorithms is addressed. An attempt is made to estimate the bounds for the acceptable errors and to place a ceiling on the measurement accuracy and computational accuracy needed for the extrapolation. It is shown that in band limited (or visible angle limited) extrapolation the larger effective aperture L' that can be realized from a finite aperture L by over sampling is a function of the accuracy of measurements. It is shown that for sampling in the interval L/b absolute value of xL, b1 the signal must be known within an error e sub N given by e sub N squared approximately = 1/4(2kL') cubed (e/8b L/L')(2kL') where L is the physical aperture, L' is the extrapolated aperture, and k = 2pi lambda.

L Band Brightness Temperature Observations over a Corn Canopy during the Entire Growth Cycle

PubMed Central

Joseph, Alicia T.; van der Velde, Rogier; O’Neill, Peggy E.; Choudhury, Bhaskar J.; Lang, Roger H.; Kim, Edward J.; Gish, Timothy

2010-01-01

During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (TB) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive characterization of land surface variables including soil moisture, soil temperature, vegetation biomass, and surface roughness. In the period May 22 to August 30, ten days of radiometer and ground measurements are available for a corn canopy with a vegetation water content (W) range of 0.0 to 4.3 kg m−2. Using this data set, the effects of corn vegetation on surface emissions are investigated by means of a semi-empirical radiative transfer model. Additionally, the impact of roughness on the surface emission is quantified using TB measurements over bare soil conditions. Subsequently, the estimated roughness parameters, ground measurements and horizontally (H)-polarized TB are employed to invert the H-polarized transmissivity (γh) for the monitored corn growing season. PMID:22163585

Ground-Based Radiometric Measurements of Slant Path Attenuation in the V/W Bands

DTIC Science & Technology

2016-04-01

GROUND-BASED RADIOMETRIC MEASUREMENTS OF SLANT PATH ATTENUATION IN THE V/W BANDS APRIL 2016 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE...2. REPORT TYPE FINAL TECHNICAL REPORT 3. DATES COVERED (From - To) OCT 2012 – SEP 2015 4. TITLE AND SUBTITLE GROUND-BASED RADIOMETRIC MEASUREMENTS ...SUPPLEMENTARY NOTES 14. ABSTRACT Ground-based radiometric techniques were applied to measure the slant path attenuation cumulative distribution function to

Band gaps and photocurrent responses of two novel alkaline earth metal(II) complexes based on 4,5-di(4‧-carboxylphenyl)benzene

NASA Astrophysics Data System (ADS)

Meng, Jiang Ping; Yan, Zhi Shuo; Long, Ji Ying; Gong, Yun; Lin, Jian Hua

2017-01-01

By using a rigid dicarboxylate ligand, 4,5-di(4‧-carboxylphenyl)benzene (H2L), two complexes formulated as SrL(DMF)(H2O)·(CH3CN) (DMF=N,N‧-dimethylformamide) (1) and BaL(H2O)2 (2) were solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 display two-dimensional (2D) layer structures. The two complexes exhibit different electrochemical and photoelectrochemical properties. Their thermal stabilities, cyclic voltammograms, UV-vis absorption and diffuse reflectance spectra and photoluminescence properties have been investigated. The band structures, the total density of states (TDOS) and partial density of states (PDOS) of the two complexes were calculated by CASTEP program. Complex 2 exhibits much higher photocurrent density than complex 1. The Mott-Schottky plots reveal that complexes 1 and 2 both are p-type semiconductors, which are in agreement with their band structure calculations.

Fractal Based Triple Band High Gain Monopole Antenna

NASA Astrophysics Data System (ADS)

Pandey, Shashi Kant; Pandey, Ganga Prasad; Sarun, P. M.

2017-10-01

A novel triple-band microstrip fed planar monopole antenna is proposed and investigated. A fractal antenna is created by iterating a narrow pulse (NP) generator model at upper side of modified ground plane, which has a rhombic patch, for enhancing the bandwidth and gain. Three iterations are carried out to study the effects of fractal geometry on the antenna performance. The proposed antenna can operate over three frequency ranges viz, 3.34-4.8 GHz, 5.5-10.6 GHz and 13-14.96 GHz suitable for WLAN 5.2/5.8 GHz, WiMAX 3.5/5.5 GHz and X band applications respectively. Simulated and measured results are in good agreements with each others. Results show that antenna provides wide/ultra wide bandwidths, monopole like radiation patterns and very high antenna gains over the operating frequency bands.

High-resolution mapping of wetland vegetation biomass and distribution with L-band radar in southeastern coastal Louisiana

NASA Astrophysics Data System (ADS)

Thomas, N. M.; Simard, M.; Byrd, K. B.; Windham-Myers, L.; Castaneda, E.; Twilley, R.; Bevington, A. E.; Christensen, A.

2017-12-01

Louisiana coastal wetlands account for approximately one third (37%) of the estuarine wetland vegetation in the conterminous United States, yet the spatial distribution of their extent and aboveground biomass (AGB) is not well defined. This knowledge is critical for the accurate completion of national greenhouse gas (GHG) inventories. We generated high-resolution baselines maps of wetland vegetation extent and biomass at the Atchafalaya and Terrebonne basins in coastal Louisiana using a multi-sensor approach. Optical satellite data was used within an object-oriented machine learning approach to classify the structure of wetland vegetation types, offering increased detail over currently available land cover maps that do not distinguish between wetland vegetation types nor account for non-permanent seasonal changes in extent. We mapped 1871 km2 of wetlands during a period of peak biomass in September 2015 comprised of flooded forested wetlands and leaf, grass and emergent herbaceous marshes. The distribution of aboveground biomass (AGB) was mapped using JPL L-band Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). Relationships between time-series radar imagery and field data collected in May 2015 and September 2016 were derived to estimate AGB at the Wax Lake and Atchafalaya deltas. Differences in seasonal biomass estimates reflect the increased AGB in September over May, concurrent with periods of peak biomass and the onset of the vegetation growing season, respectively. This method provides a tractable means of mapping and monitoring biomass of wetland vegetation types with L-band radar, in a region threatened with wetland loss under projections of increasing sea-level rise and terrestrial subsidence. Through this, we demonstrate a method that is able to satisfy the IPCC 2013 Wetlands Supplement requirement for Tier 2/Tier 3 reporting of coastal wetland GHG inventories.

Analysis of L-band radiometric data over the Mediterranean Sea from the SMOS Validation Rehearsal campaign

NASA Astrophysics Data System (ADS)

Gabarro, C.; Talone, M.; Font, J.

2009-04-01

L-band radiometric data obtained with a real aperture airborne radiometer during SMOS validation Rehearsal campaign (April-May 2008) over the NW Mediterranean Sea have been analysed. EMIRAD, a fully polarimetric radiometer developed by the Technical University of Denmark operating in the 1400 - 1427 MHz band, was mounted on board a Skyvan aircraft from the Helsinki University of Technology. Two antennas were used: one facing nadir with 37.6° full aperture at half-power; and one placed towards the rear of the aircraft at 40° zenith angle with 30.6° full aperture at half-power. Two transit flights over the sea from Marseille to Valencia (19 April 2008) and from Valencia to Marseille (3 May 2008) have been studied. Two meteorological and oceanographic buoys were moored 40 Km offshore in front of Tarragona and were overflown during these transits. Additionally, information on sea surface temperature (SST) and sea surface salinity (SSS) was obtained from operational model outputs (Mediterranean Forecasting System - Mediterranean Operational Oceanography Network) and wind speed from QuikSCAT. Measured brightness temperatures (Tb) have been compared with modelled Tb, using a semi-empirical emissivity model: Klein and Swift model is used to define the dielectric constant and Hollinger model for the rough sea emissivity contribution. Comparisons show that in general measured Tb variability fits with modelled variability, although a bias is observed in the aft V channel.

A numerical study of multiple adiabatic shear bands evolution in a 304LSS thick-walled cylinder

NASA Astrophysics Data System (ADS)

Liu, Mingtao; Hu, Haibo; Fan, Cheng; Tang, Tiegang

2017-01-01

The self-organization of multiple shear bands in a 304L stainless steel(304LSS) thick-walled cylinder (TWC) was numerically studied. The microstructures of material lead to the non-uniform distribution of the local yield stress, which play a key role in the formation of spontaneous shear localization. We introduced a probability factor satisfied the Gaussian distribution into the macroscopic constitutive relationship to describe the non-uniformity of local yield stress. Using the probability factor, the initiation and propagation of multiple shear bands in TWC were numerically replicated in our 2D FEM simulation. Experimental results in the literature indicated that the machined surface at the internal boundary of a 304L stainless steel cylinder provides a work-hardened layer (about 20˜30μm) which has significantly different microstructures from the base material. The work-hardened layer leads to the phenomenon that most shear bands propagate along a given direction, clockwise or counterclockwise. In our simulation, periodical single direction spiral perturbations were applied to describe the grain orientation in the work-hardened layer, and the single direction spiral pattern of shear bands was successfully replicated.

