Radio Beacons for Satellite Aided Search & Rescue System Characterisation and Operational...

8/7/2019 Radio Beacons for Satellite Aided Search & Rescue System Characterisation and Operational Requirements

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RadioBeacons for Satellite Aided Search & Rescue System: Characterisation and

Operational Requirements

N.K. Shrivastava, P. Gunasekhar, P. Soma, S.K. Shivakumar

Indian Mission Control Centre (INMCC)ISRO Telemetry Tracking and Command Command Network (ISTRAC)

Bangalore

Abstract

Radio beacons used by maritime, aviation and land users in distress are mandatory safety devices

as per regulations by ICAO (International Civil Aviation Organisation) and IMO (International

Maritime Organisation). The radio beacons are operated on 3 frequencies namely 121.5 MHz, 243

MHz and 406 MHz, specifically allocated for Search and Rescue (SAR) purposes. The

international Cospas-Sarsat system detects, processes and locates these signals, and distributes tothe concerned Rescue Co-ordination Centre (RCC) for initiating SAR action. These beacons are

designed to operate automatically in a distress situation. India is a member of Cospas-Sarsat

programme and provides space and ground system support to process and distributes distress

messages picked-up from these beacons to users globally. The Indian system has been operational

since 1989 and providing SAR services to users in India and its neighborhood.

This paper provides radio beacon characteristics, international specifications and regulations, and

various developments that are taking place at national and international level. It also provides

necessary guidelines to Indian users particularly from aviation sector so as to have national and

international compliance for safe travel and timely SAR support.

1. Introduction

With increasing numbers of private and commercial aircraft, the importance of having effective

search and rescue (SAR) is paramount. Often when a small aircraft crashes, a search is conducted

to locate the crash site. In a vast country like India, with huge land and coastal area, the problem

of locating a distressed site is especially challenging.

In the mid 1970s, the use of Emergency Locator Transmitter (ELT) units became mandatory for all

aviation aircraft in North America. Originally the ELT was designed to be a low power (100 mW)

radio transmitter which emits an amplitude modulated signal of carrier frequency 121.5 MHz and

optionally 243 MHz. Upon impact the ELT unit is activated automatically, or it can be switched

on manually, providing homing signal to rescue forces. However, mountainous regions or dense

forests can block or reflect the homing signal, making it difficult for the rescue plane to receive the

transmission. Hence these line of sight restrictions can cause lengthy delays in locating the

aircraft. As the old generation 121.5/243 MHz beacons were not designed to be used by a

satellite-based system, a new generation of beacons transmitting at 406 MHz, to be used

exclusively for satellite detection, was introduced at the beginning of the Cospas-Sarsat project in

1979. The performance of these beacons was found to be far superior to 121.5 MHz beacons.

It was proposed that satellites in 850 km polar orbits be equipped to receive the ELT

transmissions. The advantage offered by a satellite, compared with a rescue plane, is its extended

field of view since each satellite pass covers thousands of square kilometers. Hence the Search

And Rescue Satellite Aided Tracking (SARSAT) system was initiated.


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The United States, Canada, and France developed the SARSAT system while Russia (then Soviet

Union) conceived an equivalent system called COSPAS. The overall programme is known as

COSPAS-SARSAT and has been in operation since 1983. Ships carry an Emergency Position

Indicating Radio Beacon (EPIRB) which basically performs the same function as the ELT.

When the ELT is activated, it transmits a signal, which is received by an orbiting satellite, as it

sweeps out a path over SAR region of interest. Due to the relative motion between the satellite

and the ELT unit, the signal received at the spacecraft is Doppler shifted. A repeater onboard the

satellite relays the signal to a Local User Terminal (LUT) on the ground, which processes the

received signal and estimates the location of the ELT by analyzing the Doppler shift information,

which is embedded in the signal.

The zero Doppler frequency shift occurs at the inflection point of the Doppler curve, and is the

point of closest approach of the satellite to the accident site. Consequently, this frequency must be

determined with as much accuracy as possible since the slope of the Doppler curve at this point is

used to calculate the range from the satellite to the transmitting source. With the range and the

known position of the satellite, the location of the emergency signal source can be estimated. Thisestimate is passed to the Rescue Coordination Centre (RCC) for initiating necessary SAR action.

