Message Abstraction Layer

The Spacecraft Monitoring & Control (SM&C) Working Group of the Consultative Committee for Space Data Systems (CCSDS), which sees the active participation of 10 space agencies and of the Space Domain Task Force of the Object Management Group (OMG), is defining a service-oriented architecture consisting of a set of standard end-to-end services between functions resident on board a spacecraft or based on the ground, that are responsible for mission operations.

), these application level services are implemented in terms of a smaller set of generic interaction patterns that allow current status to be observed, operations to be invoked and bulk data transferred.

Technology adapters allow the underlying communications infrastructure to be changed (or bridged) with minimal impact on the applications themselves.

To provide implementation language and message transport independence all operations of a service must be defined by a language/platform/encoding agnostic specification.

The MAL defines this set of basic data types and how they must be used to build up the messages that make up the operations of a service.

This only then has to be mapped once, in an MO standard, to a specific implementation language or transport encoding to apply to all services that are defined in terms of the MAL.

A benefit of implementing multiple services over a message abstraction layer is that it is easier to bind these to different underlying technologies and protocol encodings.

However, the use of the MAL removes any direct dependence of the application on the protocol technologies and therefore it is possible to isolate any evolution to lower adapter layers.