1.0 Background

Per the Canadian Satellite Design Challenge (CSDC) General Rules & Requirements, attitude determination and control subsystems must maintain “at least a degraded state of performance” despite at least one attitude and/or actuator failure. ([CSDC-0430] & [CSDC-0440])

2.0 Research

2.1 General Redundancy

2.1.1 Hardware Redundancy Types

A common mission requirement is the ability to survive the failure of any one component (”single-point failure”). Such a requirement is often met by providing redundant components which can be held in three configurations. [1]

Cold Backup Configuration

• Redundant equipment unpowered until failure occurs
• Delay between backup component being powered-on and being available for use

Warm Backup Configuration

• Redundant equipment powered on but not used
• Quicker recovery if primary equipment fails

Hot Backup Configuration

• Redundant equipment used all the time
• Preferred for actuators (reaction wheels or CMGs) → increased control authority is useful

2.1.2 Redundancy Configurations

Two methods exist for connecting redundant components: block-redundant or cross-strapped. [1]

Redundancy configurations (a) Block redundant (b) Cross strapped

2.1.3 Analytic Redundancy