NASA minitrack interferometer refraction corrections
Influence of atmospheric refraction on minitrack interferometer system and correction procedures for computation accuracy
Schmid, P. E., Jr.↗
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136 MHz interferometer error due to galactic nucleus.
Extraneous interfering signals are discussed which limit the basic accuracy of the 136 MHz Minitrack radio-interferometer system providing electrical phase data from which direction cosines for determining spacecraft orbits are generated. In particular, the fundamental error due to interference caused by the passage of the galactic nucleus is investigated. An expression is developed for the lower bound of the phase error when the noise source is not uniformly distributed across the Minitrack's zenith-pointed fan beam. In addition, the threshold of the Minitrack input power levels is determined below which the electrical phase is no longer determined unambiguously. The effect of the passage of the galactic nucleus coincident with the presence of a spacecraft is analyzed, and the corresponding phase error established.
Kyriakopoulos, N.↗
Radio interferometry for international study of the earthquake mechanism
Consideration of the possibility of developing an improved technique for measuring crustal deformations over distances of hundreds to thousands of kilometers to even intercontinental distances. Attention is focused on the uses of very long baseline interferometry in the structuring of a transportable radio interferometer system capable of high-accuracy three-dimensional earth surveying. In particular, the essential elements of a system called astronomical radio interferometric earth surveying are described. This system involves the use of a pair of antennas, one fixed and one portable, which simultaneously receive random radio signals emitted from an extragalactic radio source. A combination of a readily transportable small-diameter dish for use during a limited period at a remote site with a larger-diameter antenna with a better receiver is recommended.
Macdoran, P. F.↗
Fourteen years of resonance of Vanguard orbits
Tracking of Vanguard 3 and the Vanguard 2 rocket with Baker-Nunn cameras and the U.S. Navy's Space Surveillance (radio interferometer) system over a 14 year period revealed resonant fluctuations of up to 0.035 deg in inclination (peak to peak). Six geopotential terms (lumped coefficients) of 11th order and three of 22nd order were measured using orbit inclinations derived from this tracking record. The terms of 11th order are significantly smaller than Kaula's rule. (The lumped coefficients are sensitive to geopotential effects as high as 37th degree.) These observed terms are compatible with a recent 27-satellite geopotential solution whose formal coefficient errors are increased by a factor of 3.3.
Wagner, C. A.↗
Geopotential resonances on Vanguard orbits
Since their establishment in 1959 the orbits of Vanguard 3 (1959-7A) and the Vanguard 2 rocket (1959-2B) have been slowly contracting through at least five strong resonances of eleventh order. Tracking with Baker-Nunn cameras and the U.S. Navy space surveillance (radio interferometer) system over a 14-year period has revealed resonant fluctuations on them of up to 0.035 deg in inclination (peak to peak). Six geopotential terms (lumped coefficients) of eleventh order and three of twenty-second order have been measured by using orbit inclinations derived from this tracking record. The terms of eleventh order are significantly smaller than is predicted by Kaula's rule. (The lumped coefficients are sensitive to geopotential effects as high as thirty-seventh degree.) These observed terms are compatible with a recent 27-satellite geopotential solution (GEM 7) whose formal coefficent errors are increased by a factor of 3.3.
Wagner, C. A.↗
Airborne infrared interferometric observations and analysis of stratospheric trace constituents
Infrared interferometric observations of key trace constituents of the stratosphere have been obtained. The NASA Lear Airborne Observatory with the Grumman airborne interferometer system was flown in the lower stratosphere at an altitude of 13.7 km to obtain transmission spectra in the 2800-6000 per cm region at a resolution of 2.5 per cm using the moon as a source. An atmospheric modeling program and the AFGL line parameter atlas are used to identify H2O, CH4, O3 and other trace constituents and to derive stratospheric column densities (molecules/sq cm).
Smith, L. L.↗
The Tidbinbilla interferometer
This paper describes a technique to detect and identify weak, small-diameter radio sources with flux densities in the millijansky range. An interferometer system is proposed which will use existing 64 m and 24 m antennas of the Tidbinbilla Deep Space Network near Canberra. Design parameters of the system are described, and a schematic is presented with attention to low-noise traveling wave masers, and phase oscillation devices.
