Remote sensing limitations

Technology developments are revolutionizing the spectroscopic capabilities at THz frequencies. While no one teclmique is ideal for all applications, both CW and pulsed spectrometers operating at or near the fiindamental limits imposed by quantum mechanics are now within reach. Compact, all-solid-state implementations will soon allow such spectrometers to move out of the laboratory and into a wealth of field and remote-sensing applications. From the study of the rotational motions of light molecules to the large-amplitude vibrations of... 

Luminescence, in particular photoluminescence, constitutes a well-established discipline in analytical science where the cited hallmarks include remarkable sensitivity, wide dynamic range and low detection limits (-10under suitable conditions). These collective merits are often umivaled by other optical techniques, and hence its wide adoption in the life sciences for determining trace constituents in biological and environmental samples. Moreover, its fast response, high spatial resolution and remote sensing capabilities make it attractive for real-time analytical problems such as process manufacturing (process analysis or PAT) and field applications. ... 

In theory, spatially resolved measurements of concentrations of atmospheric trace substances could be made by remote sensing from either surface-based or satellite platforms, but remote sensing capabilities have not yet been developed for many species. Furthermore, both surface- and satellite-based remote sensing methods have distinct limitations in resolving... 

The major constraint to using satellite remote sensing is the relative opacity of the ocean and clouds to electromagnetic radiation. Thus, satellite measurements are limited to the very top layer of the ocean and usually provide little evidence about processes occurring below the ocean surface. 

In the last 23 years remote sensing of atmospheric constituents has established itself as an important research field. Global remote sensing observations are essential to understand the natural processes which determine the global behaviour of the atmosphere and to assess the impact of human activity on the atmosphere. In addition, remote sensing of the atmosphere provides data needed to assess die impact of international agreements designed to limit the environmental impact of industrial activity. 

Use a remote sense line and an auxiliary filter. In that case, the sense line is not mounted integrally to the valve body but can be fitted directly onto the vessel to be protected or at a place which is less contaminated. The length of the remote sense should be limited to approximately 30 m and the pick-up... 

The EPA has proposed an enhanced IM program that would require a dynamometer test under varying engine loads, would test evaporative emissions, and would raise the repair cost limit substantially. The enhanced IM program still has some serious defects. Most notably, it lacks the necessary components of significant on-road, in situ, remote sensing to validate the emission reductions and to catch cars that have been tampered with between inspections. 

Simonson et al. [148] demonstrated remote detection of explosives in soil by combining distributed sensor particles with UV/vis fluorescence LIDAR technology. The key to this approach is that the fluorescence emission spectrum of the distributed particles is strongly affected by absorption of nitroaromatic explosives from the surrounding environment. Remote sensing of the fluorescence quenching by TNT or DNT is achieved by fluorescence LIDAR - the emission spectra were excited in field LIDAR measurements by a frequency-tripled Nd YAG laser at 355 nm and the fluorescence collected with a telescope and various detector systems housed in a 10 x 50 trailer. TNT has been detected in the ppm range at a standoff distance of 0.5 km with this system (Fig. 16). An important limitation to this technique is the pre-concentration of the explosives on the sensor particles, which requires the presence of water to facilitate the transport of the explosive from the surface of the soil particles to the sensor particles. 

The planetary reflectance spectral data constituting Table 10.1 traditionally have been obtained with Earth-based telescopes. Such remote-sensed measurements are limited by telescope availability, favourable observational conditions, and optimum viewing alignments of the planetary objects. As a result,... 

Reading the above, one might get a pessimistic view of the possibilities of remote sensing techniques to derive the composition of cosmic dust in protoplanetary disks. However, when the limitations of the techniques are properly considered, it is possible to derive a wealth of information. The above limitations force one... 

Direct sampling of mantle rocks and minerals is limited to tectonic slices emplaced at the surface (see Chapter 2.04), smaller xenoliths transported upwards by magmatic processes (see Chapter 2.05), and still smaller inclusions in such far-traveled namral sample chambers as diamonds (see Chapter 2.05). Because of such limited direct access to mantle materials, knowledge of mantle structure, composition, and processes must be augmented by geophysical remote sensing. What can various seismological observations tell us about the major-element composition of the upper mantle How can they constrain possible differences in chemical composition between the upper... 

Although such approaches offer very high sensitivity, measurements can be difficult and often dangerous to obtain, and there can be problems of postcollection reactions. Also, the inevitable delays in obtaining results limit then-value in volcanic crises. Remote sensing methods... 

As is clear from several of the earlier sections, estimation of in the field is technically difficult and results are spatially and temporally limited. Some efforts have therefore been made to investigate whether remote-sensing techniques... 

With the advent of satellite remote sensing of surface seawater properties, attempts are now being made to use remotely sensed parameters to estimate surface-ocean nutrient (including phosphate) concentrations and distributions. This approach, although it has its own set of limitations, is one that can potentially redress the data-gap problem of oceanographic surveys. As a... 

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