Fig 1 gives a basic concept of the Cospas-Sarsat system.

ISTRAC operates 2 LEOLUTs (Low Earth Orbiting Local User Terminals), one each at Bangalore

and Lucknow, 1 GEOLUT (Geostationary Earth Orbiting Local User Terminal), at Bangalore, and

a Mission Control Centre situated in ISTRAC campus at Bangalore. ISRO also provides SAR

payload on INSAT series of satellites (INSAT-2A/2B, currently INSAT-3A, future INSAT-3D) as

a part of GEOSAR space segment.

Fig.1: Basic Concept of Cospas-Sarsat System


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2. The International Co-operative Programme

This satellite system was initially developed under a Memorandum of Understanding among

Agencies of the former USSR, USA, Canada and France, signed in 1979. Following the

successful completion of the demonstration and evaluation phase started in September 1982, asecond Memorandum of Understanding was signed on 5 October 1984 by the Centre National

d'Etudes Spatiales (CNES) of France, the Department of National Defence (DND) of Canada, the

Ministry of Merchant Marine (MORFLOT) of the former USSR and the National Oceanic and

Atmospheric Administration (NOAA) of the USA. The System was then declared operational in

1985. On 1 July 1988, the four States providing the space segment signed the International

Cospas-Sarsat Programme Agreement, which ensures the continuity of the System and its

availability to all States on a non-discriminatory basis. In January 1992, the government of Russia

assumed responsibility for the obligations of the former Soviet Union. A number of States, Non-

Parties to the Agreement, have also associated themselves with the Programme and participate in

the operation and the management of the System.

3. Distress Beacons

The use of satellites to detect and locate special-purpose radiobeacons, either manually activated

or automatically activated by an aircraft crash or maritime distress situation, reduces the time

required to alert the appropriate SAR authorities and to provide location and/or identification of

the distressed object. The International Maritime Organization (IMO) and the International Civil

Aviation Organization (ICAO) recommend that ships and aircraft carry Emergency Position

Indicating Radio Beacon (EPIRBs) and Emergency Locator Transmitters (ELTs) respectively.

3.1 121.5 MHz and 243 MHz Beacons

It is estimated that there are about 650,000 121.5 MHz beacons in use world-wide. The Table -1

provides a list of typical 121.5 MHz signal characteristics. Most of these beacons are used aboardaircraft and they are required to meet specifications set by ICAO.

ICAO standards were not established with the aim of satellite reception of 121.5 MHz signals.

Therefore 121.5 MHz Cospas-Sarsat System was designed to serve the existing type of beacons,

even though system performance would be constrained by the beacons' characteristics. Parameters

such as system capacity and location accuracy would be limited. No information is usually

provided about the operator's identity. Despite the limitations indicated above, the efficiency of

121.5 MHz beacons has been greatly enhanced by the use of satellite detection and Doppler

location techniques. A block schematic of 121.5 MHz beacon is given in Fig 2.

121.5 MHz beacons carried aboard aircraft can usually be activated both manually and

automatically by shock (using a crash sensor or G-switch).

3.1.1 Processing of 121.5 MHz beacon signals

The 121.5 MHz and 243 MHz beacons were not designed to be used by a satellite based system.

The match- merge process is particularly difficult for 121.5/243 MHz transmissions. The signals,

which may originate from sources other than legitimate distress beacons, are distinguishable only

by the spectrum of the source and by the location and other parameters calculated by the LUT

from its Doppler shift. The spectrum consists of a 121.5 MHz carrier of a nominal 100 mW,

pulsed modulated at a rate that sweeps from about 1600 Hz to 300 Hz, repeated 2-4 times per

second. This modulation provides a rich sideband profile, to which is added transmitter, satellite

and LUT noise, carrier instability and interference from other sources. In addition, some beacons


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are phase incoherent with the modulation, adding to the spectrum complexity. As a result, the

individual spectra are very random in character, and determining a single central frequency is a

challenging task.

