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Development of the Brazilian Decimetric Array - BDA, in Brazil


Scientists and engineers of INPE´s interplanetary physics group have already developed radio telescopes of international standards with Brazilian technology. These telescopes are Millimeter spectroscopes known as the Variable Frequency Millimeter Wave Radiometer, in operation since 1988, and the Digital Decimetric Brazdian Solar Spectroscope with a 9-meter polar mount antenna in regular operation since 1990, at the INPE campus. The group also initiated a Space Weather Prediction program using spectral tomography techniques in 1993. Realizing the importance of imaging spectroscopy, the team of scientists/engineers initiated design and planning of the Brazilian Decimetric Array project in 1996, THE BRAZILIAN DECIMETRIC ARRAY The Brazilian Decimetric Array (BDA), under development, will have high spatial and time resolutions of ~ 5 sec of arc at 5,0 GHz and 100 ins respectively. It is planed to employ modem technology at low cost. The BDA will have the capability to observe solar and non-solar phenomena in the following radio protected bands: 1.2 - 1.7, 2.7 and 5.0 GHz. The sensitivity estimates show that the BDA will have rms. sensitivity of 3 mJy at 21 cm for a system. temperature of 50 K, using low-noise amplifiers. The final version of the BDA will be an interferometer array consisting of 39 parabolic antennas of 5 meters diameter with a compact "T" shaped array at the center having 32 antennas. The array will be located at Cachoeira Paulista (Longitude -45o.0' .20" W, Latitude - 22o.41' 19" S). AIMS OF THE BDA The BDA will produce high spatial and tune resolution images of radio sources with high dynamic range. The BDA will provide solar radio images, to be used in a spectral tomography technique being developed for application to space weather forecasting and their analysis will lead to better understanding of the fundamental problems in solar physics. BDA will be very useful for galactic and extra-galactic investigations of the southern sky not accessible to VLA. THREE PHASES OF THE BDA In phase I (May 2001 - September 2002) a fin-element interferometer will be developed at INPE using a 5-meter diameter parabolic dish with alt-azimuth mount and complete tracking capability The PLO receiver operating initially in the frequency range of 1.2 - 1.7 GHz will be also developed. The main aim of this phase is to optimize the cost of the mechanical and electronics subsystems of the BDA. Various engineering tests of the sub systems will be carried out so as to optimize the cost and the performance of the overall system . This will give us an exact cost estimate of the next BDA phases. Then the interferometer will be moved to Cachoeira Paulista. The distances of the antenna will be changed so as simulate the distances of BDA phase II. In this case spatial resolution will be ~3 x 4 minute of arc. RFI measurements will be carried out and possibilities to minimize the same will be investigated. Depending upon the results of the RFI investigations the final site of the BDA will be decided. Efforts will be made to transfer technology to small local industries so that they can participate in developing the BDA in phases II/III. In the second phase (October 2002 - April 2004) 21 antennas will be laid out over the distance of 256 meters in the east-west direction and I I antennas will be laid out over a distance of 144 meters in the southern direction, in a T format. The frequency range will be increased to 1.2- 1.7, 2.7 and 5.0 GHz. In the third phase (May 2004 - April 2005) mainly spatial resolution will be increased. Base lines will be increased in both in east-west and south directions to 2.5 km and 1.25 km respectively. Four more antennas will be added in the east-west direction and 2 antennas added in south direction which will improve spatial resolution from minutes of arc to seconds of arc e.g. ~5 sec of arc at 5.0 GHz. SCIENCE WITH THE BDA During the maximum solar activity period of 2001 - 2004 simultaneous investigations of radio images, obtained by BDA, in the decimetric frequency range and x-ray images of HESSI/YOHKOH over a wide energy range of solar phenomena, with high spatial/time resolutions, will lead for the first tune to better understanding of a number of fundamental problems in solar