Ionosphere Modelling In India For Ionosphere Modelling In India For Satellite Navigation Programme Satellite Navigation Programme A S Ganeshan A S Ganeshan Project Director, Navigation Systems Project Director, Navigation Systems Indian Space Research Organization, Indian Space Research Organization, Bangalore, India Bangalore, India WG WG ‐ ‐ B B 6 th ICG, Tokyo, Japan September 4‐9, 2011
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Ionosphere Modelling In India For Ionosphere Modelling In India For Satellite Navigation ProgrammeSatellite Navigation Programme
A S GaneshanA S GaneshanProject Director, Navigation SystemsProject Director, Navigation SystemsIndian Space Research Organization,Indian Space Research Organization,
Bangalore, IndiaBangalore, India
WGWG‐‐BB6th ICG, Tokyo, Japan September 4‐9, 2011
Consists of two Projects
• GPS AIDED GEO AUGMENTED NAVIGATION (GAGAN)
• INDIAN REGIONAL NAVIGATION SATELLITE SYSTEM (IRNSS)
Indian Satellite Navigation Program
The objective of GAGAN‐FOP is to realize a certified and operational SBAS for all phases of flight path over the Indian FIR to provide the air navigation services of
RNP 0.1 en route navigation within Indian FIR
APV‐1/1.5 precision approach over the landmass of Indian FIR
GAGAN: Performance Objective
FlightPhase
Accuracy HAL VAL
RNP 0.1 72 m (H) 185 m N/AAPV 1.5 33.5 m (H)
9.8 m (V)40 m 50 m
Performance Requirements
Iono
. mod
el
Grid Based Ionosphere Model For GAGAN
IGM‐MLDF (ISRO GIVE Model‐Multi Layer Data Fusion):
• New Multi layer Grid Based Model
• Uses Data Fusion Technique• Provides GIVD, GIVE at 350 km (as
per MOPS)
‐ This model does not call for any
change to the existing SBAS message
structure
‐ No change for the legacy users
GAGAN INRES Locations (15)
• Joint activity between ISRO and Raytheon• Algorithm evaluated using the measurement based model data (ISRO‐TEC data) for selected nominal & stormy days over 2004‐07
• Algorithm is under evaluation with high quality live data collected over 15 INRES locations
• The live data (supertruth) contains measurements from 2/3 INREEs from each of the INRES
IGM‐MLDF: Preliminary Results
GAGAN TEC Data
Activities include:
• Data Collection and Archival
• Model Comparison and
Validation
• Testing New Algorithms
Measurement Based Ionosphere Model ‐ ISRO TEC Model
• Based on real data from GAGAN TEC stations combined with Physics‐based Semi‐empirical Model
• Provides TEC Map over Indian region
Depletion Studies •Depletion:‐ Post sunset events‐ Local phenomena (i.e., Depletion observed by an user may/may not be observed by any of the INRES )
‐ User protection against depletion: Mitigated through the ground model
•Observations:‐ Indicates that the depletion with >0.5 m magnitude occur during 5:30 p.m. – 3:30 a.m. local time.
‐ Maximum observed depth:7 ‐7.5 m
14.8 15 15.2 15.4 15.6 15.8 16 16.2 16.4 16.6
5
10
15
Mumbai 25
Ver
t. D
elay
, m
Time, UTC3/24/2004 – 7.5 m
3/8/2011 – 7 m13.5 14 14.5 15 15.5 16
-2
0
2
4
6
8
10
Vert Delay from L1-L2. Rec. 3. PRN 32
Ver
tical
Del
ay, m
Time, UTC
GAGAN TEC Data
GAGAN INRES Data
Consists of two Projects
• GPS AIDED GEO AUGMENTED NAVIGATION (GAGAN)
• INDIAN REGIONAL NAVIGATION SATELLITE SYSTEM (IRNSS)
Indian Satellite Navigation Program
IRNSS: INDIAN REGIONAL NAVIGATION SATELLITE SYSTEM
Service Type Freq. Band
Standard Positioning Service L5(1176.45Mhz)S(2492.028hz)
Restricted Services for Special Users
L5S
IRNSS SERVICES
• Refers to an independent Indian Regional Navigation Satellite System providing navigation services over Indian Region.
IRNSS ELEMENTSSpace SegmentGround SegmentUser Segment
SPACE SEGMENT
IRNSS Configuration
GEO at 32.5⁰E
GSO at 55⁰E
GEO at 83⁰E
GSO at 111.75⁰E GEO at
131.5⁰E
IRNSS Data StructureIonosphere Corrections In IRNSS
1. Co-efficient based (4α & 4β) Iono. Corrections
2. Grid Based Iono. Corrections (on L5)
1200 bits
SUBFRAME 1 SUBFRAME 3
SUBFRAME 2
Fixed Format -Primary Navigation Parameters(Clock & Ephemeris)
Message Format -Secondary Navigation Parameters
SUBFRAME 2 SUBFRAME 4
Ionosphere Corrections for IRNSS
Grid Based Corrections• IGM‐MLDF model for single frequency
• Service Area: Indian Land Mass• Total Number of IGPs
- 90 (Subdivided into 6 Regions)• Message Content
- No. of Regions Serviced - Region ID- GIVD, GIVE
• Region Specific co‐efficient based model• Model developed based on
‐ GAGAN TEC data‐ GAGAN INRES data
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