Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Direct detection”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Source self-mixing in the detection of extended incoherent sources

We consider the self-beating of incoherent light from an extended source at a wideband photomixer. The intermediate frequency mean squared current is found to be proportional to the product of the direct detected source power and the power within the IF bandpass about the optical frequency and within the heterodyne field of view. Thus the ratio of the heterodyne signal to self-beating power is proportional to the ratio of local oscillator power to direct detected power. This ratio is usually large for systems employing efficient local oscillators that generate shot-noise-limited operation. In less efficient systems, such as those employing tunable diode lasers, the effects of self-mixing may be significant.

Cohen, S. C.↗
NASA NTRS2004

The Role of Coherent Detection

Many interesting astronomical objects, such as galaxies, molecular clouds, PDRs, star - forming regions, protostars, evolved stars, planets, and comets, have rich submillimeter spectra. In order to avoid line blending, and to be able to resolve the line shape, it is often necessary to measure these spectra at high resolution. This paper discusses the relative advantages and limitations of coherent and direct detection for high resolution spectroscopy in the submillimeter and far - infrared. In principle, direct detection has a fundamental sensitivity advantage. In practice, it is di.cult to realize this advantage given the sensitivities of existing detectors and reasonable constraints on the instrument volume. Thus, coherent detection can be expected to play an important role in submillimeter and far - infrared astrophysics well into the future.

Zmuidzinas, J.↗
NASA NTRSDate not supplied

On the Hunt for Detectable Biosignatures in Jezero Crater: What to Look for and Where

Introduction: The Perseverance rover, which is currently exploring Jezero crater on Mars, is equipped with seven instruments that allow for observation of textures, minerals, color, structure, and chemistry of rocks and sediments in order to search for signs of ancient life, understand the geologic history of the crater, and identify candidates for sample return (Farley et al. 2020). The first of these aims includes the direct detection of potential biosignatures, including textures, organic molecules, minerals, and elemental chemistries that are of biogenic origin (Mustard et al. 2013). The presence of these biosignatures will be constrained by the habitability of the local region, the preservation potential of the host rocks, and the sensitivity of the instrument suite, and their biogenicity will be investigated after return to Earth as part of the Mars Sample Return campaign. Here, we examine key targets on the three planned campaigns, potential biosignatures that may be present, and the capabilities of key rover instruments. High Potential Biosignature Sites in Jezero: To date, measurements have been made on multiple sites that both contain minerals known in terrestrial settings to preserve biosignatures and likely were habitable settings (Williford et al. 2021). Two examples include the fine-grained rocks at the base of the delta fan and the NW inner margin of the crater. Fine-grained Rocks at Base of Delta Fan. Fine-grained, clay-bearing rocks may have been deposited as muddy lake sediments that could have hosted life and preserved biosignatures settling out of the water column. The report of organic molecules by the Curiosity rover in the Sheepbed mudstone and Murray formation has highlighted this site in particular. Potential biosignatures in mudstones, especially those rich in silica (McMahon et al. 2018), microbialites and complex organics. NW Inner Margin of Crater. This unit, located along the inner margin of the crater, contains strong carbonate signatures and may have been the littoral zone of a lake (Horgan et al. 2020). The potential biosignatures here include microfossils, microbialites, biominerals, and complex organics. Detectability of Biosignatures by the Mars 2020 Instrument Suite: The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument comprises a Deep UV spectrometer, context imager, and color camera to generate spatially resolved chemical maps (Bhartia et al. 2020). It is sensitive to trace organics as well as a range of minerals and can detect native fluorescence from aromatic organics; the WATSON and ACI cameras can be used to observe morphologies such as stromatolitic laminations or filaments ranging from the tens of micron to millimeter scale. SHERLOC can detect organics that may be present in either of the high potential biosignature targets, as well as detect carbonates in the latter. However, the presence of high amounts of iron, such as in iron-rich clays, would cause attenuation of spectral response through UV absorption. The Planetary Instrument for X-ray Lithochemistry (PIXL) comprises an X-ray fluorescence spectrometer and camera that can scan rock surfaces to generate elemental maps (Allwood et al. 2020). PIXL can detect chemical biosignatures such as spatial variations of elemental abundances that may have resulted from biological activity. PIXL would be particularly useful in detecting fine textures and elemental chemistries in either high potential biosignature target, but cannot directly detect minerals such as carbonate. The SuperCam instrument performs three types of spectroscopy, color imaging, and acoustic recording to remotely examine elemental composition, minerals, organics, and textures (Maurice et al. 2021). Using laser induced breakdown spectroscopy and time resolved luminescence spectroscopy, SuperCam can detect major elemental building blocks of organics (i.e., C, H, N, O, P, S) and conjugated organic structures, respectively, which may be found in either site. While in other contexts, luminescence is a useful tool for biosignature identification, luminescence generated by the 532 nm laser may obscure the Raman signal. Conclusion: The three instruments discussed can be used collaboratively to establish the presence of potential biosignatures in samples. These high-priority samples may then be returned to Earth for detailed laboratory analysis.

