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  • 1
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    Very long baseline interferometric observations made with an orbiting radio telescope (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An orbiting spacecraft and ground observatories have been used to obtain interferometric observations of cosmic radio sources. The Tracking and Data Relay Satellite System (TDRSS) was used as the orbiting observatory in conjunction with two 64-meter radio telescopes at ground observatories, one in Australia and one in Japan. The quasars 1730-130 (NRAO 530), 1510-089, and 1741-038 were observed at a frequency of 2.3 gigahertz, and a maximum projected baseline of 1.4 earth diameters was achieved. All quasar observations for which valid data were acquired resulted in detected fringes. Many of the techniques proposed for a dedicated very long baseline interferometry observatory in space were used successfully in this experiment.
    Keywords: ASTRONOMY
    Type: Science (ISSN 0036-8075); 234; 187-189
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  • 2
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    Speckle interferometry of asteroids. II - 532 Herculina (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Speckle interferometry of 532 Herculina performed on January 17 and 18, 1982, yields triaxial ellipsoid dimensions of (263 + or - 14) x (218 + or - 12) x (215 + or - 12) km, and a north pole for the asteroid within 7 deg of RA = 7h47min and DEC = -39 deg (ecliptic coordinates lambda = 132 deg beta = -59 deg). In addition, a 'spot' some 75 percent brighter than the rest of the asteroid is inferred from both speckle observations and Herculina's lightcurve history. This bright complex, centered at asterocentric latitude -35 deg, longitude 145-165 deg, extends over a diameter of 55 deg (115 km) of the asteroid's surface. No evidence for a satellite is found from the speckle observations, which leads to an upper limit of 50 km for the diameter of any satellite with an albedo the same as or higher than Herculina.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 61; 232-240
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  • 3
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    Very long baseline interferometry observations using the tracking and data relay satellite as an orbiting radio telescope (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An antenna in geostationary orbit was used for VLBI observations at 2.3 GHz, in combination with ground antennas in Australia and Japan. 23 of the 25 observed sources were detected on orbiter-ground baselines, with baseline lengths as large as 2.15 earth diameters. Brightness temperatures between 10 to the 12th K and 4 x 10 to the 12th K were measured for 10 sources.
    Keywords: ASTRONOMY
    Type: IAU Symposium on the Impace of VLBI on Astrophysics and Geophysics; May 10, 1987 - May 15, 1987; Cambridge, MA; United States
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  • 4
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    Spectroscopic planetary detection (1986)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The Sun-as-a-star was monitored using the McMath Fourier transform spectometer (FTS) on Kitt Peak in 1983. In 1985 the first measurement was made using the laser heterodyne technique. The FTS measurements now extend for three years, with errors of order 3 meters/sec at a given epoch. Over this 3 year period, a 33 meter/sec change was measured in the apparent velocity of integrated sunlight. The sense of the effect is that a greater blueshift is seen near solar minimum, which is consistent with expectations based on considering the changing morphology of solar granular convection. Presuming this effect is solar-cycle-related, it will mimic the Doppler reflex produced by a planetary companion of approximately two Jupiter masses, with an 11 year orbital period. Thus, Jupiter itself is below the threshold for detection by spectroscopic means, without an additional technique for discrimination. However, for planetary companions in shorter period orbits (P approx. 3 years) the threshold for unambiguous detection is well below one Jupiter mass.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 143-144
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  • 5
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    Remote sensing of the atmosphere of Mars using infrared pressure modulation and filter radiometry (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The study of the atmosphere and climate of Mars will soon be advanced considerably by the Mars Observer mission. This paper describes the atmospheric sounder for this mission and how it will measure key Martian atmospheric parameters using IR gas correlation and filter radiometry. The instrument now under development will provide high-resolution vertical profiles of atmospheric temperature, pressure, water vapor, dust, and clouds using limb sounding techniques as well as nadir observations of surface thermal properties and polar radiative balance.
