Laser-Ranging Transponders for Science Investigations of the Moon and Mars

NASA Technical Reports Server (NTRS)

Hemmati, Hamid; Chen, Yijiang; Bimbaum, Kevin

2012-01-01

An active laser was developed ranging in real-time with two terminals, emulating interplanetary distances, and with submillimeter accuracy. In order to overcome the limitations to ranging accuracy from jitters and delay drifts within the transponders, architecture was proposed based on asynchronous paired one-way ranging with local references. A portion of the transmitted light is directed, via a reference path, to the local detector. This allows for compensation of any jitter in the timing of the emitted laser pulse. The same detector is used to measure the time of the received pulses emitted from the remote terminal. This approach removes any change in the delay caused by the detector or its electronics. Two separate terminals using commercial off-the-shelf hardware were built to emulate active laser ranging over interplanetary distances. The communication link for the command to start recording pulse arrival times and data transfer from one terminal to the other was achieved using a standard wireless link, emulating free space laser communication. The deviation is well below the goal of 1-mm precision. This leaves enough margin to achieve 1-mm precision when including the fluctuations due to atmospheric turbulence while ranging to Mars through the Earth s atmosphere. The two terminals are mounted on translation stages, which can be moved freely on rails to yield a wide range of distances with fine adjustment. The two terminals were separated by approximately 16 meters.

Demonstration of high sensitivity laser ranging system

NASA Technical Reports Server (NTRS)

Millar, Pamela S.; Christian, Kent D.; Field, Christopher T.

1994-01-01

We report on a high sensitivity semiconductor laser ranging system developed for the Gravity and Magnetic Earth Surveyor (GAMES) for measuring variations in the planet's gravity field. The GAMES laser ranging instrument (LRI) consists of a pair of co-orbiting satellites, one which contains the laser transmitter and receiver and one with a passive retro-reflector mounted in an drag-stabilized housing. The LRI will range up to 200 km in space to the retro-reflector satellite. As the spacecraft pair pass over the spatial variations in the gravity field, they experience along-track accelerations which change their relative velocity. These time displaced velocity changes are sensed by the LRI with a resolution of 20-50 microns/sec. In addition, the pair may at any given time be drifting together or apart at a rate of up to 1 m/sec, introducing a Doppler shift into the ranging signals. An AlGaAs laser transmitter intensity modulated at 2 GHz and 10 MHz is used as fine and medium ranging channels. Range is measured by comparing phase difference between the transmit and received signals at each frequency. A separate laser modulated with a digital code, not reported in this paper, will be used for coarse ranging to unambiguously determine the distance up to 200 km.

Improved pulse laser ranging algorithm based on high speed sampling

NASA Astrophysics Data System (ADS)

Gao, Xuan-yi; Qian, Rui-hai; Zhang, Yan-mei; Li, Huan; Guo, Hai-chao; He, Shi-jie; Guo, Xiao-kang

2016-10-01

Narrow pulse laser ranging achieves long-range target detection using laser pulse with low divergent beams. Pulse laser ranging is widely used in military, industrial, civil, engineering and transportation field. In this paper, an improved narrow pulse laser ranging algorithm is studied based on the high speed sampling. Firstly, theoretical simulation models have been built and analyzed including the laser emission and pulse laser ranging algorithm. An improved pulse ranging algorithm is developed. This new algorithm combines the matched filter algorithm and the constant fraction discrimination (CFD) algorithm. After the algorithm simulation, a laser ranging hardware system is set up to implement the improved algorithm. The laser ranging hardware system includes a laser diode, a laser detector and a high sample rate data logging circuit. Subsequently, using Verilog HDL language, the improved algorithm is implemented in the FPGA chip based on fusion of the matched filter algorithm and the CFD algorithm. Finally, the laser ranging experiment is carried out to test the improved algorithm ranging performance comparing to the matched filter algorithm and the CFD algorithm using the laser ranging hardware system. The test analysis result demonstrates that the laser ranging hardware system realized the high speed processing and high speed sampling data transmission. The algorithm analysis result presents that the improved algorithm achieves 0.3m distance ranging precision. The improved algorithm analysis result meets the expected effect, which is consistent with the theoretical simulation.

Eighth International Workshop on Laser Ranging Instrumentation

NASA Technical Reports Server (NTRS)

Degnan, John J. (Compiler)

1993-01-01

The Eighth International Workshop for Laser Ranging Instrumentation was held in Annapolis, Maryland in May 1992, and was sponsored by the NASA Goddard Space Flight Center in Greenbelt, Maryland. The workshop is held once every 2 to 3 years under differing institutional sponsorship and provides a forum for participants to exchange information on the latest developments in satellite and lunar laser ranging hardware, software, science applications, and data analysis techniques. The satellite laser ranging (SLR) technique provides sub-centimeter precision range measurements to artificial satellites and the Moon. The data has application to a wide range of Earth and lunar science issues including precise orbit determination, terrestrial reference frames, geodesy, geodynamics, oceanography, time transfer, lunar dynamics, gravity and relativity.

Current Trends and Challenges in Satellite Laser Ranging

NASA Astrophysics Data System (ADS)

Appleby, Graham M.; Bianco, Giuseppe; Noll, Carey E.; Pavlis, Erricos C.; Pearlman, Michael R.

2016-12-01

greatly enhancing efficiency. Discussions are ongoing with some missions that will allow the SLR network stations to provide crucial, but energy-safe, range measurements to optically vulnerable satellites. New retro-reflector designs are improving the signal link and enable daylight ranging that is now the norm for many stations. We discuss many of these laser ranging activities and some of the tough challenges that the SLR network currently faces.

Quantum cascade lasers (QCL) for active hyperspectral imaging

NASA Astrophysics Data System (ADS)

Yang, Quankui; Fuchs, Frank; Wagner, Joachim

2014-04-01

There is an increasing demand for wavelength agile laser sources covering the mid-infrared (MIR, 3.5-12 µm) wavelength range, among others in active imaging. The MIR range comprises a particularly interesting part of the electromagnetic spectrum for active hyperspectral imaging applications, due to the fact that the characteristic `fingerprint' absorption spectra of many chemical compounds lie in that range. Conventional semiconductor diode laser technology runs out of steam at such long wavelengths. For many applications, MIR coherent light sources based on solid state lasers in combination with optical parametric oscillators are too complex and thus bulky and expensive. In contrast, quantum cascade lasers (QCLs) constitute a class of very compact and robust semiconductor-based lasers, which are able to cover the mentioned wavelength range using the same semiconductor material system. In this tutorial, a brief review will be given on the state-of-the-art of QCL technology. Special emphasis will be addressed on QCL variants with well-defined spectral properties and spectral tunability. As an example for the use of wavelength agile QCL for active hyperspectral imaging, stand-off detection of explosives based on imaging backscattering laser spectroscopy will be discussed.

Stable method for estimation of laser ranging

NASA Astrophysics Data System (ADS)

Kurbasova, G. S.; Rykhlova, L. V.

A noise-immunity variant of the least squares method was developed for the preliminary analysis of laser-ranging data. The method takes into account the influence of many physical phenomena accompanying the generation of the laser-ranging signals, their passing through the optical channel, the distribution in the atmosphere, the scattering on the corner reflector, and their registration. The method was demonstrated on the example of Lageos observations made with the Intercosmos laser radar.

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

Ranging performance of satellite laser altimeters

NASA Technical Reports Server (NTRS)

Gardner, Chester S.

1992-01-01

Topographic mapping of the earth, moon and planets can be accomplished with high resolution and accuracy using satellite laser altimeters. These systems employ nanosecond laser pulses and microradian beam divergences to achieve submeter vertical range resolution from orbital altitudes of several hundred kilometers. Here, we develop detailed expressions for the range and pulse width measurement accuracies and use the results to evaluate the ranging performances of several satellite laser altimeters currently under development by NASA for launch during the next decade. Our analysis includes the effects of the target surface characteristics, spacecraft pointing jitter and waveform digitizer characteristics. The results show that ranging accuracy is critically dependent on the pointing accuracy and stability of the altimeter especially over high relief terrain where surface slopes are large. At typical orbital altitudes of several hundred kilometers, single-shot accuracies of a few centimeters can be achieved only when the pointing jitter is on the order of 10 mu rad or less.

Poisson filtering of laser ranging data

NASA Technical Reports Server (NTRS)

Ricklefs, Randall L.; Shelus, Peter J.

1993-01-01

The filtering of data in a high noise, low signal strength environment is a situation encountered routinely in lunar laser ranging (LLR) and, to a lesser extent, in artificial satellite laser ranging (SLR). The use of Poisson statistics as one of the tools for filtering LLR data is described first in a historical context. The more recent application of this statistical technique to noisy SLR data is also described.

Two-way laser ranging and time transfer experiments between LOLA and an Earth-based satellite laser ranging station

NASA Astrophysics Data System (ADS)

Mao, D.; Sun, X.; Neumann, G. A.; Barker, M. K.; Mazarico, E. M.; Hoffman, E.; Zagwodzki, T. W.; Torrence, M. H.; Mcgarry, J.; Smith, D. E.; Zuber, M. T.

2017-12-01

Satellite Laser Ranging (SLR) has established time-of-flight measurements with mm precision to targets orbiting the Earth and the Moon using single-ended round-trip laser ranging to passive optical retro-reflectors. These high-precision measurements enable advances in fundamental physics, solar system dynamics. However, the received signal strength suffers from a 1/R4 decay, which makes it impractical for measuring distances beyond the Moon's orbit. On the other hand, for a two-way laser transponder pair, where laser pulses are both transmitted to and received from each end of the laser links, the signal strength at both terminals only decreases by 1/R2, thus allowing a greater range of distances to be covered. The asynchronous transponder concept has been previously demonstrated by a test in 2005 between the Mercury Laser Altimeter (MLA) aboard the MESSENGER (MErcury Surface, Space ENvironment, Geochemistry, and Ranging) spacecraft and NASA's Goddard Geophysical and Astronomical Observatory (GGAO) at a distance of ˜0.16 AU. In October 2013, regular two-way transponder-type range measurements were obtained over 15 days between the Lunar Laser Communication Demonstration (LLCD) aboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft and NASA's ground station at White Sands, NM. The Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter (LRO) provides us a unique capability to test time-transfer beyond near Earth orbit. Here we present results from two-way transponder-type experiments between LOLA and GGAO conducted in March 2014 and 2017. As in the time-transfer by laser link (T2L2) experiments between a ground station and an earth-orbiting satellite, LOLA and GGAO ranged to each other simultaneously in these two-way tests at lunar distance. We measured the time-of-flight while cross-referencing the spacecraft clock to the ground station time. On May 4th, 2017, about 20 minutes of two-way measurements were collected. The

Current Trends in Satellite Laser Ranging

NASA Technical Reports Server (NTRS)

Pearlman, M. R.; Appleby, G. M.; Kirchner, G.; McGarry, J.; Murphy, T.; Noll, C. E.; Pavlis, E. C.; Pierron, F.

2010-01-01

Satellite Laser Ranging (SLR) techniques are used to accurately measure the distance from ground stations to retroreflectors on satellites and the moon. SLR is one of the fundamental techniques that define the international Terrestrial Reference Frame (iTRF), which is the basis upon which we measure many aspects of global change over space, time, and evolving technology. It is one of the fundamental techniques that define at a level of precision of a few mm the origin and scale of the ITRF. Laser Ranging provides precision orbit determination and instrument calibration/validation for satellite-borne altimeters for the better understanding of sea level change, ocean dynamics, ice budget, and terrestrial topography. Laser ranging is also a tool to study the dynamics of the Moon and fundamental constants. Many of the GNSS satellites now carry retro-reflectors for improved orbit determination, harmonization of reference frames, and in-orbit co-location and system performance validation. The GNSS Constellations will be the means of making the reference frame available to worldwide users. Data and products from these measurements support key aspects of the GEOSS 10-Year implementation Plan adopted on February 16, 2005, The ITRF has been identified as a key contribution of the JAG to GEOSS and the ILRS makes a major contribution for its development since its foundation. The ILRS delivers weekly additional realizations that are accumulated sequentially to extend the ITRF and the Earth Orientation Parameter (EOP) series with a daily resolution. Additional products are currently under development such as precise orbits of satellites, EOP with daily availability, low-degree gravitational harmonics for studies of Earth dynamics and kinematics, etc. SLR technology continues to evolve toward the next generation laser ranging systems as programmatic requirements become more stringent. Ranging accuracy is improving as higher repetition rate, narrower pulse lasers and faster

Test techniques for determining laser ranging system performance

NASA Technical Reports Server (NTRS)

Zagwodzki, T. W.

1981-01-01

Procedures and results of an on going test program intended to evaluate laser ranging system performance levels in the field as well as in the laboratory are summarized. Tests show that laser ranging system design requires consideration of time biases and RMS jitters of individual system components. All simple Q switched lasers tested were found to be inadequate for 10 centimeter ranging systems. Timing discriminators operating over a typical 100:1 dynamic signal range may introduce as much as 7 to 9 centimeters of range bias. Time interval units commercially available today are capable of half centimeter performance and are adequate for all field systems currently deployed. Photomultipliers tested show typical tube time biases of one centimeter with single photoelectron transit time jitter of approximately 10 centimeters. Test results demonstrate that NASA's Mobile Laser Ranging System (MOBLAS) receiver configuration is limiting system performance below the 100 photoelectron level.

Comparison of three methods reducing the beam parameter product of a laser diode stack for long range laser illumination applications

NASA Astrophysics Data System (ADS)

Lutz, Yves; Poyet, Jean-Michel; Metzger, Nicolas

2013-10-01

Laser diode stacks are interesting laser sources for active imaging illuminators. They allow the accumulation of large amounts of energy in multi-pulse mode, which is well suited for long-range image recording. Even when laser diode stacks are equipped with fast-axis collimation (FAC) and slow-axis collimation (SAC) microlenses, their beam parameter product (BPP) are not compatible with a direct use in highly efficient and compact illuminators. This is particularly true when narrow divergences are required such as for long range applications. To overcome these difficulties, we conducted investigations in three different ways. A first near infrared illuminator based on the use of conductively cooled mini-bars was designed, realized and successfully tested during outdoor experimentations. This custom specified stack was then replaced in a second step by an off-the-shelf FAC + SAC micro lensed stack where the brightness was increased by polarization overlapping. The third method still based on a commercial laser diode stack uses a non imaging optical shaping principle resulting in a virtually restacked laser source with enhanced beam parameters. This low cost, efficient and low alignment sensitivity beam shaping method allows obtaining a compact and high performance laser diode illuminator for long range active imaging applications. The three methods are presented and compared in this paper.

New methods of generation of ultrashort laser pulses for ranging

NASA Technical Reports Server (NTRS)

Jelinkova, Helena; Hamal, Karel; Kubecek, V.; Prochazka, Ivan

1993-01-01

To reach the millimeter satellite laser ranging accuracy, the goal for nineties, new laser ranging techniques have to be applied. To increase the laser ranging precision, the application of the ultrashort laser pulses in connection with the new signal detection and processing techniques, is inevitable. The two wavelength laser ranging is one of the ways to measure the atmospheric dispersion to improve the existing atmospheric correction models and hence, to increase the overall system ranging accuracy to the desired value. We are presenting a review of several nonstandard techniques of ultrashort laser pulses generation, which may be utilized for laser ranging: compression of the nanosecond pulses using stimulated Brillouin and Raman backscattering; compression of the mode-locked pulses using Raman backscattering; passive mode-locking technique with nonlinear mirror; and passive mode-locking technique with the negative feedback.

High Precision Laser Range Sensor

NASA Technical Reports Server (NTRS)

Dubovitsky, Serge (Inventor); Lay, Oliver P. (Inventor)

2003-01-01

The present invention is an improved distance measuring interferometer that includes high speed phase modulators and additional phase meters to generate and analyze multiple heterodyne signal pairs with distinct frequencies. Modulation sidebands with large frequency separation are generated by the high speed electro-optic phase modulators, requiring only a single frequency stable laser source and eliminating the need for a fist laser to be tuned or stabilized relative to a second laser. The combination of signals produced by the modulated sidebands is separated and processed to give the target distance. The resulting metrology apparatus enables a sensor with submicron accuracy or better over a multi- kilometer ambiguity range.

Evaluation of a satellite laser ranging technique using pseudonoise code modulated laser diodes

NASA Technical Reports Server (NTRS)

Ball, Carolyn Kay

1987-01-01

Several types of Satellite Laser Ranging systems exist, operating with pulsed, high-energy lasers. The distance between a ground point and an orbiting satellite can be determined to within a few centimeters. A new technique substitutes pseudonoise code modulated laser diodes, which are much more compact, reliable and less costly, for the lasers now used. Since laser diode technology is only now achieving sufficiently powerful lasers, the capabilities of the new technique are investigated. Also examined are the effects of using an avalanche photodiode detector instead of a photomultiplier tube. The influence of noise terms (including background radiation, detector dark and thermal noise and speckle) that limit the system range and performance is evaluated.

The solid state detector technology for picosecond laser ranging

NASA Technical Reports Server (NTRS)

Prochazka, Ivan

1993-01-01

We developed an all solid state laser ranging detector technology, which makes the goal of millimeter accuracy achievable. Our design and construction philosophy is to combine the techniques of single photon ranging, ultrashort laser pulses, and fast fixed threshold discrimination while avoiding any analog signal processing within the laser ranging chain. The all solid state laser ranging detector package consists of the START detector and the STOP solid state photon counting module. Both the detectors are working in an optically triggered avalanche switching regime. The optical signal is triggering an avalanche current buildup which results in the generation of a uniform, fast risetime output pulse.

Cassidy holds laser range finder in aft FD during Joint Operations

NASA Image and Video Library

2009-07-28

S127-E-011291 (28 July 2009) --- Astronauts Tom Marshburn (left) and Christopher Cassidy, both STS-127 mission specialists, look through an overhead window on the aft flight deck of Space Shuttle Endeavour during flight day 14 activities. Cassidy is holding a handheld laser ranging device -- designed to measure the range between two spacecraft.

Analysis of the restricting factors of laser countermeasure active detection technology

NASA Astrophysics Data System (ADS)

Zhang, Yufa; Sun, Xiaoquan

2016-07-01

The detection effect of laser active detection system is affected by various kinds of factors. In view of the application requirement of laser active detection, the influence factors for laser active detection are analyzed. The mathematical model of cat eye target detection distance has been built, influence of the parameters of laser detection system and the environment on detection range and the detection efficiency are analyzed. Various parameters constraint detection performance is simulated. The results show that the discovery distance of laser active detection is affected by the laser divergence angle, the incident angle and the visibility of the atmosphere. For a given detection range, the laser divergence angle and the detection efficiency are mutually restricted. Therefore, in view of specific application environment, it is necessary to select appropriate laser detection parameters to achieve optimal detection effect.

Unsynchronized scanning with a low-cost laser range finder for real-time range imaging

NASA Astrophysics Data System (ADS)

Hatipoglu, Isa; Nakhmani, Arie

2017-06-01

Range imaging plays an essential role in many fields: 3D modeling, robotics, heritage, agriculture, forestry, reverse engineering. One of the most popular range-measuring technologies is laser scanner due to its several advantages: long range, high precision, real-time measurement capabilities, and no dependence on lighting conditions. However, laser scanners are very costly. Their high cost prevents widespread use in applications. Due to the latest developments in technology, now, low-cost, reliable, faster, and light-weight 1D laser range finders (LRFs) are available. A low-cost 1D LRF with a scanning mechanism, providing the ability of laser beam steering for additional dimensions, enables to capture a depth map. In this work, we present an unsynchronized scanning with a low-cost LRF to decrease scanning period and reduce vibrations caused by stop-scan in synchronized scanning. Moreover, we developed an algorithm for alignment of unsynchronized raw data and proposed range image post-processing framework. The proposed technique enables to have a range imaging system for a fraction of the price of its counterparts. The results prove that the proposed method can fulfill the need for a low-cost laser scanning for range imaging for static environments because the most significant limitation of the method is the scanning period which is about 2 minutes for 55,000 range points (resolution of 250x220 image). In contrast, scanning the same image takes around 4 minutes in synchronized scanning. Once faster, longer range, and narrow beam LRFs are available, the methods proposed in this work can produce better results.

The integration of laser communication and ranging

NASA Astrophysics Data System (ADS)

Xu, Mengmeng; Sun, Jianfeng; Zhou, Yu; Zhang, Bo; Zhang, Guo; Li, Guangyuan; He, Hongyu; Lao, Chenzhe

2017-08-01

The method to realize the integration of laser communication and ranging is proposed in this paper. In the transmitter of two places, the ranging codes with uniqueness, good autocorrelation and cross-correlation properties are embed in the communication data and the encoded with the communication data to realize serial communication. And then the encoded data are modulated and send to each other, which can realize high speed two one-way laser communication. At the receiver, we can get the received ranging code after the demodulation, decoding and clock recovery. The received ranging codes and the local ranging codes do the autocorrelation to get a roughly range, while the phase difference between the local clock and the recovery clock to achieve the precision of the distance.

Note: Digital laser frequency auto-locking for inter-satellite laser ranging

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

Luo, Yingxin; Yeh, Hsien-Chi, E-mail: yexianji@mail.hust.edu.cn; Li, Hongyin

2016-05-15

We present a prototype of a laser frequency auto-locking and re-locking control system designed for laser frequency stabilization in inter-satellite laser ranging system. The controller has been implemented on field programmable gate arrays and programmed with LabVIEW software. The controller allows initial frequency calibrating and lock-in of a free-running laser to a Fabry-Pérot cavity. Since it allows automatic recovery from unlocked conditions, benefit derives to automated in-orbit operations. Program design and experimental results are demonstrated.

Satellite Laser Ranging operations

NASA Technical Reports Server (NTRS)

Pearlman, Michael R.

1994-01-01

Satellite Laser Ranging (SLR) is currently providing precision orbit determination for measurements of: 1) Ocean surface topography from satellite borne radar altimetry, 2) Spatial and temporal variations of the gravity field, 3) Earth and ocean tides, 4) Plate tectonic and regional deformation, 5) Post-glacial uplift and subsidence, 6) Variations in the Earth's center-of-mass, and 7) Variations in Earth rotation. SLR also supports specialized programs in time transfer and classical geodetic positioning, and will soon provide precision ranging to support experiments in relativity.

Estimability and simple dynamical analyses of range (range-rate range-difference) observations to artificial satellites. [laser range observations to LAGEOS using non-Bayesian statistics

NASA Technical Reports Server (NTRS)

Vangelder, B. H. W.

1978-01-01

Non-Bayesian statistics were used in simulation studies centered around laser range observations to LAGEOS. The capabilities of satellite laser ranging especially in connection with relative station positioning are evaluated. The satellite measurement system under investigation may fall short in precise determinations of the earth's orientation (precession and nutation) and earth's rotation as opposed to systems as very long baseline interferometry (VLBI) and lunar laser ranging (LLR). Relative station positioning, determination of (differential) polar motion, positioning of stations with respect to the earth's center of mass and determination of the earth's gravity field should be easily realized by satellite laser ranging (SLR). The last two features should be considered as best (or solely) determinable by SLR in contrast to VLBI and LLR.

Laser-Directed Ranging System Implementing Single Camera System for Telerobotics Applications

NASA Technical Reports Server (NTRS)

Wells, Dennis L. (Inventor); Li, Larry C. (Inventor); Cox, Brian J. (Inventor)

1995-01-01

The invention relates generally to systems for determining the range of an object from a reference point and, in one embodiment, to laser-directed ranging systems useful in telerobotics applications. Digital processing techniques are employed which minimize the complexity and cost of the hardware and software for processing range calculations, thereby enhancing the commercial attractiveness of the system for use in relatively low-cost robotic systems. The system includes a video camera for generating images of the target, image digitizing circuitry, and an associated frame grabber circuit. The circuit first captures one of the pairs of stereo video images of the target, and then captures a second video image of the target as it is partly illuminated by the light beam, suitably generated by a laser. The two video images, taken sufficiently close together in time to minimize camera and scene motion, are converted to digital images and then compared. Common pixels are eliminated, leaving only a digital image of the laser-illuminated spot on the target. Mw centroid of the laser illuminated spot is dm obtained and compared with a predetermined reference point, predetermined by design or calibration, which represents the coordinate at the focal plane of the laser illumination at infinite range. Preferably, the laser and camera are mounted on a servo-driven platform which can be oriented to direct the camera and the laser toward the target. In one embodiment the platform is positioned in response to movement of the operator's head. Position and orientation sensors are used to monitor head movement. The disparity between the digital image of the laser spot and the reference point is calculated for determining range to the target. Commercial applications for the system relate to active range-determination systems, such as those used with robotic systems in which it is necessary to determine the, range to a workpiece or object to be grasped or acted upon by a robot arm end

Long-range active retroreflector to measure the rotational orientation in conjunction with a laser tracker

NASA Astrophysics Data System (ADS)

Hofherr, O.; Wachten, Christian; Müller, C.; Reinecke, H.

2014-11-01

High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) accurately determine x-y-z coordinates of passive retroreflectors. Next-generation systems answer the need to measure an object`s rotational orientation (pitch, yaw, roll). So far, these devices are based either on photogrammetry or on enhanced retroreflectors. Here we present a new method to measure all six degrees of freedom in conjunction with a LT. The basic principle is to analyze the orientation to the LT's beam path by coupling-out laser radiation. The optical design is inspired by a cat's eye retroreflector equipped with an integrated beam splitter layer. The optical spherical aberration is compensated, which reduces the divergence angle for the reflected beam by one order of magnitude compared to an uncompensated standard system of the same size. The wave front distortion is reduced to less than 0.1 λ @ 633 nm for beam diameters up to 8 mm. Our active retroreflector is suitable for long-range measurements for a distance > 10 m.

Laser ranging interferometer for GRACE follow-on

NASA Astrophysics Data System (ADS)

Heinzel, Gerhard; Sheard, Benjmin; Brause, Nils; Danzmann, Karsten; Dehne, Marina; Gerberding, Oliver; Mahrdt, Christoph; Müller, Vitali; Schütze, Daniel; Stede, Gunnar; Klipstein, William; Folkner, William; Spero, Robert; Nicklaus, Kolja; Gath, Peter; Shaddock, Daniel

2017-11-01

The Gravity Recovery and Climate Experiment (GRACE) has produced a wealth of data on Earth gravity, hydrology, glaciology and climate research. To continue that data after the imminent end of the GRACE mission, a follow-on mission is planned to be launched in 2017, as a joint USGerman project with a smaller Australian contribution. The satellites will be essentially rebuilt as they were for GRACE using microwave ranging as the primary instrument for measuring changes of the intersatellite distance. In addition and in contrast to the original GRACE mission, a Laser Ranging Interferometer (LRI, previously also called `Laser Ranging Instrument') will be included as a technology demonstrator, which will operate together with the microwave ranging and supply a complimentary set of ranging data with lower noise, and new data on the relative alignment between the spacecraft. The LRI aims for a noise level of 80 nm/√Hz over a distance of up to 270km and will be the first intersatellite laser ranging interferometer. It shares many technologies with LISA-like gravitational wave observatories. This paper describes the optical architecture including the mechanisms to handle pointing jitter, the main noise sources and their mitigation, and initial laboratory breadboard experiments at AEI Hannover.

The NEAR laser ranging investigation

NASA Astrophysics Data System (ADS)

Zuber, M. T.; Smith, D. E.; Cheng, A. F.; Cole, T. D.

1997-10-01

The objective of the NEAR-Earth Asteriod Rendezvous (NEAR) laser ranging investigation is to obtain high integrity profiles and grids of topography for use in geophysical, geodetic and geological studies of asteroid 433 Eros. The NEAR laser rangefinder (NLR) will determine the slant range of the NEAR spacecraft to the asteroid surface by measuring precisely the round trip time of flight of individual laser pulses. Ranges will be converted to planetary radii measured with respect to the asteroid center of mass by subtracting the spacecraft orbit determined from X band Doppler tracking. The principal components of the NLR include a 1064 nm Cr:Nd:YAG laser, a gold-coated aluminum Dall-Kirkham Cassegrain telescope, an enhanced silicon avalanche photodiode hybrid detector, a 480-MHz crystal oscillator, and a digital processing unit. The instrument has a continuous in-flight calibration capability using a fiber-optic delay assembly. The single shot vertical resolution of the NLR is <6m, and the absolute accuracy of the global grid will be ~10m with respect to the asteroid center of mass. For the current mission orbital scenario, the laser spot size on the surface of Eros will vary from ~4-11m, and the along-track resolution for the nominal pulse repetition rate of 1 Hz will be approximately comparable to the spot size, resulting in contiguous along-track profiles. The across-track resolution will depend on the orbital mapping scenario, but will likely be <500m, which will define the spatial resolution of the global topographic model. Planned science investigations include global-scale analyses related to collisional and impact history and internal density distribution that utilize topographic grids as well as spherical harmonic topographic models that will be analyzed jointly with gravity at commensurate resolution. Attempts will be made to detect possible subtle time variations in internal structure that may be present if Eros is not a single coherent body, by analysis

Coupled-resonator vertical-cavity lasers with two active gain regions

DOEpatents

Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

2003-05-20

A new class of coupled-resonator vertical-cavity semiconductor lasers has been developed. These lasers have multiple resonant cavities containing regions of active laser media, resulting in a multi-terminal laser component with a wide range of novel properties.

Precision Lunar Laser Ranging For Lunar and Gravitational Science

NASA Technical Reports Server (NTRS)

Merkowitz, S. M.; Arnold, D.; Dabney, P. W.; Livas, J. C.; McGarry, J. F.; Neumann, G. A.; Zagwodzki, T. W.

2008-01-01

Laser ranging to retroreflector arrays placed on the lunar surface by the Apollo astronauts and the Soviet Lunar missions over the past 39 years have dramatically increased our understanding of gravitational physics along with Earth and Moon geophysics, geodesy, and dynamics. Significant advances in these areas will require placing modern retroreflectors and/or active laser ranging systems at new locations on the lunar surface. Ranging to new locations will enable better measurements of the lunar librations, aiding in our understanding of the interior structure of the moon. More precise range measurements will allow us to study effects that are too small to be observed by the current capabilities as well as enabling more stringent tests of Einstein's theory of General Relativity. Setting up retroreflectors was a key part of the Apollo missions so it is natural to ask if future lunar missions should include them as well. The Apollo retroreflectors are still being used today, and nearly 40 years of ranging data has been invaluable for scientific as well as other studies such as orbital dynamics. However, the available retroreflectors all lie within 26 degrees latitude of the equator, and the most useful ones within 24 degrees longitude of the sub-earth meridian. This clustering weakens their geometrical strength.

Tests of Gravity Using Lunar Laser Ranging.

PubMed

Merkowitz, Stephen M

2010-01-01

Lunar laser ranging (LLR) has been a workhorse for testing general relativity over the past four decades. The three retroreflector arrays put on the Moon by the Apollo astronauts and the French built arrays on the Soviet Lunokhod rovers continue to be useful targets, and have provided the most stringent tests of the Strong Equivalence Principle and the time variation of Newton's gravitational constant. The relatively new ranging system at the Apache Point 3.5 meter telescope now routinely makes millimeter level range measurements. Incredibly, it has taken 40 years for ground station technology to advance to the point where characteristics of the lunar retroreflectors are limiting the precision of the range measurements. In this article, we review the gravitational science and technology of lunar laser ranging and discuss prospects for the future.

Tests of gravity Using Lunar Laser Ranging

NASA Technical Reports Server (NTRS)

Merkowitz, Stephen M.

2010-01-01

Lunar laser ranging (LLR) has been a workhorse for testing general relativity over the pat four decades. The three retrorefiector arrays put on the Moon by the Apollo astronauts and the French built array on the second Soviet Lunokhod rover continue to be useful targets, and have provided the most stringent tests of the Strong Equivalence Principle and the time variation of Newton's gravitational constant. The relatively new ranging system at the Apache Point :3.5 meter telescope now routinely makes millimeter level range measurements. Incredibly. it has taken 40 years for ground station technology to advance to the point where characteristics of the lunar retrorefiectors are limiting the precision of the range measurements. In this article. we review the gravitational science and technology of lunar laser ranging and discuss prospects for the future.

Short range laser obstacle detector. [for surface vehicles using laser diode array

NASA Technical Reports Server (NTRS)

Kuriger, W. L. (Inventor)

1973-01-01

A short range obstacle detector for surface vehicles is described which utilizes an array of laser diodes. The diodes operate one at a time, with one diode for each adjacent azimuth sector. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser is synchronized with the vibrating mirror to enable one diode laser to be fired, by pulses from a clock pulse source, a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.

Laser Range and Bearing Finder for Autonomous Missions

NASA Technical Reports Server (NTRS)

Granade, Stephen R.

2004-01-01

NASA has recently re-confirmed their interest in autonomous systems as an enabling technology for future missions. In order for autonomous missions to be possible, highly-capable relative sensor systems are needed to determine an object's distance, direction, and orientation. This is true whether the mission is autonomous in-space assembly, rendezvous and docking, or rover surface navigation. Advanced Optical Systems, Inc. has developed a wide-angle laser range and bearing finder (RBF) for autonomous space missions. The laser RBF has a number of features that make it well-suited for autonomous missions. It has an operating range of 10 m to 5 km, with a 5 deg field of view. Its wide field of view removes the need for scanning systems such as gimbals, eliminating moving parts and making the sensor simpler and space qualification easier. Its range accuracy is 1% or better. It is designed to operate either as a stand-alone sensor or in tandem with a sensor that returns range, bearing, and orientation at close ranges, such as NASA's Advanced Video Guidance Sensor. We have assembled the initial prototype and are currently testing it. We will discuss the laser RBF's design and specifications. Keywords: laser range and bearing finder, autonomous rendezvous and docking, space sensors, on-orbit sensors, advanced video guidance sensor

Simultaneous Laser Ranging and Communication from an Earth-Based Satellite Laser Ranging Station to the Lunar Reconnaissance Orbiter in Lunar Orbit

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Skillman, David R.; Hoffman, Evan D.; Mao, Dandan; McGarry, Jan F.; Neumann, Gregory A.; McIntire, Leva; Zellar, Ronald S.; Davidson, Frederic M.; Fong, Wai H.;

Testing Fundamental Gravity with Interplanetary Laser Ranging

NASA Astrophysics Data System (ADS)

Turyshev, S. G.; Shao, M.; Hahn, I.

2018-02-01

Very accurate range measurements with the Interplanetary Laser Ranging Terminal (ILRT) will push high-precision tests of astrophysics/gravitation into a new regime. It could be used for navigation and investigations in planetary/lunar science.

A contribution to laser range imaging technology

NASA Technical Reports Server (NTRS)

Defigueiredo, Rui J. P.; Denney, Bradley S.

1991-01-01

The goal of the project was to develop a methodology for fusion of a Laser Range Imaging Device (LRID) and camera data. Our initial work in the project led to the conclusion that none of the LRID's that were available were sufficiently adequate for this purpose. Thus we spent the time and effort on the development of the new LRID with several novel features which elicit the desired fusion objectives. In what follows, we describe the device developed and built under contract. The Laser Range Imaging Device (LRID) is an instrument which scans a scene using a laser and returns range and reflection intensity data. Such a system would be extremely useful in scene analysis in industry and space applications. The LRID will be eventually implemented on board a mobile robot. The current system has several advantages over some commercially available systems. One improvement is the use of X-Y galvonometer scanning mirrors instead of polygonal mirrors present in some systems. The advantage of the X-Y scanning mirrors is that the mirror system can be programmed to provide adjustable scanning regions. For each mirror there are two controls accessible by the computer. The first is the mirror position and the second is a zoom factor which modifies the amplitude of the position of the parameter. Another advantage of the LRID is the use of a visible low power laser. Some of the commercial systems use a higher intensity invisible laser which causes safety concerns. By using a low power visible laser, not only can one see the beam and avoid direct eye contact, but also the lower intensity reduces the risk of damage to the eye, and no protective eyeware is required.

8-Channel Broadband Laser Ranging Hardware Development

NASA Astrophysics Data System (ADS)

Bennett, Corey; La Lone, Brandon; Younk, Patrick; Daykin, Ed; Rhodes, Michelle; Perry, Daniel; Tran, Vu; Miller, Edward

2017-06-01

Broadband Laser Ranging (BLR) is a new diagnostic being developed to precisely measure the position vs. time of surfaces, shock break out, particle clouds, jets, and debris moving at kilometers per second speeds. The instrument uses interferometry to encode distance into a modulation in the spectrum of pulses from a mode-locked fiber laser and uses a dispersive Fourier transformation to map the spectral modulation into time. Range information is thereby recorded on a fast oscilloscope at the repetition rate of the laser, approximately every 50 ns. Current R&D is focused on developing a compact 8-channel system utilizing one laser and one high-speed oscilloscope. This talk will emphasize the hardware being developed for applications at the Contained Firing Facility at LLNL, but has a common architecture being developed in collaboration with NSTec and LANL for applications at multiple other facilities. Prepared by LLNL under Contract DE-AC52-07NA27344, by LANL under Contract DE-AC52-06NA25396, and by NSTec Contract DE-AC52-06NA25946.

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

1995-01-01

This Interim report consists of a manuscript, 'Receiver Design for Satellite to Satellite Laser Ranging Instrument,' and copies of two papers we co-authored, 'Demonstration of High Sensitivity Laser Ranging System' and 'Semiconductor Laser-Based Ranging Instrument for Earth Gravity Measurements. ' These two papers were presented at the conference Semiconductor Lasers, Advanced Devices and Applications, August 21 -23, 1995, Keystone Colorado. The manuscript is a draft in the preparation for publication, which summarizes the theory we developed on space-borne laser ranging instrument for gravity measurements.

Detection and laser ranging of orbital objects using optical methods

NASA Astrophysics Data System (ADS)

Wagner, P.; Hampf, D.; Sproll, F.; Hasenohr, T.; Humbert, L.; Rodmann, J.; Riede, W.

2016-09-01

Laser ranging to satellites (SLR) in earth orbit is an established technology used for geodesy, fundamental science and precise orbit determination. A combined active and passive optical measurement system using a single telescope mount is presented which performs precise ranging measurements of retro reflector equipped objects in low earth orbit (LEO). The German Aerospace Center (DLR) runs an observatory in Stuttgart where a system has been assembled completely from commercial off-the-shelf (COTS) components. The visible light directed to the tracking camera is used to perform angular measurements of objects under investigation. This is done astrometrically by comparing the apparent target position with cataloged star positions. First successful satellite laser ranging was demonstrated recently using an optical fiber directing laser pulses onto the astronomical mount. The transmitter operates at a wavelength of 1064 nm with a repetition rate of 3 kHz and pulse energy of 25 μJ. A motorized tip/tilt mount allows beam steering of the collimated beam with μrad accuracy. The returning photons reflected from the object in space are captured with the tracking telescope. A special low aberration beam splitter unit was designed to separate the infrared from visible light. This allows passive optical closed loop tracking and operation of a single photon detector for time of flight measurements at a single telescope simultaneously. The presented innovative design yields to a compact and cost effective but very precise ranging system which allows orbit determination.

New progress of ranging technology at Wuhan Satellite Laser Ranging Station

NASA Technical Reports Server (NTRS)

Xia, Zhiz-Hong; Ye, Wen-Wei; Cai, Qing-Fu

1993-01-01

A satellite laser ranging system with an accuracy of the level of centimeter has been successfully developed at the Institute of Seismology, State Seismological Bureau with the cooperation of the Institute of Geodesy and Geophysics, Chinese Academy of Science. With significant improvements on the base of the second generation SLR system developed in 1985, ranging accuracy of the new system has been upgraded from 15 cm to 3-4 cm. Measuring range has also been expanded, so that the ETALON satellite with an orbit height of 20,000 km launched by the former U.S.S.R. can now be tracked. Compared with the 2nd generation SLR system, the newly developed system has the following improvements. A Q modulated laser is replaced by a mode-locked YAG laser. The new device has a pulse width of 150 ps and a repetition rate of 1-4 pps. A quick response photomultiplier has been adopted as the receiver for echo; for example, the adoption of the MCP tube has obviously reduced the jitter error of the transit time and has improved the ranging accuracy. The whole system is controlled by an IBM PC/XT Computer to guide automatic tracking and measurement. It can carry out these functions for satellite orbit calculation, real-time tracking and adjusting, data acquisition and the preprocessed of observing data, etc. The automatization level and reliability of the observation have obviously improved.

Demonstrator study for micro-ranging-laser device

NASA Astrophysics Data System (ADS)

Henkel, Hartmut; Bernhardt, Bodo; Pereira do Carmo, J.

2017-11-01

Within ESA's Innovation Triangle Initiative (ITI) a demonstrator breadboard for a micro-ranging-laser device "MYLRAD" has been developed. Its working principle is the measurement of the round-trip delay time of a laser beam as a phase shift. The demonstrator consists of the laser diode (30 mW, square wave AM), optics, APD detector, narrowband preamplifier, limiter, and a phase digitiser based on a novel noise-shaping synchroniser (NSS) circuit; this works without ADCs and can be built from rad-hard components for space. The system timing and the digitiser algorithm are performed by an FPGA. The demonstrator has been tested at ranges from 1 m to 30 m. With a static non-cooperative target an RMS noise of 1 mm at a result rate of 60 Hz was reached. The demonstrator needs less than 2.5 W power.

The Geoscience Laser Altimetry/Ranging System (GLARS)

NASA Technical Reports Server (NTRS)

Cohen, S. C.; Degnan, J. J.; Bufton, J. L.; Garvin, J. B.; Abshire, J. B.

1986-01-01

The Geoscience Laser Altimetry Ranging System (GLARS) is a highly precise distance measurement system to be used for making extremely accurate geodetic observations from a space platform. It combines the attributes of a pointable laser ranging system making observations to cube corner retroreflectors placed on the ground with those of a nadir looking laser altimeter making height observations to ground, ice sheet, and oceanic surfaces. In the ranging mode, centimeter-level precise baseline and station coordinate determinations will be made on grids consisting of 100 to 200 targets separated by distances from a few tens of kilometers to about 1000 km. These measurements will be used for studies of seismic zone crustal deformations and tectonic plate motions. Ranging measurements will also be made to a coarser, but globally distributed array of retroreflectors for both precise geodetic and orbit determination applications. In the altimetric mode, relative height determinations will be obtained with approximately decimeter vertical precision and 70 to 100 meter horizontal resolution. The height data will be used to study surface topography and roughness, ice sheet and lava flow thickness, and ocean dynamics. Waveform digitization will provide a measure of the vertical extent of topography within each footprint. The planned Earth Observing System is an attractive candidate platform for GLARS since the GLAR data can be used both for direct analyses and for highly precise orbit determination needed in the reduction of data from other sensors on the multi-instrument platform. (1064, 532, and 355 nm)Nd:YAG laser meets the performance specifications for the system.

Lunar Laser Ranging trial at Koganei SLR station

NASA Astrophysics Data System (ADS)

Noda, Hirotomo; Kunimori, Hiroo; Araki, Hiroshi

Introduction: The Lunar Laser Ranging (LLR) is a technique to measure the distance between laser stations on the Earth and retroreflectors on the Moon, by detecting the time of flight of high-powered laser emitted from the ground station. Since the Earth-Moon distance contains information of lunar orbit, lunar solid tides, and lunar orientation and rotation, observation data of LLR have contributed to the lunar science, especially for the estimation of the inner structure of the Moon through orientation, rotation and tide. There are five refroreflectors on the Moon, Apollo 11, 14, 15 (U. S. A.), Lunokhod 1 and 2 (french-made, carried by former U. S. S. R.). The Apollo 15 has largest aperture among them, and almost 75 % of the total LLR data are from Apollo 15 site. System Description: Since there is no Japanese station which can range the Moon so far, a precursor ranging experiment by using the Satellite Laser Ranging (SLR) facility in the NICT Koganei campus in Tokyo is ongoing. The SLR station has a 1.5 m Cassegrain telescope with Coude focus. Normally it is equipped with a laser with 20mJ, 20Hz repetition rate, and 35 picoseconds pulse width for satellite ranging. In addition to it, a wide-pulse width laser (3 nanoseconds, which corresponds to 45 cm in 2-way range) with energy of about 350 mJ per shot, repetition rate of 10Hz, wavelength of 532 nm is introduced to detect photons from the lunar retroreflectors for demonstration. As the pulse width is broad, the high accuracy ranging is not expected, therefore it is solely used for the confirmation of the optical link budget between the ground station and retroreflectors on the Moon. As the photon detector, we use a SPAD (Single Photon Avalanche Diode) and also an MCP (Micro Channel Plate) photo multiplier whose quantum efficiency is twice as much as that of the SPAD in use. For the pointing, a CCD imager is also available in the same detector box. They can be switched by reflecting mirrors. To suppress the

Laser-ranging scanning system to observe topographical deformations of volcanoes.

PubMed

Aoki, T; Takabe, M; Mizutani, K; Itabe, T

1997-02-20

We have developed a laser-ranging system to observe the topographical structure of volcanoes. This system can be used to measure the distance to a target by a laser and shows the three-dimensional topographical structure of a volcano with an accuracy of 30 cm. This accuracy is greater than that of a typical laser-ranging system that uses a corner-cube reflector as a target because the reflected light jitters as a result of inclination and unevenness of the target ground surface. However, this laser-ranging system is useful for detecting deformations of topographical features in which placement of a reflector is difficult, such as in volcanic regions.

