DSP implementation of integrated store-and-forward APRS payload and OBDH subsystems for low-cost small satellite

The developed system, based on the DSP (Digital Signal Processor), provides an integrated store-and-forward APRS (Automatic Packet Reporting System) payload and OBDH (On Board Data Handling) subsystems at a very low cost and on a single board with dimensions less than 10 cm × 10 cm, thereby enabling a new level of performance for CubeSat-class spacecraft. In this paper, we consider the problem of designing a low-complexity AFSK and GMSK modems for a satellite communication link where the constraints on satellite power budget, antenna size, and data rate are such that the available transmit power, aboard the Picosatellite, is 1 Watt. To cut down the cost of the Picosatellite, we give a particular attention to software optimization due to use of small amount of 8K words Radiation Hardness ROM memory containing the application program. We have defined a methodology approach based on two design steps: algorithmic optimization, and optimal programming using Assembler language. Due to the radiation in space and the constraints of the Picosatellite, some measures regarding volume, mass, power, cost and radiation tolerance, had to be taken into consideration when the system was designed.