High-perveance W-band Sheet-beam Electron Gun Design

DTIC Science & Technology

2008-04-01

APR 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00-2008 4. TITLE AND SUBTITLE High -perveance W- band Sheet-beam Electron Gun Design 5a...8-98) Prescribed by ANSI Std Z39-18 10.1: High -perveance W- band Sheet-beam Electron Gun Design Khanh T. Nguyen1, John Pasour, Edward L. Wright1...effects due to cathode temperature are also included in the simulation. Keywords: Sheet beam; W- band ; electron gun; high perveance; amplifiers

The Role of Thermodynamic Processes in the Evolution of Single and Multi-banding within Winter Storms

NASA Astrophysics Data System (ADS)

Ganetis, Sara Anne

Mesoscale precipitation bands within Northeast U.S. (NEUS) winter storms result in heterogeneous spatial and temporal snowfall. Several studies have provided analysis of snowbands focusing on larger, meso-beta scale bands with lengths (L) > 200 km known as single bands. NEUS winter storms can also exhibit multiple bands with meso-beta scale (L < 200 km) and similar spatial orientation and when ≥ 3 occur are termed multi-bands; however, the genesis and evolution of multi-bands is less well understood. Unlike single bands, there is no multi-bands climatological study. In addition, there has been little detailed thermodynamic analysis of snowbands. This dissertation utilizes radar observations, reanalyses, and high-resolution model simulations to explore the thermodynamic evolution of single and multi-bands. Bands are identified within 20 cool season (October-April) NEUS storms. The 110-case dataset was classified using a combination of automated and manual methods into: single band only (SINGLE), multi-bands only (MULTI), both single and multi-bands (BOTH), and non-banded (NONE). Multi-bands occur with the presence of a single band in 55.4% of times used in this study, without the presence of a single band 18.1% of the time, and precipitation exhibits no banded characteristics 23.8% of the time. Most MULTI events occur in the northeast quadrant of a developing cyclone poleward of weak-midlevel forcing along a warm front, whereas multi-bands associated with BOTH events mostly occur in the northwest quadrant of mature cyclones associated with strong mid-level frontogenesis and conditional symmetric instability. The non-banded precipitation associated with NONE events occur in the eastern quadrants of developing and mature cyclones lacking mid-level forcing to concentrate the precipitation into bands. A high-resolution mesoscale model is used to explore the evolution of single and multi-bands based on two case studies, one of a single band and one of multi-bands. The

[On-orbit response variation analysis of FY-3 MERSI reflective solar bands based on Dunhuang site calibration].

PubMed

Sun, Ling; Guo, Mao-Hua; Xu, Na; Zhang, Li-Jun; Liu, Jing-Jing; Hu, Xiu-Qing; Li, Yuan; Rong, Zhi-Guo; Zhao, Ze-Hui

2012-07-01

MERSI is the keystone payload of FengYun-3 and there have been two sensors operating on-orbit since 2008. The on-orbit response changes obviously at reflective solar bands (RSBs) and must be effectively monitored and corrected. However MERSI can not realize the RSBs onboard absolute radiometric calibration. This paper presents a new vicarious calibration (VC) method for RSBs based on in-situ BRDF model, and vector radiometric transfer model 6SV with gaseous absorption correction using MOTRAN. The results of synchronous VC experiments in 4 years show that the calibration uncertainties are within 5% except for band at the center of water vapor absorption, and 3% for most bands. Aqua MODIS was taken as the radiometric reference to evaluate the accuracy of this VC method. By comparison of the simulated radiation at top of atmosphere (TOA) with MODIS measurement, it was revealed that the average relative differences are within 3% for window bands with wavelengths less than 1 microm, and 5% for bands with wavelengths larger than 1 microm (except for band 7 at 2.1 microm). Besides, the synchronous nadir observation cross analysis shows the excellent agreement between re-calibrated MERSI TOA apparent reflectance and MODIS measurements. Based on the multi-year site calibration results, it was found that the calibration coefficients could be fitted with two-order polynomials, thus the daily calibration updates could be realized and the response variation between two calibration experiments could be corrected timely; there are large response changes at bands with wavelengths less than 0.6 microm, the degradation rate of the first year at band 8 (0.41 microm) is about 14%; the on-orbit response degradation is maximum at the beginning, the degradation rates slow down after one year in operation, and after two years the responses even increase at some band with wavelengths larger than 0.6 microm.

Quantum Illumination-Based Target Detection and Discrimination

DTIC Science & Technology

2014-06-30

amplifier (EDFA) was combined with the signal to simulate a high-noise environment, with a noise photon number per mode NB in the range 40–300. The...Research Triangle Park, NC 27709-2211 quantum communication, target detection, entanglement , parametric downconversion, optical parametric amplifiers...laser system of the same average transmitted photon number, when the target return has random-amplitude behavior. Receiver operating characteristic

Terra MODIS Band 27 Electronic Crosstalk Effect and Its Removal

NASA Technical Reports Server (NTRS)

Sun, Junqiang; Xiong, Xiaoxiong; Madhavan, Sriharsha; Wenny, Brian

2012-01-01

The MODerate-resolution Imaging Spectroradiometer (MODIS) is one of the primary instruments in the NASA Earth Observing System (EOS). The first MODIS instrument was launched in December, 1999 on-board the Terra spacecraft. MODIS has 36 bands, covering a wavelength range from 0.4 micron to 14.4 micron. MODIS band 27 (6.72 micron) is a water vapor band, which is designed to be insensitive to Earth surface features. In recent Earth View (EV) images of Terra band 27, surface feature contamination is clearly seen and striping has become very pronounced. In this paper, it is shown that band 27 is impacted by electronic crosstalk from bands 28-30. An algorithm using a linear approximation is developed to correct the crosstalk effect. The crosstalk coefficients are derived from Terra MODIS lunar observations. They show that the crosstalk is strongly detector dependent and the crosstalk pattern has changed dramatically since launch. The crosstalk contributions are positive to the instrument response of band 27 early in the mission but became negative and much larger in magnitude at later stages of the mission for most detectors of the band. The algorithm is applied to both Black Body (BB) calibration and MODIS L1B products. With the crosstalk effect removed, the calibration coefficients of Terra MODIS band 27 derived from the BB show that the detector differences become smaller. With the algorithm applied to MODIS L1B products, the Earth surface features are significantly removed and the striping is substantially reduced in the images of the band. The approach developed in this report for removal of the electronic crosstalk effect can be applied to other MODIS bands if similar crosstalk behaviors occur.

Modeling direct band-to-band tunneling: From bulk to quantum-confined semiconductor devices

NASA Astrophysics Data System (ADS)

Carrillo-Nuñez, H.; Ziegler, A.; Luisier, M.; Schenk, A.

2015-06-01

A rigorous framework to study direct band-to-band tunneling (BTBT) in homo- and hetero-junction semiconductor nanodevices is introduced. An interaction Hamiltonian coupling conduction and valence bands (CVBs) is derived using a multiband envelope method. A general form of the BTBT probability is then obtained from the linear response to the "CVBs interaction" that drives the system out of equilibrium. Simple expressions in terms of the one-electron spectral function are developed to compute the BTBT current in two- and three-dimensional semiconductor structures. Additionally, a two-band envelope equation based on the Flietner model of imaginary dispersion is proposed for the same purpose. In order to characterize their accuracy and differences, both approaches are compared with full-band, atomistic quantum transport simulations of Ge, InAs, and InAs-Si Esaki diodes. As another numerical application, the BTBT current in InAs-Si nanowire tunnel field-effect transistors is computed. It is found that both approaches agree with high accuracy. The first one is considerably easier to conceive and could be implemented straightforwardly in existing quantum transport tools based on the effective mass approximation to account for BTBT in nanodevices.

Generation of EMIC Waves Observed by Van Allen Probes at Low L-shells of Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Gamayunov, K. V.; Zhang, J.; Saikin, A.; Rassoul, H.

2017-12-01

In a multi-ion magnetospheric plasma, where the major species are H+, He+, and O+, the He-band of electromagnetic ion cyclotron (EMIC) waves is the dominant band observed in the inner magnetosphere, and waves are generally quasi-field-aligned inside the geostationary orbit. Almost all the satellite-based studies of EMIC waves before Van Allen Probes, however, have not reported waves below L 3.5. There is probably only one exception from the Akebono satellite where both the H-band and He-band EMIC waves were observed at L 2. The situation has changed dramatically after two Van Allen Probes spacecraft were launched on 30 August, 2012, and many EMIC wave events have been observed below L=4. The Van Allen Probes observations confirm that the He-band of EMIC waves is a dominant band in the inner magnetosphere, but the observation of the He-band waves below L=4 is a new and quite unexpected result compared to our knowledge about EMIC waves before the Van Allen Probes era. In addition, observations show that almost all the He-band EMIC waves are linearly polarized in the region L < 4. This result is also new and unexpected. Here we will present an observational test of the generation mechanism for the He-band EMIC waves observed by Van Allen Probes at L 2.8 on 18 March, 2013. All the plasma parameters, DC magnetic field, and energetic ion distribution functions will be taken from the Van Allen Probes observations during the EMIC wave event to calculate growth rates of EMIC waves. We will then identify the energetic ions responsible for instability, frequencies and normals generated, and physical mechanism of instability.

Lineage II (Serovar 1/2a and 1/2c) Human Listeria monocytogenes Pulsed-Field Gel Electrophoresis Types Divided into PFGE Groups Using the Band Patterns Below 145.5 kb.

PubMed

Lopez-Valladares, Gloria; Danielsson-Tham, Marie-Louise; Goering, Richard V; Tham, Wilhelm

2017-01-01

Among 504 clinical lineage II isolates of Listeria monocytogenes isolated during 1958-2010 in Sweden, 119 pulsed-field gel electrophoresis (PFGE) types (AscI) have been identified based on the number and distribution of all banding patterns in each DNA profile. In this study, these types were further divided into PFGE groups based on the configuration of small bands with sizes <145.5 kb. The 504 isolates included 483 serovar 1/2a isolates distributed into 114 PFGE types and 21 serovar 1/2c isolates distributed into 9 PFGE types; these were further divided into 21 PFGE groups. PFGE group, that is, configuration of small bands below 145.5 kb, and serovars were correlated. L. monocytogenes isolates belonging to PFGE groups A, B, C, E, F, H, K, L, M, S, V, W, Y, and Ö-6 to Ö-12 shared serovar 1/2a, with one exception. PFGE group E also included two PFGE types sharing serovar 1/2c and four PFGE types belonging to either serovar 1/2a or 1/2c. Isolates belonging to PFGE group N shared serovar 1/2c. In contrast to lineage I isolates, small fragments <33.3 kb were visible in all L. monocytogenes isolates belonging to lineage II. In the results from both the present and previous studies, the genomic region of small bands was genetically more conservative than in large bands. The distribution of these small bands established the relatedness of strains and defined a genetic marker for both lineages I and II, while also establishing their serogroup. The division of L. monocytogenes PFGE types into PFGE groups is advantageous as the profile of every new isolate can be identified easily and quickly through first studying the PFGE group affiliation of the isolate based on the smaller band patterns <145.5 kb, and then identifying the PFGE type based on the band patterns >145.5 kb.

