Radio telescopes: probing space

Context: Telescopes are essential tools in every astronomer’s repertoire. A radio telescope is a telescope that helps scientists ‘see’ the universe using radio waves (1 mm to more than 10,000 km in wavelength).

How Radio telescopes function?

  • These telescopes collect faint radio waves coming from deep space, and with the help of other equipment focus and amplify them for scientific study. Radio telescopes can detect radio waves from a number of celestial objects, such as stars, galaxies, and black holes. 

Where are they located and what is their shape?

  • They are ground based, and not in orbit, because they are usually quite large. This is because the size of the antenna – the dish like structure that detects the waves – is proportional to the wavelength being tracked. 
Where are they located and what is their shape?
  • In fact, the most common radio telescopes have a parabolic dish antenna. Due to its curved shape, the radio waves hitting the dish bounce to a point called the focus, where a receiver collects them. 
  • Dish antennas collect many different wavelengths at once, so scientists often use receivers picking up multiple wavelengths at once.

Significance of large size and amplifiers

  • Because of their large wavelength, radio waves can travel long distances without interruption, making them ideal to catch glimpses of stars behind dust clouds. But the longer they travel, the weaker they get. So telescopes often try to maximise their signal collection area and use amplifiers to increase their strength. 
Significance of large size and amplifiers

Significant radio telescope

  • One of the biggest radio telescopes in the world today is the FAST instrument in China, with a 500­metre­wide dish.
  • The Giant Metre wave Radio Telescope (GMRT), located near Narayangaon, Pune in India, is an array of thirty fully steerable parabolic radio telescopes of 45 metre diameter, observing at metre wavelengths. It is the largest and most sensitive radio telescope array in the world at low frequencies. It is operated by the National Centre for Radio Astrophysics (NCRA), a part of the Tata Institute of Fundamental Research, Mumbai.

SARAS (Shaped Antenna measurement of the background Radio Spectrum) is developed by Raman Research Institute and was deployed over Dandiganahalli Lake and Sharavati backwaters, located in Northern Karnataka, in early 2020.

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