S. Sharma↗
NASA NTRS2001

A Ten-Meter Ground-Station Telescope for Deep-Space Optical Communications: A Preliminary Design

This article describes a telescope design for a 10-m optical ground station for deep-space communications. The design for a direct-detection optical communications telescope differs dramatically from a telescope for imaging applications. In general, the requirements for optical manufacturing and tracking performance are much less stringent for direct detection of optical signals. The technical challenge is providing a design that will operate in the daytime/nighttime conditions required for a Deep Space Network tracking application. The design presented addresses these requirements. The design will provide higher performance at lower cost than existing designs.

Britcliffe, M.↗
NASA NTRS1989

Application of super smooth optics to extra-solar planet detection

The observational constraints on direct detection of extrasolar planets around nearby stars are defined. The design of an instrument capable of meeting these goals requires the efficient reduction of diffracted and scattered light by about three orders of magnitude below the airy wings of the unapodized aperture. The diffraction reduction is achieved through the high-efficiency coronagraph, which uses Gaussian occulting masks in the first focus to concentrate better diffracted light in the pupil plane. Laboratory experiments confirm this high efficiency to the limits set by the experimental setup. Scattering due to midspatial scale figure error in the mirrors must also be reduced to a comparable level.

Terrile, Richard J.↗
NASA NTRS2022

Cosmological constraints on dark matter interactions with ordinary matter

Dark matter interactions with electrons or protons during the early Universe leave imprints on the cosmic microwave background and the matter power spectrum, and can be probed through cosmological and astrophysical observations. These interactions lead to momentum and heat exchange between the ordinary and dark matter components, which in turn results in a transfer of pressure from the ordinary to the dark matter. We explore these interactions using a diverse suite of data: cosmic microwave background anisotropies, baryon acoustic oscillations, the Lyman-α forest, and the abundance of Milky-Way subhalos. We derive constraints using model-independent parameterizations of the dark matter–electron and dark matter–proton interaction cross sections and map these constraints onto concrete dark matter models. Our constraints are complementary to other probes of dark matter interactions with ordinary matter, such as direct detection, big bang nucleosynthesis, various astrophysical systems, and accelerator based experiments. They exclude sufficiently large cross sections for a large range of dark matter masses, which cannot be accessed by direct-detection experiments due to the overburden from the Earth’s atmosphere or crust.

Manuel A. Buen-Abad↗
NASA NTRS1985

A comparison of Doppler lidar wind sensors for Earth-orbit global measurement applications

Now, there are four Doppler lidar configurations which are being promoted for the measurement of tropospheric winds: (1) the coherent CO2 Lidar, operating in the 9 micrometer region using a pulsed, atmospheric pressure CO2 gas discharge laser transmitter, and heterodyne detection; (2) the coherent Neodymium doped YAG or Glass Lidar, operating at 1.06 micrometers, using flashlamp or diode laser optical pumping of the solid state laser medium, and heterodyne detection; (3) the Neodymium doped YAG/Glass Lidar, operating at the doubled frequency (at 530 nm wavelength), again using flashlamp or diode laser pumping of the laser transmitter, and using a high resolution tandem Fabry-Perot filter and direct detection; and (4) the Raman shifted Xenon Chloride Lidar, operating at 350 nm wavelength, using a pulsed, atmospheric pressure XeCl gas discharge laser transmitter at 308 nm, Raman shifted in a high pressure hydrogen cell to 350 nm in order to avoid strong stratospheric ozone absorption, also using a high resolution tandem Fabry-Perot filter and direct detection. Comparisons of these four systems can include many factors and tradeoffs. The major portion of this comparison is devoted to efficiency. Efficiency comparisons are made by estimating the number of transmitted photons required for a single pulse wind velocity estimate of + or - 1 m/s accuracy in the middle troposphere, from an altitude of 800 km, which is assured to be reasonable for a polar orbiting platform.