Each solution received by the MCC consists of estimates of latitude, longitude, frequency bias (i.e.offset from the carrier frequency, without Doppler shift) and possibly other parameters

characterizing the signal, such as bias drift and sweep period. Several LUTs may independently

report solutions for overlapping parts of the same pass over the beacon; the MCC must not only

match up these solutions from different LUTs, but also match them with solutions from the same

sources on previous passes. The match-merge solutions produced by an MCC are primarily based

upon the location and center frequency calculated by the LUTs. Solutions attached to the

sidebands are presumed to have the same, or close, locations and frequency bias estimates as other

solutions for the source on the same pass; solutions from different passes are also presumed to

have the same, or close, locations and frequency biases.

Usually ELT units have carrier frequencies distributed over a range of 3 kHz. When combined

with the range of Doppler shifts of 3 kHz, most of the ELT signals received at the satellite fallover within the range of approximately 12 kHz. For processing purposes, the total range of

frequencies is extended to a bandwidth of 15 kHz.

There are many problems need to be solved for processing 121.5 MHz (243 MHz) signals since

the spectral properties of ELT/EPIRB signals vary considerably. The signals generate not only

carrier peaks but also sideband peaks, which produce in-band interferers. In the real environment,

there are numerous other interferers, which add to the already crowded spectrum.

SWEEPOSC.

MULTI-

VIBRATOR

121.5243 MHz

OSC

MODULATOR

&

AMPLIFIER

PWR.AMP

2 - 4 Hz

30-50%

ANTENNAAUDIO SECTION

RF SECTION

1600 - 500Hz

FrequencySPECTRUM

Fig.2: Block Schematic of 121.5 MHz Beacon

As far as accuracy of location estimates is concerned, there are two problems which affect the

performance of these ELT units, the instability of the carrier frequency oscillator, and an

unfortunate interaction between the modulation and the carrier frequency oscillator which causes

frequency pulling. Consequently, the accuracy of location estimates is limited to a radius of 20 km


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TABLE-1

Typical 121.5 MHz Beacon Characteristics

Parameter Value

RF Signal

Transmitted power 50 - 100 mW PERP*

Battery Life 48 Hours

Frequency 121.5 MHz 6 kHz

Frequency Tolerance 50 PPM

Polarization Linear

Modulation

Sweep Rate 2 - 4 Hz

Range 300 - 1600 Hz ( swept at least 700 Hz)

Modulation Type AM

Modulation depth > 85 %Duty Cycle 40%

'*' Peak Effective Radiated Power relative to a 1/4 wavelength monopole mounted on a ground plane

3.2 406 MHz Beacons

Frequencies in the 406.0 - 406.1 MHz band have been exclusively reserved for distress beacons

operating with satellite systems. The Cospas-Sarsat 406 MHz beacons have been specifically

designed for use with the LEOSAR system to provide improved performance in comparison with

the older 121.5 MHz beacons. They are more sophisticated than the 121.5 MHz beacons because

of specific requirements on the stability of the transmitted frequency, and the inclusion of a digital

message, which allows the transmission of encoded data such as a unique beacon identification. A

block schematic of 406 MHz beacon is given in Fig.3.

A second-generation 406 MHz beacons have been introduced since 1997, which allow for the

transmission in the 406 MHz message of encoded position data acquired by the beacon from

Global satellite navigation systems, using external or internal navigation receivers. This feature is

of particular interest for GEOSAR alerts, which otherwise would not be able to provide any

position information. The 406 MHz beacons have following merits over the 121.5 MHz beacons:

Improved Doppler location accuracy and ambiguity resolution; Increased system capacity (i.e. capability to process a greater number of beacons

transmitting simultaneously in field of view of satellite); Global coverage; and Unique identification of each beacon

System performance is greatly enhanced both by the improved frequency stability of the 406 MHz

units and by operation at a dedicated frequency.

The basic characteristics of 406 MHz beacons are given in Table 2. These beacons transmit a

5 Watt RF burst of approximately 0.5 seconds duration every 50 seconds. The carrier frequency is

very stable and the pulse is phase-modulated with a digital message as shown in Table 2.

Frequency stability assures accurate location, while the high peak power increases the probability

of detection. The low duty cycle provides a multiple-access capability of more than 90 beacons

simultaneously operating in view of a polar orbiting satellite and low mean power consumption.


