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1

The Glacier and Ice Surface Topography Interferometer: UAVSAR's Single-pass Ka-Band Interferometer  

NASA Astrophysics Data System (ADS)

In May 2009 a new radar technique for mapping ice surface topography was demonstrated in a Greenland campaign as part of the NASA International Polar Year (IPY) activities. This was achieved with the airborne Glacier and Ice Surface Topography Interferometer (GLISTIN-A): a 35.6 GHz single-pass interferometer. Although the technique of using radar interferometry for mapping terrain has been demonstrated before, this is the first such application at millimeter-wave frequencies. The proof-of-concept demonstration was achieved by interfacing Ka-band RF and antenna hardware with the Uninhabited Airborne Vehicle Synthetic Aperture Radar (UAVSAR). The GLISTIN-A was implemented as a custom installation of the NASA Dryden Flight Research Center Gulfstream III. Instrument performance indicates swath widths over the ice between 5-7km, with height precisions ranging from 30cm-3m at a posting of 3m x 3m. Processing challenges were encountered in achieving the accuracy requirements on several fronts including, aircraft motion sensitivity, multipath and systematic drifts. However, through a combination of processor optimization, a modified phase-screen and motion-compensation implementations were able to minimize the impact of these systematic error sources. We will present results from the IPY data collections including system performance evaluations and imagery. This includes a large area digital elevation model (DEM) collected over Jakobshavn glacier as an illustrative science data product. Further, by intercomparison with the NASA Wallops Airborne Topographic Mapper (ATM) and calibration targets we quantify the interferometric penetration bias of the Ka-band returns into the snow cover. Following the success of the IPY campaign, we are funded under the Earth Science Techonology Office (ESTO) Airborne Innovative Technology Transition (AITT) program to transition GLISTIN-A to a permanently-available pod-only system compatible with unpressurized operation. In addition fundamental system upgrades will greatly enhance the performance and make wider-swath and higher altitude operation possible. We will show results from first flights of GLISTIN-A and summarize the plans for the near future including GLISTIN-H: GLISTIN on the NASA Global Hawk Spring 2013.

Moller, D.; Hensley, S.; Sadowy, G.; Wu, X.; Carswell, J.; Fisher, C.; Michel, T.; Lou, Y.

2012-12-01

2

The Glacier and Ice Surface Topography Interferometer: UAVSAR's Single-pass Ka-Band Interferometer  

NASA Astrophysics Data System (ADS)

In May 2009 a new radar technique for mapping ice surface topography was demonstrated in a Greenland campaign as part of the NASA International Polar Year (IPY) activities. This was achieved with the airborne Glacier and Ice Surface Topography Interferometer (GLISTIN-A): a 35.6 GHz single-pass interferometer. The proof-of-concept demonstration was achieved by interfacing Ka-band RF and antenna hardware with the Uninhabited Airborne Vehicle Synthetic Aperture Radar (UAVSAR). The GLISTIN-A was implemented as a custom installation of the NASA Dryden Flight Research Center Gulfstream III. Instrument performance indicated swath widths over the ice between 5-7km, with height precisions ranging from 30cm-3m at a posting of 3m x 3m. Following the success of the IPY campaign, the Earth Science Techonology Office (ESTO) Airborne Innovative Technology Transition (AITT) program funded the upgrade of GLISTIN-A to a permanently-available pod-only system compatible with unpressurized operation. The AITT made three fundamental upgrades to improve system performance: 1. State-of-the-art solid-state power amplifiers (80W peak) were integrated directly on the antenna panel reducing front-end losses; 2. A ping-pong capability was incorporated to effectively double the baseline thereby improving height measurement precision by a factor of two; and 3. A high-fidelity calibration loop was implemented which is critical for routine processing. Upon completion of our engineering flights in February 2013, GLISTIN-A flew a brief campaign to Alaska (4/24-4/27/13). The purpose was to fully demonstrate GLISTIN-A's ability to generate high-precision, high resolution maps of ice surface topography with swaths in excess of 10km. Furthermore, the question of the utility of GLISTIN-A for sea-ice mapping, tracking and inventory has received a great deal of interest. To address this GLISTIN-A collected data over sea-ice in the Beaufort sea including an underflight of CryoSAT II. Note that there are ongoing activities to stage GLISTIN on the Global Hawk (GLISTIN-H) for which sea ice-mapping is a primary driver. Analysis of the data will focus on assessment of performance and interpretation over ice to include: 1. intercomparison of GLISTIN-A glacier height maps with lidar data and heritage SRTM DEM's for performance validation of GLISTIN-A over ice, 2. quantitative evaluation of mass change over the Columbia glacier via repeat observations made by GLISTIN-A with a 3 day separation, 3. assessment of GLISTIN-A's ability map sea ice extent, dynamics and possibly to measure freeboard.

Moller, D.; Hensley, S.; Wu, X.; Michel, T.; Muellerschoen, R.; Carswell, J.; Fisher, C.; Miller, T.; Milligan, L.; Sadowy, G.; Sanchez-Barbetty, M.; Lou, Y.

2013-12-01

3

Information content of a single pass of phase-delay data from a short baseline connected element interferometer  

NASA Technical Reports Server (NTRS)

An analytic development of the information array obtained with a single tracking pass of phase-delay measurements made from a short baseline interferometer is presented. Phase-delay observations can be made with great precision from two antennas using a single, common distributed frequency standard, hence the name connected element. With the information array, closed-form expressions are developed for the error covariance in declination and right ascension. These equations serve as useful tools for analyzing the relative merits of candidate station locations for connected element interferometry (CEI). The navigation performance of a short baseline interferometer located at the Deep Space Network's (DSN's) Goldstone intracomplex is compared with that which is presently achievable using Very Long Baseline Interferometry (VLBI) over intercontinental baselines. The performance of an intracomplex pair of short baselines formed by three stations is also investigated, along with the use of a single baseline in conjunction with conventional two-way Doppler data. The phase-delay measurement accuracy and data rate used in the analysis are based on the expected performance of an experimental connected element system presently under construction at Goldstone. The results indicate that the VLBI system that will be used during the Galileo mission can determine the declination and right ascension of a distant spacecraft to an accuracy of 20 to 25 nrad, while the CEI triad system and the combination of CEI-Doppler system are both capable of 30 to 70 nrad performance.

Thurman, S. W.

1990-01-01

4

Echo source discrimination in single-pass airborne radar sounding data from the Dry Valleys, Antarctica: Implications for orbital sounding of Mars  

Microsoft Academic Search

The interpretation of radar sounding data from Mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface. This can be accomplished through the identification of all radar returns from the surface in order to positively identify subsurface echoes. We have developed general techniques for this using airborne

John W. Holt; Matthew E. Peters; Scott D. Kempf; David L. Morse; Donald D. Blankenship

2006-01-01

5

Dilution in single pass arc welds  

Microsoft Academic Search

A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon\\u000a steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged are welding\\u000a (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to

J. N. DuPont; A. R. Marder

1996-01-01

6

Observational evidence of high-altitude meteor trail from radar interferometer  

NASA Astrophysics Data System (ADS)

radar meteor echoes occur at high altitudes (above ~130 km) in the Earth's atmosphere is a long-standing question within the meteor radar community. Using observations from the Sanya VHF coherent radar interferometer during 11 July to 10 August 2013, we have found a new class of range-spread high-altitude meteor trail echoes (HAMEs), some of which appeared at ~170 km altitude lasting more than 10 s. A statistical analysis on the local time dependence of the identified HAME events shows a maximum around 00-04 LT. The results imply that there could be much more meteor mass input due to meteoroid sputtering at high altitudes in the Earth's atmosphere than previously thought.

Li, Guozhu; Ning, Baiqi; Wan, Weixing; Reid, I. M.; Hu, Lianhuan; Yue, Xinan; Younger, J. P.; Dolman, B. K.

2014-10-01

7

Dilution in single pass arc welds  

SciTech Connect

A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

DuPont, J.N.; Marder, A.R. [Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering

1996-06-01

8

Single Pass Streaming BLAST on FPGAs*†  

PubMed Central

Approximate string matching is fundamental to bioinformatics and has been the subject of numerous FPGA acceleration studies. We address issues with respect to FPGA implementations of both BLAST- and dynamic-programming- (DP) based methods. Our primary contribution is a new algorithm for emulating the seeding and extension phases of BLAST. This operates in a single pass through a database at streaming rate, and with no preprocessing other than loading the query string. Moreover, it emulates parameters turned to maximum possible sensitivity with no slowdown. While current DP-based methods also operate at streaming rate, generating results can be cumbersome. We address this with a new structure for data extraction. We present results from several implementations showing order of magnitude acceleration over serial reference code. A simple extension assures compatibility with NCBI BLAST. PMID:19081828

Herbordt, Martin C.; Model, Josh; Sukhwani, Bharat; Gu, Yongfeng; VanCourt, Tom

2008-01-01

9

Onboard Interferometric SAR Processor for the Ka-Band Radar Interferometer (KaRIn)  

NASA Technical Reports Server (NTRS)

An interferometric synthetic aperture radar (SAR) onboard processor concept and algorithm has been developed for the Ka-band radar interferometer (KaRIn) instrument on the Surface and Ocean Topography (SWOT) mission. This is a mission- critical subsystem that will perform interferometric SAR processing and multi-look averaging over the oceans to decrease the data rate by three orders of magnitude, and therefore enable the downlink of the radar data to the ground. The onboard processor performs demodulation, range compression, coregistration, and re-sampling, and forms nine azimuth squinted beams. For each of them, an interferogram is generated, including common-band spectral filtering to improve correlation, followed by averaging to the final 1 1-km ground resolution pixel. The onboard processor has been prototyped on a custom FPGA-based cPCI board, which will be part of the radar s digital subsystem. The level of complexity of this technology, dictated by the implementation of interferometric SAR processing at high resolution, the extremely tight level of accuracy required, and its implementation on FPGAs are unprecedented at the time of this reporting for an onboard processor for flight applications.

Esteban-Fernandez, Daniel; Rodriquez, Ernesto; Peral, Eva; Clark, Duane I.; Wu, Xiaoqing

2011-01-01

10

Terrestrial Radar Interferometer Observations of a Rapid Landslide Over Vegetated Terrain  

NASA Astrophysics Data System (ADS)

In the Spring of 2013 a landslide in the Hintergraben region of canton Obwalden in Switzerland showed a rapid increase in velocity. Hintergraben, at an elevation of about 900 meters is characterized by meadow and some trees. A region approximately 200 meters wide and 500 meters long was affected. Starting in February, the velocity increased to 30 cm/day by 1-May and continued to accelerate by deceleration to 8 cm/day by 27-May. We report on observations of this landslide using the Gamma Portable Radar Interferometer (GPRI). The GPRI is an FM-CW radar operating at 17.2 GHz (Ku-Band) with an operational range up to 10 km. Range resolution is 90 cm along the LOS. The instrument operates in real-aperture mode with 0.4 degree wide fan-beam giving an azimuth resolution better than 7 meters at 1 kilometer range. During data acquisition, the radar performed an azimuth scan of the scene at a rate of 5 degrees/sec. The radar is phase coherent and capable of acquiring data suitable for differential interferometry with a precision for measuring changes in the LOS distance > 0.1 mm. Limiting factors in the accuracy of LOS motion are interferometric phase coherence and variations in delay due to water vapor. The GPRI was deployed to map ground motion for 2 campaigns on 6 May and 26-27 May 2013. The radar position over 3.5 km from the landslide on the opposite side of Lake Sarnen. Due to rapid temporal decorrelation at Ku-Band data, acquisitions were made at 1 minute intervals. The GPRI deformation maps cover almost the entire region of the active landslide during both observation periods of 6 hours on 6 May and 9 hours on 26-27 May. Measured peak velocities were 35 and 8 cm/day respectively. Point-wise verification of the radar observations was carried out using a Leica TCR803 total station with an estimated accuracy of 1/2 mm at 3.5 km distance. A set of optical corner cubes and radar reflectors were set up in the region of the landslide on 26-May. The radar deformation measurements are within 1/2 mm of the values derived using the total station. Operating the GPRI with 1 minute intervals between successive scans permitted making accurate maps of deformation with millimeter level accuracy over meadow and permitted reconstruction of complete deformation time series. Hitergraben deformation map measured with the GPRI for 6-May 2013. Contours are in cm/day along the LOS.

Werner, C. L.; Caduff, R.; Strozzi, T.; Wegmüller, U.

2013-12-01

11

The Single Pass Multi-component Harvester  

SciTech Connect

The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2004. Title of Presentation. ASAE Paper No. 04xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at hq@asae.org or 269-429-0300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA). Abstract. In order to meet the U. S. government’s goal of supplementing the energy available from petroleum by increasing the production of energy from renewable resources, increased production of bioenergy has become one of the new goals of the United States government and our society. U.S. Executive Orders and new Federal Legislation have mandated changes in government procedures and caused reorganizations within the government to support these goals. The Biomass Research and Development Initiative is a multi-agency effort to coordinate and accelerate all U.S. Federal biobased products and bioenergy research and development. The Initiative is managed by the National Biomass Coordination Office, which is staffed by both the DOE and the USDA. One of the most readily available sources of biomass from which to produce bioenergy is an agricultural crop residue, of which straw from small grains is the most feasible residue with which to start. For the straw residue to be used its collection must be energy efficient and its removal must not impact the sustainability of the growing environment. In addition, its collection must be economically advantageous to the producer. To do all that, a single pass multi-component harvester system is most desirable. Results from our first prototype suggest that current combines probably do adequate threshing and that a separate chassis can be developed that does additional separation and that is economically feasible.

Reed Hoskinson; John R. Hess

2004-08-01

12

Ocean wave imaging using an airborne single pass across-track interferometric SAR  

Microsoft Academic Search

An airborne single pass across-track interferometric synthetic aperture radar (InSAR) is used to image ocean waves. A theoretical model explaining the imaging mechanisms is developed, and simulations of the interferogram as well as the conventional SAR intensity image are presented for given ocean wave spectra. Distortions of digital elevation models (DEM) derived from InSAR data are explained by the motion

Johannes Schulz-Stellenfleth; Susanne Lehner

2001-01-01

13

Interferometer Interferometer  

E-print Network

by NASA as engineering testbed for Keck . Specifically designed with dual star mode for narrow�phased. #12; SPIEMarch 23, 1998 Palomar Testbed Interferometer JKW�15 Constant�TermMetrology . Measures difference in optical path between the two arms for each beam combiner -- difference in metrology measurments

14

Thermal efficiency of single-pass solar air collector  

SciTech Connect

Efficiency of a finned single-pass solar air collector was studied. This paper presents the experimental study to investigate the effect of solar radiation and mass flow rate on efficiency. The fins attached at the back of absorbing plate to improve the thermal efficiency of the system. The results show that the efficiency is increased proportional to solar radiation and mass flow rate. Efficiency of the collector archived steady state when reach to certain value or can be said the maximum performance.

Ibrahim, Zamry; Ibarahim, Zahari; Yatim, Baharudin [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan (Malaysia); Ruslan, Mohd Hafidz [Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan (Malaysia)

2013-11-27

15

Brackish water desalination in RO–single pass EDR system  

Microsoft Academic Search

Electrodialysis reversal (EDR) treatment of inland brackish water reverse osmosis concentrate was examined. The resistance to CaSO4 and CaCO3 scaling in our single-pass and low residence time EDR is better than in the one that was originally developed by Ionics. Our approach is as follows. The RO concentrate of CaSO4 and CaCO3 content being close to the saturation level (or

Marian Turek; Piotr Dydo

2009-01-01

16

The Single Pass RF Driver: Final beam compression  

NASA Astrophysics Data System (ADS)

The Single Pass RF Driver (SPRFD) compacts the beam from the linac without storage rings by manipulations that take advantage of the multiplicity of isotopes (16), the preserved µbunch structure, and increased total linac current. Magnetic switches on a first set of delay lines rearrange the internal structure of the various isotopic beams. A second set of delay lines sets the relative timing of the 16 isotopic beam sections so they will telescope at the pellet, in one of multiple fusion chambers, e.g. 10.

Burke, Robert

2014-01-01

17

Comparison of medium frequency pulsed radar interferometer and correlation analysis winds, part 1  

NASA Technical Reports Server (NTRS)

In principle, the interferometer analysis determines the radial velocity and direction of single scatterers provided that each has a sufficiently different Doppler frequency to permit separation by spectral analysis. In fact, scatterers will not have constant radial velocity, and their Doppler frequencies as well as their directions will be modulated by their horizontal motion. Thus, there is a tradeoff between the poorer resolution but less smeared scatterers on shorter records and the higher resolution (longer) records. Three or more non-collinear scatterers are sufficient to determine the wind. It appears that the velocity found from the combined interferometer peaks agrees well with the apparent velocity from correlation methods, but the true velocity is a factor of 2 smaller. This difference might be resolved by searching for scatters showing regular movement between adjacent records.

Meek, C. E.; Reid, I. M.; Manson, A. H.

1986-01-01

18

Nonlinear Effects in Single-Pass ICRF Heating  

NASA Technical Reports Server (NTRS)

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept employs Ion Cyclotron Resonant Frequency (ICRF) heating as the main power deposition mechanism. Since the ions accelerate to the full energy in a single pass through the cyclotron resonance, their response to the RF-field will be essentially nonlinear - hence the motivation to amend the commonly used linear approach to the problem. In a collisionless plasma, the energy gain of an accelerated ion is limited by the time the particle spends at the resonance. This time is affected by: (1) incident flow velocity, (2) longitudinal grad B force, (3) ambipolar electric field, and (4) ponderomotive force of the RF-field. Our analysis shows that the grad B force is the dominant factor at low to moderate levels of RF-power. We present nonlinear scaling for the energy gain and the absorption efficiency with RF-power and plasma parameters. We also demonstrate that the nonlinear regime exhibits a steep decrease in the plasma density at the resonance.

Arefiev, A. V.; Breizman, B. N.

1999-01-01

19

Nonlinear Effects in Single-Pass ICRF Heating  

NASA Astrophysics Data System (ADS)

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept employs Ion Cyclotron Resonant Frequency (ICRF) heating as the main power deposition mechanism. Since the ions accelerate to the full energy in a single pass through the cyclotron resonance, their response to the RF-field will be essentially nonlinear - hence the motivation to amend the commonly used linear approach to the problem. In a collisionless plasma, the energy gain of an accelerated ion is limited by the time the particle spends at the resonance. This time is affected by: 1) incident flow velocity, 2) longitudinal grad B force, 3) ambipolar electric field, and 4) ponderomotive force of the RF-field. Our analysis shows that the grad B force is the dominant factor at low to moderate levels of RF-power. We present nonlinear scaling for the energy gain and the absorption efficiency with RF-power and plasma parameters. We also demonstrate that the nonlinear regime exhibits a steep decrease in the plasma density at the resonance.

Arefiev, A. V.; Breizman, B. N.

1999-11-01

20

SHORT-WAVELENGTH, SINGLE-PASS FREE-ELECTRON LASERS J. Rossbach, DESY, 22603 Hamburg, Germany  

E-print Network

SHORT-WAVELENGTH, SINGLE-PASS FREE-ELECTRON LASERS J. Rossbach, DESY, 22603 Hamburg, Germany in demonstration of high power gain at single- pass free-electron lasers operating in the wavelength range from in the undulator. Eq. (1) exhibits two main advantages of the free-electron laser: the free tunability

21

Simultaneously phase-matched parametric processes in a single-pass interaction for efficient visible generation  

NASA Astrophysics Data System (ADS)

We demonstrate simultaneously phase-matched cascaded optical parametric amplification (OPA) and sum-frequency generation (SFG) processes in a single-pass interaction in a BBO crystal, where the seed pulse is produced through the self-induced superfluorescence generation. Tunable femtosecond pulses in the blue-green spectral range are produced through the single-pass SFG interaction with a maximum conversion efficiency of about 12%.

Zhang, Xinping; Men, Yanbin; Wang, Li

2010-08-01

22

Practical aspects of single-pass scan Kelvin probe force microscopy  

NASA Astrophysics Data System (ADS)

The single-pass scan Kelvin probe force microscopy (KPFM) in ambient condition has a few advantages over the dual-pass lift-up scan KPFM. For example, its spatial resolution is expected to be higher; and its topographical errors caused by electrostatic forces are minimized because electrostatic forces are actively suppressed during the simultaneous topographical and KPFM measurement. Because single-pass scan KPFM in ambient condition is relatively new, it received little attention in the literature so far. In this article, we discuss several major practical aspects of single-pass scan KPFM especially in ambient condition. First, we define the resolution using a point spread function. With this definition, we analyze the relation between the resolution and the scanning parameters such as tip apex radius and tip-surface distance. We further study the accuracy of KPFM based on the point spread function. Then, we analyze the sensitivity of KPFM under different operation modes. Finally, we investigate the crosstalk between the topographical image and the surface potential image and demonstrate the practical ways to minimize the crosstalk. These discussions not only help us to understand the single-pass scan KPFM but also provide practical guidance in using single-pass scan KPFM.

Li, Guangyong; Mao, Bin; Lan, Fei; Liu, Liming

2012-11-01

23

Combining Cluster Sampling with Single Pass Methods for Efficient Sampling Regimen Design  

E-print Network

Combining Cluster Sampling with Single Pass Methods for Efficient Sampling Regimen Design Paul D sampling and non-sampling biases. Researchers have devised clever methods for effectively reducing non-sampling regimen design is proposed. Using this method, thousands of sampling regimen candidates can

Conte, Thomas M.

24

Single-pass high-gain free electron laser electron beam diagnostics  

NASA Astrophysics Data System (ADS)

Consensus reached in the last few years that fourth generation light source will most likely be a X-ray or a UV coherent source based on single-pass high-gain free electron laser (FEL), such as Self Amplified Spontaneous Emission (SASE), or seeded high-gain harmonic-generation (HGHG) free electron lasers. High-gain (>107) required for single-pass FEL puts great constrain on the quality of electron beam, and demands detailed distribution information of electron beam in six-dimension. The typical accelerator system for single-pass FEL consists of a photocathode RF gun injection system, a linac and magnetic bunch compressors, and a long undulator. The major challenges in beam diagnostics for single-pass FEL are to characterize the pico-seconds high-brightness electron beam in six-dimension produced by photocathode RF gun injector, and improve the stability and reliability of the photocathode RF gun injection system. Characterization of short electron bunch (˜100 fs) produced by the compressors, and co-align the electron beam with FEL radiation inside long undulator are also critical for FEL performance. We will discuss many diagnostic techniques developed at the Brookhaven Accelerator Test Facility (ATF) for the photocathode RF gun injection system, present several techniques for femto-seconds bunch length measurement, especially RF kicker cavity. Tomography technique for both transverse and longitudinal phase space measurements is discussed. Concept of multiple alignment-laser stations is present for beam alignment in the long undulator.

Wang, X. J.

2000-11-01

25

Evaluating single-pass catch as a tool for identifying spatial pattern in fish distribution  

USGS Publications Warehouse

We evaluate the efficacy of single-pass electrofishing without blocknets as a tool for collecting spatially continuous fish distribution data in headwater streams. We compare spatial patterns in abundance, sampling effort, and length-frequency distributions from single-pass sampling of coastal cutthroat trout (Oncorhynchus clarki clarki) to data obtained from a more precise multiple-pass removal electrofishing method in two mid-sized (500-1000 ha) forested watersheds in western Oregon. Abundance estimates from single- and multiple-pass removal electrofishing were positively correlated in both watersheds, r = 0.99 and 0.86. There were no significant trends in capture probabilities at the watershed scale (P > 0.05). Moreover, among-sample variation in fish abundance was higher than within-sample error in both streams indicating that increased precision of unit-scale abundance estimates would provide less information on patterns of abundance than increasing the fraction of habitat units sampled. In the two watersheds, respectively, single-pass electrofishing captured 78 and 74% of the estimated population of cutthroat trout with 7 and 10% of the effort. At the scale of intermediate-sized watersheds, single-pass electrofishing exhibited a sufficient level of precision to be effective in detecting spatial patterns of cutthroat trout abundance and may be a useful tool for providing the context for investigating fish-habitat relationships at multiple scales.

Bateman, D.S.; Gresswell, R.E.; Torgersen, C.E.

2005-01-01

26

Observations of ice motion changes at the terminus of Hubbard Glacier using co-located ground-based radar interferometer and LiDAR scanning systems (Invited)  

NASA Astrophysics Data System (ADS)

The tidewater terminus of Hubbard Glacier extends into Disenchantment Bay and currently blocks most of the mouth of Russell Fjord. Recent advances of Hubbard Glacier (1986 and 2002) caused the damming of Russell Fjord, creating one of the largest glacier-dammed lakes on the continent and exposing the community of Yakutat to a host of potential hazards. Detailed observations of the terminus of Hubbard Glacier were conducted during a field campaign in May 2013. Ground-based radar interferometer (GBRI) and ground-based light detection and ranging (LiDAR) scanning systems were deployed to observe changes in ice motion in response to calving events and tidal cycles. GBRI and LiDAR units were co-located and data acquisition was synchronized to maximize data recovery and to aid inter-system comparisons. Observations from ground-based scanners were also compared to meteorological and tidal measurements and to time-lapse photography and satellite data. Both ground-based scanning systems capture ice motion at very high resolution, but each offer specific technical and logistical advantages. The combination of these ground-based remote sensing techniques allows us to quantify high-frequency changes in the velocity and surface deformation at the terminus of Hubbard Glacier and to develop a better understanding of the mechanisms associated with advancing tidewater termini.

Wolken, G. J.; Finnegan, D. C.; Sharp, M. J.; LeWinter, A.; Fahnestock, M. A.; Stevens, R.

2013-12-01

27

Determining the 630nm emission altitude using modelling and observations from a tristatic configuration of Fabry-Perot Interferometers and EISCAT radars.  

NASA Astrophysics Data System (ADS)

Anasuya Aruliah, a.aruliah@ucl.ac.uk University College London, London, United Kingdom Michael Kosch, m.kosch@lancaster.ac.uk Lancaster University, Lancaster, United Kingdom Tristatic team Anasuya Aruliah,Ho-Ching Iris Yiu,Ian McWhirter, Michael Kosch,Kazuo Shiokawa,Shin-ichiro Oyama,Satonori Nozawa,Vikki Howells,Ian McCrea During early February 2010 a tristatic FPI-EISCAT experiment was run in order to investigate the peak emission altitude of the 630nm airglow and auroral emission in the region of the auroral oval. Two UCL Fabry-Perot Interferometers and a new STEL FPI have been located close to the three EISCAT radars at Tromsø, Kiruna and Sodankylü. The radars were pointed a at a common volume seen by all three FPIs, on assuming a peak emission height of 235km. This altitude is generally assumed to be fairly steady for FPI studies probing the behaviour of the upper atmosphere, though the height is a little different at other latitudes. The smoothing effect of the large viscosity of the upper thermosphere is invoked as a reason why the actual altitude is not too important, and there has been little investigation of the appropriateness of this assumption. However, mesoscale variability in the ionosphere has now been identified as producing a similar quantity of heating as does steady state convection; and FPIs and the CHAMP satellite have shown mesoscale structure in the high-latitude thermosphere. This indicates a need to revisit old assumptions that were based on the premise of thermospheric variability being large-scale. The STEL FPI at Ramfjord has a fully variable pointing direction mechanism and was programmed to point rapidly at successive volumes that would overlap the UCL KEOPS/Kiruna FPI look direction if the emission volume was 195km, 215km, 235km and 255km. Cross-correlation of the temperatures and intensity measurements would then identify the peak emission height. The EISCAT radar provided ionospheric parameters to model the 630nm emission profile for comparison with the FPI observations.

Aruliah, Anasuya; Kosch, Michael

28

A constant-quality, single-pass VBR control for DVD recorders  

Microsoft Academic Search

This paper describes a low complexity variable bit-rate (VBR) control method that achieves excellent and constant visual quality for single-pass, real time MPEG-2 encoding in DVD recorders. The bit-rate is controlled in a very accurate way. The algorithm runs in software on a very long instruction word (VLIW) processor by using less than 3 Millions of clock cycles.

Daniele Bagni; Bruno Biffi; Rui Ramalho

2003-01-01

29

Highly efficient continuous-wave single-pass second-harmonic generation using multicrystal scheme  

Microsoft Academic Search

We report a simple, compact and novel implementation for single-pass second-harmonic-generation (SP-SHG) of continuous-wave laser radiation based on a cascaded multi-crystal scheme, which can provide the highest conversion efficiency at any given fundamental power. By deploying a suitable number of identical 30-mm-long MgO:sPPLT crystals in a cascade, and a 30-W cw Yb-fiber laser at 1064 nm as the fundamental source,

Kavita Devi; S. Chaitanya Kumar; G. K. Samanta; M. Ebrahim-Zadeh

2010-01-01

30

Biodegradation of chlorinated aliphatic hydrocarbon mixtures in a single-pass packed-bed reactor  

Microsoft Academic Search

Aliphatic chlorinated compounds, such as trichloroethylene (TCE) and tetrachloroethylene (PCE), are major contaminants of\\u000a ground water. A single-pass packed-bed bioreactor was utilized to study the biodegradation of organic waste mixtures consisting\\u000a of PCE, TCE, and other short-chain chlorinated organics. The bioreactor consisted of two 1960-mL glass columns joined in a\\u000a series. One column was packed with sand containing a microbial

L. W. Lackey; T. J. Phelps; P. R. Bienkowski; D. C. White

1993-01-01

31

Single-Pass Flow Through (SPFT) Testing of Fluidized-Bed Steam Reforming (FBSR) Waste Forms  

Microsoft Academic Search

Two samples of fluidized-bed steam reforming (FBSR) mineral waste form product were subjected to single-pass flow-through (SPFT) testing. Sample LAW 1123 resulted from pilot-scale FBSR processing with a Hanford Envelope A low-activity waste (LAW) simulant. Sample SBW 1173 resulted from pilot-scale FBSR processing with an Idaho National Laboratory (INL) simulant commonly referred to as sodium-bearing waste (SBW). The pilot-scale waste

T. H. Lorier; J. M. Pareizs; C. M. Jantzen

2005-01-01

32

1834 OPTICS LETTERS / Vol. 22, No. 24 / December 15, 1997 42%-efficient single-pass cw second-harmonic generation  

E-print Network

1834 OPTICS LETTERS / Vol. 22, No. 24 / December 15, 1997 42%-efficient single-pass cw second for single-pass cw 1064-nm Nd:YAG second-harmonic generation. These samples exhibited 78% of the ideal.7 W of cw 532-nm output with 6.5 W of cw input, which corresponds to 42% power conversion efficiency

Byer, Robert L.

33

Single-pass BPM system of the Photon Factory storage ring.  

PubMed

At the 2.5 GeV ring of the Photon Factory, a single-pass beam-position monitor (BPM) system is being prepared for the storage ring and the beam transport line. In the storage ring, the injected beam position during the first several turns can be measured with a single injection pulse. The BPM system has an adequate performance, useful for the commissioning of the new low-emittance lattice. Several stripline BPMs are being installed in the beam transport line. The continuous monitoring of the orbit in the beam transport line will be useful for the stabilization of the injection energy as well as the injection beam orbit. PMID:15263597

Honda, T; Katoh, M; Mitsuhashi, T; Ueda, A; Tadano, M; Kobayashi, Y

1998-05-01

34

AN EXPERIMENTAL TEST OF SUPERRADIANCE IN A SINGLE PASS SEEDED FEL.  

SciTech Connect

Superradiance and nonlinear evolution of a FEL pulse in a single-pass FEL were experimentally demonstrated at the National Synchrotron Light Source (NSLS) Source Development Laboratory (SDL). The experiment was performed using a 1.5 ps high-brightness electron beam and a 100fs Ti:Sapphire seed laser. The seed laser and electron beam interact in the 10 meter long NISUS undulator with a period of 3.89 cm. The FEL spectrum, energy and pulse length along the undulator were measured. FEL saturation was observed, and gain of more the 200 (relative to seed laser) was measured. Both FEL spectrum widening and pulse length shortening were observed; FEL pulses as short as 65 fs FWHM were measured. The superradiance and nonlinear evolution were also simulated using the numerical code GENESIS1.3 yielding good agreement with the experimental results.

WATANABE, T.; LIU, D.; MURPHY, J.B.; ROSE, J.; SHAFTAN, T.; TSANG, T.; WANG, X.J.; YU, L.H.

2005-08-21

35

Beam-Beam Simulations for a Single Pass SuperB-Factory  

SciTech Connect

A study of beam-beam collisions for an asymmetric single pass SuperB-Factory is presented [1]. In this scheme an e{sup -} and an e{sup +} beam are first stored and damped in two Damping Rings (DR), then extracted, compressed and focused to the IP. After collision the two beams are re-injected in the DR to be damped and extracted for collision again. The explored beam parameters are similar to those used in the design of the International Linear Collider, except for the beam energies. Flat beams and round beams were compared in the simulations in order to optimize both luminosity performances and beam blowup after collision. With such approach a luminosity of the order of 10{sup 36} cm{sup -2} s{sup -1} can be achieved.

Biagini, M.E.; /Frascati; Raimondi, P.; Seeman, J.; /SLAC; Schulte, D.; /CERN

2007-05-18

36

Investigation of Single Pass Shape Rolling Using an Upper Bound Method  

NASA Astrophysics Data System (ADS)

This paper presents a generalized analytical upper bound method for the study of external shape, pressure, and torque in the single pass rolling of shaped sections. Generalized kinematically admissible velocity fields have been calculated from an assumed deforming geometry, in turn mathematically developed from a new parameterization of curves for the stream line flow of the material. An upper bound on rolling power was established based on the calculated velocity fields. Unknown variables in the velocity field were determined by minimizing rolling power with respect to unknown velocity field variables, yielding an upper limit to the actual power required as well as rolling pressure and torque. As an applied example, the single oval-to-round and rectangle-to-diamond roll passes have been chosen and analyzed. Velocity fields and power relations were obtained for each pass and computer analysis was carried out to analyze and simulate the process of shape rolling. External shape, average roll torque, and rolling pressure data from the analysis were compared with other worker’s analytical solutions, numerical analyses, and experimental data. The results were found to be in good agreement with previous research and the method was shown to be quicker and easier to use.

Abrinia, K.; Fazlirad, A.

2010-06-01

37

Double-Sided Single-Pass Submerged Arc Welding for 2205 Duplex Stainless Steel  

NASA Astrophysics Data System (ADS)

The duplex stainless steel (DSS), which combines the characteristics of ferritic steel and austenitic steel, is used widely. The submerged arc welding (SAW) method is usually applied to join thick plates of DSS. However, an effective welding procedure is needed in order to obtain ideal DSS welds with an appropriate proportion of ferrite (?) and austenite (?) in the weld zone, particularly in the melted zone and heat-affected zone. This study evaluated the effectiveness of a high efficiency double-sided single-pass (DSSP) SAW joining method for thick DSS plates. The effectiveness of the converse welding procedure, characterizations of weld zone, and mechanical properties of welded joint are analyzed. The results show an increasing appearance and continuous distribution feature of the ? phase in the fusion zone of the leading welded seam. The converse welding procedure promotes the ? phase to precipitate in the fusion zone of leading welded side. The microhardness appears to significantly increase in the center of leading welded side. Ductile fracture mode is observed in the weld zone. A mixture fracture feature appears with a shear lip and tears in the fusion zone near the fusion line. The ductility, plasticity, and microhardness of the joints have a significant relationship with ? phase and heat treatment effect influenced by the converse welding step. An available heat input controlling technology of the DSSP formation method is discussed for SAW of thick DSS plates.

Luo, Jian; Yuan, Yi; Wang, Xiaoming; Yao, Zongxiang

2013-09-01

38

Improved Reduced Models for Single-Pass and Reflective Semiconductor Optical Amplifiers  

E-print Network

We present highly accurate and easy to implement, improved lumped semiconductor optical amplifier (SOA) models for both single-pass and reflective semiconductor optical amplifiers (RSOA). The key feature of the model is the inclusion of the internal losses and we show that a few subdivisions are required to achieve an accuracy of 0.12 dB. For the case of RSOAs, we generalize a recently published model to account for the internal losses that are vital to replicate observed RSOA behavior. The results of the improved reduced RSOA model show large overlap when compared to a full bidirectional travelling wave model over a 40 dB dynamic range of input powers and a 20 dB dynamic range of reflectivity values. The models would be useful for the rapid system simulation of signals in communication systems, i.e. passive optical networks that employ RSOAs, signal processing using SOAs and for implementing digital back propagation to undo amplifier induced signal distortions.

Dúill, Seán P Ó

2014-01-01

39

History of improvements in single-pass ICRH ion acceleration in the VASIMR engine  

NASA Astrophysics Data System (ADS)

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power magnetoplasma rocket, capable of Isp/thrust modulation at constant power. The plasma is produced by helicon discharge. The bulk of the energy is added by ion cyclotron resonance heating (ICRH.) Axial momentum is obtained by adiabatic expansion of the plasma in a magnetic nozzle. Thrust/specific impulse ratio control in the VASIMR is primarily achieved by the partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. Ion dynamics in the exhaust were studied using probes, gridded energy analyzers (RPA's), microwave interferometry and optical techniques. This paper will review 3 years of single-pass ICRH ion acceleration data. During this interval, the available power to the helicon ionization stage has increased from 3 to 20 kW. The increased plasma density has produced increased plasma loading of the ICRH antenna and isignificant improvements in antenna coupling efficiency and in ion heating efficiency.

Bering, Edgar; Chang-Diaz, Franklin; Bengtson, Roger D.

2005-10-01

40

Walk off compensation, multicrystal, cascaded, single pass, second harmonic generation in LBO  

NASA Astrophysics Data System (ADS)

Walk off compensation and multi crystal (MC) cascaded single pass second harmonic generation (SP-SHG) in LBO was combined to improve the SHG conversion efficiency. We report a simple and compact implementation for (SP-SHG) of radiation, based on a cascaded multicrystal (MC) scheme that can provide high conversion efficiency without other focusing device, the enhancement factor of 2.9 was realized. At an incident pump power of 20 W, the average power of 6.1 W and pulse width of 12 ns green laser was obtained at a repetition rate of 42.4 kHz, corresponding to a peak power of 12 kW and single pulse energy of 144 ?J. The optical to optical conversion efficiency from diode to green and from IR to green laser are about 30.5 and 67.8%, the whole length of this system is about 150 mm, the output fluctuation of this system is less than 5% in 2 h.

Ji, B.; Zheng, X. S.; Cai, Z. P.; Xu, H. Y.; Jia, F. Q.

2012-09-01

41

Parametric analysis of plastic strain and force distribution in single pass metal spinning  

SciTech Connect

Metal spinning also known as spin forming is one of the sheet metal working processes by which an axis-symmetric part can be formed from a flat sheet metal blank. Parts are produced by pressing a blunt edged tool or roller on to the blank which in turn is mounted on a rotating mandrel. This paper discusses about the setting up a 3-D finite element simulation of single pass metal spinning in LS-Dyna. Four parameters were considered namely blank thickness, roller nose radius, feed ratio and mandrel speed and the variation in forces and plastic strain were analysed using the full-factorial design of experiments (DOE) method of simulation experiments. For some of these DOE runs, physical experiments on extra deep drawing (EDD) sheet metal were carried out using En31 tool on a lathe machine. Simulation results are able to predict the zone of unsafe thinning in the sheet and high forming forces that are hint to the necessity for less-expensive and semi-automated machine tools to help the household and small scale spinning workers widely prevalent in India.

Choudhary, Shashank, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Tejesh, Chiruvolu Mohan, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Regalla, Srinivasa Prakash, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Suresh, Kurra, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in [Department of Mechanical Engineering, BITS-Pilani, Hyderabad Campus, Shamirpet, Hyderabad, 500078, Andhra Pradesh (India)

2013-12-16

42

Keck Interferometer  

NASA Technical Reports Server (NTRS)

At the summit of Mauna Kea, Hawaii, NASA astronomers have linked the two 10-meter (33-foot) telescopes at the W. M. Keck Observatory. The linked telescopes, which together are called the Keck Interferometer, make up the world's most powerful optical telescope system. The Keck Interferometer will search for planets around nearby stars and study dust clouds around those stars that may hamper future space-based searches for habitable, Earthlike planets. The Keck Interferometer is part of NASA's Origins program, which seeks to answer two fundamental questions: How did we get here? Are we alone?

2003-01-01

43

A low cost single-pass fractional motion estimation architecture using bit clipping for H.264 video codec  

Microsoft Academic Search

As the video resolution increases, high computational complexity of the fractional motion estimation (FME) introduces difficulty to meet real-time constraints in a video coding. In this paper, we proposed a single-pass FME algorithm and its architecture with low hardware cost and negligible loss of the image quality. The proposed algorithm directly searches only surroundings of both the predicted fractional motion

Giwon Kim; Jaemoon Kim; Chong-Min Kyung

2010-01-01

44

VDD single pass lead pacing: sustained pacemaker mediated tachycardias unrelated to retrograde atrial activation.  

PubMed

Pacemaker mediated tachycardias (PMTs) are a well known complication of P synchronous pacing. Although the initiating mechanisms are several, all of them are associated with retrograde atrial activation, which is sensed by the atrial sensing channel, resulting in ventricular pacing. In 19 patients suffering from symptomatic AV conduction disturbances and normal sinus node function, a VDD pacing system connected to a single pass ventricular lead with dual chamber electrodes was implanted. The bipolar atrial electrode, floating in the right atrium, was used to detect endocardial atrial electrograms that were differentially processed within the pacemaker for optimal discrimination and filtering of undesirable signals. The widely programmable atrial sensitivity (amplitude and filtering) allowed stable P synchronized ventricular pacing in all patients, but in five of them, sustained PMTs not related to retrograde atrial activation was documented during the follow-up. The common mechanism for the onset and maintenance of these PMTs was traced to the abnormal sensing of the terminal forces of ventricular activation and/or of the T wave. The possibility of interferences between ventricular and atrial electrodes (crosstalk) was also considered. The reduction of atrial channel sensitivity represented in all cases the only effective procedure to prevent this type of PMT. In conclusion, the bet signal to noise ratio is an important endpoint to assure the proper function of a single lead VDD pacing system. Furthermore, using the differential amplifier built within the pacemaker, consideration should be given to the optimal mode of rejection of the terminal forces of the QRS and T wave. PMID:1279569

Sermasi, S; Marconi, M

1992-11-01

45

Study on a test of optical stochastic cooling scheme in a single pass beam line  

SciTech Connect

A feasibility study of an experiment to test the principle of optical stochastic cooling is presented. We propose to build a new beamline in the extraction area of the ALS Booster synchrotron, where we will include a bypass lattice similar to the lattice that could be used in the cooling insertion in a storage ring. Of course, in the single pass beamline we cannot achieve cooling, but we can test all the functions of the bypass lattice that are required to achieve cooling in a storage ring. As it is stated in, there are stringent requirements on the time-of-flight properties of the bypass lattice employed in a cooling scheme. The pathlengths of particle trajectories in the bypass must be fairly insensitive to the standard set of errors that usually affect the performance of storage rings. Namely, it is necessary to preserve all fluctuations in the longitudinal particle density within the beam from the beginning to the end of the bypass lattice with the accuracy of {lambda}/2{pi}, where A is the carrying (optical) wavelength. According to, cooling will completely vanish if a combined effect of all kinds of errors will produce a spread of the pathlengths of particle trajectories larger than {lambda}/2 and the cooling time will almost double if the spread of the pathlengths is {lambda}/2{pi}. At a first glance, {lambda}/2{pi} {approx_equal} 0.1/{mu}m is such a small value that satisfying this accuracy looks nearly impossible. However, simulations show that a carefully designed bypass can meet all the requirements even with rather conservative tolerance to errors.

