Ooty Radio Telescope

The Ooty Radio Telescope (ORT) is located in Muthorai near Ooty, in South Indian state of Tamil Nadu.{{cite web|url=http://www.nilgiris.tn.gov.in/ooty.htm|title=THE OOTY RADIO TELESCOPE|publisher=nilgiris.tn.gov.in|access-date=4 February 2011|archive-date=14 January 2011|archive-url=https://web.archive.org/web/20110114053740/http://www.nilgiris.tn.gov.in/ooty.htm|url-status=dead}} It is part of the National Centre for Radio Astrophysics (NCRA){{cite web|url=http://indianspacestation.com/space-institutes/120-national-centre-for-radio-astrophysics.html|archive-url=https://web.archive.org/web/20110713025014/http://indianspacestation.com/space-institutes/120-national-centre-for-radio-astrophysics.html|url-status=usurped|archive-date=13 July 2011|title=National Centre for Radio Astrophysics|publisher=Indianspacestation.com|access-date=4 February 2011}}{{cite web|url=http://www.puneeducation.net/Research/NCRA/index.aspx|archive-url=https://archive.today/20120907230214/http://www.puneeducation.net/Research/NCRA/index.aspx|url-status=usurped|archive-date=7 September 2012|title=National Centre for Radio Astrophysics|publisher=Puneeducation.net|access-date=4 February 2011}}{{cite web|url=http://www.punescoop.com/story/2008/2/25/231235/589|archive-url=https://web.archive.org/web/20171226020757/http://www.punescoop.com/story/2008/2/25/231235/589|url-status=dead|archive-date=2017-12-26|title=Science Exhibition on 28, 29 Feb at Khodad in Junnar Taluka, Approximately 80 km North of Pune|publisher=Punescoop.com|access-date=4 February 2011}} of the Tata Institute of Fundamental Research (TIFR), which is funded by the Government of India through the Department of Atomic Energy.{{cite web|url=http://www.ooty.com/travel/radiotelescope.htm|title=Ooty Radio Telescope|publisher=Ooty.com|access-date=4 February 2011}} The radio telescope is a {{convert|530|m|adj=on}} long and {{convert|30|m|adj=on}} tall cylindrical parabolic antenna.{{cite web|url=http://www.buzzle.com/articles/radio-telescope.html|archive-url=https://web.archive.org/web/20071024042051/http://www.buzzle.com/articles/radio-telescope.html|url-status=usurped|archive-date=24 October 2007|title=Cylindrical Palaboloyds telescopes|publisher=Buzzle.com|access-date=4 February 2011|work=web listing}}{{cite journal|title=The Ooty Synthesis Radio Telescope: First Results |journal=Journal of Astrophysics and Astronomy |volume=5 |issue=2 |pages=139–148 |citeseerx = 10.1.1.117.3893|bibcode=1984JApA....5..139S |last1=Swarup |first1=G. |year=1984 |doi=10.1007/BF02714986 |s2cid=707849 }} It operates at a frequency of 326.5 MHz with a maximum bandwidth of 15 MHz at the front end.{{cite journal|title=Callisto spectrum measurements in Ootacamund-1.1. Station description|publisher=E-collection.ethbib.ethz.ch|doi = 10.3929/ethz-a-005306639|year = 2006|last1 = Manoharan|first1 = P.K.|last2=Nandagopal|first2=D.|last3=Monstein|first3=Christian}}

Design

File:Reflection of sunlight from Ooty Radio telescope parabolic mirror wireframe.jpg

The Ooty Radio Telescope has been designed and fabricated with domestic Indian technological resources. The ORT was completed in 1970{{cite web|url=http://www.mapsofindia.com/ooty/tourist-attractions/radio-telescope.html|title=Ooty Radio Telescope|publisher=Mapsofindia.com|access-date=4 February 2011|url-status=dead|archive-url=https://web.archive.org/web/20110629023339/http://www.mapsofindia.com/ooty/tourist-attractions/radio-telescope.html|archive-date=29 June 2011}} and continues to be one of the most sensitive radio telescopes in the world.