Forest biomass, canopy structure, and species composition relationships with multipolarization L-band synthetic aperture radar data

NASA Technical Reports Server (NTRS)

Sader, Steven A.

1987-01-01

The effect of forest biomass, canopy structure, and species composition on L-band synthetic aperature radar data at 44 southern Mississippi bottomland hardwood and pine-hardwood forest sites was investigated. Cross-polarization mean digital values for pine forests were significantly correlated with green weight biomass and stand structure. Multiple linear regression with five forest structure variables provided a better integrated measure of canopy roughness and produced highly significant correlation coefficients for hardwood forests using HV/VV ratio only. Differences in biomass levels and canopy structure, including branching patterns and vertical canopy stratification, were important sources of volume scatter affecting multipolarization radar data. Standardized correction techniques and calibration of aircraft data, in addition to development of canopy models, are recommended for future investigations of forest biomass and structure using synthetic aperture radar.

Hyper-spectral image compression algorithm based on mixing transform of wave band grouping to eliminate redundancy

NASA Astrophysics Data System (ADS)

Xie, ChengJun; Xu, Lin

2008-03-01

This paper presents an algorithm based on mixing transform of wave band grouping to eliminate spectral redundancy, the algorithm adapts to the relativity difference between different frequency spectrum images, and still it works well when the band number is not the power of 2. Using non-boundary extension CDF(2,2)DWT and subtraction mixing transform to eliminate spectral redundancy, employing CDF(2,2)DWT to eliminate spatial redundancy and SPIHT+CABAC for compression coding, the experiment shows that a satisfied lossless compression result can be achieved. Using hyper-spectral image Canal of American JPL laboratory as the data set for lossless compression test, when the band number is not the power of 2, lossless compression result of this compression algorithm is much better than the results acquired by JPEG-LS, WinZip, ARJ, DPCM, the research achievements of a research team of Chinese Academy of Sciences, Minimum Spanning Tree and Near Minimum Spanning Tree, on the average the compression ratio of this algorithm exceeds the above algorithms by 41%,37%,35%,29%,16%,10%,8% respectively; when the band number is the power of 2, for 128 frames of the image Canal, taking 8, 16 and 32 respectively as the number of one group for groupings based on different numbers, considering factors like compression storage complexity, the type of wave band and the compression effect, we suggest using 8 as the number of bands included in one group to achieve a better compression effect. The algorithm of this paper has priority in operation speed and hardware realization convenience.

Enhanced optical gain clamping for upstream packet based traffic on hybrid WDM/TDM-PON using fiber Bragg grating

NASA Astrophysics Data System (ADS)

Neto, B.; Klingler, A.; Reis, C.; Dionísio, R. P.; Nogueira, R. N.; Teixeira, A. L. J.; André, P. S.

2011-03-01

In this paper, we propose a method to mitigate the temporal power transients arising from Erbium doped fiber amplifiers (EDFAs) on packeted/bursty scenario. The technique, applicable on hybrid WDM/TDM-PON for extended reach, is based on a low power clamping provided by a distributed feedback (DFB) laser and a fiber Bragg grating (FBG). An improvement in the data signal Q factor was achieved keeping the clamping control signal with a low power, accompanied by a maximum reduction in the gain excursion of 1.12 dB.

z'-BAND GROUND-BASED DETECTION OF THE SECONDARY ECLIPSE OF WASP-19b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burton, J. R.; Watson, C. A.; Pollacco, D.

2012-08-01

We present the ground-based detection of the secondary eclipse of the transiting exoplanet WASP-19b. The observations were made in the Sloan z' band using the ULTRACAM triple-beam CCD camera mounted on the New Technology Telescope. The measurement shows a 0.088% {+-} 0.019% eclipse depth, matching previous predictions based on H- and K-band measurements. We discuss in detail our approach to the removal of errors arising due to systematics in the data set, in addition to fitting a model transit to our data. This fit returns an eclipse center, T{sub 0}, of 2455578.7676 HJD, consistent with a circular orbit. Our measurementmore » of the secondary eclipse depth is also compared to model atmospheres of WASP-19b and is found to be consistent with previous measurements at longer wavelengths for the model atmospheres we investigated.« less

Broadband Upgrade for the 1.668-GHz (L-Band) Radio Astronomy Feed System on the DSN 70-m Antennas

NASA Astrophysics Data System (ADS)

Hoppe, D.; Khayatian, B.; Lopez, B.; Torrez, T.; Long, E.; Sosnowski, J.; Franco, M.; Teitelbaum, L.

2015-08-01

Currently, each of the three Deep Space Network (DSN) 70-m antennas provides a narrowband, 1.668-GHz (L-band) receive capability for radio astronomy observations. This capability is delivered by a large feedhorn mounted on the exterior of one of the feedcones. It provides a single polarization into a pair of redundant low-noise amplifiers. Recently, funding was obtained to upgrade this system to wideband (1.4-1.9 GHz) dual-polarization operation. This required development of a new feedhorn, polarizer, orthomode transducer (OMT), and waveguide transitions. In this article, we describe the design and laboratory testing of these components.

The electronic band structure of Ge1-x Sn x in the full composition range: indirect, direct, and inverted gaps regimes, band offsets, and the Burstein-Moss effect

NASA Astrophysics Data System (ADS)

Polak, M. P.; Scharoch, P.; Kudrawiec, R.

2017-05-01

A comprehensive and detailed study of the composition dependence of lattice constants, band gaps and band offsets has been performed for bulk Ge1-x Sn x alloy in the full composition range using state-of-the-art density functional theory methods. A spectral weight approach to band unfolding has been applied as a means of distinguishing the indirect and direct band gaps from folded supercell band structures. In this way, four characteristic regions of the band gap character have been identified for Ge1-x Sn x alloy: an indirect band gap (x  <  6.5%), a direct band gap (6.5%  <  x  <  25%) and an inverse band gap (x  >  25%) with inverse spin-orbit split-off for 45%  <  x  <  85%. In general, it has been observed that the bowing parameters of band edges (Γ and L-point in conduction band (CBΓ and CB L ), valence band (VB), and spin-orbit (SO) band) are rather large ({{b}\\text{C{{\\text{B}} Γ }}}   =  2.43  ±  0.06 eV, {{b}\\text{C{{\\text{B}}L}}}   =  0.64  ±  0.04 eV, {{b}\\text{VB}}   =  -0.59  ±  0.04 eV, and {{b}\\text{SO}}   =  -0.49  ±  0.05 eV). This indicates that Ge1-x Sn x behaves like a highly mismatched group IV alloy. The composition dependence of lattice constant shows negligible bowing (b a   =  -0.083 Å). Obtained results have been compared with available experimental data. The origin of band gap reduction and large bowing has been analyzed and conclusions have been drawn regarding the relationship between experimental and theoretical results. It is shown that due to the low DOS at the Γ-point, a significant filling of CB by electrons in the direct gap regime may easily take place. Therefore, the Burstein-Moss effect should be considered when comparing experimental data with theoretical predictions as has already been shown for other intrinsic n-type narrow gap semiconductors (e.g. InN).

Accumulation Rates in the Dry Snow Zone of the Greenland Ice Sheet Inferred from L-band InSAR Data

NASA Astrophysics Data System (ADS)

Chen, A. C.; Zebker, H. A.

2012-12-01

The Greenland ice sheet contains about 2.9 million km3 of ice and would raise global sea levels by about 7.1 m if it melted completely. Two unusually large iceberg calving events at Petermann Glacier in the past several years, along with the unusually large extent of ice sheet melt this summer point to the relevance of understanding the mass balance of the Greenland ice sheet. In this study, we use data from the PALSAR instrument aboard the ALOS satellite to form L-band (23-centimeter carrier wavelength) InSAR images of the dry snow zone of the Greenland ice sheet. We form geocoded differential interferograms, using the ice sheet elevation model produced by Howat et.al. [1]. By applying phase and radiometric calibration, we can examine interferograms formed between any pair of transmit and receive polarization channels. In co-polarized interferograms, the InSAR correlation ranges from about 0.35 at the summit (38.7 deg W, 73.0 deg N) where accumulation is about 20 cm w.e./yr to about 0.70 at the north-eastern part of the dry snow zone (35.1 deg W, 77.1 deg N), where accumulation is about 11.7 cm w.e./yr. Cross-polarized interferograms show similar geographic variation with overall lower correlation. We compare our InSAR data with in-situ measurements published by Bales et.al. [2]. We examine the applicability of dense-medium radiative transfer electromagnetic scattering models for estimating accumulation rates from L-band InSAR data. The large number and broad coverage of ALOS scenes acquired between 2007 and 2009 with good InSAR coherence at 46-day repeat times and 21.5 degree incidence angles gives us the opportunity to examine the empirical relationship between in-situ accumulation rate observations and the polarimetric InSAR correlation and radar brightness at this particular imaging geometry. This helps us quantify the accuracy of accumulation rates estimated from InSAR data. In some regions, 46-day interferograms acquired in the winters of several consecutive

The L-band PBMR measurements of surface soil moisture in FIFE. [First International satellite land surface climatology project Field Experiment

NASA Technical Reports Server (NTRS)

Wang, James R.; Shiue, James C.; Schmugge, Thomas J.; Engman, Edwin T.

1990-01-01

The NASA Langley Research Center's L-band pushbroom microwave radiometer (PBMR) aboard the NASA C-130 aircraft was used to map surface soil moisture at and around the Konza Prairie Natural Research Area in Kansas during the four intensive field campaigns of FIFE in May-October 1987. There was a total of 11 measurements was made when soils were known to be saturated. This measurement was used for the calibration of the vegetation effect on the microwave absorption. Based on this calibration, the data from other measurements on other days were inverted to generate the soil moisture maps. Good agreement was found when the estimated soil moisture values were compared to those independently measured on the ground at a number of widely separated locations. There was a slight bias between the estimated and measured values, the estimated soil moisture on the average being lower by about 1.8 percent. This small bias, however, was accounted for by the difference in time of the radiometric measurements and the soil moisture ground sampling.