Batty, M. J.↗
Structure and evolution of solar radio bursts at 26.4 MHz
Results are reported for multiple-baseline interferometric measurements of type II, III, IV, and V solar radio bursts at 26.4 MHz. Thirty-two burst events in a two-month period are analyzed by fitting a double-Gaussian two-dimensional source-brightness distribution model to the observed interferometer visibility function. The multibaseline time-sharing interferometer system employed is described in detail, the model-fitting technique is outlined, and values of the model-fit parameters are given for all 32 cases, which include two type II bursts, three type IV bursts, 17 type III bursts, seven type V bursts, and three bursts of type III, V pairs. The temporal evolution of source structure, size, and motion is examined for the different burst types. The core-halo source structure for the type III bursts is interpreted in comparison to two models, one of which assumes scattering and refraction of a point source while the other postulates primarily refraction from an ensemble of sources distributed over a wide sector in solar longitude.
Chen, H. S.-L.↗
An analysis of water in galactic infrared sources using the NASA Lear Airborne Observatory
The Michelson interferometer system on the NASA Lear Jet Airborne Observatory is described as well as the data reduction procedures. The objects observed (standard stars, M stars, a nebula, planets, and the moon) are discussed and the observing parameters are listed for each flight date. The spectra obtained from these data flights are presented, grouped by class of object.
Smith, L. L.↗
Holographic interferometry and tomography at Ames Research Center
A YAG laser holographic interferometer system and reconstruction laboratory for the Ames 2- by 2-Foot Transonic Wind Tunnel are discussed. This system provides dual plate and double pulse holography for quantitative and qualitative measurements, respectively. Interferometric measurements of two-dimensional airfoils and three-dimensional bodies of revolution for a tomography feasibility study were made. The two-dimensional work included supercritical airfoils, an oscillating airfoil undergoing dynamic stall, and a circulation control airfoil. The tomography experiments centered around hemispherical nose and tangent ogive models. In addition, the tomography work covered the development of a Fourier transform code for the retrieval of the three dimensional density distributions from the interferograms.
Lee, G.↗
Stratospheric NO and NO2 profiles at sunset from analysis of high-resolution balloon-borne infrared solar absorption spectra obtained at 33 deg N and calculations with a time-dependent photochemical model
Simultaneous stratospheric vertical profiles of NO and NO2 at sunset were derived from an analysis of infrared solar absorption spectra recorded from a float altitude of 33 km with an interferometer system during a balloon flight. A nonlinear least squares procedure was used to analyze the spectral data in regions of absorption by NO and NO2 lines. Normalized factors, determined from calculations of time dependent altitude profiles with a detailed photochemical model, were included in the onion peeling analysis to correct for the rapid diurnal changes in NO and NO2 concentrations with time near sunset. The CO2 profile was also derived from the analysis and is reported.
Rinsland, C. P.↗
Stratospheric temperature profile from balloon-borne measurements of the 10.4-micron band of CO2
The technique of nonlinear least squares spectral curve fitting has been used to derive the stratospheric vertical temperature profile from balloon-borne measurements of the 10.4 micron band of CO2. The spectral data were obtained at sunset with the approximately 0.02 per cm resolution University of Denver interferometer system from a float altitude of 33.5 km near Alamogordo, New Mexico, on 23 March 1981. The r.m.s. deviation between the retrieved temperature profile and correlative radiosonde measurements is 2.2 K.
Rinsland, C. P.↗
Feasibility study of optical boundary layer transition detection method
A high sensitivity differential interferometer was developed to locate the region where the boundary layer flow undergoes transition from laminar to turbulent. Two laboratory experimental configurations were used to evaluate the performance of the interferometer: open shear layer, and low speed wind tunnel turbulent spot configuration. In each experiment, small temperature fluctuations were introduced as the signal source. Simultaneous cold wire measurements were compared with the interferometer data. The comparison shows that the interferometer is sensitive to very weak phase variations in the order of 0.001 the laser wavelength. An attempt to detect boundary layer transition over a flat plate at NASA-Langley Unitary Supersonic Wind Tunnel using the interferometer system was performed. The phase variations during boundary layer transition in the supersonic wind tunnel were beyond the minimum signal-to-noise level of the instrument.
