GPS Basics to
GNSS Future
Hugo Fruehauf
October 2008
hxf@fei-zyfer com
[email protected]
GNSS – Global Navigation Satellite Systems
Discussion Outline
• Navigation Concepts leading to GPS
• GPS Block I (DNSDP)
• GPS Basics
• GPS Follow-on
Follow on
• Navigation and Timing Applications
• GNSS Future
2
Historical Development Of Accurate Clocks
100,000
ATOMIC
CLOCKS
10,000
100
100,000 YEARS
TO LOSE
1 SECOND
YEARS TO LOSE 1 SECOND
NAVIGATION ACCURACY
= 30 FEET *
1
VARIATIONS IN THE EARTH’S ROTATION
0.01
QUARTZ
CRYSTALS
ELECTRONIC
WRIST
WATCH
MECHANICAL
WRIST
WATCH
1000
1200
CANDLE CLOCKS
& WATER
CLOCKS
1400
2 YEARS
TO LOSE
1 SECOND
NAVIGATION ACCURACY
= 250 MILES *
1600
YEAR
1800
LOSE
15 MINUTES
PER DAY
2000
MARINE
CHRONOMETERS
MECHANICAL
CLOCKS
LOSE
3 MINUTES
PER DAY
NAVIGATION ACCURACY
NAVIGATION ACCURACY
= 170,000,000 MILES *
= 34,000,000 MILES *
LOSE
1 SECOND
PER DAY
NAVIGATION
ACCURACY
= 186,000 MILES *
* For 24-Hours of Navigation
3
Active and Passive RadioRadio-Navigation Systems
t1
SIGNAL TRAVELS TWO
WAYS
DISTANCE = C x Δ t
2
ACTIVE RADIO-NAVIGATION
t2
No precision Clocks needed
PASSIVE RADIO-NAVIGATION
SIGNAL TRAVELS
ONE WAY DISTANCE
= C x Δt
t1
Requires precision Clocks
4
1-Way 2D Electronic Ranging System
The time is . . .
Transmitter
1
The time is . . .
Transmitter
2
2D Navigation:
Perfect Clocks
• Good for Navy Ships
only – 2D
• Not useful
f for
f Navy
and USAF flyers –
need 3D
5
621B 3D Ranging Test Program Success in
mid ‘60s lead to the SpaceSpace-based GPS
3D Navigation:
Perfect Clocks
• Useful for all platforms,
Stationary and mobile:
(Ships, Planes,
Weapons, Ground
Vehicles, etc.)
Ground-based Transmitters are put into Space
The time is . . .
My location is …
Transmitter
(3)
The time is . . .
My location is …
Transmitter
(2)
The time is . . .
My location is …
Transmitter
(1)
6
Roger Easton (center) and family
at the February 2006 White House
ceremony where he received the
National Medal of Technology.
(credit: Richard Easton)
A significant technical contributor to passive ranging/navigation 7
Satellite Navigation Clock History to GPS
(Hugo Fruehauf & Ron BeardBeard-NRL 7-7-08
08))
Program /
(Service)
Dates
# of Sats /
Nav Method
Nav
Dim
Clocks
Ops Status
NNSS (Transit) / 1964 to
(Navy(Navy
~1990
1990
JHU/APL)
(7) / Doppler
2D
(1) Quartz
Oscillator
Was fully operational
Timation I & II /
(Navy- NRL)
1967 and
1969
(2) / Ranging
Tones
2D
(1) Quartz
Oscillator
Experimental
NTS I / (NavyNRL)
1974
(1) /
Hazeltine
621B Trans.
No Data
2D
(2) Efratom Com’l
Rb’s, modified by
NRL to perform in
space +(1) Quartz
Experimental:
(1) Rb operated for
more than one yyear
NTS II / (NavyNRL)
1977
(1) / ITT
PRN Nav.
Pkg
Pkg.
2D
(2) Proto space
1st Sat launched for
qualified FTS Cs + the GPS Phase I (6)
Sat Constellation
((2)) Quartz Osc’s
DNSDP, then at
contract award
called GPS; (via
G S - JPO,
GPS
O now
called “GPS
Wing”)
Devel’mt
1973-75;
RI Block I
launches
Feb.1978
(4) / ITT
PRN Nav.
