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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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NASA NTRS1982

Astrometric observations of the satellites of the outer planets. V - The oppositions of 1978-1979, 1980, and 1981

Accurate photographic positions obtained during the 1978-1979, 1980 and 1981 oppositions are presented for the positions of the Galilean and the Saturn satellites. Spherical-equatorial coordinates are presented for a total of 1032 pairs, for the equator and equinox of 1950.0 and 1316 intersatellite positions. The data were obtained by the Leander McCormick Observatory's 67-cm refractor telescope, and answers the need for more refined orbital element data on these satellites required by the Galileo Jupiter orbiter vehicle.

Rohde, J. R.↗
NASA NTRS1984

The parallax and astrometric orbit of Mu Cassiopeiae

A total of 371 photographic plates were made of the binary Mu Cassiopeia (Mu Cas) region with a 76 cm refractor. An astrometric orbit of nearly 22.09 yr was calculated, accompanied by an eccentricity of close to 0.58 and a semimajor axis close to 0.19 arcsec. The absolute magnitude was approximately 5.83 and the radial velocity 164 km/sec.

Russell, J. L.↗
NASA NTRS1984

Reduction of astrographic catalogues

An automatic program for the reduction of overlapping Carte du Ciel plates is described. The projection and transformation equations are given and the RAA subprogram flow is outlined. The program was applied to two different sets of data, namely to nine overlapping plates of the Cape Zone of the CdC, and to fifteen plates taken with the CIDA-refractor of the open cluster Tr10.

Stock, J.↗
NASA NTRS1985

Some design considerations for a satellite-borne magnetograph

The design criteria for a compact magnetograph that can monitor solar magnetic fields from a free-flying satellite for 5 to 10 years are reviewed. The signal-to-noise ratio that can be obtained with a 10-cm f/10 refractor operated with a Fabry-Perot filter and a solid-state detector array is derived. The telescope measures the longitudinal component of the magnetic field for the entire solar disk in a few minutes at a 20-G threshold and at 3-arcsec resolution. The Fabry-Perot filter has a lithium niobate etalon, which can be tuned electrically and operated at a fixed tilt angle in such a manner that it cancels the solar rotational Doppler shifts in the transmitted spectrum. Principles of operation of various types of polarization modulators are presented, and it is concluded that photoelastic modulators and liquid-crystal devices hold the most promise for use in a satellite-borne magnetograph,

Rust, D. M.↗
NASA NTRS1985

Stokes parameters modulator for birefringent filters

The Solar Birefringent Filter (Filter Polarisiant Solaire Selectif FPSS) of Meudon Observatory is presently located at the focus of a solar refractor with a 28 cm lens directly pointed at the Sun. It produces a diffraction limited image without instrumental polarization and with a spectral resolution of 46,000 in a field of 6 arc min. diameter. The instrument is calibrated for absolute Doppler velocity measurements and is presently used for quantitative imagery of the radial velocity motions in the photosphere. The short period oscillations are recorded. Work of adapting the instrument for the imagery of the solar surface in the Stokes parameters is discussed. The first polarizer of the birefringent filter, with a reference position angle 0 deg, is associated with a fixed quarter wave plate at +45 deg. A rotating quarter wave plate is set at 0 deg and can be turned by incremented steps of exactly +45 deg. Another quarter wave plate also initially set at 0 deg is simultaneously incremented by -45 deg but only on each even step of the first plate. A complete cycle of increments produces images for each of the 6 parameters I + or - Q, I + or - U and I + or - V. These images are then subtracted by pairs to produce a full image in the three Stokes parameters Q, U and V. With proper retardation tolerance and positioning accuracy of the quarter wave plates, the cross talk between the Stokes parameters was calculated and checked to be minimal.

Dollfus, A.↗
NASA NTRS1985

A preliminary look at astrometric accuracy as a function of photon counts

The importance of photon counts as a factor in the accuracy of astrometric positions is illustrated by a preliminary look at data collected with the Allegheny Observatory's photon-counting detector, the Multichannel Astrometric Photometer. Twenty estimates are plotted of the standard errors, per hour, of astrometric positions obtained with the photometer and the blue-light lens of the observatory's 30-inch refractor. The agreement between the estimated standard errors in the X and Y coordinates supports the conclusion that, as predicted by Drake, the accuracy is dependent upon the count rate.

Gatewood, G.↗
NASA NTRS1986

A survey of nearby stars for the perturbatative effects of extrasolar planetary systems

A new photoelectric astrometric system, the Multichannel Astrometric Photometer (MAP), was developed, and it was used in a regular observing program designed to detect extrasolar planetary systems. The 76-cm refractor of the Allegheny Observatory was fully renovated to make it suitable as the observing instrument for the MAP. The MAP itself was designed, constructed and tested in actual operation. A data analysis system was developed and tested.

