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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Infrared Heterodyne Spectroscopy and its Unique Application to Planetary Studies

Since the early 1970's the infrared heterodyne technique has evolved into a powerful tool for the study of molecular constituents, temperatures, and dynamics in planetary atmospheres. Its extremely high spectral resolution (Lambda/(Delta)Lambda/>10(exp 6)) and highly accurate frequency measurement (to 1 part in 10(exp 8)) enabled the detection of nonthermal/natural lasing phenomena on Mars and Venus; direct measurements of winds on Venus, Mars, and Titan; study of mid-infrared aurorae on Jupiter; direct measurement of species abundances on Mars (ozone, isotopic CO2), hydrocarbons on Jupiter, Saturn., Neptune, and Titan, and stratospheric composition in the Earth's stratosphere (O3, CIO, N2O, CO2 ....). Fully resolved emission and absorption line shapes measured by this method enabled the unambiguous retrieval of molecular abundances and local temperatures and thermal structure in regions not probed by other techniques. The mesosphere of Mars and thermosphere of Venus are uniquely probed by infrared heterodyne spectroscopy. Results of these studies tested and constrained photochemical and dynamical theoretical models describing the phenomena measured. The infrared heterodyne technique will be described. Highlights in its evolution to today's instrumentation and resultant discoveries will be presented, including work at Goddard Space Flight Center and the University of Koln. Resultant work will include studies supporting NASA and ESA space missions and collaborations between instrumental and theoretical groups.

Kostiuk, Theodore↗
NASA NTRS2010

Measuring Cyclic Error in Laser Heterodyne Interferometers

An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-

Ryan, Daniel↗
NASA NTRS2010

Ground Based Observation of Isotopic Oxygen in the Martian Atmosphere Using Infrared Heterodyne Spectroscopy

Infrared heterodyne spectra of isotopic CO2 in the Martian atmosphere were obtained using the Goddard Heterodyne Instrument for Planetary Wind and Composition, HIPWAC, which was interfaced with the 3-meter telescope at the NASA Infrared Telescope Facility- Spectra were colle cted at a resolution of lambda/delta lambda=10(exp 7). Absorption fea tures of the CO2 isotopologues have been identified from which isotop ic ratios of oxygen have been determined. The isotopic ratios O-17/O -16 and O-18/O-16 in the Martian atmosphere can be related to Martian atmospheric evolution and can be compared to isotopic ratios of oxyg en in the Earth's atmosphere. Isotopic carbon and oxygen are importa nt constraints on any theory for the erosion of the Martian primordia l atmosphere and the interaction between the atmosphere and surface o r subsurface chemical reservoirs. This investigation explored the pr esent abundance of the stable isotopes of oxygen in Mars' atmospheric carbon dioxide by measuring rovibrational line absorption in isotop ic species of CO2 using groundbased infrared heterodyne spectroscopy in the vicinity of the 9.6 micron and 10.6 micron CO2 lasing bands. T he target transitions during this observation were O-18 C-12 O-16 as well as O-178 C-12 O-16 and O-16 C-113 O-16 at higher resolving power of lambda/delta lambda=10(exp 7) and with high signal-to-noise ratio (longer integration time) in order to fully characterize the absorpt ion line profiles. The fully-resolved lineshape of both the strong n ormal-isotope and the weak isotopic CO2 lines were measured simultane ously in a single spectrum.

