Astronomy and Astrophysics for the 1980's, Volume 2 Reports of the Panels (1983) / Chapter Skim
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III. Description of Recommended Projects and Facilities
III. Description of Recommended Projects and Facilities
Pages 214-228
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From page 214... ...
Although not coherently phased owing to atmospheric and other environmental fluctuations, closure around the 36 independent triangles yields 80 percent of the phase information, and it is known from recent experiments that very accurate maps can be made. Only a dedicated Array will provide the flexibility required for observing transient phenomena and the frequency agility needed for observations in many wavebands.
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From page 215... ...
In a 1979 personal communication furnished to the panel, Sir Martin Ryle, the Astronomer Royal, has written, n If we are to have any hope of solving the problem of the origin and transmission mechanism of the huge energies involved in the main components of radio galaxies, then it will be by comparing the most compact nuclear structure with the more extended features.
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From page 216... ...
Since masers are found in interstellar regions of star formation and in the envelopes of evolved stars, their study provides unique information on the birth and death of stars. A variety of stellar objects including novae, supernovae, binary stars, flare stars, and x-ray sources emit transient radio emission from regions of interplanetary dimensions.
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From page 217... ...
A submillimeter telescope of about 10-m aperture at a high site would provide the first opportunity for detailed studies of this rich region of the electromagnetic spectrum and would give angular resolutions of as small as 8.5 arcsec -- a tremendous step forward in the study of interstellar molecules and continuum sources. Within the submillimeter band lie three major areas of interest: first, the studies of spectral lines of molecules (mainly rotational lines)
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From page 218... ...
Good submillimeter resolution will also be of great value in permitting observations of molecular envelopes around stars with mass loss. In observations of continuum radiation from quasars and bright radio sources there is a serious gap in the submillimeter band that must be filled if we are to understand the relationships among, for example, the sources of radio emission in quasars, BL Lac objects, and the sources of optical nonthermal radiation.
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From page 219... ...
This system has the multiple advantages of mapping very quickly, with higher angular resolution, with a large dynamic range, and at the same time will yield essentially complete coverage of the southern sky. Conceptual and engineering studies are now under way that could lead to an orbiting VLBI facility in the late 1980's.
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From page 220... ...
Most of the sky is accessible to the southernmost ground station in Hawaii, and by adding southern hemisphere NASA stations, combined with international arrangements, the detailed VLBI study of radio sources in the rich southern sky would be possible for the first time. The Galactic center, the Magellanic Clouds, the x-ray source Circinus X-1, and the bright radio galaxy Centaurus A are examples of the important southern sources that become accessible to VLBI study.
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From page 221... ...
The general classes of VLBI studies have already been considered in the discussion of the ground-based Array; here we briefly summarize the relevant conclusions. The study of quasar phenomena, critically dependent on the construction of densely sampled maps, can be advanced greatly when a factor of 3 in angular resolution is gained.
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From page 222... ...
The study of interstellar masers profits enormously from the enhanced capability of the space VLBI system. The masers are Galactic objects, and with the space VLBI system, the entire southern Milky Way, plus the Magellanic Clouds, is brought into view.
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From page 223... ...
3. Cost Estimates An orbiting VLBI station bearing a 25-m radio telescope can be carried on a dedicated special-purpose satellite or could be mounted on a large multipurpose platform such as the Space Science and Applications Platform now being studied by NASA.
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From page 224... ...
A filledaperture instrument also has greater frequency agility, higher instantaneous bandwidth, the ability to handle rapidly fluctuating signals, lower instrumental polarization, and higher dynamic range. All previous studies of the needs of U.S.
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From page 225... ...
Such molecular features would help to settle the ongoing argument as to whether the hydrogen clouds detected in absorption are intervening or intrinsic to the background source. Further, the finding of highrea-sn'~t molecular Lines would help to fix the constancy of the electron-to-proton mass ratio in a manner analogous to the use of neutral hydrogen and optical absorption lines to study the constancy of other fundamental constants of nature.
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From page 226... ...
Interferometric observations with the 24-inch auxiliary solar telescopes at Kitt Peak, using a CO2 laser as a local oscillator, have demonstrated the feasibility of a heterodyne interferometer working through the 10-m atmospheric window and have shown that there are a number of challenging applications for an instrument of this kind. m e work so far has been with a fixed baseline of 5.5 m; longer and variable baselines are needed to exploit the full power of the technique, and it is highly desirable to employ somewhat larger telescopes to increase the sensitivity.
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From page 227... ...
It is finally a powerful astrometric instrument, which will allow the location of infrared sources and proper motions to be determined to high precision and will permit testing of the General meory of Relativity to a new order of accuracy by measuring the deflection of radiation from sources near the limb of the Sun.
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From page 228... ...
radio astronomy are at the National Astronomy Centers, the Panel attaches a high priority to maintaining and upgrading this investment. It recommends especially that adequate funding be made available for maintaining and upgrading the VLA as the most powerful existing instrument for U.S.
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