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GAGAN (AN INDIAN EYE ON THE SKY)

SAAD BABAR ABBASIGNSS-02150511011

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CONTENTS• BACKGROUND• GNSS AUGMENTATION• SBAS• GBAS• GAGAN• ARCHITECTURE• INRES• INMCC• INLUS• PERFORMANCE• BENEFITS• REFERENCES

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BACKGROUND

• The GPS developed by the US has failed to meet the requirements of civil aviation community

• The US$115 million project is being created in three phases through 2008 by the Airport Authority of India with the help of the Indian Space Research Organization's (ISRO) technology and space support

• The goal is to provide navigation system for all phases of flight over the Indian airspace and in the adjoining area.

• It is applicable to safety-to-life operations, and meets the performance requirements of international civil aviation regulatory bodies

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GNSS AUGMENTATION

• Augmentation of a global navigation satellite system  (GNSS) is a method of improving the navigation system's attributes, such as accuracy, reliability, and availability, through the integration of external information into the calculation process

• GNSS augmentation is of two typesI. SBAS (satellite based augmentation system)II. GBAS(ground based augmentation system)

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SBAS

• Satellite-based augmentation systems (SBAS), such as EGNOS, complement existing global navigation satellite systems (GNSS). SBAS compensate for certain disadvantages of GNSS in terms of accuracy, integrity, continuity and availability

• The SBAS concept is based on GNSS measurements by accurately-located reference stations deployed across an entire continent

• The GNSS errors are then transferred to a computing center, which calculate differential corrections and integrity messages

• SBAS messages are broadcast via geostationary satellites able to cover vast areas

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SBAS CURRENT SCENARIO

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SBAS (GAGAN)

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GBAS

• Each of the terms ground-based augmentation system (GBAS) and ground-based regional augmentation system(GRAS) describe a system that supports augmentation through the use of terrestrial radio messages.

• Ground based augmentation systems are commonly composed of one or more accurately surveyed ground stations, which take measurements concerning the GNSS, and one or more radio transmitters, which transmit the information directly to the end user.

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GBAS

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GAGAN(GPS AIDED GEO AUGMENTED NAVIGATION)

• The GAGAN system consists of a network of 15 Indian Navigation Reference Earth Stations (INRES) that are precisely surveyed to compare the position determined from GPS satellite signals against the location of the receiver

• The observed deltas are then be sent to 2 Indian Navigation Master Control Centers (INMCC) where computer processing will extrapolate the data to generate correcting deltas for GPS signals anywhere within the network

• These correcting deltas will be relayed via 3 Indian Navigation Land Uplink Stations (INLUS) and  geostationary satellites to civil aircraft so more precise fixes of their position can be derived from GPS satellite signals

• INRES sites and INMCCs are connected using Optical Fiber Cable Data Communication Network as well as VSAT link

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ARCHITECTURE

• GAGAN consists of two basic components the space segment and the ground segment

• Space segment consists of I. 3 GEO satellites (2 operational one to be launched)II. GPS constellation

• Ground segment consists ofI. INRES (Indian reference stations)II. INMCC (Indian master control stations)III. INLUS (Indian navigation land earth uplink stations)

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ARCHITECTURE

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INRES

• The INRES collect measurement data and broadcast messages from all GPS and GEO satellites in view and forward to Indian Mission Control Centre (INMCC).• Altogether 8 INRES Stations are established in India

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INMCC

• An Indian Master Control Centre (INMCC) is established at Kundalahalli, Bangalore.

• The measurement data collected every second from each of the INRES receiver chains are transmitted in real time to the INMCC for correction and integrity processing and generation of SBAS messages with the aid of the navigation software resident.

• The INMCC comprises of various subsystems like Data Communication Subsystem (DCSS), Correction and Verification Subsystem (C&VS), Operation and Maintenance Subsystem (OMSS) and Service Monitoring Subsystem (SMS).

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INLUC

• The INLUS receives correction messages from the INMCC, format those messages for GPS compatibility and transmit them to the GEO satellites for broadcast to user platforms.

• The INLUS is collocated with INMCC at Bangalore. The INLUS also provides GEO satellite ranging information and corrections to the GEO satellite clocks.

• Message formats and timing will be according to the functional and performance specifications, which are derived from MOPS (Minimum Operation Performance Standard).

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PERFORMANCE

• GAGAN provides a civil aeronautical navigation signal consistent with International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPs) as established by the Global Navigation Satellite System (GNSS) Panel

• The GAGAN system provides non-precision approach (NPA) service accurate to within the radius of 1/10th of a nautical mile (required navigation performance or RNP-0.1) over the Indian FIR as well as precision approach) service of APV-1.0 (approach with Vertical guidance) over the Indian landmass on nominal days

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PERFORMANCE

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BENEFITS/APPLICATIONS

1. AVAITION

I. GAGAN enhances reliability and reduces delays to aircraftII. GAGAN reduced workload of flight crew and Air Traffic Controllers.III. It enhanced meteorological informationIV. It also reduced congestionV. It enhanced safety, reduced delays and increased airport & airspace capacity

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BENEFITS/APPLICATIONS

2. CIVIL

I. Better accuracy, reliability, and availability through the integration of external information

II. Useful for surveying, fleet management, traffic control, health and rescue and other countless applications

III. Better research and modelling of ionosphere

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REFERENCES• www.google.com• www.isro.gov• www.insidegnss.com• www.navipedia.net• www.wikipedia.org• ICAO International Standards and Recommended Practices, Annex 10 to the Convention

pm International Civil Aviation, Volume I Radio Navigation Aids, Section 3.7.1: Definitions• 2.Mishra Pratap& EngePer, Global Positioning System, Signals, Measurements and

Performance (Ganga-Jamuna Press, Lincoln, Mass, USA), 2012, pp.-123-173• 3.Parkinson Bradford W & SpilkerJames J, Global Positioning System: Theory and

Applications, Volume I, by (Jr. American Institute of Aeronautics and Astronautics Inc, USA), 2010, pp. 10-17, 478-483, 485-513.

• 4.KlobucharJ A, P H Doherty, M B El-Arini , Lejeune R, Dehel T, de Paula E R & Rodrigues F S, Ionosphere Issues for a SBAS in the Equatorial Region, Ionosphere Effects Symposium, Alexandria, Virginia, 7-9 May 2012.

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