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An important feature of 406 MHz emergency beacons is the addition of a digitally encoded

message, which provides such information as the country of origin and the identification of the

vessel or aircraft in distress, and optionally, position data derived from internal or external

navigation receivers.

An auxiliary transmitter (homing transmitter) can be included in the 406 MHz beacon to enable

suitably equipped SAR forces to home on the distress beacon. Most EPIRBs and ELTs include a

121.5 MHz homing transmitter in accordance with the requirements of IMO and ICAO. However,

the performance characteristics of the homing transmitter are not covered by the Cospas-Sarsat

system specification.

Beacons can be activated either manually or automatically by immersion or shock. These

particular features required by national administrations authorising the use of 406 MHz beacons,

are not included in the Cospas-Sarsat specifications defined in Cospas-Sarsat document C/S T.001.

Performance of the 406 MHz system depends on actual transmission characteristics of thebeacons. Consequently, Cospas-Sarsat has developed a type approval procedure for 406 MHz

beacons, which is defined in document C/S T.007. National administrations should authorise only

type approved 406 MHz beacons for use with the Cospas-Sarsat System. The list of manufacturers

and type approved beacon models is given in the document Cospas-Sarsat System Data, which is

published periodically by the Cospas-Sarsat Secretariat and also available on Cospas-Sarsat

Website. Cospas-Sarsat Website address is: http://www.cospas-sarsat.org.

3.2.1 Processing of 406 MHz beacon signals

The structure of the message burst transmitted by the 406 MHz beacon consists of three distinct

fields: an unmodulated preamble (for carrier synchronization), a bit/frame sync, and a message

field. The bit rate is 400 bits per second. The data is encoded using Biphase-L Manchester phasemodulation with a peak modulation of 1.10.1 radians. The bit size may exhibit variation of upto

1%.

The unmodulated preamble lasts for 160 ms, followed by 60 ms sync sequence, and then follows

message bits. In a standard message, the 88 message bits divided into fields, which identify the

user and (optionally) give location information. The total standard format burst lasts 440 ms (112

bits) while the total long format burst lasts 520 ms (144 bits).

Of the standard message bits, 61 are known and fixed at the time of beacon manufacture. The 61

bits in the protected data field, as illustrated in fig.4, consists of a user identity code. These bits are

subject to error correction by 21 error correction bits (BCH error correcting code). There are

additional 6 bits, which can be used to transmit either an emergency code or other data.

The bit synchronization field consists of 15 data "1" bits, while the frame synchronization

comprises the bit pattern 000101111. The Fast Fourier Transformation (FFT) provides an effective

means of detecting and recognising the presence of one or more ELT signals over the 25 kHz

frequency band.

4. Phasing out 121.5 / 243 MHz Beacons

121.5 MHz beacons are available at a very low cost, but this outdated technology which cannot be

improved easily, is the source of a very large number of false alerts (over 98% of all 121.5 MHz

Cospas-Sarsat alerts). This situation impacts on the efficiency of SAR operations and increases


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the workload of Rescue Co-ordination Centres. As a result of the 121.5 MHz system limitations,

and because of the availability of the newer 406 MHz beacons with better performance, it has lead

to a request by the IMO and CAO Joint Working Group on SAR for a termination of the satellite

processing of 121.5 MHz signals from 2008.

Fig.3 Block Schematic of 406 MHz beacon

5. 406 MHz Beacon Coding

5.1 Beacon Coding Protocols

Cospas-Sarsat 406 MHz beacons can be used in different environments and for a variety of

applications such as EPIRBs (maritime), ELTs (aviation) or PLBs (personal use). The

specification of the distress signal characteristics (document C/S T.001), which ensures that all

406 MHz beacons are compatible with the Cospas-Sarsat Space Segment, is applicable to all types

of beacons. However, different user groups have different needs, hence the need for various

coding protocols. General 406 MHz beacon-coding formats are presented in Fig 4. To satisfy

these requirements, the Cospas-Sarsat specification provides for various coding options, which are

divided in 2 groups of coding protocols: User Protocols and Location Protocols,

The user protocols can be used for encoding the beacon identification and other data in the digital

message transmitted by a 406 MHz distress beacon, but do not allow for encoding beacon position

data.

