Gagan

1. GAGAN
BACKGROUND
• The GPS developed by the US has failed to meet the requirements of civil
aviation community.
• The US$115 million project was 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.

2. 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 types
I. SBAS (Satellite based augmentation system)
II. GBAS(Ground based augmentation system)

3. 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

4. • 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.

5. 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.

6. 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 (Velocities) are then sent to 2 Indian Navigation
Master Control Centers (INMCC) to generate correcting deltas
through computer processing for GPS signals anywhere within the
network.

7. • 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 12.

8. ARCHITECTURE
• GAGAN consists of two basic components the space segment and the
ground segment
Space segment consists of
I. 3 GEO satellites
II. GPS constellation
Ground segment consists of
I. INRES (Indian reference stations)
II. INMCC (Indian master control stations)
III. INLUS (Indian navigation land earth uplink stations)

9. INRES (Indian Reference Stations)
• 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.

10. INMCC (Indian Master Control Centre )
• 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).

11. INLUC (Indian Navigation Land Earth Uplink
Stations)
• The INLUS (Indian navigation land earth uplink stations) receives
correction messages from the INMCC (Indian Master Control Centre),
format those messages for GPS compatibility and transmit them to
the GEO satellites for broadcast to user platforms.
• The INLUS is collocated with INMCC (Indian Master Control Centre) 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).

12. 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 boundaries in
sea as well as precision approach service of APV-1.0 (Approach with
Vertical guidance) over the Indian landmass on nominal days.

13. BENEFITS/APPLICATIONS
1. AVAITION
I. GAGAN enhances reliability and reduces delays to aircraft.
II. GAGAN reduced workload of flight crew and Air Traffic Controllers.
III. It enhanced meteorological information.
IV. It also reduced congestion V. It enhanced safety, reduced delays and
increased airport & airspace capacity.

14. 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.