Orbital X-band Side-Looking Radar of Cosmos-1500: Potential IEEE Milestone Candidate

We revisit the history of development and operation of the first-ever orbital X-band real aperture side-looking radar (RA-SLR) onboard the USSR satellite "Cosmos-1500." This radar was conceived, designed and tested in the early 1980s, and then supervised in orbit, by the team of Ukrainian scientists and engineers led by Professor Anatoly Kalmykov at the O. Y. Usikov Institute of Radiophysics and Electronics of the National Academy of Sciences of Ukraine (IRE NASU). It had 100-kW magnetron source, 12-m deployable slotted-waveguide antenna and onboard signal processing unit. Instead of planned experiments, only five days after placement into the polar Earth orbit in the autumn of 1983, SLR of "Cosmos-1500" rendered truly outstanding service. It provided a stream of microwave images of the polar sea ice conditions that enabled the rescue of the freighters in the Arctic Ocean. However, the way to success was far from smooth. Besides of the technical problems, A. Kalmykov had to overcome the jealousy and hostility of both his home institute administration and the USSR bureaucracy. Later, SLR of "Cosmos-1500" was released to the industry and became the main instrument of the USSR and Russian series of remote sensing satellites " Okean" and Ukrainian satellites "Sich-1" and " Sich-1M." We believe that SLR of " Cosmos-1500" is a perfect candidate to the status of IEEE Milestone in Ukraine.