Saturation Flux Density (SFD)


Saturation flux density (SFD) is a measure of how much power a signal must have to saturate a detector. Flux density is a solid angle measurement in optics, but the typical measurement is made per unit area since detectors do not respond to volumetric intensity outside of time-averaged situations. Some transponders have reduced SFD further to a power measurement in Watts since detector areas are known before ground systems are calibrated for uplink. [1]