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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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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

The Antarctic Planet Interferometer

The Antarctic Planet Interferometer is an instrument concept designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperature found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at Dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.

interferometry↗
NASA NTRS2009

Modal Filters for Infrared Interferometry

Modal filters in the approximately equal to 10-micrometer spectral range have been implemented as planar dielectric waveguides in infrared interferometric applications such as searching for Earth-like planets. When looking for a small, dim object ("Earth") in close proximity to a large, bright object ("Sun"), the interferometric technique uses beams from two telescopes combined with a 180 phase shift in order to cancel the light from a brighter object. The interferometer baseline can be adjusted so that, at the same time, the light from the dimmer object arrives at the combiner in phase. This light can be detected and its infrared (IR) optical spectra can be studied. The cancellation of light from the "Sun" to approximately equal to 10(exp 6) is required; this is not possible without special devices-modal filters- that equalize the wavefronts arriving from the two telescopes. Currently, modal filters in the approximately equal to 10-micrometer spectral range are implemented as single- mode fibers. Using semiconductor technology, single-mode waveguides for use as modal filters were fabricated. Two designs were implemented: one using an InGaAs waveguide layer matched to an InP substrate, and one using InAlAs matched to an InP substrate. Photon Design software was used to design the waveguides, with the main feature all designs being single-mode operation in the 10.5- to 17-micrometer spectral range. Preliminary results show that the filter's rejection ratio is 26 dB.

Ksendzov, Alexander↗
NASA NTRS2013

Mass Gauging Demonstrator for Any Gravitational Conditions

The present invention is a mass gauging interferometry system used to determine the volume contained within a tank. By using an optical interferometric technique to determine gas density and/or pressure a much smaller compression volume or higher fidelity measurement is possible. The mass gauging interferometer system is comprised of an optical source, a component that splits the optical source into a plurality of beams, a component that recombines the split beams, an optical cell operatively coupled to a tank, a detector for detecting fringes, and a means for compression. A portion of the beam travels through the optical cell operatively coupled to the tank, while the other beam(s) is a reference.

Korman, Valentin↗
NASA NTRS2016

Optical Telescope System-Level Design Considerations for a Space-Based Gravitational Wave Mission

The study of the Universe through gravitational waves will yield a revolutionary new perspective on the Universe, which has been intensely studied using electromagnetic signals in many wavelength bands. A space-based gravitational wave observatory will enable access to a rich array of astrophysical sources in the measurement band from 0.1 to 100 mHz, and nicely complement observations from ground-based detectors as well as pulsar timing arrays by sampling a different range of compact object masses and astrophysical processes. The observatory measures gravitational radiation by precisely monitoring the tiny change in the proper distance between pairs of freely falling proof masses. These masses are separated by millions of kilometers and, using a laser heterodyne interferometric technique, the change in their proper separation is detected to approx. 10 pm over timescales of 1000 seconds, a fractional precision of better than one part in 10(exp 19). Optical telescopes are essential for the implementation of this precision displacement measurement. In this paper we describe some of the key system level design considerations for the telescope subsystem in a mission context. The reference mission for this purpose is taken to be the enhanced Laser Interferometry Space Antenna mission (eLISA), a strong candidate for the European Space Agency's Cosmic Visions L3 launch opportunity in 2034. We will review the flow-down of observatory level requirements to the telescope subsystem, particularly pertaining to the effects of telescope dimensional stability and scattered light suppression, two performance specifications which are somewhat different from the usual requirements for an image forming telescope.

LISA↗
NASA NTRS2018

The Influence of Dihedral Angle Error Stability on Beam Deviation for Hollow Retro-Reflectors

Retro-reflectors consist of three reflective optical surfaces, which are oriented to reflect the input beam by 180 ◦. For retro-reflector components, it is common to specify an angular beam deviation tolerance, or rather the deviation from the exact 180 def return direction. Precision-aligned retro-reflectors provide 180 deg beam deviation with tolerances on the order of an arcsecond. It is well known that the performance of the retro-reflector depends on the ability to precisely orient the reflective surfaces at mutually perpendicular angles. Precision assembly is therefore critical to ensure highly accurate beam deviation. The dihedral angle errors, and hence the reflected beam deviation, can be measured for the retro-reflector after fabrication, typically by using interferometric techniques. Yet, what is not commonly reported for a fabricated retro-reflector is the stability of the angular beam deviation. For instance, thermo-mechanical effects of the components will contribute to variations in the return beam direction. While the actual stability is design-specific one can develop a mathematical representation for the expected change in the reflected beam direction as a function of the variation in the dihedral angle errors. Presented here is a mathematical formulation for a hollow retro-reflector's beam deviation as a function of the dihedral angle error stability.

