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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Wide band fiber-optic communications

A number of optical communication lines are now in use at the Kennedy Space Center (KSC) for the transmission of voice, computer data and video signals. At the present time most of these channels utilize a single carrier wavelength centered near 1300 nm. As a result of previous work the bandwidth capacity of a number of these channels is being increased by transmitting another signal in the 1550 nm region on the same fiber. This is accomplished by means of wavelength division multiplexing (WDM). It is therefore important to understand the bandwidth properties of the installed fiber plant. This work developed new procedures for measuring the bandwidth of fibers in both the 1300nm and 1550nm region. In addition, a preliminary study of fiber links terminating in the Engineering Development Laboratory was completed.

Bates, Harry E.↗
NASA NTRSDate not supplied

Fine pointing of Laser Beams by using Laser Arrays for Applications to CubeSats

A method of fine pointing of laser beams by using laser arrays has been developed. The telescope system combines a lens system and a VCSEL/Photodetector Array. It does not use moving parts. In computer simulations, it is applied to CubeSats that use body pointing. Body pointing was used by the Aerospace Corporation for CubeSats in LEO in NASA’s Optical Communications and Sensors Demonstration (OCSD) program. Computer simulations of this fine pointing capability have been applied previously to CubeSats in the OCSD program. In this paper, computer simulations of laser pointing using this telescope design are applied to CubeSats in LLO, at 100 km. These CubeSats could form part of the LunaNet, the lunar communications and navigation network, part of the NASA ARTEMIS Program. With more accurate pointing, a laser beam with smaller divergence can be used. For the case of the AeroCube-7B vehicle that was used in the OCSD program, computer simulations will show, for example, that the divergence of the output beam can be reduced from approximately 0.06° FWHM to 0.014°. For the proposed electro-optical system, reaction times to pointing changes and vibrations are on a nanosecond time scale, much faster than those for fine pointing systems that use moving parts such as fast steering mirrors, including MEMS, or that use quad-cell photodetectors to improve the body pointing of the CubeSat. Other possible applications are to Optical Multiple Access (OMA)for simultaneously communicating with ground stations at different locations and to Wavelength-Division Multiplexing (WDM)for increasing data rate transmission.

SMD↗
NASA NTRS2021

Fine Pointing of Laser Beams by Using Laser Arrays for Applications to CubeSats

A method of fine pointing of laser beams by using laser arrays has been developed. The telescope system combines a lens system and a VCSEL/Photodetector Array. It does not use moving parts. In computer simulations, it is applied to CubeSats that use body pointing. Body pointing was used by the Aerospace Corporation for CubeSats in LEO in NASA’s Optical Communications and Sensors Demonstration (OCSD) program. Computer simulations of this fine pointing capability have been applied previously to CubeSats in the OCSD program. In this paper, computer simulations of laser pointing using this telescope design are applied to CubeSats in LLO, at 100 km. These CubeSats could form part of the LunaNet, the lunar communications and navigation network, part of the NASA ARTEMIS Program. With more accurate pointing, a laser beam with smaller divergence can be used. For the case of the AeroCube-7B vehicle that was used in the OCSD program, computer simulations will show, for example, that the divergence of the output beam can be reduced from approximately 0.06° FWHM to 0.014°. For the proposed electro-optical system, reaction times to pointing changes and vibrations are on a nanosecond time scale, much faster than those for fine pointing systems that use moving parts such as fast steering mirrors, including MEMS, or that use quad-cell photodetectors to improve the body pointing of the CubeSat. Other possible applications are to Optical Multiple Access (OMA)for simultaneously communicating with ground stations at different locations and to Wavelength-Division Multiplexing (WDM)for increasing data rate transmission.

