Erbium-doped fiber ring laser with SMS modal interferometer for hydrogen sensing

NASA Astrophysics Data System (ADS)

Zhang, Ya-nan; Zhang, Lebin; Han, Bo; Peng, Huijie; Zhou, Tianmin; Lv, Ri-qing

2018-06-01

A hydrogen sensor based on erbium-doped fiber ring laser with modal interferometer is proposed. A single mode-multimode-single mode (SMS) modal interferometer structure coated with Pd/WO3 film is used as the sensing head, due to that it is easy to be fabricated and low cost. The sensing structure is inserted into an erbium-doped fiber ring laser in order to solve the problem of spectral confusion and improve the detection limit of the hydrogen sensor based on the SMS modal interferometer. The SMS sensing structure is acted as a fiber band-pass filter. When hydrogen concentration around the sensor is changed, it will induce the refractive index and strain variations of the Pd/WO3 film, and then shift the resonant spectrum of the SMS modal interferometer as well as the laser wavelength of the fiber ring laser. Therefore, the hydrogen concentration can be measured by monitoring the wavelength shift of the laser, which has high intensity and narrow full width half maximum. Experimental results demonstrate that the sensor has high sensitivity of 1.23 nm/%, low detection limit of 0.017%, good stability and excellent repeatability.

Solid-state radar switchboard

NASA Astrophysics Data System (ADS)

Thiebaud, P.; Cross, D. C.

1980-07-01

A new solid-state radar switchboard equipped with 16 input ports which will output data to 16 displays is presented. Each of the ports will handle a single two-dimensional radar input, or three ports will accommodate a three-dimensional radar input. A video switch card of the switchboard is used to switch all signals, with the exception of the IFF-mode-control lines. Each card accepts inputs from up to 16 sources and can pass a signal with bandwidth greater than 20 MHz to the display assigned to that card. The synchro amplifier of current systems has been eliminated and in the new design each PPI receives radar data via a single coaxial cable. This significant reduction in cabling is achieved by adding a serial-to-parallel interface and a digital-to-synchro converter located at the PPI.

Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets

NASA Technical Reports Server (NTRS)

Moller, Delwyn K.; Sadowy, Gregory A.; Rignot, Eric J.; Madsen, Soren N.

2007-01-01

A report discusses Ka-band (35-GHz) radar for mapping the surface topography of glaciers and ice sheets at high spatial resolution and high vertical accuracy, independent of cloud cover, with a swath-width of 70 km. The system is a single- pass, single-platform interferometric synthetic aperture radar (InSAR) with an 8-mm wavelength, which minimizes snow penetration while remaining relatively impervious to atmospheric attenuation. As exhibited by the lower frequency SRTM (Shuttle Radar Topography Mission) AirSAR and GeoSAR systems, an InSAR measures topography using two antennas separated by a baseline in the cross-track direction, to view the same region on the ground. The interferometric combination of data received allows the system to resolve the pathlength difference from the illuminated area to the antennas to a fraction of a wavelength. From the interferometric phase, the height of the target area can be estimated. This means an InSAR system is capable of providing not only the position of each image point in along-track and slant range as with a traditional SAR but also the height of that point through interferometry. Although the evolution of InSAR to a millimeter-wave center frequency maximizes the interferometric accuracy from a given baseline length, the high frequency also creates a fundamental problem of swath coverage versus signal-to-noise ratio. While the length of SAR antennas is typically fixed by mass and stowage or deployment constraints, the width is constrained by the desired illuminated swath width. As the across-track beam width which sets the swath size is proportional to the wavelength, a fixed swath size equates to a smaller antenna as the frequency is increased. This loss of antenna size reduces the two-way antenna gain to the second power, drastically reducing the signal-to-noise ratio of the SAR system. This fundamental constraint of high-frequency SAR systems is addressed by applying digital beam-forming (DBF) techniques to synthesize multiple simultaneous receive beams in elevation while maintaining a broad transmit illumination. Through this technique, a high antenna gain on receive is preserved, thereby reducing the required transmit power and thus enabling high-frequency SARs and high-precision InSAR from a single spacecraft.

Dual surface interferometer

DOEpatents

Pardue, R.M.; Williams, R.R.

1980-09-12

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 quarterwave 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.

Dual surface interferometer

DOEpatents

Pardue, Robert M.; Williams, Richard R.

1982-01-01

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.

Multi-Point Interferometric Rayleigh Scattering using Dual-Pass Light Recirculation

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Danehy, Paul M.; Cutler, Andrew D.

2008-01-01

This paper describes for the first time an interferometric Rayleigh scattering system using dual-pass light recirculation (IRS-LR) capable of simultaneously measuring at multiple points two orthogonal components of flow velocity in combustion flows using single shot laser probing. An additional optical path containing the interferometer input mirror, a quarter-wave plate, a polarization dependent beam combiner, and a high reflectivity mirror partially recirculates the light that is rejected by the interferometer. Temporally- and spatially-resolved acquisitions of Rayleigh spectra in a large-scale combustion-heated supersonic axi-symmetric jet were performed to demonstrate the technique. Recirculating of Rayleigh scattered light increases the number of photons analyzed by the system up to a factor of 1.8 compared with previous configurations. This is equivalent to performing measurements with less laser energy or performing measurements with the previous system in gas flows at higher temperatures.

Forest Structure Retrieval From EcoSAR P-Band Single-Pass Interferometry

NASA Technical Reports Server (NTRS)

Osmanoglu, Batuhan; Rincon, Rafael; Lee, Seung Kuk; Fatoyinbo, Temilola; Bollian, Tobias

2017-01-01

EcoSAR is a single-pass (dual antenna) digital beamforming, P-band radar system that is designed for remote sensing of dense forest structure. Forest structure retrievals require the measurement related to the vertical dimension, for which several techniques have been developed over the years. These techniques use polarimetric and interferometric aspects of the SAR data, which can be collected using EcoSAR. In this paper we describe EcoSAR system in light of its interferometric capabilities and investigate forest structure retrieval techniques.

Miniaturized Ka-Band Dual-Channel Radar

NASA Technical Reports Server (NTRS)

Hoffman, James P.; Moussessian, Alina; Jenabi, Masud; Custodero, Brian

2011-01-01

Smaller (volume, mass, power) electronics for a Ka-band (36 GHz) radar interferometer were required. To reduce size and achieve better control over RFphase versus temperature, fully hybrid electronics were developed for the RF portion of the radar s two-channel receiver and single-channel transmitter. In this context, fully hybrid means that every active RF device was an open die, and all passives were directly attached to the subcarrier. Attachments were made using wire and ribbon bonding. In this way, every component, even small passives, was selected for the fabrication of the two radar receivers, and the devices were mounted relative to each other in order to make complementary components isothermal and to isolate other components from potential temperature gradients. This is critical for developing receivers that can track each other s phase over temperature, which is a key mission driver for obtaining ocean surface height. Fully hybrid, Ka-band (36 GHz) radar transmitter and dual-channel receiver were developed for spaceborne radar interferometry. The fully hybrid fabrication enables control over every aspect of the component selection, placement, and connection. Since the two receiver channels must track each other to better than 100 millidegrees of RF phase over several minutes, the hardware in the two receivers must be "identical," routed the same (same line lengths), and as isothermal as possible. This level of design freedom is not possible with packaged components, which include many internal passive, unknown internal connection lengths/types, and often a single orientation of inputs and outputs.

High-resolution digital elevation models from single-pass TanDEM-X interferometry over mountainous regions: A case study of Inylchek Glacier, Central Asia

NASA Astrophysics Data System (ADS)

Neelmeijer, Julia; Motagh, Mahdi; Bookhagen, Bodo

2017-08-01

This study demonstrates the potential of using single-pass TanDEM-X (TDX) radar imagery to analyse inter- and intra-annual glacier changes in mountainous terrain. Based on SAR images acquired in February 2012, March 2013 and November 2013 over the Inylchek Glacier, Kyrgyzstan, we discuss in detail the processing steps required to generate three reliable digital elevation models (DEMs) with a spatial resolution of 10 m that can be used for glacial mass balance studies. We describe the interferometric processing steps and the influence of a priori elevation information that is required to model long-wavelength topographic effects. We also focus on DEM alignment to allow optimal DEM comparisons and on the effects of radar signal penetration on ice and snow surface elevations. We finally compare glacier elevation changes between the three TDX DEMs and the C-band shuttle radar topography mission (SRTM) DEM from February 2000. We introduce a new approach for glacier elevation change calculations that depends on the elevation and slope of the terrain. We highlight the superior quality of the TDX DEMs compared to the SRTM DEM, describe remaining DEM uncertainties and discuss the limitations that arise due to the side-looking nature of the radar sensor.

Orbit Determination of LEO Satellites for a Single Pass through a Radar: Comparison of Methods

NASA Technical Reports Server (NTRS)

Khutorovsky, Z.; Kamensky, S.; Sbytov, N.; Alfriend, K. T.

2007-01-01

The problem of determining the orbit of a space object from measurements based on one pass through the field of view of a radar is not a new one. Extensive research in this area has been carried out in the USA and Russia since the late 50s when these countries started the development of ballistic missile defense (BMD) and Early Warning systems. In Russia these investigations got additional stimulation in the early 60s after the decision to create a Space Surveillance System, whose primary task would be the maintenance of the satellite catalog. These problems were the focus of research interest until the middle 70s when the appropriate techniques and software were implemented for all radars. Then for more than 20 years no new research papers appeared on this subject. This produced an impression that all the problems of track determination based on one pass had been solved and there was no need for further research. In the late 90s interest in this problem arose again in relation to the following. It was estimated that there would be greater than 100,000 objects with size greater than 1-2 cm and collision of an operational spacecraft with any of these objects could have catastrophic results. Thus, for prevention of hazardous approaches and collisions with valuable spacecraft the existing satellite catalog should be extended by at least an order of magnitude This is a very difficult scientific and engineering task. One of the issues is the development of data fusion procedures and the software capable of maintaining such a huge catalog in near real time. The number of daily processed measurements (of all types, radar and optical) for such a system may constitute millions, thus increasing the number of measurements by at least an order of magnitude. Since we will have ten times more satellites and measurements the computer effort required for the correlation of measurements will be two orders of magnitude greater. This could create significant problems for processing data close to real time even for modern computers. Preliminary "compression" of data for one pass through the field of view of a sensor can significantly reduce the requirements to computers and data communication. This compression will occur when all the single measurements of the sensor are replaced by the orbit determined on their basis. The single measurement here means the radar parameters (range, azimuth, elevation, and in some cases range rate) measured by a single pulse.

Auroral-Region Dynamics Determined with the Chatanika Radar.

DTIC Science & Technology

1982-11-01

report) 17. DISTRIBUTION STATEMENT (of the abstract entered In Block 20, If different from report) 18 . SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on...for 1 April 1973 .......... ... 41 18 Vertical Neutral Wind Measured with the Fabry-Perot Interferometer ......... ........................ ... 44 vii...Waves Determined from Radar Observations on 18 January 1976 ..... ............... ... 50 23 Meridional Wind and Gravity Waves Determined from Radar

Fourier-transform optical microsystems

NASA Technical Reports Server (NTRS)

Collins, S. D.; Smith, R. L.; Gonzalez, C.; Stewart, K. P.; Hagopian, J. G.; Sirota, J. M.

1999-01-01

The design, fabrication, and initial characterization of a miniature single-pass Fourier-transform spectrometer (FTS) that has an optical bench that measures 1 cm x 5 cm x 10 cm is presented. The FTS is predicated on the classic Michelson interferometer design with a moving mirror. Precision translation of the mirror is accomplished by microfabrication of dovetailed bearing surfaces along single-crystal planes in silicon. Although it is miniaturized, the FTS maintains a relatively high spectral resolution, 0.1 cm-1, with adequate optical throughput.

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

NASA Technical Reports Server (NTRS)

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

2011-01-01

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.

Tribute to Jean-Marie Mariotti

NASA Astrophysics Data System (ADS)

Lena, Pierre J.

2003-02-01

Jean-Marie Mariotti (1955 - 1998) prematurely passed away after too short a career of optician and astronomer. With his students, his contributions to the nascent field of high angular resolution at optical wavelengths, and especially to interferometry, both on the ground and in space, have been remarkable. Pioneering the use of single-mode optical fibers and integrated optics, he pushed the accuracy of visibility (amplitude) measurements to a fraction of a percent. His vision of a Mauna Kea kilometric interferometer using the existing giant telescopes is now becoming a reality with the 'OHANA project. His role in the emergence of the Very Large Telescope Interferometer (VLTI) and in the birth of the space mission DARWIN for exoplanets studies has been essential.

A chevron beam-splitter interferometer

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.

1979-01-01

Fully tilt compensated double-pass chevron beam splitter, that removes channelling effects and permits optical phase tuning, is wavelength independent and allows small errors in alignment that are not tolerated in Michelson, Machzender, or Sagnac interferometers. Device is very useful in experiments where background vibration affects conventional interferometers.

Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Meng, Yichang; Zhang, Shumin; Wang, Xinzhan; Du, Juan; Li, Hongfei; Hao, Yanping; Li, Xingliang

2012-03-01

We have demonstrated an adjustable double-clad Yb 3+-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.

Height Error Correction for the New SRTM Elevation Product

NASA Technical Reports Server (NTRS)

Neumann, Maxim; Simard, Marc; Buckley, Sean; Shimada, Joanne; Gurrola, Eric; Martin, Jan; Hensley, Scott; Rosen, Paul

2013-01-01

The Shuttle Radar Topography Mission (SRTM), carrying a single-pass interferometric synthetic aperture radar(SAR) instrument, collected a global elevation data set, which has been widely used in scientific, military and commercial communities. In the new proposed NASA SRTM reprocessing task, the SRTM elevation data is going to be processed at higher spatial resolution and with improved height accuracy. Upon completion, the improved SRTM product will be freely available. This paper describes the calibration approaches for reduction of elevation ripple effects and height accuracy improvements.

Error Analysis for High Resolution Topography with Bi-Static Single-Pass SAR Interferometry

NASA Technical Reports Server (NTRS)

Muellerschoen, Ronald J.; Chen, Curtis W.; Hensley, Scott; Rodriguez, Ernesto

2006-01-01

We present a flow down error analysis from the radar system to topographic height errors for bi-static single pass SAR interferometry for a satellite tandem pair. Because of orbital dynamics the baseline length and baseline orientation evolve spatially and temporally, the height accuracy of the system is modeled as a function of the spacecraft position and ground location. Vector sensitivity equations of height and the planar error components due to metrology, media effects, and radar system errors are derived and evaluated globally for a baseline mission. Included in the model are terrain effects that contribute to layover and shadow and slope effects on height errors. The analysis also accounts for nonoverlapping spectra and the non-overlapping bandwidth due to differences between the two platforms' viewing geometries. The model is applied to a 514 km altitude 97.4 degree inclination tandem satellite mission with a 300 m baseline separation and X-band SAR. Results from our model indicate that global DTED level 3 can be achieved.

Improved double-pass michelson interferometer

NASA Technical Reports Server (NTRS)

Schindler, R. A.

1978-01-01

Interferometer design separates beams by offsetting centerlines of cat's-eye retroreflectors vertically rather than horizontally. Since beam splitter is insensitive to minimum-thickness condition in this geometry, relatively-low-cost, optically flat plate can be used.

High-resolution coherent backscatter interferometric radar images of equatorial spread F using Capon's method

NASA Astrophysics Data System (ADS)

Rodrigues, Fabiano S.; de Paula, Eurico R.; Zewdie, Gebreab K.

2017-03-01

We present results of Capon's method for estimation of in-beam images of ionospheric scattering structures observed by a small, low-power coherent backscatter interferometer. The radar interferometer operated in the equatorial site of São Luís, Brazil (2.59° S, 44.21° W, -2.35° dip latitude). We show numerical simulations that evaluate the performance of the Capon method for typical F region measurement conditions. Numerical simulations show that, despite the short baselines of the São Luís radar, the Capon technique is capable of distinguishing localized features with kilometric scale sizes (in the zonal direction) at F region heights. Following the simulations, we applied the Capon algorithm to actual measurements made by the São Luís interferometer during a typical equatorial spread F (ESF) event. As indicated by the simulations, the Capon method produced images that were better resolved than those produced by the Fourier method. The Capon images show narrow (a few kilometers wide) scattering channels associated with ESF plumes and scattering regions spaced by only a few tens of kilometers in the zonal direction. The images are also capable of resolving bifurcations and the C shape of scattering structures.

Single-pass Airborne InSAR for Wide-swath, High-Resolution Cryospheric Surface Topography Mapping

NASA Astrophysics Data System (ADS)

Moller, D.; Hensley, S.; Wu, X.; Muellerschoen, R.

2014-12-01

In May 2009 a mm-wave single-pass interferometric synthetic aperture radar (InSAR) for the first time demonstrated ice surface topography swath-mapping in Greenland. This was achieved with the airborne Glacier and Ice Surface Topography Interferometer (GLISTIN-A). Ka-band (35.6GHz) was chosen for high-precision topographic mapping from a compact sensor with minimal surface penetration. In recent years, the system was comprehensively upgraded for improved performance, stability and calibration. In April 2013, after completing the upgrades, GLISTIN-A flew a brief campaign to Alaska. The primary purpose was to demonstrate the InSAR's ability to generate high-precision, high resolution maps of ice surface topography with swaths in excess of 10km. Comparison of GLISTIN-A's elevations over glacial ice with lidar verified the precision requirements and established elevation accuracies to within 2 m without tie points. Feature tracking of crevasses on Columbia Glacier using data acquired with a 3-day separation exhibit an impressive velocity mapping capability. Furthermore, GLISTIN-A flew over the Beaufort sea to determine if we could not only map sea ice, but also measure freeboard. Initial analysis has established we can measure sea-ice freeboard using height differences from the top of the sea-ice and the sea surface in open leads. In the future, a campaign with lidar is desired for a quantitative validation. Another proof-of-concept collection mapped snow-basins for hydrology. Snow depth measurements using summer and winter collections in the Sierras were compared with lidar measurements. Unsurprisingly when present, trees complicate the interpretation, but additional filtering and processing is in work. For each application, knowledge of the interferometric penetration is important for scientific interpretation. We present analytical predictions and experimental data to upper bound the elevation bias of the InSAR measurements over snow and snow-covered ice.

Testing quantum mechanics against macroscopic realism using the output of {chi}{sup (2)} nonlinearity

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

Podoshvedov, Sergey A.; Kim, Jaewan

2006-09-15

We suggest an all-optical scheme to generate entangled superposition of a single photon with macroscopic entangled states for testing macroscopic realism. The scheme consists of source of single photons, a Mach-Zehnder interferometer in routes of which a system of coupled-down converters with type-I phase matching is inserted, and a beam splitter for the other auxiliary modes of the scheme. We use quantization of the pumping modes, depletion of the coherent states passing through the system, and interference effect in the pumping modes in the process of erasing which-path information of the single-photon on exit from the Mach-Zehnder interferometer. We showmore » the macroscopic fields of the output superposition are distinguishable states. This scheme generates macroscopic entangled state that violates Bell's inequality. Moreover, the detailed analysis concerning change of amplitudes of entangled superposition by means of repeating this process many times is accomplished. We show our scheme works without photon number resolving detection and it is robust to detector inefficiency.« less

Geocoding of AIRSAR/TOPSAR SAR Data

NASA Technical Reports Server (NTRS)

Holecz, Francesco; Lou, Yun-Ling; vanZyl, Jakob

1996-01-01

It has been demonstrated and recognized that radar interferometry is a promising method for the determination of digital elevation information and terrain slope from Synthetic Aperture Radar (SAR) data. An important application of Interferometric SAR (InSAR) data in areas with topographic variations is that the derived elevation and slope can be directly used for the absolute radiometric calibration of the amplitude SAR data as well as for scattering mechanisms analysis. On the other hand polarimetric SAR data has long been recognized as permitting a more complete inference of natural surfaces than a single channel radar system. In fact, imaging polarimetry provides the measurement of the amplitude and relative phase of all transmit and receive polarizations. On board the NASA DC-8 aircraft, NASA/JPL operates the multifrequency (P, L and C bands) multipolarimetric radar AIRSAR. The TOPSAR, a special mode of the AIRSAR system, is able to collect single-pass interferometric C- and/or L-band VV polarized data. A possible configuration of the AIRSAR/TOPSAR system is to acquire single-pass interferometric data at C-band VV polarization and polarimetric radar data at the two other lower frequencies. The advantage of this system configuration is to get digital topography information at the same time the radar data is collected. The digital elevation information can therefore be used to correctly calibrate the SAR data. This step is directly included in the new AIRSAR Integrated Processor. This processor uses a modification of the full motion compensation algorithm described by Madsen et al. (1993). However, the Digital Elevation Model (DEM) with the additional products such as local incidence angle map, and the SAR data are in a geometry which is not convenient, since especially DEMs must be referred to a specific cartographic reference system. Furthermore, geocoding of SAR data is important for multisensor and/or multitemporal purposes. In this paper, a procedure to geocode the new AIRSAR/TOPSAR data is presented. As an example an AIRSAR/TOPSAR image acquired in 1994 is geocoded and evaluated in terms of geometric accuracy.

Automated absolute phase retrieval in across-track interferometry

NASA Technical Reports Server (NTRS)

Madsen, Soren N.; Zebker, Howard A.

1992-01-01

Discussed is a key element in the processing of topographic radar maps acquired by the NASA/JPL airborne synthetic aperture radar configured as an across-track interferometer (TOPSAR). TOPSAR utilizes a single transmit and two receive antennas; the three-dimensional target location is determined by triangulation based on a known baseline and two measured slant ranges. The slant range difference is determined very accurately from the phase difference between the signals received by the two antennas. This phase is measured modulo 2pi, whereas it is the absolute phase which relates directly to the difference in slant range. It is shown that splitting the range bandwidth into two subbands in the processor and processing each individually allows for the absolute phase. The underlying principles and system errors which must be considered are discussed, together with the implementation and results from processing data acquired during the summer of 1991.

The CryoSat Interferometer after 6 years in orbit: calibration and achievable performance

NASA Astrophysics Data System (ADS)

Scagliola, Michele; Fornari, Marco; De Bartolomei, Maurizio; Bouffard, Jerome; Parrinello, Tommaso

2016-04-01

The main payload of CryoSat is a Ku-band pulse width limited radar altimeter, called SIRAL (Synthetic interferometric radar altimeter). When commanded in SARIn (synthetic aperture radar interferometry) mode, through coherent along-track processing of the returns received from two antennas, the interferometric phase related to the first arrival of the echo is used to retrieve the angle of arrival of the scattering in the across-track direction. In fact, the across-track echo direction can be derived by exploiting the precise knowledge of the baseline vector (i.e. the vector between the two antennas centers of phase) and simple geometry. The end-to-end calibration strategy for the CryoSat interferometer consists on in-orbit calibration campaigns following the approach described in [1]. From the beginning of the CryoSat mission, about once a year the interferometer calibration campaigns have been periodically performed by rolling left and right the spacecraft of about ±0.4 deg. This abstract is aimed at presenting our analysis of the calibration parameters and of the achievable performance of the CryoSat interferometer over the 6 years of mission. Additionally, some further studies have been performed to assess the accuracy of the roll angle computed on ground as function of the aberration (the apparent displacement of a celestial object from its true position, caused by the relative motion of the observer and the object) correction applied to the attitude quaternions, provided by the Star Tracker mounted on-board. In fact, being the roll information crucial to obtain an accurate estimate of the angle of arrival, the data from interferometer calibration campaigns have been used to verify how the application of the aberration correction affects the roll information and, in turns, the measured angle of arrival. [1] Galin, N.; Wingham, D.J.; Cullen, R.; Fornari, M.; Smith, W.H.F.; Abdalla, S., "Calibration of the CryoSat-2 Interferometer and Measurement of Across-Track Ocean Slope," in Geoscience and Remote Sensing, IEEE Transactions on , vol.51, no.1, pp.57-72, Jan. 2013

Observation of quasiperiodic dynamics in a one-dimensional quantum walk of single photons in space

NASA Astrophysics Data System (ADS)

Xue, Peng; Qin, Hao; Tang, Bao; Sanders, Barry C.

2014-05-01

We realize the quasi-periodic dynamics of a quantum walker over 2.5 quasi-periods by realizing the walker as a single photon passing through a quantum-walk optical-interferometer network. We introduce fully controllable polarization-independent phase shifters in each optical path to realize arbitrary site-dependent phase shifts, and employ large clear-aperture beam displacers, while maintaining high-visibility interference, to enable 10 quantum-walk steps to be reached. By varying the half-wave-plate setting, we control the quantum-coin bias thereby observing a transition from quasi-periodic dynamics to ballistic diffusion.

Phase-sensitive two-dimensional neutron shearing interferometer and Hartmann sensor

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

Baker, Kevin

2015-12-08

A neutron imaging system detects both the phase shift and absorption of neutrons passing through an object. The neutron imaging system is based on either of two different neutron wavefront sensor techniques: 2-D shearing interferometry and Hartmann wavefront sensing. Both approaches measure an entire two-dimensional neutron complex field, including its amplitude and phase. Each measures the full-field, two-dimensional phase gradients and, concomitantly, the two-dimensional amplitude mapping, requiring only a single measurement.

Ka-Band ARM Zenith Radar Corrections Value-Added Product

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

Johnson, Karen; Toto, Tami; Giangrande, Scott

The KAZRCOR Value -added Product (VAP) performs several corrections to the ingested KAZR moments and also creates a significant detection mask for each radar mode. The VAP computes gaseous attenuation as a function of time and radial distance from the radar antenna, based on ambient meteorological observations, and corrects observed reflectivities for that effect. KAZRCOR also dealiases mean Doppler velocities to correct velocities whose magnitudes exceed the radar’s Nyquist velocity. Input KAZR data fields are passed through into the KAZRCOR output files, in their native time and range coordinates. Complementary corrected reflectivity and velocity fields are provided, along with amore » mask of significant detections and a number of data quality flags. This report covers the KAZRCOR VAP as applied to the original KAZR radars and the upgraded KAZR2 radars. Currently there are two separate code bases for the different radar versions, but once KAZR and KAZR2 data formats are harmonized, only a single code base will be required.« less

Program Analyzes Radar Altimeter Data

NASA Technical Reports Server (NTRS)

Vandemark, Doug; Hancock, David; Tran, Ngan

2004-01-01

A computer program has been written to perform several analyses of radar altimeter data. The program was designed to improve on previous methods of analysis of altimeter engineering data by (1) facilitating and accelerating the analysis of large amounts of data in a more direct manner and (2) improving the ability to estimate performance of radar-altimeter instrumentation and provide data corrections. The data in question are openly available to the international scientific community and can be downloaded from anonymous file-transfer- protocol (FTP) locations that are accessible via links from altimetry Web sites. The software estimates noise in range measurements, estimates corrections for electromagnetic bias, and performs statistical analyses on various parameters for comparison of different altimeters. Whereas prior techniques used to perform similar analyses of altimeter range noise require comparison of data from repetitions of satellite ground tracks, the present software uses a high-pass filtering technique to obtain similar results from single satellite passes. Elimination of the requirement for repeat-track analysis facilitates the analysis of large amounts of satellite data to assess subtle variations in range noise.

Holography with a neutron interferometer

NASA Astrophysics Data System (ADS)

Sarenac, Dusan; Cory, David G.; Pushin, Dmitry A.; Heacock, Benjamin; Huber, Michael G.; Arif, M.; Clark, Charles W.; Shahi, Chandra B.; Cfref Collaboration

2017-01-01

We demonstrate the first neutron hologram of a macroscopic object. Using a Mach-Zehnder neutron interferometer in a configuration similar to the optical setup of Bazhenov et al., our reference beam passes through a fused silica prism that provides a linear phase gradient, and our object beam beam passes through an aluminum spiral phase plate with a topological charge of l = 2 , which was recently used in studies of neutron orbital angular momentum. Interference of reference and object beams in a two-dimensional imaging detector produces the hologram, which is a fork dislocation structure similar to those used to generate atomic and electronic vortex beams. Our neutron hologram is made in an interferometer in which at most one neutron is present at any given time.

Measuring ocean coherence time with dual-baseline interferometry

NASA Technical Reports Server (NTRS)

Carande, Richard E.

1992-01-01

Using the Jet Propulsion Laboratory (JPL) Airborne Synthetic Aperture Radar (AIRSAR) interferometer, measurements of the ocean coherence time at L and C band can be made at high spatial resolution. Fundamental to this measurement is the ability to image the ocean interferometrically at two different time-lags, or baselines. By modifying the operating procedure of the existing two antenna interferometer, a technique was developed make these measurements. L band coherence times are measured and presented.

Laser System for Precise, Unambiguous Range Measurements

NASA Technical Reports Server (NTRS)

Dubovitsky, Serge; Lay, Oliver

2005-01-01

The Modulation Sideband Technology for Absolute Range (MSTAR) architecture is the basis of design of a proposed laser-based heterodyne interferometer that could measure a range (distance) as great as 100 km with a precision and resolution of the order of 1 nm. Simple optical interferometers can measure changes in range with nanometer resolution, but cannot measure range itself because interference is subject to the well-known integer-multiple-of-2 -radians phase ambiguity, which amounts to a range ambiguity of the order of 1 m at typical laser wavelengths. Existing rangefinders have a resolution of the order of 10 m and are therefore unable to resolve the ambiguity. The proposed MSTAR architecture bridges the gap, enabling nanometer resolution with an ambiguity range that can be extended to arbitrarily large distances. The MSTAR architecture combines the principle of the heterodyne interferometer with the principle of extending the ambiguity range of an interferometer by using light of two wavelengths. The use of two wavelengths for this purpose is well established in optical metrology, radar, and sonar. However, unlike in traditional two-color laser interferometry, light of two wavelengths would not be generated by two lasers. Instead, multiple wavelengths would be generated as sidebands of phase modulation of the light from a single frequency- stabilized laser. The phase modulation would be effected by applying sinusoidal signals of suitable frequencies (typically tens of gigahertz) to high-speed electro-optical phase modulators. Intensity modulation can also be used

Demonstration of the feasibility of large-port-count optical switching using a hybrid Mach-Zehnder interferometer-semiconductor optical amplifier switch module in a recirculating loop.

PubMed

Cheng, Q; Wonfor, A; Wei, J L; Penty, R V; White, I H

2014-09-15

For what we believe is the first time, the feasibility of large-port-count nanosecond-reconfiguration-time optical switches is demonstrated using a hybrid approach, where Mach-Zehnder interferometric (MZI) switches provide low-loss, high-speed routing with short semiconductor optical amplifiers (SOAs) being integrated to enhance extinction. By repeatedly passing signals through a monolithic hybrid dilated 2×2 switch module in a recirculating loop, the potential performance of high-port-count switches using the hybrid approach is demonstrated. Experimentally, a single pass switch penalty of only 0.1 dB is demonstrated for the 2×2 module, while even after seven passes through the switch, equivalent to a 128×128 router, a penalty of only 2.4 dB is recorded at a data rate of 10 Gb/s.

Over-under double-pass interferometer

NASA Technical Reports Server (NTRS)

Schindler, R. A. (Inventor)

1977-01-01

An over-under double pass interferometer in which the beamsplitter area and thickness can be reduced to conform only with optical flatness considerations was achieved by offsetting the optical center line of one cat's-eye retroreflector relative to the optical center line of the other in order that one split beam be folded into a plane distinct from the other folded split beam. The beamsplitter is made transparent in one area for a first folded beam to be passed to a mirror for doubling back and is made totally reflective in another area for the second folded beam to be reflected to a mirror for doubling back. The two beams thus doubled back are combined in the central, beamsplitting area of the beamsplitting and passed to a detector. This makes the beamsplitter insensitive to minimum thickness requirements and selection of material.

Over-under double-pass interferometer

NASA Technical Reports Server (NTRS)

Schindler, Rudolf A. (Inventor)

1980-01-01

An over-under double-pass interferometer in which the beamsplitter area and thickness can be reduced to conform only with optical flatness considerations is achieved by offsetting the optical center line of one cat's-eye retroreflector relative to the optical center line of the other in order that one split beam be folded into a plane distinct from the other folded split beam. The beamsplitter is made transparent in one area for a first folded beam to be passed to a mirror for doubling back and is made totally reflective in another area for the second folded beam to be reflected to a mirror for doubling back. The two beams thus doubled back are combined in the central, beam-splitting area of the beamsplitter and passed to a detector. This makes the beamsplitter insensitive to minimum-thickness requirements and selection of material.

Two antenna, two pass interferometric synthetic aperture radar

DOEpatents

Martinez, Ana; Doerry, Armin W.; Bickel, Douglas L.

2005-06-28

A multi-antenna, multi-pass IFSAR mode utilizing data driven alignment of multiple independent passes can combine the scaling accuracy of a two-antenna, one-pass IFSAR mode with the height-noise performance of a one-antenna, two-pass IFSAR mode. A two-antenna, two-pass IFSAR mode can accurately estimate the larger antenna baseline from the data itself and reduce height-noise, allowing for more accurate information about target ground position locations and heights. The two-antenna, two-pass IFSAR mode can use coarser IFSAR data to estimate the larger antenna baseline. Multi-pass IFSAR can be extended to more than two (2) passes, thereby allowing true three-dimensional radar imaging from stand-off aircraft and satellite platforms.

Analytical evaluation of ILM sensors, volume 1

NASA Technical Reports Server (NTRS)

Kirk, R. J.

1975-01-01

The functional requirements and operating environment constraints are defined for an independent landing monitor ILM which provides the flight crew with an independent assessment of the operation of the primary automatic landing system. The capabilities of radars, TV, forward looking infrared radiometers, multilateration, microwave radiometers, interferometers, and nuclear sensing concepts to meet the ILM conditions are analyzed. The most critical need for the ILM appears in the landing sequence from 1000 to 2000 meters from threshold through rollout. Of the sensing concepts analyzed, the following show potential of becoming feasible ILM's: redundant microwave landings systems, precision approach radar, airborne triangulation radar, multilateration with radar altimetry, and nuclear sensing.

Evidence for highly reflecting materials on the surface and subsurface of Venus

NASA Technical Reports Server (NTRS)

Jurgens, R. F.; Slade, M. A.; Saunders, R. S.

1988-01-01

Radar images at a 12.5-centimeter wavelength made with the Goldstone radar interferometer in 1980 and 1986, together with lunar radar images and recent Venera 15 and 16 data, indicate that material on the surface and subsurface of Venus has a Fresnel reflectivity in excess of 50 percent. Such high reflectivities have been reported on the surface in mountainous regions. Material of high reflectivity may also underlie lower reflectivity surficial materials of the plains regions, where it has been excavated by impact cratering in some areas.

Liquid level and temperature sensing by using dual-wavelength fiber laser based on multimode interferometer and FBG in parallel

NASA Astrophysics Data System (ADS)

Sun, Chunran; Dong, Yue; Wang, Muguang; Jian, Shuisheng

2018-03-01

The detection of liquid level and temperature based on a fiber ring cavity laser sensing configuration is presented and demonstrated experimentally. The sensing head contains a fiber Bragg grating (FBG) and a single-mode-cladding-less-single-mode multimode interferometer, which also functions as wavelength-selective components of the fiber laser. When the liquid level or temperature is applied on the sensing head, the pass-band peaks of both multimode interference (MMI) filter and FBG filter vary and the two output wavelengths of the laser shift correspondingly. In the experiment, the corresponding sensitivities of the liquid level with four different refractive indices (RI) in the deep range from 0 mm to 40 mm are obtained and the sensitivity enhances with the RI of the liquid being measured. The maximum sensitivity of interferometer is 106.3 pm/mm with the RI of 1.391. For the temperature measurement, a sensitivity of 10.3 pm/°C and 13.8 pm/°C are achieved with the temperature ranging from 0 °C to 90 °C corresponding to the two lasing wavelengths selective by the MMI filter and FBG, respectively. In addition, the average RI sensitivity of 155.77 pm/mm/RIU is also obtained in the RI range of 1.333-1.391.

High-resolution spectrometrometry/interferometer

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Norton, R. H.; Schindler, R. A.

1980-01-01

Modified double-pass interferometer has several features that maximize its resolution. Proposed for rocket-borne probes of upper atmosphere, it includes cat's-eye retroreflectors in both arms, wedge-shaped beam splitter, and wedged optical-path compensator. Advantages are full tilt compensation, minimal spectrum "channeling," easy tunability, maximum fringe contrast, and even two-sided interferograms.

The 2008 Super Tuesday Tornado Outbreak: Synthetic Dual Doppler Analysis of Contrasting Tornadic Storm Types

NASA Technical Reports Server (NTRS)

Knupp, Kevin R.; Coleman, Timothy; Carey, Larry; Peterson, Walt; Elkins, Calvin

2008-01-01

During the Super Tuesday Tornado Outbreak on 5-6 February, a significant number of storms passed within about 40 km of WSR-88D radars. This distance, combined with the significant motion vector (from the southwest at 20-25 m per second) of relatively steady storms, is amenable to a synthetic dual Doppler analysis during the times when the storms passed the WSR-88D locations. Nine storms will be analyzed using the SDD technique. The following table provides their general characteristics and nearest approach to the 88D radars. For this data set, storm structure ranges from isolated supercell to QLCS. Each storm will be analyzed for a 40-60 min period during passage by the WSR-88D radar to determine general storm properties. Analysis of high-resolution single Doppler data around the time of passage (plus or minus 30 min), combined with 1-2 SDD analyses, will be used to examine the kinematic structure of low-level circulations (e.g., mesocyclone, downdraft) and the relation to the parent storm. This analysis may provide insights on the fundamental differences between cyclonic circulations in supercell storms and those within QCLS's.

Integrated optic single-ring filter for narrowband phase demodulation

NASA Astrophysics Data System (ADS)

Madsen, C. K.

2017-05-01

Integrated optic notch filters are key building blocks for higher-order spectral filter responses and have been demonstrated in many technology platforms from dielectrics (such as Si3N4) to semiconductors (Si photonics). Photonic-assisted RF processing applications for notch filters include identifying and filtering out high-amplitude, narrowband signals that may be interfering with the desired signal, including undesired frequencies detected in radar and free-space optical links. The fundamental tradeoffs for bandwidth and rejection depth as a function of the roundtrip loss and coupling coefficient are investigated along with the resulting spectral phase response for minimum-phase and maximum-phase responses compared to the critical coupling condition and integration within a Mach Zehnder interferometer. Based on a full width at half maximum criterion, it is shown that maximum-phase responses offer the smallest bandwidths for a given roundtrip loss. Then, a new role for passive notch filters in combination with high-speed electro-optic phase modulation is explored around narrowband phase-to-amplitude demodulation using a single ring operating on one sideband. Applications may include microwave processing and instantaneous frequency measurement (IFM) for radar, space and defense applications.

In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers

PubMed Central

Zhu, Tao; Wu, Di; Liu, Min; Duan, De-Wen

2012-01-01

In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. PMID:23112608

A data-driven and physics-based single-pass retrieval of active-passive microwave covariation and vegetation parameters for the SMAP mission

NASA Astrophysics Data System (ADS)

Entekhabi, D.; Jagdhuber, T.; Das, N. N.; Baur, M.; Link, M.; Piles, M.; Akbar, R.; Konings, A. G.; Mccoll, K. A.; Alemohammad, S. H.; Montzka, C.; Kunstmann, H.

2016-12-01

The active-passive soil moisture retrieval algorithm of NASA's SMAP mission depends on robust statistical estimation of active-passive covariation (β) and vegetation structure (Γ) parameters in order to provide reliable global measurements of soil moisture on an intermediate level (9km) compared to the native resolution of the radiometer (36km) and radar (3km) instruments. These parameters apply to the SMAP radiometer-radar combination over the period of record that was cut short with the end of the SMAP radar transmission. They also apply to the current SMAP radiometer and Sentinel 1A/B radar combination for high-resolution surface soil moisture mapping. However, the performance of the statistically-based approach is directly dependent on the selection of a representative time frame in which these parameters can be estimated assuming dynamic soil moisture and stationary soil roughness and vegetation cover. Here, we propose a novel, data-driven and physics-based single-pass retrieval of active-passive microwave covariation and vegetation parameters for the SMAP mission. The algorithm does not depend on time series analyses and can be applied using minimum one pair of an active-passive acquisition. The algorithm stems from the physical link between microwave emission and scattering via conservation of energy. The formulation of the emission radiative transfer is combined with the Distorted Born Approximation of radar scattering for vegetated land surfaces. The two formulations are simultaneously solved for the covariation and vegetation structure parameters. Preliminary results from SMAP active-passive observations (April 13th to July 7th 2015) compare well with the time-series statistical approach and confirms the capability of this method to estimate these parameters. Moreover, the method is not restricted to a given frequency (applies to both L-band and C-band combinations for the radar) or incidence angle (all angles and not just the fixed 40° incidence). Therefore, the approach is applicable to the combination of SMAP and Sentinel-1A/B data for active-passive and high-resolution soil moisture estimation.

Radar measurement of the seasonal variation in the velocity of the sunrise terminator

NASA Astrophysics Data System (ADS)

Meehan, D. H.

1990-03-01

The HF phased-array radar at Bribie Island, Australia, used to measure horizontal movements of the ionosphere, has been calibrated using the known velocity of the sunrise terminator. The seasonal variation in the velocity of the terminator has been resolved, both in magnitud and direction. The technique uses single-station ionospheric sounding, and requires the angle of arrival and Doppler shift of ionospheric echoes to be measured as the terminator passes overhead. Pfister's (1971) theorem allows calculation of the velocity of the reflecting surface. The difference between theory and experiment is less than 3 percent in speed and 2 degrees in direction on average.

Phase Distribution and Selection of Partially Correlated Persistent Scatterers

NASA Astrophysics Data System (ADS)

Lien, J.; Zebker, H. A.

2012-12-01

Interferometric synthetic aperture radar (InSAR) time-series methods can effectively estimate temporal surface changes induced by geophysical phenomena. However, such methods are susceptible to decorrelation due to spatial and temporal baselines (radar pass separation), changes in orbital geometries, atmosphere, and noise. These effects limit the number of interferograms that can be used for differential analysis and obscure the deformation signal. InSAR decorrelation effects may be ameliorated by exploiting pixels that exhibit phase stability across the stack of interferograms. These so-called persistent scatterer (PS) pixels are dominated by a single point-like scatterer that remains phase-stable over the spatial and temporal baseline. By identifying a network of PS pixels for use in phase unwrapping, reliable deformation measurements may be obtained even in areas of low correlation, where traditional InSAR techniques fail to produce useful observations. Many additional pixels can be added to the PS list if we are able to identify those in which a dominant scatterer exhibits partial, rather than complete, correlation across all radar scenes. In this work, we quantify and exploit the phase stability of partially correlated PS pixels. We present a new system model for producing interferometric pixel values from a complex surface backscatter function characterized by signal-to-clutter ratio (SCR). From this model, we derive the joint probabilistic distribution for PS pixel phases in a stack of interferograms as a function of SCR and spatial baselines. This PS phase distribution generalizes previous results that assume the clutter phase contribution is uncorrelated between radar passes. We verify the analytic distribution through a series of radar scattering simulations. We use the derived joint PS phase distribution with maximum-likelihood SCR estimation to analyze an area of the Hayward Fault Zone in the San Francisco Bay Area. We obtain a series of 38 interferometric images of the area from C-band ERS radar satellite passes between May 1995 and December 2000. We compare the estimated SCRs to those calculated with previously derived PS phase distributions. Finally, we examine the PS network density resulting from varying selection thresholds of SCR and compare to other PS identification techniques.

Optical elements formed by compressed gases: Analysis and potential applications

NASA Technical Reports Server (NTRS)

Howes, W. L.

1986-01-01

Spherical, cylindrical, and conical shock waves are optically analogous to gas lenses. The geometrical optics of these shock configurations are analyzed as they pertain to flow visualization instruments, particularly the rainbow schlieren apparatus and single-pass interferometers. It is proposed that a lens or mirror formed by gas compressed between plastic sheets has potential as a fluid visualization test object; as the objective mirror in a very large space-based telescope, communication antenna, or energy collector; as the objective mirror in inexpensive commercial telescopes; and as a component in fluid visualization apparatuses.

Quantum Interferometry

NASA Technical Reports Server (NTRS)

Dowling, Jonathan P.

2000-01-01

Recently, several researchers, including yours truly, have been able to demonstrate theoretically that quantum photon entanglement has the potential to also revolutionize the entire field of optical interferometry, by providing many orders of magnitude improvement in interferometer sensitivity. The quantum entangled photon interferometer approach is very general and applies to many types of interferometers. In particular, without nonlocal entanglement, a generic classical interferometer has a statistical-sampling shot-noise limited sensitivity that scales like 1/Sqrt[N], where N is the number of particles (photons, electrons, atoms, neutrons) passing through the interferometer per unit time. However, if carefully prepared quantum correlations are engineered between the particles, then the interferometer sensitivity improves by a factor of Sqrt[N] (square root of N) to scale like 1/N, which is the limit imposed by the Heisenberg Uncertainty Principle. For optical (laser) interferometers operating at milliwatts of optical power, this quantum sensitivity boost corresponds to an eight-order-of-magnitude improvement of signal to noise. Applications are to tests of General Relativity such as ground and orbiting optical interferometers for gravity wave detection, Laser Interferometer Gravity Observatory (LIGO) and the European Laser Interferometer Space Antenna (LISA), respectively.

The use of x-ray interferometry to investigate the linearity of the NPL Differential Plane Mirror Optical Interferometer

NASA Astrophysics Data System (ADS)

Yacoot, Andrew; Downs, Michael J.

2000-08-01

The x-ray interferometer from the combined optical and x-ray interferometer (COXI) facility at NPL has been used to investigate the performance of the NPL Jamin Differential Plane Mirror Interferometer when it is fitted with stabilized and unstabilized lasers. This Jamin interferometer employs a common path design using a double pass configuration and one fringe is realized by a displacement of 158 nm between its two plane mirror retroreflectors. Displacements over ranges of several optical fringes were measured simultaneously using the COXI x-ray interferometer and the Jamin interferometer and the results were compared. In order to realize the highest measurement accuracy from the Jamin interferometer, the air paths were shielded to prevent effects from air turbulence and electrical signals generated by the photodetectors were analysed and corrected using an optimizing routine in order to subdivide the optical fringes accurately. When an unstabilized laser was used the maximum peak-to-peak difference between the two interferometers was 80 pm, compared with 20 pm when the stabilized laser was used.

Servomechanism for Doppler shift compensation in optical correlator for synthetic aperture radar

NASA Technical Reports Server (NTRS)

Constaninides, N. J.; Bicknell, T. J. (Inventor)

1980-01-01

A method and apparatus for correcting Doppler shifts in synthetic aperture radar data is described. An optical correlator for synthetic aperture radar data has a means for directing a laser beam at a signal film having radar return pulse intensity information recorded on it. A resultant laser beam passes through a range telescope, an azimuth telescope, and a Fourier transform filter located between the range and azimuth telescopes, and forms an image for recording on an image film. A compensation means for Doppler shift in the radar return pulse intensity information includes a beam splitter for reflecting the modulated laser beam, after having passed through the Fourier transform filter, to a detection screen having two photodiodes mounted on it.

Development of HRO interferometer at Kochi University of Technology

NASA Astrophysics Data System (ADS)

Yamamoto, Masa-Yuki; Horiuchi, Hirotaka; Okamoto, Goro; Hamaguchi, Haruko; Noguchi, Kazuya

2007-12-01

As a typical radio meteor observation method, the Ham-band Radio meteor Observation (HRO) has been spread to many amateur meteor observers in the world, resulting in worldwide continuous detection of each meteor echo at precise time of appearance in any weather condition as well as in daytime. However, direction finding of incoming electromagnetic waves by meteors is difficult to obtain by a usual HRO system. An application of HRO with interferometer technique was developed in 2004-2005 in Kochi University of Technology (KUT), Japan. Within a context of the forwardscattering radar method, an HRO interferometer (HRO-IF) with 3 antennas was developed. Detailed structure of the HRO-IF system at KUT as well as calibration experiments of establishing accurate direction determination are presented.

A 3D Reconstruction Strategy of Vehicle Outline Based on Single-Pass Single-Polarization CSAR Data.

PubMed

Leping Chen; Daoxiang An; Xiaotao Huang; Zhimin Zhou

2017-11-01

In the last few years, interest in circular synthetic aperture radar (CSAR) acquisitions has arisen as a consequence of the potential achievement of 3D reconstructions over 360° azimuth angle variation. In real-world scenarios, full 3D reconstructions of arbitrary targets need multi-pass data, which makes the processing complex, money-consuming, and time expending. In this paper, we propose a processing strategy for the 3D reconstruction of vehicle, which can avoid using multi-pass data by introducing a priori information of vehicle's shape. Besides, the proposed strategy just needs the single-pass single-polarization CSAR data to perform vehicle's 3D reconstruction, which makes the processing much more economic and efficient. First, an analysis of the distribution of attributed scattering centers from vehicle facet model is presented. And the analysis results show that a smooth and continuous basic outline of vehicle could be extracted from the peak curve of a noncoherent processing image. Second, the 3D location of vehicle roofline is inferred from layover with empirical insets of the basic outline. At last, the basic line and roofline of the vehicle are used to estimate the vehicle's 3D information and constitute the vehicle's 3D outline. The simulated and measured data processing results prove the correctness and effectiveness of our proposed strategy.

Advanced Antenna Design for NASA's EcoSAR Instrument

NASA Technical Reports Server (NTRS)

Du Toit, Cornelis F.; Deshpande, Manohar; Rincon, Rafael F.

2016-01-01

Advanced antenna arrays were designed for NASA's EcoSAR airborne radar instrument. EcoSAR is a beamforming synthetic aperture radar instrument designed to make polarimetric and "single pass" interferometric measurements of Earth surface parameters. EcoSAR's operational requirements of a 435MHz center frequency with up to 200MHz bandwidth, dual polarization, high cross-polarization isolation (> 30 dB), +/- 45deg beam scan range and antenna form-factor constraints imposed stringent requirements on the antenna design. The EcoSAR project successfully developed, characterized, and tested two array antennas in an anechoic chamber. EcoSAR's first airborne campaign conducted in the spring of 2014 generated rich data sets of scientific and engineering value, demonstrating the successful operation of the antennas.

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

NASA Technical Reports Server (NTRS)

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

1978-01-01

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.

46 CFR 11.305 - Radar-Observer certificates and qualifying courses.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Radar-Observer certificates and qualifying courses. 11... SEAMEN REQUIREMENTS FOR OFFICER ENDORSEMENTS Training Schools with Approved Courses § 11.305 Radar... includes passing both a radar-theory examination and a practical demonstration on a simulator, and who...

46 CFR 11.305 - Radar-Observer certificates and qualifying courses.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Radar-Observer certificates and qualifying courses. 11... SEAMEN REQUIREMENTS FOR OFFICER ENDORSEMENTS Training Schools with Approved Courses § 11.305 Radar... includes passing both a radar-theory examination and a practical demonstration on a simulator, and who...

NASA Tech Briefs, March 2011

NASA Technical Reports Server (NTRS)

2011-01-01

Topics covered include: Optimal Tuner Selection for Kalman-Filter-Based Aircraft Engine Performance Estimation; Airborne Radar Interferometric Repeat-Pass Processing; Plug-and-Play Environmental Monitoring Spacecraft Subsystem; Power-Combined GaN Amplifier with 2.28-W Output Power at 87 GHz; Wallops Ship Surveillance System; Source Lines Counter (SLiC) Version 4.0; Guidance, Navigation, and Control Program; Single-Frame Terrain Mapping Software for Robotic Vehicles; Auto Draw from Excel Input Files; Observation Scheduling System; CFDP for Interplanetary Overlay Network; X-Windows Widget for Image Display; Binary-Signal Recovery; Volumetric 3D Display System with Static Screen; MMIC Replacement for Gunn Diode Oscillators; Feature Acquisition with Imbalanced Training Data; Mount Protects Thin-Walled Glass or Ceramic Tubes from Large Thermal and Vibration Loads; Carbon Nanotube-Based Structural Health Monitoring Sensors; Wireless Inductive Power Device Suppresses Blade Vibrations; Safe, Advanced, Adaptable Isolation System Eliminates the Need for Critical Lifts; Anti-Rotation Device Releasable by Insertion of a Tool; A Magnetically Coupled Cryogenic Pump; Single Piezo-Actuator Rotary-Hammering Drill; Fire-Retardant Polymeric Additives; Catalytic Generation of Lift Gases for Balloons; Ionic Liquids to Replace Hydrazine; Variable Emittance Electrochromics Using Ionic Electrolytes and Low Solar Absorptance Coatings; Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger; Multi-Mission Power Analysis Tool; Correction for Self-Heating When Using Thermometers as Heaters in Precision Control Applications; Gravitational Wave Detection with Single-Laser Atom Interferometers; Titanium Alloy Strong Back for IXO Mirror Segments; Improved Ambient Pressure Pyroelectric Ion Source; Multi-Modal Image Registration and Matching for Localization of a Balloon on Titan; Entanglement in Quantum-Classical Hybrid; Algorithm for Autonomous Landing; Quantum-Classical Hybrid for Information Processing; Small-Scale Dissipation in Binary-Species Transitional Mixing Layers; Superpixel-Augmented Endmember Detection for Hyperspectral Images; Coding for Parallel Links to Maximize the Expected Value of Decodable Messages; and Microwave Tissue Soldering for Immediate Wound Closure.

Airborne Radar Interferometric Repeat-Pass Processing

NASA Technical Reports Server (NTRS)

Hensley, Scott; Michel, Thierry R.; Jones, Cathleen E.; Muellerschoen, Ronald J.; Chapman, Bruce D.; Fore, Alexander; Simard, Marc; Zebker, Howard A.

2011-01-01

Earth science research often requires crustal deformation measurements at a variety of time scales, from seconds to decades. Although satellites have been used for repeat-track interferometric (RTI) synthetic-aperture-radar (SAR) mapping for close to 20 years, RTI is much more difficult to implement from an airborne platform owing to the irregular trajectory of the aircraft compared with microwave imaging radar wavelengths. Two basic requirements for robust airborne repeat-pass radar interferometry include the ability to fly the platform to a desired trajectory within a narrow tube and the ability to have the radar beam pointed in a desired direction to a fraction of a beam width. Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) is equipped with a precision auto pilot developed by NASA Dryden that allows the platform, a Gulfstream III, to nominally fly within a 5 m diameter tube and with an electronically scanned antenna to position the radar beam to a fraction of a beam width based on INU (inertial navigation unit) attitude angle measurements.

Ultra-Low-Noise W-Band MMIC Detector Modules

NASA Technical Reports Server (NTRS)

Gaier, Todd C.; Samoska, Lorene A.; Kangaslahti, Pekka P.; Van Vinkle, Dan; Tantawi, Sami; Fox, John; Church, Sarah E.; Lau, Jusy M.; Sieth, Matthew M.; Voll, Patricia E.;

Simultaneous DPSK demodulation and chirp management using delay interferometer in symmetric 40-Gb/s capability TWDM-PON system.

PubMed

Bi, Meihua; Xiao, Shilin; He, Hao; Yi, Lilin; Li, Zhengxuan; Li, Jun; Yang, Xuelin; Hu, Weisheng

2013-07-15

We propose a symmetric 40-Gb/s aggregate rate time and wavelength division multiplexed passive optical network (TWDM-PON) system with the capability of simultaneous downstream differential phase shift keying (DPSK) signal demodulation and upstream signal chirp management based on delay interferometer (DI). With the bi-pass characteristic of DI, we experimentally demonstrate the bidirectional transmission of signals at 10-Gb/s per wavelength, and achieve negligible power penalties after 50-km single mode fiber (SMF). For the uplink transmission with DI, a ~11-dB optical power budget improvement at a bit error ratio of 1e-3 is obtained and the extinction ratio (ER) of signal is also improved from 3.4 dB to 13.75 dB. Owing to this high ER, the upstream burst-mode transmitting is successfully presented in term of time-division multiplexing. Moreover, in our experiment, a ~38-dB power budget is obtained to support 256 users with 50-km SMF transmission.

Geophysical Measurements Using a Ring Laser

NASA Astrophysics Data System (ADS)

Lamb, Angela

2016-03-01

Low frequency infrasound from weather related events has been studied for a number of years. In this poster, the results from using a large active ring laser as an infrasound detector are presented. A slightly modified cavity design enhances the interferometer's sensitivity to infrasound. Our results qualitatively agree with several findings from a long term study of weather generated infrasound by NOAA. On April 27, 2014, the 66 km track of an EF-4 tornado passed within 21 km of the ring laser interferometer. An FFT of the ring laser interferometer output revealed a steady tornado generated frequency of 0.94 Hz. The track also passed close to the US Array Transportable Station W41B. This provided the opportunity to examine both the infrasound and ground motion generated by the tornado. Infrasound from three other tornadoes is also included. In all cases the infrasound was detected approximately 30 minutes before the tornado funnel was observed. This work is generously supported by the National Science Foundation and NASA/Arkansas Space Grant.

Radar remote sensing for archaeology in Hangu Frontier Pass in Xin’an, China

NASA Astrophysics Data System (ADS)

Jiang, A. H.; Chen, F. L.; Tang, P. P.; Liu, G. L.; Liu, W. K.; Wang, H. C.; Lu, X.; Zhao, X. L.

2017-02-01

As a non-invasive tool, remote sensing can be applied to archaeology taking the advantage of large scale covering, in-time acquisition, high spatial-temporal resolution and etc. In archaeological research, optical approaches have been widely used. However, the capability of Synthetic Aperture Radar (SAR) for archaeological detection has not been fully exploded so far. In this study, we chose Hangu Frontier Pass of Han Dynasty located in Henan Province as the experimental site (included into the cluster of Silk Roads World Heritage sites). An exploratory study to detect the historical remains was conducted. Firstly, TanDEM-X SAR data were applied to generate high resolution DEM of Hangu Frontier Pass; and then the relationship between the pass and derived ridge lines was analyzed. Second, the temporal-averaged amplitude SAR images highlighted archaeological traces owing to the depressed speckle noise. For instance, the processing of 20-scene PALSAR data (spanning from 2007 to 2011) enabled us to detect unknown archaeological features. Finally, the heritage remains detected by SAR data were verified by Ground Penetrating Radar (GPR) prospecting, implying the potential of the space-to-ground radar remote sensing for archaeological applications.

5.7  W cw single-frequency laser at 671  nm by single-pass second harmonic generation of a 17.2  W injection-locked 1342  nm Nd : YVO4 ring laser using periodically poled MgO : LiNbO3.

PubMed

Koch, Peter; Ruebel, Felix; Bartschke, Juergen; L'huillier, Johannes A

2015-11-20

We demonstrate a continuous wave single-frequency laser at 671.1 nm based on a high-power 888 nm pumped Nd:YVO4 ring laser at 1342.2 nm. Unidirectional operation of the fundamental ring laser is achieved with the injection-locking technique. A Nd:YVO4 microchip laser serves as the injecting seed source, providing a tunable single-frequency power of up to 40 mW. The ring laser emits a single-frequency power of 17.2 W with a Gaussian beam profile and a beam propagation factor of M2<1.1. A 60-mm-long periodically poled MgO-doped LiNbO3 crystal is used to generate the second harmonic in a single-pass scheme. Up to 5.7 W at 671.1 nm with a Gaussian shaped beam profile and a beam propagation factor of M2<1.2 are obtained, which is approximately twice the power of previously reported lasers. This work opens possibilities in cold atoms experiments with lithium, allowing the use of larger ensembles in magneto-optical traps or higher diffraction orders in atomic beam interferometers.

Improving the Representation of Snow Crystal Properties with a Single-Moment Mircophysics Scheme

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Demek, Scott R.

2010-01-01

Single-moment microphysics schemes are utilized in an increasing number of applications and are widely available within numerical modeling packages, often executed in near real-time to aid in the issuance of weather forecasts and advisories. In order to simulate cloud microphysical and precipitation processes, a number of assumptions are made within these schemes. Snow crystals are often assumed to be spherical and of uniform density, and their size distribution intercept may be fixed to simplify calculation of the remaining parameters. Recently, the Canadian CloudSat/CALIPSO Validation Project (C3VP) provided aircraft observations of snow crystal size distributions and environmental state variables, sampling widespread snowfall associated with a passing extratropical cyclone on 22 January 2007. Aircraft instrumentation was supplemented by comparable surface estimations and sampling by two radars: the C-band, dual-polarimetric radar in King City, Ontario and the NASA CloudSat 94 GHz Cloud Profiling Radar. As radar systems respond to both hydrometeor mass and size distribution, they provide value when assessing the accuracy of cloud characteristics as simulated by a forecast model. However, simulation of the 94 GHz radar signal requires special attention, as radar backscatter is sensitive to the assumed crystal shape. Observations obtained during the 22 January 2007 event are used to validate assumptions of density and size distribution within the NASA Goddard six-class single-moment microphysics scheme. Two high resolution forecasts are performed on a 9-3-1 km grid, with C3VP-based alternative parameterizations incorporated and examined for improvement. In order to apply the CloudSat 94 GHz radar to model validation, the single scattering characteristics of various crystal types are used and demonstrate that the assumption of Mie spheres is insufficient for representing CloudSat reflectivity derived from winter precipitation. Furthermore, snow density and size distribution characteristics are allowed to vary with height, based upon direct aircraft estimates obtained from C3VP data. These combinations improve the representation of modeled clouds versus their radar-observed counterparts, based on profiles and vertical distributions of reflectivity. These meteorological events are commonplace within the mid-latitude cold season and present a challenge to operational forecasters. This study focuses on one event, likely representative of others during the winter season, and aims to improve the representation of snow for use in future operational forecasts.

Three-dimensional radar imaging of structures and craters in the Martian polar caps.

