Remote sensing passive

There are two categories of remote sensing, active and passive. Passive techniques utilise electromagnetic radiation emitted from or transmitted through the atmosphere, the radiation source being for example the black body emission from the earth s surface or solar and stellar irradiances. The most critical part of a passive remote sensing instrument is its detector. In contrast, active remote sensing systems have their own radiation source and a detector, for example, radar and lidar techniques. 

Passive remote sensing by mid-infrared spectroscopy has been successfully applied to the measurement of a large number of stratospheric trace constituents and some upper tropospheric constituents. Initially measurements were made from mountain tops (e.g. Zander, 1981), and balloon and aircraft experiments were subsequently developed (Fischer et al., 1980 Murcray et al., 1975 1979 Coffey et al., 1981 Brasunas etal., 1988 Kunde etal., 1988). 

The only experiment flown up to the present, which specifically uses infrared information to probe the lower troposphere is the Measurement of Air Pollution from Satellites (MAPS) experiment. MAPS is a nadir sounding gas correlation instrument, which makes global measurements of CO in the middle and upper troposphere. It flew three times between 1981 and 1994 on the NASA Space Shuttle (Reichle et al., 1986 1990 Connors etal., 1991). Validation of MAPS was made using ground-based passive remote sensing instruments (Pougatchev et al., 1998). 

The first passive remote sensing experiment to measure successfully the abundance of atmospheric aerosols from space was the Stratospheric Aerosol Measurement (SAM II) aboard Nimbus 7 (McCormick et al. 1979). This experiment was a single channel radiometer observing in solar occultation and was the forerunner of SAGE. Stratospheric aerosols have also been measured by their infrared absorptions (e.g. HALOE). 

The most reliable and self-consistent approach for passive remote sensing of the troposphere is, therefore, the simultaneous use of limb and nadir sounding of the atmosphere (as pioneered by SCIAMACHY and related instruments). 

Passive remote sensing systems are categorized by the degree of spectral detail measured, as well as by the degree of imaging achieved—that is, whether the... 

Detection of hazardous chemicals in industrial environment [5], Passive remote sensing at hazardous and inaccessible locations [5]. 

Basically, there are two approaches to characterizing SNF analysis of the intact fuel elements by active or passive remote sensing methods (i.e., measurement of the electromagnetic radiation and neutron emission) and analysis of fuel elements after dissolution. 

Radio- and microwaves also have several other fields of application in spectroscopy. Molecular rotational transitions correspond to this wavelength region. Radiometers can be used for passive remote sensing, of e.g. temperature and air humidity, and radar systems can be utilized for active measurements of e.g. oil slicks at sea. Finally, radio astronomy is a fascinating field, yielding information on the most remote parts of the universe. 

The broad fluorescence spectrum of CDOM fills Fraunhofer lines presenting the possibility of using very sensitive remote and in situ sensors to study CDOM and chlorophyll in ocean waters (Stoertz et al., 1969 Gee et al., 1993 Vodacek et al., 1994 Hn and Voss, 1998). Although under some conditions has shown promise (i.e., Vodacek et al., 1994), Natural FDOM is very faint (f 1%) and the emission spectrum is to broad to be useful for passive remote sensing of organic matter. 

Hereia optical spectroscopy for laboratory analysis, giving some attention to remote sensing usiag either active laser-based systems (13—16) or passive (radiometric) techniques (17—20), is emphasized. 

The sun, an important factor to take into account in remote sensing using spectroscopic imaging instruments. The passive optical system and the atmosphere through which the energy passes, both from the sun to the earth s surface and back to the instrument, interferes with the data collected. Atmospheric distortions include the effect of scattered dry air molecules (haze) and absorption by air molecules. 

Sippel, S. J., S. K. Hamilton, J. M. Melack, and E. M. M. Novo. 1998. "Passive microwave observations of inundation area and the area/stage relation in the Amazon River floodplain." International Journal of Remote Sensing, 19 3055-3074. 

Remote Sensing of Aerosol Using Passive Light Sources... 

Ulaby FT, Moore RK, Fung AK (1986) Miraowave remote sensing, active and passive, vol 3, From theory to applications. Artech house, Inc, Norwood, MA... 

Preliminary studies for airborne systems were reported by Meeks et al. (87), who studied microwave radiometric detection of oil slicks. A couple of years later, Fantasia and Ingrao (88) and Ingrao et al. (89) described the development of an experimental airborne remote sensing system for oil spills, based on laser-stimulated oil fluorescence. At the Tenth International Symposium on Remote Sensing, in 1975, several techniques were reported, including a passive infrared (90), radar observation of spills (91), passive luminescence with a Fraunhofer line discriminator (FLD) (92), and active luminescence (93) and fluorescence (94). 

In many of the sophisticated experimental techniques applied to photophysical problems, the rapid development of the laser has enabled results to be obtained which were unheard of only a few years ago. These developments have been described adequately in previous and current volumes, but there are two applied uses of the laser which have not yet received significant attention, and to which readers attention is drawn by this short extra section this year. The first is concerned with the remote sensing of atmospheric pollutants. The methods available to achieve this object can be classified as passive, for example the heterodyne detection of thermal emission,209 or active, involving some radiation source. The means of attenuating the intensity of such a source are listed below. 

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