Volume 11, Number 1

11_1 cover





Atmospheric Compensation and Tracking Using Active Illumination
Charles Higgs, Herbert T. Barclay, Daniel V. Murphy, and Charles A. Primmerman

The U.S. Air Force is developing the airborne laser (ABL), whose mission is to engage and destroy theater ballistic missiles such as the SCUD while these missiles are in their boost phase. This mission capability requires high-energy laser propagation over long horizontal paths (200 to 300 km) through the upper atmosphere. To be effective in the presence of atmospheric turbulence, the ABL must utilize precision tracking and adaptive-optics compensation. Although the strength of atmospheric turbulence at ABL altitudes (35,000 to 45,000 feet) is relatively weak compared to sea level, the long horizontal laser-propagation paths create severe challenges for the adaptive-optics and tracking systems. Because the missile provides no beacon for the adaptive-optics and tracking systems, the missile must be actively illuminated so that backscatter from the missile body can be used to form an image for the tracking system and provide a beacon for the adaptive-optics system. To understand this problem better and to improve system performance, we conducted propagation experiments at the Firepond telescope facility on Millstone Hill in Westford, Mass. These tests utilized a 5.4-km horizontal propagation range between Millstone Hill and a fire tower in Groton, Mass. These experiments, which demonstrated for the first time active tracking and adaptive compensation under ABL conditions, suggest that the ABL can meet its mission goals and perform at levels required for effective theater missile defense.

The Lincoln Near-Earth Asteroid Research (LINEAR) Program
Grant H. Stokes, Frank Shelly, Herbert E.M. Viggh, Matthew S. Blythe, and Joseph S. Stuart

Lincoln Laboratory has been developing electro-optical space-surveillance technology to detect, characterize, and catalog satellites for over forty years. Recent advances in highly sensitive large-format charge-coupled devices (CCDs) allow this technology to be applied to detecting and cataloging asteroids, including near-Earth objects (NEOs). When equipped with a new focal-plane camera and signal processing technology, U.S. Air Force ground-based electro-optical deep-space surveillance (GEODSS) telescopes can conduct sensitive large-coverage searches for Earth-crossing and main-belt asteroids. Field measurements indicate that these enhanced telescopes can achieve a limiting magnitude of 22 over a 2-degree-squared field of view with less than 100 sec of integration. This sensitivity rivals that of much larger telescopes equipped with commercial cameras. Under Air Force sponsorship, we have developed technology for asteroid search operations at the Lincoln Laboratory Experimental Test Site near Socorro, New Mexico. By using a new large-format 2560 X 1960-pixel frame-transfer CCD camera, we have discovered over 10,000 asteroids, including fifty-three NEOs and four comets as designated by the Minor Planet Center (MPC). In March 1998, the Lincoln Near-Earth Asteroid Research (LINEAR) program provided over 150,000 observations of asteroids—nearly 90% of the world's asteroid observations that month—to the MPC, which resulted in the discovery of thirteen NEOs and one comet.

Solid-State Color Night Vision: Fusion of Low-Light Visible and Thermal Infrared Imagery
Allen M. Waxman, J. Mario Aguilar, David A. Fay, David B. Ireland, Joseph P. Racamato, Jr., William D. Ross, James E. Carrick, Alan N. Gove, Michael C. Seibert, Eugene D. Savoye, Robert K. Reich, Barry E. Burke, William H. McGonagle, and David M. Craig

We describe an apparatus and methodology to support real-time color imaging for night operations. Registered imagery obtained in the visible through near-infrared band is combined with thermal infrared imagery by using principles of biological opponent-color vision. Visible imagery is obtained with an image intensifier tube fiber-optically coupled to a conventional charge-coupled device (CCD), and thermal infrared imagery is obtained by using an uncooled thermal imaging array. The two fields of view are matched and imaged through a dichroic beam splitter to produce realistic color renderings of a variety of night scenes. We also demonstrate grayscale and color fusion of intensified-CCD/FLIR imagery. Progress in the development of a low-light-sensitive visible CCD imager with high resolution and wide intrascene dynamic range, operating at thirty frames per second, is described. Example low-light CCD imagery obtained under controlled illumination conditions, from full moon down to overcast starlight, processed by our adaptive dynamic-range algorithm, is shown. The combination of a low-light visible CCD imager and a thermal infrared microbolometer array in a single dual-band imager, with a portable image-processing computer implementing our neural-net algorithms, yields a compact integrated version of our system as a solid-state color night-vision device. The systems described here can be applied to a large variety of military operations and civilian needs.

top of page