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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 217 records · Page 12
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NASA NTRS1992

Spatial Heterodyne Spectroscopy - Laboratory tests of field widened, multiple order, and vacuum ultraviolet systems

We describe a new instrumental technique for interference spectroscopy, Spatial Heterodyne Spectroscopy (SHS), which promises to extend into the FUV (1200 A - 2000 A) spectral region the large throughput advantage at high spectral resolution usually associated with Fabry-Perot and Michelson interferometers. In addition, SHS systems are compact in size, can be field-widened to increase their throughput advantage even further, and have no moving parts. SHS appears to be well suited for high resolution, space-based spectroscopy of faint interstellar emission lines in the FUV. In this paper we review the first proof-of-concept laboratory demonstrations of a field widened SHS configuration and a multiple order SHS system, which extends the spectral range of the basic device and present new results of SHS performance in the VUV. The design of an SHS system capable of obtaining velocity resolved spectra of the CIV 1550 doublet from the interstellar medium is also discussed.

Harlander, J.↗
NASA NTRS1991

High-resolution studies of atmospheric IR emission spectra

Atmospheric emission spectra obtained with two different spectrometer systems are presented. The first system (the BOMEM Michelson interferometer) is designed for emission work. Spectra were obtained under adverse conditions in the Antarctic, and are still of good absolute accuracy. The second system (a modified Bruker Instruments IFS120 very high spectral resolution interferometer) demonstrates the sensitivity that can be achieved even at higher spectral resolution. This system shows that mid-IR atmospheric emission spectra can be obtained with a good SNR in a reasonable length of time at a relatively high resolution. A properly designed high resolution system should achieve high accuracy, sensitivity, and resolution, thereby permitting measurements of many atmospheric constituents when solar spectra cannot be obtained.

Murcray, F. J.↗
NASA NTRS1993

Orbiting stellar interferometer for astrometry and imaging

The orbiting stellar interferometer (OSI) is a concept for a first-generation space interferometer with astrometric and imaging goals. The OSI is a triple Michelson interferometer with articulating siderostats and optical delay lines. Two point designs for the instrument are described. The 18-m design uses an 18-m maximum baseline and aperture diameters of 40 cm; the targeted astrometric performance is a wide-field accuracy of 10 microarsec for 16-mag objects in 100 s of integration time and for 20-mag objects in 1 h. The instrument would also be capable of synthesis imaging with a resolution of 5 marcsec, which corresponds to the diffraction limit of the 18-m base line. The design uses a deployed structure, which would fold to fit into an Atlas IIAS shroud, for insertion into a 900-km sun-synchronous orbit. In addition to the 18-m point design, a 7-m point design that uses a shorter base line in order to simplify deployment is also discussed. OSI's high performance is made possible by utilizing laser metrology and controlled-optics technology.

Colavita, M. M.↗
NASA NTRS1993

WINDII, the wind imaging interferometer on the Upper Atmosphere Research Satellite

The WIND imaging interferometer (WINDII) was launched on the Upper Atmosphere Research Satellite (UARS) on September 12, 1991. This joint project, sponsored by the Canadian Space Agency and the French Centre National d'Etudes Spatiales, in collaboration with NASA, has the responsibility of measuring the global wind pattern at the top of the altitude range covered by UARS. WINDII measures wind, temperature, and emission rate over the altitude range 80 to 300 km by using the visible region airglow emission from these altitudes as a target and employing optical Doppler interferometry to measure the small wavelength shifts of the narrow atomic and molecular airglow emission lines induced by the bulk velocity of the atmosphere carrying the emitting species. The instrument used is an all-glass field-widened achromatically and thermally compensated phase-stepping Michelson interferometer, along with a bare CCD detector that images the airglow limb through the interferometer. A sequence of phase-stepped images is processed to derive the wind velocity for two orthogonal view directions, yielding the vector horizontal wind. The process of data analysis, including the inversion of apparent quantities to vertical profiles, is described.

