Seminars and Discussions on the Radio Astronomy in Asia Pacific Region.

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Seminars and Discussions on the Radio Astronomy
in Asia Pacific Region.

• RAFCAP Meeting
• Kuala Lumpur
• May 19 20, 2004

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Radio Astronomy in India

• N. Udaya Shankar RRI
• T.L. Venkatasubramani NCRA

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Introduction

• Radio Astronomy in India began with the
  installation of 32 dishes of 1.8 m dia.
• 1965 Kalyan near Bombay (Present
  Mumbai)..G.Swarup
• The latest installation
  
• GMRT Pune near Bombay
• 30 Antennas of 45m dia
• Spread over 25Km
• Freqs 150, 325, 610/235, 1000-1420 MHz

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RADIO ASTRONOMY INSTALLATIONS IN INDIA
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Radio Astronomy Installations in India
Name and Operating Agency Location Spectrum Needs
Giant Meterwave Radio Telescope, TIFR http//www.gmrt.ncra. tifr.res.in Khodad, Maharashtra 196 N 74 3 E 37.5-38.25 151-154 230-234 322-328.6 406.1-410 608-614 1400-1427 1610.6-1613.8 and 1660-1670 MHz (Licensed bands of operation)
Ooty Radio Telescope, TIFR http//www.ncra.tifr.res.in Ooty, TamilNadu 1123 N 76 40 E 322-328.6 MHz (Licensed band of operation)
mm-wave Telescope, RRI http//www.rri.res.in Bangalore, Karnataka 1258 N 77 38 E 6-7 11.5-12.5 22-24 42-49 and 80-115 GHz
TIFR Tata Institute of Fundamental Research
RRI Raman Research Institute
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Radio Astronomy Installations in India
Name and Operating Agency Location Spectrum Needs
Decameter T-array, IIA,RRI http//www.iiap.res.in Gauribidbur, Karnataka 1336 N 77 27 E 33.5-34.5 MHz
Solar Radio Heliograph, IIA Gauribidbur, Karnataka 1336 N 77 27 E 37.5-38.25 53-55 73-77 150-153 and 322-328.6 MHz
IPS Array, PRL http//www.prl.ernet.in Rajkot, Gujarat 2218 N 7056 E 103 MHz
Cluster Antenna Array (PROPOSED) RRI, TIFR Khodad, Maharashtra 196 N 74 3 E 2 to 10 GHz, supplementing current GMRT coverage up to 2 GHz.
IIA Indian Institute of Astrophysics
PRL Physical Research
Laboratory
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Introduction

• Ooty Radio Telescope 327 MHz
• 10.4 m mm wave Telescope mm wave
• Gauribidanur Radio telescope 34.5 MHz
• Mauritius Radio Telescope 150 MHz
• GMRT
  150-1400 MHz
• Future Installations
• GMRT upgrades
• Comapct Cluster /
  500-8000 MHz
• Participation in SKA

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Main Focus Of Indian RA

• Low Frequency
• Meter and Decameter wavelengths
• (Exception of 10.4m telescope)
• India Offers Unique advantages
• 1. Lesser RFI than west
• 2. Labour Intensive nature
• 3. Coverage of both N and S Hemispheres
• 4. Bootstrapping---- One Experience
• leading to
  another

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• Is it Scientifically rewarding to have such a
  focus ?
• Primordial Hydrogen
• Oldest and diffuse electrons.Source Evolution

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• Pulsars
• Sub-luminous matter in the early universe
• Deuterium Abundance
• Recombination lines of carbon
• Study of atoms which are almost of a
• micron sizen574.

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Ooty Radio Telescope
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ORT specification
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ORT

• Parabolic Cylinder 530m ? 30m
• 1100 SS wires 0.38mm dia
• Built on a hill with a slope of 11º
• Equal to the latitude of the observatory
• ORT equatorially mounted telescope
• Effective collecting area 8000 m2
• Eq of a 138m Dish

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Cosmological Evolution

• Ooty Days in 1970
• Steady State Vs Evolving Universe
• Ooty Observations Angular Size -Flux density
  Observations Using Lunar Occultations
• 1 to 10 Arcsec ..unachieved in those days for a
  large sample of weak sources
• Number density of Radio Sources higher at earlier
  epochs but had smaller linear sizes
• A very strong support for evolution

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Interplanetary Scintillations

• Twinkling of stars
• Extragalactic sources..IPM
• Solar wind studies Sweeping past the earth 400
  Km / Sec
• Source Structures
• Space Weather Studies

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10.4m telescope
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RRI 10.4m Telescope

• The first mm wave telescope of India
• Late 1970s 75 micron surface accuracy
• was an achievement
• Sio Masers 86.2 GHz..CO emission 115.3
• A study of Molecular clouds After effects of
  star formation .Condensates forming cometary
  globules..Gum Nebula.
• 6.7 GHz Methanol Maser SurveyGalactic Plane

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Gauribidanur T Array
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GBD_image
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MRT Aerial View
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Images

• Sky Coverage (1 ?)
• Right Ascension 18 to 24 hrs
• Declination -700 to -100
• Frequency 151.6 MHz
• Resolution 4'x4'
• Integration time 4 s
• Bandwidth 1 MHz
• Noise(achieved) 100-350 mJy/beam
• (expected) 50-120 mJy/beam
• Almost complete uv coverage

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Deconvolution of MRT Images

• A deconvolved image of a small region of the sky
  seems satisfactory.
• The Problems of PSF changes due to non-coplanar
  have already been addressed.
• Chromatic Aberration effects are being included.

