What is the role of millimeter wave seekers in precision guided munitions?

Millimeter wave (mmW) seekers in precision guided munitions operate primarily at 35 GHz (Ka-band) or 94 GHz (W-band) to provide autonomous target detection and guidance in the terminal phase of flight, enabling engagement through conditions that blind infrared and visible-light seekers such as fog, smoke, dust, and rain. The mmW seeker functions as a small, short-range radar mounted in the nose of the munition, with a compact antenna (typically a Cassegrain reflector or monolithic lens antenna, 50-150 mm diameter) that scans or electronically steers to detect, classify, and track the target during the final seconds of flight. At 94 GHz, atmospheric attenuation in clear air is approximately 0.4 dB/km, increasing to 4-10 dB/km in heavy rain, but the short engagement range (typically 1-10 km) makes these losses manageable. The primary advantage of mmW seekers over infrared is their ability to measure range to the target (enabling impact point prediction and fuze timing) and their robustness to obscurants. The primary limitation is lower angular resolution compared to infrared at the same aperture size, since the wavelength at 94 GHz (3.2 mm) is about 300x longer than mid-wave infrared.