Speckle interferometry of close double stars. Schielicke, Astronomische Gesellschaft 1999, p. techniques have produced visual orbits of many spectroscopic binaries with a milli arcsecond precision. An interferometer is an instrument that compares the position or surface structure of two objects. The unique combination of excellent Fourier coverage at short baselines and high-quality long-baseline fringe data allows us to determine the location and. The limitation imposed by long term irregularities in the earths atmosphere is estimated to be on the order of 0.01 arcsec. Reference: Röser, S., 1999, DIVA - Beyond HIPPARCOS and Towards GAIA, in: Rev. The Navy Precision Optical Interferometer (NPOI) is a major astronomical interferometer, with the worlds largest baselines, operated by the Naval Observatory Flagstaff Station (NOFS) in collaboration with the Naval Research Laboratory (NRL) and Lowell Observatory. The present inter- ferometric measurements are thought to be dominated by instrumental errors, indicating that a significant improvement is possible in the precision of astrometric measurements. After a few years, repeated observations of the grid allow one to determine the orientation of the interferometer baseline. In this poster we present a few examples of astrophysical topics where DIVA can open new horizons. By providing a wealth of high-quality observational data, DIVA will influence almost every field of astronomy. The performance of DIVA will significantly exceed that of the famous HIPPARCOS mission in all important aspects. Interferometer and observing mode Waveband Limiting magnitude Minimum baseline (m) (un-projected) Maximum baseline (m) Approx. Additionally, broad-band photometry will be obtained for all these 35 million objects, together with multi-channel intermediate-band photometry for the brightest 10 million stars (V <= 13.5). Swenson Abstract and Figures This chapter is concerned with the techniques by which angular positions of radio sources can be measured with the greatest possible accuracy, and with the. DIVA will measure the positions, proper motions and parallaxes of all stars down to 15th visual magnitude. If launched in 2003, final data from DIVA will be available in 2007. The poster presents a brief overview of the scientific objectives of the planned astrometric and photometric minisatellite DIVA (Double Interferometer for Visual Astrometry), to be built in collaboration of several German astronomical institutes.
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