    Keywords: ASTRONOMY
    Type: Applied Optics (ISSN 0003-6935); 25; 4232-424
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  • 6
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    Reference frame studies at JPL/CALTECH (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Studies being undertaken in order to interconnect the three principal celestial coordinate systens are reviewed. These systems are the optical frame (FK4/FK5) based on positions of Galactic stars, the planetary/lunar ephemeris frame based on the major celestial bodies of the solar system, and the radio frame constructed from observations of quasars. The optical frame is being connected to the radio frame by VLBI observations of radio-emitting stars, and the radio frame is being tied to the ephemeris frame in several ways; for example, differential VLBI measurements between quasars and planet-orbiting spacecraft. Prospects for future interconnection studies are briefly discussed.
    Keywords: ASTRONOMY
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  • 7
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    An optical heterodyne densitometer (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Researchers are developing an optical heterodyne densitometer with the potential to measure optical density over an unprecedented dynamic range with high accuracy and sensitivity. This device uses a Mach-Zender interferometer configuration with heterodyne detection to make direct comparisons between optical and RF attenuators. Researchers expect to attain measurements of filter transmittance down to 10 to the minus 12th power with better than 1 percent uncertainty. In addition, they intend to extend the technique to the problem of measuring low levels of light scattering from reflective and transmissive optics.
    Keywords: ASTRONOMY
    Type: NASA, Ames Research Center, Second Workshop on Improvements to Photometry; p 249-253
    Format: application/pdf
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  • 8
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    The 1981 outburst of the old nova GK Persei (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Old nova GK Per was observed in 1981 with the IUE, during its rise, maximum, and subsequent return to minimum. In outburst, GK Per is luminous but much redder than dwarf novae or standard model accretion disks. The observed spectrum can be explained qualitatively with the Ghosh and Lamb (1979) model for the interaction of an accretion disk with the magnetic field of the accreting white dwarf. The N V and He2 are enhanced relative to other emission lines during outburst. This can be understood with photoionization by very soft X-rays having a luminosity comparable to that of the hard X-rays.
    Keywords: ASTRONOMY
    Type: ESA, A Decade of UV Astronomy with the IUE Satellite, Volume 1; p 155-157
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  • 9
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    Einstein SSS and MPC observations of Aql X-1 and 4U1820-30 (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The results of timing and spectral analyses of the X-ray sources Aql X-1 (X1908+005) and 4U1820-30 (NGC6624) are reported using data obtained with the Einstein SSS (Solid State Spectrometer) and MPC (Monitor Proportional Counter) instruments. A classic type I burst was observed from Aql X-1 in both detectors and a coherent modulation with a period of 131.66 + or - 0.02 ms and a pulsed fraction of 10 percent was detected in the SSS data. There is no evidence for a loss of coherance during the approximately 80 sec when the burst is observable. The 2 sigma upper limit on the rate of change of the pulse period is 0.00005s/s. It is argued that an asymmetrical burst occurring on a neutron star rotating at 7.6 Hz offers a plausible explanation for the oscillation. The data from 4U1820-30 show that the amplitude of the 685 sec modulation, identified as the orbital period, is independent of energy down to 0.6 keV. The SSS data show that the light curve in the 0.6 to 4.5 keV band is smoother than at higher energies.
    Keywords: ASTRONOMY
    Type: ESA, The 23rd ESLAB Symposium on Two Topics in X Ray Astronomy. Volume 1: X Ray Binaries; p 459-465
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  • 10
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    Search for optical flashes from gamma-ray bursters (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Preliminary results of an investigation of the Ondrejov and Sonneberg plate collections for possible optical counterparts to gamma ray bursters (GRBs) are presented. The study proceeds in three directions: as time-correlated searches for GRBs with known positions, as time-correlated searches for GRBs without known positions, and as archival searches. The position of the Perseus flasher was also investigated using 1000 hours of monitoring. No evidence for true optical images associated with GRBs was found. Statistical conclusions are drawn and discussed.
    Keywords: ASTRONOMY
    Type: Advances in Space Research (ISSN 0273-1177); 6; 4, 19
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