1. SATELLITE DATA-LINK COMMUNICATION REQUIREMENTS AND ISSUES
ICAO APAC Office
8 February, 2012
This presentation is based on the information provided in the FAA document ‘Operational Authorization Information Package – Data Link Operations Controller/Pilot Data-link Communication/Automatic Dependent Surveillance – Contract’ dated 1 February, 2010, outcome of Eighteenth Meeting of FANS Interoperability Team held in Honolulu, Hawaii, USA on 22 and 23 March, 2011 and Forty Seventh Meeting of The North Atlantic Systems Planning Group (NAT SPG/47) held in Paris from 13 to 16 June Presentation also includes the outcome of APANPIRG on the subject.

2. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
STRUCTURE
Background
FANS Inter-operability Team (FIT) Outcome
ICAO NATSPG/47 Outcome
APANPIRG Outcome
Conclusion
The presentation has been divided into five sections. Starting with an introduction to the satellite data-link communication, presentation progresses with the brief description of the outcome of relevant meetings and ends with a Conclusion containing significant related issues.
SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING

3. ACARS Data Link for Aviation Started in 1978 with ACARS
Initial data-link applications included Departure Clearance, ATIS etc.
ACARS expanded to use INMARSAT AMSS in 1990
ACARS extended to IRIDIUM Satellites since 2007 through Short Burst Data transmission
Data link operations started way back in 1978 when Aircraft Communications Addressing and Reporting System or ACARS avionics was implemented and Airlines Electronic Engineering Committee or AEEC developed “Characteristics” 597 defining the first very basic ACARS avionics. ACARS was originally developed to support AOC communications and was expanded from reporting aircraft movements to transport aircraft system performance data and ATS Communications. That was followed in the mid 1980s by an AEEC Characteristics 724 specifying ACARS avionics with a digital interface to other aircraft systems.
Initially data-link applications for ATS were primarily limited to Departure Clearance and Automatic Terminal Information Services (ATIS).
The ACARS system was expanded to use the INMARSAT Aeronautical Mobile Satellite System (AMSS) on its introduction in The aircraft that use the AMSS ACARS service generally also use the VHF ACARS service and can send messages via either system.
ACARS avionics have since 2007 begun to be linked to avionics that uses the Iridium satellites which fly in low earth orbit and allow avionics to be lighter and less costly. These ACARS messages are being sent in Iridium Short Burst Data transmissions.

4. ICAO DATA-LINK SERVICES
ICAO ANC created FANS Committee in 1980s and FANS Committee recommended use of data links and satellite for CNS
Installation FANS 1 by Boeing and FANS A by AIRBUS defined CPDLC and ADS-C
ICAO AMSS Standards adopted in Standards specify standard ITU protocols for the provision of voice and data link services.
ICAO Air Navigation Commission in the 1980s created a Future Air Navigation System (FANS) committee, which recommended through its main report in 1988 use of data links and satellite for communications, navigation and surveillance. Installation of FANS 1 package by Boeing and FANS-A package by AIRBUS defined the applications Controller Pilot Data Link Communication or CPDLC and Automatic Dependent Surveillance – Contract or ADS-C. ANSPs implementation of CPDLC using ATN has been led by Eurocontrol and the EU Single European Sky programme will mandate its installation by about 2015 on all jet aircraft flying in Europe (except long haul aircraft with FANS CPDLC). USA is also planning usage of ATN for CPDLC. Eurocontrol decided in late 2003 to accelerate ATN CPDLC implementation by subsidizing aircraft operators that agreed to add ATN CPDLC software in aircraft.
ICAO AMSS standard was adopted in This standard specifies protocol for the provision of voice services and an X.25 based sub-network protocol for the provision of data link service. Aircraft uses AMSS X.25 sub-network service to access a Ground Earth Station or GES that uses ITU X.75 protocol to interconnect to terrestrial X.25 networks. Each INMARSAT satellite is assigned an X.121 Data Network Identification Code or DNIC and GES prefixes that to aircraft address in call request relayed to destination ground terminal.

