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  • 1
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    Indirect planet detection with ground-based long-baseline interferometry (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Narrow-angle astrometry with long-baseline infrared interferometers can provide extremely high accuracies as required for indirect planet detection. Narrow-angle astrometric interferometry exploits the properties of atmospheric turbulence over fields smaller than the interferometer baseline divided by the atmospheric scale height. For such fields, accuracy is linear with star separation, and nearly inversely proportional to baseline length. To exploit these properties, the interferometer observes a relatively bright (less than 13 mag(sub K)) target in the near infrared at 2.2 micrometers, and uses phase referencing to find a reference star within the 2.2-micrometers isoplanatic patch. With this technique faint references can be found for most targets. With baselines greater than 100 m, which also minimize photon-noise errors, and with careful control of systematic errors by using laser metrology, accuracies of tens of microarcseconds/square root of (hour) should be possible.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science (ISSN 0004-640X); 212; p. 385-390
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  • 2
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    Potential of long-baseline infrared interferometry for narrow-angle astrometry (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Narrow-angle astrometry has many astrophysical applications, from the measurement of parallaxes to the search for planets around nearby stars. Ground-based long-focus telescopes with photoelectric detectors have achieved accuracies of about 2-3 milliarcsec in 1 h. This accuracy is limited primarily by the atmosphere, and is consistent with models of atmospheric turbulence. However, applying these turbulence models to observations with long-baseline interferometers yields astrometric errors that are far smaller than can be achieved with long-focus telescopes. The predictions for the ultimate accuracy of ground-based narrow-angle astrometry using long-baseline IR (2.2 micron) stellar interferometers are very promising. With the excellent seeing at a high altitude site like Mauna Kea, the atmospheric limit for a 1 h astrometric measurement is expected to be of the order of 10 microarcsec for 1 h of integration. This two-order-of-magnitude improvement over conventional measurements is due to two effects. One is that a long-baseline IR interferometer can find useful reference stars very near an arbitrary target star, so that the atmospherically-induced motions of both stars are highly correlated. The second is that the baseline length can be much larger than the separation of the stellar beams in the turbulent atmosphere, resulting in a reduction in astrometric error with increasing baseline length.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 262; 1; p. 353-358.
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  • 3
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    Long-baseline optical and infrared stellar interferometry (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The history and the current status of optical and infrared long-baseline interferometry are reviewed. In particular, attention is given to Michelson interferometry; the Mark III stellar interferometer and its applications to astrometry, measurement of stellar diameters, and observations of binary stars; and advanced techniques. The discussion then focuses on astrometry and imaging with space interferometers. Finally, the future of long-baseline interferometry is briefly discussed with particular reference to the interferometry of the moon.
    Keywords: ASTRONOMY
    Type: In: Annual review of astronomy and astrophysics. Vol. 30 (A93-25826 09-90); p. 457-498.
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  • 4
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    Angular diameter measurements of stars (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Angular diameters determined with the Mark III Optical Interferometer are presented for 12 stars at wavelengths of 450 and 800 nm. The uniform disk diameters resulting from fits to the visibility observations have rms residuals of order 1 percent for the 800 nm measurements and less than 3 percent for the 450 nm measurements. The improvement over previous observations with this instrument is due to improved data analysis and the use of a wider range of baseline lengths. An analysis of the calibration systematics for the Mark III Optical Interferometer is included. There is good agreement between these measurements and previously published data. The changes in uniform disk diameter between wavelengths of 450 and 800 nm agree with models of stellar atmospheres.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 101; 2207-221
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  • 5
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    Wide-angle astrometry with the Mark III stellar interferometer (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Astrometric measurements made with the Mark III stellar interferometer on five nights in August-September 1988 yielded average formal 1-sigma errors for 12 FK5 stars of 6 mas in declination and 10 mas in right ascension. This improvement in precision over previously reported measurements with this instrument made in 1986 is attributable to several factors: a second 12 m baseline; oriented E-S, was added to the instrument to improve the determination of right ascension; two-color analysis was included in the data-reduction process, along with a new central-fringe identification algorithm using three spectral channels, in order to reduce atmospheric errors; thermal control was greatly improved; and changes were made to observational procedures and hardware to monitor variations in the delay offset due to residual thermal drifts. Approximately half of the new positions are within 50 mas of their FK5 positions. However, an extended series of measurements are needed to ascertain the accuracy that can be achieved by interferometry.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 100; 1701-171