HEC↗
DOE OSTI2026

TTDAQ: A Continuous Flow, Timing and Trigger DAQ System

Final Scientific/Technical Report for DOE Award DE-SC0019581, “TTDAQ: A Continuous Flow, Timing and Trigger DAQ System.” The report summarizes Telluric Labs’ Phase II STTR work developing silicon-photonic building blocks for a software-defined, continuous-flow, trigger-less data acquisition system for next-generation high-energy and nuclear-physics detectors. The project focused on radiation-hard photonic integrated circuits, remote optical illumination, dense wavelength-division multiplexing, and a differential microring-resonator transceiver architecture designed to improve high-speed optical link stability and bandwidth. The report describes project objectives, technical accomplishments, AIM Photonics tape-outs, bench characterization, radiation-hardness testing, deferred integration work, and potential applications beyond physics readout.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2002

An Analysis for the Use of Research and Education Networks and Commercial Network Vendors in Support of Space Based Mission Critical and Non-Critical Networking

Currently, and in the past, dedicated communication circuits and "network services" with very stringent performance requirements are being used to support manned and unmanned mission critical ground operations at GSFC, JSC, MSFC, KSC and other NASA facilities. Because of the evolution of network technology, it is time to investigate using other approaches to providing mission services for space ground operations. The current NASA approach is not in keeping with the evolution of network technologies. In the past decade various research and education networks dedicated to scientific and educational endeavors have emerged, as well as commercial networking providers, that employ advanced networking technologies. These technologies have significantly changed networking in recent years. Significant advances in network routing techniques, various topologies and equipment have made commercial networks very stable and virtually error free. Advances in Dense Wave Division Multiplexing will provide tremendous amounts of bandwidth for the future. The question is: Do these networks, which are controlled and managed centrally, provide a level of service that equals the stringent NASA performance requirements. If they do, what are the implication(s) of using them for critical space based ground operations as they are, without adding high cost contractual performance requirements? A second question is the feasibility of applying the emerging grid technology in space operations. Is it feasible to develop a Space Operations Grid and/or a Space Science Grid? Since these network's connectivity is substantial, both nationally and internationally, development of these sorts of grids may be feasible. The concept of research and education networks has evolved to the international community as well. Currently there are international RENs connecting the US in Chicago to and from Europe, South America, Asia and the Pacific rim, Russia and Canada. And most countries in these areas have their own research and education network as do many states in the USA.

Bradford, Robert N.↗
NASA NTRS2000

HTMT-class Latency Tolerant Parallel Architecture for Petaflops Scale Computation

Computational Aero Sciences and other numeric intensive computation disciplines demand computing throughputs substantially greater than the Teraflops scale systems only now becoming available. The related fields of fluids, structures, thermal, combustion, and dynamic controls are among the interdisciplinary areas that in combination with sufficient resolution and advanced adaptive techniques may force performance requirements towards Petaflops. This will be especially true for compute intensive models such as Navier-Stokes are or when such system models are only part of a larger design optimization computation involving many design points. Yet recent experience with conventional MPP configurations comprising commodity processing and memory components has shown that larger scale frequently results in higher programming difficulty and lower system efficiency. While important advances in system software and algorithms techniques have had some impact on efficiency and programmability for certain classes of problems, in general it is unlikely that software alone will resolve the challenges to higher scalability. As in the past, future generations of high-end computers may require a combination of hardware architecture and system software advances to enable efficient operation at a Petaflops level. The NASA led HTMT project has engaged the talents of a broad interdisciplinary team to develop a new strategy in high-end system architecture to deliver petaflops scale computing in the 2004/5 timeframe. The Hybrid-Technology, MultiThreaded parallel computer architecture incorporates several advanced technologies in combination with an innovative dynamic adaptive scheduling mechanism to provide unprecedented performance and efficiency within practical constraints of cost, complexity, and power consumption. The emerging superconductor Rapid Single Flux Quantum electronics can operate at 100 GHz (the record is 770 GHz) and one percent of the power required by convention semiconductor logic. Wave Division Multiplexing optical communications can approach a peak per fiber bandwidth of 1 Tbps and the new Data Vortex network topology employing this technology can connect tens of thousands of ports providing a bi-section bandwidth on the order of a Petabyte per second with latencies well below 100 nanoseconds, even under heavy loads. Processor-in-Memory (PIM) technology combines logic and memory on the same chip exposing the internal bandwidth of the memory row buffers at low latency. And holographic storage photorefractive storage technologies provide high-density memory with access a thousand times faster than conventional disk technologies. Together these technologies enable a new class of shared memory system architecture with a peak performance in the range of a Petaflops but size and power requirements comparable to today's largest Teraflops scale systems. To achieve high-sustained performance, HTMT combines an advanced multithreading processor architecture with a memory-driven coarse-grained latency management strategy called "percolation", yielding high efficiency while reducing the much of the parallel programming burden. This paper will present the basic system architecture characteristics made possible through this series of advanced technologies and then give a detailed description of the new percolation approach to runtime latency management.