Gatewood, G. D.↗
NASA NTRS1989

The Allegheny Observatory search for planetary systems

The accomplishments of the observatory's search for planetary systems are summarized. Among these were the construction, implementation, and regular use of the Multichannel Astrometric Photometer (MAP), and the design, fabrication and use of the second largest refractor objective built since 1950. The MAP parallax and planetary observing programs are described. Various developments concerning alternate solid state photodetectors and telescope instrumentation are summarized. The extreme accuracy of the system is described in relation to a study of the position and velocity of the members of the open cluster Upgren 1. The binary star system stringently tests the theory of stellar evolution since it is composed of an evolved giant F5 III and a subgiant F5 IV star. A study that attempts to measure the luminosities, surface temperatures, and masses of these stars is discussed.

Gatewood, George D.↗
NASA NTRS1990

Map-based trigonometric parallaxes of open clusters - The Pleiades

The multichannel astrometric photometer and Thaw refractor of the University of Pittsburgh's Allegheny Observatory have been used to determine the trigonometric parallax of the Pleiades star cluster. The distance determined, 150 with a standard error of 18 parsecs, places the cluster slightly farther away than generally accepted. This suggests that the basis of many estimations of the cosmic distance scale is approximately 20 percent short. The accuracy of the determination is limited by the number and choice of reference stars. With careful attention to the selection of reference stars in several Pleiades regions, it should be possible to examine differences in the photometric and trigonometric modulus at a precision of 0.1 magnitudes.

Gatewood, George↗
NASA NTRS1991

Allegheny Observatory search for planetary systems

The newly developed Multichannel Astrometric Photometer (MAP) and a rebuilt red light 0.76 meter Thaw refractor are used in an astrometric observational program to detect Jupiter-like planets in orbit about nearby stars. The program includes 15 stars and is obtaining approx. 12 good observations per year of each of them, sufficient to assure an annual normal point precision of 0.001 arcsec (1 mas) per object. The observational program will yield the first astrometric information about planetary systems in general. The astrometric technique is most sensitive to nearby planetary systems and to massive planets that have orbits that place them within the regions around a star where the temperature is sufficiently low to permit the existence of water ice grains. Thus it covers a different search space than that of radial velocity techniques. Currently the only astrometric survey program, it is complementary to other detection programs and some target stars have been included to assure overlap with them. The minimum detectable mass varies with the particular target star from objects almost twice as massive as Neptune to bodies almost twice as massive as Jupiter.

Gatewood, George D.↗
NASA NTRS1994

One milliarcsecond precision studies in the regions of Delta Equulei and Chi(sup 1) Orionis

Trigonometric parallaxes for stars in the regions of the binary stars Delta Equulei (HR 8123) and Chi(sup l) Orionis (HR 2047) are derived from data collected with the Multichannel Astrometric Photometer (MAP) and the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of all trigonometric studies of delta Equ is now +5.42 +/- 0.93 mas, corresponding to absolute magnitudes of 3.87 +/- 0.04 and 3.95 +/- 0.04 mag, respectively, for the primary and secondary. Using the Popper and Dworetsky orbit we find a photocentric semimajor axis of 2.9 +/- 0.8 mas and individual masses of 1.21 +/- 0.090 and 1.19 +/- 0.088 solar masses, respectively, for the primary and secondary components. The weighted mean trigonometric parallax of all studies of the binary star Chi(sup l) Ori is +111.0 +/- 0.92 mas, implying an absolute visual magnitude for the dominant GO V primary of 4.63 +/- 0.018 mag. The photocentric semimajor axis, derived from a fraction of the orbit, is 96.9 +/- 5.4 mas.

Gatewood, George↗
NASA NTRS1993

One-milliarsecond precision parallax studies in the regions of Delta Cephei and EV Lacertae

Trigonometric parallaxes for stars in the regions of the variable stars delta Cephei and EV Lacertae are derived from data collected with the Multichannel Astrometric Photometer (MAP) and the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of all trigonometric studies of delta Cephei is now + 0.0030 sec + or - 0.00093 sec, corresponding to a distance modulus of 7.61 + or - 0.67 mag. This indicates that this luminosity standard star is approximately one standard deviation more distance than has been generally accepted. The weighted mean trigonometric parallax of all studies of the variable star EV Lacertae (BD + 43 deg 4305) is + 0.1993 sec + or - 0.00093 sec, implying a distance modulus of - 1.498 + or - 0.0010 mag. The calculated absolute magnitude of this star is almost exactly that predicted by its (R-I)(sub Kron) magnitude and by the Gliese (R-I) main-sequence value for stars in the solar neighborhood. We also find a parallax of 0.0189 sec + or - 0.0008 sec for the FO IVn star, HR 8666 (BD + 43 sec 4300). The derived luminosity of this star is midway between that expected for luminosity class IV and V stars at the indicated temperature.

Gatewood, George↗
NASA NTRS1994

Map-based trigonometric parallaxes of open clusters: The Praesepe

Trigonometric parallaxes for stars in the Praesepe open star cluster are deduced from data collected with the Multichannel Astrometric Photometer (MAP) at the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of five cluster members is +5.21 +/- 0.79 mas (0.00079 arcsec), corresponding to a distance modulus of 6.42 +/- 0.33 mag. We briefly compare this result with that derived earlier for the Hyades and note agreement with the distance found by main-sequence fitting. We also discuss briefly an improvement in the weighting scheme of the centroiding algorithm used in this series.

