COMMUNICATION SYSTEM
Communication system of the satellite is one the most important sub system, without which the satellite is just an object revolving around the earth. Our aim is to make a working communication system which can transmit signals to the satellite and receive the mission data from the satellite.
The communication subsystem consists of two major parts:
1. Telemetry, Tracking, and Command (TT&C)
2. The Ground Systems
1. TT&C
The TT&C provides the interface between the satellite and ground systems. Payload Mission data and satellite housekeeping data pass from the satellite through this subsystem to operator at operations centre. Operator commands also pass through this subsystem to control the satellite and to operate the payload. We must design the hardware and their functions to pass data reliably for all the satellites operating nodes.
The subsystem functions include:
a. Carrier Tracking (lock onto ground station signal)
b. Command reception and detection (receive uplink signal and process it)
c. Telemetry modulation and transmission (accept data from satellite subsystems, process them and transmit them)
d. Ranging (receive, process, and transmit ranging signals to determine satellites position)
e. Subsystem operations (process subsystem data, maintain its own health and status, point the antennae, detect and recover faults)
2. Ground station
Ground stations acquire mission data from the satellite.
Main functions include
a. Maintaining RF communication links
b. Process telemetry (determine spacecraft attitude, monitor spacecraft and payload health)
c. Provide satellite and payload control (issue commands, determine orbital parameters)
d. Provide data handling
- Multiplexing and demultiplexing
- Encoding and decoding
- Encrypting and deencrypting
- Data compression
- Data storage and archiving
- Time tagging
- Quality monitoring
e. Simulation and Verification
Ground station software is an integral part of the design of a good ground station.