Observations made using this telescope have led to important discoveries and to explain various phenomena occurring in the Solar System and in other celestial bodies.{{cite web|url=http://rac.ncra.tifr.res.in/ort.html|title=Ooty Radio Telescope|publisher=Rac.ncra.tifr.res.in|access-date=4 February 2011|archive-date=9 May 2010|archive-url=https://web.archive.org/web/20100509192809/http://rac.ncra.tifr.res.in/ort.html|url-status=dead}}

The reflecting surface of the telescope is made of 1,100 thin stainless-steel wires running parallel to each other for the entire length of the cylinder and supported on 24 steerable parabolic frames.

An array of 1,056 half-wave dipoles in front of a 90-degree corner reflector forms the primary feed of the telescope.{{cite web|url=http://ncra.tifr.res.in/ncra_hpage/ort/ort.html|title=Ooty Radio Telescope (ORT)|publisher=Ncra.tifr.res.in|access-date=4 February 2011|url-status=dead|archive-url=https://web.archive.org/web/20110721043159/http://www.ncra.tifr.res.in/ncra_hpage/ort/ort.html|archive-date=21 July 2011}}{{cite web|url=http://www.indianpost.com/viewstamp.php/Alpha/R/RADIO%20TELESCOPE%20OOTY|title=IndianPost-RADIO TELESCOPE OOTY|publisher=Indianpost.com|access-date=4 February 2011}} It has an angular resolution of 2.3deg x 5.5sec(dec)'.{{cite web|url=http://ncra.tifr.res.in/ncra_hpage/ort/ort_spec.html|title=ORT Specifications|publisher=Ncra.tifr.res.in|access-date=4 February 2011|url-status=dead|archive-url=https://web.archive.org/web/20110721181220/http://ncra.tifr.res.in/ncra_hpage/ort/ort_spec.html|archive-date=21 July 2011}}

History

The structure of the radio telescope was designed in July 1963. Muthorai village near Ooty was selected as the suitable location and the construction work began in 1965. The telescope was completed in 1970.{{cite web|url=http://www.saasems.com/astronomy/radio-astronomy-centre|title=Radio Astronomy Centre - Radio Astronomy Centre, Ooty|publisher=saasems.com|access-date=4 February 2011|url-status=dead|archive-url=https://web.archive.org/web/20110715221454/http://www.saasems.com/astronomy/radio-astronomy-centre|archive-date=15 July 2011}} Normal post-commissioning and calibration use began in 1971.

The ORT was upgraded in 1992 by the addition of a phased array of 1,056 array of dipoles each followed by a GaAsFET low noise amplifier (LNA) and a four-bit PIN diode microstripline phase shifter behind each dipole. The new feed was installed along the focal line of the 530 m long and 30 m wide parabolic cylindrical reflector of the ORT. This new feed brought about an improvement in the sensitivity of the ORT by a factor greater than three compared to the previous feed. The high sensitivity of the feed system and the large collecting area of ORT has been exploited for the studies of astrophysical phenomena such as pulsars, solar wind, recombination lines, and protogalaxies.{{Cite journal|last1=Selvanayagam|first1=A. J.|last2=Praveenkumar|first2=A.|last3=Nandagopal|first3=D.|last4=Velusamy|first4=T.|date=1 July 1993|title=Sensitivity Boost to the Ooty Radio Telescope: A New Phased Array of 1056 Dipoles with 1056 Low Noise Amplifiers|journal=IETE Technical Review|volume=10|issue=4|pages=333–339|doi=10.1080/02564602.1993.11437351|issn=0256-4602}}

