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Overview of Overview of GAGANGAGAN and and IRNSSIRNSS
Indian Space Research Organization
L. Mruthyunjaya
Group Head, Navigation Programme Management Office
ISRO Satellite Centre
Bangalore.
� Navigation is an ancient science but has continuously evolved over
centuries. The requirement of quality of navigation has increased
continuously, driving the science to great sophistication. Today navigation
requirement are both widespread and exacting. This has called for the
creation of man made facilities or infrastructure for the aiding navigation.
This information is often used further for purposes such as reaching
previously known destinations, intercepting moving objects. Numerous
Navigation
2
previously known destinations, intercepting moving objects. Numerous
other location based services also utilizes position information
� Timing is very important element of observation in determining position.
Inaccuracies in observation and recording of time would lead to inaccurate
navigation. Navigation has been the strongest devices for improved time
keeping technologies.
� Navigational aids of ancient time� Landmarks
� Celestial body
� Natural satellites
� Man made navigation instruments
Dead reckoning tools
Compass Chronometer Sextant Compass RoseRadio Communication ( I & II World War)
Radar
Evolution of Navigation Systems
Global16
Cen
tury
16 C
entu
ry
17th Century and beyond …
Spee
dD
irec
tion
Longitude
What are the global
constellations available
Hyperbolic Navigation System–LORAN
Egyptian Groma
Cross-staff
Astrolable
Traverse board14th-15th century
Radar
Regional
IRNSS QZSS
14
14 --
16 C
entu
ry16
Cen
tury
Global Positioning
System (GPS)
Lat
itud
e
constellations available
now?
Any idea about regional
constellations?
� Space Segment• At least 24-30 satellites around
the earth
� Control segment• Monitoring stations
• Central processing
Satellite Navigation System
4
• Central processing
• Command and unlinking stations
• System time keeping
� User segment• GNSS receiver
• Any subsequent processing and
data utilization facilities
Triangulation method
Position Estimation
P
User receivers measure theirdistance from atleast 4 satellitesthrough one-way rangingtechnique.
Most downlink signals use CodeDivision Multiple Access (CDMA)and RF modulation such as,BPSK, Binary Offset Carrier(BOC) etc . GLONASS uses CDMA
5User position
bZZYYXXP
bZZYYXXP
bZZYYXXP
bZZYYXXP
+−+−+−=
+−+−+−=
+−+−+−=
+−+−+−=
24
24
244
23
23
233
22
22
222
21
21
211
)()()(
)()()(
)()()(
)()()(
1P
2P
3P (BOC) etc . GLONASS uses CDMAranging codes with FrequencyDivision Multiple Access (FDMA)
Errors in Position Determination
Satellite
clock bias Ephemeris
errors
Ionospheric
delay
GPS ERROR BUDGETEphemeris ~ 5m Clock ~ 1mTroposphere ~ 1mIonosphere ~7mMulti-path ~ 0.5mRx Specific ~ 2mUERE ~ 9.mAccuracy (95%) ~ 20 m
