One scenario would be if it scanned it once in 8 days and once in 4 days, due to, say, an elliptical orbit or something. Thus, twice in 12 days, but not once every 6 days.

Alternately, complex orbital tracks may result in irregular accumulation of multiple scans, with double scanning only finally being achieved after 12 days.

I think it's because they're scanning in two different wavelengths:

> In a first, the satellite combines two synthetic aperture radar (SAR) systems: an L-band system that can see through clouds and forest canopy, and an S-band system that can see through clouds as well but is more sensitive to light vegetation and moisture in snow.

Whoa incredible! Can you believe it does four scans every 24 days?!