Method of high precision interval measurement in pulse laser ranging system

NASA Astrophysics Data System (ADS)

Wang, Zhen; Lv, Xin-yuan; Mao, Jin-jin; Liu, Wei; Yang, Dong

2013-09-01

Laser ranging is suitable for laser system, for it has the advantage of high measuring precision, fast measuring speed,no cooperative targets and strong resistance to electromagnetic interference,the measuremen of laser ranging is the key paremeters affecting the performance of the whole system.The precision of the pulsed laser ranging system was decided by the precision of the time interval measurement, the principle structure of laser ranging system was introduced, and a method of high precision time interval measurement in pulse laser ranging system was established in this paper.Based on the analysis of the factors which affected the precision of range measure,the pulse rising edges discriminator was adopted to produce timing mark for the start-stop time discrimination,and the TDC-GP2 high precision interval measurement system based on TMS320F2812 DSP was designed to improve the measurement precision.Experimental results indicate that the time interval measurement method in this paper can obtain higher range accuracy. Compared with the traditional time interval measurement system,the method simplifies the system design and reduce the influence of bad weather conditions,furthermore,it satisfies the requirements of low costs and miniaturization.

CO2 laser ranging systems study

NASA Technical Reports Server (NTRS)

Filippi, C. A.

1975-01-01

The conceptual design and error performance of a CO2 laser ranging system are analyzed. Ranging signal and subsystem processing alternatives are identified, and their comprehensive evaluation yields preferred candidate solutions which are analyzed to derive range and range rate error contributions. The performance results are presented in the form of extensive tables and figures which identify the ranging accuracy compromises as a function of the key system design parameters and subsystem performance indexes. The ranging errors obtained are noted to be within the high accuracy requirements of existing NASA/GSFC missions with a proper system design.

Use of laser range finders and range image analysis in automated assembly tasks

NASA Technical Reports Server (NTRS)

Alvertos, Nicolas; Dcunha, Ivan

1990-01-01

A proposition to study the effect of filtering processes on range images and to evaluate the performance of two different laser range mappers is made. Median filtering was utilized to remove noise from the range images. First and second order derivatives are then utilized to locate the similarities and dissimilarities between the processed and the original images. Range depth information is converted into spatial coordinates, and a set of coefficients which describe 3-D objects is generated using the algorithm developed in the second phase of this research. Range images of spheres and cylinders are used for experimental purposes. An algorithm was developed to compare the performance of two different laser range mappers based upon the range depth information of surfaces generated by each of the mappers. Furthermore, an approach based on 2-D analytic geometry is also proposed which serves as a basis for the recognition of regular 3-D geometric objects.

Semiconductor laser-based ranging instrument for earth gravity measurements

NASA Technical Reports Server (NTRS)

Abshire, James B.; Millar, Pamela S.; Sun, Xiaoli

1995-01-01

A laser ranging instrument is being developed to measure the spatial variations in the Earth's gravity field. It will range in space to a cube corner on a passive co-orbiting sub-satellite with a velocity accuracy of 20 to 50 microns/sec by using AlGaAs lasers intensity modulated at 2 GHz.

Multiple-Zone Diffractive Optic Element for Laser Ranging Applications

NASA Technical Reports Server (NTRS)

Ramos-Izquierdo, Luis A.

2011-01-01

A diffractive optic element (DOE) can be used as a beam splitter to generate multiple laser beams from a single input laser beam. This technology has been recently used in LRO s Lunar Orbiter Laser Altimeter (LOLA) instrument to generate five laser beams that measure the lunar topography from a 50-km nominal mapping orbit (see figure). An extension of this approach is to use a multiple-zone DOE to allow a laser altimeter instrument to operate over a wider range of distances. In particular, a multiple-zone DOE could be used for applications that require both mapping and landing on a planetary body. In this case, the laser altimeter operating range would need to extend from several hundred kilometers down to a few meters. The innovator was recently involved in an investigation how to modify the LOLA instrument for the OSIRIS asteroid mapping and sample return mission. One approach is to replace the DOE in the LOLA laser beam expander assembly with a multiple-zone DOE that would allow for the simultaneous illumination of the asteroid with mapping and landing laser beams. The proposed OSIRIS multiple-zone DOE would generate the same LOLA five-beam output pattern for high-altitude topographic mapping, but would simultaneously generate a wide divergence angle beam using a small portion of the total laser energy for the approach and landing portion of the mission. Only a few percent of the total laser energy is required for approach and landing operations as the return signal increases as the inverse square of the ranging height. A wide divergence beam could be implemented by making the center of the DOE a diffractive or refractive negative lens. The beam energy and beam divergence characteristics of a multiple-zone DOE could be easily tailored to meet the requirements of other missions that require laser ranging data. Current single-zone DOE lithographic manufacturing techniques could also be used to fabricate a multiple-zone DOE by masking the different DOE zones during

Asynchronous Laser Transponders for Precise Interplanetary Ranging and Time Transfer

NASA Technical Reports Server (NTRS)

Degnan, John J.; Smith, David E. (Technical Monitor)

2001-01-01

The feasibility of a two-way asynchronous (i.e. independently firing) interplanetary laser transponder pair, capable of decimeter ranging and subnanosecond time transfer from Earth to a spacecraft anywhere within the inner Solar System, is discussed. In the Introduction, we briefly discuss the current state-of-the-art in Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) which use single-ended range measurements to a passive optical reflector, and the limitations of this approach in ranging beyond the Moon to the planets. In Section 2 of this paper, we describe two types of transponders (echo and asynchronous), introduce the transponder link equation and the concept of "balanced" transponders, describe how range and time can be transferred between terminals, and preview the potential advantages of photon counting asynchronous transponders for interplanetary applications. In Section 3, we discuss and provide mathematical models for the various sources of noise in an interplanetary transponder link including planetary albedo, solar or lunar illumination of the local atmosphere, and laser backscatter off the local atmosphere. In Section 4, we introduce the key engineering elements of an interplanetary laser transponder and develop an operational scenario for the acquisition and tracking of the opposite terminal. In Section 5, we use the theoretical models of th previous sections to perform an Earth-Mars link analysis over a full synodic period of 780 days under the simplifying assumption of coaxial, coplanar, circular orbits. We demonstrate that, using slightly modified versions of existing space and ground based laser systems, an Earth-Mars transponder link is not only feasible but quite robust. We also demonstrate through analysis the advantages and feasibility of compact, low output power (<300 mW photon-counting transponders using NASA's developmental SLR2000 satellite laser ranging system as the Earth terminal. Section 6 provides a summary of the results

Laser Ranging in Solar System: Technology Developments and New Science Measurement Capabilities

NASA Astrophysics Data System (ADS)

Sun, X.; Smith, D. E.; Zuber, M. T.; Mcgarry, J.; Neumann, G. A.; Mazarico, E.

2015-12-01

Laser Ranging has played a major role in geodetic studies of the Earth over the past 40 years. The technique can potentially be used in between planets and spacecrafts within the solar system to advance planetary science. For example, a direct measurement of distances between planets, such as Mars and Venus would make significant improvements in understanding the dynamics of the whole solar system, including the masses of the planets and moons, asteroids and their perturbing interactions, and the gravity field of the Sun. Compared to the conventional radio frequency (RF) tracking systems, laser ranging is potentially more accurate because it is much less sensitive to the transmission media. It is also more efficient because the laser beams are much better focused onto the targets than RF beams. However, existing laser ranging systems are all Earth centric, that is, from ground stations on Earth to orbiting satellites in near Earth orbits or lunar orbit, and to the lunar retro-reflector arrays deployed by the astronauts in the early days of lunar explorations. Several long distance laser ranging experiments have been conducted with the lidar in space, including a two-way laser ranging demonstration between Earth and the Mercury Laser Altimeter (MLA) on the MESSENGER spacecraft over 24 million km, and a one way laser transmission and detection experiment over 80 million km between Earth and the Mars Orbiting Laser Altimeter (MOLA) on the MGS spacecraft in Mars orbit. A one-way laser ranging operation has been carried out continuously from 2009 to 2014 between multiple ground stations to LRO spacecraft in lunar orbit. The Lunar Laser Communication Demonstration (LLCD) on the LADEE mission has demonstrated that a two way laser ranging measurements, including both the Doppler frequency and the phase shift, can be obtained from the subcarrier or the data clocks of a high speed duplex laser communication system. Plans and concepts presently being studied suggest we may be

Lunar laser ranging in infrared at the Grasse laser station

NASA Astrophysics Data System (ADS)

Courde, C.; Torre, J. M.; Samain, E.; Martinot-Lagarde, G.; Aimar, M.; Albanese, D.; Exertier, P.; Fienga, A.; Mariey, H.; Metris, G.; Viot, H.; Viswanathan, V.

2017-06-01

For many years, lunar laser ranging (LLR) observations using a green wavelength have suffered an inhomogeneity problem both temporally and spatially. This paper reports on the implementation of a new infrared detection at the Grasse LLR station and describes how infrared telemetry improves this situation. Our first results show that infrared detection permits us to densify the observations and allows measurements during the new and the full Moon periods. The link budget improvement leads to homogeneous telemetric measurements on each lunar retro-reflector. Finally, a surprising result is obtained on the Lunokhod 2 array which attains the same efficiency as Lunokhod 1 with an infrared laser link, although those two targets exhibit a differential efficiency of six with a green laser link.

Laser long-range remote-sensing program experimental results

NASA Astrophysics Data System (ADS)

Highland, Ronald G.; Shilko, Michael L.; Fox, Marsha J.; Gonglewski, John D.; Czyzak, Stanley R.; Dowling, James A.; Kelly, Brian; Pierrottet, Diego F.; Ruffatto, Donald; Loando, Sharon; Matsuura, Chris; Senft, Daniel C.; Finkner, Lyle; Rae, Joe; Gallegos, Joe

1995-12-01

A laser long range remote sensing (LRS) program is being conducted by the United States Air Force Phillips Laboratory (AF/PL). As part of this program, AF/PL is testing the feasibility of developing a long path CO(subscript 2) laser-based DIAL system for remote sensing. In support of this program, the AF/PL has recently completed an experimental series using a 21 km slant- range path (3.05 km ASL transceiver height to 0.067 km ASL target height) at its Phillips Laboratory Air Force Maui Optical Station (AMOS) facility located on Maui, Hawaii. The dial system uses a 3-joule, (superscript 13)C isotope laser coupled into a 0.6 m diameter telescope. The atmospheric optical characterization incorporates information from an infrared scintillometer co-aligned to the laser path, atmospheric profiles from weather balloons launched from the target site, and meteorological data from ground stations at AMOS and the target site. In this paper, we report a description of the experiment configuration, a summary of the results, a summary of the atmospheric conditions and their implications to the LRS program. The capability of such a system for long-range, low-angle, slant-path remote sensing is discussed. System performance issues relating to both coherent and incoherent detection methods, atmospheric limitations, as well as, the development of advanced models to predict performance of long range scenarios are presented.

Probing General Relativity and New Physics with Lunar Laser Ranging

NASA Astrophysics Data System (ADS)

Dell'Agnello, S.; Maiello, M.; Currie, D. G.; Boni, A.; Berardi, S.; Cantone, C.; Delle Monache, G. O.; Intaglietta, N.; Lops, C.; Garattini, M.; Martini, M.; Patrizi, G.; Porcelli, L.; Tibuzzi, M.; Vittori, R.; Bianco, G.; Coradini, A.; Dionisio, C.; March, R.; Bellettini, G.; Tauraso, R.; Chandler, J.

2012-11-01

primary goal of these innovative tools is to provide critical design and diagnostic capabilities for Satellite Laser Ranging (SLR) to Galileo and other GNSS (Global Navigation Satellite System) constellations. Implementation of new retroreflector designs being studied will help to improve GNSS orbits, which will then increase the accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF) [4], to provide better definition of the geocenter (origin) and the scale (length unit). The SCF is also actively used to develop, validate and optimize the second generation LLR arrays for precision gravity and lunar science measurements to be performed with robotic missions of the International Lunar Network in which NASA and ASI participate (ILN). The capability will allow us to optimize the design of GNSS laser retroreflector payloads to maximize ranging efficiency, to improve signal-to-noise conditions in daylight and to provide pre-launch validation of retroreflector performance under laboratory-simulated space conditions. For the MAGIA lunar orbiter Phase A study funded by ASI (Dell'Agnello et al., 2010 [14]), we studied fundamental physics and absolute positioning metrology experiments, to improve test of the gravitational redshift in the Earth-Moon system predicted by General Relativity and a precursor test of our second generation LLR payload.

Fast range estimation based on active range-gated imaging for coastal surveillance

NASA Astrophysics Data System (ADS)

Kong, Qingshan; Cao, Yinan; Wang, Xinwei; Tong, Youwan; Zhou, Yan; Liu, Yuliang

2012-11-01

Coastal surveillance is very important because it is useful for search and rescue, illegal immigration, or harbor security and so on. Furthermore, range estimation is critical for precisely detecting the target. Range-gated laser imaging sensor is suitable for high accuracy range especially in night and no moonlight. Generally, before detecting the target, it is necessary to change delay time till the target is captured. There are two operating mode for range-gated imaging sensor, one is passive imaging mode, and the other is gate viewing mode. Firstly, the sensor is passive mode, only capturing scenes by ICCD, once the object appears in the range of monitoring area, we can obtain the course range of the target according to the imaging geometry/projecting transform. Then, the sensor is gate viewing mode, applying micro second laser pulses and sensor gate width, we can get the range of targets by at least two continuous images with trapezoid-shaped range intensity profile. This technique enables super-resolution depth mapping with a reduction of imaging data processing. Based on the first step, we can calculate the rough value and quickly fix delay time which the target is detected. This technique has overcome the depth resolution limitation for 3D active imaging and enables super-resolution depth mapping with a reduction of imaging data processing. By the two steps, we can quickly obtain the distance between the object and sensor.

Time-transfer experiments between satellite laser ranging ground stations via one-way laser ranging to the Lunar Reconnaissance Orbiter

NASA Astrophysics Data System (ADS)

Mao, D.; Sun, X.; Skillman, D. R.; Mcgarry, J.; Hoffman, E.; Neumann, G. A.; Torrence, M. H.; Smith, D. E.; Zuber, M. T.

2014-12-01

Satellite laser ranging (SLR) has long been used to measure the distance from a ground station to an Earth-orbiting satellite in order to determine the spacecraft position in orbit, and to conduct other geodetic measurements such as plate motions. This technique can also be used to transfer time between the station and satellite, and between remote SLR sites, as recently demonstrated by the Time Transfer by Laser Link (T2L2) project by the Centre National d'Etudes Spatiaes (CNES) and Observatorire de la Cote d'Azur (OCA) as well as the Laser Time Transfer (LTT) project by the Shanghai Astronomical Observatory, where two-way and one-way measurements were obtained at the same time. Here we report a new technique to transfer time between distant SLR stations via simultaneous one-way laser ranging (LR) to the Lunar Reconnaissance Orbiter (LRO) spacecraft at lunar distance. The major objectives are to establish accurate ground station times and to improve LRO orbit determination via these measurements. The results of these simultaneous LR measurements are used to compare the SLR station times or transfer time from one to the other using times-of-flight estimated from conventional radio frequency tracking of LRO. The accuracy of the time transfer depends only on the difference of the times-of-flight from each ground station to the spacecraft, and is expected to be at sub-nano second level. The technique has been validated by both a ground-based experiment and an experiment that utilized LRO. Here we present the results to show that sub-nanosecond precision and accuracy are achievable. Both experiments were carried out between the primary LRO-LR station, The Next Generation Satellite Laser Ranging (NGSLR) station, and its nearby station, Mobile Laser System (MOBLAS-7), both at Greenbelt, Maryland. The laser transmit time from both stations were recorded by the same event timer referenced to a Hydrogen maser. The results have been compared to data from a common All

The application and research of the multi-receiving telescopes technology in laser ranging to space targets

NASA Astrophysics Data System (ADS)

Wu, Zhibo; Zhang, Haifeng; Zhang, Zhongping; Deng, Huarong; Li, Pu; Meng, Wendong; Cheng, Zhien; Shen, Lurun; Tang, Zhenhong

2014-11-01

Laser ranging technology can directly measure the distance between space targets and ground stations with the highest measurement precision and will play an irreplaceable role in orbit check and calibrating microwave measurement system. The precise orbit determination and accurate catalogue of space targets can also be realized by laser ranging with multi-stations. Among space targets, most of ones are inactive targets and space debris, which should be paid the great attentions for the safety of active spacecrafts. Because of laser diffuse reflection from the surface of targets, laser ranging to space debris has the characteristics of wide coverage and weak strength of laser echoes, even though the powerful laser system is applied. In order to increase the receiving ability of laser echoes, the large aperture telescope should be adopted. As well known, some disadvantages for one set of large aperture telescope, technical development difficulty and system running and maintenance complexity, will limit its flexible applications. The multi-receiving telescopes technology in laser ranging to space targets is put forward to realize the equivalent receiving ability produced by one larger aperture telescope by way of using multi-receiving telescopes, with the advantages of flexibility and maintenance. The theoretical analysis of the feasibility and key technologies of multi-receiving telescopes technology in laser ranging to space targets are presented in this paper. The experimental measurement system based on the 60cm SLR system and 1.56m astronomical telescopes with a distance of about 50m is established to provide the platform for researching on the multi-receiving telescopes technology. The laser ranging experiments to satellites equipped with retro-reflectors are successfully performed by using the above experimental system and verify the technical feasibility to increase the ability of echo detection. And the multi-receiving telescopes technology will become a

Laser materials for the 0.67-microns to 2.5-microns range

NASA Technical Reports Server (NTRS)

Toda, Minoru; Zamerowski, Thomas J.; Ladany, Ivan; Martinelli, Ramon U.

1987-01-01

Basic requirements for obtaining injection laser action in III-V semiconductors are discussed briefly. A detailed review is presented of materials suitable for lasers emitting at 0.67, 1.44, 1.93, and 2.5 microns. A general approach to the problem is presented, based on curves of materials properties published by Sasaki et al. It is also shown that these curves, although useful, may need correction in certain ranges. It is deduced that certain materials combinations, either proposed in the literature or actually tried, are not appropriate for double heterostructure lasers, because the refractive index of the cladding material is higher than the index of the active material, thus resulting in no waveguiding, and high threshold currents. Recommendations are made about the most promising approach to the achievement of laser action in the four wavelengths mentioned above.

Design and Development of High-Repetition-Rate Satellite Laser Ranging System

NASA Astrophysics Data System (ADS)

Choi, Eun-Jung; Bang, Seong-Cheol; Sung, Ki-Pyoung; Lim, Hyung-Chul; Jung, Chan-Gyu; Kim, In-Yeung; Choi, Jae-Seung

2015-09-01

The Accurate Ranging System for Geodetic Observation ? Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station ¡°data validation¡± process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retroreflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

Precise attitude determination of defunct satellite laser ranging tragets

NASA Astrophysics Data System (ADS)

Pittet, Jean-Noel; Schildknecht, Thomas; Silha, Jiri

2016-07-01

The Satellite Laser Ranging (SLR) technology is used to determine the dynamics of objects equipped with so-called retro-reflectors or retro-reflector arrays (RRA). This type of measurement allows to range to the spacecraft with very high precision, which leads to determination of very accurate orbits. Non-active spacecraft, which are not any more attitude controlled, tend to start to spin or tumble under influence of the external and internal torques. Such a spinning can be around one constant axis of rotation or it can be more complex, when also precession and nutation motions are present. The rotation of the RRA around the spacecraft's centre of mass can create both a oscillation pattern of laser range signal and a periodic signal interruption when the RRA is hidden behind the satellite. In our work we will demonstrate how the SLR ranging technique to cooperative targets can be used to determine precisely their attitude state. The processing of the obtained data will be discussed, as well as the attitude determination based on parameters estimation. Continuous SLR measurements to one target can allow to accurately monitor attitude change over time which can be further used for the future attitude modelling. We will show our solutions of the attitude states determined for the non-active ESA satellite ENVISAT based on measurements acquired during year 2013-2015 by Zimmerwald SLR station, Switzerland. The angular momentum shows a stable behaviour with respect to the orbital plane but is not aligned with orbital momentum. The determination of the inertial rotation over time, shows it evolving between 130 to 190 seconds within two year. Parameter estimation also bring a strong indication of a retrograde rotation. Results on other former satellites in low and medium Earth orbit such as TOPEX/Poseidon or GLONASS type will be also presented.

Tracking capabilities of SPADs for laser ranging

NASA Technical Reports Server (NTRS)

Zappa, F.; Ripamonti, Giancarlo; Lacaita, A.; Cova, Sergio; Samori, C.

1993-01-01

The spatial sensitivity of Single-Photon Avalanche Diodes (SPADs) can be exploited in laser ranging measurements to finely tune the laser spot in the center of the detector sensitive area. We report the performance of a SPAD with l00 micron diameter. It features a time resolution better than 80 ps rms when operated 4V above V(b) at minus 30 C, and a spatial sensitivity better than 20 microns to radial displacements of the laser spot. New SPAD structures with auxiliary delay detectors are proposed. These improved devices could allow a two dimensional sensitivity, that could be employed for the design of pointing servos.

Satellite laser ranging work at the Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

Mcgunigal, T. E.; Carrion, W. J.; Caudill, L. O.; Grant, C. R.; Johnson, T. S.; Premo, D. A.; Spadin, P. L.; Winston, G. C.

1975-01-01

Laser ranging systems, their range and accuracy capabilities, and planned improvements for future systems are discussed, the systems include one fixed and two mobile lasers ranging systems. They have demonstrated better than 10 cm accuracy both on a carefully surveyed ground range and in regular satellite ranging operations. They are capable of ranging to all currently launched retroreflector equipped satellites with the exception of Timation III. A third mobile system is discussed which will be accurate to better than 5 cm and will be capable of ranging to distant satellites such as Timation III and LAGEOS.

Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander; IAPS-team Team

2017-10-01

The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics.

PubMed

Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

2016-06-03

In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends.

Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics

PubMed Central

Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

2016-01-01

In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends. PMID:27256904

Active mode locking of quantum cascade lasers in an external ring cavity.

PubMed

Revin, D G; Hemingway, M; Wang, Y; Cockburn, J W; Belyanin, A

2016-05-05

Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents.

Active mode locking of quantum cascade lasers in an external ring cavity

PubMed Central

Revin, D. G.; Hemingway, M.; Wang, Y.; Cockburn, J. W.; Belyanin, A.

2016-01-01

Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents. PMID:27147409

Lunar laser ranging: a continuing legacy of the apollo program.

PubMed

Dickey, J O; Bender, P L; Faller, J E; Newhall, X X; Ricklefs, R L; Ries, J G; Shelus, P J; Veillet, C; Whipple, A L; Wiant, J R; Williams, J G; Yoder, C F

1994-07-22

On 21 July 1969, during the first manned lunar mission, Apollo 11, the first retroreflector array was placed on the moon, enabling highly accurate measurements of the Earthmoon separation by means of laser ranging. Lunar laser ranging (LLR) turns the Earthmoon system into a laboratory for a broad range of investigations, including astronomy, lunar science, gravitational physics, geodesy, and geodynamics. Contributions from LLR include the three-orders-of-magnitude improvement in accuracy in the lunar ephemeris, a several-orders-of-magnitude improvement in the measurement of the variations in the moon's rotation, and the verification of the principle of equivalence for massive bodies with unprecedented accuracy. Lunar laser ranging analysis has provided measurements of the Earth's precession, the moon's tidal acceleration, and lunar rotational dissipation. These scientific results, current technological developments, and prospects for the future are discussed here.

The simulation study on optical target laser active detection performance

NASA Astrophysics Data System (ADS)

Li, Ying-chun; Hou, Zhao-fei; Fan, Youchen

2014-12-01

According to the working principle of laser active detection system, the paper establishes the optical target laser active detection simulation system, carry out the simulation study on the detection process and detection performance of the system. For instance, the performance model such as the laser emitting, the laser propagation in the atmosphere, the reflection of optical target, the receiver detection system, the signal processing and recognition. We focus on the analysis and modeling the relationship between the laser emitting angle and defocus amount and "cat eye" effect echo laser in the reflection of optical target. Further, in the paper some performance index such as operating range, SNR and the probability of the system have been simulated. The parameters including laser emitting parameters, the reflection of the optical target and the laser propagation in the atmosphere which make a great influence on the performance of the optical target laser active detection system. Finally, using the object-oriented software design methods, the laser active detection system with the opening type, complete function and operating platform, realizes the process simulation that the detection system detect and recognize the optical target, complete the performance simulation of each subsystem, and generate the data report and the graph. It can make the laser active detection system performance models more intuitive because of the visible simulation process. The simulation data obtained from the system provide a reference to adjust the structure of the system parameters. And it provides theoretical and technical support for the top level design of the optical target laser active detection system and performance index optimization.

Pulse Shape Correlation for Laser Detection and Ranging (LADAR)

DTIC Science & Technology

2010-03-01

with the incoming measured laser pulse [3]. All of these shapes are symmetric. Siegman and Liu’s findings indicate that the pulse is seldom symmetric...of Engineering, Air Force Institute of Technology (AETC), Wright Pat- terson AFB, OH, March 2007. 10. Siegman , Anthony E. Lasers . University Science...Pulse Shape Correlation for Laser Detection and Ranging (LADAR) THESIS Brian T. Deas, Major, USAF AFIT/GE/ENG/10-07 DEPARTMENT OF THE AIR FORCE AIR

Development of a Low cost Ultra tiny Line Laser Range Sensor

DTIC Science & Technology

2016-12-01

Development of a Low-cost Ultra-tiny Line Laser Range Sensor Xiangyu Chen∗, Moju Zhao∗, Lingzhu Xiang†, Fumihito Sugai∗, Hiroaki Yaguchi∗, Kei Okada...and Masayuki Inaba∗ Abstract— To enable robotic sensing for tasks with require- ments on weight, size, and cost, we develop an ultra-tiny line laser ...view customizable using different laser lenses. The optimal measurement range of the sensor is 0.05[m] ∼ 2[m]. Higher sampling rates can be achieved

Research on simulation system with the wide range and high-precision laser energy characteristics

NASA Astrophysics Data System (ADS)

Dong, Ke-yan; Lou, Yan; He, Jing-yi; Tong, Shou-feng; Jiang, Hui-lin

2012-10-01

The Hardware-in-the-loop(HWIL) simulation test is one of the important parts for the development and performance testing of semi-active laser-guided weapons. In order to obtain accurate results, the confidence level of the target environment should be provided for a high-seeker during the HWIL simulation test of semi-active laser-guided weapons, and one of the important simulation parameters is the laser energy characteristic. In this paper, based on the semi-active laser-guided weapon guidance principles, an important parameter of simulation of confidence which affects energy characteristics in performance test of HWIL simulation was analyzed. According to the principle of receiving the same energy by using HWIL simulation and in practical application, HWIL energy characteristics simulation systems with the crystal absorption structure was designed. And on this basis, the problems of optimal design of the optical system were also analyzed. The measured results show that the dynamic attenuation range of the system energy is greater than 50dB, the dynamic attenuation stability is less than 5%, and the maximum energy changing rate driven by the servo motor is greater than 20dB/s.

Panoramic 3D Reconstruction by Fusing Color Intensity and Laser Range Data

NASA Astrophysics Data System (ADS)

Jiang, Wei; Lu, Jian

Technology for capturing panoramic (360 degrees) three-dimensional information in a real environment have many applications in fields: virtual and complex reality, security, robot navigation, and so forth. In this study, we examine an acquisition device constructed of a regular CCD camera and a 2D laser range scanner, along with a technique for panoramic 3D reconstruction using a data fusion algorithm based on an energy minimization framework. The acquisition device can capture two types of data of a panoramic scene without occlusion between two sensors: a dense spatio-temporal volume from a camera and distance information from a laser scanner. We resample the dense spatio-temporal volume for generating a dense multi-perspective panorama that has equal spatial resolution to that of the original images acquired using a regular camera, and also estimate a dense panoramic depth-map corresponding to the generated reference panorama by extracting trajectories from the dense spatio-temporal volume with a selecting camera. Moreover, for determining distance information robustly, we propose a data fusion algorithm that is embedded into an energy minimization framework that incorporates active depth measurements using a 2D laser range scanner and passive geometry reconstruction from an image sequence obtained using the CCD camera. Thereby, measurement precision and robustness can be improved beyond those available by conventional methods using either passive geometry reconstruction (stereo vision) or a laser range scanner. Experimental results using both synthetic and actual images show that our approach can produce high-quality panoramas and perform accurate 3D reconstruction in a panoramic environment.

Development and Implementation of Joint Programs in Laser Ranging and Other Space Geodetic Techniques

NASA Technical Reports Server (NTRS)

Pearlman, Michael R.; Carter, David (Technical Monitor)

2002-01-01

On-going activities of the NASA special consultant to WEGENER (Working group of European Geoscientists for the Establishment of Networks for Earth-science Research) program are reported. Topics cover include: the WEGENER 2002 conference in Greece and the International Laser Ranging Service (ILRS).

Laser scanning methods and a phase comparison, modulated laser range finder for terrain sensing on a Mars roving vehicle. M.S. Thesis

NASA Technical Reports Server (NTRS)

Herb, G. T.

1973-01-01

Two areas of a laser range finder for a Mars roving vehicle are investigated: (1) laser scanning systems, and (2) range finder methods and implementation. Several ways of rapidly scanning a laser are studied. Two digital deflectors and a matrix of laser diodes, are found to be acceptable. A complete range finder scanning system of high accuracy is proposed. The problem of incident laser spot distortion on the terrain is discussed. The instrumentation for a phase comparison, modulated laser range finder is developed and sections of it are tested.

Effects of turbulence on the geodynamic laser ranging system

NASA Technical Reports Server (NTRS)

Churnside, James H.

1993-01-01

The Geodynamic Laser Ranging System (GLRS) is one of several instruments being developed by the National Aeronautics and Space Administration (NASA) for implementation as part of the Earth Observing System in the mid-1990s (Cohen et al., 1987; Bruno et al., 1988). It consists of a laser transmitter and receiver in space and an array of retroreflectors on the ground. The transmitter produces short (100 ps) pulses of light at two harmonics (0.532 and 0.355 microns) of the Nd:YAG laser. These propagate to a retroreflector on the ground and return. The receiver collects the reflected light and measures the round-trip transit time. Ranging from several angles accurately determines the position of the retroreflector, and changes in position caused by geophysical processes can be monitored.

Matera Laser Ranging Observatory (MLRO): An overview

NASA Technical Reports Server (NTRS)

Varghese, Thomas K.; Decker, Winfield M.; Crooks, Henry A.; Bianco, Giuseppe

1993-01-01

The Agenzia Spaziale Italiana (ASI) is currently under negotiation with the Bendix Field Engineering Corporation (BFEC) of the Allied Signal Aerospace Company (ASAC) to build a state-of-the-art laser ranging observatory for the Centro di Geodesia Spaziale, in Matera, Italy. The contract calls for the delivery of a system based on a 1.5 meter afocal Cassegrain astronomical quality telescope with multiple ports to support a variety of experiments for the future, with primary emphasis on laser ranging. Three focal planes, viz. Cassegrain, Coude, and Nasmyth will be available for these experiments. The open telescope system will be protected from dust and turbulence using a specialized dome which will be part of the building facilities to be provided by ASI. The fixed observatory facility will be partitioned into four areas for locating the following: laser, transmit/receive optics, telescope/dome enclosure, and the operations console. The optical tables and mount rest on a common concrete pad for added mechanical stability. Provisions will be in place for minimizing the effects of EMI, for obtaining maximum cleanliness for high power laser and transmit optics, and for providing an ergonomic environment fitting to a state-of-the-art multipurpose laboratory. The system is currently designed to be highly modular and adaptable for scaling or changes in technology. It is conceived to be a highly automated system with superior performance specifications to any currently operational system. Provisions are also made to adapt and accommodate changes that are of significance during the course of design and integration.

ICESAT Laser Altimeter Pointing, Ranging and Timing Calibration from Integrated Residual Analysis

NASA Technical Reports Server (NTRS)

Luthcke, Scott B.; Rowlands, D. D.; Carabajal, C. C.; Harding, D. H.; Bufton, J. L.; Williams, T. A.

2003-01-01

On January 12, 2003 the Ice, Cloud and land Elevation Satellite (ICESat) was successfully placed into orbit. The ICESat mission carries the Geoscience Laser Altimeter System (GLAS), which has a primary measurement of short-pulse laser- ranging to the Earth s surface at 1064nm wavelength at a rate of 40 pulses per second. The instrument has collected precise elevation measurements of the ice sheets, sea ice roughness and thickness, ocean and land surface elevations and surface reflectivity. The accurate geolocation of GLAS s surface returns, the spots from which the laser energy reflects on the Earth s surface, is a critical issue in the scientific application of these data. Pointing, ranging, timing and orbit errors must be compensated to accurately geolocate the laser altimeter surface returns. Towards this end, the laser range observations can be fully exploited in an integrated residual analysis to accurately calibrate these geolocation/instrument parameters. ICESat laser altimeter data have been simultaneously processed as direct altimetry from ocean sweeps along with dynamic crossovers in order to calibrate pointing, ranging and timing. The calibration methodology and current calibration results are discussed along with future efforts.

Carbon Nanotube Mode-Locked Thulium Fiber Laser With 200 nm Tuning Range

PubMed Central

Meng, Yafei; Li, Yao; Xu, Yongbing; Wang, Fengqiu

2017-01-01

We demonstrated a mode-locked thulium/holmium (Tm/Ho) fiber laser continuously tunable across 200 nm (from 1860 nm to 2060 nm), which to the best of our knowledge represents the widest tuning range ever achieved for a passively mode-locked fiber laser oscillator. The combined use of a broadband carbon nanotube (CNT) saturable absorber and a diffraction grating mirror ensures ultra-broad tuning range, superb stability and repeatability, and makes the demonstrated laser a highly practical source for spectroscopy, imaging and optical communications. The laser emits <5 ps pulses with an optical spectral bandwidth of ∼3 nm across the full tuning range. Our results indicate that carbon nanotubes can be an excellent saturable absorber for achieving gain-bandwidth-limited tunable operation for 2 μm thulium fiber lasers. PMID:28322327

Carbon Nanotube Mode-Locked Thulium Fiber Laser With 200 nm Tuning Range

NASA Astrophysics Data System (ADS)

Meng, Yafei; Li, Yao; Xu, Yongbing; Wang, Fengqiu

2017-03-01

We demonstrated a mode-locked thulium/holmium (Tm/Ho) fiber laser continuously tunable across 200 nm (from 1860 nm to 2060 nm), which to the best of our knowledge represents the widest tuning range ever achieved for a passively mode-locked fiber laser oscillator. The combined use of a broadband carbon nanotube (CNT) saturable absorber and a diffraction grating mirror ensures ultra-broad tuning range, superb stability and repeatability, and makes the demonstrated laser a highly practical source for spectroscopy, imaging and optical communications. The laser emits <5 ps pulses with an optical spectral bandwidth of ˜3 nm across the full tuning range. Our results indicate that carbon nanotubes can be an excellent saturable absorber for achieving gain-bandwidth-limited tunable operation for 2 μm thulium fiber lasers.

Extrinsic Calibration of a Laser Galvanometric Setup and a Range Camera.

PubMed

Sels, Seppe; Bogaerts, Boris; Vanlanduit, Steve; Penne, Rudi

2018-05-08

Currently, galvanometric scanning systems (like the one used in a scanning laser Doppler vibrometer) rely on a planar calibration procedure between a two-dimensional (2D) camera and the laser galvanometric scanning system to automatically aim a laser beam at a particular point on an object. In the case of nonplanar or moving objects, this calibration is not sufficiently accurate anymore. In this work, a three-dimensional (3D) calibration procedure that uses a 3D range sensor is proposed. The 3D calibration is valid for all types of objects and retains its accuracy when objects are moved between subsequent measurement campaigns. The proposed 3D calibration uses a Non-Perspective-n-Point (NPnP) problem solution. The 3D range sensor is used to calculate the position of the object under test relative to the laser galvanometric system. With this extrinsic calibration, the laser galvanometric scanning system can automatically aim a laser beam to this object. In experiments, the mean accuracy of aiming the laser beam on an object is below 10 mm for 95% of the measurements. This achieved accuracy is mainly determined by the accuracy and resolution of the 3D range sensor. The new calibration method is significantly better than the original 2D calibration method, which in our setup achieves errors below 68 mm for 95% of the measurements.

Improved laser-based triangulation sensor with enhanced range and resolution through adaptive optics-based active beam control.

PubMed

Reza, Syed Azer; Khwaja, Tariq Shamim; Mazhar, Mohsin Ali; Niazi, Haris Khan; Nawab, Rahma

2017-07-20

Various existing target ranging techniques are limited in terms of the dynamic range of operation and measurement resolution. These limitations arise as a result of a particular measurement methodology, the finite processing capability of the hardware components deployed within the sensor module, and the medium through which the target is viewed. Generally, improving the sensor range adversely affects its resolution and vice versa. Often, a distance sensor is designed for an optimal range/resolution setting depending on its intended application. Optical triangulation is broadly classified as a spatial-signal-processing-based ranging technique and measures target distance from the location of the reflected spot on a position sensitive detector (PSD). In most triangulation sensors that use lasers as a light source, beam divergence-which severely affects sensor measurement range-is often ignored in calculations. In this paper, we first discuss in detail the limitations to ranging imposed by beam divergence, which, in effect, sets the sensor dynamic range. Next, we show how the resolution of laser-based triangulation sensors is limited by the interpixel pitch of a finite-sized PSD. In this paper, through the use of tunable focus lenses (TFLs), we propose a novel design of a triangulation-based optical rangefinder that improves both the sensor resolution and its dynamic range through adaptive electronic control of beam propagation parameters. We present the theory and operation of the proposed sensor and clearly demonstrate a range and resolution improvement with the use of TFLs. Experimental results in support of our claims are shown to be in strong agreement with theory.

Calculation of impulse laser rangefinders' utmost operating range with sensitivity in different weather

NASA Astrophysics Data System (ADS)

Chen, Yu-dan; Zhou, Bing; Ying, Jia-ju; Mao, Shao-juan; Qian, Xian-mei

2015-10-01

As one of the main weapons, impulse laser rangefinders have become the main object of the electro-optical countermeasures. So its real maximum range (defined as utmost operating range in the paper) becomes the most concerned index to evaluate the performance of electro-optical countermeasure weapons. A method for calculating laser rangefinders' utmost operating range by its sensitivity in different weather is obtained. Then a method by experiment for getting the sensitivity is supplied. By analyzing the experiment data which the detectivity is 40%-60%, the laser rangefinders' sensitivity is in the range of 1.7×10-5 W to 9.8×10-5 W. For the reason that in order to get an exact utmost operating range, the experiment accuracy of sensitivity is very important, in the last part of paper, the factors which influence the experiment accuracy of sensitivity are analyzed, such as circuit of automatic gain control, the fluctuation of laser power, incident angle of laser.

Long-range, noncoherent laser Doppler velocimeter.

PubMed

Bloom, S H; Kremer, R; Searcy, P A; Rivers, M; Menders, J; Korevaar, E

1991-11-15

An experimental demonstration of a long-range, noncoherent laser Doppler velocimeter (LDV) is presented. The LDV detects incoming Doppler-shifted signal photons by using the sharp spectral absorption features in atomic or molecular vapors. The edge of the absorption feature is used to convert changes in frequency to large changes in transmission. Preliminary measurements of wind velocity using seeded aerosols showed that the LDV results agreed with mechanical anemometer measurements to within the accuracy of the LDV measurements. With optimization the LDV will provide accurate range-resolved and vibration-tolerant wind-speed measurements at large distances.

Multi-GNSS orbit determination using satellite laser ranging

NASA Astrophysics Data System (ADS)

Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław

2018-04-01

Galileo, BeiDou, QZSS, and NavIC are emerging global navigation satellite systems (GNSSs) and regional navigation satellite systems all of which are equipped with laser retroreflector arrays for range measurements. This paper summarizes the GNSS-intensive tracking campaigns conducted by the International Laser Ranging Service and provides results from multi-GNSS orbit determination using solely SLR observations. We consider the whole constellation of GLONASS, all active Galileo, four BeiDou satellites: 1 MEO, 3 IGSO, and one QZSS. We analyze the influence of the number of SLR observations on the quality of the 3-day multi-GNSS orbit solution. About 60 SLR observations are needed for obtaining MEO orbits of sufficient quality with the root mean square (RMS) of 3 cm for the radial component when compared to microwave-based orbits. From the analysis of a minimum number of tracking stations, when considering the 3-day arcs, 5 SLR stations do not provide a sufficient geometry of observations. The solution obtained using ten stations is characterized with RMS of 4, 9, and 18 cm in the radial, along-track, and cross-track direction, respectively, for MEO satellites. We also investigate the impact of the length of orbital arc on the quality of SLR-derived orbits. Hence, 5- and 7-day arcs constitute the best solution, whereas 3-day arcs are of inferior quality due to an insufficient number of SLR observations and 9-day arcs deteriorate the along-track component. The median RMS from the comparison between 7-day orbital arcs determined using SLR data with microwave-based orbits assumes values in the range of 3-4, 11-16, and 15-27 cm in radial, along-track, and cross-track, respectively, for MEO satellites. BeiDou IGSO and QZSS are characterized by RMS values higher by a factor of 8 and 24, respectively, than MEO orbits.

Frequency-modulated laser ranging sensor with closed-loop control

NASA Astrophysics Data System (ADS)

Müller, Fabian M.; Böttger, Gunnar; Janeczka, Christian; Arndt-Staufenbiel, Norbert; Schröder, Henning; Schneider-Ramelow, Martin

2018-02-01

Advances in autonomous driving and robotics are creating high demand for inexpensive and mass-producible distance sensors. A laser ranging system (Lidar), based on the frequency-modulated continuous-wave (FMCW) method is built in this work. The benefits of an FMCW Lidar system are the low-cost components and the performance in comparison to conventional time-of-flight Lidar systems. The basic system consists of a DFB laser diode (λ= 1308 nm) and an asymmetric fiber-coupled Mach-Zehnder interferometer with a fixed delay line in one arm. Linear tuning of the laser optical frequency via injection current modulation creates a beat signal at the interferometer output. The frequency of the beat signal is proportional to the optical path difference in the interferometer. Since the laser frequency-to-current response is non-linear, a closed-loop feed-back system is designed to improve the tuning linearity, and consequently the measurement resolution. For fast active control, an embedded system with FPGA is used, resulting in a nearly linear frequency tuning, realizing a narrow peak in the Fourier spectrum of the beat signal. For free-space measurements, a setup with two distinct interferometers is built. The fully fiber-coupled Mach-Zehnder reference interferometer is part of the feed-back loop system, while the other - a Michelson interferometer - has a free-space arm with collimator lens and reflective target. A resolution of 2:0 mm for a 560 mm distance is achieved. The results for varying target distances show high consistency and a linear relation to the measured beat-frequency.

Validation and verification of the laser range safety tool (LRST)

NASA Astrophysics Data System (ADS)

Kennedy, Paul K.; Keppler, Kenneth S.; Thomas, Robert J.; Polhamus, Garrett D.; Smith, Peter A.; Trevino, Javier O.; Seaman, Daniel V.; Gallaway, Robert A.; Crockett, Gregg A.

2003-06-01

The U.S. Dept. of Defense (DOD) is currently developing and testing a number of High Energy Laser (HEL) weapons systems. DOD range safety officers now face the challenge of designing safe methods of testing HEL's on DOD ranges. In particular, safety officers need to ensure that diffuse and specular reflections from HEL system targets, as well as direct beam paths, are contained within DOD boundaries. If both the laser source and the target are moving, as they are for the Airborne Laser (ABL), a complex series of calculations is required and manual calculations are impractical. Over the past 5 years, the Optical Radiation Branch of the Air Force Research Laboratory (AFRL/HEDO), the ABL System Program Office, Logicon-RDA, and Northrup-Grumman, have worked together to develop a computer model called teh Laser Range Safety Tool (LRST), specifically designed for HEL reflection hazard analyses. The code, which is still under development, is currently tailored to support the ABL program. AFRL/HEDO has led an LRST Validation and Verification (V&V) effort since 1998, in order to determine if code predictions are accurate. This paper summarizes LRST V&V efforts to date including: i) comparison of code results with laboratory measurements of reflected laser energy and with reflection measurements made during actual HEL field tests, and ii) validation of LRST's hazard zone computations.

Photodiode Preamplifier for Laser Ranging With Weak Signals

NASA Technical Reports Server (NTRS)

Abramovici, Alexander; Chapsky, Jacob

2007-01-01

An improved preamplifier circuit has been designed for processing the output of an avalanche photodiode (APD) that is used in a high-resolution laser ranging system to detect laser pulses returning from a target. The improved circuit stands in contrast to prior such circuits in which the APD output current pulses are made to pass, variously, through wide-band or narrow-band load networks before preamplification. A major disadvantage of the prior wide-band load networks is that they are highly susceptible to noise, which degrades timing resolution. A major disadvantage of the prior narrow-band load networks is that they make it difficult to sample the amplitudes of the narrow laser pulses ordinarily used in ranging. In the improved circuit, a load resistor is connected to the APD output and its value is chosen so that the time constant defined by this resistance and the APD capacitance is large, relative to the duration of a laser pulse. The APD capacitance becomes initially charged by the pulse of current generated by a return laser pulse, so that the rise time of the load-network output is comparable to the duration of the return pulse. Thus, the load-network output is characterized by a fast-rising leading edge, which is necessary for accurate pulse timing. On the other hand, the resistance-capacitance combination constitutes a lowpass filter, which helps to suppress noise. The long time constant causes the load network output pulse to have a long shallow-sloping trailing edge, which makes it easy to sample the amplitude of the return pulse. The output of the load network is fed to a low-noise, wide-band amplifier. The amplifier must be a wide-band one in order to preserve the sharp pulse rise for timing. The suppression of noise and the use of a low-noise amplifier enable the ranging system to detect relatively weak return pulses.