{{As of|2017}}, the ORT is undergoing a major upgrade to its receiver chain, which will result in a new system called the Ooty Wide Field Array (OWFA). The OWFA is designed to function as a 264-element interferometric array, and to provide a significantly larger instantaneous bandwidth as well as field-of-view compared to the legacy ORT receiver system. This upgrade will significantly enhance the ORT's capabilities for heliospheric studies. Additionally this upgrade is also expected to open other avenues of research particularly in the newly emerging areas of {{cvt|21|cm|adj=on}} intensity mapping{{Cite journal|last1=Ali|first1=Sk. Saiyad|last2=Bharadwaj|first2=Somnath|date=2014|title=Redshifted 21 cm HI signal from post-reionization era: 326.5 MHz ORT experiments|journal=Astronomical Society of India Conference Series|volume=13|pages=325–327|bibcode=2014ASInC..13..325A}}{{Cite journal|last1=Ali|first1=Sk. Saiyad|last2=Bharadwaj|first2=Somnath|date=1 June 2014|title=Prospects for Detecting the 326.5 MHz Redshifted 21-cm HI Signal with the Ooty Radio Telescope (ORT)|journal=Journal of Astrophysics and Astronomy|volume=35|issue=2|pages=157–182|doi=10.1007/s12036-014-9301-1|issn=0250-6335|arxiv=1310.1707|bibcode=2014JApA...35..157A|s2cid=118559571 }}{{Cite journal|last1=Bharadwaj|first1=S.|last2=Sarkar|first2=A. K.|last3=Ali|first3=Sk. Saiyad|date=1 September 2015|title=Fisher Matrix Predictions for Detecting the Cosmological 21-cm Signal with the Ooty Wide Field Array (OWFA)|journal=Journal of Astrophysics and Astronomy|volume=36|issue=3|pages=385–398|doi=10.1007/s12036-015-9346-9|issn=0250-6335|arxiv=1510.01850|bibcode=2015JApA...36..385B|s2cid=119256221 }}{{Cite journal|last1=Sarkar|first1=Anjan Kumar|last2=Bharadwaj|first2=Somnath|last3=Ali|first3=Sk. Saiyad|date=1 March 2017|title=Fisher Matrix-based Predictions for Measuring the z = 3.35 Binned 21-cm Power Spectrum using the Ooty Wide Field Array (OWFA)|journal=Journal of Astrophysics and Astronomy|volume=38|issue=1|pages=14|doi=10.1007/s12036-017-9432-2|issn=0250-6335|arxiv=1703.00634|bibcode=2017JApA...38...14S|s2cid=119486733 }}{{Cite journal|last1=Chatterjee|first1=Suman|last2=Bharadwaj|first2=Somnath|last3=Marthi|first3=Visweshwar Ram|date=1 March 2017|title=Simulating the z = 3.35 HI 21-cm Visibility Signal for the Ooty Wide Field Array (OWFA)|journal=Journal of Astrophysics and Astronomy|volume=38|issue=1|pages=15|doi=10.1007/s12036-017-9433-1|issn=0250-6335|bibcode=2017JApA...38...15C|arxiv=1703.00628|s2cid=119088331 }}{{Cite journal|last1=Sarkar|first1=Anjan Kumar|last2=Bharadwaj|first2=Somnath|last3=Guha Sarkar|first3=Tapomoy|date=1 May 2018|title=Predictions for measuring the cross power spectrum of the HI 21-cm signal and the Lyman-alpha forest using OWFA|journal=Journal of Cosmology and Astro-Particle Physics|volume=2018|issue=5|pages=051|doi=10.1088/1475-7516/2018/05/051|issn=1475-7516|bibcode=2018JCAP...05..051S|arxiv=1804.00454|s2cid=54804413 }}{{Cite journal|last1=Chatterjee|first1=Suman|last2=Bharadwaj|first2=Somnath|date=1 August 2018|title=A spherical harmonic analysis of the Ooty Wide Field Array (OWFA) visibility signal|journal=Monthly Notices of the Royal Astronomical Society|volume=478|issue=3|pages=2915–2926|doi=10.1093/mnras/sty942|doi-access=free |issn=0035-8711|bibcode=2018MNRAS.478.2915C|arxiv=1804.00493}} and studies of transient radio sources.{{Cite web|url=https://www.ias.ac.in/public/blog/index.php/2017/03/31/the-ooty-radio-telescope-upgrade/|title=Home {{!}} Indian Academy of Sciences|website=www.ias.ac.in|access-date=2019-05-06}}

