Satellite Subsystems » Flight Computer » Software » Operating System

The Operating System (OS) is the piece of software running continually on the Flight Computer (FC), monitoring and managing the satellite's resources. This is the software that the bootloader enters when it's job is done (usually nothing else but load the OS). The OS that runs on BLUEsat will be a pre-emptive multitasking OS, and will be based around the L4 microkernel. The experimental nature of the satellite and the intended failsafe-ness of the bootloader will allow for other OSes to be run on BLUEsat, and even be switched once in orbit. The hugely popular open-source Linux UNIX-type OS is an example. (The penguin in the icon above is the Linux mascot).

The underlying OS will manage threads or processes, which are individual programs that perform particular tasks. Most of the satellite functionality will be provided by continuosly-running programs called daemons. These programs lie waiting for events to occur, whereupon they take action. Examples are:

• The Power daemon, which monitors the power consumption of the various systems, power input from the solar cells, battery charge levels, and takes appropriate action where necessary (for example, to turn transmitters to full power to dissipate excess power, and vice versa)
• The Telemetry daemon, which will accept telemetry node data, format them into a telemetry packet, and transmit them to earth over the beacon
• The Command daemon, which lies waiting for commands from the groundstation to initiate specific actions, such as running experiment software, or controlling the other daemons (for example to set the transmitter power output)
• The PACSAT daemon, which is essentially a file server for the amateur radio community

Specific programs may be in execution at any time, initiated by commands from the groundstation. They may be experimental software, or operating payloads.

	Author: Vaenthan Thiru © The Author, the BLUEsat project or UNSW. All rights reserved. Last Modified: May 18 2006 08:45:59.