5. FANS INTEROPERABILITY TEAM
Lessons learnt after investigating Performance Deficiencies:
Pilots: avoid sending multiple elements in downlink messages, avoid using free-text, continue to monitor HF
Air Traffic Controllers: priority for messages containing “DUE TO WEATHER”, avoid sending multiple elements
System Performance Lessons Learnt:
Performance requirements include
Message Delay: <60 seconds 95% time
Integrity: Undetected bit errors< 10-6 per hour
CPDLC System availability: > 99.9%
Reliability: message delivery success rate > 99%
FANS operating experience has shown that there is a considerable benefit to be derived from close monitoring of end-to-end performance of the system. In the South Pacific this function is being performed by the FANS Interoperability Team or FIT, an informal group reporting to Informal South Pacific Air Traffic Services Coordination Group or ISPACG, made up of representatives from operators, ATS Providers, data link service providers, regulatory authorities and aircraft manufacturers. A similar team has been formed to serve north and central pacific airspace with the monitoring functions split between the FAA and Japan Civil Aviation Bureau.
In investigating performance deficiencies and other reported problems, the FITs have learnt a number of important lessons that can be applied in other ATS data link environments:
For Pilots
Pilots should avoid sending multiple elements in downlink request messages unless one element is dependent on another
Lack of standardization in free text messages causes significant problems. Pilots should not use free text unless it is absolutely necessary.
Altitude clearances that include a deferral of the clearance until a certain position is reached or until a certain time have caused a number of problems. These are now known as “conditional clearances”
While CPDLC will be usable as the primary medium for ATC communication in the oceanic areas, pilots must continue to monitor the appropriate HF primary and secondary frequencies through SELCAL.
Correct application of FIR boundary crossing procedures has been problematical. CPDLC system allows automatic transfer from FIR to FIR with no action by the pilot.
For Controllers
Under normal operating conditions, priority should be given to messages containing the term “DUE TO WEATHER” and “REQUEST WEATHER DEVIATION”
When an aircraft leaves a data-link FIR for a non-data-link FIR or leaves CPDLC service area within the FIR, keep the aircraft in the active list until the CPDLC connection is terminated by the pilot or end service message should be uplinked
Controllers should, wherever possible avoid sending multiple elements in an uplink clearance message unless one element is a constraint on another.
When a single-word downlink response message (WILCO, ROGER, UNABLE, NEGATIVE etc.) is received from the aircraft, the controller should review the associated uplinked message if he has any questions pertaining to the response.
System Performance Lessons Learned
South Pacific operations have demonstrated that poor end-to-end system performance rapidly leads to loss of confidence in the system among both pilots and controllers. As per FAA requirements some of the performance requirements include
Message delay – one-way delay time should be less than 60 seconds 95% of the time
Integrity – undetected bit errors rate should be less than 10-6 per hour
CPDLC System Availability should be better than 99.9%
Reliability – message delivery success rate should be better than 99%

6. RECOMMENDATIONS PACIFIC DATA LINK OPERATORS
CPDLC Procedures a) Communication initiated on voice to be completed on voice b) Include only single request in each CPDLC clearance request c) Free text to supplement formatted message only d) Pilot not to expect controller response to position report e) Conflict in messaged to be resolved using voice f) Read-back of clearance/instruction on CPDLC not reqd. g) For relay messages i) only a free text message to be used ii) First word of the message should be ‘Relay’
CPDLC Procedures
Communications initiated with ATS by voice should be completed by voice. Communications initiated with ATS using CPDLC should be completed, whenever possible, using CPDLC.
Include only a single request in each CPDLC clearance request message.
Use pre-formatted message elements for CPDLC messages to the maximum extent. Free text should be used only to supplement a formatted message when no pre-formatted message element is adequate.
Send a CPDLC position report after successful logon and after each CPDLC transfer of control to the next ATS facility, Pilots should not expect a controller response to position report.
Any uncertainty concerning CPDLC clearance or instruction or any apparent conflict between a voice message and a CPDLC message must be resolved using voice communication.
Pilot readback of an ATC clearance or instruction issued via CPDLC is not required.
