Short notes on Current Affairs 21.12.2025

Tamil Nadu to conduct Hornbill Census

• Purpose of the initiative
  • Tamil Nadu Forest Department plans an extensive field exercise to estimate hornbill populations across forest landscapes.
  • The survey forms part of the State’s broader hornbill conservation initiative announced earlier in 2025.
  • The exercise aims to generate reliable population data to inform long-term conservation planning.
• Timing and rationale
  • The survey will be conducted from late December 2025 to March or early April 2026.
  • It coincides with the hornbills’ breeding season, improving visibility and accuracy of population estimates.
  • Breeding-season surveys also help identify nesting sites and critical habitats.
• Geographical coverage (Phase I)
  • Tiger Reserves:
    • Anamalai Tiger Reserve
    • Srivilliputhur–Megamalai Tiger Reserve
    • Kalakkad–Mundathurai Tiger Reserve
  • Forest ranges:
    • Karamadai Range
    • Mettupalayam Range (Coimbatore Forest Division)
  • Areas were prioritised based on historical records and previous hornbill sightings.
• Survey methodology
  • The line transect method will be employed.
  • Teams comprising forest personnel, biologists, and researchers will walk several kilometres daily through identified habitats.
  • Sightings will be recorded to estimate hornbill population density and distribution.
• Species expected to be documented
  • Great Hornbill
  • Malabar Grey Hornbill
  • Indian Grey Hornbill
  • Malabar Pied Hornbill
• Conservation focus beyond population counts
  • Emphasis on habitat protection, especially large, mature trees with natural hollows essential for hornbill nesting.
  • Recognition that habitat loss, particularly the removal of old trees, poses a major threat to hornbill survival.
• Institutional support and recent developments
  • In July 2025, Tamil Nadu announced India’s first Centre of Excellence for Hornbill Conservation.
  • The centre is located at the Anamalai Tiger Reserve in Coimbatore district.
  • It is expected to support research, monitoring, and conservation interventions.
• Expected outcomes and significance
  • The survey is expected to provide the most accurate hornbill population estimates for the State to date.
  • Data will guide targeted habitat protection, species management, and policy decisions.
  • The initiative strengthens Tamil Nadu’s leadership role in hornbill conservation at the national level.

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Drogue parachutes

Context and objective

• ISRO has successfully completed a series of qualification tests for drogue parachutes.
• These tests are part of the development of the deceleration system for the Gaganyaan crew module.
• The Gaganyaan mission is India’s first human spaceflight programme.

Nature of the tests

• The qualification tests focused specifically on drogue parachutes, a critical subsystem of the crew module.
• Tests were conducted on December 18 and 19.
• The purpose was to validate performance, reliability, and deployment under simulated re-entry conditions.

Testing facility

• The tests were carried out at the Rail Track Rocket Sled (RTRS) facility.
• The facility is operated by the Terminal Ballistics Research Laboratory (TBRL) in Chandigarh.
• RTRS enables high-speed testing required for evaluating deceleration and stability systems.

Role of drogue parachutes

• Drogue parachutes are deployed during the atmospheric re-entry phase.
• They play a crucial role in stabilising the crew module.
• They reduce the module’s velocity to a safe level before further stages of parachute deployment.

Technical significance

• Successful drogue parachute deployment is essential for crew safety during re-entry.
• It ensures controlled deceleration and proper orientation of the crew module.
• The system acts as a precursor to the deployment of larger main parachutes.

Programmatic importance

• The successful tests mark a key milestone in the Gaganyaan programme.
• They demonstrate progress toward ensuring safe human spaceflight capability.
• The results contribute to overall mission readiness and confidence in re-entry systems.

Broader implications

• The tests highlight collaboration between ISRO and defence research facilities like TBRL.
• They underscore India’s growing expertise in human-rated spaceflight technologies.
• Each successful qualification test brings the Gaganyaan mission closer to operational execution.

