File an ordered aggregation of interrelated

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Unformatted text preview: ocess. FILE: An ordered aggregation of interrelated Telecommand Packets corresponding to a single, well defined spacecraft activity. A TC File has three distinguishing characteristics: 1) it has a File name; 2) it has a pre-defined length; and 3) it must be delivered intact and complete before being released for execution. MULTIPLEXER ACCESS POINT (MAP): An input port to the TC Segmentation layer which enables all user data units who are members of the sequence present at that port to be uniquely identified. Use of MAPs permits different streams of user data to be multiplexed together onto one Virtual Channel for flow control purposes. OCTET: An 8-bit word consisting of eight contiguous bits. PACKET: The protocol data unit of the TC Packetization layer which facilitates the end-to-end transport of command application data. The application data are encapsulated within a leading packet header. PACKETIZATION LAYER: The bottom layer in the Telecommand Data Management Service. Issue 6 Page A-5 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE PHYSICAL LAYER: The bottom layer of the TC Channel Service. PHYSICAL LAYER OPERATION PROCEDURE (PLOP): A sequence of procedural activities designed to activate and deactivate the physical telecommand channel by invoking radio frequency carrier and modulation techniques. PROTOCOL: A set of standard rules and procedures, plus their accompanying format conventions, that define the orderly exchange of information between peer entities within a given layer of the TC System. RELIABLE: Meeting the data quality, quantity, continuity, and completeness performance criteria which are specified for the Telecommand System. SEGMENT: The protocol data unit of the TC Segmentation layer which facilitates breaking long user data units into shorter, communications-oriented pieces and multiplexing them together for flow control purposes. SEGMENTATION LAYER: The upper layer of the TC Data Routing Service. SESSION: A period of time throughout which the sending and receiving ends of the TC System communicate for the purpose of transferring TC data. SYMBOL: A serial representation of bits, or binary digits, which have been encoded to protect them against transmission induced errors. SYSTEM MANAGEMENT LAYER: The middle layer of the Telecommand Data Management Service. Issue 6 Page A-6 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE TELECOMMAND: A generic term used to describe command data during the time that they are being telecommunicated to the spacecraft. TELECOMMAND SYSTEM: The end-to-end system of layered space mission telecommunication services which exist to enable a user to send commands, in a reliable and transparent error-controlled environment, to receiving elements in space. TRANSFER FRAME: The protocol data unit of the TC Transfer layer, which facilitates the transfer of TC data to a spacecraft through a space data link. TRANSFER LAYER: The lower layer of the TC Data Routing Service. TRA...
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This document was uploaded on 03/06/2014.

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