Telemetry Unit

Telemetry unit is an important unit of a CubeSat, which is responsible for communication with the ground station. Half-duplex software configurable radio transceiver will be used for long range transmissions. The combination of forward error correction, AFC and digital filters results in a high sensitivity system, without sacrificing flexibility. The radio module supports full on-orbit reconfiguration of the frequency, bitrate, filter-bandwidth, and modulation type. Smart CSMA/CA (Listen before talk) medium access control combined with a small RX/TX switching duration gives a short satellite ping time, thus efficiently removing the need for full-duplex radios, even for high volume data download. In turn this simplifies satellite design, because only a single antenna is required.The integrated design of microcontroller, transmitter, receiver, RAM memory, LNA and power amplifier results in a small PCB module. Working on advanced high performance narrow-band transceiver for UHF (430-440 Mhz). Modulation technique used can be FSK/MSK/GFSK/GMSK. Data rates from 0.1 kbps to 115.2 kbps.

Communication Subsystem

The primary goal of the communication subsystem is to provide a link to relay data findings and send commands to and from the SHUNYA. Telemetry and command subsystems will ensure continuous communication between the ground station and the SHUNYA after ejection from the rocket. The SHUNYA communication system is composed primarily of the telemetry and command systems, which send and receive data, respectively. Analog and digital data collected by the sensors and payload of the satellite must be relayed to the ground station via the telemetry system, which is composed of a transmitter that acts much like a “modem in a computer”. The microcontroller will accumulates data from the sensors and convert these inputs into a stream of 8-bit binary numbers. This numerical string is encoded into AX.25 protocol by the terminal node controller (TNC), which serves to “packetize” the information and key the transmitter. The transmitter then sends the signal to the ground station through the satellite. A radio operating in the ultrahigh frequency (UHF) band at the ground station will receive the data signal and encode the stream to a form that may be interpreted by software on a laptop