Cospas‐Sarsat Ground Stations
LEOLUTs, GEOLUTs and MEOLUTs
Danis Unverdi
Cospas‐Sarsat Expert
1
2
LUT TYPES
Local User Terminals:
• LEOLUT
– Low Earth Orbit (LEO)
– Satellites: Cospas and Sarsat
• GEOLUT
– Geostationary Orbit (GEO)
– Satellites: GOES, MSG, INSAT (and ELEKTRO‐L)
• MEOLUT
– Medium Earth Orbit (MEO)
– Satellites: DASS (and GALILEO, GLONASS)
3
LEOLUTs
4
5
6
7
LEOLUT COMPONENTS
A LEOLUT consists of:
• Antenna (typical diametre: 1.5 metres)
• Rack
– Server(s)
– A/D card
– GPS card
– System test source
– Comms equipment
– UPS
• GPS antenna
8
LEOSAR PRINCIPLE OF OPERATION
• Beacon transmits omni‐directional signal from ground (406 MHz)
• LEO satellite receives signal
• Satellite motion creates Doppler shift in beacon carrier frequency
• Signals are partially processed onboard the LEO satellite
• LEOLUT receives signal (L‐band 1,544.5 MHz carrier)
• LEOLUT decodes signal and extracts beacon message (including GPS
location information, if available)
• Doppler shift used by LEOLUT for position calculation
• LEOLUT transmits beacon identification and location data to national MCC
9
LEOLUT FUNCTIONS
•
•
•
•
•
•
•
•
•
•
•
•
•
Maintain and follow a Pass Schedule to track LEO satellites (LEOLUTs most often follow an MCC‐optimized tracking schedule)
Receive and demodulate downlink signal (L‐band 1,544.5 MHz)
Decode SARP Processed Data Stream
Detect and process beacon signals from SARR stream
Perform error correction on decoded beacon message (BCH)
Determine beacon location (Doppler)
Combined LEO/GEO processing (optional, and if a GEOLUT is available)
Forward beacon identification and location data to national MCC
Maintain satellite orbit data information
Maintain accurate time using GPS
Interference monitoring in the 406 MHz band
Check and report on Status
Generate alarms and warnings
10
DOPPLER EFFECT
11
DOPPLER EFFECT
• Swift satellite motion (≈7 km/sec) creates Doppler shift on 406 MHz beacon signal
• LEOLUT determines Time of Closest Approach of the satellite to the beacon (TCA) and Cross‐Track Angle (CTA)
• LEOLUT calculates beacon location (latitude, longitude) using TCA, CTA and precise knowledge of satellite orbit
12
DOPPLER AMBIGUITY
• Location calculation using the received Doppler curve results in two positions (ambiguity)
• Taking the rotation of the Earth into account, LEOLUT determines the more probable position (A‐side)
• The less probable position is labelled B‐side
• Ambiguity is later resolved by MCC using independent location data (either from two satellite passes or the GPS location received in beacon signal)
13
LEOLUT COVERAGE
• LEO satellite altitude: 850 – 1,000 km
• At a given time, a LEO satellite covers a circle of a radius of ≈2,500 km (size of a small continent)
• A LEOLUT can “see” any LEO satellite within a circle of a radius of ≈2,500 km (size of a small continent)
14
LEOLUT COVERAGE
Therefore, depending on satellite pass geometry, a LEOLUT can locate, in real‐time, a beacon located at thousands of km from the LEOLUT location (up to ≈5,000 km in East – West direction)
15
LEOLUT COVERAGE
• The local coverage region for a LEOLUT is an oval shape, around 4,000 km in East –
West direction and 2,500 km in North –
South direction
• However, in global mode, a LEOLUT can locate a beacon anywhere in the world (store and forward capability of LEO satellites)
16
LEOSAR LOCAL COVERAGE
17
57 LEOLUTs WORLDWIDE
1 Ouargla, Algeria
2 El Palomar, Argentina
3 Rio Grande, Argentina
4 Albany, Australia
5 Bundaberg, Australia
6 Brasilia, Brazil
7 Manaus, Brazil
8 Recife, Brazil
9 Churchill, Canada
10 Edmonton, Canada
11 Goose Bay, Canada
12 Eastern Island, Chile
13 Punta Arenas, Chile
14 Santiago, Chile
15 Beijing, China*
16 Hong Kong, China*
17 Toulouse, France
18 Penteli, Greece
19 Bangalore, India
20 Luchnow, India
21 Jakarta, Indonesia
22 Bari, Italy
23 Keelung, ITDC*
24 Gunma, Japan
25 Incheon, Korea
26 Abuja, Nigeria
27 Wellington, New Zealand
28 Tromsoe, Norway
29 Spitsbergen, Norway
30 Karachi, Pakistan
31 Callao, Peru
32 Nakhodka, Russia
* These LEOLUTs are dual systems (11 dual LEOLUTs in total).
