The Delay Doppler Mapping Instrument (DDMI) is the single instrument aboard the eight individual satellites comprising NASA’s Cyclone Global Navigation Satellite System (CYGNSS) constellation. Each DDMI contains both a traditional Global Positioning System (GPS) navigation receiver integrated with a reﬂections processor. The DDMI aboard each of the eight CYGNSS micro-satellites receives signals broadcast from four orbiting GPS satellites along with the return of the same GPS satellite’s signal reflected from Earth. These signals are used to provide measurements of wind speed over the ocean to better understand and predict tropical cyclones. Each DDMI consists of a delay mapping receiver (DMR), three low noise ampliﬁers (LNAs), one right-hand circularly polarized zenith facing navigation antenna, and two left-hand circularly polarized nadir facing science antennas.