L Band Service Compatibility : Part II: Optimum GPS Receiver ABI Compatibility

DOT National Transportation Integrated Search

2015-03-12

Workshop Objectives. This is the Second of Two Parts on Compatibility. Last time, OOBE. Today examine mitigation of Adjacent Band Interference, ABI. Apply Relevant TWG and NPEF (2011) data to engage compatibility analysis. Assert Principle: Dr. Brad ...

Electronic band structures and excitonic properties of delafossites: A GW-BSE study

NASA Astrophysics Data System (ADS)

Wang, Xiaoming; Meng, Weiwei; Yan, Yanfa

2017-08-01

We report the band structures and excitonic properties of delafossites CuMO2 (M=Al, Ga, In, Sc, Y, Cr) calculated using the state-of-the-art GW-BSE approach. We evaluate different levels of self-consistency of the GW approximations, namely G0W0, GW0, GW, and QSGW, on the band structures and find that GW0, in general, predicts the band gaps in better agreement with experiments considering the electron-hole effect. For CuCrO2, the HSE wave function is used as the starting point for the perturbative GW0 calculations, since it corrects the band orders wrongly predicted by PBE. The discrepancy about the valence band characters of CuCrO2 is classified based on both HSE and QSGW calculations. The PBE wave functions, already good, are used for other delafossites. All the delafossites are shown to be indirect band gap semiconductors with large exciton binding energies, varying from 0.24 to 0.44 eV, in consistent with experimental findings. The excitation mechanisms are explained by examining the exciton amplitude projections on the band structures. Discrepancies compared with experiments are also addressed. The lowest and strongest exciton, mainly contributed from either Cu 3d → Cu 3p (Al, Ga, In) or Cu 3d → M 3d (M = Sc, Y, Cr) transitions, is always located at the L point of the rhombohedral Brillouin zone.

Novel Dual-band Band-Pass Filters Based on Surface Plasmon Polariton-like Propagation Induced by Structural Dispersion of Substrate Integrated Waveguide.

PubMed

Cselyuszka, Norbert; Sakotic, Zarko; Kitic, Goran; Crnojevic-Bengin, Vesna; Jankovic, Nikolina

2018-05-29

In this paper, we present two novel dual-band bandpass filters based on surface plasmon polariton-like (SPP-like) propagation induced by structural dispersion of substrate integrated waveguide (SIW). Both filters are realized as a three-layer SIW where each layer represents a sub-SIW structure with intrinsic effective permittivity that depends on its width and filling dielectric material. The layers are designed to have effective permittivities of opposite signs in certain frequency ranges, which enables SPP-like propagation to occur at their interfaces. Since three layers can provide two distinct SPP-like propagations, the filters exhibit dual-band behaviour. A detailed theoretical and numerical analysis and numerical optimization have been used to design the filters, which were afterwards fabricated using standard printed circuit board technology. The independent choice of geometrical parameters of sub-SIWs and/or the corresponding dielectric materials provide a great freedom to arbitrarily position the passbands in the spectrum, which is a significant advantage of the proposed filters. At the same time, they meet the requirements for low-cost low-profile configuration since they are realized as SIW structures, as well as for excellent in-band characteristics and selectivity which is confirmed by the measurement results.

L Band Brightness Temperature Observations Over a Corn Canopy During the Entire Growth Cycle

NASA Technical Reports Server (NTRS)

Joseph, Alicia T.; O'Neill, Peggy E.; Choudhury, Bhaskar J.; vanderVelde, Rogier; Lang, Roger H.; Gish, Timothy

2011-01-01

During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (T(sub B)) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive characterization of land surface variables including soil moisture, soil temperature, vegetation biomass, and surface roughness. During the period from May 22, 2002 to August 30, 2002 a range of vegetation water content (W) of 0.0 to 4.3 kg/square m, ten days of radiometer and ground measurements were available. Using this data set, the effects of corn vegetation on surface emissions are investigated by means of a semi-empirical radiative transfer model. Additionally, the impact of roughness on the surface emission is quantified using T(sub B) measurements over bare soil conditions. Subsequently, the estimated roughness parameters, ground measurements and horizontally (H)-polarized T(sub B) are employed to invert the H-polarized transmissivity (gamma-h) for the monitored corn growing season.

Searching for I-band variability in stars in the M/L spectral transition region

NASA Astrophysics Data System (ADS)

Ramsay, Gavin; Hakala, Pasi; Doyle, J. Gerry

2015-10-01

We report on I-band photometric observations of 21 stars with spectral types between M8 and L4 made using the Isaac Newton Telescope. The total amount of time for observations which had a cadence of <2.3 min was 58.5 h, with additional data with lower cadence. We test for photometric variability using the Kruskal-Wallis H-test and find that four sources (2MASS J10224821+5825453, 2MASS J07464256+2000321, 2MASS J16262034+3925190 and 2MASS J12464678+4027150) were found to be significantly variable at least on one epoch. Three of these sources are reported as photometrically variable for the first time. If we include sources which were deemed marginally variable, the number of variable sources is 6 (29 per cent). No flares were detected from any source. The percentage of sources which we found were variable is similar to previous studies. We summarize the mechanisms which have been put forward to explain the light curves of brown dwarfs.

Investigation of TM Band-to-band Registration Using the JSC Registration Processor

NASA Technical Reports Server (NTRS)

Yao, S. S.; Amis, M. L.

1984-01-01

The JSC registration processor performs scene-to-scene (or band-to-band) correlation based on edge images. The edge images are derived from a percentage of the edge pixels calculated from the raw scene data, excluding clouds and other extraneous data in the scene. Correlations are performed on patches (blocks) of the edge images, and the correlation peak location in each patch is estimated iteratively to fractional pixel location accuracy. Peak offset locations from all patches over the scene are then considered together, and a variety of tests are made to weed out outliers and other inconsistencies before a distortion model is assumed. Thus, the correlation peak offset locations in each patch indicate quantitatively how well the two TM bands register to each other over that patch of scene data. The average of these offsets indicate the overall accuracies of the band-to-band registration. The registration processor was also used to register one acquisition to another acquisition of multitemporal TM data acquired over the same ground track. Band 4 images from both acquisitions were correlated and an rms error of a fraction of a pixel was routinely obtained.

The occurrence and wave properties of H+-, He+-, and O+-band EMIC waves observed by the Van Allen Probes

NASA Astrophysics Data System (ADS)

Saikin, A. A.; Zhang, J.-C.; Allen, R. C.; Smith, C. W.; Kistler, L. M.; Spence, H. E.; Torbert, R. B.; Kletzing, C. A.; Jordanova, V. K.

2015-09-01

We perform a statistical study of electromagnetic ion cyclotron (EMIC) waves detected by the Van Allen Probes mission to investigate the spatial distribution of their occurrence, wave power, ellipticity, and normal angle. The Van Allen Probes have been used which allow us to explore the inner magnetosphere (1.1 to 5.8 RE). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes are used to identify EMIC wave events for the first 22 months of the mission operation (8 September 2012 to 30 June 2014). EMIC waves are examined in H+, He+, and O+ bands. Over 700 EMIC wave events have been identified over the three different wave bands (265 H+-band events, 438 He+-band events, and 68 O+-band events). EMIC wave events are observed between L = 2-8, with over 140 EMIC wave events observed below L = 4. Results show that H+-band EMIC waves have two peak magnetic local time (MLT) occurrence regions: prenoon (09:00 < MLT ≤ 12:00) and afternoon (15:00 < MLT ≤ 17:00) sectors. He+-band EMIC waves feature an overall stronger dayside occurrence. O+-band EMIC waves have one peak region located in the morning sector at lower L shells (L < 4). He+-band EMIC waves average the highest wave power overall (>0.1 nT2/Hz), especially in the afternoon sector. Ellipticity observations reveal that linearly polarized EMIC waves dominate in lower L shells.

A Novel Complex-Coefficient In-Band Interference Suppression Algorithm for Cognitive Ultra-Wide Band Wireless Sensors Networks.

PubMed

Xiong, Hailiang; Zhang, Wensheng; Xu, Hongji; Du, Zhengfeng; Tang, Huaibin; Li, Jing

2017-05-25

With the rapid development of wireless communication systems and electronic techniques, the limited frequency spectrum resources are shared with various wireless devices, leading to a crowded and challenging coexistence circumstance. Cognitive radio (CR) and ultra-wide band (UWB), as sophisticated wireless techniques, have been considered as significant solutions to solve the harmonious coexistence issues. UWB wireless sensors can share the spectrum with primary user (PU) systems without harmful interference. The in-band interference of UWB systems should be considered because such interference can severely affect the transmissions of UWB wireless systems. In order to solve the in-band interference issues for UWB wireless sensor networks (WSN), a novel in-band narrow band interferences (NBIs) elimination scheme is proposed in this paper. The proposed narrow band interferences suppression scheme is based on a novel complex-coefficient adaptive notch filter unit with a single constrained zero-pole pair. Moreover, in order to reduce the computation complexity of the proposed scheme, an adaptive complex-coefficient iterative method based on two-order Taylor series is designed. To cope with multiple narrow band interferences, a linear cascaded high order adaptive filter and a cyclic cascaded high order matrix adaptive filter (CCHOMAF) interference suppression algorithm based on the basic adaptive notch filter unit are also presented. The theoretical analysis and numerical simulation results indicate that the proposed CCHOMAF algorithm can achieve better performance in terms of average bit error rate for UWB WSNs. The proposed in-band NBIs elimination scheme can significantly improve the reception performance of low-cost and low-power UWB wireless systems.

