This ftp directory reports hi-res polar SSTs from 2 VIIRSs (onboard NPP and N20),
2 MODISs (on Terra and Aqua), and 3 AVHRR FRACs (on Metop-A, B, and C).

For each satellite, a 2-week rotated buffer of L2P (swath) and L3U
(0.02 deg equal-grid) data are available.

The L3S directory reports two lines of polar gridded super-collated products.
Currently, the "PM" line is derived from 2 VIIRSs, and the "AM" line from 3 AVHRR FRACs.
Adding 2 MODISs (Terra to the AM and Aqua to the PM lines) is under consideration.