Square Kilometer Array

The Square Kilometre Array (SKA) is an international mega-science project aimed at building the world’s largest and most sensitive radio telescope. Designed to explore the universe in unprecedented detail, the SKA will have a total collecting area of about one square kilometre, giving it the ability to detect faint radio signals from the earliest epochs of cosmic history.
Once completed, the SKA will revolutionise radio astronomy by enabling scientists to study galaxy formation, cosmic magnetism, dark energy, gravitational waves, and the origins of life in the universe.

Overview

• Full Name: Square Kilometre Array
• Type: International radio telescope array
• Collecting Area: Approximately 1,000,000 square metres (1 square kilometre)
• Host Countries:
  • SKA-Mid: South Africa (with additional antennas in eight African partner countries)
  • SKA-Low: Western Australia
• Headquarters: Jodrell Bank Observatory, United Kingdom
• Coordinating Organisation: SKA Observatory (SKAO), an intergovernmental organisation established in 2021

The SKA will be the most advanced and ambitious radio telescope ever constructed, combining thousands of dish antennas and millions of dipole antennas spread across continents, linked together by high-speed fibre optic networks to act as a single, giant telescope.

Historical Background

• The concept of a radio telescope with a total collecting area of one square kilometre was first proposed in the early 1990s by astronomers seeking to detect faint cosmic signals.
• An international consortium of scientists and engineers began designing the project under the International SKA Project Office (established in 2008).
• After extensive site evaluation, Australia and South Africa were jointly selected as host nations in 2012.
• The Square Kilometre Array Observatory (SKAO) was formally established as an intergovernmental organisation in 2021, with member countries including the United Kingdom, Australia, South Africa, Italy, China, the Netherlands, Portugal, and Switzerland.

Design and Components

The SKA will consist of two main telescope arrays, each optimised for different frequency ranges of radio waves:

1. SKA-Low (Low-Frequency Array)

• Location: Murchison region, Western Australia
• Frequency Range: 50 MHz to 350 MHz (low-frequency radio waves)
• Structure: Around 131,000 dipole antennas grouped into 512 stations, each resembling “Christmas tree” structures.
• Purpose: Designed to study the early universe, including the Epoch of Reionisation, when the first stars and galaxies formed.

2. SKA-Mid (Mid-Frequency Array)

• Location: Karoo desert, South Africa
• Frequency Range: 350 MHz to 15.4 GHz (mid to high radio frequencies)
• Structure: Approximately 197 parabolic dish antennas, including 64 dishes from the existing MeerKAT telescope, which will be integrated into SKA-Mid.
• Purpose: Focused on studying galaxy evolution, pulsars, cosmic magnetism, and tests of general relativity.

Working Principle

The SKA operates on the principle of interferometry, where signals received by multiple antennas are combined to simulate a single, enormous telescope.

• Each antenna collects radio waves from celestial sources.
• These signals are digitised and transmitted via high-speed optical links to a central supercomputer.
• Advanced algorithms combine the data to create high-resolution images and spectra of the sky.

This method allows the SKA to achieve an angular resolution and sensitivity far superior to any existing radio telescope, capable of detecting signals millions of times fainter than those detectable today.

Scientific Objectives

The SKA will address some of the most fundamental questions in astrophysics and cosmology:

1. Formation of the First Stars and Galaxies:
   • Study the Epoch of Reionisation to understand how the first luminous objects transformed the universe.
2. Cosmic Magnetism:
   • Map magnetic fields in galaxies and intergalactic space to understand their origin and evolution.
3. Dark Matter and Dark Energy:
   • Investigate the large-scale structure of the universe and expansion rate to shed light on dark energy.
4. Testing Einstein’s General Relativity:
   • Observe pulsars and black holes to test the limits of gravitational theories.
5. Galaxy Evolution:
   • Trace how galaxies form and evolve over cosmic time.
6. Search for Extraterrestrial Life:
   • Detect possible technosignatures or bio-signals from distant exoplanetary systems.
7. Gravitational Waves (Indirect Detection):
   • Study the timing of pulsars to detect nanohertz gravitational waves produced by supermassive black hole mergers.

Data and Computational Challenges

The SKA will generate enormous volumes of data, making it one of the largest data projects ever undertaken.

• Expected Data Rate: Over 700 petabytes per year — more than global internet traffic in a day.
• Processing Requirement: Requires supercomputing power of exascale magnitude.
• Data Centres: Distributed science data processing centres will be established in multiple countries to handle and analyse SKA data.

International Collaboration

The SKA represents one of the largest scientific collaborations in history, involving over 16 member countries and numerous partner institutions.
Member nations include:

• Australia
• South Africa
• United Kingdom
• Italy
• China
• Netherlands
• Portugal
• Switzerland
• Sweden
• Canada (associate)
• India (associate)

Each country contributes through funding, research, and development of telescope components and computing technologies.

India’s Role in the SKA

India is an associate member of the SKA Observatory and plays an active role in scientific, engineering, and data-processing aspects of the project.
Key contributions include:

• Participation through the National Centre for Radio Astrophysics (NCRA-TIFR), Pune.
• Development of signal processing algorithms, high-speed data transport, and calibration techniques.
• Collaboration on SKA-Mid instrumentation and data analytics systems.
• Indian scientists plan to use SKA data for studying pulsars, cosmic magnetism, and the early universe.

India’s experience with the Giant Metrewave Radio Telescope (GMRT) near Pune has been instrumental in supporting SKA research and design.

Current Status and Future Timeline

• SKA Phase 1 (SKA1): Construction began in 2021 and is expected to be completed by the late 2020s.
• SKA Phase 2 (SKA2): Will expand the number of antennas and extend the frequency range, ultimately reaching a total collecting area of one square kilometre.
• Initial scientific operations (Early Science) are expected by 2028–2029.

Expected Impact

1. Astronomical Breakthroughs:
   • SKA will revolutionise understanding of cosmic evolution, black holes, and the large-scale structure of the universe.
2. Technological Innovation:
   • Advances in high-speed computing, data management, signal processing, and renewable energy systems.
3. Global Scientific Collaboration:
   • A model of international cooperation in mega-science projects, fostering cross-border research.
4. Societal Benefits:
   • Development of new technologies in data storage, communications, and artificial intelligence with potential applications beyond astronomy.