Working Papers Astronomy and Astrophysics Panel Reports (1991) / Chapter Skim
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Radio Astronomy
Radio Astronomy
Pages 1-24
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From page 1... ...
Unfortunately, however, the funding for radio astronomy has not been able to keep pace with the growth of the science. Over the past ten to fifteen years, important radio telescopes have been closed, and there has been minimal new capital investment in existing national facilities to upgrade them to the state of the art, or even to maintain them and replace obsolete instrumentation.
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From page 2... ...
strengthening of efforts toward the protection from radio frequency interference (RFI) to ground, space, and lunar based radio telescopes, together with the development of effective techniques to suppress or eliminate the effects of RFI on radio astronomy observations.
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The radio observations also led toward much better understanding of a number of other astrophysical topics, including the nature of planetary atmospheres, surfaces, and spin-orbit resonances, the physical conditions in star-forming regions, the importance of galactic nuclei, the gas content of circumstellar shells and interstellar space, and conditions in the most distant parts of the Universe corresponding to epochs shortly after its creation. In the 1970's, radio astronomers undertook an ambitious radio telescope construction program to exploit these new astrophysical areas, as well as the vigorous development of the specialized technologies needed for such fruitful new techniques as very long baseline interferometry, millimeter wavelength spectroscopy, and fast data acquisition and signal processing for pulsar and planetary radar studies.
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From page 4... ...
The chemistry and composition of the interstellar medium, the earliest stages of star formation, and the internal kinematics of luminous galaxies are uniquely revealed at millimeter wavelengths. Array-type radio telescopes for millimeter and sub-millimeter wavelengths, built with recently developed technology and exploiting powerful new imaging techniques, will provide tremendous improvements in sensitivity and resolution in these spectral bands.
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The variability of Cassiopeia A at meter wavelengths is difficult to explain within the context of any conventional understanding. Solar radio bursts due to electron streams and shock waves have been observed and need to be imaged with high angular resolution, particularly in the nearly unexplored hectometer wavelength band where the radiation originates in the region of solar wind acceleration.
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The formation of planetary systems around individual stars is a fundamental problem that is best studied at millimeter wavelengths where the dynamics and chemistry of the dust and gas surrounding newly formed stars can be directly observed. The millimeter and sub-millimeter arrays and the Large Millimeter Telescope will be extremely powerful tools for probing preplanetary circumstellar disks.
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From page 7... ...
Extragalactic neutral hydrogen and carbon monoxide surveys will continue to be extremely productive, especially with the upgraded capabilities of the Arecibo telescope, the VLA, the new Green Bank Telescope, and the proposed new millimeter radio telescopes. The observation of highly redshifted atomic and molecular gas provides information about conditions in galaxy disks at early epochs.
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From page 8... ...
We note that many of the radio astronomy highlights of the 1980's—millisecond pulsars and the detection of gravitational radiation damping, the extreme isotropy of the cosmic background radiation, the ordered clumpiness of the distribution of galaxies, bi-polar outflows from very young stars, gravitational tensing, and the high-dynamic-range mapping capability of the Very Large Array were unexpected developments and largely unforeseen before their · ~ - - - - ~ —-—c;7~ ~~ ~ r - -A r ~ ~ I O~~d ~ ~- ~~~~ ~ ~ ~~~ ~ ~ ~ ~ discovery. earlier, radio galaxies, A(iN'S, quasars, pulsars, radio bursts from the Sun and Jupiter, the high surface and atmospheric temperatures of the planets, giant molecular clouds, interstellar molecular masers, and the cosmic background radiation itself were initially discovered as a result of the drive to exploit emerging new technology.
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From page 9... ...
A Large Southern Radio Telescope to be Built and Operated in Brazil in Collaboration With an International Consortium of Partners3 A Dedicated Cosmic Background Imager RADIOASTRON and VSOP Space VLBI Missions4 Establishment of University-Based SETI Research Programs A Fast All Sky Telescope A Solar Radio Telescope $ lOM $ lOM $ 10 M $ SM $ 10 M $0.4 M The Panel also recognizes the importance of developing long-range plans and instrumentation needed for new facilities in the beginning of the 21st century, including: The identif~caticn of technological innovations leading to the development of new instrumentation for radio astronomy, including receiver technology for millimeter and sub-millimeter wavelengths, broadband recording systems for VLBI, advanced computing facilities and algorithms for imaging and pulsar analysis, and the strengthening of efforts to control radio frequency interference. Radio telescopes in space for observations at sub-millimeter wavelengths An astrophysical observatory in Antarctica with large millimeter and sub-millimeter radio telescopes A low frequency radio telescope on the far side of the moon ~ Federal share representing about half of the total cost of project.
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The highest tenons of the Radio Panel for new instrumentation is for the construction of a Millimeter Wavelength Array with sensitivity, resolution, image quality, and speed adequate to investigate the wide range of astrophysical phenomena that are best studied at millimeter wavelengths. FIGURE 6 Artists conception of the Millimeter Array showing the antennas in the 250 meter configuration.