18
33 Jeddah, Saudi Arabia*
34 Singapore
35 Cape Town, South Africa
36 Maspalomas, Spain
37 Bangkok, Tailand*
38 Ankara, Turkey*
39 Abu Dhabi, UAE
40 Combe Martin, UK
41 Alaska, USA*
42 California, USA*
43 Florida, USA*
44 Guam*
45 Hawaii, USA*
46 Haiphong, Vietnam
SYSTEM WAIT TIME
•
•
•
For a given LEOLUT, it
may take anywhere
between 3-4 minutes to
several hours to detect /
locate a beacon after
beacon activation
For a beacon at midlatitudes, the average
wait time for detection
by LEOSAR is 1 to 1.5
hours with a
constellation of 4 to 6
satellites (gaps in
Southern hemisphere)
Inter-MCC
communications notifies
the relevant MCCs
19
GEOLUTs
20
21
22
GEOLUT COMPONENTS
A GEOLUT consists of:
• Antenna (typical diametre: 5 metres)
• Rack
– Server(s)
– A/D card
– GPS card
– Comms equipment
– UPS
• GPS antenna
23
GEOSAR PRINCIPLE OF OPERATION
• Beacon transmits omni‐directional signal from ground (406 MHz)
• GEO satellite receives signal
• No Doppler shift in beacon carrier frequency because GEO satellite is immobile with respect to the beacon
• No processing of signals onboard the GEO satellite
• GEOLUT receives signal (L‐band 1,544.5 MHz carrier)
• GEOLUT decodes signal and extracts beacon message (including GPS
location information, if available)
• No further position calculation possible because no Doppler shift
• GEOLUT transmits beacon identification data (and GPS location, if available) to national MCC
24
GEOLUT FUNCTIONS
•
No Pass Schedule because GEO satellite is immobile with respect to the GEOLUT
•
Receive and demodulate downlink signal (L‐band 1,544.5 MHz)
•
Detect and process beacon signals received from satellite repeater
•
Message integration
•
Perform error correction on integrated beacon message (BCH)
•
No beacon location calculation (because no Doppler)
•
Help combined LEO/GEO processing (optional, and if a LEOLUT is available)
•
Forward beacon identification data (and GPS location, if available) to national MCC
•
No need to maintain satellite orbit data information
•
Maintain accurate time using GPS
•
Check and report on Status
•
Generate alarms and warnings
25
GEOLUT COVERAGE
• GEO satellite altitude: ≈36,000 km
• At all times, a GEO satellite covers a circle of a radius of ≈8,500 km (size of an ocean)
• A GEOLUT can detect any beacon within the GEO satellite footprint within minutes (virtually no wait time)
26
GLOBAL GEOLUT COVERAGE
27
20 GEOLUTs WORLDWIDE
Geostationary Satellite
MSG-2
GOES-East
GOES-East
GOES-East
GOES-West
GOES-East
GOES-East
MSG-2
MSG-2
INSAT-3A
MSG-2
GOES-West
GOES-West
MSG-1
GOES-East
MSG-2
MSG-1
MSG-2
MSG-2 (standby GOES-East)
GOES-East
GOES-West
1 Algiers, Algeria
2 El Palomar, Argentina
3 Brasilia, Brazil
4 Recife, Brazil
5 Edmonton, Canada
6 Ottawa, Canada
7 Santiago, Chile
8 Toulouse, France
9 Penteli, Greece
10 Bangalore, India
11 Bari, Italy
12 Wellington (1), New Zealand
Wellington (2), New Zealand
13 Fauske, Norway
14 Maspalomas, Spain
15 Maspalomas (2), Spain
16 Ankara, Turkey
17 Abu Dhabi, UAE
18 Combe Martin, UK
19 Maryland (1), USA
20 Maryland (2), USA
28