Menzies, Robert T.↗
NASA NTRS1988

A laser communication experiment utilizing the ACT satellite and an airborne laser transceiver

The launch of a laser communication transmitter package into geosynchronous Earth orbit onboard the Advanced Communications Technology Satellite (ACTS) will present an excellent opportunity for the experimental reception of laser communication signals transmitted from a space orbit. The ACTS laser package includes both a heterodyne transmitter (Lincoln Labs design) and a direct detection transmitter (Goddard Space Flight Center design) with both sharing some common optical components. NASA Lewis Research Center's Space Electronics Division is planning to perform a space communication experiment utilizing the GSFC direct detection laser transceiver. The laser receiver will be installed within an aircraft provided with a glass port for the reception of the signal. This paper describes the experiment and the approach to performing such an experiment. Described are the constraints placed on the NASA Lewis experiment by the performance parameters of the laser transmitter and by the ACTS spacecraft operations. The conceptual design of the receiving terminal is given; also included is the anticipated capability of the detector.

Provencher, Charles E., Jr.↗
NASA NTRS1987

Comparison of direct and heterodyne detection optical intersatellite communication links

The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and tracking errors, optimal antenna gains exist that will minimize the required transmitter power. In addition to limiting the antenna gains, random pointing and tracking errors also impose a power penalty in the link budget. This power penalty is between 1.6 to 3 dB for a direct detection QPPM link, and 3 to 5 dB for a heterodyne QFSK system. For the heterodyne systems, the carrier phase noise presents another major factor of performance degradation that must be considered. In contrast, the loss due to synchronization error is small. The link budgets for direct and heterodyne detection systems are evaluated. It is shown that, for systems with large pointing and tracking errors, the link budget is dominated by the spatial tracking error, and the direct detection system shows a superior performance because it is less sensitive to the spatial tracking error. On the other hand, for systems with small pointing and tracking jitters, the antenna gains are in general limited by the launch cost, and suboptimal antenna gains are often used in practice. In which case, the heterodyne system has a slightly higher power margin because of higher receiver sensitivity.

Chen, C. C.↗
NASA NTRS2014

Advanced Photodetectors for Space Lidar

The detector in a space lidar plays a key role in the instrument characteristics and performance, especially in direct detection lidar. The sensitivity of the detector is usually the limiting factor when determining the laser power and the receiver aperture size, which in turn determines the instrument complexity and cost. The availability of a suitable detector is often a deciding factor in the choice of lidar wavelengths. A direct detection lidar can achieve the highest receiver performance, or the quantum limit, when its detector can detect signals at the single photon

PMT↗
NASA NTRS2005

Advanced Opto-Electronics (LIDAR and Microsensor Development)

Our overall intent in this aspect of the project were to establish a collaborative effort between several departments at Montana State University for developing advanced optoelectronic technology for advancing the state-of-the-art in optical remote sensing of the environment. Our particular focus was on development of small systems that can eventually be used in a wide variety of applications that might include ground-, air-, and space deployments, possibly in sensor networks. Specific objectives were to: 1) Build a field-deployable direct-detection lidar system for use in measurements of clouds, aerosols, fish, and vegetation; 2) Develop a breadboard prototype water vapor differential absorption lidar (DIAL) system based on highly stable, tunable diode laser technology developed previously at MSU. We accomplished both primary objectives of this project, in developing a field-deployable direct-detection lidar and a breadboard prototype of a water vapor DIAL system. Paper summarizes each of these accomplishments.

Vanderbilt, Vern C.↗
NASA NTRS2008

New Worlds Observer Formation Control Design Based on the Dynamics of Relative Motion

The New Worlds Observer (NWO) mission is designed for the direct detection and characterization of extrasolar planets. The NWO mission concept employs a two spacecraft leader-follower formation on a trajectory around the Earth/Moon-Sun L(sub 2) Libration Point. The leader spacecraft is baselined as a 4 meter optical telescope. The follower, Starshade spacecraft, is designed to suppress light from a central body star permitting direct detection of a surrounding exoplanetary system. The current design requires a nominal leader-follower separation range of 72 Megameters. NWO poses many challenges including formation control. NWO cycles between three principal control modes during the nominal mission timeline: science (fine pointing), realignment and transition. This paper examines formation control strategies in the context of dynamics of relative motion for two spacecraft operating in the vicinity of the Earth/Moon-Sun L(sub 2)libration point. The paper presents an overview of the equations of relative motion followed by a discussion of each of the control modes. Discussion and analysis characterize control strategies for each of the mission control modes, including requirements, implementation challenges and project fuel budgets.

