GSFC-STD-7000B: “General Environmental Verification Standard (GEVS) for GSFC Flight Programs and Projects”
GSFC-STD-7000, affectionately known as GEVS, is a huge document covering a wide variety of environmental testing, including shock, vibe, thermal, etc. For our purposes we’re only concerned with Section 2.5 on EMC. Written by John McCloskey and Ken Javor, it is worth making sure to get Rev B. While both revisions have the same approach--tailoring MIL-STD-461 for the kind of missions most common at Goddard Space Flight Center--Rev B has a greatly expanded Section 2.5.3, which serves the same function as the appendices of MIL-STD-461. It is a wealth of additional information and context on each test method and how it came to be specifically tailored in this document. This is hands-down one of my favorite standards documents, and I refer to it even when I’m not working on Goddard or NASA programs. The document is freely and officially available here.
The tailoring in GEVS is based on certain assumptions that hold true for the most common GSFC programs:
Uncrewed satellites
Generally cubes, generally smaller than 2 meters on a side
They have metal chassis
They never use structure for current return
28 Vdc power bus, sourced from batteries and recharged from solar panels
The table below shows a summary of the requirements they arrived at, and a top-level comparison with MIL-STD-461.
TIP:
One thing that I appreciate is that it includes a test not found in MIL-STD-461, which is a common mode conducted emissions test. It’s found in Section 2.5.2.1.2. While MIL-STD-461 CE101 and CE102 have differential measurements taken from a LISN, this test uses a current probe to measure the common mode currents flowing on the cables--which is one of the prime indications of potential crosstalk or radiated emissions problems. It also has a method for extending the test range from 30 MHz up to 200 MHz using an absorbing clamp as described in CISPR 16-1-4. GEVS section 2.5.3.3.2.1 contains an extremely thorough and well-thought-out discussion of why absorbing clamps are appropriate at the higher frequencies, and it left me thoroughly convinced. For people in the automotive industry, the 30 - 200 MHz is particularly critical for EVs seeking to pass CISPR 12 testing, and the common mode, absorber clamp method may be a useful pre-compliance test for that purpose.
TIP:
Instead of the more commonly found 50 uH or 5 uH LISNs used in much MIL-STD-461 and automotive component testing, GEVS uses a 10,000 uF cap network. It’s worth reading the rationale in Section 2.5.3.2.2 (with related discussion in MIL-STD-461 Rev G Section A.4.3.6) to broaden your thinking about LISN/Artificial Network choice. For more on LISNs, see this post.