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Space applications demand a high level of testing from the individual components to the complete satellite. In basic terms, satellites that orbit the Earth receive signals, amplify them, process and send them back to Earth or to another satellite, with filters and diplexers separating the different frequencies. In order for this to happen, cables, connectors, assemblies, active and passive components, etc., have to work in extreme conditions such as in a vacuum and are subject to severe temperature changes.
For instance, satellites always have a sunny side (temperatures up to +150°C) and a shady side (temperatures as low as -100°C). These conditions have to be simulated on Earth for the verification of the suitability of such products for space and that is why HUBER+SUHNER has developed a hermetically sealed RF-adaptor and a new range of flexible microwave cable assemblies for thermal vacuums (TVAC), specifically for space applications. An example is shown in Figure 1.
As has been mentioned, for the simulation of the space environment, test and measurement support equipment with special features is needed. Devices under test (DUT) in thermal vacuum chambers have to be connected to the test equipment outside the chamber. Satellites under test in vacuum test chambers also need to be connected with RF and LF assemblies for testing. During the preparation of the DUTs in the thermal vacuum chambers, all the components used are at ambient temperature and pressure. Such conditions demand very special components.
Another important factor is that the pressurization and depressurization of all components in the vacuum chamber, including the support equipment such as the cable assemblies, happens fast and within well defined parameters; this requires venting holes for non-hermetic components. With such holes in the connectors and defined evacuation paths in the cable and the connector interface, the best venting characteristics can be achieved, resulting in fast and non-material-stressing adaptation to the applicable pressure. Table 1 outlines the features required by assemblies and adaptors for TVAC.
HUBER+SUHNER’s range of special high quality RF assemblies and hermetically sealed RF adaptors are specially designed for these applications. They feature low out gassing cable assemblies according to European Space Agency (ESA) requirements that keep their mechanical and electrical properties to ensure the best test results. The material composition of the test support equipment in these applications is crucial; all of the company’s products that are developed and produced for space applications feature the required high quality and comply with the standardized outgassing requirements.
The new series of flexible microwave cable assemblies for thermal vacuum applications is based on the well known and proven technology of the SUCOFLEX 100 Series cable assemblies. These are the SUCOFLEX 104P with straight SMA male connectors, SUCOFLEX 104P with straight TNC male connectors, SUCOFLEX 106 with straight TNC male connectors, SUCOFLEX 103E with straight SK male connectors and SUCOFLEX 104EA with straight SK male connectors (see Table 2 for a summary of specifications), plus the 34_SK-50-0-54/199_NE adaptor (specifications shown in Table 3).
Due to its good mechanical properties, this range of cables is ideally suited to such applications when combined with connectors that have strong mechanical design and is a spin-off product of the space flight assemblies. Cable assemblies for this application don’t need to be lightweight, but they do need to be robust in order to operate efficiently and effectively in the rough test environment.
Outgassing requirements according to ESA-PSS-01-702 is also a must. Contamination of the devices under test from solvents of plastic materials has to be avoided as they can lead to corrosion of the content of the thermal vacuum chamber. Thus, all connectors in these TVAC series assemblies are vented. This ensures fast pressure adaptation and gentle treatment of the assembly and therefore a longer lifetime.
All assemblies are designed and tested to be used in a temperature range of -30° to +80°C. Other temperature ranges can be requested to meet specific customer requirements using suitable materials and designs. In addition, other connector-cable configurations are available depending on the customer’s requirements.
To be able to produce high quality components for space applications, HUBER+SUHNER has built up the necessary testing infrastructure, which includes temperature cycling chambers, thermal shock chambers, climatic chambers, salt spray cabin, vibration/shock equipment, RF-leakage equipment, flex life test equipment, hermetic leak test facility, tensile load test, cable retention force test and burn chambers, including test set ups like VNAs and spectrum analyzers for all necessary RF verification measurements.
Satellites and components that have to meet the rigors and stresses of operation in space have to face just as rigorous testing on the ground and the equipment used for that testing has to be similarly robust. HUBER+SUHNER’s range of hermetically sealed RF adaptors and new flexible microwave cable assemblies for thermal vacuums have been specifically designed for space applications. They not only meet the stringent physical and mechanical requirements, but comply with all necessary standards and specifications.
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RS No. 302
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