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AZUSA refers to a ground-based radar tracking system installed at Cape Canaveral, Florida and the NASA Kennedy Space Center. AZUSA dated back to the early 1950s and was named after the southern California town (Azusa, California) where the system was devised. ==Radar interferometry== Radio interferometry has the advantage of yielding very accurate tracking angles when the target cooperates by emitting a radio signal. The angular precision of interferometry led to the development of the Azusa tracking system as part of the Army Air Corps NUL-774 Project, forerunner of the Atlas ICBM program, at the Vultee Field Division of Consolidated Vultee Aircraft Corporation in Downey, California. Two of the basic patents (2,972,047 and 3,025,520) in the field of interferometer tracking are shared by James Crooks, Jr., Robert C. Weaver, and Robert V. Werner, all members of the Azusa design team. By the spring of 1948, the Azusa team had built an interferometer operating at 148.58 MHz. In a strange circle of history, the U.S. Naval Research Laboratory (NRL) was working on underwater sound interferometers at the time Convair was developing Azusa. Since the two groups were in close contact, there was considerable interchange of ideas. * The circle was completed in the early 1950s when the Navy picked up the Azusa interferometer work for its Viking project at White Sands, New Mexico. The Navy wanted to explore the possibility of converting the Viking or some derivative of it into a guided missile and it needed an accurate guidance system. In an early report from this program, NRL's J. Carl Seddon explained how the Viking would determine its position: "The Missile will detect its position relative to the hyperbolic guidance path by phase comparison of modulation waveforms derived from signals received from two pairs of stations." In this scheme, the missile would guide itself using onboard electronics and navigational signals received from the ground. This seems a far cry from Minitrack and satellite tracking, but phase comparison, the essence of Minitrack, is there. Within a year, NRL reports from the Viking program were diagramming ground-based, tracking interferometers, which relieved the Viking of the burden of signal-processing equipment by computing the missile's position from the ground. Two precursors of Minitrack are evident in the interferometer arrangement. First, only a tiny radio beacon needs to be carried on the Viking itself. This was to be an important feature of the Vanguard "Minitrack," in which the prefix 'Mini" applies to the minimum-weight satellite transmitter. The second precursor is the "Lff arrangement of the interferometer antennas which persisted in some early designs of Minitrack, although the final deployed version extended the bars of the "L" to make a cross.〔Corliss, William R., 'The Evolution of the Satellite Tracking and Data Acquisition Network (STADAN)'. Goddard Historical Note No. 3. Greenbelt, MD.: Goddard Space Flight Center, 1967.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「AZUSA」の詳細全文を読む スポンサード リンク
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