GPS ERROR BUDGETEphemeris ~ 5m Clock ~ 1mTroposphere ~ 1mIonosphere ~7mMulti-path ~ 0.5mRx Specific ~ 2mUERE ~ 9.mAccuracy (95%) ~ 20 m
Multi path
Receiver
Clock bias
Tropospheric
delay
Accuracy (95%) ~ 20 m Accuracy (95%) ~ 20 m
24+3 Spare
Satellites
24+3 Spare
Satellites
30
Satellites
35
Satellites
11 Hrs 11 Hrs 14 Hrs 12 Hrs
No. of
Satellites
Orbital
GPS GLONASS GALILEO COMPASS
GNSS
Constellation
11 Hrs
58 Mins
11 Hrs
16 Mins
14 Hrs
05 Mins
12 Hrs
35 Mins
1575.45MHz
1227.6 MHz
1246-1257MHz
1602-1616MHz
1164-1300MHz
1559-1591MHz
1.561098 GHz (B1)1.589742 GHz (B1-2)
1.20714 GHz (B2)
1.26852 GHz (B3)
CDMAFDMA/
CDMACDMA CDMA
Fully
Operational
Fully
Operational
4 IOV and
8 operational
19 satellites
operational
Orbital
Period
Frequency
Coding
Status
INDIANINDIAN REGIONAL NAVIGATION SATELLITE SYSTEM REGIONAL NAVIGATION SATELLITE SYSTEM -- IRNSSIRNSS
GPS GPSGPSGALILEO GLONASS GLONASSGALILEO GALILEO
Radioastronomy
1610.6 – 1613.6 MHz
L5 L2 S
E5
L1 C
Spectral bands for Radio Navigation Satellite Systems1
16
4.0
00
MH
z
11
88
.00
0 M
Hz
12
12
.00
0 M
Hz
12
15
.00
0 M
Hz
12
15
.60
0 M
Hz
12
60
.00
0 M
Hz
12
37
.82
7 M
Hz
12
39
.60
0 M
Hz
12
61
.61
0 M
Hz
13
00
.00
0 M
Hz
15
59
.00
0 M
Hz
15
92
.95
2 M
Hz
16
10
.00
0 M
Hz
16
20
.61
0 M
Hz
16
26
.50
0 M
Hz
15
87
.42
0 M
Hz
15
63
.42
0 M
Hz
50
10
.00
0 M
Hz
50
30
.00
0 M
Hz
24
83
.5 -
25
00
MH
z
• L1 (1559 – 1610 MHz), L2 (1215 – 1300 MHz), L5 (1164 – 1215 MHz),
• S-band (2483.5 – 2500 MHz)
• L1 and L2 bands are being used for 30 years now. L5 is the latest & much sought after band.
• S-band is for Regional use in Region 3. The World Radio Conference (WRC-12) will discuss global allocation for this band. Proximity of this band with MSS and the 2500-2690 MHz is an added advantage
GPS Signals
Civil Signals – L1 C/A ,L1C, L2C, L5
Military Signals – P(Y) and M Code
Modernization plan
L2 C – Accessibility of two civilian signals with L1 C/A – 2018
L5 - Safety of Life appilications - 2021
L1C – Block III with improved signal reception in challenging
Environments - 2026
GLONASS FDMA
GLONASS Signals
GLONASS CDMA
GALILEO Signals
Open Service
Public Regulated Service (PRS)
Commercial Service (CS) Public Regulated Service (PRS)
Open Service (OS) Open Service
COMPASS Signals
E5a E5b L2
ARNS Bands RNSS Bands
E6
ARNS BandsRNSS BandsL5-band L2-band
L1-band
(MHz)
L5-Band (1164-1215 MHz)
L2-Band(1215-1300 MHz)
L1-Band(1559-1610 MHz)
S-Band(2483.5- 2500 MHz)
GPS L5 L2, L2C, L2M L1, L1C, L1MGLONASS L3OC L2 L1GALILEO E5a, E5b E6 E1, E1PCOMPASS B2 B3 B1 B2
Bandwidth Allocation to GNSS Services
1180 1200 1220 1240 1260 1280 1300-80
-75
-70
-65
-60
-55
PS
D(d
B)
1560 1570 1580 1590 1600 1610-80
-75
-70
-65
-60
-55
GPS
GLONASS
GALILEO
COMPASS
L1-BandL5-Band L2-Band
E6, B3E5a E5b, B2, L3
COMPASS B2 B3 B1 B2QZSS L5 L2C, LEX L1IRNSS L5 S
Freq. MHz
TM-TC Package
S/c control
Payload
NSGU
S/c bus
elements
Nav
data
RAFS
ACMU
Navigation Signal
P/L control
I.R.S.C.F.