Sterling, Thomas↗
NASA NTRS2004

Multisensor Instrument for Real-Time Biological Monitoring

The figure schematically depicts an instrumentation system, called a fiber optic-based integration system (FOBIS), that is undergoing development to enable real-time monitoring of fluid cell cultures, bioprocess flows, and the like. The FOBIS design combines a micro flow cytometer (MFC), a microphotometer (MP), and a fluorescence-spectrum- or binding-force-measuring micro-sensor (MS) in a single instrument that is capable of measuring multiple biological parameters simultaneously or sequentially. The fiber-optic-based integration system is so named because the MFC, the MP, and the MS are integrated into a single optical system that is coupled to light sources and photometric equipment via optical fibers. The optical coupling components also include a wavelength-division multiplexer and diffractive optical elements. The FOBIS includes a laserdiode- and fiber-optic-based optical trapping subsystem (optical tweezers ) with microphotometric and micro-sensing capabilities for noninvasive confinement and optical measurement of relevant parameters of a single cell or other particle. Some of the measurement techniques implemented together by the FOBIS have long been used separately to obtain basic understanding of the optical properties of individual cells and other organisms, the optical properties of populations of organisms, and the interrelationships among these properties, physiology of the organisms, and physical processes that govern the media that surround the organisms. For example, flow cytometry yields information on numerical concentrations, cross-sectional areas, and types of cells or other particles. Micro-sensing can be used to measure pH and concentrations of oxygen, carbon dioxide, glucose, metabolites, calcium, and antigens in a cell-culture fluid, thereby providing feedback that can be helpful in improving control over a bioprocess. Microphotometry (including measurements of scattering and fluorescence) can yield further information about optically trapped individual particles. In addition to the multifunctionality not previously available in a single biological monitoring system, the FOBIS offers advantages of low mass, sensitivity, accuracy, portability, low cost, compactness (the overall dimensions of the fully developed FOBIS sensor head are expected to be less than 1 by 1 by 2 cm), and immunity to electromagnetic interference at suboptical frequencies. FOBIS could be useful in a variety of laboratory and field settings in such diverse endeavors as medical, veterinary, and general biological research; medical and veterinary diagnosis monitoring of industrial bioprocesses; and analysis of biological contaminants in air, water, and food.

Zhang, Sean (Zhanxiang)↗
NASA NTRS2001

Offering an Array of Improvements

Sensors Unlimited, Inc., with SBIR funding from NASA's Langley Research Center, Goddard Space Flight Center, Marshall Space Flight Center, and the Jet Propulsion Laboratory, developed a monolithic focal plane array for near-infrared imaging. The company developed one- (1- D) and two-dimensional (2-D) imaging arrays consisting of a highly reliable InGaAs p-I-n diode as a photodetector for monitoring a variety of applications, including single element device applications in receivers. The InGaAs 1-D and 2-D arrays have many applications. For example, they monitor the performance of dense wavelength division multiplexing (DWDM) systems- the process of packaging many channels into a single fiber-optic cable. Sensors Unlimited commercially offers its LXTM and LYTM Series InGaAs linear arrays for reliable DWDM performance monitoring. The LX and LY arrays enable instrument module designs with no moving parts, which provides for superior uniformity, and fast, linear outputs that remain stable over a wide temperature range. Innovative technologies derived from the monolithic focal plane array have enabled telecommunication companies to optimize existing bandwidth in their fiber-optic networks in order to support a high volume of network traffic. At the same time, the technologies obtained from the array have the potential for reducing costs, while increasing performance from Sensors Unlimited's current product lines.