Chattopadhyay, S.; Kim, C.; Massoletti, D.; Zholents, A. [and others

1997-01-01

46

Intestinal permeability of metformin using single-pass intestinal perfusion in rats  

PubMed Central

AIM: To characterize the intestinal transport and mechanism of metformin in rats and to investigate whether or not metformin is a substrate for P-glycoprotein (P-gp). METHODS: The effective intestinal permeability of metformin was investigated using single-pass intestinal perfusion (SPIP) technique in male Waster rats. SPIP was performed in three isolated intestinal segments (duodenum, jejunum and ileum) at the same concentration of metformin (50 ?g/mL) to test if the intestinal transport of metformin exhibited site-dependent changes, and in a same isolated intestinal segment (duodenal segment) at three different concentrations of metformin (10, 50, 200 ?g/mL) to test if the intestinal transport of metformin exhibited concentration-dependent changes. Besides, P-gp inhibitor verapamil (400 ?g/mL) was co-perfused with metformin (50 ?g/mL) in the duodenum segment to find out if the intestinal absorption of metformin was affected by P-gp exiting along the gastrointestinal track. Stability studies were conducted to ensure that the loss of metformin could be attributed to intestinal absorption. RESULTS: The effective permeability values (Peff) of metformin in the jejunum and ileum at 50 ?g/mL were significantly lower than those in the duodenum at the same concentration. Besides, Peff values in the duodenum at high concentration (200 ?g/mL) were found to be significantly lower than those at low and medium concentrations (10 and 50 ?g/mL). Moreover the co-perfusion with verapamil did not increase the Peff value of metformin at 50 ?g/mL in the duodenum. CONCLUSION: Metformin could be absorbed from the whole intestine, with the main absorption site at duodenum. This concentration-dependent permeability behavior in the duodenum indicates that metformin is transported by both passive and active carrier-mediated saturable mechanism. The Peff value can not be increased by co-perfusion with verapamil, indicating that absorption of metformin is not efficiently transported by P-gp in the gut wall. Furthermore metformin is neither a substrate nor an inducer of P-gp. Based on the Peff values obtained in the present study and using established relationships, the human fraction dose absorbed for metformin is estimated to be 74%-90% along human intestine. PMID:16810761

Song, Nai-Ning; Li, Quan-Sheng; Liu, Chang-Xiao

2006-01-01

47

Single-Pass versus Two-Pass Boat Electrofishing for Characterizing River Fish Assemblages: Species Richness Estimates and Sampling Distance  

Microsoft Academic Search

Determining adequate sampling effort for characterizing fish assemblage structure in nonwadeable rivers remains a critical issue in river biomonitoring. Two-pass boat electrofishing data collected from 500–1,000-m-long river reaches as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program were analyzed to assess the efficacy of single-pass boat electrofishing. True fish species richness was estimated by use of a

Michael R. Meador

2005-01-01

48

Experimental validation of single pass ion cyclotron resonance absorption in a high speed flowing plasma applied to the variable specific impulse magnetoplasma rocket (VASIMR)  

NASA Astrophysics Data System (ADS)

The topic of this thesis is the experimental characterization and analysis of single pass ion cyclotron resonance heating as applied to acceleration of ions for electric propulsion. The experimental work was done on the VX-10 experiment of the VASIMR (Variable Specific Impulse Magnetoplasma Rocket) concept. In ion cyclotron resonance heating (ICRH) a RF wave is launched into a magnetized plasma where it then accelerates the ions by increasing their rotational speed around the magnetic field lines. The electric field vector of the right hand component of the wave will rotate around the field lines with a frequency oRF in the same direction as the ion's cyclotron motion about the field lines. Consequently, when oRF ? oci (where oci is the ion's cyclotron frequency) the force from the electric field of the wave on the ions will result in a continuous rotational energy gain. The perpendicular velocity of the ions generated by ICRH is then converted into axial velocity by the decreasing gradient of the axial magnetic field at the exhaust of the propulsion system from conservation of the magnet moment. This increase in axial velocity is predicted to cause a decrease in density due to conservation of current in the plasma. In order to characterize this density drop during ion cyclotron heating, a single channel interferometer system was developed and implemented on the VX-10. Interferometer density measurements were taken at three different locations on the VX-10 experiment upstream and downstream of the ion acceleration zone. Measurements were made of the density drop in both Helium and Deuterium plasma discharges during ICRH under a variety of operating conditions including magnetic field profile, gas flow rate and ICRH power pulse timing, and ICRH power. A clear measurement of a density drop was observed downstream of the ion resonance zone characteristic of ion acceleration and measurement of little change in density upstream of the resonance zone where no acceleration was expected. Good agreement between the measured and predicted power scaling of ion acceleration due to ICRH was found. And experimental evidence that the shape of the magnetic field profile will influence ICRH acceleration as predicted is also presented and analyzed.

Davis, Christopher Nelson

49

Atom Interferometers  

E-print Network

Interference with atomic and molecular matter waves is a rich branch of atomic physics and quantum optics. It started with atom diffraction from crystal surfaces and the separated oscillatory fields technique used in atomic clocks. Atom interferometry is now reaching maturity as a powerful art with many applications in modern science. In this review we first describe the basic tools for coherent atom optics including diffraction by nanostructures and laser light, three-grating interferometers, and double wells on AtomChips. Then we review scientific advances in a broad range of fields that have resulted from the application of atom interferometers. These are grouped in three categories: (1) fundamental quantum science, (2) precision metrology and (3) atomic and molecular physics. Although some experiments with Bose Einstein condensates are included, the focus of the review is on linear matter wave optics, i.e. phenomena where each single atom interferes with itself.

Alexander D. Cronin; Joerg Schmiedmayer; David E. Pritchard

2007-12-21

50

Permethrin absorption not detected in single-pass perfused rabbit ear, and absorption with oxidation of 3-phenoxybenzyl alcohol  

Microsoft Academic Search

Isolated rabbit ears were single-pass perfused with a protein-free medium. Permethrin (0.05–23.5%, w\\/w) was applied in four\\u000a distinct ointments. Permethrin, 3-phenoxybenzyl alcohol, 3-phenoxybenzaldehyde, and 3-phenoxybenzoic acid were analysed by\\u000a HPLC. Permethrin was not detected in the effluent. The permeation coefficient, calculated from the detection limit was ?12 (cm\\/sec). The appearance rate of the 3-phenoxybenzyl moieties in the effluent agreed with

G. E. Bast; D. Taeschner; H. G. Kampffmeyer

1997-01-01

51

Michelson Interferometer  

NASA Technical Reports Server (NTRS)

The Michelson Interferometer is a device used in many applications, but here it was used to measure small differences in distance, in the milli-inch range, specifically for defects in the Orbiter windows. In this paper, the method of using the Michelson Interferometer for measuring small distances is explained as well as the mathematics of the system. The coherence length of several light sources was calculated in order to see just how small a defect could be measured. Since white light is a very broadband source, its coherence length is very short and thus can be used to measure small defects in glass. After finding the front and back reflections from a very thin glass slide with ease and calculating the thickness of it very accurately, it was concluded that this system could find and measure small defects on the Orbiter windows. This report also discusses a failed attempt for another use of this technology as well as describes an area of promise for further analysis. The latter of these areas has applications for finding possible defects in Orbiter windows without moving parts.

Rogers, Ryan

2007-01-01

52

{open_quotes}Optical Guiding{close_quotes} limits on extraction efficiencies of single-pass, tapered wiggler amplifiers  

SciTech Connect

Single-pass, tapered wiggler amplifiers have an attractive feature of being able, in theory at least, of extracting a large portion of the electron beam energy into light. In circumstances where an optical FEL wiggler length is significantly longer than the Rayleigh length Z{sub R} corresponding to the electron beam radius, diffraction losses must be controlled via the phenomenon of optical guiding. Since the strength of the guiding depends upon the effective refractive index n exceeding one, and since (n-1) is inversely proportional to the optical electric field, there is a natural limiting mechanism to the on-axis field strength and thus the rate at which energy may be extracted from the electron beam. In particular, the extraction efficiency for a prebunched beam asymptotically grows linearly with z rather than quadratically. We present analytical and numerical simulation results concerning this behavior and discuss its applicability to various FEL designs including oscillator/amplifier-radiator configurations.

Fawley, W.M.

1995-08-01

53

Single Pass Flow-Through (SPFT) Test Results of Fluidized Bed Steam Reforming (FBSR) Waste Forms used for LAW Immobilization  

SciTech Connect

Several supplemental technologies for treating and immobilizing Hanford low activity waste (LAW) are being evaluated. One such immobilization technology being considered is the Fluidized Bed Steam Reforming (FBSR) granular product. The FBSR granular product is composed of insoluble sodium aluminosilicate (NAS) feldspathoid minerals. Production of the FBSR mineral product has been demonstrated both at the industrial and laboratory scale. Single-Pass Flow-Through (SPFT) tests at various flow rates have been conducted with the granular products fabricated using these two methods. Results show that the materials exhibit a relatively low forward dissolution rate on the order of 10-3 g/(m2d) with the material made in the laboratory giving slightly higher values.

Neeway, James J.; Qafoku, Nikolla; Williams, Benjamin D.; Valenta, Michelle M.; Cordova, Elsa A.; Strandquist, Sara C.; Dage, DeNomy C.; Brown, Christopher F.

2012-03-20

54

Clinical evaluation of a single-pass implantable electrode for all modes of pacing. The "Crown of Thorns" lead.  

PubMed

Physiological pacing was instituted in 17 patients (11 men and 6 women), mean age 67 years (range 33-77 years), using a variety of multiprogramable generators attached to a permanent single-pass dual chamber electrode. Eleven patients were paced in VAT mode (Cordis 208A or Siemens-Elema 625 generator), two patients in DVI mode (Intermedics Cyberlith IV generator) and four patients in DDD mode (Siemens-Elema 664/P33 or Telectronics Autima unit). Mean intracardiac P wave amplitude was 2.0 mV +/- 0.78/SD, range 0.7-3.6 mV. and mean atrial and ventricular pacing thresholds were 1.0 V and 0.5 V, respectively. Fourteen patients had completely successful A-V pacing during a follow-up period of 4-13 months (mean 7 +/- 2.7 months). Two failures were associated with malposition of the atrial crown and occurred exclusively with the Cordis 208A generator. In both patients generator replacement using a more sensitive unit (Siemens-Elema 625) resulted in successful VAT pacing for most of the time. Complete failure of A-V pacing occurred in only one patient who died from coronary artery disease after four months of follow-up. Thus, all of the remaining 16 patients achieved long-term (6 months) satisfactory physiological pacing using this new lead. We conclude that the "Crown of Thorns" electrode is a successful single-pass unipolar lead and can be used with all types of dual chamber generator for all modes of pacing. PMID:6189059

Wainwright, R; Crick, J; Sowton, E

1983-03-01

55

Merits of a sub-harmonic approach to a single-pass, 1.5-{Angstrom} FEL  

SciTech Connect

SLAC/SSRL and collaborators elsewhere are studying th physics of a single-pass, FEL amplifier operating in th 1 -- 2 {Angstrom}, wavelength region based on electron beams from the SLAC linac at {approximately} 15 GeV energy. Hoping to reduce the total wiggler length needed to reach saturation when starting from shot noise, we have examined the benefits of making the first part of the wiggler resonant at a subharmonic wavelength (e.g. 4.5 {Angstrom}) at which the gain length can be significantly shorter. This leads to bunching of the electron beam at both the subharmonic and fundaments wavelengths, thus providing a strong coherent ``seed`` for exponential growth of radiation at the fundamental in the second part of the wiggler. Using both multi-harmonic and multi-frequency 2D FEL simulation codes, we have examined the predicted performance of such devices and the sensitivity to electron beam parameters such as current, emittance, and instantaneous energy spread.

Fawley, W.M. [Lawrence Berkeley Lab., CA (United States); Nuhn, H.D.; Bonifacio, R. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Scharlemann, E.T. [Lawrence Livermore National Lab., CA (United States)

1995-03-01

56

Intestinal absorptive transport of Genkwanin from Flos genkwa using a single-pass intestinal perfusion rat model.  

PubMed

To investigate the absorptive transport behavior of genkwanin and the beneficial effects of monoterpene enhancers with different functional groups, the single-pass intestinal perfusion (SPIP) of rats was used. The results showed that genkwanin was segmentally-dependent and the best absorptive site was the duodenum. The effective permeability coefficient (P eff ) was 1.97 × 10(-4) cm/s and the absorption rate constant (Ka) was 0.62 × 10(-2) s(-1). Transepithelial transportation descended with increasing concentrations of genkwanin. This was a 1.4-fold increase in P eff by probenecid, whereas a 1.4-fold or 1.6-fold decrease was observed by verapamil and pantoprazole, respectively. Furthermore, among the absorption enhancers, the enhancement with carbonyl (camphor and menthone) was higher than that with hydroxyl (borneol and menthol). The concentration-independent permeability and enhancement by coperfusion of probenecid indicated that genkwanin was transported by both passive diffusion and multidrug resistance protein (MDR)-mediated efflux mechanisms. PMID:24707867

Jiang, Cui-Ping; He, Xin; Yang, Xiao-Lin; Zhang, Su-Li; Li, Hui; Song, Zi-Jing; Zhang, Chun-Feng; Yang, Zhong-Lin; Li, Ping

2014-01-01

57

ESTIMATION OF FOREST BIOMASS FROM AN AIRBORNE SINGLE-PASS L-BAND POL-INSAR SYSTEM  

E-print Network

In this paper we describe forest height and biomass results obtained with an experimental airborne L-Band fully polarimetric, singlepass InSAR system over a test area in western Canada. The significance of the single-pass characteristic is that temporal decorrelation is avoided, allowing more robust Pol-InSAR forest parameter recovery. The derived tree height results were validated against those obtained from airborne lidar and were further supported by high resolution aerial photography. Canopy heights in coniferous stands with tree heights ranging from 15-30 meters were extracted using Pol-InSAR and relative to lidar-derived canopy heights, showed accuracies better than 10%. A forest biomass map was then created through height-biomass allometry. The goal is to demonstrate that above-ground biomass and hence carbon estimates can be provided at suitable accuracy and resolution levels using this technical approach. If successful, this would provide the potential to improve carbon baseline estimates in large forest areas, particularly in the tropics, where currently the estimated biomass uncertainty can be significant. 1.

B. Mercer A; Q. Zhang A; M. Schwaebisch B; M. Denbina A; Commission I; Wg I

58

Physicochemical properties of bio-oil and biochar produced by fast pyrolysis of stored single-pass corn stover and cobs.  

PubMed

Short harvest window of corn (Zea mays) stover necessitates its storage before utilization; however, there is not enough work towards exploring the fast pyrolysis behavior of stored biomass. This study investigated the yields and the physicochemical properties (proximate and ultimate analyses, higher heating values and acidity) of the fast pyrolysis products obtained from single-pass stover and cobs stored either inside a metal building or anaerobically within plastic wraps. Biomass samples were pyrolyzed in a 183 cm long and 2.1cm inner diameter free-fall fast pyrolysis reactor. Yields of bio-oil, biochar and non-condensable gases from different biomass samples were in the ranges of 45-55, 25-37 and 11-17 wt.%, respectively, with the highest bio-oil yield from the ensiled single-pass stover. Bio-oils generated from ensiled single-pass cobs and ensiled single-pass stover were, respectively, the most and the least acidic with the modified acid numbers of 95.0 and 65.2 mg g(-1), respectively. PMID:23069609

Shah, Ajay; Darr, Matthew J; Dalluge, Dustin; Medic, Dorde; Webster, Keith; Brown, Robert C

2012-12-01

59

Dissolution Kinetics of Titanium Pyrochlore Ceramics at 90?C by Single-Pass Flow-Through Experiments  

SciTech Connect

Corrosion resistances of titanium-based ceramics are quantified using single-pass flow-through (SPFT) experiments. The materials tested include simple pyrochlore group (B2Ti2O7, where B=Lu^3+ or Gd^3+) and complex multiphase materials that are either pyrochlore- (PY12) or zirconolite-dominated (BSL3). Experiments are conducted at 90?C over a range of pH-buffered conditions with typical duration of experiments in excess of 120 days. Apparent steady-state dissolution rates at pH=2 determined on the Gd2Ti2O7 and Lu2Ti2O7 samples indicate congruent dissolution, with rates of the former (1.3x10^-3 to 4.3x10^-3) slightly faster than the latter (4.4x10^-4 to 7.0x10^-4 g m^-2 d^-1). Rates for PY12 materials into pH=2 solutions are 5.9x10^-5 to 8.6x10^-5 g m^-2 d^-1. In contrast, experiments with BSL3 material do not reach steady-state conditions, and appear to undergo rapid physical and chemical corrosion into solution. At faster flow-through rates, dissolution rates display a shallow amphoteric behavior, with a minimum (4.6x10^-5 to 5.8x10^-5 g m^-2 d^-1) near pH values of 7. Dissolution rates display a measurable increase (~10X) with increasing flow-through rate indicating the strong influence that chemical affinity asserts on the system. These results step towards an evaluation of the corrosion mechanism and an evaluation of the long-term performance of Pu-bearing titanite engineered materials in the subsurface.

Icenhower, Jonathan P.; McGrail, B. Peter; Schaef, Herbert T.; Cordova, Elsa A.

2000-12-01

60

Geophysical fiber interferometer gyroscope  

Microsoft Academic Search

This report describes a development effort of the University of Utah Research Institute aimed at perfecting a North-seeking device based on the passive interferometer gyroscope concept. The rotation sensing mechanism of the interferometer is based on the Sagnac effect. The form of the interferometer is a fiber ring. The performance requirements of the device are developed in terms of desired

L. D. Weaver

1979-01-01

61

Radar applications  

NASA Astrophysics Data System (ADS)

Papers are presented on air-traffic control radar, surveillance radar, missile guidance radar, and high-performance tactical three-dimensional radar. Also considered are the airborne early warning radar, the Foxhunter airborne intercept radar, and environmental remote sensing. Other topics include spaceborne SARs, the Pioneer Orbiter radar, and a bistatic pulse-Doppler intruder-detection radar.

Skolnik, Merrill I.

62

Radar applications  

Microsoft Academic Search

Papers are presented on air-traffic control radar, surveillance radar, missile guidance radar, and high-performance tactical three-dimensional radar. Also considered are the airborne early warning radar, the Foxhunter airborne intercept radar, and environmental remote sensing. Other topics include spaceborne SARs, the Pioneer Orbiter radar, and a bistatic pulse-Doppler intruder-detection radar.

Merrill I. Skolnik

1988-01-01

63

Accuracy of single-pass whole-body computed tomography for detection of injuries in patients with major blunt trauma  

PubMed Central

Background: Contrast-enhanced whole-body computed tomography (also called “pan-scanning”) is considered to be a conclusive diagnostic tool for major trauma. We sought to determine the accuracy of this method, focusing on the reliability of negative results. Methods: Between July 2006 and December 2008, a total of 982 patients with suspected severe injuries underwent single-pass pan-scanning at a metropolitan trauma centre. The findings of the scan were independently evaluated by two reviewers who analyzed the injuries to five body regions and compared the results to a synopsis of hospital charts, subsequent imaging and interventional procedures. We calculated the sensitivity and specificity of the pan-scan for each body region, and we assessed the residual risk of missed injuries that required surgery or critical care. Results: A total of 1756 injuries were detected in the 982 patients scanned. Of these, 360 patients had an Injury Severity Score greater than 15. The median length of follow-up was 39 (interquartile range 7–490) days, and 474 patients underwent a definitive reference test. The sensitivity of the initial pan-scan was 84.6% for head and neck injuries, 79.6% for facial injuries, 86.7% for thoracic injuries, 85.7% for abdominal injuries and 86.2% for pelvic injuries. Specificity was 98.9% for head and neck injuries, 99.1% for facial injuries, 98.9% for thoracic injuries, 97.5% for abdominal injuries and 99.8% for pelvic injuries. In total, 62 patients had 70 missed injuries, indicating a residual risk of 6.3% (95% confidence interval 4.9%–8.0%). Interpretation: We found that the positive results of trauma pan-scans are conclusive but negative results require subsequent confirmation. The pan-scan algorithms reduce, but do not eliminate, the risk of missed injuries, and they should not replace close monitoring and clinical follow-up of patients with major trauma. PMID:22392949

Stengel, Dirk; Ottersbach, Caspar; Matthes, Gerrit; Weigeldt, Moritz; Grundei, Simon; Rademacher, Grit; Tittel, Anja; Mutze, Sven; Ekkernkamp, Axel; Frank, Matthias; Schmucker, Uli; Seifert, Julia

2012-01-01

64

Phase shifting interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

Sommargren, Gary E. (Santa Cruz, CA)

1999-01-01

65

The Glacier and Ice Sheet Topography Interferometer: An Update on a Unique Sensor for High Accuracy Swath Mapping of Land Ice  

NASA Astrophysics Data System (ADS)

We discuss the innovative concept and technology development of a Ka-band (35 GHz) radar for mapping the surface topography of glaciers and ice sheets. The "Glacier and Land Ice Surface Topography Interferometer" (GLISTIN) is a single-pass, single platform interferometric synthetic aperture radar (InSAR) with an 8mm wavelength, which minimizes snow penetration yet remains relatively impervious to atmospheric attenuation. Such a system has the potential for delivering topographic maps at high spatial resolution, high vertical accuracy, independent of cloud cover, with a subseasonal update and would greatly enhance current observational and modeling capabilities of ice mass-balance and glacial retreat. To enable such measurements, a digitally beamformed antenna array is utilized to provide a wide measurement swath at a technologically feasible transmit power. To prove this concept and advance the technology readiness of this design we are currently funded by the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) to build and test a 1m x 1m digitally-beamformed (DBF) Ka-band slotted waveguide antenna with integrated digital receivers. This antenna provides 16 simultaneous receive beams, effectively broadening the swath without reducing receive antenna gain. The implementation of such a large aperture at Ka-band presents many design, manufacturing and calibration challenges which are addressed as part of this IIP. The integrated DBF array will be fielded at the Jet Propulsion Laboratory's antenna range to demonstrate the overall calibration, beamforming and interferometric performance through creation of topographic imagery of the local Arroyo Seco. Currently entering the third year of the program, we will overview the system concept, array implementation and status of the technology. While the IIP addresses the development of the major technology challenges, an additional effort will demonstrate the phenomenology of the measurement by adapting the NASA ESTO-funded Uninhabited Aerial Vehicle - Synthetic Aperture Radar (UAVSAR) system for Ka-band single-pass interferometry. The conversion to Ka-Band will utilize the modular UAVSAR system originally designed for L-Band operation, retaining the radar control, data acquisition and processing infrastructure and requiring only minor pod and RF modifications. We will fly the Ka-Band interferometer aboard the UAVSAR platform over regions of Greenland, flying a grid over Jakobshavn glacier, then a transect from the coast to Swiss Camp ending at Greenland's Summit. Over a period of 4-5 weeks at the beginning of the melt season, these flight missions will be repeated in different snow/ice conditions. The flight data will be compared with airborne laser altimetry (Airborne Topographic Mapper lidar instrument, NASA GSFC/Wallops), field observations (GPS data at Swiss Camp, Summit), and climate data from the Automatic Weather Station (Colorado University) network (snowfall, corrected for densification) to estimate penetration and produce topographic surface maps. Topography is an essential piece of information for glaciology and a high-quality topographic map (tens of cm height accuracy over 10m pixels) will be produced. The experiment will pave the way to making more topographic products available to glaciologists and aid in the design a spaceborne mission capable of delivering similar products at the continental scale.

Moller, D.; Heavey, B.; Hensley, S.; Hodges, R.; Rengarajan, S.; Rignot, E.; Sadowy, G.; Simard, M.; Zawadzki, M.

2007-12-01

66

Lens collimation and testing using a Twyman-Green interferometer with a self-pumped phase-conjugating mirror  

NASA Technical Reports Server (NTRS)

Ordinarily Twyman-Green interferometers are employed testing optical elements. In a modification of the basic configuration, the ordinary mirror in the test arm is replaced with a self-pumped phase-conjugating mirror using a barium titanate crystal. It is shown that, with a redefinition of components, the new configuration permits retention and improvement of the optical element testing function while simultaneously serving as a sensitive test for collimation. The optical path difference resulting from the double pass in the original Twyman-Green interferometer approximately equals that of the single pass and phase conjugation in the modification.

Howes, W. L.

1986-01-01

67

A time-resolved single-pass technique for measuring optical absorption coefficients of window materials under 100 GPa shock pressures.  

PubMed

An experimental method was developed to perform time-resolved, single-pass optical absorption measurements and to determine absorption coefficients of window materials under strong shock compression up to approximately 200 GPa. Experimental details are described of (i) a configuration to generate an in situ dynamic, bright, optical source and (ii) a sample assembly with a lithium fluoride plate to essentially eliminate heat transfer from the hot radiator into the specimen and to maintain a constant optical source within the duration of the experiment. Examples of measurements of optical absorption coefficients of several initially transparent single crystal materials at high shock pressures are presented. PMID:19123545

Li, Jun; Zhou, Xianming; Li, Jiabo

2008-12-01

68

A laser unequal path interferometer for the optical shop.  

PubMed

The application of laser technology has been extended to optical shop testing by incorporating a cw, helium-neon gas laser in a package that houses a modified Twyman-Green interferometer. This modification provides for optical testing over large path differences with an auxiliary set of lenses used in the long path and a small reference flat used in the short path of the interferometer. With this technique, f/0.7 spherical mirrors have been tested (at the center of curvature) to an accuracy of 1/10 wavelength at the surface, and various other optical systems have been tested in both double pass and single pass. Two of the advantages of this testing method are (1) the capability of testing spherical concave surfaces without physically contacting the surface and (2) the ability to use small reference surfaces for large optical components or systems. The device known as a laser unequal path interferometer can be used with a set of null lenses to qualify aspheric surfaces. The unit is portable and capable of testing in any orientation under various environmental conditions. Several applications of this device are presented to illustrate its versatility. PMID:20062171

Houston, J B; Buccini, C J; O'Neill, P K

1967-07-01

69

Dual surface interferometer  

DOEpatents

A double-pass interferometer is provided which allows direct measurement of relative displacement between opposed surfaces. A conventional plane mirror interferometer may be modified by replacing the beam-measuring path cube-corner reflector with an additional quarter-wave plate. The beam path is altered to extend to an opposed plane mirrored surface and the reflected beam is placed in interference with a retained reference beam split from dual-beam source and retroreflected by a reference cube-corner reflector mounted stationary with the interferometer housing. This permits direct measurement of opposed mirror surfaces by laser interferometry while doubling the resolution as with a conventional double-pass plane mirror laser interferometer system.

Pardue, Robert M. (Knoxville, TN); Williams, Richard R. (Oak Ridge, TN)

1982-01-01

70

Phase shifting diffraction interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

Sommargren, G.E.

1996-08-29

71

Phase shifting diffraction interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

72

The Palomar Testbed Interferometer  

E-print Network

The Palomar Testbed Interferometer (PTI) is a long-baseline infrared interferometer located at Palomar Observatory, California. It was built as a testbed for interferometric techniques applicable to the Keck Interferometer. First fringes were obtained in July 1995. PTI implements a dual-star architecture, tracking two stars simultaneously for phase referencing and narrow-angle astrometry. The three fixed 40-cm apertures can be combined pair-wise to provide baselines to 110 m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 um and active delay lines with a range of +/- 38 m. Laser metrology of the delay lines allows for servo control, and laser metrology of the complete optical path enables narrow-angle astrometric measurements. The instrument is highly automated, using a multiprocessing computer system for instrument control and sequencing.

M. M. Colavita; J. K. Wallace

1998-10-17

73

The Palomar Testbed Interferometer  

E-print Network

The Palomar Testbed Interferometer (PTI) is a long-baseline infrared interferometer located at Palomar Observatory, California. It was built as a testbed for interferometric techniques applicable to the Keck Interferometer. First fringes were obtained in July 1995. PTI implements a dual-star architecture, tracking two stars simultaneously for phase referencing and narrow-angle astrometry. The three fixed 40-cm apertures can be combined pair-wise to provide baselines to 110~m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 um and active delay lines with a range of +/- 38 m. Laser metrology of the delay lines allows for servo control, and laser metrology of the complete optical path enables narrow-angle astrometric measurements. The instrument is highly automated, using a multiprocessing computer system for instrument control and sequencing.

Colavita, M M

1999-01-01

74

High-Repetition-Rate, Single-Pass Third-Harmonic Generation of 354 nm Ultraviolet Laser with 51.5% Efficiency  

NASA Astrophysics Data System (ADS)

At a high repetition rate of 1 MHz, the maximum 32.1 W TEM00 mode ultraviolet (UV) laser is generated by harmonically converting the output of semiconductor-diode-seeded four-cascaded fiber amplifiers. The master-oscillator-fiber-power-amplifier (fiber-MOPA) configuration based IR source exhibits high power with excellent spatial, temporal, spectral, and polarizing performances. The novel single-pass frequency tripling scheme, beginning with the noncritical phase matching (PM) for second-harmonic generation and the subsequent noncollinear PM for third-harmonic generation, is used to minimize the spatial walk-off effect. Due to the overall system optimization, the optic-optic conversion efficiency from IR to UV is scaled up to 51.5%.

Chen, Hailong; Liu, Qiang; Yan, Ping; Xiao, Qirong; Gong, Mali

2012-09-01

75

Mariner 9 michelson interferometer.  

PubMed

The Michelson interferometer on Mariner 9 measures the thermal emission spectrum of Mars between 200 cm(-1) and 2000 cm(-1) (between 5 microm and 50 microm) with a spectral resolution of 2.4 cm(-1) in the apodized mode. A noise equivalent radiance of 0.5 x 10(-7) W cm(-2) sr(-1)/cm(-1) is deduced from data recorded in orbit around Mars. The Mariner interferometer deviates in design from the Nimbus 3 and 4 interferometers in several areas, notably, by a cesium iodide beam splitter and certain aspects of the digital information processing. Special attention has been given to the problem of external vibration. The instrument performance is demonstrated by calibration data and samples of Mars spectra. PMID:20119381

Hanel, R; Schlachman, B; Breihan, E; Bywaters, R; Chapman, F; Rhodes, M; Rodgers, D; Vanous, D

1972-11-01

76

PDX multichannel interferometer  

SciTech Connect

A 10 channel, 140 GHz homodyne interferometer is described for use on PDX. One feature of this interferometer is the separation of the signal source and electronics from the power splitters, delay line, and receiving systems. The latter is situated near the upper and lower vacuum ports between the toroidal field magnets. A second feature is the signal stabilization of the EIO source by means of an AFC system. The complete interferometer is described including block diagrams, circuit diagrams, test data, and magnetic field test conducted on the preamplifiers, microwave diodes, isolators, etc., to determine the extent of magnetic shielding required. The description of the tracking filters and digital phase display circuit is referenced to accompanying reports.

Bitzer, R.; Ernst, W.; Cutsogeorge, G.

1980-10-01

77

Heterodyne Interferometer Angle Metrology  

NASA Technical Reports Server (NTRS)

A compact, high-resolution angle measurement instrument has been developed that is based on a heterodyne interferometer. The common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer setup, an optical mask is used to sample the measurement laser beam reflecting back from a target surface. Angular rotations, around two orthogonal axes in a plane perpendicular to the measurement- beam propagation direction, are determined simultaneously from the relative displacement measurement of the target surface. The device is used in a tracking telescope system where pitch and yaw measurements of a flat mirror were simultaneously performed with a sensitivity of 0.1 nrad, per second, and a measuring range of 0.15 mrad at a working distance of an order of a meter. The nonlinearity of the device is also measured less than one percent over the measurement range.

Hahn, Inseob; Weilert, Mark A.; Wang, Xu; Goullioud, Renaud

2010-01-01

78

Radar-Interferometric Asteroid Imaging Using a Flexible Software Correlator  

Microsoft Academic Search

We've developed a technique to use a radio interferometer to image near earth objects (NEOs) during their close Earth approach when they can be illuminated by a ground-based radar system. There is great potential for this technique to yield detailed information that is complementary to other observational methods. We are using the NAIC's Arecibo Observatory's 1 MW 13 cm radar

G. Black; D. B. Campbell; R. Treacy; M. C. Nolan

2005-01-01

79

Mesoscopic Interferometers for Electron Waves  

SciTech Connect

Mesoscopic interferometers are electronic analogues of optical interferometers, with 'quantum point contacts' playing the role of optical beam splitters. Mesoscopic analogues of two-slit, Mach-Zehnder and Fabry-Perot interferometers have been built. A fundamental difference between electron and photon interferometry is that electron interferometry is nonlocal.

Rohrlich, D. [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)

2005-09-15

80

Dual differential interferometer  

NASA Technical Reports Server (NTRS)

A dual two-beam differential interferometer that measures both the amplitude and orientation of propagating, broadband surface acoustic waves is disclosed. Four beams are focused on a surface. The four reflected beams are separated into two pairs. The two pairs are detected to produce two signals that are used to compute amplitude and orientation.

Claus, R. O.; Turner, T. M. (inventors)

1985-01-01

81

Dual beam optical interferometer  

NASA Technical Reports Server (NTRS)

A dual beam interferometer device is disclosed that enables moving an optics module in a direction, which changes the path lengths of two beams of light. The two beams reflect off a surface of an object and generate different speckle patterns detected by an element, such as a camera. The camera detects a characteristic of the surface.

Gutierrez, Roman C. (Inventor)

2003-01-01

82

Fiber ring interferometer  

Microsoft Academic Search

A ring interferometer rotation detector (gyroscope) using optical fiber waveguide is designed. The sensitivity of the device is enhanced via multiple traverses of counterrotating beams around an area, but restrictions on the optimum fiber length are imposed by the photon noise limit. A well-defined wavefront and efficient coupling of light into the fiber are required. Laser light divided by a

V. Vali; R. W. Shorthill

1976-01-01

83

The Glacier and Land Ice Surface Topography Interferometer (GLISTIN): A Novel Ka-band Digitally Beamformed Interferometer  

NASA Technical Reports Server (NTRS)

The estimation of the mass balance of ice sheets and glaciers on Earth is a problem of considerable scientific and societal importance. A key measurement to understanding, monitoring and forecasting these changes is ice-surface topography, both for ice-sheet and glacial regions. As such NASA identified 'ice topographic mapping instruments capable of providing precise elevation and detailed imagery data for measurements on glacial scales for detailed monitoring of ice sheet, and glacier changes' as a science priority for the most recent Instrument Incubator Program (IIP) opportunities. Funded under this opportunity is the technological development for a Ka-Band (35GHz) single-pass digitally beamformed interferometric synthetic aperture radar (InSAR). Unique to this concept is the ability to map a significant swath impervious of cloud cover with measurement accuracies comparable to laser altimeters but with variable resolution as appropriate to the differing scales-of-interest over ice-sheets and glaciers.

Moller, Delwyn K.; Heavey, Brandon; Hodges, Richard; Rengarajan, Sembiam; Rignot, Eric; Rogez, Francois; Sadowy, Gregory; Simard, Marc; Zawadzki, Mark

2006-01-01

84

Meteor wind observations with the MU radar  

Microsoft Academic Search

Meteor wind observations were conducted with the middle and upper atmosphere (MU) radar at Shigaraki, Japan (35 deg N, 136 deg E), utilizing an interferometer to determine the arrival angle of a meteor echo. Meteor echoes are widely distributed in zenith angles as large as 50 deg and the narrow main lobe of a transmitting antenna cannot effectively detect meteor

T. Nakamura; M. Tsutsumi; T. Uehara; S. Fukao; S. Kato

1991-01-01

85

Space reflectors for radar and astronomy.  

PubMed

A new concept to utilize large flat optical reflecting surfaces in space to increase by several orders of magnitude the sensitivity and resolution of earth laser radar and astronomy measurements is described. The physical principles on which simple structures can maintain the optical reflectance gratings in space are derived, and the data processing requirements of the measurements are discussed. Space and ground system designs are given for a high resolution earth resources laser radar sensor, a synchronous earth and planetary science laser radar system, and an astronomy observation system including a variable very long compound grating interferometer system. PMID:20134917

Yater, J C

1975-02-01

86

Single-Pass Flow-Through Test Elucidation of Weathering Behavior and Evaluation of Contaminant Release Models for Hanford Tank Residual Radioactive Waste  

SciTech Connect

Contaminant release models are required to evaluate and predict long-term environmental impacts of even residual amounts of high-level radioactive waste after cleanup and closure of radioactively contaminated sites such as the DOE’s Hanford Site. More realistic and representative models have been developed for release of uranium, technetium, and chromium from Hanford Site tanks C-202, C-203, and C-103 residual wastes using data collected with a single-pass flow-through test (SPFT) method. These revised models indicate that contaminant release concentrations from these residual wastes will be considerably lower than previous estimates based on batch experiments. For uranium, a thermodynamic solubility model provides an effective description of uranium release, which can account for differences in pore fluid chemistry contacting the waste that could occur through time and as a result of different closure scenarios. Under certain circumstances in the SPFT experiments various calcium rich precipitates (calcium phosphates and calcite) form on the surfaces of the waste particles, inhibiting dissolution of the underlying uranium phases in the waste. This behavior was not observed in previous batch experiments. For both technetium and chromium, empirical release models were developed. In the case of technetium, release from all three wastes was modeled using an equilibrium Kd model. For chromium release, a constant concentration model was applied for all three wastes.

Cantrell, Kirk J.; Carroll, Kenneth C.; Buck, Edgar C.; Neiner, Doinita; Geiszler, Keith N.

2013-01-01

87

Interferometers and Decoherence Matrices  

E-print Network

It is shown that the Lorentz group is the natural language for two-beam interferometers if there are no decoherence effects. This aspect of the interferometer can be translated into six-parameter representations of the Lorentz group, as in the case of polarization optics where there are two orthogonal components of one light beam. It is shown that there are groups of transformations which leave the coherency or density matrix invariant, and this symmetry property is formulated within the framework of Wigner's little groups. An additional mathematical apparatus is needed for the transition from a pure state to an impure state. Decoherence matrices are constructed for this process, and their properties are studied in detail. Experimental tests of this symmetry property are possible.

D. Han; Y. S. Kim; Marilyn E. Noz

2000-03-13

88

One-element interferometer  

NASA Astrophysics Data System (ADS)

We apply the phase-switching method of Ryle to convert single dish radio telescopes to one-element interferometers and thereby accord them the benefit of correlation measurements, viz. to measure only the flux from the celestial sources avoiding contributions from the receiver and the atmosphere. This application has many uses: (a) enables single dishes to image the sky efficiently without the need to scan, measuring all sources, point, extended, spectral and continuum, with both bolometric and coherent receivers; (b) enables adding reliable short-spacing data to existing interferometers such as Atacama Large Millimetre-wave Array,, mitigating calibration issues; (c) enables ground-based NIR/MIR imaging to accurately remove atmospheric contributions; (d) can be adapted to provide an alternate surface measurement method for telescopes.

Balasubramanyam, Ramesh

2014-11-01

89

Multipulsed dynamic moire interferometer  

DOEpatents

An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

Deason, Vance A. (Idaho Falls, ID)

1991-01-01

90

The Keck Interferometer  

NASA Astrophysics Data System (ADS)

The Keck Interferometer (KI) combined the two 10 m W. M. Keck Observatory telescopes on Mauna Kea, Hawaii, as a long-baseline near- and mid-infrared interferometer. Funded by NASA, it operated from 2001 until 2012. KI used adaptive optics on the two Keck telescopes to correct the individual wavefronts, as well as active fringe tracking in all modes for path-length control, including the implementation of cophasing to provide long coherent integration times. KI implemented high sensitivity fringe-visibility measurements at H (1.6 ?m), K (2.2 ?m), and L (3.8 ?m) bands, and nulling measurements at N band (10 ?m), which were used to address a broad range of science topics. Supporting these capabilities was an extensive interferometer infrastructure and unique instrumentation, including some additional functionality added as part of the NSF-funded ASTRA program. This paper provides an overview of the instrument architecture and some of the key design and implementation decisions, as well as a description of all of the key elements and their configuration at the end of the project. The objective is to provide a view of KI as an integrated system, and to provide adequate technical detail to assess the implementation. Included is a discussion of the operational aspects of the system, as well as of the achieved system performance. Finally, details on V2 calibration in the presence of detector nonlinearities as applied in the data pipeline are provided.

Colavita, M. M.; Wizinowich, P. L.; Akeson, R. L.; Ragland, S.; Woillez, J. M.; Millan-Gabet, R.; Serabyn, E.; Abajian, M.; Acton, D. S.; Appleby, E.; Beletic, J. W.; Beichman, C. A.; Bell, J.; Berkey, B. C.; Berlin, J.; Boden, A. F.; Booth, A. J.; Boutell, R.; Chaffee, F. H.; Chan, D.; Chin, J.; Chock, J.; Cohen, R.; Cooper, A.; Crawford, S. L.; Creech-Eakman, M. J.; Dahl, W.; Eychaner, G.; Fanson, J. L.; Felizardo, C.; Garcia-Gathright, J. I.; Gathright, J. T.; Hardy, G.; Henderson, H.; Herstein, J. S.; Hess, M.; Hovland, E. E.; Hrynevych, M. A.; Johansson, E.; Johnson, R. L.; Kelley, J.; Kendrick, R.; Koresko, C. D.; Kurpis, P.; Le Mignant, D.; Lewis, H. A.; Ligon, E. R.; Lupton, W.; McBride, D.; Medeiros, D. W.; Mennesson, B. P.; Moore, J. D.; Morrison, D.; Nance, C.; Neyman, C.; Niessner, A.; Paine, C. G.; Palmer, D. L.; Panteleeva, T.; Papin, M.; Parvin, B.; Reder, L.; Rudeen, A.; Saloga, T.; Sargent, A.; Shao, M.; Smith, B.; Smythe, R. F.; Stomski, P.; Summers, K. R.; Swain, M. R.; Swanson, P.; Thompson, R.; Tsubota, K.; Tumminello, A.; Tyau, C.; van Belle, G. T.; Vasisht, G.; Vause, J.; Vescelus, F.; Walker, J.; Wallace, J. K.; Wehmeier, U.; Wetherell, E.

2013-10-01

91

Radar principles  

NASA Technical Reports Server (NTRS)

Discussed here is a kind of radar called atmospheric radar, which has as its target clear air echoes from the earth's atmosphere produced by fluctuations of the atmospheric index of refraction. Topics reviewed include the vertical structure of the atmosphere, the radio refractive index and its fluctuations, the radar equation (a relation between transmitted and received power), radar equations for distributed targets and spectral echoes, near field correction, pulsed waveforms, the Doppler principle, and velocity field measurements.

Sato, Toru

1989-01-01

92

Comparison of the results of short-term static tests and single-pass flow-through tests with LRM glass.  

SciTech Connect

Static dissolution tests were conducted to measure the forward dissolution rate of LRM glass at 70 C and pH(RT) 11.7 {+-} 0.1 for comparison with the rate measured with single-pass flow-through (SPFT) tests in an interlaboratory study (ILS). The static tests were conducted with monolithic specimens having known geometric surface areas, whereas the SPFT tests were conducted with crushed glass that had an uncertain specific surface area. The error in the specific surface area of the crushed glass used in the SPFT tests, which was calculated by modeling the particles as spheres, was assessed based on the difference in the forward dissolution rates measured with the two test methods. Three series of static tests were conducted at 70 C following ASTM standard test method C1220 using specimens with surfaces polished to 600, 800, and 1200 grit and a leachant solution having the same composition as that used in the ILS. Regression of the combined results of the static tests to the affinity-based glass dissolution model gives a forward rate of 1.67 g/(m{sup 2}d). The mean value of the forward rate from the SPFT tests was 1.64 g/(m{sup 2}d) with an extended uncertainty of 1.90 g/(m{sup 2}d). This indicates that the calculated surface area for the crushed glass used in the SPFT tests is less than 2% higher than the actual surface area, which is well within the experimental uncertainties of measuring the forward dissolution rate using each test method. These results indicate that the geometric surface area of crushed glass calculated based on the size of the sieves used to isolate the fraction used in a test is reliable. In addition, the C1220 test method provides a means for measuring the forward dissolution rate of borosilicate glasses that is faster, easier, and more economical than the SPFT test method.