PubMed

Putzig, Nathaniel E; Smith, Isaac B; Perry, Matthew R; Foss, Frederick J; Campbell, Bruce A; Phillips, Roger J; Seu, Roberto

2018-07-01

Over the last decade, observations acquired by the Shallow Radar (SHARAD) sounder on individual passes of the Mars Reconnaissance Orbiter have revealed the internal structure of the Martian polar caps and provided new insights into the formation of the icy layers within and their relationship to climate. However, a complete picture of the cap interiors has been hampered by interfering reflections from off-nadir surface features and signal losses associated with sloping structures and scattering. Foss et al. (2017) addressed these limitations by assembling three-dimensional data volumes of SHARAD observations from thousands of orbital passes over each polar region and applying geometric corrections simultaneously. The radar volumes provide unprecedented views of subsurface features, readily imaging structures previously inferred from time-intensive manual analysis of single-orbit data (e.g., trough-bounding surfaces, a buried chasma, and a basal unit in the north, massive carbon-dioxide ice deposits and discontinuous layered sequences in the south). Our new mapping of the carbon-dioxide deposits yields a volume of 16,500 km 3 , 11% larger than the prior estimate. In addition, the radar volumes newly reveal other structures, including what appear to be buried impact craters with no surface expression. Our first assessment of 21 apparent craters at the base of the north polar layered deposits suggests a Hesperian age for the substrate, consistent with that of the surrounding plains as determined from statistics of surface cratering rates. Planned mapping of similar features throughout both polar volumes may provide new constraints on the age of the icy layered deposits. The radar volumes also provide new topographic data between the highest latitudes observed by the Mars Orbiter Laser Altimeter and those observed by SHARAD. In general, mapping of features in these radar volumes is placing new constraints on the nature and evolution of the polar deposits and associated climate changes.

Three-dimensional radar imaging of structures and craters in the Martian polar caps

NASA Astrophysics Data System (ADS)

Putzig, Nathaniel E.; Smith, Isaac B.; Perry, Matthew R.; Foss, Frederick J.; Campbell, Bruce A.; Phillips, Roger J.; Seu, Roberto

2018-07-01

Over the last decade, observations acquired by the Shallow Radar (SHARAD) sounder on individual passes of the Mars Reconnaissance Orbiter have revealed the internal structure of the Martian polar caps and provided new insights into the formation of the icy layers within and their relationship to climate. However, a complete picture of the cap interiors has been hampered by interfering reflections from off-nadir surface features and signal losses associated with sloping structures and scattering. Foss et al. (The Leading Edge 36, 43-57, 2017, https://doi.org/10.1190/tle36010043.1) addressed these limitations by assembling three-dimensional data volumes of SHARAD observations from thousands of orbital passes over each polar region and applying geometric corrections simultaneously. The radar volumes provide unprecedented views of subsurface features, readily imaging structures previously inferred from time-intensive manual analysis of single-orbit data (e.g., trough-bounding surfaces, a buried chasma, and a basal unit in the north, massive carbon-dioxide ice deposits and discontinuous layered sequences in the south). Our new mapping of the carbon-dioxide deposits yields a volume of 16,500 km3, 11% larger than the prior estimate. In addition, the radar volumes newly reveal other structures, including what appear to be buried impact craters with no surface expression. Our first assessment of 21 apparent craters at the base of the north polar layered deposits suggests a Hesperian age for the substrate, consistent with that of the surrounding plains as determined from statistics of surface cratering rates. Planned mapping of similar features throughout both polar volumes may provide new constraints on the age of the icy layered deposits. The radar volumes also provide new topographic data between the highest latitudes observed by the Mars Orbiter Laser Altimeter and those observed by SHARAD. In general, mapping of features in these radar volumes is placing new constraints on the nature and evolution of the polar deposits and associated climate changes.

Manufacture, alignment and measurement for a reflective triplet optics in imaging spectrometer

NASA Astrophysics Data System (ADS)

Yuan, Liyin; He, Zhiping; Wang, Yueming; Lv, Gang

2016-09-01

Reflective triplet (RT) optics is an optical form with decenters and tilts of all the three mirrors. It can be used in spectrometer as collimator and reimager to get fine optical and spectral performances. To alleviate thermal and assembly stress deformation, opto-mechanical integrated design suggests that as with all the machine elements and the mainframe, the mirrors substrates are aluminum. All the mirrors are manufactured by single-point diamond turning technology and measured by interferometer or profilometer. Because of retro-reflection by grating or prism and reimaging away from the object field, solo three mirrors optical path of RT has some aberrations. So its alignment and measurement needs an aberration corrected measuring optical system with auxiliary plane and sphere mirrors and in which the RT optics used in four pass. Manufacture, alignment and measurement for a RT optics used in long wave infrared grating spectrometer is discussed here. We realized the manufacture, alignment and test for the RT optics of a longwave infrared spectromter by CMM and interferometer. Wavefront error test by interferometer and surface profiles measured by profilometer indicate that performances of the manufactured mirrors exceed the requirements. Interferogram of the assembled RT optics shows that wavefront error rms is less than 0.0493λ@10.6μm vs design result 0.0207λ.

Effect of external digital elevation model on monitoring of mine subsidence by two-pass differential interferometric synthetic aperture radar

NASA Astrophysics Data System (ADS)

Tao, Qiuxiang; Gao, Tengfei; Liu, Guolin; Wang, Zhiwei

2017-04-01

The external digital elevation model (DEM) error is one of the main factors that affect the accuracy of mine subsidence monitored by two-pass differential interferometric synthetic aperture radar (DInSAR), which has been widely used in monitoring mining-induced subsidence. The theoretical relationship between external DEM error and monitored deformation error is derived based on the principles of interferometric synthetic aperture radar (DInSAR) and two-pass DInSAR. Taking the Dongtan and Yangcun mine areas of Jining as test areas, the difference and accuracy of 1:50000, ASTER GDEM V2, and SRTM DEMs are compared and analyzed. Two interferometric pairs of Advanced Land Observing Satellite Phased Array L-band SAR covering the test areas are processed using two-pass DInSAR with three external DEMs to compare and analyze the effect of three external DEMs on monitored mine subsidence in high- and low-coherence subsidence regions. Moreover, the reliability and accuracy of the three DInSAR-monitored results are compared and verified with leveling-measured subsidence values. Results show that the effect of external DEM on mine subsidence monitored by two-pass DInSAR is not only related to radar look angle, perpendicular baseline, slant range, and external DEM error, but also to the ground resolution of DEM, the magnitude of subsidence, and the coherence of test areas.

Contribution of the AN/TPS-3 Radar Antenna to Australian radio astronomy

NASA Astrophysics Data System (ADS)

Wendt, Harry; Orchiston, Wayne

2018-04-01

The CSIRO Division of Radiophysics used the WWII surplus AN/TPS-3 radar dishes for their early solar radio astronomy research and eclipse observations. These aerials were also used in a spaced (Michelson) interferometer configuration in the late 1940s to investigate solar limb brightening at 600 MHz. This work paralleled early solar observations at Cambridge. None of the Australian research results using the spaced interferometry technique appeared in publications, and the invention of the solar grating array in 1950 made further use of the method redundant.

Double-pass Mach-Zehnder fiber interferometer pH sensor.

PubMed

Tou, Zhi Qiang; Chan, Chi Chiu; Hong, Jesmond; Png, Shermaine; Eddie, Khay Ming Tan; Tan, Terence Aik Huang

2014-04-01

A biocompatible fiber-optic pH sensor based on a unique double-pass Mach-Zehnder interferometer is proposed. pH responsive poly(2-hydroxyethyl methacrylate-co-2-(dimethylamino)ethyl methacrylate) hydrogel coating on the fiber swells/deswells in response to local pH, leading to refractive index changes that manifest as shifting of interference dips in the optical spectrum. The pH sensor is tested in spiked phosphate buffer saline and demonstrates high sensitivity of 1.71  nm/pH, pH 0.004 limit of detection with good responsiveness, repeatability, and stability. The proposed sensor has been successfully applied in monitoring the media pH in cell culture experiments to investigate the relationship between pH and cancer cell growth.

The Ecosystems SAR (EcoSAR) an Airborne P-band Polarimetric InSAR for the Measurement of Vegetation Structure, Biomass and Permafrost

NASA Technical Reports Server (NTRS)

Rincon, Rafael F.; Fatoyinbo, Temilola; Ranson, K. Jon; Osmanoglu, Batuhan; Sun, Guoqing; Deshpande, Manohar D.; Perrine, Martin L.; Du Toit, Cornelis F.; Bonds, Quenton; Beck, Jaclyn;

Space Radar Image of West Texas - SAR Scan

NASA Image and Video Library

1999-04-15

This radar image of the Midland/Odessa region of West Texas, demonstrates an experimental technique, called ScanSAR, that allows scientists to rapidly image large areas of the Earth's surface. The large image covers an area 245 kilometers by 225 kilometers (152 miles by 139 miles). It was obtained by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) flying aboard the space shuttle Endeavour on October 5, 1994. The smaller inset image is a standard SIR-C image showing a portion of the same area, 100 kilometers by 57 kilometers (62 miles by 35 miles) and was taken during the first flight of SIR-C on April 14, 1994. The bright spots on the right side of the image are the cities of Odessa (left) and Midland (right), Texas. The Pecos River runs from the top center to the bottom center of the image. Along the left side of the image are, from top to bottom, parts of the Guadalupe, Davis and Santiago Mountains. North is toward the upper right. Unlike conventional radar imaging, in which a radar continuously illuminates a single ground swath as the space shuttle passes over the terrain, a Scansar radar illuminates several adjacent ground swaths almost simultaneously, by "scanning" the radar beam across a large area in a rapid sequence. The adjacent swaths, typically about 50 km (31 miles) wide, are then merged during ground processing to produce a single large scene. Illumination for this L-band scene is from the top of the image. The beams were scanned from the top of the scene to the bottom, as the shuttle flew from left to right. This scene was acquired in about 30 seconds. A normal SIR-C image is acquired in about 13 seconds. The ScanSAR mode will likely be used on future radar sensors to construct regional and possibly global radar images and topographic maps. The ScanSAR processor is being designed for 1996 implementation at NASA's Alaska SAR Facility, located at the University of Alaska Fairbanks, and will produce digital images from the forthcoming Canadian RADARSAT satellite. http://photojournal.jpl.nasa.gov/catalog/PIA01787

Interferometer. [high resolution

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Norton, R. H.; Schindler, R. A. (Inventor)

1981-01-01

A high resolution interferometer is described. The interferometer is insensitive to slight misalignment of its elements, avoids channeling in the spectrum, generates a maximum equal path fringe contrast, produces an even two sided interferogram without critical matching of the wedge angles of the beamsplitter and compensator wedges, and is optically phase tunable. The interferometer includes a mirror along the path of each beam component produced by the beamsplitter, for reflecting the beam component from the beamsplitter, for reflecting the beam component from the beamsplitter to a corresponding retroreflector and for reflecting the beam returned by the retroreflector back to the beamsplitter. A wedge located along each beam component path, is large enough to cover the retroreflector, so that each beam component passes through the wedge during movement towards the retroreflector and away therefrom.

Spatially modulated interferometer and beam shearing device therefor

NASA Technical Reports Server (NTRS)

Reininger, Francis M. (Inventor)

2004-01-01

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.

New data processing for multichannel FIR laser interferometer

NASA Astrophysics Data System (ADS)

Jun-Ben, Chen; Xiang, Gao

1989-10-01

Usually, both the probing and reference signals received by LATGS detectors of FIR interferometer pass through hardware phase discriminator and the output phase difference--hence the electron line densities is collected for analysis and display with a computerized data acquisition system(DAS). In this paper, a new numerical method for computing the phase difference in software has been developed instead of hardware phase discriminator, the temporal resolution and stability is improved. An asymmetrical Abel inversion is applied to processing the data from a seven-channel FIR HCN laser interferometer and the space-time distributions of plasma electron density in the HT-6M tokamak are derived.

High-accuracy self-mixing interferometer based on multiple reflections using a simple external reflecting mirror

NASA Astrophysics Data System (ADS)

Wang, Xiu-lin; Wei, Zheng; Wang, Rui; Huang, Wen-cai

2018-05-01

A self-mixing interferometer (SMI) with resolution twenty times higher than that of a conventional interferometer is developed by multiple reflections. Only by employing a simple external reflecting mirror, the multiple-pass optical configuration can be constructed. The advantage of the configuration is simple and easy to make the light re-injected back into the laser cavity. Theoretical analysis shows that the resolution of measurement is scalable by adjusting the number of reflections. The experiment shows that the proposed method has the optical resolution of approximate λ/40. The influence of displacement sensitivity gain ( G) is further analyzed and discussed in practical experiments.

New methods of multimode fiber interferometer signal processing

NASA Astrophysics Data System (ADS)

Vitrik, Oleg B.; Kulchin, Yuri N.; Maxaev, Oleg G.; Kirichenko, Oleg V.; Kamenev, Oleg T.; Petrov, Yuri S.

1995-06-01

New methods of multimode fiber interferometers signal processing are suggested. For scheme of single fiber multimode interferometers with two excited modes, the method based on using of special fiber unit is developed. This unit provides the modes interaction and further sum optical field filtering. As a result the amplitude of output signal is modulated by external influence on interferometer. The stabilization of interferometer sensitivity is achieved by using additional special modulation of output signal. For scheme of single fiber multimode interferometers with excitation of wide mode spectrum, the signal of intermode interference is registered by photodiode matrix and then special electronic unit performs correlation processing. For elimination of temperature destabilization, the registered signal is adopted to multimode interferometers optical signal temperature changes. The achieved parameters for double mode scheme: temporary stability--0.6% per hour, sensitivity to interferometer length deviations--3,2 nm; for multimode scheme: temperature stability--(0.5%)/(K), temporary nonstability--0.2% per hour, sensitivity to interferometer length deviations--20 nm, dynamic range--35 dB.

Cassini's Final Titan Radar Swath

NASA Image and Video Library

2017-08-11

During its final targeted flyby of Titan on April 22, 2017, Cassini's radar mapper got the mission's last close look at the moon's surface. On this 127th targeted pass by Titan (unintuitively named "T-126"), the radar was used to take two images of the surface, shown at left and right. Both images are about 200 miles (300 kilometers) in width, from top to bottom. Objects appear bright when they are tilted toward the spacecraft or have rough surfaces; smooth areas appear dark. At left are the same bright, hilly terrains and darker plains that Cassini imaged during its first radar pass of Titan, in 2004. Scientists do not see obvious evidence of changes in this terrain over the 13 years since the original observation. At right, the radar looked once more for Titan's mysterious "magic island" (PIA20021) in a portion of one of the large hydrocarbon seas, Ligeia Mare. No "island" feature was observed during this pass. Scientists continue to work on what the transient feature might have been, with waves and bubbles being two possibilities. In between the two parts of its imaging observation, the radar instrument switched to altimetry mode, in order to make a first-ever (and last-ever) measurement of the depths of some of the lakes that dot the north polar region. For the measurements, the spacecraft pointed its antenna straight down at the surface and the radar measured the time delay between echoes from the lakes' surface and bottom. A graph is available at https://photojournal.jpl.nasa.gov/catalog/PIA21626

Preliminary Observations of Ionospheric Response to an Auroral Driver from the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) Sounding Rocket Campaign

NASA Astrophysics Data System (ADS)

Fernandes, P. A.; Lynch, K. A.; Hysell, D. L.; Powell, S.; Miceli, R.; Hampton, D. L.; Ahrns, J.; Lessard, M.; Cohen, I. J.; Moen, J. I.; Bekkeng, T.

2012-12-01

The nightside sounding rocket MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) launched from Poker Flat, AK, on February 19, 2012, and reached an apogee of 325km. MICA was launched into several discrete, localized arcs in the wake of a westward traveling surge. The MICA instrumentation included both in situ and ground based instruments, and was designed to measure the response of the ionosphere to an auroral driver. More specifically, the science goal was to measure response of the ionosphere to a feedback instability in the ionospheric Alfvén resonator. The MICA payload included in situ particle, electric and magnetic field, and GPS instruments. The ground-based array consisted of a multitude of imagers, coherent and incoherent scatter radars, and a Fabry-Perot interferometer. We present observational characteristics of the response of the ionospheric plasma to the auroral drivers inferred from inverting camera data. We compare the measured precipitating electron population to inversions of camera images, which use a transport model to infer a 2D map of the precipitation. Comparisons show that as the payload passes through what appears to be an Alfvénic auroral arc, the in situ electron instrument shows dispersions indicative of Alfvénic activity. We then introduce measurements of the thermal ion distribution, to examine how the auroral arcs drive a response in the ionosphere. The thermal ion data show that the payload potential strengthens as the payload passes through the arc. When including electron density, temperature, and electric field data, we observe times in which the ionospheric environment changes as the precipitation changes, and times during which there is no measured response by the ionosphere. Future work will compare how the ion bulk flow as measured by the thermal ion instrument compares to the ExB drift as measured by the electric field instrument and to the neutral wind measurements from the Fabry-Perot interferometer. Further analysis of the particle data will yield the ion temperature, whose validity we will quantify by comparison to sheath models.

Laser doppler and radar interferometer for contactless measurements on unaccessible tie-rods on monumental buildings: Santa Maria della Consolazione Temple in Todi

NASA Astrophysics Data System (ADS)

Gioffré, M.; Cavalagli, N.; Pepi, C.; Trequattrini, M.

2017-01-01

Non-contact measurements can be effectively used in civil engineering to assess the variation of structural performance with time. In the last decades this approach has received considerable interests from researchers working in the field of structural health monitoring (SHM). Indeed, non-contact measurements are very attractive because it is possible to perform non intrusive and non destructive investigations even being at a significant distance from the targets. Within this context, contactless measurements of the tie-rod vibrations in the Santa Maria della Consolazione Temple in Todi (Italy) are presented in this paper. In particular, laser vibrometer and radar interferometer measurements are used to estimate natural frequencies and mode shapes. This information is crucial to obtain the tensile axial force in the tie-rods, which can be used as an indicator of structural integrity or possible failure. Furthermore, a novel approach is proposed where drones (Unmanned Aerial Vehicles) can be successfully used to improve the effectiveness and the accuracy of the experimental activities.

Photonic compressed sensing nyquist folding receiver

DTIC Science & Technology

2017-09-01

filter . Two independent photonic receiver architectures are designed and analyzed over the course of this research. Both receiver designs are...undersamples the signals using an opti- cal modulator configuration at 1550 nm and collects the detected samples in a low pass interpolation filter ...Electronic Intelligence EW Electronic Warfare FM Frequency Modulated LNA Low Noise Amplifier LPF Low Pass Filter MZI Mach-Zehnder Interferometer NYFR Nyquist

Wavelength independent interferometer

NASA Technical Reports Server (NTRS)

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

1991-01-01

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.

Space Radar Image of Kennedy Space Center, Florida

NASA Image and Video Library

1999-06-25

This image was produced during radar observations taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar as it flew over the Gulf Stream, Florida, and past the Atlantic Ocean on October 7, 1994. The data were produced using the X-band radar frequency. Knowing ahead of time that this region would be included in a regularly scheduled radar pass, the Kennedy Space Center team, who assembled and integrated the SIR-C/X-SAR equipment with the Spacelab pallet system, designed a set of radar reflectors from common construction materials and formed the letters "KSC" on the ground adjacent to the main headquarters building at the entrance to the Cape Canaveral launch facility. The point of light formed by the bright return from these reflectors are visible in the image. Other more diffuse bright spots are reflections from building faces, roofs and other large structures at the Kennedy Space Center complex. This frame covers an area of approximately 6 kilometers by 8 kilometers (4 miles by 5 miles), which was just a small portion of the data taken on this particular pass. http://photojournal.jpl.nasa.gov/catalog/PIA01747

Optical domain analog to digital conversion methods and apparatus

DOEpatents

Vawter, Gregory A

2014-05-13

Methods and apparatus for optical analog to digital conversion are disclosed. An optical signal is converted by mapping the optical analog signal onto a wavelength modulated optical beam, passing the mapped beam through interferometers to generate analog bit representation signals, and converting the analog bit representation signals into an optical digital signal. A photodiode receives an optical analog signal, a wavelength modulated laser coupled to the photodiode maps the optical analog signal to a wavelength modulated optical beam, interferometers produce an analog bit representation signal from the mapped wavelength modulated optical beam, and sample and threshold circuits corresponding to the interferometers produce a digital bit signal from the analog bit representation signal.

AGILIS: Agile Guided Interferometer for Longbaseline Imaging Synthesis. Demonstration and concepts of reconfigurable optical imaging interferometers

NASA Astrophysics Data System (ADS)

Woillez, Julien; Lai, Olivier; Perrin, Guy; Reynaud, François; Baril, Marc; Dong, Yue; Fédou, Pierre

2017-06-01

Context. In comparison to the radio and sub-millimetric domains, imaging with optical interferometry is still in its infancy. Due to the limited number of telescopes in existing arrays, image generation is a demanding process that relies on time-consuming reconfiguration of the interferometer array and super-synthesis. Aims: Using single mode optical fibres for the coherent transport of light from the collecting telescopes to the focal plane, a new generation of interferometers optimized for imaging can be designed. Methods: To support this claim, we report on the successful completion of the `OHANA Iki project: an end-to-end, on-sky demonstration of a two-telescope interferometer, built around near-infrared single mode fibres, carried out as part of the `OHANA project. Results: Having demonstrated that coherent transport by single-mode fibres is feasible, we explore the concepts, performances, and limitations of a new imaging facility with single mode fibres at its heart: Agile Guided Interferometer for Longbaseline Imaging Synthesis (AGILIS). Conclusions: AGILIS has the potential of becoming a next generation facility or a precursor to a much larger project like the Planet Formation Imager (PFI).

Detection of Transionospheric SuperDARN HF Waves by the Radio Receiver Instrument on the enhanced Polar Outflow Probe Satellite

NASA Astrophysics Data System (ADS)

Gillies, R. G.; Yau, A. W.; James, H. G.; Hussey, G. C.; McWilliams, K. A.

2014-12-01

The enhanced Polar Outflow Probe (ePOP) Canadian small-satellite was launched in September 2013. Included in this suite of eight scientific instruments is the Radio Receiver Instrument (RRI). The RRI has been used to measure VLF and HF radio waves from various ground and spontaneous ionospheric sources. The first dedicated ground transmission that was detected by RRI was from the Saskatoon Super Dual Auroral Radar Network (SuperDARN) radar on Nov. 7, 2013 at 14 MHz. Several other passes over the Saskatoon SuperDARN radar have been recorded since then. Ground transmissions have also been observed from other radars, such as the SPEAR, HAARP, and SURA ionospheric heaters. However, the focus of this study will be on the results obtained from the SuperDARN passes. An analysis of the signal recorded by the RRI provides estimates of signal power, Doppler shift, polarization, absolute time delay, differential mode delay, and angle of arrival. By comparing these parameters to similar parameters derived from ray tracing simulations, ionospheric electron density structures may be detected and measured. Further analysis of the results from the other ground transmitters and future SuperDARN passes will be used to refine these results.

Comparing Methods for Assessing Reliability Uncertainty Based on Pass/Fail Data Collected Over Time

DOE PAGES

Abes, Jeff I.; Hamada, Michael S.; Hills, Charles R.

2017-12-20

In this paper, we compare statistical methods for analyzing pass/fail data collected over time; some methods are traditional and one (the RADAR or Rationale for Assessing Degradation Arriving at Random) was recently developed. These methods are used to provide uncertainty bounds on reliability. We make observations about the methods' assumptions and properties. Finally, we illustrate the differences between two traditional methods, logistic regression and Weibull failure time analysis, and the RADAR method using a numerical example.

Comparing Methods for Assessing Reliability Uncertainty Based on Pass/Fail Data Collected Over Time

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

Abes, Jeff I.; Hamada, Michael S.; Hills, Charles R.

In this paper, we compare statistical methods for analyzing pass/fail data collected over time; some methods are traditional and one (the RADAR or Rationale for Assessing Degradation Arriving at Random) was recently developed. These methods are used to provide uncertainty bounds on reliability. We make observations about the methods' assumptions and properties. Finally, we illustrate the differences between two traditional methods, logistic regression and Weibull failure time analysis, and the RADAR method using a numerical example.

An Interferometric Study of Epoxy Polymerization Kinetics

NASA Astrophysics Data System (ADS)

Page, Melissa A.; Tandy Grubbs, W.

1999-05-01

An interferometric method for monitoring polymerization kinetics is described. The experimental apparatus can be constructed from items commonly available in undergraduate laboratories. It consists of a low power helium-neon laser, a home-built Michelson interferometer, and a photodiode light detector. When a polymerizing sample is placed in one arm of the Michelson interferometer, the variation in refractive index will cause a corresponding shift in the phase of the coherent optical beam that passes through the sample, and the output of the interferometer will subsequently fluctuate between constructive and destructive interference. The oscillation in the interferometer output intensity is monitored as a function of time with the photodiode. The time between successive maxima (or minima) is used to calculate the change in refractive index with time (Dn/Dt), which is subsequently used as a phenomenological definition of polymerization rate. We have utilized this device to collect and compare curing profiles of commercially available epoxy glues.

The measurement of carbon monoxide and methane in the national capital air quality control region. III - Correlation interferometer results

NASA Technical Reports Server (NTRS)

Goldstein, H. W.; Bortner, M. H.; Grenda, R. N.; Dick, R.; Lebel, P. J.; Lamontagne, R. A.

1976-01-01

Two types of experiments were performed with a correlation interferometer on-board a Bell Jet Ranger 206 Helicopter. The first consisted of simultaneous ground- and air-truth measurements as the instrumented helicopter passed over the Cheverly site. The second consisted of several measurement flights in and around the national capital air quality control region (Washington, D.C.). The correlation interferometer data, the infrared Fourier spectrometer data, and the integrated altitude sampling data showed agreement within the errors of the individual measurements. High values for CO were found from the D.C. flight data to be reproducible and concentrated in areas of stop-and-go traffic. It is concluded, that pollutants at low altitudes are detectable from an air-borne platform by remote correlation interferometry and that the correlation interferometer measurements agree with ground- and air-truth data.

Effects of stray lights on Faraday rotation measurement for polarimeter-interferometer system on EAST.

PubMed

Zou, Z Y; Liu, H Q; Ding, W X; Chen, J; Brower, D L; Lian, H; Wang, S X; Li, W M; Yao, Y; Zeng, L; Jie, Y X

2018-01-01

A double-pass radially view 11 chords polarimeter-interferometer system has been operated on the experimental advanced superconducting tokamak and provides important current profile information for plasma control. Stray light originating from spurious reflections along the optical path (unwanted reflections from various optical components/mounts and transmissive optical elements such as windows, waveplates, and lens as well as the detectors) and also direct feedback from the retro-reflector used to realize the double-pass configuration can both contribute to contamination of the Faraday rotation measurement accuracy. Modulation of the Faraday rotation signal due to the interference from multiple reflections is observable when the interferometer phase (plasma density) varies with time. Direct reflection from the detector itself can be suppressed by employing an optical isolator consisting of a λ/4-waveplate and polarizer positioned in front of the mixer. A Faraday angle oscillation during the density ramping up (or down) can be reduced from 5°-10° to 1°-2° by eliminating reflections from the detector. Residual modulation arising from misalignment and stray light from other sources must be minimized to achieve accurate measurements of Faraday rotation.

UAVSAR Active Electronically Scanned Array

NASA Technical Reports Server (NTRS)

Sadowy, Gregory, A.; Chamberlain, Neil F.; Zawadzki, Mark S.; Brown, Kyle M.; Fisher, Charles D.; Figueroa, Harry S.; Hamilton, Gary A.; Jones, Cathleen E.; Vorperian, Vatche; Grando, Maurio B.

2011-01-01

The Uninhabited Airborne Vehicle Synthetic Aperture Radar (UAVSAR) is a pod-based, L-band (1.26 GHz), repeatpass, interferometric, synthetic aperture radar (InSAR) used for Earth science applications. Repeat-pass interferometric radar measurements from an airborne platform require an antenna that can be steered to maintain the same angle with respect to the flight track over a wide range of aircraft yaw angles. In order to be able to collect repeat-pass InSAR data over a wide range of wind conditions, UAVSAR employs an active electronically scanned array (AESA). During data collection, the UAVSAR flight software continuously reads the aircraft attitude state measured by the Embedded GPS/INS system (EGI) and electronically steers the beam so that it remains perpendicular to the flight track throughout the data collection

47 CFR 13.201 - Qualifying for a commercial operator license or endorsement.

Code of Federal Regulations, 2014 CFR

2014-10-01

... must pass an examination for the issuance of a new Ship Radar Endorsement. Each application for the... License: Written Elements 1, 3, and 9. (7) Ship Radar Endorsement: Written Element 8. [58 FR 9124, Feb. 19...

47 CFR 13.201 - Qualifying for a commercial operator license or endorsement.

Code of Federal Regulations, 2013 CFR

2013-10-01

... must pass an examination for the issuance of a new Ship Radar Endorsement. Each application for the... License: Written Elements 1, 3, and 9. (7) Ship Radar Endorsement: Written Element 8. [58 FR 9124, Feb. 19...

Analysis of the detection materials as resonant pads for attaching the measuring arm of the interferometer when sensing mechanical vibrations

NASA Astrophysics Data System (ADS)

Nedoma, Jan; Fajkus, Marcel; Martinek, Radek; Zboril, Ondrej; Bednarek, Lukas; Novak, Martin; Witas, Karel; Vasinek, Vladimir

2017-05-01

Fiber-optic sensors (FOS), today among the most widespread measuring sensors and during various types of measuring, are irreplaceable. Among the distinctive features include immunity to electromagnetic interference, passivity regarding power supply and high sensitivity. One of the representatives FOS is the interferometric sensors working on the principle of interference of light. Authors of this article focused on the analysis of the detection material as resonant pads for attaching the measuring arm of the interferometer when sensing mechanical vibrations (low frequencies). A typical example is the use of interferometer sensors in automobile traffic while sensing a vibration response from the roadway while passing the cars. For analysis was used sensor with Mach-Zehnder interferometer. Defined were different detection materials about different size and thickness. We analyzed the influence on the sensitivity (amplitude response) of the interferometer. Based on the results we have defined the best material for sensing mechanical vibrations. The signal was processed by applications created in LabView development environment. The results were verified by repeated testing in laboratory conditions.

Advances in Ice Penetrating Radar

NASA Astrophysics Data System (ADS)

Paden, J. D.

2016-12-01

Radars have been employed for ice remote sensing since the mid-twentieth century. The original application in radioglaciology was to obtain ice thickness: an essential parameter in ice flux calculations and boundary condition in ice flow models. Later, radars were used to estimate basal conditions and track laterally persistent features in the ice. The Center for Remote Sensing of Ice Sheet's recent hardware advances include multichannel systems and radar suites covering the usable frequency spectrum. These advances coupled with increased interest in the polar regions result in a concomitant exponential growth in data. We focus on a few results that have come from these changes. Multichannel radar systems improved clutter rejection and enabled 3D imaging. Using computer vision algorithms, we have automated the process of extracting the ice bottom surface in 3D imagery for complex topographies including narrow glacier channels where the ice surface and ice bottom merge together within the 3D images. We present results of wide swath imaging which have enabled narrow, 2-3 km wide, glacier channels to be fully imaged in a single pass. When radar data are available across the frequency spectrum, we have the ability to enhance target detection and measure frequency dependent properties. For example, we can couple HF sounder measurements in warmer ice where scattering attenuates and hides the signal of interest with VHF sounder measurements in cooler ice which have much improved resolution from a single flight line. We present examples of improved bed detection with coupled HF and VHF imagery in a temperate to cold ice transition that show the strong frequency dependence of englacial scattering. To handle the increased data rate, we developed a standard processing chain and data product for CReSIS radar systems, including legacy systems. Application specific GIS tools are an essential part and enable us to merge other data products during data analysis. By using imagery, gravity, mass conservation, etc., we improve the accuracy of ice bottom tracking. We present examples of the integration of these information sources to produce improved ice thickness estimates and show examples of data products which span more than two decades.

Absolute metrology for space interferometers

NASA Astrophysics Data System (ADS)

Salvadé, Yves; Courteville, Alain; Dändliker, René

2017-11-01

The crucial issue of space-based interferometers is the laser interferometric metrology systems to monitor with very high accuracy optical path differences. Although classical high-resolution laser interferometers using a single wavelength are well developed, this type of incremental interferometer has a severe drawback: any interruption of the interferometer signal results in the loss of the zero reference, which requires a new calibration, starting at zero optical path difference. We propose in this paper an absolute metrology system based on multiplewavelength interferometry.

Instantaneous flow measurements in a supersonic wind tunnel using spectrally resolved Rayleigh scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Buggele, Alvin E.; Reeder, Mark F.

1995-01-01

Results of a feasibility study to apply laser Rayleigh scattering to non-intrusively measure flow properties in a small supersonic wind tunnel are presented. The technique uses an injection seeded, frequency doubled Nd:YAG laser tuned to an absorption band of iodine. The molecular Rayleigh scattered light is filtered with an iodine cell to block light at the laser frequency. The Doppler-shifted Rayleigh scattered light that passes through the iodine cell is analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode. An intensified CCD camera is used to record the images. The images are analyzed at several subregions, where the flow velocity is determined. Each image is obtained with a single laser pulse, giving instantaneous measurements.

Space Radar Image of Long Valley, California in 3-D

NASA Image and Video Library

1999-05-01

This three-dimensional perspective view of Long Valley, California was created from data taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar on board the space shuttle Endeavour. This image was constructed by overlaying a color composite SIR-C radar image on a digital elevation map. The digital elevation map was produced using radar interferometry, a process by which radar data are acquired on different passes of the space shuttle. The two data passes are compared to obtain elevation information. The interferometry data were acquired on April 13,1994 and on October 3, 1994, during the first and second flights of the SIR-C/X-SAR instrument. The color composite radar image was taken in October and was produced by assigning red to the C-band (horizontally transmitted and vertically received) polarization; green to the C-band (vertically transmitted and received) polarization; and blue to the ratio of the two data sets. Blue areas in the image are smooth and yellow areas are rock outcrops with varying amounts of snow and vegetation. The view is looking north along the northeastern edge of the Long Valley caldera, a volcanic collapse feature created 750,000 years ago and the site of continued subsurface activity. Crowley Lake is the large dark feature in the foreground. http://photojournal.jpl.nasa.gov/catalog/PIA01769

Cascaded-cavity Fabry-Perot interferometer for simultaneous measurement of temperature and strain with cross-sensitivity compensation

NASA Astrophysics Data System (ADS)

Tian, Jiajun; Jiao, Yuzhu; Ji, Shaobo; Dong, Xiaolong; Yao, Yong

2018-04-01

We propose and demonstrate a fiber sensor for simultaneous temperature and strain measurements. The proposed sensor is implemented by a cascaded-cavity Fabry-Perot (FP) fiber interferometer. The two cascaded FP cavities comprise a micro-air-cavity in a hollow-core tube fiber and a micro-silica-cavity in a standard single-mode fiber. To separate the interference spectrum of each FP cavity, the total spectrum is filtered in the frequency domain through band-pass filters, whose central frequencies were predesigned based on the relationship between the spatial frequency and free spectral range of each FP cavity. The different cross-sectional areas and thermal-optic coefficients of the two FP cavities confer different sensitivities to temperature and strain. Both parameters were measured simultaneously by tracking the wavelength shifts in the filtered interference spectra of the FP cavities. Moreover, the temperature-strain cross-sensitivity was compensated by solving a sensitivity-coefficient matrix equation for the two cavities, using the calibrated temperatures and strains. Other advantages of the proposed sensor are simple fabrication and an all-fiber structure. Owing to these properties, the proposed sensor is potentially applicable to real sensing applications.

The transmission of symmetric 40 Gb/s TWDM-based NG-PON2 utilizing delay interferometer (DI) for RSOA bandwidth enhancement

NASA Astrophysics Data System (ADS)

Bindhaiq, Salem; Zulkifli, Nadiatulhuda; Supa'at, AbuSahmah M.

2016-07-01

Time and wavelength-division multiplexed passive optical network (TWDM-PON) has been finally selected as the pragmatic solution for the next-generation passive optical network stage 2 (NG-PON2). In this paper, we propose a symmetric 40 Gb/s TWDM-PON system with low cost reflective semiconductor optical amplifier (RSOA) for both downstream and upstream directions. A single bi-pass delay interferometer (DI), deployed in the optical line terminal (OLT), is used to enhance the poor performance of the RSOA with respect to the low bandwidth induced by laser chirp. With the help of the 40 GHz free spectrum range (FSR) DI, we show a successful transmission of the proposed work through simulation study where an aggregate capacity of 40 Gb/s is transported over 40 km transmission distance with 32 splits. The TWDM-PON system at BER of 10-6 has shown a minimum receiver sensitivity of -22.78 dBm and -22.71 dBm for both downstream and upstream, respectively with maximum power penalty of 2 dB for downstream channel and 2.39 dB for upstream channel.

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

NASA Technical Reports Server (NTRS)

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

2003-01-01

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

Frequency-tuned microwave photon counter based on a superconductive quantum interferometer

NASA Astrophysics Data System (ADS)

Shnyrkov, V. I.; Yangcao, Wu; Soroka, A. A.; Turutanov, O. G.; Lyakhno, V. Yu.

2018-03-01

Various types of single-photon counters operating in infrared, ultraviolet, and optical wavelength ranges are successfully used to study electromagnetic fields, analyze radiation sources, and solve problems in quantum informatics. However, their operating principles become ineffective at millimeter band, S-band, and ultra-high frequency bands of wavelengths due to the decrease in quantum energy by 4-5 orders of magnitude. Josephson circuits with discrete Hamiltonians and qubits are a good foundation for the construction of single-photon counters at these frequencies. This paper presents a frequency-tuned microwave photon counter based on a single-junction superconducting quantum interferometer and flux qutrit. The control pulse converts the interferometer into a two-level system for resonance absorption of photons. Decay of the photon-induced excited state changes the magnetic flux in the interferometer, which is measured by a SQUID magnetometer. Schemes for recording the magnetic flux using a DC SQUID or ideal parametric detector, based on a qutrit with high-frequency excitation, are discussed. It is shown that the counter consisting of an interferometer with a Josephson junction and a parametric detector demonstrates high performance and is capable of detecting single photons in a microwave band.

Meteorological radar services: a brief discussion and a solution in practice

NASA Astrophysics Data System (ADS)

Nicolaides, K. A.

2014-08-01

The Department of Meteorology is the organization designated by the Civil Aviation Department and by the National Supervisory Authority of the Republic of Cyprus, as an air navigation service provider, based on the regulations of the Single European Sky. Department of Meteorology holds and maintains also an ISO: 9001/2008, Quality System, for the provision of meteorological and climatological services to aeronautic and maritime community, but also to the general public. In order to fulfill its obligations the Department of Meteorology customs the rather dense meteorological stations network, with long historical data series, installed and maintained by the Department, in parallel with modelling and Numerical Weather Prediction (NWP), along with training and gaining of expertise. Among the available instruments in the community of meteorologists is the meteorological radar, a basic tool for the needs of very short/short range forecasting (nowcasting). The Department of Meteorology installed in the mid 90's a C-band radar over «Throni» location and expanded its horizons in nowcasting, aviation safety and warnings issuance. The radar has undergone several upgrades but today technology has over passed its rather old technology. At the present the Department of Meteorology is in the process of buying Meteorological Radar Services as a result of a public procurement procedure. Two networked X-band meteorological radar will be installed (the project now is in the phase of infrastructure establishment while the hardware is in the process of assemble), and maintained from Space Hellas (the contractor) for a 13 years' time period. The present article must be faced as a review article of the efforts of the Department of Meteorology to support its weather forecasters with data from meteorological radar.

Determining Snow Depth Using Airborne Multi-Pass Interferometric Synthetic Aperture Radar

DTIC Science & Technology

2013-09-01

relatively low resolution 10m DEM of the survey area was obtained from the USDA NAIP and then geocorrected to match the SAR image area. Centered on...Propulsion Laboratory LiDAR Light Detection and Ranging METAR Meteorological reporting observations medivac Medical Evacuation NASA National...Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X- SAR) mission was a joint National Aeronautical and Space Administration ( NASA

Electro-Optics and Millimeter-Wave Technology in Japan.

DTIC Science & Technology

1987-05-01

and communication set is about the price of a car airconditioner . a The GPS could be used in an interferometer application for seismic studies to...COMMUNICATIONS SYSTEM.................. 2-16 10 BATTLE COMMUNICATIONS SYSTEMS ....................... 2-17 11 OPTICAL MODULE PARAMETERS .............. 2-18 12...Conduct follow-up visits to Japanese industries in high interest areas (e.g., displays, radar modules , detectors, and fiber optics), * Visit additional

Phase shift in atom interferometry due to spacetime curvature

NASA Astrophysics Data System (ADS)

Overstreet, Chris; Asenbaum, Peter; Kovachy, Tim; Brown, Daniel; Hogan, Jason; Kasevich, Mark

2017-04-01

In previous matter wave interferometers, the interferometer arm separation was small enough that gravitational tidal forces across the arms can be neglected. Gravitationally-induced phase shifts in such experiments arise from the acceleration of the interfering particles with respect to the interferometer beam splitters and mirrors. By increasing the interferometer arm separation, we enter a new regime in which the arms experience resolvably different gravitational forces. Using a single-source gravity gradiometer, we measure a phase shift associated with the tidal forces induced by a nearby test mass. This is the first observation of spacetime curvature across the spatial extent of a single quantum system. CO acknowledges funding from the Stanford Graduate Fellowship.

Transport phenomena in helical edge state interferometers: A Green's function approach

NASA Astrophysics Data System (ADS)

Rizzo, Bruno; Arrachea, Liliana; Moskalets, Michael

2013-10-01

We analyze the current and the shot noise of an electron interferometer made of the helical edge states of a two-dimensional topological insulator within the framework of nonequilibrium Green's functions formalism. We study, in detail, setups with a single and with two quantum point contacts inducing scattering between the different edge states. We consider processes preserving the spin as well as the effect of spin-flip scattering. In the case of a single quantum point contact, a simple test based on the shot-noise measurement is proposed to quantify the strength of the spin-flip scattering. In the case of two single point contacts with the additional ingredient of gate voltages applied within a finite-size region at the top and bottom edges of the sample, we identify two types of interference processes in the behavior of the currents and the noise. One such process is analogous to that taking place in a Fabry-Pérot interferometer, while the second one corresponds to a configuration similar to a Mach-Zehnder interferometer. In the helical interferometer, these two processes compete.

Reconfiguration of the multiwavelength operation of optical fiber ring lasers by the modifiable intra-cavity induced losses of an in-fiber tip probe modal Michelson interferometer

NASA Astrophysics Data System (ADS)

Salceda-Delgado, G.; Martinez-Rios, A.; Sierra-Hernandez, J. M.; Rodríguez-Carreón, V. C.; Toral-Acosta, D.; Selvas-Aguilar, R.; Álvarez-Tamayo, R. I.; Castillo-Guzman, A. A.; Rojas-Laguna, R.

2018-03-01

A straightforward and versatile method for switching from single to different multiwavelength laser emission in ring cavity fiber lasers is proposed and demonstrated experimentally. The method is based on using the changeable interference pattern from an optical fiber modal Michelson interferometer as a wavelength selective filter into the ring cavity laser. The interferometer is constructed using a bi-conical tapered fiber and a single-mode fiber segment, with these being spliced together to form an optical fiber tip probe. When the length of the single-mode fiber piece is modified, the phase difference between the interfering modes of the interferometer causes a change in the interferometer free spectral range. As a consequence, the laser intra-cavity losses lead to gain competition, which allows us to adjust the number of simultaneously generated laser lines. A multiwavelength reconfiguration of the laser from one up to a maximum of eight emission lines was obtained, with a maximum SNR of around 47 dBm.

Photo radar speed enforcement in a state highway work zone : demonstration project Yeon Avenue.

DOT National Transportation Integrated Search

2010-04-01

The 2007 Oregon legislative assembly passed House Bill 2466, allowing the Oregon Department of Transportation to use photo radar in ODOT work zones on non-interstate state highways and required ODOT to report back to them on the safety impacts of thi...

Nonlocal polarization interferometer for entanglement detection

DOE PAGES

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

2014-10-30

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. In conclusion, wemore » present the relevant theory and experimental results.« less

High accuracy step gauge interferometer

NASA Astrophysics Data System (ADS)

Byman, V.; Jaakkola, T.; Palosuo, I.; Lassila, A.

2018-05-01

Step gauges are convenient transfer standards for the calibration of coordinate measuring machines. A novel interferometer for step gauge calibrations implemented at VTT MIKES is described. The four-pass interferometer follows Abbe’s principle and measures the position of the inductive probe attached to a measuring head. The measuring head of the instrument is connected to a balanced boom above the carriage by a piezo translation stage. A key part of the measuring head is an invar structure on which the inductive probe and the corner cubes of the measuring arm of the interferometer are attached. The invar structure can be elevated so that the probe is raised without breaking the laser beam. During probing, the bending of the probe and the interferometer readings are recorded and the measurement face position is extrapolated to zero force. The measurement process is fully automated and the face positions of the steps can be measured up to a length of 2 m. Ambient conditions are measured continuously and the refractive index of air is compensated for. Before measurements the step gauge is aligned with an integrated 2D coordinate measuring system. The expanded uncertainty of step gauge calibration is U=\\sqrt{{{(64 nm)}2}+{{(88× {{10}-9}L)}2}} .

Compact atom interferometer using single laser

NASA Astrophysics Data System (ADS)

Chiow, Sheng-wey; Yu, Nan

2018-06-01

A typical atom interferometer requires vastly different laser frequencies at different stages of operation, e.g., near resonant light for laser cooling and far detuned light for atom optics, such that multiple lasers are typically employed. The number of laser units constrains the achievable minimum size and power in practical devices for resource critical environments such as space. We demonstrate a compact atom interferometer accelerometer operated by a single diode laser. This is achieved by dynamically changing the laser output frequency in GHz range while maintaining spectroscopic reference to an atomic transition via a sideband generated by phase modulation. At the same time, a beam path sharing configuration is also demonstrated for a compact sensor head design, in which atom interferometer beams share the same path as that of the cooling beam. This beam path sharing also significantly simplifies three-axis atomic accelerometry in microgravity using single sensor head.

Apparatus and method for measuring fluorescence intensities at a plurality of wavelengths and lifetimes

DOEpatents

Buican, T.N.

1993-05-04

Apparatus and method is described for measuring intensities at a plurality of wavelengths and lifetimes. A source of multiple-wavelength electromagnetic radiation is passed through a first interferometer modulated at a first frequency, the output thereof being directed into a sample to be investigated. The light emitted from the sample as a result of the interaction thereof with the excitation radiation is directed into a second interferometer modulated at a second frequency, and the output detected and analyzed. In this manner excitation, emission, and lifetime information may be obtained for a multiplicity of fluorochromes in the sample.

Two-photon interference of temporally separated photons.

PubMed

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2016-10-06

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms.

Gas Laser Interferometer in the Electric Conversion Laboratory

NASA Image and Video Library

1966-10-21

Richard Lancashire operates a gas laser interferometer in the Electric Conversion Laboratory at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Lewis was in the midst of a long-term effort to develop methods of delivering electrical power to spacecraft using nuclear, solar, or electrochemical technologies. Lancashire was measuring the thermionic diode’s plasma particle density. The thermionic diodes were being studied for possible use in radioisotope thermoelectric generators for use in space. Microwave interferometry was one method of measuring transient plasmas. The interferometer measured the difference between the frequencies of two laser beams, one of which passed through the diode. The electron density was measured by revealing the phase shift of the transmitted microwave beam brought about by a change in the plasma refraction. Microwave interferometry, however, offers poor spatial resolution and has limited range of applicability.

Identifying On-Orbit Test Targets for Space Fence Operational Testing

NASA Astrophysics Data System (ADS)

Pechkis, D.; Pacheco, N.; Botting, T.

2014-09-01

Space Fence will be an integrated system of two ground-based, S-band (2 to 4 GHz) phased-array radars located in Kwajalein and perhaps Western Australia [1]. Space Fence will cooperate with other Space Surveillance Network sensors to provide space object tracking and radar characterization data to support U.S. Strategic Command space object catalog maintenance and other space situational awareness needs. We present a rigorous statistical test design intended to test Space Fence to the letter of the program requirements as well as to characterize the system performance across the entire operational envelope. The design uses altitude, size, and inclination as independent factors in statistical tests of dependent variables (e.g., observation accuracy) linked to requirements. The analysis derives the type and number of necessary test targets. Comparing the resulting sample sizes with the number of currently known targets, we identify those areas where modelling and simulation methods are needed. Assuming hypothetical Kwajalein radar coverage and a conservative number of radar passes per object per day, we conclude that tests involving real-world space objects should take no more than 25 days to evaluate all operational requirements; almost 60 percent of the requirements can be tested in a single day and nearly 90 percent can be tested in one week or less. Reference: [1] L. Haines and P. Phu, Space Fence PDR Concept Development Phase, 2011 AMOS Conference Technical Papers.

Spherical grating monochromator with interferometer control and in-vacuum reference

NASA Astrophysics Data System (ADS)

Holly, D. J.; Mason, W. P.; Sailor, T.; Smith, R. E.; Wahl, D.

2002-03-01

Physical Science Laboratory's new generation of spherical grating monochromators incorporates a laser interferometer to control scan angle and an in-vacuum absolute angle reference, as well as other improvements. The design accommodates up to six gratings which can be moved axially (under motor control, with encoder position readback) at any scan angle. The gratings are cooled by means of spring-loaded clamps which conduct heat to a water-cooled plate. The instruments feature hollow roller bearings on the scan axis to minimize bearing runout, and a pseudosine-bar drive for precise control of grating angle. The interferometer angle-measuring optics are mounted inside the vacuum chamber and measure the angle between the grating scan axis and the instrument's granite base. The laser interferometer measures the grating angle with a resolution of approximately 0.02 arcsec over the entire scan range of 40°. To provide a reference for the interferometer angle measurement, we have built an in-vacuum optical reference which uses custom chrome-on-glass reticles mounted inside the vacuum chamber. Collimated light from a source outside the vacuum passes through the reticles to yield quadrature signals which precisely define an absolute reference angle for the interferometer. Repeatability of the grating angle is within a range of ±0.05 arcsec. Two of these instruments are in operation at SRRC (Taiwan) and a third instrument has been delivered to NSLS (Brookhaven).

Optical fiber tip interferometer gas pressure sensor based on anti-resonant reflecting guidance mechanism

NASA Astrophysics Data System (ADS)

Yang, Y. B.; Wang, D. N.; Xu, Ben; Wang, Z. K.

2018-05-01

We propose and demonstrate a gas pressure sensor based on an anti-resonant reflecting guidance (ARRG) mechanism in quartz capillary tube with an open cavity. The device is simple in fabrication by only fusion splicing a segment of capillary tube with single mode fiber. It has compact size, robust structure, convenient mode of operation, and high sensitivity of 4.278 nm/MPa. Moreover, as two Faby-Perot cavities exist in the device, which create the interference spectrum with several distinct resonance dips, a simultaneous gas pressure and temperature detection can be readily achieved by tracing two dip wavelengths. The error in the measurement due to the choice of different resonant dips can be effectively reduced by using the Fourier band pass filtering method.

Neutral winds in the polar thermosphere as measured from Dynamics Explorer

NASA Technical Reports Server (NTRS)

Killeen, T. L.; Hays, P. B.; Spencer, N. W.; Wharton, L. E.

1982-01-01

Remote sensing measurements of the meridional thermospheric neutral wind using the Fabry-Perot Interferometer on Dynamics Explorer have been combined with in-situ measurements of the zonal component using the Wind and Temperature Spectrometer on the same spacecraft. The two data sets with appropriate spatial phasing and averaging determine the vector wind along the track of the polar orbiting spacecraft. A study of fifty-eight passes over the Southern (sunlit) pole has enabled the average Universal Time dependence of the wind field to be determined for essentially a single solar local time cut. The results show the presence of a 'back-ground' wind field driven by solar EUV heating upon which is superposed a circulating wind field driven by high latitude momentum and energy sources.

Exploring Alternate Parameterizations for Snowfall with Validation from Satellite and Terrestrial Radars

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Dembek, Scott R.; Jedlovec, Gary J.

2009-01-01

Increases in computational resources have allowed operational forecast centers to pursue experimental, high resolution simulations that resolve the microphysical characteristics of clouds and precipitation. These experiments are motivated by a desire to improve the representation of weather and climate, but will also benefit current and future satellite campaigns, which often use forecast model output to guide the retrieval process. Aircraft, surface and radar data from the Canadian CloudSat/CALIPSO Validation Project are used to check the validity of size distribution and density characteristics for snowfall simulated by the NASA Goddard six-class, single-moment bulk water microphysics scheme, currently available within the Weather Research and Forecast (WRF) Model. Widespread snowfall developed across the region on January 22, 2007, forced by the passing of a midlatitude cyclone, and was observed by the dual-polarimetric, C-band radar King City, Ontario, as well as the NASA 94 GHz CloudSat Cloud Profiling Radar. Combined, these data sets provide key metrics for validating model output: estimates of size distribution parameters fit to the inverse-exponential equations prescribed within the model, bulk density and crystal habit characteristics sampled by the aircraft, and representation of size characteristics as inferred by the radar reflectivity at C- and W-band. Specified constants for distribution intercept and density differ significantly from observations throughout much of the cloud depth. Alternate parameterizations are explored, using column-integrated values of vapor excess to avoid problems encountered with temperature-based parameterizations in an environment where inversions and isothermal layers are present. Simulation of CloudSat reflectivity is performed by adopting the discrete-dipole parameterizations and databases provided in literature, and demonstrate an improved capability in simulating radar reflectivity at W-band versus Mie scattering assumptions.

GeoSAR: A Radar Terrain Mapping System for the New Millennium

NASA Technical Reports Server (NTRS)

Thompson, Thomas; vanZyl, Jakob; Hensley, Scott; Reis, James; Munjy, Riadh; Burton, John; Yoha, Robert

2000-01-01

GeoSAR Geographic Synthetic Aperture Radar) is a new 3 year effort to build a unique, dual-frequency, airborne Interferometric SAR for mapping of terrain. This is being pursued via a Consortium of the Jet Propulsion Laboratory (JPL), Calgis, Inc., and the California Department of Conservation. The airborne portion of this system will operate on a Calgis Gulfstream-II aircraft outfitted with P- and X-band Interferometric SARs. The ground portions of this system will be a suite of Flight Planning Software, an IFSAR Processor and a Radar-GIS Workstation. The airborne P-band and X-band radars will be constructed by JPL with the goal of obtaining foliage penetration at the longer P-band wavelengths. The P-band and X-band radar will operate at frequencies of 350 Mhz and 9.71 Ghz with bandwidths of either 80 or 160 Mhz. The airborne radars will be complemented with airborne laser system for measuring antenna positions. Aircraft flight lines and radar operating instructions will be computed with the Flight Planning Software The ground processing will be a two-step step process. First, the raw radar data will be processed into radar images and interferometer derived Digital Elevation Models (DEMs). Second, these radar images and DEMs will be processed with a Radar GIS Workstation which performs processes such as Projection Transformations, Registration, Geometric Adjustment, Mosaicking, Merging and Database Management. JPL will construct the IFSAR Processor and Calgis, Inc. will construct the Radar GIS Workstation. The GeoSAR Project was underway in November 1996 with a goal of having the radars and laser systems fully integrated onto the Calgis Gulfstream-II aircraft in early 1999. Then, Engineering Checkout and Calibration-Characterization Flights will be conducted through November 1999. The system will be completed at the end of 1999 and ready for routine operations in the year 2000.

3D Imaging and Automated Ice Bottom Tracking of Canadian Arctic Archipelago Ice Sounding Data

NASA Astrophysics Data System (ADS)

Paden, J. D.; Xu, M.; Sprick, J.; Athinarapu, S.; Crandall, D.; Burgess, D. O.; Sharp, M. J.; Fox, G. C.; Leuschen, C.; Stumpf, T. M.

2016-12-01

The basal topography of the Canadian Arctic Archipelago ice caps is unknown for a number of the glaciers which drain the ice caps. The basal topography is needed for calculating present sea level contribution using the surface mass balance and discharge method and to understand future sea level contributions using ice flow model studies. During the NASA Operation IceBridge 2014 arctic campaign, the Multichannel Coherent Radar Depth Sounder (MCoRDS) used a three transmit beam setting (left beam, nadir beam, right beam) to illuminate a wide swath across the ice glacier in a single pass during three flights over the archipelago. In post processing we have used a combination of 3D imaging methods to produce images for each of the three beams which are then merged to produce a single digitally formed wide swath beam. Because of the high volume of data produced by 3D imaging, manual tracking of the ice bottom is impractical on a large scale. To solve this problem, we propose an automated technique for extracting ice bottom surfaces by viewing the task as an inference problem on a probabilistic graphical model. We first estimate layer boundaries to generate a seed surface, and then incorporate additional sources of evidence, such as ice masks, surface digital elevation models, and feedback from human users, to refine the surface in a discrete energy minimization formulation. We investigate the performance of the imaging and tracking algorithms using flight crossovers since crossing lines should produce consistent maps of the terrain beneath the ice surface and compare manually tracked "ground truth" to the automated tracking algorithms. We found the swath width at the nominal flight altitude of 1000 m to be approximately 3 km. Since many of the glaciers in the archipelago are narrower than this, the radar imaging, in these instances, was able to measure the full glacier cavity in a single pass.

Single-photon test of hyper-complex quantum theories using a metamaterial.

PubMed

Procopio, Lorenzo M; Rozema, Lee A; Wong, Zi Jing; Hamel, Deny R; O'Brien, Kevin; Zhang, Xiang; Dakić, Borivoje; Walther, Philip

2017-04-21

In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although this has so far proven sufficient to predict experimental results, there is no theoretical reason to choose them over real numbers or generalizations of complex numbers, that is, hyper-complex numbers. Experiments performed to date have proven that real numbers are insufficient, but the need for hyper-complex numbers remains an open question. Here we experimentally probe hyper-complex quantum theories, studying one of their deviations from complex quantum theory: the non-commutativity of phases. We do so by passing single photons through a Sagnac interferometer containing both a metamaterial with a negative refractive index, and a positive phase shifter. To accomplish this we engineered a fishnet metamaterial to have a negative refractive index at 780 nm. We show that the metamaterial phase commutes with other phases with high precision, allowing us to place limits on a particular prediction of hyper-complex quantum theories.

Single-photon test of hyper-complex quantum theories using a metamaterial

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

Procopio, Lorenzo M.; Rozema, Lee A.; Wong, Zi Jing

In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although this has so far proven sufficient to predict experimental results, there is no theoretical reason to choose them over real numbers or generalizations of complex numbers, that is, hyper-complex numbers. Experiments performed to date have proven that real numbers are insufficient, but the need for hyper-complex numbers remains an open question. Here we experimentally probe hyper-complex quantum theories, studying one of their deviations from complex quantum theory: the non-commutativity of phases. We do so by passing single photons through a Sagnac interferometer containing both a metamaterial withmore » a negative refractive index, and a positive phase shifter. In order to accomplish this we engineered a fishnet metamaterial to have a negative refractive index at 780 nm. Here, we show that the metamaterial phase commutes with other phases with high precision, allowing us to place limits on a particular prediction of hyper-complex quantum theories.« less

Single-photon test of hyper-complex quantum theories using a metamaterial

DOE PAGES

Procopio, Lorenzo M.; Rozema, Lee A.; Wong, Zi Jing; ...

2017-04-21

In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although this has so far proven sufficient to predict experimental results, there is no theoretical reason to choose them over real numbers or generalizations of complex numbers, that is, hyper-complex numbers. Experiments performed to date have proven that real numbers are insufficient, but the need for hyper-complex numbers remains an open question. Here we experimentally probe hyper-complex quantum theories, studying one of their deviations from complex quantum theory: the non-commutativity of phases. We do so by passing single photons through a Sagnac interferometer containing both a metamaterial withmore » a negative refractive index, and a positive phase shifter. In order to accomplish this we engineered a fishnet metamaterial to have a negative refractive index at 780 nm. Here, we show that the metamaterial phase commutes with other phases with high precision, allowing us to place limits on a particular prediction of hyper-complex quantum theories.« less

Single-photon test of hyper-complex quantum theories using a metamaterial

PubMed Central

Procopio, Lorenzo M.; Rozema, Lee A.; Wong, Zi Jing; Hamel, Deny R.; O'Brien, Kevin; Zhang, Xiang; Dakić, Borivoje; Walther, Philip

2017-01-01

In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although this has so far proven sufficient to predict experimental results, there is no theoretical reason to choose them over real numbers or generalizations of complex numbers, that is, hyper-complex numbers. Experiments performed to date have proven that real numbers are insufficient, but the need for hyper-complex numbers remains an open question. Here we experimentally probe hyper-complex quantum theories, studying one of their deviations from complex quantum theory: the non-commutativity of phases. We do so by passing single photons through a Sagnac interferometer containing both a metamaterial with a negative refractive index, and a positive phase shifter. To accomplish this we engineered a fishnet metamaterial to have a negative refractive index at 780 nm. We show that the metamaterial phase commutes with other phases with high precision, allowing us to place limits on a particular prediction of hyper-complex quantum theories. PMID:28429711

Surface Deformation and Coherence Measurements of Kilauea Volcano, Hawaii, from SIR-C Radar Interferometry

NASA Technical Reports Server (NTRS)

Rosen, P. A.; Hensley, S.; Zebker, H. A.; Webb, F. H.; Fielding, E. J.

1996-01-01

The shuttle imaging radar C/X synthetic aperture radar (SIR-C/X-SAR) radar on board the space shuttle Endeavor imaged Kilauea Volcano, Hawaii, in April and October 1994 for the purpose of measuring active surface deformation by the methods of repeat-pass differential radar interferometry. Observations at 24 cm (L band) and 5.6 cm (C band) wavelengths were reduced to interferograms showing apparent surface deformation over the 6-month interval and over a succession of 1-day intervals in October. A statistically significant local phase signature in the 6-month interferogram is coincident with the Pu'u O'o lava vent. Interpreted as deformation, the signal implies centimeter-scale deflation in an area several kilometers wide surrounding the vent. Peak deflation is roughly 14 cm if the deformation is purely vertical, centered southward of the Pu'u O'o caldera. Delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures, at the level of 12 cm peak-to-peak in the radar line-of-sight direction. Though the phase observations are suggestive of the wide-area deformation measured by Global Positioning System (GPS) methods, the atmospheric effects are large enough to limit the interpretation of the result. It is difficult to characterize centimeter-scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous, spatially distributed measurements of reactivity along the radar line of sight. Studies of the interferometric correlation of images acquired at different times show that L band is far superior to C band in the vegetated areas, even when the observations are separated by only 1 day. These results imply longer wavelength instruments are more appropriate for studying surfaces by repeat-pass observations.