Drogue Parachutes – Explained

• What they are
  • Drogue parachutes are small, strong parachutes deployed at high speeds.
  • They are not meant for final landing but for initial stabilisation and deceleration.
• Primary purpose
  • Stabilise a fast-moving vehicle (spacecraft, aircraft, or payload).
  • Reduce velocity to a level safe enough for deploying larger main parachutes.
  • Ensure correct orientation and control during descent.
• Role in space missions (e.g., ISRO’s Gaganyaan)
  • Deployed during atmospheric re-entry of the crew module.
  • Help counter tumbling or instability caused by high-speed airflow.
  • Act as the first stage in a multi-parachute recovery system.
• Why they are critical
  • Main parachutes cannot be deployed safely at very high speeds.
  • Drogue parachutes reduce dynamic pressure and loads on the system.
  • They significantly enhance crew safety in human spaceflight missions.
• Key characteristics
  • Smaller size compared to main parachutes.
  • Designed to withstand extreme forces and temperatures.
  • Deploy reliably at supersonic or near-supersonic speeds.
• Other applications
  • Military aircraft (to shorten landing distance).
  • High-speed test vehicles and rockets.
  • Emergency recovery systems for payloads.
• In summary
  • Drogue parachutes are a critical intermediate deceleration mechanism.
  • They bridge the gap between high-speed flight and safe final descent.

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Nuclear Clocks

Background: Atomic vs Nuclear Clocks

• Conventional atomic clocks measure time by tracking electron transitions between atomic energy levels.
• Physicists aim to develop nuclear clocks, which would count transitions within the atomic nucleus.
• Nuclear energy levels are better shielded from environmental disturbances than electrons, promising greater stability and precision.

Why Thorium-229 Is Special

• Thorium-229 (²²⁹Th) has a unique nuclear excited state only 8.4 electron-volts (eV) above its ground state.
• This energy is unusually low for a nucleus and can be accessed using vacuum-ultraviolet (VUV) laser light.
• This makes ²²⁹Th the leading candidate for building a nuclear clock.

Key Experimental Challenge

• Detecting nuclear excitation in solid materials has been difficult.
• Ideally, excitation is detected by observing the VUV photon emitted when the nucleus relaxes.
• However, in many solids, relaxation occurs mainly through internal conversion, where:
  • Nuclear energy is transferred to an electron
  • The electron is ejected instead of a photon being emitted

Innovative Workaround by Researchers

• An international team (Germany, UK, USA) treated internal conversion itself as the detection signal.
• They embedded ²²⁹Th in thorium dioxide (ThO₂):
  • Material band gap ≈ 6 eV
  • Lower than the nuclear excitation energy (8.4 eV), enabling electron ejection
• Used VUV laser pulses to excite the thorium nuclei.
• Measured electrons emitted when excited nuclei decayed via internal conversion.

Experimental Techniques Used

• VUV laser pulses initially create a large burst of photoelectrons, which can overwhelm detectors.
• Researchers applied timed electric fields to:
  • Suppress immediate photoelectron bursts
  • Extract delayed electrons linked specifically to nuclear decay
• Additional electric fields guided emitted electrons efficiently to the detector.

Key Results

• Observed a clear resonance at 2,020,407.5 GHz, consistent with earlier measurements.
• Measured an internal conversion lifetime of 12.3 seconds in the sample.
• This corresponds to a clock accuracy of:
  • 1 second error in 15.8 billion years, far exceeding current atomic clock precision

Scientific and Technological Significance

• Confirms a viable method to detect nuclear transitions in solids.
• Expands the range of materials suitable for nuclear clock development.
• Enables high-precision probes of the nuclear environment within materials.

Broader Implications

• Nuclear clocks based on this design can be significantly miniaturised.
• Timekeeping could rely on measuring electron current, avoiding complex optical detection systems.
• Opens new possibilities for:
  • Ultra-precise time standards
  • Fundamental physics tests
  • Advanced sensing technologies

Expert Commentary

• Independent researchers from Texas A&M University noted that the work:
  • Broadens the experimental “toolbox” for nuclear clocks
  • Supports the development of stable, high-precision nuclear timekeeping devices

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