Electromagnetic Compatibility (EMC) Testing and Certification for Space
Electromagnetic Compatibility (EMC) testing and certification ensure that electronic devices don't emit excessive electromagnetic emissions and that equipment continues to function as intended.
Designing and certifying products to be used in space should be straightforward given that there isn’t much there, however, in reality, space has more challenges than other electromagnetic environments. A space system needs to operate without performance degradation, and the Electromagnetic Compatability (EMC) environment will change during the various phases of its mission: pre-launch, launch and deployment.
Dealing with EMC in space systems can be extremely challenging, and the cost for failing to meet these challenges can result in mission failure. Success requires robust EMC engineering - with an emphasis on detailed understanding, ongoing assessments, extensive testing, and constant vigilance throughout the life of the project. EMC problems can be resolved using tried and tested techniques, but care must be taken as space programs involve numerous contractors, so the management, integration, and partitioning become crucial to success.
Space engineering has unique EMC phenomena which include:
- Plasma charging
- Magnetic cleanliness
- Passive intermodulation
- Nuclear effects
- HIRF (High-Intensity RF)
- Conducted emissions
- Conducted susceptibility
- Radiated emissions
- Radiated susceptibility
Spacecraft charging (plasma charging)
Spacecraft charging is the build-up of electrostatic charge on spacecraft surfaces or in the spacecraft interior. It causes variations in the electrostatic potential of a spacecraft surface concerning the surrounding plasma environment, and potential differences between portions of the spacecraft (differential charging). The primary settings which contribute to spacecraft charging include:
- The thermal plasma environment
- High energy electrons
- Solar radiation
- Magnetic fields
Spacecraft charging has many effects, with differential charging rather than absolute charging being the most dangerous because it can lead to surface arcing or electrostatic discharges (ESD) between surfaces, and gives rise to various operational anomalies. To combat irregularities, design solutions include conductive bonding between different surfaces and applying conductive surface treatments to non-conductive surfaces.
The Earth's magnetic field is a magnetic dipole which is displaced from the center of the Earth by ~ 436 km. The Earth’s DC magnetic field is used for altitude navigation purposes. It is crucial to control and measure the DC magnetic fields within the spacecraft in case the payload is susceptible. (note: these methods of measurement do not appear in any Military Standard). Element’s experts have created unique test methods to achieve these fundamental goals.
Spacecraft employ multiple onboard radio transmitters and receivers for command, control, navigation, and communications. The frequency mixing effects of these co-located transmitters can cause unwanted passive intermodulation products creating new emissions and the potential to interfere with other wireless-based communication systems. As experts in the field of traditional transmitter/receiver testing, Element is well placed to advise and perform these measurements. We quantify the effects as passive intermodulation as required by the European Cooperation for Space Standardization (ECCS) and others alike.
HIRF (High-Intensity Radio Frequency)
Electromagnetic HIRF exists due to transmission of electromagnetic RF energy from radar, radio, television, and other ground-based, shipborne, or airborne RF transmitters. HIRF can upset or damage any electrical equipment, notably a spacecraft during the launch or tracking phase of the deployment. Given the extremely high levels of energy involved with assessing products and systems for HIRF, only a limited number of test facilities can offer these types of services, including Element.
An electromagnetic pulse (EMP), sometimes called a transient electromagnetic disturbance, is a short burst of electromagnetic energy. It may originate from natural or human-made sources and can occur as a radiated, electric or magnetic field, or a conducted electric current, depending on the source. A spacecraft’s electronics can be affected by these ionizing effects. While not typically considered by space EMC test requirements, Element Materials Technology can test for the secondary effects of a NEMP explosion and help with the electronic design if required.
There is a requirement to protect the space system against both direct and indirect effects of lightning. Testing at the system level is not essential but shall be verified by analysis. At Element Materials Technology, we have the expertise to test for both direct and indirect effects as well as offer design advice.
EMC test and certification challenges
Some of the well-known EMC phenomena can be a challenge in terms of testing. For example, for radiated emissions, electric field, 30 MHz to 18 GHz, the test methodology is taken from Military Standard 461. Spacecraft limits can be extremely demanding in specific notches (usually in the communication bands), and it is not possible without deviating from the standard to measure below the limit due to noise floor issues. The standard states to use a broadband horn antenna with physical dimensions giving a large antenna factor. Using the specified bandwidth, in most cases, it is not possible to be below the limit line.
At Element Materials Technology, we have numerous horn antennas that can be used for the measurement. These have a high gain and therefore a lower antenna factor. The antenna factor is added to the receiver reading which makes the overall measurement. By using a high gain horn antenna we can lower the noise floor while keeping the standard bandwidth.
Another challenge is the very low levels of field strength sometimes required of less than 1 V/m. Products require testing to ensure they work as intended and within their performance limits. Care needs to be taken not to over test given the modest levels. Testing can be a challenge as RF field sensors do not have the sensitivity to measure low field strengths.
How Element can help with EMC testing and certification
EMC testing and certification for a space environment requires bespoke tests and sensitive measurements. Element’s Advisory Services team is in a unique position, being able to draw upon a portfolio of the group’s testing facilities and knowledge, to help with EMC testing in space and meet your engineering challenges.
We are here to help provide a range of support services to generate control and test plans, define test methods, and provide guidance from a design and de-risk testing perspective.
For more information on EMC testing and EMC certification services, please contact us now.
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