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Medium Scale New Instnuments: Large Millimeter Wave Telescope: The Radio Astronomy Panel recognizes the need for a modern 50-meter class filled aperture radio telescope capable of operation to at least 230 GHz, located at a good site and available to scientists independent of their institutional affiliation. The Panel is impressed by the progress being made in the use of active optics to build a large millimeter radio telescope at relatively low cost.
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Large Southern Radio Telescope: Many important research programs require the highest attainable instantaneous sensitivity, and thus the largest possible collecting area. All of the biggest radio telescopes in the world are located in the northern hemisphere.
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radio telescopes be equipped to provide local oscillator and data links to the foreign spacecraft, and that U.S. scientists participate fully in developing and carrying out the VSOP and RADIOASTRON scientific programs.
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The upgraded Haystack radio telescope and the new Green Bank Telescope ~11 provide powerful new opportunities at longer millimeter wavelengths, while the Caltech and MPI-Arizona sub-millimeter telescopes will continue to have unique capabilities, even after the completion of the MMA. The existing millimeter and sub-millimeter radio telescopes and especially the millimeter wavelength interferometers need to be extended and enhanced, instrumentation based on the most advanced technology needs to be developed for these facilities, adequate support given for their operation, and additional resources made available to make these instruments accessible to a broad group of scientists independent of their institutional affiliation.
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The enhanced telescope will have continuous frequency coverage between 0.3 and 8 GHz, with unprecedented instantaneous sensitivity. Green Bank Telescope: The construction of a large, fully steerable, filled aperture radio telescope has been endorsed by essentially every review of the needs of U.S.
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The unblocked aperture will result in low ground pickup which will significantly reduce the system temperatures at lower frequencies and low side lobes which will allow more accurate measurements of the distribution of galactic neutral hydrogen. The GET will also have surface panels accurate enough for millimeter wavelengths and remotely controllable adjustments for the panels.
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In order to exploit the full scientific potential of the country's substantial investment in radio telescopes, and to remain competitive with the modern computing systems being found increasingly in other countries, it is important to make a wide range of advanced computing systems available at our national observatories and in our university laboratories. The computing power that is best suited to analyzing different types of interferometer observations spans an enormous range.
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for an initial high resolution spectroscopic exploration of the full submillimeter band of star-formation regions and distant galaxies as a precursor to LDR. Radio Astronomy in Antarctica: Due to the high altitude, extreme cold weather, and low water vapor content of the atmosphere, the Antarctic Plateau may be the best site on Earth for astronomical observations at infrared, sub-millimeter, and millimeter wavelengths.
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From page 19... ...
However, until the completion of the MMA, the Japanese and French-German IRAM millimeter wavelength facilities are likely to remain unmatched in this country. It has been the practice in the United States that observing time on radio telescopes at our national observatories and other major facilities be awarded without regard to nationality or country of residence, and the Panel recognizes the important role that this policy has played in maintaining the vitality of U.S.
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Most radio telescopes being used for VLBI are located in the northern hemisphere and give poor image quality for sources at low and southern declinations. A VLBI element located in South America is needed to complement the northern hemisphere VLBI networks and the VLBA.
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From page 21... ...
The field enjoyed substantial growth throughout the 1960's and early 1970's, but starting with the adoption of the Mansfield Amendment in 1968, DoD funding for radio astronomy has greatly diminished and the NSF has had to assume essentially all of the support for radio astronomy. The growth of radio astronomy has continued in the 1980's, as measured by construction of new radio telescopes, increased numbers of students and active radio astronomers, the development of new and more powerful ancillary equipment and techniques, and research activity in general.
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Good science is a highly individualistic effort, and the administrative system should impose a minimum of management or control beyond that necessary to assure reasonable accountability. The NSF has historically supported individual scientists based on peer review of proposals and without regard to the need to satisfy specific programs or missions.
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INFRARED ASTRONOMY PANEL FREDERICK GILLETT, National Optical Astronomy Observatories, Chair JAMES HOUCK, Cornell University, Vice- Chair JOHN BALLY, AT&T Bell Laboratories ERIC BECKLIN, University of California, Los Angeles ROBERT HAMILTON BROWN, Jet Propulsion Laboratory BRUCE DRAINE, Princeton University JAY FROGEL, Ohio State University IAN GATLEY, National Optical Astronomy Observatories ROBERT GEHRZ, University of Minnesota, Minneapolis ROGER HILDEBRAND, University of Chicago DAVID HOLLENBACH, NASA Ames Research Center BOB JOSEPH, University of Hawaii MICHAEL JURA, University of California, Los Angeles SUSAN G KLEINMANN, University of Massachusetts, Amherst ANDREW LANGE, University of California, Berkeley DAN LESTER, University of Texas, Austin FRANK J
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