LEOSAR / GEOSAR COMPLEMENTARITY
LEOSAR:
GEOSAR:
• No continuous coverage (“small”
footprint, few satellites)
• Continuous coverage within very large satellite footprint
• Large wait times (1.5 hours average at mid‐latitudes)
• Virtually no wait time for beacons in footprint ( a few minutes)
• Polar coverage (polar orbit)
• No polar coverage
• Doppler position (and GPS location, if available)
• No Doppler position; only GPS location, if available
• Less affected by obstructions (ground relief, etc.)
• Detection is subject to obstructions (ground relief, etc.)
• Combined LEO/GEO processing
• Combined LEO/GEO processing
• LEO alert pinpoints location
• GEO alert triggers SAR action
29
MEOLUTs
30
MEOSAR IS STILL EVOLVING !
•
MEOSAR was conceived in the late 1990’s to remedy the shortcomings of LEOSAR/GEOSAR:
– Continuous coverage anywhere on the Earth
– Instantaneous location determination (in particular, single‐burst location), assuming 3 or more channels
– Capable of tracking moving beacons (drifting vessels, aircraft before crash)
– Unaffected by obstructions (ground relief, etc.)
•
Various satellite constellations:
– DASS (GPS) from USA
– GALILEO from EU
– GLONASS from Russia
•
•
•
•
Currently limited to a “small” number of satellites (9 DASS satellites)
First GLONASS satellites expected in 2011, first GALILEO satellites in 2012
D&E to start in 2012 (D&E planning meeting in March 2011)
Operations expected to start circa 2015 (IOC)
31
TENTATIVE MEOSAR TIME LINE
32
MEOSAR SATELLITE CONSTELLATIONS
33
ADVANTAGES OF MEOSAR
LEO
Intermittent
Coverage
GEO
MEO
Limited Polar
Coverage
Virtually 100%
Continuous
Coverage
34
35
36
MEOLUT COMPONENTS
A MEOLUT consists of:
• Antenna (typical diametre: 2.4 metres or more)
• Rack
– Servers
– A/D device
– GPS device
– RF equipment
– Comms equipment
– UPS
– Auxiliary devices
• GPS antennas
37
MEOSAR SYSTEM CONCEPT
•
•
•
•
Beacon signal received by MEOLUT through a number of MEO satellites (multi‐
channel system)
Immediate location calculation using TDOA / FDOA techniques
Networking possibility in order to increase the MEOLUT’s number of channels
DASS, GALILEO and GLONASS interoperable (a MEOLUT can track and process satellites of all 3 constellations)
38
RETURN LINK SERVICE (RLS)
39
MEOSAR PRINCIPLE OF OPERATION
•
•
•
•
•
•
•
•
•
•
Beacon transmits omni‐directional signal from ground (406 MHz)
Several MEO satellites receive signal
Small Doppler shift in beacon carrier frequency because MEO satellites move slowly with respect to the beacon
No processing of signals onboard the MEO satellites
MEOLUT receives signal from several MEO satellites (S‐band 2,226.5 MHz, in the future: L‐band 1,544.1 MHz and 1,544.9 MHz carrier)
MEOLUT decodes signal and extracts beacon message (including GPS location information, if available)
Burts‐level data exchange between MEOLUTs (networking)
TDOA / FDOA techniques used by MEOLUT for position calculation
In the future: MEOLUT transmits beacon identification and location data to national MCC
In the future: Return Link Service by GALILEO (RLS) ‐ a novelty!