Quantum-cascade lasers in the 7-8 μm spectral range with full top metallization

NASA Astrophysics Data System (ADS)

Kurochkin, A. S.; Babichev, A. V.; Denisov, D. V.; Karachinsky, L. Ya; Novikov, I. I.; Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E.; Bousseksou, A.; Egorov, A. Yu

2018-03-01

The paper demonstrates the generation of multistage quantum-cascade lasers (QCL) in the 7-8 μm spectral range in the pulse generation mode. The active region structure we used is based on a two-phonon resonance scheme. The QCL heterostructure based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys was grown by molecular beam epitaxy and includes 50 identical stages. A waveguide geometry with top cladding with full top metallization (surface- plasmon quantum-cascade lasers) has been used. The developed QCLs have demonstrated multimodal generation in the 7-8 μm spectral range in the pulse mode in the 78-250 K temperature range. The threshold current density for a 1.6 mm long laser and a 20 μm ridge width amounted to ˜ 2.8 kA/cm2 at a temperature of 78 К. A temperature increase to 250 K causes a long-wave shift of the wavelength from 7.6 to 7.9 μm and a jth increase to 5.0 kA/cm2.

ICESat Laser Altimeter Pointing, Ranging and Timing Calibration from Integrated Residual Analysis: A Summary of Early Mission Results

NASA Technical Reports Server (NTRS)

Lutchke, Scott B.; Rowlands, David D.; Harding, David J.; Bufton, Jack L.; Carabajal, Claudia C.; Williams, Teresa A.

2003-01-01

On January 12, 2003 the Ice, Cloud and land Elevation Satellite (ICESat) was successfUlly placed into orbit. The ICESat mission carries the Geoscience Laser Altimeter System (GLAS), which consists of three near-infrared lasers that operate at 40 short pulses per second. The instrument has collected precise elevation measurements of the ice sheets, sea ice roughness and thickness, ocean and land surface elevations and surface reflectivity. The accurate geolocation of GLAS's surface returns, the spots from which the laser energy reflects on the Earth's surface, is a critical issue in the scientific application of these data Pointing, ranging, timing and orbit errors must be compensated to accurately geolocate the laser altimeter surface returns. Towards this end, the laser range observations can be fully exploited in an integrated residual analysis to accurately calibrate these geolocation/instrument parameters. Early mission ICESat data have been simultaneously processed as direct altimetry from ocean sweeps along with dynamic crossovers resulting in a preliminary calibration of laser pointing, ranging and timing. The calibration methodology and early mission analysis results are summarized in this paper along with future calibration activities

Laser active thermography for non-destructive testing

NASA Astrophysics Data System (ADS)

Semerok, A.; Grisolia, C.; Fomichev, S. V.; Thro, P.-Y.

2013-11-01

Thermography methods have found their applications in different fields of human activity. The non-destructive feature of these methods along with the additional advantage by automated remote control and tests of nuclear installations without personnel attendance in the contaminated zone are of particular interest. Laser active pyrometry and laser lock-in thermography for in situ non-destructive characterization of micrometric layers on graphite substrates from European tokamaks were under extensive experimental and theoretical studies in CEA (France). The studies were aimed to obtain layer characterization with cross-checking the layer thermal contact coefficients determined by active laser pyrometry and lock-in thermography. The experimental installation comprised a Nd-YAG pulsed repetition rate laser (1 Hz - 10 kHz repetition rate frequency, homogeneous spot) and a home-made pyrometer system based on two pyrometers for the temperature measurements in 500 - 2600 K range. For both methods, the layer characterization was provided by the best fit of the experimental results and simulations. The layer thermal contact coefficients determined by both methods were quite comparable. Though there was no gain in the measurements accuracy, lock-in measurements have proved their advantage as being much more rapid. The obtained experimental and theoretical results are presented. Some practical applications and possible improvements of the methods are discussed.

Precision improvement of frequency-modulated continuous-wave laser ranging system with two auxiliary interferometers

NASA Astrophysics Data System (ADS)

Shi, Guang; Wang, Wen; Zhang, Fumin

2018-03-01

The measurement precision of frequency-modulated continuous-wave (FMCW) laser distance measurement should be proportional to the scanning range of the tunable laser. However, the commercial external cavity diode laser (ECDL) is not an ideal tunable laser source in practical applications. Due to the unavoidable mode hopping and scanning nonlinearity of the ECDL, the measurement precision of FMCW laser distance measurements can be substantially affected. Therefore, an FMCW laser ranging system with two auxiliary interferometers is proposed in this paper. Moreover, to eliminate the effects of ECDL, the frequency-sampling method and mode hopping influence suppression method are employed. Compared with a fringe counting interferometer, this FMCW laser ranging system has a measuring error of ± 20 μm at the distance of 5.8 m.

Flight phasemeter on the Laser Ranging Interferometer on the GRACE Follow-On mission

NASA Astrophysics Data System (ADS)

Bachman, B.; de Vine, G.; Dickson, J.; Dubovitsky, S.; Liu, J.; Klipstein, W.; McKenzie, K.; Spero, R.; Sutton, A.; Ware, B.; Woodruff, C.

2017-05-01

As the first inter-spacecraft laser interferometer, the Laser Ranging Interferometer (LRI) on the GRACE Follow-On Mission will demonstrate interferometry technology relevant to the LISA mission. This paper focuses on the completed LRI Laser Ranging Processor (LRP), which includes heterodyne signal phase tracking at μ {{cycle/}}\\sqrt{{{Hz}}} precision, differential wavefront sensing, offset frequency phase locking and Pound-Drever-Hall laser stabilization. The LRI design has characteristics that are similar to those for LISA: 1064 nm NPRO laser source, science bandwidth in the mHz range, MHz-range intermediate frequency and Doppler shift, detected optical power of tens of picoWatts. Laser frequency stabilization has been demonstrated at a level below 30{{Hz/}}\\sqrt{{{Hz}}}, better than the LISA requirement of 300{{Hz/}}\\sqrt{{{Hz}}}. The LRP has completed all performance testing and environmental qualification and has been delivered to the GRACE Follow-On spacecraft. The LRI is poised to test the LISA techniques of tone-assisted time delay interferometry and arm-locking. GRACE Follow-On launches in 2017.

Noninvasive diode laser activation of transient receptor potential proteins and nociceptors

NASA Astrophysics Data System (ADS)

Jiang, Nan; Cooper, Brian Y.; Nemenov, Michael I.

2007-02-01

We investigated diode laser (980 nm) evoked activation of transient receptor potential proteins (TRPV1 and TRPV2). C and A-delta (Aδ) nociceptor families are primarily responsible for pain mediation in the peripheral nervous system. TRPV1 proteins have been associated with heat evoked pain in C fibers while Aδ fibers have been associated with TRPV2. Diode laser stimulation allows a margin of safety between non-invasive activation and damage 19, 22, 34. Laser pulses (20-50 ms, 0.1-10 W, 980 nm) were used to stimulate: A) in vitro: excised patches from HEK293 cells expressing TRPV1; B) in vitro: rat DRG nociceptors expressing either TRPV1 or TRPV2; and C) in vivo: C-fibers of the rat saphenous nerve (SN) trunk. Cell currents were recorded using standard patch clamp methods. The SN was also stimulated electrically with bipolar electrodes. Stimulation (20-50 ms) of HEK and DRG cells expressing TRPV1 was highly reproducible. Activation and peak currents were achieved at estimated peak temperatures of 55°C and 70°C. Threshold activation was also observed in DRG neurons expressing TRPV2. The conduction velocity for laser-activated saphenous nerve afferents was in the C fiber range (0.5-1 m/s). Electrically stimulated nerve contained stimulation artifacts and complex neural components with conduction velocities ranging from 0.3-30 m/s. Diode laser activation of TRPV1 protein is a reproducible and effective means to probe TRP activity in both in vivo and in vitro preparations

Molecular-beam epitaxy of 7-8 μm range quantum-cascade laser heterostructures

NASA Astrophysics Data System (ADS)

Babichev, A. V.; Denisov, D. V.; Filimonov, A. V.; Nevedomsky, V. N.; Kurochkin, A. S.; Gladyshev, A. G.; Karachinsky, L. Ya; Sokolovskii, G. S.; Novikov, I. I.; Bousseksou, A.; Egorov, A. Yu

2017-11-01

The method of molecular beam epitaxy demonstrates the possibility to create high quality heterostructures of quantum cascade lasers in a spectral range of 7-8 μm containing 50 quantum cascades in an active region. Design based on the principle of two-phonon resonant scattering is used. X-ray diffraction and transmission electron microscopy experiments confirm high structural properties of the created heterostructures, e.g. the identity of the composition and thickness of epitaxial layers in all 50 cascades. Edge-emitting lasers based on the grown heterostructure demonstrate lasing with threshold current density of 2.8 kA/cm2 at a temperature of 78 K.

Indetermination of particle sizing by laser diffraction in the anomalous size ranges

NASA Astrophysics Data System (ADS)

Pan, Linchao; Ge, Baozhen; Zhang, Fugen

2017-09-01

The laser diffraction method is widely used to measure particle size distributions. It is generally accepted that the scattering angle becomes smaller and the angles to the location of the main peak of scattered energy distributions in laser diffraction instruments shift to smaller values with increasing particle size. This specific principle forms the foundation of the laser diffraction method. However, this principle is not entirely correct for non-absorbing particles in certain size ranges and these particle size ranges are called anomalous size ranges. Here, we derive the analytical formulae for the bounds of the anomalous size ranges and discuss the influence of the width of the size segments on the signature of the Mie scattering kernel. This anomalous signature of the Mie scattering kernel will result in an indetermination of the particle size distribution when measured by laser diffraction instruments in the anomalous size ranges. By using the singular-value decomposition method we interpret the mechanism of occurrence of this indetermination in detail and then validate its existence by using inversion simulations.

Test technology on divergence angle of laser range finder based on CCD imaging fusion

NASA Astrophysics Data System (ADS)

Shi, Sheng-bing; Chen, Zhen-xing; Lv, Yao

2016-09-01

Laser range finder has been equipped with all kinds of weapons, such as tank, ship, plane and so on, is important component of fire control system. Divergence angle is important performance and incarnation of horizontal resolving power for laser range finder, is necessary appraised test item in appraisal test. In this paper, based on high accuracy test on divergence angle of laser range finder, divergence angle test system is designed based on CCD imaging, divergence angle of laser range finder is acquired through fusion technology for different attenuation imaging, problem that CCD characteristic influences divergence angle test is solved.

The coordinate frame of the lunar laser ranging network

NASA Technical Reports Server (NTRS)

Williams, J. G.; Newhall, X. X.; Dickey, J. O.

1986-01-01

The geocentric coordinates for four instruments, which were derived using lunar laser ranging, are compared with the 84L02 coordinates determined from the Lageos satellite. The determination of the geocentric coordinates for the 2.7 m and McDonald Observatory laser ranging system telescopes at McDonald Observatory, the Haleakala site, and the CERGA site near Grasse, France is described. Consideration is given to the McDonald Observatory colocation and station motion due to continential drift. A rms difference of 18 cm is determined for the two sets of geocentric coordinates; however, removing a data anomaly reduces the rms difference to 13 cm.

Receiver Design, Performance Analysis, and Evaluation for Space-Borne Laser Altimeters and Space-to-Space Laser Ranging Systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

1996-01-01

This progress report consists of two separate reports. The first one describes our work on the use of variable gain amplifiers to increase the receiver dynamic range of space borne laser altimeters such as NASA's Geoscience Laser Altimeter Systems (GLAS). The requirement of the receiver dynamic range was first calculated. A breadboard variable gain amplifier circuit was made and the performance was fully characterized. The circuit will also be tested in flight on board the Shuttle Laser Altimeter (SLA-02) next year. The second report describes our research on the master clock oscillator frequency calibration for space borne laser altimeter systems using global positioning system (GPS) receivers.

Satellite and lunar laser ranging in infrared

NASA Astrophysics Data System (ADS)

Courde, Clement; Torre, Jean-Marie; Samain, Etienne; Martinot-Lagarde, Gregoire; Aimar, Mourad; Albanese, Dominique; Maurice, Nicolas; Mariey, Hervé; Viot, Hervé; Exertier, Pierre; Fienga, Agnes; Viswanathan, Vishnu

2017-05-01

We report on the implementation of a new infrared detection at the Grasse lunar laser ranging station and describe how infrared telemetry improves the situation. We present our first results on the lunar reflectors and show that infrared detection permits us to densify the observations and allows measurements during the new and the full moon periods. We also present the benefit obtained on the ranging of Global Navigation Satellite System (GNSS) satellites and on RadioAstron which have a very elliptic orbit.

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

1995-01-01

Laser altimeters measure the time of flight of the laser pulses to determine the range of the target. The simplest altimeter receiver consists of a photodetector followed by a leading edge detector. A time interval unit (TIU) measures the time from the transmitted laser pulse to the leading edge of the received pulse as it crosses a preset threshold. However, the ranging error of this simple detection scheme depends on the received, pulse amplitude, pulse shape, and the threshold. In practice, the pulse shape and the amplitude are determined by the target target characteristics which has to be assumed unknown prior to the measurement. The ranging error can be improved if one also measures the pulse width and use the average of the leading and trailing edges (half pulse width) as the pulse arrival time. The ranging error becomes independent of the received pulse amplitude and the pulse width as long as the pulse shape is symmetric. The pulse width also gives the slope of the target. The ultimate detection scheme is to digitize the received waveform and calculate the centroid as the pulse arrival time. The centroid detection always gives unbiased measurement even for asymmetric pulses. In this report, we analyze the laser altimeter ranging errors for these three detection schemes using the Mars Orbital Laser Altimeter (MOLA) as an example.

Range imaging laser radar

DOEpatents

Scott, Marion W.

1990-01-01

A laser source is operated continuously and modulated periodically (typicy sinusoidally). A receiver imposes another periodic modulation on the received optical signal, the modulated signal being detected by an array of detectors of the integrating type. Range to the target determined by measuring the phase shift of the intensity modulation on the received optical beam relative to a reference. The receiver comprises a photoemitter for converting the reflected, periodically modulated, return beam to an accordingly modulated electron stream. The electron stream is modulated by a local demodulation signal source and subsequently converted back to a photon stream by a detector. A charge coupled device (CCD) array then averages and samples the photon stream to provide an electrical signal in accordance with the photon stream.

Range imaging laser radar

DOEpatents

Scott, M.W.

1990-06-19

A laser source is operated continuously and modulated periodically (typically sinusoidally). A receiver imposes another periodic modulation on the received optical signal, the modulated signal being detected by an array of detectors of the integrating type. Range to the target determined by measuring the phase shift of the intensity modulation on the received optical beam relative to a reference. The receiver comprises a photoemitter for converting the reflected, periodically modulated, return beam to an accordingly modulated electron stream. The electron stream is modulated by a local demodulation signal source and subsequently converted back to a photon stream by a detector. A charge coupled device (CCD) array then averages and samples the photon stream to provide an electrical signal in accordance with the photon stream. 2 figs.

Linear FMCW Laser Radar for Precision Range and Vector Velocity Measurements

NASA Technical Reports Server (NTRS)

Pierrottet, Diego; Amzajerdian, Farzin; Petway, Larry; Barnes, Bruce; Lockhard, George; Rubio, Manuel

2008-01-01

An all fiber linear frequency modulated continuous wave (FMCW) coherent laser radar system is under development with a goal to aide NASA s new Space Exploration initiative for manned and robotic missions to the Moon and Mars. By employing a combination of optical heterodyne and linear frequency modulation techniques and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed. Linear FMCW lidar has the capability of high-resolution range measurements, and when configured into a multi-channel receiver system it has the capability of obtaining high precision horizontal and vertical velocity measurements. Precision range and vector velocity data are beneficial to navigating planetary landing pods to the preselected site and achieving autonomous, safe soft-landing. The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to measure directly the platform velocity by extracting the Doppler shift generated from the motion, as opposed to time of flight range finders where terrain features such as hills, cliffs, or slopes add error to the velocity measurement. Doppler measurements are about two orders of magnitude more accurate than the velocity estimates obtained by pulsed laser altimeters. In addition, most of the components of the device are efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper discusses the design and performance of a second-generation brassboard system under development at NASA Langley Research Center as part of the Autonomous Landing and Hazard Avoidance (ALHAT) project.

Observing tectonic plate motions and deformations from satellite laser ranging

NASA Technical Reports Server (NTRS)

Christodoulidis, D. C.; Smith, D. E.; Kolenkiewicz, R.; Klosko, S. M.; Torrence, M. H.

1985-01-01

The scope of geodesy has been greatly affected by the advent of artificial near-earth satellites. The present paper provides a description of the results obtained from the reduction of data collected with the aid of satellite laser ranging. It is pointed out that dynamic reduction of satellite laser ranging (SLR) data provides very precise positions in three dimensions for the laser tracking network. The vertical components of the stations, through the tracking geometry provided by the global network and the accurate knowledge of orbital dynamics, are uniquely related to the center of mass of the earth. Attention is given to the observations, the methodologies for reducing satellite observations to estimate station positions, Lageos-observed tectonic plate motions, an improved temporal resolution of SLR plate motions, and the SLR vertical datum.

University of Hawaii Lure Observatory. [lunar laser ranging system construction

NASA Technical Reports Server (NTRS)

Carter, W. E.; Williams, J. D.

1973-01-01

The University of Hawaii's Institute for Astronomy is currently constructing a lunar laser ranging observatory at the 3050-meter summit of Mt. Haleakala, Hawaii. The Nd YAG laser system to be employed provides three pulses per second, each pulse being approximately 200 picoseconds in duration. The energy contained in one pulse at 5320 A lies in the range from 250 to 350 millijoules. Details of observatory construction are provided together with transmitter design data and information concerning the lunastat, the feed telescope, the relative pointing system, the receiver, and the event timer system.

Benefits Derived From Laser Ranging Measurements for Orbit Determination of the GPS Satellite Orbit

NASA Technical Reports Server (NTRS)

Welch, Bryan W.

2007-01-01

While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current research is examining methods to lower the error in the GPS satellite ephemerides below their current level. Two GPS satellites that are currently in orbit carry retro-reflectors onboard. One notion to reduce the error in the satellite ephemerides is to utilize the retro-reflectors via laser ranging measurements taken from multiple Earth ground stations. Analysis has been performed to determine the level of reduction in the semi-major axis covariance of the GPS satellites, when laser ranging measurements are supplemented to the radiometric station keeping, which the satellites undergo. Six ground tracking systems are studied to estimate the performance of the satellite. The first system is the baseline current system approach which provides pseudo-range and integrated Doppler measurements from six ground stations. The remaining five ground tracking systems utilize all measurements from the current system and laser ranging measurements from the additional ground stations utilized within those systems. Station locations for the additional ground sites were taken from a listing of laser ranging ground stations from the International Laser Ranging Service. Results show reductions in state covariance estimates when utilizing laser ranging measurements to solve for the satellite s position component of the state vector. Results also show dependency on the number of ground stations providing laser ranging measurements, orientation of the satellite to the ground stations, and the initial covariance of the satellite's state vector.

Synthesis and analysis of precise spaceborne laser ranging systems, volume 2. [Spacelab payload

NASA Technical Reports Server (NTRS)

Paddon, E. A.

1978-01-01

The performance capabilities of specific shuttle-based laser ranging systems were evaluated, and interface and support requirements were determined. The preliminary design of a shuttle-borne laser ranging experiment developed as part of the Spacelab program is discussed.

Synthesis and analysis of precise spaceborne laser ranging systems, volume 1. [link analysis

NASA Technical Reports Server (NTRS)

Paddon, E. A.

1977-01-01

Measurement accuracy goals of 2 cm rms range estimation error and 0.003 cm/sec rms range rate estimation error, with no more than 1 cm (range) static bias error are requirements for laser measurement systems to be used in planned space-based earth physics investigations. Constraints and parameters were defined for links between a high altitude, transmit/receive satellite (HATRS), and one of three targets: a low altitude target satellite, passive (LATS), and active low altitude target, and a ground-based target, as well as with operations with a primary transmit/receive terminal intended to be carried as a shuttle payload, in conjunction with the Spacelab program.

Energy scaling of passively Q-switched lasers In the Mj-range

NASA Astrophysics Data System (ADS)

Neumann, J.; Huss, R.; Kolleck, C.; Kracht, Dietmar

2017-11-01

Q-switched lasers systems with ns pulse duration and energies ranging from 1 to more than 100mJ are utilized for many spaceborne applications such as altimetry of planets and moons. Furthermore, Q-switched lasers can be used for distance measurements during docking and landing manoeuvres. To keep the diameter of the beam small over a large distance and to consequently achieve a good lateral resolution, a good beam propagation factor M² is required. Moreover, Q-switched lasers can be used directly on the planetary surface for exploration by laser-induced breakdown spectroscopy or laser desorption mass spectrometry.

View of the Laser Ranging Retro Reflector deployed by Apollo 14 astronauts

NASA Image and Video Library

1971-02-05

AS14-67-9386 (5 Feb. 1971) --- A close-up view of the laser ranging retro reflector (LR3) which the Apollo 14 astronauts deployed on the moon during their lunar surface extravehicular activity (EVA). While astronauts Alan B. Shepard Jr., commander, and Edgar D. Mitchell, lunar module pilot, descended in the Lunar Module (LM) to explore the moon, astronaut Stuart A. Roosa, command module pilot, remained with the Command and Service Modules (CSM) in lunar orbit.

Phobos laser ranging: Numerical Geodesy experiments for Martian system science

NASA Astrophysics Data System (ADS)

Dirkx, D.; Vermeersen, L. L. A.; Noomen, R.; Visser, P. N. A. M.

2014-09-01

Laser ranging is emerging as a technology for use over (inter)planetary distances, having the advantage of high (mm-cm) precision and accuracy and low mass and power consumption. We have performed numerical simulations to assess the science return in terms of geodetic observables of a hypothetical Phobos lander performing active two-way laser ranging with Earth-based stations. We focus our analysis on the estimation of Phobos and Mars gravitational, tidal and rotational parameters. We explicitly include systematic error sources in addition to uncorrelated random observation errors. This is achieved through the use of consider covariance parameters, specifically the ground station position and observation biases. Uncertainties for the consider parameters are set at 5 mm and at 1 mm for the Gaussian uncorrelated observation noise (for an observation integration time of 60 s). We perform the analysis for a mission duration up to 5 years. It is shown that a Phobos Laser Ranging (PLR) can contribute to a better understanding of the Martian system, opening the possibility for improved determination of a variety of physical parameters of Mars and Phobos. The simulations show that the mission concept is especially suited for estimating Mars tidal deformation parameters, estimating degree 2 Love numbers with absolute uncertainties at the 10-2 to 10-4 level after 1 and 4 years, respectively and providing separate estimates for the Martian quality factors at Sun and Phobos-forced frequencies. The estimation of Phobos libration amplitudes and gravity field coefficients provides an estimate of Phobos' relative equatorial and polar moments of inertia with an absolute uncertainty of 10-4 and 10-7, respectively, after 1 year. The observation of Phobos tidal deformation will be able to differentiate between a rubble pile and monolithic interior within 2 years. For all parameters, systematic errors have a much stronger influence (per unit uncertainty) than the uncorrelated Gaussian

High-energy azimuthally polarized laser beam generation from an actively Q-switched Nd:YAG laser with c-cut YVO4 crystal

NASA Astrophysics Data System (ADS)

Guo, Jing; Zhang, Baofu; Jiao, Zhongxing; He, Guangyuan; Wang, Biao

2018-05-01

A high-energy, azimuthally polarized (AP) and actively Q-switched Nd:YAG laser is demonstrated. The thermal bipolar lensing effect in the Nd:YAG laser rod is used as a polarization discriminator, and a c-cut YVO4 crystal is inserted into the laser cavity to increase the mode-selecting ability of the cavity for AP mode. The laser generated AP pulses with maximum pulse energy as high as 4.2 mJ. To the best of our knowledge, this is the highest pulse energy obtained from an actively Q-switched AP laser. The pulse energy remained higher than 1 mJ over a wide range of repetition rates from 5 kHz to 25 kHz.

Study of pseudo noise CW diode laser for ranging applications

NASA Technical Reports Server (NTRS)

Lee, Hyo S.; Ramaswami, Ravi

1992-01-01

A new Pseudo Random Noise (PN) modulated CW diode laser radar system is being developed for real time ranging of targets at both close and large distances (greater than 10 KM) to satisy a wide range of applications: from robotics to future space applications. Results from computer modeling and statistical analysis, along with some preliminary data obtained from a prototype system, are presented. The received signal is averaged for a short time to recover the target response function. It is found that even with uncooperative targets, based on the design parameters used (200-mW laser and 20-cm receiver), accurate ranging is possible up to about 15 KM, beyond which signal to noise ratio (SNR) becomes too small for real time analog detection.

Laser-ranging long-baseline differential atom interferometers for space

NASA Astrophysics Data System (ADS)

Chiow, Sheng-wey; Williams, Jason; Yu, Nan

2015-12-01

High-sensitivity differential atom interferometers (AIs) are promising for precision measurements in science frontiers in space, including gravity-field mapping for Earth science studies and gravitational wave detection. Difficulties associated with implementing long-baseline differential AIs have previously included the need for a high optical power, large differential Doppler shifts, and narrow dynamic range. We propose a configuration of twin AIs connected by a laser-ranging interferometer (LRI-AI) to provide precise information of the displacements between the two AI reference mirrors and also to phase-lock the two independent interferometer lasers over long distances, thereby drastically improving the practical feasibility of long-baseline differential AI measurements. We show that a properly implemented LRI-AI can achieve equivalent functionality to the conventional differential AI measurement configuration.

Design and Commissioning of a Transportable Laser Ranging Station STAR-C

NASA Astrophysics Data System (ADS)

Humbert, L.; Hasenohr, T.; Hampf, D.; Riede, W.

An increasing number of space debris and the rise of mega constellations as well as the deployment of small cost efficient satellites are a growing concern for space faring nations and their missions. Hence, a tight network of worldwide stations to support maintenance of catalogues for various tasks such as space surveillance tracking and space traffic management will significantly increase the reliability and availability of the collected data and therefore the safety of missions. A promising concept are transportable laser ranging stations in order to increase the number of observing stations and hence the coverage of the sky. Built and tested on a building test site they can be deployed to a desired site for operation. High energy laser with short pulses provide accurate ranging data to objects in space both cooperative and uncooperative, e.g. objects with a retroreflector and without one. This work introduces the progress of a transportable laser ranging station, of a Surveillance, Tracking and Ranging Container (STAR-C), built into a 20ft ISO container.

Modelling of Lunar Laser Ranging in the Geocentric Frame and Comparison with the Common-View Double-Difference Lunar Laser Ranging Approach

NASA Astrophysics Data System (ADS)

Svehla, D.; Rothacher, M.

2016-12-01

Is it possible to process Lunar Laser Ranging (LLR) measurements in the geocentric frame in a similar way SLR measurements are modelled for GPS satellites and estimate all global reference frame parameters like in the case of GPS? The answer is yes. We managed to process Lunar laser measurements to Apollo and Luna retro-reflectors on the Moon in a similar way we are processing SLR measurements to GPS satellites. We make use of the latest Lunar libration models and DE430 ephemerides given in the Solar system baricentric frame and model uplink and downlink Lunar laser ranges in the geocentric frame as one way measurements, similar to SLR measurements to GPS satellites. In the first part of this contribution we present the estimation of the Lunar orbit as well as the Earth orientation parameters (including UT1 or UT0) with this new formulation. In the second part, we form common-view double-difference LLR measurements between two Lunar retro-reflectors and two LLR telescopes to show the actual noise of the LLR measurements. Since, by forming double-differences of LLR measurements, all range biases are removed and orbit errors are significantly reduced (the Lunar orbit is much farther away than the GPS orbits), one can consider double-difference LLR as an "orbit-free" and "bias-free" differential approach. In the end, we make a comparison with the SLR double-difference approach with Galileo satellites, where we already demonstrated submillimeter precision, and discuss possible combination of LLR and SLR to GNSS satellites using double-difference approach.

Probing Gravity with Next Generation Lunar Laser Ranging

NASA Astrophysics Data System (ADS)

Martini, Manuele; Dell'Agnello, Simone

Lunar and satellite laser ranging (LLR/SLR) are consolidated techniques which provide a precise, and at the same time, cost-effective method to determine the orbits of the Moon and of satellites equipped with laser retroreflectors with respect to the International Celestial Reference System. We describe the precision tests of general relativity and of new theories of gravity that can be performed with second-generation LLR payloads on the surface of the Moon (NASA/ASI MoonLIGHT project), and with SLR/LLR payloads deployed on spacecraft in the Earth-Moon system. A new wave of lunar exploration and lunar science started in 2007-2008 with the launch of three missions (Chang'e by China, Kaguya by Japan, Chandrayaan by India), missions in preparation (LCROSS, LRO, GRAIL/LADEE by NASA) and other proposed missions (like MAGIA in Italy). This research activity will be greatly enhanced by the future robotic deployment of a lunar geophysics network (LGN) on the surface of the Moon. A scientific concept of the latter is the International Lunar Network (ILN, see http://iln.arc.nasa.gov/). The LLR retroreflector payload developed by a US-Italy team described here and under space qualification at the National Laboratories of Frascati (LNF) is the optimum candidate for the LGN, which will be populated in the future by any lunar landing mission.

Precision laser range finder system design for Advanced Technology Laboratory applications

NASA Technical Reports Server (NTRS)

Golden, K. E.; Kohn, R. L.; Seib, D. H.

1974-01-01

Preliminary system design of a pulsed precision ruby laser rangefinder system is presented which has a potential range resolution of 0.4 cm when atmospheric effects are negligible. The system being proposed for flight testing on the advanced technology laboratory (ATL) consists of a modelocked ruby laser transmitter, course and vernier rangefinder receivers, optical beacon retroreflector tracking system, and a network of ATL tracking retroreflectors. Performance calculations indicate that spacecraft to ground ranging accuracies of 1 to 2 cm are possible.

Single photon ranging system using two wavelengths laser and analysis of precision

NASA Astrophysics Data System (ADS)

Chen, Yunfei; He, Weiji; Miao, Zhuang; Gu, Guohua; Chen, Qian

2013-09-01

The laser ranging system based on time correlation single photon counting technology and single photon detector has the feature of high precision and low emergent energy etc. In this paper, we established a single photon laser ranging system that use the supercontinuum laser as light source, and two wavelengths (532nm and 830nm) of echo signal as the stop signal. We propose a new method that is capable to improve the single photon ranging system performance. The method is implemented by using two single-photon detectors to receive respectively the two different wavelength signals at the same time. We extracted the firings of the two detectors triggered by the same laser pulse at the same time and then took mean time of the two firings as the combined detection time-of-flight. The detection by two channels using two wavelengths will effectively improve the detection precision and decrease the false alarm probability. Finally, an experimental single photon ranging system was established. Through a lot of experiments, we got the system precision using both single and two wavelengths and verified the effectiveness of the method.

Geoscience Laser Ranging System design and performance predictions

NASA Technical Reports Server (NTRS)

Anderson, Kent L.

1991-01-01

The Geoscience Laser System (GLRS) will be a high-precision distance-measuring instrument planned for deployment on the EOS-B platform. Its primary objectives are to perform ranging measurements to ground targets to monitor crustal deformation and tectonic plate motions, and nadir-looking altimetry to determine ice sheet thicknesses, surface topography, and vertical profiles of clouds and aerosols. The system uses a mode-locked, 3-color Nd:YAG laser source, a Microchannel Plate-PMT for absolute time-of-flight (TOF) measurement (at 532 nm), a streak camera for TOF 2-color dispersion measurement (532 nm and 355 nm), and a Si avalanche photodiode for altimeter waveform detection (1064 nm). The performance goals are to make ranging measurements to ground targets with about 1 cm accuracy, and altimetry height measurements over ice with 10 cm accuracy. This paper presents an overview of the design concept developed during a phase B study. System engineering issues and trade studies are discussed, with particular attention to error budgets and performance predictions.

Laser Ranging to the Lunar Reconnaissance Orbiter: improved timing and orbits

NASA Astrophysics Data System (ADS)

Mao, D.; Mcgarry, J.; Sun, X.; Torrence, M. H.; Skillman, D.; Hoffman, E.; Mazarico, E.; Rowlands, D. D.; Golder, J.; Barker, M. K.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

2013-12-01

The Laser ranging (LR) experiment to the Lunar Reconnaissance Orbiter (LRO) has been under operation for more than 4 years, since the launch of the spacecraft in June 2009. Led by NASA's Next Generation Satellite Laser Ranging(NGSLR) station at Greenbelt, Maryland, ten laser ranging stations over the world have been participating in the experiment and have collected over 3,200 hours of ranging data. These range measurements are used to monitor the behavior of the LRO clock and to generate orbital solutions for LRO. To achieve high-quality results in range, ground stations like NGSLR are using H-maser clocks to obtain a stable and continuous time baseline for the orbit solutions. An All-View GPS receiver was included at NGSLR since January 2013 which monitors the H-maser time against the master clock at the United State Naval Observatory (USNO) via the GPS satellites. NGSLR has successfully established nano-second level epoch time accuracy and 10-15 clock stability since then. Time transfer experiments using LRO as a common receiver have been verified in ground testing between NGSLR and MOBLAS7 via a ground terminal with a Lunar Orbiter Laser Altimeter (LOLA)-like receiver at Greenbelt, Maryland. Two hour-long ground tests using a LOLA-like detector and two different ground targets yielded results consistent with each other, and those from the previous 10-minute test completed one year ago. Time transfer tests between NGSLR and MOBLAS7 via LRO are ongoing. More time transfer tests are being planned from NGSLR to McDonald Laser Ranging Station (MLRS) in Texas and later from NGSLR to European satellite laser ranging (SLR) stations. Upon the completion of these time transfer experiments, nanosecond-level epoch time accuracy will be brought to stations besides NGSLR, and such high precision of the ground time can contribute to the LRO precision orbit determination (POD) process. Presently, by using the high-resolution GRAIL gravity models, the LRO orbits determined from

Pulsed multiwavelength laser ranging system. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Abshire, J. B.

1982-01-01

A pulsed multiwavelength laser ranging system for measuring atmospheric delay was built and tested, and its theoretical performance limits were calculated. The system uses a dye modelocked ND:YAG laser, which transmits 70 psec wide pulses simultaneously at 1064, 532, and 355 nm. The differential delay of the 1064 and 355 nm pulses is measured by a specially calibrated waveform digitizer to estimate the dry atmospheric delay. The delay time of the 532 nm pulse is used to measure the target distance. Static crossed field photomultipliers are used as detectors for all wavelengths. Theoretical analysis shows that path curvature and atmospheric turbulence are fundamental limits to the ranging accuracy of both single and multicolor systems operating over horizontal paths. For two color systems, an additional error is caused by the uncertainty in the path averaged water vapor. The standard deviation of the multicolor instrument's timing measurements is directly proportional to the laser pulse width plus photomultiplier jitter divided by the square root of the received photoelectron number. The prototype system's maximum range is km, which is limited by atmospheric and system transmission losses at 355 nm. System signal detection and false alarm calculations are also presented.

Widely tunable laser frequency offset lock with 30 GHz range and 5 THz offset.

PubMed

Biesheuvel, J; Noom, D W E; Salumbides, E J; Sheridan, K T; Ubachs, W; Koelemeij, J C J

2013-06-17

We demonstrate a simple and versatile method to greatly extend the tuning range of optical frequency shifting devices, such as acousto-optic modulators (AOMs). We use this method to stabilize the frequency of a tunable narrow-band continuous-wave (CW) laser to a transmission maximum of an external Fabry-Perot interferometer (FPI) with a tunable frequency offset. This is achieved through a servo loop which contains an in-loop AOM for simple radiofrequency (RF) tuning of the optical frequency over the full 30 GHz mode-hop-free tuning range of the CW laser. By stabilizing the length of the FPI to a stabilized helium-neon (HeNe) laser (at 5 THz offset from the tunable laser) we simultaneously transfer the ~ 1 MHz absolute frequency stability of the HeNe laser to the entire 30 GHz range of the tunable laser. Thus, our method allows simple, wide-range, fast and reproducible optical frequency tuning and absolute optical frequency measurements through RF electronics, which is here demonstrated by repeatedly recording a 27-GHz-wide molecular iodine spectrum at scan rates up to 500 MHz/s. General technical aspects that determine the performance of the method are discussed in detail.

Automated tracking for advanced satellite laser ranging systems

NASA Astrophysics Data System (ADS)

McGarry, Jan F.; Degnan, John J.; Titterton, Paul J., Sr.; Sweeney, Harold E.; Conklin, Brion P.; Dunn, Peter J.

1996-06-01

NASA's Satellite Laser Ranging Network was originally developed during the 1970's to track satellites carrying corner cube reflectors. Today eight NASA systems, achieving millimeter ranging precision, are part of a global network of more than 40 stations that track 17 international satellites. To meet the tracking demands of a steadily growing satellite constellation within existing resources, NASA is embarking on a major automation program. While manpower on the current systems will be reduced to a single operator, the fully automated SLR2000 system is being designed to operate for months without human intervention. Because SLR2000 must be eyesafe and operate in daylight, tracking is often performed in a low probability of detection and high noise environment. The goal is to automatically select the satellite, setup the tracking and ranging hardware, verify acquisition, and close the tracking loop to optimize data yield. TO accomplish the autotracking tasks, we are investigating (1) improved satellite force models, (2) more frequent updates of orbital ephemerides, (3) lunar laser ranging data processing techniques to distinguish satellite returns from noise, and (4) angular detection and search techniques to acquire the satellite. A Monte Carlo simulator has been developed to allow optimization of the autotracking algorithms by modeling the relevant system errors and then checking performance against system truth. A combination of simulator and preliminary field results will be presented.

Time Biases in laser ranging measurements; impacts on geodetic products (Reference Frame and Orbitography)

NASA Astrophysics Data System (ADS)

Belli, A.; Exertier, P.; Lemoine, F. G.; Chinn, D. S.; Zelensky, N. P.

2017-12-01

The GGOS objectives are to maintain a geodetic network with an accuracy of 1 mm and a stability of 0.1 mm per year. For years, the laser ranging technique, which provide very accurate absolute distances to geodetic targets enable to determine the scale factor as well as coordinates of the geocenter. In order to achieve this goal, systematic errors appearing in the laser ranging measurements must be considered and solved. In addition to Range Bias (RB), which is the primary source of uncertainty of the technique, Time Bias (TB) has been recently detected by using the Time Transfer by Laser Link (T2L2) space instrument capability on-board the satellite Jason-2. Instead of determining TB through the precise orbit determination that is applied to commonly used geodetic targets like LAGEOS to estimate global geodetic products, we have developed, independently, a dedicated method to transfer time between remote satellite laser ranging stations. As a result, the evolving clock phase shift to UTC of around 30 stations has been determined under the form of time series of time bias per station from 2008 to 2016 with an accuracy of 3-4 ns. It demonstrated the difficulty, in terms of Time & Frequency used technologies, to locally maintain accuracy and long term stability at least in the range of 100 ns that is the current requirement for time measurements (UTC) for the laser ranging technique. Because some laser ranging stations oftently exceed this limit (from 100 ns to a few μs) we have been studying these effects first on the precision orbit determination itself, second on the station positioning. We discuss the impact of TB on LAGEOS and Jason-2 orbits, which appears to affect the along-track component essentially. We also investigate the role of TB in global geodetic parameters as the station coordinates. Finally, we propose to provide the community with time series of time bias of laser ranging stations, under the form of a data- handling-file in order to be included in

Laser range measurement for a satellite navigation scheme and mid-range path selection and obstacle avoidance. M.S. Thesis

NASA Technical Reports Server (NTRS)

Zuraski, G. D.

1972-01-01

The functions of a laser rangefinder on board an autonomous Martian roving vehicle are discussed. The functions are: (1) navigation by means of a passive satellite and (2) mid-range path selection and obstacle avoidance. The feasibility of using a laser to make the necessary range measurements is explored and a preliminary design is presented. The two uses of the rangefinder dictate widely different operating parameters making it impossible to use the same system for both functions.

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

1994-01-01

Accomplishments in the following areas of research are presented: receiver performance study of spaceborne laser altimeters and cloud and aerosol lidars; receiver performance analysis for space-to-space laser ranging systems; and receiver performance study for the Mars Environmental Survey (MESUR).

Usachev uses a laser range finder during rendezvous ops

NASA Image and Video Library

2001-03-10

STS102-E-5085 (10 March 2001) --- Cosmonaut Yury V. Usachev, STS-102 mission specialist, uses a laser ranging device on Discovery's aft flight deck during rendezvous operations. The photograph was recorded with a digital still camera.

Atmospheric refraction errors in laser ranging systems

NASA Technical Reports Server (NTRS)

Gardner, C. S.; Rowlett, J. R.

1976-01-01

The effects of horizontal refractivity gradients on the accuracy of laser ranging systems were investigated by ray tracing through three dimensional refractivity profiles. The profiles were generated by performing a multiple regression on measurements from seven or eight radiosondes, using a refractivity model which provided for both linear and quadratic variations in the horizontal direction. The range correction due to horizontal gradients was found to be an approximately sinusoidal function of azimuth having a minimum near 0 deg azimuth and a maximum near 180 deg azimuth. The peak to peak variation was approximately 5 centimeters at 10 deg elevation and decreased to less than 1 millimeter at 80 deg elevation.

Development of a passively Q-switched Nd:YAG microchip laser for use in the Satellite Laser Ranging 2000 project

NASA Astrophysics Data System (ADS)

Gompers, Samuel Leo

Presently, NASA is designing a replacement for its existing satellite laser ranging systems. These systems are used to measure Earth-satellite distances, tectonic plate movement, variations in rotational motion and other geodetic phenomena. Satellite Laser Ranging 2000 (SLR2000) is envisioned as a fully automated, sub- centimeter accuracy, eye-safe, low-cost replacement to the current SLR systems. It is expected to overcome present limitations by operating autonomously; being free of optical, chemical or electrical hazards; and having a greater average time between failures. Expected shot range precision is about one centimeter with normal point precision of better than three centimeters. This system will have twenty-four hour tracking coverage. SLR2000 specifications dictate operation at visible wavelengths with eye-safe energies on the order of one hundred microjoules and repetition rates on the order of two kilohertz. The optical subsystem of SLR2000 includes a passively Q- switched Nd:YAG microlaser. Passive Q-switching will be achieved using a saturable absorber and offers a number of advantages over the mode-locked lasers currently used in ranging stations: no need for long resonators with tight thermal control; no electro-optic switch required for single pulse selection; saturable absorbers precluding the use of carcinogenic dyes and solvents; and RF drive frequency electronics not tied to the resonator length of the laser cavity. The presented work describes the research and development of a prototype laser used to produce the energies, repetition rates and pulsewidths required for SLR2000. Optimization theories and models were applied to the laser design in order to accurately predict and assess performance characteristics of both gain medium and saturable absorber. Data were obtained which illustrated the affect of pump laser saturation and thermal lensing of the gain medium. Important laboratory skills and techniques were acquired in the design and

Optofluidic laser for dual-mode sensitive biomolecular detection with a large dynamic range

NASA Astrophysics Data System (ADS)

Wu, Xiang; Oo, Maung Kyaw Khaing; Reddy, Karthik; Chen, Qiushu; Sun, Yuze; Fan, Xudong

2014-04-01

Enzyme-linked immunosorbent assay (ELISA) is a powerful method for biomolecular analysis. The traditional ELISA employing light intensity as the sensing signal often encounters large background arising from non-specific bindings, material autofluorescence and leakage of excitation light, which deteriorates its detection limit and dynamic range. Here we develop the optofluidic laser-based ELISA, where ELISA occurs inside a laser cavity. The laser onset time is used as the sensing signal, which is inversely proportional to the enzyme concentration and hence the analyte concentration inside the cavity. We first elucidate the principle of the optofluidic laser-based ELISA, and then characterize the optofluidic laser performance. Finally, we present the dual-mode detection of interleukin-6 using commercial ELISA kits, where the sensing signals are simultaneously obtained by the traditional and the optofluidic laser-based ELISA, showing a detection limit of 1 fg ml-1 (38 aM) and a dynamic range of 6 orders of magnitude.

Data collection and simulation of high range resolution laser radar for surface mine detection

NASA Astrophysics Data System (ADS)

Steinvall, Ove; Chevalier, Tomas; Larsson, Håkan

2006-05-01

Rapid and efficient detection of surface mines, IED's (Improvised Explosive Devices) and UXO (Unexploded Ordnance) is of high priority in military conflicts. High range resolution laser radars combined with passive hyper/multispectral sensors offer an interesting concept to help solving this problem. This paper reports on laser radar data collection of various surface mines in different types of terrain. In order to evaluate the capability of 3D imaging for detecting and classifying the objects of interest a scanning laser radar was used to scan mines and surrounding terrain with high angular and range resolution. These data were then fed into a laser radar model capable of generating range waveforms for a variety of system parameters and combinations of different targets and backgrounds. We can thus simulate a potential system by down sampling to relevant pixel sizes and laser/receiver characteristics. Data, simulations and examples will be presented.