Pkg’s. each
satellite
3D
(3) RI-Efratom
Rb’s on the 1st
three Sats; 4th Sat
& up, (2)
( ) RIEfratom Rb’s + (1)
2nd gen. FTS Cs
(5) Block-I RI Sats &
(1) NTS II NRL Sat
for the initial
operational launches
of the (6) Satellite
GPS Constellation
8
Discussion Outline
• Navigation Concepts leading to GPS
• GPS Block I (DNSDP)
• GPS Basics
• GPS Follow-on
• Navigation and Timing Applications
• GNSS Future
9
No doubt, the most
significant person that
made GPS happen:
• Systems Engineering
• Program Management
• and Politically
Dr. Brad Parkinson
10
What is GPS?
•
A space-based satellite navigation system developed by the DoD in the mid
70’s for military use; managed by a Joint Program Office (GPS-JPO, now called
GPS-Wing), located at LAAFB; involving USAF, Navy, and other services.
•
A highly accurate 3D navigation, positioning, and timing system, available 24
hours a day, 7 days a week, anywhere in the world.
•
Has a clear (or coarse) acquisition signal (C/A-Code) to aid in the acquisition of
the precision military signal (P
(P-Code).
Code) Because the C/A
C/A-Code
Code is in the clear
clear, it
serves as a civil navigation, positioning, and timing system, referred to as SPS
(Standard Positioning Service), ~10m, 1σ, Spherical Error Probability (SEP).
•
Also has a more accurate (precision) P-Code
P Code signal, available only to
authorized cryptographic key users. When the P-Code is encrypted, it becomes
the ‘so-called’ P(Y)-Code. This is referred to as PPS (Precise Positioning
Service), ~1m, 1 σ, SEP.
•
SPS and PPS also provide an atomic time reference, accurate to ±100 ns of
USNO - Master Clock, referenced to UTC (Universal Coordinated Time).
•
The Satellite Constellation is controlled and maintained by the USAF from the
Master Control Station (MCS) at Schriever AFB near Colorado Springs
Springs. The
MCS is part of the Consolidated Space Operations Center (CSOC).
11
DNSDP (GPS)
Proposal 1974;
Rockwell’s
winning design
Other bidders:
• RCA,
• Philco Ford
Satellite makers
that did not bit
Prime:
• GE
(RI GPS Proposal Cover)
• Hughes
12
DNSDP- Defense
Navigation Satellite
Development Program
(l t changed
(later
h
d tto GPS)
Rockwell Design Team
13
GPS Satellite (Block I) – Rockwell (RI)
Major Characteristics
Launch mass
1,400 lb.
On-Orbit mass
735 lb.
Solar Array
500 Watts
Design Life
4.7 years MMD
Consumables
7 years
Clocks
(3) Rb (RI-Efr)
14
GPS Satellite (Block I) – Rockwell (RI)
Orbit injection
configuration
15
Initial Launches on
Atlas-F ICBMs
(Launch and orbit
injection process)
16
(From RI GPS Proposal)
GPS Satellite Sub-Systems
(From RI GPS Proposal)
17
Notable 1970s technologies, designs, and
special talent that made GPS happen…
• The key GPS technology – the invention of the Miniature Rubidium Vapor Atomic
Oscillator – Ernst Jechart and Gerhard Huebner; (instrumental in later development,
Werner Weidemann)
• First Radiation-hardened, Space-Qualified Rubidium Clock – Dale Ringer, Chuck
Wheatley, Werner Weidemann, Hugo Fruehauf, and RI-Efratom team
• Spread Spectrum Quadra-Phase C/A+P(Y) Signal Structure – Andy Codik, Charlie
Cahn, Robert Gold, Jim Spilker, AJ Van Dierendonck, and others
• Military and Civil Operational Coexistence (Selective Availability) – part of the
signal structure design
• Shaped-Beam (12) Helix Phased-Array Antenna – Allan Love
• Solid State L-Band PRN and HPAs; no TWTs – Lou Feit and the ITT team
• Ionospheric Time/Frequency delay Correction via two frequencies – part of the LBand PRN design
• Three-axes stabilized, earth-pointing, satellite-yawing ACS – William Porter and
Frank Barbera
• Orbital
O
Mechanics/Analysis
/
and Clock
C
Relativity Correction
C
– Frank Barbera, Dick
Meston, Tom Logston, Denni Galvin
• Satellite Systems design concept – Hugo Fruehauf, Myron Cantor
• Universal Coordinated Time (UTC) via satellite
• Super
S
Hi-Rel
Hi R l Parts
P
P
Program (S-Equivalent
(S E i l
Spec)
S
) – Hugo
H
F
Fruehauf,
h f RI team
• Program Mgmt – Brad Parkinson, Gaylord Green, Dick Schwartz, Al Myers, Tom Hill
18
The key GPS-applicable technology – the invention
of the Miniature Rubidium Vapor Atomic Oscillator (From RI GPS Proposal)
Clock Search for GPS, early 1974
19
Miniature Rubidium Vapor Atomic Oscillator (cont.)