40
MEOLUT FUNCTIONS
•
Maintain and follow a Pass Schedule to track MEO satellites
•
Receive and demodulate downlink signal from several MEO satellites (S‐band 2,226.5 MHz, in the future: L‐band 1,544.1 MHz and 1,544.9 MHz carrier)
•
Detect and process beacon signals received from satellite repeaters
•
Perform error correction on decoded beacon message (BCH)
•
Transmit burts‐level data to other MEOLUTs (networking)
•
Determine beacon location (TDOA / FDOA, no ambiguity unlike MEOLUT)
•
In the future: Forward beacon identification and location data to national MCC
•
Obtain satellite orbit data from GPS downlink stream
•
Maintain accurate time using GPS
•
Check and report on Status
•
Generate alarms and warnings
41
MEOLUT COVERAGE
• MEO satellite altitude: ≈20,000 km (19,000 km to 24,000 km)
• At a given time, a MEO satellite covers an area almost as large as a GEO satellite’s coverage area (size of an ocean)
• Unlike GEO satellites, MEO satellites move
42
MEOLUT COVERAGE
Coverage area of a single stand‐alone (non‐networked) MEOLUT tracking GALILEO satellites
(beacon‐satellite elevation: 5˚, MEOLUT‐satellite elevation: 15 ˚)
43
MEOLUT COVERAGE
•
Assumptions:
– Constellation: 9 DASS + 1 MSG (GEO)
– PLB antenna pattern (optimistic detection probability)
Average Number of Mutually Visible Satellites (2 MEO + 1 GEO Antenna)
80
Average Number of Mutually Visible Satellites (4 MEO + 1 GEO Antenna)
80
2.5
3
60
60
2.5
40
20
2
20
Latitude (deg N)
Latitude (deg N)
2
40
0
1.5
-20
1.5
0
1
-20
1
-40
-40
0.5
0.5
-60
-80
-20
0
20
40
Longitude (deg E)
60
80
-60
-80
0
44
-20
0
20
40
Longitude (deg E)
60
80
0
8 “MEOLUTs” TODAY
Brazil (Brasilia): 2 channels
Canada (Ottawa): 3 channels (+ GEO channels)
EU (Toulouse): 4 channels
France (Toulouse): 2 channels
Russia (Moscow): 1 channel
Turkey (Ankara): 2 channels (+ 1 GEO channel)
UK (Kinloss): 2 channels
USA (Washington DC): 4 channels
Total: 20 channels
45
DESIRED MEOSAR PERFORMANCE
•
Expected performance of combined DASS and GALILEO constellations (subsequent beacon transmissions could be used to refine the location and an accuracy of 1 km could be achievable within [TBD] minutes after a beacon started transmitting).
EWG‐1/2011 Montreal (February 2011):
•
•
First burst 2D independent location accuracy within 5 km 90% of the time;
2D independent location accuracy of:
–
–
–
•
•
46
5 km 95% of the time within 30 seconds,
1 km 95% of the time within 5 minutes,
100 m 95% of the time within 30 minutes;
Encoded location accuracy of 30 m in latitude and longitude, 95% of the time,
within 5 minutes of beacon activation; and
If available, encoded altitude information accuracy of 50 m, 95% of the time, within 5 minutes of beacon activation.
DISPLAY OF BEACON INFORMATION
47
DISPLAY OF BEACON INFORMATION
48
DISPLAY OF BEACON INFORMATION
49