Observation of the quantum paradox of separation of a single photon from one of its properties

NASA Astrophysics Data System (ADS)

Ashby, James M.; Schwarz, Peter D.; Schlosshauer, Maximilian

2016-07-01

We report an experimental realization of the quantum paradox of the separation of a single photon from one of its properties (the so-called "quantum Cheshire cat"). We use a modified Sagnac interferometer with displaced paths to produce appropriately pre- and postselected states of heralded single photons. Weak measurements of photon presence and circular polarization are performed in each arm of the interferometer by introducing weak absorbers and small polarization rotations and analyzing changes in the postselected signal. The absorber is found to have an appreciable effect only in one arm of the interferometer, while the polarization rotation significantly affects the signal only when performed in the other arm. We carry out both sequential and simultaneous weak measurements and find good agreement between measured and predicted weak values. In the language of Aharonov et al. and in the sense of the ensemble averages described by weak values, the experiment establishes the separation of a particle from one its properties during the passage through the interferometer.

All-fiber Mach-Zehnder type interferometers formed in photonic crystal fiber

NASA Astrophysics Data System (ADS)

Choi, Hae Young; Kim, Myoung Jin; Lee, Byeong Ha

2007-04-01

We propose simple and compact methods for implementing all-fiber interferometers. The interference between the core and the cladding modes of a photonic crystal fiber (PCF) is utilized. To excite the cladding modes from the fundamental core mode of a PCF, a coupling point or region is formed by using two methods. One is fusion splicing two pieces of a PCF with a small lateral offset, and the other is partially collapsing the air-holes in a single piece of PCF. By making another coupling point at a different location along the fiber, the proposed all-PCF interferometer is implemented. The spectral response of the interferometer is investigated mainly in terms of its wavelength spectrum. The spatial frequency of the spectrum was proportional to the physical length of the interferometer and the difference between the modal group indices of involved waveguide modes. For the splicing type interferometer, only a single spatial frequency component was dominantly observed, while the collapsing type was associated with several components at a time. By analyzing the spatial frequency spectrum of the wavelength spectrum, the modal group index differences of the PCF were obtained from to . As potential applications of the all-PCF interferometer, strain sensing is experimentally demonstrated and ultra-high temperature sensing is proposed.

Atom Interferometry with the Sr Optical Clock Transition.

PubMed

Hu, Liang; Poli, Nicola; Salvi, Leonardo; Tino, Guglielmo M

2017-12-29

We report on the realization of a matter-wave interferometer based on single-photon interaction on the ultranarrow optical clock transition of strontium atoms. We experimentally demonstrate its operation as a gravimeter and as a gravity gradiometer. No reduction of interferometric contrast was observed for a total interferometer time up to ∼10  ms, limited by geometric constraints of the apparatus. Single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of gravitational waves in so far unexplored frequency ranges and to enlighten the boundary between quantum mechanics and general relativity.

Imaging Stellar Surfaces with an Agile 12-Telescopes Visible Interferometer for the VLTI

NASA Astrophysics Data System (ADS)

Woillez, Julien

2018-04-01

Imaging stellar surfaces with an optical interferometer requires a large number of telescopes and the extensive use of the bootstrapping technique to reach the high spatial frequencies where the surface details are revealed. An idea would use all 6 dual-star delay lines of VLTI to deploy an agile 12-telescopes single-mode visible interferometer on the Paranal mountain. The concept relies on single-mode fiber technologies that have been demonstrated by the `OHANA and `OHANA IKI projects. We present the expected performance of this concept and explore its potential for the study of stellar surfaces.

Nano-displacement sensor based on photonic crystal fiber modal interferometer.

PubMed

Dash, Jitendra Narayan; Jha, Rajan; Villatoro, Joel; Dass, Sumit

2015-02-15

A stable nano-displacement sensor based on large mode area photonic crystal fiber (PCF) modal interferometer is presented. The compact setup requires simple splicing of a small piece of PCF with a single mode fiber (SMF). The excitation and recombination of modes is carried out in a single splice. The use of a reflecting target creates an extra cavity that discretizes the interference pattern of the mode interferometer, boosting the displacement resolution to nanometer level. The proposed modal interferometric based displacement sensor is highly stable and shows sensitivity of 32  pm/nm.

Total Lightning Observations within Electrified Snowfall using Polarimetric Radar LMA, and NWN Measurements

NASA Technical Reports Server (NTRS)

Schultz, Christopher J.; Bruning, Eric C.; Carey, Lawrence D.; Blakeslee, Richard J.

2013-01-01

Tall structures play and important role in development of winter time lightning flashes.To what extent still needs to be assessed. Tower initiated flashes typically occur as banded structures pass near/overhead. Hi resolution RHI s from polarimetric radar show that the lightning has a tendency to propagate through layered structures within these snowstorms.

Single-Pol Synthetic Aperture Radar Terrain Classification using Multiclass Confidence for One-Class Classifiers

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

Koch, Mark William; Steinbach, Ryan Matthew; Moya, Mary M

2015-10-01

Except in the most extreme conditions, Synthetic aperture radar (SAR) is a remote sensing technology that can operate day or night. A SAR can provide surveillance over a long time period by making multiple passes over a wide area. For object-based intelligence it is convenient to segment and classify the SAR images into objects that identify various terrains and man-made structures that we call “static features.” In this paper we introduce a novel SAR image product that captures how different regions decorrelate at different rates. Using superpixels and their first two moments we develop a series of one-class classification algorithmsmore » using a goodness-of-fit metric. P-value fusion is used to combine the results from different classes. We also show how to combine multiple one-class classifiers to get a confidence about a classification. This can be used by downstream algorithms such as a conditional random field to enforce spatial constraints.« less

Refractive index and absorption detector for liquid chromatography based on Fabry-Perot interferometry

DOEpatents

Yeung, E.S.; Woodruff, S.D.

1984-06-19

A refractive index and absorption detector are disclosed for liquid chromatography. It is based in part on a Fabry-Perot interferometer and is used for the improved detection of refractive index and absorption. It includes a Fabry-Perot interferometer having a normally fixed first partially reflecting mirror and a movable second partially reflecting mirror. A chromatographic flow-cell is positioned between the mirrors along the optical axis of a monochromatic laser beam passing through the interferometer. A means for deriving information about the interference fringes coming out of the interferometer is used with a mini-computer to compute the refractive index of the specimen injected into the flow cell. The minicomputer continuously scans the interferometer for continuous refractive index readings and outputs the continuous results of the scans on a chart recorder. The absorption of the specimen can concurrently be scanned by including a second optical path for an excitation laser which will not interfere with the first laser, but will affect the specimen so that absorption properties can be detected. By first scanning for the refractive index of the specimen, and then immediately adding the excitation laser and subsequently scanning for the refractive index again, the absorption of the specimen can be computed and recorded. 10 figs.

Refractive index and absorption detector for liquid chromatography based on Fabry-Perot interferometry

DOEpatents

Yeung, Edward S.; Woodruff, Steven D.

1984-06-19

A refractive index and absorption detector for liquid chromatography. It is based in part on a Fabry-Perot interferometer and is used for the improved detection of refractive index and absorption. It includes a Fabry-Perot interferometer having a normally fixed first partially reflecting mirror and a movable second partially reflecting mirror. A chromatographic flow-cell is positioned between the mirrors along the optical axis of a monochromatic laser beam passing through the interferometer. A means for deriving information about the interference fringes coming out of the interferometer is used with a mini-computer to compute the refractive index of the specimen injected into the flow cell. The minicomputer continuously scans the interferometer for continuous refractive index readings and outputs the continuous results of the scans on a chart recorder. The absorption of the specimen can concurrently be scanned by including a second optical path for an excitation laser which will not interfere with the first laser, but will affect the specimen so that absorption properties can be detected. By first scanning for the refractive index of the specimen, and then immediately adding the excitation laser and subsequently scanning for the refractive index again, the absorption of the specimen can be computed and recorded.

Investigation of the applications of GEOS-3 radar altimeter data in remote sensing of land and sea features

NASA Technical Reports Server (NTRS)

Miller, L. S.

1977-01-01

A number of GEOS-3 passes over the Atlantic Ocean and Southeastern U.S. are examined. Surface-truth and radar altimeter data comparisons are given in terms of surface correlation length, signal fluctuation characteristics, and altitude tracker dynamic response. Detailed analyses are given regarding spatial resolution and its dependency on angular backscatter behavior. These analyses include data from passes over ocean (diffuse scatter), land (large body scatter), and mirror-like inland water areas (pseudo-specular scatter). Altimeter data are examined for a pass over a large reservoir and marsh area of differing water levels; this geometry represents a stepchange in altitude which is usable in determination of the transient response of the tracker. The extent to which pulse-length limited operation pertains over-land is examined. A Wiener filter altitude algorithm is discussed which permits specification of tracker variance and geoidal spectral characteristics during operation.

Mission design for NISAR repeat-pass Interferometric SAR

NASA Astrophysics Data System (ADS)

Alvarez-Salazar, Oscar; Hatch, Sara; Rocca, Jennifer; Rosen, Paul; Shaffer, Scott; Shen, Yuhsyen; Sweetser, Theodore; Xaypraseuth, Peter

2014-10-01

The proposed spaceborne NASA-ISRO SAR (NISAR) mission would use the repeat-pass interferometric Synthetic Aperture Radar (InSAR) technique to measure the changing shape of Earth's surface at the centimeter scale in support of investigations in solid Earth and cryospheric sciences. Repeat-pass InSAR relies on multiple SAR observations acquired from nearly identical positions of the spacecraft as seen from the ground. Consequently, there are tight constraints on the repeatability of the orbit, and given the narrow field of view of the radar antenna beam, on the repeatability of the beam pointing. The quality and accuracy of the InSAR data depend on highly precise control of both orbital position and observatory pointing throughout the science observation life of the mission. This paper describes preliminary NISAR requirements and rationale for orbit repeatability and attitude control in order to meet science requirements. A preliminary error budget allocation and an implementation approach to meet these allocations are also discussed.

Two-photon interference of temporally separated photons

PubMed Central

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2016-01-01

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms. PMID:27708380

Gravitational Wave Detection with Single-Laser Atom Interferometers

NASA Technical Reports Server (NTRS)

Yu, Nan; Tinto, Massimo

2011-01-01

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.

Scientific Infrastructure to Support Atmospheric Science and Aerosol Science for the Department of Energy's Atmospheric Radiation Measurement Programs at Barrow, Alaska.

NASA Astrophysics Data System (ADS)

Lucero, D. A.; Ivey, M.; Helsel, F.; Hardesty, J.; Dexheimer, D.

2015-12-01

Scientific infrastructure to support atmospheric science and aerosol science for the Department of Energy's Atmospheric Radiation Measurement programs at Barrow, Alaska.The Atmospheric Radiation Measurement (ARM) Program's located at Barrow, Alaska is a U.S. Department of Energy (DOE) site. The site provides a scientific infrastructure and data archives for the international Arctic research community. The infrastructure at Barrow has been in place since 1998, with many improvements since then. Barrow instruments include: scanning precipitation Radar-cloud radar, Doppler Lidar, Eddy correlation flux systems, Ceilometer, Manual and state-of-art automatic Balloon sounding systems, Atmospheric Emitted Radiance Interferometer (AERI), Micro-pulse Lidar (MPL), Millimeter cloud radar, High Spectral Resolution Lidar (HSRL) along with all the standard metrological measurements. Data from these instruments is placed in the ARM data archives and are available to the international research community. This poster will discuss what instruments are at Barrow and the challenges of maintaining these instruments in an Arctic site.

AMF3 ARM's Research Facility at Oliktok Point Alaska

NASA Astrophysics Data System (ADS)

Helsel, F.; Lucero, D. A.; Ivey, M.; Dexheimer, D.; Hardesty, J.; Roesler, E. L.

2015-12-01

Scientific Infrastructure To Support Atmospheric Science And Aerosol Science For The Department Of Energy's Atmospheric Radiation Measurement Programs Mobile Facility 3 Located At Oliktok Point, Alaska.The Atmospheric Radiation Measurement (ARM) Program's Mobile Facility 3 (AMF3) located at Oliktok Point, Alaska is a U.S. Department of Energy (DOE) site. The site provides a scientific infrastructure and data archives for the international Arctic research community. The infrastructure at Oliktok is designed to be mobile and it may be relocated in the future to support other ARM science missions. AMF-3 instruments include: scanning precipitation Radar-cloud radar, Raman Lidar, Eddy correlation flux systems, Ceilometer, Balloon sounding system, Atmospheric Emitted Radiance Interferometer (AERI), Micro-pulse Lidar (MPL), Millimeter cloud radar along with all the standard metrological measurements. Data from these instruments is placed in the ARM data archives and are available to the international research community. This poster will discuss what instruments are at AMF3 and the challenges of powering an Arctic site without the use of grid power.

Developments in Science and Technology.

DTIC Science & Technology

1980-01-01

control. Sucessful completion of the testing and cer- a single unduplicated track file, thereby reducing tification of readiness represents a...Navy shipboard surveillance radar systems Service Corp., is called the single radar performance has been successfully designed, developed, and tested at...for Navy deteciion/disclosure ranges. The single radar per- shipboard surveillance radar systems are reduced by formance prediction system can be

Theory and Measurement of Partially Correlated Persistent Scatterers

NASA Astrophysics Data System (ADS)

Lien, J.; Zebker, H. A.

2011-12-01

Interferometric synthetic aperture radar (InSAR) time-series methods can effectively estimate temporal surface changes induced by geophysical phenomena. However, such methods are susceptible to decorrelation due to spatial and temporal baselines (radar pass separation), changes in orbital geometries, atmosphere, and noise. These effects limit the number of interferograms that can be used for differential analysis and obscure the deformation signal. InSAR decorrelation effects may be ameliorated by exploiting pixels that exhibit phase stability across the stack of interferograms. These so-called persistent scatterer (PS) pixels are dominated by a single point-like scatterer that remains phase-stable over the spatial and temporal baseline. By identifying a network of PS pixels for use in phase unwrapping, reliable deformation measurements may be obtained even in areas of low correlation, where traditional InSAR techniques fail to produce useful observations. PS identification is challenging in natural terrain, due to low reflectivity and few corner reflectors. Shanker and Zebker [1] proposed a PS pixel selection technique based on maximum-likelihood estimation of the associated signal-to-clutter ratio (SCR). In this study, we further develop the underlying theory for their technique, starting from statistical backscatter characteristics of PS pixels. We derive closed-form expressions for the spatial, rotational, and temporal decorrelation of PS pixels as a function of baseline and signal-to-clutter ratio. We show that previous decorrelation and critical baseline expressions [2] are limiting cases of our result. We then describe a series of radar scattering simulations and show that the simulated decorrelation matches well with our analytic results. Finally, we use our decorrelation expressions with maximum-likelihood SCR estimation to analyze an area of the Hayward Fault Zone in the San Francisco Bay Area. A series of 38 images of the area were obtained from C-band ERS radar satellite passes between May 1995 and December 2000. We show that the interferogram stack exhibits PS decorrelation trends in agreement with our analytic results. References 1. P. Shanker and H. Zebker, "Persistent scatterer selection using maximum likelihood estimation," Geophysical Research Letters, Vol. 34, L22301, 2007. 2. H. Zebker and J. Villasenor, "Decorrelation in Interferometric Radar Echos," IEEE Transactions on Geoscience and Remote Sensing, Vol. 30, No. 5, Sept. 1992.

Void-Filled SRTM Digital Elevation Model of Afghanistan

USGS Publications Warehouse

Chirico, Peter G.; Barrios, Boris

2005-01-01

EXPLANATION The purpose of this data set is to provide a single consistent elevation model to be used for national scale mapping, GIS, remote sensing applications, and natural resource assessments for Afghanistan's reconstruction. For 11 days in February of 2000, the National Aeronautics and Space Administration (NASA), the National Geospatial-Intelligence Agency ian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed Shuttle Radar Topography Mission (SRTM) DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Afghanistan DEM was gap-filling areas where the SRTM data contained a data void. These void areas are as a result of radar shadow, layover, standing water, and other effects of terrain as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:200,000 - scale Soviet General Staff Topographic Maps which date from the middle to late 1980's. Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and image processing techniques. The data contained in this publication includes SRTM DEM quadrangles projected and clipped in geographic coordinates for the entire country. An index of all available SRTM DEM quadrangles is displayed here: Index_Geo_DD.pdf. Also included are quadrangles projected into their appropriate Universal Transverse Mercator (UTM) projection. The country of Afghanistan spans three UTM Zones: Zone 41, Zone 42, and Zone 43. Maps are stored in their respective UTM Zone projection. Indexes of all available SRTM DEM quadrangles in their respective UTM zone are displayed here: Index_UTM_Z41.pdf, Index_UTM_Z42.pdf, Index_UTM_Z43.pdf.

Noise pair velocity and range echo location system

DOEpatents

Erskine, D.J.

1999-02-16

An echo-location method for microwaves, sound and light capable of using incoherent and arbitrary waveforms of wide bandwidth to measure velocity and range (and target size) simultaneously to high resolution is disclosed. Two interferometers having very long and nearly equal delays are used in series with the target interposed. The delays can be longer than the target range of interest. The first interferometer imprints a partial coherence on an initially incoherent source which allows autocorrelation to be performed on the reflected signal to determine velocity. A coherent cross-correlation subsequent to the second interferometer with the source determines a velocity discriminated range. Dithering the second interferometer identifies portions of the cross-correlation belonging to a target apart from clutter moving at a different velocity. The velocity discrimination is insensitive to all slowly varying distortions in the signal path. Speckle in the image of target and antenna lobing due to parasitic reflections is minimal for an incoherent source. An arbitrary source which varies its spectrum dramatically and randomly from pulse to pulse creates a radar elusive to jamming. Monochromatic sources which jigger in frequency from pulse to pulse or combinations of monochromatic sources can simulate some benefits of incoherent broadband sources. Clutter which has a symmetrical velocity spectrum will self-cancel for short wavelengths, such as the apparent motion of ground surrounding target from a sidelooking airborne antenna. 46 figs.

Noise pair velocity and range echo location system

DOEpatents

Erskine, David J.

1999-01-01

An echo-location method for microwaves, sound and light capable of using incoherent and arbitrary waveforms of wide bandwidth to measure velocity and range (and target size) simultaneously to high resolution. Two interferometers having very long and nearly equal delays are used in series with the target interposed. The delays can be longer than the target range of interest. The first interferometer imprints a partial coherence on an initially incoherent source which allows autocorrelation to be performed on the reflected signal to determine velocity. A coherent cross-correlation subsequent to the second interferometer with the source determines a velocity discriminated range. Dithering the second interferometer identifies portions of the cross-correlation belonging to a target apart from clutter moving at a different velocity. The velocity discrimination is insensitive to all slowly varying distortions in the signal path. Speckle in the image of target and antenna lobing due to parasitic reflections is minimal for an incoherent source. An arbitrary source which varies its spectrum dramatically and randomly from pulse to pulse creates a radar elusive to jamming. Monochromatic sources which jigger in frequency from pulse to pulse or combinations of monochromatic sources can simulate some benefits of incoherent broadband sources. Clutter which has a symmetrical velocity spectrum will self-cancel for short wavelengths, such as the apparent motion of ground surrounding target from a sidelooking airborne antenna.

Mitigation of tropospheric InSAR phase artifacts through differential multisquint processing

NASA Technical Reports Server (NTRS)

Chen, Curtis W.

2004-01-01

We propose a technique for mitigating tropospheric phase errors in repeat-pass interferometric synthetic aperture radar (InSAR). The mitigation technique is based upon the acquisition of multisquint InSAR data. On each satellite pass over a target area, the radar instrument will acquire images from multiple squint (azimuth) angles, from which multiple interferograms can be formed. The diversity of viewing angles associated with the multisquint acquisition can be used to solve for two components of the 3-D surface displacement vector as well as for the differential tropospheric phase. We describe a model for the performance of the multisquint technique, and we present an assessment of the performance expected.

Exploring Alternative Parameterizations for Snowfall with Validation from Satellite and Terrestrial Radars

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Dembek, Scott R.

2009-01-01

Increases in computational resources have allowed operational forecast centers to pursue experimental, high resolution simulations that resolve the microphysical characteristics of clouds and precipitation. These experiments are motivated by a desire to improve the representation of weather and climate, but will also benefit current and future satellite campaigns, which often use forecast model output to guide the retrieval process. The combination of reliable cloud microphysics and radar reflectivity may constrain radiative transfer models used in satellite simulators during future missions, including EarthCARE and the NASA Global Precipitation Measurement. Aircraft, surface and radar data from the Canadian CloudSat/CALIPSO Validation Project are used to check the validity of size distribution and density characteristics for snowfall simulated by the NASA Goddard six-class, single moment bulk water microphysics scheme, currently available within the Weather Research and Forecast (WRF) Model. Widespread snowfall developed across the region on January 22, 2007, forced by the passing of a mid latitude cyclone, and was observed by the dual-polarimetric, C-band radar King City, Ontario, as well as the NASA 94 GHz CloudSat Cloud Profiling Radar. Combined, these data sets provide key metrics for validating model output: estimates of size distribution parameters fit to the inverse-exponential equations prescribed within the model, bulk density and crystal habit characteristics sampled by the aircraft, and representation of size characteristics as inferred by the radar reflectivity at C- and W-band. Specified constants for distribution intercept and density differ significantly from observations throughout much of the cloud depth. Alternate parameterizations are explored, using column-integrated values of vapor excess to avoid problems encountered with temperature-based parameterizations in an environment where inversions and isothermal layers are present. Simulation of CloudSat reflectivity is performed by adopting the discrete-dipole parameterizations and databases provided in literature, and demonstrate an improved capability in simulating radar reflectivity at W-band versus Mie scattering assumptions.

[The error analysis and experimental verification of laser radar spectrum detection and terahertz time domain spectroscopy].

PubMed

Liu, Wen-Tao; Li, Jing-Wen; Sun, Zhi-Hui

2010-03-01

Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many chemical agent explosives show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons and chemical agent, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to chemical agent explosives. A kind of device on laser radar detecting and real time spectrum measuring was designed which measures the laser spectrum on the bases of Fourier optics and optical signal processing. Wedge interferometer was used as the beam splitter to wipe off the background light and detect the laser and measure the spectrum. The result indicates that 10 ns laser radar pulse can be detected and many factors affecting experiments are also introduced. The combination of laser radar spectrum detecting, THz-TDS, modern pattern recognition and signal processing technology is the developing trend of remote detection for chemical agent explosives.

Frequency noise suppression of a single mode laser with an unbalanced fiber interferometer for subnanometer interferometry.

PubMed

Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Číp, Ondřej

2015-01-12

We present a method of noise suppression of laser diodes by an unbalanced Michelson fiber interferometer. The unstabilized laser source is represented by compact planar waveguide external cavity laser module, ORIONTM (Redfern Integrated Optics, Inc.), working at 1540.57 nm with a 1.5-kHz linewidth. We built up the unbalanced Michelson interferometer with a 2.09 km-long arm based on the standard telecommunication single-mode fiber (SMF-28) spool to suppress the frequency noise by the servo-loop control by 20 dB to 40 dB within the Fourier frequency range, remaining the tuning range of the laser frequency.

Multi-Stress Monitoring System with Fiber-Optic Mandrels and Fiber Bragg Grating Sensors in a Sagnac Loop

PubMed Central

Kim, Hyunjin; Sampath, Umesh; Song, Minho

2015-01-01

Fiber Bragg grating sensors are placed in a fiber-optic Sagnac loop to combine the grating temperature sensors and the fiber-optic mandrel acoustic emission sensors in single optical circuit. A wavelength-scanning fiber-optic laser is used as a common light source for both sensors. A fiber-optic attenuator is placed at a specific position in the Sagnac loop in order to separate buried Bragg wavelengths from the Sagnac interferometer output. The Bragg wavelength shifts are measured with scanning band-pass filter demodulation and the mandrel output is analyzed by applying a fast Fourier transform to the interference signal. This hybrid-scheme could greatly reduce the size and the complexity of optical circuitry and signal processing unit, making it suitable for low cost multi-stress monitoring of large scale power systems. PMID:26230700

First Radar Images of Halloween Asteroid

NASA Image and Video Library

2015-10-30

These first radar images of 2015 TB145 from the National Science Foundation 1,000-foot 305-meter Arecibo Observatory in Puerto Rico, indicate the near-Earth object is spherical in shape and approximately 2,000 feet 600 meters in diameter. The radar images were taken on Oct. 30, 2015, and the image resolution is 25 feet (7.5 meters) per pixel. The celestial object is more than likely a dead comet that has shed its volatiles after numerous passes around the sun. http://photojournal.jpl.nasa.gov/catalog/PIA20040

Polarizing Gires-Tournois interferometer as intra-cavity frequency-selective element in high-power lasers

NASA Astrophysics Data System (ADS)

Schuhmann, Karsten; Kirch, Klaus; Marszałek, Mirosław; Pototschnig, Martin; Sinkunaite, Laura; Wichmann, Gunther; Zeyen, Manuel; Antognini, Aldo

2018-02-01

We present a frequency selective optical setup based on a Gires-Tournois interferometer suitable to enforce single-frequency operation of high power lasers. It is based on a birefringent Gires-Tournois interferometer combined with a λ/4 plate and a polarizer. The high-reflective part of the Gires-Tournois interferometer can be contacted to a heat sink to obtain efficient cooling (similar cooling principle as for the active medium in thin-disk lasers) enabling power scaling up to output powers in the kW range.

A simulation study of detection of weapon of mass destruction based on radar

NASA Astrophysics Data System (ADS)

Sharifahmadian, E.; Choi, Y.; Latifi, S.

2013-05-01

Typical systems used for detection of Weapon of Mass Destruction (WMD) are based on sensing objects using gamma rays or neutrons. Nonetheless, depending on environmental conditions, current methods for detecting fissile materials have limited distance of effectiveness. Moreover, radiation related to gamma- rays can be easily shielded. Here, detecting concealed WMD from a distance is simulated and studied based on radar, especially WideBand (WB) technology. The WB-based method capitalizes on the fact that electromagnetic waves penetrate through different materials at different rates. While low-frequency waves can pass through objects more easily, high-frequency waves have a higher rate of absorption by objects, making the object recognition easier. Measuring the penetration depth allows one to identify the sensed material. During simulation, radar waves and propagation area including free space, and objects in the scene are modeled. In fact, each material is modeled as a layer with a certain thickness. At start of simulation, a modeled radar wave is radiated toward the layers. At the receiver side, based on the received signals from every layer, each layer can be identified. When an electromagnetic wave passes through an object, the wave's power will be subject to a certain level of attenuation depending of the object's characteristics. Simulation is performed using radar signals with different frequencies (ranges MHz-GHz) and powers to identify different layers.

Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

2002-01-01

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.

Initial results of the Global Thermospheric Mapping Study (GTMS)

NASA Technical Reports Server (NTRS)

Oliver, W. L.; Salah, J. E.; Musgrove, R. G.; Holt, J. M.; Wickwar, V. B.; Hernandez, G. J.; Roble, R. G.

1986-01-01

The Global Thermospheric Mapping Study (GTMS) is a multi-technique experimental study of the thermosphere designed to map simultaneously its spatial and temporal morphology with a thoroughness and diversity of measurement techniques heretofore unachieved. The GTMS is designed around the Incoherent Scatter Radar Chain in the western hemisphere. The European incoherent scatter radars and the worldwide communities of Fabry-Perot interferometers, meteor wind radars, partial reflection drifts radars, MST radars, and satellite probes are included to extend the spatial coverage and types of measurements available. Theoretical and modeling support in the areas of thermospheric and ionospheric structure, tides, and electric fields are included to aid in program planning and data interpretation. Solar activity was low on the three observation days (F10.7 = 97, 98, 96) and magnetic conditions were unsettled to active (A = 10, 12, 20). All six incoherent scatter radar facilities collected data. Each collected F region data day and night while Saint Santin and Millstone Hill additionally collected E region data during daylight hours. Initial results from Sondrestrom and Millstone Hill are presented. Good quality Fabry Perot data were collected at Fritz Peak and San Jose dos Campos. Weather conditions produced poor results at Arequipa and Arecibo. Initial results from Fritz Peak are presented. Mesosphere/lower-thermosphere observations were conducted under the ATMAP organization. The magnetometer chains also were operational during this campaign. Initial thermospheric general circulation model predictions were made for assumed solar-geophysical conditions, and selected results are presented.

A heterodyne interferometer with periodic nonlinearities smaller than ±10 pm

NASA Astrophysics Data System (ADS)

Weichert, C.; Köchert, P.; Köning, R.; Flügge, J.; Andreas, B.; Kuetgens, U.; Yacoot, A.

2012-09-01

The PTB developed a new optical heterodyne interferometer in the context of the European joint research project ‘Nanotrace’. A new optical concept using plane-parallel plates and spatially separated input beams to minimize the periodic nonlinearities was realized. Furthermore, the interferometer has the resolution of a double-path interferometer, compensates for possible angle variations between the mirrors and the interferometer optics and offers a minimal path difference between the reference and the measurement arm. Additionally, a new heterodyne phase evaluation based on an analogue to digital converter board with embedded field programmable gate arrays was developed, providing a high-resolving capability in the single-digit picometre range. The nonlinearities were characterized by a comparison with an x-ray interferometer, over a measurement range of 2.2 periods of the optical interferometer. Assuming an error-free x-ray interferometer, the nonlinearities are considered to be the deviation of the measured displacement from a best-fit line. For the proposed interferometer, nonlinearities smaller than ±10 pm were observed without any quadrature fringe correction.

Naturally stable Sagnac–Michelson nonlinear interferometer

DOE PAGES

Lukens, Joseph M.; Peters, Nicholas A.; Pooser, Raphael C.

2016-11-16

Interferometers measure a wide variety of dynamic processes by converting a phase change into an intensity change. Nonlinear interferometers, making use of nonlinear media in lieu of beamsplitters, promise substantial improvement in the quest to reach the ultimate sensitivity limits. Here we demonstrate a new nonlinear interferometer utilizing a single parametric amplifier for mode mixing conceptually, a nonlinear version of the conventional Michelson interferometer with its arms collapsed together. We observe up to 99.9% interference visibility and find evidence for noise reduction based on phase-sensitive gain. As a result, our configuration utilizes fewer components than previous demonstrations and requires nomore » active stabilization, offering new capabilities for practical nonlinear interferometric-based sensors.« less

FIBER AND INTEGRATED OPTICS. OTHER TOPICS IN QUANTUM ELECTRONICS: Fiber-optic interferometers: control of spectral composition of the radiation and formation of high-intensity optical pulses

NASA Astrophysics Data System (ADS)

Bulushev, A. G.; Dianov, Evgenii M.; Kuznetsov, A. V.; Okhotnikov, O. G.; Paramonov, Vladimir M.; Tsarev, Vladimir A.

1990-05-01

A study was made of the use of single-mode fiber ring interferometers in narrowing the emission lines of semiconductor lasers and increasing the optical radiation power. Efficient coupling of radiation, emitted by a multifrequency injection laser with an external resonator, into a fiber ring interferometer was achieved both under cw and mode-locking conditions. Matching of the optical lengths of the external resonator and the fiber interferometer made it possible to determine the mode width for this laser. A method for generation of optical pulses in a fiber ring interferometer from cw frequency modulated radiation was developed.

Macro-motion detection using ultra-wideband impulse radar.

PubMed

Xin Li; Dengyu Qiao; Ye Li

2014-01-01

Radar has the advantage of being able to detect hidden individuals, which can be used in homeland security, disaster rescue, and healthcare monitoring-related applications. Human macro-motion detection using ultra-wideband impulse radar is studied in this paper. First, a frequency domain analysis is carried out to show that the macro-motion yields a bandpass signal in slow-time. Second, the FTFW (fast-time frequency windowing), which has the advantage of avoiding the measuring range reduction, and the HLF (high-pass linear-phase filter), which can preserve the motion signal effectively, are proposed to preprocess the radar echo. Last, a threshold decision method, based on the energy detector structure, is presented.

UAVSAR: An Airborne Window on Earth Surface Deformation

NASA Technical Reports Server (NTRS)

Hensley, Scott

2011-01-01

This study demonstrates that UAVSAR's precision autopilot and electronic steering have allowed for the reliable collection of airborne repeat pass radar interferometric data for deformation mapping. Deformation maps from temporal scales ranging from hours to months over a variety of signals of geophysical interest illustrate the utility of UAVSAR airborne repeat pass interferometry to these studies.

Faraday-effect polarimeter-interferometer system for current density measurement on EAST

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

Liu, H. Q.; Jie, Y. X., E-mail: yx-jie@ipp.ac.cn; Zou, Z. Y.

2014-11-15

A multichannel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique is under development for current density and electron density profile measurements in the EAST tokamak. Novel molybdenum retro-reflectors are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which will provide real-time Faraday rotation angle and density phase shift output, have been developed for use on the POINT system. Initial calibration indicates the electron line-integrated density resolution is less than 5 × 10{sup 16} m{sup −2} (∼2°), and the Faraday rotation angle rms phase noise is <0.1°.

Method for extracting long-equivalent wavelength interferometric information

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor)

1991-01-01

A process for extracting long-equivalent wavelength interferometric information from a two-wavelength polychromatic or achromatic interferometer. The process comprises the steps of simultaneously recording a non-linear sum of two different frequency visible light interferograms on a high resolution film and then placing the developed film in an optical train for Fourier transformation, low pass spatial filtering and inverse transformation of the film image to produce low spatial frequency fringes corresponding to a long-equivalent wavelength interferogram. The recorded non-linear sum irradiance derived from the two-wavelength interferometer is obtained by controlling the exposure so that the average interferogram irradiance is set at either the noise level threshold or the saturation level threshold of the film.

Space Radar Image of Kilauea, Hawaii - Interferometry 1

NASA Image and Video Library

1999-05-01

This X-band image of the volcano Kilauea was taken on October 4, 1994, by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar. The area shown is about 9 kilometers by 13 kilometers (5.5 miles by 8 miles) and is centered at about 19.58 degrees north latitude and 155.55 degrees west longitude. This image and a similar image taken during the first flight of the radar instrument on April 13, 1994 were combined to produce the topographic information by means of an interferometric process. This is a process by which radar data acquired on different passes of the space shuttle is overlaid to obtain elevation information. Three additional images are provided showing an overlay of radar data with interferometric fringes; a three-dimensional image based on altitude lines; and, finally, a topographic view of the region. http://photojournal.jpl.nasa.gov/catalog/PIA01763

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)

Aruliah, Anasuya; Kosch, Michael

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.

Atmospheric Phase Delay in Sentinel SAR Interferometry

NASA Astrophysics Data System (ADS)

Krishnakumar, V.; Monserrat, O.; Crosetto, M.; Crippa, B.

2018-04-01

The repeat-pass Synthetic Aperture Radio Detection and Ranging (RADAR) Interferometry (InSAR) has been a widely used geodetic technique for observing the Earth's surface, especially for mapping the Earth's topography and deformations. However, InSAR measurements are prone to atmospheric errors. RADAR waves traverse the Earth's atmosphere twice and experience a delay due to atmospheric refraction. The two major layers of the atmosphere (troposphere and ionosphere) are mainly responsible for this delay in the propagating RADAR wave. Previous studies have shown that water vapour and clouds present in the troposphere and the Total Electron Content (TEC) of the ionosphere are responsible for the additional path delay in the RADAR wave. The tropospheric refractivity is mainly dependent on pressure, temperature and partial pressure of water vapour. The tropospheric refractivity leads to an increase in the observed range. These induced propagation delays affect the quality of phase measurement and introduce errors in the topography and deformation fields. The effect of this delay was studied on a differential interferogram (DInSAR). To calculate the amount of tropospheric delay occurred, the meteorological data collected from the Spanish Agencia Estatal de Meteorología (AEMET) and MODIS were used. The interferograms generated from Sentinel-1 carrying C-band Synthetic Aperture RADAR Single Look Complex (SLC) images acquired on the study area are used. The study area consists of different types of scatterers exhibiting different coherence. The existing Saastamoinen model was used to perform a quantitative evaluation of the phase changes caused by pressure, temperature and humidity of the troposphere during the study. Unless the phase values due to atmospheric disturbances are not corrected, it is difficult to obtain accurate measurements. Thus, the atmospheric error correction is essential for all practical applications of DInSAR to avoid inaccurate height and deformation measurements.

Thermal nonlinear optical response of meso-tetraphenylporphyrin under aggregation conditions versus that in the absence of aggregation

NASA Astrophysics Data System (ADS)

Rasouli, Saifollah; Sakha, Fereshteh; Mojarrad, Aida G.; Zakavi, Saeed

2018-05-01

In this work, measurement of thermally induced nonlinear refractive index of meso-tetraphenylporphyrin (H2TPP) at different concentrations in 1,2-dicoloroethane using a double-grating interferometer set-up in a pump-probe configuration is reported. The formation of aggregates of H2TPP at concentrations greater than ca. 5 × 10-5 M was evident by deviation from Beer's law. An almost focused pump beam passes through the solution. A part of the pump beam energy is absorbed by the sample and therefore a thermal lens is generated in the sample. An expanded probe beam propagates through the sample and indicates the sample refractive index changes. Just after the sample a band-pass filter cuts off the pump beam from the path but the distorted probe beam passes through a double-grating interferometer consisting of two similar diffraction gratings with a few centimetres distance. A CCD camera is installed after the interferometer in which on its sensitive area two diffraction orders of the gratings are overlying and producing interference pattern. The refractive index changes of the sample are obtained from the phase distribution of the successive interference patterns recorded at different times after turning on of the pump beam using Fourier transform method. In this study, for different concentrations of H2TPP in 1,2-dichloroethane solution the thermal nonlinear refractive index is determined. Also, we present the measurement of the temperature changes induced by the pump beam in the solution. We found that value of nonlinear refractive index increased by increasing the concentration up to a concentration of 5 × 10-4 M and then decreased at higher concentrations. In addition, we have investigated the stability of the observed thermal nonlinearity after a period of two weeks from the sample preparation.

New Techniques for Radar Altimetry of Sea Ice and the Polar Oceans

NASA Astrophysics Data System (ADS)

Armitage, T. W. K.; Kwok, R.; Egido, A.; Smith, W. H. F.; Cullen, R.

2017-12-01

Satellite radar altimetry has proven to be a valuable tool for remote sensing of the polar oceans, with techniques for estimating sea ice thickness and sea surface height in the ice-covered ocean advancing to the point of becoming routine, if not operational, products. Here, we explore new techniques in radar altimetry of the polar oceans and the sea ice cover. First, we present results from fully-focused SAR (FFSAR) altimetry; by accounting for the phase evolution of scatterers in the scene, the FFSAR technique applies an inter-burst coherent integration, potentially over the entire duration that a scatterer remains in the altimeter footprint, which can narrow the effective along track resolution to just 0.5m. We discuss the improvement of using interleaved operation over burst-more operation for applying FFSAR processing to data acquired by future missions, such as a potential CryoSat follow-on. Second, we present simulated sea ice retrievals from the Ka-band Radar Interferometer (KaRIn), the instrument that will be launched on the Surface Water and Ocean Topography (SWOT) mission in 2021, that is capable of producing swath images of surface elevation. These techniques offer the opportunity to advance our understanding of the physics of the ice-covered oceans, plus new insight into how we interpret more conventional radar altimetry data in these regions.

Space Radar Image of Saline Valley, California

NASA Technical Reports Server (NTRS)

1999-01-01

This is a three-dimensional perspective view of Saline Valley, about 30 km (19 miles) east of the town of Independence, California created by combining two spaceborne radar images using a technique known as interferometry. Visualizations like this one are helpful to scientists because they clarify the relationships of the different types of surfaces detected by the radar and the shapes of the topographic features such as mountains and valleys. The view is looking southwest across Saline Valley. The high peaks in the background are the Inyo Mountains, which rise more than 3,000 meters (10,000 feet) above the valley floor. The dark blue patch near the center of the image is an area of sand dunes. The brighter patches to the left of the dunes are the dry, salty lake beds of Saline Valley. The brown and orange areas are deposits of boulders, gravel and sand known as alluvial fans. The image was constructed by overlaying a color composite radar image on top of a digital elevation map. The radar image was taken by the Spaceborne Imaging Radar-C/X-bandSynthetic Aperture Radar (SIR-C/X-SAR) on board the space shuttleEndeavour in October 1994. The digital elevation map was producedusing radar interferometry, a process in which radar data are acquired on different passes of the space shuttle. The two data passes are compared to obtain elevation information. The elevation data were derived from a 1,500-km-long (930-mile) digital topographic map processed at JPL. Radar image data are draped over the topography to provide the color with the following assignments: red is L-band vertically transmitted, vertically received; green is C-band vertically transmitted, vetically received; and blue is the ratio of C-band vertically transmitted, vertically received to L-band vertically transmitted, vertically received. This image is centered near 36.8 degrees north latitude and 117.7 degrees west longitude. No vertical exaggeration factor has been applied to the data. SIR-C/X-SAR, a joint mission of the German, Italian, and the United States space agencies, is part of NASA's Mission to Planet Earth.

Frequency Noise Suppression of a Single Mode Laser with an Unbalanced Fiber Interferometer for Subnanometer Interferometry

PubMed Central

Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Číp, Ondřej

2015-01-01

We present a method of noise suppression of laser diodes by an unbalanced Michelson fiber interferometer. The unstabilized laser source is represented by compact planar waveguide external cavity laser module, ORIONTM (Redfern Integrated Optics, Inc.), working at 1540.57 nm with a 1.5-kHz linewidth. We built up the unbalanced Michelson interferometer with a 2.09 km-long arm based on the standard telecommunication single-mode fiber (SMF-28) spool to suppress the frequency noise by the servo-loop control by 20 dB to 40 dB within the Fourier frequency range, remaining the tuning range of the laser frequency. PMID:25587980

Gas Sensors Based on Single-Arm Waveguide Interferometers

NASA Technical Reports Server (NTRS)

Sarkisov, Sergey; Curley, Michael; Diggs, Darnell; Adamovsky, Grigory

1998-01-01

Various optical technologies can be implemented in chemical sensing. Sensitive, rugged, and compact systems will be more likely built using interferometric waveguide sensors. Currently existing sensors comprise dual-arm systems with external reference arm, dual-arm devices with internal reference arm such as integrated Mach-Zehnder interferometer, and single-arm systems which employ the interference between different waveguide modes. These latter ones are the most compact and rugged but still sensitive enough to monitor volatile pollutants such as NH3 coming out of industrial refrigerators and fertilizer plants and stocks, NO, NO2, SO2, emitted by industrial burning processes. Single-arm devices in planar waveguide configuration most frequently use two orthogonally polarized modes TE (sub i) and TM (sub i) of the same order i. Sensing effect is based on the difference in propagation conditions for the modes caused by the environment. However, dual-mode single-order interferometers still have relatively low sensitivity with respect to the environment related changes in the waveguide core because of small difference between propagation constants of TE (sub i) and TM (sub i) modes of the same order. Substantial sensitivity improvement without significant complication can be achieved for planar waveguide interferometers using modes of different orders with much greater difference between propagation constants.

Skylab earth resources experiment package /EREP/ - Sea surface topography experiment

NASA Technical Reports Server (NTRS)

Vonbun, F. O.; Marsh, J. G.; Mcgoogan, J. T.; Leitao, C. D.; Vincent, S.; Wells, W. T.

1976-01-01

The S-193 Skylab radar altimeter was operated in a round-the-world pass on Jan. 31, 1974. The main purpose of this experiment was to test and 'measure' the variation of the sea surface topography using the Goddard Space Flight Center (GSFC) geoid model as a reference. This model is based upon 430,000 satellite and 25,000 ground gravity observations. Variations of the sea surface on the order of -40 to +60 m were observed along this pass. The 'computed' and 'measured' sea surfaces have an rms agreement on the order of 7 m. This is quite satisfactory, considering that this was the first time the sea surface has been observed directly over a distance of nearly 35,000 km and compared to a computed model. The Skylab orbit for this global pass was computed using the Goddard Earth Model (GEM 6) and S-band radar tracking data, resulting in an orbital height uncertainty of better than 5 m over one orbital period.

Earth and ocean dynamics satellites and systems

NASA Technical Reports Server (NTRS)

Vonbun, F. O.

1975-01-01

An overview is presented of the present state of satellite and ground systems making observations of the dynamics of the solid earth and the oceans. Emphasis is placed on applications of space technology for practical use. Topics discussed include: satellite missions and results over the last two decades in the areas of earth gravity field, polar motions, earth tides, magnetic anomalies, and satellite-to-satellite tracking; laser ranging systems; development of the Very Long Baseline Interferometer; and Skylab radar altimeter data applications.

A tunable, double-wavelength heterodyne detection interferometer with frequency-locked diode-pumped Nd:YAG sources for absolute measurements

NASA Astrophysics Data System (ADS)

Gelmini, E.; Minoni, U.; Docchio, F.

1995-08-01

A double heterodyne interferometric instrument using a tunable synthetic wavelength for the absolute measurements of distance and position is presented. The optical synthetic wavelength is generated by a pair of PZT-tunable diode-pumped Nd:YAG lasers operating at 1.064 μm. Based on a closed-loop scheme, a suitable electronic circuit has been developed to implement the frequency locking of the two lasers. A digital frequency comparator provides an error signal, used to control the slave laser, by comparing the laser beat frequency to a reference oscillator. Demodulation of the superheterodyne signals is obtained by a rf detector followed by low-pass filtering. Distance measurements are obtained by a digital phase meter gauging the phase difference between the demodulated signals from a measuring interferometer and from a reference interferometer. The paper presents the optical and the electronic layouts of the instrument as well as experimental results from a laboratory prototype.

Large radius of curvature measurement based on virtual quadratic Newton rings phase-shifting moiré-fringes measurement method in a nonnull interferometer.

PubMed

Yang, Zhongming; Wang, Kailiang; Cheng, Jinlong; Gao, Zhishan; Yuan, Qun

2016-06-10

We have proposed a virtual quadratic Newton rings phase-shifting moiré-fringes measurement method in a nonnull interferometer to measure the large radius of curvature for a spherical surface. In a quadratic polar coordinate system, linear carrier testing Newton rings interferogram and virtual Newton rings interferogram form the moiré fringes. It is possible to retrieve the wavefront difference data between the testing and standard spherical surface from the moiré fringes after low-pass filtering. Based on the wavefront difference data, we deduced a precise formula to calculate the radius of curvature in the quadratic polar coordinate system. We calculated the retrace error in the nonnull interferometer using the multi-configuration model of the nonnull interferometric system in ZEMAX. Our experimental results indicate that the measurement accuracy is better than 0.18% for a spherical mirror with a radius of curvature of 41,400 mm.

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.

1996-01-01

This paper first gives a heuristic description of the sensitivity of Interferometric Synthetic Aperture Radar to vertical vegetation distributions and underlying surface topography. A parameter estimation scenario is then described in which the Interferometric Synthetic Aperture Radar cross-correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous-layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of Interferometric Synthetic Aperture Radar observations for single-baseline, single-frequency, single-incidence-angle, single-polarization Interferometric Synthetic Aperture Radar. Using ancillary ground-truth data to compensate for the underdetermination of the parameters, forest depths are estimated from the INSAR data. A recently-analyzed multibaseline data set is also discussed and the potential for stand-alone Interferometric Synthetic Aperture Radar parameter estimation is assessed. The potential of combining the information content of Interferometric Synthetic Aperture Radar with that of infrared/optical remote sensing data is briefly discussed.

Optical system and method for gas detection and monitoring

NASA Technical Reports Server (NTRS)

Polzin, Kurt A. (Inventor); Sinko, John Elihu (Inventor); Korman, Valentin (Inventor); Witherow, William K. (Inventor); Hendrickson, Adam Gail (Inventor)

2011-01-01

A free-space optical path of an optical interferometer is disposed in an environment of interest. A light beam is guided to the optical interferometer using a single-mode optical fiber. The light beam traverses the interferometer's optical path. The light beam guided to the optical path is combined with the light beam at the end of the optical path to define an output light. A temporal history of the output light is recorded.

FIBER OPTICS: Polarization phase nonreciprocity in all-fiber ring interferometers

NASA Astrophysics Data System (ADS)

Andreev, A. Ts; Vasilev, V. D.; Kozlov, V. A.; Kuznetsov, A. V.; Senatorov, A. A.; Shubochkin, R. L.

1993-08-01

The polarization phase nonreciprocity in all-fiber ring interferometers based on single-mode optical fibers was studied experimentally. The results confirm existing theoretical models. Experimentally, it was possible to use fiber ring interferometers to measure the extinction coefficients of optical fiber polarizers. The largest extinction coefficients found for optical-fiber polarizers were 84 dB (for the wavelength 0.82 μm) and 86 dB (1.3 μm).

Software design for a compact interferometer

NASA Astrophysics Data System (ADS)

Vogel, Andreas

1993-01-01

Experience shows that very often a lot of similar elements have to be tested by the optician. Only a small number of input parameters are changed in a well defined manner. So it is useful to develop simplified software for special applications. The software is used in a compact phase shifting interferometer. Up to five interferometers can be controlled by a single PC-AT computer. Modular programming simplifies the software modification for new applications.

Status of a UAV SAR Designed for Repeat Pass Interferometry for Deformation Measurements

NASA Technical Reports Server (NTRS)

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

2004-01-01

Under the NASA ESTO sponsored Instrument Incubator Program we have designed a lightweight, reconfigurable polarimetric L-band SAR designed for repeat pass deformation measurements of rapidly deforming surfaces of geophysical interest such as volcanoes or earthquakes. This radar will be installed on an unmanned airborne vehicle (UAV) or a lightweight, high-altitude, and long endurance platform such as the Proteus. After a study of suitable available platforms we selected the Proteus for initial development and testing of the system. We want to control the repeat track capability of the aircraft to be within a 10 m tube to support the repeat deformation capability. We conducted tests with the Proteus using real-time GPS with sub-meter accuracy to see if pilots could fly the aircraft within the desired tube. Our results show that pilots are unable to fly the aircraft with the desired accuracy and therefore an augmented autopilot will be required to meet these objectives. Based on the Proteus flying altitude of 13.7 km (45,000 ft), we are designing a fully polarimetric L-band radar with 80 MHz bandwidth and 16 km range swath. This radar will have an active electronic beam steering antenna to achieve Doppler centroid stability that is necessary for repeat-pass interferometry (RPI). This paper will present are design criteria, current design and expected science applications.

Pan-Tropical Forest Mapping by Exploiting Textures of Multi-Temporal High Resolution SAR Data

NASA Astrophysics Data System (ADS)

Knuth, R.; Eckardt, R.; Richter, N.; Schmullius, C.

2012-12-01

Even though the first commitment period of the Kyoto Protocol is in the offing, there is still a strong demand for profound, reliable, and up to date information in order to bridge the gap of knowledge of the land cover conversion. Despite the fact that land use change is one of the largest carbon contribution factors, it is still poorly quantified. This is particularly true for many tropical forest areas worldwide. Here, preservation of such pristine forest areas is critically endangered. Enormous population growth, the increasing global demand for various resources, and the ongoing unsustainable management practices put the remaining tropical forests under a huge pressure. Yet, only the United Nations Food and Agriculture Organization's (FAO) global Forest Resources Assessment (FRA) report provides the crucial quantitative information every 5 years on a regional scale. Nonetheless, the assembled information of the FRA reports bear the burden of ambiguity and vagueness, because they were compiled based on autonomously gathered statistics, which are usually driven by the individual country needs. There is a broad consensus among the different scientific disciplines, that only the remote sensing technology allows for a large scale robust monitoring of these widespread, and remote forest areas. Consequently, the FAO decided to supplementary analyze remote sensing data for the present (2010) and upcoming FRAs. However, it is also widely accepted that currently only microwave remote sensing techniques allow for an all-day, weather independent monitoring of the frequently cloud-covered tropics. In this context, high resolution Synthetic Aperture Radar (SAR) images of the German satellites TerraSAR-X and TanDEM-X have been investigated within the pan-tropics to support the latest FRA 2010 report. Data of more than 304 predominantly cloud-covered sites in Latin America (188), Central Africa (45) and Southeast Asia (71) have been acquired. Upon delivery, the corresponding radar images were processed using an operational processing chain that includes radiometric transformation, noise reduction, and georeferencing of the SAR data. In places with pronounced topography both satellites were used as single pass interferometer to derive a digital surface model in order to perform an orthorectification followed by a topographic normalization of the SAR backscatter values. As prescribed by the FAO, the final segment-based classification algorithm was fed by multi-temporal backscatter information, a set of textural features, and information on the degree of coherence between the multi-temporal acquisitions. Validation with available high resolution optical imagery suggests that the produced forest maps possess an overall accuracy of 75 percent or higher.

Radar echo from a flat conducting plate - near and far

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

Williams, C.S.

1982-01-01

Over certain types of terrain, a radar fuze (or altimeter), by virtue of the horizontal component of its velocity, is likely to pass over various flat objects of limited size. The echo from such objects could have a duration less than that of one Doppler cycle, where the Doppler frequency is due to the vertical component of the velocity. If the terrain is principally made up of such objects, their echoes are in most cases entirely uncorrelated with each other. Hence, the total echo after mixing at the radar with the delayed transmitted wave would have a noise-like spectrum notmore » at all confined to the Doppler-frequency band where the desired echo signal is expected. This would seriously degrade the performance of a radar that utilizes correlation. This work shows that the echo from a square flat plate will be of duration greater than the time it takes to pass over the plate if the height h above it satisfies h > a/sup 2//lambda where a is the plate-edge dimension and lambda is the radar wavelength. The results presented here can be used to determine the spatial region wherein the echo exists, and the magnitude and phase of the echo from such a plate. I infer from these results that the case where the signal has a noise-like spectrum is not impossible but it is unlikely for the applications with which I am familiar.« less

Design and analysis of a multi-passband complex filter for the multiband cognitive radar system

NASA Astrophysics Data System (ADS)

Lee, Hua-Chin; Ting, Der-Hong; Tsao, Ya-Lan

2017-05-01

Multiband cognitive radar systems, operating in a variety of frequency bands and combining the different channels into a joint system, can provide significant flexibility and capability to detect and track hostile targets. This paper proposes a multi-passband complex filter (MPCF) architecture and the related circuit design for a multiband cognitive radar system. By operating under the 5.8GHz UNII band, the sensing part detects the current usage of frequency bands from 5.15GHz to 5.825GHz and provides the information of unused channels. The multiband cognitive radar system uses the whole unused channels and eliminates the used channels by using an on-chip MPCF in order to be coexistent with the Wi-Fi standard. The MPCF filters out the unwanted channels and leave the wanted channels. It dynamically changes the bandwidth of frequency from 20MHz to 80MHz using the 0.18μm CMOS technology. The MPCF is composed of the combination of 5th-order Chebyshev low-pass filters and high-pass filters, and the overall inband ripple of the MPCF is 1.2dB. The consuming current is 21.7mA at 1.8V power supply and the 20MHz bandwidth noise is 55.5nV. The total harmonic distortion (THD) is 45dB at 25MHz and the adjacent channel rejection is 24dB. The result of the MPCF guarantees the performance requirements of the multiband cognitive radar system.

Phase-shifting point diffraction interferometer mask designs

DOEpatents

Goldberg, Kenneth Alan

2001-01-01

In a phase-shifting point diffraction interferometer, different image-plane mask designs can improve the operation of the interferometer. By keeping the test beam window of the mask small compared to the separation distance between the beams, the problem of energy from the reference beam leaking through the test beam window is reduced. By rotating the grating and mask 45.degree., only a single one-dimensional translation stage is required for phase-shifting. By keeping two reference pinholes in the same orientation about the test beam window, only a single grating orientation, and thus a single one-dimensional translation stage, is required. The use of a two-dimensional grating allows for a multiplicity of pinholes to be used about the pattern of diffracted orders of the grating at the mask. Orientation marks on the mask can be used to orient the device and indicate the position of the reference pinholes.

Ultrasonic characterization of single drops of liquids

DOEpatents

Sinha, Dipen N.

1998-01-01

Ultrasonic characterization of single drops of liquids. The present invention includes the use of two closely spaced transducers, or one transducer and a closely spaced reflector plate, to form an interferometer suitable for ultrasonic characterization of droplet-size and smaller samples without the need for a container. The droplet is held between the interferometer elements, whose distance apart may be adjusted, by surface tension. The surfaces of the interferometer elements may be readily cleansed by a stream of solvent followed by purified air when it is desired to change samples. A single drop of liquid is sufficient for high-quality measurement. Examples of samples which may be investigated using the apparatus and method of the present invention include biological specimens (tear drops; blood and other body fluid samples; samples from tumors, tissues, and organs; secretions from tissues and organs; snake and bee venom, etc.) for diagnostic evaluation, samples in forensic investigations, and detection of drugs in small quantities.

Calculations of radar backscattering coefficient of vegetation-covered soils

NASA Technical Reports Server (NTRS)

Mo, T.; Schmugge, T. J.; Jackson, T. J. (Principal Investigator)

1983-01-01

A model for simulating the measured backscattering coefficient of vegetation-covered soil surfaces includes both coherent and incoherent components of the backscattered radar pulses from a rough sil surface. The effect of vegetation canopy scattering is also incorporated into the model by making the radar pulse subject to two-way attenuation and volume scattering when it passes through the vegetation layer. Model results agree well with the measured angular distributions of the radar backscattering coefficient for HH polarization at the 1.6 GHz and 4.75 GHz frequencies over grass-covered fields. It was found that the coherent scattering component is very important at angles near nadir, while the vegetation volume scattering is dominant at incident angles 30 degrees.

The Design and Implementation of the Wide-Angle Michelson Interferometer to Observe Thermospheric Winds.

NASA Astrophysics Data System (ADS)

Ward, William Edmund

The design and implementation of a Wide-Angle Michelson interferometer (WAMI) as a high spectral resolution device for measuring Doppler shifts and temperatures in the thermosphere is discussed in detail. A general theoretical framework is developed to describe the behavior of interferometers and is applied to the WAMI. Notions concerning the optical coupling of various surfaces within an interferometer are developed and used to investigate the effects of misalignments in the WAMI optics. In addition, these notions in combination with ideas on the polarization behavior of interferometers are used to suggest how complex multisurfaced interferometers might be developed, what features affect their behavior most strongly, and how this behavior might be controlled. Those aspects of the Michelson interferometer important to its use as a high resolution spectral device are outlined and expressions relating the physical features of the interferometer and the spectral features of the radiation passing through the instrument, to the form of the observed interference pattern are derived. The sensitivity of the WAMI to misalignments in its optical components is explored, and quantitative estimations of the effects of these misalignments made. A working WAMI with cube corners instead of plane mirrors was constructed and is described. The theoretical notions outlined above are applied to this instrument and found to account for most of its features. A general digital procedure is developed for the analysis of the observed interference fringes which permits an estimation of the amplitude, visibility and phase of the fringes. This instrument was taken to Bird, northern Manitoba as part of the ground based support for the Auroral Rocket and Image Excitation Study (ARIES) rocket campaign. Doppler shifts and linewidth variations in O(^1 D) and O(^1S) emissions in the aurora were observed during several nights and constitute the first synoptic wind measurements taken with a WAMI. The results from an eight hour period of O(^1 D) observations are analysed and found to be similar to those obtained with Fabry-Perot interferometers. Higher temporal resolution data than any previously published were obtained, and suggest the presence of previously undetected small scale structures in the wind and temperature data. (Abstract shortened with permission of author.).

Contrails of Small and Very Large Optical Depth

NASA Technical Reports Server (NTRS)

Atlas, David; Wang, Zhien

2010-01-01

This work deals with two kinds of contrails. The first comprises a large number of optically thin contrails near the tropopause. They are mapped geographically using a lidar to obtain their height and a camera to obtain azimuth and elevation. These high-resolution maps provide the local contrail geometry and the amount of optically clear atmosphere. The second kind is a single trail of unprecedentedly large optical thickness that occurs at a lower height. The latter was observed fortuitously when an aircraft moving along the wind direction passed over the lidar, thus providing measurements for more than 3 h and an equivalent distance of 620 km. It was also observed by Geostationary Operational Environmental Satellite (GOES) sensors. The lidar measured an optical depth of 2.3. The corresponding extinction coefficient of 0.023 per kilometer and ice water content of 0.063 grams per cubic meter are close to the maximum values found for midlatitude cirrus. The associated large radar reflectivity compares to that measured by ultrasensitive radar, thus providing support for the reality of the large optical depth.

High-speed laser anemometry based on spectrally resolved Rayleigh scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.

1991-01-01

Laser anemometry in unseeded flows based on the measurement of the spectrum of Rayleigh scattered laser light is reviewed. The use of molecular scattering avoids the well known problems (particle lag, biasing effects, seed generation, seed injection) of seeded flows. The fundamental limits on velocity measurement accuracy are determined using maximum likelihood methods. Measurement of the Rayleigh spectrum with scanning Fabry-Perot interferometers is analyzed and accuracy limits are established for both single pass and multipass configurations. Multipass configurations have much higher selectivity and are needed for measurements where there is a large amount of excess noise caused by stray laser light. It is shown that Rayleigh scattering is particularly useful for supersonic and hypersonic flows. The results of the analysis are compared with measurements obtained with a Rayleigh scattering diagnostic developed for study of the exhaust plume of a small hydrogen-oxygen rocket, where the velocities are in the range of 1000 to 5000 m/sec.

Adaptive multiphoton endomicroscopy through a dynamically deformed multicore optical fiber using proximal detection.