~5E-12
~1.5E-13
1 Sec
1000 Sec
(From RI GPS Proposal)
DNSDP (GPS) Proto-type Rad Hard Rb - Performance, RI-Efratom
FRK-Rb, 1974, D. Ringer, C. Wheatley, W. Weidemann, Hugo Fruehauf
20
The GPS BlockBlock-I, II, and IIA Rb Clock
RockwelI-Efratom GPS Rb Clock
Rb Oscillator
Control
Rb Physics
P k
Package
10 MH
MHz
OCXO
10 MH
MHz
Control,
Buffers,
etc
etc.
Satellite
Clock
Control
10.23 MHz
FEI
FleetSatCom
OCXO
10.23
10
23 MH
MHz
Output
PLL
The Switch that can
isolates the Atomic side
21
Ernst Jechart, inventor of the miniature Rb oscillator
(came to the USA in 1973 with his team from Munich)
22
The Miniature Rb Osc. Team from Efratom Inc., Munich
Werner Weidemann
Gerhard Huebner
Heinz Badura
(Chief Rb Oscillator
Circuit Designer)
(Co-Inventor
with Jechart)
(Main Developer
23
of the Market)
Efratom Rb Oscillator
Display
(Smithsonian Institution,
1982 to 1988)
24
(Smithsonian Institution, 1982 to 1988)
25
Spread Spectrum Quadra
Quadra--Phase C/A+P(Y) Signal
Structure
Carriers (L1/L2)
1540 Cycles per C/A
C/A-Chip
Chip
Phase Shift Keying
(PSK) Modulation
1.023 MCPS
C/A - Code (L1)
P- Code (L1/L2)
10.23 MCPS
Data ((L1/L2))
50 BPS
(AS) Encryption
P becomes (Y)
C/A Code
Transmitted in
Phase Quadrature
(90° Out of Phase)
(SA) Degrad.
Degrad
Now set to
Zero
Y-Code
P Code
Frequency Dither
(On All Above Signals)
26
Shaped-Beam (12) Helix PhasedShapedPhased-Array
Antenna (RH Polarization)
GPS Antenna:
12
Element
L-Band Helical Phased
Array (On-axis view)
Antenna
Pattern
Horizon
Received Power vs. SV Elevation Angle Zenith
Hi-Pwr Mode
60°
60
40°
20°
5°
0°
80° 90°
Receive
ed Power at 3dB
Linearly P
Polarized Ant. (dBw)
-158
158
-159
-161
Original GPS Signal Levels
-162
L1-P(Y)
-163
-164
-165
-166
~1x10-16
L1-C/A
-160*
watts*
L2 P(Y)
L2-P(Y)
5
20
40
60
User Elevation Angle (deg)
80
90
27
Clock Relativity Considerations
GPS = 10,898 nmi
6
Circular Orbits
4
For GPS:
2
Zero
Eff t
Effect
0
4000
2000
Altitude (nmi)
Total Relativistic Effect
on GPS Clocks
Δf/f 4.47E-10
Δf
= 5.3 x 10 −10
f
General Theory
y of Relativity
y
r ⎡
r ⎤
Δf
= + g e e ⎢1 − e ⎥
2
f
rs ⎦
C ⎣
6000
10,000
8000
12,000
14,000
-2
Special Theory of Relativity
⎡
Δf
= ⎢1 −
f
⎢⎣
-4
4
2
⎛ Vs ⎞ ⎤
⎜
⎟ ⎥
⎝ C ⎠ ⎥⎦
⎡ μ ⎤
Vs = ⎢
⎥
⎣ Vs ⎦
-6
Δt r = tone ∗
day
sec .
