A spectrogram from the Broad Band Receiver on AFRL’s Demonstration and Science Experiments (DSX) spacecraft showing “boomerang” signals on Oct. 5, 2020. Colors show radio wave power with transmissions from DSX and return echo signals (boomerangs) indicated. It shows a seven-second time period from left to right and radio frequency increasing from bottom to top. This is one of dozens of boomerangs seen by DSX, which are being analyzed to understand how very low frequency (VLF) radio waves behave in near-Earth space. (Courtesy Image/Stanford University)