The Spaceflight Now article Photos: Sentinel 3B satellite prepared for launch from Plesetsk Cosmodrome has of course lots of photos. One of them shows a dish antenna covered with shiny, metallized film of some kind.
I believe I see an small, compact array of seven corner cube retroreflectors to the left of the dish antenna. Why were these included on Sentinel 3B? Is this actually common for LEO Earth measuring satellites, or is this something new or unusual?
I've included a cropped, magnified, and heavily sharpened view of the device below as well.