PubMed

Warren, Sean C; Kim, Youngchan; Stone, James M; Mitchell, Claire; Knight, Jonathan C; Neil, Mark A A; Paterson, Carl; French, Paul M W; Dunsby, Chris

2016-09-19

This paper demonstrates multiphoton excited fluorescence imaging through a polarisation maintaining multicore fiber (PM-MCF) while the fiber is dynamically deformed using all-proximal detection. Single-shot proximal measurement of the relative optical path lengths of all the cores of the PM-MCF in double pass is achieved using a Mach-Zehnder interferometer read out by a scientific CMOS camera operating at 416 Hz. A non-linear least squares fitting procedure is then employed to determine the deformation-induced lateral shift of the excitation spot at the distal tip of the PM-MCF. An experimental validation of this approach is presented that compares the proximally measured deformation-induced lateral shift in focal spot position to an independent distally measured ground truth. The proximal measurement of deformation-induced shift in focal spot position is applied to correct for deformation-induced shifts in focal spot position during raster-scanning multiphoton excited fluorescence imaging.

Radar Movie of Asteroid 2011 UW158

NASA Image and Video Library

2015-07-23

Scientists using two giant, Earth-based radio telescopes bounced radar signals off passing asteroid 2011 UW158 to create images for this animation showing the rocky body's fast rotation. The passing asteroid made its closest approach to Earth on July 19, 2015 at 7:37 a.m. PST (4:37 a.m. EST) at a distance of about 1.5 million miles (2.4 million kilometers, or 6 times the distance from Earth to the moon). The close proximity during the pass made 2011 UW158 one of the best asteroid flybys of 2015 for imaging from Earth using radar. The radar images reveal that the shape of the asteroid is extremely irregular and quite elongated. Prominent parallel, linear features run along the length of the object that cause a large increase in brightness of the radar images as they rotate into view. Scientists note that the asteroid appears to be fairly unusual. Its fast rotation suggests the object has greater mechanical strength than other asteroids its size. A fast-rotating asteroid with lower mechanical strength would tend to split apart. To obtain the views, researchers paired the 230-foot- (70-meter-) wide Deep Space Network antenna at Goldstone, California, in concert with the National Radio Astronomy Observatory's 330-foot (100-meter) Green Bank Telescope. Using this technique, the Goldstone antenna beams a radar signal at an asteroid and Green Bank receives the reflections. The technique, referred to as a bi-static observation, dramatically improves the amount of detail that can be seen in radar images. The new views obtained with the technique show features as small as about 24 feet (7.5 meters) wide. The 171 individual images used in the movie were generated from data collected on July 18. They show the asteroid is approximately 2000 by 1000 feet (600 by 300 meters) across. The observations also confirm earlier estimates by astronomers that the asteroid rotates quickly, completing one spin in just over half an hour. The movie spans a period of about an hour and 45 minutes. The trajectory of asteroid 2011 UW158 is well understood. This flyby was the closest approach the asteroid will make to Earth for at least the next 93 years. Asteroid 2011 UW158 was discovered on October 25, 2011, by the PanSTARRS 1 telescope, located on the summit of Haleakala on Maui, Hawaii. Managed by the University of Hawaii, the PanSTARRS survey receives NASA funding. Radar is a powerful technique for studying an asteroid's size, shape, rotation state, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than if radar observations weren't available. http://photojournal.jpl.nasa.gov/catalog/PIA19644

Optical Frequency Comb Fourier Transform Spectroscopy with Resolution Exceeding the Limit Set by the Optical Path Difference

NASA Astrophysics Data System (ADS)

Foltynowicz, Aleksandra; Rutkowski, Lucile; Johanssson, Alexandra C.; Khodabakhsh, Amir; Maslowski, Piotr; Kowzan, Grzegorz; Lee, Kevin; Fermann, Martin

2015-06-01

Fourier transform spectrometers (FTS) based on optical frequency combs (OFC) allow detection of broadband molecular spectra with high signal-to-noise ratios within acquisition times orders of magnitude shorter than traditional FTIRs based on thermal sources. Due to the pulsed nature of OFCs the interferogram consists of a series of bursts rather than a single burst at zero optical path difference (OPD). The comb mode structure can be resolved by acquiring multiple bursts, in both mechanical FTS systems and dual-comb spectroscopy. However, in all existing demonstrations the resolution was ultimately limited either by the maximum available OPD between the interferometer arms or by the total acquisition time enabled by the storage memory. We present a method that provides spectral resolution exceeding the limit set by the maximum OPD using an interferogram containing only a single burst. The method allows measurements of absorption lines narrower than the OPD-limited resolution without any influence of the instrumental lineshape function. We demonstrate this by measuring undistorted CO2 and CO absorption lines with linewidth narrower than the OPD-limited resolution using OFC-based mechanical FTS in the near- and mid-infrared wavelength ranges. The near-infrared system is based on an Er:fiber femtosecond laser locked to a high finesse cavity, while the mid-infrared system is based on a Tm:fiber-laser-pumped optical parametric oscillator coupled to a multi-pass cell. We show that the method allows acquisition of high-resolution molecular spectra with interferometer length orders of magnitude shorter than traditional FTIR. Mandon, J., G. Guelachvili, and N. Picque, Nat. Phot., 2009. 3(2): p. 99-102. Zeitouny, M., et al., Ann. Phys., 2013. 525(6): p. 437-442. Zolot, A.M., et al., Opt. Lett., 2012. 37(4): p. 638-640.

Arecibo Optical Laboratory Upgrade: imaging FPI first results

NASA Astrophysics Data System (ADS)

Noto, J.; Kerr, R. B.; Migliozzi, M. A.; Tepley, C. A.; Friedman, J.; Garcia, R.; Robles, E.; Waldrop, L. S.

2006-05-01

The Optical Laboratory at the Arecibo Observatory is being upgraded to permit remote operation, to improve Fabry-Perot Interferometer (FPI) sensitivity, and to permit FPI response in the near infrared. Integration of a 2048 x 2048 Andor CCD array into the existing low-resolution Fabry Perot Interferometer is complete. Remote operation and data acquisition for this FPI is accomplished by transition from the obsolete PDP-11 data acquisition system to PC-based, internet aware control. Another upgrade stage, adding a near-infrared focal plane array to a second FPI is scheduled for the fall of this year. Configured with a spectral resolution of 0.0086 nm at 656.3 nm, the low resolution FPI sampled the geocoronal Balmer-alpha emission during three new moon periods in November and December, 2005, and January, 2006. The latter two observation campaigns were conducted using the new remote control capability. The single etalon FPI produces three orders at the CCD plane corresponding to a full field-of-view of 0.92 degrees. The FPI Hadinger ring pattern is summed annularly, and the three orders are subsequently summed, producing an instrument sensitivity that is 43 times better than the previous single channel photomultiplier detection system. Raw detector response is corrected using both linear (chip bias) and non-linear techniques (flat-field) prior to ring-summing. A frequency stabilized HeNe laser at 632.8 nm is remotely operated to establish the FPI response function. Effective exospheric temperature and line profile asymmetries are determined after decomposition of the instrument response function from the measured airglow emission. Identification and climatological characterization of non-Maxwellian H distributions, with simultaneous quantification of H+ abundance and flow in the topside ionosphere by the Arecibo incoherent scatter radar, are measurements central to our goal of improved understanding of H on H+ charge exchange escape of H.

Compact Mach-Zehnder interferometer based on photonic crystal fiber and its application in switchable multi-wavelength fiber laser

NASA Astrophysics Data System (ADS)

Chen, Weiguo; Lou, Shuqin; Wang, Liwen; Li, Honglei; Guo, Tieying; Jian, Shuisheng

2009-08-01

The compact Mach-Zehnder interferometer is proposed by splicing a section of photonic crystal fiber (PCF) and two pieces of single mode fiber (SMF) with the air-holes of PCF intentionally collapsed in the vicinity of the splices. The depedence of the fringe spacing on the length of PCF is investigated. Based on the Mach-Zehnder interferometer as wavelength-selective filter, a switchable dual-wavelength fiber ring laser is demonstrated with a homemade erbiumdoped fiber amplifier (EDFA) as the gain medium at room temperature. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-and dual -wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

Common path point diffraction interferometer using liquid crystal phase shifting

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R. (Inventor)

1997-01-01

A common path point diffraction interferometer uses dyed, parallel nematic liquid crystals which surround an optically transparent microsphere. Coherent, collimated and polarized light is focused on the microsphere at a diameter larger than that of the microsphere. A portion of the focused light passes through the microsphere to form a spherical wavefront reference beam and the rest of the light is attenuated by the dyed liquid crystals to form an object beam. The two beams form an interferogram which is imaged by a lens onto an electronic array sensor and into a computer which determines the wavefront of the object beam. The computer phase shifts the interferogram by stepping up an AC voltage applied across the liquid crystals without affecting the reference beam.

Influence of stimulated Brillouin scattering on positioning accuracy of long-range dual Mach-Zehnder interferometric vibration sensors

NASA Astrophysics Data System (ADS)

He, Xiangge; Xie, Shangran; Cao, Shan; Liu, Fei; Zheng, Xiaoping; Zhang, Min; Yan, Han; Chen, Guocai

2016-11-01

The properties of noise induced by stimulated Brillouin scattering (SBS) in long-range interferometers and their influences on the positioning accuracy of dual Mach-Zehnder interferometric (DMZI) vibration sensing systems are studied. The SBS noise is found to be white and incoherent between the two arms of the interferometer in a 1-MHz bandwidth range. Experiments on 25-km long fibers show that the root mean square error (RMSE) of the positioning accuracy is consistent with the additive noise model for the time delay estimation theory. A low-pass filter can be properly designed to suppress the SBS noise and further achieve a maximum RMSE reduction of 6.7 dB.

Non-contact measurements of ultrasonic waves on paper webs using a photorefractive interferometer

DOEpatents

Brodeur, Pierre H.; Lafond, Emmanuel F.

2000-01-01

An apparatus and method for non-contact measurement of ultrasonic waves on moving paper webs employs a photorefractive interferometer. The photorefractive interferometer employs an optical head in which the incident beam and reflected beam are coaxial, thus enabling detection of both in-plane and out-of-plane waves with a single apparatus. The incident beam and reference beams are focused into a line enabling greater power to be used without damaging the paper.

Single and double superimposing interferometer systems

DOEpatents

Erskine, David J.

2000-01-01

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.

Study on the effect of carbon nanotube coating on the refractive index sensing sensitivity of fiber modal interferometer

NASA Astrophysics Data System (ADS)

Zhang, Ya-nan; Xie, Wen-ge; Wang, Jianzhang; Wang, Pengzhao

2018-01-01

Refractive index sensing of liquid is important in the domain of chemistry and biology. Fiber optical sensors provide an excellent way to measure the refractive index due to their feasible integration to other fiber optics components, high sensitivity, small size, and distributed sensing. However, conventional optical sensors have different shortages. To find a practical way to measure the refractive index of liquid, this paper intended to combine Carbon Nanotube (CNT) with non-core fiber (NCF) to prepare a kind of modal interferometer sensor and to explore the effect of CNT coating on refractive index sensing properties of the modal interferometer. Firstly, a structure of single mode non-core single mode (SNS) fiber with a CNT film coating was proposed and simulated. The simulation results showed that the CNT coating could improve the refractive index sensitivity of the interferometer sensor. Then in the experiment part, the CNT solution was fabricated and deposited onto the NCF, and a refractive index sensing system was built to examine the property of the CNT-coated SNS interferometer sensor. During the experiment, the influence factors of sensitivity were summarized by testing the sensing performance under different conditions, and it was demonstrated that the CNT coating could improve the contrast of the interference spectrum, and also had the possibility to increase the refractive index sensitivity of the interferometer sensor.

Wide single-mode tuning in quantum cascade lasers with asymmetric Mach-Zehnder interferometer type cavities with separately biased arms

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

Zheng, Mei C., E-mail: meizheng@princeton.edu; Gmachl, Claire F.; Liu, Peter Q.

2013-11-18

We report on the experimental demonstration of a widely tunable single mode quantum cascade laser with Asymmetric Mach-Zehnder (AMZ) interferometer type cavities with separately biased arms. Current and, consequently, temperature tuning of the two arms of the AMZ type cavity resulted in a single mode tuning range of 20 cm{sup −1} at 80 K in continuous-wave mode operation, a ten-fold improvement from the lasers under a single bias current. In addition, we also observed a five fold increase in the tuning rate as compared to the AMZ cavities controlled by one bias current.

Cassini RADAR observations of lakes and seas in the Northern Polar region of Titan: Bathymetry and Composition

NASA Astrophysics Data System (ADS)

Mastrogiuseppe, Marco; Hayes, Alex; Poggiali, Valerio; Lunine, Jonathan; Seu, Roberto; Hofgartner, Jason; Le Gall, Alice; Lorenz, Ralph; Mitri, Giuseppe

2017-04-01

Recent observations by the Cassini spacecraft has revealed its RADAR to be an invaluable tool for investigating Titan's seas and lakes. The T91 (May 2013) observation of Ligeia Mare, Titan's second largest sea, has demonstrated the capabilities of the RADAR, in its altimeter mode, to measure depth, composition and seafloor topography. The 104 (August 2014) observation provided similar data over the largest sea, Kraken Mare, and the T108 (January 2015) flyby acquired an altimetry pass over Punga Mare. The T49 (December 2007) altimetry pass over Ontario Lacus, the largest southern liquid body, has also been processed to retrieve subsurface echoes. Cassini's final flyby of Titan, T126 (April 2017), is the next and unique opportunity to observe an area in the Northern Polar region of Titan, where several small - medium size (5 - 30 km) lakes are present and have been previously imaged by Cassini. In our presentation, we will report the integrated results of these investigations and discuss them in the overall context of Titan's hydrologic cycle.

Results from the Maine 1992 foliage penetration experiment

NASA Astrophysics Data System (ADS)

Toups, Michael F.; Ayasli, Serpil

1993-11-01

In order to investigate the detection of targets which are hidden by foliage, an experiment was designed which utilized a forest region located near Portage, Maine. The experiment was designed to address four issues. First, the properties of the backscatter or clutter which competes with the desired target were investigated. Second, the foliage induced attenuation that is experienced by the radar energy traversing the foliage were measured. Third, the ability of a synthetic aperture radar system to focus on a target obscured by foliage was investigated. Fourth, target signatures of foliage obscured and unobscured targets were measured. The forest region was investigated using two different airborne synthetic aperture radar (SAR) systems. A UHF wide-band SAR operated by SRI International was used as well as a L-, C-, and X-band SAR installed on a P-3 aircraft operated by the U.S. Navy. The SRI system was used to collect data over 16 square kilometers with repeat passes for verification of system performance. The P-3 system was used to collect over 50 square kilometers of data at three different depression angles with several repeat passes.

Space Radar Image of West Texas - SAR scan

NASA Technical Reports Server (NTRS)

1999-01-01

This radar image of the Midland/Odessa region of West Texas, demonstrates an experimental technique, called ScanSAR, that allows scientists to rapidly image large areas of the Earth's surface. The large image covers an area 245 kilometers by 225 kilometers (152 miles by 139 miles). It was obtained by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) flying aboard the space shuttle Endeavour on October 5, 1994. The smaller inset image is a standard SIR-C image showing a portion of the same area, 100 kilometers by 57 kilometers (62 miles by 35 miles) and was taken during the first flight of SIR-C on April 14, 1994. The bright spots on the right side of the image are the cities of Odessa (left) and Midland (right), Texas. The Pecos River runs from the top center to the bottom center of the image. Along the left side of the image are, from top to bottom, parts of the Guadalupe, Davis and Santiago Mountains. North is toward the upper right. Unlike conventional radar imaging, in which a radar continuously illuminates a single ground swath as the space shuttle passes over the terrain, a Scansar radar illuminates several adjacent ground swaths almost simultaneously, by 'scanning' the radar beam across a large area in a rapid sequence. The adjacent swaths, typically about 50 km (31 miles) wide, are then merged during ground processing to produce a single large scene. Illumination for this L-band scene is from the top of the image. The beams were scanned from the top of the scene to the bottom, as the shuttle flew from left to right. This scene was acquired in about 30 seconds. A normal SIR-C image is acquired in about 13 seconds. The ScanSAR mode will likely be used on future radar sensors to construct regional and possibly global radar images and topographic maps. The ScanSAR processor is being designed for 1996 implementation at NASA's Alaska SAR Facility, located at the University of Alaska Fairbanks, and will produce digital images from the forthcoming Canadian RADARSAT satellite. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v.(DLR), the major partner in science, operations, and data processing of X-SAR.

Metamaterial for Radar Frequencies

DTIC Science & Technology

2012-09-01

Circuit Board RAM Radar Absorbing Material RCS Radar Cross Section SNR Signal-to-Noise Ratio SNG Single-Negative SRR Split Ring Resonator...although some can be single-negative ( SNG ). DNG refers to material with simultaneous negative real parts of the permittivity r  and permeability

TELAER: a multi-mode/multi-antenna interferometric airborne SAR system

NASA Astrophysics Data System (ADS)

Perna, Stefano; Amaral, Tiago; Berardino, Paolo; Esposito, Carmen; Jackson, Giuseppe; Pauciullo, Antonio; Vaz Junior, Eurico; Wimmer, Christian; Lanari, Riccardo

2014-05-01

The present contribution is aimed at showing the capabilities of the TELAER airborne Synthetic Aperture Radar (SAR) system recently upgraded to the interferometric mode [1]. TELAER is an Italian airborne X-Band SAR system, mounted onboard a LearJet 35A aircraft. Originally equipped with a single TX/RX antenna, it now operates in single-pass interferometric mode thanks to a system upgrading [1] funded by the Italian National Research Council (CNR), via the Italian Ministry of Education, Universities and Research (MIUR), in the framework of a cooperation between CNR and the Italian Agency for Agriculture Subsidy Payments (AGEA). In the frame of such cooperation, CNR has entrusted the Institute for Electromagnetic Sensing of the Environment (IREA) for managing all the activities, included the final flight tests, related to the system upgrading. According to such an upgrading, two additional receiving X-band antennas have been installed in order to allow, simultaneously, single-pass Across-Track and Along-Track interferometry [1]. More specifically, the three antennas are now installed in such a way to produce three different across-track baselines and two different along-track baselines. Moreover, in the frame of the same system upgrading, it has been mounted onboard the Learjet an accurate embedded Global Navigation Satellite System and Inertial Measurement Unit equipment. This allows precise measurement of the tracks described by the SAR antennas during the flight, in order to accurately implement Motion Compensation (MOCO) algorithms [2] during the image formation (focusing) step. It is worth remarking that the TELAER system upgraded to the interferometric mode is very flexible, since the user can set different operational modes characterized by different geometric resolutions and range swaths. In particular, it is possible to reach up to 0.5 m of resolution with a range swath of 2km; conversely, it is possible to enlarge the range swath up to 10 km at expenses of a degradation of the geometric resolution, which in this case becomes equal to 5m. Such an operational flexibility, added to the above discussed single-pass interferometric capability and to the intrinsic flexibility of airborne platforms, renders the TELAER airborne SAR system a powerful instrument for fast generation of high resolution Digital Elevation Models, even in natural disaster scenarios. Accordingly, this system can play today a key role not only for strictly scientific purposes, but also for the monitoring of natural hazards, especially if properly integrated with other remote sensing sensors. [1] S. Perna et al., "Capabilities of the TELAER airborne SAR system upgraded to the multi-antenna mode", In Proceedings IGARSS 2012 Symposium, Munich, 2012. [2] G. Franceschetti, and R.Lanari, Synthetic Aperture Radar Processing, CRC PRESS, New York, 1999.

Identification of corn fields using multidate radar data

NASA Technical Reports Server (NTRS)

Shanmugan, K. S.; Ulaby, F. T.; Narayanan, V.; Dobson, C.

1983-01-01

Airborne C- and L-band radar data acquired over a test site in western kansas were analyzed to determine corn-field identification accuracies obtainable using single-channel, multichannel, and multidate radar data. An automated pattern-recognition procedure was used to classify 144 fields into three categories: corn, pasture land, and bare soil (including wheat stubble and fallow). Corn fields were identified with accuracies ranging from 85 percent for single channel, single-date data to 100 percent for single-channel, multidate data. The effects of radar parameters such as frequency, polarization, and look angle as well as the effects of soil moisture on the classification accuracy are also presented.

Borehole radar interferometry revisited

USGS Publications Warehouse

Liu, Lanbo; Ma, Chunguang; Lane, John W.; Joesten, Peter K.

2014-01-01

Single-hole, multi-offset borehole-radar reflection (SHMOR) is an effective technique for fracture detection. However, commercial radar system limitations hinder the acquisition of multi-offset reflection data in a single borehole. Transforming cross-hole transmission mode radar data to virtual single-hole, multi-offset reflection data using a wave interferometric virtual source (WIVS) approach has been proposed but not fully demonstrated. In this study, we compare WIVS-derived virtual single-hole, multi-offset reflection data to real SHMOR radar reflection profiles using cross-hole and single-hole radar data acquired in two boreholes located at the University of Connecticut (Storrs, CT USA). The field data results are similar to full-waveform numerical simulations developed for a two-borehole model. The reflection from the adjacent borehole is clearly imaged by both the real and WIVS-derived virtual reflection profiles. Reflector travel-time changes induced by deviation of the two boreholes from the vertical can also be observed on the real and virtual reflection profiles. The results of this study demonstrate the potential of the WIVS approach to improve bedrock fracture imaging for hydrogeological and petroleum reservoir development applications.

UAVSAR Program: Initial Results from New Instrument Capabilities

NASA Technical Reports Server (NTRS)

Lou, Yunling; Hensley, Scott; Moghaddam, Mahta; Moller, Delwyn; Chapin, Elaine; Chau, Alexandra; Clark, Duane; Hawkins, Brian; Jones, Cathleen; Marks, Phillip;

NASA Tech Briefs, November 2008

NASA Technical Reports Server (NTRS)

2008-01-01

Topics covered include: Digital Phase Meter for a Laser Heterodyne Interferometer; Vision System Measures Motions of Robot and External Objects; Advanced Precipitation Radar Antenna to Measure Rainfall From Space; Wide-Band Radar for Measuring Thickness of Sea Ice; Vertical Isolation for Photodiodes in CMOS Imagers; Wide-Band Microwave Receivers Using Photonic Processing; L-Band Transmit/Receive Module for Phase-Stable Array Antennas; Microwave Power Combiner/Switch Utilizing a Faraday Rotator; Compact Low-Loss Planar Magic-T; Using Pipelined XNOR Logic to Reduce SEU Risks in State Machines; Quasi-Optical Transmission Line for 94-GHz Radar; Next Generation Flight Controller Trainer System; Converting from DDOR SASF to APF; Converting from CVF to AAF; Documenting AUTOGEN and APGEN Model Files; Sequence History Update Tool; Extraction and Analysis of Display Data; MRO DKF Post-Processing Tool; Rig Diagnostic Tools; MRO Sequence Checking Tool; Science Activity Planner for the MER Mission; UAVSAR Flight-Planning System; Templates for Deposition of Microscopic Pointed Structures; Adjustable Membrane Mirrors Incorporating G-Elastomers; Hall-Effect Thruster Utilizing Bismuth as Propellant; High-Temperature Crystal-Growth Cartridge Tubes Made by VPS; Quench Crucibles Reinforced with Metal; Deep-Sea Hydrothermal-Vent Sampler; Mars Rocket Propulsion System; Two-Stage Passive Vibration Isolator; Improved Thermal Design of a Compression Mold; Enhanced Pseudo-Waypoint Guidance for Spacecraft Maneuvers; Altimetry Using GPS-Reflection/Occultation Interferometry; Thermally Driven Josephson Effect; Perturbation Effects on a Supercritical C7H16/N2 Mixing Layer; Gold Nanoparticle Labels Amplify Ellipsometric Signals; Phase Matching of Diverse Modes in a WGM Resonator; WGM Resonators for Terahertz-to-Optical Frequency Conversion; Determining Concentration of Nanoparticles from Ellipsometry; Microwave-to-Optical Conversion in WGM Resonators; Four-Pass Coupler for Laser-Diode-Pumped Solid-State Laser; Low-Resolution Raman-Spectroscopy Combustion Thermometry; Temperature Sensors Based on WGM Optical Resonators; Varying the Divergence of Multiple Parallel Laser Beams; Efficient Algorithm for Rectangular Spiral Search; Algorithm-Based Fault Tolerance Integrated with Replication; Targeting and Localization for Mars Rover Operations; Terrain-Adaptive Navigation Architecture; Self-Adjusting Hash Tables for Embedded Flight Applications; Schema for Spacecraft-Command Dictionary; Combined GMSK Communications and PN Ranging; System-Level Integration of Mass Memory; Network-Attached Solid-State Recorder Architecture; Method of Cross-Linking Aerogels Using a One-Pot Reaction Scheme; An Efficient Reachability Analysis Algorithm.

Producing Science-Ready Radar Datasets for the Retrieval of Forest Structure Parameters from Backscatter: Correcting for Terrain Topography and Changes in Vegetation Reflectivity

NASA Technical Reports Server (NTRS)

Simard, M.; Riel, Bryan; Hensley, S.; Lavalle, Marco

2011-01-01

Radar backscatter data contain both geometric and radiometric distortions due to underlying topography and the radar viewing geometry. Our objective is to develop a radiometric correction algorithm specific to the UAVSAR system configuration that would improve retrieval of forest structure parameters. UAVSAR is an airborne Lband radar capable of repeat?pass interferometry producing images with a spatial resolution of 5m. It is characterized by an electronically steerable antenna to compensate for aircraft attitude. Thus, the computation of viewing angles (i.e. look, incidence and projection) must include aircraft attitude angles (i.e. yaw, pitch and roll) in addition to the antenna steering angle. In this presentation, we address two components of radiometric correction: area projection and vegetation reflectivity. The first correction is applied by normalization of the radar backscatter by the local ground area illuminated by the radar beam. The second is a correction due to changes in vegetation reflectivity with viewing geometry.

Optical alignment of high resolution Fourier transform spectrometers

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Ocallaghan, F. G.; Cassie, A. G.

1980-01-01

Remote sensing, high resolution FTS instruments often contain three primary optical subsystems: Fore-Optics, Interferometer Optics, and Post, or Detector Optics. We discuss the alignment of a double-pass FTS containing a cat's-eye retro-reflector. Also, the alignment of fore-optics containing confocal paraboloids with a reflecting field stop which relays a field image onto a camera is discussed.

Using the Subsurface Soil Sounding Radar for Investigating the Structure and Total Electron Content of the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Smirnov, V. M.; Yushkova, O. V.; Marchuk, V. N.

2018-05-01

The possibilities of using the Martian soil subsurface sounding radar for investigating the structure of the plasma shell surrounding the planet have been considered. Based on the numerical modeling results and actual soil sounding data, it has been shown that the soil sounding mode of the radio-locating MARSIS radar can be used to assess the structure of the Martian ionosphere. As the emitted signals pass to the planet's surface, it is possible to use the reflected signals to estimate the total electron content of the Martian ionosphere along the flight track of the spacecraft.

Zero-phonon-line emission of single molecules for applications in quantum information processing

NASA Astrophysics Data System (ADS)

Kiraz, Alper; Ehrl, M.; Mustecaplioglu, O. E.; Hellerer, T.; Brauchle, C.; Zumbusch, A.

2005-07-01

A single photon source which generates transform limited single photons is highly desirable for applications in quantum optics. Transform limited emission guarantees the indistinguishability of the emitted single photons. This, in turn brings groundbreaking applications in linear optics quantum information processing within an experimental reach. Recently, self-assembled InAs quantum dots and trapped atoms have successfully been demonstrated as such sources for highly indistinguishable single photons. Here, we demonstrate that nearly transform limited zero-phonon-line (ZPL) emission from single molecules can be obtained by using vibronic excitation. Furthermore we report the results of coincidence detection experiments at the output of a Michelson-type interferometer. These experiments reveal Hong-Ou-Mandel correlations as a proof of the indistinguishability of the single photons emitted consecutively from a single molecule. Therefore, single molecules constitute an attractive alternative to single InAs quantum dots and trapped atoms for applications in linear optics quantum information processing. Experiments were performed with a home-built confocal microscope keeping the sample in a superfluid liquid Helium bath at 1.4K. We investigated terrylenediimide (TDI) molecules highly diluted in hexadecane (Shpol'skii matrix). A continuous wave single mode dye laser was used for excitation of vibronic transitions of individual molecules. From the integral fluorescence, the ZPL of single molecules was selected with a spectrally narrow interference filter. The ZPL emission was then sent to a scanning Fabry-Perot interferometer for linewidth measurements or a Michelson-type interferometer for coincidence detection.

Lunar Lava Tube Sensing

NASA Technical Reports Server (NTRS)

York, Cheryl Lynn; Walden, Bryce; Billings, Thomas L.; Reeder, P. Douglas

1992-01-01

Large (greater than 300 m diameter) lava tube caverns appear to exist on the Moon and could provide substantial safety and cost benefits for lunar bases. Over 40 m of basalt and regolith constitute the lava tube roof and would protect both construction and operations. Constant temperatures of -20 C reduce thermal stress on structures and machines. Base designs need not incorporate heavy shielding, so lightweight materials can be used and construction can be expedited. Identification and characterization of lava tube caverns can be incorporated into current precursor lunar mission plans. Some searches can even be done from Earth. Specific recommendations for lunar lava tube search and exploration are (1) an Earth-based radar interferometer, (2) an Earth-penetrating radar (EPR) orbiter, (3) kinetic penetrators for lunar lava tube confirmation, (4) a 'Moon Bat' hovering rocket vehicle, and (5) the use of other proposed landers and orbiters to help find lunar lava tubes.

KARIN: The Ka-Band Radar Interferometer for the Proposed Surface Water and Ocean Topography (SWOT) Mission

NASA Technical Reports Server (NTRS)

Esteban-Fernandez, Daniel; Peral, Eva; McWatters, Dalia; Pollard, Brian; Rodriguez, Ernesto; Hughes, Richard

2013-01-01

Over the last two decades, several nadir profiling radar altimeters have provided our first global look at the ocean basin-scale circulation and the ocean mesoscale at wavelengths longer than 100 km. Due to sampling limitations, nadir altimetry is unable to resolve the small wavelength ocean mesoscale and sub-mesoscale that are responsible for the vertical mixing of ocean heat and gases and the dissipation of kinetic energy from large to small scales. The proposed Surface Water and Ocean Topography (SWOT) mission would be a partnership between NASA, CNES (Centre National d'Etudes Spaciales) and the Canadian Space Agency, and would have as one of its main goals the measurement of ocean topography with kilometer-scale spatial resolution and centimeter scale accuracy. In this paper, we provide an overview of all ocean error sources that would contribute to the SWOT mission.

Space Radar Image of Owens Valley, California

NASA Technical Reports Server (NTRS)

1999-01-01

This is a three-dimensional perspective view of Owens Valley, near the town of Bishop, California that was created by combining two spaceborne radar images using a technique known as interferometry. Visualizations like this one are helpful to scientists because they clarify the relationships of the different types of surfaces detected by the radar and the shapes of the topographic features such as mountains and valleys. The view is looking southeast along the eastern edge of Owens Valley. The White Mountains are in the center of the image, and the Inyo Mountains loom in the background. The high peaks of the White Mountains rise more than 3,000 meters (10,000 feet) above the valley floor. The runways of the Bishop airport are visible at the right edge of the image. The meandering course of the Owens River and its tributaries appear light blue on the valley floor. Blue areas in the image are smooth, yellow areas are rock outcrops, and brown areas near the mountains are deposits of boulders, gravel and sand known as alluvial fans. The image was constructed by overlaying a color composite radar image on top of a digital elevation map. The radar data were taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on board the space shuttle Endeavour in October 1994. The digital elevation map was produced using radar interferometry, a process in which radar data are acquired on different passes of the space shuttle. The two data passes are compared to obtain elevation information. The elevation data were derived from a 1,500-km-long (930-mile) digital topographic map processed at JPL. Radar image data are draped over the topography to provide the color with the following assignments: red is L-band vertically transmitted, vertically received; green is C-band vertically transmitted, vertically received; and blue is the ratio of C-band vertically transmitted, vertically received to L-band vertically transmitted, vertically received. This image is centered near 37.4 degrees north latitude and 118.3 degrees west longitude. No vertical exaggeration factor has been applied to the data. SIR-C/X-SAR, a joint mission of the German, Italian, and the United States space agencies, is part of NASA's Mission to Planet Earth.

4D measurements of biological and synthetic structures using a dynamic interferometer

NASA Astrophysics Data System (ADS)

Toto-Arellano, Noel-Ivan

2017-12-01

Considering the deficiency of time elapsed for phase-stepping interferometric techniques and the need of developing non-contact and on-line measurement with high accuracy, a single-shot phase-shifting triple-interferometer (PSTI) is developed for analysis of characteristics of transparent structures and optical path difference (OPD) measurements. In the proposed PSTI, coupled three interferometers which generate four interference patterns, and a polarizer array is used as phase shifters to produce four spatially separated interferograms with π/2-phase shifts, which are recorded in a single capture by a camera. The configuration of the PSTI allows dynamic measurements (4D measurements) and does not require vibration isolation. We have applied the developed system to examine the size and OPD of cells, and the slope of thin films

All-Optical Fiber Hanbury Brown & Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot

PubMed Central

Muñoz-Matutano, G.; Barrera, D.; Fernández-Pousa, C.R.; Chulia-Jordan, R.; Seravalli, L.; Trevisi, G.; Frigeri, P.; Sales, S.; Martínez-Pastor, J.

2016-01-01

New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure splitting for the neutral exciton transition within our spectral resolution (46 μeV), metamorphic QD single photon emission studied with our all-fiber Hanbury Brown & Twiss interferometer could lead to a more efficient analysis of entangled photon sources at telecom wavelength. This all-optical fiber scheme opens the door to new first and second order interferometers to study photon indistinguishability, entangled photon and photon cross correlation in the more interesting telecom wavelengths. PMID:27257122

Feasibility study of a microwave radar system for agricultural inspection

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

Okelo-Odongo, S.

1994-10-03

The feasibility of an impulse radar system for agricultural inspection is investigated. This system would be able to quickly determine the quality of foodstuffs that are passed through the system. A prototype was designed at the Lawrence Livermore National Laboratory and this report discusses it`s evaluation. A variety of apples were used to test the system and preliminary data suggests that this technology holds promise for successful application on a large scale in food processing plants.

A Comparison of Structurally Connected and Multiple Spacecraft Interferometers

NASA Technical Reports Server (NTRS)

Surka, Derek M.; Crawley, Edward F.

1996-01-01

Structurally connected and multiple spacecraft interferometers are compared in an attempt to establish the maximum baseline (referred to as the "cross-over baseline") for which it is preferable to operate a single-structure interferometer in space rather than an interferometer composed of numerous, smaller spacecraft. This comparison is made using the total launched mass of each configuration as the comparison metric. A framework of study within which structurally connected and multiple spacecraft interferometers can be compared is presented in block diagram form. This methodology is then applied to twenty-two different combinations of trade space parameters to investigate the effects of different orbits, orientations, truss materials, propellants, attitude control actuators, onboard disturbance sources, and performance requirements on the cross-over baseline. Rotating interferometers and the potential advantages of adding active structural control to the connected truss of the structurally connected interferometer are also examined. The minimum mass design of the structurally connected interferometer that meets all performance-requirements and satisfies all imposed constraints is determined as a function of baseline. This minimum mass design is then compared to the design of the multiple spacecraft interferometer. It is discovered that the design of the minimum mass structurally connected interferometer that meets all performance requirements and constraints in solar orbit is limited by the minimum allowable aspect ratio, areal density, and gage of the struts. In the formulation of the problem used in this study, there is no advantage to adding active structural control to the truss for interferometers in solar orbit. The cross-over baseline for missions of practical duration (ranging from one week to thirty years) in solar orbit is approximately 400 m for non-rotating interferometers and 650 m for rotating interferometers.

High resolution Fourier interferometer-spectrophotopolarimeter

NASA Technical Reports Server (NTRS)

Fymat, A. L. (Inventor)

1976-01-01

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.

Landau-Zener interferometry in a Cooper pair box

NASA Astrophysics Data System (ADS)

Sillanpää, Mika; Lehtinen, Teijo; Paila, Antti; Makhlin, Yuriy; Hakonen, Pertti

2006-03-01

Quantum-mechanical systems having two crossing energy levels are ubiquitous in nature. The rate v = d (E1- E0)/dt at which such levels in a driven system approach each other determines the probability PLZ of a Landau-Zener (LZ) tunneling between them. The traditional treatment of the LZ process, however, ignores quantum-mechanical interference. Here we report an observation of phase-sensitive interference between consecutive LZ tunneling attempts in an artificial two-state system, a superconducting charge qubit. We interpret the experiment in terms of a multi-pass analog to the optical Mach- Zehnder interferometer: The beam splitting occurs by LZ tunneling at the charge degeneracy, while the arms of the Mach- Zehnder interferometer in energy space are represented by the ground and excited state. In accord with theory, we observe constructive interference when the Stokes phase φS picked up during the LZ interaction, and the dynamical phase of one drive period φ= (E1- E0) dt satisfy the condition: (φ- 2 φS) = m .2π. Our LZ interferometer can be used as a high-resolution detector for phase and charge owing to interferometric sensitivity- enhancement.

Detection of atmospheric infrasound with a ring laser interferometer

NASA Astrophysics Data System (ADS)

Dunn, Robert W.; Meredith, John A.; Lamb, Angela B.; Kessler, Elijah G.

2016-09-01

In this paper, the results from using a large active ring laser interferometer as an infrasound detector are presented. On April 27, 2014, an EF4 tornado struck Central Arkansas and passed within 21 km of the ring laser interferometer. The tornado resulted in 16 fatalities and millions of dollars in damage. Using the ring laser to study the tornado infrasound produced results that qualitatively agree with several findings from a long-term study of weather generated infrasound by the National Oceanic and Atmospheric Administration. A Fast Fourier Transform of the ring laser output revealed a coherent frequency of approximately 0.94 Hz that lasted during the life of the storm. The 0.94 Hz frequency was initially observed 30 min before the funnel was reported on the ground. Infrasound signatures from four separate tornadoes are presented. In each case, coherent infrasound was detected at least 30 min before the tornado was reported on the ground. Examples of the detection of distant coherent acoustic-gravity waves from volcanoes and typhoons are also presented. In addition, buoyancy waves were recorded.

Beyond Radar Backscatter: Estimating Forest Structure and Biomass with Radar Interferometry and Lidar Remote Sensing

NASA Astrophysics Data System (ADS)

Lavalle, M.; Ahmed, R.

2014-12-01

Mapping forest structure and aboveground biomass globally is a major challenge that the remote sensing community has been facing for decades. Radar backscatter is sensitive to biomass only up to a certain amount (about 150 tons/ha at L-band and 300 tons/ha at P-band), whereas lidar remote sensing is strongly limited by poor spatial coverage. In recent years radar interferometry, including its extension to polarimetric radar interferometry (PolInSAR), has emerged as a new technique to overcome the limitations of radar backscatter. The idea of PolInSAR is to use jointly interferometric and polarimetric radar techniques to separate different scattering mechanisms and retrieve the vertical structure of forests. The advantage is to map ecosystem structure continuously over large areas and independently of cloud coverage. Experiments have shown that forest height - an important proxy for biomass - can be estimated using PolInSAR with accuracy between 15% and 20% at plot level. At AGU we will review the state-of-art of repeat-pass PolInSAR for biomass mapping, including its potential and limitations, and discuss how merging lidar data with PolInSAR data can be beneficial not only for product cross-validation but also for achieving better estimation of ecosystem properties over large areas. In particular, lidar data are expected to aid the inversion of PolInSAR models by providing (1) better identification of ground under the canopy, (2) approximate information of canopy structure in limited areas, and (3) maximum tree height useful for mapping PolInSAR temporal decorrelation. We will show our tree height and biomass maps using PolInSAR L-band JPL/UAVSAR data collected in tropical and temperate forests, and P-band ONERA/TROPISAR data acquired in French Guiana. LVIS lidar data will be used, as well as SRTM data, field measurements and inventory data to support our study. The use of two different radar frequencies and repeat-pass JPL UAVSAR data will offer also the opportunity to compare our results with the new airborne P-band ECOSAR and L-band DBSAR instruments developed at the NASA Goddard Space Flight Center.

Ultrasonic characterization of single drops of liquids

DOEpatents

Sinha, D.N.

1998-04-14

Ultrasonic characterization of single drops of liquids is disclosed. The present invention includes the use of two closely spaced transducers, or one transducer and a closely spaced reflector plate, to form an interferometer suitable for ultrasonic characterization of droplet-size and smaller samples without the need for a container. The droplet is held between the interferometer elements, whose distance apart may be adjusted, by surface tension. The surfaces of the interferometer elements may be readily cleansed by a stream of solvent followed by purified air when it is desired to change samples. A single drop of liquid is sufficient for high-quality measurement. Examples of samples which may be investigated using the apparatus and method of the present invention include biological specimens (tear drops; blood and other body fluid samples; samples from tumors, tissues, and organs; secretions from tissues and organs; snake and bee venom, etc.) for diagnostic evaluation, samples in forensic investigations, and detection of drugs in small quantities. 5 figs.

A multi-core fiber based interferometer for high temperature sensing

NASA Astrophysics Data System (ADS)

Zhou, Song; Huang, Bo; Shu, Xuewen

2017-04-01

In this paper, we have verified and implemented a Mach-Zehnder interferometer based on seven-core fiber for high temperature sensing application. This proposed structure is based on a multi-mode-multi-core-multi-mode fiber structure sandwiched by a single mode fiber. Between the single-mode and multi-core fiber, a 3 mm long multi-mode fiber is formed for lead-in and lead-out light. The basic operation principle of this device is the use of multi-core modes, single-mode and multi-mode interference coupling is also utilized. Experimental results indicate that this interferometer sensor is capable of accurate measurements of temperatures up to 800 °C, and the temperature sensitivity of the proposed sensor is as high as 170.2 pm/°C, which is much higher than the current existing MZI based temperature sensors (109 pm/°C). This type of sensor is promising for practical high temperature applications due to its advantages including high sensitivity, simple fabrication process, low cost and compactness.

Ultrasonic characterization of single drops of liquids

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

Sinha, D.N.

Ultrasonic characterization of single drops of liquids is disclosed. The present invention includes the use of two closely spaced transducers, or one transducer and a closely spaced reflector plate, to form an interferometer suitable for ultrasonic characterization of droplet-size and smaller samples without the need for a container. The droplet is held between the interferometer elements, whose distance apart may be adjusted, by surface tension. The surfaces of the interferometer elements may be readily cleansed by a stream of solvent followed by purified air when it is desired to change samples. A single drop of liquid is sufficient for high-qualitymore » measurement. Examples of samples which may be investigated using the apparatus and method of the present invention include biological specimens (tear drops; blood and other body fluid samples; samples from tumors, tissues, and organs; secretions from tissues and organs; snake and bee venom, etc.) for diagnostic evaluation, samples in forensic investigations, and detection of drugs in small quantities. 5 figs.« less

Direct Measurement of Scattered Light Effect on the Sensitivity in TAMA300

NASA Astrophysics Data System (ADS)

Takahashi, R.; Arai, Koji; Kawamaru, Seiji; Smith, Michael R.

2003-07-01

Laser interferometer gravitational wave detectors need vacuum tubes through which the laser beams pass. The light scattered from the arm cavity mirrors will make multiple reflections from the inside wall of the polished tube back onto the mirrors causing phase noise on the interferometer output beam. The TAMA300 has two 300-m length arms enclosed by vacuum tubes. By vibrating one of the tubes of the TAMA300, we directly observed the effect of scattered light on the displacement sensitivity. It was found that a tube vibration amplitude of 5.6 µm at 776.5 Hz increased the mirror displacement noise to 1.2 × 10-17 m. This noise level is consistent with the calculated noise due to the scattered light effect.

A THz Spectroscopy System Based on Coherent Radiation from Ultrashort Electron Bunches

NASA Astrophysics Data System (ADS)

Saisut, J.; Rimjaem, S.; Thongbai, C.

2018-05-01

A spectroscopy system will be discussed for coherent THz transition radiation emitted from short electron bunches, which are generated from a system consisting of an RF gun with a thermionic cathode, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator for post-acceleration. The THz radiation is generated as backward transition radiation when electron bunches pass through an aluminum foil. The emitted THz transition radiation, which is coherent at wavelengths equal to and longer than the electron bunch length, is coupled to a Michelson interferometer. The performance of the spectroscopy system employing a Michelson interferometer is discussed. The radiation power spectra under different conditions are presented. As an example, the optical constant of a silicon wafer can be obtained using the dispersive Fourier transform spectroscopy (DFTS) technique.

High Resolution Displacement Monitoring for Urban Environments in Seattle, Washington using Terrestrial Radar Interferometry

NASA Astrophysics Data System (ADS)

Lowry, B. W.; Schrock, G.; Werner, C. L.; Zhou, W.; Pugh, N.

2015-12-01

Displacement monitoring using Terrestrial Radar Interferometry (TRI) over an urban environment was conducted to monitor for potential movement of buildings, roadways, and urban infrastructure in Seattle, Washington for a 6 week deployment in March and April of 2015. A Gamma Portable Radar Interferometer was deployed on a the lower roof of the Smith Tower at an elevation of about 100 m, overlooking the historical district of Pioneer Square. Radar monitoring in this context provides wide area coverage, sub millimeter precision, near real time alarming, and reflectorless measurement. Image georectification was established using a previously collected airborne lidar scan which was used to map the radar image onto a 3D 1st return elevation model of downtown Seattle. Platform stability concerns were monitored using high rate GPS and a 3-axis accelerometer to monitor for building movement or platform instability. Displacements were imaged at 2 minute intervals and stacked into 2 hour averages to aid in noise characterization. Changes in coherence are characterized based on diurnal fluctuations of temperature, cultural noise, and target continuity. These informed atmospheric and image selection filters for optimizing interferogram generation and displacement measurement quality control. An urban monitoring workflow was established using point target interferometric analysis to create a monitoring set of approximately 100,000 stable monitoring points measured at 2 minute to 3 hour intervals over the 6 week deployment. Radar displacement measurements were verified using ongoing survey and GPS monitoring program and with corner reflector tests to verify look angle corrections to settlement motion. Insights from this monitoring program can be used to design TRI monitoring programs for underground tunneling, urban subsidence, and earthquake damage assessment applications.

Holographic Twyman-Green interferometer

NASA Technical Reports Server (NTRS)

Chen, C. W.; Breckinridge, J. B.

1982-01-01

A dichromated gelatin off-axis Fresnel zone plate was designed, fabricated, and used in a new type of interferometer for optical metrology. This single hologram optical element combines the functions of a beam splitter, beam diverger, and aberrated null lens. Data presented show the successful application for an interferometric test of an f/6, 200-mm diam parabolic mirror.

Analytically solvable model of an electronic Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Ngo Dinh, Stéphane; Bagrets, Dmitry A.; Mirlin, Alexander D.

2013-05-01

We consider a class of models of nonequilibrium electronic Mach-Zehnder interferometers built on integer quantum Hall edges states. The models are characterized by the electron-electron interaction being restricted to the inner part of the interferometer and transmission coefficients of the quantum quantum point contacts, defining the interferometer, which may take arbitrary values from zero to one. We establish an exact solution of these models in terms of single-particle quantities, determinants and resolvents of Fredholm integral operators. In the general situation, the results can be obtained numerically. In the case of strong charging interaction, the operators acquire the block Toeplitz form. Analyzing the corresponding Riemann-Hilbert problem, we reduce the result to certain singular single-channel determinants (which are a generalization of Toeplitz determinants with Fisher-Hartwig singularities) and obtain an analytic result for the interference current (and, in particular, for the visibility of Aharonov-Bohm oscillations). Our results, which are in good agreement with experimental observations, show an intimate connection between the observed “lobe” structure in the visibility of Aharonov-Bohm oscillations and multiple branches in the asymptotics of singular integral determinants.

Critical dimensional linewidth calibration using UV microscope and laser interferometry

NASA Astrophysics Data System (ADS)

Li, Qi; Gao, Si-tian; Li, Wei; Lu, Ming-zhen; Zhang, Ming-kai

2013-10-01

In order to calibrate the critical dimensional (CD) uncertainty of lithography masks in semiconductor manufacturing, NIM is building a two dimensional metrological UV microscope which has traceable measurement ability for nanometer linewidths and pitches. The microscope mainly consists of UV light receiving components, piezoelectric ceramics (PZT) driven stage and interferometer calibration framework. In UV light receiving components they include all optical elements on optical path. The UV light originates from Köhler high aperture transmit/reflect illumination sources; then goes through objective lens to UV splitting optical elements; after that, one part of light attains UV camera for large range calibration, the other part of light passes through a three dimensional adjusted pinhole and is collected by PMT for nanoscale scanning. In PZT driven stage, PZT stick actuators with closed loop control are equipped to push/pull a flexural hinge based platform. The platform has a novel designed compound flexural hinges which nest separate X, Y direction moving mechanisms within one layer but avoiding from mutual cross talk, besides this, the hinges also contain leverage structures to amplify moving distance. With these designs, the platform can attain 100 μm displacement ranges as well as 1 nm resolution. In interferometer framework a heterodyne multi-pass interferometer is mounted on the platform, which measures X-Y plane movement and Z axis rotation, through reference mirror mounted on objective lens tube and Zerodur mirror mounted on PZT platform, the displacement is traced back to laser wavelength. When development is finished, the apparatus can offer the capability to calibrate one dimensional linewidths and two dimensional pitches ranging from 200nm to 50μm with expanded uncertainty below 20nm.

Radar, target and ranging

NASA Astrophysics Data System (ADS)

1984-09-01

This Test Operations Procedure (TOP) provides conventional test methods employing conventional test instrumentation for testing conventional radars. Single tests and subtests designed to test radar components, transmitters, receivers, antennas, etc., and system performance are conducted with single item instruments such as meters, generators, attenuators, counters, oscillators, plotters, etc., and with adequate land areas for conducting field tests.

C(G)-Band and X(I)-Band Noncoherent Radar Transponder Performance Specification Standard

DTIC Science & Technology

2014-06-01

transmitter with an integral power supply. The transponder must accept interrogation signals from single or multiple radar sets and provide a...the transponder receives a coded pulse interrogation from the ground radar and transmits a single pulse reply in the same frequency band. The...obtained by using either a single tracking station or several tracking stations along the flight path of the target vehicle. The accuracy gained by use

Sensitivity of an imaging space infrared interferometer.

PubMed

Nakajima, T; Matsuhara, H

2001-02-01

We study the sensitivities of space infrared interferometers. We formulate the signal-to-noise ratios of infrared images obtained by aperture synthesis in the presence of source shot noise, background shot noise, and detector read noise. We consider the case in which n beams are combined pairwise at n(n-1)/2 detectors and the case in which all the n beams are combined at a single detector. We apply the results to future missions, Terrestrial Planet Finder and Darwin. We also discuss the potential of a far-infrared interferometer for a deep galaxy survey.

Wavelength-division and spatial multiplexing using tandem interferometers for Bragg grating sensor networks

NASA Astrophysics Data System (ADS)

Kalli, K.; Brady, G. P.; Webb, D. J.; Jackson, D. A.; Zhang, L.; Bennion, I.

1995-12-01

We present a new method for the interrogation of large arrays of Bragg grating sensors. Eight gratings operating between the wavelengths of 1533 and 1555 nm have been demultiplexed. An unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source provides a high-phase-resolution output for each sensor, the outputs of which are sequentially selected in wavelength by a tunable Fabry-Perot interferometer. The minimum detectable strain measured was 90 n 3 / \\radical Hz \\end-radical at 7 Hz for a wavelength of 1535 nm.

Self-referenced interferometer for cylindrical surfaces.

PubMed

Šarbort, Martin; Řeřucha, Šimon; Holá, Miroslava; Buchta, Zdeněk; Lazar, Josef

2015-11-20

We present a new interferometric method for shape measurement of hollow cylindrical tubes. We propose a simple and robust self-referenced interferometer where the reference and object waves are represented by the central and peripheral parts, respectively, of the conical wave generated by a single axicon lens. The interferogram detected by a digital camera is characterized by a closed-fringe pattern with a circular carrier. The interference phase is demodulated using spatial synchronous detection. The capabilities of the interferometer are experimentally tested for various hollow cylindrical tubes with lengths up to 600 mm.

Reflection-induced linear polarization rotation and phase modulation between orthogonal waves for refractive index variation measurement.

PubMed

Twu, Ruey-Ching; Wang, Jhao-Sheng

2016-04-01

An optical phase interrogation is proposed to study reflection-induced linear polarization rotation in a common-path homodyne interferometer. This optical methodology can also be applied to the measurement of the refractive index variation of a liquid solution. The performance of the refractive index sensing structure is discussed theoretically, and the experimental results demonstrated a very good ability based on the proposed schemes. Compared with a conventional common-path heterodyne interferometer, the proposed homodyne interferometer with only a single channel reduced the usage of optic elements.

NASADEM Initial Production Processing Results: Shuttle Radar Topography Mission (SRTM) Reprocessing with Improvements

NASA Astrophysics Data System (ADS)

Buckley, S.; Agram, P. S.; Belz, J. E.; Crippen, R. E.; Gurrola, E. M.; Hensley, S.; Kobrick, M.; Lavalle, M.; Martin, J. M.; Neumann, M.; Nguyen, Q.; Rosen, P. A.; Shimada, J.; Simard, M.; Tung, W.

2016-12-01

NASADEM is a significant modernization of SRTM digital elevation model (DEM) data supported by the NASA MEaSUREs program. We are reprocessing the raw radar signal data using improved algorithms and incorporating ICESat and DEM data unavailable during the original processing. The NASADEM products will be freely-available through the Land Processes Distributed Active Archive Center (LPDAAC) at one-arcsecond spacing and delivered by continent: North America, South America, Australia, Eurasia, Africa, and Island Groups. We are in the production phase of the project. This involves radar interferometry (InSAR) processing on thousands of radar datatakes. New phase unwrapping and height ripple error correction (HREC) procedures are applied to the data. The resulting strip DEMs and ancillary information are passed to a back-end processor to create DEM mosaics and new geocoded single-swath products. Manual data quality assessment (QA) and fixes are performed at several steps in the processing chain. Post-production DEM void-filling is described in a companion AGU Fall Meeting presentation. The team completed the InSAR processing for all continents and the manual QA of the strip DEMs for more than half the world. North America strip DEM void areas are reduced by more than 50%. The ICESat data is used for height ripple error correction and as control for continent-scale adjustment of the strip DEMs. These ripples are due to uncompensated mast motion most pronounced after Shuttle roll angle adjustment maneuvers. After an initial assessment of the NASADEM production processing for the Americas, we further refined the selection of ICESat data for control by excluded data over glaciers, snow cover, forest clear cuts, and sloped areas. The HREC algorithm reduces the North America ICESat-SRTM bias from 80 cm to 3 cm and the RMS from 5m to 4m.

Highly sensitive force sensor based on balloon-like interferometer

NASA Astrophysics Data System (ADS)

Wu, Yue; Xiao, Shiying; Xu, Yao; Shen, Ya; Jiang, Youchao; Jin, Wenxing; Yang, Yuguang; Jian, Shuisheng

2018-07-01

An all-fiber highly sensitive force sensor based on modal interferometer has been presented and demonstrated. The single-mode fiber (SMF) with coating stripped is designed into a balloon-like shape to form a modal interferometer. Due to the bent SMF, the interference occurs between the core mode and cladding modes. With variation of the force applied to the balloon-like interferometer, the bending diameter changes, which caused the wavelength shift of the modal interference. Thus the measurement of the force variation can be achieved by monitoring the wavelength shift. The performances of the interferometer with different bending diameter are experimentally investigated, and the maximum force sensitivity of 24.9 pm/ μ N can be achieved with the bending diameter 14 mm ranging from 0 μ N to 1464.12 μ N. Furthermore, the proposed fiber sensor exhibits the advantages of easy fabrication and low cost, making it a suitable candidate in the optical fiber sensing field.

Combining shearography and interferometric fringe projection in a single device for complete control of industrial applications

NASA Astrophysics Data System (ADS)

Blain, Pascal; Michel, Fabrice; Piron, Pierre; Renotte, Yvon; Habraken, Serge

2013-08-01

Noncontact optical measurement methods are essential tools in many industrial and research domains. A family of new noncontact optical measurement methods based on the polarization states splitting technique and monochromatic light projection as a way to overcome ambient lighting for in-situ measurement has been developed. Recent works on a birefringent element, a Savart plate, allow one to build a more flexible and robust interferometer. This interferometer is a multipurpose metrological device. On one hand the interferometer can be set in front of a charge-coupled device (CCD) camera. This optical measurement system is called a shearography interferometer and allows one to measure microdisplacements between two states of the studied object under coherent lighting. On the other hand, by producing and shifting multiple sinusoidal Young's interference patterns with this interferometer, and using a CCD camera, it is possible to build a three-dimensional structured light profilometer.

Spaceborne synthetic aperture radar pilot study

NASA Technical Reports Server (NTRS)

1974-01-01

A pilot study of a spaceborne sidelooking radar is summarized. The results of the system trade studies are given along with the electrical parameters for the proposed subsystems. The mechanical aspects, packaging, thermal control and dynamics of the proposed design are presented. Details of the data processor are given. A system is described that allows the data from a pass over the U. S. to be in hard copy form within two hours. Also included are the proposed schedule, work breakdown structure, and cost estimate.

High-sensitivity pressure sensor based on fiber Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Wu, Yue; Xu, Yao; Yang, Yuguang; Jin, Wenxing; Jiang, Youchao; Shen, Ya; Jian, Shuisheng

2017-10-01

In this paper we propose and experimentally demonstrate an optical fiber structure sensor based on a Mach-Zehnder interferometer for pressure measurement. The fiber sensor is composed of a single-mode-no-core-single-mode structure, a section of capillary pure silica tube and refractive index matching fluid (RIMF). As the pressure decreases, the sealed air in the tube expands and the liquid level of the RIMF increases, which causes a wavelength shift of the interferometer. The measurement of the pressure variation can thus be achieved by monitoring the wavelength shift. The experimental results agree well with the numerical simulation, and a maximum pressure sensitivity of 266.6 nm Mpa-1 is achieved experimentally. Furthermore, the proposed fiber sensor has the potential to obtain higher sensitivity by enlarging the length of the air cavity.

Slant path rain attenuation and path diversity statistics obtained through radar modeling of rain structure

NASA Technical Reports Server (NTRS)

Goldhirsh, J.

1984-01-01

Single and joint terminal slant path attenuation statistics at frequencies of 28.56 and 19.04 GHz have been derived, employing a radar data base obtained over a three-year period at Wallops Island, VA. Statistics were independently obtained for path elevation angles of 20, 45, and 90 deg for purposes of examining how elevation angles influences both single-terminal and joint probability distributions. Both diversity gains and autocorrelation function dependence on site spacing and elevation angles were determined employing the radar modeling results. Comparisons with other investigators are presented. An independent path elevation angle prediction technique was developed and demonstrated to fit well with the radar-derived single and joint terminal radar-derived cumulative fade distributions at various elevation angles.

Observations of the Sea Ice Cover Using Satellite Radar Interferometry

NASA Technical Reports Server (NTRS)

Kwok, Ronald

1995-01-01

The fringes observed in repeat pass interferograms are expressions of surface relief and relative displacements. The limiting condition in the application of spaceborne radar interferometry to the remote sensing of the sea ice cover is the large magnitude of motion between repeat passes. The translation and rotation of ice floes tend to decorrelate the observations rendering radar interferometry ineffective. In our study, we have located three images in the high Arctic during a period when there was negligible motion between repeat observations. The fringes obtained from these images show a wealth of information about the sea ice cover which is important in atmosphere-ice interactions and sea ice mechanics. These measurements provide the first detailed remote sensing view of the sea ice cover. Ridges can be observed and their heights estimated if the interferometric baseline allows. We have observed ridges with heights greater than 4m. The variability in the phase measurements over an area provides an indication of the large scale roughness. Relative centimetric displacements between rigid ice floes have been observed. We illustrate these observations with examples extracted from the interferograms formed from this set of ERS-1 SAR images.

Advanced Passive Microwave Radiometer Technology for GPM Mission

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Im, Eastwood; Kummerow, Christian; Principe, Caleb; Ruf, Christoper; Wilheit, Thomas; Starr, David (Technical Monitor)

2002-01-01

An interferometer-type passive microwave radiometer based on MMIC receiver technology and a thinned array antenna design is being developed under the Instrument Incubator Program (TIP) on a project entitled the Lightweight Rainfall Radiometer (LRR). The prototype single channel aircraft instrument will be ready for first testing in 2nd quarter 2003, for deployment on the NASA DC-8 aircraft and in a ground configuration manner; this version measures at 10.7 GHz in a crosstrack imaging mode. The design for a two (2) frequency preliminary space flight model at 19 and 35 GHz (also in crosstrack imaging mode) has also been completed, in which the design features would enable it to fly in a bore-sighted configuration with a new dual-frequency space radar (DPR) under development at the Communications Research Laboratory (CRL) in Tokyo, Japan. The DPR will be flown as one of two primary instruments on the Global Precipitation Measurement (GPM) mission's core satellite in the 2007 time frame. The dual frequency space flight design of the ERR matches the APR frequencies and will be proposed as an ancillary instrument on the GPM core satellite to advance space-based precipitation measurement by enabling better microphysical characterization and coincident volume data gathering for exercising combined algorithm techniques which make use of both radar backscatter and radiometer attenuation information to constrain rainrate solutions within a physical algorithm context. This talk will discuss the design features, performance capabilities, applications plans, and conical/polarametric imaging possibilities for the LRR, as well as a brief summary of the project status and schedule.

