Dynamic Command and Data Handling Ground Station Software

After launch of a spacecraft, the role of the ground station software becomes critically important. The command and data handling software issues telecommands to the spacecraft, and retrieves, displays and stores telemetry from the spacecraft. The key feature of the dynamic design of the software described in this paper lies in the independence of the software graphical user interface (GUI) from the number of subsystems, telemetry channels and telecommands required at the design time and number of remote users at runtime. This independence enables to software to produce various graphical user interfaces with a unique number of telemetry channels and telecommands for users with different needs, preferences or privileges. The dynamic software layout is definable in the form of a configuration database. The data file is read by software at the time of initialization and user interface is built as defined in the file. Out-of-limit values for every telemetry channel are highlighted as defined in the configuration database. The user interface is powerful enough display a single telemetry channel into multiple units by simply defining different parameters for the channel. The graphical user interface is designed using multiple pages, with a tables of telemetry and telecommands on each page. Every telemetry and telecommand database entry contains page number, row and column of position, caption, unit, channel number, data type, minimum and maximum values and calibration equation for the channel to convert raw digital values to standard units. User account information and privileges in the form of allowed channels are also stored in the database. The reliability of the software is implemented by inherent redundancy of its distributed design. Multiple instances of the software may execute on different machines with multiple users with various privileges. These instances are made able to communicate with the spacecraft simultaneously without any data collision using a master-slave communication architecture. The software is designed to be built on widely used platforms. A Microsoft Windows platform was selected for the development of the software and Visual C++ 6.0 was selected as the language to build the system. The complete software system enables a user to log in from remote locations, view and analyze telemetry and issue sequences of telecommands. Security is implemented by privilege assignments to every user account. The paper gives a brief introduction about ground station, followed by the software requirements, architecture, security issues, and dynamic interface implementation. The overall performance, results of the software are described.