This is the dried up salt lake in Turkey called Lake Tersakan. Satellites are using it as a calibration tool. How so?

Lake Tersakan dries up completely in the summer months to reveal a thick layer of salt. The surface is so bright and white that satellites use it to calibrate their sensors for the color white.

The image, provided by the European Space Agency, was captured by Japan’s Advanced Land Observing Satellite (ALOS) using its Advanced Visible and Near Infrared Radiometer type-2 instrument. [ESA]