Shepherd, G. G.↗
NASA NTRS1993

The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment - The ATLAS-1 mission

ATMOS is an investigation of the chemistry and composition of the middle atmosphere using a modified Michelson interferometer designed to be carried on board the Space Shuttle. During orbital sunsets and sunrises it obtains high resolution infrared solar spectra every 2 seconds. The instrument was first flown on the Spacelab 3 mission in April, 1985, and is being reflown as part of the ATLAS series of payloads which started with the ATLAS-1 flight in March 1992. A summary of the results from the Spacelab 3 mission will be presented. These results included several first detections of critical atmospheric species in addition to the thirty or more constituents for which profiles were derived at altitudes between 10 and 150 km. Preliminary results from the ATLAS-1 mission will be described as part of an update to the status of this long term effort.

Gunson, Michael R.↗
NASA NTRS1991

Micro-displacement fiber sensor using two-frequency interferometry

A He-Ne Zeeman laser has been utilized as a two-frequency light source in a Michelson-type micro-displacement fiber sensor. A polarization maintaining fiber has been installed in the sensing arm, which facilitates flexibility and allows the sensing region to be remotely located. This fiber sensing arm is arranged to replace a quarterwave plate component. The fiber sensor system has a resolution of half a micrometer.

Tedjojuwono, Ken K.↗
NASA NTRS1993

Study of Einstein-Podolsky-Rosen state for space-time variables in a two photon interference experiment

A pair of correlated photons generated from parametric down conversion was sent to two independent Michelson interferometers. Second order interference was studied by means of a coincidence measurement between the outputs of two interferometers. The reported experiment and analysis studied this second order interference phenomena from the point of view of Einstein-Podolsky-Rosen paradox. The experiment was done in two steps. The first step of the experiment used 50 psec and 3 nsec coincidence time windows simultaneously. The 50 psec window was able to distinguish a 1.5 cm optical path difference in the interferometers. The interference visibility was measured to be 38 percent and 21 percent for the 50 psec time window and 22 percent and 7 percent for the 3 nsec time window, when the optical path difference of the interferometers were 2 cm and 4 cm, respectively. By comparing the visibilities between these two windows, the experiment showed the non-classical effect which resulted from an E.P.R. state. The second step of the experiment used a 20 psec coincidence time window, which was able to distinguish a 6 mm optical path difference in the interferometers. The interference visibilities were measured to be 59 percent for an optical path difference of 7 mm. This is the first observation of visibility greater than 50 percent for a two interferometer E.P.R. experiment which demonstrates nonclassical correlation of space-time variables.

Shih, Y. H.↗
NASA NTRS1993

Solid state laser systems for space application

Work on the development of an interferometric system for the purpose of absolute length determination commenced in January of this year. Our goal is to develop a system capable of measurements on the order of one meter with an accuracy of 1 part in 10 or greater. A modified Michelson bread board with stabilized laser diode source was assembled. Some preliminary measurements began using the tunable Santek laser in an FM modulation scheme. During this same period a literature search yielded a paper by Suematsu and Takeda which discusses a promising fourier transform technique for real time data analysis. We are in the process of evaluating this technique while we continue to change and upgrade the system configuration.

Kay, Richard B.↗
NASA NTRS1994

Mesospheric and lower thermospheric winds, temperatures densities, and volume emission rates

This memo has been written to report on the progress made under grant NAG1-1315 and to request a continuation of funding for this work. Our proposal involved a plan to utilize an existing ground-based chain of optical and radar facilities to assemble a comprehensive, long-term, multi-station base of upper-mesospheric and lower thermospheric measurements of neutral winds, temperatures, and volume emission rates that can be used to make comparisons with data from the HRDI and WINDII instruments that are flying aboard the UARS spacecraft. The ground-based, optical data were to be obtained on a routine basis from five geographically separated observatories at: Thule, Greenland; Sondrestrom, Greenland; Watson Lake, Yukon (replacing Calgary, Alberta); Ann Arbor, Michigan; and Maynooth, Eire. Several different optical instruments are present at these sites: the total array of instruments is comprised of five Fabry-Perot interferometers, two half meter Ebert-Fastie spectrometers, one all-sky CCD imager, and a near infra-red Michelson Fourier transform spectrometer. In addition to these optical instruments, data were to be obtained from the incoherent scatter radar at Sondrestrom, Greenland. These radar measurements are comprised of neutral winds, temperatures, and densities from altitudes between approximately 70 - 120 km. The optical measurements are obtained locally from specific altitudes depending on the emission line studied. For example, red line optical data come from about 220 km. In this report we summarize the progress made in obtaining these data and relate it to the specific tasks outlined in the original grant application. These tasks are discussed in the next section. Progress towards their completion is discussed in section three, while future plans and summary are described in section four.

