The Cospas-Sarsat Data Distribution Plan
Cospas-Sarsat alert data generated by LEOLUTs and GEOLUTs are distributed to the appropriate Rescue Coordination Centre (RCC), according to the computed position of the distress and/or the country code of the beacon. Due to the high degree of redundancy in the Cospas-Sarsat Ground Segment (each operational LUT is capable of providing essentially the same data in the global mode of operation), such distribution must be coordinated and redundant data filtered out of the ground communication network.
Each LUT is linked to an associated Mission Control Centre (MCC) and alert messages are forwarded to the appropriate RCC through the MCC communication network, in accordance with the procedures described in the Cospas-Sarsat Data Distribution Plan (C/S A.001).
For the purpose of distributing alerts, Cospas-Sarsat has established five data distribution regions (DDRs), each being supported by a nodal MCC. Within each DDR there may be several MCCs responsible for the distribution of alerts for a specific geographic area (MCC service area). Alerts are routed by the Cospas-Sarsat data distribution network to the MCC whose service area supports the region where the alert was located. It is that MCC responsibility to forward the alert to the appropriate RCC or Search and rescue Point Of Contact (SPOC). Alerts which must be distributed beyond DDR boundaries are routed via nodal MCCs, and then onto the MCC responsible for the service area concerned. Cospas-Sarsat allows for additional bilateral communication arrangements to exist between MCCs to facilitate the transfer of alert information in certain cases.
Cospas-Sarsat MCC Service Area
Each Cospas-Sarsat MCC is responsible for distributing all alert data for distresses located in its Service Area. An MCC Service Area includes aeronautical and maritime Search and Rescue Regions (SRRs) in which the MCC's national authorities facilitate or provide SAR services, and includes in addition such regions of other countries with which the MCC's national authorities have appropriate agreements for the provision of Cospas-Sarsat alert data.
MCC Service Areas are established following coordination among Cospas-Sarsat Ground Segment Providers (i.e. LUT-MCC Operators), through the Cospas- Sarsat Joint Committee, taking into account:
- geographical location and common SRR boundaries
- communication capabilities
- existing national SAR arrangements and existing bilateral operational agreements
Agreed MCC Service Areas are described in the Cospas-Sarsat Data Distribution Plan. When a Cospas-Sarsat beacon transmission is located outside the Service Area of the MCC which receives the alert, the alert message is either forwarded to the MCC serving the area where the distress has been located, or is filtered out if the alert data has already been received through another LUT/MCC.
Cospas-Sarsat alert messages are exchanged among MCCs according to standardized message formats. The detailed structure of messages for distribution of alert data and system information are described in document C/S A.002 "Cospas-Sarsat Mission Control Centres Standard Interface Description (SID)".
The Cospas-Sarsat SID formats have been defined to allow for the transmission of alert messages on any communication system as agreed between MCCs and between a Cospas-Sarsat MCC and its associated RCCs or SPOCs. Alert messages in SID formats can be routed and processed by MCCs automatically.
In addition to telephone (voice and/or facsimile) communications, all Cospas- Sarsat MCCs are required to have access to at least two international data networks for transmitting alert messages in order to provide maximum availability and adequate flexibility for the exchange of alert data. MCCs transmit alert data to other MCCs, SPOCs or RCCs using the following systems:
- Automatic Fixed Telecommunication Network (AFTN) of Civil Aviation
- Packet data networks (X.25)
- File Transfer Protocol over Virtual Private Network (FTP-VPN)
AFTN addresses, telephone or facsimile numbers are given in the Cospas-Sarsat Data Distribution Plan (C/S A.001). Prior coordination may be necessary between the MCC operator and SPOCs in its Service Area to agree on communication systems and interfaces to be used.
To ensure that Cospas-Sarsat alert and location data is distributed efficiently, IMO and ICAO have invited each of their Member states to designate a national SPOC and to provide the required information on available communication links either to IMO, ICAO, or the Cospas-Sarsat Secretariat.