AIAA-S-121: “Electromagnetic Compatibility Requirements for Space Equipment and Systems”
AIAA-S-121 is an interesting beast. It is a tailoring of the combination of both MIL-STD-464 (system level) and -461 (equipment/module level) with an eye to making them specifically applicable to space systems. It can be purchased from the AIAA. It was reaffirmed in 2023, and there’s an effort underway to make it a joint standard with the IEEE. It’s something that the EMC Society standards committee and also Technical Committee 8 (Aerospace EMC) have been involved in, so if that’s of interest to you, please get in touch (standards@emcunited.com).
AIAA-S-121 draws from MIL-STD-1541 and SMC-S-008 (both freely available), and has similarities with GSFC-STD-7000. However it is very much its own document and should be read independently. Generally speaking, Section 6 follows MIL-STD-464, Section 7 follows MIL-STD-461 Section 4, and Section 8 follows MIL-STD-461 Section 5. Section 7 starts with a helpful table that explains many of its deviations from MIL-STD-461. Like MIL-STDs 464 and 461, it has appendices with excellent additional information that reward the thorough reader.
TIP:
Just because a unit is compliant to MIL-STD-464 and -461 does not guarantee that it will be successful in meeting AIAA-S-121. At a minimum, the radiated susceptibility levels are different. MIL-STD-461 RS103 for space systems specifies a threat level of 20 V/m, where AIAA-S-121 requires levels up to 50 or 100 V/m depending on frequency range and mission phase.
TIP:
For those concerned about Multipaction in space RF systems, MIL-STD-464 requires verification by test but does not specify or even recommend or reference a specific test method. AIAA-S-121 helps us out by pointing to “ECSS-E-20-01A, Space Engineering – Multipaction and Test, European Space Agency (ESA) for the European Cooperation for Space Standardization (ECSS), 5 May 2003.”