An analysis was performed, using MODTRAN, to determine the best filters to use for detecting the
muzzle flash of an AK-47 in daylight conditions in the desert. Filters with bandwidths of 0.05, 0.1,
0.5, 1.0, 3.0, and 5.0 nanometers (nm) were analyzed to understand how the optical bandwidth affects
the signal-to-solar clutter ratio. These filters were evaluated near the potassium D1 and D2 doublet
emission lines that occur at 769.89 and 766.49 nm respectively that are observed where projectile
propellants are used. The maximum spectral radiance, from the AK-47 muzzle flash, is 1.88 x 10-2
W/cm2 str micron, and is approximately equal to the daytime atmospheric spectral radiance. The
increased emission, due to the potassium doublet lines, and decreased atmospheric transmission, due to
oxygen absorption, combine to create a condition where the signal-to-solar clutter ratio is greater than
1. The 3 nm filter, has a signal-to-solar clutter ratio of 2.09 when centered at 765.37 nm and provides
the best combination of both cost and signal sensitivity.
The optical performance of an infrared sparse sensor detector system is modeled. Such a system, due to its low cost, uses single element, spherical, off-the-shelf optical components that may produce poor quality off-axis images. Since sensors will not populate the entire focal plane, it is necessary to evaluate how the optics will affect sensor placement. This analysis will take into account target location, optical system aberrations, and wavelength, in an effort to determine the proper placement of the sparsely populated sensors.
A potential calibration strategy for the N-P series Solar X-ray Imager (SXI), on the Geostationary Operational Environmental Satellite (GOES), that uses an astronomical X-ray source (the Crab Nebula) is analyzed below. The Crab Nebula is one of the brightest X-ray sources in the sky, and is located near the ecliptic, making consideration of such a calibration possible due to its annual proximity to the sun. The results of these analyses show that in-flight calibration of SXI N-P using the Crab Nebula is possible. Using the longest single exposure which the instrument is capable of making (65 sec) yields a signal-to noise-ratio somewhat insufficient to meet SXI N-P's 20% photometric accuracy requirement. However, summing several 65 second images would increase the signal to noise ratio, making such a calibration readily possible. This analysis demonstrates that effective calibration of SXI N-P could be carried out with only the relatively small cost of operations and analysis to the government, using approximately 12 hours of observing time per year. Expensive calibration underflights, using sounding rockets, would not be needed for SXI N-P. It is important to note that if the GOES R SXI, the follow on series to GOES N-P, uses a normal incidence primary mirror design, an astrophysical calibration with the Crab nebula will not be possible because of the change in instrument spectral response. However, other astrophysical sources could be examined.