Source record↗
NASA NTRS1990

Digital angular position sensor using wavelength division multiplexing

Future aircraft will use fly-by-light control systems with fiber-linked optical sensors for such measurands as temperature, pressure, and linear and angular position. A digital optical sensor is described which was developed to transmit the angular position of such slowly rotating parts as a throttle of fuel flow control valve on an aircraft. The sensor employs a reflective code plate with ten channels providing a resolution of 0.35 degrees. Two light-emitting diodes with overlapping spectra are used as light sources. A single microoptic multiplexer-demultiplexer composed of a GRIN rod lens and a miniature grating is used to disperse the spectrum and recombine the spectral components from each channel after reflection by the code plate. The results of preliminary environmental tests of this unit are discussed. The sensor has been operated for brief periods of time between -60 C and +125 without adverse effects. Preliminary vibration tests indicate that the unit will work properly at the maximum vibration levels expected in a jet-engine environment.

Fritsch, Klaus↗
NASA NTRS1988

Service offerings and interfaces for the ACTS network of Earth stations

The Advanced Communications Satellite (ACTS) is capable of two modes of communication. Mode 1 is a mesh network of Earth stations using baseband-switched, time-division multiple-access (BBS-TDMA) and hopping beams. Mode 2 is a mesh network using satellite-switched, time-division multiple-access (SS-TDMA) and fixed (or hopping) beams. The purpose of this paper is to present the functional requirements and the design of the ACTS Mode 1 Earth station terrestrial interface. Included among the requirements are that: (1) the interface support standard telecommunications service offerings (i.e., voice, video and data at rates ranging from 9.6 kbps to 44 Mbps); (2) the interface support the unique design characteristics of the ACTS communications systems (e.g., the real time demand assignment of satellite capacity); and (3) the interface support test hardware capable of validating ACTS communications processes. The resulting interface design makes use of an appropriate combination of T1 or T3 multiplexers and a small central office (maximum capacity 56 subscriber lines per unit).

Coney, Thom A.↗
NASA NTRS1995

Overview of techniques for mitigation of fading and shadowing in the direct broadcast satellite radio environment

The DBS radio propagation environment is divided into three sub-environments, indoor, rural-suburban mobile and urban mobile. Indoor propagation effects are in a large part determined by construction material. Non-metallic materials afford direct, albeit attenuated penetration of the satellite signal with a minimum of multipath signal scattering. Signal penetration into structures using significant metallic materials is often indirect, through openings such as doors and windows and propagation will involve significant multipath components. Even so, delay spread in many situations is on the order of 10's of nanoseconds resulting in relatively flat fading. Thus frequency diversity techniques such as Orthogonal Frequency Division Multiplex (OFDM) and Code Division Multiple Access (CDMA) or equalization techniques do not realize their intended performance enhancement. Antenna diversity, directivity and placement are key mitigation techniques for the indoor environment. In the Rural-Suburban mobile environment with elevation angles greater than 20 deg, multipath components from the satellite signal are 15-20 dB below the line-of-sight signal level and often originate from nearby reflectors. Thus shadowing is the dominant signal impairment and fading effects are again found to be relatively flat for a large fading margin. Because receiver motion induces rapid variations in the signal level, temporal diversity techniques such as interleaving, channel coding and retransmission can be used to combat short intermittent fading events. Antenna diversity and directivity techniques are again useful in this environment. Finally, in the Urban mobile environment, slower vehicle speeds and blockage by buildings causes signal fades that are too long and too deep to combat with signal margin or time diversity. Land-based signal boosters are needed to fill in the coverage gaps of the satellite only broadcast scheme. On frequency boosters are suggested to conserve bandwidth yet these produce long delay multipath and create a frequency selective fading environment. Enter now OFDM, spread spectrum, equalization and other techniques that are capable of deconvolving the channel effects and effecting significant performance improvements by extracting the frequency diversity or time diversity components comprising the received signal.