? 0.05 upto 3? Hogbom clean
Raw Image
Deconvolved Image
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GMRT
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GMRT Y
18 Arm antennas ---25 Longest Baseline 12 CSQ
ant 1.1 SqKm
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Current PerformanceMeasured System Parameters
Frequency (MHz) ? 153 235 325 610 1420
Primary Beam (Degrees) 3.8 2.5 1.8 0.9 0.4
System Temperature (K) 450 180 100 90 70
Ant Temp (K/ Jy/ Antenna) 0.35 0.3 0.35 0.3 0.25
Synthesised Beam Whole Array (arcsec) 20 12 9 5 2
Largest Detectable source (arcmin) 68 44 32 17 7
Sensitivity (rms image noise mJy/MHz/min) 5.2 3.9 1.2 1.2 1.2
Astronomically Usable Frequency Range (MHz) 146-158 230-240 305-360 580-640 850-1450
x20 with only the Central Square x2,
with only the Central Square
Source The Giant Meterwave Radio Telescope
S. Ananthakrishnan and A. Pramesh Rao.
Multicolour Universe Conference, 2001
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Current PerformanceAstronomical Usage

• An independent GMRT Time Allocation Committee
  (GTAC), appointed by the NCRA Management Board
  issues periodic calls for proposals to observe
  with the GMRT, rates the proposals for scientific
  merit and allots time.
• 1st Cycle Jan May 1992 About 1600 hours of
  time has been allotted per cycle.
• Time Allotment for 70 proposals for the 4th
  GTAC Cycle in progress
• 26 publications from GMRT (end-2002 status)
• We are able to go down to 30-40 microJansky flux
  density level.
• A point source map with 0.11 million dynamic
  range has been recently made.

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Research areas covered by GMRT during the GTAC
Cycle 3
Category of proposal No. of Prop. Time Allotted (in Hrs)
Key Projects (Galactic Plane, Pulsars, Nearby Galaxies, Clusters of galaxies, DLAs) 4 252
HI Emission 7 170
HI Absorption 4 130
OH/ HI Absorption 2 80
Continuum Imaging (Extragalactic) 12 364
Continuum Imaging (Galactic) 8 178
Pulsars 3 192
Micro- Quasars 2 30
Solar System (Jupiter) 1 80
Sun 2 24
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3C236 Red shift.09 Dist300 Mpc V20,000Km/s
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New Pulsar 0514-40A

• In Globular Cluster NGC 1851
• Most eccentric orbit known, e0.89
• Period4.99 (common Tens of millisecs)
• Companion Mass gt 0.9 Solar Mass
• First Pulsar Discovered by GMRT

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GMRT Specifications   Parabolic Reflector
Diameter 45m Focal Length 18.54
m Physical aperture 1590 m2 Sensitivity of
single dish 0.3 K/Jy Feed Support Quadripo
d Mounting Altitude-azimuth Elevation
Limits Software Limit 17-90 degrees Hardwa
re Limit 15-110 degrees Azimuth
Limits Software Limit -265 to 265
degrees Hardware Limit -270 to 270
degrees Slew rate Azimuth 30
degree/minute Elevation 20
degree/minute Design wind speeds Operation up
to 40 km/h (3 sec peak at 10 m height) Slew up
to 80 km/h Survival 133 km/h Size of wire
mesh of 20x20 mm, outer 1/3 area reflecting
surface 15x15 mm, middle 1/3 area 10x10
mm, inner 1/3 area Maximum rms surface
errors, 20 mm, outer 1/3 area at wind speed of
40 kmph 12 mm, middle 1/3 area 08 mm,
inner 1/3 area Tracking and pointing
accuracy 1' rms at wind speeds of lt 20 km/h
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Interference Excision at MRT
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Problem areas for the future

• Mobile phones (2004-05?)
• -- Rich village with turn-over of 500,000 per
  year in grapes (Note Excellent champagne! )
  and onion
• 4-lane Super Highway (2007??)
• -- 1 vehicle/ 3 minutes in 1985 with 2 lanes
• -- 3 vehicles/ 1 minute in 2004 with 2.25
  lanes!
• New International Airport at Chakan, about
  half-way between Pune and Narayangaon (2010???)
• New Railway line linking Pune and Nashik,
  probably crossing through the array (2015????)
• An intensive Interference Monitoring is under way
• Joardar etal

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Why should we take up A New Cluster Antenna Array
At GMRT Campus??

• Certain science drivers
• Projection of this as Indias initiative in SKA
  related activities
• Attempt to get into cm-wavelengths which would be
  of common interest to Radio Astronomers and ISRO

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• Need for creating a pool of young talented
  engineers interested in RA
• A Platform to test ideas and instruments meant
  for GMRT- Upgrade
• Important drivers for initiating a collaborative
  project

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Scientific Goals

• Compact Cluster to measure short spacings
• Profitable Usage of a Modest Collecting Area
  Rather than Scattering a Smaller Number Of
  Antennas For Higher Angular Resolution.
• Low Surface Brightness Radio Sources

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A possible remedy..
Nine- 12m antennas in reuleuxaux
configuration placed within the central square
C9-C2 C5-D0
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24 antennas in a reuleuxaux triangle
24 antennas in a reuleuxaux triangle
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Conclusion

• Definitely a cluster added to GMRT will improve
  its low spatial frequency coverage
• What is optimum ?
• Where to locate it ?
• What should be the antenna sizes ?
• Effects of shadowing ?
• A lot more interesting questions..