Nile Delta Fisheries, Egypt

NASA Image and Video Library

2015-12-09

On the left is a radar image of asteroid 1998 WT24 taken in December 2001 by scientists using NASA's the 230-foot (70-meter) DSS-14 antenna at Goldstone, California. On the right is a radar image of the same asteroid acquired on Dec. 11, 2015, during the asteroid's most recent Earth flyby. The radar images from 2001 (on the left), have a resolution of about 60 feet (19 meters) per pixel. The radar image from 2015 (on the right) achieved a spatial resolution as fine as 25 feet (7.5 meters) per pixel. The 2015 radar image was obtained using the same DSS-14 antenna at Goldstone to transmit high-power microwaves toward the asteroid. However, this time, the radar echoes bounced off the asteroid were received by the National Radio Astronomy Observatory's 100-meter (330-foot) Green Bank Telescope in West Virginia. The next visit of asteroid 1998 WT24 to Earth's neighborhood will be on Nov. 11, 2018, when it will make a distant pass at about 12.5-million miles (52 lunar distances). http://photojournal.jpl.nasa.gov/catalog/PIA20216

[RADAR: a program for the prevention of suicide in adolescents in the region of Aysen, Chile, preliminary results].

PubMed

Bustamante, Francisco; Urquidi, Cinthya; Florenzano, Ramón; Barrueto, Carolina; de Los Hoyos, Jaime; Ampuero, Karla; Terán, Laura; Figueroa, María Inés; Farías, Magdalena; Rueda, María Livia; Giacaman, Eduardo

2018-02-01

We present the preliminary results of the implementation of RADAR: a community suicide prevention program in adolescents implemented in two high schools in a south region of Chile. In a pilot study, during 2016, we implemented RADAR in two high schools of Puerto Aysen, in in the Region of Aysen of Chile. A total of 409 actors were trained (among students, school teachers, caregivers and health professionals) for the screening and referral of high suicide risk adolescents. Out of a total of 144 students who passed the RADAR screening systems, 29 cases were detected as suicide risk (20%) and 27 of them were opportunely referred to the Emergency Service of the Hospital of Puerto Aysen. In the second RADAR screening campaign, 3 months later, 90% of the cases no longer presented suicide risk. These results show the high proportion of ado lescents at risk of suicide who are not visible by the health system and the feasibility of implementing RADAR in the community as an effective suicide prevention intervention.

Optically phase-locked electronic speckle pattern interferometer system performance for vibration measurement in random displacement fields

NASA Astrophysics Data System (ADS)

Moran, Steve E.; Lugannani, Robert; Craig, Peter N.; Law, Robert L.

1989-02-01

An analysis is made of the performance of an optically phase-locked electronic speckle pattern interferometer in the presence of random noise displacements. Expressions for the phase-locked speckle contrast for single-frame imagery and the composite rms exposure for two sequentially subtracted frames are obtained in terms of the phase-locked composite and single-frame fringe functions. The noise fringe functions are evaluated for stationary, coherence-separable noise displacements obeying Gauss-Markov temporal statistics. The theoretical findings presented here are qualitatively supported by experimental results.

From CryoSat-2 to Sentinel-3 and Beyond

NASA Astrophysics Data System (ADS)

Francis, R.

2011-12-01

CryoSat-2 carried into Earth orbit the first altimeter using SAR principles, although similar techniques had been used on earlier Venusian missions. Furthermore, it carries a second antenna and receive chain, and has been very carefully calibrated, allowing interferometry between these antennas. The results of the SAR mode and of the interferometer have met all expectations, with handsome margins. Even before the launch of CryoSat-2 the further development of this concept was underway with the radar for the oceanography mission Sentinel-3. While this radar, named SRAL (SAR Radar Altimeter) does not have the interferometer capability of CryoSat-2's SIRAL (SAR Interferometric Radar Altimeter), it does have a second frequency, to enable direct measurement of the delay induced by the ionospheric electron content. Sentinel-3 will have a sun-synchronous orbit, like ERS and EnviSat, and will have a similar latitudinal range: about 82° north and south, compared to CryoSat's 88°. Sentinel-3 will operate its radar altimeter in the high-resolution SAR mode over coastal oceans and inland water, and will revert to the more classical pulse-width limited mode over the open oceans. The SAR mode generates data at a high rate, so the major limiting factor is the amount of on-board storage. The power consumption is also higher, imposing less critical constraints. For sizing purposes the coastal oceans are defined as waters within 300 km of the continental shorelines. Sentinel-3 is expected to be launched in 2013 and be followed 18 months later by a second satellite of the same design. The next step in the development of this family of radar altimeters is Jason-CS, which will provide Continuity of Service to the existing Jason series of operational oceanography missions. Jason-CS has a very strong heritage from CryoSat but will fly the traditional Jason orbit, which covers latitudes up to 66° from a high altitude of 1330 km. The new radar is called Poseidon-4, to emphasise the connection to Jason, but its concept owes more to Sentinel-3's SRAL. It retains SRAL's dual frequencies and its SAR mode, but adds some further refinements. Most notably, an operating mode in which SAR operations and full performance pulse-width limited mode are available simultaneously, is under study. This would enable the benefits of SAR mode to be achieved over all ocean areas if the volume of data generated could be stored and downlinked to the ground. This problem only becomes tractable if an on-board processing system can be introduced to perform the first level of SAR processing, reducing the data volume by several orders of magnitude. This is also under study. The architecture of the radar has a further improvement, in the extension of digital technology further into the domain of analog radio-frequency electronics. While this is essentially invisible to the scientific user, it will yield an instrument with higher quality and markedly superior stability. The Jason-CS missions (at least two satellites are planned) are currently in a study phase with an implementation decision expected at the end of 2012. The planned launch date for the first mission is 2017.

Impact Craters on Titan? Cassini RADAR View

NASA Technical Reports Server (NTRS)

Wood, Charles A.; Lopes, Rosaly; Stofan, Ellen R.; Paganelli, Flora; Elachi, Charles

2005-01-01

Titan is a planet-size (diameter of 5,150 km) satellite of Saturn that is currently being investigated by the Cassini spacecraft. Thus far only one flyby (Oct. 26, 2004; Ta) has occurred when radar images were obtained. In February, 2005, and approximately 20 more times in the next four years, additional radar swaths will be acquired. Each full swath images about 1% of Titan s surface at 13.78 GHz (Ku-band) with a maximum resolution of 400 m. The Ta radar pass [1] demonstrated that Titan has a solid surface with multiple types of landforms. However, there is no compelling detection of impact craters in this first radar swath. Dione, Tethys and other satellites of Saturn are intensely cratered, there is no way that Titan could have escaped a similar impact cratering past; thus there must be ongoing dynamic surface processes that erase impact craters (and other landforms) on Titan. The surface of Titan must be very young and the resurfacing rate must be significantly higher than the impact cratering rate.

Magellan radar to reveal secrets of enshrouded Venus

NASA Technical Reports Server (NTRS)

Saunders, R. Stephen

1990-01-01

Imaging Venus with a synthetic aperture radar (SAR) with 70 percent global coverage at 1-km optical line-pair resolution to provide a detailed global characterization of the volcanic land-forms on Venus by an integration of image data with altimetry is discussed. The Magellan radar system uses navigation predictions to preset the radar data collection parameters. The data are collected in such a way as to preserve the Doppler signature of surface elements and later they are transmitted to the earth for processing into high-resolution radar images. To maintain high accuracy, a complex on-board filter algorithm allows the altitude control logic to respond only to a narrow range of expected photon intensity levels and only to signals that occur within a small predicted interval of time. Each mapping pass images a swath of the planet that varies in width from 20 to 25 km. Since the orbital plane of the spacecraft remains fixed in the inertial space, the slow rotation of Venus continually brings new areas into view of the spacecraft.

Single-mode fiber, velocity interferometry

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

Krauter, K. G.; Jacobson, G. F.; Patterson, J. R.

2011-04-15

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, wemore » demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats--this interference occurs between the ''recently'' shifted and ''formerly unshifted'' paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber.« less

Single-mode fiber, velocity interferometry.

PubMed

Krauter, K G; Jacobson, G F; Patterson, J R; Nguyen, J H; Ambrose, W P

2011-04-01

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, we demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats-this interference occurs between the "recently" shifted and "formerly unshifted" paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber. © 2011 American Institute of Physics

Three-Centimeter Doppler Radar Observations of Wingtip-Generated Wake Vortices in Clear Air

NASA Technical Reports Server (NTRS)

Marshall, Robert E.; Mudukutore, Ashok; Wissel, Vicki L. H.; Myers, Theodore

1997-01-01

This report documents a high risk, high pay-off experiment with the objective of detecting, for the first time, the presence of aircraft wake vortices in clear air using X-band Doppler radar. Field experiments were conducted in January 1995 at the Wallops Flight Facility (WFF) to demonstrate the capability of the 9.33 GHz (I=3 cm) radar, which was assembled using an existing nine-meter parabolic antenna reflector at VVTT and the receiver/transmitter from the NASA Airborne Windshear Radar-Program. A C-130-aircraft, equipped with wingtip smoke generators, created visually marked wake vortices, which were recorded by video cameras. A C-band radar also observed the wake vortices during detection attempts with the X-band radar. Rawinsonde data was used to calculate vertical soundings of wake vortex decay time, cross aircraft bearing wind speed, and water vapor mixing ratio for aircraft passes over the radar measurement range. This experiment was a pathfinder in predicting, in real time, the location and persistence of C-130 vortices, and in setting the flight path of the aircraft to optimize X-band radar measurement of the wake vortex core in real time. This experiment was conducted in support of the NASA Aircraft Vortex Spacing System (AVOSS).

Eye investigation with optical microradar techniques

NASA Astrophysics Data System (ADS)

Molebny, Vasyl V.; Pallikaris, Ioannis G.; Naoumidis, Leonidas P.; Kurashov, Vitalij N.; Chyzh, Igor H.

1997-08-01

Many problems exist in ophthalmology, where accurate measurements of eye structure and its parameters can be provided using optical radar concept is of remote sensing. Coherent and non-coherent approaches are reviewed aiming cornea shape measurement and measurement of aberration distribution in the elements and media of an eye. Coherent radar techniques are analyzed taking into account non- reciprocity of eye media and anisoplanatism of the fovea, that results in an exiting image being not an auto- correlation of the point-spread function of a single pass, even in the approximation of spatial invariance of the system. It is found, that aberrations of the cornea and lens are not additive, and may not be brought to summary aberrations on the entrance aperture of the lens. Anisoplanatism of the fovea and its roughness lead to low degree of coherence in scattered light. To estimate the result of measurements, methodology has been developed using Zernike polynomials expansions. Aberration distributions were gotten from measurements in 16 points of an eye situated on two concentric circles. Wave aberration functions have been approximated using least-square criterion. Thus, all data were provided necessary for cornea ablation with PRK procedure.

Sea bottom topography imaging with SAR

NASA Technical Reports Server (NTRS)

Vanderkooij, M. W. A.; Wensink, G. J.; Vogelzang, J.

1992-01-01

It is well known that under favorable meteorological and hydrodynamical conditions the bottom topography of shallow seas can be mapped with airborne or spaceborne imaging radar. This phenomenon was observed for the first time in 1969 by de Loor and co-workers in Q-band Side Looking Airborne Radar (SLAR) imagery of sandwaves in the North Sea. It is now generally accepted that the imaging mechanism consists of three steps: (1) interaction between (tidal) current and bottom topography causes spatial modulations in the surface current velocity; (2) modulations in the surface current velocity give rise to variations in the spectrum of wind-generated waves, as described by the action balance equation; and (3) variations in the wave spectrum show up as intensity modulations in radar imagery. In order to predict radar backscatter modulations caused by sandwaves, an imaging model, covering the three steps, was developed by the Dutch Sea Bottom Topography Group. This model and some model results will be shown. On 16 Aug. 1989 an experiment was performed with the polarimetric P-, L-, and C-band synthetic aperture radar (SAR) of NASA/JPL. One scene was recorded in SAR mode. On 12 Jul. 1991 another three scenes were recorded, of which one was in the ATI-mode (Along-Track Interferometer). These experiments took place in the test area of the Sea Bottom Topography Group, 30 km off the Dutch coast, where the bottom topography is dominated by sand waves. In-situ data were gathered by a ship in the test area and on 'Measuring Platform Noordwijk', 20 km from the center of the test area. The radar images made during the experiment were compared with digitized maps of the bottom. Furthermore, the profiles of radar backscatter modulation were compared with the results of the model. During the workshop some preliminary results of the ATI measurements will be shown.

An in-line Mach-Zehnder Interferometer Using Thin-core Fiber for Ammonia Gas Sensing With High Sensitivity

NASA Astrophysics Data System (ADS)

Huang, Xinyue; Li, Xueming; Yang, Jianchun; Tao, Chuanyi; Guo, Xiaogang; Bao, Hebin; Yin, Yanjun; Chen, Huifei; Zhu, Yuhua

2017-04-01

Ammonia is an important indicator among environmental monitoring parameters. In this work, thin-core fiber Mach-Zehnder interferometer deposited with poly (acrylic acid) (PAA), poly (allyamine hydrochloride) (PAH) and single-walled carbon nanotubes (SWCNTs-COOH) sensing film for the detection of ammonia gas has been presented. The thin-core fiber modal interferometer was made by fusion splicing a small section of thin-core fiber (TCF) between two standard single mode fibers (SMF). A beam propagation method (BPM) is employed for the design of proposed interferometer and numerical simulation. Based on the simulation results, interferometer with a length of 2 cm of thin-core fiber is fabricated and experimentally studied. (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film is deposited on the outer surface of thin-core fiber via layer-by-layer (LbL) self-assembly technique. The gas sensor coated with (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film towards NH3 gas exposure at concentrations range from 1 to 960 ppm are analyzed and the sensing capability is demonstrated by optical spectrum analyzer (OSA). Experimental results show that the characteristic wavelength shift has an approximately linear relationship in the range 1-20 ppm, which is in accordance with the numerical simulation. Thus, this paper reveals the potential application of this sensor in monitoring low concentration NH3 gas.

Optical device for measuring a surface characteristic of an object by multi-color interferometry

NASA Technical Reports Server (NTRS)

Meyer, William V. (Inventor); Smart, Anthony E. (Inventor)

2001-01-01

An interferometer having a light beam source that produces a plurality of separate and distinct wavelengths of light. Optic fibers are used to transport the wavelengths of light toward an object surface and to allow light reflected from the object to pass through a polarizer to improve the polarization ratio of the reflected light to determine a characteristic of the object surface.

First Image Products from EcoSAR - Osa Peninsula, Costa Rica

NASA Technical Reports Server (NTRS)

Osmanoglu, Batuhan; Lee, SeungKuk; Rincon, Rafael; Fatuyinbo, Lola; Bollian, Tobias; Ranson, Jon

2016-01-01

Designed especially for forest ecosystem studies, EcoSAR employs state-of-the-art digital beamforming technology to generate wide-swath, high-resolution imagery. EcoSARs dual antenna single-pass imaging capability eliminates temporal decorrelation from polarimetric and interferometric analysis, increasing the signal strength and simplifying models used to invert forest structure parameters. Antennae are physically separated by 25 meters providing single pass interferometry. In this mode the radar is most sensitive to topography. With 32 active transmit and receive channels, EcoSARs digital beamforming is an order of magnitude more versatile than the digital beamforming employed on the upcoming NISAR mission. EcoSARs long wavelength (P-band, 435 MHz, 69 cm) measurements can be used to simulate data products for ESAs future BIOMASS mission, allowing scientists to develop algorithms before the launch of the satellite. EcoSAR can also be deployed to collect much needed data where BIOMASS satellite wont be allowed to collect data (North America, Europe and Arctic), filling in the gaps to keep a watchful eye on the global carbon cycle. EcoSAR can play a vital role in monitoring, reporting and verification schemes of internationals programs such as UN-REDD (United Nations Reducing Emissions from Deforestation and Degradation) benefiting global society. EcoSAR was developed and flown with support from NASA Earth Sciences Technology Offices Instrument Incubator Program.

Topography and Landforms of Ecuador

USGS Publications Warehouse

Chirico, Peter G.; Warner, Michael B.

2005-01-01

EXPLANATION The digital elevation model of Ecuador represented in this data set was produced from over 40 individual tiles of elevation data from the Shuttle Radar Topography Mission (SRTM). Each tile was downloaded, converted from its native Height file format (.hgt), and imported into a geographic information system (GIS) for additional processing. Processing of the data included data gap filling, mosaicking, and re-projection of the tiles to form one single seamless digital elevation model. For 11 days in February of 2000, NASA, the National Geospatial-Intelligence Agency (NGA), the German Aerospace Center (DLR), and the Italian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed SRTM DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Ecuador DEM was gap-filling areas where the SRTM data contained a data void. These void areas are a result of radar shadow, layover, standing water, and other effects of terrain, as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:50,000 - scale topographic maps which date from the mid-late 1980's (Souris, 2001). Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and remote sensing image-processing techniques. The data contained in this publication includes a gap filled, countrywide SRTM DEM of Ecuador projected in Universal Transverse Mercator (UTM) Zone 17 North projection, Provisional South American, 1956, Ecuador datum and a non gap filled SRTM DEM of the Galapagos Islands projected in UTM Zone 15 North projection. Both the Ecuador and Galapagos Islands DEMs are available as an ESRI Grid, stored as ArcInfo Export files (.e00), and in Erdas Imagine (IMG) file formats with a 90 meter pixel resolution. Also included in this publication are high and low resolution Adobe Acrobat (PDF) files of topography and landforms maps in Ecuador. The high resolution map should be used for printing and display, while the lower resolution map can be used for quick viewing and reference purposes.

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

Porter, Edward K.; Cornish, Neil J.

Massive black hole binaries are key targets for the space based gravitational wave Laser Interferometer Space Antenna (LISA). Several studies have investigated how LISA observations could be used to constrain the parameters of these systems. Until recently, most of these studies have ignored the higher harmonic corrections to the waveforms. Here we analyze the effects of the higher harmonics in more detail by performing extensive Monte Carlo simulations. We pay particular attention to how the higher harmonics impact parameter correlations, and show that the additional harmonics help mitigate the impact of having two laser links fail, by allowing for anmore » instantaneous measurement of the gravitational wave polarization with a single interferometer channel. By looking at parameter correlations we are able to explain why certain mass ratios provide dramatic improvements in certain parameter estimations, and illustrate how the improved polarization measurement improves the prospects for single interferometer operation.« less

A transceiver module of the Mu radar

NASA Technical Reports Server (NTRS)

Kato, S.; Ogawa, T.; Tsuda, T.; Sato, T.; Kimura, I.; Fukao, S.

1983-01-01

The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.

All optical logic for optical pattern recognition and networking applications

NASA Astrophysics Data System (ADS)

Khoury, Jed

2017-05-01

In this paper, we propose architectures for the implementation 16 Boolean optical gates from two inputs using externally pumped phase- conjugate Michelson interferometer. Depending on the gate to be implemented, some require single stage interferometer and others require two stages interferometer. The proposed optical gates can be used in several applications in optical networks including, but not limited to, all-optical packet routers switching, and all-optical error detection. The optical logic gates can also be used in recognition of noiseless rotation and scale invariant objects such as finger prints for home land security applications.

High-Visibility Photonic Crystal Fiber Interferometer as Multifunctional Sensor

PubMed Central

Cárdenas-Sevilla, G.A.; Fávero, Fernando C.; Villatoro, Joel

2013-01-01

A photonic crystal fiber (PCF) interferometer that exhibits record fringe contrast (∼40 dB) is demonstrated along with its sensing applications. The device operates in reflection mode and consists of a centimeter-long segment of properly selected PCF fusion spliced to single mode optical fibers. Two identical collapsed zones in the PCF combined with its modal properties allow high-visibility interference patterns. The interferometer is suitable for refractometric and liquid level sensing. The measuring refractive index range goes from 1.33 to 1.43 and the maximum resolution is ∼1.6 × 10−5. PMID:23396192

Per-point and per-field contextual classification of multipolarization and multiple incidence angle aircraft L-band radar data

NASA Technical Reports Server (NTRS)

Hoffer, Roger M.; Hussin, Yousif Ali

1989-01-01

Multipolarized aircraft L-band radar data are classified using two different image classification algorithms: (1) a per-point classifier, and (2) a contextual, or per-field, classifier. Due to the distinct variations in radar backscatter as a function of incidence angle, the data are stratified into three incidence-angle groupings, and training and test data are defined for each stratum. A low-pass digital mean filter with varied window size (i.e., 3x3, 5x5, and 7x7 pixels) is applied to the data prior to the classification. A predominately forested area in northern Florida was the study site. The results obtained by using these image classifiers are then presented and discussed.

Nonlinear Phase Distortion in a Ti:Sapphire Optical Amplifier for Optical Stochastic Cooling

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

Andorf, Matthew; Lebedev, Valeri; Piot, Philippe

2016-06-01

Optical Stochastic Cooling (OSC) has been considered for future high-luminosity colliders as it offers much faster cooling time in comparison to the micro-wave stochastic cooling. The OSC technique relies on collecting and amplifying a broadband optical signal from a pickup undulator and feeding the amplified signal back to the beam. It creates a corrective kick in a kicker undulator. Owing to its superb gain qualities and broadband amplification features, Titanium:Sapphire medium has been considered as a gain medium for the optical amplifier (OA) needed in the OSC*. A limiting factor for any OA used in OSC is the possibility ofmore » nonlinear phase distortions. In this paper we experimentally measure phase distortions by inserting a single-pass OA into one leg of a Mach-Zehnder interferometer. The measurement results are used to estimate the reduction of the corrective kick a particle would receive due to these phase distortions in the kicker undulator.« less

2-D inner-shelf current observations from a single VHF WEllen RAdar (WERA) station

USGS Publications Warehouse

Voulgaris, G.; Kumar, N.; Gurgel, K.-W.; Warner, J.C.; List, J.H.

2011-01-01

The majority of High Frequency (HF) radars used worldwide operate at medium to high frequencies (8 to 30 MHz) providing spatial resolutions ranging from 3 to 1.5 km and ranges from 150 to 50 km. This paper presents results from the deployment of a single Very High Frequency (VHF, 48 MHz) WEllen RAdar (WERA) radar with spatial resolution of 150 m and range 10-15 km, used in the nearshore off Cape Hatteras, NC, USA. It consisted of a linear array of 12 antennas operating in beam forming mode. Radial velocities were estimated from radar backscatter for a variety of wind and nearshore wave conditions. A methodology similar to that used for converting acoustically derived beam velocities to an orthogonal system is presented for obtaining 2-D current fields from a single station. The accuracy of the VHF radar-derived radial velocities is examined using a new statistical technique that evaluates the system over the range of measured velocities. The VHF radar velocities showed a bias of 3 to 7 cm/s over the experimental period explainable by the differences in radar penetration and in-situ measurement height. The 2-D current field shows good agreement with the in-situ measurements. Deviations and inaccuracies are well explained by the geometric dilution analysis. ?? 2011 IEEE.

Creep Deformation and Rupture Behavior of Single- and Dual-Pass 316LN Stainless-Steel-Activated TIG Weld Joints

NASA Astrophysics Data System (ADS)

Vijayanand, V. D.; Vasudevan, M.; Ganesan, V.; Parameswaran, P.; Laha, K.; Bhaduri, A. K.

2016-06-01

Creep deformation and rupture behavior of single-pass and dual-pass 316LN stainless steel (SS) weld joints fabricated by an autogenous activated tungsten inert gas welding process have been assessed by performing metallography, hardness, and conventional and impression creep tests. The fusion zone of the single-pass joint consisted of columnar zones adjacent to base metals with a central equiaxed zone, which have been modified extensively by the thermal cycle of the second pass in the dual-pass joint. The equiaxed zone in the single-pass joint, as well as in the second pass of the dual-pass joint, displayed the lowest hardness in the joints. In the dual-pass joint, the equiaxed zone of the first pass had hardness comparable to the columnar zone. The hardness variations in the joints influenced the creep deformation. The equiaxed and columnar zone in the first pass of the dual-pass joint was more creep resistant than that of the second pass. Both joints possessed lower creep rupture life than the base metal. However, the creep rupture life of the dual-pass joint was about twofolds more than that of the single-pass joint. Creep failure in the single-pass joint occurred in the central equiaxed fusion zone, whereas creep cavitation that originated in the second pass was blocked at the weld pass interface. The additional interface and strength variation between two passes in the dual-pass joint provides more restraint to creep deformation and crack propagation in the fusion zone, resulting in an increase in the creep rupture life of the dual-pass joint over the single-pass joint. Furthermore, the differences in content, morphology, and distribution of delta ferrite in the fusion zone of the joints favors more creep cavitation resistance in the dual-pass joint over the single-pass joint with the enhancement of creep rupture life.

Progress on the FIReTIP Diagnostic on NSTX-U

NASA Astrophysics Data System (ADS)

Scott, Evan; Barchfeld, Robert; Riemenschneider, Paul; Muscatello, Chris; Sohrabi, Mohammad; Domier, Calvin; Ren, Yang; Kaita, Robert; Luhmann, Neville, Jr.; NSTX-U Team

2016-10-01

The Far-infrared Tangential Interferometer/Polarimeter (FIReTIP) system on NSTX-U at the PPPL aims to provide robust, line-averaged electron density measurements. The system consists of three optically-pumped 119 µm methanol lasers, one of which can be tuned via Stark broadening, allowing for uniquely high intermediate frequencies and time resolutions. One of the major goals of FIReTIP is to incorporate it into the NSTX-U plasma control system (PCS) for real-time plasma density feedback control. The front-end optics mounted to Bay G, which shape and position the beam going into the plasma, and internal retroreflector located near Bay B, which facilitates double-pass measurements, are hard-mounted to the NSTX-U vacuum vessel. Because interferometric density measurements are sensitive to vibrational effects, FIReTIP has been upgraded to a two-color interferometer system with the inclusion of a 633 nm laser interferometer for the direct measurement of vibrations and a field programmable gate array (FPGA) for the subsequent subtraction of vibrational effects from the density measurement in real-time. This work is supported by the U.S. Department of Energy Grant DE-FG02-99ER54518.

Target & Propagation Models for the FINDER Radar

NASA Technical Reports Server (NTRS)

Cable, Vaughn; Lux, James; Haque, Salmon

2013-01-01

Finding persons still alive in piles of rubble following an earthquake, a severe storm, or other disaster is a difficult problem. JPL is currently developing a victim detection radar called FINDER (Finding Individuals in Emergency and Response). The subject of this paper is directed toward development of propagation & target models needed for simulation & testing of such a system. These models are both physical (real rubble piles) and numerical. Early results from the numerical modeling phase show spatial and temporal spreading characteristics when signals are passed through a randomly mixed rubble pile.

Symmetrical Josephson vortex interferometer as an advanced ballistic single-shot detector

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

Soloviev, I. I., E-mail: isol@phys.msu.ru; Lukin Scientific Research Institute of Physical Problems, 124460 Zelenograd, Moscow; Laboratory of Cryogenic Nanoelectronics, Nizhny Novgorod State Technical University n.a. R.E. Alekseev, 603950 Nizhny Novgorod

2014-11-17

We consider a ballistic detector formed in an interferometer manner which operational principle relies on Josephson vortex scattering at a measurement potential. We propose an approach to symmetrize the detector scheme and explore arising advantages in the signal-to-noise ratio and in the back-action on a measured object by means of recently presented numerical and analytical methods for modeling of a soliton scattering dynamics in the presence of thermal fluctuations. The obtained characteristics for experimentally relevant parameters reveal practical applicability of the considered schemes including possibility of coupling with standard digital rapid single flux quantum circuits.

Enhancement of fiber-optic low-coherence Fabry-Pérot interferometer with ZnO ALD films

NASA Astrophysics Data System (ADS)

Hirsch, Marzena; Listewnik, Paulina; Jedrzejewska-Szczerska, Małgorzata

2018-04-01

In this paper investigation of the enhanced fiber-optic low coherence Fabry-Pérot interferometer with zinc oxide (ZnO) film deposited by atomic layer deposition (ALD) was presented. Model of the interferometer, which was constructed of single-mode optical fiber with applied ZnO ALD films, was built. The interferometer was also examined by means of experiment. Measurements were performed for both reflective and transmission modes, using wavelengths of 1300 nm and 1500 nm. The measurements with the air cavity showed the best performance in terms of a visibility of the interference signal can be achieved for small cavity lengths ( 50μm) in both configurations. Combined with the enhancement of reflectance of the interferometer mirrors due to the ALD film, proposed construction could be successfully applied in refractive index (RI) sensor that can operate with improved visibility of the signal even in 1.3-1.5 RI range as well as with small volume samples, as shown by the modeling.

A combined phase contrast imaging-interferometer system for the detection of multiscale density fluctuations on DIII-D

NASA Astrophysics Data System (ADS)

Davis, E. M.; Rost, J. C.; Porkolab, M.; Marinoni, A.; van Zeeland, M. A.

2016-10-01

A heterodyne interferometer channel has been added to the DIII-D phase contrast imaging (PCI) system. Both measurements share a single 10.6 μm probe beam. Whereas the PCI excels at detecting medium- to high- k fluctuations (1.5 cm-1 <= k <= 20 cm-1), the interferometer extends the system sensitivity to low- k fluctuations (k <= 5 cm-1), allowing simultaneous measurement of electron- and ion-scale instabilities with sub-microsecond resolution. Further, correlating measurements from the interferometer channel with those from DIII-D's pre-existing, toroidally separated interferometer (Δ∅ = 45°) allows identification of low- n modes. This new capability has been corroborated against magnetic measurements and may allow novel investigations of core - localized MHD that is otherwise inaccessible via external magnetic measurements, with potential applications to fast particle transport and disruptions. Work supported by USDOE under DE-FG02-94ER54235, DE-FC02-04ER54698, and DE-FC02-99ER54512.

Tilt sensor based on intermodal photonic crystal fiber interferometer

NASA Astrophysics Data System (ADS)

Zhang, Xiaotong; Ni, Kai; Zhao, Chunliu; Ye, Manping; Jin, Yongxing

2014-09-01

A tilt sensor based on an intermodal photonic crystal fiber (PCF) interferometer is demonstrated. The sensor consists of a tubular filled with NaCl aqueous solutions and an intermodal PCF interferometer, which is formed by using a short PCF with two single-mode fibers (SMFs) spliced at both ends, and the air-holes in the splice regions are fully collapsed. The intermodal PCF interferometer is fixed in a rigid glass tubular with a slant orientation, and a half of the PCF is immersed in the NaCl aqueous solutions, while the other half is exposed in air. When tilting the tubular, the length of the PCF immersed changes so that the transmission spectrum moves. Therefore, by monitoring the wavelength shift, the tilt angle can be achieved. In the experiment, a 0.8-cm-length intermodal PCF interferometer was adopted. The sensitivity of the proposed sensor was obtained from -1.5461 nm/° to -30.1244 nm/° when measuring from -35.1° to 37.05°.

Apparatus and method for performing two-frequency interferometry

DOEpatents

Johnston, Roger G.

1990-01-01

The present apparatus includes a two-frequency, Zeeman-effect laser and matched, doubly refracting crystals in the construction of an accurate interferometer. Unlike other interferometric devices, the subject invention exhibits excellent phase stability owing to the use of single piece means for producing parallel interferometer arms, making the interferometer relatively insensitive to thermal and mechanical instabilities. Interferometers respond to differences in optical path length between their two arms. Unlike many interferometric techniques, which require the measurement of the location of interference fringes in a brightly illuminated background, the present invention permits the determination of the optical path length difference by measuring the phase of an electronic sine wave. The present apparatus is demonstrated as a differential thermooptic spectrometer for measuring differential optical absorption simply and accurately which is but one of many applications therefor. The relative intensities of the heating beams along each arm of the interferometer can be easily adjusted by observing a zero phase difference with identical samples when this condition is obtained.

Apparatus and method for performing two-frequency interferometry

DOEpatents

Johnston, R.G.

1988-01-25

The present apparatus includes a two-frequency, Zeeman Effect laser and matched, doubly refracting crystals in the construction of an accurate interferometer. Unlike other interferometric devices, the subject invention exhibits excellent phase stability owing to the use of single piece means for producing parallel interferometer arms, making the interferometer relatively insensitive to thermal and mechanical instabilities. Interferometers respond to differences in optical path length between their two arms. Unlike many interferometric techniques, which require the measurement of the location of interference fringes in a brightly illuminated background, the present invention permits the determination of the optical path length difference by measuring the phase of an electronic sine wave. The present apparatus is demonstrated as a differential thermooptic spectrometer for measuring differential optical absorption simply and accurately which is but one of many applications therefor. The relative intensities of the heating beams along each arm of the interferometer can be easily adjusted by observing a zero phase difference with identical samples when this condition is obtained. 6 figs.

Improving interferometers by quantum light: toward testing quantum gravity on an optical bench

NASA Astrophysics Data System (ADS)

Ruo-Berchera, Ivano; Degiovanni, Ivo P.; Olivares, Stefano; Traina, Paolo; Samantaray, Nigam; Genovese, M.

2016-09-01

We analyze in detail a system of two interferometers aimed at the detection of extremely faint phase fluctuations. The idea behind is that a correlated phase-signal like the one predicted by some phenomenological theory of Quantum Gravity (QG) could emerge by correlating the output ports of the interferometers, even when in the single interferometer it confounds with the background. We demonstrated that injecting quantum light in the free ports of the interferometers can reduce the photon noise of the system beyond the shot-noise, enhancing the resolution in the phase-correlation estimation. Our results confirm the benefit of using squeezed beams together with strong coherent beams in interferometry, even in this correlated case. On the other hand, our results concerning the possible use of photon number entanglement in twin beam state pave the way to interesting and probably unexplored areas of application of bipartite entanglement and, in particular, the possibility of reaching surprising uncertainty reduction exploiting new interferometric configurations, as in the case of the system described here.

Preliminary design study of a high resolution meteor radar

NASA Technical Reports Server (NTRS)

Lee, W.; Geller, M. A.

1973-01-01

A design study for a high resolution meteor radar system is carried out with the objective of measuring upper atmospheric winds and particularly studying short period atmospheric waves in the 80 to 120 km altitude region. The transmitter that is to be used emits a peak power of 4 Mw. The system is designed to measure the wind velocity and height of a meteor trail very accurately. This is achieved using a specially developed digital reduction procedure to determine wind velocity and range together with an interferometer for measuring both the azimuth and elevation angles of the region with a long baseline vernier measurement being used to refine the elevation angle measurement. The resultant accuracies are calculated to be + or - 0.9 m/s for the wind, + or - 230 m for the range and + or - 0.12 deg for the elevation angle, giving a height accuracy of + or - 375 m. The prospects for further development of this system are also discussed.

A experiment on radio location of objects in the near-Earth space with VLBI in 2012

NASA Astrophysics Data System (ADS)

Nechaeva, M.; Antipenko, A.; Bezrukovs, V.; Bezrukov, D.; Dementjev, A.; Dugin, N.; Konovalenko, A.; Kulishenko, V.; Liu, X.; Nabatov, A.; Nesteruk, V.; Pupillo, G.; Reznichenko, A.; Salerno, E.; Shmeld, I.; Shulga, O.; Sybiryakova, Y.; Tikhomirov, Yu.; Tkachenko, A.; Volvach, A.; Yang, W.-J.

An experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (RT-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.

Ring-Resonator/Sol-Gel Interferometric Immunosensor

NASA Technical Reports Server (NTRS)

Bearman, Gregory; Cohen, David

2007-01-01

A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

Space Radar Image of Long Valley, California - 3-D view

NASA Image and Video Library

1999-05-01

This is a three-dimensional perspective view of Long Valley, California by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar on board the space shuttle Endeavour. This view was constructed by overlaying a color composite SIR-C image on a digital elevation map. The digital elevation map was produced using radar interferometry, a process by which radar data are acquired on different passes of the space shuttle and, which then, are compared to obtain elevation information. The data were acquired on April 13, 1994 and on October 3, 1994, during the first and second flights of the SIR-C/X-SAR radar instrument. The color composite radar image was produced by assigning red to the C-band (horizontally transmitted and vertically received) polarization; green to the C-band (vertically transmitted and received) polarization; and blue to the ratio of the two data sets. Blue areas in the image are smooth and yellow areas are rock outcrops with varying amounts of snow and vegetation. The view is looking north along the northeastern edge of the Long Valley caldera, a volcanic collapse feature created 750,000 years ago and the site of continued subsurface activity. Crowley Lake is off the image to the left. http://photojournal.jpl.nasa.gov/catalog/PIA01757

ON THE DETECTION OF GLOBAL 21-cm SIGNAL FROM REIONIZATION USING INTERFEROMETERS

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

Singh, Saurabh; Subrahmanyan, Ravi; Shankar, N. Udaya

2015-12-20

Detection of the global redshifted 21-cm signal is an excellent means of deciphering the physical processes during the Dark Ages and subsequent Epoch of Reionization (EoR). However, detection of this faint monopole is challenging due to the high precision required in instrumental calibration and modeling of substantially brighter foregrounds and instrumental systematics. In particular, modeling of receiver noise with mK accuracy and its separation remains a formidable task in experiments aiming to detect the global signal using single-element spectral radiometers. Interferometers do not respond to receiver noise; therefore, here we explore the theory of the response of interferometers to globalmore » signals. In other words, we discuss the spatial coherence in the electric field arising from the monopole component of the 21-cm signal and methods for its detection using sensor arrays. We proceed by first deriving the response to uniform sky of two-element interferometers made of unit dipole and resonant loop antennas, then extend the analysis to interferometers made of one-dimensional arrays and also consider two-dimensional aperture antennas. Finally, we describe methods by which the coherence might be enhanced so that the interferometer measurements yield improved sensitivity to the monopole component. We conclude (a) that it is indeed possible to measure the global 21-cm from EoR using interferometers, (b) that a practically useful configuration is with omnidirectional antennas as interferometer elements, and (c) that the spatial coherence may be enhanced using, for example, a space beam splitter between the interferometer elements.« less

An in-line Mach-Zehnder Interferometer Using Thin-core Fiber for Ammonia Gas Sensing With High Sensitivity

PubMed Central

Huang, Xinyue; Li, Xueming; Yang, Jianchun; Tao, Chuanyi; Guo, Xiaogang; Bao, Hebin; Yin, Yanjun; Chen, Huifei; Zhu, Yuhua

2017-01-01

Ammonia is an important indicator among environmental monitoring parameters. In this work, thin-core fiber Mach-Zehnder interferometer deposited with poly (acrylic acid) (PAA), poly (allyamine hydrochloride) (PAH) and single-walled carbon nanotubes (SWCNTs-COOH) sensing film for the detection of ammonia gas has been presented. The thin-core fiber modal interferometer was made by fusion splicing a small section of thin-core fiber (TCF) between two standard single mode fibers (SMF). A beam propagation method (BPM) is employed for the design of proposed interferometer and numerical simulation. Based on the simulation results, interferometer with a length of 2 cm of thin-core fiber is fabricated and experimentally studied. (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film is deposited on the outer surface of thin-core fiber via layer-by-layer (LbL) self-assembly technique. The gas sensor coated with (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film towards NH3 gas exposure at concentrations range from 1 to 960 ppm are analyzed and the sensing capability is demonstrated by optical spectrum analyzer (OSA). Experimental results show that the characteristic wavelength shift has an approximately linear relationship in the range 1–20 ppm, which is in accordance with the numerical simulation. Thus, this paper reveals the potential application of this sensor in monitoring low concentration NH3 gas. PMID:28378783

System engineering approach to GPM retrieval algorithms

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

Rose, C. R.; Chandrasekar, V.

2004-01-01

System engineering principles and methods are very useful in large-scale complex systems for developing the engineering requirements from end-user needs. Integrating research into system engineering is a challenging task. The proposed Global Precipitation Mission (GPM) satellite will use a dual-wavelength precipitation radar to measure and map global precipitation with unprecedented accuracy, resolution and areal coverage. The satellite vehicle, precipitation radars, retrieval algorithms, and ground validation (GV) functions are all critical subsystems of the overall GPM system and each contributes to the success of the mission. Errors in the radar measurements and models can adversely affect the retrieved output values. Groundmore » validation (GV) systems are intended to provide timely feedback to the satellite and retrieval algorithms based on measured data. These GV sites will consist of radars and DSD measurement systems and also have intrinsic constraints. One of the retrieval algorithms being studied for use with GPM is the dual-wavelength DSD algorithm that does not use the surface reference technique (SRT). The underlying microphysics of precipitation structures and drop-size distributions (DSDs) dictate the types of models and retrieval algorithms that can be used to estimate precipitation. Many types of dual-wavelength algorithms have been studied. Meneghini (2002) analyzed the performance of single-pass dual-wavelength surface-reference-technique (SRT) based algorithms. Mardiana (2003) demonstrated that a dual-wavelength retrieval algorithm could be successfully used without the use of the SRT. It uses an iterative approach based on measured reflectivities at both wavelengths and complex microphysical models to estimate both No and Do at each range bin. More recently, Liao (2004) proposed a solution to the Do ambiguity problem in rain within the dual-wavelength algorithm and showed a possible melting layer model based on stratified spheres. With the No and Do calculated at each bin, the rain rate can then be calculated based on a suitable rain-rate model. This paper develops a system engineering interface to the retrieval algorithms while remaining cognizant of system engineering issues so that it can be used to bridge the divide between algorithm physics an d overall mission requirements. Additionally, in line with the systems approach, a methodology is developed such that the measurement requirements pass through the retrieval model and other subsystems and manifest themselves as measurement and other system constraints. A systems model has been developed for the retrieval algorithm that can be evaluated through system-analysis tools such as MATLAB/Simulink.« less

Velocity measurement using frequency domain interferometer and chirped pulse laser

NASA Astrophysics Data System (ADS)

Ishii, K.; Nishimura, Y.; Mori, Y.; Hanayama, R.; Kitagawa, Y.; Sekine, T.; Sato, N.; Kurita, T.; Kawashima, T.; Sunahara, A.; Sentoku, Y.; Miura, E.; Iwamoto, A.; Sakagami, H.

2017-02-01

An ultra-intense short pulse laser induces a shock wave in material. The pressure of shock compression is stronger than a few tens GPa. To characterize shock waves, time-resolved velocity measurement in nano- or pico-second time scale is needed. Frequency domain interferometer and chirped pulse laser provide single-shot time-resolved measurement. We have developed a laser-driven shock compression system and frequency domain interferometer with CPA laser. In this paper, we show the principle of velocity measurement using a frequency domain interferometer and a chirped pulse laser. Next, we numerically calculated spectral interferograms and show the time-resolved velocity measurement can be done from the phase analysis of spectral interferograms. Moreover we conduct the laser driven shock generation and shock velocity measurement. From the spectral fringes, we analyze the velocities of the sample and shockwaves.

Highly versatile in-reflection photonic crystal fibre interferometer

NASA Astrophysics Data System (ADS)

Jha, Rajan; Villatoro, Joel; Kreuzer, Mark; Finazzi, Vittoria; Pruneri, Valerio

2009-10-01

We report a simple and highly versatile photonic crystal fiber (PCF) interferometer that operates in reflection mode. The device consists of a short section of PCF fusion spliced at the distal end of a standard single mode fiber. The air-holes of the PCF are intentionally collapsed over a microscopic region around the splice. The collapsed region broadens the propagating mode because of diffraction. This allows the coupling and recombination of two PCF modes. Depending on the PCF structure two core modes or a core and a cladding mode can be excited. In either case the devices exhibit sinusoidal interference patterns with fringe spacing depending on the PCF length. The interferometers are highly stable over time and can operate at high temperatures with minimal degradation. The interferometers are suitable for highresolution sensing of strain, refractive index (biosensing), gases, volatile organic compounds, etc.

High-extinction virtually imaged phased array-based Brillouin spectroscopy of turbid biological media

NASA Astrophysics Data System (ADS)

Fiore, Antonio; Zhang, Jitao; Shao, Peng; Yun, Seok Hyun; Scarcelli, Giuliano

2016-05-01

Brillouin microscopy has recently emerged as a powerful technique to characterize the mechanical properties of biological tissue, cell, and biomaterials. However, the potential of Brillouin microscopy is currently limited to transparent samples, because Brillouin spectrometers do not have sufficient spectral extinction to reject the predominant non-Brillouin scattered light of turbid media. To overcome this issue, we combined a multi-pass Fabry-Perot interferometer with a two-stage virtually imaged phased array spectrometer. The Fabry-Perot etalon acts as an ultra-narrow band-pass filter for Brillouin light with high spectral extinction and low loss. We report background-free Brillouin spectra from Intralipid solutions and up to 100 μm deep within chicken muscle tissue.

Large-scale quantum photonic circuits in silicon

NASA Astrophysics Data System (ADS)

Harris, Nicholas C.; Bunandar, Darius; Pant, Mihir; Steinbrecher, Greg R.; Mower, Jacob; Prabhu, Mihika; Baehr-Jones, Tom; Hochberg, Michael; Englund, Dirk

2016-08-01

Quantum information science offers inherently more powerful methods for communication, computation, and precision measurement that take advantage of quantum superposition and entanglement. In recent years, theoretical and experimental advances in quantum computing and simulation with photons have spurred great interest in developing large photonic entangled states that challenge today's classical computers. As experiments have increased in complexity, there has been an increasing need to transition bulk optics experiments to integrated photonics platforms to control more spatial modes with higher fidelity and phase stability. The silicon-on-insulator (SOI) nanophotonics platform offers new possibilities for quantum optics, including the integration of bright, nonclassical light sources, based on the large third-order nonlinearity (χ(3)) of silicon, alongside quantum state manipulation circuits with thousands of optical elements, all on a single phase-stable chip. How large do these photonic systems need to be? Recent theoretical work on Boson Sampling suggests that even the problem of sampling from e30 identical photons, having passed through an interferometer of hundreds of modes, becomes challenging for classical computers. While experiments of this size are still challenging, the SOI platform has the required component density to enable low-loss and programmable interferometers for manipulating hundreds of spatial modes. Here, we discuss the SOI nanophotonics platform for quantum photonic circuits with hundreds-to-thousands of optical elements and the associated challenges. We compare SOI to competing technologies in terms of requirements for quantum optical systems. We review recent results on large-scale quantum state evolution circuits and strategies for realizing high-fidelity heralded gates with imperfect, practical systems. Next, we review recent results on silicon photonics-based photon-pair sources and device architectures, and we discuss a path towards large-scale source integration. Finally, we review monolithic integration strategies for single-photon detectors and their essential role in on-chip feed forward operations.

Peak height of OH airglow derived from simultaneous observations a Fabry-Perot interferometer and a meteor radar

NASA Astrophysics Data System (ADS)

Yu, Tao; Zuo, Xiaomin; Xia, Chunliang; Li, Mingyuan; Huang, Cong; Mao, Tian; Zhang, Xiaoxin; Zhao, Biqiang; Liu, Libo

2017-04-01

A new method for estimating daily averaged peak height of the OH airglow layer from a ground-based meteor radar (MR) and a Fabry-Perot interferometer (FPI) is presented. The first results are derived from 4 year simultaneous measurements of winds by a MR and a FPI at two adjacent stations over center China and are compared with observations from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. The OH airglow peak heights, which are derived by using correlation analysis between winds of the FPI and MR, are found to generally peak at an altitude of 87 km and frequently varied between 80 km and 90 km day to day. In comparison with SABER OH 1.6 μm observations, reasonable similarity of airglow peak heights is found, and rapid day-to-day variations are also pronounced. Lomb-Scargle analysis is used to determine cycles of temporal variations of airglow peak heights, and there are obvious periodic variations both in our airglow peak heights and in the satellite observations. In addition to the annual, semiannual, monthly, and three monthly variations, the shorter time variations, e.g., day-to-day and several days' variations, are also conspicuous. The day-to-day variations of airglow height obviously could reduce observation accuracy and lead to some deviations in FPI measurements. These FPI wind deviations arising from airglow height variations are also estimated to be about 3-5 m/s from 2011 to 2015, with strong positive correlation with airglow peak height variation. More attention should be paid to the wind deviations associated with airglow height variation when using and interpreting winds measured by FPI.

A Proposed Robotic Astronomy Mission to the Lunar South Polar Regions

NASA Technical Reports Server (NTRS)

Lowman, Paul D., Jr.

2003-01-01

This paper outlines a possible mission to emplace a robotic infrared / submillimeter wave interferometer array near the lunar south pole. This region has now been investigated by the Clementine and Lunar Prospector missions, and by Earth-based radar, and its topography and thermal environment are fairly well-known. The area would be exceptionally suitable for infrared / submillimeter astronomy because of the continually low temperatures, approaching that of liquid nitrogen (77K) in some places. A submillimeter spaceborne interferometer mission, Submillimeter Probe of the Evolution of the Cosmic Structure (SPECS) has been proposed by John Mather and others, covering the 40 - 500 micron region with 3 formation flying telescopes. The present paper proposes a lunar adaptation of the SPECS concept, LSPECS. This adaptation would involve landing 4 telescopes on the area north of Shackleton crater at zero degrees longitude. This is in nearly year round darkness but is continually radar visible from Earth. The landed payload of LSPECS would include a telerobotic rover, 4 three meter submm telescopes, a solar power array to be emplaced on the continually sunlit north rim of Shackleton crater, and an S-band antenna for data relay to Earth. Passive cooling without the use of expendable cryogenics. might be possible, trading long exposure time for instrument temperatures above that of liquid helium. The LSPECS would permit long-term study of an extremely wide range of cosmic and solar system phenomena in the southern celestial hemisphere. For complete sky coverage, a similar installation near the north pole would be required. The LSPECS site would also be suitable other types of observation, such as optical interferometry or centimeter wavelength radio astronomy. The lunar south pole is also of great interest because of its extensive ice deposits, which may represent cometary infall with pre-biotic compounds.

A refractive index sensor based on taper Michelson interferometer in multimode fiber

NASA Astrophysics Data System (ADS)

Fu, Xinghu; Zhang, Jiangpeng; Wang, Siwen; Fu, Guangwei; Liu, Qiang; Jin, Wa; Bi, Weihong

2016-11-01

A refractive index sensor based on taper Michelson interferometer in multimode fiber is proposed. The Hydrofluoric acid corrosion processing is studied in the preparation of single cone multimode optical fiber sensor. The taper Michelson interferometer is fabricated by changing corrosion time. The relationship between fiber sensor feature and corrosion time is analyzed. The experimental results show that the interference spectrum shift in the direction of short wave with the increase of the refractive index. The refractive index sensitivity can reach 115.8008 nm/RIU. Thereby, it can be used in detecting the refractive index in different areas including the environmental protection, health care and food production.

Simultaneous interrogation of interferometric and Bragg grating sensors

NASA Astrophysics Data System (ADS)

Brady, G.; Kalli, K.; Webb, D. J.; Jackson, D. A.; Reekie, L.; Archambault, J. L.

1995-06-01

We propose a new method for the simultaneous interrogation of conventional two-beam interferometers and Bragg grating sensors. The technique employs an unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source, which acts as a wavelength-tunable source for the grating and as a path-matched filter for the Fizeau interferometer, thus providing a high phase resolution output for each sensor. The grating sensor demonstrates a dynamic strain resolution of \\similar 0.05 mu 3 / \\radical Hz \\end-radical at 20 Hz, while the interferometric phase resolution is better than 1mrad/ \\radical Hz \\end-radical at 20 Hz, corresponding to an rms mirror displacement of 0.08 nm.

AMF3 ARM's Research Facility and MAOS at Oliktok Point Alaska

NASA Astrophysics Data System (ADS)

Helsel, F.; Ivey, M.; Dexheimer, D.; Hardesty, J.; Lucero, D. A.; Roesler, E. L.

2016-12-01

Scientific Infrastructure To Support Atmospheric Science And Aerosol Science For The Department Of Energy's Atmospheric Radiation Measurement Programs Mobile Facility 3 Located At Oliktok Point, Alaska.The Atmospheric Radiation Measurement (ARM) Program's Mobile Facility 3 (AMF3) located at Oliktok Point, Alaska is a U.S. Department of Energy (DOE) site designed to collect data to determine the impact that clouds and aerosols have on solar radiation. The site provides a scientific infrastructure and data archives for the international Arctic research community. The infrastructure at Oliktok is designed to be mobile and it may be relocated in the future to support other ARM science missions. AMF3's present instruments include: scanning precipitation Radar-cloud radar, Raman Lidar, Eddy correlation flux systems, Ceilometer, Balloon sounding system, Atmospheric Emitted Radiance Interferometer (AERI), Micro-pulse Lidar (MPL), Millimeter cloud radar along with all the standard metrological measurements. A Mobile Aerosol Observing System (MAOS) has been added to AMF3 in 2016 more details of the instrumentation at www.arm.gov/sites/amf/mobile-aos. Data from these instruments are placed in the ARM data archives and are available to the international research community. This poster will discuss what instruments are at the ARM Program's AMF3 and highlight the newest addition to AMF3, the Mobile Aerosol Observing System (MAOS).

Investigating and Improving Student Understanding of Quantum Mechanics in the Context of Single Photon Interference

ERIC Educational Resources Information Center

Marshman, Emily; Singh, Chandralekha

2017-01-01

Single photon experiments involving a Mach-Zehnder interferometer can illustrate the fundamental principles of quantum mechanics, e.g., the wave-particle duality of a single photon, single photon interference, and the probabilistic nature of quantum measurement involving single photons. These experiments explicitly make the connection between the…

Rayleigh Scattering Diagnostic for Dynamic Measurement of Velocity and Temperature

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Panda, J.

2001-01-01

A new technique for measuring dynamic gas velocity and temperature is described. The technique is based on molecular Rayleigh scattering of laser light, so no seeding of the flow is necessary. The Rayleigh scattered light is filtered with a fixed cavity, planar mirror Fabry-Perot interferometer. A minimum number of photodetectors were used in order to allow the high data acquisition rate needed for dynamic measurements. One photomultiplier tube (PMT) was used to measure the total Rayleigh scattering, which is proportional to the gas density. Two additional PMTs were used to detect light that passes through two apertures in a mask located in the interferometer fringe plane. An uncertainty analysis was used to select the optimum aperture parameters and to predict the measurement uncertainty due to photon shot-noise. Results of an experiment to measure the velocity of a subsonic free jet are presented.

A very high frequency radio interferometer for investigating ionospheric disturbances using geostationary satellites. Determination of changes in exospheric electron content by a comparison of group delay and Faraday rotation

NASA Technical Reports Server (NTRS)

Terry, R.; Flaherty, B. J.; Dubroff, R. E.

1972-01-01

The theory and development of a VHF correlation radio interferometer for investigating ionospheric disturbances are discussed. The system was developed to receive signals from the geostationary Applications Technology Satellites. Amplitude and phase variations of the signal passing through the ionosphere can be detected by this instrument. The system consists of two superheterodyne receivers separated by a distance known as the baseline of the system. Since the system is a phase sensitive instrument, the local oscillators of the two receivers must be phase coherent. This is accomplished by using phase-locked loops for generating the local oscillators. The two signals from the separate receivers are cross-correlated by multiplying the two signals together and then time averaging the result. The sensitivity of the instrument is increased by off-setting one of the local oscillators by a small amount.

Real-time multiple-look synthetic aperture radar processor for spacecraft applications

NASA Technical Reports Server (NTRS)

Wu, C.; Tyree, V. C. (Inventor)

1981-01-01

A spaceborne synthetic aperture radar (SAR) having pipeline multiple-look data processing is described which makes use of excessive azimuth bandwidth in radar echo signals to produce multiple-looking images. Time multiplexed single-look image lines from an azimuth correlator go through an energy analyzer which analyzes the mean energy in each separate look to determine the radar antenna electric boresight for use in generating the correct reference functions for the production of high quality SAR images. The multiplexed single look image lines also go through a registration delay to produce multi-look images.

TanDEM-X calibrated Raw DEM generation

NASA Astrophysics Data System (ADS)

Rossi, Cristian; Rodriguez Gonzalez, Fernando; Fritz, Thomas; Yague-Martinez, Nestor; Eineder, Michael

2012-09-01

The TanDEM-X mission successfully started on June 21st 2010 with the launch of the German radar satellite TDX, placed in orbit in close formation with the TerraSAR-X (TSX) satellite, and establishing the first spaceborne bistatic interferometer. The processing of SAR raw data to the Raw DEM is performed by one single processor, the Integrated TanDEM-X Processor (ITP). The quality of the Raw DEM is a fundamental parameter for the mission planning. In this paper, a novel quality indicator is derived. It is based on the comparison of the interferometric measure, the unwrapped phase, and the stereo-radargrammetric measure, the geometrical shifts computed in the coregistration stage. By stating the accuracy of the unwrapped phase, it constitutes a useful parameter for the determination of problematic scenes, which will be resubmitted to the dual baseline phase unwrapping processing chain for the mitigation of phase unwrapping errors. The stereo-radargrammetric measure is also operationally used for the Raw DEM absolute calibration through an accurate estimation of the absolute phase offset. This paper examines the interferometric algorithms implemented for the operational TanDEM-X Raw DEM generation, focusing particularly on its quality assessment and its calibration.

Evolution of Precipitation Structure During the November DYNAMO MJO Event: Cloud-Resolving Model Intercomparison and Cross Validation Using Radar Observations

NASA Astrophysics Data System (ADS)

Li, Xiaowen; Janiga, Matthew A.; Wang, Shuguang; Tao, Wei-Kuo; Rowe, Angela; Xu, Weixin; Liu, Chuntao; Matsui, Toshihisa; Zhang, Chidong

2018-04-01

Evolution of precipitation structures are simulated and compared with radar observations for the November Madden-Julian Oscillation (MJO) event during the DYNAmics of the MJO (DYNAMO) field campaign. Three ground-based, ship-borne, and spaceborne precipitation radars and three cloud-resolving models (CRMs) driven by observed large-scale forcing are used to study precipitation structures at different locations over the central equatorial Indian Ocean. Convective strength is represented by 0-dBZ echo-top heights, and convective organization by contiguous 17-dBZ areas. The multi-radar and multi-model framework allows for more stringent model validations. The emphasis is on testing models' ability to simulate subtle differences observed at different radar sites when the MJO event passed through. The results show that CRMs forced by site-specific large-scale forcing can reproduce not only common features in cloud populations but also subtle variations observed by different radars. The comparisons also revealed common deficiencies in CRM simulations where they underestimate radar echo-top heights for the strongest convection within large, organized precipitation features. Cross validations with multiple radars and models also enable quantitative comparisons in CRM sensitivity studies using different large-scale forcing, microphysical schemes and parameters, resolutions, and domain sizes. In terms of radar echo-top height temporal variations, many model sensitivity tests have better correlations than radar/model comparisons, indicating robustness in model performance on this aspect. It is further shown that well-validated model simulations could be used to constrain uncertainties in observed echo-top heights when the low-resolution surveillance scanning strategy is used.

Detection of hail signatures from single-polarization C-band radar reflectivity

NASA Astrophysics Data System (ADS)

Kunz, Michael; Kugel, Petra I. S.

2015-02-01

Five different criteria that estimate hail signatures from single-polarization radar data are statistically evaluated over a 15-year period by categorical verification against loss data provided by a building insurance company. The criteria consider different levels or thresholds of radar reflectivity, some of them complemented by estimates of the 0 °C level or cloud top temperature. Applied to reflectivity data from a single C-band radar in southwest Germany, it is found that all criteria are able to reproduce most of the past damage-causing hail events. However, the criteria substantially overestimate hail occurrence by up to 80%, mainly due to the verification process using damage data. Best results in terms of highest Heidke Skill Score HSS or Critical Success Index CSI are obtained for the Hail Detection Algorithm (HDA) and the Probability of Severe Hail (POSH). Radar-derived hail probability shows a high spatial variability with a maximum on the lee side of the Black Forest mountains and a minimum in the broad Rhine valley.

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging

NASA Technical Reports Server (NTRS)

Carter, Lynn M.; Campbell, Donald B.; Campbell, Bruce A.

2010-01-01

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transmits a single sense of circular polarization, and both senses of circular polarization are received, which allows for the construction of the Stokes polarization vector. From the Stokes vector, daughter products such as the circular polarization ratio, the degree of linear polarization, and linear polarization angle are obtained. Recent polarimetric imaging using Arecibo has included Venus and the Moon. These observations can be compared to radar data for terrestrial surfaces to better understand surface physical properties and regional geologic evolution. For example, polarimetric radar studies of volcanic settings on Venus, the Moon and Earth display some similarities, but also illustrate a variety of different emplacement and erosion mechanisms. Polarimetric radar data provides important information about surface properties beyond what can be obtained from single-polarization radar. Future observations using polarimetric synthetic aperture radar will provide information on roughness, composition and stratigraphy that will support a broader interpretation of surface evolution.

A second look at the CloudSat/TRMM intersect data

NASA Astrophysics Data System (ADS)

Haddad, Z.; Kuo, K.; Smith, E. A.; Kiang, D.; Turk, F. J.

2010-12-01

The original objective motivating the creation of the CloudSat+TRMM intersect products (by E.A. Smith, K.-S. Kuo et al) was to provide new opportunities in research related to precipitating clouds. The data products consist of near-coincident CloudSat Cloud Profiling Radar calibrated 94-GHz reflectivity factors and detection flag, sampled every 240 m in elevation, and the TRMM Precipitation Radar calibrated 13.8-GHz reflectivity factors, attenuation-adjusted reflectivity factors and rain rate estimates, sampled every 250 m in elevation, in the TRMM beam whose footprint encompasses the CloudSat beam footprint. Because retrieving precipitation distributions from single-frequency radar measurements is a very under-constrained proposition, we decided to restrict our analyses to CloudSat data that were taken within 3 minutes of a TRMM pass. We ended up with over 5000 beams of nearly simultaneous observations of precipitation, and proceeded in two different ways: 1) we attempted to perform retrievals based on simultaneous radar reflectivity measurements at Ku and W bands. At low precipitation rates, the Ku-band radar does not detect much of the rain. At higher precipitation rates, the W-band radar incurs high attenuation, and this makes “Hitschfeld-Bordan” retrievals (from the top of the column down toward the surface) diverge because of numerical instability. The main question for this portion of the analysis was to determine if these two extremes are indeed extremes that still afford us a significant number of “in-between” cases, on which we can apply a careful dual-frequency retrieval algorithm; 2) we also attempted to quantify the ability of the Ku-band measurements to provide complementary information to the W-band estimates outside their overlap region, and vice versa. Specifically, instead of looking at the admittedly small vertical region where both radars detect precipitation and where their measurements are unambiguously related to the underlying physics (unaffected by multiple scattering), we considered the TRMM estimates in the rain below the freezing level, and tried to infer the joint behavior of the overlying CloudSat measurements above the freezing level as a function of the rain - and, conversely, we considered the vertical variability of the CloudSat estimates in the above-freezing region, and derived the joint behavior of the TRMM measurements in the rain as a function of the CloudSat estimates. The results are compiled in databases that should allow users of less-sensitive lower-frequency radars to infer some quantitative information about the storm structure above the precipitating core in the absence of higher-frequency measurements, just as it will allow users of too-sensitive higher-frequency radars to infer some quantitative information about the precipitation closer to the surface in the absence of lower-frequency measurements.

