Characteristics of spacecraft charging in low Earth orbit

It has been found that the DMSP spacecraft at 840 km can charge to very large negative voltages (up to −2000 V) when encountering intense precipitating electron events (auroral arcs). We present an 11‐year study of over 1600 charging events, defined as when the spacecraft charged to levels exceeding 100 V negative during an auroral crossing. The occurrence frequency of events was highly correlated with the 11‐year solar cycle with the largest number of events occurring during solar minimum. This was due to the requirement that the background thermal plasma density be low, at most 10 4 cm −3 . During solar maximum, the plasma density is typically well above that level due to the solar EUV ionizing radiation, and although the occurrence frequency of auroral arcs is considerably greater than at solar minimum, the occurrence of high‐level charging is minimal. As a result of this study, we produced a model spectrum for precipitating electrons that can be used as a specification for the low‐altitude auroral charging environment. There are implications from this study on a number of LEO satellite programs, including the International Space Station, which does enter the auroral zone, particularly during geomagnetic activity when the auroral boundary can penetrate to very low latitudes. The plasma density in the ISS orbit is usually well above the minimum required density for charging. However, in the wake of the ISS, the plasma density can be 2 orders of magnitude or more lower than the background density and thus conditions are ripe for charging.