OCO Footprint Scale — from one orbit to one sounding

Each OCO-2 sounding is a sliver about 1 km along the spectrometer slit and 2 km along the orbit (the smear during one third of a second); eight sit end to end along the slit, only ~9 km in total, three frames every second. Footprint pitch is 1.29 km but the sampled width is 1.09 km (20 of 24 detector rows are summed per footprint), which is why small gaps show between the polygons — they are drawn as the L1b vertices describe them. The satellite rotates its slit along the orbit, so over Los Angeles the eight footprints happen to line up almost along the track instead of across it. A single 99-minute orbit traces one thin line around the Earth, so global maps are built from thousands of such lines over sixteen days. OCO-3 on the Space Station instead sweeps its pointing mirror to lay adjacent swaths over a city, a "snapshot area map".