Luquette, Richard J.↗
NASA NTRS2003

Survey for Life-related Species During a Planetary Surface Exploration; System Type I - UV Stimulated Fluorescent Sensor

The widely accepted minimum requirements for life on Earth include the presence of water and accessible sources of carbon. We assume that the same criteria must hold for putative life on past or present Mars. The evidence for CO2 and H2O at or near the Martian surface, carbon in Martian meteorites, aqueous alteration, and probable hydrothermal activity suggest that conditions conducive to the origin and evolution of life on Mars may have existed for long periods of time and may still obtain at present. Surface exploration on Mars that enables the direct detection of water in minerals and of organic carbon (including not just organic and biogenic materials but their degradation products such as kerogen-like hydrocarbons and graphitized carbon) that might be products or residues of biologic activity, is crucial. The search for evidence of life, past or present, will nevertheless be difficult. The lack of direct evidence for organic carbon and the low amounts of water found in the soils at the Viking sites demonstrated the difficulties. Recent results of GRS experiment of Odyssey mission indicated the existence of abundant water ice beneath the Mars surface. Mineralogical evidence for the presence of carbonate, sulfates, or clay minerals, products of weathering and aqueous deposition, have not been identified unambiguously on Mars. Rocks such as shales and, more particularly, limestones, which we associate with moist and benign environments on Earth, are evidently not abundant. Presumably, then, neither were the photosynthetic organisms that might have produced them. In addition, the harsh present environment on Mars (e.g., dryness, low temperatures, large temperature cycles, high level of UV light on the surface, frequent dust storms, etc.) can both destroy carbon- and water-bearing materials and hide them. Therefore, directly detecting life-related materials on Mars was likened to seeking and examining proverbial needles in haystacks. We argue that survey type instruments, that can frequently and quickly check a relatively large amount of material at many locations during a mission, are essential.

Wang, Alian↗
NASA NTRS1994

Conceptual radiometer design studies for Earth observations from low Earth orbit

A conceptual radiometer design study was performed to determine the optimum design approach for spaceborne radiometers in low Earth orbit. Radiometric system configurations which included total power radiometers, unbalanced Dicke radiometers, and balanced Dicke, or as known as noise injection, radiometers were studied. Radiometer receiver configurations which were analyzed included the direct detection radiometer receiver, the double sideband homodyne radiometer receiver, and the single sideband heterodyne radiometer receiver. Radiometer system performance was also studied. This included radiometric sensitivity analysis of the three different radiometer system configurations studied. Both external and internal calibration techniques were analyzed. An accuracy analysis with and without mismatch losses was performed. It was determined that the balanced Dicke radiometer system configuration with direct detection receivers and external calibrations was optimum where frequent calibration such as once per minute were not feasible.

Harrington, Richard F.↗
NASA NTRS1994

Integration and test of high-speed transmitter electronics for free-space laser communications

The NASA Lewis Research Center in Cleveland, Ohio, has developed the electronics for a free-space, direct-detection laser communications system demonstration. Under the High-Speed Laser Integrated Terminal Electronics (Hi-LITE) Project, NASA Lewis has built a prototype full-duplex, dual-channel electronics transmitter and receiver operating at 325 megabit S per second (Mbps) per channel and using quaternary pulse-position modulation (QPPM). This paper describes the integration and testing of the transmitter portion for future application in free-space, direct-detection laser communications. A companion paper reviews the receiver portion of the prototype electronics. Minor modifications to the transmitter were made since the initial report on the entire system, and this paper addresses them. The digital electronics are implemented in gallium arsenide integrated circuits mounted on prototype boards. The fabrication and implementation issues related to these high-speed devices are discussed. The transmitter's test results are documented, and its functionality is verified by exercising all modes of operation. Various testing issues pertaining to high-speed circuits are addressed. A description of the transmitter electronics packaging concludes the paper.