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  • 6
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    A mission and system design option for the Orbiting Stellar Interferometer (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Orbiting Stellar Interferometer (OSI) is a proposed space-based observatory that will open exciting new vistas in astronomy and address fundamental scientific questions by making extremely accurate (3 to 30 microarcsecond) astrometric measurements of the positions of stars, quasars, and other astronomical objects as faint as magnitude 20. In addition, it will be able to image objects with a resolution of about 13 milliarcseconds. Using the lessons learned from the development of a point design for OSI, the Jet Propulsion Laboratory has developed a new conceptual design, with emphasis on reducing its cost and complexity while maximizing the return of valuable science.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: IAF PAPER 92-0527
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  • 7
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    A moderate space mission for optical interferometry (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Orbiting Stellar Interferometer (OSI) is a proposed space-based observatory which will open exciting new vistas in astronomy and address fundamental scientific questions by making extremely accurate (3 - 30 microarcsecond) astrometric measurements of the positions of stars, quasars, and other astronomical objects as faint as magnitude 20. In addition, it will be able to image objects with a resolution of 5 milliarcseconds. As the first optical interferometer in space, OSI will provide major advances in astrophysics while demonstrating a powerful concept applicable to major space-based observations of the future. The Jet Propulsion Laboratory has developed a preliminary design of OSI to establish its feasibility and to estimate performance that can be achieved in a mission of moderate scale. In this first publication of the results of the first year of study, the science objectives are presented, and the design of the mission, instrument, and spacecraft are discussed.
    Keywords: ASTRONOMY
    Type: IAF PAPER 91-421
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  • 8
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    Planetary searches using optical astrometric interferometers (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The detectability of planets is discussed, and observations made with an astrometric interferometer (AI) at Mount Wilson are presented. Planets are detectable as a result of their periodic perturbation of the position of a central observable star. This detection requires relative astrometric accuracies of about 3 x 10 to the -4th for Jovian planets and about 3 x 10 to the -7th arcsec for terrestrial planets. The principles governing astrometric interferometry are explained, and it is conjectured that a two-color optical AI on earth should be capable of about 0.0001 arcsec rms accuracy for stars brighter than magnitude 7-10; small one-color space systems should achieve at least 0.00001 arcsec. Owing to atmospheric turbulence, two-color systems permit correction every few milliseconds for the random wavefront tilt. A 3.4-meter baseline interferometer on Mount Wilson has demonstrated arcsec rms fluctuations of about 0.02 for 1-sec samples. Space-based optical astrometric interferometry is also discussed.
    Keywords: ASTRONOMY
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  • 9
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    Hubble Extra Solar Planet Interferometer (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper describes a proposed third-generation Hubble instrument for extra-solar planet detection, the Hubble Extra-Solar Planet Interferometer (HESPI). This instrument would be able to achieve starlight cancellation at the 10 exp 6 to 10 exp 8 level, given a stellar wavefront with phase errors comparable to the present Hubble telescope wavefront. At 10 exp 6 starlight cancellation, HESPI would be able to detect a Jupiter-like planet next to a star at a distance of about 10 parsec, for which there are about 400 candidate stars. This paper describes a novel approach for starlight suppression, using a combination of active control and single-mode spatial filters, to achieve starlight suppression far below the classical limit set by scattering due to microsurface imperfections. In preliminary lab experiments, suppression by a factor of 40 below the classical scatter limit due to optical wavefront errors has been demonstrated.
    Keywords: ASTRONOMY
    Type: Space Astronomical Telescopes and Instruments; Apr 01, 1991 - Apr 04, 1991; Orlando, FL; United States
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  • 10
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    System design for lunar-based optical and submillimeter interferometers (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The designs and performances of lunar optical and submillimeter interferometer systems for the Space Exploration Initiative (SEI) are described. Attention is given to the conceptual design of these systems and to the concepts for the launch, transport, deployment, maintenance, and toleration of the lunar environment (both natural and induced by crew activity). Consideration is also given to the requirements for SEI resources (such as cargo space and crew time), the data return concepts, and the flight system technonogy develpment needs.
    Keywords: ASTRONOMY
    Type: SPIE Meeting on Space astronomical Telescopes and Instruments; Apr 01, 1991 - Apr 04, 1991; Orlando, FL; United States
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