Ebert, W. L.; Chemical Engineering

2007-01-29

93

SPIE March 23, 1998 Palomar Testbed Interferometer Palomar Testbed Interferometer  

E-print Network

March 23, 1998 Palomar Testbed Interferometer JKW-5 PTI History · Funded by NASA as engineering testbed March 23, 1998 Palomar Testbed Interferometer JKW-15 Constant-Term Metrology · Measures difference in optical path between the two arms for each beam combiner ­ difference in metrology measurments between

94

Wavelength independent interferometer  

NASA Technical Reports Server (NTRS)

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

1991-01-01

95

The Stress-Relief Cracking Susceptibility of a New Ferritic Steel - Part I: Single-Pass Heat-Affected Zone Simulations  

SciTech Connect

The stress-relief cracking susceptibility of single-pass welds in a new ferritic steel, HCM2S, has been evaluated and compared to 2.25Cr-1Mo steel using Gleeble techniques. Simulated coarse-grained heat-affected zones (CGHAZ) were produced under a range of energy inputs and tested at various post-weld heat treatment (PWHT) temperatures. Both alloys were tested at a stress of 325 MPa. The 2.25 Cr-1Mo steel was also tested at 270 MPa to normalize for the difference in yield strength between the two materials. Light optical and scanning electron microscopy were used to characterize the CGHAZ microstructure. The ''as-welded'' CGHAZ of each alloy consisted of lath martensite or bainite and had approximately equal prior austenite grain sizes. The as-welded hardness of the 2.25Cr-1Mo steel CGHAZ was significantly higher than that of the HCM2S alloy. Over the range studied energy input had no effect on the as-welded microstructure or hardness of either alloy. The energy input also had no effect on the stress-relief cracking susceptibility of either material. Both alloys failed intergranularly along prior austenite grain boundaries under all test conditions. The 2.25Cr-1Mo steel samples experienced significant macroductility and some microductility when tested at 325 MPa. The ductility decreased significantly when tested at 270 MPa but was still higher that than of HCM2S at each test condition. The time to failure decreased with increasing PWHT Temperature for each material. There was no significant difference in the times to failure between the two materials. Varying energy input and stress had no effect on the time-to failure. The ductility, as measured by reduction in are% increased with increasing PWHT temperature for 2.25 Cr-1Mo steel tested at both stresses. However, PWHT temperature had no effect on the ductility of HCM2S. The hardness of the CGHAZ for 2.25Cr-1Mo steel decreased significantly after PWHT, but remained constant for HCM2S. The differences in stress-relief cracking response are discussed in terms of the differences in composition and expected carbide precipitation sequence for each alloy during PWHT.

NAWROCKI,J.G.; DUPONT,J.N.; ROBINO,CHARLES V.; MARDER,A.R.

1999-12-15

96

An Interferometric Ka-band Synthetic Aperture Radar: A New Technique for Glacier and Ice- sheet Topography Mapping  

NASA Astrophysics Data System (ADS)

The estimation of the mass balance of ice sheets and glaciers on Earth is a problem of considerable scientific and societal importance. The Greenland and Antarctic ice sheets together hold enough ice to raise global sea level by 80 m. The annual exchange of mass on the ice sheets is equivalent to 8mm/yr sea level, so that any fluctuation in that level of exchange is significant on the global scale. A key measurement to understanding, monitoring and forecasting these changes is ice-surface topography, both for ice-sheet and glacial regions. As such NASA identified "ice topographic mapping instruments capable of providing precise elevation and detailed imagery data for measurements on glacial scales for detailed monitoring of ice sheet, and glacier changes" as a science priority for the most recent ESTO- Instrument Incubator Program (IIP) opportunities. Funded under this opportunity is the technological development for a Ka-Band (35GHz) single-pass digitally beamformed interferometric synthetic aperture radar (InSAR). Unique to this concept is the ability to map a significant swath impervious of cloud cover with measurement accuracies comparable to lidar altimeters but with variable resolution as appropriate to the differing scales-of-interest over ice-sheets and glaciers. By diverging from the more traditional profiling measurements employed to date (ie radar altimeters and lidars) we are able to offer the potential to significantly advance the spaciotemporal observational capabilities of both ice sheets and glaciers. Dubbed the Glacier and Land Ice Surface Topography Interferometer (GLISTIN), the instrument and mission presents several significant challenges. In particular, under the IIP program we are designing, building and demonstrating a large Ka-band antenna array with integrated digital receivers and utilizing digital beamforming to preserve both antenna gain and swath. These technology items will ultimately be integrated into a complete interferometric ground-based system and demonstrated from the local JPL mesa antenna range. While the demonstration addresses the key technology hurdles, an additional component to this program is to address the systematic and geophysical calibration issues that will arise for a dedicated mission of this type. We discuss our proposed calibration methodology and present several of the critical issues, including correction of systematic errors and surface and volume decorrelation effects. We conclude with a discussion of the impact of snow penetration on the height measurements, and discuss a proposed campaign to field a Ka-band interferometric synthetic aperture radar based on the Jet Propulsion Laboratory's new "UAVSAR" platform.

Moller, D. K.; Aaron, K.; Gim, Y.; Heavey, B.; Hodges, R.; Nicolson, A.; Rengarajan, S.; Rignot, E.; Rogez, F.; Sadowy, G.; Simard, M.; Zawadzki, M.

2006-12-01

97

MIT's interferometer CST testbed  

NASA Astrophysics Data System (ADS)

The MIT Space Engineering Research Center (SERC) has developed a controlled structures technology (CST) testbed based on one design for a space-based optical interferometer. The role of the testbed is to provide a versatile platform for experimental investigation and discovery of CST approaches. In particular, it will serve as the focus for experimental verification of CSI methodologies and control strategies at SERC. The testbed program has an emphasis on experimental CST--incorporating a broad suite of actuators and sensors, active struts, system identification, passive damping, active mirror mounts, and precision component characterization. The SERC testbed represents a one-tenth scaled version of an optical interferometer concept based on an inherently rigid tetrahedral configuration with collecting apertures on one face. The testbed consists of six 3.5 meter long truss legs joined at four vertices and is suspended with attachment points at three vertices. Each aluminum leg has a 0.2 m by 0.2 m by 0.25 m triangular cross-section. The structure has a first flexible mode at 31 Hz and has over 50 global modes below 200 Hz. The stiff tetrahedral design differs from similar testbeds (such as the JPL Phase B) in that the structural topology is closed. The tetrahedral design minimizes structural deflections at the vertices (site of optical components for maximum baseline) resulting in reduced stroke requirements for isolation and pointing of optics. Typical total light path length stability goals are on the order of lambda/20, with a wavelength of light, lambda, of roughly 500 nanometers. It is expected that active structural control will be necessary to achieve this goal in the presence of disturbances.

Hyde, Tupper; Kim, Ed; Anderson, Eric; Blackwood, Gary; Lublin, Leonard

1990-12-01

98

The Keck Interferometer Nuller  

NASA Astrophysics Data System (ADS)

The Keck Interferometer Nuller (KIN), the first operational separated-aperture infrared nulling interferometer, was designed to null the mid-infrared emission from nearby stars so as to ease the measurement of faint circumstellar emission. This paper describes the basis of the KIN's four-beam, two-stage measurement approach and compares it to the simpler case of a two-beam nuller. In the four-beam KIN system, the starlight is first nulled in a pair of nullers operating on parallel 85 m Keck-Keck baselines, after which "cross-combination" on 4 m baselines across the Keck apertures is used to modulate and detect residual coherent off-axis emission. Comparison to the constructive stellar fringe provides calibration. The response to an extended source is similar in the two cases, except that the four-beam response includes a term due to the visibility of the source on the cross-combiner baseline—a small effect for relatively compact sources. The characteristics of the dominant null depth errors are also compared for the two cases. In the two-beam nuller, instrumental imperfections and asymmetries lead to a series of quadratic, positive-definite null leakage terms. For the four-beam nuller, the leakage is instead a series of correlation cross-terms combining corresponding errors in each of the two nullers, which contribute offsets only to the extent that these errors are correlated on the timescale of the measurement. This four-beam architecture has allowed a significant (~order of magnitude) improvement in mid-infrared long-baseline fringe-visibility accuracies.

Serabyn, E.; Mennesson, B.; Colavita, M. M.; Koresko, C.; Kuchner, M. J.

2012-03-01

99

The single antenna interferometer  

SciTech Connect

Air and space borne platforms using synthetic aperture radars (SAR) have made interferometric measurements by using either two physical antennas mounted on one air-frame or two passes of one antenna over a scene. In this paper, a new interferometric technique using one pass of a single-antenna SAR system is proposed and demonstrated on data collected by the NASA-JPL AirSAR. Remotely sensed L-band microwave data are used to show the sensitivity of this technique to ocean surface features as well as a baseline for comparison with work by others using two-antenna systems. 7 refs., 3 figs.

Fitch, J.P.

1990-01-15

100

Laser radar  

Microsoft Academic Search

The general theory of laser tracking and ranging and the principles governing the design of laser radar systems are examined. Major problems related to optimum reception of laser radar signals and parameter measurement are analyzed from the standpoint of the theory of statistical solutions. Attention is given to methods for processing trajectory measurements and various methods for obtaining noncoordinate information,

I. N. Matveev; V. V. Protopopov; I. N. Troitskii; N. D. Ustinov

1984-01-01

101

Evaluation of the Long-Term Performance of Titanate Ceramics for Immobilization of Excess Weapons Plutonium: Results from Pressurized Unsaturated Flow and Single Pass Flow-Through Testing  

SciTech Connect

This report summarizes our findings from pressurized unsaturated flow (PUF) and single-pass flow-through (SPFT) experiments to date. Results from the PUF test of a Pu-bearing ceramic with enclosing surrogate high-level waste glass show that the glass reacts rapidly to alteration products. Glass reaction causes variations in the solution pH in contact with the ceramic materials. We also document variable concentrations of Pu in solution, primarily in colloidal form, which appear to be related to secular variations in solution composition. The apparent dissolution rate of the ceramic waste form, based on Ba concentrations in the effluent, is estimated at {le} 10{sup {minus}5} g/(m{sup 2} {center_dot} d). Pu-bearing colloids were recovered in the size range of 0.2 to 2 {micro}m, but it is not clear that such entities would be transported in a system that is not advective-flow dominated. Results from SPFT experiments give information on the corrosion resistance of two surrogate Pu-ceramics (Ce-pyrochlore and Ce-zirconolite) at 90 C over a pH range of 2 to 12. The two ceramics were doped with minor quantities ({approximately}0.1 mass%) of MoO{sub 3}, so that concentrations of Mo in the effluent solution could be used to monitor the reaction behavior of the materials. The data obtained thus far from experiments with durations up to 150 d do not conclusively prove that the solid-aqueous solution systems have reached steady-state conditions. Therefore, the dissolution mechanism cannot be determined. Apparent dissolution rates of the two ceramic materials based on Ce, Gd, and Mo concentrations in the effluent solutions from the SPFT are nearly identical and vary between 1.1 to 8.5 x 10{sup {minus}4} g/(m{sup 2} {center_dot} d). In addition, the data reveal a slightly amphoteric dissolution behavior, with a minimum apparent rate at pH = 7 to 8, over the pH range examined. Results from two related ceramic samples suggest that radiation damage can have a measurable effect on the dissolution of titanium-based ceramics. The rare earth pyrochlores, Gd{sub 2}Ti{sub 2}O{sub 7} and Lu{sub 2}Ti{sub 2}O{sub 7}, are being studied as part of the DOE Environmental Management Science Program, and the results are germane to this study. The corrosion resistances of both heavy-ion bombarded and pristine (non-bombarded) specimens are being examined with the SPFT test. Initial data indicate that the dissolution rate may increase by a factor of 3 times or more when these materials become amorphous from radiation damage.

BP McGrail; HT Schaef; JP Icenhower; PF Martin; RD Orr; VL Legore

1999-09-13

102

Balloon Exoplanet Nulling Interferometer (BENI)  

NASA Technical Reports Server (NTRS)

We evaluate the feasibility of using a balloon-borne nulling interferometer to detect and characterize exosolar planets and debris disks. The existing instrument consists of a 3-telescope Fizeau imaging interferometer with 3 fast steering mirrors and 3 delay lines operating at 800 Hz for closed-loop control of wavefront errors and fine pointing. A compact visible nulling interferometer is under development which when coupled to the imaging interferometer would in-principle allow deep suppression of starlight. We have conducted atmospheric simulations of the environment above 100,000 feet and believe balloons are a feasible path forward towards detection and characterization of a limited set of exoplanets and their debris disks. Herein we will discuss the BENI instrument, the balloon environment and the feasibility of such as mission.

Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Ford, Holland; Petro, Larry; Herman, Jay; Rinehart, Stephen; Carpenter, Kenneth; Marzouk, Joe

2009-01-01

103

Fiber Sagnac interferometer temperature sensor  

SciTech Connect

A modified Sagnac interferometer-based fiber temperature sensor is proposed. Polarization independent operation and high temperature sensitivity of this class of sensors make them cost effective instruments for temperature measurements. A comparison of the proposed sensor with Bragg grating and long-period grating fiber sensors is derived. A temperature-induced spectral displacement of 0.99 nm/K is demonstrated for an internal stress birefringent fiber-based Sagnac interferometer. {copyright} {ital 1997 American Institute of Physics.}

Starodumov, A.N.; Zenteno, L.A.; Monzon, D.; De La Rosa, E. [Centro de Investigaciones en Optica, 37150 Leon, Gto (Mexico)] [Centro de Investigaciones en Optica, 37150 Leon, Gto (Mexico)

1997-01-01

104

Surface profiling interferometer  

DOEpatents

The design of a long-trace surface profiler for the non-contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirrors. The optical system is based upon the concept of a pencil-beam interferometer with an inherent large depth-of-field. The key feature of the optical system is the zero-path-difference beam splitter, which separates the laser beam into two colinear, variable-separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.

Takacs, Peter Z. (P.O. Box 385, Upton, NY 11973); Qian, Shi-Nan (Hefei Synchrotron Radiation Laboratory, University of Science and, Hefei, Anhui, CN)

1989-01-01

105

Michelson Interferometer (MINT)  

NASA Astrophysics Data System (ADS)

MINT is a Michelson interferometer designed to measure the thermal emission from the earth at high spectral resolution (2/cm) over a broad spectral range (250-1700/cm, 6-40 mu m) with contiguous 3-pixel wide (12 mrad, 8 km field of view) along-track sampling. MINT is particularly well suited for monitoring cloud properties (cloud cover, effective temperature, optical thickness, ice/water phase, and effective particle size) both day and night, as well as tropospheric water vapor, ozone, and temperature. The key instrument characteristics that make MINT ideally suited for decadal monitoring purposes are: high wavelength to wavelength precision across the full IR spectrum with high spectral resolution; space-proven long-term durability and calibration stability; and small size, low cost, low risk instrument incorporating the latest detector and electronics technology. MINT also incorporates simplicity in design and operation by utilizing passively cooled DTGS detectors and nadir viewing geometry (with target motion compensation). MINT measurement objectives, instrument characteristics, and key advantages are summarized in this paper.

Lacis, Andrew; Carlson, Barbara

1993-09-01

106

Michelson Interferometer (MINT)  

NASA Technical Reports Server (NTRS)

MINT is a Michelson interferometer designed to measure the thermal emission from the earth at high spectral resolution (2/cm) over a broad spectral range (250-1700/cm, 6-40 mu m) with contiguous 3-pixel wide (12 mrad, 8 km field of view) along-track sampling. MINT is particularly well suited for monitoring cloud properties (cloud cover, effective temperature, optical thickness, ice/water phase, and effective particle size) both day and night, as well as tropospheric water vapor, ozone, and temperature. The key instrument characteristics that make MINT ideally suited for decadal monitoring purposes are: high wavelength to wavelength precision across the full IR spectrum with high spectral resolution; space-proven long-term durability and calibration stability; and small size, low cost, low risk instrument incorporating the latest detector and electronics technology. MINT also incorporates simplicity in design and operation by utilizing passively cooled DTGS detectors and nadir viewing geometry (with target motion compensation). MINT measurement objectives, instrument characteristics, and key advantages are summarized in this paper.

Lacis, Andrew; Carlson, Barbara

1993-01-01

107

First Results of the TOPSAR C-Band / L-Band Interferometer: Calibration and Differential Penetration  

NASA Technical Reports Server (NTRS)

The NASA/JPL TOPSAR instrument recently was extended from a single wavelength C-band dual aperture synthetic aperture radar (SAR) interferometer to include a second wavelength at the L-band. Adding the second wavelength invites comparison of wavelength-diverse effects in topographic mapping of surfaces, with the principal goal of understanding the penetration of the radar signals in vegetation canopies, and determining the inferred topographic height. A first analysis of these data was conducted at two sites. Elkhorn Slough near Monterey, California presented flat, vegetation free terrain required for calibrating the radar interferometer parameters. A second site stretching from San Jose to Santa Cruz, California, which is heavily vegetated, provided the first test case for wavelength diverse penetration studies. Preliminary results show that: (a) the interferometer calibration determined at Elkhorn Slough is extenable to Laurel Quad and gives confidence in the C- and L-band height measurements; (b) Clear differences were observed between the C- and L-band heights associated with vegetation, with the C-band derived topographic heights generally higher than those from L-band. The noise level in the L-band interferometer is presently the limiting factor in penetration studies.

Rosen, Paul A.; Hensley, Scott

1996-01-01

108

An improved interferometer design for use with meteor radars  

Microsoft Academic Search

The measurement of the directions of radio meteors with an inter- ferometric system is beset by two problems: (1) The ambiguity in the measured directions for antennas spaced by more than )\\/2 and (2) the effects of mutual impedance when the antennas are spaced at )\\/2 and less to avoid these ambiguities. In this paper we discuss the effects of

J. Jones; A. R. Webster; W. K. Hocking

1998-01-01

109

Anomalous dynamic backaction in interferometers  

NASA Astrophysics Data System (ADS)

We analyze the dynamic optomechanical backaction in signal-recycled Michelson and Michelson-Sagnac interferometers that are operated off the dark port. We show that in this case—and in contrast to the well-studied canonical form of dynamic backaction on the dark port—optical damping in a Michelson-Sagnac interferometer acquires a nonzero value on cavity resonance, and additional stability and instability regions on either side of the resonance, revealing additional regimes of cooling and heating of micromechanical oscillators. In a free-mass Michelson interferometer for a certain region of parameters we predict a stable single-carrier optical spring (positive spring and positive damping), which can be utilized for the reduction of quantum noise in future-generation gravitational-wave detectors.

Tarabrin, Sergey P.; Kaufer, Henning; Khalili, Farid Ya.; Schnabel, Roman; Hammerer, Klemens

2013-08-01

110

Single-pass sum-frequency-generation of 589-nm yellow light based on dual-wavelength Nd:YAG laser with periodically-poled LiTaO(3) crystal.  

PubMed

We demonstrate a compact all-solid-state yellow laser source based on Q-switched dual-wavelength Nd:YAG laser and periodically-poled LiTaO(3) crystal. 589-nm yellow light was generated by single-pass sum-frequency generation of the fundamental IR waves at 1064 and 1319 nm. The maximum output power of yellow light was 506 mW and the corresponding conversion efficiency was approximately 5.5% [W(-1)cm(-1)]. PMID:20588462

Zhao, L N; Su, J; Hu, X P; Lv, X J; Xie, Z D; Zhao, G; Xu, P; Zhu, S N

2010-06-21

111

Quasimonochromatic white light fringe interferometer.  

PubMed

Quasimonochromatic light sources, such as laser diodes and high power LEDs, are investigated to determine their suitability for zero path difference determination using white light fringes in a Michelson interferometer. Fringe visibility curves are theoretically determined for various combinations of light sources and compared with experimental results when used in a Michelson interferometer with a 25-m path length. A resolution of 2-3 microm was obtained for a pair of multimode laser diodes and also for a single multimode laser diode operated as an LED. This is more than adequate for the calibration of survey baselines. PMID:20581948

Ward, B K; Seta, K

1991-01-01

112

AN ATOM INTERFEROMETER GYROSCOPE JAMES GREENBERG  

E-print Network

phase to determine the Earth's rotation rate as well as the orientation of our interferometer polarizability made in our apparatus. #12;4 TABLE OF CONTENTS CHAPTER 1 Introduction 5 CHAPTER 2 Contrast vs interferometer to measure the Earth's rotation rate as well as the orientation of our interferometer with respect

Cronin, Alex D.

113

Coupled fiber ring interferometer array: theory  

Microsoft Academic Search

A novel fiber-optic interferometer, the coupled fiber ring interferometer array (CFRIA) is proposed. The addition of one or more single-mode fiber directional couplers to the fiber ring interferometer results in a CFRIA. The theory based on the matrix method has been proposed for the calculation of the electric field intensity output of the CFRIA. Equations for calculating the transmittance are

An Wang; Haiming Xie

1991-01-01

114

White Light Extended Source Shearing Interferometer  

Microsoft Academic Search

A grating lateral shear interferometer is described that can be used with a white light source. The use of the interferometer with certain types of extended sources is also demonstrated. In a recent paper a simple double frequency grat- ing shearing interferometer, similar to a Ronchi in- terferometer, was described for use with a quasi- monochromatic point light source. l

J. C. Wyant

1974-01-01

115

A triangular path inverting interferometer  

Microsoft Academic Search

A triangular path inverting interferometer is described with application to the study of thermal 'schlieren'. This is practically free of any vibration and coherence troubles, and possesses the unique feature that either differential or total shear may be obtained only with proper positioning of the object; once aligned, the optical components need not be disturbed further. This simple and stable

D. Chakrabarti; S. P. Basu; M. De

1977-01-01

116

Mesospheric wind measurements using a medium-frequency imaging Doppler interferometer  

NASA Technical Reports Server (NTRS)

Wind results from a medium-frequency radar operated as an imaging Doppler interferometer are presented. Ten independent antennas, together with mesospheric wind motions, were used to Doppler-sort and then echo-locate individual scattering points. The three-dimensional location and radial velocity of each discrete scattering point was determined. Mean winds were then determined by a least squares fit to the radial velocities of the ensemble of scatterers.

Adams, G. W.; scatterers.

1986-01-01

117

First Results of the TOPSAR C-Band/L-Band Interferometer: Calibration and Differential Penetration  

NASA Technical Reports Server (NTRS)

The NASA/JPL TOPSAR instrument recently was extended from a single- wavelength C-band (5.6 cm-lambda) dual aperture synthetic aperture radar interferometer to include a second wavelength at L-band (24 cm). Adding the second wavelength invites comparison of wavelength-diverse effects in topographic mapping of surfaces, with the principal goal of understanding the penetration of the radar signals in vegetation canopies, and determining the inferred topographic height. A first analysis of these data was conducted at two sites. Elkhorn Slough near Monterey, California presented flat, vegetation free terrain required for calibrating the radar interferometric parameters. A second site stretching from San Jose to Santa Cruz, CA, which is heavily vegetated, provided the first test case for wavelength diverse penetration studies. Preliminary results show that: (a) the interferometer calibration determined at Elkhorn Slough is extendable to Laurel Quad and gives confidence in the C- and L-band height measurements; and (b) Clear differences are observed between the C- and L-band heights associated with vegetation, with C-band-derived topographic heights generally higher than those from L-band. The noise level in the L-band interferometer is presently the limiting factor in penetration studies.

Rosen, Paul A.; Hensley, Scott

1996-01-01

118

Nulling at the Keck Interferometer  

NASA Technical Reports Server (NTRS)

The nulling mode of the Keck Interferometer is being commissioned at the Mauna Kea summit. The nuller combines the two Keck telescope apertures in a split-pupil mode to both cancel the on-axis starlight and to coherently detect the residual signal. The nuller, working at 10 um, is tightly integrated with the other interferometer subsystems including the fringe and angle trackers, the delay lines and laser metrology, and the real-time control system. Since first 10 um light in August 2004, the system integration is proceeding with increasing functionality and performance, leading to demonstration of a 100:1 on-sky null in 2005. That level of performance has now been extended to observations with longer coherent integration times. An overview of the overall system is presented, with emphasis on the observing sequence, phasing system, and differences with respect to the V2 system, along with a presentation of some recent engineering data.

Colavita, M. Mark; Serabyn, Gene; Wizinowich, Peter L.; Akeson, Rachel L.

2006-01-01

119

Room-temperature, continuous-wave 1-W green power by single-pass frequency doubling in a bulk periodically poled MgO:LiNbO3 crystal.  

PubMed

Continuous-wave high-power green light generation at room temperature is reported in a single-pass frequency-doubling configuration with bulk periodically poled MgO:LiNbO3 crystal placed outside a diode end-pumped Nd:GdVO4 laser. The MgO:LiNbO3 samples of 6.95-microm domain period, uniform periodicity, and 50% duty cycle along the entire crystal length are fabricated by use of a high-voltage multipulse poling method. A maximum power of 1.18 W at 531 nm with 16.8% conversion efficiency is obtained from a 2-mm-thick, 25-mm-long MgO:LiNbO3 crystal; the corresponding internal green power and conversion efficiency are 1.38 W and 19.6%, respectively, whereas the normalized conversion efficiency is 3.3%/W. PMID:15119392

Pavel, N; Shoji, I; Taira, T; Mizuuchi, K; Morikawa, A; Sugita, T; Yamamoto, K

2004-04-15

120

Continuous-wave quasi-phase-matched generation of 60thinspthinspmW at 465thinspthinspnm by single-pass frequency doubling of a laser diode in backswitch-poled lithium niobate  

SciTech Connect

We report continuous-wave single-pass second-harmonic generation (SHG) in 4-{mu}m -period 0.5-mm-thick backswitch-poled lithium niobate. Pump sources at 920{endash}930thinspthinspnm include both Ti:sapphire and diode-oscillator{endash}amplifier lasers. SHG of a Ti:sapphire laser at 6.1{percent}/W efficiency, producing 61thinspthinspmW of power at 460thinspthinspnm, is demonstrated in 50-mm-long periodically poled lithium niobate samples with a nonlinear coefficient d{sub eff}{approx}9 pm/V , and 60thinspthinspmW at 465thinspthinspnm and 2.8{percent}/W efficiency is obtained by SHG of a laser-diode source. {copyright} {ital 1999} {ital Optical Society of America}

Batchko, R.G.; Fejer, M.M.; Byer, R.L. [Ginzton Laboratory, Stanford University, Stanford, California 94305-4085 (United States); Woll, D.; Wallenstein, R. [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse 46, D-67663 Kaiserslautern (Germany); Shur, V.Y. [Institute of Physics and Applied Mathematics, Ural State University, Ekaterinburg 620083 (Russia); Erman, L. [Coherent Laser Group, 5100 Patrick Henry Drive, Santa Clara, California 95054 (United States)

1999-09-01

121

Weather Radar Fundamentals  

NSDL National Science Digital Library

This 2-hour module presents the fundamental principles of Doppler weather radar operation and how to interpret common weather phenomena using radar imagery. This is accomplished via conceptual animations and many interactive radar examples in which the user can practice interpreting both radar reflectivity and radar velocity imagery. Although intended as an accelerated introduction to understanding and using basic Doppler weather radar products, the module can also serve as an excellent refresher for more experienced users.

Comet

2012-03-21

122

Nonlocal polarization interferometer for entanglement detection  

NASA Astrophysics Data System (ADS)

We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the antidiagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization-entangled source. Correlations between these interferometers exhibit nonlocal interference, while single-photon interference is suppressed. This interferometer also allows for a unique version of the Clauser-Horne-Shimony-Holt-Bell test where the local reality is the photon polarization. We present the relevant theory and experimental results.

Williams, Brian P.; Humble, Travis S.; Grice, Warren P.

2014-10-01

123

Dual-probe homodyne quadrature laser interferometer.  

PubMed

We present a dual-probe homodyne quadrature laser interferometer for the measurements of displacement at two separate spatial locations. This is a coupled homodyne interferometer with inverted polarity of probe signals featuring a wide dynamic range and constant sensitivity. As an application of this dual-probe interferometer, we demonstrate how to locate the pulsed-laser interaction site on a plate without knowing the propagation velocities of the laser-induced mechanical waves. PMID:22722276

Požar, Tomaž; Možina, Janez

2012-06-20

124

Radar electronic warfare  

Microsoft Academic Search

An overview of radar and electronic warfare is given. Definitions, common terms, and principles of radar and electronic warfare, and simple analyses of interactions between radar systems and electronic countermeasures (ECM) are presented. Electronic counter-countermeasure and electronic support measures are discussed. Background material in mathematics, electromagnetics, and probability necessary for an understanding of radar and electronic warfare is given and

August Golden Jr.

1987-01-01

125

Radar cross section  

Microsoft Academic Search

The technological evolution in signal processing that has been made in last decades led to improvements in radar performances. Increasing the radar range by improving its sensitivity has been made by the designers of aircraft and other military systems to try to decrease the radar cross section of these types of equipment. The radar cross section is a matter of

L. Nicolaescu; Teofil Oroian

2001-01-01

126

Wind shear radar simulation  

NASA Technical Reports Server (NTRS)

Viewgraphs used in a presentation on wind shear radar simulation are given. Information on a microburst model of radar reflectivity and wind velocity, radar pulse output, the calculation of radar return, microburst power spectrum, and simulation plans are given. A question and answer session is transcribed.

Britt, Charles L.

1988-01-01

127

Interferometer for Space Station Windows  

NASA Technical Reports Server (NTRS)

Inspection of space station windows for micrometeorite damage would be a difficult task insitu using current inspection techniques. Commercially available optical profilometers and inspection systems are relatively large, about the size of a desktop computer tower, and require a stable platform to inspect the test object. Also, many devices currently available are designed for a laboratory or controlled environments requiring external computer control. This paper presents an approach using a highly developed optical interferometer to inspect the windows from inside the space station itself using a self- contained hand held device. The interferometer would be capable as a minimum of detecting damage as small as one ten thousands of an inch in diameter and depth while interrogating a relatively large area. The current developmental state of this device is still in the proof of concept stage. The background section of this paper will discuss the current state of the art of profilometers as well as the desired configuration of the self-contained, hand held device. Then, a discussion of the developments and findings that will allow the configuration change with suggested approaches appearing in the proof of concept section.

Hall, Gregory

2003-01-01

128

Thermal stability of laser tracking interferometer calibration  

Microsoft Academic Search

Uncompensated thermomechanical errors in laser tracking interferometers are examined by evaluating the difference between tracking interferometer compensations in a controlled laboratory environment versus being compensated in a factory environment. The hypothesis under test was that compensation in a factory environment does not adversely affect, and may actually improve, the uncertainty of laser tracker systems. This hypothesis was confirmed by measuring

Scott C. Sandwith

1999-01-01

129

CIST....CORRTEX interferometer simulation test  

SciTech Connect

Testing was performed in order to validate and cross calibrate an RF interferometer and the crush threshold of cable. Nitromethane was exploded (inside of PVC pipe). The explosion was used to crush the interferometer sensor cables which had been placed inside and outside the pipe. Results are described.

Heinle, R.A.

1994-12-01

130

Metrology and pointing for astronomical interferometers  

Microsoft Academic Search

Metrology and pointing will be enabling technologies for a new generation of astronomical missions having large and distributed apertures and delivering unprecedented performance. The UV interferometer Stellar Imager would study stellar dynamos by imaging magnetic activity on the disks of stars in our Galaxy. The X-ray interferometer Black Hole Imager would study strong gravity physics and the formation of jets

James D. Phillips; Kenneth G. Carpenter; Keith C. Gendreau; Margarita Karovska; Philip E. Kaaret; Robert D. Reasenberg

2004-01-01

131

Beam shuttering interferometer and method  

DOEpatents

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Deason, Vance A. (Idaho Falls, ID); Lassahn, Gordon D. (Idaho Falls, ID)

1993-01-01

132

Beam shuttering interferometer and method  

DOEpatents

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Deason, V.A.; Lassahn, G.D.

1993-07-27

133

Widespread Uplift and Trapdoor Faulting of Galapagos Volcanoes Observed with Satellite Radar Interferometry  

Microsoft Academic Search

Satellite radar interferometer observations reveal widespread and continuous surface deformation on the western Galapagos Islands of Isabela and Fernandina during the period 1992-2001. All seven major volcanoes, save one, showed sigificant signs of activity although only two eruptions occurred during the observation period. These basaltic shield volcanoes are characterized by large summit calderas and a lack of rift zones. The

H. Zebker; S. Jonsson; F. Amelung; P. Segall

2001-01-01

134

Temperature fluctuations near the mesopause inferred from meteor observations with the middle and upper atmosphere radar  

Microsoft Academic Search

Using meteor echo measurements with the middle and upper atmosphere (MU) radar (35 deg N, 136 deg E), operated at 46.5 MHz, we examined time-height variation of the ambipolar diffusion coefficient D, determined from the decay rate of meteor echoes. The height of a meteor trail was determined with an accuracy of about 1 km, by using an interferometer for

Masaki Tsutsumi; Toshitaka Tsuda; Takuji Nakamura; Shoichiro Fukao

1994-01-01

135

The Analysis of Moonborne Cross Track Synthetic Aperture Radar Interferometry for Global Environment Change Monitoring  

NASA Astrophysics Data System (ADS)

Faced to the earth observation requirement of large scale global environment change, a SAR (Synthetic Aperture Radar) antenna system is proposed to set on Moon's surface for interferometry in this paper. With several advantages superior to low earth obit SAR, such as high space resolution, large range swath and short revisit interval, the moonborne SAR could be a potential data resource of global changes monitoring and environment change research. Due to the high stability and ease of maintenance, the novel system is competent for offering a long and continuous time series of remote sensing imagery. The Moonborne SAR system performance is discussed at the beginning. Then, the peculiarity of interferometry is analyzed in both repeat pass and single pass cases. The chief distinguishing feature which is worth to research the potentiality of repeat pass interferometry is that the revisit interval is reduced to one day in most cases, and in worst case one month. Decorrelation deriving from geometry variety is discussed in detail. It turns out that the feasibility of moonborne SAR repeat pass interferometry depends on the declination of Moon. The severity of shift effects in radar echoes increased as Moon approaches to the equatorial plane. Moreover, referring to the single pass interferometry, two antennas are assumed to set on different latitude of Moon. There is enough space on Moon to form a long baseline, which is highly related to the interferogram precision.

Yixing, Ding; Huadong, Guo; Guang, Liu; Daowei, Zhang

2014-03-01

136

Radar electronic warfare  

NASA Astrophysics Data System (ADS)

An overview of radar and electronic warfare is given. Definitions, common terms, and principles of radar and electronic warfare, and simple analyses of interactions between radar systems and electronic countermeasures (ECM) are presented. Electronic counter-countermeasure and electronic support measures are discussed. Background material in mathematics, electromagnetics, and probability necessary for an understanding of radar and electronic warfare is given and radar tracking models are examined. The effects of various ECM emissions on radar systems are analyzed, including discussion of active ECM and angle scanning systems, angle measurement in monopulse, and automatic gain control.

Golden, August, Jr.

137

Dispersion cancellation in a triple Laue interferometer  

NASA Astrophysics Data System (ADS)

The concept of dispersion cancellation has been established in light optics to improve the resolution of interferometric measurements on dispersive media. Odd order dispersion cancellation allows to measure phase shifts without defocusing the interferometer due to wave packet displacements, while even order dispersion cancellation allows to measure time lags without losing resolution due to wave packet spreading. We report that either type of dispersion cancellation can be realized very easily in a triple Laue interferometer. Such interferometers are Mach-Zehnder interferometers based on Bragg diffraction, and are commonly used for neutrons and x-rays. Although the first x-ray interferometer was built nearly five decades ago, the feature of dispersion cancellation hasn't been recognized so far because the concept was hardly known in the neutron and x-ray community. However, it explains right away the surprising decoupling of phase shift and spatial displacement that we have discovered recently in neutron interferometry (Lemmel and Wagh 2010 Phys. Rev. A 82 033626). Furthermore, this article might inspire the light optics community to consider whether a triple Laue interferometer for laser light would be useful and feasible. We explain how dispersion cancellation works in neutron interferometry, and we describe the setup rigorously by solving the Schrödinger equation and by calculating the path integral. We point out, that the latter has to be evaluated with special care since in our setup the beam trajectory moves with respect to the crystal lattice of the interferometer.

Lemmel, Hartmut

2014-10-01

138

Comparative Sensitivities of Gravitational Wave Detectors Based on Atom Interferometers and Light Interferometers  

NASA Technical Reports Server (NTRS)

We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe. Whether this potential advantage outweighs the additional complexity associated with including atom interferometers will require further study.

Baker, John G.; Thorpe, J. I.

2012-01-01

139

Customizable Digital Receivers for Radar  

NASA Technical Reports Server (NTRS)

Compact, highly customizable digital receivers are being developed for the system described in 'Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets' (NPO-43962), NASA Tech Briefs, Vol. 31, No. 7 (August 2007), page 72. The receivers are required to operate in unison, sampling radar returns received by the antenna elements in a digital beam-forming (DBF) mode. The design of these receivers could also be adapted to commercial radar systems. At the time of reporting the information for this article, there were no commercially available digital receivers capable of satisfying all of the operational requirements and compact enough to be mounted directly on the antenna elements. A provided figure depicts the overall system of which the digital receivers are parts. Each digital receiver includes an analog-to-digital converter (ADC), a demultiplexer (DMUX), and a field-programmable gate array (FPGA). The ADC effects 10-bit band-pass sampling of input signals having frequencies up to 3.5 GHz. The input samples are demultiplexed at a user-selectable rate of 1:2 or 1:4, then buffered in part of the FPGA that functions as a first-in/first-out (FIFO) memory. Another part of the FPGA serves as a controller for the ADC, DMUX, and FIFO memory and as an interface between (1) the rest of the receiver and (2) a front-panel data port (FPDP) bus, which is an industry-standard parallel data bus that has a high data-rate capability and multichannel configuration suitable for DBF. Still other parts of the FPGA in each receiver perform signal-processing functions. The digital receivers can be configured to operate in a stand-alone mode, or in a multichannel mode as needed for DBF. The customizability of the receiver makes it applicable to a broad range of system architectures. The capability for operation of receivers in either a stand-alone or a DBF mode enables the use of the receivers in an unprecedentedly wide variety of radar systems.

Moller, Delwyn; Heavey, Brandon; Sadowy, Gregory

2008-01-01

140

Least-Squares Estimation and Group Delay in Astrometric Interferometers  

E-print Network

-mail: lawson@huey.jpl.nasa.gov #12; As implemented at PTI, changes in c(t) are monitored with metrology Interferometer and other interferometers within NASA's Origins program. Astrometric interferometers estimate of imperfect mirror mounts and thermal drifts within the interferometer. PTI uses separate laser metrology

141

Significance and Regional Dependency of Peptide Transporter (PEPT) 1 in the Intestinal Permeability of Glycylsarcosine: In Situ Single-Pass Perfusion Studies in Wild-Type and Pept1 Knockout Mice  

PubMed Central

The purpose of this study was to evaluate the role, relevance, and regional dependence of peptide transporter (PEPT) 1 expression and function in mouse intestines using the model dipeptide glycylsarcosine (GlySar). After isolating specific intestinal segments, in situ single-pass perfusions were performed in wild-type and Pept1 knockout mice. The permeability of [3H]GlySar was measured as a function of perfusate pH, dipeptide concentration, potential inhibitors, and intestinal segment, along with PEPT1 mRNA and protein. We found the permeability of GlySar to be saturable (Km = 5.7 mM), pH-dependent (maximal value at pH 5.5), and specific for PEPT1; other peptide transporters, such as PHT1 and PHT2, were not involved, as judged by the lack of GlySar inhibition by excess concentrations of histidine. GlySar permeabilities were comparable in the duodenum and jejunum of wild-type mice but were much larger than that in ileum (approximately 2-fold). A PEPT1-mediated permeability was not observed for GlySar in the colon of wild-type mice (<10% residual uptake compared to proximal small intestine). Moreover, GlySar permeabilities were very low and not different in the duodenum, jejunum, ileum, and colon of Pept1 knockout mice. Functional activity of intestinal PEPT1 was confirmed by real-time polymerase chain reaction and immunoblot analyses. Our findings suggest that a loss of PEPT1 activity (e.g., due to polymorphisms, disease, or drug interactions) should have a major effect in reducing the intestinal absorption of di-/tripeptides, peptidomimetics, and peptide-like drugs. PMID:20660104

Jappar, Dilara; Wu, Shu-Pei; Hu, Yongjun

2010-01-01

142

Rain-Mapping Radar  

NASA Technical Reports Server (NTRS)

Orbiting radar system measures rates of rainfall from 0.5 to 60 mm/h. Radar waves scattered and absorbed by rainfall to extents depending on wavelength, polarization, rate of rainfall, and distribution of sizes and shapes of raindrops. Backscattered radar signal as function of length of path through rain used to infer detailed information about rain. Accumulated radar return signals processed into global maps of monthly average rainfall for use in climatological studies.

Im, K. E.; Li, F. K.; Wilson, W. J.; Rosing, D.

1988-01-01

143

Exploring the QED vacuum with laser interferometers  

Microsoft Academic Search

It is demonstrated that the nonlinear, and as yet unobserved, QED effect of slowing down light by application of a strong magnetic field may be observable with large laser interferometers like for instance LIGO or GEO600.

Daniel Boer; Jan-Willem van Holten

2002-01-01

144

Polarization mismatch errors in radio phase interferometers.  

NASA Technical Reports Server (NTRS)

An analysis is presented which deals with the effects of polarization mismatch errors on the accuracy of a phase interferometer used for position location of unknown emitters relative to known calibration emitters. Closed-form expressions for the induced phase difference between interferometer antennas are derived for several combinations of receiving and transmitting antenna polarizations. Errors contributed by mechanical misalignment between antennas, as well as effects of power loss attributable to polarization mismatch, are also considered. The analysis leads to the conclusion that circularly polarized interferometer and transmitter antennas are best suited for the position location application, if it is assumed that polarization tracking of the interferometer antennas is not available. It is shown that a reasonable amount of ellipticity can be tolerated before the phase error becomes significant.

Muehldorf, E. I.; Teichman, M. A.; Kramer, E.

1972-01-01

145

Temperature compensated two-mode fiber interferometer  

E-print Network

In this thesis we propose an innovative approach of designing and implementing a temperature compensated two-mode optical fiber interferometer in a control system of stabilizing the wavelength of a laser. We give the procedure for designing...

Doma, Jagdish Ramchandra

2012-06-07

146

The effect of rotations on Michelson interferometers  

NASA Astrophysics Data System (ADS)

In the contest of the special theory of relativity, it is shown that uniform rotations induce a phase shift in Michelson interferometers. The effect is second order in the ratio of the interferometer's speed to the speed of light, further suppressed by the ratio of the interferometer's arms length to the radius of rotation and depends on the interferometer's position in the co-rotating frame. The magnitude of the phase shift is just beyond the sensitivity of turntable rotated optical resonators used in present tests of Lorentz invariance. It grows significantly large in Earth's rotated kilometer-scale Fabry-Perot enhanced interferometric gravitational-wave detectors where it appears as a constant bias. The effect can provide the means of sensing center and radius of rotations.

Maraner, Paolo

2014-11-01

147

Active noise cancellation in a suspended interferometer  

E-print Network

We demonstrate feed-forward vibration isolation on a suspended Fabry-Perot interferometer using Wiener filtering and a variant of the common least mean square adaptive filter algorithm. We compare the experimental results ...

Driggers, Jennifer C.

148

GRATING INTERFEROMETER THE FAR-INFRARED  

E-print Network

A LAMELLAR FOR GRATING INTERFEROMETER THE FAR-INFRARED R. L. HENRYand D. B. TANNER Department Of and Dowl- ing,(s) Nolt, Kirby, Lytle and Sievers,@' and Milward."' 163 #12;R. L. HENRY and D. B. TANNER Fig

Tanner, David B.

149

Quantum correlations in a noisy neutron interferometer  

E-print Network

We investigate quantum coherences in the presence of noise by entangling the spin and path degrees of freedom of the output neutron beam from a noisy three-blade perfect crystal neutron interferometer. We find that in the ...

Wood, Christopher J.

150

Radar augmentation device  

NASA Technical Reports Server (NTRS)

The radar augmentation device (RAD) serves to increase the radar response of a target body and thus expedite radar acquisition. The design and development of the RAD are discussed with particular emphasis on technical problems that were encountered and solved. Discussions of the mode of operation of the RAD and the ground test history are also included.

Riedel, J. K.

1972-01-01

151

Micropower impulse radar  

Microsoft Academic Search

Invented and developed at Lawrence Livermore National Laboratory is an inexpensive and highly sensitive, low-power radar system that produces and samples extremely short pulses of energy at the rate of 2 million per second. Called micropower impulse radar (MIR), it can detect objects at a greater variety of distances with greater sensitivity than conventional radar. Its origins in the Laboratory`s

S. Azevedo; T. E. McEwan

1996-01-01

152

Lunar radar backscatter studies  

NASA Technical Reports Server (NTRS)

The lunar surface material in the Plato area is characterized using Earth based visual, infrared, and radar signatures. Radar scattering in the lunar regolith with an existing optical scattering computer program is modeled. Mapping with 1 to 2 km resolution of the Moon using a 70 cm Arecibo radar is presented.

Thompson, T. W.