Smith, R. L.↗
NASA NTRS2011

Laser Heterodyne Radiometer for Sensitive Detection of CO2 and CH4

We propose to develop an inexpensive, miniaturized, passive laser heterodyne radiometer (LHR) using commercially available telecommunications laser components to measure two significant carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). This instrument would operate in tandem with the passive aerosol sensor currently used in AERONET (an established network of more than 450 ground aerosol monitoring instruments worldwide). Because aerosols induce a radiative effect that influences terrestrial carbon exchange, simultaneous detection of aerosols with these key carbon cycle gases offers a uniquely comprehensive measurement approach that supports the Decadal Survey. Laser heterodyne radiometry is a technique for detecting weak signals that was adapted from radio receiver technology. In a radio receiver, a weak input signal from a radio antenna is mixed with a stronger local oscillator signal. The mixed signal (beat note, or intermediate frequency) has a frequency equal to the difference between the input signal and the local oscillator. The intermediate frequency is amplified and sent to a detector that extracts the audio from the signal. In a laser heterodyne radiometer, the weak input signal is light that has undergone absorption by a trace gas. The local oscillator is a laser at a near-by frequency - in this case a low-cost distributed feedback (DFB) telecommunications laser. These two light waves are superimposed in either a beamsplitter or in a fiber coupler (as is the case in this design). The signals are mixed in the detector, and the RF beat frequency is extracted. Changes in concentration of the trace gas are realized through analyzing changes in the beat frequency amplitude. A schematic of the progression of the LHR development project is shown in the figure below. At the center (within the dashed line), light from the local oscillator is superimposed upon light that has undergone absorption by a trace gas, in a single mode fiber coupler. Superimposed light is mixed in a fast photoreceiver, and the beat signal is analyzed for changes in absorption. The left portion of the figure depicts a progression of light sources that pass through the trace gas, increasing in complexity in the downward direction. On the right side of the figure, RF signal processing progresses from a commercially available spectrum analyzer to a RF receiver, and finally to an RF filter bank to deconvolute portions of the beat frequency more heavily weighted for different altitudes.

Wilson, Emily L.↗
NASA NTRS2012

Greenhouse Gas Concentration Data Recovery Algorithm for a Low Cost, Laser Heterodyne Radiometer

The goal of a coordinated effort between groups at GWU and NASA GSFC is the development of a low-cost, global, surface instrument network that continuously monitors three key carbon cycle gases in the atmospheric column: carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), as well as oxygen (O2) for atmospheric pressure profiles. The network will implement a low-cost, miniaturized, laser heterodyne radiometer (mini-LHR) that has recently been developed at NASA Goddard Space Flight Center. This mini-LHR is designed to operate in tandem with the passive aerosol sensor currently used in AERONET (a well established network of more than 450 ground aerosol monitoring instruments worldwide), and could be rapidly deployed into this established global network. Laser heterodyne radiometry is a well-established technique for detecting weak signals that was adapted from radio receiver technology. Here, a weak light signal, that has undergone absorption by atmospheric components, is mixed with light from a distributed feedback (DFB) telecommunications laser on a single-mode optical fiber. The RF component of the signal is detected on a fast photoreceiver. Scanning the laser through an absorption feature in the infrared, results in a scanned heterodyne signal io the RF. Deconvolution of this signal through the retrieval algorithm allows for the extraction of altitude contributions to the column signal. The retrieval algorithm is based on a spectral simulation program, SpecSyn, developed at GWU for high-resolution infrared spectroscopies. Variations io pressure, temperature, composition, and refractive index through the atmosphere; that are all functions of latitude, longitude, time of day, altitude, etc.; are modeled using algorithms developed in the MODTRAN program developed in part by the US Air Force Research Laboratory. In these calculations the atmosphere is modeled as a series of spherically symmetric shells with boundaries specified at defined altitudes. Temperature, pressure, and species mixing ratios are defined at these boundaries. Between the boundaries, temperature is assumed to vary linearly with altitude while pressure (and thus gas density) vary exponentially. The observed spectrum at the LHR instrument will be the integration of the contributions along this light path. For any absorption measurement the signal at a particular spectral frequency is a linear combination of spectral line contributions from several species. For each species that might absorb in a spectral region, we have pre-calculated its contribution as a function of temperature and pressure. The integrated path absorption spectrum can then by calculated using the initial sun angle (from location, date, and time) and assumptions about pressure and temperature profiles from an atmospheric model. The modeled spectrum is iterated to match the experimental observation using standard multilinear regression techniques. In addition to the layer concentrations, the numerical technique also provides uncertainty estimates for these quantities as well as dependencies on assumptions inherent in the atmospheric models.

