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Introduction to Glonass

Kees de Jong, Fugro Intersite B.V., Leidschendam

March 2009

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Contents

• History

• System

• Signals

• Augmentation

• Performance

Global’naya Navigatsionnaya Sputnikovaya Sistema

Global Navigation Satellite System

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History

• Development started by Soviet Union in 1960’s-1970’s

• Successor of Tsikada

• First launch 1982

• Full constellation (24 satellites) in 1996

Tsikada satellite

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Tsikada satellite

History

• Development started by Soviet Union in 1960’s-1970’s

• Successor to Tsikada

• First launch 1982

• Full constellation (24 satellites) in 1996

1978

United States

Transit

1994

Transit

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Glonass system components

Ground control

segment

Orbit

constellationLaunchers

Spacecraft

control

Orbit

determination

Time

synchronization

Glonass

Glonass-M

Glonass-K

Proton

Soyuz

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Ground control segment

SCC System Control Center

TT&C Telemetry, Tracking & Commanding station

ULS Uplink Station

MS Monitoring Station

CC Central Clock

SLR Satellite Laser Ranging station

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Satellites

• Glonass (one operational satellite)

• Glonass-M (19 operational satellites)

• Glonass-K (from 2010 onwards)

Status March 2009

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Satellite launches

• Recent

– September 2008

– December 2008

• Near future

– September 2009

– December 2009

Three satellites per launch

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Constellation age

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Satellite

Age (months)

Glonass Glonass-MStatus March 2009

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180°

225°

270°

315°

0°

45°

90°

135°

Plane I Plane II Plane III

22

24

17

23

18

19

20

21

14

16

9

15

10

11

12

13

6

8

1

7

2

3

4

5

120° 120°

64.8° 64.8° 64.8°

Latitude

- Not available

- Available

180°

225°

270°

315°

0°

45°

90°

135°

Plane I Plane II Plane III

22

24

17

23

18

19

20

21

14

16

9

15

10

11

12

13

6

8

1

7

2

3

4

5

120° 120°

64.8° 64.8° 64.8°

Latitude

180°

225°

270°

315°

0°

45°

90°

135°

Plane I Plane II Plane III

22

24

17

23

18

19

20

21

14

16

9

15

10

11

12

13

6

8

1

7

2

3

4

5

120°120° 120°120°

64.8° 64.8° 64.8°

Latitude

- Not available

- Available

Satellite constellation

Status March 2009

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Orbital characteristics

System Glonass GPS

Number of satellites 24 30+

Number of orbital planes 3 6

Semi-major axis 25500 km 26550 km

Eccentricity < 0.01 < 0.01

Inclination 64.8° 55°

Period of revolution 11h16m 11h58m

Repeat period 8 days 1 day

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Satellite orbits (1)

One satellite, eight consecutive days

GlonassGlonassGlonassGlonass

0 0 0 03030303060606060

0 0 0 0

30303030

60606060

90909090

NorthNorthNorthNorth

EastEastEastEastWestWestWestWest

SouthSouthSouthSouth

GPSGPSGPSGPS

0 0 0 03030303060606060

0 0 0 0

30303030

60606060

90909090

NorthNorthNorthNorth

EastEastEastEastWestWestWestWest

SouthSouthSouthSouth

GPSGlonass

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Satellite orbits (2)

GlonassGlonassGlonassGlonass

0 0 0 03030303060606060

0 0 0 0

30303030

60606060

90909090

NorthNorthNorthNorth

EastEastEastEastWestWestWestWest

SouthSouthSouthSouth

Two adjacent satellites, three consecutive days

Glonass

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Signals – carriers

• Nominal carrier frequencies

– L1: 1602 MHz (GPS: 1575.42 MHz)

– L2: 1246 MHz (GPS: 1227.60 MHz)

• Satellite specific frequencies

– L1k = L1 + k×0.5625 MHz

– L2k = L2 + k×0.4375 MHzk = -7…13

Note: L1k/ L2k = 9/7 for all k

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GNSS spectrum

Frequency (MHz) 1176.45

1207.14

1246

1278.75

1227.6

1575.42

1602

L5 L2 L1

E5a E5b E6 E1

L2 L1

Glonass

Galileo

GPS

(L3)

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Signals – codes

Glonass GPS

C/A code

Frequency 0.511 MHz 1.023 MHz

Chip length 587 m 293 m

P-code

Frequency 5.11 MHz 10.23 MHz

Chip length 59 m 29 m

Modulation scheme FDMA CDMA

FDMA - Frequency Division Multiple Access (Glonass: same

code for all satellites, different frequencies)

CDMA - Code Division Multiple Access (GPS: different codes

for all satellites, same frequencies)

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Signals – navigation message

