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Lightning in all corners of the world is monitored by one or more land- or space-based lightning locating systems (LLSs). The applications that have driven these developments are numerous and varied. This paper describes the history leading to modern LLSs that sense lightning radiation fields at multiple remote sensors, focusing on the interactions between enabling technology, scientific discovery, technical development, and uses of the data. An overview of all widely used detection and location methods is provided, including a general discussion of their relative strengths and weaknesses for various applications. The U.S. National Lightning Detection Network (NLDN) is presented as a case study, since this LLS has been providing real-time lightning information since the early 1980s, and has provided continental-scale (U.S.) information to research and operational users since 1989. This network has also undergone a series of improvements during its >20-year life in response to evolving detection technologies and expanding requirements for applications. Recent analyses of modeled and actual performance of the current NLDN are also summarized. The paper concludes with a view of the short- and long-term requirements for improved lightning measurements that are needed to address some open scientific questions and fill the needs of emerging applications. [ABSTRACT FROM AUTHOR]

Abstract: We present spectroscopic and photometric observations, spanning the optical UV to the far red, before, during, and after the NASA Deep Impact event of July 4, 2005. The inner 2000 km of the pre- and post-impact coma was about 0.3 magnitude redder in B–R than in the outer coma. The pre-impact spectrum was a faint reflected solar spectrum dominated by molecular emissions extending from the nucleus. The post-impact light curve in R and I showed a rapid rise consistent with an expanding optically thick cloud during the first 18 min after impact. During the next 8 min the cloud became optically thin. Sixty minutes after impact the impact R-band flux reached a plateau at , the comet brightening by a factor of ∼4.3 above its pre-impact value observed in a 15″ aperture. The mean expansion velocity of the grains during the first 49 min was . The spectrum became dominated by scattered sunlight during the first hour after impact. The volume scattering function (VSF) observed 32 min after impact shows strong reddening. At 49 min, however, the VSF shows an additional twofold increase in the blue but only a 20% increase at 5500 Å. Post-impact spectra and R–I photometry showed rapid reddening. The particle size distribution, dominated by 1–2.5 μm particles shortly after impact, changed dramatically during the first hour due to sublimation of water-ice particles of this size. On the night following impact the comet was still substantially brighter than before impact, but R–I had returned to its pre-impact value. B–R remained significantly redder. The ejecta 25 h after impact was fan-shaped subtending ∼180° roughly symmetrical about position angle 225°. The mean expansion velocity 90° from the direction to the Sun was . [Copyright &y& Elsevier]

Abstract: On UT 2000 August 21 we obtained simultaneous visible and mid-infrared observations of Comet 9P/Tempel 1, the target of the upcoming NASA Discovery Program mission Deep Impact. The comet was still quite active while 2.55 AU from the Sun (post-perihelion). Two independent analyses of our data, one parameterizing the coma morphology and the other modeling infrared spectrophotometry, show that the nucleus''s cross section at the time the data were taken corresponds to an effective radius of . Based on visible-wavelength photometry of the comet taken during this observing run and others in the summer of 2000, all of which show the rotational modulation of the nucleus''s brightness, we find that the infrared data were obtained near the maximum of the light curve. If we assume that the nucleus''s light curve had a peak-to-valley range of , then the mean effective radius is . Visible-wavelength photometry of the nucleus, including data published by other groups, lets us constrain the nucleus''s R-band geometric albedo: . The nucleus''s flux contributed about 85% of the light in the mid-infrared images. [Copyright &y& Elsevier]

The Surface Radiation budget (SURFRAD) network was developed for the United States in the middle 1990s in response to a growing need for more sophisticated in situ surface radiation measurements to support satellite system validation; numerical model verification; and modern climate, weather, and hydrology research applications. Operational data collection began in 1995 with four stations; two stations were added in 1998. Since its formal introduction to the research community in 2000, several additions and improvements have been made to the network’s products and infrastructure. To better represent the climate types of the United States, a seventh SURFRAD station was installed near Sioux Falls, South Dakota, in June 2003. In 2001, the instrument used for the diffuse solar measurement was replaced with a type of pyranometer that does not have a bias associated with infrared radiative cooling of its receiving surface. Subsequently, biased diffuse solar data from 1996 to 2001 were corrected using a generally accepted method. Other improvements include the implementation of a clear-sky diagnostic algorithm and associated products, better continuity in the ultraviolet-B (UVB) data record, a reduced potential for error in the downwelling infrared measurements, and development of an aerosol optical depth algorithm. Of these, only the aerosol optical depth product has yet to be finalized. All SURFRAD stations are members of the international Baseline Surface Radiation Network (BSRN). Data are submitted regularly in monthly segments to the BSRN archive in Zurich, Switzerland. Through this affiliation, the SURFRAD network became an official part of the Global Climate Observing System (GCOS) in April 2004. [ABSTRACT FROM AUTHOR]

The accuracy of most widely used empirical models are investigated using the spectrally accelerated forward-backward (FBSA) method as a benchmark solution. First, FBSA results are obtained for propagation over large scale terrain profiles and compared with measurements to assess the accuracy of FBSA. Then, accuracy of some International Telecommunication Union (ITU) and Federal Communications Commission (FCC) propagation models are investigated. It has been observed that, for rural areas, the prediction of the most recent ITU recommended propagation model (Rec. 1546) deviates much more than older models do. [ABSTRACT FROM AUTHOR]

The Herschel space observatory, a cornerstone mission of the European Space Agency, with a Principal-Investigator-provided science payload, and contributions from the US National Aeronautics and Space Administration, is designed to explore the far-infrared and submillimeter spectral range with a powerful set of astronomical instruments built by multinational consortia of scientists and engineers. Herschel is expected to be launched in the spring of 2007. It will house a 3.5-m passively cooled telescope and three instruments operating in the wavelength range from 60 to 650 μm. The photodetector array camera and spectrometer will be capable of imaging photometry and imaging-line-spectroscopy in the 60–210 μm regime with a spectral resolution of ∼175 km s-1, corresponding to a spectral resolving power R∼1500. The spectral and photometric imaging receiver will operate in the 200–650 μm range, to map large areas of the sky. It will also carry out low resolution Fourier transform spectroscopy, whose resolution can be varied at least over the range of 1–0.4 cm-1, corresponding to R∼19 to 48 at 520 μm, but with a goal of increasing this range from 2 to 0.04 cm-1. The heterodyne instrument for the far-infrared will provide very high spectral resolving power up to R∼3×106 in the spectral frequency band from ∼480 to 1910 GHz (625–158 μm). This article describes these instruments and the astronomical problems they are expected to address. [Copyright &y& Elsevier]

Hyperspectral sensors can make narrow-band measurements for several hundred regions of the electromagnetic spectrum, and with increasing frequency, multi-dates of remotely sensed data are being used for Earth observation purposes. The use of more spectral bands is creating greater demand for larger computer storage capacity and faster data processors. This study evaluates the use of raw Thematic Mapper (TM) band combinations and several derived vegetation indices to determine optimal vegetation indices and band combinations for discriminating among six grassland management practices in eastern Kansas. Results showed that among the transformed dataset, the Greenness Vegetation Index was found to be the best for discriminating among grassland management types. When evaluating the raw TM bands, TM4 (NIR) was always selected in Discriminate Analysis as the best discriminating variable. There is no significant improvement in grassland discrimination by using a combination of the raw TM bands and the vegetation indices. Increasing the number of TM bands by using multiple dates of imagery will improve discrimination accuracy up to a point, but the use of too many bands (greater than 10 or 12) can actually decrease discrimination accuracy. [ABSTRACT FROM AUTHOR]