The location protocols can be used for encoding beacon position data, in addition to the beacon

identification data, in the digital message transmitted by a 406 MHz distress beacon. Protocols in

both groups (i.e. user protocols and location protocols) can be implemented using either the short

message format or the long message format as given in Fig. 4 (A & B).

The choice of the protocol option to be used in a particular beacon type depends on:

a) the user category (maritime, aviation, or personal);b) the method used to provide beacon identification data as required by the responsible

administration; and

c) the required resolution of encoded position data (only for location protocols).

STABLE

OSCILLATORMULTIPLIER

PHASE

MODULATOR

POWER

AMPLIFIER

POWER

SUPPLY

CONTROL

UNIT

DIGITAL MESSAGE

GENERATOR

406.025 MHz

DISTRESS MESSAGEACTIVATION


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Fig.4A: Data fields for the short message format

BCH error-

correcting code

Bit

Synchronization

Frame

SynchronizationFirst Protected Data Field (PDF-1) BCH-1

Non-Protected

Data Field

Unmodulated

Carrier

(160 ms)

Bit

Synchronization

Pattern

Frame

Synchronization

Pattern

Format

Flag

Protocol

Flag

Country

Code

Identification or

Identification

plus Position

21-Bit

BCH

code

Emergency Code/

National Use or

Supplement. Data

Bit No. 1-15 16-24 25 26 27-36 37-85 86-106 107-112

15 bits 9 bits 1 bit 1 bit 10 bits 49 bits 21 bits 6 bits

Bit

Synchronization

Frame

SynchronizationFirst Protected Data Field (PDF-1) BCH-1

Second Protected Data

Field (PDF-2)BCH-

Unmodulated

Carrier

(160 ms)

Bit

Synchronization

Pattern

Frame

Synchronization

Pattern

Format

Flag

Protocol

Flag

Country

Code

Identification or

Identification

plus Position

21-Bit

BCH

code

Supplementary and

Position or National Use

Data

12-Bi

BCH co

Bit No. 1-15 16-24 25 26 27-36 37-85 86-106 107-132 133-14

15 bits 9 bits 1 bit 1 bit 10 bits 49 bits 21 bits 26 bits 12 bit

Non-protected field

160 ms

carrier15

bits

9

bits21 bits 6

bits

Frame

synchronization

1 16 2586 107- 112

Bit

synchronizationProtected field

61

bits

Fig.4B: Data fields for the long message format

Second protected field

First BCH error-

Correcting code

160 mscarrier

15bits 9bits 61 bits 21 bits 26 bits

116 25 86 107

133-

First protected field

Frame

synchronization

Bit

synchronization

12bits

Second BCH

error-correctin

code

144

Figure 4 : General Format of the 406 MHz Beacon Message


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Figure 5: Bit Assignment for the First Protected Data Field (PDF-1) of User Protocols

1. MARITIME USER PROTOCOL

Bits 25 26 27 36 37 39 40 81 82 83 84 85

..... 0 1 Country Code 0 1 0 MMSI or Radio Call Sign (42 bits) 0 0 R L

2. RADIO CALL SIGN USER PROTOCOL

Bits 25 26 27 36 37 39 40 81 82 83 84 85

..... 0 1 Country Code 1 1 0 Radio Call Sign (42 bits) 0 0 R L

3. SERIAL USER PROTOCOL

Bits 25 26 27 36 37 39 40 42 43 44 73 74 83 84 85

..... 0 1 Country Code 0 1 1 T T T C Serial Number and other Data C/S Cert. No or

National Use

R L

4. AVIATION USER PROTOCOL

Bits 25 26 27 36 37 39 40 81 82 83 84 85

..... 0 1 Country Code 0 0 1 Aircraft Registration Marking (42 bits) 0 0 R L

5. NATIONAL USER PROTOCOL

Bits 25 26 27 36 37 39 40 85

...... F 1 Country Code 1 0 0 National Use (46 bits)

6. TEST USER PROTOCOL

Bits 25 26 27 36 37 39 40 85

..... F 1 Country Code 1 1 1 Test Beacon Data (46 bits)

