Standardization of Spacecraft and Ground Systems Based on a Spacecraft Functional Model

This paper proposes a method of standardizing spacecraft and their ground systems by using a spacecraft functional model. This model provides a standard way of designing and describing the functions of onboard components. It also enables development of a standard database that stores functional information on any spacecraft and any component. To monitor and control spacecraft and their components, we have developed a standard protocol called the Spacecraft Monitor and Control Protocol (SMCP). By using the fact that the functional information on any spacecraft and any component can be retrieved from the standard database, the design of SMCP is kept very simple. SMCP specifies types of command and telemetry messages, and the formats of command and telemetry messages for each specific spacecraft are stored in the standard database, too. Although onboard components are not necessarily standardized by this method, it can be said that the functional and operational aspects of components can be “virtually” standardized because the functional and operational information on components can be retrieved from the standard database. Furthermore, software that can be used to monitor and control any spacecraft and any component can be developed because it can retrieve the functional and operational information on specific spacecraft and their components from the standard database. This software can be used for testing components and spacecraft at the test center, operating spacecraft at the control center, and operating spacecraft autonomously on an onboard computer. Therefore, this method leads to standardization of both spacecraft and ground systems. I. Introduction RESENTLY the functional design of spacecraft onboard components is performed almost independently for each spacecraft and each component without using standards. This prevents reuse of onboard components and their supporting ground systems from spacecraft to spacecraft. Furthermore, there are no standards for description of functional design and operations rules for onboard components. Therefore, each designer has to devise a way of describing the functional design and operations rules for his or her components, and each operator has to learn how to read the descriptions written by the designers. In order to solve these problems, this paper proposes a method of standardizing spacecraft and their ground systems by using a spacecraft functional model. The Functional Model of Spacecraft (FMS) provides a standard way of designing the functions of onboard components. By using this model, reuse of functional design of onboard components will be easier because similar functions will be realized in similar ways. The FMS is based on the object-oriented software technology and uses the concept of functional objects. The functional object is a unit for the functions of spacecraft and onboard components and captures information necessary for operating spacecraft. By using a formal way (a data description language like XML or a graphical representation method like UML) of describing functional objects, a standard way of describing the characteristics of functional objects can also be obtained. The FMS enables development of a standard database that stores the functional information on any spacecraft and components by using the standard way of describing the characteristics of functional objects. This standard database is called the Spacecraft Information Base (SIB). Furthermore, by using the fact that there is a standard database that stores information on any spacecraft and any component, it becomes possible to develop application programs that can be used for any spacecraft and any component because information on specific spacecraft or component can be retrieved from the database.