It should also be noted that the layered hierarchy

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Unformatted text preview: ure work for the CCSDS. It should also be noted that the layered hierarchy does not also imply that the time-ordered FLOW of operations through the layers is necessarily sequential. For instance, it is perfectly valid to pre-assemble and pre-number TC Frames, pre-encode them, batch them into CLTUs and then put the prefabricated CLTUs "on the shelf" for later radiation under control of the Transfer layer FOP and the Physical layer PLOP. The inter-layer control instructions must accommodate such non-time-sequential operations. 3 . 5 INTER-AGENCY CROSS-SUPPORT SERVICES A major feature of the layered CCSDS TC System architecture is its potential for providing a significantly more comprehensive level of cross support between Agencies than is possible at present, thus enabling the development of simple and cost-effective interfaces for the wide range of international space missions which are anticipated in the future. However, the present CCSDS Recommendations have not addressed the physical implications of cross support. The CCSDS has established a systems panel to study and recommend the various inter-Agency cross-support gateways and service access points. The current status of this work may be found in Reference [10]. Issue 6 Page 3-15 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE ANNEX A ACRONYMS AND TERMINOLOGY Issue 6 Page A-1 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE ACRONYMS CCSDS : CLCW: CLTU: CMD: CMM: COP: FARM: FOP: HDR: ID: MAP: N(R) : CONSULTATIVE COMMITTEE FOR SPACE DATA SYSTEMS COMMAND LINK CONTROL WORD COMMAND LINK TRANSMISSION UNIT COMMAND CARRIER MODULATION MODE COMMAND OPERATION PROCEDURE FRAME ACCEPTANCE AND REPORTING MECHANISM FRAME OPERATION PROCEDURE HEADER IDENTIFIER MULTIPLEXER ACCESS POINT THE VALUE OF V(R) WHICH IS OBSERVED BY THE FOP IN A PARTICULAR CLCW N(S) : THE SEQUENCE NUMBER ASSIGNED BY THE FOP TO A PARTICULAR TRANSMITTED TC FRAME PKT: PACKET PLOP: PHYSICAL LINK OPERATIONS PROCEDURE RF, rf: RADIO FREQUENCY S/C : SPACECRAFT SEG : SEGMENT ST SEQ: START SEQUENCE TC: TELECOMMAND TLM: TELEMETRY VC: VIRTUAL CHANNEL V(R) : THE NEXT EXPECTED TC FRAME SEQUENCE NUMBER; A COUNTER MAINTAINED BY THE FARM V(S) : THE SEQUENCE NUMBER WHICH THE FOP WILL ASSIGN TO THE NEXT TRANSMITTED TC FRAME Issue 6 Page A-2 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE TERMINOLOGY ACCEPT: Within the Transfer layer, recognition by the receiving end that a TC Frame has passed the validation and acceptance test criteria as programmed into the Frame Acceptance and Reporting Mechanism. APPLICATION PROCESS LAYER: The upper layer of the Telecommand Data Management Service. CHANNEL SERVICE: In the space data systems layered service architecture, the bottom service of the Telecommand System. Among its services it delivers the encoded bits of a buffer of transfer frames across the physical communications link under error-controlled conditions. CLEAN: Data which are declared to be error free within the error detection and (optional) error correction capabilities of the...
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