Payload transmitter unit

Abstract

The payload transmitter unit is primarily the living brain of a satellite and comprises of several small modules. Initially, it was accepted as part of PNSS-1 from SUPARCO but, due to delay in funding instead of space/military grade components, normal off the shelf low cost components have been utilized to achieve almost the same results as envisaged through PNSS-1. It consists of transceiver and is capable of receiving the control signal from ground station transmitter on the basis of which it transmits all telemetry information i.e. temperature, current and humidity to ground station employing BPSK modulation at data rate of 256Kbps. In addition it is capable of receiving frequency modulated voice/audio signal from ground station and retransmit at another frequency of 110MHz to the ground station. In order to incorporate the telemetry information in the payload transmitter, only temperature sensor and one humidity sensor are being used along with current sensing design, interfaced through PIC microcontroller 16F877A. Arrangements have been made to display the received information on LCD device.