News in Shorts: 29 December 2025

Frequency Comb

Context: A frequency comb–based laser system is increasingly used in astronomy and precision physics to measure light frequencies with extraordinary accuracy.

About Frequency Comb

• A frequency comb is a specialised laser source whose spectrum consists of a large number of evenly spaced, discrete frequencies resembling the teeth of a comb.
• The invention of optical frequency combs earned the 2005 Nobel Prize in Physics

Key Features

• Equally Spaced Frequencies: Unlike conventional lasers emitting a single frequency, a frequency comb produces thousands of precisely spaced frequency lines with exceptional regularity.
• Mode-Locked Laser Origin: It is commonly generated using mode-locked lasers that emit ultra-short, periodic pulses of light at a fixed repetition rate.
• Extreme Precision and Stability: The uniform spacing of frequencies allows unknown light frequencies to be measured by comparison with a stable reference, enabling ultra-high precision.

Applications

• Atomic Clock Calibration: Frequency combs serve as a bridge between optical frequencies and microwave standards, enabling highly accurate timekeeping in atomic clocks.
• Precision Measurements in Physics: They are used to detect tiny frequency shifts caused by gravity, motion, or fundamental physical effects.
• Astronomy and Spectroscopy: Instruments such as planet-searching spectrographs use frequency combs to calibrate measurements and detect exoplanets through minute stellar wobbles.

Mount Etna

Context: Mount Etna in Sicily erupted again in December 2025, releasing ash and lava, prompting aviation alerts while scientific monitoring was intensified.

About Mount Etna

• Mount Etna is the most active stratovolcano in Europe and one of the most studied volcanoes globally due to its frequent eruptions.
  • A stratovolcano is a steep, conical volcano built from alternating layers of lava flows, ash, and volcanic debris, often producing explosive eruptions
• Location: It is situated on the eastern coast of Sicily, Italy, overlooking the Ionian Sea.
• Geographical Features: Etna rises as the highest mountain on a Mediterranean island and hosts summit craters, cinder cones, extensive lava flows, and the Valle de Bove depression.
• Ecological Significance: The volcano exhibits distinct ecological zones, ranging from fertile agricultural slopes to alpine and lava-dominated zones with endemic flora at higher elevations.
• Recognition: Mount Etna was officially inscribed on the UNESCO World Heritage List in 2013 for its outstanding volcanic activity and scientific value.

Tiger State

Context: Gujarat regained its “Tiger State” status after 33 years as NTCA confirmed a tiger’s presence in Ratanmahal Wildlife Sanctuary.

Conditions for Being a ‘Tiger State’

• Confirmed Tiger Presence: A state qualifies as a Tiger State when the National Tiger Conservation Authority (NTCA) officially confirms the presence of tigers through scientific evidence such as camera traps or pugmarks.
• Inclusion in All-India Tiger Estimation: The state must be included in the national Tiger Census, conducted periodically under NTCA supervision.
• Habitat Viability: Availability of prey base, water sources, habitat connectivity, and protection mechanisms are essential to sustain tiger populations.

Gujarat as a Tiger State

• NTCA Confirmation: Tiger presence in Gujarat was confirmed in 2025 after camera-trap evidence from Ratanmahal Wildlife Sanctuary in central Gujarat.
• Historical Context: Gujarat lost its Tiger State status after being excluded from the 1992 Tiger Census, following the local extinction of tigers.
• Conservation Measures: The Gujarat Forest Department has intensified ecosystem management, including prey augmentation, water provisioning, fire prevention, and enhanced camera-trap monitoring.
• Ecological Significance: Gujarat has become the only Indian state to host three big cats simultaneously, lion, tiger, and leopard, highlighting successful wildlife conservation efforts.
• Future Outlook: Steps are underway to strengthen tiger habitat and pursue declaration of Ratanmahal as a Tiger Reserve, ensuring long-term conservation.

