NASA-HDBK-4002: “Mitigating In-Space Charging Effects–A Guideline”
As spacecraft orbit the Earth, they are constantly interacting with the environment around them (falling less into the “EMC” category and more into the “electromagnetic environmental effects (E3)” category). While we think of space as a vacuum, depending on your orbit and altitude the craft will interact with different densities of particles with different energetic properties. NASA-HDBK-4002 is a valuable guide for dealing with the effects of these interactions. The current revision is “B” as of 2022, and you can download a publicly available copy here.
Possibly one of the most useful parts of NASA-HDBK-4002 is Figure 1, showing the risk of spacecraft charging per orbital altitude and range of latitudes covered (see below). This gives you a first indication of how much you need to worry about this threat given your mission profile
Rev B has a number of useful updates, including the incorporation of all the new data that’s come in since the last revision in 2017. A similar graph in Figure 2, relating charging risk for orbital inclination and altitude, is vastly more granular than the equivalent graph in 2017, reflecting the rapidly growing body of knowledge in this area.
There are two main spacecraft charging risks. The first is when surfaces charge up to high potentials relative to other surfaces or relative to the space plasma surrounding the vehicle. When this occurs you can have significant ESD events. Solar arrays are particularly susceptible to this risk, and 4002 has some sobering pictures, as shown below.
A more insidious threat is that high energy electrons can penetrate the chassis and even electronics enclosures and bury themselves in printed circuit boards, charging them up over time and potentially leading to internal damage.
There are a lot of nuances involved in analyzing these risks, including the difference in charging when a satellite is in shadow vs. in sunlight, the distribution of high energy electrons in different orbital regions, the different materials and thicknesses involved, etc. While not a comprehensive textbook, the 209 pages of 4002 Rev B give a good overview of the different factors involved and how they should drive design decisions.
TIP:
As I’ve mentioned before, most ESD testing is based on a human body model of electrostatic discharge. There’s an older military standard that addresses how to set up a test for different discharge profiles, MIL-STD-1541. NASA-HDBK-4002B takes that MIL-STD-1541 setup and customizes it for spacecraft charging risks in Section 6.3.1.1, which may come in handy for others looking to represent non-human discharge threats.
If you are working in this area, there are a few other documents that you might want to have on hand:
NASA-STD-4005, “Low Earth Orbit Spacecraft Charging Design Standard”; this is a set of requirements for missions in common low-risk low earth orbits such as that occupied by the International Space Station
NASA-HDBK-4006, “Low Earth Orbit Spacecraft Charging Design Handbook”; this gives more context and guidance for how to meet the 4005 requirements
NASA-HDBK-4007, “Spacecraft High-Voltage Paschen and Corona Design Handbook”; covering ways to insulate and protect high voltage systems that may be subject to more severe risks over time
SLS-SPEC-159, “Cross-Program Design Specification for Natural Environments (DSNE)”; this broadly defines the environments you’ll see throughout the solar system, from the launch pad to GEO to Jupiter. This includes electromagnetic and plasma environments, but also thermal, gravitational, ionizing radiation, and more