Killeen, Timothy L.↗
NASA NTRS1993

Three high duty cycle, space-qualified mechanisms

The Michelson Doppler Imager (MDI) is a scientific instrument aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. In 1995, the spacecraft will be put into a halo orbit about the L1 Lagrangian point (equal Sun and Earth gravity). The MDI looks at the sun continuously and takes a picture with a large format CCD camera every 3 seconds. The design goal of the mission is 6 years, so over 60 million pictures will be taken. The sun, being a high intensity source, provides a signal with a single pixel noise level of 0.2 percent. Many images are combined to measure the oscillatory motion of the sun so very high performance is required of the mechanisms in order that they not add noise to the data. The MDI instrument is made up of two parts, the electronics package and the optics package. This paper describes the design and testing of three mechanisms on the MDI which are required to operate large numbers of times.

Akin, David↗
NASA NTRS1994

Solid state laser systems for space application

Since the last report several things have happened to effect the research effort. In laser metrology, measurements using Michelson type interferometers with an FM modulated diode laser source have been performed. The discrete Fourier transform technique has been implemented. Problems associated with this technique as well as the overall FM scheme were identified. The accuracy of the technique is not at the level we would expect at this point. We are now investigating the effect of various types of noise on the accuracy as well as making changes to the system. One problem can be addressed by modifying the original optical layout. Our research effort was also expanded to include the assembly and testing of a diode pumped\Nd:YAG laser pumped\Ti sapphire laser for possible use in sounding rocket applications. At this stage, the diode pumped Nd:YAG laser has been assembled and made operational.

Kay, Richard B.↗
NASA NTRS1994

Development of long-life, low-noise linear bearings for atmospheric interferometry

This paper describes the development of dry-lubricated linear bearings for use on the Michelson interferometer for passive atmospheric sounding (MIPAS). Two candidate bearing systems were developed and tested. In the first, use was made of linear roller (needle) bearings equipped with a pulley-and-cable arrangement to prevent cage drift and to minimize roller slip. The second design was of a roller-guided bearing system in which guidance was provided by all bearings rolling along guide rods. The paper focuses on the development of these linear bearings systems and describes the approach taken in terms of bearing design, lubrication methods, screening programs, and thermal-vacuum testing. Development difficulties are highlighted and the solutions ultimately adopted are described.

Roberts, E. W.↗
NASA NTRS1994

The MIPAS balloon borne trace constitutent experiment

A novel cryogenic Fourier transform spectrometer (FTS) has been developed for limb emission measurements in the mid IR-region from balloon-borne platforms. The FTS is a rapid scanning interferometer using a modified Michelson arrangement which allows a spectral resolution of 0.04 cm(exp -1) to be achieved. Solid carbon-dioxide cooling of the spectrometer and liquid-helium cooling of the detectors provide adequate sensitivity. The line of sight can be stabilized in terms of azimuth and elevation. A three-mirror off-axis telescope provides good vertical resolution and straylight rejection. Calibration is performed by high elevation and internal blackbody measurements. Four balloon flights were performed, two of them during spring turn-around 1989 and 1990 over mid-latitudes (Aire sur L'Adour, France, 44 deg N) and two near the northern polar circle in winter 1992 (Esrange, Sweden, 68 deg N). Limb emission spectra were collected from 32 km to 39 km floating altitudes covering tangent heights between the lower troposphere and the floating altitude. The trace gases CO2, H2O, O3, CH4, N2O, HNO3, N2O5, ClONO2, CF2Cl2, CFCl3, CHF2Cl, CCl4, and C2H6 have been identified in the measured spectra. The 1989 data have been analyzed to retrieve profiles of O3, HNO3, CFCl3 and CF2Cl2. The flights over Kiruna have provided the first ever reported profile measurements of the key reservoir species ClONO2 and N2O5 inside the polar vortex.