Using CPDLC to relay messages because an ATSU and aircraft cannot communication, and an intermediary data link aircraft is used for relaying messages, the following shall apply:
Only a free text message shall be used
The first word of the message should be ‘Relay’

7. Project title (Insert, Header & Footer)
FIT/18 OUTCOME
Network availability improved
Performance measured against GOLD
ANSPs improved their Automation systems
Recommend ISPACG develop performance based framework for Comm./Surveillance
All ANSPs encouraged to support system performance monitoring outlined in GOLD
Current configuration, flight crew cannot cancel or modify crew reminder.
Typing errors in logon request may result flight crew waiting for 10 minutes before airplane function times out
Eighteenth Meeting of FANS Interoperability Team held in Honolulu, Hawaii 22 and 23 March, 2011 observed that the performance of FANS 1/A aircraft and network availability in the region had improved over the previous period. Network availability, CPDLC and ADS-C performance is measured against criteria specified in the ICAO Global Operational Data-link Document or GOLD. These measurements provide verification that system safety objectives that rely on the FANS 1/A communications and surveillance infrastructure are met, and provide the basis for system performance improvement where deficiencies are found.
Meeting also observed that ANSPs had made improvements in their automation systems which are anticipated to provide additional benefits.
FIT recommended that ISPACG support the development of a performance based framework for communications and surveillance within the ICAO Asia/Pacific region that will complement existing performance based navigation framework. This is in line with the regional policy adopted. The performance based communication and surveillance framework will apply performance specifications to FANS1/A controller-pilot data link communication or CPDLC, automatic dependent surveillance – contract or ADS-C, the satellite communication voice for air traffic control or SATCOM etc. Currently, performance based navigation (PBN) has been implemented by reference in appropriate airspace specifications. However, none of these documents invoke the RCP Manual or Doc 9869, the GOLD or any guidance material used for SATCOM voice for ATC communication. Adopting a performance based framework will enable regions to take advantage of new communication systems like Swift Broadband or SBB, Iridium NEXT, INMARSAT Ku/Ka I-5 satellites, MTSAT etc. etc..
Post implementation monitoring provides performance data on the FANS1/A, ADS-C and CPDLC applications that can be measured against Required Communications Performance or RCP and Required Surveillance Performance or RSP. Measurement of availability is based on outages that are notified by the Communication Service Providers or CSPs and outages that are detected by observation of the collected FANS1/A. These measurements provide verification that system objectives that rely on the FANS1/A communications and surveillance infrastructure are met, and are part of the ATSUs overall Safety Management System or SMS requirements as stated by ICAO.
All ANSP members are encouraged to support system performance monitoring as outlined in the GOLD and to use this performance monitoring data as an element of their respective SMS programmes.
ATSUs indicated that there were a number of interoperability issues relating to route downlinks they receive from airplanes that can result in the inability to create a corresponding uplink clearance. One particular issue was that airplanes can transmit latitude/longitude fixes where either the latitude or longitude is in whole degree, while the other part includes minutes (and even tenths of minutes). Another issue was that some airplanes send multiple airways without the intersection fix between them. This is a result of an error in the airborne implementations, and manufacturers should be encouraged to fix those avionics systems that exhibit this deficiency in support of enhanced operational benefits.
FAA Technical Center has determined that airplanes in the Pacific using either the AOR-W or AOR-E satellite have exhibited worse performance than the other satellites. One possible/probable reason is that where this happens, both the Pacific and Atlantic satellites are at low elevation angles, so some switching of satellites (and corresponding delays) can be expected in those regions. The FAA Technical Center will continue the analysis. INMARSAT, SATCOM system manufacturers and OEMs were assigned an Action Item to see if there is a way to improve the performance in this region.
The latest issue is if the controller needs to move the airplane, he would send the message to the airplane and then wait until a non-response timer times out within the ground system since the message has been discarded and not displayed to the pilot. Boeing was encouraged to find a solution to this problem.