Quantum Strategies: Proposal to Experimentally Test a Quantum Economics Protocol

DTIC Science & Technology

2009-04-09

fact that this al- gorithm requires only bipartite entangled states what makes it feasible to implement, and a key focus of a larger program in quantum...passes through what is effectively a huge Mach-Zender fiber-interferometer bounded by the Sagnac loop and PPBS1- is affected by this time-varying...strategy, no matter what the other players do. As we noted above, this means that there is no (classical) correlated equilibrium other than the Nash

Bell theorem without inequalities for two spinless particles

NASA Astrophysics Data System (ADS)

Bernstein, Herbert J.; Greenberger, Daniel M.; Horne, Michael A.; Zeilinger, Anton

1993-01-01

We use the Greenberger-Horne-Zeilinger [in Bell's Theorem, Quantum Theory,and Conceptions of the Universe, edited by M. Kafatos (Kluwer Academic, Dordrecht, 1989)] approach to present three demonstrations of the failure of Einstein-Podolsky-Rosen (EPR) [Phys. Rev. 47, 777 (1935)] local realism for the case of two spinless particles in a two-particle interferometer. The original EPR assumptions of locality and reality do not suffice for this. First, we use the EPR assumptions of locality and reality to establish that in a two-particle interferometer, the path taken by each particle is an element of reality. Second, we supplement the EPR premises by the postulate that when the path taken by a particle is an element of reality, all paths not taken are empty. We emphasize that our approach is not applicable to a single-particle interferometer because there the path taken by the particle cannot be established as an element of reality. We point out that there are real conceptual differences between single-particle, two-particle, and multiparticle interferometry.

Research in millimeter wave techniques

NASA Technical Reports Server (NTRS)

Mcmillan, R. W.

1978-01-01

During the past six months, efforts on this project have been devoted to: (1) continuation of construction and testing of a 6 GHz subharmonic mixer model with extension of the pumping frequency of this mixer to omega sub s/4, (2) construction of a 183 GHz subharmonic mixer based on the results of tests on this 6 GHz model, (3) ground-based radiometric measurements at 183 GHz, (4) fabrication and testing of wire grid interferometers, (5) calculations of reflected and lost power in these interferometers, and (6) calculations of the antenna temperature due to water vapor to be expected in down-looking radiometry as a function of frequency. Significant events during the past six months include: (1) Receipt of a 183 GHz single-ended fundamental mixer, (2) attainment of 6 db single sideband conversion loss with the 6 GHz subharmonic mixer model by using a 1.5 GHz (omega sub s/4) pump frequency, (3) additional ground-based radiometric measurements and (4) derivation of equations for reflection and loss for wire grid interferometers.

Fly Ear Inspired Miniature Acoustic Sensors for Detection and Localization

DTIC Science & Technology

2011-07-31

Micro-Opto-Electro-Mechnical-System ( MOEMS ) sensor platform that is capable of integrating multiplexed Fabry-Perot (FP) interferometer based sensors. A...on a single MOEMS chip is shown in Figure 8. Light from a low coherence light source with a coherence length Lc is first sent to the reference...towards developing a low coherence interferometer based MOEMS detection system. An optical Micro-Electro-Mechanical-System (MEMS) sensor platform was

A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D

DOE PAGES

Davis, E. M.; Rost, J. C.; Porkolab, M.; ...

2016-08-15

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. Here, we describe the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10:6 μm probe beam, two interference schemes, and two detectors to measure electron density uctuations at large spatiotemporal bandwidth (10 kHz < f < 5MHz and 0 cm -1 ≤ k ≤ 20 cm -1), allowing simultaneous measurement of ion- and electron-scale instabilities. Further, correlating our interferometer's measurements with those from DIII-D's pre-existing, toroidally separated interferometer allows core-localized, low-n MHD studies that may otherwisemore » be inaccessible via external magnetic measurements. In the combined diagnostic's small port requirements and minimal access restrictions make it well-suited to the harsh neutron environments and limited port space expected in next-step devices.« less

A phase contrast imaging-interferometer system for detection of multiscale electron density fluctuations on DIII-D

NASA Astrophysics Data System (ADS)

Davis, E. M.; Rost, J. C.; Porkolab, M.; Marinoni, A.; Van Zeeland, M. A.

2016-11-01

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz

Advanced Gouy phase high harmonics interferometer

NASA Astrophysics Data System (ADS)

Mustary, M. H.; Laban, D. E.; Wood, J. B. O.; Palmer, A. J.; Holdsworth, J.; Litvinyuk, I. V.; Sang, R. T.

2018-05-01

We describe an extreme ultraviolet (XUV) interferometric technique that can resolve ∼100 zeptoseconds (10‑21 s) delay between high harmonic emissions from two successive sources separated spatially along the laser propagation in a single Gaussian beam focus. Several improvements on our earlier work have been implemented in the advanced interferometer. In this paper, we report on the design, characterization and optimization of the advanced Gouy phase interferometer. Temporal coherence for both atomic argon and molecular hydrogen gases has been observed for several harmonic orders. It has been shown that phase shift of XUV pulses mainly originates from the emission time delay due to the Gouy phase in the laser focus and the observed interference is independent of the generating medium. This interferometer can be a useful tool for measuring the relative phase shift between any two gas species and for studying ultrafast dynamics of their electronic and nuclear motion.

Comparison of Image Processing Techniques using Random Noise Radar

DTIC Science & Technology

2014-03-27

detection UWB ultra-wideband EM electromagnetic CW continuous wave RCS radar cross section RFI radio frequency interference FFT fast Fourier transform...several factors including radar cross section (RCS), orientation, and material makeup. A single monostatic radar at some position collects only range and...Chapter 2 is to provide the theory behind noise radar and SAR imaging. Section 2.1 presents the basic concepts in transmitting and receiving random

Relationship of strength of turbulence to received power

NASA Technical Reports Server (NTRS)

Rottger, J.

1983-01-01

Because of contributions due to reflection, the determination of the turbulence refractive index structure constant may be affected. For pure scattering from turbulence in the inertial subrange, the radar echo power can be used to calculate the refractive index structure constant. The radar power is determined by a convolution integral. If the antenna beam is swung to sufficiently large off-zenith angles ( 12.5 deg) so that a quasi-isotropic response from the tail ends of the Gaussian angular distribution can be anticipated, the evaluation of the convolution integral depends only on the known antenna pattern of the radar. This procedure, swinging the radar beam to attenuate the reflected component, may be called angular or direction filtering. The tilted antenna also may be pick up reflected components from near the zenith through the sidelobes. This can be tested by the evaluation of the correlation function. This method applies a time domain filtering of the intensity time series but needs a very careful selection of the high pass filters.

Digital processing of orbital radar data to enhance geologic structure - Examples from the Canadian Shield

NASA Technical Reports Server (NTRS)

Masuoka, Penny M.; Harris, Jeff; Lowman, Paul D., Jr.; Blodget, Herbert W.

1988-01-01

Various digital enhancement techniques for SAR are compared using SIR-B and Seasat images of the Canadian Shield. The three best methods for enhancing geological structure were found to be: (1) a simple linear contrast stretch; (2) a mean or median low-pass filter to reduce speckle prior to edge enhancement or a K nearest-neighbor average to cosmetically reduce speckle; and (3) a modification of the Moore-Waltz (1983) technique. Three look directions were coregistered and several means of data display were investigated as means of compensating for radar azimuth biasing.

Digest of NASA earth observation sensors

NASA Technical Reports Server (NTRS)

Drummond, R. R.

1972-01-01

A digest of technical characteristics of remote sensors and supporting technological experiments uniquely developed under NASA Applications Programs for Earth Observation Flight Missions is presented. Included are camera systems, sounders, interferometers, communications and experiments. In the text, these are grouped by types, such as television and photographic cameras, lasers and radars, radiometers, spectrometers, technology experiments, and transponder technology experiments. Coverage of the brief history of development extends from the first successful earth observation sensor aboard Explorer 7 in October, 1959, through the latest funded and flight-approved sensors under development as of October 1, 1972. A standard resume format is employed to normalize and mechanize the information presented.

Harmonic Phase Response of Nonlinear Radar Targets

DTIC Science & Technology

2015-10-01

while allowing its harmonics to pass through. The weak harmonic responses are then amplified to allow for easier detection and measurement . 4...where the phase of the 2nd and 3rd harmonic of the received electromagnetic wave from nonlinear targets was measured and plotted against the frequency

Measured Changes in C-Band Radar Reflectivity of Clear Air Caused by Aircraft Wake Vortices

NASA Technical Reports Server (NTRS)

Mackenzie, Anne I.

1997-01-01

Wake vortices from a C-130 airplane were observed at the NASA Wallops Flight Facility with a ground-based, monostatic C-band radar and an antenna-mounted boresight video camera. The airplane wake was viewed from a distance of approximately 1 km, and radar scanning was adjusted to cross a pair of marker smoke trails generated by the C-130. For each airplane pass, changes in radar reflectivity were calculated by subtracting the signal magnitudes during an initial clutter scan from the signal magnitudes during vortex-plus-clutter scans. The results showed both increases and decreases in reflectivity on and near the smoke trails in a characteristic sinusoidal pattern of heightened reflectivity in the center and lessened reflectivity at the sides. Reflectivity changes in either direction varied from -131 to -102 dBm(exp -1); the vortex-plus-clutter to noise ratio varied from 20 to 41 dB. The radar recordings lasted 2.5 min each; evidence of wake vortices was found for up to 2 min after the passage of the airplane. Ground and aircraft clutter were eliminated as possible sources of the disturbance by noting the occurrence of vortex signatures at different positions relative to the ground and the airplane. This work supports the feasibility of vortex detection by radar, and it is recommended that future radar vortex detection be done with Doppler systems.

Tunable thulium-doped fiber laser based on an abrupt-tapered in-fiber interferometer

NASA Astrophysics Data System (ADS)

Hernández-Arriaga, M. V.; Durán-Sánchez, M.; Ibarra-Escamilla, B.; Álvarez-Tamayo, R. I.; Santiago-Hernández, H.; Bello-Jiménez, M.; Kuzin, E. A.

2017-11-01

An experimental study of an all-fiber tunable thulium-doped fiber laser based on an abrupt-tapered in-fiber interferometer is presented. A microfiber filter with length of 6 mm and diameter of 20 μm is used to achieve single laser wavelength tuning in a range of 19.4 nm and dual-wavelength laser operation at 1761.8 and 1793.4 nm with a channel spacing of 31.6 nm. The abrupt-tapered structure allows multi-modal interference at the air-cladding interface. The proposed in-fiber interferometer exhibits characteristics of low cost and simple fabrication, making it suitable for practical applications in wavelength filtering and wavelength selection in all-fiber lasers.

The Western Hemisphere of Venus: 3.5 CM Dual Circular-Polarization Radar Images

NASA Astrophysics Data System (ADS)

Haldemann, Albert F. C.; Muhleman, Duane O.; Butler, Bryan J.; Slade, Martin A.

1997-08-01

We present new dual circular-polarization radar maps of the western hemisphere of Venus. The results are from a 1993 experiment imaging Venus with 3.5 cm radar. Continuous-wave right circularly polarized flux was transmitted toward Venus from the 70 m Deep Space Network antenna in Goldstone, California. The echo was received in both the same sense (SS) and the opposite sense (OS) of circular polarization at the Very Large Array in New Mexico. By spatially reconstructing the echo with the interferometer, maps of Venusian radar albedo were made for each of two days of observation in both OS (echo principally due to specular reflection) and SS (diffuse echo) channels. On both days, the sub-earth longitude was near 300 E. The SS maps are dominated by a significant component of diffuse backscatter from the 285 E longitude highlands: Beta, Phoebe, and Themis Regiones. Beta Regio includes radar-anomalous regions with high reflectivity and low emissivity. The nature of these altitude-related electrical properties on Venus is one of the outstanding surface process questions that remain after Magellan. Our experiment adds the first full-disk polarization ratio (μc) maps to the discussion. The data show that different geology determines different radar scattering properties within Beta. Diffuse scattering is very important in Beta, and may be due to either surface or volume scattering. We find a strong correlation of the SS albedo σSSwith altitudeRp(km) in Beta, σSS∝ 0.3Rp. Also, σOS∝ 0.7Rp. The onset of this relationship is at theRp∼ 6054 km planetary radius contour. The nature and morphology of the highland radar anomalies in Beta is consistent with a diffuse scattering mechanism. In Beta Regio we find μc> 0.5 in general, with μcas high as 0.8 between Rhea and Theia Montes, to the west of Devana Chasma. These values are compatible with measurements of blocky terrestrial lava flows if surface scattering dominates. If volume scattering is important, the high RCP cross-sections may indicate an important decrease in embedded scatterer size with altitude, which could be related to enhanced weathering.

RADAR: A novel fast-screening method for reading difficulties with special focus on dyslexia.

PubMed

Smyrnakis, Ioannis; Andreadakis, Vassilios; Selimis, Vassilios; Kalaitzakis, Michail; Bachourou, Theodora; Kaloutsakis, Georgios; Kymionis, George D; Smirnakis, Stelios; Aslanides, Ioannis M

2017-01-01

Dyslexia is a developmental learning disorder of single word reading accuracy and/or fluency, with compelling research directed towards understanding the contributions of the visual system. While dyslexia is not an oculomotor disease, readers with dyslexia have shown different eye movements than typically developing students during text reading. Readers with dyslexia exhibit longer and more frequent fixations, shorter saccade lengths, more backward refixations than typical readers. Furthermore, readers with dyslexia are known to have difficulty in reading long words, lower skipping rate of short words, and high gaze duration on many words. It is an open question whether it is possible to harness these distinctive oculomotor scanning patterns observed during reading in order to develop a screening tool that can reliably identify struggling readers, who may be candidates for dyslexia. Here, we introduce a novel, fast, objective, non-invasive method, named Rapid Assessment of Difficulties and Abnormalities in Reading (RADAR) that screens for features associated with the aberrant visual scanning of reading text seen in dyslexia. Eye tracking parameter measurements that are stable under retest and have high discriminative power, as indicated by their ROC (receiver operating characteristic) curves, were obtained during silent text reading. These parameters were combined to derive a total reading score (TRS) that can reliably separate readers with dyslexia from typical readers. We tested TRS in a group of school-age children ranging from 8.5 to 12.5 years of age. TRS achieved 94.2% correct classification of children tested. Specifically, 35 out of 37 control (specificity 94.6%) and 30 out of 32 readers with dyslexia (sensitivity 93.8%) were classified correctly using RADAR, under a circular validation condition (see section Results/Total Reading Score) where the individual evaluated was not included in the test construction group. In conclusion, RADAR is a novel, automated, fast and reliable way to identify children at high risk of dyslexia that is amenable to large-scale screening. Moreover, analysis of eye movement parameters obtained with RADAR during reading will likely be useful for implementing individualized treatment strategies and for monitoring objectively the success of chosen interventions. We envision that it will be possible to use RADAR as a sensitive, objective, and quantitative first pass screen to identify individuals with reading disorders that manifest with abnormal oculomotor reading strategies, like dyslexia.

RADAR: A novel fast-screening method for reading difficulties with special focus on dyslexia

PubMed Central

Smyrnakis, Ioannis; Andreadakis, Vassilios; Selimis, Vassilios; Kalaitzakis, Michail; Bachourou, Theodora; Kaloutsakis, Georgios; Kymionis, George D.; Smirnakis, Stelios; Aslanides, Ioannis M.

2017-01-01

Dyslexia is a developmental learning disorder of single word reading accuracy and/or fluency, with compelling research directed towards understanding the contributions of the visual system. While dyslexia is not an oculomotor disease, readers with dyslexia have shown different eye movements than typically developing students during text reading. Readers with dyslexia exhibit longer and more frequent fixations, shorter saccade lengths, more backward refixations than typical readers. Furthermore, readers with dyslexia are known to have difficulty in reading long words, lower skipping rate of short words, and high gaze duration on many words. It is an open question whether it is possible to harness these distinctive oculomotor scanning patterns observed during reading in order to develop a screening tool that can reliably identify struggling readers, who may be candidates for dyslexia. Here, we introduce a novel, fast, objective, non-invasive method, named Rapid Assessment of Difficulties and Abnormalities in Reading (RADAR) that screens for features associated with the aberrant visual scanning of reading text seen in dyslexia. Eye tracking parameter measurements that are stable under retest and have high discriminative power, as indicated by their ROC (receiver operating characteristic) curves, were obtained during silent text reading. These parameters were combined to derive a total reading score (TRS) that can reliably separate readers with dyslexia from typical readers. We tested TRS in a group of school-age children ranging from 8.5 to 12.5 years of age. TRS achieved 94.2% correct classification of children tested. Specifically, 35 out of 37 control (specificity 94.6%) and 30 out of 32 readers with dyslexia (sensitivity 93.8%) were classified correctly using RADAR, under a circular validation condition (see section Results/Total Reading Score) where the individual evaluated was not included in the test construction group. In conclusion, RADAR is a novel, automated, fast and reliable way to identify children at high risk of dyslexia that is amenable to large-scale screening. Moreover, analysis of eye movement parameters obtained with RADAR during reading will likely be useful for implementing individualized treatment strategies and for monitoring objectively the success of chosen interventions. We envision that it will be possible to use RADAR as a sensitive, objective, and quantitative first pass screen to identify individuals with reading disorders that manifest with abnormal oculomotor reading strategies, like dyslexia. PMID:28800632

Wall characterization for through-the-wall radar applications

NASA Astrophysics Data System (ADS)

Greneker, Gene; Rausch, E. O.

2008-04-01

There has been continuing interest in the penetration of multilayer building materials, such as wood walls with air gaps and concrete hollow core block, using through-the-wall (TTW) radar systems. TTW operational techniques and signal propagation paths vary depending on how the TTW system is intended to be operated. For example, the operator of a TTW radar may be required to place the radar against the intervening wall of interest while collecting data. Other operational doctrines allow the radar to be operated in a stand-off mode from the wall. The stand-off distances can vary from feet to hundreds of feet, depending on the type of radar being used. When a signal is propagated through a multilayer wall with air gaps between the material and the wall construction uses materials of radically different dielectric constants, attenuation may not be the only effect that the probing signal experiences passing through the wall. This paper presents measurements of a hollow core concrete block wall and the measurement of a standard wall constructed of siding and wallboard. Both types of walls are typically found in most U.S. homes. These limited measurements demonstrate that the type of wall being penetrated by a wideband signal can modify the probing signal.

Preliminary Limited Surveillance Radar (LSR) Cost/Benefit Analysis

DOT National Transportation Integrated Search

1977-10-01

This report presents the findings of a cost/benefit analysis of the deployment of a new Limited Surveillance Radar (LSR). An LSR is an inexpensive, single channel, short-range (about 20 miles), primary radar for use at approach control facilities whi...

Compact all-fiber interferometer system for shock acceleration measurement

NASA Astrophysics Data System (ADS)

Zhao, Jiang; Pi, Shaohua; Hong, Guangwei; Zhao, Dong; Jia, Bo

2013-08-01

Acceleration measurement plays an important role in a variety of fields in science and engineering. In particular, the accurate, continuous and non-contact recording of the shock acceleration profiles of the free target surfaces is considered as a critical technique in shock physics. Various kinds of optical interferometers have been developed to monitor the motion of the surfaces of shocked targets since the 1960s, for instance, the velocity interferometer system for any reflector, the fiber optic accelerometer, the photonic Doppler velocimetry system and the displacement interferometer. However, most of such systems rely on the coherent quasi-monochromatic illumination and discrete optic elements, which are costly in setting-up and maintenance. In 1996, L. Levin et al reported an interferometric fiber-optic Doppler velocimeter with high-dynamic range, in which fiber-coupled components were used to replace the discrete optic elements. However, the fringe visibility of the Levin's system is low because of the coupled components, which greatly limits the reliability and accuracy in the shock measurement. In this paper, a compact all-fiber interferometer system for measuring the shock acceleration is developed and tested. The advantage of the system is that not only removes the non-interfering light and enhances the fringe visibility, but also reduces polarization induced signal fading and the polarization induced phase shift. Moreover, it also does not require a source of long coherence length. The system bases entirely on single-mode fiber optics and mainly consists of a polarization beam splitter, a faraday rotator, a depolarizer and a 3×3 single-mode fiber coupler which work at 1310 nm wavelength. The optical systems of the interferometer are described and the experimental results compared with a shock acceleration calibration system with a pneumatic exciter (PneuShockTM Model 9525C by The Modal Shop) are reported. In the shock acceleration test, the interferometer system measured shock acceleration with peak accelerations of ~100,000 m/s2 and the durations of ~0.2 ms which are conformed to the results of the shock acceleration calibration system. The measured relative error of the acceleration is within 3%.

A sensitive and stable confocal Fabry-Pérot interferometer for surface ultrasonic vibration detection

NASA Astrophysics Data System (ADS)

Ding, Hong-sheng; Tong, Li-ge; Chen, Geng-hua

2001-08-01

A new confocal Fabry-Pérot interferometer (CFPI) has been constructed. By using both of the conjugate rays, the sensitivity of the system was doubled. Moreover, the negative feedback control loop of a single-chip microcomputer (MCS-51) was applied to stabilize the working point at an optimum position. The system has been used in detecting the piezoelectric ultrasonic vibration on the surface of an aluminium sample.

A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D

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

Davis, E. M.; Rost, J. C.; Porkolab, M.

2016-11-15

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI–interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz

Multipulsed dynamic moire interferometer

DOEpatents

Deason, Vance A.

1991-01-01

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.

Rain/snow radar remote sensing with two X-band radars operating over an altitude gradient in the French Alps

NASA Astrophysics Data System (ADS)

Delrieu, Guy; Cazenave, Frédéric; Yu, Nan; Boudevillain, Brice; Faure, Dominique; Gaussiat, Nicolas

2017-04-01

Operating weather radars in high-mountain regions faces the following well-known dilemma: (1) installing radar on top of mountains allows for the detection of severe summer convective events over 360° but may give poor QPE performance during a very significant part of the year when the 0°C isotherm is located below or close to the radar altitude; (2) installing radar at lower altitudes may lead to better QPE over sensitive areas such as cities located in valleys, but at the cost of reduced visibility and detection capability in other geographical sectors. We have the opportunity to study this question in detail in the region of Grenoble (an Alpine city of 500 000 inhabitants with an average altitude of 210 m asl) with a pair of X-band polarimetric weather radars operated respectively by Meteo-France on top of Mount Moucherotte (1920 m asl) and by IGE on the Grenoble Campus (213 m asl). The XPORT radar (IGE) performs a combination of PPIs at elevations of 3.5, 7.5, 15 and 25° complemented by two RHIs in the vertical plane passing by the two radar sites, in order to document the 4D precipitation variability within the Grenoble intermountain valley. In the proposed communication, preliminary results of this experiment (started in September 2016) will be presented with highlights on (1) the calibration of the two radar systems, (2) the characterization of the melting layer during significant precipitation events (>5mm/day) occurring in autumn, winter and spring; (3) the simulation of the relative effects of attenuation and non-uniform beam filling at X-band and (4) the possibility to use the mountain returns for quantifying the attenuation by the rain and the melting layer.

Engineering studies related to the Skylab program. Task H: Microwave/optical/infrared image processing for ocean current recognition. [from radar altimeter data

NASA Technical Reports Server (NTRS)

Smith, A. G.

1974-01-01

Images from the Skylab S-193 radar altimeter were selected from data obtained on appropriate passes made by Skylabs 2, 3, and 4 missions for the following three objectives: (1) to serve as a precursor to an investigation for the planned GEOS-C mission, in which radar altimeter data will be analyzed to reveal ocean current related to surface topography; (2) to determine the value of satellite infrared and visual radiometer data as potential sources of ground truth data, the results of which be incorporated in the planning of the SEASAT program; and (3) to determine whether optimal data reduction techniques are useful for revealing clues on Gulf Stream topographic signature characteristics. The results obtained which apply to the stated objectives are discussed.

Optical Properties of Compressible Inhomogeneous Shear Layers Relevant to High Power Lasers.

DTIC Science & Technology

1987-09-30

trend of laser development towards shorter wavelenghts , the fluid optics challenge is increased con- siderahly. In general, the conditioning of the gas...tion pattern of laser beams passing through the layer. We hoped to under- ", stand and to predict compressible shear layer growth rate and optical per...layer growth rates for jet Mach numbers of 0.1, 0.3 and n.6 were measured using a Mach-Zehnder interferometer. Interferograms using a He-Ne laser source

Data Acquisition System for Multi-Frequency Radar Flight Operations Preparation

NASA Technical Reports Server (NTRS)

Leachman, Jonathan

2010-01-01

A three-channel data acquisition system was developed for the NASA Multi-Frequency Radar (MFR) system. The system is based on a commercial-off-the-shelf (COTS) industrial PC (personal computer) and two dual-channel 14-bit digital receiver cards. The decimated complex envelope representations of the three radar signals are passed to the host PC via the PCI bus, and then processed in parallel by multiple cores of the PC CPU (central processing unit). The innovation is this parallelization of the radar data processing using multiple cores of a standard COTS multi-core CPU. The data processing portion of the data acquisition software was built using autonomous program modules or threads, which can run simultaneously on different cores. A master program module calculates the optimal number of processing threads, launches them, and continually supplies each with data. The benefit of this new parallel software architecture is that COTS PCs can be used to implement increasingly complex processing algorithms on an increasing number of radar range gates and data rates. As new PCs become available with higher numbers of CPU cores, the software will automatically utilize the additional computational capacity.

Birds and insects as radar targets - A review

NASA Technical Reports Server (NTRS)

Vaughn, C. R.

1985-01-01

A review of radar cross-section measurements of birds and insects is presented. A brief discussion of some possible theoretical models is also given and comparisons made with the measurements. The comparisons suggest that most targets are, at present, better modeled by a prolate spheroid having a length-to-width ratio between 3 and 10 than by the often used equivalent weight water sphere. In addition, many targets observed with linear horizontal polarization have maximum cross sections much better estimated by a resonant half-wave dipole than by a water sphere. Also considered are birds and insects in the aggregate as a local radar 'clutter' source. Order-of-magnitude estimates are given for many reasonable target number densities. These estimates are then used to predict X-band volume reflectivities. Other topics that are of interest to the radar engineer are discussed, including the doppler bandwidth due to the internal motions of a single bird, the radar cross-section probability densities of single birds and insects, the variability of the functional form of the probability density functions, and the Fourier spectra of single birds and insects.

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

NASA Astrophysics Data System (ADS)

Chen, W. G.; Lou, S. Q.; Feng, S. C.; Wang, L. W.; Li, H. L.; Guo, T. Y.; Jian, S. S.

2009-11-01

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

A Compact Band-Pass Filter with High Selectivity and Second Harmonic Suppression

PubMed Central

Hadarig, Ramona Cosmina; de Cos Gomez, Maria Elena; Las-Heras, Fernando

2013-01-01

The design of a novel band-pass filter with narrow-band features based on an electromagnetic resonator at 6.4 GHz is presented. A prototype is manufactured and characterized in terms of transmission and reflection coefficient. The selective passband and suppression of the second harmonic make the filter suitable to be used in a C band frequency range for radar systems and satellite/terrestrial applications. To avoid substantial interference for this kind of applications, passive components with narrow band features and small dimensions are required. Between 3.6 GHz and 4.2 GHz the band-pass filter with harmonic suppression should have an attenuation of at least 35 dB, whereas for a passband, less than 10% is sufficient. PMID:28788412

Joint synthetic aperture radar plus ground moving target indicator from single-channel radar using compressive sensing

DOEpatents

Thompson, Douglas; Hallquist, Aaron; Anderson, Hyrum

2017-10-17

The various embodiments presented herein relate to utilizing an operational single-channel radar to collect and process synthetic aperture radar (SAR) and ground moving target indicator (GMTI) imagery from a same set of radar returns. In an embodiment, data is collected by randomly staggering a slow-time pulse repetition interval (PRI) over a SAR aperture such that a number of transmitted pulses in the SAR aperture is preserved with respect to standard SAR, but many of the pulses are spaced very closely enabling movers (e.g., targets) to be resolved, wherein a relative velocity of the movers places them outside of the SAR ground patch. The various embodiments of image reconstruction can be based on compressed sensing inversion from undersampled data, which can be solved efficiently using such techniques as Bregman iteration. The various embodiments enable high-quality SAR reconstruction, and high-quality GMTI reconstruction from the same set of radar returns.

New Radio Telescope Makes First Scientific Observations

NASA Astrophysics Data System (ADS)

2001-05-01

The world's two largest radio telescopes have combined to make detailed radar images of the cloud-shrouded surface of Venus and of a tiny asteroid that passed near the Earth. The images mark the first scientific contributions from the National Science Foundation's (NSF) new Robert C. Byrd Green Bank Telescope in West Virginia, which worked with the NSF's recently-upgraded Arecibo telescope in Puerto Rico. The project used the radar transmitter on the Arecibo telescope and the huge collecting areas of both telescopes to receive the echoes. GBT-Arecibo Radar Image of Maxwell Montes on Venus "These images are the first of many scientific contributions to come from the Robert C. Byrd Green Bank Telescope, and a great way for it to begin its scientific career," said Paul Vanden Bout, director of the National Radio Astronomy Observatory (NRAO). "Our congratulations go to the scientists involved in this project as well as to the hard-working staffs at Green Bank and Arecibo who made this accomplishment possible," Vanden Bout added. To the eye, Venus hides behind a veil of brilliant white clouds, but these clouds can be penetrated by radar waves, revealing the planet's surface. The combination of the Green Bank Telescope (GBT), the world's largest fully-steerable radio telescope, and the Arecibo telescope, the world's most powerful radar, makes an unmatched tool for studying Venus and other solar-system bodies. "Having a really big telescope like the new Green Bank Telescope to receive the radar echoes from small asteroids that are really close to the Earth and from very distant objects like Titan, the large moon of Saturn, will be a real boon to radar studies of the solar system." said Cornell University professor Donald Campbell, leader of the research team. Ten years ago, the radar system on NASA's Magellan spacecraft probed though the clouds of Venus to reveal in amazing detail the surface of the Earth's twin planet. These new studies using the GBT and Arecibo, the first since Magellan to cover large areas of the planet's surface, will provide images showing surface features as small as about 1 km (3,000 ft), only three times the size of the Arecibo telescope itself. Venus may be a geologically active planet similar to the Earth, and the new images will be used to look for changes on Venus due to volcanic activity, landslides and other processes that may have modified the surface since the Magellan mission. The radar echoes received by both telescopes also can be combined to form a radar interferometer capable of measuring altitudes over some of the planet's mountainous regions with considerably better detail than was achieved by Magellan. These were the first scheduled observations with the new Robert C. Byrd Green Bank Telescope, demonstrating its capabilities for solar-system studies. In addition to the observations of Venus, a tiny 150m (500 ft) asteroid, 2001 EC16, was imaged with the two telescopes working as a combined radar system on March 26 when the asteroid was only 8 times the distance of the Moon from the Earth. The image could show details on the asteroid's surface only 15 meters (50 ft) in size and shows EC16 to be an irregularly shaped object rotating about once every 200 hrs, one of the slowest rotation rates so far measured for these objects. It took about 20 seconds for the radar signal to go to EC16 and back, compared with the almost 5 minutes needed to go to Venus and back. EC16 was discovered by the NEAT asteroid survey on March 15, 11 days prior to the radar observations. Very large numbers of these near-Earth asteroids are being discovered and the combined Arecibo-GBT radar system will be needed to properly study a significant number of them. The Robert C. Byrd Green Bank Telescope The observing team led by Campbell also included Jean-Luc Margot of Caltech, Lynn Carter of Cornell, and Bruce Campbell of the Smithsonian Institution. The 100-meter (330 feet) Robert C. Byrd Green Bank Telescope was dedicated in August 2000 and now is being prepared for routine scientific operation. It is operated by the National Radio Astronomy Observatory, headquartered in Charlottesville, Virginia. It is the largest fully-steerable telescope in the world. It is a highly advanced telescope with a mechanized reflecting surface and a laser measurement system for continuous adjustments to its structure. The 305-meter (1,000 feet) Arecibo telescope recently has completed a major upgrade funded by the NSF and NASA to improve its observing capabilities, including a more powerful radar transmitter for planetary studies. It is operated by the National Astronomy and Ionosphere Center (NAIC) headquartered at Cornell University. Its reflector is fixed to the ground, and is the largest telescope of any type in the world. The radar capability of Arecibo, combined with the large reflectors of Arecibo and Green Bank, make for a uniquely powerful radar imaging capability. Both observatories are facilities of the National Science Foundation. The NRAO is operated for the NSF by Associated Universities, Inc., under a cooperative agreement. NAIC is operated by Cornell University, also under a cooperative agreement with the NSF.

Radar systems for the water resources mission, volume 1

NASA Technical Reports Server (NTRS)

Moore, R. K.; Claassen, J. P.; Erickson, R. L.; Fong, R. K. T.; Hanson, B. C.; Komen, M. J.; Mcmillan, S. B.; Parashar, S. K.

1976-01-01

The state of the art determination was made for radar measurement of: soil moisture, snow, standing and flowing water, lake and river ice, determination of required spacecraft radar parameters, study of synthetic-aperture radar systems to meet these parametric requirements, and study of techniques for on-board processing of the radar data. Significant new concepts developed include the following: scanning synthetic-aperture radar to achieve wide-swath coverage; single-sideband radar; and comb-filter range-sequential, range-offset SAR processing. The state of the art in radar measurement of water resources parameters is outlined. The feasibility for immediate development of a spacecraft water resources SAR was established. Numerous candidates for the on-board processor were examined.

FIBER AND INTEGRATED OPTICS. FIBER WAVEGUIDE DEVICES: Fiber Michelson interferometer with a 50-km difference between its arms

NASA Astrophysics Data System (ADS)

Dianov, Evgenii M.; Kuznetsov, A. V.; Makarenko, A. Yu; Okhotnikov, O. G.; Prokhorov, A. M.; Shcherbakov, E. A.

1990-12-01

Single-mode fiber waveguides were used in constructing a Michelson interferometer with a 50-km difference between its arm lengths. An analysis was made of its resolving power as a function of the parameters of the optical part and of the characteristics of the electronic apparatus used in the system. The width of a spectral emission line of a semiconductor laser with a distributed Rayleigh fiber resonator was determined.

High Resolution Rapid Response Observations of Compact Radio Sources with the Ceduna Hobart Interferometer (CHI)

NASA Technical Reports Server (NTRS)

Blanchard, Jay M.; Lovell, James E. J.; Ojha, Roopesh; Kadler, Matthias; Dickey, John M.; Edwards, Philip G.

2011-01-01

Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including Active Galactic Nuclei. A key tool of such studies is the ability to observe an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific observational procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer. that can rapidly observe a flaring object. This is the only facility that is dedicated to rapid high resolution radio observations of an object south of -30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at y-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our observing strategy within half an hour of a triggering event. These observations can be calibrated with amplitude errors better than 20%. Lower limits to the brightness temperatures of the sources can also be calculated using CHI. Key words. instrumentation:interferometers - galaxies:active - galaxies:jets - galaxies:nuclei quasars:general gamma rays:galaxies- 1.

Electro-optic modulation of a laser at microwave frequencies for interferometric purposes

NASA Astrophysics Data System (ADS)

Specht, Paul E.; Jilek, Brook A.

2017-02-01

A multi-point microwave interferometer (MPMI) concept was previously proposed by the authors for spatially-resolved, non-invasive tracking of a shock, reaction, or detonation front in energetic media [P. Specht et al., AIP Conf. Proc. 1793, 160010 (2017).]. The advantage of the MPMI concept over current microwave interferometry techniques is its detection of Doppler shifted microwave signals through electro-optic (EO) modulation of a laser. Since EO modulation preserves spatial variations in the Doppler shift, collecting the EO modulated laser light into a fiber array for recording with an optical heterodyne interferometer yields spatially-resolved velocity information. This work demonstrates the underlying physical principle of the MPMI diagnostic: the monitoring of a microwave signal with nanosecond temporal resolution using an optical heterodyne interferometer. For this purpose, the MPMI concept was simplified to a single-point construction using two tunable 1550 nm lasers and a 35.2 GHz microwave source. A (110) ZnTe crystal imparted the microwave frequency onto a laser, which was combined with a reference laser for determination of the microwave frequency in an optical heterodyne interferometer. A single, characteristic frequency associated with the microwave source was identified in all experiments, providing a means to monitor a microwave signal on nanosecond time scales. Lastly, areas for improving the frequency resolution of this technique are discussed, focusing on increasing the phase-modulated signal strength.

Electro-optic modulation of a laser at microwave frequencies for interferometric purposes.

PubMed

Specht, Paul E; Jilek, Brook A

2017-02-01

A multi-point microwave interferometer (MPMI) concept was previously proposed by the authors for spatially-resolved, non-invasive tracking of a shock, reaction, or detonation front in energetic media [P. Specht et al., AIP Conf. Proc. 1793, 160010 (2017).]. The advantage of the MPMI concept over current microwave interferometry techniques is its detection of Doppler shifted microwave signals through electro-optic (EO) modulation of a laser. Since EO modulation preserves spatial variations in the Doppler shift, collecting the EO modulated laser light into a fiber array for recording with an optical heterodyne interferometer yields spatially-resolved velocity information. This work demonstrates the underlying physical principle of the MPMI diagnostic: the monitoring of a microwave signal with nanosecond temporal resolution using an optical heterodyne interferometer. For this purpose, the MPMI concept was simplified to a single-point construction using two tunable 1550 nm lasers and a 35.2 GHz microwave source. A (110) ZnTe crystal imparted the microwave frequency onto a laser, which was combined with a reference laser for determination of the microwave frequency in an optical heterodyne interferometer. A single, characteristic frequency associated with the microwave source was identified in all experiments, providing a means to monitor a microwave signal on nanosecond time scales. Lastly, areas for improving the frequency resolution of this technique are discussed, focusing on increasing the phase-modulated signal strength.

Comparative measurements of piezoelectric coefficient of PZT films by Berlincourt, interferometer, and vibrometer methods.

PubMed

Huang, Zhaorong; Zhang, Qi; Corkovic, Silvana; Dorey, Robert; Whatmore, Roger W

2006-12-01

Chemical solution deposition (CSD) techniques were used to prepare lead zirconate (Zr) titanate (Ti) (PZT) thin films with Zr/Ti ratios of 30/70 and 52/48. Usually CSD processing is restricted to making crack-free, single-layer films of 70-nm thick, but modifications to the sol-gel process have permitted the fabrication of dense, crack-free, single layers up to 200 to 300 nm thick, which can be built-up into layers up to 3-microm thick. Thicker PZT films (> 2-microm single layer) can be produced by using a composite sol-gel/ceramic process. Knowledge of the electroactive properties of these materials is essential for modeling and design of novel micro-electromechanical systems (MEMS) devices, but accurate measurement of these properties is by no means straightforward. A novel, double-beam, common-path laser interferometer has been developed to measure the longitudinal (d33) piezoelectric coefficient in films; the results were compared with the values obtained by Berlin-court and laser scanning vibrometer methods. It was found that, for thin-film samples, the d(33,f) values obtained from the Berlincourt method are usually larger: than those obtained from the interferometer and the vibrometer methods; the reasons for this are discussed.

Spatially continuous distributed fiber optic sensing using optical carrier based microwave interferometry.

PubMed

Huang, Jie; Lan, Xinwei; Luo, Ming; Xiao, Hai

2014-07-28

This paper reports a spatially continuous distributed fiber optic sensing technique using optical carrier based microwave interferometry (OCMI), in which many optical interferometers with the same or different optical path differences are interrogated in the microwave domain and their locations can be unambiguously determined. The concept is demonstrated using cascaded weak optical reflectors along a single optical fiber, where any two arbitrary reflectors are paired to define a low-finesse Fabry-Perot interferometer. While spatially continuous (i.e., no dark zone), fully distributed strain measurement was used as an example to demonstrate the capability, the proposed concept may also be implemented on other types of waveguide or free-space interferometers and used for distributed measurement of various physical, chemical and biological quantities.

Radio-frequency low-coherence interferometry.

PubMed

Fernández-Pousa, Carlos R; Mora, José; Maestre, Haroldo; Corral, Pablo

2014-06-15

A method for retrieving low-coherence interferograms, based on the use of a microwave photonics filter, is proposed and demonstrated. The method is equivalent to the double-interferometer technique, with the scanning interferometer replaced by an analog fiber-optics link and the visibility recorded as the amplitude of its radio-frequency (RF) response. As a low-coherence interferometry system, it shows a decrease of resolution induced by the fiber's third-order dispersion (β3). As a displacement sensor, it provides highly linear and slope-scalable readouts of the interferometer's optical path difference in terms of RF, even in the presence of third-order dispersion. In a proof-of-concept experiment, we demonstrate 20-μm displacement readouts using C-band EDFA sources and standard single-mode fiber.

Temperature- and phase-independent lateral force sensor based on a core-offset multi-mode fiber interferometer.

PubMed

Dong, Bo; Zhou, Da-Peng; Wei, Li; Liu, Wing-Ki; Lit, John W Y

2008-11-10

A novel lateral force sensor based on a core-offset multi-mode fiber (MMF) interferometer is reported. High extinction ratio can be obtained by misaligning a fused cross section between the single-mode fiber (SMF) and MMF. With the variation of the lateral force applied to a short section of the MMF, the extinction ratio changes while the interference phase remains almost constant. The change of the extinction ratio is independent of temperature variations. The proposed force sensor has the advantages of temperature- and phase-independency, high extinction ratio sensitivity, good repeatability, low cost, and simple structure. Moreover, the core-offset MMF interferometer is expected to have applications in fiber filters and tunable phase-independent attenuators.

When and where is thaw slump mass wasting energy limited? A landscape-scale assessment using TanDEM-X single-pass radar interferometry

NASA Astrophysics Data System (ADS)

Zwieback, S.; Kokelj, S.; Günther, F.; Berg, A. A.; Bernhard, P.; Boike, J.; Grosse, G.; Hajnsek, I.

2017-12-01

Thermokarst is expected to drive major changes in ice-rich permafrost regions, but its current and future extent and rates of change remain only partially understood; in part due to limited broad-scale observations. Here we show that time-lapse digital elevation models from single-pass interferometry can provide important synoptic observations of thermokarst-induced terrain changes and novel insight into the drivers and controls of thermokarst. We focus on retrogressive thaw slumps, an important and dynamic form of thermokarst. On sub-seasonal time scales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other factors such as rainfall or the formation of an insulating veneer are also thought important. To study the sub-seasonal drivers, we use TanDEM-X observations (12 m resolution) acquired during the Science Phase in summer 2015 over two study regions. The high vertical precision (30 cm), frequent observations (11 days) and large coverage (5000 km2) allow us to track volume losses as drivers (e.g. available energy) vary through time. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm/day) despite the ample available energy, indicating the widespread presence of an insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm/day), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August, respectively. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting. This complexity reinforces the need for circum-arctic monitoring efforts, for which remote sensing approaches such as single-pass interferometry are indispensable.

Generation and performance assessment of the global TanDEM-X digital elevation model

NASA Astrophysics Data System (ADS)

Rizzoli, Paola; Martone, Michele; Gonzalez, Carolina; Wecklich, Christopher; Borla Tridon, Daniela; Bräutigam, Benjamin; Bachmann, Markus; Schulze, Daniel; Fritz, Thomas; Huber, Martin; Wessel, Birgit; Krieger, Gerhard; Zink, Manfred; Moreira, Alberto

2017-10-01

The primary objective of the TanDEM-X mission is the generation of a global, consistent, and high-resolution digital elevation model (DEM) with unprecedented global accuracy. The goal is achieved by exploiting the interferometric capabilities of the two twin SAR satellites TerraSAR-X and TanDEM-X, which fly in a close orbit formation, acting as an X-band single-pass interferometer. Between December 2010 and early 2015 all land surfaces have been acquired at least twice, difficult terrain up to seven or eight times. The acquisition strategy, data processing, and DEM calibration and mosaicking have been systematically monitored and optimized throughout the entire mission duration, in order to fulfill the specification. The processing of all data has finally been completed in September 2016 and this paper reports on the final performance of the TanDEM-X global DEM and presents the acquisition and processing strategy which allowed to obtain the final DEM quality. The results confirm the outstanding global accuracy of the delivered product, which can be now utilized for both scientific and commercial applications.

Planar waveguide integrated spatial filter array

NASA Astrophysics Data System (ADS)

Ai, Jun; Dimov, Fedor; Lyon, Richard; Rakuljic, Neven; Griffo, Chris; Xia, Xiaowei; Arik, Engin

2013-09-01

An innovative integrated spatial filter array (iSFA) was developed for the nulling interferometer for the detection of earth-like planets and life beyond our solar system. The coherent iSFA comprised a 2D planar lightwave circuit (PLC) array coupled with a pair of 2D lenslet arrays in a hexagonal grid to achieve the optimum fill factor and throughput. The silica-on-silicon waveguide mode field diameter and numerical aperture (NA) were designed to match with the Airy disc and NA of the microlens for optimum coupling. The lenslet array was coated with a chromium pinhole array at the focal plane to pass the single-mode waveguide but attenuate the higher modes. We assembled a 32 by 30 array by stacking 32 chips that were produced by photolithography from a 6-in. silicon wafer. Each chip has 30 planar waveguides. The PLC array is inherently polarization-maintaining (PM) and requires much less alignment in contrast to a fiber array, where each PM fiber must be placed individually and oriented correctly. The PLC array offers better scalability than the fiber bundle array for large arrays of over 1,000 waveguides.

Relative Sensor with 4(pi) Coverage for Formation Flying Missions

NASA Technical Reports Server (NTRS)

Tien, Jeffrey Y.; Purcell, George H., Jr.; Sirinivasan, Jeffrey M.; Young, Lawrence E.

2004-01-01

The Terrestrial Planet Finder (TPF) pre-project, an element of NASA's Origins program, is currently developing two architectures for a mission to search for earth-like planets around nearby stars. One of the architectures being developed is the Formation Flying Interferometer (FFI). The FFI is envisioned to consist of up to seven spacecraft (as many as six 'collectors' with IR telescopes, and a 'combiner') flying in precise formation within f 1 cm of pre-determined trajectories for synchronized observations. The spacecraft-to-spacecraft separations are variable between 20 m and 100 m or more during observations to support various configurations of the interferometer in the planet-finding mode. The challenges involved with TPF autonomous operations, ranging from formation acquisition and formation maneuvering to high precision formation control during science observations, are unprecedented. In this paper we discuss the development of the formation acquisition sensor, which uses novel modulation and duplexing schemes to enable fast signal acquisition, multiple-spacecraft operation, and mitigation of inherent jamming conditions, while providing precise formation sensing and integrated radar capability. This approach performs delay synthesis and carrier cycle ambiguity resolution to improve range measurement, and uses differential carrier cycle ambiguity resolution to make precise bearing angle measurements without calibration maneuvers.

Relative Sensor with 4Pi Coverage for Formation Flying Missions

NASA Technical Reports Server (NTRS)

Tien, Jeffrey Y.; Purcell, George H., Jr.; Srinivasan, Jeffrey M.; Young, Lawrence E.

2004-01-01

The Terrestrial Planet Finder (TPF) pre-project, an element of NASA s Origins program, is currently developing two architectures for a mission to search for earth-like planets around nearby stars. One of the architectures being developed is the Formation Flying Interferometer (FFI). The FFI is envisioned to consist of up to seven spacecraft (as many as six "collectors" with IR telescopes, and a "combiner") flying in precise formation within +/-1 cm of pre-determined trajectories for synchronized observations. The spacecraft-to-spacecraft separations are variable between 20 m and 100 m or more during observations to support various configurations of the interferometer in the planet-finding mode. The challenges involved with TPF autonomous operations, ranging from formation acquisition and formation maneuvering to high precision formation control during science observations, are unprecedented. In this paper we discuss the development of the formation acquisition sensor, which uses novel modulation and duplexing schemes to enable fast signal acquisition, multiple-spacecraft operation, and mitigation of inherent jamming conditions, while providing precise formation sensing and integrated radar capability. This approach performs delay synthesis and carrier cycle ambiguity resolution to improve range measurement, and uses differential carrier cycle ambiguity resolution to make precise bearing angle measurements without calibration maneuvers.

Doppler radar flowmeter

DOEpatents

Petlevich, Walter J.; Sverdrup, Edward F.

1978-01-01

A Doppler radar flowmeter comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.

A Coupled Model System for Southeast Florida: Wave Model Validation Using Radar and In Situ Observations

DTIC Science & Technology

2012-02-24

also included. The “ground truth” for waves validation includes in situ data (ADCP and buoy) and high frequency Wellen Radar (WERA HF) data...which swells are able to pass through islands and shoals to arrive at the in situ data region is highly sensitive to whether currents are included...grid 1: WW3 • ∆x = ∆y = 0.5° ≈ 55 km • Longitude: x = -100° to -0.5° W (260° to 359.5° E), nx =200 • Latitude: y =17° to 59° N, ny =85 • no

Ionospheric footprint of magnetosheathlike particle precipitation observed by an incoherent scatter radar

NASA Technical Reports Server (NTRS)

Watermann, Jurgen; Lummerzheim, Dirk; De La Beaujardiere, Odile; Newell, Patrick T.; Rich, Frederic J.

1994-01-01

We have examined Sondrestrom incoherent scatter radar observations of ionospheric plasma density and temperature distributions and measurements of F region ion drifts that were made during a prenoon pass of the Defense Meteorological Satellite Program (DMSP)-F7 satellite through the radar field of view. The spacecraft traversed a region of intense electron precipitation with a characteristic energy below approximately 200 eV. Particles with such low characteristic energies are believed to be directly or indirectly of magnetosheath origin. The precipitation region had a width about 2 deg invariant latitude and covered the low-latitude boundary layer (LLBL), the cusp, and the equatorward section of the plasma mantle (PM). The corotating radar observed a patch of enhanced electron density and elevated electron temperature in the F2 region between about 10.5 and 12 magnetic local time in the same invariant latitude range where DMSP-F7 detected the soft-electron flux. The ion drift pattern, also obtained by radar, shows that it is unlikely that the plasma patch was produced by solar radiation and advected into the radar field of view. We suggest that the radar observed modifications of the ionospheric plasma distribution, which resulted from direct entry of magnetosheath electrons into the magnetosphere and down to ionospheric altitudes. Model calculations of the ionospheric response to the observed electron precipitation support our interpretation. The spectral characteristics of the electron flux in the LLBL, cusp, and equatorward section of the PM were in this case too similar to allow to distinguish between them by using incoherent scatter radar measurements only.

Development and implementation of a portable grating interferometer system as a standard tool for testing optics at the Advanced Photon Source beamline 1-BM

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

Assoufid, Lahsen; Shi, Xianbo; Marathe, Shashidhara

We developed a portable X-ray grating interferometer setup as a standard tool for testing optics at the Advanced Photon Source (APS) beamline 1-BM. The interferometer can be operated in phase-stepping, Moiré, or single-grating harmonic imaging mode with 1-D or 2-D gratings. All of the interferometer motions are motorized; hence, it is much easier and quicker to switch between the different modes of operation. A novel aspect of this new instrument is its designed portability. While the setup is designed to be primarily used as a standard tool for testing optics at 1-BM, it could be potentially deployed at other APSmore » beamlines for beam coherence and wavefront characterization or imaging. The design of the interferometer system is described in detail and coherence measurements obtained at the APS 34-ID-E beamline are presented. The coherence was probed in two directions using a 2-D checkerboard, a linear, and a circular grating at X-ray energies of 8 keV, 11 keV, and 18 keV.« less

Switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer

NASA Astrophysics Data System (ADS)

Zhou, Yuxin; Wang, Xin; Tang, Zijuan; Lou, Shuqin

2018-05-01

In this paper, a switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer is proposed. The in-line Mach–Zehnder interferometer is fabricated by splicing a large-core fiber between two segments of single mode fibers, in which the first splicing point is tapered and the second splicing point is connected directly. By carefully rotating the polarization controller, switchable single-, dual-, triple- and quad-wavelength lasing outputs can be obtained with a side mode suppression ratio higher than 50 dB. The maximal peak power difference of multi-wavelength lasing is 3.67 dB, demonstrating a good power equalization performance. Furthermore, the proposed laser is proven to be very stable at room temperature. The wavelength shifts and peak power fluctuations are less than 0.02 nm and 1.3 dB over half an hour. In addition, stable quintuple-wavelength lasing with a side mode suppression ratio higher than 50 dB can also be realized when the filter length is changed.

Use of multi-frequency, multi-polarization, multi-angle airborne radars for class discrimination in a southern temperature forest

NASA Technical Reports Server (NTRS)

Mehta, N. C.

1984-01-01

The utility of radar scatterometers for discrimination and characterization of natural vegetation was investigated. Backscatter measurements were acquired with airborne multi-frequency, multi-polarization, multi-angle radar scatterometers over a test site in a southern temperate forest. Separability between ground cover classes was studied using a two-class separability measure. Very good separability is achieved between most classes. Longer wavelength is useful in separating trees from non-tree classes, while shorter wavelength and cross polarization are helpful for discrimination among tree classes. Using the maximum likelihood classifier, 50% overall classification accuracy is achieved using a single, short-wavelength scatterometer channel. Addition of multiple incidence angles and another radar band improves classification accuracy by 20% and 50%, respectively, over the single channel accuracy. Incorporation of a third radar band seems redundant for vegetation classification. Vertical transmit polarization is critically important for all classes.

A universal matter-wave interferometer with optical ionization gratings in the time-domain

PubMed Central

Haslinger, Philipp; Dörre, Nadine; Geyer, Philipp; Rodewald, Jonas; Nimmrichter, Stefan; Arndt, Markus

2015-01-01

Matter-wave interferometry with atoms1 and molecules2 has attracted a rapidly growing interest throughout the last two decades both in demonstrations of fundamental quantum phenomena and in quantum-enhanced precision measurements. Such experiments exploit the non-classical superposition of two or more position and momentum states which are coherently split and rejoined to interfere3-11. Here, we present the experimental realization of a universal near-field interferometer built from three short-pulse single-photon ionization gratings12,13. We observe quantum interference of fast molecular clusters, with a composite de Broglie wavelength as small as 275 fm. Optical ionization gratings are largely independent of the specific internal level structure and are therefore universally applicable to different kinds of nanoparticles, ranging from atoms to clusters, molecules and nanospheres. The interferometer is sensitive to fringe shifts as small as a few nanometers and yet robust against velocity-dependent phase shifts, since the gratings exist only for nanoseconds and form an interferometer in the time-domain. PMID:25983851

Reference Interferometer Using a Semiconductor Laser/LED Reference Source in a Cryogenic Fourier-Transform Spectrometer

NASA Technical Reports Server (NTRS)

Martino, Anthony J.; Cornwell, Donald M.

1998-01-01

A combination of a single mode AlGaAs laser diode and broadband LED was used in a Michelson interferometer to provide reference signals in a Fourier transform spectrometer, the Composite Infrared Spectrometer, on the Cassini mission to Saturn. The narrowband light from the laser produced continuous fringes throughout the travel of the interferometer, which were used to control the velocity of the scan mechanism and to trigger data sampling. The broadband light from the LED produced a burst of fringes at zero path difference, which was used as a fixed position reference. The system, including the sources, the interferometer, and the detectors, was designed to work both at room temperature and instrument operating temperature of 170 Kelvin. One major challenge that was overcome was preservation, from room temperature to 170 K, of alignment sufficient for high modulation of fringes from the broadband source. Another was the shift of the source spectra about 30 nm toward shorter wavelengths upon cooldown.

Physical measurement with in-line fiber Mach-Zehnder interferometer using differential phase white light interferometry

NASA Astrophysics Data System (ADS)

Aref, Seyed Hashem

2017-11-01

In this letter, the sensitivity to strain, curvature, and temperature of a sensor based on in-line fiber Mach-Zahnder interferometer (IFMZI) is studied and experimentally demonstrated. The sensing structure is simply a section of single mode fiber sandwiched between two abrupt tapers to achieve a compact IFMZI. The phase of interferometer changes with the measurand interaction, which is the basis for considering this structure for sensing. The physical parameter sensitivity of IFMZI sensor has been evaluated using differential white light interferometry (DWLI) technique as a phase read-out system. The differential configuration of the IFMZI sensor is used to achieve a high phase resolving power of ±0.062° for read-out interferometer by means of omission of phase noise of environment perturbations. The sensitivity of the sensor to the strain, curvature, and temperature has been measured 0.0199 degree/με, 757.00 degree/m-1, and 3.25 degree/°C, respectively.

Twin-Core Fiber-Based Mach Zehnder Interferometer for Simultaneous Measurement of Strain and Temperature

PubMed Central

Kowal, Dominik; Urbanczyk, Waclaw; Mergo, Pawel

2018-01-01

In this paper we present an all-fiber interferometric sensor for the simultaneous measurement of strain and temperature. It is composed of a specially fabricated twin-core fiber spliced between two pieces of a single-mode fiber. Due to the refractive index difference between the two cores in a twin-core fiber, a differential interference pattern is produced at the sensor output. The phase response of the interferometer to strain and temperature is measured in the 850–1250 nm spectral range, showing zero sensitivity to strain at 1000 nm. Due to the significant difference in sensitivities to both parameters, our interferometer is suitable for two-parameter sensing. The simultaneous response of the interferometer to strain and temperature was studied using the two-wavelength interrogation method and a novel approach based on the spectral fitting of the differential phase response. As the latter technique uses all the gathered spectral information, it is more reliable and yields the results with better accuracy. PMID:29558386

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

NASA Technical Reports Server (NTRS)

Wheeler, Kevin; Hensley, Scott; Lou, Yunling

2004-01-01

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

Radargrams Indicating Ice-Rich Subsurface Deposit

NASA Image and Video Library

2016-11-22

These two images show data acquired by the Shallow Radar (SHARAD) instrument while passing over two ground tracks in a part of Mars' Utopia Planitia region where the orbiting, ground-penetrating radar detected subsurface deposits rich in water ice. The instrument on NASA's Mars Reconnaissance Orbiter emits radio waves and times their echo off of radio-reflective surfaces and interfaces on Mars. The white arrows indicate a subsurface reflector interpreted as the bottom of the ice-rich deposit. The deposit is about as large in area as the state of New Mexico and contains about as much water as Lake Superior. The horizontal scale bar indicates 40 kilometers (25 miles) along the ground track of the radar, as flown by the orbiter overhead. The vertical scale bar indicates a return time of one microsecond for the reflected radio signal, equivalent to a distance of about 90 meters (295 feet). http://photojournal.jpl.nasa.gov/catalog/PIA21137

Design of CO2 dispersion interferometer based on the ratio of modulation amplitudes on EAST

NASA Astrophysics Data System (ADS)

Li, W. M.; Liu, H. Q.; Yang, Y.; Zeng, L.; Yao, Y.; Zou, Z. Y.; Wei, X. C.; Jie, Y. X.

2018-02-01

A dispersion interferometer (DI) system is one of the more promising density measurement methods for large, high density fusion devices as they have considerable immunity to mechanical vibration and a shorter wavelength which helps to prevent fringe jump errors. In this paper, a DI system with a photoelastic modulator (PEM) has been designed for high density measurements on the EAST tokamak with vertical double pass optical layout. The bench test of all system components was done, especially for the specific nonlinear crystal for DI system. The second hamonic power with the AgGaSe2 nonlinear crystal can reach to 22.85 μW at 20 W fundamental power of CO2 laser. The second-harmonic power based on the AgGaSe2 show a good linear relationship with the various power of the CO2 laser. Based on the bench test results, the new DI system design will be realized and utilized on EAST.

Universal sensitivity of speckle intensity correlations to wavefront change in light diffusers

PubMed Central

Kim, KyungDuk; Yu, Hyeonseung; Lee, KyeoReh; Park, YongKeun

2017-01-01

Here, we present a concept based on the realization that a complex medium can be used as a simple interferometer. Changes in the wavefront of an incident coherent beam can be retrieved by analyzing changes in speckle patterns when the beam passes through a light diffuser. We demonstrate that the spatial intensity correlations of the speckle patterns are independent of the light diffusers, and are solely determined by the phase changes of an incident beam. With numerical simulations using the random matrix theory, and an experimental pressure-driven wavefront-deforming setup using a microfluidic channel, we theoretically and experimentally confirm the universal sensitivity of speckle intensity correlations, which is attributed to the conservation of optical field correlation despite multiple light scattering. This work demonstrates that a light diffuser works as a simple interferometer, and presents opportunities to retrieve phase information of optical fields with a compact scattering layer in various applications in metrology, analytical chemistry, and biomedicine. PMID:28322268

Parameter estimation by decoherence in the double-slit experiment

NASA Astrophysics Data System (ADS)

Matsumura, Akira; Ikeda, Taishi; Kukita, Shingo

2018-06-01

We discuss a parameter estimation problem using quantum decoherence in the double-slit interferometer. We consider a particle coupled to a massive scalar field after the particle passing through the double slit and solve the dynamics non-perturbatively for the coupling by the WKB approximation. This allows us to analyze the estimation problem which cannot be treated by master equation used in the research of quantum probe. In this model, the scalar field reduces the interference fringes of the particle and the fringe pattern depends on the field mass and coupling. To evaluate the contrast and the estimation precision obtained from the pattern, we introduce the interferometric visibility and the Fisher information matrix of the field mass and coupling. For the fringe pattern observed on the distant screen, we derive a simple relation between the visibility and the Fisher matrix. Also, focusing on the estimation precision of the mass, we find that the Fisher information characterizes the wave-particle duality in the double-slit interferometer.