Swank, Aaron J.↗
NASA NTRS2019

Spectrally Resolved Synthetic Aperture Imaging Interferometer: Final Report of NASA Innovative Advanced Concepts - Phase 1 Study

The Spectrally Resolved Synthetic-Aperture Imaging Interferometer (SRSAII) is a system proposed to provide high-resolution and high-sensitivity measurements of astronomical objects. SRSAII uses long baseline interferometric methods to achieve the resolution and low-noise, high time-precision detection to achieve the sensitivity. The primary goal of the SRSAII study was to lay out a framework for using new optical physics technologies to directly resolve, both spatially and spectrally, the disk of an exoplanet. In addition to the ambitious goal of directly resolving an exoplanet, the SRSAII team also sought to identify science opportunities achievable with intermediate system configurations which may offer resolution significantly higher than the current state of the art, but insufficient for direct resolution of an exoplanetary disk. An operational SRSAII system can function with essentially arbitrarily large baselines, achieving correspondingly high angular resolution. The primary limitation occurs in the system sensitivity, which became the major technical focus for study. In this report, we compare the predicted performance (sensitivity in SNR (Signal-to-Noise Ratio) along with angular resolution) of three interferometric techniques: direct detection (also known as homodyne interferometry), multi-channel intensity interferometry (using the Hanbury Brown and Twiss effect), and multi-channel heterodyne interferometry (using an optical frequency comb as a local oscillator). Additionally, quantum-assisted interferometry is also explored as a prospective enhancement of established methods. This report presents a survey of the technologies that enable the SRSAII techniques - optical frequency combs, single photon detectors, and photonic integrated circuits. These technologies are the basis of methods critical to SRSAII's success: precision timing, length and frequency metrology, sensitive photodetection, fine-scale wavelength filtering, and dense multi-channel operation. Lastly, we give some notional performance metrics and propose some possible experimental observations.

High Resolultion↗
NASA NTRS2018

NASA’s and ESA’s Tracking Networks, A Decade of Strategic Partnership for Solar System Exploration

Planetary missions travel vast distances in the Solar System for valuable scientific exploration. Spacecraft return data to Earth via radio links that suffer power losses inversely proportional to the square of the distance, which forms a tremendous engineering challenge compounded by relatively low onboard transmitter power, typically 20 Watts at X-band (~8 GHz). Deep space missions are enabled only because leading space agencies invested in developing very large communications antennas as well as provided a sophisticated suite of tracking, telemetry and command standard services. NASA’s Deep Space Network and ESA’s ESTRACK network are distributed geographically to provide global coverage and utilize stations ranging in size from 34 meters to 70 meters in diameter. Over time, the expanding number of missions, increased requirements for redundancy during critical events as well as the drive for improved navigation accuracy via long-baseline interferometric techniques, increased the networks’ loading and strongly motivated collaboration between the two agencies. Ten years ago, NASA and ESA established a cross-support agreement in addition to multiple on-going mission-specific agreements to meet this need. This strategic partnership was enabled by the development of international inter-operability technical standards and compatible spectrum usage. Over recent years, many critical events were supported via these agreements and some scientific breakthroughs were enabled. A multi-nation tracking contention period envisioned in the near future will also benefit from this partnership. Due to its success over the last decade, the DSN-ESTRACK partnership is serving as a model for other agencies with deep space communication facilities and similar interest. This paper reviews the benefits and lessons learned from collaborative deep space exploration, especially via communications networks, and discusses the potential implementation of similar NASA agreements with other space agencies.

Costrell, Jim↗
NASA NTRS2023

Radioastron Discovery of A Mini-Cocoon Around the Restarted Parsec-Scale Jet in 3C 84

We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C 84 (NGC 1275) at the centre of the Perseus cluster. The observations were carried out during a perigee passage of the Spektr-R spacecraft on September 21–22, 2013 and involved a global array of 24 ground radio telescopes observing at 5 GHz and 22 GHz, together with the Space Radio Telescope (SRT). Furthermore, the Very Long Baseline Array (VLBA) and the phased Very Large Array (VLA) observed the source quasi-simultaneously at 15 GHz and 43 GHz. Fringes between the ground array and the SRT were detected on baseline lengths up to 8.1 times the Earth’s diameter, providing unprecedented resolution for 3C 84 at these wavelengths. We note that the corresponding fringe spacing is 125 μas at 5 GHz and 27 μas at 22 GHz. Our space-VLBI images reveal a previously unseen sub-structure inside the compact ∼1 pc long jet that was ejected about ten years earlier. In the 5 GHz image, we detected, for the first time, low-intensity emission from a cocoon-like structure around the restarted jet. Our results suggest that the increased power of the young jet is inflating a bubble of hot plasma as it carves its way through the ambient medium of the central region of the galaxy. Here, we estimate the minimum energy stored in the mini-cocoon, along with its pressure, volume, expansion speed, and the ratio of heavy particles to relativistic electrons, as well as the density of the ambient medium. About half of the energy delivered by the jet is dumped into the mini-cocoon and the quasi-spherical shape of the bubble suggests that this energy may be transferred to a significantly larger volume of the interstellar medium than what would be accomplished by the well-collimated jet on its own. The pressure of the hot mini-cocoon also provides a natural explanation for the almost cylindrical jet profile seen in the 22 GHz RadioAstron image.

galaxies: jets↗
NASA NTRS1986

A modified hybrid mapping technique for VLBI data

A modified interferometric mapping technique is presented for observations where absolute phase information is not available. This is especially applicable to VLBI observations. The technique corrects weaknesses of conventional hybrid mapping methods in measuring source symmetry, particularly for arrays with an outrigger antenna. An example of such an array is a set of earth-based antennas plus an orbiting antenna.

