I.B. + M.A. DE LANDE LONG
SOFTWARE + CONSULTANCY

Telecommand Decoder Shell

The Telecommand Decoder Shell package is a commercial off-the-shelf software component which implements the space based parts of a telecommand system, including the TC Space Data Link Protocol, the Communications Operation Procedure (COP-1) and the channel coding (BCH code).

It is designed to be highly portable so that it is easy to use for building into different software systems, such as spacecraft simulators and on-board telecommand decoders. It is also ideal for building demonstration systems. To demonstrate ground system telecommand elements to users or customers, there is no need for spacecraft hardware: the Shell can be used to build a software-based simulation of the spacecraft behaviour.

The Shell has an API (Application Programming Interface) which provides access to the telecommand facilities. The API uses calls in ANSI-C.

TC Decoder Shell on-board application

The Telecommand Decoder Shell accepts the incoming telecommand data. The data can be supplied as Communications Link Transmission Units (CLTUs) each containing a telecommand transfer frame, or as the candidate BCH codeblocks of a CLTU. The Shell delivers packets and the other SDUs (service data units) defined for the TC Space Data Link Protocol. It also delivers Communications Link Control Words (CLCWs) for the spacecraft telemetry.

The facilities and interfaces of the Telecommand Decoder Shell package are described further in the detailed description.

Optional feature: Telecommand authentication with ESA AU

The Shell can provide support for ESA Telecommand Authentication as an optional extra. When this option is selected, the Shell validates the authentication tail of telecommand segments.

Optional feature: Interface for external security

The Shell can provide an interface for external implementation of security features such as authentication. The Segment Level Security Interface (SLSI) is an optional extra. When this option is selected, the Shell passes incoming segments to the interface for processing.

Optional feature: Failure simulation for test systems

The Telecommand Decoder Shell package has a unique feature: Built-In-Failures (BIFs). The BIFs can be switched on and off for testing the response of the ground system to spacecraft exceptions. This controlled generation of spacecraft errors is an advantage of our software-based telecommand decoder. However, the capability could create a risk in operational applications, so the BIF interface is not in a standard release. A modified release of the Telecommand Decoder Shell which includes the BIF interface is available on request.

Please contact us for further information on technical questions or licensing conditions for the Telecommand Decoder Shell package.

Detailed Description TC Features Operational Applications