Over the past fifteen years, the Mid-Infrared Advanced Chemical Laser (M[RACL) and SeaLite Beam Director (SLBD) have been completed, moved to the High Energy Laser System Test Facility (HELSTF) at White Sands Missile Range, New Mexico, and integrated into the largest and most powerful high energy laser system in the U.S. The high energy laser system was modified, incorporating a shared aperture (pointing and tracking) capability to improve pointing performance. High power propagation, tracking, and beam control experiments over near vertical beam paths have been conducted. The system modifications, instrumentation, and test results are descnbed.Keywords: high energy lasers, beam control, pointing & tracking, power beaming, full aperture upgrade, shared aperture 2. HISTORY The Navy's High Energy Laser (HEL) Program began th the establishment ofa dedicated program office in 1971. The objective was to develop HEL technology for defending surface ships against antiship missiles. In 1977, the Navy began construction of the Mid-Infrared Advanced Chemical Laser (MIRACL) and initiated the SEA LIFE Program whose goals were to build a weapon power chemical laser system, to install and characterize that system at HELSTF, and to test it against targets ofmterest to the Navy and others.In September 1980, the MIRACL had been completed by TRW and was tested for the first time. MIRACL was a megawatt class laser, thus making it the highest average power continuous wave laser in the free world. Also in 1980, Hughes Aircraft began work on the SEA LifE Beam Director (SLBD) which was designed to accommodate the MJRACL beam and to have an aperture of 1.5 meters. In 1983, after an initial performance evaluation at TRW, MIRACL was moved to HELSTF. SLBD was completed in 1984 and it was then relocated to HELSTF for integration into the IVIIRACL.In December of 1988, a decision was made to modify the MJRACL/SLBD system for exploration of technology and engineering issues associated th the precision pointing of a high energy laser beam from the ground to high altitUde or to space. These modifications were completed in 1991 and a series oftracking, pointing, and propagation experiments were conducted to assess our abifity to track through the HEL aperture, and to validate our propagation models along this near vertical proffle.
HIEL SYSTEM DESCRIPTIONThe MJRACL was build for the Navy by TRW in the late 1970's as the result of a multi-year technology and engineering development program. Beginning with the Baseline Demonstration Laser, and followed by the Navy-ARPA Chemical Laser, the MIRACL was the first megawatt class continuous-wave chemical laser. It is a deuterium fluoride chemical laser with its energy distributed among about 10 lasing lines between 3.6 and 4.0 microns wavelength. MIRACL's operation has been described in detail in previous SPIE proceedings and ll only be summarized here for completeness.The laser is similar to a rocket engine in which a ftiel (ethylene -C2H4) is burned with an oxidizer (nitrogen tri.fluoride -NF3). Free, ...