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Unformatted text preview: RNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE (5) Annex C describes a concept for the protection of Telecommand data sets so that
security measures may be implemented if required by a particular mission. (6) Annex D contains some application notes which discuss the performance aspects of
the telecommand system. Issue 6 Page 1-2 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE 2 OVERVIEW OF THE CCSDS TELECOMMAND SYSTEM 2 . 1 INTRODUCTION
A telecommand system must reliably and transparently convey control information from an
originating source (e.g., a human user) to a remotely located physical device or process. For a
space mission telecommand system, the controlled devices and processes are scientific payload
instruments or engineering subsystems onboard a spacecraft. Conventional space mission
telecommand systems often display a centralized, mission-unique data handling architecture,
with only a low level of data system standardization.
The introduction of more capable microprocessor-based spacecraft payloads and engineering
subsystems will result in data systems with greater throughput needs, and in a corresponding
increase in spacecraft autonomy and complexity. This technical environment, coupled with
fiscal constraints, leads to a common space mission requirement for greater telecommanding
capability and efficiency with reduced costs. The CCSDS telecommand concept addresses this
requirement by recommending standardized approaches to space mission data handling: it is
intended for use in conjunction with the standardized flow of telemetry data from instruments
and subsystems to the user, in accordance with the CCSDS concept for "Packet Telemetry"
(References  and ). Recognizing the need to cover a broad spectrum of mission needs,
the new CCSDS telecommand concept is applicable to spacecraft and ground data system
architectures which range from very simple and highly centralized to very complex and highly
For most past space missions, the telecommanding resources have been wholly contained
within one cognizant space agency. With the exception of elements of the ground tracking
networks, most of these telecommanding resources are completely dedicated and customized to
the requirements of each mission. The lack of effective standardization among the various
missions has forced the "multi-mission" elements of the tracking networks to implement a very
low level of supporting command service, i.e., the transport of bitstreams. Higher level
command services, oriented toward computer to computer transfers and typical of modern day
commercial and military data networks, must presently be custom designed and implemented
for space missions.
The CCSDS telecommanding architecture defines a comprehensive set of layered, standardized
command services which are applicable to a very wide range of mission needs. This
architecture will not only ease the transition towards the provision of more missionindependent command services within each individual space agency, but also will promote
technical harmony among all space agencies that can result in greater cross-support
opportunities and services. As more and more space missions look toward...
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This document was uploaded on 03/06/2014.
- Spring '14