A problem report was identified in the North-Atlantic relating to a crew reminder function on an Airbus airplane. The reminder function is armed when a conditional clearance is received by CPDLC and accepted by the crew. In this case the conditional clearance was superseded by a subsequent clearance. Sometime later the airplane automation reminded the crew to descend. After some discussions the crew descended and were questioned by ATC why they descended without a clearance. In the current configuration the flight crew cannot cancel or modify the crew reminder and erroneous reminders must be igonored. This feature is on all FANS equipped Airbus aircraft. Manufacturers were strongly urged to provide a means to cancel reminders that are superseded by subsequent clearances.
Currently typing errors in logon requests will result in the flight crew waiting 10 minutes before the airplane function times out and informs the crew of an unsuccessful logon attempt. However the crew is not given any feedback why the logon attempt failed. Currently the DSP must perform a 4-character ICAO ID to 7-character address translation similar to what they do today for D-ATIS. For that service DSP provides “NO PARTICIPATING AIRPORT” message. It was suggested that the DSP could provide a “INCORRECT LOGON ID” message.
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8. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
INMARSAT IRIDIUM
FAA agrees that IRIDIUM that meets appropriate requirements be allowed CPDLC/ADS-C
Approval of IRIDIUM SATCOM for use CPDLC/ADS-C still pending
AIRBUS informed IRIDIUM SATCOM tested for voice/data. Results promising
Some interference with INMARSAT
Voice calls good quality
IRIDIUM “NEXT” initial launch 2015, Operational 2017.
INMARSAT could not be present in the meeting.
FIT has been monitoring the use of Iridium SATCOM for the provision of FANS communications supporting CPDLC and ADS-C since In conjunction with FAA sponsored Communication Working Group (CWG), ATSUs in the region have participated in the trials and have applied the same system performance monitoring criteria as used with INMARSAT systems. As a result of the efforts undertaken by the FIT and CWG, the FAA stated that they are drafting a letter agreeing with the assessment of the CWG, that Iridium systems that meet the appropriate requirements be allowed for use with FANS CPDLC and ADS-C without restrictions and on equivalent basis as traditional INMARSAT systems. The meeting was however reminded that the approval of Iridium satcom for use with FANS based CPDLC and ADS-C systems was still pending.
Airbus informed the meeting that they were evaluating use of Iridium satcom both for voice and data-link services and the early results of these tests were looking promising. An A320 flight test aircraft had been fitted with an Iridium based satcom system providing both voice and data link communications over Iridium network. No interference was noted with GPS system. However some interference was experienced with INMARSAT satcom, but not measured. Voice calls were established with a good quality during up to 30 min, including the flight maneuvers, with successful recording on CVR. Simultaneously, FANS A+ over Iridium capability (using SITA service) had also been successfully assessed, as well as AOC messages exchange and F-PLN uplink.
Iridium SATCOM is working with both the DSPs and internally to ensure timely notification of any outages. It was noted by at least one ATSU in the meeting that they are still not getting service notifications. Iridium also provided an update to the meeting on their plans to replenish the existing satellite constellation. Iridium “NEXT” is a funded programme to the tune of three billion dollars US. Both satellite manufacture and launch partners are under contact and are working on the programme. Initial launch is targeted for Eighty one space vehicles will be built and seventy one will be launched. The new constellation is expected to be operational in The new constellation will be backward compatible with the existing aircraft equipment and for transceiver it is being designed to provide 1.4 Mbps throughput to the aircraft. The Iridium “NEXT” implementation will also provide additional ground earth station access points to mitigate the “rain fade” issues which has been identified as a concern area.
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9. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
NATSPG
NATSPG Conclusion 46/02 endorsing draft proposal to amend NAT SUPPs mandating carriage/use of CPDLC & ADS-C
NAT DLMA providing service, but needs data in format from ATSUs for becoming operational
Noted Satellite data-link met 95% criteria for RCP 240
SBB & oceanic safety trials planned for 2012
INMARSAT clarified I-3 Classic Aero equipped aircraft will gradually begin utilizing I4 network.
Forty Seventh Meeting of The ICAO North Atlantic Systems Planning Group (NAT SPG/47) was held in Paris from 13 to 16 June 2011.
