Researchers have found that the number of electrical discharges on a spacecraft directly correlates to the number of electrons in the surrounding environment—information that could help scientists better understand how to protect equipment in space. Spacecraft environment discharges (SEDs) are transient electrical breakdowns that can damage sensitive onboard electronics and communication systemsSpacecraft charging effects that lead to ESD events, as well as the associated immunity testing required, the measurement requirements, as well as the test setups, regarding the immunity testing to power leads transients are described thoroughly.
ISO 14302: Space Systems - Electromagnetic Compatibility Requirements
SCOPE OF ISO 14302
This International Standard establishes performance requirements for the purpose of ensuring space systems electromagnetic compatibility (EMC). The engineering issues to be addressed in order to achieve system-level EMC are identified herein, with guidance and rationale towards achieving specification conformance. The method for the derivation of typical equipment-level requirements from a space-system-level requirement is illustrated. Satellite equipment needs to be immune to electrostatic discharges (ESD) likely to occur in flight.
Testing the susceptibility against ESD on spacecraft equipment is therefore an important part of the EMC test program. The test method according ISO 14302, which is commonly used in space industry, leaves a lot of freedom to the test conductor on how the test is performed, which in turn has an influence on the injected current and therefore on the test results. In this paper various standard ESD test methods, set-ups and instrumentation are assessed with respect to repeatability and influence factors and a new test method is proposed, overcoming the deficits of the standard methods while ensuring a very good reproducibility of the injected current waveform.
ISO 14302 improves upon the ESD test method for testing spacecraft equipment described in Mil-STD 1541A, originally released in 1973 and revised in 1987 by the USAF.
ESD TESTING POINTS OF EMPHASIS
- Tailored Space Environment Focus: The standard is geared toward ensuring that spacecraft equipment survives, rather than just operates, in a vacuum. It often mandates testing against ESD on flight hardware that could occur during launch, deployment, or operation.
- Methodology Flexibility: ISO 14302 leaves significant freedom to the test conductor regarding how the ESD test is performed, allowing for customization to the specific space system being tested.
- Emphasis on Worst-Case Scenarios: It focuses on identifying and testing against "worst-case ESD" scenarios rather than arbitrary standard levels, sometimes accepting higher voltage tests if justified.
- Surface and Internal Charging Focus: The standard provides guidelines on mitigating risks from both surface charging (external environment) and internal charging (dielectric charging), allowing for analysis to justify acceptance.
- High-Voltage Spark Gap Preference: For creating repeatable discharges, the standard emphasizes the use of specialized tools, such as pressurized overvoltage spark gaps (e.g., PGP-575-6KV), rather than relying solely on commercial handheld ESD guns.
- Integration with System-Level EMC: The ESD requirements are part of a broader EMC control program, focusing on how component-level ESD impacts the entire spacecraft system.