The construction of a highly transportable laser ranging station

NASA Technical Reports Server (NTRS)

1980-01-01

The technology of the transportable Laser Ranging Station (TLRS) used in crustal dynamics studies was examined. The TLRS used a single photoelectron beam of limited energy density returned from the Laser Geodynamic Satellite (LAGEOS). Calibration was accomplished by the diversion of a small portion of the outgoing beam attenuated to the same level as the satellite return. Timing for the system was based on a self calibrating Ortec TD811, 100 picosec time interval device. The system was contained in a modified, single chassis recreational vehicle that allowed rapid deployment. The TLRS system was only airmobile on the largest transport aircraft. A 30 cm simple plano/concave transfer lens telescope aided in beam direction. The TLRS system fulfills the need for an accurate method of obtaining range measurements to the LAGEOS satellite incorporated in a mobile, air transportable, and economical configuration.

Advanced technologies in the ASI MLRO towards a new generation laser ranging system

NASA Technical Reports Server (NTRS)

Varghese, Thomas; Bianco, Giuseppe

1994-01-01

Matera Laser Ranging Observatory (MLRO) is a high performance, highly automated optical and astronomical observatory currently under design and development by AlliedSignal for the Italian Space Agency (ASI). It is projected to become operational at the Centro Geodesia Spaziale in Matera, Italy, in 1997. MLRO, based on a 1.5-meter astronomical quality telescope, will perform ranging to spacecraft in earthbound orbits, lunar reflectors, and specially equipped deep space missions. The primary emphasis during design is to incorporate state-of-the-art technologies to produce an intelligent, automated, high accuracy ranging system that will mimic the characteristic features of a fifth generation laser ranging system. The telescope has multiple ports and foci to support future experiments in the areas of laser communications, lidar, astrometry, etc. The key features providing state-of-the-art ranging performance include: a diode-pumped picosecond (50 ps) laser, high speed (3-5 GHz) optoelectronic detection and signal processing, and a high accuracy (6 ps) high resolution (less than 2 ps) time measurement capability. The above combination of technologies is expected to yield millimeter laser ranging precision and accuracy on targets up to 300,000 km, surpassing the best operational instrument performance to date by a factor of five or more. Distributed processing and control using a state-of-the-art computing environment provides the framework for efficient operation, system optimization, and diagnostics. A computationally intelligent environment permits optimal planning, scheduling, tracking, and data processing. It also supports remote access, monitor, and control for joint experiments with other observatories.

Validating data analysis of broadband laser ranging

NASA Astrophysics Data System (ADS)

Rhodes, M.; Catenacci, J.; Howard, M.; La Lone, B.; Kostinski, N.; Perry, D.; Bennett, C.; Patterson, J.

2018-03-01

Broadband laser ranging combines spectral interferometry and a dispersive Fourier transform to achieve high-repetition-rate measurements of the position of a moving surface. Telecommunications fiber is a convenient tool for generating the large linear dispersions required for a dispersive Fourier transform, but standard fiber also has higher-order dispersion that distorts the Fourier transform. Imperfections in the dispersive Fourier transform significantly complicate the ranging signal and must be dealt with to make high-precision measurements. We describe in detail an analysis process for interpreting ranging data when standard telecommunications fiber is used to perform an imperfect dispersive Fourier transform. This analysis process is experimentally validated over a 27-cm scan of static positions, showing an accuracy of 50 μm and a root-mean-square precision of 4.7 μm.

Laser Range and Bearing Finder with No Moving Parts

NASA Technical Reports Server (NTRS)

Bryan, Thomas C.; Howard, Richard T.; Book, Michael L.

2007-01-01

A proposed laser-based instrument would quickly measure the approximate distance and approximate direction to the closest target within its field of view. The instrument would not contain any moving parts and its mode of operation would not entail scanning over of its field of view. Typically, the instrument would be used to locate a target at a distance on the order of meters to kilometers. The instrument would be best suited for use in an uncluttered setting in which the target is the only or, at worst, the closest object in the vicinity; for example, it could be used aboard an aircraft to detect and track another aircraft flying nearby. The proposed instrument would include a conventional time-of-flight or echo-phase-shift laser range finder, but unlike most other range finders, this one would not generate a narrow cylindrical laser beam; instead, it would generate a conical laser beam spanning the field of view. The instrument would also include a quadrant detector, optics to focus the light returning from the target onto the quadrant detector, and circuitry to synchronize the acquisition of the quadrant-detector output with the arrival of laser light returning from the nearest target. A quadrant detector constantly gathers information from the entire field of view, without scanning; its output is a direct measure of the position of the target-return light spot on the focal plane and is thus a measure of the direction to the target. The instrument should be able to operate at a repetition rate high enough to enable it to track a rapidly moving target. Of course, a target that is not sufficiently reflective could not be located by this instrument. Preferably, retroreflectors should be attached to the target to make it sufficiently reflective.

High performance, low dissipation quantum cascade lasers across the mid-IR range.

PubMed

Bismuto, Alfredo; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Muller, Antoine

2015-03-09

In this work, we present the development of low consumption quantum cascade lasers across the mid-IR range. In particular, short cavity single-mode lasers with optimised facet reflectivities have been fabricated from 4.5 to 9.2 μm. Threshold dissipated powers as low as 0.5 W were obtained in continuous wave operation at room temperature. In addition, the beneficial impact of reducing chip length on laser mounting yield is discussed. High power single-mode lasers from the same processed wafers are also presented.

Using mid-range laser scanners to digitize cultural-heritage sites.

PubMed

Spring, Adam P; Peters, Caradoc; Minns, Tom

2010-01-01

Here, we explore new, more accessible ways of modeling 3D data sets that both professionals and amateurs can employ in areas such as architecture, forensics, geotechnics, cultural heritage, and even hobbyist modeling. To support our arguments, we present images from a recent case study in digital preservation of cultural heritage using a mid-range laser scanner. Our appreciation of the increasing variety of methods for capturing 3D spatial data inspired our research. Available methods include photogrammetry, airborne lidar, sonar, total stations (a combined electronic and optical survey instrument), and midand close-range scanning.1 They all can produce point clouds of varying density. In our case study, the point cloud produced by a mid-range scanner demonstrates how open source software can make modeling and disseminating data easier. Normally, researchers would model this data using expensive specialized software, and the data wouldn't extend beyond the laser-scanning community.

Thomas uses laser range finder during rendezvous ops

NASA Image and Video Library

2001-03-10

STS102-E-5064 (10 March 2001) --- Astronaut Andrew S.W. Thomas, STS-102 mission specialist, uses a laser ranging device on aft flight deck of the Space Shuttle Discovery. This instrument is a regularly called-on tool during rendezvous operations with the International Space Station (ISS). The photograph was recorded with a digital still camera.

Upgrading and performance of the SAO laser ranging system in Matera

NASA Technical Reports Server (NTRS)

Maddox, J.; Pearlman, M.; Throp, J.; Wohn, J.

1983-01-01

The performance of the SAO lasers was improved considerably in terms of accuracy, range noise, data yield, and reliability. With the narrower laser pulse (2.5-3.0 nsec) and a new analog pulse processing system, the systematic range errors were reduced to 3-5 cm and range noise has been reduced to 5-15 cm on low satellites and 10-18 cm on Lageos. Pulse repetition rate was increased to 30 ppm and considerable improvement has been made in signal-to-noise ratio by using a 3 Angstrom interference filter and by reducing the range gate window down to 200-400 nsec. The first upgraded system was installed in Arequipa, Peru in the spring of 1982. The second upgraded system is now in operation in Matera, Italy. The third system is expected to be installed in Israel during 1984.

NASA ground-based and space-based laser ranging systems

NASA Technical Reports Server (NTRS)

Fitzmaurice, M. W.

1978-01-01

Laser ranging is expected to help unlock the mysteries of the earthquake phenomenon by producing unique results of crustal motions of the Earth. The current state of the art and future projections are presented, including principal applications and characteristics of typical systems.

Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

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

Kita, Tomohiro, E-mail: tkita@ecei.tohoku.ac.jp; Tang, Rui; Yamada, Hirohito

2015-03-16

We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

The Apache Point Observatory Lunar Laser-ranging Operation: Instrument Description and First Detections

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

Murphy, TW; Adelberger, Eric G.; Battat, J.

2008-01-01

A next-generation lunar laser ranging apparatus using the 3.5 m telescope at the Apache Point Observatory in southern New Mexico has begun science operation. APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) has achieved one-millimeter range precision to the moon which should lead to aproximately one-orderof-magnitude improvements in the precision of several tests of fundamental properties of gravity. We briefly motivate the scientific goals, and then give a detailed discussion of the APOLLO instrumentation.

MLRS - A lunar/artificial satellite laser ranging facility at the McDonald Observatory

NASA Technical Reports Server (NTRS)

Shelus, P. J.

1985-01-01

Experience from lunar and satellite laser ranging experiments carried out at McDonald Observatory has been used to design the McDonald Laser Ranging Station (MLRS). The MLRS is a dual-purpose installation designed to obtain observations from the LAGEOS satellite and lunar targets. The instruments used at the station include a telescope assembly 0.76 meters in diameter; a Q-switched doubled neodymium YAG laser with a pulse rate of three nanoseconds; and a GaAs photodetector with Fabry-Perot interferometric filter. A functional diagram of the system is provided. The operating parameters of the instruments are summarized in a table.

Measuring laser reflection cross-sections of small unmanned aerial vehicles for laser detection, ranging and tracking

NASA Astrophysics Data System (ADS)

Laurenzis, Martin; Bacher, Emmanuel; Christnacher, Frank

2017-05-01

An increasing number of incidents are reported where small unmanned aerial vehicles (UAV) are involved flying at low altitude. Thus UAVs are becoming more and more a serious threat in civilian and military scenarios leading to serious danger to safety or privacy issues. In this context, the detection and tracking of small UAV flying at low altitude in urban environment or near background structures is a challenge for state of the art detection technologies. In this paper, we focus on detection, tracking and identification by laser sensing technologies that are Laser Gated Viewing and scanning LiDAR. The laser reflection cross-sections (LRCS) has direct impact on the probability to detection and capability for range measurement. Here, we present methods to determine the laser reflection cross-sections by experimental and computational approaches.

Development and Implementation of Joint Programs in Laser Ranging and Other Space Geodetic Techniques

NASA Technical Reports Server (NTRS)

Pearlman, Michael R.; Carter, David (Technical Monitor)

2004-01-01

This progress report discusses the status and progress made in joint international programs including: 1) WEGENER; 2) Arabian Peninsula program; 3) Asia-Pacific Space Geodynamics (APSG) program; 4) the Fourteenth International Workshop on Laser Ranging; 5) the International Laser Ranging Service; and 6) current support for the NASA network.

Influence of temperature on the spectral characteristics of semiconductor lasers in the visible range

NASA Astrophysics Data System (ADS)

Adamov, A. A.; Baranov, M. S.; Khramov, V. N.

2018-04-01

The results of studies on the effect of temperature on the output spectral characteristics of continuous semiconductor lasers of the visible range are presented. The paper presents the results of studying the spectral-optical radiation parameters of semiconductor lasers, their coherence lengths, and the dependence of the position of the spectral peak of the wavelength on temperature. This is necessary for the selection of the most optimal laser in order to use it for medical ophthalmologic diagnosis. The experiment was carried out using semiconductor laser modules based on a laser diode. The spectra were recorded by using a two-channel automated spectral complex based on the MDR-23 monochromator. Spectral dependences on the temperature of semiconductor lasers are obtained, in the range from 300 to 370 K. The possibility of determining the internal damage to the stabilization of laser modules without opening the case is shown, but only with the use of their spectral characteristics. The obtained data allow taking into account temperature characteristics and further optimization of parameters of such lasers when used in medical practice, in particular, in ophthalmologic diagnostics.

Laser ranging with the MéO telescope to improve orbital accuracy of space debris

NASA Astrophysics Data System (ADS)

Hennegrave, L.; Pyanet, M.; Haag, H.; Blanchet, G.; Esmiller, B.; Vial, S.; Samain, E.; Paris, J.; Albanese, D.

2013-05-01

Improving orbital accuracy of space debris is one of the major prerequisite to performing reliable collision prediction in low earth orbit. The objective is to avoid false alarms and useless maneuvers for operational satellites. This paper shows how laser ranging on debris can improve the accuracy of orbit determination. In March 2012 a joint OCA-Astrium team had the first laser echoes from space debris using the MéO (Métrologie Optique) telescope of the Observatoire de la Côte d'Azur (OCA), upgraded with a nanosecond pulsed laser. The experiment was conducted in full compliance with the procedures dictated by the French Civil Aviation Authorities. To perform laser ranging measurement on space debris, the laser link budget needed to be improved. Related technical developments were supported by implementation of a 2J pulsed laser purchased by ASTRIUM and an adapted photo detection. To achieve acquisition of the target from low accuracy orbital data such as Two Lines Elements, a 2.3-degree field of view telescope was coupled to the original MéO telescope 3-arcmin narrow field of view. The wide field of view telescope aimed at pointing, adjusting and acquiring images of the space debris for astrometry measurement. The achieved set-up allowed performing laser ranging and angular measurements in parallel, on several rocket stages from past launches. After a brief description of the set-up, development issues and campaigns, the paper discusses added-value of laser ranging measurement when combined to angular measurement for accurate orbit determination. Comparison between different sets of experimental results as well as simulation results is given.

Nd:YLF laser for airborne/spaceborne laser ranging

NASA Technical Reports Server (NTRS)

Dallas, Joseph L.; Selker, Mark D.

1993-01-01

In order to meet the need for light weight, long lifetime, efficient, short pulse lasers, a diode-pumped, Nd:YLF oscillator and regenerative amplifier is being developed. The anticipated output is 20 mJ per 10 picosecond pulse, running at a repetition rate of 40 Hz. The fundamental wavelength is at 1047 nm. The oscillator is pumped by a single laser diode bar and mode locked using an electro-optic, intra-cavity phase modulator. The output from the oscillator is injected as a seed into the regenerative amplifier. The regenerative amplifier laser crystal is optically pumped by two 60W quasi-cw laser diode bars. Each diode is collimated using a custom designed micro-lens bar. The injected 10 ps pulse from the oscillator is kept circulating within the regenerative amplifier until this nanojoule level seed pulse is amplified to 2-3 millijoules. At this point the pulse is ejected and sent on to a more standard single pass amplifier where the energy is boosted to 20 mJ. The footprint of the entire laser (oscillator-regenerative amplifier-amplifier) will fit on a 3 by 4 ft. optical pallet.

Tunable radio-frequency photonic filter based on an actively mode-locked fiber laser.

PubMed

Ortigosa-Blanch, A; Mora, J; Capmany, J; Ortega, B; Pastor, D

2006-03-15

We propose the use of an actively mode-locked fiber laser as a multitap optical source for a microwave photonic filter. The fiber laser provides multiple optical taps with an optical frequency separation equal to the external driving radio-frequency signal of the laser that governs its repetition rate. All the optical taps show equal polarization and an overall Gaussian apodization, which reduces the sidelobes. We demonstrate continuous tunability of the filter by changing the external driving radio-frequency signal of the laser, which shows good fine tunability in the operating range of the laser from 5 to 10 GHz.

Long range coherence in free electron lasers

NASA Technical Reports Server (NTRS)

Colson, W. B.

1984-01-01

The simple free electron laser (FEL) design uses a static, periodic, transverse magnetic field to undulate relativistic electrons traveling along its axis. This allows coupling to a co-propagating optical wave and results in bunching to produce coherent radiation. The advantages of the FEL are continuous tunability, operation at wavelengths ranging from centimeters to angstroms, and high efficiency resulting from the fact that the interaction region only contains light, relativistic electrons, and a magnetic field. Theoretical concepts and operational principles are discussed.

Single photon detection and timing in the Lunar Laser Ranging Experiment.

NASA Technical Reports Server (NTRS)

Poultney, S. K.

1972-01-01

The goals of the Lunar Laser Ranging Experiment lead to the need for the measurement of a 2.5 sec time interval to an accuracy of a nanosecond or better. The systems analysis which included practical retroreflector arrays, available laser systems, and large telescopes led to the necessity of single photon detection. Operation under all background illumination conditions required auxiliary range gates and extremely narrow spectral and spatial filters in addition to the effective gate provided by the time resolution. Nanosecond timing precision at relatively high detection efficiency was obtained using the RCA C31000F photomultiplier and Ortec 270 constant fraction of pulse-height timing discriminator. The timing accuracy over the 2.5 sec interval was obtained using a digital interval with analog vernier ends. Both precision and accuracy are currently checked internally using a triggerable, nanosecond light pulser. Future measurements using sub-nanosecond laser pulses will be limited by the time resolution of single photon detectors.

Active laser radar (lidar) for measurement of corresponding height and reflectance images

NASA Astrophysics Data System (ADS)

Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

1997-08-01

For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments

Light Detection and Ranging (LIDAR) From Space - Laser Altimeters

NASA Technical Reports Server (NTRS)

Sun, Xiaoli

2016-01-01

Light detection and ranging, or lidar, is like radar but atoptical wavelengths. The principle of operation and theirapplications in remote sensing are similar. Lidars havemany advantages over radars in instrument designs andapplications because of the much shorter laser wavelengthsand narrower beams. The lidar transmitters and receiveroptics are much smaller than radar antenna dishes. Thespatial resolution of lidar measurement is much finer thanthat of radar because of the much smaller footprint size onground. Lidar measurements usually give a better temporalresolution because the laser pulses can be much narrowerthan radio frequency (RF) signals. The major limitation oflidar is the ability to penetrate clouds and ground surfaces.

Earth orientation from lunar laser range-differencing. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Leick, A.

1978-01-01

For the optimal use of high precision lunar laser ranging (LLR), an investigation regarding a clear definition of the underlying coordinate systems, identification of estimable quantities, favorable station geometry and optimal observation schedule is given.

Detecting Topological Defect Dark Matter Using Coherent Laser Ranging System

PubMed Central

Yang, Wanpeng; Leng, Jianxiao; Zhang, Shuangyou; Zhao, Jianye

2016-01-01

In the last few decades, optical frequency combs with high intensity, broad optical bandwidth, and directly traceable discrete wavelengths have triggered rapid developments in distance metrology. However, optical frequency combs to date have been limited to determine the absolute distance to an object (such as satellite missions). We propose a scheme for the detection of topological defect dark matter using a coherent laser ranging system composed of dual-combs and an optical clock via nongravitational signatures. The dark matter field, which comprises a defect, may interact with standard model particles, including quarks and photons, resulting in the alteration of their masses. Thus, a topological defect may function as a dielectric material with a distinctive frequency-depend index of refraction, which would cause the time delay of a periodic extraterrestrial or terrestrial light. When a topological defect passes through the Earth, the optical path of long-distance vacuum path is altered, this change in optical path can be detected through the coherent laser ranging system. Compared to continuous wavelength(cw) laser interferometry methods, dual-comb interferometry in our scheme excludes systematic misjudgement by measuring the absolute optical path length. PMID:27389642

Heterostructures for quantum-cascade lasers of the wavelength range of 7-8 μm

NASA Astrophysics Data System (ADS)

Babichev, A. V.; Gladyshev, A. G.; Filimonov, A. V.; Nevedomskii, V. N.; Kurochkin, A. S.; Kolodeznyi, E. S.; Sokolovskii, G. S.; Bugrov, V. E.; Karachinsky, L. Ya.; Novikov, I. I.; Bousseksou, A.; Egorov, A. Yu.

2017-07-01

It is shown that molecular-beam-epitaxy technology can be used to fabricate heterostructures for quantum-cascade lasers of the wavelength range of 7-8 μm with an active region comprising 50 cascades based on a heterojunction of In0.53Ga0.47As/Al0.48In0.52As solid solutions. The optical emission is obtained using a quantum-cascade design operating on the principle of two-phonon resonance scattering. The properties of heterostructures were studied by the methods of X-ray diffraction and transmission electron microscopy, which showed their high quality with respect to the identical compositions and thicknesses of all 50 cascades. Stripe-geometry lasers made of these heterostructures exhibited lasing with a threshold current density below 1.6 kA/cm2 at a temperature of 78 K.

Analysis of One-Way Laser Ranging Data to LRO, Time Transfer and Clock Characterization

NASA Technical Reports Server (NTRS)

Bauer, S.; Hussmann, H.; Oberst, J.; Dirkx, D.; Mao, D.; Neumann, G. A.; Mazarico, E.; Torrence, M. H.; McGarry, J. F.; Smith, D. E.;

Satellite laser ranging to low Earth orbiters: orbit and network validation

NASA Astrophysics Data System (ADS)

Arnold, Daniel; Montenbruck, Oliver; Hackel, Stefan; Sośnica, Krzysztof

2018-04-01

Satellite laser ranging (SLR) to low Earth orbiters (LEOs) provides optical distance measurements with mm-to-cm-level precision. SLR residuals, i.e., differences between measured and modeled ranges, serve as a common figure of merit for the quality assessment of orbits derived by radiometric tracking techniques. We discuss relevant processing standards for the modeling of SLR observations and highlight the importance of line-of-sight-dependent range corrections for the various types of laser retroreflector arrays. A 1-3 cm consistency of SLR observations and GPS-based precise orbits is demonstrated for a wide range of past and present LEO missions supported by the International Laser Ranging Service (ILRS). A parameter estimation approach is presented to investigate systematic orbit errors and it is shown that SLR validation of LEO satellites is not only able to detect radial but also along-track and cross-track offsets. SLR residual statistics clearly depend on the employed precise orbit determination technique (kinematic vs. reduced-dynamic, float vs. fixed ambiguities) but also reveal pronounced differences in the ILRS station performance. Using the residual-based parameter estimation approach, corrections to ILRS station coordinates, range biases, and timing offsets are derived. As a result, root-mean-square residuals of 5-10 mm have been achieved over a 1-year data arc in 2016 using observations from a subset of high-performance stations and ambiguity-fixed orbits of four LEO missions. As a final contribution, we demonstrate that SLR can not only validate single-satellite orbit solutions but also precise baseline solutions of formation flying missions such as GRACE, TanDEM-X, and Swarm.

Arm-Locking with the GRACE Follow-On Laser Ranging Instrument

NASA Technical Reports Server (NTRS)

Thorpe, James Ira; Mckenzie, Kirk

2016-01-01

Arm-locking is a technique for stabilizing the frequency of a laser in an inter-spacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA), arm-locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the Laser Ranging Instrument flying aboard the upcoming Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly two orders of magnitude around a Fourier frequency of 1Hz with conservative margins on the system's stability. We further demonstrate that `pulling' of the master laser frequency due to fluctuating Doppler shifts and lock acquisition transients is less than 100MHz over several GRACE-FO orbits. These findings motivate further study of the implementation of such a demonstration.

Arm locking with the GRACE follow-on laser ranging interferometer

NASA Astrophysics Data System (ADS)

Thorpe, James Ira; McKenzie, Kirk

2016-02-01

Arm locking is a technique for stabilizing the frequency of a laser in an interspacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna, arm locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the laser ranging interferometer instrument flying aboard the upcoming Gravity Recovery and Climate Experiment follow-on (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly 2 orders of magnitude around a Fourier frequency of 1 Hz with conservative margins on the system's stability. We further demonstrate that "pulling" of the master laser frequency due to fluctuating Doppler shifts and lock acquisition transients is less than 100 MHz over several GRACE-FO orbits. These findings motivate further study of the implementation of such a demonstration.

Doppler and range determination for deep space vehicles using active optical transponders.

PubMed

Kinman, P W; Gagliardi, R M

1988-11-01

This paper describes and analyzes two types of laser system employing active transponders that could accurately determine Doppler and range to deep space vehicles from earth-orbiting satellites. The first is a noncoherent optical system in which the Doppler effect on an intensity-modulating subcarrier is measured. The second is a coherent optical system in which the Doppler effect of the optical carrier itself is measured. Doppler and range measurement errors are mathematically modeled and, for three example systems, numerically evaluated.

Doppler and range determination for deep space vehicles using active optical transponders

NASA Technical Reports Server (NTRS)

Kinman, Peter W.; Gagliardi, Robert M.

1988-01-01

This paper describes and analyzes two types of laser system employing active transponders that could accurately determine Doppler and range to deep space vehicles from earth-orbiting satellites. The first is a noncoherent optical system in which the Doppler effect on an intensity-modulating subcarrier is measured. The second is a coherent optical system in which the Doppler effect of the optical carrier itself is measured. Doppler and range measurement errors are mathematically modeled and, for three example systems, numerically evaluated.

Research on effect of rough surface on FMCW laser radar range accuracy

NASA Astrophysics Data System (ADS)

Tao, Huirong

2018-03-01

The non-cooperative targets large scale measurement system based on frequency-modulated continuous-wave (FMCW) laser detection and ranging technology has broad application prospects. It is easy to automate measurement without cooperative targets. However, the complexity and diversity of the surface characteristics of the measured surface directly affects the measurement accuracy. First, the theoretical analysis of range accuracy for a FMCW laser radar was studied, the relationship between surface reflectivity and accuracy was obtained. Then, to verify the effect of surface reflectance for ranging accuracy, a standard tool ball and three standard roughness samples were measured within 7 m to 24 m. The uncertainty of each target was obtained. The results show that the measurement accuracy is found to increase as the surface reflectivity gets larger. Good agreements were obtained between theoretical analysis and measurements from rough surfaces. Otherwise, when the laser spot diameter is smaller than the surface correlation length, a multi-point averaged measurement can reduce the measurement uncertainty. The experimental results show that this method is feasible.

Comparison of laser-activated tissue solders and thrombin-activated cryoprecipitate for wound closure

NASA Astrophysics Data System (ADS)

Kayton, Mark L.; Libutti, Steven K.; Bessler, Marc; Allendorf, John D. F.; Eiref, Simon D.; Marx, Gerard; Mou, Xiaode; Morales, Alfredo M.; Treat, Michael R.; Nowygrod, Roman

1994-09-01

To determine the relative strengths of various biologic adhesives at several timepoints, we compared thrombin-activated SD (solvent-detergent treated) cryoprecipitate with laser- activated SD cryoprecipitate and a laser-activated, albumin-based glue. Male Sprague-Dawley rats (n equals 79) received four, 3-cm, dorsal skin incisions which were closed with either laser- activated cryoprecipitate, laser-activated albumin solder, thrombin-activated cryoprecipitate, or standard skin staples. The cryoprecipitate was derived from pooled human plasma and was treated with a solvent-detergent process, rendering it free of envelope-coated viruses (i.e., HBV, HIV). An 808-nm diode laser was used to activate each solder with an average duration of exposure of 75 seconds per incision. Animals were sacrificed for evaluation of wound tensile strength and histology at 0 hours, 2 hours, 4 hours, and 4 days. At all timepoints tested, laser-activated solders were significantly stronger than thrombin-activated cryoprecipitate (p < 0.03) and control wounds (p < 0.003). There was no significant difference in tensile strength between the two types of laser-activated solder at any timepoint.

Curvature-Based Environment Description for Robot Navigation Using Laser Range Sensors

PubMed Central

Vázquez-Martín, Ricardo; Núñez, Pedro; Bandera, Antonio; Sandoval, Francisco

2009-01-01

This work proposes a new feature detection and description approach for mobile robot navigation using 2D laser range sensors. The whole process consists of two main modules: a sensor data segmentation module and a feature detection and characterization module. The segmentation module is divided in two consecutive stages: First, the segmentation stage divides the laser scan into clusters of consecutive range readings using a distance-based criterion. Then, the second stage estimates the curvature function associated to each cluster and uses it to split it into a set of straight-line and curve segments. The curvature is calculated using a triangle-area representation where, contrary to previous approaches, the triangle side lengths at each range reading are adapted to the local variations of the laser scan, removing noise without missing relevant points. This representation remains unchanged in translation or rotation, and it is also robust against noise. Thus, it is able to provide the same segmentation results although the scene will be perceived from different viewpoints. Therefore, segmentation results are used to characterize the environment using line and curve segments, real and virtual corners and edges. Real scan data collected from different environments by using different platforms are used in the experiments in order to evaluate the proposed environment description algorithm. PMID:22461732

Nanosecond time transfer via shuttle laser ranging experiment

NASA Technical Reports Server (NTRS)

Reinhardt, V. S.; Premo, D. A.; Fitzmaurice, M. W.; Wardrip, S. C.; Cervenka, P. O.

1978-01-01

A method is described to use a proposed shuttle laser ranging experiment to transfer time with nanosecond precision. All that need be added to the original experiment are low cost ground stations and an atomic clock on the shuttle. It is shown that global time transfer can be accomplished with 1 ns precision and transfer up to distances of 2000 km can be accomplished with better than 100 ps precision.

International Laser Ranging Services (ILRS) 2001 Annual Report

NASA Technical Reports Server (NTRS)

Pearlman, Michael (Editor); Torrence, Mark (Editor); Noll, Carey (Editor)

2002-01-01

This 2001 Annual Report of the International Laser Ranging Services (ILRS) is comprised of individual contributions from ILRS components within the international geodetic community. This report documents the work of the ILRS components for the year 2001. The report documents changes and progress of the ILRS. This document is also available on the ILRS Web site at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrsar_2001.html.

International Laser Ranging Service (ILRS) 1999 Annual Report

NASA Technical Reports Server (NTRS)

Pearlman, Michael (Editor); Taggert, Linda (Editor)

2000-01-01

This 1999 Annual Report of the International Laser Ranging Service (ILRS) is comprised of individual contributions from ILRS components within the international geodetic community. This report documents the work of the ILRS components from the inception of the Service through December 31,1999. Since the service has only recently been established, the ILRS associates decided to publish this Annual report as a reference to our organization and its components.

Overview of the laser activities at Rheinmetall Waffe Munition

NASA Astrophysics Data System (ADS)

Ludewigt, Klaus; Riesbeck, Thomas; Schünemann, B.; Graf, A.; Jung, Markus; Schreiber, Th.; Eberhardt, Ramona; Tünnermann, A.

2012-11-01

The paper will give an overview over the laser weapon activities at RWM (Rheinmetall Waffe Munition) over the last years. Starting from the actual scenarios for laser weapon applications as: CRAM (Counter Rocket Artillery Mortar), Air Defence and UXO (unexploded ordnance) clearing. The basic requirements of a future laser weapon as beam diameter, beam quality, tracking capability, adaptive optics were deduced. For the UXO scenario a mobile directed energy laser demonstrator for humanitarian mine and UXO clearing based on fiber lasers is presented. Based on the parameters the system concept including the cooling system, power supply and the integration into the armoured vehicle TM 170 are explained. The contribution show first experiments of UXO and IED clearing. Different technical approaches to achieve laser power in the 100 kW regime combined with very good beam quality are discussed to fulfil the requirements of the CRAM and Air Defence scenario. Spectral coupling and the beam superimposing both are performed by Rheinmetall Waffe Munition. At the spectral coupling the basic technology parameters for the fiber laser and the dielectric grating as the latest results were put into context with the power levels reached at other groups. For the beam super imposing technology the basic experiments regarding the tracking capability and compensation of the atmosphere on the test range at Unterlüß will be explained. A generic 10 kW Laser Weapon Demonstrator based on 2 Laser Weapon Modules (LWM) from RWM each 5 kW fiber Laser with beam forming and tracking integrate by the team of RWM and RAD (Rheinmetall Air Defense) into a Ground based Air Defend system consisting of Skyguard and Millenium turret are presented. The flight path of the UAV within the valley of the life firing range at Ochsenboden Switzerland is shown. Selected results of the successful tests against UAV's are presented. It shows the capability of the generic 10 kW Laser Weapon Demonstrator to track and

Measuring Relativistic effects in the field of the Earth with Laser Ranged Satellites and the LARASE research program

NASA Astrophysics Data System (ADS)

Lucchesi, David; Anselmo, Luciano; Bassan, Massimo; Magnafico, Carmelo; Pardini, Carmen; Peron, Roberto; Pucacco, Giuseppe; Stanga, Ruggero; Visco, Massimo

2017-04-01

The main goal of the LARASE (LAser RAnged Satellites Experiment) research program is to obtain refined tests of Einstein's theory of General Relativity (GR) by means of very precise measurements of the round-trip time among a number of ground stations of the International Laser Ranging Service (ILRS) network and a set of geodetic satellites. These measurements are guaranteed by means of the powerful and precise Satellite Laser Ranging (SLR) technique. In particular, a big effort of LARASE is dedicated to improve the dynamical models of the LAGEOS, LAGEOS II and LARES satellites, with the objective to obtain a more precise and accurate determination of their orbit. These activities contribute to reach a final error budget that should be robust and reliable in the evaluation of the main systematic errors sources that come to play a major role in masking the relativistic precession on the orbit of these laser-ranged satellites. These error sources may be of gravitational and non-gravitational origin. It is important to stress that a more accurate and precise orbit determination, based on more reliable dynamical models, represents a fundamental prerequisite in order to reach a sub-mm precision in the root-mean-square of the SLR range residuals and, consequently, to gather benefits in the fields of geophysics and space geodesy, such as stations coordinates knowledge, geocenter determination and the realization of the Earth's reference frame. The results reached over the last year will be presented in terms of the improvements achieved in the dynamical model, in the orbit determination and, finally, in the measurement of the relativistic precessions that act on the orbit of the satellites considered.

Long range laser propagation: power scaling and beam quality issues

NASA Astrophysics Data System (ADS)

Bohn, Willy L.

2010-09-01

This paper will address long range laser propagation applications where power and, in particular beam quality issues play a major role. Hereby the power level is defined by the specific mission under consideration. I restrict myself to the following application areas: (1)Remote sensing/Space based LIDAR, (2) Space debris removal (3)Energy transmission, and (4)Directed energy weapons Typical examples for space based LIDARs are the ADM Aeolus ESA mission using the ALADIN Nd:YAG laser with its third harmonic at 355 nm and the NASA 2 μm Tm:Ho:LuLiF convectively cooled solid state laser. Space debris removal has attracted more attention in the last years due to the dangerous accumulation of debris in orbit which become a threat to the satellites and the ISS space station. High power high brightness lasers may contribute to this problem by partially ablating the debris material and hence generating an impulse which will eventually de-orbit the debris with their subsequent disintegration in the lower atmosphere. Energy transmission via laser beam from space to earth has long been discussed as a novel long term approach to solve the energy problem on earth. In addition orbital transfer and stationkeeping are among the more mid-term applications of high power laser beams. Finally, directed energy weapons are becoming closer to reality as corresponding laser sources have matured due to recent efforts in the JHPSSL program. All of this can only be realized if he laser sources fulfill the necessary power requirements while keeping the beam quality as close as possible to the diffraction limited value. And this is the rationale and motivation of this paper.

Long axial imaging range using conventional swept source lasers in optical coherence tomography via re-circulation loops

NASA Astrophysics Data System (ADS)

Bradu, Adrian; Jackson, David A.; Podoleanu, Adrian

2018-03-01

Typically, swept source optical coherence tomography (SS-OCT) imaging instruments are capable of a longer axial range than their camera based (CB) counterpart. However, there are still various applications that would take advantage for an extended axial range. In this paper, we propose an interferometer configuration that can be used to extend the axial range of the OCT instruments equipped with conventional swept-source lasers up to a few cm. In this configuration, the two arms of the interferometer are equipped with adjustable optical path length rings. The use of semiconductor optical amplifiers in the two rings allows for compensating optical losses hence, multiple paths depth reflectivity profiles (Ascans) can be combined axially. In this way, extremely long overall axial ranges are possible. The use of the recirculation loops produces an effect equivalent to that of extending the coherence length of the swept source laser. Using this approach, the achievable axial imaging range in SS-OCT can reach values well beyond the limit imposed by the coherence length of the laser, to exceed in principle many centimeters. In the present work, we demonstrate axial ranges exceeding 4 cm using a commercial swept source laser and reaching 6 cm using an "in-house" swept source laser. When used in a conventional set-up alone, both these lasers can provide less than a few mm axial range.

Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

PubMed

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-03-01

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.

Polar motion results from GEOS 3 laser ranging

NASA Technical Reports Server (NTRS)

Schutz, B. E.; Tapley, B. D.; Ries, J.; Eanes, R.

1979-01-01

The observability of polar motion from laser range data has been investigated, and the contributions from the dynamical and kinematical effects have been evaluated. Using 2-day arcs with GEOS 3 laser data, simultaneous solutions for pole position components and orbit elements have been obtained for a 2-week interval spanning August 27 to September 10, 1975, using three NASA Goddard Space Flight Center stations located at Washington, D.C., Bermuda, and Grand Turk. The results for the y-component of pole position from this limited data set differenced with the BIH linearly interpolated values yield a mean of 39 cm and a standard deviation of 1.07 m. Consideration of the variance associated with each estimate yields a mean of 20 cm and a standard deviation of 81 cm. The results for the x-component of pole position indicate that the mean value is in fair agreement with the BIH; however, the x-coordinate determination is weaker than the y-coordinate determination due to the distribution of laser sites (all three are between 77 deg W and 65 deg W) which results in greater sensitivity to the data distribution. In addition, the sensitivity of these results to various model parameters is discussed.

Transport of biologically active material in laser cutting.

PubMed

Frenz, M; Mathezloic, F; Stoffel, M H; Zweig, A D; Romano, V; Weber, H P

1988-01-01

The transport of biologically active material during laser cutting with CO2 and Er lasers is demonstrated. This transport mechanism removes particles from the surface of gelatin, agar, and liver samples into the depth of the laser-formed craters. The transport phenomenon is explained by a contraction and condensation of enclosed hot water vapor. We show by cultivating transported bacteria in agar that biological particles can survive the shock of the transport. Determination of the numbers of active cells evidences a more pronounced activity of the cultivated bacteria after impact with an Er laser than with a CO2 laser.

Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

DOEpatents

MacPherson, David C.; Nelson, Loren D.; O'Brien, Martin J.

1996-01-01

Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength.

Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

DOEpatents

MacPherson, D.C.; Nelson, L.D.; O`Brien, M.J.

1996-12-10

Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength. 30 figs.

generation of picosecond pulses in solid-state lasers using new active media

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

Lisitsyn, V.N.; Matrosov, V.N.; Pestryakov, E.V.

Results are reported of investigations aimed at generating nanosecond radiation pulses in solid-state lasers using new active media having broad gain lines. Passive mode locking is accomplished for the first time in a BeLa:Nd/sup 3/ laser at a wavelength 1.354 microm, and in a YAG:Nd/sup 3/ laser on a 1.32-microm transition. The free lasing and mode-locking regimes were investigated in an alexandrite (BeA1/sub 2/O/sub 4/:Cr/sup 3/) laser in the 0.72-0.78-microm range and in a synchronously pumped laser on F/sub 2//sup -/ centers in LiF in the 1.12-1.24-microm region. The features of nonlinear perception of IR radiation by the eye, usingmore » a developed picosecond laser on F/sub 2//sup -/ centers, are investigated for the first time.« less

Broadband Laser Ranging for Position Measurements in Shock Physics Experiments

NASA Astrophysics Data System (ADS)

Rhodes, Michelle; Bennett, Corey; Daykin, Edward; Younk, Patrick; Lalone, Brandon; Kostinski, Natalie

2017-06-01

Broadband laser ranging (BLR) is a recently developed measurement system that provides an attractive option for determining the position of shock-driven surfaces. This system uses broadband, picosecond (or femtosecond) laser pulses and a fiber interferometer to measure relative travel time to a target and to a reference mirror. The difference in travel time produces a delay difference between pulse replicas that creates a spectral beat frequency. The spectral beating is recorded in real time using a dispersive Fourier transform and an oscilloscope. BLR systems have been designed that measure position at 12.5-40 MHz with better than 100 micron accuracy over ranges greater than 10 cm. We will give an overview of the basic operating principles of these systems. Prepared by LLNL under Contract DE-AC52-07NA27344, by LANL under Contract DE-AC52-06NA25396, and by NSTec Contract DE-AC52-06NA25946.

Broadband laser ranging development at the DOE Labs

NASA Astrophysics Data System (ADS)

Bennett, Corey V.; La Lone, Brandon M.; Younk, Patrick W.; Daykin, Ed P.; Rhodes, Michelle A.

2017-02-01

Broadband Laser Ranging (BLR) is a new diagnostic being developed in collaboration across multiple USA Dept. of Energy (DOE) facilities. Its purpose is to measure the precise position of surfaces and particle clouds moving at speeds of a few kilometers per second. The diagnostic uses spectral interferometry to encode distance into a modulation in the spectrum of pulses from a mode-locked fiber laser and uses a dispersive Fourier transformation to map the spectral modulation into time. This combination enables recording of range information in the time domain on a fast oscilloscope every 25-80 ns. Discussed here are some of the hardware design issues, system tradeoffs, calibration issues, and experimental results. BLR is being developed as an add-on to conventional Photonic Doppler Velocimetry (PDV) systems because PDV often yields incomplete information when lateral velocity components are present, or when there are drop-outs in the signal amplitude. In these cases, integration of the velocity from PDV can give incorrect displacement results. Experiments are now regularly fielded with over 100 channels of PDV, and BLR is being developed in a modular way to enable high channel counts of BLR and PDV recorded from the same probes pointed at the same target location. In this way instruments, will independently record surface velocity and distance information along the exact same path.

Surface roughness measurement in the submicrometer range using laser scattering

NASA Astrophysics Data System (ADS)

Wang, S. H.; Quan, Chenggen; Tay, C. J.; Shang, H. M.

2000-06-01

A technique for measuring surface roughness in the submicrometer range is developed. The principle of the method is based on laser scattering from a rough surface. A telecentric optical setup that uses a laser diode as a light source is used to record the light field scattered from the surface of a rough object. The light intensity distribution of the scattered band, which is correlated to the surface roughness, is recorded by a linear photodiode array and analyzed using a single-chip microcomputer. Several sets of test surfaces prepared by different machining processes are measured and a method for the evaluation of surface roughness is proposed.

Active eye-tracking for an adaptive optics scanning laser ophthalmoscope

PubMed Central

Sheehy, Christy K.; Tiruveedhula, Pavan; Sabesan, Ramkumar; Roorda, Austin

2015-01-01

We demonstrate a system that combines a tracking scanning laser ophthalmoscope (TSLO) and an adaptive optics scanning laser ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone. PMID:26203370

Covariance analysis of the airborne laser ranging system

NASA Technical Reports Server (NTRS)

Englar, T. S., Jr.; Hammond, C. L.; Gibbs, B. P.

1981-01-01

The requirements and limitations of employing an airborne laser ranging system for detecting crustal shifts of the Earth within centimeters over a region of approximately 200 by 400 km are presented. The system consists of an aircraft which flies over a grid of ground deployed retroreflectors, making six passes over the grid at two different altitudes. The retroreflector baseline errors are assumed to result from measurement noise, a priori errors on the aircraft and retroreflector positions, tropospheric refraction, and sensor biases.

Single diode laser sensor for wide-range H2O temperature measurements.

PubMed

Gharavi, Mohammadreza; Buckley, Steven G

2004-04-01

A single diode laser absorption sensor (near 1477 nm) useful for simultaneous temperature and H2O concentration measurements is developed. The diode laser tunes approximately 1.2 cm(-1) over three H2O absorption transitions in each measurement. The line strengths of the transitions are measured over a temperature range from 468 to 977 K, based on high-resolution absorption measurements in a heated static cell. The results indicate that the selected transitions are suitable for sensitive temperature measurements in atmospheric pressure combustion systems using absorption line ratios. Comparing the results with HITRAN 96 data, it appears that these transitions will be sensitive over a wide range of temperatures (450-2000 K), suggesting applicability for combustion measurements.

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

NASA Astrophysics Data System (ADS)

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

2001-10-01

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

Approach range and velocity determination using laser sensors and retroreflector targets

NASA Technical Reports Server (NTRS)

Donovan, William J.

1991-01-01

A laser docking sensor study is currently in the third year of development. The design concept is considered to be validated. The concept is based on using standard radar techniques to provide range, velocity, and bearing information. Multiple targets are utilized to provide relative attitude data. The design requirements were to utilize existing space-qualifiable technology and require low system power, weight, and size yet, operate from 0.3 to 150 meters with a range accuracy greater than 3 millimeters and a range rate accuracy greater than 3 mm per second. The field of regard for the system is +/- 20 deg. The transmitter and receiver design features a diode laser, microlens beam steering, and power control as a function of range. The target design consists of five target sets, each having seven 3-inch retroreflectors, arranged around the docking port. The target map is stored in the sensor memory. Phase detection is used for ranging, with the frequency range-optimized. Coarse bearing measurement is provided by the scanning system (one set of binary optics) angle. Fine bearing measurement is provided by a quad detector. A MIL-STD-1750 A/B computer is used for processing. Initial test results indicate a probability of detection greater than 99 percent and a probability of false alarm less than 0.0001. The functional system is currently at the MIT/Lincoln Lab for demonstration.

Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

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

Danilov, P A; Zayarnyi, D A; Ionin, A A

The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fieldsmore » and their applications)« less

Lunar laser ranging data processing in a Unix/X windows environment

NASA Technical Reports Server (NTRS)

Ricklefs, Randall L.; Ries, Judit G.

1993-01-01

In cooperation with the NASA Crustal Dynamics Project initiative placing workstation computers at each of its laser ranging stations to handle data filtering and normalpointing, MLRS personnel have developed a new generation of software to provide the same services for the lunar laser ranging data type. The Unix operating system and X windows/Motif provides an environment for both batch and interactive filtering and normalpointing as well as prediction calculations. The goal is to provide a transportable and maintainable data reduction environment. This software and some sample displays are presented. that the lunar (or satellite) datacould be processed on one computer while data was taken on the other. The reduction of the data was totally interactive and in no way automated. In addition, lunar predictions were produced on-site, another first in the effort to down-size historically mainframe-based applications. Extraction of earth rotation parameters was at one time attempted on site in near-realtime. In 1988, the Crustal Dynamics Project SLR Computer Panel mandated the installation of Hewlett-Packard 9000/360 Unix workstations at each NASA-operated laser ranging station to relieve the aging controller computers of much of their data and communications handling responsibility and to provide on-site data filtering and normal pointing for a growing list of artificial satellite targets. This was seen by MLRS staff as an opportunity to provide a better lunar data processing environment as well.