1979-01-01

153

Controlling radar signature  

SciTech Connect

Low observable technologies for military and tactical aircraft are reviewed including signature-reduction techniques and signal detection/jamming. Among the applications considered are low-signature sensors and the reduction of radar cross section in conjunction with radar-absorbing structures and materials. Technologies for reducing radar cross section are shown to present significant technological challenges, although they afford enhanced aircraft survivability.

Foulke, K.W. (U.S. Navy, Naval Air Warfare Center, China Lake, CA (United States))

1992-08-01

154

Controlling radar signature  

Microsoft Academic Search

Low observable technologies for military and tactical aircraft are reviewed including signature-reduction techniques and signal detection\\/jamming. Among the applications considered are low-signature sensors and the reduction of radar cross section in conjunction with radar-absorbing structures and materials. Technologies for reducing radar cross section are shown to present significant technological challenges, although they afford enhanced aircraft survivability.

Foulke

1992-01-01

155

Radar hydrology: rainfall estimation  

Microsoft Academic Search

Radar observations of rainfall and their use in hydrologic research provide the focus for the paper. Radar-rainfall products are crucial for input to runoff and flood prediction models, validation of satellite remote sensing algorithms, and for statistical characterization of extreme rainfall frequency. In this context we discuss the issues of radar-rainfall product development, and the theoretical and practical requirements of

W. F. Krajewski; J. A. Smith

2002-01-01

156

Development of newly designed VHF interferometer system for observing earthquake-related atmospheric anomalies  

PubMed Central

Temporal correlation between atmospheric anomalies and earthquakes has recently been verified statistically through measuring VHF FM radio waves transmitted beyond the line-of-sight. In order to locate the sources of such atmospheric anomalies, we developed a VHF interferometer system (bistatic-radar type) capable of finding the arrival direction of FM radio waves scattered possibly by earthquake-related atmospheric anomalies. In general, frequency modulation of FM radio waves produces ambiguity of arrival direction. However, our system, employing high-sampling rates of the order of kHz, can precisely measure the arrival direction of FM radio waves by stacking received signals. PMID:20009381

Yamamoto, Isao; Fujiwara, Hironobu; Kamogawa, Masashi; Iyono, Atsushi; Kroumov, Valeri; Azakami, Takashi

2009-01-01

157

Dual-beam skin friction interferometer  

NASA Technical Reports Server (NTRS)

A portable dual-laser beam interferometer is described that nonintrusively measures skin friction by monitoring the thickness change of an oil film at two locations while said oil film is subjected to shear stress. An interferometer flat is utilized to develop the two beams. Light detectors sense the beam reflections from the oil film and the surface thereunder. The signals from the detectors are recorded so that the number of interference fringes produced over a given time span may be counted.

Monson, D. J. (inventor)

1981-01-01

158

An overview of the IRAM interferometer  

Microsoft Academic Search

The general characteristics of the IRAM interferometer are described. The interferometer has three antennas movable on a quasi-T-shaped track and two front-ends per antenna on two orthogonal linear polarizations. The calibration system has 30 Hz chopping between sky and ambient load and LO reference and IF return on one single coaxial cable per station and per front end. The first

L. Weliachew

1985-01-01

159

Quantum theory of the nonlinear interferometer  

SciTech Connect

A full quantum theory of the Mach-Zehnder interferometer with nonlinear Kerr media in both arms is presented. The nonlinear operator equations can be integrated, and the result can be normal-ordered. This permits the evaluation of the factorial moments of the photon number to all orders of the nonlinearity. Various excitations and phase biases are studied. The degree of squeezing by the interferometer is determined.

Shirasaki, M.; Haus, H.A.; Wong, D.L.

1989-01-01

160

Single and double superimposing interferometer systems  

DOEpatents

Interferometers which can imprint a coherent delay on a broadband uncollimated beam are described. The delay value can be independent of incident ray angle, allowing interferometry using uncollimated beams from common extended sources such as lamps and fiber bundles, and facilitating Fourier Transform spectroscopy of wide angle sources. Pairs of such interferometers matched in delay and dispersion can measure velocity and communicate using ordinary lamps, wide diameter optical fibers and arbitrary non-imaging paths, and not requiring a laser.

Erskine, David J. (Oakland, CA)

2000-01-01

161

Keck Interferometer status and plans  

NASA Astrophysics Data System (ADS)

Keck Interferometer is a NASA-funded project to combine the two 10 m Keck telescopes for high sensitivity near-infrared fringe visibility measurements, nulling interferometry at 10 ?m to measure the quantity of exozodiacal emission around nearby stars, and differential-phase measurements to detect "hot-Jupiters" by their direct emission. It is being developed by the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the Michelson Science Center. Recent activity has included formal visibility mode commissioning, as well as science observations, and we briefly review some of the significant technical aspects and updates to the system. We have also completed laboratory development of the nuller. The nuller uses two modified Mach-Zehnder input nullers, a Michelson cross combiner, and a 10 ?m array camera to produce background-limited null measurements. To provide required temporal stability for the nuller, the system incorporates end-to-end laser metrology with phase referencing from two 2.2 ?m fringe trackers. The nuller recently completed its pre-ship review and is being installed on the summit. After nuller integration and test, the differential phase mode will be deployed, which will use a 2-5 ?m fringe detector in combination with a precision path length modulator and a vacuum delay line for dispersion control.

Colavita, M. M.; Wizinowich, Peter L.; Akeson, Rachel L.

2004-10-01

162

Keck Interferometer Nuller science highlights  

NASA Astrophysics Data System (ADS)

We report here on some of the major astronomical observations obtained by the Keck Interferometer Nuller (KIN), the high dynamic range instrument recombining the Keck Telescopes at wavelengths of 8 to 13 microns. A few science targets were observed during the commissioning phase (2004-2007). These early observations aimed at demonstrating the KIN’s ability to spatially resolve and characterize circumstellar dust emission around a variety of targets, ranging from evolved stars to young debris disks. Science operations started then in 2008 with the more demanding KIN exozodi key science programs, augmented by observations of YSOs and hot debris disks between 2009 and 2011. The last KIN observations were gathered in 2011B, and the interpretation of some of the results depicted here is still preliminary (exo-zodi survey) or pending (complicated behavior observed in YSOs). We discuss in particular the initial results of the KIN’s exo-zodi observations, which targeted a total of 40 nearby main sequence single stars. We look for trends in this sample, searching for possible correlations between the measured KIN excesses and basic stellar properties such as spectral type or the presence of dust inferred from separate observations.

Mennesson, Bertrand; Millan-Gabet, Rafael; Colavita, M. M.; Serabyn, E.; Hinz, P.; Kuchner, M.; Liu, W.; Barry, R.; Stark, C.; Ragland, S.; Woillez, J.; Traub, W.; Absil, O.; Defrère, Denis; Augereau, J. C.; Lebreton, J.

2012-07-01

163

Cloud and Precipitation Radar  

NASA Astrophysics Data System (ADS)

Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

164

Use of a Radial Shear Interferometer as a Self Reference Interferometer in Adaptive Optics  

Microsoft Academic Search

A radial shear interferometer (rsi) is produced by the interference of two different sized images of the test wavefront. When the center of curvature of the wavefronts are at the same location, they produce a shear in the radial direction. The rsi has a unique attribute which distinguishes it from other wavefront shear interferometers. For sufficiently large shears S, where

R. Tansey; A. Phenis; K. Shu

2006-01-01

165

2. VIEW SOUTHWEST, prime search radar tower, height finder radar ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. VIEW SOUTHWEST, prime search radar tower, height finder radar towards, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

166

Comparison of Atom Interferometers and Light Interferometers as Space-Based Gravitational Wave Detectors  

E-print Network

We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

John G. Baker; James Ira Thorpe

2012-01-26

167

Comparison of Atom Interferometers and Light Interferometers as Space-Based Gravitational Wave Detectors  

NASA Technical Reports Server (NTRS)

We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

Baker, John G.

2012-01-01

168

Furnace control apparatus using polarizing interferometer  

DOEpatents

A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1995-03-28

169

High resolution Fourier interferometer-spectrophotopolarimeter  

NASA Technical Reports Server (NTRS)

A high-resolution Fourier interferometer-spectrophotopolarimeter is provided using a single linear polarizer-analyzer the transmission axis azimuth of which is positioned successively in the three orientations of 0 deg, 45 deg, and 90 deg, in front of a detector; four flat mirrors, three of which are switchable to either of two positions to direct an incoming beam from an interferometer to the polarizer-analyzer around a sample cell transmitted through a medium in a cell and reflected by medium in the cell; and four fixed focussing lenses, all located in a sample chamber attached at the exit side of the interferometer. This arrangement can provide the distribution of energy and complete polarization state across the spectrum of the reference light entering from the interferometer; the same light after a fixed-angle reflection from the sample cell containing a medium to be analyzed; and the same light after direct transmission through the same sample cell, with the spectral resolution provided by the interferometer.

Fymat, A. L. (inventor)

1976-01-01

170

Quantum correlations in a noisy neutron interferometer  

NASA Astrophysics Data System (ADS)

We investigate quantum coherences in the presence of noise by entangling the spin and path degrees of freedom of the output neutron beam from a noisy three-blade perfect crystal neutron interferometer. We find that in the presence of dephasing noise on the path degree of freedom the entanglement of the output state reduces to 0, however the quantum discord remains nonzero for all noise values. Hence even in the presence of strong phase noise nonclassical correlations persist between the spin and the path of the neutron beam. This indicates that measurements performed on the spin of the neutron beam will induce a disturbance on the path state. We calculate the effect of the spin measurement by observing the changes in the observed contrast of the interferometer for an output beam postselected on a given spin state. In doing so we demonstrate that these measurements allow us to implement a quantum eraser and a which-way measurement of the path taken by the neutron through the interferometer. While strong phase noise removes the quantum eraser, the spin-filtered which-way measurement is robust to phase noise. We experimentally demonstrate this disturbance by comparing the contrasts of the output beam with and without spin measurements of three neutron interferometers with varying noise strengths. This demonstrates that even in the presence of noise that suppresses path coherence and spin-path entanglement, a neutron interferometer still exhibits uniquely quantum behavior.

Wood, Christopher J.; Abutaleb, Mohamed O.; Huber, Michael G.; Arif, Muhammad; Cory, David G.; Pushin, Dmitry A.

2014-09-01

171

The AEI 10 m prototype interferometer  

NASA Astrophysics Data System (ADS)

A 10 m prototype interferometer facility is currently being set up at the AEI in Hannover, Germany. The prototype interferometer will be housed inside a 100 m3 ultra-high vacuum envelope. Seismically isolated optical tables inside the vacuum system will be interferometrically interconnected via a suspension platform interferometer. Advanced isolation techniques will be used, such as inverted pendulums and geometrical anti-spring filters in combination with multiple-cascaded pendulum suspensions, containing an all-silica monolithic last stage. The light source is a 35 W Nd:YAG laser, geometrically filtered by passing it through a photonic crystal fibre and a rigid pre-modecleaner cavity. Laser frequency stabilisation will be achieved with the aid of a high finesse suspended reference cavity in conjunction with a molecular iodine reference. Coating thermal noise will be reduced by the use of Khalili cavities as compound end mirrors. Data acquisition and control of the experiments is based on the AdvLIGO digital control and data system. The aim of the project is to test advanced techniques for GEO 600 as well as to conduct experiments in macroscopic quantum mechanics. Reaching standard quantum-limit sensitivity for an interferometer with 100 g mirrors and subsequently breaching this limit, features most prominently among these experiments. In this paper we present the layout and current status of the AEI 10 m Prototype Interferometer project.

Goßler, S.; Bertolini, A.; Born, M.; Chen, Y.; Dahl, K.; Gering, D.; Gräf, C.; Heinzel, G.; Hild, S.; Kawazoe, F.; Kranz, O.; Kühn, G.; Lück, H.; Mossavi, K.; Schnabel, R.; Somiya, K.; Strain, K. A.; Taylor, J. R.; Wanner, A.; Westphal, T.; Willke, B.; Danzmann, K.

2010-04-01

172

3. VIEW NORTHWEST, height finder radar towers, and radar tower ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. VIEW NORTHWEST, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

173

Planetary radar studies  

NASA Technical Reports Server (NTRS)

A catalog of lunar and radar anomalies was generated to provide a base for comparison with Venusian radar signatures. The relationships between lunar radar anomalies and regolith processes were investigated, and a consortium was formed to compare lunar and Venusian radar images of craters. Time was scheduled at the Arecibo Observatory to use the 430 MHz radar to obtain high resolution radar maps of six areas of the lunar suface. Data from 1978 observations of Mare Serenitas and Plato are being analyzed on a PDP 11/70 computer to construct the computer program library necessary for the eventual reduction of the May 1981 and subsequent data acquisitions. Papers accepted for publication are presented.

Thompson, T. W.; Cutts, J. A.

1981-01-01

174

Laser radar in robotics  

SciTech Connect

In this paper the authors describe the basic operating principles of laser radar sensors and the typical algorithms used to process laser radar imagery for robotic applications. The authors review 12 laser radar sensors to illustrate the variety of systems that have been applied to robotic applications wherein information extracted from the laser radar data is used to automatically control a mechanism or process. Next, they describe selected robotic applications in seven areas: autonomous vehicle navigation, walking machine foot placement, automated service vehicles, manufacturing and inspection, automotive, military, and agriculture. They conclude with a discussion of the status of laser radar technology and suggest trends seen in the application of laser radar sensors to robotics. Many new applications are expected as the maturity level progresses and system costs are reduced.

Carmer, D.C.; Peterson, L.M. [Environmental Research Inst. of Michigan, Ann Arbor, MI (United States)

1996-02-01

175

A Novel Cavity-Based Atom Interferometer  

NASA Astrophysics Data System (ADS)

The world's leading atom interferometers are housed in bulky atomic fountains. They employ a variety of techniques to increase the spatial separation between atomic clouds including high order Bragg diffraction. The largest momentum transfer in a single Bragg beamsplitter has been limited to 24 k by laser power and beam quality. We present an atom interferometer in a 40 cm optical cavity to enhance the available laser power, minimize wavefront distortions, and control other systematic effects symptomatic to atomic fountains. We expect to achieve spatial separations between atomic trajectories comparable to larger scale fountains within a more compact device. We report on our progress in developing this new interferometer using cold Cs atoms and discuss its prospects for exploring large momentum transfer up to 100 k in a single Bragg diffraction process. The compact design will enable the first demonstration of the gravitostatic Aharonov-Bohm effect.

Brown, Justin; Estey, Brian; Müller, Holger

2012-06-01

176

Full-field Fabry-Perot interferometer  

SciTech Connect

This paper describes the use of a Fabry-Perot interferometer for simultaneously measuring velocity at many points on the surface of a shock-loaded solid. The method is based upon work reported by S. Gidon and G. Behar in 1986, but the data analysis has been improved by the application of image-processing techniques. Light from a pulsed single-frequency laser is focused onto a moving target and the returned Doppler-shifted image passed through a Fabry-Perot interferometer. Output of the interferometer is a set of fringes that are formed for specific combinations of wavelength and light angle. These fringes are recorded on film for subsequent analysis. Fringe position determines the velocity for each point on the target that forms a fringe. A method for determining the velocity as a function of both position and time will also be discussed. 5 refs., 6 figs.

Mathews, A.R.; Boat, R.M.; Hemsing, W.F.; Warnes, R.H.; Whittemore, G.R.

1991-01-01

177

A heterodyne interferometer for angle metrology.  

PubMed

We have developed a compact, high-resolution, angle measurement instrument based on a heterodyne interferometer. Common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer set up, an optical mask is used to sample the laser beam reflecting back from four areas on a target surface. From the relative displacement measurements of the target surface areas, we can simultaneously determine angular rotations around two orthogonal axes in a plane perpendicular to the measurement beam propagation direction. The device is used in a testbed for a tracking telescope system where pitch and yaw angle measurements of a flat mirror are performed. Angle noise measurement of the device shows 0.1 nrad/square root of Hz at 1 Hz, at a working distance of 1 m. The operation range and nonlinearity of the device when used with a flat mirror is approximately +/-0.15 mrad, and 3 microrad rms, respectively. PMID:20441364

Hahn, Inseob; Weilert, M; Wang, X; Goullioud, R

2010-04-01

178

Modeling the Laser Interferometer Space Antenna Optics  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA), shown below, will detect gravitational waves produced by objects such as binary black holes or objects falling into black holes (extreme mass ratio inspirals) over a frequency range of l0(exp -4) to 0.1 Hz. Within the conceptual frame work of Newtonian physics, a gravitational wave produces a strain, (Delta)l/l, with magnitudes of the order of Earth based gravitational wave detectors, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) project, use Michelson interferometers with arm lengths l = 4 km to detect these strains. Earth induced seismic noise limits ground-based instruments detecting gravitational waves with frequencies lower than approx. 1 Hz.

Waluschka, Eugene; Pedersen, Tracy R.; McNamara, paul

2005-01-01

179

A heterodyne interferometer for angle metrology  

SciTech Connect

We have developed a compact, high-resolution, angle measurement instrument based on a heterodyne interferometer. Common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer set up, an optical mask is used to sample the laser beam reflecting back from four areas on a target surface. From the relative displacement measurements of the target surface areas, we can simultaneously determine angular rotations around two orthogonal axes in a plane perpendicular to the measurement beam propagation direction. The device is used in a testbed for a tracking telescope system where pitch and yaw angle measurements of a flat mirror are performed. Angle noise measurement of the device shows 0.1 nrad/{radical}(Hz) at 1 Hz, at a working distance of 1 m. The operation range and nonlinearity of the device when used with a flat mirror is approximately {+-}0.15 mrad, and 3 {mu}rad rms, respectively.

Hahn, Inseob; Weilert, M.; Wang, X.; Goullioud, R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

2010-04-15

180

Fabry-Perot interferometer based Mie Doppler lidar for low tropospheric wind observation.  

PubMed

Similar in principle to recent implementations of a lidar system at 355 nm [Opt. Lett. 25, 1231 (2000), Appl. Opt. 44, 6023 (2005)], an incoherent-detection Mie Doppler wind lidar at 1064 nm was developed and deployed in 2005 [Opt. Rev. 12, 409 (2005)] for wind measurements in the low troposphere, taking advantage of aerosol scattering for signal enhancement. We present a number of improvements made to the original 1064 nm system to increase its robustness for long-period operation. These include a multimode fiber for receiving the reference signal, a mode scrambler to allow uniform illumination over the Fabry-Perot interferometer, and a fast scannable Fabry-Perot interferometer for calibration and for the determination of outgoing laser frequency during the wind observation. With these improvements in stability, the standard deviation of peak transmission and FWHM of the Fabry-Perot interferometer was determined to be 0.49% and 0.36%, respectively. The lidar wind measurements were validated within a dynamic range of +/-40 m/s. Comparison experiments with both wind profiler radar and Vaisala wiresonde show good agreement with expected observation error. An example of 24 h continuous observations of wind field and aerosol backscatter coefficients in the boundary layer with 1 min and 30 m temporal and spatial resolution and 3 m/s tolerated wind velocity error is presented and fully demonstrates the stability and robustness of this lidar. PMID:17932519

Xia, Haiyun; Sun, Dongsong; Yang, Yuanhong; Shen, Fahua; Dong, Jingjing; Kobayashi, Takao

2007-10-10

181

Caribbean Radar Cases  

NSDL National Science Digital Library

This module presents radar case studies taken from events in the Caribbean that highlight radar signatures of severe weather. These cases include examples of deep convection, squall lines, bow echoes, tornadoes, and heavy rain resulting in flooding. Each case study includes a discussion of the conceptual models of each type of event as a review before showing the radar signatures and allowing the learner to analyze each one.

Comet

2013-12-31

182

Observing NGC 4151 with the Keck Interferometer  

NASA Technical Reports Server (NTRS)

Observations of the nucleus of NGC 4151 at 2.2 microns using the two 10-meter Keck telescopes as an interferometer show a marginally resolved source less than or equal to 0.1 pc in diameter. These observations are the first measurement of an extragalactic source with an optical/IR interferometer. These observations represent a ten-fold improvement in angular resolution when compared to previous near-infrared measurements of AGN and make it possible to test the subparsecscale, near-infrared emission models of NGC 4151.

Swain, Mark R.

2004-01-01

183

Computer control of a far infrared interferometer  

NASA Technical Reports Server (NTRS)

A simple interface has been designed for the automatic control and data collection from a Grubb Parsons Mark III cube interferometer. A computer is used to automatically step the movable mirror on the interferometer. Data may be directly input into the computer for immediate transformation or stored for later analysis via a fast Fourier transformation. The interface is based on a commercial analog-to-digital converter having a parallel-to-serial data converter. The device can also display ASCII characters sent from the computer in parallel binary code. The system is applicable to recording interferograms having long time durations and to measuring multiple interferograms for statistical averaging.

Breecher, J.

1977-01-01

184

Polarized point diffraction interferometer for fringe stabilization  

NASA Astrophysics Data System (ADS)

We propose a new point diffraction interferometer using a polarizer with a pinholed for qualitative optical analysis. Diffraction from a polarizer with a pinholed makes reference and measurement waves. Interference fringe between diffracted-undiffracted measurement wave and undiffracted-diffracted reference wave is stabilized by common-path configuration. We examined the pinhole size and divergence angle of the diffracted wave for test optics with various numerical aperture. Optical parts comprising the interferometer can be assembled into a small monolithic component and embedded into an imaging target for easy alignment. Optical systems evaluating imaging performances such as modulation transfer function would benefit in aligning target objects.

Kihm, Hagyong; Lee, Yun-Woo

2010-08-01

185

Leggett-Garg inequality in electron interferometers  

NASA Astrophysics Data System (ADS)

We consider the violation of the Leggett-Garg inequality in electronic Mach-Zehnder inteferometers. This setup has two distinct advantages over earlier quantum-transport proposals: Firstly, the required correlation functions can be obtained without time-resolved measurements. Secondly, the geometry of an interferometer allows one to construct the correlation functions from ideal negative measurements, which addresses the noninvasiveness requirement of the Leggett-Garg inequality. We discuss two concrete realizations of these ideas: the first in quantum Hall edge-channels, the second in a double quantum dot interferometer.

Emary, Clive; Lambert, Neill; Nori, Franco

2012-12-01

186

The Invisible Radar Triangle  

NSDL National Science Digital Library

Students learn about radar imaging and its various military and civilian applications that include recognition and detection of human-made targets, and the monitoring of space, deforestation and oil spills. They learn how the concepts of similarity and scaling are used in radar imaging to create three-dimensional models of various targets. Students apply the critical attributes of similar figures to create scale models of a radar imaging scenario using infrared range sensors (to emulate radar functions) and toy airplanes (to emulate targets). They use technology tools to measure angles and distances, and relate the concept of similar figures to real-world applications.

RET-ENET Program, Electrical Engineering Department,

187

(presentation) Precision Mechanisms for Space Interferometers: A Tutorial  

NASA Technical Reports Server (NTRS)

To maximize salability, spaceborne interferometer designs must minimize actuator cost while maximizing science quality and quantity. Interferometer designers must have the knowledge to design a system with the simplist, most reliable, and least expensive actuators possible.

Agronin, Michael L.

1993-01-01

188

The Conceptual Design of the Magdalena Ridge Observatory Interferometer  

E-print Network

We describe the scientific motivation for and conceptual design of the Magdalena Ridge Observatory Interferometer, an imaging interferometer designed to operate at visible and near-infrared wavelengths. The rationale for the major technical decisions in the interferometer design is discussed, the success of the concept is appraised, and the implications of this analysis for the design of future arrays are drawn out.

Buscher, David F; Farris, Allen; Haniff, Christopher A; Young, John S

2013-01-01

189

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment A. Boxer, J. Kesner the density profile of the plasma in LDX, we are constructing a multi-channel microwave interferometer be inverted to reconstruct a radially symmetric density profile. The microwave interferometer of LDX

190

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment A. Boxer, J. Kesner design follows other microwave interferometers in the literature, in particular C.W. Domier et. al. Rev.Sci.Instrum. 59 [1988], 1588 · An RF beam of 60 GHz puts our interferometer in the microwave spectrum. · Our

191

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment A. Boxer, J. Kesner a multi-channel microwave interferometer. Such a device makes use the relationship between a plasma;Basic Design · An RF of 60 GHz puts our interferometer in the microwave spectrum. · The primary design

192

An electron Talbot-Lau interferometer and magnetic field sensing  

SciTech Connect

We present a demonstration of a three grating Talbot-Lau interferometer for electrons. As a proof of principle, the interferometer is used to measure magnetic fields. The device is similar to the classical Moiré deflectometer. The possibility to extend this work to build a scaled-up electron deflectometer or interferometer for sensitive magnetic field sensing is discussed.

Bach, Roger; Batelaan, Herman [Department of Physics and Astronomy, University of Nebraska-Lincoln, Theodore P. Jorgensen Hall, Lincoln, Nebraska 68588 (United States)] [Department of Physics and Astronomy, University of Nebraska-Lincoln, Theodore P. Jorgensen Hall, Lincoln, Nebraska 68588 (United States); Gronniger, Glen [The National Secure Manufacturing Center (NSMC), National Nuclear Security Administration's Kansas City Plant, National Security Campus, 14520 Botts Road, Kansas City, Missouri 64147 (United States)] [The National Secure Manufacturing Center (NSMC), National Nuclear Security Administration's Kansas City Plant, National Security Campus, 14520 Botts Road, Kansas City, Missouri 64147 (United States)

2013-12-16

193

A stellar interferometer on the Moon  

Microsoft Academic Search

The work I present in this document has been divided into two main parts, the first one related to the IOTA project and the second one related to the study on the lunar interferometer, and an introduction section. Each section can be read independently from the other, however they are presented following the logical order in which the research work

Irene Porro

1997-01-01

194

An overview of the Keck Interferometer Nuller  

NASA Technical Reports Server (NTRS)

The first high dynamic range interferometry mode planned to come on line at the Keck Observatory is mid-infrared nulling interferometry. In this paper, an overview is given of the goals and experimental configuration of the Keck Interferometer Nuller (KIN).

Serabyn, Eugen

2003-01-01

195

Pair of accelerated frames: a perfect interferometer  

E-print Network

The four Rindler quadrants of a pair of oppositely accelerated frames are identified as a (Lorentzian) Mach-Zehnder interferometer. The Rindler frequency dependence of the interference process is expressed by means of a (Lorentzian) differential cross section. The Rindler frequencies of the waves in the two acccelerated frames can be measured directly by means of a simple inertially moving detector.

Ulrich H. Gerlach

1999-11-01

196

Differential Phase Mode with the Keck Interferometer  

NASA Technical Reports Server (NTRS)

We describe the differential phase mode of the Keck Interferometer. The scientific goal of this mode is the direct detection and spectroscopic characterization of hot, Jupiter mass planets. We describe the differential phase effect, the basic observational mode, and the expected differential phase signatures for the extrasolar planets discovered through radial velocity searches.

Akeson, Rachel; Swain, Mark

2000-01-01

197

Development of the test interferometer for ALMA  

NASA Astrophysics Data System (ADS)

The ALMA Test Interferometer appeared as an infrastructure solution to increase both ALMA time availability for science activities and time availability for Software testing and Engineering activities at a reduced cost (<30000K USD) and a low setup time of less than 1 hour. The Test Interferometer could include up to 16 Antennas when used with only AOS resources and a possible maximum of 4 Antennas when configured using Correlator resources at OSF. A joined effort between ADC and ADE-IG took the challenge of generate the Test Interferometer from an already defined design for operations which imposed a lot of complex restrictions on how to implement it. Through and intensive design and evaluation work it was determined that is possible to make an initial implementation using the ACA Correlator and now it is also being tested the feasibility to implement the Testing Interferometer connecting the Test Array at AOS with Correlator equipment installed at the OSF, separated by 30 km. app. Lastly, efforts will be done to get interferometry between AOS and OSF Antennas with a baseline of approximately 24 km.

Olguin, R.; Shen, T.; Brito, R.; Saez, A.; Soto, R.; Asayama, S.; Follert, C.; Knee, L.; Quintana, A.; Rabanus, D.; Reynolds, E.; Saez, N.; Sepulveda, J.

2012-09-01

198

The StarLight Space Interferometer  

NASA Technical Reports Server (NTRS)

Two papers describe the StarLight space interferometer a Michelson interferometer that would be implemented by two spacecraft flying in formation. The StarLight formation flying interferometer project has been testing and demonstrating engineering concepts for a new generation of space interferometers that would be employed in a search for extrasolar planets and in astrophysical investigations. As described in the papers, the original StarLight concept called for three spacecraft, and the main innovation embodied is a modification that makes it possible to reduce complexity by eliminating the third spacecraft. The main features of the modification are (1) introduction of an optical delay line on one spacecraft and (2) controlling the flying formation such that the two spacecraft are located at two points along a specified parabola so as to define the required baseline of specified length (which could be varied up to 125 m) perpendicular to the axis of the parabola. One of the papers presents a detailed description of the optical layout and discusses computational modeling of the performance; the other paper presents an overview of the requirements for operation and design, the overall architecture, and subsystems.

Folkner, William; Shao, Michael; Gorham, Peter

2004-01-01

199

Path matched vibration insensitive Fizeau interferometer  

Microsoft Academic Search

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization path matching mechanism. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and

Bradley Trent Kimbrough

2006-01-01

200

Development of a multichannel integrated interferometer immunosensor  

Microsoft Academic Search

This report describes the design, realization and testing of a highly sensitive two-channel integrated optical (IO) Young interferometer (YI) as well as the design of a first multichannel YI. An integrated channel waveguide Y-splitter with two output parallel branches has been used as the basic optical component for building the YI. The generated interference pattern as result of the overlap

Aurel Ymeti; Johannes S. Kanger; Robert Wijn; Paul V. Lambeck; Jan Greve

2002-01-01

201

Smart photogalvanic running-grating interferometer  

NASA Astrophysics Data System (ADS)

Photogalvanic effect produces actuation of periodic motion of macroscopic LiNbO3 crystal. This effect was applied to the development of an all-optical moving-grating interferometer usable for optical trapping and transport of algae chlorella microorganisms diluted in water with a concentration of 27×104ml-1.

Kukhtarev, N. V.; Kukhtareva, T.; Edwards, M. E.; Jones, J.; Bayssie, M.; Wang, J.; Lyuksyutov, S. F.; Reagan, M. A.; Buchhave, P.

2005-03-01

202

A Microwave Interferometer on an Air Track.  

ERIC Educational Resources Information Center

Uses an air track and microwave transmitters and receivers to make a Michelson interferometer. Includes three experiments: (1) measuring the wavelength of microwaves, (2) measuring the wavelength of microwaves by using the Doppler Effect, and (3) measuring the Doppler shift. (MVL)

Polley, J. Patrick

1993-01-01

203

Kramers-Kronig relations for an interferometer.  

E-print Network

dependence of all the optical parameters, including the complex index of refraction, is properly taken the amplitude of light reflected from a Gires-Tournois interferometer are presented. 1 Introduction The Kramers of Preprint submitted to Elsevier Preprint 25 March 1999 #12;refraction. The real part of the index

Sprik, Rudolf

204

Ramsey-Bordé interferometer for electrons  

NASA Astrophysics Data System (ADS)

A scheme to realize an electron interferometer using low-intensity, bichromatic laser pulses as beam splitter is proposed. The splitting process is based on a modification of the Kapitza-Dirac effect, which produces a momentum kick for electrons with a specific initial momentum. A full interferometric setup in Ramsey-Bordé configuration is theoretically analyzed.

Marzlin, Karl-Peter

2013-10-01

205

Theory of fractional quantum Hall interferometers  

NASA Astrophysics Data System (ADS)

Interference of fractionally charged quasiparticles is expected to lead to Aharonov-Bohm oscillations with periods larger than the flux quantum. However, according to the Byers-Yang theorem, observables of an electronic system are invariant under an adiabatic insertion of a quantum of singular flux. We resolve this seeming paradox by considering a microscopic model of electronic interferometers made from a quantum Hall liquid at filling factor 1/m with the shape of a Corbino disk. In such interferometers, the quantum Hall edge states are utilized in place of optical beams, the quantum point contacts play the role of beam splitters connecting different edge channels, and Ohmic contacts represent a source and drain of quasiparticle currents. Depending on the position of Ohmic contacts, one distinguishes interferometers of Fabry-Pérot (FP) and Mach-Zehnder (MZ) type. An approximate ground state of such interferometers is described by a Laughlin-type wave function, and low-energy excitations are incompressible deformations of this state. We construct a low-energy effective theory by restricting the microscopic Hamiltonian of electrons to the space of incompressible deformations and show that the theory of the quantum Hall edge so obtained is a generalization of a chiral conformal field theory. In our theory, a quasiparticle tunneling operator is found to be a single-valued function of tunneling point coordinates, and its phase depends on the topology determined by the positions of Ohmic contacts. We describe strong coupling of the edge states to Ohmic contacts and the resulting quasiparticle current through the interferometer with the help of a master equation. We find that the coherent contribution to the average quasiparticle current through MZ interferometers does not vanish after summation over quasiparticle degrees of freedom. However, it acquires oscillations with the electronic period, in agreement with the Byers-Yang theorem. Importantly, our theory does not rely on any ad hoc constructions, such as Klein factors, etc. When the magnetic flux through an FP interferometer is varied with a modulation gate, current oscillations have the quasiparticle periodicity, thus allowing for spectroscopy of quantum Hall edge states.

Levkivskyi, Ivan P.; Fröhlich, Jürg; Sukhorukov, Eugene V.

2012-12-01

206

Noncooperative rendezvous radar system  

NASA Technical Reports Server (NTRS)

A fire control radar system was developed, assembled, and modified. The baseline system and modified angle tracking system are described along with the performance characteristics of the baseline and modified systems. Proposed changes to provide additional techniques for radar evaluation are presented along with flight test data.

1974-01-01

207

Micropower impulse radar  

Microsoft Academic Search

Invented and developed at LLNL (Lawrence Livermore National Laboratory), this inexpensive and highly sensitive radar system produces and samples extremely short pulses of energy. This novel technology is finding dozens of new uses in Laboratory programs and in sensor devices for homes, automobiles, factories, and hospitals. We have invented and patented a fundamentally different type of compact, low-power radar system

S. Azevedo; T. E. McEwan

1997-01-01

208

Radar illusion via metamaterials  

NASA Astrophysics Data System (ADS)

An optical illusion is an image of a real target perceived by the eye that is deceptive or misleading due to a physiological illusion or a specific visual trick. The recently developed metamaterials provide efficient approaches to generate a perfect optical illusion. However, all existing research on metamaterial illusions has been limited to theory and numerical simulations. Here, we propose the concept of a radar illusion, which can make the electromagnetic (EM) image of a target gathered by radar look like a different target, and we realize a radar illusion device experimentally to change the radar image of a metallic target into a dielectric target with predesigned size and material parameters. It is well known that the radar signatures of metallic and dielectric objects are significantly different. However, when a metallic target is enclosed by the proposed illusion device, its EM scattering characteristics will be identical to that of a predesigned dielectric object under the illumination of radar waves. Such an illusion device will confuse the radar, and hence the real EM properties of the metallic target cannot be perceived. We designed and fabricated the radar illusion device using artificial metamaterials in the microwave frequency, and good illusion performances are observed in the experimental results.

Jiang, Wei Xiang; Cui, Tie Jun

2011-02-01

209

Java Radar Analysis Tool  

NASA Technical Reports Server (NTRS)

Java Radar Analysis Tool (JRAT) is a computer program for analyzing two-dimensional (2D) scatter plots derived from radar returns showing pieces of the disintegrating Space Shuttle Columbia. JRAT can also be applied to similar plots representing radar returns showing aviation accidents, and to scatter plots in general. The 2D scatter plots include overhead map views and side altitude views. The superposition of points in these views makes searching difficult. JRAT enables three-dimensional (3D) viewing: by use of a mouse and keyboard, the user can rotate to any desired viewing angle. The 3D view can include overlaid trajectories and search footprints to enhance situational awareness in searching for pieces. JRAT also enables playback: time-tagged radar-return data can be displayed in time order and an animated 3D model can be moved through the scene to show the locations of the Columbia (or other vehicle) at the times of the corresponding radar events. The combination of overlays and playback enables the user to correlate a radar return with a position of the vehicle to determine whether the return is valid. JRAT can optionally filter single radar returns, enabling the user to selectively hide or highlight a desired radar return.

Zaczek, Mariusz P.

2005-01-01

210

Equatorial MU Radar project  

NASA Astrophysics Data System (ADS)

Research Institute for Sustainable Humanosphere, Kyoto University (RISH) has been studying the atmosphere by using radars. The first big facility was the MU (Middle and Upper atmosphere) radar installed in Shiga, Japan in 1984. This is one of the most powerful and multi-functional radar, and is successful of revealing importance of atmospheric waves for the dynamical vertical coupling processes. The next big radar was the Equatorial Atmosphere Radar (EAR) installed at Kototabang, West Sumatra, Indonesia in 2001. The EAR was operated under close collaboration with LAPAN (Indonesia National Institute for Aeronautics and Space), and conducted the long-term continuous observations of the equatorial atmosphere/ionosphere for more than 10 years. The MU radar and the EAR are both utilized for inter-university and international collaborative research program for long time. National Institute for Polar Research (NIPR) joined EISCAT Scientific Association together with Nagoya University, and developed the PANSY radar at Syowa base in Antarctica as a joint project with University of Tokyo. These are the efforts of radar study of the atmosphere/ionosphere in the polar region. Now we can find that Japan holds a global network of big atmospheric/ionospheric radars. The EAR has the limitation of lower sensitivity compared with the other big radars shown above. RISH now proposes a plan of Equatorial MU Radar (EMU) that is to establish the MU-radar class radar next to the EAR. The EMU will have an active phased array antenna with the 163m diameter and 1055 cross-element Yagis. Total output power of the EMU will be more than 500kW. The EMU can detect turbulent echoes from the mesosphere (60-80km). In the ionosphere incoherent-scatter observations of plasma density, drift, and temperature would be possible. Multi-channel receivers will realize radar-imaging observations. The EMU is one of the key facilities in the project "Study of coupling processes in the solar-terrestrial system" for Master Plan 2014 of the Science Council of Japan (SCJ). We show the EMU project and its science in the presentation.

Yamamoto, Mamoru; Hashiguchi, H.; Tsuda, Toshitaka; Yamamoto, Masayuki

211

Path matched vibration insensitive Fizeau interferometer  

NASA Astrophysics Data System (ADS)

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization path matching mechanism. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. Microwave modulation of a high powered red laser diode is used to create a 15 mW laser source having a coherence length of 250 um with minimal sidelobe ringing. With a 15 mW source, the maximum camera shutter speed, used when measuring a 4% reflector, was 150 usec, resulting in very robust vibration insensitivity. Additionally, stray light interference is substantially reduced due to the source's short coherence, allowing the measurement of thin transparent optics. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers. This work starts with a basic review of interferometry, phase shifting, and polarization as a lead in to a description of the theory and operation of the pixelated mask spatial carrier phase shifting technique. An analysis of the standard Fizeau Interferometer is then given. This is followed by detailed theoretical discussion of the path matched vibration insensitive (PMVI) Fizeau, which includes a theoretical model of the effects of multiple beam return from the test surface when measuring high value reflectors. The coherence properties of laser diodes are then discussed, a theoretical model for the effects of high frequency drive current is derived, and experimental results are given. Finally, the performance of the PMVI Fizeau is experimentally analyzed, potential error sources discussed, and suggestions for improvements provided.

Kimbrough, Bradley Trent

212

Spaceborne weather radar  

NASA Technical Reports Server (NTRS)

The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

Meneghini, Robert; Kozu, Toshiaki

1990-01-01

213

Micropower impulse radar imaging  

SciTech Connect

From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

Hall, M.S.

1995-11-01

214

Laser radar improvements  

NASA Astrophysics Data System (ADS)

A short history of the uses of various laser radars is presented, and appropriate applications of laser and microwave radars are discussed. CO2 laser radar, operating at 10.6 microns, is considered for use in aircraft navigation systems, fire-control systems for armored vehicle and aircraft, missile guidance, severe storm research, line-of-sight command of missiles, wind turbine site surveys, clear-air turbulence monitors for aircraft, and satellite tracking. Microwave radar is all-weather, but is subject to multipath inaccuracies, countermeasures, and angular resolution limitations, so hybrid laser microwave systems look promising for microwave target acquisition and laser tracking. Advantages and disadvantages of the use of ruby, YAG, and CO2 lasers in varying atmospheric conditions are discussed. Development of a laser radar pod for obstacle detection, Doppler navigation, automatic terrain following, hover control, weapon delivery, and precision searching is noted.

Jelalian, A. V.

1981-11-01

215

4. VIEW NORTHEAST, radar tower (unknown function), prime search radar ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. VIEW NORTHEAST, radar tower (unknown function), prime search radar tower, emergency power building, and height finder radar tower - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

216

5. VIEW EAST, height finder radar towers, radar tower (unknown ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. VIEW EAST, height finder radar towers, radar tower (unknown function), prime search radar tower, operations building, and central heating plant - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

217

Quantum metrology with parametric amplifier-based photon correlation interferometers.  

PubMed

Conventional interferometers usually utilize beam splitters for wave splitting and recombination. These interferometers are widely used for precision measurement. Their sensitivity for phase measurement is limited by the shot noise, which can be suppressed with squeezed states of light. Here we study a new type of interferometer in which the beam splitting and recombination elements are parametric amplifiers. We observe an improvement of 4.1±0.3?dB in signal-to-noise ratio compared with a conventional interferometer under the same operating condition, which is a 1.6-fold enhancement in rms phase measurement sensitivity beyond the shot noise limit. The improvement is due to signal enhancement. Combined with the squeezed state technique for shot noise suppression, this interferometer promises further improvement in sensitivity. Furthermore, because nonlinear processes are involved in this interferometer, we can couple a variety of different waves and form new types of hybrid interferometers, opening a door for many applications in metrology. PMID:24476950

Hudelist, F; Kong, Jia; Liu, Cunjin; Jing, Jietai; Ou, Z Y; Zhang, Weiping

2014-01-01

218

Quantum metrology with parametric amplifier-based photon correlation interferometers  

PubMed Central

Conventional interferometers usually utilize beam splitters for wave splitting and recombination. These interferometers are widely used for precision measurement. Their sensitivity for phase measurement is limited by the shot noise, which can be suppressed with squeezed states of light. Here we study a new type of interferometer in which the beam splitting and recombination elements are parametric amplifiers. We observe an improvement of 4.1±0.3?dB in signal-to-noise ratio compared with a conventional interferometer under the same operating condition, which is a 1.6-fold enhancement in rms phase measurement sensitivity beyond the shot noise limit. The improvement is due to signal enhancement. Combined with the squeezed state technique for shot noise suppression, this interferometer promises further improvement in sensitivity. Furthermore, because nonlinear processes are involved in this interferometer, we can couple a variety of different waves and form new types of hybrid interferometers, opening a door for many applications in metrology. PMID:24476950

Hudelist, F.; Kong, Jia; Liu, Cunjin; Jing, Jietai; Ou, Z.Y.; Zhang, Weiping

2014-01-01

219

Spaceborne meteorological radar studies  

NASA Technical Reports Server (NTRS)

Various radar designs and methods are studied for the estimation of rainfall parameters from space. An immediate goal is to support the development of the spaceborne radar that has been proposed for the Tropical Rain Measuring Mission (TRMM). The effort is divided into two activities: a cooperative airborne rain measuring experiment with the Radio Research Laboratory of Japan (RRL), and the modelling of spaceborne weather radars. An airborne rain measuring experiment was conducted at Wallops Flight Facility in 1985 to 1986 using the dual-wavelength radar/radiometer developed by RRL. The data are presently being used to test a number of methods that are relevant to spaceborne weather radars. An example is shown of path-averaged rain rates as estimated from three methods: the standard reflectivity rain rate method (Z-R), a dual-wavelength method, and a surface reference method. The results from the experiment shows for the first time the feasibility of using attenuation methods from space. The purposes of the modelling are twofold: to understand in a quantitative manner the relationships between a particular radar design and its capability for estimating precipitation parameters and to help devise and test new methods. The models are being used to study the impact of various TRMM radar designs on the accuracy of rain rate estimation as well as to test the performance of range-profiling algorithms, the mirror-image method, and some recently devised graphical methods for the estimation of the drop size distribution.

Meneghini, R.

