Internal Responses of a Complex Satellite Model to Two Electron-Induced Discharge Simulation Techniques

A complex two-thirds scale electromagnetic model of the P78-2 (SCATHA) satellite has been constructed and tested using simulations of two different aspects of an electron-induced discharge (EID). These are a MIL-STD 1541 arc injection which simulates a punchthrough or flashover discharge and capacitive direct injection (CDI) which simulates charge blowoff which accompanies the breakdown. The results show that CDI generally produces larger internal responses per ampere of drive current, by factors of two to almost one hundred, than does arc injection except when the arc point is closely coupled to the measurement point, e.g., on the solar array. Then arc injection can produce greater responses. It was also found that, because of their diode nature, the response of the solar arrays may be dependent on the drive current polarity. The scale model test results were used to estimate the P78-2 responses to both arc injection and CDI. These data confirm the observation that no upsets occurred during arc injection tests of the P78-2. However, CDI tests on the model indicate that some critical circuits in the spacecraft may suffer upsets for blowoff discharges involving dielectric areas of ~100 cm2. The limited on-orbit data presently available appears to be consistent with predictions based on the model tests. The program results to date suggest two changes to the MIL-STD 1541 tests: (1) CDI should be added as a more meaningful EID worst-case stress, and (2) proper polarity of injection (especially to solar arrays) should be considered.