Soni, Nitin J.↗
NASA NTRS1986

The NCAR Airborne Infrared Lidar System (NAILS)

A planned airborne lidar system is presented which is intended to provide a remote sensing facility for a variety of applications. The eventual goal of the system development is a Doppler wind measurement capability for boundary layer dynamics and cloud physics applications. The first stage of development is focused initially on a direct detection lidar to measure aerosol profiles and depolarization from cloud backscatter. Because of the Doppler goal, interest in larger particles to define the top of the mixed layer, and eye safety, the first stage of the system is based on a pulsed CO2 laser. A compact, relatively simple and inexpensive system that achieves flexibility to meet the data requirements of a variety of investigators by being easily modified rather than having many different capabilities built in is the goal. Although the direct detection sensitivity is less than that for heterodyne detection, the simpler system allows the achievement of useful scientific results and operating experience towards more complex lidars while staying within budget and time constraints.

Schwiesow, R. L.↗
NASA NTRS2010

TPSAS-NF1676L-10746-DND

This paper presents the design, development, and field testing of a high sensitivity ground-based Differential Absorption Lidar (DIAL) system that was developed under the NASA Instrument Incubator Program. The investigation presents a significant advancement towards the development of future CO2 profiling capability as it incorporates key elements of technologies needed for a future development of global CO2 measuring systems including: (1) 2-μm laser technologies that have been developed under a number of NASA programs including the Laser Risk Reduction Program (LRRP) (2) A novel high quantum efficiency (QE), high gain (without excess noise factor), and low noise phototransistor, and (3) Direct detection DIAL system using a large collection area receiver that is insensitive to speckle and coherence length effects from atmospheric turbulence that influences heterodyne detection systems. The objective of the project was a system TRL of 4, and the goal was TRL 5. Development and testing of the laser, new detector, and receiver systems during the project, integration into a complete lidar system into a trailer, field testing of system at West Branch, IA and comparison of the lidar CO2 measurements with in situ sensors advanced the system to a TRL of 5. The system demonstrated high vertical resolution CO2 profiling capability within the boundary layer and column measurements to long ranges. This is the first direct detection demonstration of a 2-micron CO2 DIAL high vertical resolution capability from instrument concept to field demonstration.

Syed Ismail↗
NASA NTRS2004

Extra Solar Planetary Imaging Coronagraph and Science Requirements for the James Webb Telescope Observatory

1) Extra solar planetary imaging coronagraph. Direct detection and characterization of Jovian planets, and other gas giants, in orbit around nearby stars is a necessary precursor to Terrestrial Planet Finder 0 in order to estimate the probability of Terrestrial planets in our stellar neighborhood. Ground based indirect methods are biased towards large close in Jovian planets in solar systems unlikely io harbor Earthlike planets. Thus to estimate the relative abundances of terrestrial planets and to determine optimal observing strategies for TPF a pathfinder mission would be desired. The Extra-Solar Planetary Imaging Coronagraph (EPIC) is such a pathfinder mission. Upto 83 stellar systems are accessible with a 1.5 meter unobscured telescope and coronagraph combination located at the Earth-Sun L2 point. Incorporating radiometric and angular resolution considerations show that Jovians could be directly detected (5 sigma) in the 0.5 - 1.0 micron band outside of an inner working distance of 5/D with integration times of -10 - 100 hours per observation. The primary considerations for a planet imager are optical wavefront quality due to manufacturing, alignment, structural and thermal considerations. pointing stability and control, and manufacturability of coronagraphic masks and stops to increase the planetary-to- stellar contrast and mitigate against straylight. Previously proposed coronagraphic concepts are driven to extreme tolerances. however. we have developed and studied a mission, telescope and coronagraphic detection concept, which is achievable in the time frame of a Discovery class NASA mission. 2) Science requirements for the James Webb Space Telescope observatory. The James Webb Space Observatory (JWST) is an infrared observatory, which will be launched in 201 1 to an orbit at L2. JWST is a segmented, 18 mirror segment telescope with a diameter of 6.5 meters, and a clear aperture of 25 mA2. The telescope is designed to conduct imaging and spectroscopic observations from 0.6-27 microns. The primary mirror find and understand predicted first light objects, observe galaxies back to their earliest precursors so that we can understand their growth and evolution, unravel the birth and early evolution of stars and planetary systems, and study planetary systems and the origins of life. In this paper we discuss the science goals for JWST in the context of the performance requirements they levy on the observatory.

Clampin, Mark↗