The NAT SPG was provided information on the status of NAT SPG Conclusion 46/02 which had endorsed a draft proposal for amendment to the NAT SUPPs mandating the carriage and use of CPDLC and ADS-C in the specified portion of ICAO NAT Regional. It was recalled that the proposal had been distributed for global circulation by the EUR/NAT Office on 14 September The proposal was revised consequent to consultations and was forwarded to ICAO for approval. Issues related to the exemption of this requirement were also discussed. It was informed that though the NAT Data Link Monitoring Agency (NAT DLMA) was providing its service, several NAT service providers were still in the process of upgrading their ground automation systems in order to be able to provide data in the format required. It was reiterated that the completion of these actions will allow the establishment of a fully functional NAT data link monitoring system and enable the declaration of NAT data link fully operational.
go to para 3.2
3.2.2 NAT SPG noted that the reported satellite and VHF data link performance met the 95% criteria for RCP It was informed as a part of the FANS 1/A over Iridium (FOI) project performance observed over New York FIR indicated encouraging results. It was informed that Swift Broadband oceanic safety trials are planned for mid INMARSAT clarified that the I3 Classic Aero equipped fleet, with the exception of a decreasing portion of older generation aircraft, should largely continue to be “FANS 1/1 over INMARSAT” capable, would gradually begin utilizing the I4 network and would not require any changes to the on-board equipment. This, however has not been formally included in the INMARSAT policy document.
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10. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
APANPIRG
SAT DATA-LINK performance issues raised in APANPIRG Sub-Groups in 2008
APANPIRG/19 asks ICAO to organize meeting of stake-holders to develop solutions
SOCM/1 organized from 26 to 28 August, 2009
56 participants from 13 States, International Organizations, Industry attended
5 Working and 16 Information papers were presented and several presentations were made
In our region, concern over satellite data-link performance and related funding and technical issues was raised in APANPIRG Sub-Group meetings in APANPIRG in September 2008 adopted Conclusion 19/24 inviting ICAO to organize a meeting for the stakeholders to review the performance and provision of satellite data-link communication in the Asia/Pacific region and develop a solution to mitigate the problems faced, both technical and operational by the civil aviation community.
First meeting of Satellite Data-link Operational Continuity Meeting of SOCM/1 was organized here in ICAO Asia/Pacific Office from 26 to 28 August, The meeting was attended by 56 participants from 13 States, IATA, IFALPA, ARINC, SITA, Boeing, INMARSAT, MTSAT and Thrane & Thrane.
5 Working and 16 Information Papers were presented in addition to a number of presentations made on the relevant subject.
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11. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
SOCM/1 OUTCOME
Communication and Surveillance specifications included in the GOLD as Appendices B and C
States and IATA urged to provide information for Appendices E and F of the GOLD Document
Satellite data-link critical requirement for the implementation of RNP-4 -- IATA
ICAO views that multiple redundant connectivity has potential of improving availability
Significant Outcome of the First Satellite Data-link Operational Continuity Meeting or SOCM 1 included
Stake holders including ATS organizations and service providers provided information on the developments that have been carried out by them to improve performance and reliability of the Satellite Data-link Communication system.
Communication and Surveillance performance specifications to support operations were reviewed, including for RCP 240/D and RCP 400/D and it was noted that relevant RCP and Surveillance specifications had been included in the GOLD as Appendices B and C
A draft Conclusion was formulated, urging States to provide relevant Regional and State information and urged IATA to coordinate with member airlines in order to provide operator and aircraft information for inclusion in GOLD Appendices E and F
States provided information on the status of implementation of satellite data-link in their administrations and highlighted the trials being conducted
IATA provided airline’s perspective on the subject and was of the view that unless satellite data-links were deployed, the plans to implement RNP-4 could not be completed.
SITA, MTSAT, ARIN, INMARSAT, Thrane and Thrane and other agencies engaged in the provision of infrastructure informed about the developments their organizations were carrying out to improve access, performance and reliability of their systems; and
ICAO was of the view that multiple redundant connnectivity (accessing the same satellite through multiple ground stations and/or achieving connectivity through multiple redundant satellites) had the potential of significantly improving overall network availability.