Miller, J. Houston↗
NASA NTRS2012

Towards an Imaging Mid-Infrared Heterodyne Spectrometer

We are developing a concept for a compact, low-mass, low-power, mid-infrared (MIR; 5- 12 microns) imaging heterodyne spectrometer that incorporates fiber optic coupling, Quantum Cascade Laser (QCL) local oscillator, photomixer array, and Radio Frequency Software Defined Readout (RFSDR) for spectral analysis. Planetary Decadal Surveys have highlighted the need for miniaturized, robust, low-mass, and minimal power remote sensing technologies for flight missions. The drive for miniaturization of remote sensing spectroscopy and radiometry techniques has been a continuing process. The advent of MIR fibers, and MEMS techniques for producing waveguides has proven to be an important recent advancement for miniaturization of infrared spectrometers. In conjunction with well-established photonics techniques, the miniaturization of spectrometers is transitioning from classic free space optical systems to waveguide/fiber-based structures for light transport and producing interference effects. By their very nature, these new devices are compact and lightweight. Mercury-Cadmium-Telluride (MCT) and Quantum Well Infrared Photodiodes (QWIP) arrays for heterodyne applications are also being developed. Bulky electronics is another barrier that precluded the extension of heterodyne systems into imaging applications, and our RFSDR will address this aspect.

Hewagama, T.↗
NASA NTRS2005

Future of heterodyne receivers at submillimeter wavelengths

In this review paper we examine these issues very carefully and describe the novel receivers being designed to make heterodyne instruments more competitive. It will be shown that heterodyne instruments will still have significant roles to play in the near future.

heterodyne↗
NASA NTRS2016

A Low-Cost Miniaturized Laser Heterodyne Radiometer (Mini-LHR) for Near-ir Measurements of CO2 and CH4 in the Atmospheric Column

The miniaturized laser heterodyne radiometer (mini-LHR) is a ground-based passive variation of a laser heterodyne radiometer that uses sunlight to measure absorption of CO2 andCH4 in the infrared. Sunlight is collected using collimation optics mounted to an AERONET sun tracker, modulated with a fiber switch and mixed with infrared laser light in a fast photoreciever.The amplitude of the resultant RF (radio frequency) beat signal correlates with the concentration of the gas in the atmospheric column.

heterodyne radiometer (mini-LHR)↗
NASA NTRS2016

Khayyam; Progress and Prospects of Coupling a Spatial Heterodyne Spectrometer (SHS) to a Cassegrain Telescope for Optical Interferometry

In the temporal study of faint, extended sources at high resolving power, Spatial Heterodyne Spectrometer (SHS) can offer significant advantages about conventional dispersive grating spectrometers. We describe here a four-year continuous progress in Mt. Hamilton, Lick Observatory, toward development of a prototype reflective Spacial Heterodyne Spectrometer, Khayyam, instrument-telescope configuration to combine all of the capabilities necessary to obtain high resolving power visible band spectra of diffuse targets from small aperture on-axis telescopes where significant observing time can be obtained. We will discuss the design considerations going into this new system, installation, testing of the interferometer-telescope combination, the technical challenges and procedures moving forward.

extended targets↗
NASA NTRS2019

A Laser Heterodyne Radiometer for Sampling Plumes of Icy Moons

We propose to develop an instrument capable of passively sampling plumes in icy moon environments for the components needed for life and habitability. The compact, low-mass and power, orbital instrument would be an occultation-viewing laser heterodyne radiometer (LHR) that collects sunlight passing through the plumes of icy moons to measure abundancies of key trace gases such as water vapor, methane, ethane, carbon dioxide, and their isotopes. Laser heterodyne radiometers are based on radio receiver technology and have been applied to measurements of trace gases in Earth and planetary atmospheres since the 1960s. Our team has recently adapted this technology into a 4U (20cm x 20cm x 10cm) CubeSat instrument to measure carbon dioxide, methane and water vapor in the Earth's atmosphere (launching on Virgin Orbit in 2019) and have the experience to develop this into a compact science payload to monitor gases emerging from icy moons of Saturn and Jupiter.

laser heterodyne radiometer (LHR)↗
NASA NTRS2020

Evaluation of a Method to Retrieve Temperature and Wind Velocity Profiles of the Venusian Nightside Mesosphere from Mid-Infrared CO2 Absorption Line Observed by Heterodyne Spectroscopy