physics. The Brazilian Solar Spectroscope's observations will complement spectral information. This will enable for the first tune detailed investigations of solar flares and CMEs for following fundamental problems in the solar physics, localization of particle acceleration regions and liberation of energy to flares. Chromospheric; faint patches associated with CMEs may detect trigger locations of CMEs. For the first time CMEs will be detected in their initial phase by their thermal emissions that can be only observed by BDA type instruments. Statistical investigations of spectral data of the various active regions recorded by the BDA during a couple of years will serve as an indicator of the prediction of occurrence of the flare during some time. During the declining phase of the solar activity cycle (2004- 2006) when the BDA will be in full operation, radio images of the fall sun and of isolated active regions having minimum interaction among themselves win be obtained regularly. Observations of CMEs during the declining phase and associated solar phenomena will lead to better understanding of the ejection/propagation mechanism of CMEs. Thus, better understanding of the acceleration regions of the flares and CMEs in their initial phase will help in improved modelling of space weather forecasts, which is one of the aims of the project. In phased array mode the BDA may allow HI studies in specific directions of our galaxy. 'The BDA can be used for a survey of the Southern Sky at 1.4. 2.7 and 5.0 GHz order to supplement radio surveys done by the Molonglo and Australian telescope, particularly for the regions of the sky not accessible to the VLA. Studies of the variability of extended sources using the BDA are planned. INSTITUTES AND SCIENTISTS/ENGINEERS INVOLVED Institutes: 1.0 Dept. Of Computer Engineering of Federal University of São Carlos, 2.0 Dept. of Computer Sciences of University of PUC of Minas Gerais, 3.0 Dept of Physics, Federal University of Santa Maria, MG 4.0 CRAM/INPE 5.0 National Center of Radio Astrophysics, Giant Meter Radio Telescope - TIFR Pune, India. 6.0 Indian Institute of Astrophysics, Banglore, India. 7.0 Nobeyarna Radiheliograph, Japan. Scientists/engineers: Most of the scientists/engineers are involved since the beginning of the project although a few of them have joined the BDA project recently. There are 7 Brazilian Radio Astronomers and 3 international Radio Astronomers, 7 researchers from the area of computer engineering/sciences, 6 electronic/mechanical engineers from INPE/Brazil and 3 from India. Also 2 highly qualified technicians are actively participating in developing BDA FINANCIAL SUPPORT REQUESTED TO FAPESP RS$ 170.000,00 for first phase of BDA. (May 2001 - April 2002), and 3 Scholarships IC type. RS$ 800.000.00 up to this value MAY be requested for phase 11 and III of IDA (May 2002-April 2005) ACQUIRED RS$ 120.000,00 has been funded by INPE. RS$ 220.000,00 is in the process of funding from FINEP. RS$ 100.000,00 is being funded by the supporting development of the digital part of the system by the Indian Institute of Astrophysics, using correlator chips donated by the Nobeyama Radiheliograph group It should be emphasized that fund requested to FAPESP, is only for antennas,receivers and communication lines from control room to them and back. Associated electrical interfaces will be funded by INPE. Digital system for 38-antenna i.e. is developed at Indian Institute of Astrophysics at Banglore in India. Data acquisition its storage and tools for dada analysis are being developed with financial support of FINEP. Total cost of additional, 33, antennas/receivers and cabling will not exceed RS$ 800.000,00. The exact cost per unit of the antenna /receiver and cabling will be known after development of first phase of the BDA. For this motive the funds for BDA phase II/III will be requested only after completion of phase I. It should be also noted that Brazilian Space Agency is requesting funds in their budget to support BDA phases II/III. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
SAWANT‚ HS; RAMESH‚ R.; CECATTO‚ JR; FARIA‚ C.; FERNANDES‚ F.C.R.; ROSA‚ RR; ANDRADE‚ MC; STEPHANY‚ S.; CIVIDANES‚ L.B.T.; MIRANDA‚ C.A.I.; et al. Brazilian Decimetric Array (Phase-I). SOLAR PHYSICS, v. 242, n. 1, p. 213-220, . (01/00056-9)

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