7. ORBITOGRAPHY PROTOCOL

Bits 25 26 27 36 37 39 40 85

...... F 1 Country Code 0 0 0 Orbitography Data (46 bits)

Notes: RL = Auxiliary radio-locating device

TTT = 000 - ELT with serial number 010 - float free EPIRB with serial number

011 - ELT with 24-bit aircraft address 100 - non float free EPIRB with serial number

001 - ELT with aircraft operator 110 - personal locator beacon (PLB) with serial number

designator and serial numberC = C/S Type Approval Certificate Flag:

"1" C/S Type Approval Certificate number encoded in bits 74 to 83

"0" other national use

F = Format Flag (0 = short message, 1 = long message)

Radio call sign of six or fewer alphanumeric characters can be encoded in Maritime User Protocol.

Radio call sign of up to seven characters (four alphanumeric and three digits) can be encoded in Radio Call

Sign User Protocol.


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5.3 Coding Location Protocols

This section defines the protocols which can be used for encoding beacon position data, as well as the

beacon identification data, in the digital message transmitted by a 406 MHz distress beacon.

Five types of location protocols are defined for use either with the long message format or with the

short message format, as illustrated in Fig 6. The five protocol types available are:

User-location Protocol; Standard Location Protocol; Standard-Short Location Protocol; National Location Protocol; and National-Short Location Protocol.

Figure 6: Outline of Location Protocols

U s e r - L o c a t i o n P r o t o c o l s

bit

26

bits

27-39

bits 40-83 bits

84-85

bits 86-106 bit 107 bits 108-132 bits

133-144

Identification Data

(44 bits)

Radio-

locatingDevice

21-Bit

BCH code

Position.

DataSource

Position Data

to 4 min Resolution(25 bits)

12-Bit

BCH code1 .......

S t a n d a r d L o c a t i o n P r o t o c o l s

bit26

bits27-40

bits 41-64 bits 65-85 bits 86-106 bits 107-112 bits 113-132 bits133-144

0 .......Identification Data

(24 bits)Position Data


21-BitBCH code

SupplementaryData

Position Datato 4 sec Resolution

(20 bits)

12-BitBCH code

S t a n d a r d - S h o r t L o c a t i o n P r o t o c o l s

N a t i o n a l L o c a t i o n P r o t o c o l

bit

26

bits

27-40

bits 41-58 bits 59-85 bits 86-106 bits 107-112 bits 113-126 bits

127-132

bits

133-144

0 .......Identification Data

(18 bits)Position Data


21-BitBCH code

SupplementaryData

Position Datato 4 sec Resolution

(14 bits)

NationalUse

12-BitBCH code

N a t i o n a l - S h o r t L o c a t i o n P r o t o c o l

6. Beacon Registration

6.1 Purpose of Beacon Registration

One of the advantages of 406 MHz beacons is that each beacon is designed to transmit a unique

message allowing its identification. However, to take advantage of this feature, a register is needed to

relate each beacon to a particular ship, aircraft or individual user. Beacon registration is valuable for the

resolution of SAR cases. Identification of the beacon user (ship, aircraft or individual user) helps SAR

services to properly respond to a distress alert provided that the registration database contains the

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information listed below in Table-3. This information provides important search planning data to

allow the timely rescue of people in distress. Registration information also helps to resolve false alerts

without diverting SAR resources.

All 406 MHz beacons (EPIRBs, ELTs or PLBs) should, therefore, be registered. Every administration

requiring or allowing the use of 406 MHz beacons should make suitable arrangements for the

registration of 406 MHz beacons, and enforce their registration.

6.2 General Principles for Registering 406 MHz Beacons

6.2.1 Country of Registration - Coding Procedure

The IMO and the ICAO require that administrations authorising the use of 406 MHz beacons make

provisions for registering these beacons in a database register that is accessible by SAR services 24

hours a day.

As the administration authorising the use of the beacon, is not always maintaining the beacon

registration database but could, alternatively, use the service of another administration, the country

code in the 406 MHz beacon message (bits 27 - 36) must provide a link to the administrationmaintaining the beacon registration database. The country code should always enable SAR services to

retrieve pertinent registration data through the point of contact associated with that country code.

