SMAP Antenna Beam Footprint
[25-Jan-18] SMAP's orbital motion combined with the spin of its antenna (14.6 revolutions per minute) sweeps a small field of view in a series of overlapping loops that create a swath 1000 km (621 mi) wide. This large swath coverage allows SMAP to make complete maps of the Earth every 2 to 3 days.
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.
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