Source: IT
Subject: Science and Technology
Context: ISRO recently reported that the atomic clock on the IRNSS-1F satellite has failed, reducing the number of functional positioning satellites in the NavIC constellation.
About NavIC’s Atomic Clock Failure:
What is an Atomic Clock?
- An atomic clock is an ultra-precise timekeeping device that uses the vibrations of atoms (usually Rubidium or Cesium) to measure time. In navigation satellites, these clocks are essential because even a billionth of a second of error can lead to a location inaccuracy of several meters on the ground.
How it Works?
- Atomic Resonance: The clock measures the precise frequency of electromagnetic radiation emitted or absorbed by electrons when they change energy levels within an atom.
- Ultra-Stability: Unlike mechanical or quartz clocks, atoms vibrate at a perfectly constant rate, providing a stable frequency that does not drift over time.
- Time-of-Flight Measurement: The satellite sends a signal with a timestamp. By comparing when the signal was sent to when it was received, the receiver calculates the distance.
- Trilateration: By calculating distances from at least four different satellites simultaneously, a receiver can pin-point a user’s exact latitude, longitude, and altitude.
Features:
- Precision: They are accurate to within one second every few million years.
- Redundancy: Satellites usually carry multiple clocks (often three or four) in case one fails.
- Indigenization: While earlier NavIC clocks were imported, the new generation (NVS series) features India-developed Rubidium atomic clocks.
About The NavIC Satellite System:
What it is?
- NavIC (Navigation with Indian Constellation), originally called the IRNSS (Indian Regional Navigation Satellite System), is India’s independent, regional satellite navigation system.
Launched In:
- The first satellite, IRNSS-1A, was launched in July 2013. The constellation was intended to be completed with seven satellites by 2016, though replenishment launches (like NVS-01 in 2023) continue to sustain the system.
Aim: The primary goal is to provide reliable position, navigation, and timing services over India and a region extending approximately 1,500 km around its borders, ensuring strategic independence from foreign systems like the American GPS.
Features:
- Dual Service: Provides Standard Positioning Service (SPS) for civilians and Restricted Service (RS)—an encrypted signal for military use.
- Geosynchronous Orbit: Unlike GPS satellites that move around the Earth, NavIC satellites are placed in higher orbits (36,000 km) that keep them permanently visible over the Indian region.
- Superior Accuracy: Because the satellites are always overhead for India, they provide better accuracy (approx. 10 meters) in dense forests and mountainous terrain compared to GPS.
- Frequency Bands: It operates in the L5 and S bands. Newer satellites (NVS series) have added the L1 band, making them compatible with common wearable devices like smartwatches.
