Design of Telecommand Software and Packet Structure for Lunar Landing Mission

TeamIndus lunar landing mission objectives include enabling lunar lander to soft land on Moon, traverse the rover on the surface of Moon and send high definition videos and images to Earth. The lander is controlled by a Lander On-Board Computer (LOBC) card consisting of a SPARC processor. The spacecraft is required to be commanded by ground station for multiple scenarios: execute commands immediately, execute commands at a particular time, execute sequence of commands, execute commands after certain event has expired and execute memory management commands. The limited availability of uplink bandwidth requires optimal design of telecommand packet structure. In order to provide ease of operation of spacecraft and reuse of already uplinked command, programmability and flexibility features are provided by telecommand processing (TCP) software. This paper describes telecommand processing software implementation on LOBC and packet structure design for Real time commands, Absolute time tagged commands, Differential time tagged commands, Patch commands, Configurable command blocks and Event based commands. The autonomy features of the designed TCP software has minimized ground intervention and hardcoding of sequence based modules. The general purpose TCP software does not change with modifications in the packet structure or commands in the mission command dictionary, making it reusable across various missions.