Δf
Δf
= 86,400 ∗ 4.46 x 10 −10
f
Δtr = 38,621 nsec
1
2
1
2
−1
For GPS:
Δf
= −0.83 x 10 −10
f
Original Clocks set to:
10,229,999.995433 Hz
28
Military and Civil Operational Coexistence
(Selective Availability)
Dat
a
PRN-Gen (A)
C/A
Code
÷10
1.023 MCPS
÷20
Uplink
Control
Atomic
Osc.
Rb or Cs
10.23 Hz
Uplink
Control
Data
50 BPS
Carrier
C
i
Synth.
Σ
(L1) 1575.42 MHz
HPA
Mult.
S.A.
S
A
Clock
Dither
(L2) 1227.6
1227 6 MH
MHz
HPA
Mult.
(L1)
(L2)
12Helix
Array
Ant.
Σ
~
(L3)
Mult.
PRN-Gen
(B)
P
C d
Code
10.23
MCPS
HPA
Other
A.S.
c yp
Encryp’n
Device
Y-Code
Uplink Control
(L3)
90°
29
Discussion Outline
• Navigation Concepts leading to GPS
• GPS Block I (DNSDP)
• GPS Basics
• GPS Follow-on
• Navigation and Timing Applications
• GNSS Future
30
GPS Satellite Signals
21.3o
L1
Ionosphere
75 to 400 Km
13.9o
Δt
L1
• L1 1575.42 MHz
C/A-Code 1.023 Mcps,
P-Code 10.23 Mcps
Data 50 bps
Δt ≅ A/f2
Free Electrons
Charged Particles
2 tto 50 ns d
delay
l
L2
5o Mask
Angle
• L2 1227.6 MHz
P-Code 10.23 Mcps
Data 50 bps
• Four Satellites
needed for
3-D navigation
• Maximum Doppler
Shift
between Satellites
~ ± 6KHz
31
Space Borne 11-Way 3D Ranging System
“...The time is
My position is...”
The Realistic GPS System
1 1
0
0
0 1
1
1 1
0 1 0
0
0 1
1
1 0
0
0 1 1
1
1 1
0 1 0
0
0 1
1
1 1
1 0
1
1 1
0 1 0
0
0 1
1
1 1
0
0 0 1
1 1
1 1 0
0
0 1
1
0 1 1
1 1
0 0
0
1
Δt1
1 0
0
0
0 1
1
R1 = C(Δt1 + ΔT - τ1)
τ1
1 0
Δt2
Δt3
←ΔT→
0 1 0
Δt4
τ2
0
0 1 1
1
1 1
0 1 0
0
0 1
1
R2 = C(Δt2 + ΔT- τ2)
1 1
1 0
0 0
1
1 1
0 1 0
0
0 1
1
R3 = C(Δt3 + ΔT - τ3)
τ3
1 1
0
0
0 0 1
1 1
1 1 0
0
0 1
1
R4 = C(Δt4 + ΔT - τ4)
τ4
4 Equations — 4 Unknowns
RCVR Clock Error
Signal Travel Time
SV Clock Error
SV C/A Gold Code
32
Civil and Military Signal Relationships
GPS Sats
L2 P(Y)
+ 50 bps
L2
~6.2 x 1012 Chips; repeat each week
Mil P(Y) Code
Mod. + Data
Mil P(Y) Code
Mod. + Data
Real-time
Ionospheric
Corrections
P(Y)
PNT
C/A
PNT
L1 C/A, P(Y)
+ 50 bps
L1
1023 Chips; repeat each ms
Acquisition Aid
Civil C/A Code
(<100ns Clock)
Mod. + Data +
<100ns Clock
Crypto Key
Partial Ionos.
Corrections
(Model only)
Typical GPS Receiver
Military SAASM
Europe’s Galileo
Other GNSS Systems
Data + 1PPS
33
Satellite Geometry and GDOP
σ p = DOP ∗ σ m
Positioning
Accuracy
(X, Y, Z)
Geometry
(Dilution of
Precision)
Measurement
Accuracy
(UERE)
Error
Ellipsoid
Elongated
Good GDOP
(ideal case)
Poor GDOP
Satellites bunched
together
• One satellite overhead
• 3 on horizon,
120° apart in azimuth
34
Discussion Outline
• Navigation Concepts leading to GPS
• GPS Block I (DNSDP)
• GPS Basics
• GPS Follow
Follow-on
on
• Navigation and Timing Applications
• GNSS Future
35
GPS Satellite ((Block II, IIA)) – Rockwell ((RI))
Major Characteristics
Launch mass
3,675 lb.
