W-band GaN amplifiers developed for the NASA Earth Science Technology Office, ESTO, enable compact active electronically steerable arrays (AESA's) for cloud Doppler radar. This paper describes the design fabrication and test of 100 nm GaN HEMT low noise amplifiers for NASA's latest 3-band Doppler radar instrument concept. Our results show state-of-the-art performance for a 92 GHz to 96 GHz channel with gain greater than 17 dB and noise figure less than 5 dB. Detailed on-wafer testing shows record low measured noise figure of 3.0 dB with 20 dB of gain and dc power of 128 mW using a 5 Volt supply.