21 Sep

Satellite Navigation (SAT-NAV)

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Content

• Basics about SATNAV
• Methods used in SATNAV
• GPS
• BeiDou
• NAVIC/IRNSS
• About NVS-01

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A) Basics About SATNAV

• A satellite navigation (SATNAV) system is a technology that allows users to determine their precise location, velocity, and time information anywhere on or near Earth’s surface.
• It uses a network of satellite in space and provide accurate positioning data.

Methods used in SATNAV: Triangulation and Trilateration:

• Triangulation: Satnav systems use a technique called triangulation to determine the precise location of a receiver on the Earth’s surface.
• Trilateration: GPS receiver use the method of trilateration. Trilateration involves measuring the distance between your GPS receiver (e.g. a smartphone) and multiple satellite in the network. Each GPS satellite broadcasts a signal that includes a timestamp and information about its location
• [Please note that GPS doesn’t use triangulation (which measure angles), they really don’t use angles at all].
• Trilateration involve measuring distance

Accuracy: They generally provide high levels of positioning accuracy (within a few meters), depending on the quality of receiver and the number of satellites in view. However, various factors such as signal obstruction, atmospheric conditions, and receiver limitations can affect the accuracy.

Applications: Navigation purposes -> helping users find their way while driving, hiking, or boating. It is also used in aviation, surveying, geolocation-based services, precision agriculture, and even in some outdoor recreational activities. It can be used for vehicle tracking, fleet management, precise timing etc.

B) Global Positioning System (GPS)

• The best-known satnav system, GPS, uses 24 active satellites (including backups). Day and night, 365 days a year, they whiz around earth once every 12 hours on orbital plane inclined 55 degrees to the equator.

How GPS Finds your location?

• It uses Trilateration

C)  BeiDou

Details

• China initiated Beidou in 1994 with first BeiDou satellite launched in 2000.
• Second generation BeiDou (BDS-2) provided coverage to Asia Pacific region starting in 2012.
• Third generation BeiDou (BDS-3) satellite deployment started in 2015 and it started providing navigation services in 2018 to countries taking part in BRI. In 2020, the system has been completed and it can now provide global services. With this they have joined United States’ GPS and Russia’s GLONASS in providing global PNT services, with Europe’s Galileo to follow. These are all compatible and interoperable, meaning users can draw services from all of those to improve accuracy.

Plans of Expansion:

• In Nov 2022, China outlined plans to further expand the global reach of its home grown Beidou satellite navigation system.
  • Pakistan in 2014 became the first foreign country to set up a Beidou network.
  • Beidou has set up a first of three Continuously Operating Reference Stations (CORS) for its network in Thailand in 2013, to serve as a hub for ASEAN.

D) NAVIC (Navigation using Indian Constellation) 

• Indian Regional Navigation Satellite System (IRNSS) (also called Navigation Using Indian Constellation (NAVIC)), is a regional satnav system developed by ISRO. It aims to provide reliable position, navigation and timing (PNT) services over India and its neighbourhood, upto 1500 km from its boundary. In addition it is also capable of broadcasting messages. This can be used for broadcasting safety-of-life alerts in areas with poor or no communication, particularly in Ocean.

Need of IRNSS when services like GPS are easily available.

• The access to foreign controlled global navigation satellite systems is not guaranteed in hostile situations, as happened to Indian military depending on American GPS during Kargil War.

NAVIC provides two types of services:

• Standard Positioning Service (Open for Civilian Use)
• Restricted Services (Encrypted one, for authorized users (military))

 Components of IRNSS System:

• Space segments consists of 7 satellites, 3 satellites in GEO stationary orbit (GEO) and 4 satellites in GEO synchronous orbit(GSO) with inclination of 29 degree to the equatorial plane.
• All the satellites will always be visible in the Indian region.

First of the 2^nd generation satellite – NVS-01 was successfully launched in May 2023

• ISRO’s GSLV F12 (GSLV-MK-II mission)successfully places navigation satellite NVS-01 into intended orbit.

About GSLV F12:

• It is the 15^th flight of India’s GSLV and the 9^th flight with indigenous cryo stage.

About NVS-01:

• Heavier: It weighs 2232 kg and has been placed in geosynchronous orbit (older IRNSS satellites weighed 1,425 kg)
• Indigenous Atomic Clock: For the first time, the satellite carries an indigenous atomic clock. The space qualified Rubidium atomic clock has been indigenously developed by Space Application Centre – Ahmedabad.
• L1 signals for better use in wearable devices: The second generation satellites have send signals in a third frequency, L1, besides the L5 and S frequency signals that the existing satellites provide. This will increase operability with other satellite based navigation systems. L1 frequency is the most commonly used in the GPS and will increase the use of NavIC in wearable devices which use low power signal frequency chip.
• Longer Mission Life of 12 years (earlier NavIC satellites have a mission life of 10 years).

Criticism of NaVIC:

• Delay in developing user receiver: A 2018 report by the CAG of India has said that even though the cabinet cleared funding of Rs 200 crore to develop user receivers in 2006, work on the project started only in March 2017, by which time seven launches of NavIC was already done.

• Current Situation (June 2023)
  • The receivers have now been deployed, and NavIC is in use for projects like public safety, power grid synchronization, real-time train information system, and fishermen’s safety.
  • Other upcoming initiatives (such as) common alert protocol based emergency warning, time dissemination, geodetic network, unmanned aerial vehicles are in the process of adopting NavIC system.
  • Some cell phone chipsets build by Qualcomm, MediaTek integrated NaVIC receivers in 2019. Some example phones which are NavIC enabled include Redmi Note 9, Realme 6, the OnePlus Nord.

 Way Forward:

• Promoting the Use of IRNSS:
  • NavIC chip -> affordable
  • Spreading awareness -> Positional accuracy better than 20 m and timing accuracy better than 50 ns (20);
  • Make compulsory for phones marketing in India: Mobile phones haven’t been made compatible to process its signals.
  • Government apps -> start using NaVIC for various purpose.
  • HEIs -> Promote use in Labs, among students etc.
• Fast track the plans for making NavIC global
• The next generation NVS series of satellites will make the NavIC more versatile and promote ease of use.

Example Questions

• What do you understand by ‘Standard Positioning Systems’ and ‘Precision Positioning Systems’ in the GPS era? Discuss the advantages India perceives from its ambitious IRNSS program employing just seven satellites [Mains 2015, 12.5 marks, 200 words]
• Why is Indian Regional Navigational Satellite System (IRNSS) needed? How does it help in navigation? [Mains 2018, 10 marks, 150 words]
• What is satellite navigation? Discuss the key economic and social uses of Satellite navigation. [10 marks, 150 words]
• Why did India need its own regional satellite navigation system when we already had access to GPS services? Discuss the key features of NAVIC. [10 marks, 150 words]