Nav-dataS/c control
command
Tele - command
Generation
Spacecraft Control Earth Station
Ranging
data
IRIMS
Timing Info
IRNWT
CDMA
Ranging Data
IRCDRIRCDR
Laser
Ranging Data
IRLRSIRLRS
I.N.C
IRMNCNav
S/w
SCHE
MACSIDOS
� IRNSS is an independent Navigation Satellite Systemproviding Navigation services in the Indian region. It isbeing implemented by ISRO
�Provides the user with a targeted position accuracy ofbetter than 20m over India and the region extending toabout 1500 km around India.
IRNSS OBJECTIVE
The IRNSS shall provide two types of navigation services to its
users.
Standard Positioning Service (SPS):
An unencrypted service provided to all users.
Restricted Service (RS):
An encrypted service provided only to authorized users.
Navigation Down Link Signals
Frequency Band SPS RS
L5 band (1176.45 MHz ) BPSK BOC(5,2)
S band (2492.028 MHz) BPSK BOC(5,2)
IRNSS SIGNAL SPECTRUM
RS BOC(5,2) PILOT
S – BAND
2483.5 – 2500 MHz
RS BOC(5,2)
1176.45 MHz
2492.028 MHz
L5 – BAND
1164.45 – 1188.45MHz
SPS BPSK - R(1)
GEO at 32.5⁰⁰⁰⁰E
GSO at 55⁰⁰⁰⁰E
GEO at 83⁰⁰⁰⁰E
GSO at 111.75⁰⁰⁰⁰E
GEO at 131.5⁰⁰⁰⁰E
IRNSS SEGMENTS - INTERACTIONS
�IRNSS constellation consists
of 7 satellites
�3 Satellites in Geo-Stationary
orbit at 32.5°, 83°and 131.5°E
�4 Satellites in Geo-
IRNSS CONSTELLATION
GEO at 83˚ E
GSO at 111.75˚ E
GEO at 131.5˚ E
GSO at 55˚ E
GEO at 32.5˚ E
�4 Satellites in Geo-
Synchronous orbit placed at
inclination of 29° with
Longitude crossings 55°&
111.75°E
�The Satellites are specially
configured for the Navigation.
�IRNSS Satellites are to be
launched by the Indian
launcher PSLV.
Orbital Location : Geosynchronous / Geostationary
Bus : I-1K Bus
Payload :Navigation Payload in S & L5 bands
Ranging Payload in C Band
Power : 1600 Watts
IRNSS SPACECRAFTS
Power : 1600 Watts
Spacecraft
Mass: 1426 Kg
Mission Life : 10 Years
Launch Date :
IRNSS-1A - Jul 01, 2013
IRNSS-1B - Apr 04, 2014
IRNSS-1C - Oct 15, 2014
IRNSS-1D - Mar 28, 2015
IRNSS-1E – Jan 20, 2016
• NAVIGATION PAYLOAD
– GENERATES SPS & RS NAVIGATION SIGNALS
• CDMA RANGING PAYLOAD
– TWO WAY RANGING SYSTEM IN EXTENDED C
IRNSS PAYLOADS
– TWO WAY RANGING SYSTEM IN EXTENDED C
BAND
• CORNER CUBE LASER RETRO REFLECTOR
– TWO LASER RANGING FROM ILRS
Navigational Payload details
• Main elements:
• Navigation signal generator
Navigational Payload Functions
• Received TTC data is demodulated
• Navigation data is formatted along with timing information
NAVIGATION PAYLOAD
• Rb Atomic Frequency Standards
• Atomic Clock Monitoring Unit
• L5 and S band TWTAs
• L5 and S Band Antenna
along with timing information
• Encryption, FEC and spreading functions are performed
• BPSK Modulation, Up-Conversion and Amplification
• Navigation Signals transmission via L-S Band antenna
Navigation software deployed in IRNSS Navigation Centre (INC)
The software modules interface with various subsystems of the
ground segment and generate navigation parameters.
�Primary Parameters
� Satellite ephemeris & clock
�Secondary Parameters
Navigation Software
�Secondary Parameters
� Satellite almanac
� Differential corrections
� Ionospheric gird delay parameters
� Ionospheric corrections-coefficients
� IRNSS time difference w.r.t UTC /GNSS
� Earth orientation parameters
� Auto-Nav Parameters etc.