1988-01-01

220

Planetary Radar Astronomy  

NASA Technical Reports Server (NTRS)

Radar is a powerful technique that has furnished otherwise unavailable information about solar system bodies for three decades. The advantages of radar in planetary astronomy result from: (1) the observer's control of all the attributes of the coherent signal used to illuminate the target, especially the wave form's time/frequency modulation and polarization; (2) the ability of radar to resolve objects spatially via measurements of the distribution of echo power in time delay and Doppler frequency; (3) the pronounced degree to which delay-Doppler measurements constrain orbits and spin vectors; and (4) centimeter-to-meter wavelengths, which easily penetrate optically opaque planetary clouds and cometary comae, permit investigation of near-surface macrostructure and bulk density, and are sensitive to high concentrations of metal or, in certain situations, ice. Planetary radar astronomy has primarily involved observations with Earth-based radar telescopes, but also includes some experiments with a spaceborne transmitter or receiver. In addition to providing a wealth of information about the geological and dynamical properties of asteroids, comets, the inner planets, and natural satellites, radar experiments have established the scale of the solar system, have contributed significantly to the accuracy of planetary ephemerides, and have helped to constrain theories of gravitation. This review outlines radar astronomical techniques and describes principal observational results.

Ostro, Steven J.

1993-01-01

221

GEOS-3 ocean current investigation using radar altimeter profiling. [Gulf Stream surface topography  

NASA Technical Reports Server (NTRS)

Both quasi-stationary and dynamic departures from the marine geoid were successfully detected using altitude measurements from the GEOS-3 radar altimeter. The quasi-stationary departures are observed either as elevation changes in single pass profiles across the Gulf Stream or at the crowding of contour lines at the western and northern areas of topographic maps generated using altimeter data spanning one month or longer. Dynamic features such as current meandering and spawned eddies can be monitored by comparing monthly mean maps. Comparison of altimeter inferred eddies with IR detected thermal rings indicates agreement of the two techniques. Estimates of current velocity are made using derived slope estimates in conjunction with the geostrophic equation.

Leitao, C. D.; Huang, N. E.; Parra, C. G.

1978-01-01

222

Space object observation with radar  

NASA Astrophysics Data System (ADS)

FGAN developed a High Power Radar System, able to track and image low Earth orbiting objects, for experimental radar research. The system is unique in Germany; it consists of a narrow band tracking radar and a high resolution imaging radar. The radars are supported from one 34-m parabolic dish antenna. They operate simultaneously on the object of interest. All information which a radar can gain about physical characteristics of targets have to be extracted from the backscattered electromagnetic field of transmitted pulses. L-band tracking data provide information on range, range rate, angular direction, and radar cross-section. From high resolution polarimetric Ku-band radar data projections of the 1- and 2-dimensional scatter centre distributions are computed. This paper gives a brief description of the FGAN radar and summarizes some radar based methods for orbit analysis, orbital lifetime prediction, reconstruction of object images, assessment of object dimensions, shape, attitude, and mass.

Mehrholz, D.

1993-08-01

223

Radar applications overview  

NASA Astrophysics Data System (ADS)

During the fifty years since its initial development as a means of providing early warning of airborne attacks against allied countries during World War II, radar systems have developed to the point of being highly mobile and versatile systems capable of supporting a wide variety of remote sensing applications. Instead of being tied to stationary land-based sites, radar systems have found their way into highly mobile land vehicles as well as into aircraft, missiles, and ships of all sizes. Of all these applications, however, the most exciting revolution has occurred in the airborne platform arena where advanced technology radars can be found in all shapes and sizes...ranging from the large AWACS and Joint STARS long range surveillance and targeting systems to small millimeter wave multi-spectral sensors on smart weapons that can detect and identify their targets through the use of highly sophisticated digital signal processing hardware and software. This paper presents an overview of these radar applications with the emphasis on modern airborne sensors that span the RF spectrum. It will identify and describe the factors that influence the parameters of low frequency and ultra wide band radars designed to penetrate ground and dense foliage environments and locate within them buried mines, enemy armor, and other concealed or camouflaged weapons of war. It will similarly examine the factors that lead to the development of airborne radar systems that support long range extended endurance airborne surveillance platforms designed to detect and precision-located both small high speed airborne threats as well as highly mobile time critical moving and stationary surface vehicles. The mission needs and associated radar design impacts will be contrasted with those of radar systems designed for high maneuverability rapid acquisition tactical strike warfare platforms, and shorter range cued air-to-surface weapons with integral smart radar sensors.

Greenspan, Marshall

1996-06-01

224

Holographic surveillance radar  

NASA Astrophysics Data System (ADS)

Since the 1940s, radar development has focused on narrow-beam, scanning sensors. A wide field of view has advantages in terms of extended acquisition time for any target, and when combined with a high Doppler sampling frequency can yield high-resolution Doppler spectra. Unambiguous range and Doppler can be achieved under certain circumstances, resulting in enhanced ability to evaluate the characteristics of targets and clutter. Holographic radar has a range of applications in which the ability to discriminate targets among clutter is key. An example of such an application is in mitigation of wind farm interference with Air Traffic Control radar.

Oswald, Gordon K. A.

2009-05-01

225

Micropower impulse radar  

SciTech Connect

Invented and developed at Lawrence Livermore National Laboratory is an inexpensive and highly sensitive, low-power radar system that produces and samples extremely short pulses of energy at the rate of 2 million per second. Called micropower impulse radar (MIR), it can detect objects at a greater variety of distances with greater sensitivity than conventional radar. Its origins in the Laboratory`s Laser Directorate stem from Nova`s transient digitizer. The MIR`s extraordinary range of applications include security, search and rescue, life support, nondestructive evaluation, and transportation.

Azevedo, S.; McEwan, T.E.

1996-01-01

226

Meso-scale measurements of the thermosphere using co-located FPIs and EISCAT radars  

Microsoft Academic Search

The presence of co-located Fabry-Perot Interferometers (FPIs) and EISCAT radars in three sites in northern Scandinavia is providing a unique opportunity to perform tristatic measurements of the thermosphere and ionosphere. The FPIs measure the height profile of the 630nm red emission line and tristatic measurements will allow the location of the emitting volume to be identified. We will study how

E. A. K. Ford; A. L. Aruliah; E. M. Griffin; I. McWhirter; A. D. Aylward; M. J. Kosch

2003-01-01

227

An imaging interferometer for compact sources  

NASA Astrophysics Data System (ADS)

This paper presents the results of a study designed to test the feasibility of imaging satellites in geostationary orbit from the ground. We argue that the instrument should be an interferometer consisting of > 30 telescopes mounted on a common, steerable boom. Light from the telescopes is fed to the beam combiner with optical fibers. The delays are equalized by steering the boom and stretching the fibers. The feed system and delay lines are replaced with single mode fibers. This system should be better throughput than the optical interferometers in use today and should be able to reach the sensitivity needed to image these targets with meter-scale telescopes. Calculations supporting this claim and a system design are presented.

Mozurkewich, D.; Armstrong, J. T.; Hindsley, R. B.; Jorgensen, A. M.; Restaino, S. R.; Schmitt, H. R.

2011-09-01

228

Bright solitonic matter-wave interferometer.  

PubMed

We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×10(4) atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud. PMID:25032924

McDonald, G D; Kuhn, C C N; Hardman, K S; Bennetts, S; Everitt, P J; Altin, P A; Debs, J E; Close, J D; Robins, N P

2014-07-01

229

Data Processing for Atmospheric Phase Interferometers  

NASA Technical Reports Server (NTRS)

This paper presents a detailed discussion of calibration procedures used to analyze data recorded from a two-element atmospheric phase interferometer (API) deployed at Goldstone, California. In addition, we describe the data products derived from those measurements that can be used for site intercomparison and atmospheric modeling. Simulated data is used to demonstrate the effectiveness of the proposed algorithm and as a means for validating our procedure. A study of the effect of block size filtering is presented to justify our process for isolating atmospheric fluctuation phenomena from other system-induced effects (e.g., satellite motion, thermal drift). A simulated 24 hr interferometer phase data time series is analyzed to illustrate the step-by-step calibration procedure and desired data products.

Acosta, Roberto J.; Nessel, James A.; Morabito, David D.

2009-01-01

230

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Space interferometers consisting of several free flying telescopes, such as the planned Darwin mission, require a complex metrology system to make all the components operate as a single instrument. Our research focuses on one of its sub-systems that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy would be in the order of 10 µm over 250 meter. To measure this absolute distance, we are currently exploring the frequency sweeping interferometry technique. Its measurement principle is to first measure a phase in the interferometer, sweep a tunable laser over a known frequency interval and finally measure a second phase. By also counting the number of fringes during the sweep it is possible to determine the absolute path length difference without ambiguities. The wavelength at the endpoints of the sweep is stabilized on a Fabry-Perot cavity. In this way the unknown distance is directly referenced to the length of the Fabry-Perot cavity.

Swinkels, Bas L.; Wendrich, Thijs J.; Bhattacharya, Nandini; Wielders, Arno A.; Braat, Joseph J.

2004-09-01

231

Coupled Mach-Zehnder interferometer memory element.  

PubMed

Two active Mach-Zehnder interferometers are integrated in a monolithic InP/InGaAsP photonic integrated circuit. Together they form a crucial component for optical signal processing: an optical memory element or set-reset flip-flop. The switching time for this initial device is approximately 200 ps. The photonic integrated circuit contains active and passive optical components, including electro-optic phase shifters. PMID:16075546

Hill, Martin T; Dorren, H J S; Leijtens, X J M; den Besten, J H; de Vries, T; van Zantvoort, J H C; Smalbrugge, E; Oei, Y S; Binsma, J J M; Khoe, G D; Smit, M K

2005-07-01

232

A Study of Imaging Interferometer Simulators  

NASA Technical Reports Server (NTRS)

Several new space science mission concepts under development at NASA-GSFC for astronomy are intended to carry out synthetic imaging using Michelson interferometers or direct (Fizeau) imaging with sparse apertures. Examples of these mission concepts include the Stellar Imager (SI), the Space Infrared Interferometric Telescope (SPIRIT), the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS), and the Fourier-Kelvin Stellar Interferometer (FKSI). We have been developing computer-based simulators for these missions. These simulators are aimed at providing a quantitative evaluation of the imaging capabilities of the mission by modelling the performance on different realistic targets in terms of sensitivity, angular resolution, and dynamic range. Both Fizeau and Michelson modes of operation can be considered. Our work is based on adapting a computer simulator called imSIM, which was initially written for the Space Interferometer Mission in order to simulate the imaging mode of new missions such as those listed. In a recent GSFC-funded study we have successfully written a preliminary version of a simulator SISIM for the Stellar Imager and carried out some preliminary studies with it. In a separately funded study we have also been applying these methods to SPECS/SPIRIT.

Allen, Ronald J.

2002-01-01

233

Fiber Fizeau interferometer for remote passive sensing  

NASA Astrophysics Data System (ADS)

Fizeau sensors constitute a large proportion of the fiber optic interferometric type sensors in use today. These include EFPI, FFPI, certain MEMS devices and in-line fiber intrinsic dual-reflector type sensors. The vast majority of the published literature covering these sensor types models them with a "2-beam" interferometer approximation, and implement interrogation approaches considering the same. Analysis performed and results presented show that the 2-beam model is not sufficient when reflection coefficients exceed 1% and traditional quadrature interrogation can result in linearity or distortion errors roughly in directly proportion to the reflectivity coefficients of the Fizeau sensor. A 4-beam multi-path interferometer model is developed and exercised to demonstrate this problem. Further this model shows that the "errors" in comparison to an ideal 2-beam interferometer model are symmetric across the unit circle and suggests that linear interrogation may be accomplished if orthonormal sample sets over the entire unit circle are used to replace the traditional (simple) quadrature sampling. This is shown to be true in both modeling and lab evaluations. The resulting approach has capabilities of remote, passive sensor operation, high frequency response, large, linear dynamic range and low noise. The interrogation technique demonstrated involves a phase generated carrier with full fringe sampling and quadrature determination which cancels the errors experienced from simple quadrature determination. Such an improvement enables higher reflectivity, higher SNR, high-fidelity fiber Fizeau sensor designs. Applications include embedded sensors, line sensors, or mechanically adapted for acoustic, pressure, vibration, acceleration or seismic sensing.

Bush, Jeff; Suh, Kwang

2012-06-01

234

Hybrid photonic chip interferometer for embedded metrology  

NASA Astrophysics Data System (ADS)

Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the work piece. Providing closer integration of metrology upon the manufacturing platform can lead to the better control and increased throughput. In this work we present the development of a high precision hybrid optical chip interferometer metrology device. The complete metrology sensor system is structured into two parts; optical chip and optical probe. The hybrid optical chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. The key structure in the device is a tunable laser module based upon an external-cavity diode laser (ECDL). Within the cavity is a multi-layer thin film filter which is rotated to select the longitudinal mode at which the laser operates. An optical probe, which uses a blazed diffracting grating and collimating objective lens, focuses light of different wavelengths laterally over the measurand. Incident laser light is then tuned in wavelength time to effectively sweep an `optical stylus' over the surface. Wavelength scanning and rapid phase shifting can then retrieve the path length change and thus the surface height. We give an overview of the overall design of the final hybrid photonic chip interferometer, constituent components, device integration and packaging as well as experimental test results from the current version now under evaluation.

Kumar, P.; Martin, H.; Maxwell, G.; Jiang, X.

2014-03-01

235

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Space interferometers consisting of several free flying telescopes, such as the planned Darwin mission, require a complex metrology system to make all the components operate as a single instrument. This metrology system consists of various sub-systems to monitor distances, angles and speeds. Our research focuses on one of these sub-systems that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy would be in the order of 10 ?m over 250 meter. To measure this absolute distance, we are currently building a frequency sweeping interferometer. It is operated by first measuring a phase in the interferometer, sweeping a tunable laser over a known frequency interval and finally measuring a second phase. By also counting the number of fringes during the sweep it is possible to determine the absolute path length difference without ambiguities. We plan on actively stabilizing the wavelength at the endpoints of the sweep on a Fabry-Perot cavity using the Pound-Drever-Hall technique. In this way the unknown distance is directly referenced to the length of the Fabry-Perot cavity.

Swinkels, B. L.; Wendrich, T. J.; Bhattacharya, N.; Wielders, A. A.; Braat, J. J. M.

2004-06-01

236

Caribbean Radar Products  

NSDL National Science Digital Library

This module provides examples of radar imagery from various locations in the Caribbean to demonstrate the different types of images available. Also, examples of different meteorological and non meteorological features are presented to show features seen in island locations.

Comet

2013-12-31

237

Radar Calibration Test Satellite  

Microsoft Academic Search

A satellite has been designed for application to radar calibration. Electromagnetic and mechanical characteristics of the satellite and their influence on the selection of shape and other parameters are discussed. Theoretical and experimental scattering data are included.

L. J. Kaplan; J. F. A. Ormsby; EVERT N. FOWLE; KENT R. JOHNSON; Richard T. Bates; S. H. Bickel

1969-01-01

238

A smart radar absorber  

Microsoft Academic Search

This paper proposes a configuration for a smart radar absorber which is capable of both self-tuning and absorb while scan operation. The discussion is complemented by modelled and measured performance data.

Barry Chambers

1999-01-01

239

Laser Radar Animation  

NASA Video Gallery

Laser and radar instruments aboard NASA aircraft provide measurements of the snow and ice surface and down to the bedrock under the ice. Lasers, with a shorter wavelength, measure the surface eleva...

240

Phased-array radars  

NASA Astrophysics Data System (ADS)

The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US military systems COBRA DANE and PAVE PAWS as examples.

Brookner, E.

1985-02-01

241

Downhole pulse radar  

DOEpatents

A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole. 7 figs.

Chang, Hsi-Tien

1987-09-28

242

Downhole pulse radar  

DOEpatents

A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole.

Chang, Hsi-Tien (Albuquerque, NM)

1989-01-01

243

On wave radar measurement  

NASA Astrophysics Data System (ADS)

The SAAB REX WaveRadar sensor is widely used for platform-based wave measurement systems by the offshore oil and gas industry. It offers in situ surface elevation wave measurements at relatively low operational costs. Furthermore, there is adequate flexibility in sampling rates, allowing in principle sampling frequencies from 1 to 10 Hz, but with an angular microwave beam width of 10° and an implied ocean surface footprint in the order of metres, significant limitations on the spatial and temporal resolution might be expected. Indeed there are reports that the accuracy of the measurements from wave radars may not be as good as expected. We review the functionality of a WaveRadar using numerical simulations to better understand how WaveRadar estimates compare with known surface elevations. In addition, we review recent field measurements made with a WaveRadar set at the maximum sampling frequency, in the light of the expected functionality and the numerical simulations, and we include inter-comparisons between SAAB radars and buoy measurements for locations in the North Sea.

Ewans, Kevin; Feld, Graham; Jonathan, Philip

2014-09-01

244

Cloud Base Height and Effective Cloud Emissivity Retrieval with Ground-Based Infrared Interferometer  

NASA Astrophysics Data System (ADS)

Based on ground-based Atmospheric Emitted Radiance Interferometer (AERI) observations in Shouxian, Anhui province, China, the cloud base height (CBH) and effective cloud emissivity are retrieved by using the minimum root-mean-square difference method. This method was originally developed for satellite remote sensing. The high-temporal-resolution retrieval results can depict the trivial variations of the zenith clouds continuously. The retrieval results are evaluated by comparing them with observations by the cloud radar. The comparison shows that the retrieval bias is smaller for the middle and low clouds, especially for opaque clouds. When two layers of clouds exist, the retrieval results reflect the weighting radiative contribution of the multi-layer cloud. The retrieval accuracy is affected by uncertainties of the AERI radiances and sounding profiles, in which the role of uncertainty in the temperature profile is dominant.

Pan, L.; Lu, D.

2012-12-01

245

Development of highly sensitive monolithic interferometer for infrared planet search  

Microsoft Academic Search

We present the design, fabrication and testing of a highly sensitive monolithic interferometer for InfraRed Exoplanet Tracker (IR-ET). This interferometer is field-compensated, thermal-stable for working in the wavelength range between 0.8 and 1.35 mum. Two arms of the interferometer creates a fixed delay of 18.0 mm, which is optimized to have the best sensitivity for radial velocity measurements of slow-rotating

J. Wang; J. Ge; X. Wan; P. Jiang; B. Lee

2011-01-01

246

Special topics in infrared interferometry. [Michelson interferometer development  

NASA Technical Reports Server (NTRS)

Topics in IR interferometry related to the development of a Michelson interferometer are treated. The selection and reading of the signal from the detector to the analog to digital converter is explained. The requirements for the Michelson interferometer advance speed are deduced. The effects of intensity modulation on the interferogram are discussed. Wavelength and intensity calibration of the interferometer are explained. Noise sources (Nyquist or Johnson noise, phonon noise), definitions of measuring methods of noise, and noise measurements are presented.

Hanel, R. A.

1985-01-01

247

Gravitational Wave Detection with Single-Laser Atom Interferometers  

NASA Technical Reports Server (NTRS)

A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

Yu, Nan; Tinto, Massimo

2011-01-01

248

Optomechanical design of the Micro-Arcsecond Metrology testbed interferometer  

Microsoft Academic Search

The Micro Arcsecond Metrology Testbed (MAM) is a laboratory- based, long baseline, white-light interferometer inside a vibration-isolated vacuum tank. The single baseline, high precision interferometer will be able to observe a translating, artificial star at a distance of 10.74 meters with 5 (mu) as accuracy. The MAM testbed consists of an artificial star, laser metrology and a high precision interferometer.

Andrew E. Carlson; Stuart B. Shaklan; Randall D. Bartos; Steve Azevedo

1998-01-01

249

Detecting Fulde-Ferrell superconductors by an Andreev interferometer  

NASA Astrophysics Data System (ADS)

We propose an Andreev interferometer, based on a branched Y-junction, to detect the finite momentum pairing in Fulde-Ferrell (FF) superconductors. In this interferometer, the oscillation of subgap conductance is a unique function of phase difference between the two channels of the Y-junction, which is determined by the phase modulation of the order parameter in the FF superconductors. This interferometer has the potential not only to determine the magnitude but also the direction of the momentum of Cooper pairs in the FF superconductor. The possible applications of the interferometer in the identification of the finite momentum pairing in non-centrosymmetric superconductors are also discussed.

Chen, Wei; Gong, Ming; Shen, R.; Xing, D. Y.

2014-08-01

250

CONFOCAL FABRY-PEROT INTERFEROMETER BASED HIGH SPECTRAL RESOLUTION LIDAR  

E-print Network

CONFOCAL FABRY-PEROT INTERFEROMETER BASED HIGH SPECTRAL RESOLUTION LIDAR by David Swick Hoffman....................................................................................3 Lidar............................................................................................................4 High Spectral Resolution Lidar

Lawrence, Rick L.

251

Combined shearing interferometer and hartmann wavefront sensor  

SciTech Connect

A sensitive wavefront sensor combining attributes of both a Hartmann type of wavefront sensor and an AC shearing interferometer type of wavefront sensor. An incident wavefront, the slope of which is to be detected, is focussed to first and second focal points at which first and second diffraction gratings are positioned to shear and modulate the wavefront, which then diverges therefrom. The diffraction patterns of the first and second gratings are positioned substantially orthogonal to each other to shear the wavefront in two directions to produce two dimensional wavefront slope data for the AC shearing interferometer portion of the wavefront sensor. First and second dividing optical systems are positioned in the two diverging wavefronts to divide the sheared wavefront into an array of subapertures and also to focus the wavefront in each subaperture to a focal point. A quadrant detector is provided for each subaperture to detect the position of the focal point therein, which provides a first indication, in the manner of a Hartmann wavefront sensor, of the local wavefront slope in each subaperture. The total radiation in each subaperture, as modulated by the diffraction grating, is also detected by the quadrant detector which produces a modulated output signal representative thereof, the phase of which relative to modulation by the diffraction grating provides a second indication of the local wavefront slope in each subaperture, in the manner of an AC shearing interferometer wavefront sensor. The data from both types of sensors is then combined by long term averaging thereof to provide an extremely sensitive wavefront sensor.

Hutchin, R. A.

1985-05-21

252

Measuring Cyclic Error in Laser Heterodyne Interferometers  

NASA Technical Reports Server (NTRS)

An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-

Ryan, Daniel; Abramovici, Alexander; Zhao, Feng; Dekens, Frank; An, Xin; Azizi, Alireza; Chapsky, Jacob; Halverson, Peter

2010-01-01

253

Interferometer observations of RS Canum Venaticorum binaries  

NASA Astrophysics Data System (ADS)

We present radio flux measurements at 5 GHz for a sample of RS CVn-type chromospherically active binary systems made from 1988 to 1992 using the Nuffield Radio Astronomy Laboratories (NRAL) broad-band interferometer (BBI). The derived radio luminosities are consistent with previous observations but show that radio flaring is a common feature which will effect the results of rotation-activity studies. The mean brightness temperature for our sample, assuming a radio source size equal to twice the radius of the active stellar component, is consistent with a gyrosynchrotron emission process from mildly relativistic electrons.

Gunn, A. G.; Spencer, R. E.; Abdul Aziz, H.; Doyle, J. G.; Davis, R. J.; Pavelin, P. E.

1994-11-01

254

Mach-Zehnder interferometer for movement monitoring  

NASA Astrophysics Data System (ADS)

Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used Mach- Zehnder interferometer with conventional SM fibers excited with the DFB laser at wavelength of 1550 nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two waves passing through single interferometer arm. The optical fiber SMF 28e in one arm is referential; the second one is positioned on measuring slab at dimensions of 1x2m. A movement of persons around the slab was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero to 10 kHz. It was also displayed in experiments that the experimental subjects, who walked around the slab and at the same time they have had changed their state of motion (knee joint fixation), embodied characteristic changes in their frequency spectra. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability measurements and the gained spectra at repeated drops of balls were compared. Those stroked upon the same place and from the same elevation and dispersion of the obtained frequency spectra was evaluated. These experiments were performed on the series of 20 repeated drops from highs of 0,5 and 1m. The evaluation of experiments displayed that the dispersion of measured values is lower than 4%. Frequency response has been verified with the loudspeaker connected to signal generator and amplifier. Various slabs have been measured and frequency ranges were compared for particular slab designs.

Vasinek, Vladimir; Cubik, Jakub; Kepak, Stanislav; Doricak, Jan; Latal, Jan; Koudelka, Petr

2012-06-01

255

Micro-Precision Interferometer: Pointing Control System  

NASA Technical Reports Server (NTRS)

This paper describes the development of the wavefront tilt (pointing) control system for the JPL Micro-Precision Interferometer (MPI). This control system employs piezo-electric actuators and a digital imaging sensor with feedback compensation to reject errors in instrument pointing. Stringent performance goals require large feedback, however, several characteristics of the plant tend to restrict the available bandwidth. A robust 7th-order wavefront tilt control system was successfully implemented on the MPI instrument, providing sufficient disturbance rejection performance to satisfy the established interference fringe visibility.

O'Brien, John

1995-01-01

256

Modified Phasemeter for a Heterodyne Laser Interferometer  

NASA Technical Reports Server (NTRS)

Modifications have been made in the design of instruments of the type described in "Digital Averaging Phasemeter for Heterodyne Interferometry". A phasemeter of this type measures the difference between the phases of the unknown and reference heterodyne signals in a heterodyne laser interferometer. The phasemeter design lacked immunity to drift of the heterodyne frequency, was bandwidth-limited by computer bus architectures then in use, and was resolution-limited by the nature of field-programmable gate arrays (FPGAs) then available. The modifications have overcome these limitations and have afforded additional improvements in accuracy, speed, and modularity. The modifications are summarized.

Loya, Frank M.

2010-01-01

257

Commissioning status of the Virgo interferometer  

NASA Astrophysics Data System (ADS)

The Virgo interferometer is one of the big observatories aimed at detecting gravitational waves. This paper will describe the Virgo + upgrades and the commissioning work performed between the first Virgo science run (VSR1) and the second Virgo science run (VSR2). Some first results of VSR2 will be discussed, which was recently started with a good duty cycle and an inspiral range for the detection of binary neutron-star inspirals of 10 Mpc. To conclude, an outlook will be given on some future upgrades of the detector.

Accadia, T.; Swinkels, B. L.; Virgo Collaboration

2010-04-01

258

The Virgo Interferometer for Gravitational Wave Detection  

NASA Astrophysics Data System (ADS)

The Virgo interferometer for gravitational wave detection is described. During the commissioning phase that followed the first scientific data taking run an unprecedented sensitivity was obtained in the range 10-60 Hz. Since then an upgrade program has begun, with the aim of increasing the sensitivity, mainly through the introduction of fused silica wires to suspend mirrors and by increasing the Finesse of the Fabry-Perot cavities. Plans until the shutdown for the construction of the Advanced Virgo detector are given as well as the status of the upgrade.

Accadia, T.; Acernese, F.; Antonucci, F.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Bauer, Th. S.; Beker, M. G.; Belletoile, A.; Birindelli, S.; Bitossi, M.; Bizouard, M. A.; Blom, M.; Boccara, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brillet, A.; Brisson, V.; Budzy?ski, R.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calloni, E.; Campagna, E.; Canuel, B.; Carbognani, F.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chassande-Mottin, E.; Chincarini, A.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Corsi, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; Rosa, R. De; Debreczeni, G.; Del Prete, M.; di Fiore, L.; di Lieto, A.; di Paolo Emilio, M.; di Virgilio, A.; Dietz, A.; Dietz, A.; Drago, M.; Fafone, V.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Freise, A.; Galimberti, M.; Gammaitoni, L.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Giazotto, A.; Gouaty, R.; Granata, M.; Greverie, C.; Guidi, G. M.; Hayau, J.-F.; Heitmann, H.; Hello, P.; Hild, S.; Huet, D.; Jaranowski, P.; Kowalska, I.; Królak, A.; Leroy, N.; Letendre, N.; Li, T. G. F.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Majorana, E.; Maksimovic, I.; Man, N.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Masserot, A.; Michel, C.; Milano, L.; Minenkov, Y.; Mohan, M.; Moreau, J.; Morgado, N.; Morgia, A.; Mosca, S.; Moscatelli, V.; Mours, B.; Neri, I.; Nocera, F.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Paoletti, F.; Pardi, S.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Persichetti, G.; Pichot, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Poggiani, R.; Prato, M.; Prodi, G. A.; Punturo, M.; Puppo, P.; Rabeling, D. S.; Rácz, I.; Rapagnani, P.; Re, V.; Regimbau, T.; Ricci, F.; Robinet, F.; Rocchi, A.; Rolland, L.; Romano, R.; Rosi?ska, D.; Ruggi, P.; Sassolas, B.; Sentenac, D.; Sperandio, L.; Sturani, R.; Swinkels, B.; Toncelli, A.; Tonelli, M.; Torre, O.; Tournefier, E.; Travasso, F.; Vajente, G.; van den Brand, J. F. J.; van der Putten, S.; Vasuth, M.; Vavoulidis, M.; Vedovato, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vocca, H.; Was, M.; Yvert, M.

259

Microwave emissions from police radar  

E-print Network

The purpose of this study was to evaluate police officers exposures to microwaves emitted by traffic radar units at the ocular and testicular level. Additionally, comparisons were made of the radar manufacturers published maximum power density...

Fink, John Michael

2012-06-07

260

Venus wind-altitude radar  

NASA Technical Reports Server (NTRS)

A design study on adding a radar altimeter to the Pioneer Venus small probe is review. Block and timing diagrams are provided. The inherent and interface ambiguities, resolution, and data handling logic for radar altimeters are described.

Levanon, N.

1974-01-01

261

Phase modulating the Urbana radar  

NASA Technical Reports Server (NTRS)

The design and operation of a switched phase modulation system for the Urbana Radar System are discussed. The system is implemented and demonstrated using a simple procedure. The radar system and circuits are described and analyzed.

Herrington, L. J., Jr.; Bowhill, S. A.

1983-01-01

262

Special applications of radar systems  

Microsoft Academic Search

Developments at Dornier in radar equipment are discussed. Characteristics of the Tasyll-1 scoring system for air target simulation are examined with emphasis on the Doppler radar principle for missile location. The RADOBS-R (Radar-object shield panorama sensor) system creates a ring-shaped alarm zone around an object for protection and has an operating frequency around 14 GHz. A Synthetic Aperture Radar and

U. Knepper; R. Kremer; H. Lamprecht; R. Schotter

1980-01-01

263

Radar data smoothing filter study  

NASA Technical Reports Server (NTRS)

The accuracy of the current Wallops Flight Facility (WFF) data smoothing techniques for a variety of radars and payloads is examined. Alternative data reduction techniques are given and recommendations are made for improving radar data processing at WFF. A data adaptive algorithm, based on Kalman filtering and smoothing techniques, is also developed for estimating payload trajectories above the atmosphere from noisy time varying radar data. This algorithm is tested and verified using radar tracking data from WFF.

White, J. V.

1984-01-01

264

A Software Tool for Processing the Displacement Time Series Extracted from Raw Radar Data  

NASA Astrophysics Data System (ADS)

The application of high-resolution radar waveform and interferometric principles recently led to the development of a microwave interferometer, suitable to simultaneously measuring the (static or dynamic) deflection of several points on a large structure. From the technical standpoint, the sensor is a Stepped Frequency Continuous Wave (SF-CW), coherent radar, operating in the Ku frequency band. In the paper, the main procedures adopted to extract the deflection time series from raw radar data and to assess the quality of data are addressed, and the MATLAB toolbox developed is described. Subsequently, other functions implemented in the software tool (e.g. evaluation of the spectral matrix of the deflection time-histories, identification of natural frequencies and operational mode shapes evaluation) are described and the application to data recorded on full-scale bridges is exemplified.

Coppi, Francesco; Gentile, Carmelo; Paolo Ricci, Pier

2010-05-01

265

Characteristics of Sunset radar  

NASA Technical Reports Server (NTRS)

Located in a narrow canyon 15 km west of Boulder, Colorado, the Sunset pulsed Doppler radar was the first radar designed and constructed specifically as a VHF ST radar. The antenna system is a phased array of coaxial-colinear dopoles with computer-controlled phase shifters for each line of dipoles. It operates at a frequency of 40.475 MHz and a wavelength of 7.41M. Peak transmitter power is 100 kW. Aperture efficiency is 0.58 and resistive loss is 0.30 for its 3600 sq m area. The practical steering rate is 1 record/minute/position to any arbitrary antenna beam position. The first clear-air turbulence echoes and wind velocity measurements were obtained in 1974. Significant accomplishments are listed.

Green, J. L.

1983-01-01

266

Radar sector blanker  

NASA Astrophysics Data System (ADS)

A radar sector blanker comprises in analog-to-digital converter and a sector controller unit. The analog-to-digital converter receives the analog synchro voltages describing the positioning of a radar antenna and changes these voltages into binary-coded decimal (BCD) information. The sector controller unit comprises a portable housing, a controller system, and a power supply. The controller system includes an OFF comparator circuit, an ON comparator circuit, an S-R latch, and a solid-state switch. Each comparator circuit comprises three cascaded transistor-transistor logic (TTL) integrated chips. The power supply gives a direct-current voltage to the solid-state switch and the TTL chips. The sector blanker blocks transmission for a predetermined rotational region or sector of a radar system.

Hall, Roger B.

1994-03-01

267

Side looking radar calibration study  

NASA Technical Reports Server (NTRS)

Calibration of an airborne sidelooking radar is accomplished by the use of a model that relates the radar parameters to the physical mapping situation. Topics discussed include: characteristics of the transmitters; the antennas; target absorption and reradiation; the receiver and map making or radar data processing; and the calibration process.

Edwards, W. D.

1975-01-01

268

White-light Sagnac interferometer for snapshot polarimetric and multispectral imaging  

E-print Network

White-light Sagnac interferometer for snapshot polarimetric and multispectral imaging Michael W diffraction gratings inside the interferometer enables white- light interference fringes to be generated: Stokes, polarimetry, interferometry, Sagnac interferometer, Savart plate, spectral imaging. 1

Dereniak, Eustace L.

269

Method and Apparatus for Providing a Servodrive Signal in a High Speed Stepping Interferometer.  

National Technical Information Service (NTIS)

In infrared spectroscopy utilizing an interferometer, position stepping of the optical path difference in the interferometer must be accomplished quite rapidly. This is accomplished by applying a drive signal to the moveable mirror in the interferometer. ...

R. A. Schindler

1975-01-01

270

Method and Apparatus for Providing a Servo Drive Signal in a High-Speed Stepping Interferometer.  

National Technical Information Service (NTIS)

In infrared spectroscopy utilizing an interferometer, position stepping of the optical path difference in the interferometer is accomplished by causing a drive signal to be applied to the movable mirror in the interferometer. This signal is proportional t...

R. A. Schindler

1977-01-01

271

HF radar ionospheric clutter  

NASA Astrophysics Data System (ADS)

The characteristics of HF radar echoes reflected from ionization irregularities aligned along the lines of force of the Earth's magnetic field are presented. Utilizing experimental radar-ionospheric clutter data acquired at frequencies between HF and UHF, an analysis is made of the amplitude, the cross-sectional area and the angular extent statistics of HF field-aligned echoes. The Doppler frequency variation, the frequency of occurrence and the diurnal and seasonal variation of HF ionospheric backscatter echoes and their correlation with solar-geophysical conditions are also discussed.

Millman, G. H.

1982-08-01

272

Polarization diversity in radars  

NASA Astrophysics Data System (ADS)

Many polarization techniques, which have been proposed and analyzed to enhance radar performance, are reviewed in this paper in order to assess the possible improvement they can provide in the signal-to-disturbance ratio, target detectability, target discrimination and resolution, and target classification and identification. Some recent experimentally-based results relating to these applications are also presented. Those techniques are emphasized for which polarization-based capabilities appear sufficiently assessed, such as adaptive polarization cancellation of clutter, chaff, and jamming. Polarization Doppler processing of dual-polarization radar signals, meteorologic applications, and polarization adaptation for target detection in the clear (in free space) are also examined.

Giuli, D.

1986-02-01

273

Spaceborne Imaging Radar Symposium  

NASA Technical Reports Server (NTRS)

An overview of the present state of the art in the different scientific and technological fields related to spaceborne imaging radars was presented. The data acquired with the SEASAT SAR (1978) and Shuttle Imaging Radar, SIR-A (1981) clearly demonstrated the important emphasis in the 80's is going to be on in-depth research investigations conducted with the more flexible and sophisticated SIR series instruments and on long term monitoring of geophysical phenomena conducted from free-flying platforms such as ERS-1 and RADARSAT.

Elachi, C.

1983-01-01

274

Retrievals with the Infrared Atmospheric Sounding Interferometer  

NASA Technical Reports Server (NTRS)

The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on October 19, 2006. The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25/cm and a spectral coverage from 645 to 2760/cm. Ultraspectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations during the JAIVEx are obtained and presented. These retrievals are further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed Interferometer (NAST-I), dedicated dropsondes, radiosondes, and ground based Raman Lidar. The capabilities of satellite ultra-spectral sounder such as the IASI are investigated.

Zhou, Daniel K.; Liu, Xu; Larar, Allen M.; Smith, William L.; Taylor, Jonathan P.; Schlussel, Peter; Strow, L. Larrabee; Calbet, Xavier; Mango, Stephen A.

2007-01-01

275

Ultraviolet-Infrared Mapping Interferometic Spectrometer  

NASA Technical Reports Server (NTRS)

Prism and grating spectrometers have been the defacto devices for spectral mapping and imaging (hereafter referred to as hyperspectra). We have developed a new, hybrid instrument with many superior capabilities, the Digital Array Scanned Interferometer, DASI. The DASI performs the hyperspectral data acquisition in the same way as a grating or prism spectrograph, but retains the substantial advantages of the two-beam (Michelson) interferometer with additional capabilities not possessed by either of the other devices. The DASI is capable of hyperspectral studies in virtually any space or surface environment at any wavelength from below 50 nm to beyond 12 microns with available array detectors. By our efforts, we have defined simple, low cost, no-moving parts DASI's capable of carrying out hyperspectral science measurements for solar system exploration missions, e.g. for martian, asteroid, lunar, or cometary surveys. DASI capabilities can be utilized to minimize cost, weight, power, pointing, and other physical requirements while maximizing the science data return for spectral mapping missions. Our success in the development of DASI's has become and continues to be an important influence on the efforts of the best research groups developing remote sensing instruments for space and other applications.

1994-01-01

276

An Imaging Interferometer for Terrestrial Remote Sensing  

NASA Technical Reports Server (NTRS)

A prototype imaging interferometer called DASI (digital array scanned interferometer) is under development at our laboratories. Our objective is to design an instrument for remote sensing of Earth's atmosphere and surface. This paper describes the unusual characteristics of DASIs which make them promising candidates for ground and aircraft-based terrestrial measurements. These characteristics include superior signal-to-noise, design simplicity and compactness, relative to dispersion based imaging spectrometers. Perhaps one of the most notable features of DASIs is their ability to acquire an entire interferogram simultaneously without any moving optical elements. We also describe selected laboratory and ground based field measurements using the prototype DASI. A CCD detector array was placed at the DASI detector plane for wavelength coverage from 0.4 to 1.0 micron. A NICMOS MCT detector was used for coverage from 1.1 to 2.2 micron. The DASI was configured to have a spectral resolution of about 300 1/cm, a spatial field of view of 5 degrees, and a constant number of transverse spatial elements (detector dependent) for each exposure frame. Frame exposure rates were up to 0.6 Hz with the potential to achieve 5 Hz. Image cube measurements of laboratory targets and terrestrial scenes were obtained by multiple frame scanning over the field of view. These data sets reveal the potential science yields from obtaining simultaneous high resolution spatial and spectral information.

Hammer, Philip D.; Valero, Francisco P. J.; Peterson, David L.; Smith, William Hayden

1993-01-01

277

An X-ray BBB Michelson interferometer.  

PubMed

A new X-ray Michelson interferometer based on the BBB interferometer of Bonse and Hart and designed for X-rays of wavelength approximately 1 A was described in a previous paper. Here, a further test carried out at the SPring-8 1 km beamline BL29XUL is reported. One of the BBB's mirrors was displaced by a piezo to introduce the required path-length difference. The resulting variation of intensity with piezo voltage as measured by an avalanche photodiode could be ascribed to the phase variation resulting from the path-length change, with a small additional contribution from the change of the position of the lattice planes of the front mirror relative to the rest of the crystal. This 'Michelson fringe' interpretation is supported by the observed steady movement across the output beam of the interference fringes produced by a refractive wedge when the piezo voltage was ramped. The front-mirror displacement required for one complete fringe at the given wavelength is only 0.675 A; therefore, a quiet environment is vital for operating this device, as previous experiments have shown. PMID:15310953

Sutter, John P; Ishikawa, Tetsuya; Kuetgens, Ulrich; Materlik, Gerhard; Nishino, Yoshinori; Rostomyan, Armen; Tamasaku, Kenji; Yabashi, Makina

2004-09-01

278

Adaptive DFT-Based Interferometer Fringe Tracking  

NASA Astrophysics Data System (ADS)

An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier-transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on offline data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse. One example of such an application might be to the field of thin-film measurement by ellipsometry, using a broadband light source and a Fourier-transform spectrometer to detect the resulting fringe patterns.

Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

279

header for SPIE use Astrometry with the Keck Interferometer  

E-print Network

`outrigger' telescopes at the Keck Observatory on Mauna Kea. In addition to the imaging scienceheader for SPIE use Astrometry with the Keck Interferometer G. T. van Belle, A. F. Boden, M. M manner from the ground has led NASA to begin work on the Keck Interferometer, which will add 4 1.8m

van Belle, Gerard

280

Polarization Sagnac interferometer with a common-path  

E-print Network

interferometer. © 1999 Optical Society of America [S0740-3224(99)02609-0] OCIS codes: 120.2130, 120.3180, 120.5790, 120.5050. 1. INTRODUCTION For shot-noise­limited interferometric measurements the maximum sensitivity be ex- tended to allow detection of the dark fringe on the sym- metric port of the interferometer

Byer, Robert L.

281

Demodulators for optical fiber interferometers with (3 x 3) outputs  

Microsoft Academic Search

A highly sensitive optical fiber interferometer sensor comprising a laser light source, a (2 x 2) optical fiber coupler to split the beam in two, a differential transducer which converts a signal of interest into optical phase shift in the laser light transmitted through the two optical fibers in the interferometer and a (3 x 3) optical fiber complex which

Robert M. Keolian; Steven L. Garrett; Charles B. Cameron

1994-01-01

282

Fiber-optic interferometer for remote subangstrom vibration measurement  

Microsoft Academic Search

A single-mode fiber-optic interferometer for measuring subangstrom vibrations has been designed and constructed. The interferometer is based on the Fizeau configuration and employs peak detection schemes in the signal processing. The instrument has been used to measure the displacement of a cricket’s tympanic membrane.

Allen Dean Drake; Dennis C. Leiner

1984-01-01

283

Automated Editing of Radio Interferometer Data with pieflag  

Microsoft Academic Search

Editing radio interferometer data, a process commonly known as `flagging', can be laborious and time-consuming. One quickly tends to flag more data than actually required, sacrificing sensitivity and image fidelity in the process. I describe a program, pieflag, which can analyze radio interferometer data to filter out measurements which are likely to be affected by interference. pieflag uses two algorithms

Enno Middelberg

2006-01-01

284

Two-Dimensional X-Ray Grating Interferometer  

SciTech Connect

We report on the design and experimental realization of a 2D x-ray grating interferometer. We describe how this interferometer has been practically implemented, discuss its performance, and present multidirectional scattering (dark-field) maps and quantitative phase images that have been retrieved using this device.

Zanette, Irene [European Synchrotron Radiation Facility, Grenoble (France); Weitkamp, Timm [European Synchrotron Radiation Facility, Grenoble (France); Synchrotron Soleil, Gif-sur-Yvette (France); Donath, Tilman; Rutishauser, Simon; David, Christian [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, Villigen (Switzerland)

2010-12-10

285

Fiber-optic interferometer for remote subangstrom vibration measurement  

NASA Astrophysics Data System (ADS)

A single-mode fiber-optic interferometer for measuring subangstrom vibrations has been designed and constructed. The interferometer is based on the Fizeau configuration and employs peak detection schemes in the signal processing. The instrument has been used to measure the displacement of a cricket's tympanic membrane.

Drake, Allen Dean; Leiner, Dennis C.