A Novel Complex-Coefficient In-Band Interference Suppression Algorithm for Cognitive Ultra-Wide Band Wireless Sensors Networks

PubMed Central

Xiong, Hailiang; Zhang, Wensheng; Xu, Hongji; Du, Zhengfeng; Tang, Huaibin; Li, Jing

2017-01-01

With the rapid development of wireless communication systems and electronic techniques, the limited frequency spectrum resources are shared with various wireless devices, leading to a crowded and challenging coexistence circumstance. Cognitive radio (CR) and ultra-wide band (UWB), as sophisticated wireless techniques, have been considered as significant solutions to solve the harmonious coexistence issues. UWB wireless sensors can share the spectrum with primary user (PU) systems without harmful interference. The in-band interference of UWB systems should be considered because such interference can severely affect the transmissions of UWB wireless systems. In order to solve the in-band interference issues for UWB wireless sensor networks (WSN), a novel in-band narrow band interferences (NBIs) elimination scheme is proposed in this paper. The proposed narrow band interferences suppression scheme is based on a novel complex-coefficient adaptive notch filter unit with a single constrained zero-pole pair. Moreover, in order to reduce the computation complexity of the proposed scheme, an adaptive complex-coefficient iterative method based on two-order Taylor series is designed. To cope with multiple narrow band interferences, a linear cascaded high order adaptive filter and a cyclic cascaded high order matrix adaptive filter (CCHOMAF) interference suppression algorithm based on the basic adaptive notch filter unit are also presented. The theoretical analysis and numerical simulation results indicate that the proposed CCHOMAF algorithm can achieve better performance in terms of average bit error rate for UWB WSNs. The proposed in-band NBIs elimination scheme can significantly improve the reception performance of low-cost and low-power UWB wireless systems. PMID:28587085

Experimental L-Band Airborne SAR for Oil Spill Response at Sea and in Coastal Waters

PubMed Central

Jones, Cathleen E.; Holt, Benjamin

2018-01-01

Satellite synthetic aperture radar (SAR) is frequently used during oil spill response efforts to identify oil slick extent, but suffers from the major disadvantages of potential long latency between when a spill occurs and when a satellite can image the site and an inability to continuously track the spill as it develops. We show using data acquired with the Uninhabited Aerial Vehicle SAR (UAVSAR) instrument how a low noise, high resolution, L-band SAR could be used for oil spill response, with specific examples of tracking slick extent, position and weathering; determining zones of relatively thicker or more emulsified oil within a slick; and identifying oil slicks in coastal areas where look-alikes such as calm waters or biogenic slicks can confound the identification of mineral oil spills. From these key points, the essential features of an airborne SAR system for operational oil spill response are described, and further research needed to determine SAR’s capabilities and limitations in quantifying slick thickness is discussed. PMID:29470391

System and method for progressive band selection for hyperspectral images

NASA Technical Reports Server (NTRS)

Fisher, Kevin (Inventor)

2013-01-01

Disclosed herein are systems, methods, and non-transitory computer-readable storage media for progressive band selection for hyperspectral images. A system having module configured to control a processor to practice the method calculates a virtual dimensionality of a hyperspectral image having multiple bands to determine a quantity Q of how many bands are needed for a threshold level of information, ranks each band based on a statistical measure, selects Q bands from the multiple bands to generate a subset of bands based on the virtual dimensionality, and generates a reduced image based on the subset of bands. This approach can create reduced datasets of full hyperspectral images tailored for individual applications. The system uses a metric specific to a target application to rank the image bands, and then selects the most useful bands. The number of bands selected can be specified manually or calculated from the hyperspectral image's virtual dimensionality.

C-Band Airport Surface Communications System Standards Development, Phase I

NASA Technical Reports Server (NTRS)

Hall, Edward; Isaacs, James; Zelkin, Natalie; Henriksen. Steve

2010-01-01

This document is being provided as part of ITT's NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: "New ATM Requirements--Future Communications, C-Band and L-Band Communications Standard Development." The proposed future C-band (5091- to 5150-MHz) airport surface communication system, referred to as the Aeronautical Mobile Airport Communications System (AeroMACS), is anticipated to increase overall air-to-ground data communications systems capacity by using a new spectrum (i.e., not very high frequency (VHF)). Although some critical services could be supported, AeroMACS will also target noncritical services, such as weather advisory and aeronautical information services as part of an airborne System Wide Information Management (SWIM) program. AeroMACS is to be designed and implemented in a manner that will not disrupt other services operating in the C-band. This report defines the AeroMACS concepts of use, high-level system requirements, and architecture; the performance of supporting system analyses; the development of AeroMACS test and demonstration plans; and the establishment of an operational AeroMACS capability in support of C-band aeronautical data communications standards to be advanced in both international (International Civil Aviation Organization, ICAO) and national (RTCA) forums. This includes the development of system parameter profile recommendations for AeroMACS based on existing Institute of Electrical and Electronics Engineering (IEEE) 802.16e- 2009 standards

Per-point and per-field contextual classification of multipolarization and multiple incidence angle aircraft L-band radar data

NASA Technical Reports Server (NTRS)

Hoffer, Roger M.; Hussin, Yousif Ali

1989-01-01

Multipolarized aircraft L-band radar data are classified using two different image classification algorithms: (1) a per-point classifier, and (2) a contextual, or per-field, classifier. Due to the distinct variations in radar backscatter as a function of incidence angle, the data are stratified into three incidence-angle groupings, and training and test data are defined for each stratum. A low-pass digital mean filter with varied window size (i.e., 3x3, 5x5, and 7x7 pixels) is applied to the data prior to the classification. A predominately forested area in northern Florida was the study site. The results obtained by using these image classifiers are then presented and discussed.

Vascular Adaptations to Transverse Aortic Banding in Mice

DTIC Science & Technology

2001-10-25

hypertrophy (B-C) via pressure overload. A Doppler probe (D) was used to measure flow velocity at the aortic valve (1), the mitral valve (2), the...L) carotid artery (CA), aortic, and mitral blood velocity 1 day later. At 7 days the heart- weight/body-weight ratio (HW/BW) was measured. Mean...aortic, mitral , and carotid velocities were similar in sham and banded mice, but peak RCA/LCA velocities were much higher in banded mice and were highly

Radio frequency electromagnetic field compliance assessment of multi-band and MIMO equipped radio base stations.

PubMed

Thors, Björn; Thielens, Arno; Fridén, Jonas; Colombi, Davide; Törnevik, Christer; Vermeeren, Günter; Martens, Luc; Joseph, Wout

2014-05-01

In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances. © 2014 Wiley Periodicals, Inc.

Infrared diffuse interstellar bands

NASA Astrophysics Data System (ADS)

Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.

2017-05-01

We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.

The importance of different frequency bands in predicting subcutaneous glucose concentration in type 1 diabetic patients.

PubMed

Lu, Yinghui; Gribok, Andrei V; Ward, W Kenneth; Reifman, Jaques

2010-08-01

We investigated the relative importance and predictive power of different frequency bands of subcutaneous glucose signals for the short-term (0-50 min) forecasting of glucose concentrations in type 1 diabetic patients with data-driven autoregressive (AR) models. The study data consisted of minute-by-minute glucose signals collected from nine deidentified patients over a five-day period using continuous glucose monitoring devices. AR models were developed using single and pairwise combinations of frequency bands of the glucose signal and compared with a reference model including all bands. The results suggest that: for open-loop applications, there is no need to explicitly represent exogenous inputs, such as meals and insulin intake, in AR models; models based on a single-frequency band, with periods between 60-120 min and 150-500 min, yield good predictive power (error <3 mg/dL) for prediction horizons of up to 25 min; models based on pairs of bands produce predictions that are indistinguishable from those of the reference model as long as the 60-120 min period band is included; and AR models can be developed on signals of short length (approximately 300 min), i.e., ignoring long circadian rhythms, without any detriment in prediction accuracy. Together, these findings provide insights into efficient development of more effective and parsimonious data-driven models for short-term prediction of glucose concentrations in diabetic patients.

Impurity-Band Model for GaP1-xNx

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fluegel, B.; Zhang, Y.; Geisz, J. F.

2005-11-01

Low-temperature absorption studies on free-standing GaP1-xNx films provide direct experimental evidence that the host conduction-band minimum (CBM) near X1C does not plunge downward with increased nitrogen doping, contrary to what has been suggested recently; rather, it remains stationary for x up to 0.1%. This fact, combined with the results of earlier studies of the CBM at ..GAMMA.. and conduction-band edge near L, confirms that the giant bandgap lowering observed in GaP1-xNx results from a CBM that evolves purely from nitrogen impurity bands.

Modelling Ground Based X- and Ku-Band Observations of Tundra Snow

NASA Astrophysics Data System (ADS)

Kasurak, A.; King, J. M.; Kelly, R. E.

2012-12-01

As part of a radar-based remote sensing field experiment in Churchill, Manitoba ground based Ku- and X-band scatterometers were deployed to observe changing tundra snowpack conditions from November 2010 to March 2011. The research is part of the validation effort for the Cold Regions Hydrology High-resolution Observatory (CoReH2O) mission, a candidate in the European Space Agency's Earth Explorer program. This paper focuses on the local validation of the semi-empirical radiative transfer (sRT) model proposed for use in snow property retrievals as part of the CoReH2O mission. In this validation experiment, sRT was executed in the forward mode, simulating backscatter to assess the ability of the model. This is a necessary precursor to any inversion attempt. Two experiments are considered, both conducted in a hummocky tundra environment with shallow snow cover. In both cases, scatterometer observations were acquired over a field of view of approximately 10 by 20 meters. In the first experiment, radar observations were made of a snow field and then repeated after the snow had been removed. A ground-based scanning LiDAR system was used to characterize the spatial variability of snow depth through measurements of the snow and ground surface. Snow properties were determined in the field of view from two snow pits, 12 density core measurements, and Magnaprobe snow depth measurements. In the second experiment, a site was non-destructively observed from November through March, with snow properties measured out-of-scene, to characterize the snow evolution response. The model results from sRT fit the form of the observations from the two scatterometer field experiments but do not capture the backscatter magnitude. A constant offset for the season of 5 dB for X-band co- and cross-polarization response was required to match observations, in addition to a 3 dB X- and Ku-band co-polarization offset after the 6th of December. To explain these offsets, it is recognized that the two

The mechanism and realization of a band-agile coaxial relativistic backward-wave oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ge, Xingjun; Zhang, Jun; Zhong, Huihuang