Lunar laser ranging data processing in a Unix/X windows environment

NASA Astrophysics Data System (ADS)

Ricklefs, Randall L.; Ries, Judit G.

1993-06-01

In cooperation with the NASA Crustal Dynamics Project initiative placing workstation computers at each of its laser ranging stations to handle data filtering and normalpointing, MLRS personnel have developed a new generation of software to provide the same services for the lunar laser ranging data type. The Unix operating system and X windows/Motif provides an environment for both batch and interactive filtering and normalpointing as well as prediction calculations. The goal is to provide a transportable and maintainable data reduction environment. This software and some sample displays are presented. that the lunar (or satellite) datacould be processed on one computer while data was taken on the other. The reduction of the data was totally interactive and in no way automated. In addition, lunar predictions were produced on-site, another first in the effort to down-size historically mainframe-based applications. Extraction of earth rotation parameters was at one time attempted on site in near-realtime. In 1988, the Crustal Dynamics Project SLR Computer Panel mandated the installation of Hewlett-Packard 9000/360 Unix workstations at each NASA-operated laser ranging station to relieve the aging controller computers of much of their data and communications handling responsibility and to provide on-site data filtering and normal pointing for a growing list of artificial satellite targets. This was seen by MLRS staff as an opportunity to provide a better lunar data processing environment as well.

Cassidy uses laser range finder in the aft FD during Joint Operations

NASA Image and Video Library

2009-07-28

S127-E-011166 (28 July 2009) --- Astronaut Christopher Cassidy, STS-127 mission specialist, uses a handheld laser ranging device -- designed to measure the range between two spacecraft -- through one of the overhead windows on the aft flight deck of Space Shuttle Endeavour after undocking from the International Space Station.

Broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity

NASA Astrophysics Data System (ADS)

Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.

2018-05-01

We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.

Satellite Laser Ranging in the 1990s: Report of the 1994 Belmont Workshop

NASA Technical Reports Server (NTRS)

Degnan, John J. (Editor)

1994-01-01

An international network of 43 stations in 30 countries routinely collects satellite ranging data which is used to study the solid Earth and its interactions with the oceans, atmosphere, and Moon. Data products include centimeter accuracy site positions on a global scale, tectonic plate motions, regional crustal deformation, long wavelength gravity field and geoid, polar motion, and variations in the Earth's spin rate. By calibrating and providing precise orbits for spaceborne microwave altimeters, satellite laser ranging also enables global measurement of sea and ice surface topography, mean sea level, global ocean circulation, and short wavelength gravity fields and marine geoids. It provides tests of general relativity and a means or subnanosecond time transfer. This workshop was convened to define future roles and directions in satellite laser ranging.

The Moon as a Laser-ranged Test Body for General Relativity and New Gravitational Physics

NASA Astrophysics Data System (ADS)

Dell'Agnello, Simone; Currie, Douglas

Since the 1970s Lunar Laser Ranging (LLR) to the Apollo/Lunokhod Cube Corner Retroreflector (CCR) Arrays supplied some of the best tests of General Relativity (GR): possible changes in the gravitational constant, gravitational self-energy (PPN parameter beta), weak equivalence principle, geodetic precession, inverse-square force-law. Secondly, LLR has provided significant information on the composition of the deep interior of the Moon. LLR physics analysis also allows to set constraints on extensions of GR (like spacetime torsion) and, possibly, on new gravitational physics which may explain the gravitational universe without Dark Matter and Dark Energy (like, for example, Non-Minimally Coupled gravity, NMC). LLR is the only Apollo/Lunokhod experiment still in operation, since 45 years. In the 1970s Apollo/Lunokohd LLR Arrays contributed a negligible fraction of the ranging error budget. Since the ranging capabilities of ground stations improved by more than two orders of magnitude, now, because of the lunar librations, Apollo/Lunokhod CCR arrays dominate the error budget. With the US/Italy project "LLRRA21/MoonLIGHT (Lunar Laser Ranging Retroreflector Array for the 21st century / Moon Laser Instrumentation for General relativity High accuracy Tests)", University of Maryland and INFN-LNF developed and tested a next-generation LLR payload made by a single, large CCR (100 mm diameter), unaffected by the effect of librations. In fact, we will show that MoonLIGHT reflectors will improve the LLR accuracy by a factor of ten to one hundred in a few years. INFN-LNF also developed a laser retroreflector micropayload to be deployed on the lunar surface to be laser-ranged by lunar orbiters. The latter micropayload will further extend the physics reach of Apollo, Lunokhod and MoonLIGHT CCRs to improve all precision tests of GR and new gravitational physics using LLR data. As an added value for the LRR and SLR (Satellite Laser ranging) disciplines INFN-LNF built and is

Ranging error analysis of single photon satellite laser altimetry under different terrain conditions

NASA Astrophysics Data System (ADS)

Huang, Jiapeng; Li, Guoyuan; Gao, Xiaoming; Wang, Jianmin; Fan, Wenfeng; Zhou, Shihong

2018-02-01

Single photon satellite laser altimeter is based on Geiger model, which has the characteristics of small spot, high repetition rate etc. In this paper, for the slope terrain, the distance of error's formula and numerical calculation are carried out. Monte Carlo method is used to simulate the experiment of different terrain measurements. The experimental results show that ranging accuracy is not affected by the spot size under the condition of the flat terrain, But the inclined terrain can influence the ranging error dramatically, when the satellite pointing angle is 0.001° and the terrain slope is about 12°, the ranging error can reach to 0.5m. While the accuracy can't meet the requirement when the slope is more than 70°. Monte Carlo simulation results show that single photon laser altimeter satellite with high repetition rate can improve the ranging accuracy under the condition of complex terrain. In order to ensure repeated observation of the same point for 25 times, according to the parameters of ICESat-2, we deduce the quantitative relation between the footprint size, footprint, and the frequency repetition. The related conclusions can provide reference for the design and demonstration of the domestic single photon laser altimetry satellite.

MS Reilly with laser range finder on aft flight deck

NASA Image and Video Library

2001-07-14

STS104-E-5026 (14 July 2001) --- Positioned near a window on the aft flight deck of the Space Shuttle Atlantis, astronaut James F. Reilly, STS-104 mission specialist, uses a laser ranging device to hone in on the International Space Station (ISS) during pre-docking operations about 237 miles above Earth.

SLR2000: a microlaser-based single photoelectron satellite laser ranging system

NASA Technical Reports Server (NTRS)

Degnan, John J.; McGarry, Jan F.

1998-01-01

SLR2000 is an autonomous and eyesafe satellite laser ranging (SLR) station with an expected single shot range precision of about one centimeter and a normal point (time-averaged) precision better than 3 mm. The system wil provide continuous 24 hour tracking coverage for a constellation of over twenty artificial satellites. Replication costs are expected to be roughly an order of magnitude less than current operational systems, and the system will be about 75% less expensive to operate and maintain relative to manned systems. Computer simulations have predicted a daylight tracking capability to GPS and lower satellites with telescope apertures of 40 cm and have demonstrated the ability of our current autotracking algorithm to extract mean signal strengths below .001 photoelectrons per pulse from daytime background noise. The dominant cost driver in present SLR systems is the onsite and central infrastructure manpower required to operate the system, to service and maintain the complex subsystems, and to ensure that the transmitted laser beam is not a hazard to onsite personnel or to overflying aircraft. To keep development, fabrication, and maintenance costs at a minimum, we adopted the following design philosophies: (1) use off the shelf commercial components wherever possible; this allows rapid component replacement and "outsourcing" of engineering support; (2) use smaller telescopes (less than 50 cm) since this constrains the cost, size, and weight of the telescope and tracking mount; and (3) for low maintenance and failsafe reliability, choose simple versus complex technical approaches and, where possible, use passive techniques and components rather than active ones. Adherence to these philosophies has led to the SLR2000 design described here.

Laser Ranging for Effective and Accurate Tracking of Space Debris in Low Earth Orbits

NASA Astrophysics Data System (ADS)

Blanchet, Guillaume; Haag, Herve; Hennegrave, Laurent; Assemat, Francois; Vial, Sophie; Samain, Etienne

2013-08-01

The paper presents the results of preliminary design options for an operational laser ranging system adapted to the measurement of the distance of space debris. Thorough analysis of the operational parameters is provided with identification of performance drivers and assessment of enabling design options. Results from performance simulation demonstrate how the range measurement enables improvement of the orbit determination when combined with astrometry. Besides, experimental results on rocket-stage class debris in LEO were obtained by Astrium beginning of 2012, in collaboration with the Observatoire de la Côte d'Azur (OCA), by operating an experimental laser ranging system supported by the MéO (Métrologie Optique) telescope.

Close-range laser scanning in forests: towards physically based semantics across scales.

PubMed

Morsdorf, F; Kükenbrink, D; Schneider, F D; Abegg, M; Schaepman, M E

2018-04-06

Laser scanning with its unique measurement concept holds the potential to revolutionize the way we assess and quantify three-dimensional vegetation structure. Modern laser systems used at close range, be it on terrestrial, mobile or unmanned aerial platforms, provide dense and accurate three-dimensional data whose information just waits to be harvested. However, the transformation of such data to information is not as straightforward as for airborne and space-borne approaches, where typically empirical models are built using ground truth of target variables. Simpler variables, such as diameter at breast height, can be readily derived and validated. More complex variables, e.g. leaf area index, need a thorough understanding and consideration of the physical particularities of the measurement process and semantic labelling of the point cloud. Quantified structural models provide a framework for such labelling by deriving stem and branch architecture, a basis for many of the more complex structural variables. The physical information of the laser scanning process is still underused and we show how it could play a vital role in conjunction with three-dimensional radiative transfer models to shape the information retrieval methods of the future. Using such a combined forward and physically based approach will make methods robust and transferable. In addition, it avoids replacing observer bias from field inventories with instrument bias from different laser instruments. Still, an intensive dialogue with the users of the derived information is mandatory to potentially re-design structural concepts and variables so that they profit most of the rich data that close-range laser scanning provides.

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Field, Christopher T.; Sun, Xiaoli

1996-01-01

We report here the design and the performance measurements of the breadboard receiver of the Geoscience Laser Altimeter System (GLAS). The measured ranging accuracy was better than 2 cm and 10 cm for 5 ns and 30 ns wide received laser pulses under the expected received signal level, which agreed well with the theoretical analysis. The measured receiver sensitivity or the link margin was also consistent with the theory. The effects of the waveform digitizer sample rate and resolution were also measured.

Endoscopic laser range scanner for minimally invasive, image guided kidney surgery

NASA Astrophysics Data System (ADS)

Friets, Eric; Bieszczad, Jerry; Kynor, David; Norris, James; Davis, Brynmor; Allen, Lindsay; Chambers, Robert; Wolf, Jacob; Glisson, Courtenay; Herrell, S. Duke; Galloway, Robert L.

2013-03-01

Image guided surgery (IGS) has led to significant advances in surgical procedures and outcomes. Endoscopic IGS is hindered, however, by the lack of suitable intraoperative scanning technology for registration with preoperative tomographic image data. This paper describes implementation of an endoscopic laser range scanner (eLRS) system for accurate, intraoperative mapping of the kidney surface, registration of the measured kidney surface with preoperative tomographic images, and interactive image-based surgical guidance for subsurface lesion targeting. The eLRS comprises a standard stereo endoscope coupled to a steerable laser, which scans a laser fan beam across the kidney surface, and a high-speed color camera, which records the laser-illuminated pixel locations on the kidney. Through calibrated triangulation, a dense set of 3-D surface coordinates are determined. At maximum resolution, the eLRS acquires over 300,000 surface points in less than 15 seconds. Lower resolution scans of 27,500 points are acquired in one second. Measurement accuracy of the eLRS, determined through scanning of reference planar and spherical phantoms, is estimated to be 0.38 +/- 0.27 mm at a range of 2 to 6 cm. Registration of the scanned kidney surface with preoperative image data is achieved using a modified iterative closest point algorithm. Surgical guidance is provided through graphical overlay of the boundaries of subsurface lesions, vasculature, ducts, and other renal structures labeled in the CT or MR images, onto the eLRS camera image. Depth to these subsurface targets is also displayed. Proof of clinical feasibility has been established in an explanted perfused porcine kidney experiment.

The precision of today's satellite laser ranging systems

NASA Astrophysics Data System (ADS)

Dunn, Peter J.; Torrence, Mark H.; Hussen, Van S.; Pearlman, Michael R.

1993-06-01

Recent improvements in the accuracy of modern satellite laser ranging (SLR) systems are strengthened by the new capability of many instruments to track an increasing number of geodetic satellite targets without significant scheduling conflict. This will allow the refinement of some geophysical parameters, such as solid Earth tidal effects and GM, and the improved temporal resolution of others, such as Earth orientation and station position. Better time resolution for the locations of fixed observatories will allow us to monitor more subtle motions at the stations, and transportable systems will be able to provide indicators of long term trends with shorter occupations. If we are to take advantage of these improvements, care must be taken to preserve the essential accuracy of an increasing volume of range observations at each stage of the data reduction process.

The precision of today's satellite laser ranging systems

NASA Technical Reports Server (NTRS)

Dunn, Peter J.; Torrence, Mark H.; Hussen, Van S.; Pearlman, Michael R.

1993-01-01

Recent improvements in the accuracy of modern satellite laser ranging (SLR) systems are strengthened by the new capability of many instruments to track an increasing number of geodetic satellite targets without significant scheduling conflict. This will allow the refinement of some geophysical parameters, such as solid Earth tidal effects and GM, and the improved temporal resolution of others, such as Earth orientation and station position. Better time resolution for the locations of fixed observatories will allow us to monitor more subtle motions at the stations, and transportable systems will be able to provide indicators of long term trends with shorter occupations. If we are to take advantage of these improvements, care must be taken to preserve the essential accuracy of an increasing volume of range observations at each stage of the data reduction process.

Research on the laser angle deception jamming technology of laser countermeasure

NASA Astrophysics Data System (ADS)

Ma, Shi-wei; Chen, Wen-jian; Gao, Wei; Duan, Yuan-yuan

2015-10-01

In recent years , laser guided weapons behave very well at destroying the military goals in the local wars, the single-shot probability, effective range and hitting precision getting better. And the semi-active laser guided weapons are the most widely used laser guided weapons. In order to improve the viability and protect important military goals, it's necessary to study the technology to against the semi-active guided weapons. This paper studies the working principle, the advantages and disadvantages of the semi-active guided weapons at first, and analyze the possibility of laser angle deception jamming system working. Then it analyzes the working principle and process of laser angle deception jamming technology. Finally it designs a half-real simulation system of laser angle deception jamming, which consists of semi-active laser guided weapons simulation system and laser angle deception jamming system. The simulation system demonstrates the working process of the laser angle deception jamming system. This paper provides fundamental base for the research on the countermeasure technology of semi-active laser guided weapons.

Impact of Infrared Lunar Laser Ranging on Lunar Dynamics

NASA Astrophysics Data System (ADS)

Viswanathan, Vishnu; Fienga, Agnès; Manche, Hervé; Gastineau, Mickael; Courde, Clément; Torre, Jean-Marie; Exertier, Pierre; Laskar, Jacques; LLR Observers : Astrogeo-OCA, Apache Point, McDonald Laser Ranging Station, Haleakala Observatory, Matera Laser Ranging Observatory

2016-10-01

Since 2015, in addition to the traditional green (532nm), infrared (1064nm) has been the preferred wavelength for lunar laser ranging at the Calern lunar laser ranging (LLR) site in France. Due to the better atmospheric transmission of IR with respect to Green, nearly 3 times the number of normal points have been obtained in IR than in Green [ C.Courde et al 2016 ]. In our study, in addition to the historical data obtained from various other LLR sites, we include the recent IR normal points obtained from Calern over the 1 year time span (2015-2016), constituting about 4.2% of data spread over 46 years of LLR. Near even distribution of data provided by IR on both the spatial and temporal domain, helps us to improve constraints on the internal structure of the Moon modeled within the planetary ephemeris : INPOP [ Fienga et al 2015 ]. IERS recommended models have been used in the data reduction software GINS (GRGS,CNES) [ V.Viswanathan et al 2015 ]. Constraints provided by GRAIL, on the Lunar gravitational potential and Love numbers have been taken into account in the least-square fit procedure. New estimates on the dynamical parameters of the lunar core will be presented.

Laser Ranging to the Moon: How Evolving Technology Enables New Science

NASA Astrophysics Data System (ADS)

Faller, James

2010-03-01

Technological advances have long been the enabler of scientific progress. The invention of the laser is a prime example of this symbiotic relationship between technical progress and scientific advances. The laser, which today is omnipresent in each of our lives, made its first appearance during the time that I was a graduate student in Professor Dicke's group at Princeton. A major change occurring during that time period was that technology was transforming the study of gravitational physics from just a theoretical subject into also an experimental subject where one could hope to measure things using by-then-available laboratory technologies and techniques. During this same time, the idea for the lunar laser ranging experiment was born. The history and accomplishments of this experiment--a still ongoing experiment which is one of the real scientific triumphs of NASA's Apollo program--will be given.

The research of multi-frame target recognition based on laser active imaging

NASA Astrophysics Data System (ADS)

Wang, Can-jin; Sun, Tao; Wang, Tin-feng; Chen, Juan

2013-09-01

Laser active imaging is fit to conditions such as no difference in temperature between target and background, pitch-black night, bad visibility. Also it can be used to detect a faint target in long range or small target in deep space, which has advantage of high definition and good contrast. In one word, it is immune to environment. However, due to the affect of long distance, limited laser energy and atmospheric backscatter, it is impossible to illuminate the whole scene at the same time. It means that the target in every single frame is unevenly or partly illuminated, which make the recognition more difficult. At the same time the speckle noise which is common in laser active imaging blurs the images . In this paper we do some research on laser active imaging and propose a new target recognition method based on multi-frame images . Firstly, multi pulses of laser is used to obtain sub-images for different parts of scene. A denoising method combined homomorphic filter with wavelet domain SURE is used to suppress speckle noise. And blind deconvolution is introduced to obtain low-noise and clear sub-images. Then these sub-images are registered and stitched to combine a completely and uniformly illuminated scene image. After that, a new target recognition method based on contour moments is proposed. Firstly, canny operator is used to obtain contours. For each contour, seven invariant Hu moments are calculated to generate the feature vectors. At last the feature vectors are input into double hidden layers BP neural network for classification . Experiments results indicate that the proposed algorithm could achieve a high recognition rate and satisfactory real-time performance for laser active imaging.

Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal

PubMed Central

Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I.; Wang, Jiyang

2016-01-01

With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc. PMID:27461819

Long range laser traversing system

NASA Technical Reports Server (NTRS)

Caudill, L. O. (Inventor)

1974-01-01

The relative azimuth bearing between first and second spaced terrestrial points which may be obscured from each other by intervening terrain is measured by placing at one of the points a laser source for projecting a collimated beam upwardly in the vertical plane. The collimated laser beam is detected at the second point by positioning the optical axis of a receiving instrument for the laser beam in such a manner that the beam intercepts the optical axis. In response to the optical axis intercepting the beam, the beam is deflected into two different ray paths by a beam splitter having an apex located on the optical axis. The energy in the ray paths is detected by separate photoresponsive elements that drive logic networks for proving indications of: (1) the optical axis intercepting the beam; (2) the beam being on the left of the optical axis and (3) the beam being on the right side of the optical axis.

Combined Infrared Stereo and Laser Ranging Cloud Measurements from Shuttle Mission STS-85

NASA Technical Reports Server (NTRS)

Lancaster, R. S.; Spinhirne, J. D.; Manizade, K. F.

2004-01-01

Multiangle remote sensing provides a wealth of information for earth and climate monitoring, such as the ability to measure the height of cloud tops through stereoscopic imaging. As technology advances so do the options for developing spacecraft instrumentation versatile enough to meet the demands associated with multiangle measurements. One such instrument is the infrared spectral imaging radiometer, which flew as part of mission STS-85 of the space shuttle in 1997 and was the first earth- observing radiometer to incorporate an uncooled microbolometer array detector as its image sensor. Specifically, a method for computing cloud-top height with a precision of +/- 620 m from the multispectral stereo measurements acquired during this flight has been developed, and the results are compared with coincident direct laser ranging measurements from the shuttle laser altimeter. Mission STS-85 was the first space flight to combine laser ranging and thermal IR camera systems for cloud remote sensing.

Combined Infrared Stereo and Laser Ranging Cloud Measurements from Shuttle Mission STS-85

NASA Technical Reports Server (NTRS)

Lancaster, Redgie S.; Spinhirne, James D.; OCStarr, David (Technical Monitor)

2001-01-01

Multi-angle remote sensing provides a wealth of information for earth and climate monitoring. And, as technology advances so do the options for developing instrumentation versatile enough to meet the demands associated with these types of measurements. In the current work, the multiangle measurement capability of the Infrared Spectral Imaging Radiometer is demonstrated. This instrument flew as part of mission STS-85 of the space shuttle Columbia in 1997 and was the first earth-observing radiometer to incorporate an uncooled microbolometer array detector as its image sensor. Specifically, a method for computing cloud-top height from the multi-spectral stereo measurements acquired during this flight has been developed and the results demonstrate that a vertical precision of 10.6 km was achieved. Further, the accuracy of these measurements is confirmed by comparison with coincident direct laser ranging measurements from the Shuttle Laser Altimeter. Mission STS-85 was the first space flight to combine laser ranging and thermal IR camera systems for cloud remote sensing.

State-of-the-art satellite laser range modeling for geodetic and oceanographic applications

NASA Technical Reports Server (NTRS)

Klosko, Steve M.; Smith, David E.

1993-01-01

Significant improvements have been made in the modeling and accuracy of Satellite Laser Range (SLR) data since the launch of LAGEOS in 1976. Some of these include: improved models of the static geopotential, solid-Earth and ocean tides, more advanced atmospheric drag models, and the adoption of the J2000 reference system with improved nutation and precession. Site positioning using SLR systems currently yield approximately 2 cm static and 5 mm/y kinematic descriptions of the geocentric location of these sites. Incorporation of a large set of observations from advanced Satellite Laser Ranging (SLR) tracking systems have directly made major contributions to the gravitational fields and in advancing the state-of-the-art in precision orbit determination. SLR is the baseline tracking system for the altimeter bearing TOPEX/Poseidon and ERS-1 satellites and thus, will play an important role in providing the Conventional Terrestrial Reference Frame for instantaneously locating the geocentric position of the ocean surface over time, in providing an unchanging range standard for altimeter range calibration, and for improving the geoid models to separate gravitational from ocean circulation signals seen in the sea surface. Nevertheless, despite the unprecedented improvements in the accuracy of the models used to support orbit reduction of laser observations, there still remain systematic unmodeled effects which limit the full exploitation of modern SLR data.

Wide range optofluidically tunable multimode interference fiber laser

NASA Astrophysics Data System (ADS)

Antonio-Lopez, J. E.; Sanchez-Mondragon, J. J.; LiKamWa, P.; May-Arrioja, D. A.

2014-08-01

An optofluidically tunable fiber laser based on multimode interference (MMI) effects with a wide tuning range is proposed and demonstrated. The tunable mechanism is based on an MMI fiber filter fabricated using a special fiber known as no-core fiber, which is a multimode fiber (MMF) without cladding. Therefore, when the MMI filter is covered by liquid the optical properties of the no-core fiber are modified, which allow us to tune the peak wavelength response of the MMI filter. Rather than applying the liquid on the entire no-core fiber, we change the liquid level along the no-core fiber, which provides a highly linear tuning response. In addition, by selecting the adequate refractive index of the liquid we can also choose the tuning range. We demonstrate the versatility of the optofluidically tunable MMI filter by wavelength tuning two different gain media, erbium doped fiber and a semiconductor optical amplifier, achieving tuning ranges of 55 and 90 nm respectively. In both cases, we achieve side-mode suppression ratios (SMSR) better than 50 dBm with output power variations of less than 0.76 dBm over the whole tuning range.

Small image laser range finder for planetary rover

NASA Technical Reports Server (NTRS)

Wakabayashi, Yasufumi; Honda, Masahisa; Adachi, Tadashi; Iijima, Takahiko

1994-01-01

A variety of technical subjects need to be solved before planetary rover navigation could be a part of future missions. The sensors which will perceive terrain environment around the rover will require critical development efforts. The image laser range finder (ILRF) discussed here is one of the candidate sensors because of its advantage in providing range data required for its navigation. The authors developed a new compact-sized ILRF which is a quarter of the size of conventional ones. Instead of the current two directional scanning system which is comprised of nodding and polygon mirrors, the new ILRF is equipped with the new concept of a direct polygon mirror driving system, which successfully made its size compact to accommodate the design requirements. The paper reports on the design concept and preliminary technical specifications established in the current development phase.

Laser ranging application to time transfer using geodetic satellite and to other Japanese space programs

NASA Technical Reports Server (NTRS)

Kunimori, Hiroo; Takahashi, Fujinobu; Itabe, Toshikazu; Yamamoto, Atsushi

1993-01-01

Communications Research Laboratory (CRL) has been developing a laser time transfer system using a satellite laser ranging (SLR) system. We propose Japanese geodetic satellite 'AJISAI', launched in 1986 as a target satellite. The surface is covered not only with corner cube reflectors but also with mirrors. The mirrors are originally designed for observation of flushing solar light reflected by the separate mirrors while the satellite is spinning. In the experiment, synchronized laser pulses are transferred via specified mirror from one station to another while the satellite is up on the horizon to both stations. The system is based on the epoch timing ranging system with 40 ps ranging precision, connected together with UTC(CRL). Simulation study indicates that two stations at thousands of km distance from each other can be linked with signal strength of more than 10 photons and the distributed images of laser beam from AJISAI mirrors give many chances for two stations to link each other during a single AJISAI pass. Retro-reflector In Space for Advanced Earth Observation Satellite (ADEOS) and RendDezVous docking mission of Experimental Technology Satellite-7 (ETS-7) are briefly presented.

Short Range Photoassociation of Rb2 by a high power fiber laser

NASA Astrophysics Data System (ADS)

Passagem, Henry; Rodriguez, Ricardo; Ventura, Paulo; Bouloufa, Nadia; Dulieu, Olivier; Marcassa, Luis

2016-05-01

Photoassociation has been studied using cold trapped atomic samples for the last 20 years. Due to poor Franck-Condon overlap, a free-to-bound transition followed by spontaneous decay results in a small production of electronic ground state molecules. If the photoassociation is done at short range, deeply bound ground state molecules can be formed. Optical pumping schemes can be used to populate a single state. In our experiment, we have performed trap loss spectroscopy on trapped 85 Rb atoms in a MOT using a high power fiber laser. Our single mode fiber laser (linewidth < 1 MHz) produces about 50 W, which can be tuned in the 1060-1070 nm range. Two vibrational bound states of the 0u+ potential were observed (ν = 137 and 138). The frequency positions as well as the rotational constants of these states are in good agreement with theoretical predictions. We have also measured the lifetime of a crossed optical dipole trap using such fiber laser. The lifetime on resonance is shorter than off resonance as expected. A simple theoretical model indicates that the molecules decay to deeply bound vibrational levels in the ground state. This work was supported by Fapesp and INCT-IQ.

Lunar Science from Lunar Laser Ranging

NASA Technical Reports Server (NTRS)

Williams, J. G.; Boggs, D. H.; Ratcliff, J. T.

2013-01-01

Variations in rotation and orientation of the Moon are sensitive to solid-body tidal dissipation, dissipation due to relative motion at the fluid-core/solid-mantle boundary, tidal Love number k2, and moment of inertia differences. There is weaker sensitivity to flattening of the core/mantle boundary (CMB) and fluid core moment of inertia. Accurate Lunar Laser Ranging (LLR) measurements of the distance from observatories on the Earth to four retroreflector arrays on the Moon are sensitive to variations in lunar rotation, orientation and tidal displacements. Past solutions using the LLR data have given results for Love numbers plus dissipation due to solid-body tides and fluid core. Detection of the fluid core polar minus equatorial moment of inertia difference due to CMB flattening is weakly significant. This strengthens the case for a fluid lunar core. Future approaches are considered to detect a solid inner core.

Earth rotation, station coordinates and orbit determination from satellite laser ranging

NASA Astrophysics Data System (ADS)

Murata, Masaaki

The Project MERIT, a special program of international colaboration to Monitor Earth Rotation and Intercompare the Techniques of observation and analysis, has come to an end with great success. Its major objective was to evaluate the ultimate potential of space techniques such as VLBI and satellite laser ranging, in contrast with the other conventional techniques, in the determination of rotational dynamics of the earth. The National Aerospace Laboratory (NAL) has officially participated in the project as an associate analysis center for satellite laser technique for the period of the MERIT Main Campaign (September 1983-October 1984). In this paper, the NAL analysis center results are presented.

Phillips CO-oxidation catalyts for long-lived CO2 lasers: Activity and initial characterization studies

NASA Technical Reports Server (NTRS)

Kolts, J. H.; Elliott, D. J.; Pennella, F.

1990-01-01

Four different catalysts have been developed specifically for use in sealed carbon dioxide lasers. The catalysts have been designed to be low dusting, stable to shock and vibration, have high activity at low temperatures and have long active lifetimes. Measured global CO oxidation rates range from 1.4 to 2.2 cc CO converted per minute per gram of catalyst at ambient temperature. The catalysts also retain substantial activity at temperatures as low as -35 C. The Phillips laser catalysts are prepared in a variety of different shapes to meet the different pressure drop and gas flow profiles present in the many different styles of lasers. Each catalyst has been tested in sealed TEA lasers and has been shown to substantially increase the sealed life of the laser. Activity measurements made on the precious metal catalysts which were prepared with and without activity promoters showed that the promoter materials increase catalyst CO oxidation activity at least an order of magnitude at ambient temperature. Initial studies using H2 and CO chemisorption, X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS) have shown that the activity promoters do not significantly affect the precious metal crystallite size or the electronic structure around the precious metal. In addition, the formation or lack of formation of solid solutions between the precious metal and promoters has also been shown not to affect the activity of the promoted catalyst.

Upgrading NASA/DOSE laser ranging system control computers

NASA Technical Reports Server (NTRS)

Ricklefs, Randall L.; Cheek, Jack; Seery, Paul J.; Emenheiser, Kenneth S.; Hanrahan, William P., III; Mcgarry, Jan F.

1993-01-01

Laser ranging systems now managed by the NASA Dynamics of the Solid Earth (DOSE) and operated by the Bendix Field Engineering Corporation, the University of Hawaii, and the University of Texas have produced a wealth on interdisciplinary scientific data over the last three decades. Despite upgrades to the most of the ranging station subsystems, the control computers remain a mix of 1970's vintage minicomputers. These encompass a wide range of vendors, operating systems, and languages, making hardware and software support increasingly difficult. Current technology allows replacement of controller computers at a relatively low cost while maintaining excellent processing power and a friendly operating environment. The new controller systems are now being designed using IBM-PC-compatible 80486-based microcomputers, a real-time Unix operating system (LynxOS), and X-windows/Motif IB, and serial interfaces have been chosen. This design supports minimizing short and long term costs by relying on proven standards for both hardware and software components. Currently, the project is in the design and prototyping stage with the first systems targeted for production in mid-1993.

Surface-emitting terahertz quantum cascade lasers with continuous-wave power in the tens of milliwatt range

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

Xu, Gangyi, E-mail: gangyi.xu@mail.sitp.ac.cn; Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083; Li, Lianhe

2014-03-03

We demonstrate efficient surface-emitting terahertz frequency quantum cascade lasers with continuous wave output powers of 20–25 mW at 15 K and maximum operating temperatures of 80–85 K. The devices employ a resonant-phonon depopulation active region design with injector, and surface emission is realized using resonators based on graded photonic heterostructures (GPHs). GPHs can be regarded as energy wells for photons and have recently been implemented through grading the period of the photonic structure. In this paper, we show that it is possible to keep the period constant and grade instead the lateral metal coverage across the GPH. This strategy ensures spectrally single-mode operationmore » across the whole laser dynamic range and represents an additional degree of freedom in the design of confining potentials for photons.« less

Range Resolved CO2 Atmospheric Backscattering Measurements Using Fiber Lasers and RZPN Code Modulation

NASA Technical Reports Server (NTRS)

Burris, John

2011-01-01

We report the use of a return-to- zero (RZPN) pseudo noise modulation technique for making range resolved measurements of CO2 within the planetary boundary layer (PBL) using commercial, off-the-shelf, components. Conventional, range resolved, DIAL measurements require laser pulse widths that are significantly shorter than the desired spatial resolution and necessitate using pulses whose temporal spacing is such that scattered returns from only a single pulse are observed by the receiver at any one time (for the PBL pulse separations must be greater than approximately 20 microseconds). This imposes significant operational limitations when using currently available fiber lasers because of the resulting low duty cycle (less than approximately 0.0005) and consequent low average laser output power. The RZPN modulation technique enables a fiber laser to operate at much higher duty cycles (approaching 0.04) thereby more effectively utilizing the amplifier's output. This increases the counts received by approximately two orders of magnitude. Our approach involves employing two distributed feedback lasers (DFB), each modulated by a different RPZN code, whose outputs are then amplified by a CW fiber amplifier. One laser is tuned to a CO2 absorption line; the other operates offline thereby permitting the simultaneous acquisition of both on and offline signals using independent RZPN codes. This minimizes the impact of atmospheric turbulence on the measurement. The on and offline signals are retrieved by deconvolving the return signal using the appropriate kernels.

Research on techniques for laser ranging to optical corner reflectors on the moon. Research on laser techniques and single photo-electron detection and timing

NASA Technical Reports Server (NTRS)

Alley, C. O.

1976-01-01

Experimental studies using a pulsed LED, Cerenkov source, and a 100 ps laser were made of various photomultipliers and discriminator combinations. In addition, a new type of neodymium-YAG frequency doubled laser was used as the basis for the development of a stable, short pulse, high repetition rate laser system. This laser was then used in conjunction with atomic clocks to study the effect of gravitational potential on elapsed time. Avenues to promote the development of international cooperation in the area of lunar laser ranging were also explored.

Physics of the Brain. Prevention of the Epileptic Seizures by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies.

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander; IAPS Team

The novel study of the epileptogenesis mechanisms is proposed. It is based on the pulsed-operated (amplitude modulation) multi-photon (frequency modulation) fiber-laser interaction with the brain epilepsy-topion (the epilepsy onset area), so as to prevent the excessive electrical discharge (epileptic seizure) in the brain. The repetition frequency, Ω, matches the low frequency (epileptic) phonon waves in the brain. The laser repetition frequency (5-100 pulses per second) enables the resonance-scanning of the wide range of the phonon (possible epileptic-to-be) activity in the brain. The tunable fiber laser frequencies, Δω (multi photon operation), are in the ultraviolet frequency range, thus enabling monitoring of the electrical charge imbalance (within the 10s of milliseconds), and the DNA-corruption in the epilepsy-topion, as the possible cause of the disease. Supported by Nikola Tesla Labs., Stefan University.

Operating range of a differential-absorption lidar based on a CO{sub 2} laser

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

Ivashchenko, M V; Sherstov, I V

2000-08-31

The echolocation range and the remote sensing of ethylene in the atmosphere are simulated for a differential-absorption lidar based on TEA CO{sub 2} lasers. The dependence of the lidar echolocation range on the energy and the peak power of probe pulses is shown to be close to logarithmic. It is demonstrated that the use of narrow-band spectral filters is justified only for low-noise detectors and viewing angles of the receiver exceeding 5 mrad. The relative measurement error of the ethylene concentration in the atmosphere is estimated for various detection modes. (laser applications and other topics in quantum electronics)

Microdisk Injection Lasers for the 1.27-μm Spectral Range

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

Kryzhanovskaya, N. V.; Maximov, M. V.; Blokhin, S. A.

2016-03-15

Microdisk injection lasers on GaAs substrates, with a minimum diameter of 15 μm and an active region based on InAs/InGaAs quantum dots, are fabricated. The lasers operate in the continuous-wave mode at room temperature without external cooling. The lasing wavelength is around 1.27 μm at a minimum threshold current of 1.6 mA. The specific thermal resistance is estimated to be 5 × 10–3 °C cm{sup 2}/W.

A novel laser ranging system for measurement of ground-to-satellite distances

NASA Technical Reports Server (NTRS)

Golden, K. E.; Kind, D. E.; Leonard, S. L.; Ward, R. C.

1973-01-01

A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid.

Baseline monitoring using aircraft laser ranging. [spaceborne laser simulation and aircraft laser tracking

NASA Technical Reports Server (NTRS)

Krabill, W. B.; Hoge, F. E.; Martin, C. F.

1982-01-01

The use of aircraft laser ranging for the determination of baselines between ground based retroreflectors was investigated via simulations and with tests at Wallops Flight Center using the Airborne Oceanographic Lidar (AOL) on the Wallops C-54 aircraft ranging to a reflector array deployed around one of the Wallops runways. The aircraft altitude and reflector spacing were chosen on the basis of scaled down modeling of spacecraft tracking from 1000 km of reflectors separated by some 52 km, or of high altitude (10 km) aircraft tracking of reflectors separated by some 500 m. Aircraft altitudes flown for different passes across the runway reflector array varied from 800 m to 1350 m, with 32 reflectors deployed over an approximtely 300 m x 500 m ground pattern. The AOL transmitted 400 pulses/sec with a scan rate of 5/sec in a near circular pattern, so that the majority of the pulses were reflected by the runway surface or its environs rather than by retroreflectors. The return pulse characteristics clearly showed the high reflectivity of portions of the runway, with several returns indistinguishable in amplitude from reflector returns. For each pass across the reflector field, typically six to ten reflector hits were identified, consistent with that predicted by simulations and the observed transmitted elliptical pulse size.

Laser Remote Sensing at NASA

NASA Technical Reports Server (NTRS)

Barnes, Norman P.

2005-01-01

NASA is developing active remote sensors to monitor the health of Planet Earth and for exploration of other planets. Development and deployment of these remote sensors can have a huge economic impact. Lasers for these active remote sensors span the spectral range from the ultraviolet to the mid infrared spectral regions. Development activities range from quantum mechanical modeling and prediction of new laser materials to the design, development, and demonstration be deployed in the field.

Preliminary results from the portable standard satellite laser ranging intercomparison with MOBLAS-7

NASA Technical Reports Server (NTRS)

Selden, Michael; Varghese, Thomas K.; Heinick, Michael; Oldham, Thomas

1993-01-01

Conventional Satellite Laser Ranging (SLR) instrumentation has been configured and successfully used to provide high-accuracy laboratory measurements on the LAGEOS-2 and TOPEX cube-corner arrays. The instrumentation, referred to as the Portable Standard, has also been used for field measurements of satellite ranges in tandem with MOBLAS-7. Preliminary results of the SLR measurements suggest that improved range accuracy can be achieved using this system. Results are discussed.

Cumulative detection probabilities and range accuracy of a pulsed Geiger-mode avalanche photodiode laser ranging system

NASA Astrophysics Data System (ADS)

Luo, Hanjun; Ouyang, Zhengbiao; Liu, Qiang; Chen, Zhiliang; Lu, Hualan

2017-10-01

Cumulative pulses detection with appropriate cumulative pulses number and threshold has the ability to improve the detection performance of the pulsed laser ranging system with GM-APD. In this paper, based on Poisson statistics and multi-pulses cumulative process, the cumulative detection probabilities and their influence factors are investigated. With the normalized probability distribution of each time bin, the theoretical model of the range accuracy and precision is established, and the factors limiting the range accuracy and precision are discussed. The results show that the cumulative pulses detection can produce higher target detection probability and lower false alarm probability. However, for a heavy noise level and extremely weak echo intensity, the false alarm suppression performance of the cumulative pulses detection deteriorates quickly. The range accuracy and precision is another important parameter evaluating the detection performance, the echo intensity and pulse width are main influence factors on the range accuracy and precision, and higher range accuracy and precision is acquired with stronger echo intensity and narrower echo pulse width, for 5-ns echo pulse width, when the echo intensity is larger than 10, the range accuracy and precision lower than 7.5 cm can be achieved.

Active/passive mode-locked laser oscillator

DOEpatents

Fountain, William D.; Johnson, Bertram C.

1977-01-01

A Q-switched/mode-locked Nd:YAG laser oscillator employing simultaneous active (electro-optic) and passive (saturable absorber) loss modulation within the optical cavity is described. This "dual modulation" oscillator can produce transform-limited pulses of duration ranging from about 30 psec to about 5 nsec with greatly improved stability compared to other mode-locked systems. The pulses produced by this system lack intrapulse frequency or amplitude modulation, and hence are idealy suited for amplification to high energies and for other applications where well-defined pulses are required. Also, the pulses of this system have excellent interpulse characteristics, wherein the optical noise between the individual pulses of the pulse train has a power level well below the power of the peak pulse of the train.

MoonLIGHT: A USA-Italy lunar laser ranging retroreflector array for the 21st century

NASA Astrophysics Data System (ADS)

Martini, M.; Dell'Agnello, S.; Currie, D.; Delle Monache, G.; Vittori, R.; Chandler, J. F.; Cantone, C.; Boni, A.; Berardi, S.; Patrizi, G.; Maiello, M.; Garattini, M.; Lops, C.; March, R.; Bellettini, G.; Tauraso, R.; Intaglietta, N.; Tibuzzi, M.; Murphy, T. W.; Bianco, G.; Ciocci, E.

2012-12-01

Since the 1970s Lunar Laser Ranging (LLR) to the Apollo Cube Corner Retroreflector (CCR) arrays (developed by the University of Maryland, UMD) have supplied significant tests of General Relativity: possible changes in the gravitational constant, gravitational self-energy, weak equivalence principle, geodetic precession, inverse-square force-law. LLR has also provided significant information on the composition and origin of the Moon. This is the only Apollo experiment still in operation. In the 1970s Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Since the ranging capabilities of ground stations improved by more than two orders of magnitude, now, because of the lunar librations, Apollo CCR arrays dominate the error budget. With the project MoonLIGHT (Moon Laser Instrumentation for General relativity High-accuracy Tests), in 2006 INFN-LNF joined UMD in the development and test of a new-generation LLR payload made by a single, large CCR (100 mm diameter) unaffected by librations. In particular, INFN-LNF built and is operating a new experimental apparatus (Satellite/lunar laser ranging Characterization Facility, SCF) and created a new industry-standard test procedure (SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of CCRs in laboratory-simulated space conditions, for industrial and scientific applications. Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of retroreflector payloads under thermal conditions produced with a solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time payload movement to simulate satellite orientation on orbit with respect to solar illumination and laser interrogation beams. These capabilities provide: unique pre-launch performance validation of the space segment of LLR/SLR (Satellite Laser

Testing gravity with Lunar Laser Ranging: An update on the APOLLO experiment

NASA Astrophysics Data System (ADS)

Battat, James; Colmenares, Nick; Davis, Rodney; Ruixue, Louisa Huang; Murphy, Thomas W., Jr.; Apollo Collaboration

2017-01-01

The mystery of dark energy and the incompatibility of quantum mechanics and General Relativity indicate the need for precision experimental probes of gravitational physics. The Earth-Moon-Sun system is a fertile laboratory for such tests. The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) makes optical range measurements to retro-reflectors on the Moon with one millimeter precision. These measurements of the lunar orbit enable incisive constraints on gravitational phenomena such as the Strong Equivalence Principle and dG / dt (among others). Until now, the APOLLO team had not been able to assess the accuracy of our data, in large part because known limitations to lunar range models ensure data-model residuals at the centimeter scale. To directly measure the APOLLO system timing accuracy, we have built an Absolute timing Calibration System (ACS) that delivers photons to our detector at known, stable time intervals using a pulsed fiber laser locked to a cesium frequency standard. This scheme provides real-time calibration of the APOLLO system timing, synchronous with the range measurements. We installed the calibration system in August, 2016. In this talk, we will describe the ACS design, and present present preliminary results from the ACS calibration campaign. We acknowledge the support of both NSF and NASA

Laser and optics activities at CREOL

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

Stickley, C.M.