1984-02-01

286

Magdalena Ridge Observatory Interferometer: Progress Towards First Light  

E-print Network

-moving objects and targets of opportunity, owing to its very high slew and tracking rates; its operations A of the interferometer build will include 6 telescopes and infrared fringe-tracking and scientific imaging capabilities aperture optical and near-infrared interferometer being built at 3,200 meters altitude on Magdalena Ridge

Young, John

287

Fiber optic acoustic sensor based on the Sagnac interferometer  

Microsoft Academic Search

Advances in technology have reshaped the fiber optic acoustic sensing landscape. The Sagnac interferometer configuration can be used to sense environmental parameters other than rotation simply by creating a path length difference. The output of the acoustic sensor contains information about the amplitude and location of an acoustic disturbance. The Sagnac interferometer has the ability to generate polarization effects. These

Angeline Yap; Thuy Vo; Hendra Wijaya

1995-01-01

288

Imaging interferometer using dual broadband quantum well infrared photodetectors  

NASA Technical Reports Server (NTRS)

The Jet Propulsion Laboratory is developing a new imaging interferometer that has double the efficiency of conventional interferometers and only a fraction of the mass and volume. The project is being funded as part of the Defense Advanced Research Projects Agency (DARPA) Photonic Wavelength And Spatial Signal Processing program (PWASSSP).

Reininger, F.; Gunapala, S.; Bandara, S.; Grimm, M.; Johnson, D.; Peters, D.; Leland, S.; Liu, J.; Mumolo, J.; Rafol, D.; Thomas, I.; Ting, D.; Wilson, D.

2002-01-01

289

Numerical simulation and experimental verification of extended source interferometer  

NASA Astrophysics Data System (ADS)

Extended source interferometer, compared with the classical point source interferometer, can suppress coherent noise of environment and system, decrease dust scattering effects and reduce high-frequency error of reference surface. Numerical simulation and experimental verification of extended source interferometer are discussed in this paper. In order to provide guidance for the experiment, the modeling of the extended source interferometer is realized by using optical design software Zemax. Matlab codes are programmed to rectify the field parameters of the optical system automatically and get a series of interferometric data conveniently. The communication technique of DDE (Dynamic Data Exchange) was used to connect Zemax and Matlab. Then the visibility of interference fringes can be calculated through adding the collected interferometric data. Combined with the simulation, the experimental platform of the extended source interferometer was established, which consists of an extended source, interference cavity and image collection system. The decrease of high-frequency error of reference surface and coherent noise of the environment is verified. The relation between the spatial coherence and the size, shape, intensity distribution of the extended source is also verified through the analysis of the visibility of interference fringes. The simulation result is in line with the result given by real extended source interferometer. Simulation result shows that the model can simulate the actual optical interference of the extended source interferometer quite well. Therefore, the simulation platform can be used to guide the experiment of interferometer which is based on various extended sources.

Hou, Yinlong; Li, Lin; Wang, Shanshan; Wang, Xiao; Zang, Haijun; Zhu, Qiudong

2013-12-01

290

Integrated multimode interferometers with arbitrary designs for photonic boson sampling  

NASA Astrophysics Data System (ADS)

The evolution of bosons undergoing arbitrary linear unitary transformations quickly becomes hard to predict using classical computers as we increase the number of particles and modes. Photons propagating in a multiport interferometer naturally solve this so-called boson sampling problem, thereby motivating the development of technologies that enable precise control of multiphoton interference in large interferometers. Here, we use novel three-dimensional manufacturing techniques to achieve simultaneous control of all the parameters describing an arbitrary interferometer. We implement a small instance of the boson sampling problem by studying three-photon interference in a five-mode integrated interferometer, confirming the quantum-mechanical predictions. Scaled-up versions of this set-up are a promising way to demonstrate the computational advantage of quantum systems over classical computers. The possibility of implementing arbitrary linear-optical interferometers may also find applications in high-precision measurements and quantum communication.

Crespi, Andrea; Osellame, Roberto; Ramponi, Roberta; Brod, Daniel J.; Galvão, Ernesto F.; Spagnolo, Nicolò; Vitelli, Chiara; Maiorino, Enrico; Mataloni, Paolo; Sciarrino, Fabio

2013-07-01

291

Solar Confocal Interferometers for Sub-Picometer-Resolution Spectral Filters  

NASA Technical Reports Server (NTRS)

The confocal Fabry-Perot interferometer allows sub-picometer spectral resolution of Fraunhofer line profiles. Such high spectral resolution is needed to keep pace with the higher spatial resolution of the new set of large-aperture solar telescopes. The line-of-sight spatial resolution derived for line profile inversions would then track the improvements of the transverse spatial scale provided by the larger apertures. The confocal interferometer's unique properties allow a simultaneous increase in both etendue and spectral power. Methods: We have constructed and tested two confocal interferometers. Conclusions: In this paper we compare the confocal interferometer with other spectral imaging filters, provide initial design parameters, show construction details for two designs, and report on the laboratory test results for these interferometers, and propose a multiple etalon system for future testing of these units and to obtain sub-picometer spectral resolution information on the photosphere in both the visible and near-infrared.

Gary, G. Allen; Pietraszewski, Chris; West, Edward A.; Dines, Terence C.

2006-01-01

292

Dispersion interferometer using modulation amplitudes on LHD (invited)a)  

NASA Astrophysics Data System (ADS)

Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 1017 m-3 is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 1020 m-3 can be overcome by a sufficient sampling rate of about 100 kHz.

Akiyama, T.; Yasuhara, R.; Kawahata, K.; Okajima, S.; Nakayama, K.

2014-11-01

293

Highly stable polarization independent Mach-Zehnder interferometer  

E-print Network

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27x40 cm offers individually accessible paths and shows phase deviation less than 0.4 deg during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 deg or 7 nm for 1.5 hours without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not ...

Micuda, Michal; Straka, Ivo; Mikova, Martina; Dusek, Miloslav; Fiurasek, Jaromir; Jezek, Miroslav

2014-01-01

294

Spaceborne precipitation radar  

NASA Technical Reports Server (NTRS)

The performances and characteristics of a satelliteborne radar operating in the millimeter wavelength region of the spectrum with emphasis placed on the 35 and 94 GH3 frequency bands are discussed. It is concluded that millimetric wavelengths provide an acceptable solution for the design of satelliteborne active microwave equipment.

Eckerman, J.; Meneghini, R.

1981-01-01

295

The Newcastle meteor radar  

NASA Technical Reports Server (NTRS)

A brief history and development of the Newcastle Meteor Radar system is given. Also described are its geographical coordinates and its method of operation. The initial objective when the project was commenced was to develop an entirely digital analyzer capable of recognizing meteor echo signals and recording as many of their parameters as possible. This objective was achieved.

Keay, Colin

1987-01-01

296

RADAR “SAIL” satellite concept  

Microsoft Academic Search

The Radar SAIL concept is based on the use of a rectangular antenna lying in the dawn-dusk orbital plane with the length (along speed vector) smaller than the height. Such geometry makes it possible to place the solar cells on the back of the antenna, to use gravity gradient stabilisation, and to implement multipath-free GPS interferometric measurement of the antenna

Jean Paul Aguttes; Jacques Sombrin; Eric Conde

1996-01-01

297

Thin Wideband Radar Absorbers  

Microsoft Academic Search

A procedure for the optimal design of thin wideband radar absorbers is presented. The resulting absorbers are implemented by printing a frequency selective surface on a lossy perforated substrate. A binary hill climbing optimization scheme with random restart is used to find optimal solutions. The method of moments in conjunction with the transmission line method is used to calculate the

Arya Fallahi; Alireza Yahaghi; Hans-Rudolf Benedickter; Habibollah Abiri; Mahmoud Shahabadi; Christian Hafner

2010-01-01

298

Solar Confocal interferometers for Sub-Picometer-Resolution Spectral Filters  

NASA Technical Reports Server (NTRS)

The confocal Fabry-Perot interferometer allows sub-picometer spectral resolution of Fraunhofer line profiles. Such high spectral resolution is needed to keep pace with the higher spatial resolution of the new set of large-aperture solar telescopes. The line-of-sight spatial resolution derived for line profile inversions would then track the improvements of the transverse spatial scale provided by the larger apertures. In particular, profile inversion allows improved velocity and magnetic field gradients to be determined independent of multiple line analysis using different energy levels and ions. The confocal interferometer's unique properties allow a simultaneous increase in both etendue and spectral power. The higher throughput for the interferometer provides significant decrease in the aperture, which is important in spaceflight considerations. We have constructed and tested two confocal interferometers. A slow-response thermal-controlled interferometer provides a stable system for laboratory investigation, while a piezoelectric interferometer provides a rapid response for solar observations. In this paper we provide design parameters, show construction details, and report on the laboratory test for these interferometers. The field of view versus aperture for confocal interferometers is compared with other types of spectral imaging filters. We propose a multiple etalon system for observing with these units using existing planar interferometers as pre-filters. The radiometry for these tests established that high spectral resolution profiles can be obtained with imaging confocal interferometers. These sub-picometer spectral data of the photosphere in both the visible and near-infrared can provide important height variation information. However, at the diffraction-limited spatial resolution of the telescope, the spectral data is photon starved due to the decreased spectral passband.

Gary, G. Allen; Pietraszewski, Chris; West, Edward A.; Dines. Terence C.

2007-01-01

299

Towards a Suspension Platform Interferometer for the AEI 10 m Prototype Interferometer  

NASA Astrophysics Data System (ADS)

Currently, the AEI 10 m Prototype is being set up at the Albert Einstein Institute in Hannover, Germany. The Suspension Platform Interferometer (SPI) will be an additional interferometer set up inside the vacuum envelope of the AEI 10 m Prototype. It will interferometrically link the three suspended in-vacuum tables. The inter-table distance will be 11.65 m. The SPI will measure and stabilise the relative motions between these tables for all degrees of freedom, except roll around the optical axis. In this way, all tables can be regarded as one large platform. The design goal is 100 pm/ differential distance stability between 10mHz and 100Hz.

Dahl, K.; Bertolini, A.; Born, M.; Chen, Y.; Gering, D.; Goßler, S.; Gräf, C.; Heinzel, G.; Hild, S.; Kawazoe, F.; Kranz, O.; Kühn, G.; Lück, H.; Mossavi, K.; Schnabel, R.; Somiya, K.; Strain, K. A.; Taylor, J. R.; Wanner, A.; Westphal, T.; Willke, B.; Danzmann, K.

2010-05-01

300

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Future space missions, among which the Darwin Space Interferometer, will consist of several free flying satellites. A complex metrology system is required to have all the components fly accurately in formation and have it operate as a single instrument. Our work focuses on a possible implementation of the sub-system that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy is on the order of 70 micrometer over a distance of 250 meter. We are exploring a technique called frequency sweeping interferometry, which involves interferometrically measuring a phase difference while sweeping the wavelength of a tunable laser. This phase difference is directly proportional to the absolute distance. A very high finesse Fabry-Perot cavity is used as a reference standard, to which the laser is locked at the end-points of the sweep. We will discuss our measurement scheme, our set-up and some first measurements.

Swinkels, Bas L.; Latoui, Abdelhalim; Bhattacharya, Nandini; Wielders, Arno A.; Braat, Joseph J. M.

2005-08-01

301

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Future space missions, among which the Darwin Space Interferometer, will consist of several free flying satellites. A complex metrology system is required to have all the components fly accurately in formation and have it operate as a single instrument. Our work focuses on a possible implementation of the sub-system that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy is on the order of 70 micrometer over a distance of 250 meter. We are exploring a technique called frequency sweeping interferometry, which involves interferometrically measuring a phase difference while sweeping the wavelength of a tunable laser. This phase difference is directly proportional to the absolute distance. A very high finesse Fabry-Perot cavity is used as a reference standard, to which the laser is locked end-points of the sweep. We will discuss the control system that drives the setup and show some first experimental results.

Swinkels, Bas L.; Bhattacharya, Nandini; Wielders, Arno A.; Braat, Joseph J. M.

2005-06-01

302

Coherent Thermoelectric Effects in Mesoscopic Andreev Interferometers  

E-print Network

We investigate thermoelectric transport through Andreev interferometers. We show that the ratio of the thermal and the charge conductance exhibits large oscillations with the phase difference $\\phi$ between the two superconducting contacts, and that the Wiedemann-Franz law holds only when $\\phi=\\pi$. A large average thermopower furthermore emerges whenever there is an asymmetry in the dwell times to reach the superconducting contacts. When this is the case, the thermopower is odd in $\\phi$. In contrast, when the average times to reach either superconducting contact are the same, the average thermopower is zero, however mesoscopic effects (analogous to universal conductance fluctuations) lead to a sample-dependent thermopower which is systematically even in $\\phi$.

Ph. Jacquod; R. S. Whitney

2009-10-15

303

The Millimeter-wave Bolometric Interferometer  

NASA Astrophysics Data System (ADS)

The Millimeter-wave Bolometeric Interferometer (MBI) is a novel instrument for measuring signals from the cosmic microwave background (CMB) radiation. MBI is a proof-of-concept designed to control systematic effects with the use of bolometers and interferometry. This scheme extends radio astronomy techniques of spatial interferometry, which rely on coherent receivers, to a system using incoherent detectors. In this thesis we outline the principles upon which MBI works and provide the reader with an understanding of both the particulars involved in the design and operation of MBI as well as the analysis of the resulting data. MBI observes the sky directly with 4 corrugated horn antennas in a band centered on l = 3 mm . A quasi-optical beam combiner forms interference fringes on an array of bolometers cooled to 300 mK. Phase modulation of the signals modulates the fringe patterns on the array and allows decoding of the visibilities formed by each pair of antennas. An altitude-azimuth mounting structure allows the horns to observe any point on the sky; rotation about the boresite extends the u - v coverage of the interferometer and allows for systematics checks and measurements of the Stokes parameters. MBI was deployed at the Pine Bluff Observatory near UW - Madison in winter 2008 for its first test observations of astronomical and artificial sources. Interference fringes were seen from a microwave generator located in the far- field, verifying our basic model of bolometric interferometry. Further analysis is needed to measure the scattering matrix of the instrument and to compare it against simulations.

Hyland, Peter Owen

2008-12-01

304

Ultra deep nulling interferometry using fractal interferometers  

NASA Astrophysics Data System (ADS)

The difficult goal of directly detecting a planet around a star requires the cancellation of, as far as possible, the stellar light and nulling interferometry is one way to do so: the star is put on a central dark fringe while the planet is supposed to be on a bright fringe. One problem is, however, leaks due to the finite angular dimension of the stellar disk, resolved by the interferometer. The solution is to increase the exponent of the term ? which describes the cancellation efficiency with respect to the angular distance to the axis of the central dark fringe. Efficient configurations have been found, using basically guess and check methods until recently. I present here one method to define configurations of telescopes that achieve any given power of ?. The principle is based on a peculiar property of a partition into two sets of the first 2 integers; the partition is built using the Prouhet Thué Morse sequence which presents some fractal properties. A phase shift (0 or ?) between 2 telescopes is applied according to this partition. I first examine 1-D pattern of identical telescopes, then extend the method to 2-D configurations of identical telescopes, to 1-D arrays and 2-D arrays of non-identical telescopes and finally to arrays where the phase shift between n groups of telescopes is 2k?/n. I examine then how a non-perfect fractal interferometer behaves and show that its robustness with respect to nulling stability is an important advantage. To cite this article: D. Rouan, C. R. Physique 8 (2007).

Rouan, Daniel

2007-04-01

305

Michelson-type Radio Interferometer for University Education  

NASA Astrophysics Data System (ADS)

Despite the increasing importance of interferometry in astronomy, the lack of educational interferometers is an obstacle to training the futue generation of astronomers. Students need hands-on experiments to fully understand the basic concepts of interferometry. Professional interferometers are often too complicated for education, and it is difficult to guarantee access for classes in a university course. We have built a simple and affordable radio interferometer for education and used it for an undergraduate and graduate laboratory project. This interferometer's design is based on the Michelson & Peace's stellar optical interferometer, but operates at a radio wavelength using a commercial broadcast satellite dish and receiver. Two side mirrors are surfaced with kitchen aluminum foil and slide on a ladder, providing baseline coverage. This interferometer can resolve and measure the diameter of the Sun, a nice daytime experiment which can be carried out even under a marginal weather (i.e., partial cloud coverage). Commercial broadcast satellites provide convenient point sources. By comparing the Sun and satellites, students can learn how an interferometer works and resolves structures in the sky.

Koda, Jin; Barrett, J. W.; Hasegawa, T.; Hayashi, M.; Shafto, G.; Slechta, J.

2013-01-01

306

41. Perimeter acquisition radar building radar element and coaxial display, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

41. Perimeter acquisition radar building radar element and coaxial display, with drawing of typical antenna section. Drawing, from left to right, shows element, aluminum ground plane, cable connectors and hardware, cable, and back-up ring. Grey area is the concrete wall - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

307

Developing a new hyperspectral imaging interferometer for earth observation  

NASA Astrophysics Data System (ADS)

The Aerospace Leap-frog Imaging Stationary interferometer for Earth Observation (ALISEO) is a hyperspectral imaging interferometer for Earth remote sensing. The instrument belongs to the class of Sagnac stationary interferometers and acquires the image of the target superimposed to the pattern of autocorrelation functions of the electromagnetic field coming from each pixel. The ALISEO sensor together with the data processing algorithms that retrieve the at-sensor spectral radiance are discussed. A model describing the instrument OPD and interferogram center is also discussed, improving the procedures for phase retrieval and spectral estimation. Images acquired by ALISEO are shown, and examples of retrieved reflectance spectra are presented.

Barducci, Alessandro; Castagnoli, Francesco; Castellini, Guido; Guzzi, Donatella; Lastri, Cinzia; Marcoionni, Paolo; Nardino, Vanni; Pippi, Ivan

2012-11-01

308

Fiber optic interferometer for testing conic section surfaces.  

PubMed

A null test method for testing aspheric optical surfaces based on geometric considerations of conic sections is presented. The basic principles have been investigated experimentally by designing and building a modified Mach-Zehnder interferometer. By using optical fibers the inconvenience of alignment has partly been overcome. Phase shifting has been implemented and the measurements are performed with the help of a microcomputer. The performance of the interferometer has been investigated by testing an elliptical toroid mirror. Further improvement of the test procedure by Zernike polynomial decomposition is discussed and performed. Finally, an even more compact conic section interferometer is proposed. PMID:20700348

Bétend-Bon, J P; Wosinski, L; Breidne, M; Robertsson, L

1991-05-01

309

Multiplex Fabry-Perot interferometer: II. Laboratory prototype.  

PubMed

The Multiplex Fabry-Perot interferometer (MFPI) consists of a Fabry-Perot interferometer in which the étalon plate separation is changed over a large optical distance. Fourier transformation of the resultant interferogram allows one to treat the multiple reflections within the étalon cavity in a manner analogous to an array of Michelson-type interferometers. However, the scan distance required by the MFPI is much less than for a comparable Michelson. The design and construction of the MFPI are described. Solar absorption spectra measured with this instrument are compared with results from the FASCODE atmospheric model. PMID:21060344

Snell, H E; Cook, W B; Hays, P B

1995-08-20

310

Results from a Grazing Incidence X-Ray Interferometer  

NASA Technical Reports Server (NTRS)

A prototype grazing incidence interferometer has been built and tested at EUV and X-ray wavelengths using a 120 meter long vacuum test facility at Marshall Space Flight Center. We describe the design and construction of the interferometer, the EUV and x-ray sources, the detector systems, and compare the interferometric fringe measurements with theoretical predictions. We also describe the next-generation grazing incidence system which is designed to provide laboratory demonstration of key technologies that will be needed for a space-based x-ray interferometer.

Joy, Marshall K.; Shipley, Ann; Cash, Webster; Carter, James

2000-01-01

311

RADAR Reveals Titan Topography  

NASA Technical Reports Server (NTRS)

The Cassini Titan RADAR Mapper is a K(sub u)-band (13.78 GHz, lambda = 2.17 cm) linear polarized RADAR instrument capable of operating in synthetic aperture (SAR), scatterometer, altimeter and radiometer modes. During the first targeted flyby of Titan on 26 October, 2004 (referred to as Ta) observations were made in all modes. Evidence for topographic relief based on the Ta altimetry and SAR data are presented here. Additional SAR and altimetry observations are planned for the T3 encounter on 15 February, 2005, but have not been carried out at this writing. Results from the T3 encounter relevant to topography will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath

Kirk, R. L.; Callahan, P.; Seu, R.; Lorenz, R. D.; Paganelli, F.; Lopes, R.; Elachi, C.

2005-01-01

312

Floor-plan radar  

NASA Astrophysics Data System (ADS)

Urban-warfare specialists, law-enforcement officers, counter-drug agents, and counter-terrorism experts encounter operational situations where they must assault a target building and capture or rescue its occupants. To minimize potential casualties, the assault team needs a picture of the building's interior and a copy of its floor plan. With this need in mind, we constructed a scale model of a single- story house and imaged its interior using synthetic-aperture techniques. The interior and exterior walls nearest the radar set were imaged with good fidelity, but the distal ones appear poorly defined and surrounded by ghosts and artifacts. The latter defects are traceable to beam attenuation, wavefront distortion, multiple scattering, traveling waves, resonance phenomena, and other effects not accounted for in the traditional (noninteracting, isotropic point scatterer) model for radar imaging.

Falconer, David G.; Ueberschaer, Ronald M.

2000-07-01

313

Advanced ground penetrating radar  

SciTech Connect

An advanced Ground Penetrating Radar (GPR) system has the potential for efficiently and reliably providing high resolution images for inspecting concrete civil structures for defects and damage assessment. To achieve the required performance, improvements in radar hardware, and development and adaptation of advanced 2- and 3-dimensional synthetic aperture imaging techniques are needed. Recent and continuing advancement in computer and computer-related technology areas have made it possible to consider more complex and capable systems for a variety of imaging applications not previously conceived. The authors developed conceptual designs, analyzed system requirements, and performed experiments, modeling, and image reconstructions to study the feasibility of improving GPR technology for non-destructive evaluation of bridge decks and other high-value concrete structures. An overview and summary of practical system concepts and requirements, are presented.

Warhus, J.P.; Mast, J.E.; Johansson, E.M.; Nelson, S.D. [Lawrence Livermore National Lab., CA (United States). Electronics Engineering Dept.

1994-07-26

314

New weather radar coming  

NASA Astrophysics Data System (ADS)

What would you call the next generation of radar for severe weather prediction? NEXRAD, of course. A prototype for the new system was recently completed in Norman, Okla., and by the early 1990s up to 195 stations around the United States will be tracking dangerous weather and sending faster, more accurate, and more detailed warnings to the public.NEXRAD is being built for the Departments of Commerce, Transportation, and Defense by the Unisys Corporation under a $450 million contract signed in December 1987. Th e system will be used by the National Weather Service, the Federal Aviation Administration (FAA), and the U.S. Air Force and Navy. The NEXRAD radar tower in Norman is expected to be operational in October.

Maggs, William Ward

315

Radar signal processing  

NASA Astrophysics Data System (ADS)

The role of clutter in radar signal processing is considered with particular reference to an air-traffic environment. The characteristics of clutter are described, and the use of conventional moving-target indication filters to reduce the effects of clutter is considered. Adaptive clutter suppression schemes are addressed, and the adaptive detection of a moving target in the presence of clutter of unknown statistics is discussed. The use of a parametric spectrum estimation procedure as the basis of clutter classification is described.

Haykin, S.

1985-04-01

316

Airborne bistatic radar applications  

Microsoft Academic Search

Applications of bistatic radar when one or both of the units are airborne are discussed. Scenarios that merit deeper consideration are covert strike and head-on SAR using a stand-off illuminator, either airborne or space-based; area air defense with passive ground-based receivers and stand-off illuminators; an airborne picket line to detect stealth aircraft and missiles; AWACS aircraft providing mutual support in

James A. Foster

1987-01-01

317

Imaging synthetic aperture radar  

DOEpatents

A linear-FM SAR imaging radar method and apparatus to produce a real-time image by first arranging the returned signals into a plurality of subaperture arrays, the columns of each subaperture array having samples of dechirped baseband pulses, and further including a processing of each subaperture array to obtain coarse-resolution in azimuth, then fine-resolution in range, and lastly, to combine the processed subapertures to obtain the final fine-resolution in azimuth. Greater efficiency is achieved because both the transmitted signal and a local oscillator signal mixed with the returned signal can be varied on a pulse-to-pulse basis as a function of radar motion. Moreover, a novel circuit can adjust the sampling location and the A/D sample rate of the combined dechirped baseband signal which greatly reduces processing time and hardware. The processing steps include implementing a window function, stabilizing either a central reference point and/or all other points of a subaperture with respect to doppler frequency and/or range as a function of radar motion, sorting and compressing the signals using a standard fourier transforms. The stabilization of each processing part is accomplished with vector multiplication using waveforms generated as a function of radar motion wherein these waveforms may be synthesized in integrated circuits. Stabilization of range migration as a function of doppler frequency by simple vector multiplication is a particularly useful feature of the invention; as is stabilization of azimuth migration by correcting for spatially varying phase errors prior to the application of an autofocus process.

Burns, Bryan L. (Tijeras, NM); Cordaro, J. Thomas (Albuquerque, NM)

1997-01-01

318

Radar response to vegetation  

Microsoft Academic Search

Active microwave measurements of vegetation backscatter were conducted to determine the utility of radar in 1) mapping soil moisture through vegetation and 2) mapping crop types. Using a truck-mounted boom, spectral response data were obtained for four crop types (corn, milo, soybeans, and alfalfa) over the 4-8 GHz frequency band, at incidence angles of0deg-70degin10degsteps, and for all four linear polarization

F. Ulaby

1975-01-01

319

Giant Eyes for the VLT Interferometer  

NASA Astrophysics Data System (ADS)

First Scientific Results with Combined Light Beams from Two 8.2-m Unit Telescopes Summary It started as a preparatory technical experiment and it soon developed into a spectacular success. Those astronomers and engineers who were present in the control room that night now think of it as the scientific dawn of the Very Large Telescope Interferometer (VLTI) . On October 29, 2001, ANTU and MELIPAL , two of the four VLT 8.2-m Unit Telescopes at the ESO Paranal Observatory, were linked for the first time. Light from the southern star Achernar (Alpha Eridani) was captured by the two telescopes and sent to a common focus in the observatory's Interferometric Laboratory. Following careful adjustments of the optical paths, interferometric fringes were soon recorded there, proving that the beams from the two telescopes had been successfully combined "in phase" . From an analysis of the observed pattern (the "fringe contrast"), the angular diameter of Achernar was determined to be 1.9 milli-arcsec. At the star's distance (145 light-years), this corresponds to a size of 13 million km. The observation is equivalent to measuring the size of a 4-metre long car on the surface of the Moon. This result marks the exciting starting point for operations with the Very Large Telescope Interferometer (VLTI) and it was immediately followed up by other scientific observations. Among these were the first measurements of the diameters of three red dwarf stars ("Kapteyn's star" - HD 33793, HD 217987 and HD 36395), a precise determination of the variable diameters of the pulsating Cepheid stars Beta Doradus and Zeta Geminorum (of great importance for the calibration of the universal distance scale), as well as a first interferometric measurement of the core of Eta Carinae , an intriguing, massive southern object that may possibly become the next supernova in our galaxy. This milestone is another important step towards the ultimate goal of the VLT project - to combine all four 8.2-m telescopes into the most powerful optical/infrared telescope system on Earth. When ready, it will be able to reveal at least 15 times finer details in astronomical objects than what is possible with any existing, single ground-based telescope. PR Photo 30a/01 : Overview of the VLT Interferometer . PR Photo 30b/01 : "Joint" stellar light-spot produced via ANTU and MELIPAL at the VLTI focus. PR Photo 30c/01 : Interferometric fringes from the star Achernar . PR Photo 30d/01 : Time sequence of fringes from Achernar. PR Photo 30e/01 : "Visibility curve" of the star Psi Phoenicis . Scientific Appendix First VLTI observations with two 8.2-m telescopes ESO PR Photo 30a/01 ESO PR Photo 30a/01 [Preview - JPEG: 357 x 400 pix - 82k] [Normal - JPEG: 713 x 800 pix - 208k] [Hi-Res - JPEG: 2673 x 3000 pix - 1.4M] ESO PR Photo 30b/01 ESO PR Photo 30b/01 [Preview - JPEG: 400 x 350 pix - 57k] [Normal - JPEG: 800 x 700 pix - 176k] Caption : PR Photo 30a/01 : Overview of the VLT Interferometer as it was operated when the light beams from two of the 8.2-m telescopes were combined. The VINCI instrument that was used for the present test, is located at the common focus in the Interferometric Laboratory. PR Photo 30b/01 shows one of the first "joint" light-spots from a star as seen at this VLTI focus and resulting from the superposition of light collected with the 8.2-m VLT ANTU and MELIPAL telescopes. Despite the long optical paths (about 200 m), the quality is excellent (FWHM = 0.45 arcsec). Note that this is not (yet) an image of the stellar surface. At 1 o'clock in the morning of October 30, 2001, ESO astronomers and engineers working in the VLTI Control Room successfully combined the light from ANTU and MELIPAL , two of the four 8.2-m VLT Unit Telescopes at the Paranal Observatory. The same night, a series of high-resolution test observations with the VINCI instrument [1] at the focus of the VLT Interferometer (VLTI) proved that this complex system was functioning extremely well, and within the technical specifications . Following abo

2001-11-01

320

A review of array radars  

NASA Astrophysics Data System (ADS)

Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting (phase-phase steered arrays); arrays steered + or - 60 deg, limited scan arrays, hemispherical coverage, and omnidirectional coverage arrays; array radars steering electronically in only one dimension, either by frequency or by phase steering; and array radar antennas which use no electronic scanning but instead use array antennas for achieving low antenna sidelobes.

Brookner, E.

1981-10-01

321

Cognitive processing for nonlinear radar  

NASA Astrophysics Data System (ADS)

An increasingly cluttered electromagnetic environment (EME) is a growing problem for radar systems. This problem is becoming critical as the available frequency spectrum shrinks due to growing wireless communication device usage and changing regulations. A possible solution to these problems is cognitive radar, where the cognitive radar learns from the environment and intelligently modifies the transmit waveform. In this paper, a cognitive nonlinear radar processing framework is introduced where the main components of this framework consist of spectrum sensing processing, target detection and classification, and decision making. The emphasis of this paper is to introduce a spectrum sensing processing technique that identifies a transmit-receive frequency pair for nonlinear radar. It will be shown that the proposed technique successfully identifies a transmit-receive frequency pair for nonlinear radar from data collected from the EME.

Martone, Anthony; Ranney, Kenneth; Hedden, Abigail; Mazzaro, Gregory; McNamara, David

2013-05-01

322

Radar gun hazards  

SciTech Connect

Radar guns - hand-held units used by the law to nail speeders - have been in use since the early '60s. Now they've been accused of causing cancer. Police officers in several states have so far filed eight suits against the manufacturer, claiming that they have contracted rare forms of cancer, such as of the eyelid and the testicle, from frequent proximity to the devices. Spurred by concerns expressed by police groups, researchers at the Rochester Institute of Technology are conducting what they believe to be the first research of its kind in the nation. Last month psychologist John Violanti, an expert in policy psychology and health, sent out a one-page survey to 6,000 active and retired police officers in New York State, asking them about their health and their use of radar guns. Violanti says melanoma, leukemia, and lymph node cancer may be linked to these as well as other electromagnetic devices. The Food and Drug Administration earlier this year issued a warning about radar guns, telling users not to operate them closer than 6 inches from the body. But this may not be a sufficient safeguard since the instruments can give off crisscrossing wave emissions within a police vehicle. The survey will be used to help determine if it would be safer to mount the guns, which are currently either hand-held or mounted on dashboards, outside troopers' cars.

Not Available

1991-12-20

323

Spaceborne Imaging Radar Project  

NASA Technical Reports Server (NTRS)

In June of 1985 the Project Initiation Agreement was signed by the Jet Propulsion Laboratory and the NASA Office of Space Science and Applications for the Spaceborne Imaging Radar Project (SIR). The thrust of the Spaceborne Imaging Radar Project is to continue the evolution of synthetic aperture radar (SAR) science and technology developed during SEASAT, SIR-A and SIR-B missions to meet the needs of the Earth Observing System (EOS) in the mid 1990's. As originally formulated, the Project plans were for a reflight of the SIR-B in 1987, the development of a new SAR, SIR-C, for missions in mid 1989 and early 1990, and the upgrade of SIR-C to EOS configuration with a qualification flight aboard the shuttle in the 1993 time frame (SIR-D). However, the loss of the shuttle Challenger has delayed the first manifest for SIR to early 1990. This delay prompted the decision to drop SIR-B reflight plans and move ahead with SIR-C to more effectively utilize this first mission opportunity. The planning for this project is discussed.

Herman, Neil

1986-01-01

324

Characterization of exozodiacal dust with the Keck interferometer, VLTI, and SIM  

NASA Technical Reports Server (NTRS)

This overview discusses three interferometers for characterization of exozodiacal dust: Keck Interferometer, the Very Large Telescope Interferometer (VLTI), and the Space Interferometry Mission (SIM). The emphasis will be toward the Keck Interferometer, as exozodiacal dust characterization is one of its science requirements.

Colavita, Mark

1998-01-01

325

Radar studies of bird migration  

NASA Technical Reports Server (NTRS)

Observations of bird migration with NASA radars were made at Wallops Island, Va. Simultaneous observations were made at a number of radar sites in the North Atlantic Ocean in an effort to discover what happened to those birds that were observed leaving the coast of North America headed toward Bermuda, the Caribbean and South America. Transatlantic migration, utilizing observations from a large number of radars is discussed. Detailed studies of bird movements at Wallops Island are presented.

Williams, T. C.; Williams, J. M.

1974-01-01

326

Output Tube Emission Characteristics of Operational Radars.  

National Technical Information Service (NTIS)

This report contains the emission spectra of 19 different types of radars, selected to show the different emission spectrum characteristics produced by a variety of radar output tube technologies. The radars include examples of ground-based search, airpor...

R. J. Matheson, J. D. Smilley, G. D. Falcon, V. S. Lawrence

1982-01-01

327

Automatic Alignment of Displacement-Measuring Interferometer  

NASA Technical Reports Server (NTRS)

A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error. On the basis of the geometrical optics of corner-cube reflectors, the length of the optical path can be shown to be L = L(sub 0)cos theta, where L(sub 0) is the distance between the corner points and theta is the misalignment angle. Therefore, the measurement error is given by DeltaL = L(sub 0)(cos theta - 1). In the usual case in which the misalignment is small, this error can be approximated as DeltaL approximately equal to -L(sub 0)theta sup 2/2. The control system (see figure) is implemented partly in hardware and partly in software. The control system includes three piezoelectric actuators for rapid, fine adjustment of the direction of the laser beam. The voltages applied to the piezoelectric actuators include components designed to scan the beam in a circular pattern so that the beam traces out a narrow cone (60 microradians wide in the initial application) about the direction in which it is nominally aimed. This scan is performed at a frequency (2.5 Hz in the initial application) well below the resonance frequency of any vibration of the interferometer. The laser beam makes a round trip to both corner-cube reflectors and then interferes with the launched beam. The interference is detected on a photodiode. The length of the optical path is measured by a heterodyne technique: A 100- kHz frequency shift between the launched beam and a reference beam imposes, on the detected signal, an interferometric phase shift proportional to the length of the optical path. A phase meter comprising analog filters and specialized digital circuitry converts the phase shift to an indication of displacement, generating a digital signal proportional to the path length.

Halverson, Peter; Regehr, Martin; Spero, Robert; Alvarez-Salazar, Oscar; Loya, Frank; Logan, Jennifer

2006-01-01

328

Superfluid helium-4 interferometers: construction and experiments  

NASA Astrophysics Data System (ADS)

This dissertation has two main goals: to highlight some new results in the field of superfluid 4He interferometry and to provide an in-depth, "hands-on" guide to the physics, design, construction, testing and operation of a continuously operating, fluxlocked 4 He dc-SHeQUID (Superfluid Helium Quantum Interference Device). Many of these topics haven't really been addressed in writing and the hapless new experimenter seeking to develop a SHeQUID is generally forced to reinvent the wheel rather than start at the frontier and push it forward. We would like to prevent that by making this a comprehensive guide to building and operating SHeQUIDs. We have optimized the fabrication of the nanoscale aperture arrays that are the very heart of the SHeQUID and resolved long-standing issues with their durability and long-term usability. A detailed report on this should assist in avoiding the many pitfalls that await those who fabricate and use these aperture arrays. We have constructed a new, modular SHeQUID that is designed to be easily adaptable to a wide array of proposed experiments without the necessity of rebuilding and reassembling key components like the displacement transducer. We have automated its working as a continuously operating, linearized (flux-locked) interferometer by using the so-called "chemical potential battery" in conjunction with a feedback system. We have also constructed a new reorientation system that is several orders of magnitude quieter than its predecessors. Together, these developments have allowed us to measure a changing rotation field in real time, a new development for this kind of device. We have also developed a module that allows control of the reorientation stage by automated data-taking software for investigating long-term drifts (by safely sweeping the stage back and forth). We have also investigated the chemical potential battery in further detail and report some fascinating nonlinear mode locking phenomena that have important consequences for practical applications of these devices. We present a crude model that should help in designing and optimizing future devices by giving us at least an initial predictive tool for the critical heater power needed to initiate battery states. Finally, we analyze some misconceptions about SHeQUIDs regarding what may be considered the logical next step towards improving a double-slit interferometer---the superfluid diffraction grating. We present evidence (experiments, simulations and analytical results) for the somewhat subtle reasons why gratings would be less useful than previously believed and clarifies the proper, limited sense in which such devices do improve SHeQUIDs. We also discuss some possible implications of these issues for the field of (electronic) dc-SQUIDs.

Joshi, Aditya Ajit

329

Stroboscopic Interferometer for Measuring Mirror Vibrations  

NASA Technical Reports Server (NTRS)

Stroboscopic interferometry is a technique for measuring the modes of vibration of mirrors that are lightweight and, therefore, unavoidably flexible. The technique was conceived especially for modal characterization of lightweight focusing mirror segments to be deployed in outer space; however, the technique can be applied to lightweight mirrors designed for use on Earth as well as the modal investigation of other optical and mechanical structures. To determine the modal structure of vibration of a mirror, it is necessary to excite the mirror by applying a force that varies periodically with time at a controllable frequency. The excitation can utilize sinusoidal, square, triangular, or even asynchronous waveforms. Because vibrational modes occur at specific resonant frequencies, it is necessary to perform synchronous measurements and sweep the frequency to locate the significant resonant modes. For a given mode it is possible to step the phase of data acquisition in order to capture the modal behavior over a single cycle of the resonant frequency. In order to measure interferometrically the vibrational response of the mirror at a given frequency, an interferometer must be suitably aligned with the mirror and adjustably phase-locked with the excitation signal. As in conventional stroboscopic photography, the basic idea in stroboscopic interferometry is to capture an image of the shape of a moving object (in this case, the vibrating mirror) at a specified instant of time in the vibration cycle. Adjusting the phase difference over a full cycle causes the interference fringes to vary over the full range of motion for the mode at the excitation frequency. The interference-fringe pattern is recorded as a function of the phase difference, and, from the resulting data, the surface shape of the mirror for the given mode is extracted. In addition to the interferometer and the mirror to be tested, the equipment needed for stroboscopic interferometry includes an arbitrary-function generator (that is, a signal generator), an oscilloscope, a trigger filter, and an advanced charge-coupled-device (CCD) camera. The optical components are positioned to form a pupil image of the mirror under test on the CCD chip, so that the interference pattern representative of the instantaneous mirror shape is imaged on the CCD chip.

Stahl, H. Philip; Robers, Ted

2005-01-01

330

Neural-network laser radar.  

PubMed

A laser radar whose resolution is greater than 1 µm is reported. We present the radar results when they are used for such purposes as determining the size of a void inside a silicon wafer, profiling a cross-sectional pattern of an optical fiber, studying the birefringence of a lithium-niobate crystal, or finding a fault in an optical guide in an optical integrated-circuit wafer. Neural-network theory was used in processing the radar signal. Radar processing based on neural-network theory gave significantly superior resolution compared with Fourier-transform-based processing. PMID:20885600

Lizuka, K; Fujii, S

1994-05-01

331

Radar data processing and analysis  

NASA Technical Reports Server (NTRS)

Digitized four-channel radar images corresponding to particular areas from the Phoenix and Huntington test sites were generated in conjunction with prior experiments performed to collect X- and L-band synthetic aperture radar imagery of these two areas. The methods for generating this imagery are documented. A secondary objective was the investigation of digital processing techniques for extraction of information from the multiband radar image data. Following the digitization, the remaining resources permitted a preliminary machine analysis to be performed on portions of the radar image data. The results, although necessarily limited, are reported.

Ausherman, D.; Larson, R.; Liskow, C.

1976-01-01

332

Orthogonal polarization Mirau interferometer using reflective-type waveplate.  

PubMed

This work proposes an orthogonal polarization Mirau interferometry using a reflective-type waveplate to generate different polarization orientations for broadband white light interferometry. The reflective-type half-waveplate is employed as the reference arm of the Mirau interferometer to convert polarization and it generates a reference light with an orientation orthogonal to the object light. An advantage of the proposed interferometer is its ability to control the ratio of light intensity between the object and reference arms to maximize the interferometric fringe contrast. Better, more accurate calibration of standard step height has been achieved by the developed interferometer, which also can measure solder bumps that traditional Mirau interferometers usually cannot measure. PMID:23939094

Tapilouw, Abraham Mario; Chen, Liang-Chia; Jen, Yi-Jun; Lin, Shyh-Tsong; Yeh, Sheng-Lih

2013-07-15

333

A polarization sensitive interferometer for Faraday rotation detection.  

E-print Network

??Time-resolved Faraday rotation (TRFR) is a pulsed laser pump/probe optical measurement used to characterize electron spin dynamics in semiconductor materials. A Mach-Zehnder type interferometer with… (more)

LaForge, Joshua Michael

2007-01-01

334

On the design of lithographic interferometers and their application  

E-print Network

Interference lithography is presented as an ideal technique for fabricating large-area periodic structures with sub-100nm dimensions. A variety of interferometer designs are discussed and implemented, each of which emphasizes ...

Walsh, Michael E. (Michael Edward), 1975-

2004-01-01

335

Coupled-Cavity Interferometer for the Optics Laboratory  

ERIC Educational Resources Information Center

Describes the construction of a flexible coupled-cavity interferometer for student use. A helium-neon laser and phonograph turntable are the main components. Lists activities which may be performed with the apparatus. (Author/CP)

Peterson, R. W.

1975-01-01

336

Double heterodyne interferometer using a multimode laser diode  

Microsoft Academic Search

A double heterodyne interferometer using a multimode laser diode with a synthetic wavelength of approximately 1 mm has been established and the stability of the synthetic wavelength has been investigated.

S. Han; E. Dalhoff; Edgar Fischer; S. Heim; Hans J. Tiziani

1994-01-01

337

Novel double path shearing interferometer in corneal topography measurements  

NASA Astrophysics Data System (ADS)

The paper presents an approach for measurements of corneal topography by use of a patent pending double path shearing interferometer (DPSI). Laser light reflected from the surface of the cornea is divided and directed to the inputs of two interferometers. The interferometers use lateral shearing of wavefronts in two orthogonal directions. A tilt of one of the mirrors in each interferometric setup perpendicularly to the lateral shear introduces parallel carrier frequency fringes at the output of each interferometer. There is orthogonal linear polarization of the laser light used in two DPSI. Two images of fringe patters are recorded by a high resolution digital camera. The obtained fringe patterns are used for phase difference reconstruction. The phase of the wavefront was reconstructed by use of algorithms for a large grid based on discrete integration. The in vivo method can also be used for tear film stability measurement, artificial tears and contact lens tests.

Licznerski, Tomasz J.; Jaronski, Jaroslaw; Kosz, Dariusz

2005-09-01

338

Millimeter Wave Cloud Radar (MMCR) Handbook  

SciTech Connect

The millimeter cloud radar (MMCR) systems probe the extent and composition of clouds at millimeter wavelengths. The MMCR is a zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20 km. The radar possesses a doppler capability that will allow the measurement of cloud constituent vertical velocities.

KB Widener; K Johnson

2005-01-30

339

Fiber in-line Michelson Interferometer for refractive index sensing  

NASA Astrophysics Data System (ADS)

A fiber in-line Michelson interferometer based on open micro-cavity is demonstrated, which is fabricated by femtosecond laser micromachining and thin film coating technique. In refractive index sensing, this interferometer operates in a reflection mode of detection, exhibits compact sensor head, good mechanical reliability, wide operation range and high sensitivity of 975nm/RIU (refractive index unit) at the refractive index value of 1.484.