2014-11-03

The mechanism and realization of a band-agile coaxial relativistic backward-wave oscillator (RBWO) are presented. The operation frequency tuning can be easily achieved by merely altering the inner-conductor length. The key effects of the inner-conductor length contributing to the mechanical frequency tunability are investigated theoretically and experimentally. There is a specific inner-conductor length where the operation frequency can jump from one mode to another mode, which belongs to a different operation band. In addition, the operation frequency is tunable within each operation band. During simulation, the L-band microwave with a frequency of 1.61 GHz is radiated when the inner-conductor length ismore » 39 cm. Meanwhile, the S-band microwave with a frequency of 2.32 GHz is radiated when the inner-conductor length is 5 cm. The frequency adjustment bandwidths of L-band and S-band are about 8.5% and 2%, respectively. Moreover, the online mechanical tunability process is described in detail. In the initial experiment, the generated microwave frequencies remain approximately 1.59 GHz and 2.35 GHz when the inner-conductor lengths are 39 cm and 5 cm. In brief, this technical route of the band-agile coaxial RBWO is feasible and provides a guide to design other types of band-agile high power microwaves sources.« less

Channel characterisation for future Ka-band Mobile Satellite Systems and preliminary results

NASA Technical Reports Server (NTRS)

Sforza, Mario; Buonomo, Sergio; Arbesser-Rastburg, Bertram

1994-01-01

Mobile satellite systems (MSS) are presently designed or planned to operate, with the exception of OMNITRACKS, in the lower part of the frequency spectrum (UHF to S-bands). The decisions taken at the last World Administrative Radio Conference in 1992 to increase the allocated L- and S-bands for MSS services will only partly alleviate the problem of system capacity. In addition the use of L-and S-band frequencies generally requires large antenna apertures on board the satellite terminal side. The idea of exploiting the large spectrum resources available at higher frequencies (20-30 GHz) and the perspective of reducing user terminal size (and possibly price too) have spurred the interest of systems designers and planners. On the other hand, Ka-band frequencies suffer from increased slant path losses due to atmospheric attenuation phenomena. The European Space Agency (ESA) has recently embarked on a number of activities aimed at studying the effect of the typical mobile propagation impairments at Ka-band. This paper briefly summarizes ESA efforts in this field of research and presents preliminary experimental results.

UWB Filtering Power Divider with Two Narrow Notch-bands and Wide Stop-band

NASA Astrophysics Data System (ADS)

Wei, Feng; Wang, Xin-Yi; Zou, Xin Tong; Shi, Xiao Wei

2017-12-01

A compact filtering ultra-wideband (UWB) microstrip power divider (PD) with two sharply rejected notch-bands and wide stopband is analyzed and designed in this paper. The proposed UWB PD is based on a conventional Wilkinson power divider, while two stub loaded resonators (SLRs) are coupled into two symmetrical output ports to achieve a bandpass filtering response. The simplified composite right/left-handed (SCRLH) resonators are employed to generate the dual notched bands. Defected ground structure (DGS) is introduced to improve the passband performance. Good insertion/return losses, isolation and notch-band rejection are achieved as demonstrated in both simulation and experiment.

The hierarchically organized splitting of chromosome bands into sub-bands analyzed by multicolor banding (MCB).

PubMed

Lehrer, H; Weise, A; Michel, S; Starke, H; Mrasek, K; Heller, A; Kuechler, A; Claussen, U; Liehr, T

2004-01-01

To clarify the nature of chromosome sub-bands in more detail, the multicolor banding (MCB) probe-set for chromosome 5 was hybridized to normal metaphase spreads of GTG band levels at approximately 850, approximately 550, approximately 400 and approximately 300. It could be observed that as the chromosomes became shorter, more of the initial 39 MCB pseudo-colors disappeared, ending with 18 MCB pseudo-colored bands at the approximately 300-band level. The hierarchically organized splitting of bands into sub-bands was analyzed by comparing the disappearance or appearance of pseudo-color bands of the four different band levels. The regions to split first are telomere-near, centromere-near and in 5q23-->q31, followed by 5p15, 5p14, and all GTG dark bands in 5q apart from 5q12 and 5q32 and finalized by sub-band building in 5p15.2, 5q21.2-->q21.3, 5q23.1 and 5q34. The direction of band splitting towards the centromere or the telomere could be assigned to each band separately. Pseudo-colors assigned to GTG-light bands were resistant to band splitting. These observations are in concordance with the recently proposed concept of chromosome region-specific protein swelling. Copyright 2003 S. Karger AG, Basel

Bands selection and classification of hyperspectral images based on hybrid kernels SVM by evolutionary algorithm

NASA Astrophysics Data System (ADS)

Hu, Yan-Yan; Li, Dong-Sheng

2016-01-01

The hyperspectral images(HSI) consist of many closely spaced bands carrying the most object information. While due to its high dimensionality and high volume nature, it is hard to get satisfactory classification performance. In order to reduce HSI data dimensionality preparation for high classification accuracy, it is proposed to combine a band selection method of artificial immune systems (AIS) with a hybrid kernels support vector machine (SVM-HK) algorithm. In fact, after comparing different kernels for hyperspectral analysis, the approach mixed radial basis function kernel (RBF-K) with sigmoid kernel (Sig-K) and applied the optimized hybrid kernels in SVM classifiers. Then the SVM-HK algorithm used to induce the bands selection of an improved version of AIS. The AIS was composed of clonal selection and elite antibody mutation, including evaluation process with optional index factor (OIF). Experimental classification performance was on a San Diego Naval Base acquired by AVIRIS, the HRS dataset shows that the method is able to efficiently achieve bands redundancy removal while outperforming the traditional SVM classifier.

Tunable dual-band nearly perfect absorption based on a compound metallic grating

NASA Astrophysics Data System (ADS)

Gao, Hua; Zheng, Zhi-Yuan; Feng, Juan

2017-02-01

Traditional metallic gratings and novel metamaterials are two basic kinds of candidates for perfect absorption. Comparatively speaking, metallic grating is the preferred choice for the same absorption effect because it is structurally simpler and more convenient to fabricate. However, to date, most of the perfect absorption effects achieved based on metamaterials are also available using an metallic grating except the tunable dual(multi)-band perfect absorption. To fill this gap, in this paper, by adding subgrooves on the rear surface as well as inside the grating slits to a free-standing metallic grating, tunable dual-band perfect absorption is also obtained for the first time. The grooves inside the slits is to tune the frequency of the Cavity Mode(CM) resonance which enhances the transmission and suppresses the reflectance simultaneously. The grooves on the rear surface give rise to the phase resonance which not only suppresses the transmission but also reinforces the reflectance depression effect. Thus, when the phase resonance and the frequency tunable CM resonance occur together, transmission and reflection can be suppressed simultaneously, dual-band nearly perfect absorption with tunable frequencies is obtained. To our knowledge, this perfect absorption phenomenon is achieved for the first time in a designed metallic grating structure.

E-band Nd 3+ amplifier based on wavelength selection in an all-solid micro-structured fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, Jay W.; Kiani, Leily S.; Pax, Paul H.

Here, a Nd 3+ fiber amplifier with gain from 1376 nm to 1466 nm is demonstrated. This is enabled by a wavelength selective waveguide that suppresses amplified spontaneous emission between 850 nm and 1150 nm. It is shown that while excited state absorption (ESA) precludes net gain below 1375 nm with the exception of a small band from 1333 nm to 1350 nm, ESA diminishes steadily beyond 1375 nm allowing for the construction of an efficient fiber amplifier with a gain peak at 1400 nm and the potential for gain from 1375 nm to 1500 nm. A peak small signalmore » gain of 13.3 dB is measured at 1402 nm with a noise figure of 7.6 dB. Detailed measurements of the Nd 3+ emission and excited state absorption cross sections suggest the potential for better performance in improved fibers. Specifically, reduction of the fiber mode field diameter from 10.5 µm to 5.25 µm and reduction of the fiber background loss to <10 dB/km at 1400 nm should enable construction of an E-band fiber amplifier with a noise figure < 5 dB and a small signal gain > 20 dB over 30 nm of bandwidth. Such an amplifier would have a form factor and optical properties similar to current erbium fiber amplifiers, enabling modern fiber optic communication systems to operate in the E-band with amplifier technology similar to that employed in the C and L bands.« less

E-band Nd 3+ amplifier based on wavelength selection in an all-solid micro-structured fiber

DOE PAGES

Dawson, Jay W.; Kiani, Leily S.; Pax, Paul H.; ...

2017-03-13

Here, a Nd 3+ fiber amplifier with gain from 1376 nm to 1466 nm is demonstrated. This is enabled by a wavelength selective waveguide that suppresses amplified spontaneous emission between 850 nm and 1150 nm. It is shown that while excited state absorption (ESA) precludes net gain below 1375 nm with the exception of a small band from 1333 nm to 1350 nm, ESA diminishes steadily beyond 1375 nm allowing for the construction of an efficient fiber amplifier with a gain peak at 1400 nm and the potential for gain from 1375 nm to 1500 nm. A peak small signalmore » gain of 13.3 dB is measured at 1402 nm with a noise figure of 7.6 dB. Detailed measurements of the Nd 3+ emission and excited state absorption cross sections suggest the potential for better performance in improved fibers. Specifically, reduction of the fiber mode field diameter from 10.5 µm to 5.25 µm and reduction of the fiber background loss to <10 dB/km at 1400 nm should enable construction of an E-band fiber amplifier with a noise figure < 5 dB and a small signal gain > 20 dB over 30 nm of bandwidth. Such an amplifier would have a form factor and optical properties similar to current erbium fiber amplifiers, enabling modern fiber optic communication systems to operate in the E-band with amplifier technology similar to that employed in the C and L bands.« less

FIR filters for hardware-based real-time multi-band image blending

NASA Astrophysics Data System (ADS)

Popovic, Vladan; Leblebici, Yusuf

2015-02-01

Creating panoramic images has become a popular feature in modern smart phones, tablets, and digital cameras. A user can create a 360 degree field-of-view photograph from only several images. Quality of the resulting image is related to the number of source images, their brightness, and the used algorithm for their stitching and blending. One of the algorithms that provides excellent results in terms of background color uniformity and reduction of ghosting artifacts is the multi-band blending. The algorithm relies on decomposition of image into multiple frequency bands using dyadic filter bank. Hence, the results are also highly dependant on the used filter bank. In this paper we analyze performance of the FIR filters used for multi-band blending. We present a set of five filters that showed the best results in both literature and our experiments. The set includes Gaussian filter, biorthogonal wavelets, and custom-designed maximally flat and equiripple FIR filters. The presented results of filter comparison are based on several no-reference metrics for image quality. We conclude that 5/3 biorthogonal wavelet produces the best result in average, especially when its short length is considered. Furthermore, we propose a real-time FPGA implementation of the blending algorithm, using 2D non-separable systolic filtering scheme. Its pipeline architecture does not require hardware multipliers and it is able to achieve very high operating frequencies. The implemented system is able to process 91 fps for 1080p (1920×1080) image resolution.