A High-Quality Mach-Zehnder Interferometer Fiber Sensor by Femtosecond Laser One-Step Processing

PubMed Central

Zhao, Longjiang; Jiang, Lan; Wang, Sumei; Xiao, Hai; Lu, Yongfeng; Tsai, Hai-Lung

2011-01-01

During new fiber sensor development experiments, an easy-to-fabricate simple sensing structure with a trench and partially ablated fiber core is fabricated by using an 800 nm 35 fs 1 kHz laser. It is demonstrated that the structure forms a Mach-Zehnder interferometer (MZI) with the interference between the laser light passing through the air in the trench cavity and that in the remained fiber core. The fringe visibilities are all more than 25 dB. The transmission spectra vary with the femtosecond (fs) laser ablation scanning cycle. The free spectral range (FSR) decreases as the trench length increases. The MZI structure is of very high fabrication and sensing repeatability. The sensing mechanism is theoretically discussed, which is in agreement with experiments. The test sensitivity for acetone vapor is about 104 nm/RIU, and the temperature sensitivity is 51.5 pm/°C at 200 ∼ 875 °C with a step of 25 °C. PMID:22346567

The advanced LIGO input optics

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

Mueller, Chris L., E-mail: cmueller@phys.ufl.edu; Arain, Muzammil A.; Ciani, Giacomo

The advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics subsystem is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions requiredmore » every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article, we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design.« less

Measurement of ultrasonic fields in transparent media using a scanning differential interferometer

NASA Technical Reports Server (NTRS)

Dockery, G. D.; Claus, R. O.

1983-01-01

An experimental system for the detection of three dimensional acoustic fields in optically transparent media using a dual beam differential interferometer is described. In this system, two coherent, parallel, focused laser beams are passed through the specimen and the interference fringe pattern which results when these beams are combined shifts linearly by an amount which is related to the optical pathlength difference between the two beams. It is shown that for small signals, the detector output is directly proportional to the amplitude of the acoustic field integrated along the optical beam path through the specimen. A water tank and motorized optical platform were constructed to allow these dual beams to be scanned through an ultrasonic field generated by a piezoelectric transducer at various distances from the transducer. Scan data for the near, Fresnel, and far zones of a uniform, circular transducer are presented and an algorithm for constructing the radial field profile from this integrated optical data, assuming cylindrical symmetry, is described.

Elongated Asteroid Will Safely Pass Earth on Christmas Eve

NASA Image and Video Library

2015-12-23

The elongated asteroid in this radar image, named 2003 SD220, will safely fly past Earth on Thursday, Dec. 24, 2015, at a distance of 6.8 million miles (11 million kilometers). The image was taken on Dec. 22 by scientists using NASA's 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, when the asteroid was approaching its flyby distance. This asteroid is at least 3,600 feet (1,100 meters) long. In 2018, it will safely pass Earth at a distance of 1.8 million miles (2.8 million kilometers). http://photojournal.jpl.nasa.gov/catalog/PIA20280

Multichannel, Active Low-Pass Filters

NASA Technical Reports Server (NTRS)

Lev, James J.

1989-01-01

Multichannel integrated circuits cascaded to obtain matched characteristics. Gain and phase characteristics of channels of multichannel, multistage, active, low-pass filter matched by making filter of cascaded multichannel integrated-circuit operational amplifiers. Concept takes advantage of inherent equality of electrical characteristics of nominally-identical circuit elements made on same integrated-circuit chip. Characteristics of channels vary identically with changes in temperature. If additional matched channels needed, chips containing more than two operational amplifiers apiece (e.g., commercial quad operational amplifliers) used. Concept applicable to variety of equipment requiring matched gain and phase in multiple channels - radar, test instruments, communication circuits, and equipment for electronic countermeasures.

Ultrabright, narrow-band photon-pair source for atomic quantum memories

NASA Astrophysics Data System (ADS)

Tsai, Pin-Ju; Chen, Ying-Cheng

2018-06-01

We demonstrate an ultrabright, narrow-band and frequency-tunable photon-pair source based on cavity-enhanced spontaneous parametric down conversion (SPDC) which is compatible with atomic transition of rubidium D 2-line (780 nm) or cesium D 2-line (852 nm). With the pump beam alternating between a high and a low power phase, the output is switching between the optical parametric oscillator (OPO) and photon-pair generation mode. We utilize the OPO output light to lock the cavity length to maintain the double resonances of signal and idler, as well as to lock the signal frequency to cesium atomic transition. With a type-II phase matching and a double-passed pump scheme such that the cluster frequency spacing is larger than the SPDC bandwidth, the photon-pair output is in a nearly single-mode operation as confirmed by a scanning Fabry–Perot interferometer with its output detected by a photomultiplier. The achieved generation and detection rates are 7.24× {10}5 and 6142 s‑1 mW‑1, respectively. The correlation time of the photon pair is 21.6(2.2) ns, corresponding to a bandwidth of 2π × 6.6(6) MHz. The spectral brightness is 1.06× {10}5 s‑1 mW‑1 MHz‑1. This is a relatively high value under a single-mode operation with the cavity-SPDC scheme. The generated single photons can be readily used in experiments related to atomic quantum memories.

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

Alekseev, A E; Potapov, V T; Gorshkov, B G

We report the results of studying statistical properties of the intensity of partially polarised coherent light backscattered by a single mode optical fibre. An expression is derived for the deviation of the backscattered light intensity depending on the scattering region length, the degree of the light source coherence and the degree of scattered light polarisation. It is shown that the backscattered light in a fibre scattered-light interferometer is partially polarised with the polarisation degree P = 1/3 in the case of external perturbations of the interferometer fibre. (scattering of light)

Continuously active interferometer stabilization and control for time-bin entanglement distribution

DOE PAGES

Toliver, Paul; Dailey, James M.; Agarwal, Anjali; ...

2015-02-10

In this study, we describe a new method enabling continuous stabilization and fine-level phase control of time-bin entanglement interferometers. Using this technique we demonstrate entangled photon transmission through 50 km of standard single-mode fiber. This technique reuses the entangled-pair generation pump which is co-propagated with the transmitted entangled photons. In addition, the co-propagating pump adds minimal noise to the entangled photons which are characterized by measuring a two-photon interference fringe.

Removing left-right asymmetry in a Sagnac interferometer applied to cancel its reflectance dependence on birefringence.

PubMed

Golub, Ilya; Exir, Hourieh

2013-05-01

We present a left-right symmetry restoring method, which removes the detrimental birefringence in the single-mode fiber Sagnac interferometer, achieved with the aid of a half waveplate oriented at a specific angle. We show theoretically and demonstrate experimentally that adding a π-shift between clockwise and counterclockwise propagating, horizontally (in fiber loop plane) polarized field components, the Sagnac loop mirror's reflection becomes independent on birefringence of an element placed in the loop.

Terrestrial Planet Finder Interferometer Technology Status and Plans

NASA Technical Reports Server (NTRS)

Lawson, Perter R.; Ahmed, A.; Gappinger, R. O.; Ksendzov, A.; Lay, O. P.; Martin, S. R.; Peters, R. D.; Scharf, D. P.; Wallace, J. K.; Ware, B.

2006-01-01

A viewgraph presentation on the technology status and plans for Terrestrial Planet Finder Interferometer is shown. The topics include: 1) The Navigator Program; 2) TPF-I Project Overview; 3) Project Organization; 4) Technology Plan for TPF-I; 5) TPF-I Testbeds; 6) Nulling Error Budget; 7) Nulling Testbeds; 8) Nulling Requirements; 9) Achromatic Nulling Testbed; 10) Single Mode Spatial Filter Technology; 11) Adaptive Nuller Testbed; 12) TPF-I: Planet Detection Testbed (PDT); 13) Planet Detection Testbed Phase Modulation Experiment; and 14) Formation Control Testbed.

Robust interferometric frequency lock between cw lasers and optical frequency combs.

PubMed

Benkler, Erik; Rohde, Felix; Telle, Harald R

2013-02-15

A transfer interferometer is presented which establishes a versatile and robust optical frequency locking link between a tunable single frequency laser and an optical frequency comb. It enables agile and continuous tuning of the frequency difference between both lasers while fluctuations and drift effects of the transfer interferometer itself are widely eliminated via common mode rejection. Experimental results will be presented for a tunable extended-cavity 1.5 μm laser diode locked to an Er-fiber based frequency comb.

Parallel Wavefront Analysis for a 4D Interferometer

NASA Technical Reports Server (NTRS)

Rao, Shanti R.

2011-01-01

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.

Use of Borehole-Radar Methods to Monitor a Steam-Enhanced Remediation Pilot Study at a Quarry at the Former Loring Air Force Base, Maine

USGS Publications Warehouse

Gregoire, Colette; Joesten, Peter K.; Lane, John W.

2007-01-01

Single-hole radar reflection and crosshole radar tomography surveys were used in conjunction with conventional borehole-geophysical methods to evaluate the effectiveness of borehole-radar methods for monitoring the movement of steam and heat through fractured bedrock. The U.S. Geological Survey, in cooperation with U.S. Environmental Protection Agency (USEPA), conducted surveys in an abandoned limestone quarry at the former Loring Air Force Base during a field-scale, steam-enhanced remediation (SER) pilot project conducted by the USEPA, the U.S. Air Force, and the Maine Department of Environmental Protection to study the viability of SER to remediate non-aqueous phase liquid contamination in fractured bedrock. Numerical modeling and field experiments indicate that borehole-radar methods have the potential to monitor the presence of steam and to measure large temperature changes in the limestone matrix during SER operations. Based on modeling results, the replacement of water by steam in fractures should produce a decrease in radar reflectivity (amplitude of the reflected wave) by a factor of 10 and a change in reflection polarity. In addition, heating the limestone matrix should increase the bulk electrical conductivity and decrease the bulk dielectric permittivity. These changes result in an increase in radar attenuation and an increase in radar-wave propagation velocity, respectively. Single-hole radar reflection and crosshole radar tomography data were collected in two boreholes using 100-megahertz antennas before the start of steam injection, about 10 days after the steam injection began, and 2 months later, near the end of the injection. Fluid temperature logs show that the temperature of the fluid in the boreholes increased by 10?C (degrees Celsius) in one borehole and 40?C in the other; maximum temperatures were measured near the bottom of the boreholes. The results of the numerical modeling were used to interpret the borehole-radar data. Analyses of the single-hole radar reflection data showed almost no indication that steam replaced water in fractures near the boreholes because (1) no change of polarity was observed in the radar reflections; (2) variations in the measured traveltimes were unsubstantial; and (3) most of the observed decreases in reflectivity were too small to have resulted from the replacement of water by steam. Analyses of the crosshole radar tomography data also support the conclusion that steam did not replace water in the fractures around the boreholes because traveltime-difference and attenuation-difference tomograms showed only small decreases in velocity and small increases in attenuation accompanying the steam injection. The radar data are consistent with an increase in the conductivity of the limestone as a result of heating of the limestone matrix near the boreholes. Single-hole radar reflection data collected near the end of the steam injection near the bottom of the borehole with the largest temperature increase showed substantial attenuation. Also, reflector analysis showed small decreases in the amplitudes of radar-wave reflections in data collected before injection and data collected near the end of the collection period. In the crosshole radar tomography data, decreases in velocity and small increases in attenuation also are consistent with temperature increases in the matrix.

Electro-optic routing of photons from a single quantum dot in photonic integrated circuits

NASA Astrophysics Data System (ADS)

Midolo, Leonardo; Hansen, Sofie L.; Zhang, Weili; Papon, Camille; Schott, Rüdiger; Ludwig, Arne; Wieck, Andreas D.; Lodahl, Peter; Stobbe, Søren

2017-12-01

Recent breakthroughs in solid-state photonic quantum technologies enable generating and detecting single photons with near-unity efficiency as required for a range of photonic quantum technologies. The lack of methods to simultaneously generate and control photons within the same chip, however, has formed a main obstacle to achieving efficient multi-qubit gates and to harness the advantages of chip-scale quantum photonics. Here we propose and demonstrate an integrated voltage-controlled phase shifter based on the electro-optic effect in suspended photonic waveguides with embedded quantum emitters. The phase control allows building a compact Mach-Zehnder interferometer with two orthogonal arms, taking advantage of the anisotropic electro-optic response in gallium arsenide. Photons emitted by single self-assembled quantum dots can be actively routed into the two outputs of the interferometer. These results, together with the observed sub-microsecond response time, constitute a significant step towards chip-scale single-photon-source de-multiplexing, fiber-loop boson sampling, and linear optical quantum computing.

Integrated Optics Achromatic Nuller for Stellar Interferometry

NASA Technical Reports Server (NTRS)

Ksendzov, Alexander

2012-01-01

This innovation will replace a beam combiner, a phase shifter, and a mode conditioner, thus simplifying the system design and alignment, and saving weight and space in future missions. This nuller is a dielectric-waveguide-based, four-port asymmetric coupler. Its nulling performance is based on the mode-sorting property of adiabatic asymmetric couplers that are intrinsically achromatic. This nuller has been designed, and its performance modeled, in the 6.5-micrometer to 9.25-micrometer spectral interval (36% bandwidth). The calculated suppression of starlight for this 15-cm-long device is 10(exp -5) or better through the whole bandwidth. This is enough to satisfy requirements of a flagship exoplanet-characterization mission. Nulling interferometry is an approach to starlight suppression that will allow the detection and spectral characterization of Earth-like exoplanets. Nulling interferometers separate the light originating from a dim planet from the bright starlight by placing the star at the bottom of a deep, destructive interference fringe, where the starlight is effectively cancelled, or nulled, thus allowing the faint off-axis light to be much more easily seen. This process is referred to as nulling of the starlight. Achromatic nulling technology is a critical component that provides the starlight suppression in interferometer-based observatories. Previously considered space-based interferometers are aimed at approximately 6-to-20-micrometer spectral range. While containing the spectral features of many gases that are considered to be signatures of life, it also offers better planet-to-star brightness ratio than shorter wavelengths. In the Integrated Optics Achromatic Nuller (IOAN) device, the two beams from the interferometer's collecting telescopes pass through the same focusing optic and are incident on the input of the nuller.

Techniques in Broadband Interferometry

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

Erskine, D J

2004-01-04

This is a compilation of my patents issued from 1997 to 2002, generally describing interferometer techniques that modify the coherence properties of broad-bandwidth light and other waves, with applications to Doppler velocimetry, range finding, imaging and spectroscopy. Patents are tedious to read in their original form. In an effort to improve their readability I have embedded the Figures throughout the manuscript, put the Figure captions underneath the Figures, and added section headings. Otherwise I have resisted the temptation to modify the words, though I found many places which could use healthy editing. There may be minor differences with the officialmore » versions issued by the US Patent and Trademark Office, particularly in the claims sections. In my shock physics work I measured the velocities of targets impacted by flyer plates by illuminating them with laser light and analyzing the reflected light with an interferometer. Small wavelength changes caused by the target motion (Doppler effect) were converted into fringe shifts by the interferometer. Lasers having long coherence lengths were required for the illumination. While lasers are certainly bright sources, and their collimated beams are convenient to work with, they are expensive. Particularly if one needs to illuminate a wide surface area, then large amounts of power are needed. Orders of magnitude more power per dollar can be obtained from a simple flashlamp, or for that matter, a 50 cent light bulb. Yet these inexpensive sources cannot practically be used for Doppler velocimetry because their coherence length is extremely short, i.e. their bandwidth is much too wide. Hence the motivation for patents 1 & 2 is a method (White Light Velocimetry) for allowing use of these powerful but incoherent lamps for interferometry. The coherence of the illumination is modified by passing it through a preparatory interferometer.« less

UAVSAR Phased Array Aperture

NASA Technical Reports Server (NTRS)

Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

2009-01-01

This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

Reconfigurable L-Band Radar

NASA Technical Reports Server (NTRS)

Rincon, Rafael F.

2008-01-01

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

Japan contribution to studies of low-latitude and equatorial ionosphere over Southeast Asia

NASA Astrophysics Data System (ADS)

Yamamoto, M.; Ishii, M.; Otsuka, Y.; Shiokawa, K.; Saito, A.; Tsuda, T.; Fukao, S.

2008-12-01

A dense observation network to study ionosphere is deployed over Southeast Asian countries of Indonesia, Thailand, and Vietnam. The Equatorial Atmosphere Radar (EAR) at Kototabang, Indonesia is the center facility, and supporting instruments, i.e., an ionosonde, a VHF ionosphere radar, an optical imager, a GPS scintillation receiver, a magnetometer, a meteor radar, etc. are collocated. NICT operates the ionosonde network SEALION (South East Asian Low-latitude IOnosonde Network) that meridionally extends from the EAR site to Chumphong and Chiang Mai in Thailand, and two more sites (Baq Liu and Phy Thuy) in Vietnam. Additional facilities are an MF radar at Pameungpeuk, Indonesia, and an optical imager at Darwin, Australia. We have been observing plasma bubbles since 2001, that, for example, contributed clarification of time- spatial structures of the phenomena, their relationship to the pre-reversal enhancement, control of bubble occurrence by the meridional winds, etc. We are starting studies of their seeding by means of atmospheric waves that propages from the lower atmosphere, too. In 2008, Nagoya University will soon install three Fabry-Perot interferometers at the EAR site, Chiang Mai, and Darwin. We also have a plan to install digital beacon receivers in some of these sites. Next research program that follows CPEA (Coupling Processes in the Equatorial Atmosphere, 2001-2007) is under planning now. Our main facilities cover ± 10° of geomagnetic latitude, where the magnetic declination is relatively small, and the geomagnetic equator is in the geographic northern hemisphere. We will review our achievements, and show on-going efforts and future plans. Collaboration with the C/NOFS satellite, and comparisons to results from the American sector should be beneficial for global-scale understanding of the equatorial ionosphere/atmosphere.

NASA Tech Briefs, July 2007

NASA Technical Reports Server (NTRS)

2007-01-01

Topics covered include: Miniature Intelligent Sensor Module; "Smart" Sensor Module; Portable Apparatus for Electrochemical Sensing of Ethylene; Increasing Linear Dynamic Range of a CMOS Image Sensor; Flight Qualified Micro Sun Sensor; Norbornene-Based Polymer Electrolytes for Lithium Cells; Making Single-Source Precursors of Ternary Semiconductors; Water-Free Proton-Conducting Membranes for Fuel Cells; Mo/Ti Diffusion Bonding for Making Thermoelectric Devices; Photodetectors on Coronagraph Mask for Pointing Control; High-Energy-Density, Low-Temperature Li/CFx Primary Cells; G4-FETs as Universal and Programmable Logic Gates; Fabrication of Buried Nanochannels From Nanowire Patterns; Diamond Smoothing Tools; Infrared Imaging System for Studying Brain Function; Rarefying Spectra of Whispering-Gallery-Mode Resonators; Large-Area Permanent-Magnet ECR Plasma Source; Slot-Antenna/Permanent-Magnet Device for Generating Plasma; Fiber-Optic Strain Gauge With High Resolution And Update Rate; Broadband Achromatic Telecentric Lens; Temperature-Corrected Model of Turbulence in Hot Jet Flows; Enhanced Elliptic Grid Generation; Automated Knowledge Discovery From Simulators; Electro-Optical Modulator Bias Control Using Bipolar Pulses; Generative Representations for Automated Design of Robots; Mars-Approach Navigation Using In Situ Orbiters; Efficient Optimization of Low-Thrust Spacecraft Trajectories; Cylindrical Asymmetrical Capacitors for Use in Outer Space; Protecting Against Faults in JPL Spacecraft; Algorithm Optimally Allocates Actuation of a Spacecraft; and Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets.

Multibeam synthetic aperture radar for global oceanography

NASA Technical Reports Server (NTRS)

Jain, A.

1979-01-01

A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

Gildas and Class

NASA Astrophysics Data System (ADS)

Pety, Jérôme

2018-03-01

GILDAS is a collection of state-of-the-art software oriented toward (sub-)millimeter radioastronomical applications (either single-dish or interferometer). It is also used for APEX heterodyne data reduction.

Spectrally controlled interferometry for measurements of flat and spherical optics

NASA Astrophysics Data System (ADS)

Salsbury, Chase; Olszak, Artur G.

2017-10-01

Conventional interferometry is widely used to measure spherical and at surfaces with nanometer level precision but is plagued by back reflections. We describe a new method of isolating the measurement surface by controlling spectral properties of the source (Spectrally Controlled Interferometry - SCI). Using spectral modulation of the interferometer's source enables formation of localized fringes where the optical path difference is non-zero. As a consequence it becomes possible to form white-light like fringes in common path interferometers, such as the Fizeau. The proposed setup does not require mechanical phase shifting, resulting in simpler instruments and the ability to upgrade existing interferometers. Furthermore, it allows absolute measurement of distance, including radius of curvature of lenses in a single setup with possibility of improving the throughput and removing some modes of failure.

Dual-optical-response photonic crystal fibre interferometer for multi-parameter sensing

NASA Astrophysics Data System (ADS)

Villatoro, Joel; Minkovich, Vladimir P.; Zubia, Joseba

2014-05-01

An all-fiber mode interferometer consisting of a short segment of photonic crystal fiber (PCF) fusion spliced to standard single mode optical fiber and pressed on localized regions is proposed for multi-parameter sensing. In our configuration, the physical parameter being sensed changes the fringe contrast (or visibility) of the interference pattern and also causes a shift to the same. To achieve this dual effect the device is pressed on localized regions over a few millimeters. In this manner we introduce losses and effective refractive index changes to the interference modes, hence visibility and shift to the interference pattern. Our interferometer is suitable for monitoring diverse physical parameters such as weight, force, pressure, load, etc. The advantage is that no temperature or power fluctuations compensation is required.

Discrimination of chemical vapor and temperature using an in-line modal interferometer based on an exterior hole-assisted polarization-maintaining photonic crystal fiber

NASA Astrophysics Data System (ADS)

Yoon, Min-Seok; Jun, Naram; Lee, Sang Bae; Han, Young-Geun

2014-05-01

A reflective in-line modal interferometer based on a polarization-maintaining photonic crystal fiber (PM-PCF) with two exterior air holes is proposed for simultaneous measurement of chemical vapor and temperature. After fusion-splicing the PM-PCF with a standard single-mode fiber, we collapse all of air holes in the PM-PCF resulting in two types of interference patterns between the core and the cladding modes in the PM-PCF depending on two polarization states. Since two large air holes at the facet of the proposed modal interferometer are left open, a chemical vapor can be infiltrated into the voids. Different sensitivities corresponding to input polarization states are utilized for discrimination between chemical vapor and temperature sensitivities.

Analysis of X-band radar images for the detection of the reflected and diffracted waves in coastal zones

NASA Astrophysics Data System (ADS)

Ludeno, Giovanni; Natale, Antonio; Soldovieri, Francesco; Vicinanza, Diego; Serafino, Francesco

2014-05-01

The observation of nearshore waves and the knowledge of the sea state parameters can play a crucial role for the safety of harbors and ocean engineering. In the last two decades, different algorithms for the estimation of sea state parameters, surface currents and bathymetry from X-band radar data have been developed and validated [1, 2]. The retrieval of ocean wave parameters such as significant height, period, direction and wavelength of the dominant wave is based on the spectral analysis of data sequences collected by nautical X-band radars [3]. In particular, the reconstruction of the wave motion is carried out through the inversion procedure explained in [1-3], which exploits the dispersion relationship to define a band pass filter used to separate the energy associated with the ocean waves from the background noise. It is worth to note that the shape of such a band pass filter depends upon the value of both the surface currents and bathymetry; in our reconstruction algorithm these parameters are estimated through the (Normalized Scalar Product) procedure [1], which outperforms other existing methods (e.g., the Least Squares) [4]. From the reconstructed wave elevation sequences we can get the directional spectrum that provides useful information (i.e., wavelength, period, direction and amplitude) relevant to the main waves contributing to the wave motion. Of course, in coastal zones a number of diffraction and reflection phenomena can be observed, due to sea-waves impinging obstacles as jetties, breakwaters and boats. In the present paper we want to show the capability to detect reflected and diffracted sea-waves offered by the processing of X-band radar data. Further details relevant to the obtained results will be provided in the full paper and at the conference time. References [1] F. Serafino, C. Lugni, F. Soldovieri, "A novel strategy for the surface current determination from marine X-Band radar data", IEEE Geosci. and Remote Sensing Letters, vol. 7, no.2, pp. 231-235, April 2010. [2] Senet, C. M., Seemann, J., Flampouris, S., and Ziemer, F. (2008). Determination of bathymetric and current maps by the method DiSC based on the analysis of nautical X-Band radar image sequences of the sea surface (November 2007). IEEE Trans. on Geoscience and Remote Sensing, 46(8), 2267-2279. [3] F. Ziemer, and W. Rosenthal, "Directional spectra from shipboard navigation radar during LEWEX". Directional Ocean Wave Spectra: Measuring, Modeling, Predicting, and Applying, 1991 R. C. Beal, Ed., The Johns Hopkins University Press, pp. 125-127. [4] Weimin Huang ; Gill, E.," Surface Current Measurement Under Low Sea State Using Dual Polarized X-Band Nautical Radar", Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of, vol. 5, no.6, page 186-1873, 2012.

Arcsecond and Sub-arcsedond Imaging with X-ray Multi-Image Interferometer and Imager for (very) small sattelites

NASA Astrophysics Data System (ADS)

Hayashida, K.; Kawabata, T.; Nakajima, H.; Inoue, S.; Tsunemi, H.

2017-10-01

The best angular resolution of 0.5 arcsec is realized with the X-ray mirror onborad the Chandra satellite. Nevertheless, further better or comparable resolution is anticipated to be difficult in near future. In fact, the goal of ATHENA telescope is 5 arcsec in the angular resolution. We propose a new type of X-ray interferometer consisting simply of an X-ray absorption grating and an X-ray spectral imaging detector, such as X-ray CCDs or new generation CMOS detectors, by stacking the multi images created with the Talbot interferenece (Hayashida et al. 2016). This system, now we call Multi Image X-ray Interferometer Module (MIXIM) enables arcseconds resolution with very small satellites of 50cm size, and sub-arcseconds resolution with small sattellites. We have performed ground experiments, in which a micro-focus X-ray source, grating with pitch of 4.8μm, and 30 μm pixel detector placed about 1m from the source. We obtained the self-image (interferometirc fringe) of the grating for wide band pass around 10keV. This result corresponds to about 2 arcsec resolution for parrallel beam incidence. The MIXIM is usefull for high angular resolution imaging of relatively bright sources. Search for super massive black holes and resolving AGN torus would be the targets of this system.

Inferring drivers of California's Big Sur Landslide from precursory slope deformations measured with spaceborne radar interferometry.

NASA Astrophysics Data System (ADS)

Jacquemart, M. F.; Barba, M.; Tiampo, K. F.; Willis, M. J.

2017-12-01

Hours before the landslide that came to be known as the Big Sur slide destroyed a stretch of Highway 1 in southern California, the European Space Agency's Sentinel-1B satellite passed over the area and acquired the last radar images of the still intact slope. Shortly thereafter, an estimated 1 million tons of soil and debris plunged into the Pacific Ocean, enlarging California's land area by roughly 13 acres. Results from differential interferometric synthetic aperture radar (DInSAR) produced from the most recent Sentinel images show a clear signal of the impending landslide, measured prior to the slope failure. In fact, an entire time-series of precursory slope displacements emerges from the radar data that extend back several months. Over southern California, the Sentinel-1A and 1B satellites acquire images every 6 or 12 days, providing a unique dataset that allows us to investigate the physical processes that drive the displacement leading up to the final failure. Here we explore the role of pore water pressure and rainfall as drivers of slope motion and we investigate whether precursory displacement can provide indication about the timing of the detachment. We also analyze the influence of DEM and interferogram resolution on the displacement results and evaluate the suitability of radar interferometry for landslide monitoring.

Method and apparatus for Doppler frequency modulation of radiation

NASA Technical Reports Server (NTRS)

Margolis, J. S.; Mccleese, D. J.; Shumate, M. S.; Seaman, C. H. (Inventor)

1980-01-01

A method and apparatus are described for frequency modulating radiation, such as from a laser, for optoacoustic detectors, interferometers, heterodyne spectrometers, and similar devices. Two oppositely reciprocating cats-eye retroreflectors are used to Doppler modulate the radiation. By reciprocally moving both retroreflectors, the center of mass is maintained constant to permit smooth operation at many Hertz. By slightly offsetting the axis of one retroreflector relative to the other, multiple passes of a light beam may be achieved for greater Doppler shifts with the same reciprocating motion of the retroreflectors.

On a two-pass scheme without a faraday mirror for free-space relativistic quantum cryptography

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

Kravtsov, K. S.; Radchenko, I. V.; Korol'kov, A. V.

2013-05-15

The stability of destructive interference independent of the input polarization and the state of a quantum communication channel in fiber optic systems used in quantum cryptography plays a principal role in providing the security of communicated keys. A novel optical scheme is proposed that can be used both in relativistic quantum cryptography for communicating keys in open space and for communicating them over fiber optic lines. The scheme ensures stability of destructive interference and admits simple automatic balancing of a fiber interferometer.

Which role does multiphoton interference play in small phase estimation in quantum Fourier transform interferometers?

NASA Astrophysics Data System (ADS)

Zimmermann, Olaf; Tamma, Vincenzo

Recently, quantum Fourier transform interferometers have been demonstrated to allow a quantum metrological enhancement in phase sensitivity for a small number n of identical input single photons [J. P. Olson, K. R. Motes, P. M. Birchall, N. M. Studer, M. LaBorde, T. Moulder, P. P. Rohde and J. P. Dowling, Phys. Rev. A 96 (2017) 013810; K. R. Motes, J. P. Olson, E. J. Rabeaux, J. P. Dowling, S. J. Olson and P. P. Rohde, Phys. Rev. Lett. 114 (2015) 170802; O. Zimmermann, Bachelor Thesis (Ulm University, 2015) arXiv: 1710.03805.]. However, multiphoton distinguishability at the detectors can play an important role from an experimental point of view [V. Tamma and S. Laibacher, Phys. Rev. Lett. 114 (2015) 243601.]. This raises a fundamental question: How is the phase sensitivity affected when the photons are completely distinguishable at the detectors and therefore do not interfere? In other words, which role does multiphoton interference play in these schemes? Here, we show that for small phase values, the phase sensitivity achievable in the proposed schemes with indistinguishable photons is enhanced only by a constant factor with respect to the case of completely distinguishable photons at the detectors. Interestingly, this enhancement arises from the interference of only a polynomial number (in n) of the total n! multiphoton path amplitudes in the n-port interferometer. These results are independent of the number n of single photons and of the phase weight factors employed at each interferometer channel.

Assessing the efficacy of single-pass backpack electrofishing to characterize fish community structure

USGS Publications Warehouse

Meador, M.R.; McIntyre, J.P.; Pollock, K.H.

2003-01-01

Two-pass backpack electrofishing data collected as part of the U.S. Geological Survey's National Water-Quality Assessment Program were analyzed to assess the efficacy of single-pass backpack electrofishing. A two-capture removal model was used to estimate, within 10 river basins across the United States, proportional fish species richness from one-pass electrofishing and probabilities of detection for individual fish species. Mean estimated species richness from first-pass sampling (ps1) ranged from 80.7% to 100% of estimated total species richness for each river basin, based on at least seven samples per basin. However, ps1 values for individual sites ranged from 40% to 100% of estimated total species richness. Additional species unique to the second pass were collected in 50.3% of the samples. Of these, cyprinids and centrarchids were collected most frequently. Proportional fish species richness estimated for the first pass increased significantly with decreasing stream width for 1 of the 10 river basins. When used to calculate probabilities of detection of individual fish species, the removal model failed 48% of the time because the number of individuals of a species was greater in the second pass than in the first pass. Single-pass backpack electrofishing data alone may make it difficult to determine whether characterized fish community structure data are real or spurious. The two-pass removal model can be used to assess the effectiveness of sampling species richness with a single electrofishing pass. However, the two-pass removal model may have limited utility to determine probabilities of detection of individual species and, thus, limit the ability to assess the effectiveness of single-pass sampling to characterize species relative abundances. Multiple-pass (at least three passes) backpack electrofishing at a large number of sites may not be cost-effective as part of a standardized sampling protocol for large-geographic-scale studies. However, multiple-pass electrofishing at some sites may be necessary to better evaluate the adequacy of single-pass electrofishing and to help make meaningful interpretations of fish community structure.

Perspective View with Landsat Overlay, Palm Springs, Calif.

NASA Technical Reports Server (NTRS)

2002-01-01

The city of Palm Springs nestles at the base of Mount San Jacinto in this computer-generated perspective viewed from the east. The many golf courses in the area show up as irregular green areas while the two prominent lines passing through the middle of the image are Interstate 10 and the adjacent railroad tracks. The San Andreas Fault passes through the middle of the sandy Indio Hills in the foreground.

This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise,Washington, D.C.

Size: scale varies in this perspective image Location: 33.8 deg. North lat., 116.3 deg. West lon. Orientation: looking west Image Data: Landsat Bands 3, 2, 1 as red, green, blue, respectively Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Thematic Mapper 1 arcsecond (30 meters or 98 feet) Date Acquired: February 2000 (SRTM)

LSPECS: A Proposed Robotic Astronomy Mission to the Lunar South Polar Regions

NASA Technical Reports Server (NTRS)

Lowman, Paul D., Jr.

2003-01-01

This paper outlines a possible mission to emplace a robotic infrared/submillimeter wave interferometer array near the lunar south pole. This region has now been investigated by the Clementine and Lunar Prospector missions, and by Earth-based radar, and its topography and thermal environment are fairly well-known. The area would be exceptionally suitable for infrared/submillimeter astronomy because of the continually low temperatures, approaching that of liquid nitrogen (77K) in some places. The presence of ice has been inferred independently from Clementine and Lunar Prospector, providing another incentive for a south polar mission. A submillimeter spaceborne interferometer mission, Submillimeter Probe of the Evolution of the Cosmic Structure (SPECS) has been proposed by John Mather and others, covering the 40 - 500 micron region with 3 formation flying telescopes. The present paper proposes a lunar adaptation of the SPECS concept, LSPECS. This adaptation would involve landing 4 telescopes on the area north of Shackleton crater at zero degrees longitude. This is in nearly year round darkness but is continually radar visible from Earth. The landed payload of LSPECS would include a telerobotic rover, 4 three meter submm telescopes, a solar power array to be emplaced on the continually sunlit north rim of Shackleton crater, and an S-band antenna for data relay to Earth. Operation without the use of expendable cryogenics for cooling might be possible, trading long exposure time for instrument temperatures above that of liquid helium. The LSPECS would permit long-term study of an extremely wide range of cosmic and solar system phenomena in the southern celestial hemisphere. For complete sky coverage, a similar installation near the north pole would be required. The LSPECS site would also be suitable other types of observation, such as optical interferometry or centimeter wavelength radio astronomy. The lunar south pole is also of great interest because of its extensive ice deposits, which may represent cometary infall with pre-biotic compounds.

Investigation on the impact of irregular fringe patterns of a single-fiber Mach-Zehnder interferometer on its sensing capabilities

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Kumar, Ashish

2018-07-01

A novel single-mode single-fiber (SMSF) MZI formed by cascading of two non-adiabatic fiber tapers, with stable and repeatable spectrum, has been found to be useful in sensing applications in recent times. A multimode interference based novel simulation approach is proposed to predict the sensing characteristics of SMSF-MZI and is validated with experimental observation. The proposed method includes solving of simultaneous non-homogenous equations for determining the amplitudes of the interfering modes excited in the tapered section of the interferometer. The simulated fringe pattern and the experimental spectral response converge to some important comprehension reported for the first time. A linear shift in output spectral response, of SMSF-MZI, due to change in optical path length induced by temperature/strain etc., is likely to be characterized by three modes interference occurring in the interference region of the interferometer. Whereas if the spectral shift starts saturating at moderately higher temperature/strain, then the formation of interference fringes are possibly governed by two modes interference. Further, it was also explained that a SMSF-MZI with variable fringe widths in its spectral pattern exhibits higher sensitivity than that of the SMSF-MZI having wavelength spectrum with uniform free spectral range. These findings are useful in selecting and predicting the sensitivity of a given SMSF-MZI, based on its spectrum, for sensing applications.

Time Series of Tropical-Forest Structure from TanDEM-X, Transformed to Time Series of Biomass by MODIS

NASA Astrophysics Data System (ADS)

Treuhaft, R. N.; Baccini, A.; Goncalves, F. G.; Lei, Y.; Keller, M.; Walker, W. S.

2017-12-01

Tropical forests account for about 50% of the world's forested biomass, and play a critical role in the control of atmospheric carbon dioxide. Large-scale (1000's of km) changes in forest structure and biomass bear on global carbon source-sink dynamics, while small-scale (< 100 m) changes bear on deforestation and degradation monitoring. After describing the interferometric SAR (InSAR) phase-height observation, we show forest phase-height time series from the TanDEM-X radar interferometer at X-band (3 cm), taken with monthly and sub-hectare temporal and spatial resolution, respectively. The measurements were taken with more than 30 TanDEM-X passes over Tapajós National Forest in the Brazilian Amazon between 2011 and 2014. The transformation of phase-height rates into aboveground biomass (AGB) rates is based on the idea that the change in AGB due to a change in phase-height depends on the plot's AGB. Plots with higher AGB will produce more AGB for a given increase in height or phase-height. Postulating a power-law dependence of plot-level mass density on physical height, we previously found that the best conversion factors for transforming phase-height rate to AGB rate were indeed dependent on AGB. For 78 plots, we demonstrated AGB rates from InSAR phase-height rates using AGB from field measurements. For regional modeling of the Amazon Basin, field measurements of AGB, to specify the conversion factors, is impractical. Conversion factors from InSAR phase-height rate to AGB rate in this talk will be based on AGB derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). AGB measurement from MODIS is based on the spectral reflectance of 7 bands from the visible to short wave infrared, and auxiliary metrics describing the variance in reflectance. The mapping of MODIS reflectance to AGB is enabled by training a machine learning algorithm with lidar-derived AGB data, which are in turn trained by field measurements for small areas. The performance of TanDEM-X AGB rate from MODIS-derived conversion factors will be compared to that derived from field-based conversion factors. We will also attempt to improve phase-height rate to AGB rate transformation by deriving improved models of mass density dependences on height, based on the aggregation of single-stem allometrics.

The application of digital signal processing techniques to a teleoperator radar system

NASA Technical Reports Server (NTRS)

Pujol, A.

1982-01-01

A digital signal processing system was studied for the determination of the spectral frequency distribution of echo signals from a teleoperator radar system. The system consisted of a sample and hold circuit, an analog to digital converter, a digital filter, and a Fast Fourier Transform. The system is interfaced to a 16 bit microprocessor. The microprocessor is programmed to control the complete digital signal processing. The digital filtering and Fast Fourier Transform functions are implemented by a S2815 digital filter/utility peripheral chip and a S2814A Fast Fourier Transform chip. The S2815 initially simulates a low-pass Butterworth filter with later expansion to complete filter circuit (bandpass and highpass) synthesizing.

Compensation of non-ideal beam splitter polarization distortion effect in Michelson interferometer

NASA Astrophysics Data System (ADS)

Liu, Yeng-Cheng; Lo, Yu-Lung; Liao, Chia-Chi

2016-02-01

A composite optical structure consisting of two quarter-wave plates and a single half-wave plate is proposed for compensating for the polarization distortion induced by a non-ideal beam splitter in a Michelson interferometer. In the proposed approach, the optimal orientations of the optical components within the polarization compensator are determined using a genetic algorithm (GA) such that the beam splitter can be treated as a free-space medium and modeled using a unit Mueller matrix accordingly. Two implementations of the proposed polarization controller are presented. In the first case, the compensator is placed in the output arm of Michelson interferometer such that the state of polarization of the interfered output light is equal to that of the input light. However, in this configuration, the polarization effects induced by the beam splitter in the two arms of the interferometer structure cannot be separately addressed. Consequently, in the second case, compensator structures are placed in the Michelson interferometer for compensation on both the scanning and reference beams. The practical feasibility of the proposed approach is introduced by considering a Mueller polarization-sensitive (PS) optical coherence tomography (OCT) structure with three polarization controllers in the input, reference and sample arms, respectively. In general, the results presented in this study show that the proposed polarization controller provides an effective and experimentally-straightforward means of compensating for the polarization distortion effects induced by the non-ideal beam splitters in Michelson interferometers and Mueller PS-OCT structures.

A Theoretical Study and Numerical Simulation of a Quasi-Distributed Sensor Based on the Low-Finesse Fabry-Perot Interferometer: Frequency-Division Multiplexing

PubMed Central

Guillen Bonilla, José Trinidad; Guillen Bonilla, Alex; Rodríguez Betancourtt, Verónica M.; Guillen Bonilla, Héctor; Casillas Zamora, Antonio

2017-01-01

The application of the sensor optical fibers in the areas of scientific instrumentation and industrial instrumentation is very attractive due to its numerous advantages. In the industry of civil engineering for example, quasi-distributed sensors made with optical fiber are used for reliable strain and temperature measurements. Here, a quasi-distributed sensor in the frequency domain is discussed. The sensor consists of a series of low-finesse Fabry-Perot interferometers where each Fabry-Perot interferometer acts as a local sensor. Fabry-Perot interferometers are formed by pairs of identical low reflective Bragg gratings imprinted in a single mode fiber. All interferometer sensors have different cavity length, provoking frequency-domain multiplexing. The optical signal represents the superposition of all interference patterns which can be decomposed using the Fourier transform. The frequency spectrum was analyzed and sensor’s properties were defined. Following that, a quasi-distributed sensor was numerically simulated. Our sensor simulation considers sensor properties, signal processing, noise system, and instrumentation. The numerical results show the behavior of resolution vs. signal-to-noise ratio. From our results, the Fabry-Perot sensor has high resolution and low resolution. Both resolutions are conceivable because the Fourier Domain Phase Analysis (FDPA) algorithm elaborates two evaluations of Bragg wavelength shift. PMID:28420083

Vibrational dephasing in matter-wave interferometers

NASA Astrophysics Data System (ADS)

Rembold, A.; Schütz, G.; Röpke, R.; Chang, W. T.; Hwang, I. S.; Günther, A.; Stibor, A.

2017-03-01

Matter-wave interferometry is a highly sensitive tool to measure small perturbations in a quantum system. This property allows the creation of precision sensors for dephasing mechanisms such as mechanical vibrations. They are a challenge for phase measurements under perturbing conditions that cannot be perfectly decoupled from the interferometer, e.g. for mobile interferometric devices or vibrations with a broad frequency range. Here, we demonstrate a method based on second-order correlation theory in combination with Fourier analysis, to use an electron interferometer as a sensor that precisely characterizes the mechanical vibration spectrum of the interferometer. Using the high spatial and temporal single-particle resolution of a delay line detector, the data allows to reveal the original contrast and spatial periodicity of the interference pattern from ‘washed-out’ matter-wave interferograms that have been vibrationally disturbed in the frequency region between 100 and 1000 Hz. Other than with electromagnetic dephasing, due to excitations of higher harmonics and additional frequencies induced from the environment, the parts in the setup oscillate with frequencies that can be different to the applied ones. The developed numerical search algorithm is capable to determine those unknown oscillations and corresponding amplitudes. The technique can identify vibrational dephasing and decrease damping and shielding requirements in electron, ion, neutron, atom and molecule interferometers that generate a spatial fringe pattern on the detector plane.

Plasmonic interferometers: From physics to biosensing applications

NASA Astrophysics Data System (ADS)

Zeng, Xie

Optical interferometry has a long history and wide range of applications. In recent years, plasmonic interferometer arouses great interest due to its compact size and enhanced light-matter interaction. They have demonstrated attractive applications in biomolecule sensing, optical modulation/switching, and material characterization, etc. In this work, we first propose a practical far-field method to extract the intrinsic phase dispersion, revealing important phase information during interactions among free-space light, nanostructure, and SPs. The proposed approach is confirmed by both simulation and experiment. Then we design novel plasmonic interferometer structure for sensitive optical sensing applications. To overcome two major limitations suffered by previously reported double-slit plasmonic Mach-Zehnder interferometer (PMZI), two new schemes are proposed and investigated. (1) A PMZI based on end-fire coupling improves the SP coupling efficiency and enhance the interference contrast more than 50 times. (2) In another design, a multi-layered metal-insulator-metal PMZI releases the requirement for single-slit illumination, which enables sensitive, high-throughput sensing applications based on intensity modulation. We develop a sensitive, low-cost and high-throughput biosensing platform based on intensity modulation using ring-hole plasmonic interferometers. This biosensor is then integrated with cell-phone-based microscope, which is promising to develop a portable sensor for point-of-care diagnostics, epidemic disease control and food safety monitoring.

A Theoretical Study and Numerical Simulation of a Quasi-Distributed Sensor Based on the Low-Finesse Fabry-Perot Interferometer: Frequency-Division Multiplexing.

PubMed

Guillen Bonilla, José Trinidad; Guillen Bonilla, Alex; Rodríguez Betancourtt, Verónica M; Guillen Bonilla, Héctor; Casillas Zamora, Antonio

2017-04-14

The application of the sensor optical fibers in the areas of scientific instrumentation and industrial instrumentation is very attractive due to its numerous advantages. In the industry of civil engineering for example, quasi-distributed sensors made with optical fiber are used for reliable strain and temperature measurements. Here, a quasi-distributed sensor in the frequency domain is discussed. The sensor consists of a series of low-finesse Fabry-Perot interferometers where each Fabry-Perot interferometer acts as a local sensor. Fabry-Perot interferometers are formed by pairs of identical low reflective Bragg gratings imprinted in a single mode fiber. All interferometer sensors have different cavity length, provoking frequency-domain multiplexing. The optical signal represents the superposition of all interference patterns which can be decomposed using the Fourier transform. The frequency spectrum was analyzed and sensor's properties were defined. Following that, a quasi-distributed sensor was numerically simulated. Our sensor simulation considers sensor properties, signal processing, noise system, and instrumentation. The numerical results show the behavior of resolution vs. signal-to-noise ratio. From our results, the Fabry-Perot sensor has high resolution and low resolution. Both resolutions are conceivable because the Fourier Domain Phase Analysis (FDPA) algorithm elaborates two evaluations of Bragg wavelength shift.

Optofluidic in-fiber interferometer based on hollow optical fiber with two cores.

PubMed

Yuan, Tingting; Yang, Xinghua; Liu, Zhihai; Yang, Jun; Li, Song; Kong, Depeng; Qi, Xiuxiu; Yu, Wenting; Long, Qunlong; Yuan, Libo

2017-07-24

We demonstrate a novel integrated optical fiber interferometer for in-fiber optofluidic detection. It is composed of a specially designed hollow optical fiber with a micro-channel and two cores. One core on the inner surface of the micro-channel is served as sensing arm and the other core in the annular cladding is served as reference arm. Fusion-and-tapering method is employed to couple light from a single mode fiber to the hollow optical fiber in this device. Sampling is realized by side opening a microhole on the surface of the hollow optical fiber. Under differential pressure between the end of the hollow fiber and the microhole, the liquids can form steady microflows in the micro-channel. Simultaneously, the interference spectrum of the interferometer device shifts with the variation of the concentration of the microfluid in the channel. The optofluidic in-fiber interferometer has a sensitivity of refractive index around 2508 nm/RIU for NaCl. For medicine concentration detection, its sensitivity is 0.076 nm/mmolL -1 for ascorbic acid. Significantly, this work presents a compact microfluidic in-fiber interferometer with a micro-channel which can be integrated with chip devices without spatial optical coupling and without complex manufacturing procedure of the waveguide on the chips.

Polydyne displacement interferometer using frequency-modulated light

NASA Astrophysics Data System (ADS)

Arablu, Masoud; Smith, Stuart T.

2018-05-01

A radio-frequency Frequency-Modulated (FM) signal is used to diffract a He-Ne laser beam through an Acousto-Optic Modulator (AOM). Due to the modulation of the FM signal, the measured spectra of the diffracted beams comprise a series of phase-synchronized harmonics that have exact integer frequency separation. The first diffraction side-beam emerging from the AOM is selected by a slit to be used in a polydyne displacement interferometer in a Michelson interferometer topology. The displacement measurement is derived from the phase measurement of selected modulation harmonic pairs. Individual harmonic frequency amplitudes are measured using discrete Fourier transform applied to the signal from a single photodetector. Phase signals are derived from the changes in the amplitudes of different harmonic pairs (typically odd-even pairs) with the phase being extracted using a standard quadrature method. In this study, two different modulation frequencies of 5 and 10 kHz are used at different modulation depths. The measured displacements by different harmonic pairs are compared with a commercial heterodyne interferometer being used as a reference for these studies. Measurements obtained from five different harmonic pairs when the moving mirror of the interferometer is scanned over ranges up to 10 μm all show differences of less than 50 nm from the reference interferometer measurements. A drift test was also used to evaluate the differences between the polydyne interferometer and reference measurements that had different optical path lengths of approximately 25 mm and 50 mm, respectively. The drift test results indicate that about half of the differences can be attributed to temperature, pressure, and humidity variations. Other influences include Abbe and thermal expansion effects. Rough magnitude estimates using simple models for these two effects can account for remaining observed deviations.

The Era After the ELT: Optical Interferometry With Kilometer Baselines

NASA Astrophysics Data System (ADS)

Bakker, Eric J.

2007-12-01

The 8-meter class telescopes seen first light in 1993-1998 (Keck, 1993, VLT 1998). The ELT will see first light in the 2013-2018 time frame. The follow-up of the ELT will see first light around 2023. That is 15 years from today. The sequence from 8-meter to 30 meter telescopes (started as a goal of 100m), will suggest a follow-up telescope with an aperture of 300 meter as initial goal. Cleary a 300 meter or more ambitiously a 1000-meter telescope can no longer be structural one piece that has to point to any point on the sky and track the objects. The more likely scenario is to follow the process applied in radio astronomy and move from single telescopes to interferometers. Optical interferometry is maturing very quickly with the de-commissioning of experimental instruments (COAST, GT2I, IOTA, and probably PTI and ISI in the near future) and the use of precision mechanics and automation. The remaining interferometers are grouped in three categories: large telescopes (VLTI and KECK-I), mid-size interferometers (MROI) and small interferometers (CHARA and NPOI). The Magdalena Ridge Observatory Interferometer (MROI) is scheduled for first light/fringe in 2009 and will provide unique observing capabilities to astronomers with limiting magnitudes in the same range as those currently achieved by Keck-I and VLTI. The Magdalena Ridge Observatory Interferometer (near Socorro, NM) invites interested engineers, scientists, and astronomers to participate in the construction and science program of MRO at all levels. Ranging from visitors instruments, support of large procurements in return for access, to individual contributions related to the science program, shared risk observations, etc. For more information, contact the Project Manager at the Magdalena Ridge Observatory Interferometer.

Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

PubMed Central

van den Berg, Steven. A.; van Eldik, Sjoerd; Bhattacharya, Nandini

2015-01-01

Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme. Comparison with a fringe counting laser interferometer shows an agreement within <10−8 for a distance of 50 m. PMID:26419282

Robust laser-based detection of Lamb waves using photo-EMF sensors

NASA Astrophysics Data System (ADS)

Klein, Marvin B.; Bacher, Gerald D.

1998-03-01

Lamb waves are easily generated and detected using laser techniques. It has been shown that both symmetric and antisymmetric modes can be produced, using single-spot and phased array generation. Detection has been demonstrated with Michelson interferometers, but these instruments can not function effectively on rough surfaces. By contrast, the confocal Fabry-Perot interferometer can interrogate rough surfaces, but generally is not practical for operation below 300 kHz. In this paper we will present Lamb wave data on a number of parts using a robust, adaptive receiver based on photo-emf detection. This receiver has useful sensitivity down to at least 100 kHz, can process speckled beams and can be easily configured to measure both out-of-plane and in- plane motion with a single probe beam.

Single Mode SU8 Polymer Based Mach-Zehnder Interferometer for Bio-Sensing Application

NASA Astrophysics Data System (ADS)

Boiragi, Indrajit; Kundu, Sushanta; Makkar, Roshan; Chalapathi, Krishnamurthy

2011-10-01

This paper explains the influence of different parameters to the sensitivity of an optical waveguide Mach-Zehnder Interferometer (MZI) for real time detection of biomolecules. The sensing principle is based on the interaction of evanescence field with the biomolecules that get immobilized on sensing arm. The sensitivity has been calculated by varying the sensing window length, wavelength and concentration of bio-analyte. The maximum attainable sensitivity for the preferred design is the order of 10-8 RIU at 840 nm wavelength with a sensing window length of 1cm. All the simulation work has been carried out with Opti-BPMCAD for the optimization of MZI device parameters. The SU8 polymers are used as a core and clad material to fabricate the waveguide. The refractive index of cladding layer is optimized by varying the curing temperature for a fixed time period and the achieved index difference between core and clad is Δn = 0.0151. The fabricated MZI device has been characterized with LASER beam profiler at 840 nm wavelength. This study demonstrates the effectiveness of the different parameter to the sensitivity of a single mode optical waveguide Mach-Zehnder Interferometer for bio-sensing application.

High stability laser for next generation gravity missions

NASA Astrophysics Data System (ADS)

Nicklaus, K.; Herding, M.; Wang, X.; Beller, N.; Fitzau, O.; Giesberts, M.; Herper, M.; Barwood, G. P.; Williams, R. A.; Gill, P.; Koegel, H.; Webster, S. A.; Gohlke, M.

2017-11-01

With GRACE (launched 2002) and GOCE (launched 2009) two very successful missions to measure earth's gravity field have been in orbit, both leading to a large number of publications. For a potential Next Generation Gravity Mission (NGGM) from ESA a satellite-to-satellite tracking (SST) scheme, similar to GRACE is under discussion, with a laser ranging interferometer instead of a Ka-Band link to enable much lower measurement noise. Of key importance for such a laser interferometer is a single frequency laser source with a linewidth <10 kHz and extremely low frequency noise down to 40 Hz / √Hz in the measurement frequency band of 0.1 mHz to 1 Hz, which is about one order of magnitude more demanding than LISA. On GRACE FO a laser ranging interferometer (LRI) will fly as a demonstrator. The LRI is a joint development between USA (JPL,NASA) and Germany(GFZ,DLR). In this collaboration the JPL contributions are the instrument electronics, the reference cavity and the single frequency laser, while STI as the German industry prime is responsible for the optical bench and the retroreflector. In preparation of NGGM an all European instrument development is the goal.

Optimal combining of ground-based sensors for the purpose of validating satellite-based rainfall estimates

NASA Technical Reports Server (NTRS)

Krajewski, Witold F.; Rexroth, David T.; Kiriaki, Kiriakie

1991-01-01

Two problems related to radar rainfall estimation are described. The first part is a description of a preliminary data analysis for the purpose of statistical estimation of rainfall from multiple (radar and raingage) sensors. Raingage, radar, and joint radar-raingage estimation is described, and some results are given. Statistical parameters of rainfall spatial dependence are calculated and discussed in the context of optimal estimation. Quality control of radar data is also described. The second part describes radar scattering by ellipsoidal raindrops. An analytical solution is derived for the Rayleigh scattering regime. Single and volume scattering are presented. Comparison calculations with the known results for spheres and oblate spheroids are shown.

Photonic Crystal Fiber Mach-Zehnder Interferometer for Refractive Index Sensing

PubMed Central

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10−4–8.88 × 10−4 RIU or 1.02 × 10−4–9.04 × 10−4 RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications. PMID:22736988

Research on the Application of Fast-steering Mirror in Stellar Interferometer

NASA Astrophysics Data System (ADS)

Mei, R.; Hu, Z. W.; Xu, T.; Sun, C. S.

2017-07-01

For a stellar interferometer, the fast-steering mirror (FSM) is widely utilized to correct wavefront tilt caused by atmospheric turbulence and internal instrumental vibration due to its high resolution and fast response frequency. In this study, the non-coplanar error between the FSM and actuator deflection axis introduced by manufacture, assembly, and adjustment is analyzed. Via a numerical method, the additional optical path difference (OPD) caused by above factors is studied, and its effects on tracking accuracy of stellar interferometer are also discussed. On the other hand, the starlight parallelism between the beams of two arms is one of the main factors of the loss of fringe visibility. By analyzing the influence of wavefront tilt caused by the atmospheric turbulence on fringe visibility, a simple and efficient real-time correction scheme of starlight parallelism is proposed based on a single array detector. The feasibility of this scheme is demonstrated by laboratory experiment. The results show that starlight parallelism meets the requirement of stellar interferometer in wavefront tilt preliminarily after the correction of fast-steering mirror.

Photonic crystal fiber Mach-Zehnder interferometer for refractive index sensing.

PubMed

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10(-4)-8.88 × 10(-4) RIU or 1.02 × 10(-4)-9.04 × 10(-4) RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications.

An interferometer having fused optical fibers, and apparatus and method using the interferometer

NASA Technical Reports Server (NTRS)

Hellbaum, Richard F. (Inventor); Claus, Richard O. (Inventor); Murphy, Kent A. (Inventor); Gunther, Michael F. (Inventor)

1992-01-01

An interferometer includes a first optical fiber coupled to a second optical fiber by fusing. At a fused portion, the first and second optical fibers are cut to expose respective cores. The cut or fused end of the first and second optical fibers is arranged to oppose a diaphragm or surface against which a physical phenomenon such as pressure or stress, is applied. In a first embodiment, a source light which is generally single-mode monochromatic, coherent light, is input to the first optical fiber and by evanescence, effectively crosses to the second optical fiber at the fused portion. Source light from the second optical fiber is reflected by the diaphragm or surface, and received at the second optical fiber to generate an output light which has an intensity which depends upon interference of reference light based on the source light, and the reflected light reflected from the diaphragm or surface. The intensity of the output light represents a positional relationship or displacement between the interferometer and the diaphragm or surface.

AC Josephson effect without superconductivity, and other effects of radio frequency quantum nanoelectronics

NASA Astrophysics Data System (ADS)

Waintal, Xavier; Gaury, Benoit; Weston, Joseph

With single coherent electron sources and electronic interferometers now available in the lab, the time resolved dynamics of electrons can now be probed directly. I will discuss how a fast raise of voltage propagates inside an electronic interferometer and leads to an oscillating current of well controled frequency. This phenomena is the normal counterpart to the AC josephson effect. I will also briefly advertize our software for computing quantum transport properties, Kwant (http://kwant-project.org) and its time-dependent extension T-Kwant.

Torsion sensing setup based on a Mach-Zehnder interferometer with photonics crystal fiber

NASA Astrophysics Data System (ADS)

Pacheco-Chacon, Eliana I.; Gallegos-Arellano, E.; Sierra-Hernandez, Juan M.; Rojas-Laguna, Roberto; Estudillo-Ayala, Julian M.; Hernandez, Emmanuel; Jauregui-Vazquez, D.; Hernandez-Garcia, J. C.

2017-02-01

A torsion experimental sensing setup based on a Mach-Zehnder interferometer (MZI) with photonics crystal fiber is presented. The MZI was fabricated by fusion splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber (SMF). Here, a spectral MZI fringe shifting is induced by applying torsion over the SMF-PCF-SMF. As a result a torsion sensitivity of 35.79 pm/ and a high visibility of 10 dB were achieved. Finally, it is shown that the sensing arrangement is compact and robust.

The modulation and demodulation module of a high resolution MOEMS accelerometer

NASA Astrophysics Data System (ADS)

Jiao, Xufen; Bai, Jian; Lu, Qianbo; Lou, Shuqi

2016-02-01

A MOEMS accelerometer with high precision based on grating interferometer is demonstrated in this paper. In order to increase the signal-to-noise ratio (SNR) and accuracy, a specific modulator and an orthogonal phase-lock demodulator are proposed. Phase modulation is introduced to this accelerometer by applying a sinusoidal signal to a piezoelectric translator (PZT) amounted to the accelerometer. Phase demodulation module consists of a circuit design and a digital design. In the circuit design, the modulated light intensity signal is converted to a voltage signal and processed. In the digital part, the demodulator is mainly composed of a Band Pass Filter, two Phase-Sensitive Detectors, a phase shifter, and two Low Pass Filters based on virtual instrument. Simulation results indicate that this approach can decrease the noise greatly, and the SNR of this demodulator is 50dB and the relative error is less than 4%.

Rapid, Repeat-sample Monitoring of Crustal Deformations and Environmental Phenomena with the Uninhabited Aerial Vehicle Synthetic Aperture Radar

NASA Technical Reports Server (NTRS)

Smith, Robert C.

2006-01-01

The Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) is a precision repeat-pass Interferometric Synthetic Aperture Radar (InSAR) mission being developed by the Jet Propulsion Laboratory and the Dryden Flight Research Center in support of NASA s Science Mission Directorate. UAVSAR's unique ability to fly a repeatable flight path, along with an electronically steerable array, allows interferometric data to be obtained with accuracies measured in millimeters. Deploying the radar on an airborne platform will also allow for radar images to be collected and compared with images from the same area taken hours or even years later - providing for long-term trending and near real-time notification of changes and deformations. UAVSAR s data processing algorithms will provide for near-real time data reduction providing disaster planning and response teams with highly accurate data to aid in the prediction of, and response to, natural phenomena. UAVSAR data can be applied to increasing our understanding of the processes behind solid earth, cryosphere, carbon cycle and other areas of interest in earth science. Technologies developed for UAVSAR may also be applicable to a future earth-orbiting InSAR mission and possibly for missions to the Moon or Mars. The UAVSAR is expected to fly on a Gulfstream III aircraft this winter, followed by a flight test program lasting until the second half of 2007. Following radar calibration and data reduction activities, the platform will be ready for science users in the summer of 2008.

Frequency-Tracking CW Doppler Radar Solving Small-Angle Approximation and Null Point Issues in Non-Contact Vital Signs Monitoring.