User Segment
The user segment mainly consists of:
� A dual frequency IRNSS receiver capable of receiving navigation
signals in L5 and S band frequencies, for SPS & RS.
� Single frequency receiver for SPS.
� A multi-mode GNSS receiver compatible between IRNSS and� A multi-mode GNSS receiver compatible between IRNSS and
other service providers like GPS, GLONASS, GALILEO etc.
SUBSUB FRAME 2 SUB FRAME 3 SUB FRAME 4
IRNSS Master Frame is of 1200bits made of four sub frames each 300bits.Current IRNSSdata structure is designed to broadcast IRNSS satellite ephemeris, which has 15 navigationparameters. These parameters are transmitted in SF1 and SF2 occupying 600 bits of 1200bitsmaster frame with data rate of 25bps.
Current IRNSS data structure
IRNSS DATA STRUCTURE
SUB
FRAME 1SUB FRAME 2 SUB FRAME 3 SUB FRAME 4
600 Symbols 600 Symbols 600 Symbols 600 Symbols
Sync
codeSubframe Data
16 bits584 symbols (292
bits)
Master Frame Structure
Subframe 1 & 2 (Primary Parameters)
IRNSS FRAME STRUCTURE
Subframe 3 & 4 (Secondary Parameters)
Secondary Parameters: SubSecondary Parameters: Sub--frame 3 & 4 (Messages)frame 3 & 4 (Messages)
Parameter MSG ID
Ionospheric grid parameters for 15 grid points (1 of
6 regions) (Grid delay and GIVE on L5; Interpolation alongusers’line of sight)
5
Almanac parameters 7
UTC and Time Sync Parameters w.r.t GNSS 9
IRNSS MESSAGES
EOP and Ionosphere coefficients(User algorithm to compute line of sight iono. delay using 8 co-efficients on L5)
11
Differential corrections for one satellite 14
Text message 18
UTC and Time Sync Parameters with respect to
GNSS (Currently IRNSS offsets w.r.t UTC, UTC (NPLI), GPS,GLONASS being broadcasted)
26
Null Message 0
Reserved for future 1-4, 6, 8, 10, 12, 13, 15-17,
19-25, 27-63
IRNSS SISIRNSS SIS--ICD: Is hosted in ISRO web site ICD: Is hosted in ISRO web site
•Provides the Signal and the Data Structure for Standard
Positioning Service (SPS) of IRNSS
•Addresses the following and their interpretations:
– Signal modulations, Frequency bands
IRNSS SIS - ICD
– Signal modulations, Frequency bands
– Data structure: Contents
– User algorithms
Position Accuracy over a day with 4 S/C
Bangalore Bhopal
IRNSS NAVIGATION PERFORMANCE
HyderabadPort Blair
Position Accuracy with 4 and 5 Satellites (Stn: Ban galore)
POSITION ACCURACY WITH 5 S/C
GPS AIDED GEO AUGMENTED NAVIGATION
GAGAN GAGAN GAGAN GAGAN ----Redefining NavigationRedefining NavigationRedefining NavigationRedefining Navigation
GPS ERROR BUDGETEphemeris ~ 5m Clock ~ 1mTroposphere ~ 1mIonosphere ~7mMulti-path ~ 0.5mRx Specific ~ 2mUERE ~ 9.mAccuracy (95%) ~ 20 m
GPS ERROR BUDGETEphemeris ~ 5m Clock ~ 1mTroposphere ~ 1mIonosphere ~7mMulti-path ~ 0.5mRx Specific ~ 2mUERE ~ 9.mAccuracy (95%) ~ 20 m
Limitation of GNSS
Accuracy (95%) ~ 20 m Accuracy (95%) ~ 20 m
All these call for a special system
addressing all the above, which
could be done by augmenting the
GPS system
Current GPS and GLONASS Constellations Cannot
Support Requirements for all Phases of Flight
– Accuracy is Not Sufficient
• Even with SA off, vertical accuracy > 10 m
– Integrity is Not Guaranteed
• Not all satellites are monitored at all times
• Time-to-alarm is from minutes to hours