1995-06-01

CREOL is an interdisciplinary institute with a mission to foster and support research and education in the optical and laser sciences and engineering. CREOL`s principal members are its 21-strong faculty. The faculty are encouraged and supported in developing, maintaining, and expanding innovative and sponsored research programs, especially ones that are coupled to industry`s needs. The CREOL Director and Assistant Director, through empowerment by the CREOL faculty, coordinate and oversee the interactive, interdisciplinary projects of the faculty, the 85 graduate students and the 39 research staff. CREOL integrates these research efforts with the general educational mission and goals of the university,more » develops comprehensive course work in the optical and laser sciences and engineering, provides guidance and instruction to graduate students, administers MS and PhD programs, and provides facilities, funds, and administrative support to assist the faculty in carrying out CREOL`s mission and obtaining financial support for the research projects. CREOL`s specific areas of research activity include the following: IR systems; nonlinear optics; crystal growth; nonlinear integrated optics; new solid-state lasers; tunable far-infrared lasers; thin-film optics; theory; semiconductor lasers; x-ray/optical scattering; laser-induced damage; free-electron lasers; solid-state spectroscopy; x-ray sources and applications; laser propagation; laser processing of materials; optical design; optical limiting/sensor protection; diffractive optics; quantum well optoelectronics; dense plasmas/high-field physics; laser radar and remote sensing; diode-based lasers; and glass science.« less

Long-range open-path greenhouse gas monitoring using mid-infrared laser dispersion spectroscopy

NASA Astrophysics Data System (ADS)

Daghestani, Nart; Brownsword, Richard; Weidmann, Damien

2015-04-01

Accurate and sensitive methods of monitoring greenhouse gas (GHG) emission over large areas has become a pressing need to deliver improved estimates of both human-made and natural GHG budgets. These needs relate to a variety of sectors including environmental monitoring, energy, oil and gas industry, waste management, biogenic emission characterization, and leak detection. To address the needs, long-distance open-path laser spectroscopy methods offer significant advantages in terms of temporal resolution, sensitivity, compactness and cost effectiveness. Path-integrated mixing ratio measurements stemming from long open-path laser spectrometers can provide emission mapping when combined with meteorological data and/or through tomographic approaches. Laser absorption spectroscopy is the predominant method of detecting gasses over long integrated path lengths. The development of dispersion spectrometers measuring tiny refractive index changes, rather than optical power transmission, may offer a set of specific advantages1. These include greater immunity to laser power fluctuations, greater dynamic range due to the linearity of dispersion, and ideally a zero baseline signal easing quantitative retrievals of path integrated mixing ratios. Chirped laser dispersion spectrometers (CLaDS) developed for the monitoring of atmospheric methane and carbon dioxide will be presented. Using quantum cascade laser as the source, a minimalistic and compact system operating at 7.8 μm has been developed and demonstrated for the monitoring of atmospheric methane over a 90 meter open path2. Through full instrument modelling and error propagation analysis, precision of 3 ppm.m.Hz-0.5 has been established (one sigma precision for atmospheric methane normalized over a 1 m path and 1 s measurement duration). The system was fully functional in the rain, sleet, and moderate fog. The physical model and system concept of CLaDS can be adapted to any greenhouse gas species. Currently we are

Satellite laser ranging using superconducting nanowire single-photon detectors at 1064  nm wavelength.

PubMed

Xue, Li; Li, Zhulian; Zhang, Labao; Zhai, Dongsheng; Li, Yuqiang; Zhang, Sen; Li, Ming; Kang, Lin; Chen, Jian; Wu, Peiheng; Xiong, Yaoheng

2016-08-15

Satellite laser ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SNSPDs) is successfully demonstrated. A SNSPD with an intrinsic quantum efficiency of 80% and a dark count rate of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory in China. With improved closed-loop telescope systems (field of view of about 26^''), satellites including Cryosat, Ajisai, and Glonass with ranges of 1600 km, 3100 km, and 19,500 km, respectively, are experimentally ranged with mean echo rates of 1200/min, 4200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of laser ranging for satellites using SNSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicate that it is possible for a SNSPD to range satellites from low Earth orbit to geostationary Earth orbit.

Eye-Safe KGd(WO4)2:Nd Laser: Nano- and Subnanosecond Pulse Generation in Self-Frequency Raman Conversion Mode with Active Q-Switching

NASA Astrophysics Data System (ADS)

Dashkevich, V. I.; Orlovich, V. A.

2017-03-01

The shape of the multimode Stokes pulse generated by an eye-safe KGd(WO4)2:Nd laser with self-frequency Raman conversion and active Q-switching was shown to depend on the inhomogeneity of the active-medium pump. The laser generated a short and undistorted Stokes pulse of length 2.5 ns that increased with increasing laser cavity length for a moderately inhomogeneous pump characterized by a higher population inversion in the center of the active element. The energy of the Stokes pulse ( 11.5 mJ) varied little as the output-mirror reflectivity varied in the range 5-45%. The Raman pulse became distorted if the inhomogeneity of the pump was increased considerably. The degree of pump inhomogeneity was negligible with fundamental TEM00 mode selection. The laser generated subnanosecond Stokes pulses with peak power in the MW range.

Dense range map reconstruction from a versatile robotic sensor system with an active trinocular vision and a passive binocular vision.

PubMed

Kim, Min Young; Lee, Hyunkee; Cho, Hyungsuck

2008-04-10

One major research issue associated with 3D perception by robotic systems is the creation of efficient sensor systems that can generate dense range maps reliably. A visual sensor system for robotic applications is developed that is inherently equipped with two types of sensor, an active trinocular vision and a passive stereo vision. Unlike in conventional active vision systems that use a large number of images with variations of projected patterns for dense range map acquisition or from conventional passive vision systems that work well on specific environments with sufficient feature information, a cooperative bidirectional sensor fusion method for this visual sensor system enables us to acquire a reliable dense range map using active and passive information simultaneously. The fusion algorithms are composed of two parts, one in which the passive stereo vision helps active vision and the other in which the active trinocular vision helps the passive one. The first part matches the laser patterns in stereo laser images with the help of intensity images; the second part utilizes an information fusion technique using the dynamic programming method in which image regions between laser patterns are matched pixel-by-pixel with help of the fusion results obtained in the first part. To determine how the proposed sensor system and fusion algorithms can work in real applications, the sensor system is implemented on a robotic system, and the proposed algorithms are applied. A series of experimental tests is performed for a variety of configurations of robot and environments. The performance of the sensor system is discussed in detail.

Effect of shorter pulse duration in cochlear neural activation with an 810-nm near-infrared laser.

PubMed

Wang, Jingxuan; Tian, Lan; Lu, Jianren; Xia, Ming; Wei, Ying

2017-02-01

Optical neural stimulation in the cochlea has been presented as an alternative technique to the electrical stimulation due to its potential in spatially selectivity enhancement. So far, few studies have selected the near-infrared (NIR) laser in cochlear neural stimulation and limited optical parameter space has been examined. This paper focused on investigating the optical parameter effect on NIR stimulation of auditory neurons, especially under shorter pulse durations. The spiral ganglion neurons in the cochlea of deafened guinea pigs were stimulated with a pulsed 810-nm NIR laser in vivo. The laser radiation was delivered by an optical fiber and irradiated towards the modiolus. Optically evoked auditory brainstem responses (OABRs) with various optical parameters were recorded and investigated. The OABRs could be elicited with the cochlear deafened animals by using the 810-nm laser in a wide pulse duration ranged from 20 to 1000 μs. Results showed that the OABR intensity increased along with the increasing laser radiant exposure of limited range at each specific pulse duration. In addition, for the pulse durations from 20 to 300 μs, the OABR intensity increased monotonically along with the pulse duration broadening. While for pulse durations above 300 μs, the OABR intensity basically kept stable with the increasing pulse duration. The 810-nm NIR laser could be an effective stimulus in evoking the cochlear neuron response. Our experimental data provided evidence to optimize the pulse duration range, and the results suggested that the pulse durations from 20 to 300 μs could be the optimized range in cochlear neural activation with the 810-nm-wavelength laser.

Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design.

PubMed

Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

2016-06-08

Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm(-1)) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing.

Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design

PubMed Central

Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

2016-01-01

Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm−1) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing. PMID:27270634

Value added cleaning and disinfection of the root canal: laser-activated irrigation and laser-induced photoporation

NASA Astrophysics Data System (ADS)

De Moor, Roeland J. G.; Meire, Maarten A.

2016-03-01

Among present-day marketed systems ultrasonic activation appears to be the best way to activate and potentiate endodontic irrigants. An alternative for ultrasonic activation of irrigants is laser activated irrigation (LAI) or photoninitiated acoustic streaming. Based on present-day research it appears that LAI (especially with Erbium lasers) can be more efficient for debris removal out of root canals and interaction with the endodontic biofilms thanks to the induction of specific cavitation phenomena and acoustic streaming. Other wavelengths are now explored to be used for LAI. Another way to interact with biofilms is to rely on laser-induced photoporation in combination with gold nanoparticles ( AuNPs). The latter is an alternative physical method for delivering macromolecules in cells. Nanosized membrane pores can be created upon pulsed laser illumination. Depending on the laser energy, pores are created through either direct heating of the AuNPs or by vapour nanobubbles that can emerge around the AuNPs.

Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

PubMed

Macleod, Neil A; Molero, Francisco; Weidmann, Damien

2015-01-26

A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm^-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers.

Semiconductor lasers with a continuous tuning range above 100 nm in the nearest IR spectral region

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

Kostin, Yu O; Lobintsov, A A; Shramenko, M V

2015-08-31

We have developed two new types of lasers based on quantum-confined semiconductor optical amplifiers with an acousto-optic tunable filter in an external fibre ring cavity. The lasers offer continuous wavelength tuning ranges from 780 to 885 and from 880 to 1010 nm, 20 mW of cw output power, and a tuning rate up to 10{sup 4} nm s{sup -1} at an instantaneous spectral linewidth less than 0.1 nm. (lasers)

The Solaris-Panoptes Global Network of Robotic Telescopes and the Borowiec Satellite Laser Ranging System for SST: A Progress Report

NASA Astrophysics Data System (ADS)

Konacki, M.; Lejba, P.; Sybilski, P.; Pawłaszek, R.; Kozłowski, S.; Suchodolski, T.; Słonina, M.; Litwicki, M.; Sybilska, A.; Rogowska, B.; Kolb, U.; Burwitz, V.; Baader, J.; Groot, P.; Bloemen, S.; Ratajczak, M.; Hełminiak, K.; Borek, R.; Chodosiewicz, P.; Chimicz, A.

We present an update on the preparation of our assets that consists of a robotic network of eight optical telescopes and a laser ranging station for regular services in the SST domain. We report the development of new optical assets that include a double telescope system, Panoptes-1AB, and a new astrograph on our Solaris-3 telescope at the Siding Spring Observatory, Australia. Progress in the software development necessary for smooth SST operation includes a web based portal and an XML Azure Queue scheduling for the network giving easy access to our sensors. Astrometry24.net our new prototype cloud service for fast astrometry, streak detection and measurement with precision and performance results is also described. In the laser domain, for more than a year, Space Research Centre Borowiec laser station has regularly tracked space debris cooperative and uncooperative targets. The efforts of the stations’ staff have been focused on the tracking of typical rocket bodies from the LEO regime. Additionally, a second independent laser system fully dedicated to SST activities is under development. It will allow for an increased pace of operation of our consortium in the global SST laser domain.

Up-conversion multiwave (White) luminescence in the visible spectral range under excitation by IR laser diodes in the active BaY2F8:Yb3+,Pr3+ medium

NASA Astrophysics Data System (ADS)

Pushkar', A. A.; Uvarova, T. V.; Kiiko, V. V.

2011-08-01

The possibilities of occupying high-lying 4 f states of Pr3+ ions in the active BaY2F8:Yb3+,Pr3+ medium according to the photon avalanche and step-by-step sensitization mechanisms are compared. It is shown that the photon avalanche is unlikely to occur in the BaY2F8:Yb3+,Pr3+ crystal. The multiband luminescence spectra in the visible spectral range (white emission) under single- and multiwave pumping of BaY2F8:Yb3+,Pr3+ crystal by IR laser diodes are reported.

Infrared Lunar Laser Ranging at Calern : Impact on Lunar Dynamics

NASA Astrophysics Data System (ADS)

Viswanathan, Vishnu; Fienga, Agnes; Manche, Herve; Gastineau, Mickael; Courde, Clement; Torre, Jean Marie; Exertier, Pierre; Laskar, Jacques

2017-04-01

Introduction: Since 2015, in addition to the traditional green (532nm), infrared (1064nm) has been the preferred wavelength for lunar laser ranging at the Calern lunar laser ranging (LLR) site in France. Due to the better atmospheric transmission of IR with respect to Green, nearly 3 times the number of normal points have been obtained in IR than in Green [1]. Dataset: In our study, in addition to the historical data obtained from various other LLR sites, we include the recent IR normal points obtained from Calern over the 1 year time span (2015-2016), constituting about 4.2% of data spread over 46 years of LLR. Near even distribution of data provided by IR on both the spatial and temporal domain, helps us to improve constraints on the internal structure of the Moon modeled within the planetary ephemeris : INPOP [2]. Data reduction: IERS recommended models have been used in the data reduction software GINS (GRGS,CNES) [3]. Constraints provided by GRAIL [4], on the Lunar gravitational potential and Love numbers have been taken into account in the least-square fit procedure. Earth orientation parameters from KEOF series have been used as per a recent study [5]. Results: New estimates on the dynamical parameters of the lunar core will be presented. Acknowledgements: We thank the lunar laser ranging observers at Observatoire de la Côte d'Azur, France, McDonald Observatory, Texas, Haleakala Observatory, Hawaii, and Apache Point Observatory in New Mexico for providing LLR observations that made this study possible. The research described in this abstract was carried out at Geoazur-CNRS, France, as a part of a PhD thesis funded by Observatoire de Paris and French Ministry of Education and Research. References: [1] Clement C. et al. (2016) submitted to A&A [2] Fienga A. et al. (2015) Celest Mech Dyn Astr, 123: 325. doi:10.1007/s10569-015-9639-y [3] Viswanathan V. et al. (2015) EGU, Abstract 18, 13995 [4] Konopliv A. S. et al. (2013) J. Geophys. Res. Planets, 118, 1415

Airborne laser sensors and integrated systems

NASA Astrophysics Data System (ADS)

Sabatini, Roberto; Richardson, Mark A.; Gardi, Alessandro; Ramasamy, Subramanian

2015-11-01

The underlying principles and technologies enabling the design and operation of airborne laser sensors are introduced and a detailed review of state-of-the-art avionic systems for civil and military applications is presented. Airborne lasers including Light Detection and Ranging (LIDAR), Laser Range Finders (LRF), and Laser Weapon Systems (LWS) are extensively used today and new promising technologies are being explored. Most laser systems are active devices that operate in a manner very similar to microwave radars but at much higher frequencies (e.g., LIDAR and LRF). Other devices (e.g., laser target designators and beam-riders) are used to precisely direct Laser Guided Weapons (LGW) against ground targets. The integration of both functions is often encountered in modern military avionics navigation-attack systems. The beneficial effects of airborne lasers including the use of smaller components and remarkable angular resolution have resulted in a host of manned and unmanned aircraft applications. On the other hand, laser sensors performance are much more sensitive to the vagaries of the atmosphere and are thus generally restricted to shorter ranges than microwave systems. Hence it is of paramount importance to analyse the performance of laser sensors and systems in various weather and environmental conditions. Additionally, it is important to define airborne laser safety criteria, since several systems currently in service operate in the near infrared with considerable risk for the naked human eye. Therefore, appropriate methods for predicting and evaluating the performance of infrared laser sensors/systems are presented, taking into account laser safety issues. For aircraft experimental activities with laser systems, it is essential to define test requirements taking into account the specific conditions for operational employment of the systems in the intended scenarios and to verify the performance in realistic environments at the test ranges. To support the

240 GHz pedestal-free colliding-pulse mode-locked laser with a wide operation range

NASA Astrophysics Data System (ADS)

Hou, L.; Haji, M.; Marsh, J. H.

2014-11-01

A 240 GHz, sixth-harmonic monolithic ~1.55 μm colliding-pulse mode-locked laser is reported using a three-quantum-well active layer design and a passive far-field reduction layer. The device emits 0.88 ps pulses with a peak power of 65 mW and intermediate longitudinal modes suppressed by >30 dB. The device demonstrates a wide operation range compared to the conventional five-quantum-well design as well as having a low divergence angle (12.7° × 26.3°), granting a twofold improvement in butt-coupling efficiency into a flat cleaved single-mode fibre.

Lunar Laser Ranging: Glorious Past And A Bright Future

NASA Astrophysics Data System (ADS)

Shelus, Peter J.

Lunar Laser Ranging (LLR), a part of the NASA Apollo program, has beenon-going for more than 30 years. It provides the grist for a multi-disciplinarydata analysis mill. Results exist for solid Earth sciences, geodesy and geodynamics,solar system ephemerides, terrestrial and celestial reference frames, lunar physics,general relativity and gravitational theory. Combined with other data, it treatsprecession of the Earth''s spin axis, lunar induced nutation, polar motion/Earthrotation, Earth orbit obliquity to the ecliptic, intersection of the celestial equatorwith the ecliptic, luni-solar solid body tides, lunar tidal deceleration, lunar physicaland free librations, structure of the moon and energy dissipation in the lunar interior.LLR provides input to lunar surface cartography and surveying, Earth station and lunar retroreflector location and motion, mass of the Earth-moon system, lunar and terrestrial gravity harmonics and Love numbers, relativistic geodesic precession, and the equivalence principle of general relativity. With the passive nature of the reflectors and steady improvement in observing equipment and data analysis, LLR continues to provide state-of-the-art results. Gains are steady as the data-base expands. After more than 30 years, LLR remains the only active Apollo experiment. It is important to recognize examples of efficient and cost effective progress of research. LLR is just such an example.

Ultraviolet light and laser irradiation enhances the antibacterial activity of glucosamine-functionalized gold nanoparticles

PubMed Central

Govindaraju, Saravanan; Ramasamy, Mohankandhasamy; Baskaran, Rengarajan; Ahn, Sang Jung; Yun, Kyusik

2015-01-01

Here we report a novel method for the synthesis of glucosamine-functionalized gold nanoparticles (GlcN-AuNPs) using biocompatible and biodegradable glucosamine for antibacterial activity. GlcN-AuNPs were prepared using different concentrations of glucosamine. The synthesized AuNPs were characterized for surface plasmon resonance, surface morphology, fluorescence spectroscopy, and antibacterial activity. The minimum inhibitory concentrations (MICs) of the AuNPs, GlcN-AuNPs, and GlcN-AuNPs when irradiated by ultraviolet light and laser were investigated and compared with the MIC of standard kanamycin using Escherichia coli by the microdilution method. Laser-irradiated GlcN-AuNPs exhibited significant bactericidal activity against E. coli. Flow cytometry and fluorescence microscopic analysis supported the cell death mechanism in the presence of GlcN-AuNP-treated bacteria. Further, morphological changes in E. coli after laser treatment were investigated using atomic force microscopy and transmission electron microscopy. The overall results of this study suggest that the prepared nanoparticles have potential as a potent antibacterial agent for the treatment of a wide range of disease-causing bacteria. PMID:26345521

STS-109 MS Linnehan with laser range finder on aft flight deck

NASA Image and Video Library

2002-03-02

STS109-E-5003 (3 March 2002) --- Astronaut Richard M. Linnehan, mission specialist, uses a laser ranging device designed to measure the range between two spacecraft. Linnehan positioned himself on the cabin's aft flight deck as the Space Shuttle Columbia approached the Hubble Space Telescope. A short time later, the STS-109 crew captured and latched down the giant telescope in the vehicle's cargo bay for several days of work on the Hubble. The image was recorded with a digital still camera.

STS-109 MS Linnehan with laser range finder on aft flight deck

NASA Image and Video Library

2002-03-02

STS109-E-5002 (3 March 2002) --- Astronaut Richard M. Linnehan, mission specialist, uses a laser ranging device designed to measure the range between two spacecraft. Linnehan positioned himself on the cabin's aft flight deck as the Space Shuttle Columbia approached the Hubble Space Telescope. A short time later, the STS-109 crew captured and latched down the giant telescope in the vehicle's cargo bay for several days of work on the Hubble. The image was recorded with a digital still camera.

Radiation Effects on an Active Ytterbium doped Fiber Laser

DTIC Science & Technology

laser. While the gain medium of the laser was irradiated , the power was measured in-situ and the spectrum was recorded intermittently. The results...with a lower initial power. Power recovery experiments were conducted post- irradiation with the fiber laser off and actively lasing. Passively, the...total power recovery of 12.6 and 4.4 for YDF1 and YDF2 respectively. The active recovery rate declined as the number of days following irradiation

Airborne laser ranging system for monitoring regional crustal deformation

NASA Technical Reports Server (NTRS)

Degnan, J. J.

1981-01-01

Alternate approaches for making the atmospheric correction without benefit of a ground-based meteorological network are discussed. These include (1) a two-color channel that determines the atmospheric correction by measuring the time delay induced by dispersion between pulses at two optical frequencies; (2) single-color range measurements supported by an onboard temperature sounder, pressure altimeter readings, and surface measurements by a few existing meteorological facilities; and (3) inclusion of the quadratic polynomial coefficients as variables to be solved for along with target coordinates in the reduction of the single-color range data. It is anticipated that the initial Airborne Laser Ranging System (ALRS) experiments will be carried out in Southern California in a region bounded by Santa Barbara on the norht and the Mexican border on the south. The target area will be bounded by the Pacific Ocean to the west and will extend eastward for approximately 400 km. The unique ability of the ALRS to provide a geodetic 'snapshot' of such a large area will make it a valuable geophysical tool.

In-line process control for laser welding of titanium by high dynamic range ratio pyrometry and plasma spectroscopy

NASA Astrophysics Data System (ADS)

Lempe, B.; Taudt, C.; Baselt, T.; Rudek, F.; Maschke, R.; Basan, F.; Hartmann, P.

2014-02-01

The production of complex titanium components for various industries using laser welding processes has received growing attention in recent years. It is important to know whether the result of the cohesive joint meets the quality requirements of standardization and ultimately the customer requirements. Erroneous weld seams can have fatal consequences especially in the field of car manufacturing and medicine technology. To meet these requirements, a real-time process control system has been developed which determines the welding quality through a locally resolved temperature profile. By analyzing the resulting weld plasma received data is used to verify the stability of the laser welding process. The determination of the temperature profile is done by the detection of the emitted electromagnetic radiation from the material in a range of 500 nm to 1100 nm. As detectors, special high dynamic range CMOS cameras are used. As the emissivity of titanium depends on the wavelength, the surface and the angle of radiation, measuring the temperature is a problem. To solve these a special pyrometer setting with two cameras is used. That enables the compensation of these effects by calculating the difference between the respective pixels on simultaneously recorded images. Two spectral regions with the same emissivity are detected. Therefore the degree of emission and surface effects are compensated and canceled out of the calculation. Using the spatially resolved temperature distribution the weld geometry can be determined and the laser process can be controlled. The active readjustment of parameters such as laser power, feed rate and inert gas injection increases the quality of the welding process and decreases the number of defective goods.

Determination of crustal motions using satellite laser ranging

NASA Technical Reports Server (NTRS)

1991-01-01

Satellite laser ranging has matured over the last decade into one of the essential space geodesy techniques. It has demonstrated centimeter site positioning and millimeter per year velocity determinations in a frame tied dynamically to the mass center of the solid Earth hydrosphere atmosphere system. Such a coordinate system is a requirement for studying long term eustatic sea level rise and other global change phenomena. Earth orientation parameters determined with the coordinate system have been produced in near real time operationally since 1983, at a relatively modest cost. The SLR ranging to Lageos has also provided a rich spectrum of results based upon the analysis of Lageos orbital dynamics. These include significant improvements in the knowledge of the mean and variable components of the Earth's gravity field and the Earth's gravitational parameter. The ability to measure the time variations of the Earth's gravity field has opened as exciting area of study in relating global processes, including meteorologically derived mass transport through changes in the satellite dynamics. New confirmation of general relativity was obtained using the Lageos SLR data.

Determining the 3-D structure and motion of objects using a scanning laser range sensor

NASA Technical Reports Server (NTRS)

Nandhakumar, N.; Smith, Philip W.

1993-01-01

In order for the EVAHR robot to autonomously track and grasp objects, its vision system must be able to determine the 3-D structure and motion of an object from a sequence of sensory images. This task is accomplished by the use of a laser radar range sensor which provides dense range maps of the scene. Unfortunately, the currently available laser radar range cameras use a sequential scanning approach which complicates image analysis. Although many algorithms have been developed for recognizing objects from range images, none are suited for use with single beam, scanning, time-of-flight sensors because all previous algorithms assume instantaneous acquisition of the entire image. This assumption is invalid since the EVAHR robot is equipped with a sequential scanning laser range sensor. If an object is moving while being imaged by the device, the apparent structure of the object can be significantly distorted due to the significant non-zero delay time between sampling each image pixel. If an estimate of the motion of the object can be determined, this distortion can be eliminated; but, this leads to the motion-structure paradox - most existing algorithms for 3-D motion estimation use the structure of objects to parameterize their motions. The goal of this research is to design a rigid-body motion recovery technique which overcomes this limitation. The method being developed is an iterative, linear, feature-based approach which uses the non-zero image acquisition time constraint to accurately recover the motion parameters from the distorted structure of the 3-D range maps. Once the motion parameters are determined, the structural distortion in the range images is corrected.

Compensation for the distortion in satellite laser range predictions due to varying pulse travel times

NASA Technical Reports Server (NTRS)

Paunonen, Matti

1993-01-01

A method for compensating for the effect of the varying travel time of a transmitted laser pulse to a satellite is described. The 'observed minus predicted' range differences then appear to be linear, which makes data screening or use in range gating more effective.

Satellite Laser Ranging and the Modelling of Non-gravitational Perturbations: the LARASE experiment

NASA Astrophysics Data System (ADS)

Lucchesi, David; Anselmo, Luciano; Pardini, Carmen; Peron, Roberto; Pucacco, Giuseppe; Visco, Massimo

-gravitational forces modelling. This is also particularly important for the role played by these satellites in general relativity theory tests in the field of the Earth, wherever the tiny predictions of Einstein’s geometrodynamics need a quite reliable and robust POD. The aim of LARASE (LAser RAnged Satellites Experiment) is to go a step further in the tests of the gravitational interaction in the field of the Earth and, as highlighted above, a key role to reach such a goal is played by high-quality updated models for the perturbing non-gravitational forces acting on the surface of the satellites. Therefore, in the context of the LARASE collaboration, we started an activity dedicated to revisit, extend and improve current models for the non-gravitational perturbations in the case of LAGEOS-type satellites. We discuss the spin modelling problem and its intimate relationship with the thermal thrust forces; also the atmospheric drag impact on the orbit will be discussed, especially in the case of LARES due to its much lower altitude with respect to that of the two LAGEOS. Finally, we present our recent results on the data analysis of the orbit of the two LAGEOS satellites and on that of LARES.

Dynamic time-correlated single-photon counting laser ranging

NASA Astrophysics Data System (ADS)

Peng, Huan; Wang, Yu-rong; Meng, Wen-dong; Yan, Pei-qin; Li, Zhao-hui; Li, Chen; Pan, Hai-feng; Wu, Guang

2018-03-01

We demonstrate a photon counting laser ranging experiment with a four-channel single-photon detector (SPD). The multi-channel SPD improve the counting rate more than 4×107 cps, which makes possible for the distance measurement performed even in daylight. However, the time-correlated single-photon counting (TCSPC) technique cannot distill the signal easily while the fast moving targets are submersed in the strong background. We propose a dynamic TCSPC method for fast moving targets measurement by varying coincidence window in real time. In the experiment, we prove that targets with velocity of 5 km/s can be detected according to the method, while the echo rate is 20% with the background counts of more than 1.2×107 cps.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Picosecond laser with active mode locking and calcium lithium niobium gallium disordered Nd3+-activated garnet

NASA Astrophysics Data System (ADS)

Basiev, Tasoltan T.; Grudinin, A. B.; Karasik, Aleksandr Ya; Senatorov, A. K.; Sobol, A. A.; Fedorov, V. V.; Shubochkin, R. L.

1994-01-01

A laser was constructed in which the active medium was a crystal of calcium lithium niobium gallium garnet activated with Nd3+ ions. An acoustooptic modulator made of an LiNbO3 crystal and a passive LiF switch with F2 colour centres were used in this laser. The combination of active mode locking and Q switching made it possible to generate laser pulses of 10-15 ps duration at the wavelength λ = 1061.2 nm with a peak power of about 15 MW.

Ring-shaped active mode-locked tunable laser using quantum-dot semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Zhang, Mingxiao; Wang, Yongjun; Liu, Xinyu

2018-03-01

In this paper, a lot of simulations has been done for ring-shaped active mode-locked lasers with quantum-dot semiconductor optical amplifier (QD-SOA). Based on the simulation model of QD-SOA, we discussed about the influence towards mode-locked waveform frequency and pulse caused by QD-SOA maximum mode peak gain, active layer loss coefficient, bias current, incident light pulse, fiber nonlinear coefficient. In the meantime, we also take the tunable performance of the laser into consideration. Results showed QD-SOA a better performance than original semiconductor optical amplifier (SOA) in recovery time, line width, and nonlinear coefficients, which makes it possible to output a locked-mode impulse that has a higher impulse power, narrower impulse width as well as the phase is more easily controlled. After a lot of simulations, this laser can realize a 20GHz better locked-mode output pulse after 200 loops, where the power is above 17.5mW, impulse width is less than 2.7ps, moreover, the tunable wavelength range is between 1540nm-1580nm.

Analysis of optical scheme for medium-range directed energy laser weapon system

NASA Astrophysics Data System (ADS)

Jabczyński, Jan K.; Kaśków, Mateusz; Gorajek, Łukasz; Kopczyński, Krzysztof

2017-10-01

The relations between range of operation and aperture of laser weapon system were investigated, taking into account diffraction and technical limitations as beam quality, accuracy of point tracking, technical quality of optical train, etc. As a result for the medium ranges of 1 - 2 km we restricted the analysis to apertures not wider than 150 mm and the optical system without adaptive optics. To choose the best laser beam shape, the minimization of aperture losses and thermooptical effects inside optics as well as the effective width of laser beam in far field should be taken into account. We have analyzed theoretically such a problem for the group of a few most interesting from that point of view profiles including for reference two limiting cases of Gaussian beam and `top hat' profile. We have found that the most promising is the SuperGaussian profile of index p = 2 for which the surfaces of beam shaper elements can be manufactured in the acceptable cost-effective way and beam quality does not decrease noticeably. Further, we have investigated the thermo-optic effects on the far field parameters of Gaussian and `top hat' beams to determine the influence of absorption in optical elements on beam quality degradation. The simplified formulae were derived for beam quality measures (parameter M2 and Strehl ratio) which enables to estimate the influence of absorption losses on degradation of beam quality.

Testing Gravity via Lunar Laser Ranging: Maximizing Data Quality

NASA Astrophysics Data System (ADS)

Murphy, Thomas

We propose to continue leading-edge observations with the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO), in an effort to subject gravity to the most stringent tests yet. APOLLO has delivered a dramatic improvement in the measurement of the lunar orbit: now at the millimeter level. Yet incomplete models are thus far unable to confirm the accuracy. We therefore seek to build a calibration system to ensure that APOLLO meets its millimeter measurement goal. Gravity--the most evident force of nature--is in fact the weakest of the fundamental forces, and consequently the most poorly tested. Einstein’s general relativity, which is currently our best description of gravity, is fundamentally incompatible with quantum mechanics and is likely to be replaced by a more complete theory in the future. A modified theory would predict small deviations in the solar system that could have profound consequences for our understanding of the Universe as a whole. Lunar laser ranging (LLR), in which short laser pulses launched from a telescope are bounced off of reflectors placed on the Moon by U.S. astronauts and Soviet landers, has for decades produced some of the leading tests of gravity by mapping the shape of the lunar orbit to high precision. These include tests of the strong equivalence principle, the time-rate-ofchange of Newton’s gravitational constant, gravitomagnetism, the inverse-square law, and many others. Among the attributes that contribute to APOLLO’s superior observations, routine ranging to all five lunar reflectors on timescales of minutes dramatically improves our ability to gauge lunar orientation and body distortion. This information produces insights into the interior structure and dynamics of the Moon, allowing a more precise determination of the path for the Moon’s center of mass, lending to tests of fundamental gravity. Simultaneously, higher precision range measurements, together with data from a superconducting gravimeter at the

Characterization of the Q-switched MOBLAS Laser Transmitter and Its Ranging Performance Relative to a PTM Q-switched System

NASA Technical Reports Server (NTRS)

Degnan, J. J., III; Zagwodski, T. W.

1979-01-01

A prototype Q-switched Nd:YAG laser transmitter intended for use in the NASA mobile laser ranging system was subjected to various tests of temporal pulse shape and stability, output energy and stability, beam divergence, and range bias errors. Peak to peak variations in the mean range were as large as 30 cm and drift rates of system bias with time as large as 6 mm per minute of operation were observed. The incorporation of a fast electro-optic cavity dump into the oscillator gave significantly improved results. Reevaluation of the ranging performance after modification showed a reduction in the peak to peak variation in the mean range to the 2 or 3 cm level and a drift rate of system time biases of less than 1 mm per minute of operation. A qualitative physical explanation for the superior performance of cavity dumped lasers is given.

SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

NASA Astrophysics Data System (ADS)

Agarwal, N. R.; Tommasini, M.; Fazio, E.; Neri, F.; Ponterio, R. C.; Trusso, S.; Ossi, P. M.

2014-10-01

Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 × 10). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

Active Plasma Lensing for Relativistic Laser-Plasma-Accelerated Electron Beams

DOE PAGES

van Tilborg, J.; Steinke, S.; Geddes, C. G. R.; ...

2015-10-28

The compact, tunable, radially symmetric focusing of electrons is critical to laser-plasma accelerator (LPA) applications. Experiments are presented demonstrating the use of a discharge-capillary active plasma lens to focus 100-MeV-level LPA beams. The lens can provide tunable field gradients in excess of 3000 T/m, enabling cm-scale focal lengths for GeV-level beam energies and allowing LPA-based electron beams and light sources to maintain their compact footprint. For a range of lens strengths, excellent agreement with simulation was obtained.

The power of the bubble: comparing ultrasonic and laser activated irrigation

NASA Astrophysics Data System (ADS)

De Moor, Roeland J. G.; Meire, Maarten A.; Verdaasdonk, Rudolf M.

2014-01-01

The major problem of irrigation is the fluid motion within the confined geometry of the root canal : efficient dispersion of the liquid is difficult, conventional irrigation is limited due to the absence of turbulence over much of the canal volume, vapour lock may limit apical cleaning and disinfection, there is also a stagnation plane beyond the needle tip. The best way to improve irrigant penetration and biofilm removal is achieved by means of the agitation of the fluid. Today ultrasonic activation appears to be the best way to activate and potentiate irrigants among the present-day used means and marketed systems. Another way to activate irrigation solutions is the use of lasers: laser activated irrigation or photon-initiated acoustic streaming have been investigated. Based on present-day research it appears that the efficacy of laser activation (especially with Erbium lasers) can be more efficient thanks to the induction of specific cavitation phenomena and acoustic streaming. Other wavelengths are now explored to be used for laser activated irrigation.

Role of ROS-mediated TGF beta activation in laser photobiomodulation

NASA Astrophysics Data System (ADS)

Arany, Praveen R.; Chen, Aaron Chih-Hao; Hunt, Tristan; Mooney, David J.; Hamblin, Michael

2009-02-01

The ability of laser light to modulate specific biological processes has been well documented but the precise mechanism mediating these photobiological interactions remains an area of intense investigation. We recently published the results of our clinical trial with 30 patients in an oral tooth-extraction wound healing model using a 904nm GaAs laser (Oralaser 1010, Oralia, Konstnaz, Germany), assessing healing parameters using routine histopathology and immunostaining (Arany et al Wound Rep Regen 2007, 15, 866). We observed a better organized healing response in laser irradiated oral tissues that correlated with an increased expression of TGF-beta1 immediately post laser irradiation. Our data suggested the source of latent TGF-beta1 might be from the degranulating platelets in the serum, an abundant source of in vivo latent TGF-beta, in the freshly wounded tissues. Further, we also demonstrated the ability of the low power near-infrared laser irradiation to activate the latent TGF-beta complexes in vitro at varying fluences from 10sec (0.1 J/cm2) to 600secs (6 J/cm2). Using serum we observed two isoforms, namely TGF-beta1 and TGF-beta3, were capable of being activated by laser irradiation using an isoform-specific ELISA and a reporter based (p3TP) assay system. We are presently pursuing the precise photomolecular mechanisms focusing on potential chromophores, wavelength and fluence parameters affecting the Latent TGF-beta activation process in serum. As ROS mediated TGF-beta activation has been previously demonstrated and we are also exploring the role of Laser generated-ROS in this activation process. In summary, we present evidence of a potential molecular mechanism for laser photobiomodulation in its ability to activate latent TGF-beta complexes.

Active retroreflector to measure the rotational orientation in conjunction with a laser tracker

NASA Astrophysics Data System (ADS)

Hofherr, O.; Wachten, C.; Müller, C.; Reinecke, H.

2012-10-01

High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) can determine accurately x-y-z coordinates of passive retroreflectors. Next-generation systems answer the additional need to measure an object's rotational orientation (pitch, yaw, roll). These devices are based on photogrammetry or on enhanced retroreflectors. However, photogrammetry relies on camera systems and time-consuming image processing. Enhanced retroreflectors analyze the LT's beam but are restricted in roll angle measurements. Here we present an integrated laser based method to evaluate all six degrees of freedom. An active retroreflector directly analyzes its orientation to the LT's beam path by outcoupling laser light on detectors. A proof of concept prototype has been designed with a specified measuring range of 360° for roll angle measurements and +/-15° for pitch and yaw angle respectively. The prototype's optical design is inspired by a cat's eye retroreflector. First results are promising and further improvements are under development. We anticipate our method to facilitate simple and cost-effective six degrees of freedom measurements. Furthermore, for industrial applications wide customizations are possible, e.g. adaptation of measuring range, optimization of accuracy, and further system miniaturization.

Lasing of multiperiod quantum-cascade lasers in the spectral range of (5.6–5.8)-μm under current pumping

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

Egorov, A. Yu., E-mail: anton@beam.ioffe.ru; Babichev, A. V.; Karachinsky, L. Ya.

2015-11-15

The lasing of multiperiod quantum-cascade lasers in the spectral range of (5.6–5.8)-μm under current pumping are demonstrated. The quantum-cascade laser heterostructure is grown by molecular-beam epitaxy technique. Despite the relatively short laser cavity length and high level of external loss the laser shows the lasing in the temperature range of 80–220 K. The threshold current density below 4 kA/cm{sup 2} at 220 K with the characteristic temperature T{sub 0} = 123 K was demonstrated.

Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

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

Li, Shuo; Chen, Rongzhang; Nelsen, Bryan

2016-03-15

This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, andmore » limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.« less

Lens Coupled Quantum Cascade Laser

NASA Technical Reports Server (NTRS)

Lee, Alan Wei Min (Inventor); Hu, Qing (Inventor)

2013-01-01

Terahertz quantum cascade (QC) devices are disclosed that can operate, e.g., in a range of about 1 THz to about 10 THz. In some embodiments, QC lasers are disclosed in which an optical element (e.g., a lens) is coupled to an output facet of the laser's active region to enhance coupling of the lasing radiation from the active region to an external environment. In other embodiments, terahertz amplifier and tunable terahertz QC lasers are disclosed.

Experimental evaluation of the performance of pulsed two-color laser-ranging systems

NASA Technical Reports Server (NTRS)

Im, Kwaifong E.; Gardner, Chester S.; Abshire, James B.; Mcgarry, Jan F.

1987-01-01

Two-color laser-ranging systems can be used to estimate the atmospheric delay by measuring the difference in propagation times between two optical pulses transmitted at different wavelengths. This paper describes horizontal-path ranging experiments that were conducted using flat diffuse targets and cube-corner reflector arrays. Measurements of the timing accuracy of the cross-correlation estimator, atmospheric delay, received pulse shapes, and signal power spectra are presented. The results are in general agreement with theory and indicate that target speckle can be the dominant noise source when the target is small and is located far from the ranging system or when the target consists of a small number of cube-corner reflectors.

High-energy laser activities at MBDA Germany

NASA Astrophysics Data System (ADS)

Mohring, Bernd; Dietrich, Stephan; Tassini, Leonardo; Protz, Rudolf; Geidek, Franz; Zoz, Jürgen

2013-05-01

At MBDA Germany a concept for a high-energy laser weapon system is investigated, which is based on existing industrial laser sources. Due to the enormous progress in the field of high-power fiber lasers, commercial industrial fiber lasers are now available delivering a nearly-diffraction limited beam quality with power levels of up to 10 kW. By using a geometric beam coupling scheme, a number of individual high-power fiber laser beams are combined together using one common beam director telescope. A total laser beam power of more than 100 kW can be achieved, which is sufficient for an operational laser weapon system. The individual beams from the different lasers are steered by servo-loops using fast tip-tilt mirrors. This principle enables the concentration of the total laser beam power at one common focal point on a distant target, also allowing fine tracking of target movements and first-order compensation of turbulence effects on laser beam propagation. The proposed beam combination concept was demonstrated by using different experimental set-ups. A number of experiments were performed successfully to investigate laser beam target interaction and target fine tracking, also at large distances and at moving targets. Content and results of these investigations are reported, which demonstrate the complete engagement sequence for a C-RAM scenario. This includes subsequent steps of target acquisition by radar and IR optics, followed by large angle coarse tracking, active fine tracking and destruction of the target by the laser system. This successful implementation of geometric beam combining is an important step for the realization of a laser weapon system in the near future.

Design and performance of a SWaP short-range fully fibered monostatic laser rangefinder

NASA Astrophysics Data System (ADS)

Pallier, G.; Portalis, A.; Canat, G.; Chiquet, F.; Auffray, P.; Le, S.-D.; Le Flohic, M.

2017-10-01

The development of a multisensor optronic device requires Size, Weight and Power (SWaP), cost-effective and modular rangefinders while keeping a good range performance. We report on a fully fibered monostatic laser rangerfinder based on a one lens collimator used as the aperture of both the emission and reception channels. This has been possible thanks to the use of a diplexer. This design makes the system compacter and achieves a 200g system weight. In addition to its low volume, the fully fibered architecture allows designing a building block rangefinder with the collimator sub-system on one side and the laser and electronics cards module on the other side. Both are linked up by only an optical fiber. This kit format enables the rangefinder to better fit in any available space in higher level systems such as gimbals and multi-function imagers. Besides, no alignment is needed, and no parallax error is possible: the alignment between channels is guaranteed by design over the whole range. The emission/reception channels of the first prototype has a 28mm diameter 80mm focal length lens, and a 1.55μm 100μJ pulsed laser firing in a burst mode. The rangefinder is set in a class 1 configuration, and measures at 1Hz. The achieved Extinction Ratio is 30dB, which is equivalent to a range on NATO targets of 7km. The achieved ER being class 1M at 5Hz is even 32dB, which is equivalent to a range of 8.5km on NATO targets. More configurations are reported in this article with their associated performance.

Injection seeded, diode pumped regenerative ring Nd:YAG amplifier for spaceborne laser ranging technology development

NASA Technical Reports Server (NTRS)

Coyle, D. Barry; Kay, Richard B.; Degnan, John J.; Krebs, Danny J.; Seery, Bernard D.

1992-01-01

A small, all solid state, regenerative ring amplifier designed as a prototype for space application is discussed. Novel features include dual side pumping of the Nd:YAG crystal and a triangular ring cavity design which minimizes the number of optical components and losses. The amplifier is relatively small (3 ns round trip time) even though standard optical elements are employed. The ring regeneratively amplifies a 100 ps single pulse by approximately 10(exp 5) at a repetition rate of 10 to 100 Hz. The amplifier is designed to be injection seeded with a pulsed, 100 ps laser diode at 1.06 microns, but another Nd:YAG laser system supplying higher pulse energies was employed for laboratory experiment. This system is a prototype laser oscillator for the Geoscience Laser Ranging System (GLRS) platform. Results on measurements of beam quality, astigmatism, and gain are given.

Environmental stability of actively mode locked fibre lasers

NASA Astrophysics Data System (ADS)

Hill, Calum H.; Lee, Stephen T.; Reid, Derryck T.; Baili, Ghaya; Davies, John

2016-10-01

Lasers developed for defence related applications typically encounter issues with reliability and meeting desired specification when taken from the lab to the product line. In particular the harsh environmental conditions a laser has to endure can lead to difficulties. This paper examines a specific class of laser, namely actively mode-locked fibre lasers (AMLFLs), and discusses the impact of environmental perturbations. Theoretical and experimental results have assisted in developing techniques to improve the stability of a mode-locked pulse train for continuous operation. Many of the lessons learned in this research are applicable to a much broader category of lasers. The AMLFL consists of a fibre ring cavity containing a semiconductor optical amplifier (SOA), an isolator, an output coupler, a circulator, a bandpass filter and a modulator. The laser produces a train of 6-ps pulses at 800 nm with a repetition rate in the GHz regime and a low-noise profile. This performance is realisable in a laboratory environment. However, even small changes in temperature on the order of 0.1 °C can cause a collapse of mode-locked dynamics such that the required stability cannot be achieved without suitable feedback. Investigations into the root causes of this failure were performed by changing the temperature of components that constitute the laser resonator and observing their properties. Several different feedback mechanisms have been investigated to improve laser stability in an environment with dynamic temperature changes. Active cavity length control will be discussed along with DC bias control of the Mach-Zehnder modulator (MZM).

Optodynamic Phenomena During Laser-Activated Irrigation Within Root Canals

NASA Astrophysics Data System (ADS)

Lukač, Nejc; Gregorčič, Peter; Jezeršek, Matija

2016-07-01

Laser-activated irrigation is a powerful endodontic treatment for smear layer, bacteria, and debris removal from the root canal. In this study, we use shadow photography and the laser-beam-transmission probe to examine the dynamics of laser-induced vapor bubbles inside a root canal model and compare ultrasonic needle irrigation to the laser method. Results confirm important phenomenological differences in the two endodontic methods with the laser method resulting in much deeper irrigation. Observations of simulated debris particles show liquid vorticity effects which in our opinion represents the major cleaning mechanism.

Active solution of homography for pavement crack recovery with four laser lines.