We evaluated a method for retrieving vertical temperature and Doppler wind velocity profiles of the Venusian nightside mesosphere from the CO2 absorption line resolved by mid-infrared heterodyne spectroscopy. The achievable sensitive altitude and retrieval accuracy were derived with multiple model spectra generated from various temperature and wind velocity profiles with several noise levels. The temperature profiles were retrieved at altitudes of 70–100 km with a vertical resolution of 5 km and a retrieval accuracy of ±15 K. The wind velocity was also retrieved at an altitude of approximately 85 km with a vertical resolution of 10 km and a retrieval accuracy of ± 25–50 m/s. In addition, we studied an event and applied our method to spectra obtained by the HIPWAC instrument attached to the NASA/IRTF 3-m telescope on May 19–22, 2012. Retrieved wind velocities in a latitude of 33° S at 3:00 LT were interpreted as subsolar-to-antisolar (SS-AS) flows at altitudes of 84 ±6 km and 94 ±7 km, and they were stronger than expected. This result suggested that the transition between the retrograde super rotational zonal (RSZ) wind and SS-AS flow may occur at altitudes below 90 km which previously was predicted to be the transition region. This work provides a basis for our analysis of further observations obtained by a mid-infrared heterodyne spectrometer MILAHI attached to the Tohoku University 60-cm telescope at Haleakalā, Hawaii.

Venus↗
NASA NTRS1971

Usefulness of the infrared heterodyne radiometer in remote sensing of atmospheric pollutants.

The application of narrow-band optical receivers to the problem of sensing atmospheric pollution is discussed. The emission/absorption lines of many major atmospheric pollutant molecules overlap the operating frequency bands of CO2 laser and CO laser heterodyne receivers. Several remote pollution sensing systems which are based upon utilization of these spectral overlaps are described, and an analysis of their potential is presented. The possibility of using other lasers (e.g.: the PbSnTe tunable diode laser) as local oscillators is also considered. Results of laboratory experiments with a CO2 laser heterodyne radiometer are presented.

Menzies, R. T.↗
NASA NTRS1971

N-type mercury-cadmium-telluride photoconductors in optical heterodyne communication systems.

Discussion of the performance of a photoconductive (Hg,Cd)Te detector/mixer in a carbon dioxide laser heterodyne communication system. The utility of computer simulation of the performance of an optical heterodyne detector/mixer is demonstrated. Certain unusual properties of this device are pointed out that, while having a substantial impact on device performance, have received little previous attention.

Cohen, S. C.↗
NASA NTRS1972

Infrared heterodyne solar radiometry.

An infrared heterodyne radiometer has sufficient sensitivity for application to high resolution spectrometric studies of the sun and the absorption of sunlight in the atmosphere. In the 10-micron region, the resolution can typically range from less than .0067/cm to .067/cm. The minimum detectable signal can approach 10 to the -24th power W/Hz. The infrared heterodyne radiometer (IHR) can also be used for atmospheric propagation studies at the emission frequencies of the CO2 laser for the examination of the feasibility of space-to-ground laser communication links.

Mcelroy, J. H.↗
NASA NTRS1972

High sensitivity infrared 10.6 micrometer heterodyne receiver development

The results are presented for a study on the design of an infrared 10.6-micrometer quantum-noise-limited optical receiver subsystem. Performance measurements of the HgCdTe photomixer preamplifier combination were carried out for photomixer temperatures up to 152 K and a photomixer frequency response of up to 420 MHz was obtained. Results of temperature and bias cycling of HgCdTe photomixers are reported. Design considerations for an operational 10.6 micrometer heterodyne receiver are presented. These consist of design data on required laser LO illumination, heat load levels for photomixer cooler, photomixer uniformity and the effects of photomixer impedance match on receiver sensitivity. Analysis and measurements of 10.6 micrometer heterodyne detection in an extrinsic photoconductive (p-type) HgCdTe photomixer are also presented.

Source record↗
NASA NTRS1974

Infrared heterodyne spectroscopy of astronomical and laboratory sources at 8.5 micron

The first infrared heterodyne spectrometer using tuneable semiconductor (PbSe) diode lasers has been constructed and was used near 8.5 micron to measure absorption line profiles of N2O in the laboratory and black body emission from the Moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz and the minimum detectable (black body) power was 1 x 10 to the minus 16th power watts for 8 minutes of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.

Mumma, M.↗
NASA NTRS1974

Infrared heterodyne spectroscopy of CO2 on Mars

An infrared heterodyne spectrometer operating near 11 micrometers with a resolving power of 1,500,000 has been used to obtain spectral line profiles of carbon dioxide absorption in the Martian atmosphere. For a periodic calibration of the system sensitivity, a black body at 500 K was placed in front of the chopper. Atmospheric transmission was determined by measuring heterodyne signals from the moon and Mars as a function of the zenith angle.

Peterson, D. W.↗