Giant Metrewave Radio Telescope
Encyclopedia
Giant Metrewave Radio Telescope (GMRT), located near Pune
in India
, is the world's largest, array of radio telescope
s at metre wavelength
s. It is operated by the National Centre for Radio Astrophysics
, a part of the Tata Institute of Fundamental Research
, Mumbai
.
at Khodad(Located 19° 5'47.46"N 74° 2'59.07"E). A nearby town is Narayangaon which is around 15 km from the telescope. The office of NCRA is located in the University of Pune campus right next to IUCAA.
to make images of radio sources. The GMRT operates in six frequency bands centered at 38, 153, 233, 327, 610, and 1420 MHz.
Each antenna is 45 metres in diameter with the reflector made of wire rope stretched between metal struts in a parabolic configuration. This configuration works because of the long wavelengths (21 cm and longer) at which the telescope operates. Each antenna has four different receivers mounted at the focus. Each individual receiver assembly can rotate so that the user can select the frequency
at which to observe.
The maximum baseline in the array gives the telescope an angular resolution
(the smallest angular scale that can be distinguished) of about 1 arcsecond at the frequency of neutral hydrogen
(1420 MHz).
Astronomers from all over the world regularly use this telescope to observe many different astronomical objects such as HII regions, galaxies, pulsars, supernovae, and sun and solar winds.
the observatory invites the public and pupils from schools and colleges in the surrounding area to visit the site where they can listen to explanations of radio astronomy, receiver technology and astronomy from the engineers and astronomers who work there. Nearby schools/colleges are also invited to put their individual science experiments in exhibition and the best one in each level (primary, secondary school and Jr. college) are awarded.
Visitors are allowed into GMRT only on Fridays in two sessions - Morning(1100 hrs - 1300 hrs) and Evening (1500 hrs to 1700 hrs). The GMRT is open to the public on National Science Day.
Pune
Pune , is the eighth largest metropolis in India, the second largest in the state of Maharashtra after Mumbai, and the largest city in the Western Ghats. Once the centre of power of the Maratha Empire, it is situated 560 metres above sea level on the Deccan plateau at the confluence of the Mula ...
in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, is the world's largest, array of radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
s at metre wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s. It is operated by the National Centre for Radio Astrophysics
National Centre for Radio Astrophysics
India's National Centre for Radio Astrophysics , located on the Pune University Campus, is part of the Tata Institute of Fundamental Research. NCRA carries out research in the specialized field of Radio Astronomy and Radio instrumentation...
, a part of the Tata Institute of Fundamental Research
Tata Institute of Fundamental Research
The Tata Institute of Fundamental Research is a research institution in India dedicated to basic research in mathematics and the sciences. It is a Deemed University and works under the umbrella of the Department of Atomic Energy of the Government of India. It is located at Navy Nagar, Colaba, Mumbai...
, Mumbai
Mumbai
Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...
.
Location
The GMRT is located around 80 km north of PunePune
Pune , is the eighth largest metropolis in India, the second largest in the state of Maharashtra after Mumbai, and the largest city in the Western Ghats. Once the centre of power of the Maratha Empire, it is situated 560 metres above sea level on the Deccan plateau at the confluence of the Mula ...
at Khodad(Located 19° 5'47.46"N 74° 2'59.07"E). A nearby town is Narayangaon which is around 15 km from the telescope. The office of NCRA is located in the University of Pune campus right next to IUCAA.
Technical Information
The GMRT contains 30 fully steerable telescopes. There are fourteen telescopes randomly arranged in the central square 1 km by 1 km in size, with a further sixteen arranged in three arms of a nearly "Y"-shaped array each having a length of 14 km from the array centre. The GMRT is an interferometer which uses a technique known as aperture synthesisAperture synthesis
Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection...
to make images of radio sources. The GMRT operates in six frequency bands centered at 38, 153, 233, 327, 610, and 1420 MHz.
Each antenna is 45 metres in diameter with the reflector made of wire rope stretched between metal struts in a parabolic configuration. This configuration works because of the long wavelengths (21 cm and longer) at which the telescope operates. Each antenna has four different receivers mounted at the focus. Each individual receiver assembly can rotate so that the user can select the frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
at which to observe.
The maximum baseline in the array gives the telescope an angular resolution
Angular resolution
Angular resolution, or spatial resolution, describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object...
(the smallest angular scale that can be distinguished) of about 1 arcsecond at the frequency of neutral hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
(1420 MHz).
Science and Observations
One of the important aims of the telescope is to search for the highly redshifted 21-cm line radiation from primordial neutral hydrogen clouds in order to determine the epoch of galaxy formation in the universe. Pulsar research is another major area for GMRT study.Astronomers from all over the world regularly use this telescope to observe many different astronomical objects such as HII regions, galaxies, pulsars, supernovae, and sun and solar winds.
Activities
Each year on National Science DayNational Science Day
National Science Day is celebrated in India on February 28 every year to mark the discovery of Raman effect by C.V. Raman. The event is commemorated in honour of Sir C.V. Raman for his legacy and discovery of the Raman effect on February 28, 1927, for which he was awarded the Nobel Prize in 1930.-...
the observatory invites the public and pupils from schools and colleges in the surrounding area to visit the site where they can listen to explanations of radio astronomy, receiver technology and astronomy from the engineers and astronomers who work there. Nearby schools/colleges are also invited to put their individual science experiments in exhibition and the best one in each level (primary, secondary school and Jr. college) are awarded.
Visitors are allowed into GMRT only on Fridays in two sessions - Morning(1100 hrs - 1300 hrs) and Evening (1500 hrs to 1700 hrs). The GMRT is open to the public on National Science Day.
External links
- GMRT Homepage
- Y-shaped array
- Article on Science Day
- Visit GMRT retrieved on May 25, 2009
- GMRT site in Google map