Azzazy, M.↗
Upper limits for stratospheric H2O2 and HOCl from high resolution balloon-borne infrared solar absorption spectra
Solar absorption spectra from two stratospheric balloon flights have been analyzed for the presence of H2O2 and HOCl absorption in the 1230.0 to 1255.0 per cm region. The data were recorded at 0.02 per cm resolution during sunset with the University of Denver interferometer system on October 27, 1978 and March 23, 1981. Selected spectral regions were analyzed with the technique of nonlinear least squares spectral curve fitting. Upper limits of 0.33 ppbv for H2O2 and 0.36 ppbv for HOCl near 28 km are derived from the 1978 flight data while upper limits of 0.44 ppbv for H2O2 and 0.43 ppbv for HOCl at 29.5 km are obtained from the 1981 flight data.
Larsen, J. C.↗
Optical boundary-layer transition detection in a transonic wind tunnel
A high-sensitivity interferometer has been developed and used to detect boundary-layer transitions over a symmetric airfoil. The tests, which included both natural and roughness-induced transitions, were performed in a transonic wind tunnel. The measurements showed a peak amplitude rms and higher energy in the spectrum of the signal associated with transition. The tests revealed that the interferometer system can be used to locate the transition region over three-dimensional aerodynamic models.
Azzazy, M.↗
New spectral features of stratospheric trace gases
A new Michelson-type interferometer system operating in the infrared at very high resolution (0.002 to 0.003 wavenumber FWHM) was used to record numerous balloon-borne solar absorption spectra of the stratosphere, ground-based solar absorption spectra, and laboratory spectra of molecules of atmospheric interest. Results obtained are reported for several important stratospheric trace gases, HNO3, ClONO2, HO2NO2, NO2, and COF2, in the 8 to 12 micron spectral region. Many features of these gases were identified in the stratospheric spectra. Comparison of the spectra with line-by-line simulations shows previous spectral parameters are often inadequate. New analysis of high resolution laboratory and atmospheric spectra and improved theoretical calculations will be required for all bands. Preliminary versions of several sets of improved line parameters are presented.
Goldman, A.↗
New spectral features of stratospheric trace gases identified from high-resolution infrared balloon-borne and laboratory spectra
A new Michelson-type interferometer system operating in the infrared at very high resolution has been used to record numerous balloon-borne solar absorption spectra of the stratosphere, ground-based solar absorption spectra, and laboratory spectra of molecules of atmospheric interest. In the present work results obtained for several important stratospheric trace gases, HNO3, CIONO2, HO2NO2, NO2, and COF2, in the 8- to 12-micron spectral region are reported. Many new features of these gases have been identified in the stratospheric spectra. Comparison of the new spectra with line-by-line simulations shows that previous spectral line parameters are often inadequate and that new analysis of high-resolution laboratory and atmospheric spectra and improved theoretical calculations will be required for many bands. Preliminary versions of several sets of improved line parameters under development are discussed.
Goldman, A.↗
Explosive component acceptance tester using laser interferometer technology
Acceptance testing of explosive components requires a reliable and simple to use testing method that can discern less than optimal performance. For hot-wire detonators, traditional techniques use dent blocks or photographic diagnostic methods. More complicated approaches are avoided because of their inherent problems with setup and maintenance. A recently developed tester is based on using a laser interferometer to measure the velocity of flying plates accelerated by explosively actuated detonators. Unlike ordinary interferometers that monitor displacement of the test article, this device measures velocity directly and is commonly used with non-spectral surfaces. Most often referred to as the VISAR technique (Velocity Interferometer System for Any Reflecting Surface), it has become the most widely-accepted choice for accurate measurement of velocity in the range greater than 1 mm/micro-s. Traditional VISAR devices require extensive setup and adjustment and therefore are unacceptable in a production-testing environment. This paper describes a new VISAR approach which requires virtually no adjustments, yet provides data with accuracy comparable to the more complicated systems. The device, termed the Fixed-Cavity VISAR, is currently being developed to serve as a product verification tool for hot-wire detonators and slappers. An extensive data acquisition and analysis computer code was also created to automate the manipulation of raw data into final results.
Wickstrom, Richard D.↗