Features

The large size of the telescope makes it highly sensitive. As an example, it is in principle capable of detecting signals from a 1 watt radio station located {{convert|10|e6km}} away in space. The telescope sits on a natural slope of 11°, which matches the latitude of the location. This gives the telescope an equatorial mount that allows tracking of celestial sources for up to ten hours in the east–west direction.{{cite web|url=http://www.ias.ac.in/resonance/Sept1998/pdf/Sept1998IA.pdf|title=Information and Announcements - The National Centre for Radio Astrophysics (NCRA)|publisher=Ias.ac.in|access-date=4 February 2011}} In the north–south direction, the telescope operates as a phased-array and is steerable by varying the phase gradients{{cite journal |last1=Kapahi|first1=V. K|date=2007|title=The National Centre for Radio Astrophysics(NCRA)Resonance|journal=Resonance|volume=3|pages=90–92|doi=10.1007/BF02836088 |issue=9|s2cid=122214854 }}

The telescope can be operated in either total power or correlation mode. In each mode, 12 beams are formed; beam 1 is the southernmost beam and beam 12 is the northernmost. These 12-beam systems are useful in sky survey observations. Recently, the reflecting surface of the ORT has been refurbished. A new digital back-end has been built for the ORT by the colleagues at Raman Research Institute (RRI), Bangalore.

Observations

The ORT has produced results on radio galaxies, quasars, supernovae and pulsars,{{cite web|url=http://dspace.rri.res.in/bitstream/2289/971/1/1995%20JAA%20Sup.%20V16%20p239.pdf|title=A digital signal pre processor for pulsar search using Ooty radio telescope|publisher=Dspace.rri.res.in|access-date=4 February 2011}}{{cite web|url=http://cdsweb.cern.ch/record/345886/files/9802206.pdf|title=Study of the LISM using Pulsar Scintillation - 2 Observations and Data Analysis|publisher=Cdsweb.cern.ch|access-date=4 February 2011}} One long-term program determined the angular structure of several hundred distant radio galaxies and quasars using the lunar occultation method.

The application of this database to observational cosmology provided independent evidence against the steady state theory and supported the Big Bang model of the universe.

The telescope is currently being used mainly to observe interplanetary scintillation, which may provide valuable information about the solar wind and magnetic storms that affect the near-Earth environment. Interplanetary scintillation observations provide a database to understand space weather changes and their predictability.

= Analog correlator =

This is widely used for IPS observations.

Upgrade

The upgraded telescope has been used for observing pulse nulling.{{cite journal |journal=Monthly Notices of the Royal Astronomical Society |title=Observation of nulling in radio pulsars with the Ooty Radio Telescope |last=Vivekanand |first=M. |volume=274 |issue=3 |pages=785–792 |date=June 1995 |bibcode=1995MNRAS.274..785V|doi=10.1093/mnras/274.3.785 |doi-access=free }} The interferometer can be used at Channel 37 (608 MHz to 614 MHz, important radio astronomy frequencies) with lesser performance.

Ongoing projects

IPS observations:{{cite encyclopedia|url=http://www.britannica.com/bps/additionalcontent/18/33993644/Geoeffectiveness-of-CMEs|title=Geo-effectiveness of CMEs|encyclopedia=Britannica.com|access-date=4 February 2011}}{{cite journal |last1=Ajaysinh|first1=K|last2= Iyer|first2= K. N|last3= Vats|first3= Hari Om|last4= Manoharan|first4= P. K|date=2007|title=Geo-effectiveness of CMEs|journal=Journal of Astrophysics and Astronomy |volume=29|issue=1–2|pages=287–291|doi=10.1007/s12036-008-0038-6 |bibcode = 2008JApA...29..287J |s2cid=120907411}} The interplanetary scintillation (IPS) observations obtained from the Ooty Radio Telescope on a large number of radio sources provide the day-to-day changes of the solar wind speed and density turbulence in the inner heliosphere.{{cite web|url=http://smei.ucsd.edu/Toyokawa_IPS_abstract.pdf|title=Toyokawa IPS Workshop 2007-Ooty IPS Studies and IPS Network|publisher=Smei.ucsd.edu|access-date=4 February 2011}}{{cite web|url=http://cdaw.gsfc.nasa.gov/publications/ilws_goa2006/00011_Inaugural_Swarup.pdf|title=Historical perspective and research centres in India in the fields of solar astronomy and Sun-Earth relationship - National Centre for Radio Astrophysics (NCRA/TIFR)|publisher=Cdaw.gsfc.nasa.gov|access-date=4 February 2011}}
Pulsar timing observations
Spectral line observations