Oelhaf, H.↗
NASA NTRS1994

Ultraviolet-Infrared Mapping Interferometic Spectrometer

Prism and grating spectrometers have been the defacto devices for spectral mapping and imaging (hereafter referred to as hyperspectra). We have developed a new, hybrid instrument with many superior capabilities, the Digital Array Scanned Interferometer, DASI. The DASI performs the hyperspectral data acquisition in the same way as a grating or prism spectrograph, but retains the substantial advantages of the two-beam (Michelson) interferometer with additional capabilities not possessed by either of the other devices. The DASI is capable of hyperspectral studies in virtually any space or surface environment at any wavelength from below 50 nm to beyond 12 microns with available array detectors. By our efforts, we have defined simple, low cost, no-moving parts DASI's capable of carrying out hyperspectral science measurements for solar system exploration missions, e.g. for martian, asteroid, lunar, or cometary surveys. DASI capabilities can be utilized to minimize cost, weight, power, pointing, and other physical requirements while maximizing the science data return for spectral mapping missions. Our success in the development of DASI's has become and continues to be an important influence on the efforts of the best research groups developing remote sensing instruments for space and other applications.

Source record↗
NASA NTRS1995

SOI/MDI studies of active region seismology and evolution

The solar oscillations investigation (SOI) will study solar active regions using both helioseismic and conventional observation techniques. The Michelson Doppler imager (MDI) can perform Doppler continuum and line depth imagery and can produce longitudinal magnetograms, showing either the full disk or a high resolution field of view. A dynamics program of continuous full disk Doppler observations for two months per year, campaign programs of eight hours of continuous observation per day, and a synoptic magnetic program of about 15 full disk magnetograms per day, are planned. The scientific plans, measurements and observation programs, are described.

Tarbell, Ted D.↗
NASA NTRS1995

Plane-wave analysis of solar acoustic-gravity waves: A (slightly) new approach

The plane-wave decomposition of the acoustic-gravity wave effects observed in the photosphere provides a computationally efficient technique that probes the structure of the upper convective zone and boundary. In this region, the flat sun approximation is considered as being reasonably accurate. A technique to be used for the systematic plane-wave analysis of Michelson Doppler imager data, as part of the solar oscillations investigation, is described. Estimates of sensitivity are presented, and the effects of using different planar mappings are discussed. The technique is compared with previous approaches to the three dimensional plane-wave problem.

Bogart, Richard S.↗
NASA NTRS1995

Potential contribution of MDI to understanding large-scale structures in the corona

In relation to the understanding of the structure and dynamics of the solar atmosphere which requires realistic coronal magnetic field models, a horizontal current-current sheet (HCCS) coronal model was developed. The model includes large-scale, low altitude, horizontal currents and the effect of thin current sheets in the streamer belt of the field above cusp-type neutral points. The effect of the streamer current sheet on the field below the cusp points is accounted for. In order to suggest what can be anticipated from Michelson Doppler imager (MDI) photospheric magnetic field data calculations of the coronal magnetic field using low spatial resolution data, are presented, and results from the calculations of solar eclipses are compared with solar eclipse images.

Zhao, Xuepu↗
NASA NTRS1995

The upper convective boundary layer

Progress made in understanding of the physics of the upper boundary layer of the sun, its influence on frequencies of five-minute oscillations, and its role in the excitation of the oscillations, are reviewed. The approaches taken for the seismological diagnosis of the properties of the layer are discussed. Information concerning the properties of the layer are obtained from Michelson Doppler imagery high-resolution data. The structure of the convective boundary layer is discussed considering high-resolution observations, three dimensional numerical simulations, the mean stratification of the convective layers, and the effects of momentum transfer by convection. The effects of convection on the oscillation frequencies, mode excitation, and mode damping, are discussed.

Kosovichev, Alexander G.↗