Glonass GPS

Orbit Position, velocity, Keplerian elements

acceleration at and corrections

at reference time at reference time

Clock Clock offset and Clock offset, drift

drift at reference and drift rate at

time reference time

Update period 30 minutes Two hours

Almanac Keplerian elements Keplerian elements

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Differential corrections and integrity

• SDCM

– System of Differential Correction and Monitoring

• Similar to

– WAAS (USA)

– EGNOS (Europe)

– MSAS (Japan)

– GAGAN (India)

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SDCM – principle of operation

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SDCM – characteristics

• Service area

– Russian Federation

• Real-time differential positioning

– Code

• Horizontal positioning accuracy 1-1.5 m

• Vertical positioning accuracy 2-3 m

– Carrier

• Horizontal positioning accuracy 0.01-0.02 m

• Vertical positioning accuracy 0.04-0.06 m

• GNSS monitoring

– Real-time integrity monitoring

– A posteriori system performance evaluation

• Two geostationary satellites

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SDCM – reference stations

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Modernization

• New (Glonass-K) satellites (from 2010 onwards)

• More satellites (30, probably not before 2015)

• Improved accuracy

• Modernized ground control segment

• New signals:

– L3 (1201-1212 MHz, to be defined

(Galileo E5b 1207.14 MHz))

– CDMA (on first Glonass-K

demonstration satellite in 2010)

• Interoperability with GPS and Galileo

Glonass-K satellite

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Availability of signals

L1OF – L1 Open FDMA

L2OF – L2 Open FDMA

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Recent accomplishments

• New geodetic datum

– Change from PZ90 to PZ90.02 in September 2007

– PZ90.02, differences with ITRS less than 0.5 m

• User range accuracy

– ICD 3.7 m

– Actual 1.8

• Clock stability

– 10-13 s/s

ICD – Interface Control Document

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Example of current geometry

PDOP

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GPS/Glonass reference stations

Fugro’s G2 network, 40+ GPS/Glonass reference stations

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Fugro G2 GPS/Glonass positioning service

• Real-time GPS/Glonass orbit and clock corrections

– Accuracy better than 0.15 m

• Precise Point Positioning (PPP)

– Global accuracy 0.1 – 0.2 m

• Combined GPS/Glonass solution

– Improved reliability

– Increased availability

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Increased availability

0

5

10

15

20

25

0:00:00.0

1:00:00.0

2:00:00.0

3:00:00.0

4:00:00.0

5:00:00.0

6:00:00.0

7:00:00.0

8:00:00.0

9:00:00.0

10:00:00.0

11:00:00.0

12:00:00.0

13:00:00.0

14:00:00.0

15:00:00.0

16:00:00.0

17:00:00.0

18:00:00.0

19:00:00.0

20:00:00.0

21:00:00.0

22:00:00.0

23:00:00.0

Number of satellites

GPS Glonass

Delft, Netherlands, March 2009

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-15

-12

-9

-6

-3

0

3

6

9

12

15

10:30:00.0

10:45:00.0

11:00:00.0

11:15:00.0

11:30:00.0

11:45:00.0

12:00:00.0

12:15:00.0

12:30:00.0

12:45:00.0

13:00:00.0

13:15:00.0

13:30:00.0

13:45:00.0

14:00:00.0

14:15:00.0

14:30:00.0

14:45:00.0

15:00:00.0

15:15:00.0

Error (m

)

Clock X Y Z

-5

-4

-3

-2

-1

0

1

2

3

4

510:30:00.0

10:45:00.0

11:00:00.0

11:15:00.0

11:30:00.0

11:45:00.0

12:00:00.0

12:15:00.0

12:30:00.0

12:45:00.0

13:00:00.0

13:15:00.0

13:30:00.0

13:45:00.0

14:00:00.0

14:15:00.0

14:30:00.0

14:45:00.0

15:00:00.0

15:15:00.0

Error (m

)

Clock X Y Z

Broadcast clock and orbit errors

Satellite 2

Satellite 24

Mean (m) RMS (m)

Clock -0.3 3.0

X -2.4 3.6

Y 0.1 1.4

Z 4.9 5.8

Mean (m) RMS (m)

Clock -3.1 0.5

X 1.5 0.7

Y -2.6 0.7

Z 0.9 1.6

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G2 PPP GPS only

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G2 PPP GPS and Glonass

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G2 PPP Glonass only

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Resources

• Russian Space Agency, status and ICD

– http://www.glonass-ianc.rsa.ru

• Trimble GPS/Glonass almanacs

– ftp://ftp.trimble.com/pub/eph/almanac.alm

• University of New Brunswick, constellation

– http://gge.unb.ca/Resources/GLONASSConstellationStatus.txt

• Wikipedia, general information

– http://en.wikipedia.org/wiki/Glonass