| Popis: |
Many luminous sources provide continuous or quasi-continuous radiation at near IR and longer wavelengths. The radiation continuum serves as a source of background photons, which can be used for discrete line-of-site absorption measurements by-known atmospheric constituents. The intensity ratio is uniquely determined by the absorption coefficient and range, is independent of broadband attenuations and scattering. The absorption coefficients are known and/or can be accurately calculated for a wide range of practical viewing conditions (i.e., sensor height, viewing angle, etc.). Hence, the intensity ratio and/or integrated intensity ratio can be used to uniquely derive the range of the radiating source. Fabry-Perot interferometers can provide the high throughputs and resolving powers required in compact packages. The measurements and analyses show that ranging accuracies representing down to 1 - 2% of the total range should be achievable at stand-off ranges of upto hundreds of kilometers depending on the size of the collection optics, brightness of the source and available observation times. The paper will provide an overview of the patented Textron concepts, trade-offs associated with instrument resolving powers and hardware implementation issues. |
