Dante LaurettaMar 03, 2016

OSIRIS-REx Passes EMI/EMC Testing

This article originally appeared on Dante Lauretta's blog and is reposted here with permission.

The OSIRIS-REx spacecraft has completed the Electromagnetic Interference/Electromagnetic Compatibility (EMI/EMC) system level test. This test has three objectives. The first objective is to test for Radiated Emissions, which are the release of electromagnetic energy from the spacecraft. To pass this test, the team had to verify that the emissions from the Spacecraft do not violate the limit specified for both the Launch Vehicle and the Spacecraft.

OSIRIS-REx EMI/EMC test - 1 The OSIRIS-REx team sets up the anechoic wall (yellow) and emission test equipment for the EMI/EMC test.Image: Dante Lauretta

The second objective is to test for Radiated Susceptibility, which is the response of the spacecraft to external electric fields.  This test verifies that the Spacecraft will perform as required at the launch site, during launch, and during operations in space, when it is exposed to these electromagnetic environments.

OSIRIS-REx EMI/EMC test - 2 The spacecraft was mounted on the acoustic stand for this test.Image: Dante Lauretta

The final objective is to test for spacecraft Self-Compatibility, which demonstrates that the spacecraft will not electrically interfere with itself. To pass this test, the team had to verify 1) that the spacecraft operates as expected when it is not connected to any external ground-support equipment; 2) that there is no degradation in receiver (X-band) performance when exposed to the emissions generated by the spacecraft itself; 3) that the individual components on the spacecraft do not interfere with each other when all systems are operating; and 4) that there is no degradation in unit performance while the onboard transmitters (X-band) are transmitting.

OSIRIS-REx EMI/EMC test - 3 The test chamber simulates free space by absorbing all electromagnetic radiation.Image: Dante Lauretta

This test was performed in the same chamber as the mechanical environmental tests. This facility was modified to create an “anechoic chamber”. The term anechoic can be broken down to “an-echoic”, which basically means that the walls are non-reflective, non-echoing, or echo-free. For this test, we had to create a shielded room whose walls have been covered with a material that scatters or absorbs so much of the incident electromagnetic energy that it simulates free space.

OSIRIS-REx EMI/EMC test - 4 Testing for electromagnetic interference/electromagnetic compatibility (EMI/EMC) testing on the OSIRIS-REx spacecraft at Lockheed Martin.Image: Dante Lauretta

Overall, the test was completed without issue. At one point in the test an unexpected emission in the Global Positioning System (GPS) band was recognized. However, after a bit of troubleshooting, this emission was shown to be within specification. With the EMI/EMC test behind us, the last major environmental test, thermal vacuum testing, is up next. Watch for a future post to describe the results from “T-Vac”.

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