Ionospheric drag on spacecraft in low-Earth-orbit

Spacecraft in Low-Earth-Orbit (LEO) experience a range of perturbing forces that affect their trajectories, such as drag due to neutral gas in the residual atmosphere. A less well-studied drag mechanism is that from charged particles in the ionosphere, which is a plasma environment between altitudes of about 60-1000 km. Collection of such charged particles causes spacecraft charging that can generate unwanted electrostatic discharges or arcing, and the formation of a complex plasma sheath/wake structure. But, direct collection, and indirect deflection, of charged particles also results in momentum transfer and the formation of an additional drag force. While the neutral gas density is typically 1-2 orders of magnitude higher than the ionospheric plasma density, sheath expansion around a spacecraft can artificially increase its effective collecting area. Here, we present a model accounting for charged particle flow effects around objects in LEO and show that ionospheric drag can be significant, and in some cases, similar, or even higher, than drag due to the residual atmosphere. Aside from having important orbit prediction implications for space domain awareness and space traffic management, ionospheric drag can also potentially be exploited for active satellite control.