On-Orbit mass
1,862 lb.
Solar Array
1,000 Watts
g Life
Design
7.5 y
years
Consumables
10 years
Clocks
(2) Rb, (2) Cs
RI Efr FTS
RI-Efr
All Have Been Launched
36
GPS Satellite (Block IIR) – Lockheed
Lockheed--Martin
Major
j Characteristics
Launch mass
4,480 lb.
On-Orbit mass
2,210 lb.
Solar Array
1,100 Watts
Design Life
7.5 years
Consumables
10 years
Clocks
(3) Rb
EG&G
EG&G*
*now Perkin-Elmer
In Launching Phase
37
GPS Satellite (Block IIF) – Boeing*
* Was Rockwell International
Major Characteristics
Launch mass
On-Orbit mass
4,634
,
lb.
~2,400 lb.
Solar Array
1,560 Watts
Design Life
15 years
Consumables
15 years
Clocks
(2) Rb, (1) Cs
EG&G* FTS**
*Now Perkin-Elmer
**Now Symmetricom
In Launching Phase soon
38
Satellite Constellation
• All near p
perfect circular orbits
• 21 to 24 Satellites required for
24 x 7 coverage
30 GPS Satellites in Operation at present
39
The Other Operational GNSS
GLONASS (Russia)
ops since late ‘80s
80s
GLObal NAvigation Satellite System (GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) 40
Comparison of GPS and GLONASS
Parameter
Ephemeris information
presentation method
Geodesic coordinate system
GLONASS
GPS
Interpolation coefficients of
satellite orbits
To the timer of GLONASS
system
UTC (SU)
To the timer of GPS system
2.5 min
12.5 min
WGS 84
Referencing of the ranging
signal phases
System time corrections
relative to the Universal
Coordinated Time (UTC)
Duration of the almanac
transmission
Number of satellites in the full
operational system
Number of orbital planes
21 + 3 spares
21 + 3 spares
3
6
Inclination
Orbit altitude
64.8°
19100 km
55°
20180 km
Orbital period
11 h 15 min
12 h
Satellite signal division
method
Frequency band allocated (L1)
Frequency Division
Code Division
1602.5625-1615.5
± 0.5 MHz
PRN-sequence of maximal
length
511
1575.42 ± 1MHz
Gold Code
Timing frequency of code
(C/A)
Crosstalk level between two
neighboring channels
Synchrocode repetition period
0.511 MHz
1.023 MHz
-48 dB
-21.6 dB
2 sec
6 sec
Symbol number in the
synchrocode
30
8
Type of ranging code
Number of code elements
GPS
GLONASS
9 parameters of s/c motion in
the geocentric rectangular
rotated coordinate system
SGS 85
UTC (USNO)
1023
41
GPS New Signal Additions
L2
M
10.23
MHz
1227.6
MHz
P(Y)
New
M-Code
C
(Future)
M
10.23
MHz
1215.6
MHz
New
L2C
L1
M 1.023
1.023 M
MHz
MHz
10.23
MHz
1239.6
MHz
1563.42
MHz
10.23
MHz
C/A
P(Y)
1587.42
MHz
1575.42
MHz
Spread Spectrum Signal, ~30 dB below the receiver ambient noise level
(Said to represent energy of a 25 watt light bulb at 11,000 miles distance)
42
Discussion Outline
• Navigation Concepts leading to GPS
• GPS Block I (DNSDP)
• GPS Basics
• GPS Follow-on
• Navigation and Timing Applications
•
GNSS Future
43
Civil and Mil Applications Overview
P(Y)
PVT
C/A
PVT
Augmented
GPS
Aided GPS
Oscillator
(Local Flywheel
Devices)
Telcom
Wireless
Wi li
Wireline
Networks,
Internet
Grd.
M bil
Mobile
Comm.
Airborne
Comm.
Time
T
Transf.
f
UTC,
PRS’s
Sat. Terminals
Hi-Value
Mobile
Platforms
Loran-C
Sync
Last Mile
E911
(Remote Aid
Devices)
IMU/Gyro
Comm’d
Control
Utilities,
Grids
Survey
Depot,
Meas’m
Signal
Anal.
Broadcast
Radar
FAA-ATC
Ranges
Weapons
Targeting
Unaided
GPS
DGPS
Grd.
