Lewis was an American satellite which was to have been operated by NASA as part of the . It carried two experimental Earth imaging instruments, and an ultraviolet astronomy payload. Due to a design flaw it failed within three days of reaching orbit, before it became operational. Lewis was a 288 kilograms (635 lb) spacecraft, which was designed to operate for between one and three years. It was built by TRW under a contract which was signed on 11 July 1994. Its primary instruments were the , the and the experiment. A number of technology demonstration payloads were also flown.