Unformatted text preview: ng network,
are completely dedicated to that mission. The lack of effective standardization among various
missions forces the ‘multi-mission’ tracking network to implement the lowest level of
telemetry transport service, i.e., bit transport. Higher level data delivery services, oriented
more toward computer-to-computer transfers and typical of modern day commercial and
military networks, had to be custom designed and implemented on a mission-to-mission
The intent of the CCSDS Telemetry System is not only to ease the transition toward greater
automation within individual space agencies, but also to ensure harmony among the
agencies, thereby resulting in greater cross-support opportunities and services.
The CCSDS Telemetry System is broken down into two major conceptual categories: a ‘TM
Space Data Link Protocol’ concept (references  and ) and a ‘TM Synchronization and
Channel Coding’ concept (reference ).
a) TM Space Data Link Protocol is a concept which facilitates the transfer of spaceacquired data from source to user in a standardized and highly automated manner.
TM Space Data Link Protocol provides a mechanism for implementing common data
structures and protocols which can enhance the development and operation of space
mission systems. TM Space Data Link Protocol addresses the following two
1) The end-to-end transport of space mission data sets from source application
processes located in space to distributed user application processes located in
space or on Earth.
2) The intermediate transfer of these data sets through space data networks; more
specifically, those elements which contain spacecraft, radio links, tracking
stations and mission control centers as some of their components. CCSDS 130.1-G-1 Page 2-1 June 2006 TM SYNCHRONIZATION AND CHANNEL CODING —SUMMARY OF CONCEPT AND RATIONALE The TM Space Data Link Protocol Recommended Standard contained in
references  and  is primarily concerned with describing the telemetry formats
which are generated by spacecraft in order to execute their roles in the above processes.
b) TM Synchronization and Channel Coding (reference ) is a method by which data
can be sent from a source to a destination by processing it in such a way that distinct
messages are created which are easily distinguishable from one another. This allows
reconstruction of the data with low error probability, thus improving the performance
of the channel. The TM Synchronization and Channel Coding Recommended
Standard contained in reference  describes several space TM Synchronization and
Channel Coding schemes. The characteristics of the codes are specified only to the
extent necessary to ensure interoperability and cross-support.
Together, TM Space Data Link Protocol and TM Synchronization and Channel Coding
services provide to the user reliable and transparent delivery of telemetry information.
Figure 2-1 illustrates the CCSDS Telemetry System in terms of a layered service
model. It should be noted that the CCSDS TM Space Data Link Protocol and TM
Synchronization and Channel Coding Recommended Standards only address the five
lower layers of this model.
LAYER SERVICE PROVIDED BY LAYER
PROVIDES USERS A METHOD TO INVESTIGATE PHYSICAL
PHENOMENA BY USING THEIR INSTRUMENTS IN SPACE
FOR DATA COLLECTION AND THEIR APPLICATION
PROCESSES FOR ANALYSIS. PROVIDES TRANSLATION OF PHYSICAL MEASUREMENTS
INTO SETS OF APPLICATION DATA UNITS. TLM
LAYER PROVIDES END-TO-END DELIVERY OF APPLICATION
DATA UNITS. PACKET
LAYER (OPTIONAL) PREPARES LONGER PACKETIZED DATA UNITS
FOR MULTIPLEXING AND TRANSFER THROUGH A SPACE
DATA CHANNEL. SEGMENT
LAYER PROVIDES RELIABLE TRANSFER OF PACKETS AND SEGMENTS
IN A COMMON STRUCTURE FOR THEIR TRANSPORT THROUGH
THE SPACECRAFT-TO-GROUND COMMUNICATION LINK. TRANSFER
LAYER PROTECTS TRANSFER FRAMES AGAINST ERRORS INDUCED
DURING TRANSMISSION THROUGH THE NOISY PHYSICAL
COMMUNICATIONS CHANNEL. TLM
LAYER PROVIDES THE PHYSICAL CONNECTION, VIA RADIO
FREQUENCY SIGNALS, BETWEEN A TRANSMITTING
SPACECRAFT AND THE RECEIVING STATION. PHYSICAL
WAVEFORM Figure 2-1: Layered Telemetry Service Model CCSDS 130.1-G-1 Page 2-2 June 2006 TM SYNCHRONIZATION AND CHANNEL CODING —SUMMARY OF CONCEPT AND RATIONALE 2.2
2.2.1 TELEMETRY SYSTEM CONCEPT
GENERAL The system design technique known as layering was found to be a very useful tool for
transforming the Telemetry System concept into sets of operational and formatting
procedures. The layering approach is patterned after the International Organization for
Standardization’s Open Systems Interconnection layered network model (reference ),
which is a seven layer architecture that groups functions logically and provides conventions
for connecting functions at each layer. Layering allows a complex procedure such as the
telemetering of spacecraft data to the users to be decomposed into sets of peer functions
residing in common architectural strata.
Within each layer, the functions ex...
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- Spring '14
- Information Theory, ........., Error detection and correction, CCSDS