C&DH

(Command & Data Handling)

Function of C&DH subsystem

Interpreting and processing unplink commands from the ground station

Uplink commands from the ground station are decoded by RxTNC (Communication subsystem) and sent to OBC (OnBoard Computer) through CAN bus.
Then, OBC interprets the command and work function.

Health monitoring

Voltage and current data of the satellite and other sensor data (such as magnetic sensor and gyro data) is stored in serial EEPROM, which is space-qualified on XI-IV. To improve the precision of A/D conversion, which was not high for XI-IV, stabilized supply of reference voltage for A/D conversion and the use of A/D conversion IC is required.

Storage of mission data

Large volume of image data should be stored onboard. High-capacity data ROM is used for this purpose instead of the serial EEPROM onboard XI-IV.

Making telemetry data for downlink

Edit telemetry data and mission data in a format suitable for downlink and send them to TxTNC as needed.

Mutual monitoring with power subsystem

To enhance the survivability of the satellite, mutual monitoring with the CPU of power subsystem is implemented. If C&DH OBC overdrives, the power subsystem detects and resets.

In-orbit Reconfiguration (Advance mission)

We can correct a part of the C&DH software code in orbit with uplinked data.

C&DH subsystem has the following functions:

The block Diagram of C&DH is as following figure.
Main OBC operates each component with I2C Bus, Address Bus and Data Bus.
The communication with other subsystem is conducted through CAN Bus.
The program of Main CPU is stored in the Main OBC inner ROM.
The primary storage of Main CPU is the Main OBC inner RAM.
Telemetry and Misson Data are stored with three ROMs: ADCS ROM, Image ROM, Telemetry ROM.