PubMed

Xu, Guan; Chen, Fang; Wu, Guangwei; Li, Xiaotao

2018-05-08

An active solution method of the homography, which is derived from four laser lines, is proposed to recover the pavement cracks captured by the camera to the real-dimension cracks in the pavement plane. The measurement system, including a camera and four laser projectors, captures the projection laser points on the 2D reference in different positions. The projection laser points are reconstructed in the camera coordinate system. Then, the laser lines are initialized and optimized by the projection laser points. Moreover, the plane-indicated Plücker matrices of the optimized laser lines are employed to model the laser projection points of the laser lines on the pavement. The image-pavement homography is actively determined by the solutions of the perpendicular feet of the projection laser points. The pavement cracks are recovered by the active solution of homography in the experiments. The recovery accuracy of the active solution method is verified by the 2D dimension-known reference. The test case with the measurement distance of 700 mm and the relative angle of 8° achieves the smallest recovery error of 0.78 mm in the experimental investigations, which indicates the application potentials in the vision-based pavement inspection.

Stable room-temperature LiF:F2+* tunable color-center laser for the 830-1060-nm spectral range pumped by second-harmonic radiation from a neodymium laser

NASA Astrophysics Data System (ADS)

Ter-Mikirtychev, V. V.

1995-09-01

Simultaneous photostability and thermostability of a room-temperature LiF:F2+ * tunable color-center laser, with an operating range over 830-1060 nm, pumped by second-harmonic radiation of a YAG:Nd3+ laser with a 532-nm wavelength has been achieved. The main lasing characteristics of the obtained LiF:F2+* laser have been measured. Twenty-five percent real efficiency in a nonselective resonator cavity and 15% real efficiency in a selective resonator cavity have been obtained. The stable LiF:F2 +* laser operates at a 1-100-Hz pulse-repetition rate with a 15-ns pulse duration, a 1-1.5-cm-1 narrow-band oscillation bandwidth, and divergency of better than 6 \\times 10-4. Doubling the fundamental frequencies of F2+ * oscillation made it possible to obtain stable blue-green tunable radiation over the 415-530-nm range.

Eye safe high power laser diode in the 1410-1550nm range

NASA Astrophysics Data System (ADS)

Boucart, Julien; de Largy, Brian; Kearley, Mark; Lichtenstein, Norbert

2010-02-01

The demand for high power lasers emitting in the 14xx-15xxnm range is growing for applications in fields such as medical or homeland security. We demonstrate high power laser diodes with emission at 1430, 1470 and 1560 nm. Single multimode emitters at 1470nm emit about 3.5W in CW operation. Power conversion efficiency can reach values as high as 38.5%. With this base material, single and multi-emitter fiber coupled modules are built. Additionally, bars on passive and microchannel coolers are fabricated that deliver 25W and 38W respectively in CW mode, while obtaining more than 80 W in pulsed mode. All reliability tests show an outstanding stability of the material with no signs of wearout after 3750 hrs under strong acceleration conditions.

Range indices of geomagnetic activity

USGS Publications Warehouse

Stuart, W.F.; Green, A.W.

1988-01-01

The simplest index of geomagnetic activity is the range in nT from maximum to minimum value of the field in a given time interval. The hourly range R was recommended by IAGA for use at observatories at latitudes greater than 65??, but was superceded by AE. The most used geomagnetic index K is based on the range of activity in a 3 h interval corrected for the regular daily variation. In order to take advantage of real time data processing, now available at many observatories, it is proposed to introduce a 1 h range index and also a 3 h range index. Both will be computed hourly, i.e. each will have a series of 24 per day, the 3 h values overlapping. The new data will be available as the range (R) of activity in nT and also as a logarithmic index (I) of the range. The exponent relating index to range in nT is based closely on the scale used for computing K values. The new ranges and range indices are available, from June 1987, to users in real time and can be accessed by telephone connection or computer network. Their first year of production is regarded as a trial period during which their value to the scientific and commercial communities will be assessed, together with their potential as indicators of regional and global disturbances' and in which trials will be conducted into ways of eliminating excessive bias at quiet times due to the rate of change of the daily variation field. ?? 1988.

III-nitride nanowire LEDs and diode lasers: monolithic light sources on (001) Si emitting in the 600-1300nm range

NASA Astrophysics Data System (ADS)

Bhattacharya, P.; Hazari, A.; Jahangir, S.

2018-02-01

GaN-based nanowire heterostructure arrays epitaxially grown on (001)Si substrates have unique properties and present the potential to realize useful devices. The active light-emitting region in the nanowire heterostructures are usually InGaN disks, whose composition can be varied to tune the emission wavelength. We have demonstrated light emitting diodes and edgeemitting diode lasers with power outputs 10mW with emission in the 600-1300nm wavelength range. These light sources are therefore useful for a variety of applications, including silicon photonics. Molecular beam epitaxial growth of the nanowire heterostructure arrays on (001)Si substrates and the characteristics of 1.3μm nanowire array edge emitting lasers, guided wave photodiodes and a monolithic photonic integrated circuit designed for 1.3μm operation are described.

Fusing Range Measurements from Ultrasonic Beacons and a Laser Range Finder for Localization of a Mobile Robot

PubMed Central

Ko, Nak Yong; Kuc, Tae-Yong

2015-01-01

This paper proposes a method for mobile robot localization in a partially unknown indoor environment. The method fuses two types of range measurements: the range from the robot to the beacons measured by ultrasonic sensors and the range from the robot to the walls surrounding the robot measured by a laser range finder (LRF). For the fusion, the unscented Kalman filter (UKF) is utilized. Because finding the Jacobian matrix is not feasible for range measurement using an LRF, UKF has an advantage in this situation over the extended KF. The locations of the beacons and range data from the beacons are available, whereas the correspondence of the range data to the beacon is not given. Therefore, the proposed method also deals with the problem of data association to determine which beacon corresponds to the given range data. The proposed approach is evaluated using different sets of design parameter values and is compared with the method that uses only an LRF or ultrasonic beacons. Comparative analysis shows that even though ultrasonic beacons are sparsely populated, have a large error and have a slow update rate, they improve the localization performance when fused with the LRF measurement. In addition, proper adjustment of the UKF design parameters is crucial for full utilization of the UKF approach for sensor fusion. This study contributes to the derivation of a UKF-based design methodology to fuse two exteroceptive measurements that are complementary to each other in localization. PMID:25970259

Method of calculating retroreflector-array transfer functions. [laser range finders

NASA Technical Reports Server (NTRS)

Arnold, D. A.

1978-01-01

Techniques and equations used in calculating the transfer functions to relate the observed return laser pulses to the center of mass of the Lageos satellite retroflector array, and for most of the retroreflector-equipped satellites now in orbit are described. The methods derived include the effects of coherent interference, diffraction, polarization, and dihedral-angle offsets. Particular emphasis is given to deriving expressions for the diffraction pattern and active reflecting area of various cube-corner designs.

Actively mode-locked fiber laser using a deformable micromirror.

PubMed

Fabert, Marc; Kermène, Vincent; Desfarges-Berthelemot, Agnès; Blondy, Pierre; Crunteanu, Aurelian

2011-06-15

We present what we believe to be the first fiber laser system that is actively mode-locked by a deformable micromirror. The micromirror device is placed within the laser cavity and performs a dual function of modulator and end-cavity mirror. The mode-locked laser provides ~1-ns-long pulses with 20 nJ/pulse energy at 5 MHz repetition rates.

New test of the equivalence principle from lunar laser ranging

NASA Technical Reports Server (NTRS)

Williams, J. G.; Dicke, R. H.; Bender, P. L.; Alley, C. O.; Currie, D. G.; Carter, W. E.; Eckhardt, D. H.

1976-01-01

An analysis of six years of lunar-laser-ranging data gives a zero amplitude for the Nordtvedt term in the earth-moon distance yielding the Nordtvedt parameter eta = 0.00 plus or minus 0.03. Thus, earth's gravitational self-energy contributes equally, plus or minus 3%, to its inertial mass and passive gravitational mass. At the 70% confidence level this result is only consistent with the Brans-Dicke theory for omega greater than 29. We obtain the absolute value of beta - 1 less than about 0.02 to 0.05 for five-parameter parametrized post-Newtonian theories of gravitation with energy-momentum conservation.

Advanced computer graphic techniques for laser range finder (LRF) simulation

NASA Astrophysics Data System (ADS)

Bedkowski, Janusz; Jankowski, Stanislaw

2008-11-01

This paper show an advanced computer graphic techniques for laser range finder (LRF) simulation. The LRF is the common sensor for unmanned ground vehicle, autonomous mobile robot and security applications. The cost of the measurement system is extremely high, therefore the simulation tool is designed. The simulation gives an opportunity to execute algorithm such as the obstacle avoidance[1], slam for robot localization[2], detection of vegetation and water obstacles in surroundings of the robot chassis[3], LRF measurement in crowd of people[1]. The Axis Aligned Bounding Box (AABB) and alternative technique based on CUDA (NVIDIA Compute Unified Device Architecture) is presented.

Clinical and Spectrophotometric Evaluation of LED and Laser Activated Teeth Bleaching.

PubMed

Lo Giudice, R; Pantaleo, G; Lizio, A; Romeo, U; Castiello, G; Spagnuolo, G; Giudice, G Lo

2016-01-01

Auxiliary power sources (LED and laser) are used in in-office teeth bleaching techniques to accelerate the redox reaction of the whitening gel to increase ease of use, to improve comfort and safety, and to decrease the procedure time. The aim this study is to evaluate the efficiency of the teeth whitening procedures performed with hydrogen peroxide and carbamide peroxide, LED or Laser activated. 18 patients, affected by exogenous dyschromia, were treated with a bleaching agent composed by 35% hydrogen peroxide and 10% carbamide peroxide. They were divided into two groups: in the first group the bleaching agent was activated by a LED lamp; in the second group it was activated by a Laser diode lamp. Both groups were subjected to 3 bleaching cycle of 15' each. The chromatic evaluations were performed before and after one week from the treatment, using a chromatic scale and a spectrophotometer. The mean value of pre, post bleaching and follow-up were analyzed using a T-test, with results statistically significant for P<0,05. Results showed that the variations in brightness, chroma and hue are significantly influenced by the interaction between the whitening agent and the original colour of the teeth. Laser-activation has marginally improved the bleaching effectiveness. All patients treated with laser activation complained an increase in dental sensitivity. The use of laser-activating systems did not improve the efficacy of bleaching.

Optimal speckle noise reduction filter for range gated laser illuminated imaging

NASA Astrophysics Data System (ADS)

Dayton, David; Gonglewski, John; Lasche, James; Hassall, Arthur

2016-09-01

Laser illuminated imaging has a number of applications in the areas of night time air-to-ground target surveillance, ID, and pointing and tracking. Using a laser illuminator, the illumination intensity and thus the signal to noise ratio can be controlled. With the advent of high performance range gated cameras in the short-wave infra-red band, higher spatial resolution can be achieved over passive thermal night imaging cameras in the mid-wave infra-red due to the shorter wave-length. If a coherent illuminator is used the resulting imagery often suffers from speckle noise due to the scattering off of a rough target surface, which gives it a grainy "salt and pepper" appearance. The probability density function for the intensity of focal plane speckle is well understood to follow a negative exponential distribution. This can be exploited to develop a Bayesian speckle noise filter. The filter has the advantage over simple frame averaging approaches in that it preserves target features and motion while reducing speckle noise without smearing or blurring the images. The resulting filtered images have the appearance of passive imagery and so are more amenable to sensor fusion with simultaneous mid-wave infra-red thermal images for enhanced target ID. The noise filter improvement is demonstrated using examples from real world laser imaging tests on tactical targets.

The Precision Expandable Radar Calibration Sphere (PERCS) With Applications for Laser Imaging and Ranging

NASA Astrophysics Data System (ADS)

Bernhardt, P.; Nicholas, A.; Thomas, L.; Davis, M.; Hoberman, C.; Davis, M.

The Naval Research Laboratory will provide an orbiting calibration sphere to be used with ground-based laser imaging telescopes and HF radio systems. The Precision Expandable Radar Calibration Sphere (PERCS) is a practical, reliable, high-performance HF calibration sphere and laser imaging target to orbit at about 600 km altitude. The sphere will be made of a spherical wire frame with aspect independent radar cross section in the 3 to 35 MHz frequency range. The necessary launch vehicle to place the PERCS in orbit will be provided by the Department of Defense Space Test Program. The expandable calibration target has a stowed diameter of 1 meter and a fully deployed diameter of 10.2 meters. A separate deployment mechanism is provided for the sphere. After deployment, the Precision Expandable Radar Calibration Sphere (PERCS) with 180 vertices will be in a high inclination orbit to scatter radio pulses from a number of ground systems, including (1) over-the-horizon (OTH) radars operated by the United States and Australia; (2) high power HF facilities such as HAARP in Alaska, EISCAT in Norway, and Arecibo in Puerto Rico; (3) the chain of high latitude SuperDARN radars used for auroral region mapping; and (4) HF direction finding for Navy ships. With the PERCS satellite, the accuracy of HF radars can be periodically checked for range, elevation, and azimuth errors. In addition, each of the 360 vertices on the PERCS sphere will support an optical retro-reflector for operations with ground laser facilities used to track satellites. The ground laser systems will be used to measure the precise location of the sphere within one cm accuracy and will provide the spatial orientation of the sphere as well as the rotation rate. The Department of Defense facilities that can use the corner-cube reflectors on the PERCS include (1) the Air Force Maui Optical Site (AMOS), (2) the Starfire Optical Range (SOR), and (3) the NRL Optical Test Facility (OTF).

Micro-joule pico-second range Yb3+-doped fibre laser for medical applications in acupuncture

NASA Astrophysics Data System (ADS)

Alvarez-Chavez, J. A.; Rivera-Manrique, S. I.; Jacques, S. L.

2011-08-01

The work described here is based on the optical design, simulation and on-going implementation of a pulsed (Q-switch) Yb3+-doped, 1-um diffraction-limited fibre laser with pico-second, 10 micro-Joule-range energy pulses for producing the right energy pulses which could be of benefit for patients who suffer chronic headache, photophobia, and even nausea which could is sometimes triggered by a series of factors. The specific therapeutic effect known as acupunctural analgesia is the main objective of this medium-term project. It is a simple design on which commercially available software was employed for laser cavity design. Monte Carlo technique for skin light-transport, thermal diffusion and the possible thermal de-naturalization optical study and prediction will also be included in the presentation. Full optical characterization will be included and a complete set of recent results on the laser-skin interaction and the so called moxi-bustion from the laser design will be extensively described.

Station coordinates, baselines, and earth rotation from Lageos laser ranging - 1976-1984

NASA Technical Reports Server (NTRS)

Tapley, B. D.; Schultz, B. E.; Eanes, R. J.

1985-01-01

The orbit of the Lageos satellite is well suited as a reference frame for studying the rotation of the earth and the relative motion of points on the earth's crust. The satellite laser measurements can determine the location of a set of tracking stations in an appropriate terrestrial coordinate system. The motion of the earth's rotation axis relative to this system can be studied on the basis of the established tracking station locations. The present investigation is concerned with an analysis of 7.7 years of Lageos laser ranging data. In the first solution considered, the entire data span was used to adjust a single set of station positions simultaneously with orbit and earth rotation parameters. Attention is given to the accuracy of earth rotation parameters which are determined as an inherent part of the solution process.

Clinical and Spectrophotometric Evaluation of LED and Laser Activated Teeth Bleaching

PubMed Central

Lo Giudice, R.; Pantaleo, G.; Lizio, A.; Romeo, U.; Castiello, G.; Spagnuolo, G.; Giudice, G. Lo

2016-01-01

Background: Auxiliary power sources (LED and laser) are used in in-office teeth bleaching techniques to accelerate the redox reaction of the whitening gel to increase ease of use, to improve comfort and safety, and to decrease the procedure time. Objective: The aim this study is to evaluate the efficiency of the teeth whitening procedures performed with hydrogen peroxide and carbamide peroxide, LED or Laser activated. Method: 18 patients, affected by exogenous dyschromia, were treated with a bleaching agent composed by 35% hydrogen peroxide and 10% carbamide peroxide. They were divided into two groups: in the first group the bleaching agent was activated by a LED lamp; in the second group it was activated by a Laser diode lamp. Both groups were subjected to 3 bleaching cycle of 15’ each. The chromatic evaluations were performed before and after one week from the treatment, using a chromatic scale and a spectrophotometer. The mean value of pre, post bleaching and follow-up were analyzed using a T-test, with results statistically significant for P<0,05. Results: Results showed that the variations in brightness, chroma and hue are significantly influenced by the interaction between the whitening agent and the original colour of the teeth. Laser-activation has marginally improved the bleaching effectiveness. All patients treated with laser activation complained an increase in dental sensitivity. Conclusion: The use of laser-activating systems did not improve the efficacy of bleaching. PMID:27386010

New semiconductor laser technology for gas sensing applications in the 1650nm range

NASA Astrophysics Data System (ADS)

Morrison, Gordon B.; Sherman, Jes; Estrella, Steven; Moreira, Renan L.; Leisher, Paul O.; Mashanovitch, Milan L.; Stephen, Mark; Numata, Kenji; Wu, Stewart; Riris, Haris

2017-08-01

Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with approximately 25 times the radiative forcing of carbon dioxide (CO2) per molecule. CH4 also contributes to pollution in the lower atmosphere through chemical reactions leading to ozone production. Recent developments of LIDAR measurement technology for CH4 have been previously reported by Goddard Space Flight Center (GSFC). In this paper, we report on a novel, high-performance tunable semiconductor laser technology developed by Freedom Photonics for the 1650nm wavelength range operation, and for LIDAR detection of CH4. Devices described are monolithic, with simple control, and compatible with low-cost fabrication techniques. We present 3 different types of tunable lasers implemented for this application.

Laser action in chromium-activated forsterite for near infrared excitation

NASA Technical Reports Server (NTRS)

Petricevic, V.; Gayen, S. K.; Alfano, R. R.

1988-01-01

This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

Interfacing with Neural Activity via Femtosecond Laser Stimulation of Drug-Encapsulating Liposomal Nanostructures

PubMed Central

Mackay, Sean M.; Wui Tan, Eng

2016-01-01

External control over rapid and precise release of chemicals in the brain potentially provides a powerful interface with neural activity. Optical manipulation techniques, such as optogenetics and caged compounds, enable remote control of neural activity and behavior with fine spatiotemporal resolution. However, these methods are limited to chemicals that are naturally present in the brain or chemically suitable for caging. Here, we demonstrate the ability to interface with neural functioning via a wide range of neurochemicals released by stimulating loaded liposomal nanostructures with femtosecond lasers. Using a commercial two-photon microscope, we released inhibitory or excitatory neurochemicals to evoke subthreshold and suprathreshold changes in membrane potential in a live mouse brain slice. The responses were repeatable and could be controlled by adjusting laser stimulation characteristics. We also demonstrate the release of a wider range of chemicals—which previously were impossible to release by optogenetics or uncaging—including synthetic analogs of naturally occurring neurochemicals. In particular, we demonstrate the release of a synthetic receptor-specific agonist that exerts physiological effects on long-term synaptic plasticity. Further, we show that the loaded liposomal nanostructures remain functional for weeks in a live mouse. In conclusion, we demonstrate new techniques capable of interfacing with live neurons, and extendable to in vivo applications. PMID:27896311

High power laser diodes at 14xx nm wavelength range for industrial and medical applications

NASA Astrophysics Data System (ADS)

Telkkälä, Jarkko; Boucart, Julien; Krejci, Martin; Crum, Trevor; Lichtenstein, Norbert

2014-03-01

We report on the development of the latest generation of high power laser diodes at 14xx nm wavelength range suitable for industrial applications such as plastics welding and medical applications including acne treatment, skin rejuvenation and surgery. The paper presents the newest chip generation developed at II-VI Laser Enterprise, increasing the output power and the power conversion efficiency while retaining the reliability of the initial design. At an emission wavelength around 1440 nm we applied the improved design to a variety of assemblies exhibiting maximum power values as high as 7 W for broad-area single emitters. For 1 cm wide bars on conductive coolers and for bars on active micro channel coolers we have obtained 50 W and 72 W in continuous wave (cw) operation respectively. The maximum power measured for a 1 cm bar operated with 50 μs pulse width and 0.01% duty cycle was 184 W, demonstrating the potential of the chip design for optimized cooling. Power conversion efficiency values as high as 50% for a single emitter device and over 40% for mounted bars have been demonstrated, reducing the required power budget to operate the devices. Both active and conductive bar assembly configurations show polarization purity greater than 98%. Life testing has been conducted at 95 A, 50% duty cycle and 0.5 Hz hard pulsed operation for bars which were soldered to conductive copper CS mounts using our hard solder technology. The results after 5500 h, or 10 million "on-off" cycles show stable operation.

Building block diode laser concept for high brightness laser output in the kW range and its applications

NASA Astrophysics Data System (ADS)

Ferrario, Fabio; Fritsche, Haro; Grohe, Andreas; Hagen, Thomas; Kern, Holger; Koch, Ralf; Kruschke, Bastian; Reich, Axel; Sanftleben, Dennis; Steger, Ronny; Wallendorf, Till; Gries, Wolfgang

2016-03-01

applications, materials processing such as cutting and welding of copper aluminum or steel and also medical application. Typical operating at wavelengths in the 9XX nm range, these systems are designed for and mainly used in cutting and welding applications, but adapted wavelength ranges such as 793 nm and 1530 nm are also offered. Around 15XX nm the diodes are already successfully used for resonant pumping of Erbium lasers [1]. Furthermore, the fully integrated electronic concept allows addressing further applications, as due to short lead lengths it is capable of generating very short μs pulses up to cw mode operation by simple software commands.

Tunable semiconductor laser at 1025-1095 nm range for OCT applications with an extended imaging depth

NASA Astrophysics Data System (ADS)

Shramenko, Mikhail V.; Chamorovskiy, Alexander; Lyu, Hong-Chou; Lobintsov, Andrei A.; Karnowski, Karol; Yakubovich, Sergei D.; Wojtkowski, Maciej

2015-03-01

Tunable semiconductor laser for 1025-1095 nm spectral range is developed based on the InGaAs semiconductor optical amplifier and a narrow band-pass acousto-optic tunable filter in a fiber ring cavity. Mode-hop-free sweeping with tuning speeds of up to 104 nm/s was demonstrated. Instantaneous linewidth is in the range of 0.06-0.15 nm, side-mode suppression is up to 50 dB and polarization extinction ratio exceeds 18 dB. Optical power in output single mode fiber reaches 20 mW. The laser was used in OCT system for imaging a contact lens immersed in a 0.5% intra-lipid solution. The cross-section image provided the imaging depth of more than 5mm.

Geophysical parameters from the analysis of laser ranging to starlette

NASA Technical Reports Server (NTRS)

Schutz, B. E.; Shum, C. K.

1987-01-01

Starlette Satellite Laser Ranging (SLR) data were used, along with several other satellite data sets, for the solution of a preliminary gravity field model for TOPEX, PTGF1. A further improvement in the earth gravity model was accomplished using data collected by 12 satellites to solve another preliminary gravity model for TOPEX, designated PTGF2. The solution for the Earth Rotation Parameter (ERP) was derived from the analysis of SLR data to Starlette during the MERIT Campaign. Starlette orbits in 1976 and 1983 were analyzed for the mapping of the tidal response of the earth. Publications and conference presentations pertinent to research are listed.

Active modulation of laser coded systems using near infrared video projection system based on digital micromirror device (DMD)

NASA Astrophysics Data System (ADS)

Khalifa, Aly A.; Aly, Hussein A.; El-Sherif, Ashraf F.

2016-02-01

Near infrared (NIR) dynamic scene projection systems are used to perform hardware in-the-loop (HWIL) testing of a unit under test operating in the NIR band. The common and complex requirement of a class of these units is a dynamic scene that is spatio-temporal variant. In this paper we apply and investigate active external modulation of NIR laser in different ranges of temporal frequencies. We use digital micromirror devices (DMDs) integrated as the core of a NIR projection system to generate these dynamic scenes. We deploy the spatial pattern to the DMD controller to simultaneously yield the required amplitude by pulse width modulation (PWM) of the mirror elements as well as the spatio-temporal pattern. Desired modulation and coding of high stable, high power visible (Red laser at 640 nm) and NIR (Diode laser at 976 nm) using the combination of different optical masks based on DMD were achieved. These spatial versatile active coding strategies for both low and high frequencies in the range of kHz for irradiance of different targets were generated by our system and recorded using VIS-NIR fast cameras. The temporally-modulated laser pulse traces were measured using array of fast response photodetectors. Finally using a high resolution spectrometer, we evaluated the NIR dynamic scene projection system response in terms of preserving the wavelength and band spread of the NIR source after projection.

The Long Range Reconnaissance and Observation System (LORROS) with the Kollsman, Inc. Model LH-40, Infrared (Erbium) Laser Rangefinder hazard analysis and safety assessment.

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

Augustoni, Arnold L.

A laser hazard analysis and safety assessment was performed for the LH-40 IR Laser Rangefinder based on the 2000 version of the American National Standard Institute's Standard Z136.1, for the Safe Use of Lasers and Z136.6, for the Safe Use of Lasers Outdoors. The LH-40 IR Laser is central to the Long Range Reconnaissance and Observation System (LORROS). The LORROS is being evaluated by the Department 4149 Group to determine its capability as a long-range assessment tool. The manufacture lists the laser rangefinder as 'eye safe' (Class 1 laser classified under the CDRH Compliance Guide for Laser Products and 21more » CFR 1040 Laser Product Performance Standard). It was necessary that SNL validate this prior to its use involving the general public. A formal laser hazard analysis is presented for the typical mode of operation.« less

Relativistic tests with lunar laser ranging

NASA Astrophysics Data System (ADS)

Hofmann, F.; Müller, J.

2018-02-01

This paper presents the recent version of the lunar laser ranging (LLR) analysis model at the Institut für Erdmessung (IfE), Leibniz Universität Hannover and highlights a few tests of Einstein’s theory of gravitation using LLR data. Investigations related to a possible temporal variation of the gravitational constant, the equivalence principle, the PPN parameters β and γ as well as the geodetic precession were carried out. The LLR analysis model was updated by gravitational effects of the Sun and planets with the Moon as extended body. The higher-order gravitational interaction between Earth and Moon as well as effects of the solid Earth tides on the lunar motion were refined. The basis for the modeled lunar rotation is now a 2-layer core/mantle model according to the DE430 ephemeris. The validity of Einstein’s theory was studied using this updated analysis model and an LLR data set from 1970 to January 2015. Within the estimated accuracies, no deviations from Einstein’s theory are detected. A relative temporal variation of the gravitational constant is estimated as \\dot{G}/G_0=(7.1+/-7.6)×10-14~yr-1 , the test of the equivalence principle gives Δ(m_g/m_i)EM=(-3+/-5)×10-14 and the Nordtvedt parameter \

Laser stimulation can activate autophagy in HeLa cells

NASA Astrophysics Data System (ADS)

Wang, Yisen; Lan, Bei; He, Hao; Hu, Minglie; Cao, Youjia; Wang, Chingyue

2014-10-01

For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flash of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca2+ dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.

Laser stimulation can activate autophagy in HeLa cells

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

Wang, Yisen; Hu, Minglie; Wang, Chingyue

For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flashmore » of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca{sup 2+} dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.« less

Long-range pulselength scaling of 351nm laser damage thresholds

NASA Astrophysics Data System (ADS)

Foltyn, S. R.; Jolin, L. J.

1986-12-01

In a series of experiments incorporating 351nm pulselength of 9, 26, 54, and 625ns, it was found that laser damage thresholds increased as (pulselength)/sup x/, and that the exponent averaged 0.36 and ranged, for different samples, from 0.23 to 0.48. Similar results were obtained when only catastrophic damage was considered. Samples included Al2O3/SiO2 in both AR and HR multilayers, HR's of Sc2O3/SiO2 and HfO2/SiO2, and Al-on-pyrex mirror; 9ns thresholds were between 0.2 to 5.6 J/sq cm. When these data were compared with a wide range of other results - for wavelengths from 0.25 to 10.6 microns and pulselengths down to 4ps - a remarkably consistent picture emerged. Damage thresholds, on average, increase approximately as the cube-root of pulselength from picoseconds to nearly a microsecond, and do so regardless of wavelength or material under test.

Soliton microcomb range measurement

NASA Astrophysics Data System (ADS)

Suh, Myoung-Gyun; Vahala, Kerry J.

2018-02-01

Laser-based range measurement systems are important in many application areas, including autonomous vehicles, robotics, manufacturing, formation flying of satellites, and basic science. Coherent laser ranging systems using dual-frequency combs provide an unprecedented combination of long range, high precision, and fast update rate. We report dual-comb distance measurement using chip-based soliton microcombs. A single pump laser was used to generate dual-frequency combs within a single microresonator as counterpropagating solitons. We demonstrated time-of-flight measurement with 200-nanometer precision at an averaging time of 500 milliseconds within a range ambiguity of 16 millimeters. Measurements at distances up to 25 meters with much lower precision were also performed. Our chip-based source is an important step toward miniature dual-comb laser ranging systems that are suitable for photonic integration.

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.

PubMed

Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

2012-06-10

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (λ(1)=905 nm) and visible (λ(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm.

Compact Hybrid Laser Rod and Laser System

NASA Technical Reports Server (NTRS)

Pierrottet, Diego F. (Inventor); Busch, George E. (Inventor); Amzajerdian, Farzin (Inventor)

2017-01-01

A hybrid fiber rod includes a fiber core and inner and outer cladding layers. The core is doped with an active element. The inner cladding layer surrounds the core, and has a refractive index substantially equal to that of the core. The outer cladding layer surrounds the inner cladding layer, and has a refractive index less than that of the core and inner cladding layer. The core length is about 30 to 2000 times the core diameter. A hybrid fiber rod laser system includes an oscillator laser, modulating device, the rod, and pump laser diode(s) energizing the rod from opposite ends. The rod acts as a waveguide for pump radiation but allows for free-space propagation of laser radiation. The rod may be used in a laser resonator. The core length is less than about twice the Rayleigh range. Degradation from single-mode to multi-mode beam propagation is thus avoided.

Laser ranging interferometer on Grace follow-on

NASA Astrophysics Data System (ADS)

Dahl, C.; Baatzsch, A.; Dehne, M.; Gilles, F.; Hager, P.; Herding, M.; Nicklaus, K.; Voss, K.; Abich, K.; Braxmaier, C.; Gohlke, M.; Guenther, B.; Sanjuan, J.; Zender, B.; Barranco, G. F.; Görth, A.; Mahrdt, C.; Müller, V.; Schütze, D.; Stede, G.; Heinzel, G.

2017-09-01

The Gravity Recovery and Climate Experiment (GRACE) is a successful Earth observation mission launched in 2002 consisting of two identical satellites in a polar low-Earth orbit [1]. The distance variations between these two satellites are measured with a Micro Wave Instrument (MWI) located in the central axis. In data postprocessing the spatial and temporal variations of the Earth's gravitational field are recovered, which are among other things introduced by changing groundwater levels or ice-masses [2, 3, 4, 5]. The Laser Ranging Interferometer (LRI) on-board the GRACE Follow-On (GFO) mission, which will be launched in 2017 by the joint collaboration between USA (NASA) and Germany (GFZ), is a technology demonstrator to provide about two orders of magnitude higher measurement accuracy than the initial GRACE MWI, about 80 nm/√Hz in the measurement band between 2 mHz and 0.1 Hz. The integration of the LRI units on both GFO S/C has been finished in summer 2016. The design as well as the functional, performance, and thermal-vacuum tests results of the German LRI flight units will be presented.

Active Dendrites Enhance Neuronal Dynamic Range

PubMed Central

Gollo, Leonardo L.; Kinouchi, Osame; Copelli, Mauro

2009-01-01

Since the first experimental evidences of active conductances in dendrites, most neurons have been shown to exhibit dendritic excitability through the expression of a variety of voltage-gated ion channels. However, despite experimental and theoretical efforts undertaken in the past decades, the role of this excitability for some kind of dendritic computation has remained elusive. Here we show that, owing to very general properties of excitable media, the average output of a model of an active dendritic tree is a highly non-linear function of its afferent rate, attaining extremely large dynamic ranges (above 50 dB). Moreover, the model yields double-sigmoid response functions as experimentally observed in retinal ganglion cells. We claim that enhancement of dynamic range is the primary functional role of active dendritic conductances. We predict that neurons with larger dendritic trees should have larger dynamic range and that blocking of active conductances should lead to a decrease in dynamic range. PMID:19521531

Documenting a Complex Modern Heritage Building Using Multi Image Close Range Photogrammetry and 3d Laser Scanned Point Clouds

NASA Astrophysics Data System (ADS)

Vianna Baptista, M. L.

2013-07-01

Integrating different technologies and expertises help fill gaps when optimizing documentation of complex buildings. Described below is the process used in the first part of a restoration project, the architectural survey of Theatre Guaira Cultural Centre in Curitiba, Brazil. To diminish time on fieldwork, the two-person-field-survey team had to juggle, during three days, the continuous artistic activities and performers' intense schedule. Both technologies (high definition laser scanning and close-range photogrammetry) were used to record all details in the least amount of time without disturbing the artists' rehearsals and performances. Laser Scanning was ideal to record the monumental stage structure with all of its existing platforms, light fixtures, scenery walls and curtains. Although scanned with high-definition, parts of the exterior façades were also recorded using Close Range Photogrammetry. Tiny cracks on the marble plaques and mosaic tiles, not visible in the point clouds, were then able to be precisely documented in order to create the exterior façades textures and damages mapping drawings. The combination of technologies and the expertise of service providers, knowing how and what to document, and what to deliver to the client, enabled maximum benefits to the following restoration project.

Tracking strategies for laser ranging to multiple satellite targets

NASA Technical Reports Server (NTRS)

Robbins, J. W.; Smith, D. E.; Kolenkiewicz, R.

1994-01-01

By the middle of the decade, several new Laser Geodynamic Satellites will be launched to join the current constellation comprised of the laser geodynamic satellite (LAGEOS) (US), Starlette (France), Ajisai (Japan), and Etalon I and II (USSR). The satellites to be launched, LAGEOS II and III (US & Italy), and Stella (France), will be injected into orbits that differ from the existing constellation so that geodetic and gravimetric quantities are sampled to enhance their resolution and accuracy. An examination of various possible tracking strategies adopted by the network of laser tracking stations has revealed that the recovery of precise geodetic parameters can be obtained over shorter intervals than is currently obtainable with the present constellation of satellites. This is particularly important in the planning of mobile laser tracking operations, given a network of permanently operating tracking sites. Through simulations, it is shown that laser tracking of certain satellite passes, pre-selected to provide optimal sky-coverage, provides the means to acquire a sufficient amount of data to allow the recovery of 1 cm station positions.

Video sensor with range measurement capability

NASA Technical Reports Server (NTRS)

Howard, Richard T. (Inventor); Briscoe, Jeri M. (Inventor); Corder, Eric L. (Inventor); Broderick, David J. (Inventor)

2008-01-01

A video sensor device is provided which incorporates a rangefinder function. The device includes a single video camera and a fixed laser spaced a predetermined distance from the camera for, when activated, producing a laser beam. A diffractive optic element divides the beam so that multiple light spots are produced on a target object. A processor calculates the range to the object based on the known spacing and angles determined from the light spots on the video images produced by the camera.

Correction of laser range tracking data for atmospheric refraction at elevations above 10 degrees

NASA Technical Reports Server (NTRS)

Marini, J. W.; Murray, C. W., Jr.

1973-01-01

A formula for correcting laser measurements of satellite range for the effect of atmospheric refraction is given. The corrections apply above 10 deg elevation to satellites whose heights exceed 70 km. The meteorological measurements required are the temperature, pressure, and relative humidity of the air at the laser site at the time of satellite pass. The accuracy of the formula was tested by comparison with corrections obtained by ray-tracing radiosonde profiles. The standard deviation of the difference between the refractive retardation given by the formula and that calculated by ray-tracing was less than about 0.04% of the retardation or about 0.5 cm at 10 deg elevation, decreasing to 0.04 cm near zenith.

Micro-Laser Range Finder Development: Using the Monolithic Approach

DTIC Science & Technology

1999-02-01

components can be joined together, optically aligned to form the laser cavity and then sliced to produce MLC modules . This batch process can greatly reduce...the overall fabrication costs of the µLRF system. The MLC module is ultra-compact. Its overall size is approximately 56 mm (L) x 3 mm (W) x 3 mm (H) as...MLC module is placed on a laser pallet for stiffness, mechanical stability. The laser pallet size is selected as part of the integration design

Feasibility Study of Interstellar Missions Using Laser Sail Probes Ranging in Size from the Nano to the Macro

NASA Technical Reports Server (NTRS)

Malroy, Eric T.

2010-01-01

This paper presents the analysis examining the feasibility of interstellar travel using laser sail probes ranging in size from the nano to the macro. The relativistic differential equations of motion for a laser sail are set up and solved using the Pasic Method. The limitations of the analysis are presented and discussed. The requirements for the laser system are examined, including the thermal analysis of the laser sails. Black holes, plasma fields, atmospheric collisions and sun light are several methods discussed to enable the deceleration of the interstellar probe. A number of novel mission scenarios are presented including the embryonic transport of plant life as a precursor to the arrival of space colonies

Experimental study on rat NK cell activity improvement by laser acupoint irradiation

NASA Astrophysics Data System (ADS)

Yang, Dongxiao; Chen, Xiufeng; Ruan, Buqing; Yang, Feng

1998-08-01

To study the improvement of the natural killer (NK) cell activity by semiconductor laser acupoint irradiation, rats were used in this experiment and were injected immunosuppressant in their abdomen. The immunoassay was made after the surface irradiation and inner irradiation at Baihui point by semiconductor laser. The NK cell activity is an important index of immunologic function. The results showed that the NK cell activity after laser acupoint irradiation was enhanced. This enhancement is relatively important in the clinical therapy of tumor.

A highly integrated single-mode 1064 nm laser with 8.5 kHz linewidth for dual-wavelength active optical clock

NASA Astrophysics Data System (ADS)

Shi, Tiantian; Pan, Duo; Chang, Pengyuan; Shang, Haosen; Chen, Jingbiao

2018-04-01

Without exploiting any frequency selective elements, we have realized a highly integrated, single-mode, narrow-linewidth Nd:YAG 1064 nm laser, which is end-pumped by the 808.6 nm diode laser in an integrated invar cavity. It turns out that each 1064 nm laser achieves a most probable linewidth of 8.5 kHz by beating between two identical laser systems. The output power of the 1064 nm laser increases steadily as the 808.6 nm pump power is raised, which can be up to 350 mW. Moreover, the resonant wavelength of cavity grows continuously in a certain crystal temperature range. Such a 1064 nm laser will be frequency stabilized to an ultrastable cavity by using the Pound-Drever-Hall technique and used as the good cavity laser to lock the main cavity length of 1064/1470 nm good-bad cavity dual-wavelength active optical clock.

Night firing range performance following photorefractive keratectomy and laser in situ keratomileusis.

PubMed

Bower, Kraig S; Burka, Jenna M; Subramanian, Prem S; Stutzman, Richard D; Mines, Michael J; Rabin, Jeff C

2006-06-01

To investigate the effect of laser refractive surgery on night weapons firing. Firing range performance was measured at baseline and postoperatively following photorefractive keratectomy and laser in situ keratomileusis. Subjects fired the M-16A2 rifle with night vision goggles (NVG) at starlight, and with iron sight (simulated dusk). Scores, before and after surgery, were compared for both conditions. No subject was able to acquire the target using iron sight without correction before surgery. After surgery, the scores without correction (95.9 +/- 4.7) matched the preoperative scores with correction (94.3 +/- 4.0; p = 0.324). Uncorrected NVG scores after surgery (96.4 +/- 3.1) exceeded the corrected scores before surgery (91.4 +/- 10.2), but this trend was not statistically significant (p = 0.063). Night weapon firing with both the iron sight and the NVG sight improved after surgery. This study supports the operational benefits of refractive surgery in the military.

Suspected time errors along the satellite laser ranging network and impact on the reference frame

NASA Astrophysics Data System (ADS)

Belli, Alexandre; Exertier, Pierre; Lemoine, Frank; Zelensky, Nikita

2017-04-01

Systematic errors in the laser ranging technologies must be considered when considering the GGOS objective to maintain a network with an accuracy of 1 mm and a stability of 0.1 mm per year for the station ground coordinates in the ITRF. Range and Time biases are identified to be part of these systematic errors, for a major part, and are difficult to detect. Concerning the range bias, analysts and working groups estimate their values from LAGEOS-1 & 2 observations (c.f. Appleby et al. 2016). On the other hand, time errors are often neglected (they are presumed to be < 100 ns) and remain difficult to estimate (at this level), from using the observations of geodetic satellites passes and precise orbit determination (i.e. LAGEOS). The Time Transfer by Laser Link (T2L2) experiment on-board Jason-2 is a unique opportunity to determine, globally and independently, the synchronization of all laser stations. Because of the low altitude of Jason-2, we computed the time transfer in non-common view from the Grasse primary station to all other SLR stations. We used a method to synchronize the whole network which consists of the integration of an Ultra Stable Oscillator (USO) frequency model, in order to take care of the frequency instabilities caused by the space environment. The integration provides a model which becomes an "on-orbit" time realization which can be connected to each of the SLR stations by the ground to space laser link. We estimated time biases per station, with a repeatability of 3 - 4 ns, for 25 stations which observe T2L2 regularly. We investigated the effect on LAGEOS and Starlette orbits and we discuss the impact of time errors on the station coordinates. We show that the effects on the global POD are negligible (< 1 mm) but are at the level of 4 - 6 mm for the coordinates. We conclude and propose to introduce time errors in the future analyses (IDS and ILRS) that would lead to the computation of improved reference frame solutions.

Laser assisted anticancer activity of benzimidazole based metal organic nanoparticles.

PubMed

Praveen, P A; Ramesh Babu, R; Balaji, P; Murugadas, A; Akbarsha, M A

2018-03-01

Recent studies showed that the photothermal therapy can be effectively used for the targeted cancerous cells destruction. Hence, in the present study, benzimidazole based metal organic complex nanoparticles, dichloro cobalt(II) bis-benzimidazole (Co-BMZ) and dichloro copper(II) bis-benzimidazole (Cu-BMZ), were synthesized by reprecipitation method and their anti-cancer activity by means of photothermal effect has been studied. Transmission electron microscopy analysis shows that the particle size of Cu-BMZ is ∼100 nm and Co-BMZ is in the range between 100 and 400 nm. Zeta potential analysis ensures the stability of the synthesized nanoparticles. It is found that the nonlinear absorption of the nanoparticles increases with increase in laser power intensity. Phototoxicity of human lung cancer (A549) and the normal mouse embryonic fibroblast (NIH-3T3) cells was studied using a 650 nm laser. Even though both the cell lines were affected by laser irradiation, A549 cells show higher cell destruction and lower IC 50 values than the normal cells. Docking studies were used to analyse the interaction site and the results showed that the Cu-BMZ molecules have higher dock score than the Co-BMZ molecules. The obtained results indicate that Cu-BMZ samples have lesser particle size, higher nonlinear absorption and higher interaction energy than the Co-BMZ samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Olivas uses a laser ranging device on STS-117 Space Shuttle Atlantis

NASA Image and Video Library

2007-06-10

S117-E-06953 (10 June 2007) --- Astronaut John "Danny" Olivas, STS-117 mission specialist, aims a laser range finder through one of the overhead windows on the aft flight deck of the Space Shuttle Atlantis at it approaches the International Space Station. This instrument is a regularly called-on tool during rendezvous operations with the station. The subsequent docking will allow the STS-117 astronauts and the Expedition 15 crew to team up for several days of key tasks in space.

A Hybrid Fiber/Solid-State Regenerative Amplifier with Tunable Pulse Widths for Satellite Laser Ranging

NASA Technical Reports Server (NTRS)

Coyle, Barry; Poulios, Demetrios

2013-01-01

A fiber/solid-state hybrid seeded regenerative amplifier, capable of achieving high output energy with tunable pulse widths, has been developed for satellite laser ranging applications. The regenerative amplifier cavity uses a pair of Nd:YAG zigzag slabs oriented orthogonally to one another in order to make thermal lensing effects symmetrical and simplify optical correction schemes. The seed laser used is a fiber-coupled 1,064-nm narrowband (<0.02 nm) diode laser that is discretely driven in a new short-pulsed mode, enabling continuously tunable seed pulse widths in the 0.2-to-0.4-ns range. The amplifier gain unit consists of a pair of Brewster-cut 6-bounce zigzag Nd:YAG laser slabs, oriented 90deg relative to each other in the amplifier head. This arrangement creates a net-symmetrical thermal lens effect (an opposing singleaxis effect in each slab), and makes thermo-optical corrections simple by optimizing the curvature of the nearest cavity mirror. Each slab is pumped by a single 120-W, pulsed 808-nm laser diode array. In this configuration, the average pump beam distribution in the slabs had a 1-D Gaussian shape, which matches the estimated cavity mode size. A half-wave plate between the slabs reduces losses from Fresnel reflections due to the orthogonal slabs Brewster-cut end faces. Successful "temporal" seeding of the regenerative amplifier cavity results in a cavity Q-switch pulse envelope segmenting into shorter pulses, each having the width of the input seed, and having a uniform temporal separation corresponding to the cavity round-trip time of approx. =10 ns. The pulse energy is allowed to build on successive passes in the regenerative amplifier cavity until a maximum is reached, (when cavity gains and losses are equal), after which the pulse is electro- optically switched out on the next round trip The overall gain of the amplifier is approx. =82 dB (or a factor of 1.26 million). After directing the amplified output through a LBO frequency doubling

Actively Q-switched laser with novel Nd:YAG/YAG polygonal active-mirror

NASA Astrophysics Data System (ADS)

Lang, Ye; Chen, Yanzhong; Ge, Wenqi; He, Jianguo; Zhang, Hongbo; Liao, Lifen; Xin, Jianguo; Zhang, Jian; Fan, Zhongwei

2018-03-01

In this work, we demonstrate an efficient actively Q-switched laser based on a novel crystal Nd:YAG/YAG polygonal active mirror. A passively cooled crystal Nd:YAG/YAG polygonal active mirror with an end pump scheme was used as the gain medium. For the overlap between the TEM00 laser mode and large gain profile, a cavity was carefully designed with a large fundamental mode volume. With a maximum absorbed power of 3.1 W, a 685 mW average output power with a pulse repetition of 5 kHz was attained, and the corresponding optical-optical and slope efficiency were 22.1% and 27.7%, respectively. The pulse width was 133.9 ns. The beam quality (M 2) was 1.561 in the horizontal direction and 1.261 in the vertical direction.