PubMed

Mercuri, Marco; Liu, Yao-Hong; Lorato, Ilde; Torfs, Tom; Bourdoux, Andre; Van Hoof, Chris

2017-06-01

A Doppler radar operating as a Phase-Locked-Loop (PLL) in frequency demodulator configuration is presented and discussed. The proposed radar presents a unique architecture, using a single channel mixer, and allows to detect contactless vital signs parameters while solving the null point issue and without requiring the small angle approximation condition. Spectral analysis, simulations, and experimental results are presented and detailed to demonstrate the feasibility and the operational principle of the proposed radar architecture.

Photonic crystal fiber in-line Mach-Zehnder interferometer for explosive detection.

PubMed

Tao, Chuanyi; Wei, Heming; Feng, Wenlin

2016-02-08

We report a photonic crystal fiber (PCF) in-line Mach-Zehnder interferometer used as a gas sensor device which exhibits high sensitivity to the explosive trinitrotoluene (TNT). The interferometric sensor head is formed by embedding a segment of large-mode-area/grapefruit PCF between standard single-mode fibers via butt coupling, which produces two small air gaps in between terminated fiber ends with ceramic ferrule connectors as coupling regions, which also serve as inlet/outlet for the gas. The spectral response of the interferometer is investigated in terms of its wavelength spectrum. The selectivity to TNT vapor is achieved by immobilizing a molecular recognition ployallylamine layer on the inner surface of the holey region of the PCF. The TNT-induced variations of the interference fringes are measured and the sensing capability of the proposed sensor is demonstrated experimentally.

Temperature sensor based on an isopropanol-sealed photonic crystal fiber in-line interferometer with enhanced refractive index sensitivity.

PubMed

Qiu, Sun-jie; Chen, Ye; Xu, Fei; Lu, Yan-qing

2012-03-01

We fabricate a simple, compact, and stable temperature sensor based on a liquid-sealed photonic crystal fiber (PCF) in-line nonpolarimetric modal interferometer. Different from other reported PCF devices, it does not need expensive polarimetric devices, and the liquid is sealed in one fiber. The device consists of a stub of isopropanol-filled PCF spliced between standard single-mode fibers. The temperature sensitivity (-166 pm/°C) increases over an order of magnitude compared with those of the previous sensors based on air-sealed PCF interferometers built via fusion splicing with the same mechanism. In addition, the refractive index sensitivity also increases. Higher temperature sensitivity can be realized by infiltrating some liquid having a higher thermo-optic coefficient into the microholes of the PCF. © 2012 Optical Society of America

Efficient Single-Pass Index Construction for Text Databases.

ERIC Educational Resources Information Center

Heinz, Steffen; Zobel, Justin

2003-01-01

Discusses index construction for text collections, reviews principal approaches to inverted indexes, analyzes their theoretical cost, and presents experimental results of the use of a single-pass inversion method on Web document collections. Shows that the single-pass approach is faster and does not require the complete vocabulary of the indexed…

Laser-based ultrasonics by dual-probe interferometer detection and narrow-band ultrasound generation

NASA Astrophysics Data System (ADS)

Huang, Jin

1993-01-01

Despite the advantages of laser-based ultrasonic (LBU) systems, the overall sensitivity of LBU systems needs to be improved for practical applications. Progress is reported to achieve better LBU detection accuracy and sensitivity for applications with surface waves and Lamb waves. A novel dual-probe laser interferometer has been developed to measure the same signal at two points. The dual-probe interferometer is a modification of a conventional single-probe interferometer in that the reference beam is guided to a second detecting point on the specimen surface to form a differential measurement mode, which measure the difference of the displacements at the two points. This dual-probe interferometer is particularly useful for accurate measurements of the speed and attenuation of surface waves and Lamb waves. The dual-probe interferometer has been applied to obtain accurate measurements of the surface wave speed and attenuation on surfaces of increasing surface roughness. It has also been demonstrated that with an appropriate signal processing method, namely, the power cepstrum method, the dual-probe interferometer is applicable to measure the local surface wave speed even when the probe separation is so small that the two waveforms in the interferometer output signal overlap in the time domain. Narrow-band signal generation and detection improve the sensitivity of LBU systems. It is proposed to use a diffraction grating to form an array of illuminating strips which form a source of narrowband surface and Lamb waves. The line-array of thermoelastic sources generates narrow-band signals whose frequency and bandwidth can be easily controlled. The optimum line-array parameters, such as width, spacing and the number of lines in the array have been derived theoretically and verified experimentally. Narrow-band signal generation with optimum parameters has been demonstrated. The enhanced LBU system with dual-probe detection and narrowband signal generation has been successfully applied to the detection of cracks emanating from rivet holes in aircraft fuselage panel samples. A compact fiber-optic dual-probe interferometer has also been developed and applied to the above mentioned problem of crack detection. Results agree well with those obtained with a bulk LBU system.

Direct Visual and Radar Methods for the Detection, Quantification, and Prediction of Bird Migration.

DTIC Science & Technology

1980-04-30

domesticus), 12 cm2 ; and Rock Dove ( Columba livia ), 80 cm’. Eastwood (1967) has given the radar cross sections of a number of European birds as mea...in Table 4 and Table 5 it is apparent that a single pigeon ( Columba livia ) flying toward the radar should theoretically produce an echo on the ASR-4

Simulation of double-pass stimulated Raman backscattering

NASA Astrophysics Data System (ADS)

Wu, Z.; Chen, Q.; Morozov, A.; Suckewer, S.

2018-04-01

Experiments on Stimulated Raman Backscattering (SRBS) in plasma have demonstrated significantly higher energy conversion in a double-pass amplifier where the laser pulses go through the plasma twice compared with a single-pass amplifier with double the plasma length of a single pass. In this paper, the improvement in understanding recent experimental results is presented by considering quite in detail the effects of plasma heating on the modeling of SRBS. Our simulation results show that the low efficiency of single-pass amplifiers can be attributed to Landau damping and the frequency shift of Langmuir waves. In double-pass amplifiers, these issues can be avoided, to some degree, because pump-induced heating could be reduced, while the plasma cools down between the passes. Therefore, double-pass amplifiers yield considerably enhanced energy transfer from the pump to the seed, hence the output pulse intensity.

A convenient technique for polarimetric calibration of single-antenna radar systems

NASA Technical Reports Server (NTRS)

Sarabandi, Kamal; Ulaby, Fawwaz T.

1990-01-01

A practical technique for calibrating single-antenna polarimetric radar systems is introduced. This technique requires only a single calibration target such as a conducting sphere or a trihedral corner reflector to calibrate the radar system, both in amplitude and phase, for all linear polarization configurations. By using a metal sphere, which is orientation independent, error in calibration measurement is minimized while simultaneously calibrating the crosspolarization channels. The antenna system and two orthogonal channels (in free space) are modeled as a four-port passive network. Upon using the reciprocity relations for the passive network and assuming the crosscoupling terms of the antenna to be equal, the crosstalk factors of the antenna system and the transmit and receive channel imbalances can be obtained from measurement of the backscatter from a metal sphere. For an X-band radar system with crosspolarization isolation of 25 dB, comparison of values measured for a sphere and a cylinder with theoretical values shows agreement within 0.4 dB in magnitude and 5 deg in phase. An effective polarization isolation of 50 dB is achieved using this calibration technique.

Radar Astrometry of Asteroid 99942 (2004 MN4): Predicting the 2029 Earth Encounter and Beyond

NASA Astrophysics Data System (ADS)

Giorgini, J. D.; Benner, L. A. M.; Nolan, M. C.; Ostro, S. J.

2005-08-01

Asteroid 2004 MN4 is expected to pass 4.6 (+/- 1.6) Earth-radii above the surface of the Earth on 2029-Apr-13. Such close approaches by objects as large as 2004 MN4 (D ≳ 0.3 km) are thought to occur at ≳ 1000-year intervals on average. 2004 MN4 is expected to reach 3rd magnitude and thus be visible to the unaided eye. With a disk 2-4 arcseconds across, it may be resolved by ground-based telescopes. Arecibo (2380-MHz) delay-Doppler radar astrometry, obtained in late January 2005, significantly corrected 2004 MN4's orbit by revealing a 1.4 arcsecond bias in pre-discovery optical measurements. Doppler-shifted echoes were acquired 4.8σ (176.4 mm/s) away from the predicted frequency on Jan 27. Range on Jan 29 was found to be 747 km (2.8σ ) closer to Earth than the pre-radar orbit predicted. Incorporation of these delay-Doppler measurements into a new weighted least-squares orbit solution moved the 2029-Apr-13 encounter prediction 5σ closer to the Earth, illustrating the problematic nature of prediction and statistical analysis with single-apparition optical data-sets. Without delay-Doppler data, the bias was not apparent, even when optical measurements spanned a full orbit period. The current combined data-set does not permit reliable trajectory propagation to encounters beyond 2029; Monte Carlo analysis shows that, by 2036, the 3σ confidence region wraps >300 degrees of heliocentric longitude around the Sun, with some sections of this statistical region experiencing low-probability encounters with the Earth in the 2030's, gravitationally scattering some possible trajectories inward to the orbit of Venus, or outward toward Mars. Future measurements from radar opportunities in August 2005 and May 2006 (SNR ≈5-10) have the potential to eliminate statistical encounters in the 2030's. Delay-Doppler astrometry from 2013 (SNR ≈30) should permit deterministic encounter prediction through 2070, shrinking the along-track uncertainty in 2036 by two orders of magnitude,from ≳ 8(10)8 km to ≲7(10)6 km.

Glacier and snow hydrology investigation in the Upper Indus Basin using Synthetic Aperture Radar

NASA Astrophysics Data System (ADS)

Jouvet, G.; Stastny, T.; Oettershagen, P.; Hugentobler, M.; Mantel, T.; Melzer, A.; Weidmann, Y.; Funk, M.; Siegwart, R.; Lund, J.; Forster, R. R.; Burgess, E. W.

2017-12-01

The flows of the Indus River are a vital resource for food security, ecosystem services, hydropower and economy for China, India and Pakistan. Glaciers of the Karakoram Mountains are the largest drivers of discharge in the Upper Indus Basin, and combined with snowmelt constitute the majority of runoff. While recently verified in near balance, the glaciers of the Karakoram exhibit substantial variation both spatially and temporally. Complex climatology, coupled with the challenges of field study in this rugged range, illicit notable uncertainties in observation and prediction of glacial status. Satellite-borne radar sensors acquire imagery regardless of cloud cover or time of day, and offer unique insights into physical processes due to their wavelength. Here we utilize Sentinel-1 synthetic aperture radar (SAR) imagery to track transient snow lines on glaciers of the Shigar watershed throughout multiple ablation seasons, and discuss the utility of this information in relation to snow and glacier mass balance. As the Sentinel-1 sensor ascending and descending passes capture morning and evening imagery in this region, diurnal radar variations will also be explored as indicators of melt-refreeze cycles and their correlation with peak runoff.

The relationship of storm severity to directionally resolved radio emissions

NASA Astrophysics Data System (ADS)

Johnson, R. L.

1986-04-01

The objective was to provide continuous observation of atmospheric electrical activity occurring in association with tropical storms in the Gulf of Mexico. The observations were to include the location of all detected intracloud and cloud-to-ground lightning activity occurring in the storm. To provide synoptic scale coverage, a phase linear interferometer high frequency direction finder (HFDF) system was constructed and developed at Marshall Space Flight Center (MSFC). This was used in concert with the existing HFDF interferometer at the southwest research institute to provide lightning location data through triangulation. Atmospheric electrical events were synchronized through the use of satellite receivers at each site. The intent of the data analysis was to correlate the location of electrical centers of activity with radar and satellite imagry to identify areas of intense convection within the tropical storm system. Analysis of the hurricane Alicia data indicate a center of atmospheric electrical activity associated with the vortex of the storm. The center appears to rotate from the Northern side of the vortex to the Southern side during the period of observation. An analysis of the atmospheric electrical burst rates associated with hurrican Alicia indicates that the electrical activity appears to maximize at the time of greatest storm intensity, i.e., maximum winds and lowest central pressure.

Code-modulated interferometric imaging system using phased arrays

NASA Astrophysics Data System (ADS)

Chauhan, Vikas; Greene, Kevin; Floyd, Brian

2016-05-01

Millimeter-wave (mm-wave) imaging provides compelling capabilities for security screening, navigation, and bio- medical applications. Traditional scanned or focal-plane mm-wave imagers are bulky and costly. In contrast, phased-array hardware developed for mass-market wireless communications and automotive radar promise to be extremely low cost. In this work, we present techniques which can allow low-cost phased-array receivers to be reconfigured or re-purposed as interferometric imagers, removing the need for custom hardware and thereby reducing cost. Since traditional phased arrays power combine incoming signals prior to digitization, orthogonal code-modulation is applied to each incoming signal using phase shifters within each front-end and two-bit codes. These code-modulated signals can then be combined and processed coherently through a shared hardware path. Once digitized, visibility functions can be recovered through squaring and code-demultiplexing operations. Pro- vided that codes are selected such that the product of two orthogonal codes is a third unique and orthogonal code, it is possible to demultiplex complex visibility functions directly. As such, the proposed system modulates incoming signals but demodulates desired correlations. In this work, we present the operation of the system, a validation of its operation using behavioral models of a traditional phased array, and a benchmarking of the code-modulated interferometer against traditional interferometer and focal-plane arrays.

Ground-based Observations for the Upper Atmosphere at King Sejong Station, Antarctica

NASA Astrophysics Data System (ADS)

Jee, Geonhwa; Kim, Jeong-Han; Lee, Changsup; Kim, Yong Ha

2014-06-01

Since the operation of the King Sejong Station (KSS) started in Antarctic Peninsula in 1989, there have been continuous efforts to perform the observation for the upper atmosphere. The observations during the initial period of the station include Fabry-Perot Interferometer (FPI) and Michelson Interferometer for the mesosphere and thermosphere, which are no longer in operation. In 2002, in collaboration with York University, Canada, the Spectral Airglow Temperature Imager (SATI) was installed to observe the temperature in the mesosphere and lower thermosphere (MLT) region and it has still been producing the mesopause temperature data until present. The observation was extended by installing the meteor radar in 2007 to observe the neutral winds and temperature in the MLT region during the day and night in collaboration with Chungnam National University. We also installed the all sky camera in 2008 to observe the wave structures in the MLT region. All these observations are utilized to study on the physical characteristics of the MLT region and also on the wave phenomena such as the tide and gravity wave in the upper atmosphere over KSS that is well known for the strong gravity wave activity. In this article, brief introductions for the currently operating instruments at KSS will be presented with their applications for the study of the upper atmosphere

The relationship of storm severity to directionally resolved radio emissions

NASA Technical Reports Server (NTRS)

Johnson, R. L.

1986-01-01

The objective was to provide continuous observation of atmospheric electrical activity occurring in association with tropical storms in the Gulf of Mexico. The observations were to include the location of all detected intracloud and cloud-to-ground lightning activity occurring in the storm. To provide synoptic scale coverage, a phase linear interferometer high frequency direction finder (HFDF) system was constructed and developed at Marshall Space Flight Center (MSFC). This was used in concert with the existing HFDF interferometer at the southwest research institute to provide lightning location data through triangulation. Atmospheric electrical events were synchronized through the use of satellite receivers at each site. The intent of the data analysis was to correlate the location of electrical centers of activity with radar and satellite imagry to identify areas of intense convection within the tropical storm system. Analysis of the hurricane Alicia data indicate a center of atmospheric electrical activity associated with the vortex of the storm. The center appears to rotate from the Northern side of the vortex to the Southern side during the period of observation. An analysis of the atmospheric electrical burst rates associated with hurrican Alicia indicates that the electrical activity appears to maximize at the time of greatest storm intensity, i.e., maximum winds and lowest central pressure.

Analysis of Borehole-Radar Reflection Data from Machiasport, Maine, December 2003

USGS Publications Warehouse

Johnson, Carole D.; Joesten, Peter K.

2005-01-01

In December 2003, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, collected borehole-radar reflection logs in two boreholes in Machiasport, Maine. These bedrock boreholes were drilled as part of a hydrogeologic investigation of the area surrounding the former Air Force Radar Tracking Station site on Howard Mountain near Bucks Harbor. The boreholes, MW09 and MW10, are located approximately 50 meters (m) from, and at the site of, respectively, the locations of former buildings where trichloroethylene was used as part of defense-site operations. These areas are thought to be potential source areas for contamination that has been detected in downgradient bedrock wells. This investigation focused on testing borehole-radar methods at this site. Single-hole radar-reflection surveys were used to identify the depth, orientation, and spatial continuity of reflectors that intersect and surround the boreholes. In addition, the methods were used to (1) identify the radial depth of penetration of the radar waves in the electrically resistive bimodal volcanic formation at the site, (2) provide information for locating additional boreholes at the site, and (3) test the potential applications of borehole-radar methods for further aquifer characterization and (or) evaluation of source-area remediation efforts. Borehole-radar reflection logging uses a pair of downhole transmitting and receiving antennas to record the reflected wave amplitude and transit time of high-frequency electromagnetic waves. For this investigation, 60- and 100-megahertz antennas were used. The electromagnetic waves emitted by the transmitter penetrate into the formation surrounding the borehole and are reflected off of a material with different electromagnetic properties, such as a fracture or change in rock type. Single-hole directional radar surveys indicate the bedrock surrounding these boreholes is highly fractured, because several reflectors were identified in the radar-reflection data. There are several steeply dipping reflectors with orientations similar to the fracture patterns observed with borehole imaging techniques and in outcrops. The radar-reflection data showed that the vitrophyre in borehole MW09 was more highly fractured than the underlying gabbroic unit. The velocities of radar waves in the bedrock surrounding the boreholes were determined using single-hole vertical radar profiling. Velocities of 114 and 125 meters per microsecond were used to determine the distance to reflectors, the radial depth of penetration, and the dip of reflectors. The bimodal volcanic units appear to be ideal for radar-wave propagation. For the radar surveys collected at this site, radar reflections were detected up to 40 m into the rock from the borehole. These results indicate that boreholes could conservatively be spaced about 15-20 m apart for hole-to-hole radar methods to be effective for imaging between the boreholes and monitoring remediation. Integrated analysis of drilling and borehole-geophysical logs indicates the vitrophyric formation is more fractured than the more mafic gabbroic units in these boreholes. There does not, however, appear to be a quantifiable difference in the radar-wave penetration in these two rock units.

UAVSAR - A New Airborne L-Band Radar for Repeat Pass Interferometry

NASA Technical Reports Server (NTRS)

Mace, Thomas H.; Lou, Yunling

2009-01-01

NASA/JPL has developed a new airborne Synthetic Aperture Radar (SAR) which has become available for use by the scientific community in January, 2009. Pod mounted, the UAVSAR was designed to be portable among a variety of aircraft, including unmanned aerial systems (UAS). The instrument operates in the L-Band, has a resolution under 2m from a GPS altitude of 12Km and a swath width of approximately 20Km. UAVSAR currently flies on a modified Gulfstream-III aircraft, operated by NASA s Dryden Flight Research Center at Edwards, California. The G-III platform enables repeat-pass interferometric measurements, by using a modified autopilot and precise kinematic differential GPS to repeatedly fly the aircraft within a specified 10m tube. The antenna is electronically steered along track to assure that the antenna beam can be directed independently, regardless of speed and wind direction. The instrument can be controlled remotely, AS AN OPTION, using the Research Environment for Vehicle Embedded Analysis on Linux (REVEAL). This allows simulation of the telepresence environment necessary for flight on UAS. Potential earth science research and applications include surface deformation, volcano studies, ice sheet dynamics, and vegetation structure.

An evaluation of processing InSAR Sentinel-1A/B data for correlation of mining subsidence with mining induced tremors in the Upper Silesian Coal Basin (Poland)

NASA Astrophysics Data System (ADS)

Krawczyk, Artur; Grzybek, Radosław

2018-01-01

The Satellite Radar Interferometry is one of the common methods that allow to measure the land subsidence caused by the underground black coal excavation. The interferometry images processed from the repeat-pass Synthetic Aperture Radar (SAR) systems give the spatial image of the terrain subjected to the surface subsidence over mining areas. Until now, the InSAR methods using data from the SAR Systems like ERS-1/ERS-2 and Envisat-1 were limited to a repeat-pass cycle of 35-day only. Recently, the ESA launched Sentinel-1A and 1B, and together they can provide the InSAR coverage in a 6-day repeat cycle. The studied area was the Upper Silesian Coal Basin in Poland, where the underground coal mining causes continuous subsidence of terrain surface and mining tremors (mine-induced seismicity). The main problem was with overlapping the subsidence caused by the mining exploitation with the epicentre tremors. Based on the Sentinel SAR images, research was done in regard to the correlation between the short term ground subsidence range border and the mine-induced seismicity epicentres localisation.

Polymer Waveguides for Quantum Information

DTIC Science & Technology

2005-01-01

a single photon or a very small amount of light plays a critical role in establishing the quantum nature of the process. These materials offer...realizations of Mach-Zehnder interferometers for use in single- photon quantum communication systems. The Scope of the research for this grant: This...to the waveguide we make. We also intend to investigate the transmission of highly attenuated signals mimicking the single photon , which in turn

Linear optical quantum metrology with single photons: exploiting spontaneously generated entanglement to beat the shot-noise limit.

PubMed

Motes, Keith R; Olson, Jonathan P; Rabeaux, Evan J; Dowling, Jonathan P; Olson, S Jay; Rohde, Peter P

2015-05-01

Quantum number-path entanglement is a resource for supersensitive quantum metrology and in particular provides for sub-shot-noise or even Heisenberg-limited sensitivity. However, such number-path entanglement has been thought to be resource intensive to create in the first place--typically requiring either very strong nonlinearities, or nondeterministic preparation schemes with feedforward, which are difficult to implement. Very recently, arising from the study of quantum random walks with multiphoton walkers, as well as the study of the computational complexity of passive linear optical interferometers fed with single-photon inputs, it has been shown that such passive linear optical devices generate a superexponentially large amount of number-path entanglement. A logical question to ask is whether this entanglement may be exploited for quantum metrology. We answer that question here in the affirmative by showing that a simple, passive, linear-optical interferometer--fed with only uncorrelated, single-photon inputs, coupled with simple, single-mode, disjoint photodetection--is capable of significantly beating the shot-noise limit. Our result implies a pathway forward to practical quantum metrology with readily available technology.

A novel apparatus for non-contact measurement of heart rate variability: a system to prevent secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, in monitoring sepsis or in predicting multiple organ dysfunction syndrome.

PubMed

Matsui, T; Arai, I; Gotoh, S; Hattori, H; Takase, B; Kikuchi, M; Ishihara, M

2005-10-01

The impaired balance of the low-frequency/high-frequency ratio obtained from spectral components of RR intervals can be a diagnostic test for sepsis. In addition, it is known that a reduction of heart rate variability (HRV) is useful in identifying septic patients at risk of the development of multiple organ dysfunction syndrome (MODS). We have reported a non-contact method using a microwave radar to monitor the heart and respiratory rates of a healthy person placed inside an isolator or of experimental animals exposed to toxic materials. With the purpose of preventing secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, we designed a novel apparatus for non-contact measurement of HRV using a 1215 MHz microwave radar, a high-pass filter, and a personal computer. The microwave radar monitors only the small reflected waves from the subject's chest wall, which are modulated by the cardiac and respiratory motion. The high-pass filter enhances the cardiac signal and attenuates the respiratory signal. In a human trial, RR intervals derived from the non-contact apparatus significantly correlated with those derived from ECG (r=0.98, P<0.0001). The non-contact apparatus showed a similar power spectrum of RR intervals to that of ECG. Our non-contact HRV measurement apparatus appears promising for future pre-hospital monitoring of septic patients or for predicting MODS patients, inside isolators or in the field for mass casualties under biochemical hazard circumstances.

Early results from NASA's SnowEx campaign

NASA Astrophysics Data System (ADS)

Kim, Edward; Gatebe, Charles; Hall, Dorothy; Misakonis, Amy; Elder, Kelly; Marshall, Hans Peter; Hiemstra, Chris; Brucker, Ludovic; Crawford, Chris; Kang, Do Hyuk; De Marco, Eugenia; Beckley, Matt; Entin, Jared

2017-04-01

SnowEx is a multi-year airborne snow campaign with the primary goal of addressing the question: How much water is stored in Earth's terrestrial snow-covered regions? Year 1 (2016-17) focuses on the distribution of snow-water equivalent (SWE) and the snow energy balance in a forested environment. The year 1 primary site is Grand Mesa and the secondary site is the Senator Beck Basin, both in western, Colorado, USA. Ten core sensors on four core aircraft will make observations using a broad suite of airborne sensors including active and passive microwave, and active and passive optical/infrared sensing techniques to determine the sensitivity and accuracy of these potential satellite remote sensing techniques, along with models, to measure snow under a range of forest conditions. SnowEx also includes an extensive range of ground truth measurements—in-situ samples, snow pits, ground based remote sensing measurements, and sophisticated new techniques. A detailed description of the data collected will be given and some early results will be presented. Seasonal snow cover is the largest single component of the cryosphere in areal extent (covering an average of 46M km2 of Earth's surface (31 % of land areas) each year). This seasonal snow has major societal impacts in the areas of water resources, natural hazards (floods and droughts), water security, and weather and climate. The only practical way to estimate the quantity of snow on a consistent global basis is through satellites. Yet, current space-based techniques underestimate storage of snow water equivalent (SWE) by as much as 50%, and model-based estimates can differ greatly vs. estimates based on remotely-sensed observations. At peak coverage, as much as half of snow-covered terrestrial areas involve forested areas, so quantifying the challenge represented by forests is important to plan any future snow mission. Single-sensor approaches may work for certain snow types and certain conditions, but not for others. Snow simply varies too much. Thus, the snow community consensus is that a multi-sensor approach is needed to adequately address global snow, combined with modeling and data assimilation. What remains at issue, then, is how best to combine and use the various sensors in an optimal way. That requires field measurements. NASA's SnowEx airborne campaign is designed to do exactly that. A list of core sensors is as follows. All are from NASA unless otherwise noted. • Radar (volume scattering): European Space Agency's SnowSAR, operated by MetaSensing • Lidar & hyperspectral imager: Airborne Snow Observatory (ASO) • Passive microwave: Airborne Earth Science Microwave Imaging Radiometer (AESMIR) • Bi-directional Reflectance Function (BRDF): the Cloud Absorption Radiometer (CAR) • Thermal Infrared imager • Thermal infrared non-imager from U. Washington • Video camera The ASO suite flew on a King Air, and the other sensors flew on a Navy P-3. In addition, two NASA radars flew on G-III aircraft to test more experimental retrieval techniques: • InSAR altimetry: Glacier and Ice Surface Topography Interferometer (GLISTIN-A) • Radar phase delay: Uninhabited Aerial Vehicle Synthetic Aperture Radar, (UAVSAR)

Geologic remote sensing study of the Hayden pass-Orient Mine Area, Northern Sangre de Cristo Mountains, Colorado

NASA Technical Reports Server (NTRS)

Wychgram, D. C.

1972-01-01

Remote sensor data from a NASA Convair 990 radar flight and Mission 101 and 105 have been interpreted and evaluated. Based on interpretation of the remote sensor data, a geologic map has been prepared and compared with a second geologic map, prepared from interpretation of both remote sensor data and field data. Comparison of the two maps gives one indication of the usefulness and reliability of the remote sensor data. Color and color infrared photography provided the largest amount of valuable information. Multiband photography was of lesser value and side-looking radar imagery provided no new information that was not available on small scale photography. Thermal scanner imagery proved to be a very specialized remote sensing tool that should be applied to areas of low relief and sparse vegetation where geologic features produce known or suspected thermal contrast. Low sun angle photography may be a good alternative to side-looking radar imagery but must be flown with critical timing.

A Comparison of Swarm Cross-Track Ion-Drifts and SuperDARN Line-of-Sight Velocities

NASA Astrophysics Data System (ADS)

Koustov, A. V.; Lavoie, D. B.; Kouznetsov, A.; Burchill, J. K.; Knudsen, D. J.

2017-12-01

Cross-track ion drifts measured by the Swarm-A satellite are compared with line-of-sight SuperDARN HF velocities in approximately the same directions. More than 200 Swarm-A passes over four polar cap SuperDARN radars in the northern and southern hemispheres are considered. Overall, the radar velocities are found to be smaller than the Swarm-derived velocities with the slope of the best linear fit line on the order of 0.5. Such relationship is in effect only for points with good quality of measurements by both instruments. In a number of cases, disagreements not only in the magnitude but also in the direction of the velocity are found. Potential reasons for disagreements are discussed. The comparison implies that Swarm cross-track velocity data are often compatible with those from SuperDARN radars and thus can be used for research. However, a careful examination of each piece of Swarm data is still highly desirable.

Preliminary Regional Analysis of the Kaguya Lunar Radar Sounder (LRS) Data through Eastern Mare Imbrium

NASA Technical Reports Server (NTRS)

Cooper, B.L.; Antonenko, I.; Yamaguchi, Y.; Osinski, G.; Ono, T.; Ku-mamoto, A.

2009-01-01

The Lunar Radar Sounder (LRS) experiment on board the Kaguya spacecraft is observing the subsurface structure of the Moon, using ground-penetrating radar operating in the frequency range of 5 MHz [1]. Because LRS data provides in-formation about lunar features below the surface, it allows us to improve our understanding of the processes that formed the Moon, and the post-formation changes that have occurred (such as basin formation and volcanism). We look at a swath of preliminary LRS data, that spans from 7 to 72 N, and from 2 to 10 W, passing through the eastern portion of Mare Imbrium (Figure 1). Using software, designed for the mineral exploration industry, we produce a preliminary, coarse 3D model, showing the regional structure beneath the study area. Future research will involve smaller subsets of the data in regions of interest, where finer structures, such as those identified in [2], can be studied.

Ultrastructural evaluation of multiple pass low energy versus single pass high energy radio-frequency treatment.

PubMed

Kist, David; Burns, A Jay; Sanner, Roth; Counters, Jeff; Zelickson, Brian

2006-02-01

The radio-frequency (RF) device is a system capable of volumetric heating of the mid to deep dermis and selective heating of the fibrous septa strands and fascia layer. Clinically, these effects promote dermal collagen production, and tightening of these deep subcutaneous structures. A new technique of using multiple low energy passes has been described which results in lower patient discomfort and fewer side effects. This technique has also been anecdotally described as giving more reproducible and reliable clinical results of tissue tightening and contouring. This study will compare ultrastructural changes in collagen between a single pass high energy versus up to five passes of a multiple pass lower energy treatment. Three subjects were consented and treated in the preauricular region with the RF device using single or multiple passes (three or five) in the same 1.5 cm(2) treatment area with a slight delay between passes to allow tissue cooling. Biopsies from each treatment region and a control biopsy were taken immediately, 24 hours or 6 months post treatment for electron microscopic examination of the 0-1 mm and 1-2 mm levels. Sections of tissue 1 mm x 1 mm x 80 nm were examined with an RCA EMU-4 Transmission Electron Microscope. Twenty sections from 6 blocks from each 1 mm depth were examined by 2 blinded observers. The morphology and degree of collagen change in relation to area examined was compared to the control tissue, and estimated using a quantitative scale. Ultrastructural examination of tissue showed that an increased amount of collagen fibril changes with increasing passes at energies of 97 J (three passes) and 122 J (five passes), respectively. The changes seen after five multiple passes were similar to those detected after much more painful single pass high-energy treatments. This ultrastructural study shows changes in collagen fibril morphology with an increased effect demonstrated at greater depths of the skin with multiple low-fluence passes and at lesser depths with single pass higher fluence settings. Findings suggest that similar collagen fibril alteration can occur with multiple pass low-energy treatments and single pulse high-energy treatments. The lower fluence multiple pass approach is associated with less patient discomfort, less side effects, and more consistent clinical results. Copyright 2005 Wiley-Liss, Inc.

Intercomparison of attenuation correction algorithms for single-polarized X-band radars

NASA Astrophysics Data System (ADS)

Lengfeld, K.; Berenguer, M.; Sempere Torres, D.

2018-03-01

Attenuation due to liquid water is one of the largest uncertainties in radar observations. The effects of attenuation are generally inversely proportional to the wavelength, i.e. observations from X-band radars are more affected by attenuation than those from C- or S-band systems. On the other hand, X-band radars can measure precipitation fields in higher temporal and spatial resolution and are more mobile and easier to install due to smaller antennas. A first algorithm for attenuation correction in single-polarized systems was proposed by Hitschfeld and Bordan (1954) (HB), but it gets unstable in case of small errors (e.g. in the radar calibration) and strong attenuation. Therefore, methods have been developed that restrict attenuation correction to keep the algorithm stable, using e.g. surface echoes (for space-borne radars) and mountain returns (for ground radars) as a final value (FV), or adjustment of the radar constant (C) or the coefficient α. In the absence of mountain returns, measurements from C- or S-band radars can be used to constrain the correction. All these methods are based on the statistical relation between reflectivity and specific attenuation. Another way to correct for attenuation in X-band radar observations is to use additional information from less attenuated radar systems, e.g. the ratio between X-band and C- or S-band radar measurements. Lengfeld et al. (2016) proposed such a method based isotonic regression of the ratio between X- and C-band radar observations along the radar beam. This study presents a comparison of the original HB algorithm and three algorithms based on the statistical relation between reflectivity and specific attenuation as well as two methods implementing additional information of C-band radar measurements. Their performance in two precipitation events (one mainly convective and the other one stratiform) shows that a restriction of the HB is necessary to avoid instabilities. A comparison with vertically pointing micro rain radars (MRR) reveals good performance of two of the methods based in the statistical k-Z-relation: FV and α. The C algorithm seems to be more sensitive to differences in calibration of the two systems and requires additional information from C- or S-band radars. Furthermore, a study of five months of radar observations examines the long-term performance of each algorithm. From this study conclusions can be drawn that using additional information from less attenuated radar systems lead to best results. The two algorithms that use this additional information eliminate the bias caused by attenuation and preserve the agreement with MRR observations.

Distortion effects in a switch array UWB radar for time-lapse imaging of human heartbeats

NASA Astrophysics Data System (ADS)

Brovoll, Sverre; Berger, Tor; Aardal, Åyvind; Lande, Tor S.; Hamran, Svein-Erik

2014-05-01

Cardiovascular diseases (CVD) are a major cause of deaths all over the world. Microwave radar can be an alternative sensor for heart diagnostics and monitoring in modern healthcare that aids early detection of CVD symptoms. In this paper measurements from a switch array radar system are presented. This UWB system operates below 3 GHz and does time-lapse imaging of the beating heart inside the human body. The array consists of eight fat dipole elements. With a switch system, every possible sequence of transmit/receive element pairs can be selected to build a radar image from the recordings. To make the radar waves penetrate the human tissue, the antenna array is placed in contact with the body. Removal of the direct signal leakage through the antennas and body surface are done by high-pass (HP) filtering of the data prior to image processing. To analyze the results, measurements of moving spheres in air and simulations are carried out. We see that removal of the direct signal introduces amplitude distortion in the images. In addition, the effect of small target motion between the collection times of data from the individual elements is analyzed. With low pulse repetition frequency (PRF) this motion will distort the image. By using data from real measurements of heart motion in simulations, we analyze how the PRF and the antenna geometry influence this distortions.

Real-data tests of a single-Doppler radar assimilation system

NASA Astrophysics Data System (ADS)

Nehrkorn, Thomas; Hegarty, James; Hamill, Thomas M.

1994-06-01

Real data tests of a single-Doppler radar data assimilation and forecast system have been conducted for a Florida sea breeze case. The system consists of a hydrostatic mesoscale model used for prediction of the preconvective boundary layer, an objective analysis that combines model first guess fields with radar derived horizontal winds, a thermodynamic retrieval scheme that obtains temperature information from the three-dimensional wind field and its temporal evolution, and a Newtonian nudging scheme for forcing the model forecast to closer agreement with the analysis. As was found in earlier experiments with simulated data, assimilation using Newtonian nudging benefits from temperature data in addition to wind data. The thermodynamic retrieval technique was successful in retrieving a horizontal temperature gradient from the radar-derived wind fields that, when assimilated into the model, led to a significantly improved forecast of the seabreeze strength and position.

Terrain detection and classification using single polarization SAR

DOEpatents

Chow, James G.; Koch, Mark W.

2016-01-19

The various technologies presented herein relate to identifying manmade and/or natural features in a radar image. Two radar images (e.g., single polarization SAR images) can be captured for a common scene. The first image is captured at a first instance and the second image is captured at a second instance, whereby the duration between the captures are of sufficient time such that temporal decorrelation occurs for natural surfaces in the scene, and only manmade surfaces, e.g., a road, produce correlated pixels. A LCCD image comprising the correlated and decorrelated pixels can be generated from the two radar images. A median image can be generated from a plurality of radar images, whereby any features in the median image can be identified. A superpixel operation can be performed on the LCCD image and the median image, thereby enabling a feature(s) in the LCCD image to be classified.

Coherent combining of high brightness tapered lasers in master oscillator power amplifier configuration

NASA Astrophysics Data System (ADS)

Albrodt, P.; Hanna, M.; Moron, F.; Decker, J.; Winterfeldt, M.; Blume, G.; Erbert, G.; Crump, P.; Georges, P.; Lucas-Leclin, G.

2018-02-01

Improved diode laser beam combining techniques are in strong demand for applications in material processing. Coherent beam combining (CBC) is the only combining approach that has the potential to maintain or even improve all laser properties, and thus has high potential for future systems. As part of our ongoing studies into CBC of diode lasers, we present recent progress in the coherent superposition of high-power single-pass tapered laser amplifiers. The amplifiers are seeded by a DFB laser at λ = 976 nm, where the seed is injected into a laterally single-mode ridge-waveguide input section. The phase pistons on each beam are actively controlled by varying the current in the ridge section of each amplifier, using a sequential hill-climbing algorithm, resulting in a combined beam with power fluctuations of below 1%. The currents into the tapered sections of the amplifiers are separately controlled, and remain constant. In contrast to our previous studies, we favour a limited number of individual high-power amplifiers, in order to preserve a high extracted power per emitter in a simple, low-loss coupling arrangement. Specifically, a multi-arm interferometer architecture with only three devices is used, constructed using 6 mm-long tapered amplifiers, mounted junction up on C-mounts, to allow separate contact to single mode and amplifier sections. A maximum coherently combined power of 12.9 W is demonstrated in a nearly diffraction-limited beam, corresponding to a 65% combining efficiency, with power mainly limited by the intrinsic beam quality of the amplifiers. Further increased combined power is currently sought.

Aligning Arrays of Lenses and Single-Mode Optical Fibers

NASA Technical Reports Server (NTRS)

Liu, Duncan

2004-01-01

A procedure now under development is intended to enable the precise alignment of sheet arrays of microscopic lenses with the end faces of a coherent bundle of as many as 1,000 single-mode optical fibers packed closely in a regular array (see Figure 1). In the original application that prompted this development, the precise assembly of lenses and optical fibers serves as a single-mode spatial filter for a visible-light nulling interferometer. The precision of alignment must be sufficient to limit any remaining wavefront error to a root-mean-square value of less than 1/10 of a wavelength of light. This wavefront-error limit translates to requirements to (1) ensure uniformity of both the lens and fiber arrays, (2) ensure that the lateral distance from the central axis of each lens and the corresponding optical fiber is no more than a fraction of a micron, (3) angularly align the lens-sheet planes and the fiber-bundle end faces to within a few arc seconds, and (4) axially align the lenses and the fiber-bundle end faces to within tens of microns of the focal distance. Figure 2 depicts the apparatus used in the alignment procedure. The beam of light from a Zygo (or equivalent) interferometer is first compressed by a ratio of 20:1 so that upon its return to the interferometer, the beam will be magnified enough to enable measurement of wavefront quality. The apparatus includes relay lenses that enable imaging of the arrays of microscopic lenses in a charge-coupled-device (CCD) camera that is part of the interferometer. One of the arrays of microscopic lenses is mounted on a 6-axis stage, in proximity to the front face of the bundle of optical fibers. The bundle is mounted on a separate stage. A mirror is attached to the back face of the bundle of optical fibers for retroreflection of light. When a microscopic lens and a fiber are aligned with each other, the affected portion of the light is reflected back by the mirror, recollimated by the microscopic lens, transmitted through the relay lenses and the beam compressor/expander, then split so that half goes to a detector and half to the interferometer. The output of the detector is used as a feedback control signal for the six-axis stage to effect alignment.

Parametric analysis of synthetic aperture radar data acquired over truck garden vegetation

NASA Technical Reports Server (NTRS)

Wu, S. T.

1984-01-01

An airborne X-band SAR acquired multipolarization and multiflight pass SAR images over a truck garden vegetation area. Based on a variety of land cover and row crop direction variations, the vertical (VV) polarization data contain the highest contrast, while cross polarization contains the least. When the radar flight path is parallel to the row direction, both horizontal (HH) and VV polarization data contain very high return which masks out the specific land cover that forms the row structure. Cross polarization data are not that sensitive to row orientation. The inclusion of like and cross polarization data help delineate special surface features (e.g., row crop against non-row-oriented land cover, very-rough-surface against highly row-oriented surface).

MOBILE GAMMA IRRADIATORS FOR FRUIT PRODUCE (Engineering Materials)

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

None

1963-10-31

Mobile irradiators used for the radiopasteurization of strawberries, grapes, peaches, tomatoes, and lemons are described. The irradiators are mounted on trailers and each irradiator, including the trailer, weighs 70 to 80 tons. Radiatton doses range from 100,000 to 200,000 rads. Minimum production is 500 lb of fruit per hour. Drawings are included for four types of irradiators: the single-slab twopass, double-slab one-pass, single-slab four-pass, and line-source rotary. In the single-slab two-pass system, the packages make two passes in front of the source. The length of the packages is parallel to the direction of travel. The packages are irradiated on eachmore » side. This system is light in weight, has low capital cost, and is simple to fabricate. The double-slab one- pass system is the same as the above except the source strength is doubled and irradiation time is cut in half. The same arrangement is used in the single-slab four-pass system that is used in the singleslab two-pass system except the packages make two passes on each side of the source. The rotary system combines a linear and rotary motion to provide high dosage. It uses a small Co/sup 60/ source but costs more than a single-slab twopass system. (F.E.S.)« less

Suppression of thermal transients in advanced LIGO interferometers using CO2 laser preheating

NASA Astrophysics Data System (ADS)

Jaberian Hamedan, V.; Zhao, C.; Ju, L.; Blair, C.; Blair, D. G.

2018-06-01

In high optical power interferometric gravitational wave detectors, such as Advanced LIGO, the thermal effects due to optical absorption in the mirror coatings and the slow thermal response of fused silica substrate cause time dependent changes in the mirror profile. After locking, high optical power builds up in the arm cavities. Absorption induced heating causes optical cavity transverse mode frequencies to drift over a period of hours, relative to the fundamental mode. At high optical power this can cause time dependent transient parametric instability, which can lead to interferometer disfunction. In this paper, we model the use of CO2 laser heating designed to enable the interferometer to be maintained in a thermal condition such that transient changes in the mirrors are greatly reduced. This can minimize transient parametric instability and compensate dark port power fluctuations. Modeling results are presented for both single compensation where a CO2 laser acting on one test mass per cavity, and double compensation using one CO2 laser for each test mass. Using parameters of the LIGO Hanford Observatory X-arm as an example, single compensation allows the maximum mode frequency shift to be limited to 6% of its uncompensated value. However, single compensation causes transient degradation of the contrast defect. Double compensation minimise contrast defect degradation and reduces transients to less than 1% if the CO2 laser spot is positioned within 2 mm of the cavity beam position.

Radar investigation of asteroids

NASA Astrophysics Data System (ADS)

Ostro, S. J.

1984-07-01

The initial radar observations of the mainbelt asteroids 9 Metis, 27 Euterpe, and 60 Echo are examined. For each target, data are taken simultaneously in the same sense of circular polarization as transmitted as well as in the opposite (OC) sense. Estimates of the radar cross sections provide estimates of the circular polarization ratio, and the normalized OC radar cross section. The circular polarization ratio, is comparable to values measured for other large S type asteroids and for a few much smaller, Earth approaching objects, most of the echo is due to single reflection backscattering from smooth surface elements.

Radar investigation of asteroids

NASA Technical Reports Server (NTRS)

Ostro, S. J.

1984-01-01

The initial radar observations of the mainbelt asteroids 9 Metis, 27 Euterpe, and 60 Echo are examined. For each target, data are taken simultaneously in the same sense of circular polarization as transmitted as well as in the opposite (OC) sense. Estimates of the radar cross sections provide estimates of the circular polarization ratio, and the normalized OC radar cross section. The circular polarization ratio, is comparable to values measured for other large S type asteroids and for a few much smaller, Earth approaching objects, most of the echo is due to single reflection backscattering from smooth surface elements.

A microprogrammable radar controller

NASA Technical Reports Server (NTRS)

Law, D. C.

1986-01-01

The Wave Propagation Lab. has completed the design and construction of a microprogrammable radar controller for atmospheric wind profiling. Unlike some radar controllers using state machines or hardwired logic for radar timing, this design is a high speed programmable sequencer with signal processing resources. A block diagram of the device is shown. The device is a single 8 1/2 inch by 10 1/2 inch printed circuit board and consists of three main subsections: (1) the host computer interface; (2) the microprogram sequencer; and (3) the signal processing circuitry. Each of these subsections are described in detail.

An Initial Assessment of the Surface Reference Technique Applied to Data from the Dual-Frequency Precipitation Radar (DPR) on the GPM Satellite

NASA Technical Reports Server (NTRS)

Meneghini, Robert; Kim, Hyokyung; Liao, Liang; Jones, Jeffrey A.; Kwiatkowski, John M.

2015-01-01

It has long been recognized that path-integrated attenuation (PIA) can be used to improve precipitation estimates from high-frequency weather radar data. One approach that provides an estimate of this quantity from airborne or spaceborne radar data is the surface reference technique (SRT), which uses measurements of the surface cross section in the presence and absence of precipitation. Measurements from the dual-frequency precipitation radar (DPR) on the Global Precipitation Measurement (GPM) satellite afford the first opportunity to test the method for spaceborne radar data at Ka band as well as for the Ku-band-Ka-band combination. The study begins by reviewing the basis of the single- and dual-frequency SRT. As the performance of the method is closely tied to the behavior of the normalized radar cross section (NRCS or sigma(0)) of the surface, the statistics of sigma(0) derived from DPR measurements are given as a function of incidence angle and frequency for ocean and land backgrounds over a 1-month period. Several independent estimates of the PIA, formed by means of different surface reference datasets, can be used to test the consistency of the method since, in the absence of error, the estimates should be identical. Along with theoretical considerations, the comparisons provide an initial assessment of the performance of the single- and dual-frequency SRT for the DPR. The study finds that the dual-frequency SRT can provide improvement in the accuracy of path attenuation estimates relative to the single-frequency method, particularly at Ku band.

The low coherence Fabry-Pérot interferometer with diamond and ZnO layers

NASA Astrophysics Data System (ADS)

Majchrowicz, D.; Den, W.; Hirsch, M.

2016-09-01

The authors present a fiber-optic Fabry-Pérot interferometer built with the application of diamond and zinc oxide (ZnO) thin layers. Thin ZnO films were deposited on the tip of a standard telecommunication single-mode optical fiber (SMF- 28) while the diamond layer was grown on the plate of silicon substrate. Investigated ZnO layers were fabricated by atomic layer deposition (ALD) and the diamond films were deposited using Microwave Plasma Enhanced Chemical Vapor Deposition (μPE CVD) system. Different thickness of layers was examined. The measurements were performed for the fiber-optic Fabry-Pérot interferometer working in the reflective mode. Spectra were registered for various thicknesses of ZnO layer and various length of the air cavity. As a light source, two superluminescent diodes (SLD) with central wavelength of 1300 nm and 1550 nm were used in measurement set-up.

Optical Fiber-Tip Sensors Based on In-Situ µ-Printed Polymer Suspended-Microbeams.

PubMed

Yao, Mian; Ouyang, Xia; Wu, Jushuai; Zhang, A Ping; Tam, Hwa-Yaw; Wai, P K A

2018-06-05

Miniature optical fiber-tip sensors based on directly µ-printed polymer suspended-microbeams are presented. With an in-house optical 3D μ-printing technology, SU-8 suspended-microbeams are fabricated in situ to form Fabry⁻Pérot (FP) micro-interferometers on the end face of standard single-mode optical fiber. Optical reflection spectra of the fabricated FP micro-interferometers are measured and fast Fourier transform is applied to analyze the cavity of micro-interferometers. The applications of the optical fiber-tip sensors for refractive index (RI) sensing and pressure sensing, which showed 917.3 nm/RIU to RI change and 4.29 nm/MPa to pressure change, respectively, are demonstrated in the experiments. The sensors and their optical µ-printing method unveil a new strategy to integrate complicated microcomponents on optical fibers toward 'lab-on-fiber' devices and applications.

Fabry-Perot Interferometry in the Integer and Fractional Quantum Hall Regimes

NASA Astrophysics Data System (ADS)

McClure, Douglas; Chang, Willy; Kou, Angela; Marcus, Charles; Pfeiffer, Loren; West, Ken

2011-03-01

We present measurements of electronic Fabry-Perot interferometers in the integer and fractional quantum Hall regimes. Two classes of resistance oscillations may be seen as a function of magnetic field and gate voltage, as we have previously reported. In small interferometers in the integer regime, oscillations of the type associated with Coulomb interaction are ubiquitous, while those consistent with single-particle Aharonov-Bohm interference are seen to co-exist in some configurations. The amplitude scaling of both types with temperature and device size is consistent with a theoretical model. Oscillations are further observed in the fractional quantum Hall regime. Here the dependence of the period on the filling factors in the constrictions and bulk of the interferometer can shed light on the effective charge of the interfering quasiparticles, but care is needed to distinguish these oscillations from those associated with integer quantum Hall states. We acknowledge funding from Microsoft Project Q and IBM.

Mach-Zehnder interferometry using broken symmetry quantum Hall edges in graphene

NASA Astrophysics Data System (ADS)

Wei, Di; van der Sar, Toeno; Sanchez-Yamagishi, Javier; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo; Halperin, Bertrand; Yacoby, Amir

Graphene has emerged as a unique platform for studying electron optics, particularly in the presence of a magnetic field. Here, we engineer a Mach-Zehnder interferometer using quantum Hall edge states that co-propagate along a single gate-defined NP interface. We use encapsulated monolayer graphene, clean enough to lift the four-fold spin and valley degeneracy. In order to create two separate co-propagating paths, we exploit the suppression of edge state scattering along gate defined edges, and use scattering sites at the ends of the NP interface to form our beam splitters. We observe conductance oscillations as a function of magnetic and electric field indicative of coherent transport, and measure values consistent with spin-selective scattering. We can tune our interferometer to regimes of high visibility (>98 %), surpassing the values reported for GaAs quantum-well Mach-Zehnder interferometers. These results demonstrate a promising method to observe interference between fractional charges in graphene.

Application of thin dielectric films in low coherence fiber-optic Fabry-Pérot sensing interferometers: comparative study

NASA Astrophysics Data System (ADS)

Hirsch, Marzena; Wierzba, Paweł; Jedrzejewska-Szczerska, Małgorzata

2016-11-01

We examine the application of selected thin dielectric films, deposited by atomic layer deposition (ALD), in a low coherence fiber-optic Fabry-Pérot interferometer designed for sensing applications. Such films can be deposited on the end-face of a single mode optical fiber (SMF-28) in order to modify the reflectivity of the Fabry-Pérot cavity, to provide protection of the fibers from aggressive environments or to create a multi-cavity interferometric sensor. Spectral reflectance of films made from zinc oxide (ZnO), titanium dioxide (TiO2), aluminum oxide (Al2O3) and boron nitride (BN) was calculated for various thickness of the films and compared. The results show that the most promising materials for use in fiber-optic Fabry-Pérot interferometer are TiO2 and ZnO, although Al2O3 is also suitable for this application.

Pressure sensing of Fabry-Perot interferometer with a microchannel demodulated by a FBG

NASA Astrophysics Data System (ADS)

Yu, Yongqin; Chen, Xue; Huang, Quandong; Du, Chenlin; Ruan, Shuangchen

2015-07-01

A novel and compact fiber-probe pressure sensor was demonstrated based on micro Fabry-Perot interferometer (FPI). The device was fabricated by splicing both ends of a short section simplified hollow-core photonic crystal fiber (SHCPCF) with single mode fibers (SMFs), and then a micro channel was drilled by femtosecond laser micromachining in the SHC-PCF to significantly enhance the pressure sensitivity. The pressure sensing characteristics based on micro-FPI have been investigated by measuring the signals through the demodulation of phase since the external signal imposing on the interferometer will induce the phase change of interference signal. Then a FBG was cascaded to demodulate the signal. A micro FPI demonstrates a maximum pressure sensitivity of 32 dB/MPa, while a low temperature cross-sensitivity of 0.27 KPa/°C. Hence it may have potential for pressure applications in harsh environment.

First planet confirmation with the exoplanet tracker

NASA Astrophysics Data System (ADS)

van Eyken, Julian C.; Ge, Jian C.; Mahadevan, Suvrath; DeWitt, Curtis; Ren, Deqing

2003-11-01

The Exoplanet Tracker (ET) is a new concept of instrument for measuring stellar radial velocity variations. ET is based on a dispersed fixed-delay interferometer, a combination of Michelson interferometer and medium resolution (R~6700) spectrograph which overlays interferometer fringes on a long-slit stellar spectrum. By measuring shifts in the fringes rather than the Doppler shifts in the absorption lines themselves, we are able to make accurate stellar radial velocity measurements with a high throughput and low cost instrument. The single-order operation of the instrument can also in principle allow multi-object observations. We plan eventually to conduct deep large scale surveys for extra-solar planets using this technique. We present confirmation of the planetary companion to 51Peg from our first stellar observations at the Kitt Peak 2.1m telescope, showing results consistent with previous observations. We outline the fundamentals of the instrument, and summarize our current progress in terms of accuracy and throughput.

Search for Transient Gravitational Waves in Coincidence with Short-Duration Radio Transients During 2007-2013

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Hughey, Brennan; Zanolin, Michele; Szczepanczyk, Marek; Gill, Kiranjyot; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.;

Weak values of spin and momentum in atomic systems.

NASA Astrophysics Data System (ADS)

Flack, Robert; Hiley, Basil; Barker, Peter; Monachello, Vincenzo; Morley, Joel

2017-04-01

Weak values have a long history and were first considered by Landau and London in connection with superfluids. Hirschfelder called them sub-observables and Dirac anticipatied them when discussing non-commutative geometry in quantum mechanics. The idea of a weak value has returned to prominence due to Aharonov, Albert and Vaidman showing how they can be measured. They are not eigenvalues of the system and can not be measured by a collapse of the wave function with the traditional Von Neumann (strong) measurement which is a single stage process. In contrast the weak measurement process has three stages; preselection, weak stage and finally a post selection. Although weak values have been observed using photons and neutrons, we are building two experiments to observe weak values of spin and momentum in atomic systems. For spin we are following the method outlined by Duck et al which is a variant on the original Stern-Gerlach experiment using a metastable, 23S1 , form of helium. For momentum we are using a method similar to that used by Kocsis with excited argon atoms in the 3P2 state, passing through a 2-slit interferometer. The design, simulation and re John Fetzer Memorial Trust.

Increase in velocimeter depth of focus through astigmatism. Revision 1

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

Erskine, D.J.

1995-09-26

Frequently, velocimeter targets are illuminated by a laser beam passing through a hole in a mirror. This mirror is responsible for diverting returning light from a target lens to a velocity interferometer system for any reflector (VISAR). This mirror is often a significant distance from the target lens. Consequently, at certain target focus positions the returning light is strongly vignetted by the hole, causing a loss of signal. The authors find that they can prevent loss of signal and greatly increase the useful depth of focus by attaching a cylindrical lens to the target lens.

Analysis of the fluctuations of a laser beam due to thermal turbulence

NASA Astrophysics Data System (ADS)

Ndlovu, Sphumelele C.; Chetty, Naven

2014-07-01

A laser beam propagating in air and passing through a point diffraction interferometer (PDI) produces stable interferograms that can be used to extract wavefront data such as major atmospheric characteristics: turbulence strength, inner scale and outer scale of the refractive index. These parameters need to be taken into consideration when developing defense laser weapons since they can be affected by thermal fluctuations that are due to the changes in temperature in close proximity to the propagating beam and results in phase shifts that can be used to calculate the temperature which causes wavefront perturbations on a propagating beam.

Using TRMM and GPM precipitation radar for calibration of weather radars in the Philippines

NASA Astrophysics Data System (ADS)

Crisologo, Irene; Bookhagen, Bodo; Smith, Taylor; Heistermann, Maik

2016-04-01

Torrential and sustained rainfall from tropical cyclones, monsoons, and thunderstorms frequently impact the Philippines. In order to predict, assess, and measure storm impact, it is imperative to have a reliable and accurate monitoring system in place. In 2011, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) established a weather radar network of ten radar devices, eight of which are single-polarization S-band radars and two dual-polarization C-band radars. Because of a low-density hydrometeorological monitoring networks in the Philippines, calibration of weather radars becomes a challenging, but important task. In this study, we explore the potential of scrutinizing the calibration of ground radars by using the observations from the Tropical Rainfall Measuring Mission (TRMM). For this purpose, we compare different TRMM level 1 and 2 orbital products from overpasses over the Philippines, and compare these products to reflectivities observed by the Philippine ground radars. Differences in spatial resolution are addressed by computing adequate zonal statistics of the local radar bins located within the corresponding TRMM cell in space and time. The wradlib package (Heistermann et al. 2013; Heistermann et al. 2015) is used to process the data from the Subic S-band single-polarization weather radar. These data will be analyzed in conjunction with TRMM data for June to August 2012, three months of the wet season. This period includes the enhanced monsoon of 2012, locally called Habagat 2012, which brought sustained intense rainfall and massive floods in several parts of the country including the most populated city of Metro Manila. References Heistermann, M., Jacobi, S., Pfaff, T. (2013): Technical Note: An open source library for processing weather radar data (wradlib). Hydrol. Earth Syst. Sci., 17, 863-871, doi: 10.5194/hess-17-863-2013. Heistermann, M., S. Collis, M. J. Dixon, S. Giangrande, J. J. Helmus, B. Kelley, J. Koistinen, D. Michelson, M. Peura, T. Pfaff, D. B. Wolff (2015): The Emergence of Open Source Software for the Weather Radar Community, Bull. Amer. Meteor. Soc., doi: 10.1175/BAMS-D-13-00240.1

Arrayed waveguide Sagnac interferometer.

PubMed

Capmany, José; Muñoz, Pascual; Sales, Salvador; Pastor, Daniel; Ortega, Beatriz; Martinez, Alfonso

2003-02-01

We present a novel device, an arrayed waveguide Sagnac interferometer, that combines the flexibility of arrayed waveguides and the wide application range of fiber or integrated optics Sagnac loops. We form the device by closing an array of wavelength-selective light paths provided by two arrayed waveguides with a single 2 x 2 coupler in a Sagnac configuration. The equations that describe the device's operation in general conditions are derived. A preliminary experimental demonstration is provided of a fiber prototype in passive operation that shows good agreement with the expected theoretical performance. Potential applications of the device in nonlinear operation are outlined and discussed.

OHANA, the Optical Hawaiian Array for Nanoradian Astronomy. Towards kilometric infrared arrays

NASA Astrophysics Data System (ADS)

Perrin, G.

Optical/Infrared Interferometry has become a mature technique with more and more astrophysical results in the past years. For historical and technical reasons, the traditional field of investigation of interferometers is stellar physics. With the advent of large telescopes and adaptive optics, more resolving and more sensitive interferometers are within reach with the promise to widen the target list. In particular, extragalactic sources will benefit from this revolution. A prototype instrument, 'OHANA, is described here. 'OHANA uses single-mode fibers to turn the large telescopes of the Mauna Kea summit into a large near-infrared kilometric array.

Microvibrations in a 20 M Long Ka-Band SAR Interferometer

NASA Astrophysics Data System (ADS)

Rodriques, G.; Ludwig, M.; Santiago-Prowald, J.

2014-06-01

Interferometric SAR operating at Ka-band has the potential for offering high-resolution 3D images of the surface of the Earth taken from a single-platform.The stability of the mechanical baseline of such an instrument has been considered as a key critical area for the feasibility of the concept.This paper is devoted to the analysis of the micro- vibrations in a 20-m long Ka-band SAR interferometer arising during typical attitude changing manoeuvers and the mechanical noise transmitted from reaction wheels. It is preliminarily concluded that the expected microvibration levels are within the requirements of the instrument.

Fiber Fabry-Perot interferometer sensor for measuring resonances of piezoelectric elements

NASA Astrophysics Data System (ADS)

da Silva, Ricardo E.; Oliveira, Roberson A.; Pohl, Alexandre A. P.

2011-05-01

The development of a fiber extrinsic Fabry-Perot interferometer for measuring vibration amplitude and resonances of piezoelectric elements is reported. The signal demodulation method based on the use of an optical spectrum analyzer allows the measurement of displacements and resonances with high resolution. The technique consists basically in monitoring changes in the intensity or the wavelength of a single interferometric fringe at a point of high sensitivity in the sensor response curve. For sensor calibration, three signal processing techniques were employed. Vibration amplitude measurement with 0.84 nm/V sensitivity and the characterization of the piezo resonance is demonstrated.

Study of Optical Fiber Sensors for Cryogenic Temperature Measurements.

PubMed

De Miguel-Soto, Veronica; Leandro, Daniel; Lopez-Aldaba, Aitor; Beato-López, Juan Jesus; Pérez-Landazábal, José Ignacio; Auguste, Jean-Louis; Jamier, Raphael; Roy, Philippe; Lopez-Amo, Manuel

2017-11-30

In this work, the performance of five different fiber optic sensors at cryogenic temperatures has been analyzed. A photonic crystal fiber Fabry-Pérot interferometer, two Sagnac interferometers, a commercial fiber Bragg grating (FBG), and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser have been studied. Their sensitivities and resolutions as sensors for cryogenic temperatures have been compared regarding their advantages and disadvantages. Additionally, the results have been compared with the given by a commercial optical backscatter reflectometer that allowed for distributed temperature measurements of a single mode fiber.