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Design, construction, and performance of the Leighton 10.4-m-diameter radio telescopes
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| Pengarang | : | D. Woody |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 82-5, MAY (No. 5) |
| Halaman | : | 673-686 |
| Abstrak | : | The design, construction, and measurement of 10-m-class radio telescopes operating at millimeter and submillimeter wavelengths present many challenges. The radio telescopes developed by Robert Leighton provide a solution to these problems. These 10.4-m-diameter telescopes have diffraction-limited beams at wavelengths as short as 300 /spl mu/m. The paper describes the techniques Robert Leighton developed to solve many of the problems in building precision telescopes. The areas covered include the design of the homologous reflector support structure, the computer program used to accurately predict the deformation of the surface, the construction techniques used to minimize the stress and bending moments in the structure, and the methods developed for producing and measuring a 10.4-m-diameter reflector surface to the required accuracy. The reflectors for the Leighton telescopes consist of honeycomb Al panels supported on a steel spaceframe backing structure. The spaceframe utilizes precision machined members and pin joints. The 84 panels form a hexagonal tiling pattern in the aperture plane and are figured using a custom-built machine. The Al reflecting surface is then applied to the front of each panel. The telescopes are routinely fabricated and installed with an rms surface accuracy of less than 35 /spl mu/m without any adjustments/corrections. Computer calculations of the homologous deformation of the telescopes as they move in elevation have been verified by holography. A Leighton telescope installed at the Caltech Submillimeter Observatory on Mauna Kea, HI, has achieved an accuracy of <20 /spl mu/m. |
The Very Long Baseline Array
| Pengarang | : | P.J. Napier |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 82-5, MAY (No. 5) |
| Halaman | : | 658-672 |
| Abstrak | : | The Very Long Baseline Array (VLBA) consists of ten high performance antennas and a 20-station correlator. The 25-m-diameter reflector antennas are located geographically to optimize spatial frequency coverage for high-duality imaging using VLBI techniques. The antennas are equipped with receivers for nine frequency bands over the range 300 MHz to 45 GHz. A wideband, high-density, recording system allows unattended operation at a sustained data rate of 125 Mb/s for a day, and peak rates of up to 512 Mb/s. The antennas operate unattended most of the time, and are controlled by a single operator in the Array Operations Center (AOC) at Socorro, NM. The correlator, located in the AOC, supports processing of all observations with the array. |
Japanese deep-space station with 64-m-diameter antenna fed through beam waveguides and its mission applications
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 82-5, MAY (No. 5) |
| Halaman | : | 646-657 |
| Abstrak | : | The Usuda Deep Space Center of the Institute of Space and Astronautical Science is a Japanese spacecraft tracking station constructed in October 1984. The station is equipped with a 64-m diameter antenna and associated electronics to support deep-space missions. The paper describes the 3-year development process of the station. The beam-waveguide configuration is described in detail to demonstrate its flexibility to modifications in order to adapt to subsequent missions. System configuration and operation examples are also given for several missions. |
Ground antennas in NASA's deep space telecommunications
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 82-5, MAY (No. 5) |
| Halaman | : | 636-645 |
| Abstrak | : | Ground antennas are the major visible components of NASA's Deep Space Network (DSN). The role, key characteristics, and performance of these antennas in deep-space telecommunications are described. The system analyses and tradeoffs to optimize the overall ground-to-spacecraft link and to define future missions are elaborated from an antenna perspective. Overall performance of receiving systems is compared using the widely accepted G/T figure-of-merit, i.e., net antenna gain divided by the operating system noise temperature. Performance of past, present, and future antennas and receiving systems is discussed, including the planned development of a world-wide network of 34-m diameter beam-waveguide antennas. The need for multifrequency operation, presently in the S- and X-bands, and in the future in the Ka-band, is discussed. The resulting requirements placed on antenna technology are highlighted. Beam-waveguide antenna performance to further improve performance and operational advantages is discussed. |
Scanning the special issue on radio telescopes
| Pengarang | : | W.A. Imbriale |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 82-5, MAY (No. 5) |
| Halaman | : | 633-635 |
| Abstrak | : | The present issue (vol.82, no.2, 1994) is the third in the Proceedings of the IEEE to be devoted to radio and radar astronomy. The first appeared in January 1958, a significant date because it was 25 years after Karl G. Jansky's first report of his discovery of Galactic radio noise. The second was 15 years later in September 1973, and was devoted to reporting how the science had progressed. The 15-year timespan had marked a period of rapid advance that had yielded a wealth of discoveries. Now, 21 years later, the field is still dynamic and continues to produce an abundance of findings, due in part to the large number of new observatories. In the present issue, the focus is on the design and performance of the antennas and the instrumentation used in radio astronomy. The issue concentrates on already existing and operational telescopes. Perhaps yet a future issue is merited, one devoted to those new telescopes that are still on the drawing boards. |
From silence to melody: Adding a post-structuralist lens to more-than-representational theory to analyze power dynamics in the classroom
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Journal of The Learning Sciences |
| Volume / Edisi | : | 34 (No. 2) |
| Halaman | : | 140-178 |
| Abstrak | : | This study examines power dynamics within a Humanistic Knowledge Building Community (HKBC) in an Israeli BA education course at the University of Haifa—a setting shaped by diverse and conflicting narratives. Using post-structuralist frameworks and More-Than-Representational (MTR) theory, we investigate how MTR mediums interact with representational mediums to either reinforce or challenge power structures. |
Blackness, place and learning: Youth cultivating a sense of identity-in-place through spatial storylines
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Journal of The Learning Sciences |
| Volume / Edisi | : | 34 (No. 2) |
| Halaman | : | 91-139 |
| Abstrak | : | This paper examines how five youth in Seattle’s Central District and Southend participated in an architectural design-build project that centered Black spatial histories. The project aimed to foster a meaningful context for identity development, learning, and spacemaking as intertwined relational processes. |
PERJALANAN DI SUATU DESA
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Ave Maria: Per Mariam Ad Jesum |
| Volume / Edisi | : | (No. 47) |
| Halaman | : | 24-27 |
| Abstrak | : | - |
PELINDUNG ORANG-ORANG AMERIKA
| Pengarang | : | Vera Hasmo Yuwono |
| Nama Majalah/Jurnal | : | Ave Maria: Per Mariam Ad Jesum |
| Volume / Edisi | : | (No. 47) |
| Halaman | : | 21-23 |
| Abstrak | : | - |
PADRE PIO DAN MALAIKAT PELINDUNGNYA
| Pengarang | : | Father Eusebio Notte, OFM Cap |
| Nama Majalah/Jurnal | : | Ave Maria: Per Mariam Ad Jesum |
| Volume / Edisi | : | (No. 47) |
| Halaman | : | 12-20 |
| Abstrak | : | - |