Ooty Radio Telescope

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The Ooty Radio Telescope (ORT) is located in Muthorai near Ooty, in South Indian state of Tamil Nadu.^[1] It is part of the National Centre for Radio Astrophysics (NCRA)^[2][3][4] of the Tata Institute of Fundamental Research (TIFR), which is funded by the Government of India through the Department of Atomic Energy.^[5] The radio telescope is a 530-metre (1,740 ft) long and 30-metre (98 ft) tall cylindrical parabolic antenna.^[2][6][7] It operates at a frequency of 326.5 MHz with a maximum bandwidth of 15 MHz at the front end.^[8]

Design

The Ooty Radio Telescope has been designed and fabricated with domestic Indian technological resources. The ORT was completed in 1970^[9] 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.^[10]

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.^[8][11][12] It has an angular resolution of 2.3deg x 5.5sec(dec)'.^[13]

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.^[14] 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.^[15]

As of 2017^[update], 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 21 cm (8.3 in) intensity mapping^{[16][17][18][19][20][21][22]} and studies of transient radio sources.^[23]

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 10 million kilometres (6.2×10^⁶ mi) away in space.^[10] 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.^[24] In the north–south direction, the telescope operates as a phased-array and is steerable by varying the phase gradients^[11][25]

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.^[10]

Observations

The ORT has produced results on radio galaxies, quasars, supernovae and pulsars,^[26][27] 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.^[8] Interplanetary scintillation observations provide a database to understand space weather changes and their predictability.^[5]

Analog correlator

This is widely used for IPS observations.

Upgrade

The upgraded telescope has been used for observing pulse nulling.^[28] The interferometer can be used at Channel 37 (608 MHz to 614 MHz, important radio astronomy frequencies) with lesser performance.

Ongoing projects

• IPS observations:^[29][30] 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.^[31][32]
• Pulsar timing observations^[11]
• Spectral line observations^[10]

