Self-Timed DCP Messages are generated by a platform according to an internal schedule. NOAA assigns time-slices and GOES channel numbers.
- Random DCP Messages are generated by a platform in response to some environmental trigger. These are sent over a separate ‘random’ channel. Since there is a possibility of collision, the DCP will typically send 3 copies of the message at random time intervals.
- Retransmitted DCP messages: If you are receiving data from one of the DAPS rebroadcasts (DOMSAT, NOAAPORT, LRIT, DDS) you may see historical messages. These are sent from time to time in response to a user’s request.
- DAPS-generated status messages: In many cases, DAPS will generate a separate status message transmitted immediately after the normal DCP message to indicate some type of failure (e.g. a message received on an unexpected channel). The header will contain the DCP address and the message body will explain the error condition. See the above discussion on ‘Failure Code’ for a list of possible codes.
- Global Bulletins: The DCP address is hex 11111111. These are from the DAPS administrator addressed to all users of the DCS.
- DCP Bulletins: The DCP address is hex 22222222. These are messages from the DAPS administrator addressed to all users of a particular DCP. The platform address is contained in the first 8 bytes of message data.
- Electronic Mail: The DCP address is hex 33333333. These are from the DAPS administrator addressed to a particular DCS user. The first 8 characters of message data contain the DAPS user-ID of the addressee.
- ‘DAPS-ALIVE’ Messages: The DCP address is hex DADADADA. This message is sent out periodically only if there is no other DOMSAT traffic to guarantee that at least one message will be sent per minute over DOMSAT.