Liao, C. R.; Wang, D. N.; Wang, Min; Yang, Minghong; Wang, Yiping

2013-09-01

340

Laser frequency stability transfer using a fiber-based interferometer.  

PubMed

We have demonstrated a method for laser frequency stability transfer using a fiber-based Young's interferometer. An 858 nm external cavity diode laser is stabilized to within 1e-8 from 10 s to 4000 s, referenced to a Rubidium stabilized 780 nm DBR diode laser using the interferometer as a frequency-stability-transferring link. The system is simple to build and can link any two laser wavelengths within the fiber operating range. PMID:24922216

Wang, Z B; Zhang, J W; Wang, S G; Miao, K; Wang, L J

2014-05-20

341

Rainbow schlieren vs Mach-Zehnder interferometer - A comparison  

NASA Technical Reports Server (NTRS)

The rainbow schlieren apparatus is simpler, cheaper, and more easily built to large scale than the interferometer. The accuracies of the two instruments are similar but only if refraction is properly accounted for in interferometry. The measurement thresholds of both instruments are similar. The rainbow schlieren device provides more detailed information because the detection threshold of the rainbow schlieren is an order of magnitude better than that of the interferometer.

Howes, W. L.

1985-01-01

342

Phase-dependent multiple Andreev reflections in SNS interferometers  

Microsoft Academic Search

A theory of coherent multiple Andreev reflections (MAR) is developed for superconductor-normal-metal-superconductor interferometers. We consider a Y-shaped normal-electron-beam splitter connecting two superconducting reservoirs, where the two connection points to the same superconductor can have different phases. The current is calculated in the quantum transport regime as a function of applied voltage and phase difference, I(V,phi). MAR in interferometers incorporate two

J. Lantz; V. S. Shumeiko; E. Bratus; G. Wendin

2002-01-01

343

Pulsed laser diode optical fiber interferometer for absolute distance measurement  

NASA Astrophysics Data System (ADS)

An interferometry system for absolute distance measurement is described. In the system, an optical fiber Mach-Zehnder interferometer with a chirped laser diode is employed to position the measured object. Another interferometer with He-Ne laser is used to measure the optical path difference. The coherence-length of the pulsed multimode laser diode is studied. In the experiments, the system measured the absolute distance up to 1 meter with the accuracy of 2 micrometer.

Wang, Chunhe; Xiao, Hai; Hong, Haitao; Ye, Shenghua

1996-10-01

344

Development of a Grazing Incidence X-Ray Interferometer  

NASA Technical Reports Server (NTRS)

A grazing incidence x-ray interferometer design capable of micro-arcsecond level resolution is discussed. This practical design employs a Michelson Stellar interferometer approach to create x-ray interference fringes without the use of Wolter style optics or diffraction crystals. Design solutions accommodating alignment, vibration, and thermal constraints are reviewed. We present the development and demonstration of a working experiment along with tolerance studies, data analysis, and results.

Shipley, Ann; Cash, Webster; Osterman, Steve; Joy, Marshall; Carter, James

1999-01-01

345

Planned improvements to the Owens Valley frequency-agile interferometer  

NASA Technical Reports Server (NTRS)

Three small antennas will be added to the OVRO interferometer to form a five-element solar-dedicated array. This would provide up to 7 or 10 baselines (compared to the present 1 or 3). This would be sufficient to apply microwave diagnostics to most active region and burst sources. By using frequency-synthesis it would also provide an imaging capability comparable to that of an approximately 100 baseline interferometer. Expansion of the array is discussed.

Hurford, Gordon J.; Gary, D. E.

1988-01-01

346

First sky validation of an optical polarimetric interferometer  

Microsoft Academic Search

Aims.We present the first lab and sky validation of spectro-polarimetric equipment put at the combined focus of an optical long-baseline interferometer. We tested the polarimetric mode designed for the visible GI2T Interferometer to offer spectropolarimetric diagnosis at the milliarcsecond scale. Methods.We first checked the whole instrumental polarization in the lab with a fringe simulator, and then we observed alpha Cep

K. Rousselet-Perraut; J. B. Le Bouquin; D. Mourard; F. Vakili; O. Chesneau; D. Bonneau; J. L. Chevassut; A. Crocherie; A. Glentzlin; S. Jankov; S. Ménardi; R. Petrov; C. Stehlé

2006-01-01

347

Vibration-insensitive interferometer for on-line measurements.  

PubMed

We have realized a digital Twyman-Green interferometer to measure the quality of optical surfaces in unstable environments. The system yields accurate measurements even in the presence of severe mechanical vibrations. The interferograms are decoded by application of a spatial-carrier phase-shifting fringe-analysis technique. The interferometer was mounted over a production machine and used for on-line measurements of aspheric mirror surfaces during the figuring and polishing process. PMID:21060385

Melozzi, M; Pezzati, L; Mazzoni, A

1995-09-01

348

Effect of Telescope Alignment on a Stellar Interferometer  

Microsoft Academic Search

For a ground-based stellar interferometer, we investigate the effect of wave-front distortions that are due to telescope alignment errors and other factors. We apply the results to the IRyOptical Telescope Array ~IOTA! interferometer. We present the computational method used in our simulation program to calculate explicitly the wave-front shape from an arbitrarily misaligned telescope. We calculate the wave-front shape and

Irene L. Porro; Wesley A. Traub; Nathaniel P. Carleton

1999-01-01

349

Demonstration of a Corner-cube-interferometer LWIR Hyperspectral Imager  

Microsoft Academic Search

An interferometric long-wavelength infrared (LWIR) hyperspectral imager is demonstrated, based on a Michelson corner-cube\\u000a interferometer. This class of system is inherently mechanically robust, and should have advantages over Sagnac-interferometer\\u000a systems in terms of relaxed beamsplitter-coating specifications, and wider unvignetted field of view. Preliminary performance\\u000a data from the laboratory prototype system are provided regarding imaging, spectral resolution, and fidelity of acquired

Ingmar G. E. Renhorn; Thomas Svensson; Staffan Cronström; Tomas Hallberg; Rolf Persson; Roland Lindell; Glenn D. Boreman

2010-01-01

350

Observation of a classical cheshire cat in an optical interferometer  

E-print Network

A recent neutron interferometry experiment claims to demonstrate a paradoxical phenomena dubbed the "quantum Cheshire Cat" \\cite{Denkmayr2014}. We have reproduced and extended these results with an equivalent optical interferometer. The results suggest that the photon travels through one arm of the interferometer, while its polarization travels through the other. However, we show that these experimental results belong to the domain where quantum and classical wave theories coincide; there is nothing uniquely quantum about the illusion of this cheshire cat.

David P. Atherton; Gambhir Ranjit; Andrew A. Geraci; Jonathan D. Weinstein

2014-10-08

351

Single-pass rub testing of abradable seal materials  

NASA Technical Reports Server (NTRS)

A pendulum-type test device has been built for use in studying rubs between a turbine or compressor blade tip or labyrinth seal knife edge and specimens of abradable gas path seal materials. The device allows measurement of the rub energy dissipated in a single wear event, along with friction and normal forces and wear. Subsequent rubs over the same surface can also be monitored, with microscopic observation of the rub surface being possible after any of the passes. The device was used in tests of several potential abradable materials, ranging from porous to fully dense. It was shown that the rub energy dissipated in initial and subsequent passes is a fundamental parameter in the evaluation of material abradability. Rub energy was found to be influenced by such factors as: density and tensile (or yield) strength of the abradable material, prior densification or work hardening of the rub surface, and the sharpness of the leading edge of the blade tip.

Kennedy, F. E.; Hine, N. P.

1981-01-01

352

Orbital Single-Pass Interferometry for Vessel Detection and Classification  

Microsoft Academic Search

This manuscript tackles the possible usage of Polarimetric SAR interferometry in vessel classification. It presents a simple technique that combines the retrieved height information with a Pauli analysis of polarimetric data to build a tri-dimensional map of scattering centers. By comparing this output with a vessel pattern database generated from previous scattering studies, a decision on vessel identification can then

Gerard Margarit; Jordi J. Mallorqui; J. M. Rius; Jesus Sanz-Marcos; Xavier Fabregas

2006-01-01

353

Hanford Single-Pass Reactor Fuel Storage Basin Demolition.  

PubMed

ABSTRACT The Environmental Restoration Contractor at the Hanford Site is tasked with removing auxiliary reactor structures and leaving the remaining concrete structure surrounding each reactor core. This is referred to as Interim Safe Storage. Part of placing the F Reactor into Interim Safe Storage is the demolition of the fuel storage basin, which was deactivated in 1970 by placing debris material into the basin prior to back filling with soil. Besides the debris material (wooden floor decking, handrails, and monorail pieces), the fuel storage basin contents included the possibility of spent nuclear fuel, fuel buckets, fuel spacers, process tubes, and tongs. Demolition of the fuel storage basin offered many unique radiological control challenges and innovative approaches to demolition. This paper describes how the total effective dose equivalent and contamination were controlled, how the use of a remote operated excavator was employed to remove high-dose-rate material, and how wireless technology was used to monitor changing radiological conditions. PMID:12555029

Armstrong, Jason A.

2003-02-01

354

Hanford single-pass reactor fuel storage basin demolition.  

PubMed

The Environmental Restoration Contractor at the Hanford Site is tasked with removing auxiliary reactor structures and leaving the remaining concrete structure surrounding each reactor core. This is referred to as Interim Safe Storage. Part of placing the F Reactor into Interim Safe Storage is the demolition of the fuel storage basin, which was deactivated in 1970 by placing debris material into the basin prior to back filling with soil. Besides the debris material (wooden floor decking, handrails, and monorail pieces), the fuel storage basin contents included the possibility of spent nuclear fuel, fuel buckets, fuel spacers, process tubes, and tongs. Demolition of the fuel storage basin offered many unique radiological control challenges and innovative approaches to demolition. This paper describes how the total effective dose equivalent and contamination were controlled, how the use of a remote operated excavator was employed to remove high-dose-rate material, and how wireless technology was used to monitor changing radiological conditions. PMID:12564339

Armstrong, Jason A

2003-02-01

355

A Quasioptical Vector Interferometer for Polarization Control  

NASA Technical Reports Server (NTRS)

We present a mathematical description of a Quasioptical Vector Interferometer (QVI), a device that maps an input polarization state to an output polarization state by introducing a phase delay between two linear orthogonal components of the input polarization. The advantages of such a device over a spinning wave-plate modulator for measuring astronomical polarization in the far-infrared through millimeter are: 1. The use of small, linear motions eliminates the need for cryogenic rotational bearings, 2. The phase flexibility allows measurement of Stokes V as well as Q and U, and 3. The QVI allows for both multi-wavelength and broadband modulation. We suggest two implementations of this device as an astronomical polarization modulator. The first involves two such modulators placed in series. By adjusting the two phase delays, it is possible to use such a modulator to measure Stokes Q, U, and V for passbands that are not too large. Conversely, a single QVI may be used to measure Q and V independent of frequency. In this implementation, Stokes U must be measured by rotating the instrument. We conclude this paper by presenting initial laboratory results.

Chuss, David T.; Wollack, Edward J.; Moseley, Harvey S.; Novak, Giles

2005-01-01

356

Planetary observations with the Tidbinbilla interferometer  

NASA Technical Reports Server (NTRS)

Radio observations at a wavelength of 13.1 cm of Saturn and Uranus made with the Tidbinbilla interferometer during 1978 and 1979 are summarized. The observations were made with 64-m and 26-m antennas on a 200-m north-south baseline at a bandwidth of 12 MHz with RCP polarization and a primary beamwidth of about 12 arcmin. A flux density of 198 + or - 15 mJy was measured for Saturn, which indicates a surface temperature, corrected for the occulting effect of the rings, of 191 + or - 15 K, in excellent agreement with previous determinations. With the use of a background subtraction technique to remove the local background confusion, Uranus was found to have a flux density of 11.7 + or - 0.8 mJy, indicating a disk-averaged brightness temperature of 255 + or - 18 K. The increase in Uranus brightness temperature over that measured 15 years previously is attributed to variations in temperature or opacity below the cloud tops, or to a reduction in relative ammonia abundance most likely reflecting a change in the aspect of the planet as viewed from earth.

Batty, M. J.; Jauncey, D. L.; Rayner, P. T.; Gulkis, S.

1980-01-01

357

Atmospheric Emitted Radiance Interferometer (AERI) Handbook  

SciTech Connect

The atmospheric emitted radiance interferometer (AERI) measures the absolute infrared (IR) spectral radiance (watts per square meter per steradian per wavenumber) of the sky directly above the instrument. The spectral measurement range of the instrument is 3300 to 520 wavenumbers (cm-1) or 3-19.2 microns for the normal-range instruments and 3300 to 400 cm-1 or 3-25 microns, for the extended-range polar instruments. Spectral resolution is 1.0 cm-1. Instrument field-of-view is 1.3 degrees. A calibrated sky radiance spectrum is produced every 8 minutes in normal mode and every minute in rapid sampling mode. The actual sample scan time is 20-30 sec in rapid sampling mode with periodic gaps when the instrument is looking at the blackbodies. Rapid sampling will become available in all AERIs. Rapid sampling time will eventually be reduced to data every 20 seconds. The AERI data can be used for 1) evaluating line-by-line radiative transport codes, 2) detecting/quantifying cloud effects on ground-based measurements of infrared spectral radiance (and hence is valuable for cloud property retrievals), and 3) calculating vertical atmospheric profiles of temperature and water vapor and the detection of trace gases.

Demirgian, J; Dedecker, R

2005-01-01

358

Miniaturized Optical Fiber Inline Interferometers for Chemical Sensing  

NASA Astrophysics Data System (ADS)

This chapter reviews the miniaturized optical fiber inline interferometers for chemical sensing based on the detection of composition variation induced refractive index changes. When used as chemical sensors, these miniaturized devices have the common advantages of small size, all-glass ruggedized structure, high sensitivity, fast response time, and large dynamic range. These advantages make them particularly attractive for real-world applications where, in situ, continuous monitoring is required. Specifically, two general types of interferometers are reviewed including the low-finesse Fabry-Perot interferometer and the core-cladding mode interferometer. The operation principles of these two types of interferometers are described. The signal processing methods are discussed. The representative structures, fabrication methods, and application examples of each interferometer type are provided with certain level of details. The advantages and disadvantages of each sensor structure are also highlighted in the discussions, with the hope that innovative researches will be stimulated to solve the technical challenges and explore future applications of these devices.

Xiao, Hai; Wei, Tao

359

Highly stable polarization independent Mach-Zehnder interferometer.  

PubMed

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually. PMID:25173242

Mi?uda, Michal; Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav

2014-08-01

360

Highly stable polarization independent Mach-Zehnder interferometer  

E-print Network

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27x40 cm offers individually accessible paths and shows phase deviation less than 0.4 deg during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 deg or 7 nm for 1.5 hours without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually.

Michal Micuda; Ester Dolakova; Ivo Straka; Martina Mikova; Miloslav Dusek; Jaromir Fiurasek; Miroslav Jezek

2014-07-19

361

Planetary radar studies. [radar mapping of the Moon and radar signatures of lunar and Venus craters  

NASA Technical Reports Server (NTRS)

Progress made in studying the evolution of Venusian craters and the evolution of infrared and radar signatures of lunar crater interiors is reported. Comparison of radar images of craters on Venus and the Moon present evidence for a steady state Venus crater population. Successful observations at the Arecibo Observatory yielded good data on five nights when data for a mix of inner and limb areas were acquired. Lunar craters with radar bright ejects are discussed. An overview of infrared radar crater catalogs in the data base is included.

Thompson, T. W.; Cutts, J. A.

1981-01-01

362

Millimeter radar improves target identification  

NASA Astrophysics Data System (ADS)

Recently developed millimeter wave radar has advantages for target identification over conventional microwave radar which typically use lower frequencies. We describe the pertinent features involved in the construction of the new millimeter wave radar, the pseudo-optical cavity source and the quasi-optical duplexer. The long wavelength relative to light allows the radar beam to penetrate through most weather because the wavelength is larger than the particle size for dust, drizzle rain, fog. Further the mm wave beam passes through an atmospheric transmission window that provides a dip in attenuation. The higher frequency than conventional radar provides higher Doppler frequencies, for example, than X-band radar. We show by simulation that small characteristic vibrations and slow turns of an aircraft become visible so that the Doppler signature improves identification. The higher frequency also reduces beam width, which increases transmit and receive antenna gains. For the same power the transmit beam extends to farther range and the increase in receive antenna gain increases signal to noise ratio for improved detection and identification. The narrower beam can also reduce clutter and reject other noise more readily. We show by simulation that the radar can be used at lower elevations over the sea than conventional radar.

McAulay, Alastair D.

2011-06-01

363

Imaging Radar for Ecosystem Studies  

NASA Technical Reports Server (NTRS)

Recently a number of satellites have been launched with radar sensors, thus expanding opportunities for global assessment. In this article we focus on the applications of imaging radar, which is a type of sensor that actively generates pulses of microwaves and, in the interval between sending pulses, records the returning signals reflected back to an antenna.

Waring, Richard H.; Way, JoBea; Hunt, E. Raymond J.; Morrissey, Leslie; Ranson, K. Jon; Weishampel, John F.; Oren, Ram; Franklin, Steven E.

1996-01-01

364

Landform Identification on Radar Images  

NASA Technical Reports Server (NTRS)

Polarized radar echo images of the Moon acquired using 3.8 and 70 cm wavelengths were examined to learn more about (1) the relationships between theoretical resolutions of the radars and the sizes of landforms that can be identified and (2) the factors that effect landform identification.

Moore, H. J.; Thompson, T. W.

1985-01-01

365

4, 695729, 2004 Radar observations  

E-print Network

ACPD 4, 695­729, 2004 Radar observations of meteor trails W. G. Elford Title Page Abstract Discussion © EGU 2004 Atmos. Chem. Phys. Discuss., 4, 695­729, 2004 www.atmos-chem-phys.org/acpd/4/695/ SRef Discussions Radar observations of meteor trails, and their interpretation using Fresnel holography: a new tool

Paris-Sud XI, Université de

366

New Radar and Navigation Systems  

Microsoft Academic Search

It is not the intention of this paper to give a complete coverage of all new radar and navigation systems, but to concentrate rather more on specific areas and examples where microwaves are used. Also, general coverage of the radar area is felt to be unnecessary following the invited paper given by R. Voles at Microwave 74, however recent advances

K L Fuller

1975-01-01

367

CO2 laser radar  

NASA Astrophysics Data System (ADS)

CO2 laser-based radars operating at 10 microns are both highly energy-efficient and eye-safe, as well as compact and rugged; they also furnish covertness-enhancing fine pointing accuracy, and are difficult to jam or otherwise confuse. Two modes of operation are generally employed: incoherent, in which the laser is simply used as a high power illumination source, and in the presently elaborated coherent or heterodyne mode. Applications encompass terrain-following and obstacle avoidance, Doppler discrimination of missile and aircraft targets, pollutant gas detection, wind measurement for weapons-aiming, and global wind field monitoring.

Brown, D.; Callan, R.; Constant, G.; Davies, P. H.; Foord, R.

368

Mitigation of atmospheric effects in SIM's astrometric interferometer testbed 3  

NASA Astrophysics Data System (ADS)

The Space Interferometry Mission's (SIM) shared-baseline astrometric interferometer System Test Bed 3 (STB3) has been constructed at JPL. STB3's objective is to use two of its interferometers (guides) for low frequency (0 to 1 Hz) fringe stabilization in the third one (science). This approach - being proposed for the first time in the context of space based observatories - is needed given the dim nature of science stars to be observed by SIM. Fringe stability is mostly affected by the low frequency attitude motion of the test bed's instrument table, with the inevitable exception of instrument vibration, thermal drift, and atmospheric fluctuations. Relative changes in table attitude cause optical path changes in the guide interferometers, which are tracked, linearly combined and fed forward to the science interferometer's active delay line to stabilize its optical path. This technique for tracking fringes in the science interferometer is possible because the position of the guide stars relative to the science star is well known. This open loop fringe tracking technique is dubbed Path-length Feed Forward, or PFF. In STB3, current fringe stability in the science interferometer using the PFF technique is at 50 to 60 nanometers RMS (from 0 to 500 Hz). Compare this to 15 to 20 nm RMS fringe stability in the guide interferometers, which operate in closed loop mode. Vibration, thermal drift and atmospherics in the science and guide interferometers are largely eliminated with the use of an internal metrology system. By design, mechanical vibrations are above the bandwidth of the interferometer system, and are passively rejected. Nevertheless, the internal metrology system can easily reject current low-level vibrations in STB3 down to the 6-nanometer RMS level. Fringe tracking error in the science interferometer due to atmospherics is currently about 40 nanometers RMS at frequencies below 1.0 Hz. In SIM, the error in this low frequency band must be no more than 6 nm RMS. This error arises because the optical path stabilized by the internal metrology system is not equal to taht of the starlight, so not all atmospheric fluctuations in the starlight path can be stabilized. Therefore, there is a need to reduce the strength of atmospheric fluctuations or to filter them from the PFF command. In STB3 the strength of atmospheric fluctuations is already reduced with the use of optical path enclosures, which brought these fluctuations down from ~170nm RMS to their current levels of ~66nm RMS with a spread of 20nm. Simulations show that signal to noise ratios are generally not sufficient to filter atmospheric errors on-line.

Alvarez-Salazar, Oscar S.; Goullioud, Renaud; Nemati, Bijan; Azizi, Alireza

2003-02-01

369

Radar image registration and rectification  

NASA Technical Reports Server (NTRS)

Two techniques for radar image registration and rectification are presented. In the registration method, a general 2-D polynomial transform is defined to accomplish the geometric mapping from one image into the other. The degree and coefficients of the polynomial are obtained using an a priori found tiepoint data set. In the second part of the paper, a rectification procedure is developed that models the distortion present in the radar image in terms of the radar sensor's platform parameters and the topographic variations of the imaged scene. This model, the ephemeris data and the digital topographic data are then used in rectifying the radar image. The two techniques are then used in registering and rectifying two examples of radar imagery. Each method is discussed as to its benefits, shortcomings and registration accuracy.

Naraghi, M.; Stromberg, W. D.

1983-01-01

370

A radar image time series  

NASA Technical Reports Server (NTRS)

A set of ten side-looking radar images of a mining area in Arizona that were aquired over a period of 14 yr are studied to demonstrate the photogrammetric differential-rectification technique applied to radar images and to examine changes that occurred in the area over time. Five of the images are rectified by using ground control points and a digital height model taken from a map. Residual coordinate errors in ground control are reduced from several hundred meters in all cases to + or - 19 to 70 m. The contents of the radar images are compared with a Landsat image and with aerial photographs. Effects of radar system parameters on radar images are briefly reviewed.

Leberl, F.; Fuchs, H.; Ford, J. P.

1981-01-01

371

Dual-domain point diffraction interferometer  

DOEpatents

A hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI is provided. The dual-domain PS/PDI combines the separate noise-suppression capabilities of the widely-used phase-shifting and Fourier-transform fringe pattern analysis methods. The dual-domain PS/PDI relies on both a more restrictive implementation of the image plane PS/PDI mask and a new analysis method to be applied to the interferograms generated and recorded by the modified PS/PDI. The more restrictive PS/PDI mask guarantees the elimination of spatial-frequency crosstalk between the signal and the scattered-light noise arising from scattered-reference-light interfering with the test beam. The new dual-domain analysis method is then used to eliminate scattered-light noise arising from both the scattered-reference-light interfering with the test beam and the scattered-reference-light interfering with the "true" pinhole-diffracted reference light. The dual-domain analysis method has also been demonstrated to provide performance enhancement when using the non-optimized standard PS/PDI design. The dual-domain PS/PDI is essentially a three-tiered filtering system composed of lowpass spatial-filtering the test-beam electric field using the more restrictive PS/PDI mask, bandpass spatial-filtering the individual interferogram irradiance frames making up the phase-shifting series, and bandpass temporal-filtering the phase-shifting series as a whole.

Naulleau, Patrick P. (5239 Miles Ave., Apt. A, Oakland, CA 94618); Goldberg, Kenneth Alan (1195 Keeler Ave., Berkeley, CA 94708)

2000-01-01

372

A panoramic electronic speckle pattern interferometer  

NASA Astrophysics Data System (ADS)

Electronic Speckle Pattern Interferometry (ESPI) measurements are typically restricted to specimens that are flat or have some minimal curvature associated with them due to errors introduced by the geometry of the object and the shape of the wave front used for illumination and viewing. The objective of this research was to develop an ESPI system capable of obtaining full field, out-of-plane displacement measurements on the interior walls of a cylindrically shaped tube. It was accomplished in a relatively simple and accurate manner, when compared to conventional systems that attempt to make out-of-plane measurements on the walls of a pipe, by designing a unique electronic speckle pattern interferometer. The Panoramic ESPI system developed relies on two collinear panoramic annular lenses, one to illuminate and the other to image the entire circumference of a section of pipe. Phase stepping is performed to remove the sign ambiguity of the displacement vector using a piezotranslator. Images obtained with a CCD Camera are acquired and stored using a frame grabber. Customized software is employed to map the PAL image into a conventional format. Finally, the intensity distribution is analyzed with customized fringe analysis routines: filtering is performed with the addition of a digital carrier fringe to remove noise and phase unwrapping is used to obtain the phase map associated with the displacements. The governing equation relating the change in phase, obtained with the dual PAL interferometry system, to the displacements has been derived. Development of the equation is based on a detailed optical analysis performed in this study to determine the sensitivity vector associated with the system over its field of view. The results of the sensitivity analysis were used in processing the experimental fringe data. Experimental results obtained for out-of-plane displacements agree with those found analytically using a known solution and demonstrate the accuracy in making full field measurements using panoramic ESPI.

Fair, Sara Beth Batson

1999-11-01

373

Antarctic Mapping Project ACTIVE RADAR CALIBRATOR  

E-print Network

and Space Administration and National Science Foundation sponsored second mapping of Antarctica using satellite radar. The ARC is required in the calibration of these radar image data. This active radar. The first radar mapping of Antarctica was completed in 1997. The second mapping will also be accomplished

Howat, Ian M.

374

A new algorithm for radar emitter recognition  

Microsoft Academic Search

A radar electronic support measures (ESM) system performs the functions of threat detection and area surveillance. The received radar pulses are sorted and segregated by the deinterleaver into a number of radar cells depending on the measured parameters of the received pulses. These radar cells will be submitted to the threat library and compared with the stored parameters of known

H. E. Hassan

2003-01-01

375

Joint deinterleaving\\/recognition of radar pulses  

Microsoft Academic Search

A radar electronic support measures (ESM) system performs the functions of threat detection and area surveillance to determine the bearing and the identity of the surrounding radar emitters. The received pulses arc sorted and segregated into a number of deinterleaved radar cells depending on their measured parameters. The parameters of the deinterleaved radar cells will be submitted to the threat

H. E. Hassan

2003-01-01

376

Radar absorbing materials used for target camouflage  

Microsoft Academic Search

As a result of the developments within signal processing, transmitters and receivers areas radar technology has improved steadily over the past 50 years gaining in the sensor sensitivity, miniaturisation, power consumption, etc which allow to build smaller, more reliable and user friendly radar sensors. The effectiveness of these radar sensors is sufficiently threatening to merit the reduction of radar signature

I. NICOLAESCU

2006-01-01

377

Radar, Insect Population Ecology, and Pest Management  

NASA Technical Reports Server (NTRS)

Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives.

Vaughn, C. R. (editor); Wolf, W. (editor); Klassen, W. (editor)

1979-01-01

378

Course Syllabus Course name: Radar Meteorology  

E-print Network

Course Syllabus Course name: Radar Meteorology Course number: AT741 Instructor: Prof. Steven652, or permission of instructor Course goals and Objectives: AT741 is designed to provide principles, polarimetric radar, dual-wavelength radar, mm-wave radars with applications. The course also

379

Multichannel Density Measurements with a Millimeter Wave Interferometer on CTH  

NASA Astrophysics Data System (ADS)

A three-channel 1,m wave interferometer has been installed on the Compact Toroidal Hybrid torsatron (CTH). The interferometer design makes novel use of a subharmonic mixer for detection, which simplifies alignment. It employs a single electronically tunable source that is repetitively chirped using a sawtooth waveform of frequency up to 1,Hz. The 15.25,Hz drive oscillator is multiplied in two stages to 122,Hz before a final doubler stage brings it to 244,Hz. Local oscillator (LO) power at 122,Hz is directed through waveguide to the LO input of the subharmonic mixer of each viewing chord, simplifying alignment. Phase detection is performed by directly digitizing the amplified mixer outputs at 50,Hz and processing them with a software algorithm. Measurements made with the central chord of the new interferometer agree with those from the existing 4,m system at low densities. The 1,m system performs well in current-driven discharges reaching densities over 10^19 m-3, whereas the lower frequency interferometer is found to be less reliable due to loss of fringes. This is a critical improvement for experiments studying disruptions in the CTH device. Results from the fully implemented three-channel interferometer will be presented and discussed.

Archmiller, M. C.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.

2012-10-01

380

Modeling the imaging process in optical stellar interferometers  

NASA Astrophysics Data System (ADS)

Optical interferometers on the ground, like ESO's Very Large Telescope Interferometer (VLTI) and the Keck Interferometer, and in space, like the InfraRed Space Interferometer (IRSI/Darwin) and the Space Interferometry Mission (SIM), will bring a major breakthrough in optical and near-infrared high angular resolution astronomy at the beginning of the next millennium. These instruments are complex systems with an exceptionally interdisciplinary character involving active/adaptive optics, structural mechanics, control engineering, electronics and various environmental disturbances (e.g. atmospheric turbulence and absorption, wind, seismic noise). For their design and development an approach from two sides is appropriate: laboratory testbeds are used for experimental investigations while numerical modeling tools perform an End-to-End instrument simulation. We have developed a set of numerical modeling tools to simulate the dynamic imaging process of an interferometer. The time-dependent point spread function (PSF) mainly characterizes the imaging performance of the instrument. It is computed by an optomechanical model. Based on the knowledge of the PSF the image of an incoherently radiating extended object is computed using a Fourier optical method. This article describes the modeling approach including an extension to more than two interferometric beams. Some results of simulations on the VLTI as a representative example are shown.

Schöller, M.; Wilhelm, R.; Koehler, B.

2000-06-01

381

Development of super-broadband interferometer in FIR  

NASA Astrophysics Data System (ADS)

We are developing the super broad band interferometer by applying the Fourier Transform Spectrometer(FTS) to aperture synthesis system in mm and sub-mm bands. We have constructed a compact system based on the Martin and Puplett type Fourier Transform spectrometer (MP-FT). We call this equipment Multi-Fourier Transform interferometer (MuFT). The band width of the system can be extended as large as one wants contrary to the severely limited band width of the usual interferometer due to the speed of the AD converter. The direct detectors, e.g. bolometer, SIS video detector, can be used as the focal plane detectors. This type of detectors have a great advantage in FIR band since they are free from the quantum limit of the noise which limits the sensitivity of the heterodyne detectors used in the usual interferometers. Further, the direct detectors are able to make a large format array contrary to the heterodyne detectors for which construction of a large format array is practically difficult. These three characteristics make one be possible to develop high sensitive super broad band FIR interferometer with wide field of view. In the laboratory experiments, we have succeeded in measuring the spectroscopically resolved 2D image of the source in 150GHz-900GHz band. The future application of this technique to the observations from the space could open new interesting possibilities in FIR astronomy.

Ohta, Izumi S.; Hattori, Makoto; Matsuo, Hiroshi

2004-10-01

382

Application of stochastic resonance in gravitational-wave interferometer  

E-print Network

We investigate novel approach, which improves the sensitivity of gravitational wave (GW) interferometer due to stochastic resonance (SR) phenomenon, performing in additional nonlinear cavity (NC). The NC is installed in the output of interferometer before photodetector, so that optical signal emerging interferometer incidents on the NC and passes through it. Under appropriate circumstances a specific transformation of noisy signal inside the NC takes place, which results in the increase of output signal-to-noise ratio (SNR). As a result optical noisy signal of interferometer becomes less noisy after passing through the NC. The improvement of SNR is especially effective in bistable NC for wideband (several hundreds Hz) detection, when chirp GW signal is detected. Then SNR gain reaches amount ~ 10. When detection bandwidth is narrowed, the influence of SR mechanism gradually disappears, and SNR gain tends to 1. SNR gain also tends to 1 when the NC is gradually transformed to linear cavity. Proposed enhancement of SNR due to the SR is not dependent of noise type, which is prevalent in interferometer. Particularly proposed approach is capable to increase signal-to-displacement noise ratio.

G. G. Karapetyan

2006-01-30

383

Historical aspects of radar atmospheric dynamics  

NASA Technical Reports Server (NTRS)

A review of the history of radar techniques which have been applied to atmospheric observation is given. The author starts with ionosphere observation with the ionosonde, symbolizing as it does the earliest history of radar observation, and proceeds to later developments in radar observation such as the use of partial reflection, meteor, and incoherent scatter radars. Mesosphere stratosphere troposphere (MST) radars are discussed in terms of lower atmosphere observation.

Kato, Susumu

1989-01-01

384

Airborne bistatic radar applications  

NASA Astrophysics Data System (ADS)

Applications of bistatic radar when one or both of the units are airborne are discussed. Scenarios that merit deeper consideration are covert strike and head-on SAR using a stand-off illuminator, either airborne or space-based; area air defense with passive ground-based receivers and stand-off illuminators; an airborne picket line to detect stealth aircraft and missiles; AWACS aircraft providing mutual support in ECM environments; and passive surveillance of hostile air space using illuminators of opportunity and an airborne receiver. Scenarios considered impractical are bistatic air-to-air missile guidance using an aircraft other than the launch aircraft as illuminator; passive interdiction using illuminators of opportunity; and scenarios involving a ground based illuminator and an aircraft as the receiver.

Foster, James A.

1987-09-01

385

Radar backscatter modelling  

NASA Technical Reports Server (NTRS)

The terrain analysis software package was restructured and documentation was added. A program was written to test Johnson Space Center's four band scatterometer data for spurious signals data. A catalog of terrain roughness statistics and calibrated four frequency multipolarization scatterometer data is being published to support the maintenance of Death Valley as a radar backscatter calibration test site for all future airborne and spacecraft missions. Test pits were dug through sand covered terrains in the Eastern Sahara to define the depth and character of subsurface interfaces responsible for either backscatter or specular response in SIR-A imagery. Blocky sandstone bedrock surfaces at about 1 m depth were responsible for the brightest SIR-A returns. Irregular very dense CaCO3 cemented sand interfaces were responsible for intermediate grey tones. Ancient river valleys had the weakest response. Reexamination of SEASAT l-band imagery of U.S. deserts continues.

Schaber, G. G.; Kozak, R. C.; Gurule, R. L.

1984-01-01

386

Synthetic aperture radar interferometry of Okmok volcano, Alaska: Radar observations  

Microsoft Academic Search

ERS-1\\/ERS-2 synthetic aperture radar interferometry was used to study the 1997 eruption of Okmok volcano in Alaska. First, we derived an accurate digital elevation model (DEM) using a tandem ERS-1\\/ERS-2 image pair and the preexisting DEM. Second, by studying changes in interferometric coherence we found that the newly erupted lava lost radar coherence for 5-17 months after the eruption. This

Zhong Lu; Dörte Mann; Jeffrey T. Freymueller; David J. Meyer

2000-01-01

387

Ultrasensitive Atomic Spin Measurements with a Nonlinear Interferometer  

NASA Astrophysics Data System (ADS)

We study nonlinear interferometry applied to a measurement of atomic spin and demonstrate a sensitivity that cannot be achieved by any linear-optical measurement with the same experimental resources. We use alignment-to-orientation conversion, a nonlinear-optical technique from optical magnetometry, to perform a nondestructive measurement of the spin alignment of a cold Rb87 atomic ensemble. We observe state-of-the-art spin sensitivity in a single-pass measurement, in good agreement with covariance-matrix theory. Taking the degree of measurement-induced spin squeezing as a figure of merit, we find that the nonlinear technique's experimental performance surpasses the theoretical performance of any linear-optical measurement on the same system, including optimization of probe strength and tuning. The results confirm the central prediction of nonlinear metrology, that superior scaling can lead to superior absolute sensitivity.

Sewell, R. J.; Napolitano, M.; Behbood, N.; Colangelo, G.; Martin Ciurana, F.; Mitchell, M. W.

2014-04-01

388

A faster scaling in acceleration-sensitive atom interferometers  

NASA Astrophysics Data System (ADS)

Atom interferometers have been used to measure acceleration with at best a T2 scaling in sensitivity as the interferometer time T is increased. This limits the sensitivity to acceleration which is theoretically achievable by these configurations for a given frequency of acceleration. We predict and experimentally measure the acceleration-sensitive phase shift of a large-momentum-transfer atom interferometer based upon Bloch oscillations. Using this novel interferometric scheme we demonstrate an improved scaling of sensitivity which will scale as T3. This enhanced scaling will allow an increase in achievable sensitivity for any given frequency of an oscillatory acceleration signal, which will be of particular use for inertial and navigational sensors, and proposed gravitational wave detectors. A straightforward extension should allow a T4 scaling in acceleration sensitivity.

McDonald, G. D.; Kuhn, C. C. N.; Bennetts, S.; Debs, J. E.; Hardman, K. S.; Close, J. D.; Robins, N. P.

2014-03-01

389

Spatially modulated interferometer and beam shearing device therefor  

NASA Technical Reports Server (NTRS)

A spatially modulated interferometer incorporates a beam shearing system having a plurality of reflective surfaces defining separate light paths of equal optical path length for two separate output beams. The reflective surfaces are arranged such that when the two beams emerge from the beam shearing system they contain more than 50 percent of the photon flux within the selected spectral pass band. In one embodiment, the reflective surfaces are located on a number of prism elements combined to form a beam shearing prism structure. The interferometer utilizing the beam sharing system of the invention includes fore-optics for collecting light and focusing it into a beam to be sheared, and a detector located at an exit pupil of the device. In a preferred embodiment, the interferometer has no moving parts.

Reininger, Francis M. (Inventor)

2004-01-01

390

Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics  

NASA Technical Reports Server (NTRS)

The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal tends to become more transparent, thus introducing a rather large amount of error into the phase-shifting measurement. While that error can be greatly reduced by normalization, we prefer eliminating the source of the error. To that end, we have pursued development of a 'blend' of custom dyes that will not exhibit these properties. That goal has not yet been fully achieved. Guardalben, et al, presented a similar set of interferograms in a paper partially funded by this grant. Shearing interferometers are a second class of common path interferometers. Typically they consist of a thick glass plate optimized for equal reflection from the front and back surface. While not part of the original thrust of the project, through the course of laboratory work, we demonstrated a prototype of a shearing interferometer capable of phase shifting using a commercial liquid crystal retardation plate. A schematic of this liquid crystal shearing interferometer (LCSI) and a sample set of interferograms are in the reference. This work was also supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. Additional information is included in the original extended abstract.

Griffin, DeVon W.; Marshall, Keneth L.

2002-01-01

391

The GOSAT / TANSO interferometer after five years on orbit  

NASA Astrophysics Data System (ADS)

GOSAT (Greenhouse Gases Observing Satellite) is a Japanese Earth observation satellite dedicated to the monitoring of total column amount of carbon dioxide and methane over different locations on the planet. The main instrument of GOSAT is the TANSO Fourier Transform Spectrometer (TANSO FTS). NEC-Toshiba Space Systems was the prime integrator of the TANSO FTS. ABB provided the interferometer and its control electronics. The satellite was launched in January 2009. The mission, planned for five years, has exceeded its design life-time. This paper presents an overview of the interferometer and of its development. Special emphasis is accorded to the life time qualification activities. Analysis of the health of the interferometer on-orbit is also presented.

Moreau, Louis; Veilleux, James; Suto, Hiroshi

2014-09-01

392

Improving the performance of interferometers in metrological scanning probe microscopes  

NASA Astrophysics Data System (ADS)

The traceability of metrological scanning probe microscopes (MSPMs) is achieved in most cases by laser interferometers. Different means have been adopted to account for the nonlinearity of those interferometers. The thorough investigation of an existing MSPM shows the necessity of interferometrical position measurement with real time full-bandwidth nonlinearity correction. The paper demonstrates that the ellipse parameters of Heydemann nonlinearity correction are sufficiently stable and position independent. This is used in reducing the signal processing time by calculating the ellipse parameters in advance and fixing them during real time nonlinearity correction. As a result, a real time signal processing system with the ability of executing Heydemann correction in 0.32 µs and a complete demodulation in 2.2 µs is designed and implemented. It reduces the residual nonlinearity of interferometers from about 3.5 to <0.3 nm. Some measurement results of a flatness standard illustrate the effectiveness of this new method.

Dai, Gaoliang; Pohlenz, Frank; Danzebrink, Hans-Ulrich; Hasche, Klaus; Wilkening, Guenter

2004-02-01

393

New system of miniaturization online testing of spherical interferometer  

NASA Astrophysics Data System (ADS)

With the aim to measure the radius of curvature deviation and the surface form deviation of optical elements online in the workshop, based on laser testing technique, two solutions of miniaturization without precision guider sphericity interferometer systems are described, and the principle of systems are analyzed. Compared with the traditional sphericity interferometer, the systems designed are particularly suitable for testing mirror noncontact online in workshop, advantaged in compact structure, no precision guider, high efficiency and low costs. The interferometer systems use the different radius of curvature of existing spherical test plates in the production workshop to produce reference wavefront. The systems can not only get the astigmatism and local deviation of lens, but also can reflect the radius of curvature deviation, which provides rapid and nondestructive noncontact online testing.

Lin, Jian; Han, Zhenhua; Zhuo, Jinzhai; Wang, Min

2011-11-01

394

Probing angular momentum coherence in a twin-atom interferometer  

E-print Network

We propose to use a double longitudinal Stern-Gerlach atom interferometer in order to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular momentum, we investigate the propagation of the corresponding atomic fragments in the apparatus. We show that the envisioned interferometer enables one to distinguish unambiguously a spin-coherent from a spin-incoherent dissociation, as well as to estimate the purity of the angular momentum density matrix associated with the fragments. This setup, which may be seen as an atomic analogue of a twin-photon interferometer, can be used to investigate the suitability of molecule dissociation processes -- such as the metastable hydrogen atoms H($2^2 S$)-H($2^2 S$) dissociation - for coherent twin-atom optics.

de Carvalho, Carlos R; Impens, François; Robert, J; Medina, Aline; Zappa, F; Faria, N V de Castro

2014-01-01

395

A faster scaling in acceleration-sensitive atom interferometers  

E-print Network

Atom interferometers have been used to measure acceleration with at best a $T^2$ scaling in sensitivity as the interferometer time $T$ is increased. This limits the sensitivity to acceleration which is theoretically achievable by these configurations for a given frequency of acceleration. We predict and experimentally measure the acceleration-sensitive phase shift of a large-momentum-transfer atom interferometer based upon Bloch oscillations. Using this novel interferometric scheme we demonstrate an improved scaling of sensitivity which will scale as $T^3$. This enhanced scaling will allow an increase in achievable sensitivity for any given frequency of an oscillatory acceleration signal, which will be of particular use for inertial and navigational sensors, and proposed gravitational wave detectors. A straight forward extension should allow a $T^4$ scaling in acceleration sensitivity.

Gordon D. McDonald; Carlos C. N. Kuhn; Shayne Bennetts; John E. Debs; Kyle S. Hardman; John D. Close; Nicholas P. Robins

2013-11-09

396

Multipath induced errors in meteorological Doppler/interferometer location systems  

NASA Technical Reports Server (NTRS)

One application of an RF interferometer aboard a low-orbiting spacecraft to determine the location of ground-based transmitters is in tracking high-altitude balloons for meteorological studies. A source of error in this application is reflection of the signal from the sea surface. Through propagating and signal analysis, the magnitude of the reflection-induced error in both Doppler frequency measurements and interferometer phase measurements was estimated. The theory of diffuse scattering from random surfaces was applied to obtain the power spectral density of the reflected signal. The processing of the combined direct and reflected signals was then analyzed to find the statistics of the measurement error. It was found that the error varies greatly during the satellite overpass and attains its maximum value at closest approach. The maximum values of interferometer phase error and Doppler frequency error found for the system configuration considered were comparable to thermal noise-induced error.