See also

1. ^ "THE OOTY RADIO TELESCOPE". nilgiris.tn.gov.in. Archived from the original on 14 January 2011. Retrieved 4 February 2011.
2. ^ ^{a b} "National Centre for Radio Astrophysics". Indianspacestation.com. Retrieved 4 February 2011.
3. ^ "National Centre for Radio Astrophysics". Puneeducation.net. Retrieved 4 February 2011.
4. ^ "Science Exhibition on 28, 29 Feb at Khodad in Junnar Taluka, Approximately 80 km North of Pune". Punescoop.com. Archived from the original on 26 December 2017. Retrieved 4 February 2011.
5. ^ ^{a b} "Ooty Radio Telescope". Ooty.com. Retrieved 4 February 2011.
6. ^ "Cylindrical Palaboloyds telescopes". web listing. Buzzle.com. Retrieved 4 February 2011.
7. ^ Swarup, G. (1984). "The Ooty Synthesis Radio Telescope: First Results". Journal of Astrophysics and Astronomy. 5 (2): 139–148. Bibcode:1984JApA....5..139S. CiteSeerX 10.1.1.117.3893. doi:10.1007/BF02714986. S2CID 707849.
8. ^ ^{a b c} Manoharan, P.K.; Nandagopal, D.; Monstein, Christian (2006). "Callisto spectrum measurements in Ootacamund-1.1. Station description". E-collection.ethbib.ethz.ch. doi:10.3929/ethz-a-005306639. {{cite journal}}: Cite journal requires |journal= (help)
9. ^ "Ooty Radio Telescope". Mapsofindia.com. Archived from the original on 29 June 2011. Retrieved 4 February 2011.
10. ^ ^{a b c d} "Ooty Radio Telescope". Rac.ncra.tifr.res.in. Archived from the original on 9 May 2010. Retrieved 4 February 2011.
11. ^ ^{a b c} "Ooty Radio Telescope (ORT)". Ncra.tifr.res.in. Archived from the original on 21 July 2011. Retrieved 4 February 2011.
12. ^ "IndianPost-RADIO TELESCOPE OOTY". Indianpost.com. Retrieved 4 February 2011.
13. ^ "ORT Specifications". Ncra.tifr.res.in. Archived from the original on 21 July 2011. Retrieved 4 February 2011.
14. ^ "Radio Astronomy Centre - Radio Astronomy Centre, Ooty". saasems.com. Archived from the original on 15 July 2011. Retrieved 4 February 2011.
15. ^ Selvanayagam, A. J.; Praveenkumar, A.; Nandagopal, D.; Velusamy, T. (1 July 1993). "Sensitivity Boost to the Ooty Radio Telescope: A New Phased Array of 1056 Dipoles with 1056 Low Noise Amplifiers". IETE Technical Review. 10 (4): 333–339. doi:10.1080/02564602.1993.11437351. ISSN 0256-4602.
16. ^ Ali, Sk. Saiyad; Bharadwaj, Somnath (2014). "Redshifted 21 cm HI signal from post-reionization era: 326.5 MHz ORT experiments". Astronomical Society of India Conference Series. 13: 325–327. Bibcode:2014ASInC..13..325A.
17. ^ Ali, Sk. Saiyad; Bharadwaj, Somnath (1 June 2014). "Prospects for Detecting the 326.5 MHz Redshifted 21-cm HI Signal with the Ooty Radio Telescope (ORT)". Journal of Astrophysics and Astronomy. 35 (2): 157–182. arXiv:1310.1707. Bibcode:2014JApA...35..157A. doi:10.1007/s12036-014-9301-1. ISSN 0250-6335. S2CID 118559571.
18. ^ Bharadwaj, S.; Sarkar, A. K.; Ali, Sk. Saiyad (1 September 2015). "Fisher Matrix Predictions for Detecting the Cosmological 21-cm Signal with the Ooty Wide Field Array (OWFA)". Journal of Astrophysics and Astronomy. 36 (3): 385–398. arXiv:1510.01850. Bibcode:2015JApA...36..385B. doi:10.1007/s12036-015-9346-9. ISSN 0250-6335. S2CID 119256221.
19. ^ Sarkar, Anjan Kumar; Bharadwaj, Somnath; Ali, Sk. Saiyad (1 March 2017). "Fisher Matrix-based Predictions for Measuring the z = 3.35 Binned 21-cm Power Spectrum using the Ooty Wide Field Array (OWFA)". Journal of Astrophysics and Astronomy. 38 (1): 14. arXiv:1703.00634. Bibcode:2017JApA...38...14S. doi:10.1007/s12036-017-9432-2. ISSN 0250-6335. S2CID 119486733.
20. ^ Chatterjee, Suman; Bharadwaj, Somnath; Marthi, Visweshwar Ram (1 March 2017). "Simulating the z = 3.35 HI 21-cm Visibility Signal for the Ooty Wide Field Array (OWFA)". Journal of Astrophysics and Astronomy. 38 (1): 15. arXiv:1703.00628. Bibcode:2017JApA...38...15C. doi:10.1007/s12036-017-9433-1. ISSN 0250-6335. S2CID 119088331.
21. ^ Sarkar, Anjan Kumar; Bharadwaj, Somnath; Guha Sarkar, Tapomoy (1 May 2018). "Predictions for measuring the cross power spectrum of the HI 21-cm signal and the Lyman-alpha forest using OWFA". Journal of Cosmology and Astro-Particle Physics. 2018 (5): 051. arXiv:1804.00454. Bibcode:2018JCAP...05..051S. doi:10.1088/1475-7516/2018/05/051. ISSN 1475-7516. S2CID 54804413.
22. ^ Chatterjee, Suman; Bharadwaj, Somnath (1 August 2018). "A spherical harmonic analysis of the Ooty Wide Field Array (OWFA) visibility signal". Monthly Notices of the Royal Astronomical Society. 478 (3): 2915–2926. arXiv:1804.00493. Bibcode:2018MNRAS.478.2915C. doi:10.1093/mnras/sty942. ISSN 0035-8711.
23. ^ "Home | Indian Academy of Sciences". www.ias.ac.in. Retrieved 6 May 2019.
24. ^ "Information and Announcements - The National Centre for Radio Astrophysics (NCRA)" (PDF). Ias.ac.in. Retrieved 4 February 2011.
25. ^ Kapahi, V. K (2007). "The National Centre for Radio Astrophysics(NCRA)Resonance". Resonance. 3 (9): 90–92. doi:10.1007/BF02836088. S2CID 122214854.
26. ^ "A digital signal pre processor for pulsar search using Ooty radio telescope" (PDF). Dspace.rri.res.in. Retrieved 4 February 2011.
27. ^ "Study of the LISM using Pulsar Scintillation - 2 Observations and Data Analysis" (PDF). Cdsweb.cern.ch. Retrieved 4 February 2011.
28. ^ Vivekanand, M. (June 1995). "Observation of nulling in radio pulsars with the Ooty Radio Telescope". Monthly Notices of the Royal Astronomical Society. 274 (3): 785–792. Bibcode:1995MNRAS.274..785V. doi:10.1093/mnras/274.3.785.
29. ^ "Geo-effectiveness of CMEs". Britannica.com. Retrieved 4 February 2011.
30. ^ Ajaysinh, K; Iyer, K. N; Vats, Hari Om; Manoharan, P. K (2007). "Geo-effectiveness of CMEs". Journal of Astrophysics and Astronomy. 29 (1–2): 287–291. Bibcode:2008JApA...29..287J. doi:10.1007/s12036-008-0038-6. S2CID 120907411.
31. ^ "Toyokawa IPS Workshop 2007-Ooty IPS Studies and IPS Network" (PDF). Smei.ucsd.edu. Retrieved 4 February 2011.
32. ^ "Historical perspective and research centres in India in the fields of solar astronomy and Sun-Earth relationship - National Centre for Radio Astrophysics (NCRA/TIFR)" (PDF). Cdaw.gsfc.nasa.gov. Retrieved 4 February 2011.

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