Lorentz Symmetry Violations from Matter-Gravity Couplings with Lunar Laser Ranging

NASA Astrophysics Data System (ADS)

Bourgoin, A.; Le Poncin-Lafitte, C.; Hees, A.; Bouquillon, S.; Francou, G.; Angonin, M.-C.

2017-11-01

The standard-model extension (SME) is an effective field theory framework aiming at parametrizing any violation to the Lorentz symmetry (LS) in all sectors of physics. In this Letter, we report the first direct experimental measurement of SME coefficients performed simultaneously within two sectors of the SME framework using lunar laser ranging observations. We consider the pure gravitational sector and the classical point-mass limit in the matter sector of the minimal SME. We report no deviation from general relativity and put new realistic stringent constraints on LS violations improving up to 3 orders of magnitude previous estimations.

Tidal dissipation in the Earth and Moon from lunar laser ranging

NASA Technical Reports Server (NTRS)

Yoder, C. F.; Williams, J. G.; Dickey, J. O.; Newhall, X. X.

1984-01-01

The evolution of the Moon's orbit which is governed by tidal dissipation in the Earth while the evolution of its spin is controlled by its own internal dissipation is discussed. Lunar laser ranging data from August 1969 through May 1982 yields the values of both of these parameters. It is suggested that if the Moon was orbited the Earth since its formation, this must be an anomalously high value presumably due to changes in dissipation in the oceans due to continental drift. The explanation that the dissipation occurs at the interface between the mantle and a liquid core of shell is preferred.

Earth orientation from lunar laser ranging and an error analysis of polar motion services

NASA Technical Reports Server (NTRS)

Dickey, J. O.; Newhall, X. X.; Williams, J. G.

1985-01-01

Lunar laser ranging (LLR) data are obtained on the basis of the timing of laser pulses travelling from observatories on earth to retroreflectors placed on the moon's surface during the Apollo program. The modeling and analysis of the LLR data can provide valuable insights into earth's dynamics. The feasibility to model accurately the lunar orbit over the full 13-year observation span makes it possible to conduct relatively long-term studies of variations in the earth's rotation. A description is provided of general analysis techniques, and the calculation of universal time (UT1) from LLR is discussed. Attention is also given to a summary of intercomparisons with different techniques, polar motion results and intercomparisons, and a polar motion error analysis.

Simulation of laser propagation through a three-layer human skin model in the spectral range from 1000 to 1900 nm.

PubMed

Nasouri, Babak; Murphy, Thomas E; Berberoglu, Halil

2014-01-01

For understanding the mechanisms of low-level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. We present a three-dimensional, multilayer reduced-variance Monte Carlo simulation tool for studying light penetration and absorption in human skin. Local profiles of light penetration and volumetric absorption were calculated for uniform as well as Gaussian profile beams with different spreads over the spectral range from 1000 to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as achieve large penetration depths for treating deep tissues, without causing skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could increase as much as three times for otherwise similar lasers. We expect that this tool along with the results presented will aid researchers in selecting wavelength and laser power in LLLT.

Simulation of laser propagation through a three-layer human skin model in the spectral range from 1000 to 1900 nm

NASA Astrophysics Data System (ADS)

Nasouri, Babak; Murphy, Thomas E.; Berberoglu, Halil

2014-07-01

For understanding the mechanisms of low-level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. We present a three-dimensional, multilayer reduced-variance Monte Carlo simulation tool for studying light penetration and absorption in human skin. Local profiles of light penetration and volumetric absorption were calculated for uniform as well as Gaussian profile beams with different spreads over the spectral range from 1000 to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as achieve large penetration depths for treating deep tissues, without causing skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could increase as much as three times for otherwise similar lasers. We expect that this tool along with the results presented will aid researchers in selecting wavelength and laser power in LLLT.

Chemical bond activation observed with an x-ray laser

DOE PAGES

Beye, Martin; Öberg, Henrik; Xin, Hongliang; ...

2016-09-01

The concept of bonding and anti-bonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Lastly, we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding–anti-bonding splitting following bond-activation using an ultra short optical laser pulse.

LASER RADIATION CHARACTERISTICS (BRIEF COMMUNICATIONS): Conversion of KrCl and XeCl laser radiation to the visible spectral range by stimulated Raman scattering in lead vapor

NASA Astrophysics Data System (ADS)

Evtushenko, Gennadii S.; Mel'chenko, S. V.; Panchenko, Aleksei N.; Tarasenko, Viktor F.

1990-04-01

Conversion of KrCl and XeCl laser radiation by stimulated Raman scattering was achieved in lead vapor. The KrCl laser radiation was converted into three lines in the visible region at λ = 406, 590, and 723 nm by transitions from both the ground and first excited levels of the lead atom. The conversion efficiency of XeCl laser radiation of low spatial coherence was found to be limited by the activation of a competing nonlinear process.

Activity of respiratory system during laser irradiation of brain structures

NASA Astrophysics Data System (ADS)

Merkulova, N. A.; Sergeyeva, L. I.

1984-06-01

The performance of one of the principal links of the respiratory system, the respiratory center, was studied as a function of the exposure of the medulla oblongata and the sensomotor zone of the cerebral hemisphere cortex to low level laser irradiation in the red wavelength of the spectrum. Experiments were done on white rats under barbital anesthesia. Under such conditions a substantial effect was observed on the activity of the respiratory center. Laser light may display activating or inhibitory influences, in some cases the bilateral symmetry of the activity of the respiratory center is affected indicating deep changes in the integrative mechanism of the functioning of the right and left sides of the hemispheres. The laser beam effect depends on many factors: specific light properties, duration of the exposure, repetition of exposures, initial functional state of the CNS, etc.

Ti : sapphire laser synchronised with femtosecond Yb pump laser via nonlinear pulse coupling in Ti : sapphire active medium

NASA Astrophysics Data System (ADS)

Didenko, N. V.; Konyashchenko, A. V.; Konyashchenko, D. A.; Kostryukov, P. V.; Kuritsyn, I. I.; Lutsenko, A. P.; Mavritskiy, A. O.

2017-02-01

A laser system utilising the method of synchronous pumping of a Ti : sapphire laser by a high-power femtosecond Yb3+-doped laser is described. The pulse repetition rate of the Ti : sapphire laser is successfully locked to the repetition rate of the Yb laser for more than 6 hours without the use of any additional electronics. The measured timing jitter is shown to be less than 1 fs. A simple qualitative model addressing the synchronisation mechanism utilising the cross-phase modulation of oscillation and pump pulses within a Ti : sapphire active medium is proposed. Output parameters of the Ti : sapphire laser as functions of its cavity length are discussed in terms of this model.

Development of Shanghai satellite laser ranging station

NASA Technical Reports Server (NTRS)

Yang, Fu-Min; Tan, De-Tong; Xiao, Chi-Kun; Chen, Wan-Zhen; Zhang, J.-H.; Zhang, Z.-P.; Lu, Wen-Hu; Hu, Z.-Q.; Tang, W.-F.; Chen, J.-P.

1993-01-01

The topics covered include the following: improvement of the system hardware; upgrading of the software; the observation status; preliminary daylight tracking capability; testing the new type of laser; and future plans.

Laser action in chromium-doped forsterite

NASA Technical Reports Server (NTRS)

Petricevic, V.; Gayen, S. K.; Alfano, R. R.; Yamagishi, Kiyoshi; Anzai, H.

1988-01-01

This paper reports on pulsed laser operation obtained in chromium-activated forsterite Cr(3+):Mg2SiO4 at room temperature. The spectrum of the free-running laser peaks at 1235 nm and a bandwidth of about 22 nm. The spectral range of the laser emission is expected to extend from 850 to 1300, provided the parasitic impurity absorption may be minimized by improved crystal growth techique.

Research of laser stealth performance test technology

NASA Astrophysics Data System (ADS)

Chen, Zhen-xing; Shi, Sheng-bing; Han, Fu-li; Wu, Yan-lin; Song, Chun-yan

2014-09-01

Laser stealth is an important way of photoelectric stealth weapons systems. According to operational principle of laser range finder, we actively explore and study the stealth performance approval testing technology of laser stealth materials, and bring forward and establish the stealth performance field test methods of stealth efficiency evaluation. Through contrastive test of two kinds of materials, the method is correct and effective.

Soliton microcomb range measurement.

PubMed

Suh, Myoung-Gyun; Vahala, Kerry J

2018-02-23

Laser-based range measurement systems are important in many application areas, including autonomous vehicles, robotics, manufacturing, formation flying of satellites, and basic science. Coherent laser ranging systems using dual-frequency combs provide an unprecedented combination of long range, high precision, and fast update rate. We report dual-comb distance measurement using chip-based soliton microcombs. A single pump laser was used to generate dual-frequency combs within a single microresonator as counterpropagating solitons. We demonstrated time-of-flight measurement with 200-nanometer precision at an averaging time of 500 milliseconds within a range ambiguity of 16 millimeters. Measurements at distances up to 25 meters with much lower precision were also performed. Our chip-based source is an important step toward miniature dual-comb laser ranging systems that are suitable for photonic integration. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, Robert R.

1992-01-01

Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

Prototype Test Results for the Single Photon Detection SLR2000 Satellite Laser Ranging System

NASA Technical Reports Server (NTRS)

Zagwodzki, Thomas W.; McGarry, Jan F.; Degnan, John J.; Cheek, Jack W.; Dunn, Peter J.; Patterson, Don; Donovan, Howard

2004-01-01

NASA's aging Satellite Laser Ranging (SLR) network is scheduled to be replaced over the next few years with a fully automated single photon detection system. A prototype of this new system, called SLR2000, is currently undergoing field trials at the Goddard Space Flight Center in Greenbelt, Maryland to evaluate photon counting techniques and determine system hardware, software, and control algorithm performance levels and limitations. Newly developed diode pumped microchip lasers and quadrant microchannel plate-based photomultiplier tubes have enabled the development of this high repetition rate single photon detection SLR system. The SLR2000 receiver threshold is set at the single photoelectron (pe) level but tracks satellites with an average signal level typically much less than 1 pe. The 2 kHz laser fire rate aids in satellite acquisition and tracking and will enable closed loop tracking by accumulating single photon count statistics in a quadrant detector and using this information to correct for pointing errors. Laser transmitter beamwidths of 10 arcseconds (FWHM) or less are currently being used to maintain an adequate signal level for tracking while the receiver field of view (FOV) has been opened to 40 arcseconds to accommodate point ahead/look behind angular offsets. In the near future, the laser transmitter point ahead will be controlled by a pair of Risley prisms. This will allow the telescope to point behind and enable closure of the receiver FOV to roughly match the transmitter beam divergence. Bandpass filters (BPF) are removed for night tracking operations while 0.2 nm or 1 nm filters are used during daylight operation. Both day and night laser tracking of Low Earth Orbit (LEO) satellites has been achieved with a laser transmitter energy of only 65 microjoules per pulse. Satellite tracking is presently limited to LEO satellites until the brassboard laser transmitter can be upgraded or replaced. Simultaneous tracks have also been observed with NASA s

Lunar Laser Ranging Science: Gravitational Physics and Lunar Interior and Geodesy

NASA Technical Reports Server (NTRS)

Williams, James G.; Turyshev, Slava G.; Boggs, Dale H.; Ratcliff, J. Todd

2004-01-01

Laser pulses fired at retroreflectors on the Moon provide very accurate ranges. Analysis yields information on Earth, Moon, and orbit. The highly accurate retroreflector positions have uncertainties less than a meter. Tides on the Moon show strong dissipation, with Q=33+/-4 at a month and a weak dependence on period. Lunar rotation depends on interior properties; a fluid core is indicated with radius approx.20% that of the Moon. Tests of relativistic gravity verify the equivalence principle to +/-1.4x10(exp -13), limit deviations from Einstein's general relativity, and show no rate for the gravitational constant G/G with uncertainty 9x10(exp -13)/yr.

Recognition of three dimensional obstacles by an edge detection scheme. [for Mars roving vehicle using laser range finder

NASA Technical Reports Server (NTRS)

Reed, M. A.

1974-01-01

The need for an obstacle detection system on the Mars roving vehicle was assumed, and a practical scheme was investigated and simulated. The principal sensing device on this vehicle was taken to be a laser range finder. Both existing and original algorithms, ending with thresholding operations, were used to obtain the outlines of obstacles from the raw data of this laser scan. A theoretical analysis was carried out to show how proper value of threshold may be chosen. Computer simulations considered various mid-range boulders, for which the scheme was quite successful. The extension to other types of obstacles, such as craters, was considered. The special problems of bottom edge detection and scanning procedure are discussed.

Dielectrophoretic focusing integrated pulsed laser activated cell sorting

NASA Astrophysics Data System (ADS)

Zhu, Xiongfeng; Kung, Yu-Chun; Wu, Ting-Hsiang; Teitell, Michael A.; Chiou, Pei-Yu

2017-08-01

We present a pulsed laser activated cell sorter (PLACS) integrated with novel sheathless size-independent dielectrophoretic (DEP) focusing. Microfluidic fluorescence activated cell sorting (μFACS) systems aim to provide a fully enclosed environment for sterile cell sorting and integration with upstream and downstream microfluidic modules. Among them, PLACS has shown a great potential in achieving comparable performance to commercial aerosol-based FACS (>90% purity at 25,000 cells sec-1). However conventional sheath flow focusing method suffers a severe sample dilution issue. Here we demonstrate a novel dielectrophoresis-integrated pulsed laser activated cell sorter (DEP-PLACS). It consists of a microfluidic channel with 3D electrodes laid out to provide a tunnel-shaped electric field profile along a 4cmlong channel for sheathlessly focusing microparticles/cells into a single stream in high-speed microfluidic flows. All focused particles pass through the fluorescence detection zone along the same streamline regardless of their sizes and types. Upon detection of target fluorescent particles, a nanosecond laser pulse is triggered and focused in a neighboring channel to generate a rapidly expanding cavitation bubble for precise sorting. DEP-PLACS has achieved a sorting purity of 91% for polystyrene beads at a throughput of 1,500 particle/sec.

Laser Technology in Interplanetary Exploration: The Past and the Future

NASA Technical Reports Server (NTRS)

Smith, David E.

2000-01-01

Laser technology has been used in planetary exploration for many years but it has only been in the last decade that laser altimeters and ranging systems have been selected as flight instruments alongside cameras, spectrometers, magnetometers, etc. Today we have an active laser system operating at Mars and another destined for the asteroid Eros. A few years ago a laser ranging system on the Clementine mission changed much of our thinking about the moon and in a few years laser altimeters will be on their way to Mercury, and also to Europa. Along with the increased capabilities and reliability of laser systems has came the realization that precision ranging to the surface of planetary bodies from orbiting spacecraft enables more scientific problems to be addressed, including many associated with planetary rotation, librations, and tides. In addition, new Earth-based laser ranging systems working with similar systems on other planetary bodies in an asynchronous transponder mode will be able to make interplanetary ranging measurements at the few cm level and will advance our understanding of solar system dynamics and relativistic physics.

Raman-shifted alexandrite laser for soft tissue ablation in the 6- to 7-µm wavelength range

PubMed Central

Kozub, John; Ivanov, Borislav; Jayasinghe, Aroshan; Prasad, Ratna; Shen, Jin; Klosner, Marc; Heller, Donald; Mendenhall, Marcus; Piston, David W.; Joos, Karen; Hutson, M. Shane

2011-01-01

Prior work with free-electron lasers (FELs) showed that wavelengths in the 6- to 7-µm range could ablate soft tissues efficiently with little collateral damage; however, FELs proved too costly and too complex for widespread surgical use. Several alternative 6- to 7-µm laser systems have demonstrated the ability to cut soft tissues cleanly, but at rates that were much too low for surgical applications. Here, we present initial results with a Raman-shifted, pulsed alexandrite laser that is tunable from 6 to 7 µm and cuts soft tissues cleanly—approximately 15 µm of thermal damage surrounding ablation craters in cornea—and does so with volumetric ablation rates of 2–5 × 10−3 mm3/s. These rates are comparable to those attained in prior successful surgical trials using the FEL for optic nerve sheath fenestration. PMID:21559139

2.3 µm range InP-based type-II quantum well Fabry-Perot lasers heterogeneously integrated on a silicon photonic integrated circuit.

PubMed

Wang, Ruijun; Sprengel, Stephan; Boehm, Gerhard; Muneeb, Muhammad; Baets, Roel; Amann, Markus-Christian; Roelkens, Gunther

2016-09-05

Heterogeneously integrated InP-based type-II quantum well Fabry-Perot lasers on a silicon waveguide circuit emitting in the 2.3 µm wavelength range are demonstrated. The devices consist of a "W"-shaped InGaAs/GaAsSb multi-quantum-well gain section, III-V/silicon spot size converters and two silicon Bragg grating reflectors to form the laser cavity. In continuous-wave (CW) operation, we obtain a threshold current density of 2.7 kA/cm² and output power of 1.3 mW at 5 °C for 2.35 μm lasers. The lasers emit over 3.7 mW of peak power with a threshold current density of 1.6 kA/cm² in pulsed regime at room temperature. This demonstration of heterogeneously integrated lasers indicates that the material system and heterogeneous integration method are promising to realize fully integrated III-V/silicon photonics spectroscopic sensors in the 2 µm wavelength range.

Tracking on non-active collaborative objects from San Fernando Laser station

NASA Astrophysics Data System (ADS)

Catalán, Manuel; Quijano, Manuel; Cortina, Luis M.; Pazos, Antonio A.; Martín-Davila, José

2016-04-01

The Royal Observatory of the Spanish Navy (ROA) works on satellite geodesy from the early days of the space age, when the first artificial satellite tracking telescope was installed in 1958: the Baker-Nunn camera. In 1975 a French satellite Laser ranging (SLR) station was installed and operated at ROA . Since 1980, ROA has been operating this instrument which was upgraded to a third generation and it is still keep into a continuous update to reach the highest level of operability. Since then ROA has participated in different space geodesy campaigns through the International Laser Service Stations (ILRS) or its European regional organization (EUROLAS), tracking a number of artificial satellites types : ERS, ENVISAT, LAGEOS, TOPEX- POSEIDON to name but a few. Recently we opened a new field of research: space debris tracking, which is receiving increasing importance and attention from international space agencies. The main problem is the relatively low accuracy of common used methods. It is clear that improving the predicted orbit accuracy is necessary to fulfill our aims (avoiding unnecessary anti-collision maneuvers,..). Following results obtained by other colleagues (Austria, China, USA,...) we proposed to share our time-schedule using our satellite ranging station to obtain data which will make orbital elements predictions far more accurate (sub-meter accuracy), while we still keep our tracking routines over active satellites. In this communication we report the actions fulfill until nowadays.

Improved Range Estimation Model for Three-Dimensional (3D) Range Gated Reconstruction

PubMed Central

Chua, Sing Yee; Guo, Ningqun; Tan, Ching Seong; Wang, Xin

2017-01-01

Accuracy is an important measure of system performance and remains a challenge in 3D range gated reconstruction despite the advancement in laser and sensor technology. The weighted average model that is commonly used for range estimation is heavily influenced by the intensity variation due to various factors. Accuracy improvement in term of range estimation is therefore important to fully optimise the system performance. In this paper, a 3D range gated reconstruction model is derived based on the operating principles of range gated imaging and time slicing reconstruction, fundamental of radiant energy, Laser Detection And Ranging (LADAR), and Bidirectional Reflection Distribution Function (BRDF). Accordingly, a new range estimation model is proposed to alleviate the effects induced by distance, target reflection, and range distortion. From the experimental results, the proposed model outperforms the conventional weighted average model to improve the range estimation for better 3D reconstruction. The outcome demonstrated is of interest to various laser ranging applications and can be a reference for future works. PMID:28872589

Receiver performance of laser ranging measurements between the Lunar Observer and a subsatellite for lunar gravity studies

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli

1992-01-01

The optimal receiver for a direct detection laser ranging system for slow Doppler frequency shift measurement is shown to consist of a phase tracking loop which can be implemented approximately as a phase lock loop with a 2nd or 3rd order loop filter. The laser transmitter consists of an AlGaAs laser diode at a wavelength of about 800 nm and is intensity modulated by a sinewave. The receiver performance is shown to be limited mainly by the preamplifier thermal noise when a silicon avalanche photodiode is used. A high speed microchannel plate photomultiplier tube is shown to outperform a silicon APD despite its relatively low quantum efficiency at wavelengths near 800 nm. The maximum range between the Lunar Observer and the subsatellite for lunar gravity studies is shown to be about 620 km when using a state-of-the-art silicon APD and about 1000 km when using a microchannel plate photomultiplier tube in order to achieve a relative velocity measurement accuracy of 1 millimeter per second. Other parameters such as the receiver time base jitter and drift also limit performance and have to be considered in the design of an actual system.

Three-dimensional obstacle classification in laser range data

NASA Astrophysics Data System (ADS)

Armbruster, Walter; Bers, Karl-Heinz

1998-10-01

The threat of hostile surveillance and weapon systems require military aircraft to fly under extreme conditions such as low altitude, high speed, poor visibility and incomplete terrain information. The probability of collision with natural and man-made obstacles during such contour missions is high if detection capability is restricted to conventional vision aids. Forward-looking scanning laser rangefinders which are presently being flight tested and evaluated at German proving grounds, provide a possible solution, having a large field of view, high angular and range resolution, a high pulse repetition rate, and sufficient pulse energy to register returns from wires at over 500 m range (depends on the system) with a high hit-and-detect probability. Despite the efficiency of the sensor, acceptance of current obstacle warning systems by test pilots is not very high, mainly due to the systems' inadequacies in obstacle recognition and visualization. This has motivated the development and the testing of more advanced 3d-scene analysis algorithm at FGAN-FIM to replace the obstacle recognition component of current warning systems. The basic ideas are to increase the recognition probability and to reduce the false alarm rate for hard-to-extract obstacles such as wires, by using more readily recognizable objects such as terrain, poles, pylons, trees, etc. by implementing a hierarchical classification procedure to generate a parametric description of the terrain surface as well as the class, position, orientation, size and shape of all objects in the scene. The algorithms can be used for other applications such as terrain following, autonomous obstacle avoidance, and automatic target recognition.

Laser processing with specially designed laser beam

NASA Astrophysics Data System (ADS)

Asratyan, A. A.; Bulychev, N. A.; Feofanov, I. N.; Kazaryan, M. A.; Krasovskii, V. I.; Lyabin, N. A.; Pogosyan, L. A.; Sachkov, V. I.; Zakharyan, R. A.

2016-04-01

The possibility of using laser systems to form beams with special spatial configurations has been studied. The laser systems applied had a self-conjugate cavity based on the elements of copper vapor lasers (LT-5Cu, LT-10Cu, LT-30Cu) with an average power of 5, 10, or 30 W. The active elements were pumped by current pulses of duration 80-100 ns. The duration of laser generation pulses was up to 25 ns. The generator unit included an unstable cavity, where one reflector was a special mirror with a reflecting coating. Various original optical schemes used were capable of exploring spatial configurations and energy characteristics of output laser beams in their interaction with micro- and nanoparticles fabricated from various materials. In these experiments, the beam dimensions of the obtained zones varied from 0.3 to 5 µm, which is comparable with the minimum permissible dimensions determined by the optical elements applied. This method is useful in transforming a large amount of information at the laser pulse repetition rate of 10-30 kHz. It was possible to realize the high-precision micromachining and microfabrication of microscale details by direct writing, cutting and drilling (with the cutting width and through-hole diameters ranging from 3 to 100 µm) and produce microscale, deep, intricate and narrow grooves on substrate surfaces of metals and nonmetal materials. This system is used for producing high-quality microscale details without moving the object under treatment. It can also be used for microcutting and microdrilling in a variety of metals such as molybdenum, copper and stainless steel, with a thickness of up to 300 µm, and in nonmetals such as silicon, sapphire and diamond with a thickness ranging from 10 µm to 1 mm with different thermal parameters and specially designed laser beam.

Satellite laser ranging and geological constraints on plate motion

NASA Technical Reports Server (NTRS)

Harrison, C. G. A.; Douglas, Nancy B.

1990-01-01

Satellite laser ranging (SLR) observed baseline rates of change were measured and compared with rates determined from sea floor spreading rates and directions, and earth-quake solutions. With the number of years of observation now over six for many of the baselines, the inaccuracy of determining baseline rates of change has diminished so that in some cases it is less than a few mm per year. Thus, a direct comparison between baseline rates of change and rates of change established using geophysical information (called geological rates) is now feasible. In most cases, there is good agreement between the rates determined from SLR and geological rates, but in some cases there appear to be discrepancies. These discrepancies involve many of the data for which one end of the baseline is either Quincy (California), Huahine (French Polynesia), or Simosato (Japan). A method for looking at the discrepancies for these SLR observatories has been devised which makes it possible to calculate the motion not modeled by the geologic information.

A comparative study of optimum and suboptimum direct-detection laser ranging receivers

NASA Technical Reports Server (NTRS)

Abshire, J. B.

1978-01-01

A summary of previously proposed receiver strategies for direct-detection laser ranging receivers is presented. Computer simulations are used to compare performance of candidate implementation strategies in the 1- to 100-photoelectron region. Under the condition of no background radiation, the maximum-likelihood and minimum mean-square error estimators were found to give the same performance for both bell-shaped and rectangular optical-pulse shapes. For signal energies greater than 100 photoelectrons, the root-mean-square range error is shown to decrease as Q to the -1/2 power for bell-shaped pulses and Q to the -1 power for rectangular pulses, where Q represents the average pulse energy. Of several receiver implementations presented, the matched-filter peak detector was found to be preferable. A similar configuration, using a constant-fraction discriminator, exhibited a signal-level dependent time bias.

High precision laser ranging by time-of-flight measurement of femtosecond pulses

NASA Astrophysics Data System (ADS)

Lee, Joohyung; Lee, Keunwoo; Lee, Sanghyun; Kim, Seung-Woo; Kim, Young-Jin

2012-06-01

Time-of-flight (TOF) measurement of femtosecond light pulses was investigated for laser ranging of long distances with sub-micrometer precision in the air. The bandwidth limitation of the photo-detection electronics used in timing femtosecond pulses was overcome by adopting a type-II nonlinear second-harmonic crystal that permits the production of a balanced optical cross-correlation signal between two overlapping light pulses. This method offered a sub-femtosecond timing resolution in determining the temporal offset between two pulses through lock-in control of the pulse repetition rate with reference to the atomic clock. The exceptional ranging capability was verified by measuring various distances of 1.5, 60 and 700 m. This method is found well suited for future space missions based on formation-flying satellites as well as large-scale industrial applications for land surveying, aircraft manufacturing and shipbuilding.

Achieving comb formation over the entire lasing range of quantum cascade lasers.

PubMed

Yang, Yang; Burghoff, David; Reno, John; Hu, Qing

2017-10-01

Frequency combs based on quantum cascade lasers (QCLs) are finding promising applications in high-speed broadband spectroscopy in the terahertz regime, where many molecules have their "fingerprints." To form stable combs in QCLs, an effective control of group velocity dispersion plays a critical role. The dispersion of the QCL cavity has two main parts: a static part from the material and a dynamic part from the intersubband transitions. Unlike the gain, which is clamped to a fixed value above the lasing threshold, dispersion associated with the intersubband transitions changes with bias, even above the threshold, and this reduces the dynamic range of comb formation. Here, by incorporating tunability into the dispersion compensator, we demonstrate a QCL device exhibiting comb operation from I th to I max , which greatly expands the operation range of the frequency combs.

Real-time multi-target ranging based on chaotic polarization laser radars in the drive-response VCSELs.

PubMed

Zhong, Dongzhou; Xu, Geliang; Luo, Wei; Xiao, Zhenzhen

2017-09-04

According to the principle of complete chaos synchronization and the theory of Hilbert phase transformation, we propose a novel real-time multi-target ranging scheme by using chaotic polarization laser radar in the drive-response vertical-cavity surface-emitting lasers (VCSELs). In the scheme, to ensure each polarization component (PC) of the master VCSEL (MVCSEL) to be synchronized steadily with that of the slave VCSEL, the output x-PC and y-PC from the MVCSEL in the drive system and those in the response system are modulated by the linear electro-optic effect simultaneously. Under this condition, by simulating the influences of some key parameters of the system on the synchronization quality and the relative errors of the two-target ranging, related operating parameters can be optimized. The x-PC and the y-PC, as two chaotic radar sources, are used to implement the real-time ranging for two targets. It is found that the measured distances of the two targets at arbitrary position exhibit strong real-time stability and only slight jitter. Their resolutions are up to millimeters, and their relative errors are very small and less than 2.7%.

Laser range pole field evaluation report

NASA Technical Reports Server (NTRS)

1973-01-01

A field evaluation was made of the laser pole equipment. The basic plan for the evaluation was to expose the equipment to the actual people and environment for which it was intended and determine, through the use of the equipment, its resultant effectivity in terms of improved performance. Results show the equipment performed better than expected in the high elevation clean air of Colorado, and did as well in Tennessee.

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

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

Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Bimberg, D.

2015-01-19

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 tomore » 300 mA leads to 30 MHz frequency tuning.« less

Testing Lorentz Symmetry with Lunar Laser Ranging

NASA Astrophysics Data System (ADS)

Bourgoin, A.; Hees, A.; Bouquillon, S.; Le Poncin-Lafitte, C.; Francou, G.; Angonin, M.-C.

2016-12-01

Lorentz symmetry violations can be parametrized by an effective field theory framework that contains both general relativity and the standard model of particle physics called the standard-model extension (SME). We present new constraints on pure gravity SME coefficients obtained by analyzing lunar laser ranging (LLR) observations. We use a new numerical lunar ephemeris computed in the SME framework and we perform a LLR data analysis using a set of 20 721 normal points covering the period of August, 1969 to December, 2013. We emphasize that linear combination of SME coefficients to which LLR data are sensitive and not the same as those fitted in previous postfit residuals analysis using LLR observations and based on theoretical grounds. We found no evidence for Lorentz violation at the level of 10-8 for s¯T X, 10-12 for s¯X Y and s¯X Z, 10-11 for s¯X X-s¯Y Y and s¯X X+s¯Y Y-2 s¯Z Z-4.5 s¯Y Z, and 10-9 for s¯T Y+0.43 s¯T Z. We improve previous constraints on SME coefficient by a factor up to 5 and 800 compared to postfit residuals analysis of respectively binary pulsars and LLR observations.

Long-range Coulomb effect in above-threshold ionization of Ne subject to few-cycle and multicycle laser fields

NASA Astrophysics Data System (ADS)

Xu, SongPo; Quan, Wei; Chen, YongJu; Xiao, ZhiLei; Wang, YanLan; Kang, HuiPeng; Hua, LinQiang; Gong, Cheng; Lai, XuanYang; Liu, XiaoJun; Hao, XiaoLei; Hu, ShiLin; Chen, Jing

2017-06-01

The long-range Coulomb effect (LRCE) is demonstrated experimentally and theoretically by investigating the pulse duration dependence of low-energy structure (LES) in above-threshold ionization of Ne. It is found experimentally that at 800 nm the LES shows itself as a double-hump structure (DHS) in momentum distribution of singly charged ion for Ne, and moreover, this structure is more prominent for multicycle laser fields than for few-cycle cases. This result can be reproduced and explained qualitatively with a semiclassical model and attributed to the paramount role of LRCE. That is to say, after the laser field vanishes, the electrons decelerate while flying away from the core by the long-range tail of Coulomb potential, which eventually makes DHS less notable.

Could low level laser therapy and highly active antiretroviral therapy lead to complete eradication of HIV-1 in vitro?

NASA Astrophysics Data System (ADS)

Lugongolo, Masixole Yvonne; Manoto, Sello Lebohang; Ombinda-Lemboumba, Saturnin; Maaza, Malik; Mthunzi-Kufa, Patience

2017-02-01

Human immunodeficiency virus (HIV-1) infection remains a major health problem despite the use of highly active antiretroviral therapy (HAART), which has greatly reduced mortality rates. Due to the unavailability of an effective vaccine or a treatment that would completely eradicate the virus, the quest for new and combination therapies continues. In this study we explored the influence of Low Level Laser Therapy (LLLT) in HIV-1 infected and uninfected cells. Literature reports LLLT as widely used to treat different medical conditions such as diabetic wounds, sports injuries and others. The technique involves exposure of cells or tissue to low levels of red and near infrared laser light. Both HIV infected and uninfected cells were laser irradiated at a wavelength of 640 nm with fluencies ranging from 2 to 10 J/cm2 and cellular responses were assessed 24 hours post laser treatment. In our studies, laser therapy had no inhibitory effects in HIV-1 uninfected cells as was indicated by the cell morphology and proliferation results. However, laser irradiation enhanced cell apoptosis in HIV-1 infected cells as the laser fluencies increased. This led to further studies in which laser irradiation would be conducted in the presence of HAART to determine whether HAART would minimise the detrimental effects of laser irradiation in infected cells.

Proposed satellite laser ranging and very long baseline interferometry sites for crustal dynamics investigations

NASA Technical Reports Server (NTRS)

Lowman, P. D.; Allenby, R. J.; Frey, H. V.

1979-01-01

Recommendations are presented for a global network of 125 sites for geodetic measurements by satellite laser ranging and very long baseline interferometry. The sites were proposed on the basis of existing facilities and scientific value for investigation of crustal dynamics as related to earthquake hazards. Tectonic problems are discussed for North America peripheral regions and for the world. The sites are presented in tables and maps, with bibliographic references.

Ultralow-jitter and -amplitude-noise semiconductor-based actively mode-locked laser.

PubMed

Quinlan, Franklyn; Gee, Sangyoun; Ozharar, Sarper; Delfyett, Peter J

2006-10-01

We report a semiconductor-based, low-noise, 10.24 GHz actively mode-locked laser with 4.65 fs of relative timing jitter and a 0.0365% amplitude fluctuation (1 Hz to 100 MHz) of the optical pulse train. The keys to obtaining this result were the laser's high optical power and the low phase noise of the rf source used to mode lock the laser. The low phase noise of the rf source not only improves the absolute and relative timing jitter of the laser, but also prevents coupling of the rf source phase noise to the pulse amplitude fluctuations by the mode-locked laser.

Investigation of tidal displacements of the Earth's surface by laser ranging to GEOS-3

NASA Technical Reports Server (NTRS)

Bower, D. R.; Halpenny, J.; Paul, M. K.; Lambert, A.

1980-01-01

An analysis of laser ranging data from three stations was carried out in an attempt to measure the geometric Earth tide. Two different approaches to the problem were investigated. The dynamic method computes pass to pass apparent movements in stations height relative to short arcs fitted to several passes of data from the same station by the program GEODYNE. The quasi-geometric method reduces the dependence on unmodelled satellite dynamics to a knowledge of only the radial position of the satellite by considering two station simultaneous ranging at the precise time that the satellite passes through the plane defined by two stations and the center of mass of the Earth.

Passive, active, and hybrid mode-locking in a self-optimized ultrafast diode laser

NASA Astrophysics Data System (ADS)

Alloush, M. Ali; Pilny, Rouven H.; Brenner, Carsten; Klehr, Andreas; Knigge, Andrea; Tränkle, Günther; Hofmann, Martin R.

2018-02-01

Semiconductor lasers are promising sources for generating ultrashort pulses. They are directly electrically pumped, allow for a compact design, and therefore they are cost-effective alternatives to established solid-state systems. Additionally, their emission wavelength depends on the bandgap which can be tuned by changing the semiconductor materials. Theoretically, the obtained pulse width can be few tens of femtoseconds. However, the generated pulses are typically in the range of several hundred femtoseconds only. Recently, it was shown that by implementing a spatial light modulator (SLM) for phase and amplitude control inside the resonator the optical bandwidth can be optimized. Consequently, by using an external pulse compressor shorter pulses can be obtained. We present a Fourier-Transform-External-Cavity setup which utilizes an ultrafast edge-emitting diode laser. The used InGaAsP diode is 1 mm long and emits at a center wavelength of 850 nm. We investigate the best conditions for passive, active and hybrid mode-locking operation using the method of self-adaptive pulse shaping. For passive mode-locking, the bandwidth is increased from 2.34 nm to 7.2 nm and ultrashort pulses with a pulse width of 216 fs are achieved after external pulse compression. For active and hybrid mode-locking, we also increased the bandwidth. It is increased from 0.26 nm to 5.06 nm for active mode-locking and from 3.21 nm to 8.7 nm for hybrid mode-locking. As the pulse width is strongly correlated with the bandwidth of the laser, we expect further reduction in the pulse duration by increasing the bandwidth.

Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

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

Adraider, Y.; Pang, Y.X., E-mail: F6098038@tees.ac.uk; Nabhani, F.

2014-06-01

Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surfacemore » morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.« less

Satellite laser ranging as a tool for the recovery of tropospheric gradients

NASA Astrophysics Data System (ADS)

Drożdżewski, M.; Sośnica, K.

2018-11-01

Space geodetic techniques, such as Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI) have been extensively used for the recovery of the tropospheric parameters. Both techniques employ microwave observations, for which the troposphere is a non-dispersive medium and which are very sensitive to the water vapor content. Satellite laser ranging (SLR) is the only space geodetic technique used for the definition of the terrestrial reference frames which employs optical - laser observations. The SLR sensitivity to the hydrostatic part of the troposphere delay is similar to that of microwave observations, whereas the sensitivity of laser observations to non-hydrostatic part of the delay is about two orders of magnitude smaller than in the case of microwave observations. Troposphere is a dispersive medium for optical wavelengths, which means that the SLR tropospheric delay depends on the laser wavelength. This paper presents the sensitivity and capability of the SLR observations for the recovery of azimuthal asymmetry over the SLR stations, which can be described as horizontal gradients of the troposphere delay. For the first time, the horizontal gradients are estimated, together with other parameters typically estimated from the SLR observations to spherical LAGEOS satellites, i.e., station coordinates, earth rotation parameters, and satellite orbits. Most of the SLR stations are co-located with GNSS receivers, thus, a cross-correlation between both techniques is possible. We compare our SLR horizontal gradients to GNSS results and to the horizontal gradients derived from the numerical weather models (NWM). Due to a small number of the SLR observations, SLR is not capable of reconstructing short-period phenomena occurring in the atmosphere. However, the long-term analysis allows for the recovery of the atmosphere asymmetry using SLR. As a result, the mean offsets of the SLR-derived horizontal gradients agree to the level of 47%, 74%, 54

Surface registration technique for close-range mapping applications

NASA Astrophysics Data System (ADS)

Habib, Ayman F.; Cheng, Rita W. T.

2006-08-01

Close-range mapping applications such as cultural heritage restoration, virtual reality modeling for the entertainment industry, and anatomical feature recognition for medical activities require 3D data that is usually acquired by high resolution close-range laser scanners. Since these datasets are typically captured from different viewpoints and/or at different times, accurate registration is a crucial procedure for 3D modeling of mapped objects. Several registration techniques are available that work directly with the raw laser points or with extracted features from the point cloud. Some examples include the commonly known Iterative Closest Point (ICP) algorithm and a recently proposed technique based on matching spin-images. This research focuses on developing a surface matching algorithm that is based on the Modified Iterated Hough Transform (MIHT) and ICP to register 3D data. The proposed algorithm works directly with the raw 3D laser points and does not assume point-to-point correspondence between two laser scans. The algorithm can simultaneously establish correspondence between two surfaces and estimates the transformation parameters relating them. Experiment with two partially overlapping laser scans of a small object is performed with the proposed algorithm and shows successful registration. A high quality of fit between the two scans is achieved and improvement is found when compared to the results obtained using the spin-image technique. The results demonstrate the feasibility of the proposed algorithm for registering 3D laser scanning data in close-range mapping applications to help with the generation of complete 3D models.

Effects of horizontal refractivity gradients on the accuracy of laser ranging to satellites

NASA Technical Reports Server (NTRS)

Gardner, C. S.

1976-01-01

Numerous formulas have been developed to partially correct laser ranging data for the effects of atmospheric refraction. All the formulas assume the atmospheric refractivity profile is spherically symmetric. The effects of horizontal refractivity gradients are investigated by ray tracing through spherically symmetric and three-dimensional refractivity profiles. The profiles are constructed from radiosonde data. The results indicate that the horizontal gradients introduce an rms error of approximately 3 cm when the satellite is near 10 deg elevation. The error decreases to a few millimeters near zenith.

Light detection and ranging (LIDAR): an emerging tool for multiple resource inventory.

Treesearch

Stephen E. Reutebuch; Hans-Erik Andersen; Robert J. McGaughey

2005-01-01

Airborne laser scanning of forests has been shown to provide accurate terrain models and, at the same time, estimates of multiple resource inventory variables through active sensing of three-dimensional (3D) forest vegetation. Brief overviews of airborne laser scanning technology [often referred to as "light detection and ranging" (LIDAR)] and research...

Spin motion determination of the Envisat satellite through laser ranging measurements from a single pass measured by a single station

NASA Astrophysics Data System (ADS)

Pittet, Jean-Noël; Šilha, Jiří; Schildknecht, Thomas

2018-02-01

The Satellite Laser Ranging (SLR) technology is used to accurately determine the position of space objects equipped with so-called retro-reflectors or retro-reflector arrays (RRA). This type of measurement allows to measure the range to the spacecraft with high precision, which leads to determination of very accurate orbits for these targets. Non-active spacecraft, which are not attitude controlled any longer, tend to start to spin or tumble under influence of the external and internal torques and forces. If the return signal is measured for a non-spherical non-active rotating object, the signal in the range residuals with respect to the reference orbit is more complex. For rotating objects the return signal shows an oscillating pattern or patterns caused by the RRA moving around the satellite's centre of mass. This behaviour is projected onto the radial component measured by the SLR. In our work, we demonstrate how the SLR ranging technique from one sensor to a satellite equipped with a RRA can be used to precisely determine its spin motion during one passage. Multiple SLR measurements of one target over time allow to accurately monitor spin motion changes which can be further used for attitude predictions. We show our solutions of the spin motion determined for the non-active ESA satellite Envisat obtained from measurements acquired during years 2013-2015 by the Zimmerwald SLR station, Switzerland. All the necessary parameters are defined for our own so-called point-like model which describes the motion of a point in space around the satellite centre of mass.

First aircraft experiment results with the wide-angle airborne laser ranging system

NASA Astrophysics Data System (ADS)

Bock, Olivier; Thom, Christian; Kasser, Michel

1999-12-01

The first aircraft experiment with the Wide-Angle Airborne Laser Ranging System has been conducted in May 1998 over an air base in France equipped with a network of 64 cub-corner retroreflectors. The ranging system was operated from the Avion de Recherche Atmospherique et de Teledetection of CNES/IGN/INSU. Data have been collected during two 4-hour flights. The paper describes the data processing methods and presents the first experimental results. The precision is of 2 cm on the difference of vertical coordinates from two sets of 3 X 103 distance measurements, which is consistent with simulations and a posteriori covariance. The precision is mainly limited by the smallness of the number of efficient measurements remaining after a drastic data sorting for outliers. Higher precision is expected for future experiments after some instrumental improvements (achieving higher link budget) and measurement of aircraft attitude during the flight.

Next-generation hollow retroreflectors for lunar laser ranging.

PubMed

Preston, Alix; Merkowitz, Stephen

2013-12-20

The three retroreflector arrays put on the Moon 40 years ago by the Apollo astronauts and the French-built arrays on the Soviet Lunokhod rovers continue to be useful targets, and have provided the most stringent tests of the Strong Equivalence Principle and the time variation of Newton's gravitational constant, as well as valuable insight into the Moon's interior. However, the precision of the ranging measurements are now being limited by the physical size of the arrays and a new generation of retroreflectors is required to make significant advances over current capabilities. Large single-cube retroreflectors represent the most promising approach to overcoming current limitations, and hollow retroreflectors in particular have the potential to maintain their good optical performance over the nearly 300 K temperature swing that occurs during the lunar cycle. Typically, epoxies are used for aligning and bonding hollow retroreflectors, but their thermal stability will predominantly be limited by the difference of the coefficient of thermal expansion (CTE) between the epoxy and the glass. A relatively new bonding method known as hydroxide catalysis bonding (HCB) has been used to adhere complex optical components for space-based missions. HCB has an extremely thin bond, a low CTE, and a high breaking strength that makes it an ideal candidate for bonding hollow retroreflectors for lunar laser ranging (LLR). In this work, we present results of a feasibility study of bonded Pyrex and fused silica hollow retroreflectors using both epoxy and HCB methods, including the results of thermally cycling the hollow retroreflectors from 295 to 185 K. Finally, we discuss the potential for using these retroreflectors for future LLR.