Wallace, R. G.

1984-01-01

397

Phase closure bias versus dispersion in a stellar interferometer  

NASA Astrophysics Data System (ADS)

Phase closure is a well-known technique able to eliminate phase biases in a three-arm interferometer. This property is very useful to avoid the phase effect of the atmosphere in stellar interferometry. In this paper we theoretically investigate the effect of differential dispersion in a three-arm interferometer. We demonstrate that phase closure can be corrupted by differential dispersion between the interferometric arms. We begin by a general demonstration of such effect and propose a few examples where symmetry properties avoid phase closure errors. An analytical model for gaussian shaped spectrum and second order dispersion development is proposed. This analytical solution is illustrated by experimental results on a fibre version of a stellar interferometer.

Huss, G.; Longueteau, E.; Delage, L.; Reynaud, F.

2003-02-01

398

Fly eye radar or micro-radar sensor technology  

NASA Astrophysics Data System (ADS)

To compensate for its eye's inability to point its eye at a target, the fly's eye consists of multiple angularly spaced sensors giving the fly the wide-area visual coverage it needs to detect and avoid the threats around him. Based on a similar concept a revolutionary new micro-radar sensor technology is proposed for detecting and tracking ground and/or airborne low profile low altitude targets in harsh urban environments. Distributed along a border or around a protected object (military facility and buildings, camp, stadium) small size, low power unattended radar sensors can be used for target detection and tracking, threat warning, pre-shot sniper protection and provides effective support for homeland security. In addition it can provide 3D recognition and targets classification due to its use of five orders more pulses than any scanning radar to each space point, by using few points of view, diversity signals and intelligent processing. The application of an array of directional antennas eliminates the need for a mechanical scanning antenna or phase processor. It radically decreases radar size and increases bearing accuracy several folds. The proposed micro-radar sensors can be easy connected to one or several operators by point-to-point invisible protected communication. The directional antennas have higher gain, can be multi-frequency and connected to a multi-functional network. Fly eye micro-radars are inexpensive, can be expendable and will reduce cost of defense.

Molchanov, Pavlo; Asmolova, Olga

2014-05-01

399

An interferometric radar for displacement measurement and its application in civil engineering structures  

NASA Astrophysics Data System (ADS)

Recent progress in radar techniques and systems has led to the development of a microwave interferometer, potentially suitable for non-contact displacement monitoring of civil engineering structures. This paper describes a new interferometric radar system, named IBIS-S, which is possible to measure the static or dynamic displacement at multiple points of structures simultaneously with high accuracy. In this paper, the technical characteristics and specification of the radar system is described. Subsequently, the actual displacement sensitivity of the equipment is illustrated using the laboratory tests with random motion upon a shake table. Finally the applications of the radar system to the measurement on a cable-stayed bridge and a prestressed concrete bridge are presented and discussed. Results show that the new system is an accurate and effective method to measure displacements of multiple targets of structures. It should be noted that the current system can only measure the vibration of the target position along the sensor's line of sight. Hence, proper caution should be taken when designing the sensor posture and prior knowledge of the direction of motion is necessary.

Su, D.; Nagayama, T.; Sun, Z.; Fujino, Y.

2012-04-01

400

Parallel Wavefront Analysis for a 4D Interferometer  

NASA Technical Reports Server (NTRS)

This software provides a programming interface for automating data collection with a PhaseCam interferometer from 4D Technology, and distributing the image-processing algorithm across a cluster of general-purpose computers. Multiple instances of 4Sight (4D Technology s proprietary software) run on a networked cluster of computers. Each connects to a single server (the controller) and waits for instructions. The controller directs the interferometer to several images, then assigns each image to a different computer for processing. When the image processing is finished, the server directs one of the computers to collate and combine the processed images, saving the resulting measurement in a file on a disk. The available software captures approximately 100 images and analyzes them immediately. This software separates the capture and analysis processes, so that analysis can be done at a different time and faster by running the algorithm in parallel across several processors. The PhaseCam family of interferometers can measure an optical system in milliseconds, but it takes many seconds to process the data so that it is usable. In characterizing an adaptive optics system, like the next generation of astronomical observatories, thousands of measurements are required, and the processing time quickly becomes excessive. A programming interface distributes data processing for a PhaseCam interferometer across a Windows computing cluster. A scriptable controller program coordinates data acquisition from the interferometer, storage on networked hard disks, and parallel processing. Idle time of the interferometer is minimized. This architecture is implemented in Python and JavaScript, and may be altered to fit a customer s needs.

Rao, Shanti R.

2011-01-01

401

Highlights from Ground-Based O/IR Interferometers  

NASA Astrophysics Data System (ADS)

Ground-based optical/infrared long-baseline interferometry has continued to extend its capabilities in the U.S., where several existing facilites demonstrate its capabilites in a broad range of scientific applications. This poster presents brief overviews of the CHARA Array and the Infrared Spatial Interferometer (ISI) on Mt. Wilson, CA; the Palomar Testbed Interferometer (PTI) on Mt. Palomar, CA; the Navy Prototype Optical Interferometer (NPOI) located on Anderson Mesa near Flagstaff, AZ; and the Keck Interferometer (KI) on Mauna Kea, HI; as well as the Magdalena Ridge Observatory Interferometer (MROI) now under construction at the highest elevation of the Magdalena Mountains of New Mexico. The poster also includes pointers to a small fraction of the scientific results from U.S. interferometers. Recent scientific highlights range from stellar atmospheres (precise diameters, including G/K dwarfs; limb darkening; Cepheid pulsations) to circumstellar material (water detected in a protoplanetary disk; debris disks; Be star disks; warped circumbinary disks; dust shells) to orbits and stellar masses in double, triple, and quadruple systems, to images of stellar surfaces (rapid rotators such Altair), to name a few. While the great majority of results to date have focused on stellar astrophysics, the MROI strives to have sensitivity sufficient to access a number of AGN. Research with these independently operated facilities is sponsored by the California Institute of Technology and the Jet Propulsion Laboratory for PTI; the Oceanographer of the Navy and the Office of Naval Research for NPOI; the National Aeronautics and Space Administration for KI; the National Science Foundation and Georgia State University for the CHARA Array; and the Office of Naval Research, the National Science Foundation, and the Gordon and Betty Moore Foundation for ISI. Funding for MROI is administered through the Office of Naval Research.

Armstrong, J. Thomas; Creech-Eakman, M. J.; Akeson, R. L.; Bakker, E. J.; Hutter, D. J.; McAlister, H. A.; ten Brummelaar, T.; Townes, C. H.

2009-01-01

402

Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology  

NASA Technical Reports Server (NTRS)

A new method to control microparticles was developed in-house at the NASA Glenn Research Center in support of the nanotechnology project under NASA's Aerospace Propulsion and Power Base Research Program. A prototype interferometer-controlled optical tweezers was constructed to manipulate scanning probe microscope (SPM) tips. A laser beam passed through a Mach-Zehnder interferometer, and a microscope objective then produced an optical trap from the coaxial beams. The trap levitated and generated the coarse motion of a 10-mm polystyrene sphere used to simulate a SPM tip. The interference between the beams provided fine control of the forces and moments on the sphere. The interferometer included a piezoelectric-scanned mirror to modulate the interference pattern. The 10-mm sphere was observed to oscillate about 1 mm as the mirror and fringe pattern oscillated. The prototype tweezers proved the feasibility of constructing a more sophisticated interferometer tweezers to hold and manipulate SPM tips. The SPM tips are intended to interrogate and manipulate nanostructures. A more powerful laser will be used to generate multiple traps to hold nanostructures and SPM tips. The vibrating mirror in the interferometer will be replaced with a spatial light modulator. The modulator will allow the optical phase distribution in one leg of the interferometer to be programmed independently at 640 by 480 points for detailed control of the forces and moments. The interference patterns will be monitored to measure the motion of the SPM tips. Neuralnetwork technology will provide fast analysis of the interference patterns for diagnostic purposes and for local or remote feedback control of the tips. This effort also requires theoretical and modeling support in the form of scattering calculations for twin coherent beams from nonspherical particles.

Decker, Arthur J.

2002-01-01

403

Systematic error elimination by correction of variable interferometer aberrations  

NASA Astrophysics Data System (ADS)

The possibility of reducing the variable systematic error in interferometry measurements via a higher degree of compensation of residual aberrations of the interferometer is shown theoretically and verified experimentally. It is proven that, in the case when interferometer aberrations are variable, one reference hologram is insufficient to correct aberrations. However, using several reference holograms on which the aberrations are recorded, it is possible to reconstruct interference patterns in which the influence of residual aberrations on the behavior of bands is reduced to a definite minimal level.

But', A. I.; Lyalikov, A. M.

2011-05-01

404

Prospects for Stochastic Background Searches Using Virgo and LSC Interferometers  

E-print Network

We consider the question of cross-correlation measurements using Virgo and the LSC Interferometers (LIGO Livingston, LIGO Hanford, and GEO600) to search for a stochastic gravitational-wave background. We find that inclusion of Virgo into the network will substantially improve the sensitivity to correlations above 200 Hz if all detectors are operating at their design sensitivity. This is illustrated using a simulated isotropic stochastic background signal, generated with an astrophysically-motivated spectrum, injected into 24 hours of simulated noise for the LIGO and Virgo interferometers.

Giancarlo Cella; Carlo Nicola Colacino; Elena Cuoco; Angela Di Virgilio; Tania Regimbau; Emma L Robinson; John T Whelan

2007-04-23

405

Rational choices for the wavelengths of a two color interferometer  

SciTech Connect

If in a two color interferometer for plasma density measurements, the two wavelengths are chosen to have a ratio that is a rational number, and if the signals from each of the wavelengths are multiplied in frequency by the appropriate integer of the rational number and then heterodyned together, the resultant signal will have all effects of component motion nulled out. A phase measurement of this signal will have only plasma density information in it. With CO{sub 2} lasers, it is possible to find suitable wavelength pairs which are close enough to rational numbers to produce an improvement of about 100 in density resolution, compared to standard two color interferometers.

Jobes, F.C.

1995-07-01

406

Testing the optical bench of the Laser Interferometer Space Antenna  

NASA Astrophysics Data System (ADS)

The space-based gravitational-wave detector Laser Interferometer Space Antenna (LISA) shall detect gravitational-waves by measuring distance changes between its three satellites with in-terferometers. Currently, the first prototype of the so-called optical bench, that contains the interferometric setups for the lengths measurements of LISA, is being built for the European Space Agengy (ESA). This optical bench will be tested at the Albert-Einstein-Institute and its functionality and sensitivity will be characterised. For this purpose, special tools and pre-experiments are necessary, that will be discussed in this talk.

Tröbs, Michael; Baune, Christoph; Bogenstahl, Johanna; D'Arcio, Luigi; Dehne, Marina; Diekmann, Christian; Fitzsimons, Ewan; Fleddermann, Roland; Granova, Evgenia; Heinzel, Gerhard; Hogenhuis, Harm; Killow, Christian; Perreur-Lloyd, Michael; Pijnenburg, Joep; Robertson, David; Schütte, Dirk; Schwarze, Thomas; Vogt, Malte; Wanner, Gudrun; Ward, Henry; Weise, Dennis; Danzmann, Karsten

407

Optical image encryption based on a radial shearing interferometer  

NASA Astrophysics Data System (ADS)

We present a novel method for optical image encryption based on a modified radial shearing interferometer (MRSI), which is generally used for wavefront reconstruction. In this method, a plaintext image is first encoded into a phase-only mask (POM) and then modulated by a random phase mask (RPM), the result is regarded as the input of the radial shearing interferometer and is divided into two coherent lights, which interfere with each other, leading to an interferogram (ciphertext). The aforementioned encryption process can be achieved digitally or optically while the decryption process can only be analytically accomplished. Numerical simulation is provided to demonstrate the validity of this method.

Lu, Dajiang; He, Wenqi; Peng, Xiang

2013-10-01

408

Polarization Considerations for the Laser Interferometer Space Antenna  

NASA Technical Reports Server (NTRS)

A polarization ray trace model of the Laser Interferometer Space Antenna s (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required, very long path length, picometer level dynamic interferometry. The computational steps are described. This should eliminate any ambiguities associated with polarization ray tracing of interferometers and provide a basis for determining the computer model s limitations and serve as a clearly defined starting point for future work.

Waluschka, Eugene; Pedersen, Tracy R.; McNamara, Paul

2005-01-01

409

Hong-Ou-Mandel interferometer with cavities: Theory  

NASA Astrophysics Data System (ADS)

We study the number of coincidences in a Hong-Ou-Mandel interferometer exit whose arms have been supplemented with the addition of one or two optical cavities. The fourth-order correlation function at the beam splitter exit is calculated. In the regime where the cavities lengths are larger than the one-photon coherence length, photon coalescence and anticoalescence interference is observed. Feynman’s path diagrams for the indistinguishable processes that lead to quantum interference are presented. The construction of an optical XOR gate is discussed as an application for the Hong-Ou-Mandel interferometer with two cavities.

Olindo, C.; Sagioro, M. A.; Monken, C. H.; Pádua, S.; Delgado, A.

2006-04-01

410

Photoacoustic tomography using a Michelson interferometer with quadrature phase detection  

NASA Astrophysics Data System (ADS)

We present a pressure sensor based on a Michelson interferometer, for use in photoacoustic tomography. Quadrature phase detection is employed allowing measurement at any point on the mirror surface without having to retune the interferometer, as is typically required by Fabry-Perot type detectors. This opens the door to rapid full surface detection, which is necessary for clinical applications. Theory relating acoustic pressure to detected acoustic particle displacements is used to calculate the detector sensitivity, which is validated with measurement. Proof-of-concept tomographic images of blood vessel phantoms have been taken with sub-millimeter resolution at depths of several millimeters.

Speirs, Rory W.; Bishop, Alexis I.

2013-07-01

411

A two-dimensional white-light amplitude interferometer  

NASA Technical Reports Server (NTRS)

A review of the applications of a point-symmetric, 180-degree, rotational shearing interferometer is given. Material includes, photographs of the Michelson stellar interferometer fringes from Alpha-Lyr, measures of amplitude of phase excursions in the atmosphere, and a measure of the order of interference of speckle patterns. New material includes unpublished double star speckle patterns to illustrate the isoplanatic patch, a measure of the time fluctuations in the earth's atmosphere, and measurements of the properties of a 256 channel linear reticon.

Breckinridge, J. B.

1979-01-01

412

Progress in smart radar absorbers  

NASA Astrophysics Data System (ADS)

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance, Identification-Friend-or-Foe (IFF) and Absorb-While-Scan (AWS) This paper outlines the concept and basic properties of a novel type of active radar absorber, the so-called Phase-Switched Screen (PSS). The basic PSS topology is then modified so as to enable it to operate as a smart radar absorber when used together with an external sensor and feedback control loop. The theoretical predictions are confirmed using data measured on transmission-line analogues of the smart PSS structure.

Chambers, Barry; Tennant, Alan

2003-07-01

413

A plea for radar brightness  

Microsoft Academic Search

The radar reflectivity coefficient of a distributed scatterer, expressed either as ?0 or ?, depends on local incidence angle. Prior to incidence angle projection, the reflectivity coefficient may be called \\

R. K. Raney; T. Freeman; R. W. Hawkins; R. Bamler

1994-01-01

414

NASA Radar Images Asteroid Toutatis  

NASA Video Gallery

This 64-frame movie of asteroid Toutatis was generated from data by Goldstone's Solar System Radar on Dec. 12 and 13, 2012. In the movie clips, the rotation of the asteroid appears faster than it o...

415

Radar imaging of Saturn's rings  

Microsoft Academic Search

We present delay–Doppler images of Saturn's rings based on radar observations made at Arecibo Observatory between 1999 and 2003, at a wavelength of 12.6 cm and at ring opening angles of 20.1°?|B|?26.7°. The average radar cross-section of the A ring is ?77% relative to that of the B ring, while a stringent upper limit of 3% is placed on the

Philip D. Nicholson; Richard G. French; Donald B. Campbell; Jean-Luc Margot; Michael C. Nolan; Gregory J. Black; Heikki J. Salo

2005-01-01

416

Radar Observations of Meteor Deceleration  

Microsoft Academic Search

By using a narrow-beam high-power radar operating at 68 cm it has been possible to detect meteors traveling radially toward the radar. In these observations the antenna is directed at the radiant point of an intense meteor shower, and the receiver is tuned to the expected Doppler-shifted signal. Because the actual Doppler shift can be measured with pre- cision, both

J. V. Evans

1966-01-01

417

High-resolution radar imaging  

Microsoft Academic Search

The goal of this project is to formulate and investigate new approaches for forming images of radar targets from spotlight-mode, delay-Doppler measurements. These measurements can be acquired with a high-resolution radar-imaging operating with an optical- or radio-frequency carrier. Work in this reporting period has concentrated on our estimation-theory approach to forming high resolution images. This approach accounts for measurement noise

Donald L. Snyder

1990-01-01

418

Laser Heterodyne Radars and Lidars  

Microsoft Academic Search

\\u000a The title of this chapter is so contradictory that it needs special clarification before commencing the detailed discussion\\u000a of the chapter matter. The term RADAR emerged in 1941 as an acronym for radio detection and ranging. Thus, the two words “laser\\u000a radar” being put together represent first contradiction. It sounds even more curios, considering the fact that both words\\u000a are

Vladimir Protopopov

419

Progress in smart radar absorbers  

Microsoft Academic Search

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance,

Barry Chambers; Alan Tennant

2003-01-01

420

LIGO interferometer operating at design sensitivity with application to gravitational radiometry  

E-print Network

During the last decade the three interferometers of the Laser Interferometer Gravitational Wave Observatory (LIGO) were built and commissioned. In fall 2005 design sensitivity was achieved, corresponding to a strain ...

Ballmer, Stefan W. (Stefan Werner)

2006-01-01

421

PRACTICAL ASPECTS OF CALIBRATING NEAR-INFRARED INTERFEROMETER DATA: PREDICTING STELLAR ANGULAR SIZES  

E-print Network

PRACTICAL ASPECTS OF CALIBRATING NEAR-INFRARED INTERFEROMETER DATA: PREDICTING STELLAR ANGULAR Dr., Pasadena, CA 91109 gerard@huey.jpl.nasa.gov Abstract Reliable prediction of stellar diameters of calibrating visibility amplitude information from astronomical interferometers often requires the ability

van Belle, Gerard

422

A novel white-light scanning interferometer for absolute nano-scale gap thickness measurement  

E-print Network

This paper presents a special configuration of white-light scanning interferometer, in which the measured gap is not located in any interference arm of the interferometer, but acts as an amplitude-and-phase modulator of ...

Xu, Zhiguang

423

Landform identification: Lunar radar images  

NASA Technical Reports Server (NTRS)

Three sets of polarized radar-echo images of the Moon were examined to establish the relation between radar resolution and landform-identification resolution. After comparison with lunar maps and photographs, real and apparent landforms on the radar images were grouped into one of seven classes. Results show strong relations between radar resolution and diameter or relief of landforms that are clearly identified and those that would probably be correctly identified (class 1 and class 2). Landforms are not detected (class 5) at all diameters and reliefs, but the percentage of undetected landforms decreases with increasing mean diameter and mean relief. Landforms are simply detected (class 4) at most mean diameters and reliefs. Ambiguous arrays (class 6) portrayed by the radar constitute up to about 16, 22, and 15% of the landforms at various diameters and relief values for the 3.8 cm, 70 cm high resolution, and 70 cm low resolution images, respectively. Only a few percent of the landforms portrayed by the radar images at various diameters and relief values are fictitious (class 7).

Moore, Henry J.; Thompson, T. W.

1987-01-01

424

Remote sensing of sea ice thickness by a combined spatial and frequency domain interferometer : formulations, instrument design & development  

NASA Technical Reports Server (NTRS)

The thickness of Arctic sea ice plays a critical role in Earth's climate and ocean circulation. An accurate measurement of this parameter on synoptic scales at regular intervals would enable characterization of this important component for the understanding of ocean circulation and the global heat balance. Presented in this paper is a low frequency VHF interferometer technique and associated radar instrument design to measure sea ice thickness based on the use of backscatter correlation functions. The sea ice medium is represented as a multi-layered medium consisting of snow, seaice and sea water, with the interfaces between layers characterized as rough surfaces. This technique utilizes the correlation of two radar waves of different frequencies and incident and observation angles, scattered from the sea ice medium. The correlation functions relate information about the sea ice thickness. Inversion techniques such as the genetic algorithm, gradient descent, and least square methods, are used to derive sea ice thickness from the phase information related by the correlation functions.

Hussein, Ziad A.; Holt, Benjamin; McDonald, Kyle C.; Jordan, Rolando; Huang, John; Kuga, Yasuo; Ishimaru, Akira; Jaruwatanadilok, Sermsak; Gogineni, Prasad; Heavey, Brandon; Akins, Torry; Perovich, Don; Sturm, Matthew

2005-01-01

425

Simultaneous measurement of temperature and pressure with cascaded extrinsic Fabry-Perot interferometer and intrinsic Fabry-Perot interferometer sensors  

NASA Astrophysics Data System (ADS)

This paper presents an approach for simultaneous measurement of temperature and pressure using miniaturized fiber inline sensors. The approach utilizes the cascaded optical fiber inline intrinsic Fabry-Perot interferometer and extrinsic Fabry-Perot interferometer as temperature and pressure sensing elements, respectively. A CO2 laser was used to create a loss between them to balance their reflection power levels. The multiplexed signals were demodulated using a Fast Fourier transform-based wavelength tracking method. Experimental results showed that the sensing system could measure temperature and pressure unambiguously in a pressure range of 0 to 6.895×105 Pa and a temperature range from 20°C to 700°C.

Zhang, Yinan; Huang, Jie; Lan, Xinwei; Yuan, Lei; Xiao, Hai

2014-06-01

426

High-sensitivity rotation sensing with atom interferometers using Aharonov-Bohm effect  

Microsoft Academic Search

In recent years there has been significant activity in research and development of high sensitivity accelerometers and gyroscopes using atom interferometers. In these devices, a fringe shift in the interference of atom de Broglie waves indicates the rotation rate of the interferometer relative to an inertial frame of reference. In both optical and atomic conventional Sagnac interferometers, the resultant phase

2006-01-01

427

Application of holographic optical elements in active interferometers for nondestructive testing  

Microsoft Academic Search

Active interferometers can continuously adapt themselves to the change of measuring conditions and environment. This type of interferometers is investigated in the article. As a major feature, the wave fronts of the interferometer are formed by different holographic optical elements. Using this technique the fringe density at highly deformed points can be decreased or different components of the complicated fringe

János Kornis; Richárd Séfel

2010-01-01

428

PLUME: A Fast, High Precision Interferometer for Trace Gas Localization  

NASA Astrophysics Data System (ADS)

PLUME is a collection of small nadir viewing Fabry-Perot interferometer-based radiometers that make simultaneous measurements of key species: carbon dioxide (CO2), methane (CH4), water vapor (H2O), formaldehyde (CH2O), and "heavy" water (HDO).

Heaps, Wm. S.; Georgieva, E. M.

2012-10-01

429

Analysis of imperfections in a micromachined tunable-cavity interferometer  

E-print Network

are presented in Fig. 1, they include diffraction grating filter, tunable cavity inter- ferometer, variable angle entail, and "linear sliding" Fabry-Perot interferometer. Diffraction grating filter induces-cavity) is the implementation of wide band tunable filter using Micro-Electro- Mechanical Systems (MEMS) technology

Tang, William C

430

Analysis of resolution criterion and aberrations for Fizeau interferometer  

Microsoft Academic Search

The quest for higher angular resolution in astronomy will inevitably require the telescope with large aperture. However, the primary mirror diameter is limited by the fabrication problems, and the cost of monolithic optics increases faster than diameter squared. The Fizeau interferometer imaging system represents a promising new technology to overcome the above-mentioned problems. The sub-apertures of the system are phased

Shengqian Wang; Changhui Rao; Wenhan Jiang

2008-01-01

431

Multicomponent wavefield characterization with a novel scanning laser interferometer  

E-print Network

noncontacting technique to transducers.1 Ultra- sonic laser interferometers and vibrometers have a broad- band a fixed optical path inside the device. The receiver uses two-wave mixing in a photorefrac- tive crystal in the photorefractive crystal to form a real-time hologram which diffracts each beam into the other direction

Boise State University

432

A Shack Interferometer Setup for Optical Testing in Undergraduate Courses  

ERIC Educational Resources Information Center

The Shack interferometer is a simple and effective device to test optical surfaces in reflection and optical systems in transmission. An essential setup on a reduced scale with a minimum number of components is presented, suited to gain familiarity and practice with optical testing in a laboratory course for undergraduate students. The basic…

Vannoni, Maurizio; Righini, Alberto; Salas, Matias; Sordini, Andrea; Vanzi, Leonardo

2012-01-01

433

A robust sinusoidal signal processing method for interferometers  

NASA Astrophysics Data System (ADS)

Laser interferometers are widely used as a reference for length measurement. Reliable bidirectional optical fringe counting is normally obtained by using two orthogonally sinusoidal signals derived from the two outputs of an interferometer with path difference. These signals are subject to be disturbed by the geometrical errors of the moving target that causes the separation and shift of two interfering light spots on the detector. It results in typical Heydemann errors, including DC drift, amplitude variation and out-of-orthogonality of two sinusoidal signals that will seriously reduce the accuracy of fringe counting. This paper presents a robust sinusoidal signal processing method to correct the distorted waveforms by hardware. A corresponding circuit board has been designed. A linear stage equipped with a laser displacement interferometer and a height gauge equipped with a linear grating interferometer are used as the test beds. Experimental results show that, even with a seriously disturbed input waveform, the output Lissajous circle can always be stabilized after signal correction. This robust method increases the stability and reliability of the sinusoidal signals for data acquisition device to deal with pulse count and phase subdivision.

Wu, Xiang-long; Zhang, Hui; Tseng, Yang-Yu; Fan, Kuang-Chao

2013-10-01

434

Sawtooth profile fringes with a two-grating interferometer  

NASA Astrophysics Data System (ADS)

The theory of fringe formation of arbitrary profile in a two-grating interferometer is developed emphasizing sawtooth profile fringes. Two methods of fringe synthesis are given: the spatially incoherent illumina tion method, leading to a coherent synthesis and the temporally incoherent (polychromatic) illumination method, leading to an incoherent synthesis.

Chen, Hsuan; Hershey, Robert R.; Leith, Emmett N.

1988-03-01

435

Fiber optic interferometer for testing conic section surfaces  

Microsoft Academic Search

A null test method for testing aspheric optical surfaces based on geometric considerations of conic sections is presented. The basic principles have been investigated experimentally by designing and building a modified Mach-Zehnder interferometer. By using optical fibers the inconvenience of alignment has partly been overcome. Phase shifting has been implemented and the measurements are performed with the help of a

Jean-Pierre Betend-Bon; Lech Wosinski; Magnus Breidne; Lennart Robertsson

1991-01-01

436

The effect of the Tides on the LIGO Interferometers  

E-print Network

We present data on the modulation of the dark port power at the free spectral range frequency of the LIGO 4 km interferometers. It is found that the power is modulated exactly at the tidal frequencies to a precision of 6e-9 Hz.

Adrian Melissinos

2010-01-04

437

A coaxial cable Fabry-Perot interferometer for sensing applications.  

PubMed

This paper reports a novel coaxial cable Fabry-Perot interferometer for sensing applications. The sensor is fabricated by drilling two holes half-way into a coaxial cable. The device physics was described. The temperature and strain responses of the sensor were tested. The measurement error was calculated and analyzed. PMID:24212121

Huang, Jie; Wang, Tao; Hua, Lei; Fan, Jun; Xiao, Hai; Luo, Ming

2013-01-01

438

POINTS: a small low-cost spaceborne astrometric optical interferometer  

Microsoft Academic Search

POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometry from space. In a five-year mission, POINTS could yield, e.g., a 1% Cepheid distance scale, galactic mass distribution, knowledge of cluster dynamics, and stellar masses and luminosities. POINTS could also perform a deep search for other planetary systems. The search would have a reliable detection threshold that would reach

R. D. Reasenberg; R. W. Babcock; M. A. Murison; M. C. Noecker; J. D. Phillips; B. L. Schumaker; J. S. Ulvestad; W. McKinley; R. J. Zielinski; C. F. Lillie

1995-01-01

439

Low-coherence interferometer using a pulsation laser diode  

NASA Astrophysics Data System (ADS)

A self-pulsation laser diode interferometer based on spectral-domain optical coherence tomography is proposed. A visible multimode laser diode allows easy optical alignment and an economical, configurable system. A cylindrical lens and acousto-optic deflector used in our system enable rapid and stable scanning. Experimental results confirm that full-field measurement is possible without mechanical scanning devices.

Suzuki, Takamasa; Ueno, Yusuke; Choi, Samuel; Sasaki, Osami

2014-05-01

440

DESIGN AND CHARACTERISATION OF MULTIPHASE LPG INTERFEROMETER USING DROPLET MICROFLUIDICS  

Microsoft Academic Search

This paper reports an integrated micro-optical fluidic system (MOFS) for the re- alization of long-period grating interferometer using droplet microfluidics. Compar- ing to normal fiber LPG, it provides a wide tuning range in the parameters of LPG, such as the grating period by changing the flow rate of the liquids and the index modulation in the core by changing the

L. K. Chin; C. S. Lim; A. Q. Liu

441

Drift correction in a multichannel integrated optical Young interferometer  

Microsoft Academic Search

We demonstrate that in a sensor based on a multichannel Young interferometer, the phase information obtained for different pairs of channels can be used to correct the long-term instability (drift) due to temperature differences between measuring and reference channels, the drift in the alignment of the setup, etc. Experiments show that the nature of a major part of the drift

Aurel Ymeti; Jan Greve; Paul V. Lambeck; Robert Wijn; Rene G. Heideman; Johannes S. Kanger

2005-01-01

442

Differential heterodyne interferometer for measuring thickness of glass panels  

Microsoft Academic Search

Differential heterodyne interferometer is applied for measuring spatial thickness variations across glass panels of liquid-crystal displays. This system uses the Zeeman laser as a source of two-frequency shifted orthogonally linearly polarized probe waves, passing through the glass in two spatially separated points. These waves are then recombined in a single beam to produce the intermediate frequency signal with the phase

Vladimir Protopopov; Sunghoon Cho; Kwangso Kim; Sukwon Lee; Hyuk Kim

2007-01-01

443

A project to construct a radio-interferometer in Argentina  

NASA Astrophysics Data System (ADS)

In this presentation we briefly describe a synthesis interferometer as a new radioastronomical facility operating in the frequency range from 500 MHz up to 7000 MHz. The scientific goals to be achieved with the construction of such an instrument and the technical characteristics needed to meet the scientific objectives are enumerated. FULL TEXT IN SPANISH

Arnal, E. M.; Benaglia, P.; Romero, G. E.; Morras, R.; Cappa, C. E.; Martín, M. C.; Testori, J. C.

444

Two-laser heterodyne metrology for a separated spacecraft interferometer  

Microsoft Academic Search

The proposed New Millennium Interferometer consists of three spacecraft separated by up to several kilometers. A heterodyne laser metrology system is proposed to measure the relative distances between the spacecraft. Because diffraction losses for a round-trip measurement are prohibitively large, a two-laser metrology system has been suggested in which each spacecraft has both a laser and a receiver. The system

Rhonda Morgan; Stuart B. Shaklan; Jeffrey W. Yu

1996-01-01

445

Elementary analysis of interferometers for wave-particle duality test  

E-print Network

Wave-particle duality and complementarity principle stand at the conceptual core of quantum theory in its orthodox Copenhagen interpretation. They imply that the wave behavior and particle behavior of quantum objects are mutually exclusive to each other in experimental observation. Here we make a systematic analysis using the elementary methodology of quantum mechanics upon Young`s two-slit interferometer and Mach-Zehnder two-arm interferometer with the focus placed on how to measure the interference pattern (wave nature) and which-way information (particle nature) of quantum objects. We design several schemes to simultaneously acquire the which-way information for an individual quantum object and the high-contrast interference pattern for an ensemble of these quantum objects by placing two sets of measurement instrument that are well separated in space and whose perturbation on each other is negligibly small within the interferometer at the same time. Yet, improper arrangement and cooperation of these two sets of measurement instrument in the interferometer would lead to failure of simultaneous observation of wave and particle behavior. The internal freedoms of quantum object could be harnessed to probe both the which-way information and interference pattern for the center-of-mass motion. That quantum objects can behave beyond the wave-particle duality and complementarity principle would stimulate new conceptual examination and exploration of quantum theory at a deeper level.

Zhi-Yuan Li

2014-09-05

446

Research on beam splitting prism in laser heterodyne interferometer  

NASA Astrophysics Data System (ADS)

With the rapid development of optical testing technology, laser heterodyne interferometer has been used more and more widely. As the testing precision requirements continue to increase, the technical prism is an important component of heterodyne interference. The research utilizing thin film technology to improve optical performance of interferometer has been a new focus. In the article, based on the use requirements of interferometer beam splitting prism, select Ta2O5 and SiO2 as high and low refractive index materials respectively, deposit on substrate K9. With the help of TFCalc design software and Needle method, adopting electron gun evaporation and ion assisted deposition, the beam splitting prism is prepared successfully and the ratio of transmittance and reflectance for this beam splitting prism in 500~850 nm band, incident angle 45 degree is 8:2. After repeated tests, solved the difference problem of film deposition process parameters ,controlled thickness monitoring precision effectively and finally prepared the ideal beam splitting prism which is high adhesion and stable optics properties. The film the laser induced damage threshold and it meet the requirements of heterodyne interferometer for use.

Fu, Xiu-hua; Xiong, Shi-fu; Kou, Yang; Pan, Yong-gang; Chen, Heng; Li, Zeng-yu; Zhang, Chuan-xin

2014-08-01

447

White-Light Nulling Interferometers for Detecting Planets  

NASA Technical Reports Server (NTRS)

A report proposes the development of a white-light nulling interferometer to be used in conjunction with a singleaperture astronomical telescope that would be operated in outer space. When such a telescope is aimed at a given star, the interferometer would suppress the light of that star while passing enough light from planets (if any) orbiting the star, to enable imaging or spectroscopic examination of the planets. In a nulling interferometer, according to the proposal, scattered light would be suppressed by spatial filtering in an array of single-mode optical fibers rather than by requiring optical surfaces to be accurate within 1/4,000 wavelength as in a coronagraph or an apodized telescope. As a result, angstrom-level precision would be needed in only the small nulling combiner, and not in large, meter-sized optics. The nulling interferometer could work as an independent instrument in space or in conjunction with a coronagraphic system to detect planets outside our solar system.

Mennesson, Bertrand; Serabyn, Eugene; Shao, Michael; Levine, Bruce

2004-01-01

448

Australian Weather Watch Radar Home Page  

NSDL National Science Digital Library

The Commonwealth Bureau of Meteorology's Weather Watch Radar website provides up-to-date radar images of the locations of rain in Australia in relation to local features such as coast lines. The newly developed Loops provide four consecutive radar images so that users can view how the weather has been changing in the last forty to fifty minutes. The website provides radar images of past cyclone events as well as updates on severe weather throughout Australia. Those interested in radar systems can discover how the weather radars work and how to interpret the maps. [RME

449

High resolution radar map of the Moon  

NASA Technical Reports Server (NTRS)

Previous radar mappings of the Moon at 70 cm wavelength in the late 1960's by Thompson have been replaced with a new set of observations using the 430 MHz radar at the Arecibo Observatory, Puerto Rico. Radar resolution was reduced to 2 to 5 km radar cell size and a beam-sweep, limb-to-limb calibration was conducted. Advances in computer technology provided the principle means of improving lunar radar mapping at this wavelength. Observation techniques and data processing are described and scattering differences found in the orthographic projection of the radar data are discussed.

Thompson, T. W.

1987-01-01

450

Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space  

NASA Technical Reports Server (NTRS)

POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; the other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging, instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the 'instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as is required when out-of-plane observations are made. An instrument for astrometry, unlike those for imaging, can be compact and yet scientifically productive. The POINTS instrument is compact and therefore requires no deployment of precision structures, has no low-frequency (i.e., under 100 Hz) vibration modes, and is relatively easy to control thermally. Because of its small size and mass, it is easily and quickly repointed between observations. Further, because of the low mass, it can be economically launched into high Earth orbit which, in conjunction with a solar shield, yields nearly unrestricted sky coverage and a stable thermal environment.

Reasenberg, Robert D.; Babcock, Robert W.; Murison, Marc A.; Noecker, M. Charles; Phillips, James D.; Schumaker, Bonny L.; Ulvestad, James S.; McKinley, William; Zielinski, Robert J.; Lillie, Charles F.

1996-01-01

451

Overview of the control system for the Keck Interferometer  

NASA Astrophysics Data System (ADS)

The Keck Interferometer links the two 10m Keck Telescopes located atop Mauna Kea in Hawaii. It is the first 10m class, fully AO equipped interferometer to enter operation. Further, it is the first large interferometer designed to be handed over from a design and implementation team to a separate operations team, and be used by astronomers who are not interferometer specialists. As such it offers unique challenges in reducing an extremely complex and powerful system to an apparently simple user interface, and providing a well engineered system that can be maintained by people who did not develop it. This paper gives an overview of the control system that has been implemented for the single baseline operation of the instrument, and indicates how this will be extended to allow control of the future modes of the instrument (nulling, differential phase and astrometry). The control system has several parts. One is for control of "slow" sub-systems, which is based in the EPICS architecture, already ubiquitous at the Keck Observatory. Another, used to control hard real time sub-systems, is based on a new infrastructure developed at JPL, programmed in C++, Java, and using CORBA for communication. This infrastructure has been developed specifically with the problems of interferometric control in mind and is used in JPL's flight testbeds as well as the Keck Interferometer. Finally, a user interface and high level control layer is in development using a variety of tools including UML based modeling in the Rhapsody tool (using C++ and CORBA), Java, and Tcl/Tk for prototyping.

Booth, Andrew J.; Eychaner, Glenn; Hovland, Erik; Johnson, Richard L., Jr.; Lupton, William; Niessner, Al; Palmer, Dean L.; Reder, Leonard J.; Rudeen, Andy C.; Smythe, Robert F.; Tsubota, Kevin

2002-12-01

452

Four beam interferometer manual: Operating instructions for the INEL diffraction Moire interferometer  

SciTech Connect

Moire interferometry is an interferometric method for measuring changes of in-plane geometry. It is essentially insensitive to out-of-plane topography or changes in that topography. Changes in geometry are referenced to a particular moment in time when the moire` sensor, a diffraction grating, was attached to the specimen. Distortions experienced by the specimen prior to that time are not directly detectable, although they may be inferred from specimen behavior or condition. In its most common form, moire interferometry is not well suited to large (> 50 mm square), curved (< 300 mm diameter) or high temperature (> 200 C) regions. However, various efforts have been made to handle each of these conditions. In general, the moire` process is most straightforward for flat, 25 mm diameter regions of coverage and room temperature. Much smaller or larger regions require more specialized optics, which can become very expensive. This report will discuss various aspects of moire interferometry. In particular, a new four beam (bi-axial) interferometer is described in detail. Issues involved in safety, assembly, calibration and use are fully explained.

Deason, V.A.

1993-11-01

453

Radar MeteorologyRadar Meteorology Feb 20, 1941 10 cm (S-band) radar used to track rain showers (Ligda)  

E-print Network

Radar MeteorologyRadar Meteorology Feb 20, 1941 10 cm (S-band) radar used to track rain showers, or wavelengths from 1 meter to 1 mm. Immediately above this portion of the spectrum is the infrared region of objects, determining their direction and range, recognizing their characteristics and employing the data

Rutledge, Steven

454

Effects of Radar Beam Shielding on Rainfall Estimation for the Polarimetric C-Band Radar  

E-print Network

-based rainfall estimates to beam shielding for C-band radar data during four typical rain events encounteredEffects of Radar Beam Shielding on Rainfall Estimation for the Polarimetric C-Band Radar KATJA. Introduction Rainfall estimation by radar is subject to smaller er- rors when measurements are made at levels

455

A 100 GHz Polarimetric Compact Radar Range for Scale-Model Radar Cross Section Measurements  

E-print Network

William E. Nixon U.S. Army National Ground Intelligence Center Charlottesville, VA 22902 l Abstract for obtaining radar cross section, inverse synthetic aperture radar imagery and high range resolution profiles. Keywords: Compact Radar Range, Doppler, Imagery, Instrumentation, ISAR, Millimeter-Wave, Radar, RCS

Massachusetts at Lowell, University of

456

Radar absorbing material (RAM) and shaping on radar cross section reduction of dihedral corners  

Microsoft Academic Search

How far can a radar system detect an object depends the radar cross section (RCS) of the target. Corner reflectors are the major scattering centers in the radar signatures of vehicles. The monostatic return from such structures can be reduced by ensuring that surfaces never meet at right angles and by application of radar absorbing materials (RAM). This paper deals

G. G. Peixoto; A. L. de Paula; L. A. Andrade; C. M. A. Lopes; M. C. Rezende

2005-01-01

457

MIMO Radar Waveform Constraints for GMTI  

E-print Network

Ground moving-target indication (GMTI) provides both an opportunity and challenge for coherent multiple-input multiple-output (MIMO) radar. MIMO techniques can improve a radar's angle estimation and the minimum detectable ...

Forsythe, Keith W.

458

A Through-Dielectric Radar Imaging System  

E-print Network

Through-lossy-slab radar imaging will be shown at stand-off ranges using a low-power, ultrawideband (UWB), frequency modulated continuous wave (FMCW) radar system. FMCW is desirable for through-slab applications because ...

Charvat, Gregory L.

459

Radar Mosaic of Africa  

NASA Technical Reports Server (NTRS)

This is an image of equatorial Africa, centered on the equator at longitude 15degrees east. This image is a mosaic of almost 4,000 separate images obtained in 1996 by the L-band imaging radar onboard the Japanese Earth Resources Satellite. Using radar to penetrate the persistent clouds prevalent in tropical forests, the Japanese Earth Resources Satellite was able for the first time to image at high resolution this continental scale region during single flooding seasons. The area shown covers about 7.4 million square kilometers (2.8 million square miles) of land surface, spans more than 5,000 kilometers(3,100 miles) east and west and some 2,000 kilometers (1,240 miles) north and south. North is up in this image. At the full resolution of the mosaic (100 meters or 330 feet), this image is more than 500 megabytes in size, and was processed from imagery totaling more than 60 gigabytes.

Central Africa was imaged twice in 1996, once between January and March, which is the major low-flood season in the Congo Basin, and once between October and November, which is the major high-flood season in the Congo Basin. The red color corresponds to the data from the low-flood season, the green to the high-flood season, and the blue to the 'texture' of the low-flood data. The forests appear green as a result, the flooded and palm forests, as well as urban areas, appear yellow, the ocean and lakes appear black, and savanna areas appear blue, black or green, depending on the savanna type, surface topography and other factors. The areas of the image that are black and white were mapped only between January and March 1996. In these areas, the black areas are savanna or open water, the gray are forests, and the white areas are flooded forests or urban areas. The Congo River dominates the middle of the image, where the nearby forests that are periodically flooded by the Congo and its tributaries stand out as yellow. The Nile River flows north from Lake Victoria in the middle right of the color portion of the mosaic.

This image is one of the products resulting from the Global Rain Forest Mapping project, a joint project between the National Space Development Agency of Japan, the Space Applications Institute of the Joint Research Centre of the European Commission, NASA's Jet Propulsion Laboratory and an international team of scientists. The goal of the Global Rain Forest Mapping mission is to map with the Japanese Earth Resources Satellite the world's tropical rain forests. The Japanese satellite was launched in 1992 by the National Space Development Agency of Japan and the Japanese Ministry of International Trade and Industry, with support from the Remote Sensing Technology Center of Japan.

1999-01-01

460

Bird-aircraft strike avoidance radar  

Microsoft Academic Search

Avian radar system has been developed for bird-aircraft strike hazard avoidance. Two representative systems, which are countrywide and airport-based avian radar systems, are surveyed to summarize the state-of-the-art in this research field. Avian radar experimental system built by Beihang University is introduced in detail, including system architecture, performance analysis, and processing algorithm for bird target detection and tracking. This radar

Ning Huansheng; Chen Weishi; Mao Xia; Li Jing

2010-01-01