We analyze the processes governing current collection by a positively charged spacecraft moving through the ionospheric magnetoplasma. We consider separately the situations of a suborbital rocket payload and a tethered subsatellite, such as TSS-1. For the latter case, our analysis leads to an upper-bound electron-current prediction of 6.4 times the Parker and Murphy [1967> current, independently of the subsatellite's voltage with respect to its surroundings. This result is consistent with the experimental results of Dobrowolny et al. [1995>, who measured currents which were generally between 4 and 6 times the Parker and Murphy [1967> values. Iterative refinement of our model decreases our prediction to about 6.0 and 5.9 times their values, for ambient electron-to-ion temperature ratios Te/Ti=1 and 2, respectively. Incorporation of estimated effects of thermalization due to instabilities in the magnetic presheath decreases our prediction further to about 5.6 and 5.3 times their values, respectively. Features of our model include a quasineutral magnetic presheath region, which extends very far from the spacecraft in both directions along the geomagnetic field; an ion-enhancement region, also quasineutral, which is located forward of the magnetic presheath and concentrates the electron flux passing into it; and an elongation, along the drift direction, of the electron collection area perpendicular to the geomagnetic field. This elongation further increases the electron collection.¿ 1997 American Geophysical Union