Portable
WAAS
EGNOS
MSAS
GAGAN
Grd.
Mobile
Airborne
Nav.
Tracking
Space
Nav.
Scientific
Meas’mt
Meas
mt
Sport
JPALS
LAAS
SBAS
44
GPS--aided Time and Frequency Systems
GPS
Quartz
Crystal
O ill t
Oscillator
T/F System
GPS
Rcvr
GPS
Compare
Tune
Qz
Osc.
Output
Freq.
Or…
Rubidium Vapor
Atomic Oscillator
GPS
Rcvr
T
Tune
Compare
Rb Vapor
Phy Pkg
Qz
Osc.
Output
Freq.
• Rb oscillator 100
to 500 times
better Holdover
Performance
T/F System
45
SAASM Hardware and Software Security
GPS
Key Delivery
OTAR (after
authentication)
L1-C/A, L1P(Y), L2P(Y), +
D t
Data
ELECTRONIC
RECORDKEEPING
for HAE
PHYSICAL
SAASM RCVR
PORTABLE
USERS
SAASM RCVR HOST
EQUIPMENT(HAE)
SAASM GPS
P(Y)-CODE
RECEIVER
46
Discussion Outline
• Navigation Concepts leading to GPS
• GPS Block I (DNSDP)
• GPS basics
• GPS Follow-on
• Navigation and Timing Applications
•
GNSS Future
47
Where is GNSS Going?
Up-Coming
U
C
i GPS-like
GPS lik
GNSS & Space-based
Augmentation
Chi
China
- 1st, was part of EU’s
Galileo GNSS
- Since March 07, building
own GNSS “Compass”
Galileo (EU)
• Test Sats launched
(not representative of
the final Sat)
• IOC: 2012-2015?
GLONASS (Russia)
• Revitalization of
Glonass; 18+ Sats
operational now
• FDMA to CDMA
Upgrade being
considered
India
1st, was part of Galileo Now joined GLONASS
Ground
G
d and
d SpaceS
based Augmentation
Systems (DGPS SBAS)) for Civil
Aviation, globally:
US - WAAS
EU - EGNOS
Japan - MSAS
China/India - GAGAN
Japan
Part of US GPS,
Building Figure-8 GNSSGPS augmentation using
Quasi-Zenith Satellites
Far Future
Cislunar and beyond Moon
orbit GNSS
48
Wide Area Augmentation System Concept
(21 to 30) GPSs
(½ GeoSync Orbits)
InmarSats,
plus other
((GeoSync
y Sats))
Transponded “bent-pipe”
to L1 - C/A
L1-C/A
from
GPS
Sats
Ionospheric
Eff t
Effects
L1-C/A
50 bps
L1-C/A
“l k lik ”
“look-alike”
250 bps
C-Band C/A
from Uplink
Station
GPS
ANT.
USER
WRS
WRS
Data-Link
C-Band
Uplink, 6.4 GHz
WRS
WMS
DGPS Data
GUS Time USNO
(2) Wide Area
Master Stations
(2) Ground Uplink
Wide Area Reference Stations:
Stations
WAAS - 18 WRSs for USA Mainland, ~25 Total (13 more being added, ~38 Total)
EGNOS - 44 WRSs for Europe, Africa, Venezuela
MSAS - 6 WRSs for Japan, Australia, Hawaii
GAGAN - 18 WRSs for India, China and other Asian areas
49
Present & Upcoming GPS,
Glonass & Galileo Signals
1176.45
1191.795
GAL-E5a
1207.14
1214 M
1201
1164
1227.6
GAL-E5b
GPS-L5
Future
GLO-L3
GPS-L2
L2 P(Y)
P
1575.42
C/A
L1 C/A
1559 L1C
1591
1545 1563
1587
C/A
1544
M
M
GPS--L1
GPS
L1 P(Y)
GAL-E2
GAL-E1
1602
1251.03
M 1246
1300
1260
1256.06
1237
1215
L1-Band (MHz)
SAR
L2C
GAL-E6b
1278.75
GAL-E6a
L2-Band (MHz)
GLO-L2
P
Pilot
WAAS, EGNOS, MSAS,
GAGAN – generated
L1-C/A Look-alike
C-Band (MHz)
~5020
1614 94
1614.94
GLO-L1
Black and
Blue Signals
Operational
~5010
~5030
GAL-C1
P
1608.47
Gone
50