Implementation of body area networks based on MICS/WMTS medical bands for healthcare systems.

PubMed

Yuce, Mehmet R; Ho, Chee Keong

2008-01-01

A multi-hoping sensor network system has been implemented to monitor physiological parameters from multiple patient bodies by means of medical communication standards MICS (Medical Implant Communication Service) and WMTS (Wireless Medical Telemetry Service). Unlike the other medical sensor networks (they usually use 2.4 GHz ISM band), we used the two medical standards occupying the frequency bands that are mainly assigned to medical applications. The prototype system uses the MICS band (402-405 MHz) between the sensor nodes and a remote central control unit (CCU). And WMTS frequencies (608-614MHz) are used between the CCUs and the remote base stations allowing for a much larger range acting as an intermediate node. The sensor nodes in the prototype can measure up to four body signals (i.e. 4-channel) where one is dedicated to a continuous physiological signal such as ECC/EEG. The system includes firmware and software designs that can provide a long distance data transfer through the internet or a mobile network.

Band-Gap and Band-Edge Engineering of Multicomponent Garnet Scintillators from First Principles

NASA Astrophysics Data System (ADS)

Yadav, Satyesh K.; Uberuaga, Blas P.; Nikl, Martin; Jiang, Chao; Stanek, Christopher R.

2015-11-01

Complex doping schemes in R3 Al5 O12 (where R is the rare-earth element) garnet compounds have recently led to pronounced improvements in scintillator performance. Specifically, by admixing lutetium and yttrium aluminate garnets with gallium and gadolinium, the band gap is altered in a manner that facilitates the removal of deleterious electron trapping associated with cation antisite defects. Here, we expand upon this initial work to systematically investigate the effect of substitutional admixing on the energy levels of band edges. Density-functional theory and hybrid density-functional theory (HDFT) are used to survey potential admixing candidates that modify either the conduction-band minimum (CBM) or valence-band maximum (VBM). We consider two sets of compositions based on Lu3 B5O12 where B is Al, Ga, In, As, and Sb, and R3Al5 O12 , where R is Lu, Gd, Dy, and Er. We find that admixing with various R cations does not appreciably affect the band gap or band edges. In contrast, substituting Al with cations of dissimilar ionic radii has a profound impact on the band structure. We further show that certain dopants can be used to selectively modify only the CBM or the VBM. Specifically, Ga and In decrease the band gap by lowering the CBM, while As and Sb decrease the band gap by raising the VBM, the relative change in band gap is quantitatively validated by HDFT. These results demonstrate a powerful approach to quickly screen the impact of dopants on the electronic structure of scintillator compounds, identifying those dopants which alter the band edges in very specific ways to eliminate both electron and hole traps responsible for performance limitations. This approach should be broadly applicable for the optimization of electronic and optical performance for a wide range of compounds by tuning the VBM and CBM.

Soil Moisture Estimate under Forest using a Semi-empirical Model at P-Band

NASA Astrophysics Data System (ADS)

Truong-Loi, M.; Saatchi, S.; Jaruwatanadilok, S.

2013-12-01

In this paper we show the potential of a semi-empirical algorithm to retrieve soil moisture under forests using P-band polarimetric SAR data. In past decades, several remote sensing techniques have been developed to estimate the surface soil moisture. In most studies associated with radar sensing of soil moisture, the proposed algorithms are focused on bare or sparsely vegetated surfaces where the effect of vegetation can be ignored. At long wavelengths such as L-band, empirical or physical models such as the Small Perturbation Model (SPM) provide reasonable estimates of surface soil moisture at depths of 0-5cm. However for densely covered vegetated surfaces such as forests, the problem becomes more challenging because the vegetation canopy is a complex scattering environment. For this reason there have been only few studies focusing on retrieving soil moisture under vegetation canopy in the literature. Moghaddam et al. developed an algorithm to estimate soil moisture under a boreal forest using L- and P-band SAR data. For their studied area, double-bounce between trunks and ground appear to be the most important scattering mechanism. Thereby, they implemented parametric models of radar backscatter for double-bounce using simulations of a numerical forest scattering model. Hajnsek et al. showed the potential of estimating the soil moisture under agricultural vegetation using L-band polarimetric SAR data and using polarimetric-decomposition techniques to remove the vegetation layer. Here we use an approach based on physical formulation of dominant scattering mechanisms and three parameters that integrates the vegetation and soil effects at long wavelengths. The algorithm is a simplification of a 3-D coherent model of forest canopy based on the Distorted Born Approximation (DBA). The simplified model has three equations and three unknowns, preserving the three dominant scattering mechanisms of volume, double-bounce and surface for three polarized backscattering

Performance of high-temperature superconducting band-pass filters with high selectivity for base transceiver applications of digital cellular communication systems

NASA Astrophysics Data System (ADS)

Kwak, J. S.; Lee, J. H.; Kim, C. O.; Hong, J. P.; Han, S. K.; Char, K.

2002-07-01

Highly selective high-temperature superconducting band-pass filters based on spiral meander line structures have been developed for base transceiver station applications of digital cellular communication systems. The filter comprised 12-pole microstrip line resonators with a circuit size of 0.5 × 17 × 41 mm3. The filter was designed to have a bandwidth of 25 MHz at a centre frequency of 834 MHz. Particularly, the physical size of each resonator was chosen not only to reduce far-field radiation, but also to have reasonable tunability in the filter. Device characteristics exhibited a low insertion loss of 0.4 dB with a 0.2 dB ripple and a return loss better than 10 dB in the pass-band at 65 K. The out-of-band signals were attenuated better than 60 dB at about 3.5 MHz from the lower band edge, and 3.8 MHz from the higher band edge.

Morphologies of omega band auroras

NASA Astrophysics Data System (ADS)

Sato, Natsuo; Yukimatu, Akira Sessai; Tanaka, Yoshimasa; Hori, Tomoaki

2017-08-01

We examined the morphological signatures of 315 omega band aurora events observed using the Time History of Events and Macroscale Interactions during Substorm ground-based all-sky imager network over a period of 8 years. We find that omega bands can be classified into the following three subtypes: (1) classical (O-type) omega bands, (2) torch or tongue (T-type) omega bands, and (3) combinations of classical and torch or tongue (O/T-type) omega bands. The statistical results show that T-type bands occur the most frequently (45%), followed by O/T-type bands (35%) and O-type bands (18%). We also examined the morphologies of the omega bands during their formation, from the growth period to the declining period through the maximum period. Interestingly, the omega bands are not stable, but rather exhibit dynamic changes in shape, intensity, and motion. They grow from small-scale bumps (seeds) at the poleward boundary of preexisting east-west-aligned auroras, rather than via the rotation or shear motion of preexisting east-west-aligned auroras, and do not exhibit any shear motion during the periods of auroral activity growth. Furthermore, the auroral luminosity is observed to increase during the declining period, and the total time from the start of the growth period to the end of the declining period is found to be about 20 min. Such dynamical signatures may be important in determining the mechanism responsible for omega band formation.

The Mass-Luminosity Relation in the L/T Transition: Individual Dynamical Masses for the New J-band Flux Reversal Binary SDSSJ105213.51+442255.7AB

NASA Astrophysics Data System (ADS)

Dupuy, Trent J.; Liu, Michael C.; Leggett, S. K.; Ireland, Michael J.; Chiu, Kuenley; Golimowski, David A.

2015-05-01

We have discovered that SDSS J105213.51+442255.7 (T0.5 ± 1.0) is a binary in Keck laser guide star adaptive optics imaging, displaying a large J- to K-band flux reversal ({Δ }J=-0.45+/- 0.09 mag, {Δ }K=0.52+/- 0.05 mag). We determine a total dynamical mass from Keck orbital monitoring (88 ± 5 {{M}Jup}) and a mass ratio by measuring the photocenter orbit from CFHT/WIRCam absolute astrometry ({{M}B}/{{M}A}=0.78+/- 0.07). Combining these provides the first individual dynamical masses for any field L or T dwarfs, 49 ± 3 {{M}Jup} for the L6.5±1.5 primary and 39 ± 3 {{M}Jup} for the T1.5±1.0 secondary. Such a low mass ratio for a nearly equal luminosity binary implies a shallow mass-luminosity relation over the L/T transition ({Δ }log {{L}bol}/{Δ }log M=0.6-0.8+0.6). This provides the first observational support that cloud dispersal plays a significant role in the luminosity evolution of substellar objects. Fully cloudy models fail our coevality test for this binary, giving ages for the two components that disagree by 0.2 dex (2.0σ). In contrast, our observed masses and luminosities can be reproduced at a single age by “hybrid” evolutionary tracks where a smooth change from a cloudy to cloudless photosphere around 1300 K causes slowing of luminosity evolution. Remarkably, such models also match our observed JHK flux ratios and colors well. Overall, it seems that the distinguishing features SDSS J1052+4422AB, like a J-band flux reversal and high-amplitude variability, are normal for a field L/T binary caught during the process of cloud dispersal, given that the age (1.11-0.20+0.17 Gyr) and surface gravity (log g = 5.0-5.2) of SDSS J1052+4422AB are typical for field ultracool dwarfs. Based on data obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, at the Canada-France-Hawaii Telescope, which is operated by the National Research Council of Canada, the Institute National des Sciences de l’Univers of the Centre National de la

Bands dispersion and charge transfer in β-BeH2

NASA Astrophysics Data System (ADS)

Trivedi, D. K.; Galav, K. L.; Joshi, K. B.

