Design of command and Data Management System for IITMSAT

In this paper we describe the design and development of the Command and Data Management System (CDMS) of the nano-satellite of IIT Madras, named IITMSAT. The CDMS module uses a 32-bit ARM microcontroller from Freescale - KL46Z256VLL4. This module is responsible for decoding the telecommands sent from the ground station, and transmits the time-stamped payload data back as telemetry packets. The SD card on the CDMS board stores the satellite's health and science data as and when it is acquired in the orbit. The data is transmitted to the ground station (GS) during the satellite's visibility period. The interface board (I/F) links the Flight Computer module and CDMS board along with other electronics onboard. Throughout the design phase, the cost was kept as low as possible, without compromising on performance of the system. Custom-designed protocol and data frame format for communication between the satellite and ground station was completely developed from scratch, based on CCSDS cubesat standards.