Electro-optical MASINT - Spectroscopic MASINT

Spectroscopic MASINT

Spectroscopy can be applied either to targets that are already excited, such as an engine exhaust, or stimulated with a laser or other energy source. It is not an imaging technique, although it can be used to extract greater information from images.

Where an IMINT sensor would take a picture that fills a frame, the Spectroscopic MASINT sensor gives a list, by coordinate, of wavelengths and energy. Multispectral IMINT is likely to discriminate more wavelengths, especially if it extends into the IR or UV, than a human being, even with an excellent color sense, could discriminate.

The results plot energy versus frequency. A spectral plot represents radiant intensity versus wavelength at an instant in time. The number of spectral bands in a sensor system determines the amount of detail that can be obtained about the source of the object being viewed. Sensor systems range from

• multispectral (2 to 100 bands) to
• hyperspectral (100 to 1,000 bands) to
• ultraspectral (1,000+ bands).

More bands provide more discrete information, or greater resolution. The characteristic emission and absorption spectra serve to fingerprint or define the makeup of the feature that was observed. A radiometric plot represents the radiant intensity versus time; there can be plots at multiple bands or wavelengths. For each point along a time-intensity radiometric plot, a spectral plot can be generated based on the number of spectral bands in the collector, such as the radiant intensity plot of a missile exhaust plume as the missile is in flight. The intensity or brightness of the object is a function of several conditions including its temperature, surface properties or material, and how fast it is moving. Remember that additional, non-electro-optical sensors, such as ionizing radiation detectors, can correlate with these bands.

Advancing optical spectroscopy was identified as a high priority by a National Science Foundation workshop in supporting counterterrorism and general intelligence community needs. These needs were seen as most critical in the WMD context. The highest priority was increasing the sensitivity of spectroscopic scanners, since, if an attack has not actually taken place, the threat needs to be analyzed remotely. In the real world of attempting early warning, expecting to get a signature of something, which is clearly a weapon, is unrealistic. Consider that the worst chemical poisoning in history was an industrial accident, the Bhopal disaster. The participants suggested that the "intelligence community must exploit signatures of feedstock materials, precursors, by-products of testing or production, and other inadvertent or unavoidable signatures." False positives are inevitable, and other techniques need to screen them out.

Second to detectability, as a priority was rejecting noise and background. It is especially difficult for biowarfare agents, which are the greatest WMD challenge to detect by remote sensing rather than laboratory analysis of a sample. Methods may need to depend on signal enhancement, by clandestine dispersion of reagents in the area of interest, which variously could emit or absorb particular spectra. Fluorescent reactions are well known in the laboratory; could they be done remotely and secretly? Other approaches could pump the sample with an appropriately tuned laser, perhaps at several wavelengths. The participants stressed that the need to miniaturize sensors, which might enter the area in question using unmanned sensors, including miniaturized aerial, surface, and even subsurface vehicles.

Electro-optical spectroscopy is one means of chemical detection, especially using non-dispersive infrared spectroscopy is one MASINT technology that lends itself to early warning of deliberate or actual releases. In general, however, chemical sensors tend to use a combination of gas chromatography and mass spectrometry, which are more associated with materials MASINT. See Chemical Warfare and Improvised Chemical Devices.

Laser excitation with multispectral return analysis is a promising chemical and possibly biological analysis method.