TELESCOPES ON AND AROUND THE MOON

Source: The Hindu

Disclaimer: Copyright infringement not intended.

Context

• Astronomers are considering placing optical and radio telescopes on and around the moon to overcome limitations faced by terrestrial and Earth-orbiting telescopes.
• The moon's far side offers pristine, airless conditions, shielded from Earth's radio interference and electromagnetic noise.

Details

Challenges and Solutions

• Deployment Challenges: Deploying telescopes on the moon poses logistical challenges due to the harsh lunar environment and high costs.
• Alternative Approaches: Orbiting telescopes around the moon offer an alternative approach, allowing for observations without the need for lunar landings.

Technological Advancements

• Instrumentation: Lunar telescopes will utilize advanced instrumentation, including wideband frequency-independent antennas, self-calibrating receivers, and digital correlators.
• International Collaboration: Space agencies like NASA, ESA, and China's CNSA are actively developing lunar telescope projects, leveraging technological advancements for space exploration.

Scientific Objectives

• Studying the Dark Ages: Lunar telescopes aim to observe signals from the Dark Ages of the universe, providing insights into the evolution of the cosmos from its early stages.
• Cosmic Microwave Background (CMB): By capturing the oldest light in the universe, lunar telescopes can study the cosmic microwave background and its implications for cosmology.

Global Initiatives and Future Prospects

• LuSEE Night Project:
  • Led by Aritogi Suzuki, the LuSEE Night project, a collaboration between NASA and Berkeley Lab, aims to land instruments on the moon's far side.
  • The project targets a landing near the moon's equator, opposite Earth, to minimize radio frequency noise from our planet.
• Future Moon-Bound Instruments:
  • Numerous instruments are in planning stages with space agencies like NASA and ESA for deployment on the moon.
  • NASA's Long-Baseline Optical Imaging Interferometer will study magnetic activity in stars and galaxies using visible and ultraviolet wavelengths.
  • ESA plans to launch a radio telescope aboard its lunar lander, 'Argonaut', by 2030, along with other projects focusing on gravitational wave detection and infrared observations.
• China's Moon-Orbiting Radio Telescope:
  • China is set to launch a moon-orbiting radio telescope in 2026, positioning itself at the forefront of lunar exploration and astronomical research.
  • The Queqiao-2 satellite, deployed in lunar orbit, carries a 4.2-meter antenna for radio astronomy, demonstrating China's commitment to space science.
• PRATUSH Mission: India's PRATUSH project represents a significant contribution to lunar astronomy, offering unique opportunities for scientific exploration.

About PRATUSH: Probing ReionizATion of the Universe using Signal from Hydrogen

• PRATUSH is a pioneering space telescope designed to reveal the Cosmic Dawn of the universe by studying the radiation from neutral hydrogen gas.

Objective:

• PRATUSH aims to answer fundamental questions about the early universe, including:
  • When did the first stars form?
  • What were the nature and characteristics of the first stars?
  • What was the color of the light emitted by the first stars during the Cosmic Dawn?

Importance of Cosmic Dawn and Epoch of Reionization (EoR):

• The Cosmic Dawn marks the period when the first sources of radiation, such as stars and galaxies, formed in the universe.
• EoR refers to the epoch when these sources of radiation reionized most of the neutral hydrogen atoms in the universe, transitioning it from a neutral to an ionized state.

21-cm Signal from Neutral Hydrogen:

• PRATUSH utilizes the natural emission signal of neutral hydrogen atoms at a wavelength of 21-cm (or 1420 MHz) to study distant galaxies and the evolution of the universe.
• By tracing the strength and shape of this 21-cm signal as a function of cosmic time, PRATUSH aims to understand the process of reionization and the characteristics of the early universe.

Unique Capabilities:

• Wideband Frequency-Independent Antenna: Operates over the frequency band of 30-250 MHz, enabling comprehensive coverage of the radio spectrum.
• Self-Calibratable Analog Receiver: Ensures precise calibration of instrument response, essential for accurate signal detection.
• Digital Correlator with High Spectral Resolution: Records spectra of radio emission with a resolution of 100 kHz, enabling detailed analysis of the signal.
• Custom Design for Instrument Sensitivity: Aims for sensitivity at the level of few millikelvin without systematic limitations, achieved through meticulous calibration strategies.

Funding and Collaboration:

• PRATUSH is funded for pre-project studies by the Indian Space Research Organization (ISRO).
• The project involves collaboration between the Raman Research Institute (RRI) and ISRO.

About Telescopes

• Telescopes are devices designed to gather and focus light to form magnified images of distant objects.
• History: Developed over centuries, with early telescopes credited to inventors like Galileo Galilei and Johannes Kepler in the 17th century.
• Function: Telescopes work by using lenses or mirrors to collect and concentrate light, resulting in an enlarged and clearer view of celestial objects.

Types of Telescopes:

• Refracting Telescopes: Use lenses to bend and focus light. Consist of an objective lens and an eyepiece.
• Reflecting Telescopes: Use mirrors to reflect and focus light. Consist of a primary mirror, secondary mirror, and an eyepiece.
• Compound Telescopes: Combine both lenses and mirrors for focusing light. Examples include Schmidt-Cassegrain and Maksutov-Cassegrain telescopes.
• Radio Telescopes: Detect radio waves emitted by celestial objects. Comprise large dish antennas and receivers.
• Space Telescopes: Orbit Earth to observe celestial objects without atmospheric interference. Examples include the Hubble Space Telescope and the James Webb Space Telescope.

Components of a Telescope:

• Objective Lens/Mirror: Gathers light and forms an image at the focal point.
• Eyepiece: Magnifies the image formed by the objective lens/mirror for viewing.
• Mount: Supports the telescope and allows it to be pointed and tracked.
• Tube: Encases the optical components and protects them from environmental factors.
• Finder Scope: A smaller telescope attached to the main telescope to aid in locating objects.
• Focuser: Adjusts the position of the eyepiece to achieve sharp focus.

Key Features:

• Aperture: Diameter of the objective lens/mirror, determining the telescope's light-gathering ability and resolution.
• Focal Length: Distance between the objective lens/mirror and the focal point, affecting magnification.
• Magnification: Ratio of the focal length of the telescope to the focal length of the eyepiece.
• Field of View: The angular size of the area visible through the telescope.
• Mount Type: Equatorial mounts for tracking celestial objects as the Earth rotates, and altazimuth mounts for simpler up-down and left-right movements.
• Optical Coatings: Anti-reflective coatings on lenses and mirrors to enhance light transmission and reduce glare.

Must read articles:

Moons in the solar system

Sources:

The Hindu

Pratush