Construction of a large scale natural gas pipeline network system in the Northeast Asian area has been proposed by several researchers, including Prof. Masaru Hirata, which will extend over tens of thousands of kilometers. To monitor the gas leakage, and to cope with any other hazardous problems, continuous surveillance of the network will be required.For this purpose, an environmental observation system for the large scale pipeline network is proposed. In this system unmanned airships are used as platforms for various environmental diagnostics. The unmanned airship is routed along the pipeline with the aid of GPS. Propulsion power of the air ship is transmitted from the ground bases by microwave; the microwave power stations are located every 100–200km along the pipeline.This paper describes the unmanned airships, environmental diagnostic systems, microwave generation tubes, and microwave powering system. © 2004 American Institute of Physics