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12. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
QUESTIONS RAISED
Options available for Satellite data-link considering business model
Service life left on I3 Network to recover investment after implementing upgrades
PARC CWG investigating use of IRIDIUM Satellite Short Burst Data (SBD)
Requirement of performance specs to support “longer term” operational initiatives.
Following questions were raised during the SOCM/1
Is maintaining I-3 network the best option considering the business model and planned initiatives from the users’ perspective, or other alternatives should be considered
Given the lead time required for implementing upgrades for the Satellite Data Unit or SDU, will there be enough service life left on the I-3 network (through 2017) to recover the investment.
Are there other viable solutions which can be considered? Subsequently it has been learnt that at the IPACG/29 FIT/16, FAA briefed the group on the work currently underway within the Performance Based Operations Aviation Rule making Committee’s or PRC Communication Working Group or CWG which is investigating use of the IRIDIUM Satellite Short Burst Data (SBD) for FANS 1/A data-link applications. FAA PARC CWG/25 meeting was held in Seattle along with the Second Meeting of ICAO Inter-Regional SATCOM Voice Ad Hoc Task Force from 12 to 16 September, 2011
Will aviation community need new performance specifications to support planned “longer term” operational initiatives? However new standards may be required to reduce separation further or for other operational capabilities that would require ‘more stringent’ RCP specifications.
SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING

13. Project title (Insert, Header & Footer)
SOCM/2
Following issues were recommended in SOCM/1 for discussion in SOCM/2
Review Status of Satellite Data-link Communication in the Region
Develop common Outage/Maintenance Reporting Template for STATEs/ANSPs/CRAs
Develop a common service level agreement between CSPs and States/ANSPs
Mid/Long Term Strategy for Satellite Communication beyond 2016
SOCM/1 expressed its concern about the availability of data link services after the life of some INMARSAT and MTSAT satellite expires in 2016 and recommended the Second SOCM to address issues which include:
Review the status of Satellite Data-link Communication in the region
Implementation of improvements plan by the stake holders to develop a common outage/maintenance reporting template and process by Communication Service Providers which is useful for States/ANSPs/CRAs
Develop a common service level agreement between CSPs and the States/ANSPs based on the recommendations in the GOLD
Develop a Mid/Long Term Strategy for Satellite Communication beyond 2016 including requirements for the modification to SATCOM satellite data unit or SDU to enhance the capability to access multi-satellite service providers and whole I3/I4 networks.
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14. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
DATALINK PERFORMANCE
Data-link performance significantly improved, safety target being achieved, efficiency target to be met
APANPIRG/22 noting the pre- and post-implementation system performance monitoring requirements, urged States in the APAC Region to ensure that the appropriate data link performance monitoring is undertaken and reported to CRAs/FITs, as required, in a timely manner. (APANPIRG Conclusion 22/12)
New Zealand, providing satellite data-link monitoring results from Auckland Oceanic FIR to the CNS/MET SG/15 in July 2011 informed that the performance had shown significant improvement since July Statistical data collected from December 2008 to June 2011 indicated that the safety targets for network availability were being achieved, however considerable work needs to be done to meet the efficiency targets.
The Requirements specified in the Annex 11, GOLD and the GM for end-to end safety and performance
Monitoring of ATS data link system in the Asia/Pacific Region, urged States in the APAC Region to ensure that the appropriate data link performance monitoring is undertaken and reported to CRAs/FITs, as required, in a timely manner.
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15. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
CONCLUSION
Safety targets for RNP-4 met, Efficiency target yet to be met
ICAO recommends use of two or more autonomous systems
Mid/Long Term strategy to be developed in view of end of lifetime of satellites
The presentation concludes with the highlighting of the following significant issues, which need to be worked upon
It can be concluded that though currently the safety targets prescribed for the RNP-4 operations are being met, considerable work needs to be done to meet efficiency targets.
ICAO recommends usage of two or more autonomous satellite data-link systems, both for the ground and on board the aircraft to enhance availability of the system
With the end of life approaching for some INMARSAT and MTSAT satellites, continuity of service beyond 2016 needs to be ensured.
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16. SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING
THANK YOU
SECOND SATELLITE OPERATIONAL DATA-LINK CONTINUITY MEETING