Division — Astrionics

Deals with the design of electronic and radio systems for the Spacecraft.

Telemetry, Tracking & Command Subsystem (TTC)

The Telemetry, Tracking and Command (TT&C) or communication subsystem of the SRMSAT - 2 provides the interface between the spacecraft and ground systems. Payload mission data and spacecraft housekeeping data pass from the spacecraft through this system to the operations center. Operator commands are also passed to the spacecraft through this subsystem to control the spacecraft and to operate the payload. As part of carrier tracking, most spacecraft TT&C subsystems generate a downlink RF signal that is phase coherent to the uplink signal. This two-way coherent mode allows measuring Doppler shift from which range rate or line of sight velocity between the spacecraft and tracking antenna is calculated. This knowledge allows operators to scan fewer frequencies and thus, acquire spacecraft more quickly. This Doppler ranging operation can also be used for navigation.

The functions of the TTC subsystem include Carrier Tracking, Command Reception and Detection, Ranging, and some subsystem operations.

Visibility analysis simulation showing the radiation pattern of the antenna.
Visibility analysis simulation showing the radiation pattern of the antenna.

Electrical Power System (EPS)

The Electrical Power System ensures that a continuous source of electrical power is present to the spacecraft loads throughout the mission duration. The subsystem generates power through the solar panels on the spacecraft and stores it in the battery, and supplies the stored power when necessary. EPS uses regulators to ensure that power is supplied at the rated voltages for components. All power lines are monitored by voltage and current sensors and protection is provided for loads against damage from electrical fault. EPS also provides command and telemetry capability for EPS health and status, as well as control by ground station.

On-Board Computer (OBC)

On-Board Computer (OBC) is figuratively the brain to SRMSAT-2. It controls all the other subsystems of the satellite. It collects, analyses, and takes necessary actions from the information collected from different parts of the satellite. This is done with the help of a software architecture which provides a complete functional overview of the OBC. It is responsible for data communication between the satellite and the ground station. It collects the telemetry data and then encodes it for transmitting it to the ground station. This is achieved by using recommended standards like CCSDS which increases inter-operability and efficiency. The on-board software is developed around ATSAMA5D35-CM, a microcontroller which plays a vital role in the functioning of the satellite. Error Detection and Correction techniques like Reed Solomon and Hamming Codes are used to handle memory corruption issues caused by the rough and harsh space environment.