Download - Introduction to glonass, march 2009
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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