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)