Bell, David↗
NASA NTRS2004

Model of Atmospheric Links on Optical Communications from High Altitude

Optical communication links have the potential to solve many of the problems of current radio and microwave links to satellites and high-altitude aircraft. The higher frequency involved in optical systems allows for significantly greater signal bandwidth, and thus information transfer rate, in excess of 10 Gbps, and the highly directional nature of laser-based signals eliminates the need for frequency-division multiplexing seen in radio and microwave links today. The atmosphere, however, distorts an optical signal differently than a microwave signal. While the ionosphere is one of the most significant sources of noise and distortion in a microwave or radio signal, the lower atmosphere affects an optical signal more significantly. Refractive index fluctuations, primarily caused by changes in atmospheric temperature and density, distort the incoming signal in both deterministic and nondeterministic ways. Additionally, suspended particles, such as those in haze or rain, further corrupt the transmitted signal. To model many of the atmospheric effects on the propagating beam, we use simulations based on the beam-propagation method. This method, developed both for simulation of signals in waveguides and propagation in atmospheric turbulence, separates the propagation into a diffraction and refraction problem. The diffraction step is an exact solution, within the limits of numerical precision, to the problem of propagation in free space, and the refraction step models the refractive index variances over a segment of the propagation path. By applying refraction for a segment of the propagation path, then diffracting over that same segment, this method forms a good approximation to true propagation through the atmospheric medium. Iterating over small segments of the total propagation path gives a good approximation to the problem of propagation over the entire path. Parameters in this model, such as initial beam profile and atmospheric constants, are easily modified in a simulation such as this, which allows for the rapid analysis of different propagation scenarios. Therefore, this method allows the development of a near-optimal system design for a wide range of situations, typical of what would be seen in different atmospheric conditions over a receiving ground station. A simulation framework based upon this model was developed in FORTRAN, and for moderate grid sizes and propagation distances these simulations are computable in reasonable time on a standard workstation. This presentation will discuss results thus far.

Subich, Christopher↗
NASA NTRS2004

Whispering-Gallery-Mode Tunable Narrow-Band-Pass Filter

An experimental tunable, narrow-band-pass electro-optical filter is based on a whispering-gallery resonator. This device is a prototype of tunable filters needed for the further development of reconfigurable networking wavelength-division multiplexers and communication systems that utilize radio-frequency (more specifically, microwave) subcarrier signals on optical carrier signals. The characteristics of whispering-gallery resonators that make them attractive for such applications include high tuning speed, compactness, wide tuning range, low power consumption, and compatibility with single-mode optical fibers. In addition, relative to Fabry-Perot resonators, these devices offer advantages of greater robustness and lower cost. As described in several prior NASA Tech Briefs articles, a whispering-gallery resonator is a spheroidal, disk-like, or toroidal body made of a highly transparent material. It is so named because it is designed to exploit whispering-gallery electromagnetic modes, which are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. The experimental whispering-gallery tunable filter (see figure) is made from a disk of Z-cut LiNbO3 of 4.8-mm diameter and 0.17-mm thickness. The perimeter of the disk is rounded to a radius of curvature of 100 m. Metal coats on the flat faces of the disk serve as electrodes for exploiting the electro-optical effect in LiNbO3 for tuning. There is no metal coat on the rounded perimeter region, where the whispering-gallery modes propagate. Light is coupled from an input optical fiber into the whispering-gallery modes by means of a diamond prism. Another diamond prism is used to couple light from the whispering-gallery modes to an output optical fiber. This device is designed and operated to exploit transverse magnetic (TM) whispering- gallery modes, rather than transverse electric (TE) modes because the resonance quality factors (Q values) of the TM modes are higher. If Q values were not of major concern, it would be better to use the TE modes because the electro-optical shifts of the TE modes are 3 times those of the TM modes.

Savchenkov, Anatoliy↗