DTU space is developing an airborne P-band radar capable of measuring the thickness and the internal layering of the Antarctic ice sheet. The European Earth-sciences community has proposed a spaceborne, P-band ice sounding radar as a possible Earth Explorer mission, but scattering and propagation through ice-sheets at P-band (435 MHz) is not fully understood, as most ice sounders operate at lower frequencies. Therefore, ESA has assigned DTU Space to develop an airborne demonstrator. The task includes design, implementation, aircraft installation, and a proof-of-concept campaign in Greenland.