Flight Code

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The flight code of the satellite is expected to perform the following functions:

Scheduling

Flight code has to contain the scheduling of all events, i.e. the order in which the tasks have to be performed as well as the time duration in which they have to be completed. If a part of the code doesn’t finish in the scheduled time, the code should reset and start execution from the beginning. This could be done with the help of watchdog timers. The time that the entire code takes to run should be large enough that all required functionality is completed and small enough that there is required amount of precision in sensor data and data required by Attitude Determination and Control Subsystem

Control Law Implementation

The flight code is required to interface with sensors and actuators in a periodic fashion and hence execute the control law as designed by the control subsystem. This includes performing the requisite numerical calculations with the desired accuracy as well as according to a predefined sequence.

Power Management

A strategy has to be planned to manage power from solar cells to users, with some redundancy included. Flight code thus has to contain all commands regarding acquiring, regulating, and distributing power to the various subsystems. It must also ingrain the scheduled command to interact with all subsystems to exchange data about the system’s health. This health data will also be stored, with timestamps, while the satellite is in orbit. The flight code should have the functionality to take decisions in case a component is showing bad health, i.e. it is misbehaving (say it is drawing excess power).
It also has to contain the command in accordance with the device priority - and commands to shut down the low-priority device in case of power-crisis.

Data Handling for Communications

For the purpose of monitoring the status of the mission, as well as payload requirements(like imaging payloads) in some other cases, the satellite will transmit the health of various components during downlink. Without communications, a satellite is essentially a rock in space. In this regard, the flight code must be prepared to send the payload data and health data in packets encoded using the communications protocol, at designed rate whenever the satellite is over the ground station.
Also the provision for receiving commands via uplink (commands like kill, reset etc.) has to be present, and the flight code should know what necessary actions to take thereafter.


If you are done reading this page, you can go back to Electrical Subsystem