About Ratanmahal Wildlife Sanctuary

• Ratanmahal Wildlife Sanctuary is ecologically significant for its dense forests, rugged terrain, and high concentration of sloth bears, making it a key wildlife habitat in Gujarat.
• Location: The sanctuary is located in Dahod district of central Gujarat, near Baria and Chhota Udepur, along the Gujarat–Madhya Pradesh border.
• Vegetation: It comprises dry teak forests at foothills, mixed deciduous forests, dry bamboo brakes, and pure patches of timru and sadad trees.
• Wildlife: Ratanmahal hosts Gujarat’s largest population of sloth bears and also supports a substantial population of leopards.
• Focused Conservation: Abundant mahuda and jamun trees provide critical food resources, making the sanctuary ideal for studying sloth bear behaviour.
• Ecological Significance: The forests form the catchment of the Panam River, supporting water conservation and irrigation needs in central Gujarat.

Regional Level Pollution Response Exercise (RPREX-2025)

Context: The Indian Coast Guard conducted RPREX-2025 off the Mumbai coast to strengthen preparedness for large-scale marine oil pollution amid rising maritime trade.

About RPREX-2025

• RPREX-2025 is a regional-level pollution response exercise conducted by the Indian Coast Guard to test India’s readiness to manage major marine oil spills.
• Location: The exercise was carried out in the Arabian Sea off the Mumbai coast, a high-traffic maritime zone vulnerable to oil pollution incidents.
• Participants: The drill involved the Indian Coast Guard , ONGC (Oil and Natural Gas Corporation), Mumbai Port Authority, state forest and fisheries departments, coastal police, port operators, and private oil-handling agencies.
• Focus Areas
  • Multi-Agency Coordination: Emphasis on integrated response involving central, state, port, and commercial stakeholders under a collective responsibility model.
  • Operational Readiness: Deployment of pollution control vessels, skimmers, containment booms, and real-time communication systems to test response speed and effectiveness.
  • Coastal and Environmental Protection: Special focus on shoreline defence, mangrove protection, and safeguarding local livelihoods such as fisheries during pollution incidents.
• Exercise Design: RPREX-2025 followed a two-phase approach, beginning with planning conferences and tabletop exercises, followed by a full-scale live sea simulation of an oil tanker collision.
• Significance: The exercise validated the National Oil Spill Disaster Contingency Plan (NOSDCP) and reinforced India’s capacity for swift, coordinated marine pollution response.

About National Oil Spill Disaster Contingency Plan (NOSDCP) 

• The National Oil Spill Disaster Contingency Plan (NOSDCP) is India’s framework for preparing for and responding to marine oil and chemical spills.
• The NOSDCP was approved in 1993 and officially promulgated in 1996.
• The Indian Coast Guard (ICG) was designated as the Central Coordinating Authority for combating oil spills in Indian waters in March 1986, prior to the plan’s approval

INS Vaghsheer

Context: President Droupadi Murmu undertook a dive sortie onboard INS Vaghsheer off Karnataka, becoming the second Indian President to sail on a submarine.

• A. P. J. Abdul Kalam became the first Indian head of state to sail in a submarine in 2006 when he sailed in INS Sindhurakshak.

About INS Vaghsheer

• Introduction: INS Vaghsheer is the sixth and final submarine of the first batch of Kalvari-class (Scorpene-class) submarines inducted under Project-75 of the Indian Navy.
  • Commissioned on 15 January 2025
  • Named after the sandfish, a lethal deep-sea predator
  • Built by Mazagon Dock Shipbuilders Limited (MDL) with French technology transfer
• Sister submarines: INS Kalvari, Khanderi, Karanj, Vela, and Vagir
• Features
  • Advanced Stealth: Extremely low radiated noise and superior hydrodynamic design, making it among the world’s quietest submarines.
  • Operational Capabilities:
    • Length: 67.5 metres
    • Speed: 20 knots (submerged)
    • Diving depth: Over 350 metres
    • Endurance: Up to 50 days
  • Weapon Systems: Torpedoes, anti-ship missiles, mine-laying capability, and anti-torpedo countermeasures.
  • Indigenous Systems: Air-conditioning plant, internal communication network, and Ku-band SATCOM.
  • Crew Capacity: 8 officers and 35 sailors.
• Applications 
  • Maritime Security: Anti-surface and anti-submarine warfare in the Indian Ocean Region.
  • Strategic Deterrence Support: Intelligence gathering, surveillance, and sea-denial operations.
  • Self-Reliance in Defence: Strengthens India’s indigenous submarine-building capability under Atmanirbhar Bharat.

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