2018-04-01

Predictive capabilities of ab-initio method are utilised to explore bands dispersion and charge transfer in β-BeH2. Investigations are carried out using the linear combination of atomic orbitals method at the level of density functional theory. The crystal structure and related parameters are settled by coupling total energy calculations with the Murnaghan equation of state. Electronic bands dispersion from PBE-GGA is reported. The PBE-GGA, and PBE0 hybrid functional, show that β-BeH2 is a direct gap semiconductor with 1.18 and 2.40 eV band gap. The band gap slowly decreases with pressure and beyond l00 GPa overlap of conduction and valence bands at the r point is observed. Charge transfer is studied by means of Mullikan population analysis.

A novel design of optical CDMA system based on TCM and FFH

NASA Astrophysics Data System (ADS)

Fang, Jun-Bin; Xu, Zhi-Hai; Huang, Hong-bin; Zheng, Liming; Chen, Shun-er; Liu, Wei-ping

2005-02-01

For the application in Passive Optical Network (PON), a novel design of OCDMA system scheme is proposed in this paper. There are two key components included in this scheme: a new kind of OCDMA encoder/decoder system based on TCM and FFH and an improved Optical Line Terminal (OLT) receiving system with improved anti-interference performance by the use of Long Period Fiber Grating (LPFG). In the encoder/decoder system, Trellis Coded Modulation (TCM) encoder is applied in front of the FFH modulator. Original signal firstly is encoded through TCM encoder, and then the redundant code out of the TCM encoder will be mapped into one of the FFH modulation signal subsets for transmission. On the receiver (decoder) side, transmitting signal is demodulated through FFH and decoded by trellis decoder. Owing to the fact that high coding gain can be acquired by TCM without adding transmitting band and reducing transmitting speed, TCM is utilized to ameliorate bit error performance and reduce multi-user interference. In the OLT receiving system, EDFA and LPFG are placed in front of decoder to get excellent gain flatness on a large bandwidth, and Optical Hard Limiter (OHL) is also deployed to improve detection performance, through which the anti-interference performance of receiving system can be greatly enhanced. At the same time, some software is used to simulate the system performance for further analysis and authentication. The related work in this paper provides a valuable reference to the research.

3D-Subspace-Based Auto-Paired Azimuth Angle, Elevation Angle, and Range Estimation for 24G FMCW Radar with an L-Shaped Array

PubMed Central

Nam, HyungSoo; Choi, ByungGil; Oh, Daegun

2018-01-01

In this paper, a three-dimensional (3D)-subspace-based azimuth angle, elevation angle, and range estimation method with auto-pairing is proposed for frequency-modulated continuous waveform (FMCW) radar with an L-shaped array. The proposed method is designed to exploit the 3D shift-invariant structure of the stacked Hankel snapshot matrix for auto-paired azimuth angle, elevation angle, and range estimation. The effectiveness of the proposed method is verified through a variety of experiments conducted in a chamber. For the realization of the proposed method, K-band FMCW radar is implemented with an L-shaped antenna. PMID:29621193

Beam Dynamics a Integrated Plane Wave Transformer Photoinjector at S- and X- band

NASA Astrophysics Data System (ADS)

Rosenzweig, J. B.; Ding, X.; Pellegrini, X.; Serafini, L.; Yu, D.

1997-05-01

The beam dynamics of an integrated S-band rf photoinjector based on the plane wave transformer concept, proposed as part of an SBIR collaboration between UCLA and DULY Research, are studied. The intial design, which calls for an 11.5 cell structure run at a peak on-axis accelerating field of 60 MV/m, and has a compact solenoid around the intial 2.5 cells, is based on the recently developed theory of emittance compensation(L.Serafini, and J.B. Rosenzweig, submitted to Physical Review E.). It calls for matching the beam onto an envelope which is a generalized Brillouin flow, producing a beam which diminishes in transverse size as the square root of the accelerating beam energy. This condition produces a minimized emittance, which for the S-band case is 1 mm-rad at at charge of 1 nC. This design is also scaled to produce nearly identical performance at X-band, giving an injector appropriate to running an FEL at the SLAC NLCTA. It is noted that these designs are insensitive to rf emittance increase, allowign a choice of injection phase, and the option to compress the emitted pulse.

Band excitation method applicable to scanning probe microscopy

DOEpatents

Jesse, Stephen; Kalinin, Sergei V.

2015-08-04

Scanning probe microscopy may include a method for generating a band excitation (BE) signal and simultaneously exciting a probe at a plurality of frequencies within a predetermined frequency band based on the excitation signal. A response of the probe is measured across a subset of frequencies of the predetermined frequency band and the excitation signal is adjusted based on the measured response.

Band excitation method applicable to scanning probe microscopy

DOEpatents

Jesse, Stephen; Kalinin, Sergei V.

2017-01-03

Scanning probe microscopy may include a method for generating a band excitation (BE) signal and simultaneously exciting a probe at a plurality of frequencies within a predetermined frequency band based on the excitation signal. A response of the probe is measured across a subset of frequencies of the predetermined frequency band and the excitation signal is adjusted based on the measured response.

Time-Dependent Response Versus Scan Angle for MODIS Reflective Solar Bands

NASA Technical Reports Server (NTRS)

Sun, Junqiang; Xiong, Xiaoxiong; Angal, Amit; Chen, Hongda; Wu, Aisheng; Geng, Xu

2014-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments currently operate onboard the National Aeronautics and Space Administration (NASA's) Terra and Aqua spacecraft, launched on December 18, 1999 and May 4, 2002, respectively. MODIS has 36 spectral bands, among which 20 are reflective solar bands (RSBs) covering a spectral range from 0.412 to 2.13 µm. The RSBs are calibrated on orbit using a solar diffuser (SD) and an SD stability monitor and with additional measurements from lunar observations via a space view (SV) port. Selected pseudo-invariant desert sites are also used to track the RSB on-orbit gain change, particularly for short-wavelength bands. MODIS views the Earth surface, SV, and the onboard calibrators using a two-sided scan mirror. The response versus scan angle (RVS) of the scan mirror was characterized prior to launch, and its changes are tracked using observations made at different angles of incidence from onboard SD, lunar, and Earth view (EV) measurements. These observations show that the optical properties of the scan mirror have experienced large wavelength-dependent degradation in both the visible and near infrared spectral regions. Algorithms have been developed to track the on-orbit RVS change using the calibrators and the selected desert sites. These algorithms have been applied to both Terra and Aqua MODIS Level 1B (L1B) to improve the EV data accuracy since L1B Collection 4, refined in Collection 5, and further improved in the latest Collection 6 (C6). In C6, two approaches have been used to derive the time-dependent RVS for MODIS RSB. The first approach relies on data collected from sensor onboard calibrators and mirror side ratios from EV observations. The second approach uses onboard calibrators and EV response trending from selected desert sites. This approach is mainly used for the bands with much larger changes in their time-dependent RVS, such as the Terra MODIS bands 1-4, 8, and 9 and the Aqua MODIS bands 8- and 9

Pringle's Maneuver With a Releasable Insulok Band.

PubMed

Chang, Yu-Chung

2015-10-01

Currently, there are many conventional instruments being applied to perform hepatic inflow control, the Pringle's maneuver, distal to the hepatic hilum during hepatic resections. We wondered if a commonly used Insulok band can be added. Insulok band is a plastic tying device molded in one piece with an excellent cam-lock mechanism. We have applied releasable Insulok band to the Pringle's maneuver in 10 partial hepatectomy cases, which are not suitable for application of Chang's needle. After opening the lesser omentum, the band was passed through the Winslow foramen to the lesser sac, and the portal triad was occluded by locking the band. During the intermittent reperfusion period, this Insulok band allowed easy and fast control of hepatic inflow with its simple releasable locking device. Single inflow block was used on 6 cases while repeated block on 4 cases for partial hepatectomy. The average ischemic time was 15.2 ± 8.2 minutes with an interval of 5 minutes. There was neither procedure-related morbidity nor mortality. No patient had developed postoperative hepatic failure or prolonged liver dysfunction. The efficacy of bleeding control was excellent and the average blood loss during Pringle's maneuver was 6 ± 12.6 mL. Furthermore, locking and unlocking of the Insulok band each took only 5 seconds. Releasable Insulok band is a simpler, faster, cheaper, and safe alternative to the conventional methods for blocking hepatic inflow in Pringle's maneuver, especially in those cases not suitable for using the Chang's needle. © The Author(s) 2014.

A low-power current-reuse dual-band analog front-end for multi-channel neural signal recording.

PubMed

Sepehrian, H; Gosselin, B

2014-01-01

Thoroughly studying the brain activity of freely moving subjects requires miniature data acquisition systems to measure and wirelessly transmit neural signals in real time. In this application, it is mandatory to simultaneously record the bioelectrical activity of a large number of neurons to gain a better knowledge of brain functions. However, due to limitations in transferring the entire raw data to a remote base station, employing dedicated data reduction techniques to extract the relevant part of neural signals is critical to decrease the amount of data to transfer. In this work, we present a new dual-band neural amplifier to separate the neuronal spike signals (SPK) and the local field potential (LFP) simultaneously in the analog domain, immediately after the pre-amplification stage. By separating these two bands right after the pre-amplification stage, it is possible to process LFP and SPK separately. As a result, the required dynamic range of the entire channel, which is determined by the signal-to-noise ratio of the SPK signal of larger bandwidth, can be relaxed. In this design, a new current-reuse low-power low-noise amplifier and a new dual-band filter that separates SPK and LFP while saving capacitors and pseudo resistors. A four-channel dual-band (SPK, LFP) analog front-end capable of simultaneously separating SPK and LFP is implemented in a TSMC 0.18 μm technology. Simulation results present a total power consumption per channel of 3.1 μw for an input referred noise of 3.28 μV and a NEF for 2.07. The cutoff frequency of the LFP band is fc=280 Hz, and fL=725 Hz and fL=11.2 KHz for SPK, with 36 dB gain for LFP band 46 dB gain for SPK band.

47 CFR 15.713 - TV bands database.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false TV bands database. 15.713 Section 15.713... TV bands database. (a) Purpose. The TV bands database serves the following functions: (1) To... channels are determined based on the interference protection requirements in § 15.712. A database must...

47 CFR 15.713 - TV bands database.

Code of Federal Regulations, 2012 CFR