• No indication of quality of service
– Availability and Continuity Must Meet
Requirements
SBAS-WAAS
- EGNOS
-MSAS
- GAGANGAGAN
GAGAN
• Improve integrity via real time monitoring
• Improve availability and continuity
• Improve accuracy via corrections
Types of Augmentation
Augmentation Systems
- GAGANGAGAN
GBAS-LAAS
-GRAS
ABAS
-RAIM
-Inertials
-BaroAltimeter
3 GEO Satellites
3 Uplink stations
UsersGPS
constellation
GAGAN-Indian SBAS
3 Uplink stations
2 Control Centres
15 Reference Stations
4 Data communication networks
MONITOR MONITOR
CORRECT CORRECT
BOUND BOUND
TRANSMITTRANSMIT
APPLYAPPLY
Approach Category
FlightPhase
Accuracy Time to Alert
HAL VAL Expected Date of
Completion
RNP 0.1 En-route 85 m N/A 185 m N/A June 2011
APV 1.5 Precision Approach
7.6 m 6 sec 40 m 50 m June 2013
Ion
o.
Mo
de
l
IGM-MLDF (ISRO GIVE Model - Multi Layer Data Fusion): (with Raytheon)
• Algorithm for computing the ionosphere corrections at pre-defined grid points
• Fuses the delays and confidences at two different layers
GAGAN: Ionosphere model development
450
350
250
150
He
igh
t (k
m)
Performance: IGM-MLDF
IGM-MLDF
Realize a certifiable and operational SBAS toprovide
air navigation services of
- RNP 0.1 en route navigation within Indian
FIR (Flight Information Region)
- APV-1/1.5 precision approach over
Indian landmass
3 GEOs carry GAGAN payload
GAGAN-FINAL OPERATIONAL PHASE
GSAT-8 at 55o : Launched on 21-May 2011 , Broadcasting
GAGAN signal with PRN127
GSAT-10 at 83o : Launched on 21Sept’12. Broadcasting
GAGAN signal with PRN128
GSAT-15 (PRN139) at 93o : To be launched in 3/4th quarter
of 2015
Compatible and Interoperable with other SBAS to provide Seamless
navigation
GAGAN Signal –In-Space available since Dec2011
GAGAN-TDS (Technology Demonstration System) : 2004 – 2007
Target: To demonstrate the proof of concept over Indian region
Realization : Ground Segment-On time Space Segment- Hired INMARSAT 4F1
due to GSAT-4 launch failure. But no delay in project completion
GAGAN-FOP (Final Operational Phase) : 2009 – 2013
Target: To realize a certifiable SBAS over India and to achieve an RNP0.1 capability over
Indian FIR along with APV-1/1.5 service over Indian land mass on nominal days as
specified in ICAO specification
Realization : Ground Segment - On time Space Segment – Met with GSAT8 and
CURRENT STATUS
Realization : Ground Segment - On time Space Segment – Met with GSAT8 and
GSAT10. Project completion on time
GAGAN certified for RNP 0.1 (Required Navigation Performance, 0.1 Nautical
Mile) service level on December 30, 2013 and commissioned on 14-Feb’14 for
En-route Operations
• On April 21, 2015 GAGAN certified for precision approach services (APV 1).
• APV1 Certified GAGAN signals are being broadcast with effect from May 19, 2015
• GAGAN is the first SBAS system in the world to serve the equatorial region.
• India has become the third country in the world to have such precision approach
capabilities
Accuracy Improvement with GAGAN
GAGAN versus GPS scatter plot and position GAGAN versus GPS scatter plot and position
uncertainties (15-Sep-2011)GAGAN versus GPS scatter plot and position
uncertainties (01-Oct-2011)