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internationalization as the key to affordability, these standardized cross-support services will
become increasingly important.
Figure 2-1 illustrates the recommended CCSDS Telecommand System architecture in terms of
a layered set of telecommand services: the operations within each layer are detailed in
Issue 6 Page 2-1 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE APPLICATION PROCESS LAYER
COMMAND DIRECTIVE TELECOMMAND,
PART 3: DATA
MANAGEMENT SERVICE SYSTEM MANAGEMENT LAYER
TC APPLICATION DATA
PACKETIZATION LAYER PACKET SEGMENTATION LAYER TELECOMMAND,
PART 2: DATA
ROUTING SERVICE SEGMENT
TRANSFER LAYER TRANSFER FRAME CODING LAYER TELECOMMAND,
PART 1: CHANNEL
PHYSICAL WAVEFORM Figure 2-1: Issue 6 CCSDS Telecommand System Page 2-2 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE Figure2-2. The layers of TC service are functionally grouped into a "Data Management
Service", a "Data Routing Service", and a "Channel Service". Each of these three major
architectural components of service is separately specified in its own CCSDS technical
Recommendation, i.e., References , , and . The detailed retransmission protocols
associated with the Data Routing Service are contained in Reference . Taken as a whole,
these four Recommendations (three architectural specifications and one detailed specification)
form a system which provides the user with reliable and transparent delivery of telecommand
The three main architectural components of service reflect increasing sophistication in terms of
telecommand delivery. The Channel Service provides and controls a single reliable physical
connection to the spacecraft. The Data Routing Service may be overlayed on the Channel
Service to provide channel multiplexing capabilities, and to ensure the reliable delivery of
buffers of telecommand data. The Data Management Service may be overlayed on the Data
Routing Service to supply individually addressed end-to-end transportable command data units
to each user, and to provide overall TC System coordination, integration, and management.
Since each layer is independent of the layers above, individual missions may make their own
decisions concerning how "high" in the layered hierarchy they wish to be compatible. 2 . 2 TELECOMMAND SERVICE CONCEPT
The system design technique of layering is a key tool for transforming service concepts into
sets of operational and data formatting procedures. Layering (the strategy of "dividing and
conquering") allows a complex procedure such as spacecraft commanding to be decomposed
into sets of relatively simple peer functions residing in common architectural strata. Within
each layer, the functions exchange information using standard data formatting techniques and
standard procedural rules or "protocols".
Each layer of the TC System draws upon a well defined set of services provided by the layer
below, and provides a similarly well defined set of services to the layer above. As lo...
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This document was uploaded on 03/06/2014.
- Spring '14