Another major nuclear weapon effect is system generated EMP (SGEMP). SGEMP is caused by the interaction of the x-rays with the system under consideration. These x-rays create fairly high energy photoelectrons, which in turn produce electron currents (or displacement currents, in the case of dielectric insulators). The overall system structure can also lose electrons, generating replacement currents on the surface of the system. System cables are especially susceptible to SGEMP effects. SGEMP signals of thousand of volts and/or amperes can be the result, even in circuits internal to spacecraft. C.1.2 Typical Space System Vulnerability Levels The nuclear vulnerability levels of space systems are typically controlled by the dominant semiconductor technology used in the circuits of space systems. SGEMP response is more capricious than semiconductor response in that degradation is dependent upon many more factors than just the intrinsic response of the semiconductor devices themselves. In some instances, system vulnerability may be most strongly dependent on the response of the photovoltaic arrays. The assumptions used to define representative vulnerability levels are as follows: Unhardened Satellite - Semiconductor technology is MOS (metal oxide semiconductor). Degradation at 500 rads. Satellites with Hardened - Semiconductor technology is hardened Circuits bipolar with some selected CMOS (complementary metal oxide semiconductor) . Degradation at 104 rads. Hardened Satellites (system - Semiconductor technology is CMOS, level approach to hardening) Shielding, circuit level hardening, and captive line semiconductors are employed. Degradation at 10$ rads. The term degradation, as used above, denotes permanent damage within the semiconductor integrated circuit devices of sufficient extent to reduce performance seriously. Circuit upset, such as reset of logical states, etc., generally occurs at somewhat lower levels; our estimates of vulnerability levels for both degradation and upset are based upon past experience with integrated circuits of the types specified.
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