If a registration database is implemented and maintained regionally by agreement between several

countries, the administration of the country of registration should arrange with Cospas-Sarsat and

appropriate SAR authorities that its country code be recognised as one associated with that particular

database, and provide information about such arrangements to the beacon owner.

6.2.2 Control and Updating of Registered Information

Administrations should provide the means for beacon owners to readily and expeditiously update

information in the registration database. Owners of beacons are responsible for reporting any changein the registered information, including de-registration of the beacon in the case of a change of

ownership. Administrations should also regularly verify the accuracy of the database information by

contacting the beacon owners. A census of registered 406 MHz beacons should be undertaken by

administrations at least every two years. Administrations should also require a check of the beacon

registration during mandatory periodic inspections of the beacon. Authorities maintaining or using

databases should ensure that information supplied for beacon registration is treated as proprietary, and

ensure that it is used only by appropriate recognised authorities.

6.2.3 Access to Registration Databases

Administrations maintaining registration databases should provide the means for SAR services to

obtain relevant information on a 24 hours, seven days a week basis.

6.2.4 Content of Registration Databases

It is desirable that the appropriate information from Tables-3 be recorded in beacon registration

databases or in other appropriate registers and be made available to SAR services in case of distress

alerts. Examples of beacon registration cards are provided in document Handbook of Regulations on

406 MHz and 121.5 MHz Beacons, which is annually updated by the Cospas-Sarsat Secretariat.

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Table-3: Example of Basic Information to Be Recorded and

Made Available through Beacon Registration

PLB ELT EPIRB

Beacon IdentificationBeacon IdentificationBeacon Identification

(15 Hex ID*)(15 Hex ID*)(15 Hex ID*)

Full length (22/30 Hex) message

with default position bits

Full length (22/30 Hex) message

with default position bits

Full length (22/30 Hex)

message with default position

bits

Name of vessel/Aircraft registration number/Name of owner/

call sign/MMSIname of aircraft operatororganization

Name, address and phoneName, address and phoneName, address and phonenumber of emergencynumber of emergencynumber of emergencycontact personcontact personcontact person

Alternative 24-hourAlternative 24-hourAlternative 24-hour

emergency phoneemergency phoneemergency phonenumbernumbernumber

Brief vessel description **Type of aircraft, colour,Town, city of residenceaircraft markingor base

Capacity for persons on Capacity for persons onAny critical personalboard (passengers, crew) board (passengers, crew)information

Home base Home port

Emergency equipment Ship radio installationNavigation/communication (see Table 4-3)

equipment

Notes: (*) Beacon Identification (Beacon 15 Hex ID) - the 15 hexadecimal characters that

uniquely identify each 406 MHz beacon. This Beacon Identification is derived from

bits 26 to 85 of the 406 MHz beacon message. For location protocols, the position

data in the first protected data field (PDF-1) is set to specified default values to obtain

the unique Beacon 15 HexID.

(**) A brief vessel description may include:

- Length of vessel - Vessel type

- Hull colour - Hull type

- Superstructure colour - Propulsion

7. 406 MHz Beacon Type Approval

7.1 Objectives and Scope of Type Approval

The issuing of performance requirements, carriage regulations and the testing and type approving of

406 MHz distress beacons are the responsibilities of national authorities. However, to ensure beacon

compatibility with Cospas-Sarsat Space Segment and Ground Segment equipment, it is essential that

beacons meet specified Cospas-Sarsat performance requirements. Compliance with these requirements

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provides assurance that the tested beacon performance is compatible with, and will not degrade, the

Cospas-Sarsat System.

The Cospas-Sarsat type approval tests are designed to ensure that the signals transmitted by the

beacons and their coding meet all applicable requirements of the Cospas-Sarsat specification for 406

MHz distress beacons (document C/S T.001). These tests primarily measure the electrical

characteristics of beacon transmissions on 406 MHz and, with the exception of temperature, do nottake into account environmental conditions the beacon may encounter during normal use.