Linfield, R. P.↗
NASA NTRS1993

Fiber optic and laser sensors X; Proceedings of the Meeting, Boston, MA, Sept. 8-11, 1992

Topics addressed include acoustic and pressure sensors; fiber optic gyros; electric and magnetic field sensors; bend, strain, and temperature sensors; industrial applications of sensors; and processing techniques. Particular attention is given to fiber optic interferometric acoustic sensors for wind tunnel applications, polished coupler and resonator fabrication, second-harmonic detection for rotation sensing in fiber optic gyros, simplified control theory in closed-loop fiber optic gyroscopes, and a Fabry-Perot sensor with digital signal processing for the measurement of magnetostriction. Also discussed are a Bragg fiber laser sensor, commercialization of fiber optic strain gauge systems, thermal ignition in hazardous environments due to stray light from optical fibers, a system for absolute measurements by interferometric sensors, and high-performance interferometric demodulation techniques.

Udd, Eric↗
NASA NTRS1994

Direct observation of crystal growth from solution using optical investigation of a growing crystal face

The first technical report for the period 1 Jan. 1993 till 31 Dec. 1993 for the research entitled, 'Direct observation of crystal growth from solution using Optical Investigation of a growing crystal Face' is presented. The work on the project did not start till 1 June 1993 due to the non-availability of the required personnel. The progress of the work during the period 1 June 1993 till the end of 1993 is described. Significant progress was made for testing various optical diagnostic techniques for monitoring crystal solution. Some of the techniques that are being tested are: heterodyne detection technique, in which changes in phase are measured as a interferometric function of time/crystal growth; a conventional technique, in which a fringe brightness is measured as a function of crystal growth/time; and a Mach-Zehnder interferometric technique in which a fringe brightness is measured as a function of time to obtain information on concentration changes. During the second year it will be decided to incorporate the best interferometric technique along with the ellipsometric technique, to obtain real time in-situ growth rate measurements. A laboratory mock-up of the first two techniques were made and tested.

Lal, Ravindra↗
NASA NTRS2017

ALMA Mapping of Rapid Gas and Dust Variations in Comet C/2012 S1 (ISON): New Insights into the Origin of Cometary HNC

Observations of the sungrazing comet C/2012 S1 (ISON) were carried out using the Atacama Large Millimeter/submillimeter Array at a heliocentric distance of 0.58-0.54 AU (Astronomical Units) (pre-perihelion) on 2013 November 16-17. Temporally resolved measurements of the coma distributions of HNC, CH3OH, H2CO, and dust were obtained over the course of about an hour on each day. During the period UT 10:10-11:00 on November 16, the comet displayed a remarkable drop in activity, manifested as a greater than 42 percent decline in the molecular line and continuum fluxes. The H2CO observations are consistent with an abrupt, approximately 50 percent reduction in the cometary gas production rate soon after the start of our observations. On November 17, the total observed fluxes remained relatively constant during a similar period, but strong variations in the morphology of the HNC distribution were detected as a function of time, indicative of a clumpy, intermittent outflow for this species. Our observations suggest that at least part of the detected HNC originated from degradation of nitrogen-rich organic refractory material, released intermittently from confined regions of the nucleus. By contrast, the distributions of CH3OH and H2CO during the November 17 observations were relatively uniform, consistent with isotropic outflow and stable activity levels for these species. These results highlight a large degree of variability in the production of gas and dust from comet ISON during its pre-perihelion outburst, consistent with repeated disruption of the nucleus interspersed with periods of relative quiescence.

techniques: interferometric↗
NASA NTRS2017

Snow Accumulation Variability on a West Antarctic Ice Stream Observed with GPS Reflectometry, 2007-2017

Land ice loss from Antarctica is a significant and accelerating contribution to global sea level rise; however, Antarctic mass balance estimates are complicated by insufficient knowledge of surface mass balance processes such as snow accumulation. Snow accumulation is challenging to observe on a continental scale and in situ data are sparse, so we largely rely on estimates from atmospheric models. Here we employ a novel technique, GPS interferometric reflectometry (GPS-IR), to measure upper (less than 2 m) firn column thickness changes across a 23-station GPS array in West Antarctica. We compare the results with antenna heights measured in situ to establish the method's daily uncertainty (0.06 m) and with output from two atmospheric reanalysis products to categorize spatial and temporal variability of net snow accumulation. GPS-IR is an effective technique for monitoring surface mass balance processes that can be applied to both historic GPS data sets and future experiments to provide critical in situ observations of processes driving surface height evolution.

snow↗