SMAP Antenna Beam Footprint
SMAP's orbit is 685 km (426 miles) above Earth's surface. Because Earth spins while SMAP orbits, swaths from each orbit are offset from each other and after 8 days, the same swath is repeated.
Data taken by SMAP's two instruments run from pole to pole. The orbit is oriented such that it crosses Earth's terminator at the equator. (The terminator is the boundary between day and night, either at sunrise or at sunset). Credit: NASA.