Gatewood, George↗
NASA NTRS1995

Map-based trigonometric parallaxes of open clusters: Coma

This is the fourth study in a series to determine the direct trigonometric parallaxes of four of the nearest open star clusters, the Hyades, the Pleiades, the Praesepe, and the nearby cluster in Coma (Gatewood et al. 1990; Gatewood et al. 1992); Gatewood & Kiewiet de Jonge 1994). The results for the open star cluster in Coma are compared with those of the other three clusters, and the members are found to be significantly subluminous. The trigonometric parallax of the cluster is estimated from that of three members studied with the Multichannel Astrometric Photometer (MAP) at the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of the cluster is +13.53 +/- 0.54 mass (0.00054 min), corresponding to a distance modulus of 4.34 +/- 0.09 mag. The U-B excess of the Coma cluster members may be used to adjust the observed absolute magnitudes and the B-V measurements as suggested by Sandage & Eggen (1959). The agreement obtained in this manner suggests that, like subdwarf stars, the stars of the Coma cluster appear subluminous because of line blanketing. One of the three members observed in this study was recognized as a member by its parallax and is the faintest known member of the cluster.

Gatewood, George↗
NASA NTRS2006

Optical Interferometry Motivation and History

A history and motivation of stellar interferometry is presented. The topics include: 1) On Tides, Organ Pipes, and Soap Bubbles; 2) Armand Hippolyte Fizeau (1819-1896); 3) Fizeau Suggests Stellar Interferometry 1867; 4) Edouard Stephan (1837-1923); 5) Foucault Refractor; 6) Albert A. Michelson (1852-1931); 7) On the Application of Interference Methods to Astronomy (1890); 8) Moons of Jupiter (1891); 9) Other Applications in 19th Century; 10) Timeline of Interferometry to 1938; 11) 30 years goes by; 12) Mount Wilson Observatory; 13) Michelson's 20 ft Interferometer; 14) Was Michelson Influenced by Fizeau? 15) Work Continues in the 1920s and 30s; 16) 50 ft Interferometer (1931-1938); 17) Light Paths in the 50 ft Interferometer; 18) Ground-level at the 50 ft; 19) F.G. Pease (1881-1938); 20) Timeline of Optical Interferometry to 1970; 21) A New Type of Stellar Interferometer (1956); 22) Intensity Interferometer (1963- 1976; 23) Robert Hanbury Brown; 24) Interest in Optical Interferometry in the 1960s; 25) Interferometry in the Early 1970s; and 26) A New Frontier is Opened up in 1974.

history↗
NASA NTRSDate not supplied

Reducing OCO-2 regional biases through novel 3D cloud, albedo, and meteorology estimation

This ROSES project tests the addition of novel 3D cloud, albedo fine structure, temperature and water vapor profile to the OCO-2 retrieved system. All new parameters have been added to the ReFRACtor / TROPESS system for testing. Currently, we are comparing 3d-cloud retrievals from OCO-2 radiances to the MODIS-derived EAR3T cloud properties. The water and temperature profile retrievals have been implemented and result in improved XCO2 comparisons to TCCON, and now are implementing principal-component analysis (PCA) to reduce the number of parameters added. We are also studying ECOSTRESS spectral library, AVIRIS-ng, OCO-2 spectral residuals, and albedo retrievals with additional parameters to determine the appropriate characterization of albedo. We find that the current albedo parametrization (2nd order polynomial) is adequate for ocean and vegetation, but not adequate for soil and rock observations.

Reducing OCO-2↗
NASA NTRS2020

Small Aperture Telescopes for the Simons Observatory

The Simons Observatory (SO) is an upcoming cosmic microwave background(CMB) experiment located on Cerro Toco, Chile, that will map the microwave sky in temperature and polarization in six frequency bands spanning 27 to 285 GHz. SO will consist of one 6-meter Large Aperture Telescope (LAT) fielding∼30,000 detectors and an array of three 0.42-meter Small Aperture Telescopes (SATs) fielding an additional 30,000 detectors. This synergy will allow for the extremely sensitive characterization of the CMB over an-gular scales ranging from an arcmin to tens of degrees, enabling a wide range of scientific output. Here we focus on the SATs targeting degree angular scales with successive dichroic instruments observing at Mid-Frequency (MF: 93/145 GHz), Ultra-High-Frequency (UHF:225/285 GHz), and Low-Frequency (LF: 27/39 GHz). The three SATs will be able to map∼10% of the sky to a noise level of∼2 μK-arcmin when combining 93 and 145 GHz. The multiple frequency bands will allow the CMB to be separated from galactic foregrounds (primarily synchrotron and dust), with the primary science goal of characterizing the primordial tensor-to-scalar ratio, r, at a target level ofσ(r)≈0.003.

Small aperature telescope↗