7.2 Cospas-Sarsat Type Approval Testing

In order to ensure that beacons do not degrade the System and to ensure uniformity of testing, Cospas-

Sarsat has defined the necessary tests and overall procedure which a manufacturer must follow to

receive Cospas-Sarsat type approval (document C/S T.007 Cospas-Sarsat 406 MHz Distress Beacon

Type Approval Standard). The tests described in C/S T.007 consist of a series of indoor laboratory

tests in which the beacon does not transmit to the satellite, and an outdoor functional test of the beacon

transmitting to the satellite.

The beacon manufacturers should submit for Cospas-Sarsat type approval testing beacons codedwith a test protocol of appropriate type and format (user-short or long, user-location, standard

location-short or long, national location-short or long). All protocol types intended for use with the

beacon should be verified. The verification of the different coding options within each type is not

required. However, sample messages should be provided for each applicable coding protocol as

required by C/S T.007.

7.3 Cospas-Sarsat Type Approval Certificate

After successful completion of Cospas-Sarsat type approval testing, the test report and other technical

documentation (as specified in C/S T.007) is submitted to the Secretariat. A Cospas-Sarsat type

approval certificate will be issued to the beacon manufacturer by the Cospas-Sarsat Secretariat, after

review and approval of the test results by Cospas-Sarsat.

Should it be demonstrated subsequently that the production models do not meet the same standard as

the type approved model, Cospas-Sarsat reserves the right to revoke the certificate.

406 MHz beacons that have received Cospas-Sarsat type approval are listed in the Cospas-Sarsat

System Data which is published periodically by the Secretariat.

7.4 National Type Approval

Cospas-Sarsat encourages national administrations to adopt national requirements (e.g., radio-locating,

environmental, activation, etc.) for 406 MHz beacons.

National administrations should also consider requirements, which may contribute to reducing false

alerts such as:

visual/audio indicators; 2-step activation mechanism; and including a description of testing procedures in the beacon user manual.

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Depending on the intended use of the beacon, administrations should also consider the

recommendations of international organizations (e.g. IMO, ICAO, ITU, etc.). Administrations are

urged to harmonise their requirements with those defined by other administrations or international

organizations.

8. Guidelines to Administrations

406 MHz beacon coding protocols have been developed to satisfy maritime (EPIRB), aeronautical

(ELT) and personal (PLB) applications.

Regardless of the application or protocol used, the creation and maintenance of a registration database

is very important. Administrations are responsible for the definition and control of beacon

identifications registered in their national databases. All measures should be undertaken to avoid

possible duplication of beacon identifications.

Using the Cospas-Sarsat type approval certificate number may help ensuring that the serial number

assigned by a manufacturer provides a unique beacon 15 Hex ID, independently of the country of

registration indicated by the country code. When a beacon 15 Hex ID is assigned by the national

administration of the country designated by the country code, bit 43 can be set to 0 and the content ofbits 44 to 83 redefined as required. However, in that case, the national administration must ensure that

the beacon 15 Hex ID is unique.

9. Conclusion

Following user growth and potential application of the Cospas-Sarsat system beacons, several new

developments are expected to be introduced in the beacon technologies and ground processing

system to further enhance and improve the efficiency of the system. Some of these developments

are:

In view of the termination of 121.5 MHz beacons and to make 406 MHz beacons moreaffordable, newer technologies are being investigated to lower the cost of the beacons and will

be shortly available to user. Recognising the need for lower cost beacons, the Cospas-SarsatCouncil in its 33rd meeting (CSC-33) in October 2004, approved the change of the beacon

medium-term frequency stability for temperature stressed conditions to be 2 *10 E9 per minute

from the original requirement of 1 * 10 E9 per minute. For non-temperature stressed

conditions, the 1 X 10 E 9 requirement remains valid. ISRO is already in advance stage of

developing such beacons.

Frequency spectrum of 406 MHz beacon is spread over a wider band to accommodate expectedgrowth of the 406 MHz beacons.

International beacon registration database is being developed to handle false alarm issues moreefficiently.

Ship Security Alarm System (SSAS) is being implemented for security of the maritime users.For this, a separate beacon protocol and data distribution procedure has been approved by theCospas-Sarsat for implementation by all ground systems.

Development of MEOSAR (Medium Earth Orbiting Search and Rescue) system for real-timealerting using single burst of the beacon signal, with redundancy of satellites and availability

and possibility of having return link to beacon.

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