Field Of Regard Research Articles

Some aspects of ROCSAT-2 system engineering

The ROCSAT-2 is designated to the second satellite of the Republic of China. It is expected to be launched in 2003, and is designed primarily to image the region of Taiwan Island. The satellite will be operated in a circular sun-synchronous orbit with exactly 14 revolutions per day. By virtue of the nearly global coverage of the orbit, the images taken by ROCSAT-2 can also be acquired through international cooperation if the foreign ground stations are capable of receiving the downlink data. The satellite will provide high tasking agility for along-track or cross-track imaging with 45° field of regard. The remote sensing instrument (RSI) has four Landsat-like multi-spectral visible bands. It will provide images for 2 m ground sampling distance (GSD) in panchromatic band and 8 m GSD in multi-spectral bands over 24 km swath in the nadir direction. The secondary payload of ROCSAT-2 is a scientific instrument called the imager of sprite, the upper atmospheric lightning (ISUAL). It will be the first payload to observe the upper atmospheric lightning from space. The objective of this experiment is to study the nature of the electrodynamic coupling between thundercloud and upper atmosphere. The system engineering analysis for ROCSAT-2 is presented in this paper.

Bomb damage assessment using a dispensed sensor projectile

The problem of obtaining images of a target site after munition impact is approached by releasing a small projectile equipped with a camera from a dropped munition. A ballute is deployed from the sensor projectile shortly after release from the munition. This type of system is capable of viewing munition impact and subsequent target effects over a wide variety of conditions and offers the possibility of real-time battle damage assessment (BDA). However, fundamental limits exist on the duration that the camera is able to view the target after impact for a particular required separation distance between the sensor projectile and the target at impact and the field of regard (FOR) of the camera. Munition release altitude and velocity significantly affect these fundamental limits. Optimal performance is attained under high altitude and low speed munition drop conditions. Basic characteristics of the camera projectile also significantly influence system performance. Maximum target view time is attained with a low weight high drag configuration., To reduce the maximum acceleration experienced by the sensor projectile, a small delay time between the release of the small sensor projectile from the munition and inflation of ballute is required.

Space-bandwidth product enhancement of a monostatic, multiaperture infrared image upconversion ladar receiver incorporating periodically poled liNbO3.

We investigate the space-bandwidth product of a ladar system incorporating an upconversion receiver. After illuminating a target with an eye-safe beam, we direct the return into a piece of periodically poled LiNbO3 where it is upconverted into the visible spectrum and detected with a CCD camera. The theoretical and experimental transfer functions are then found. We show that the angular acceptance of the upconversion process severely limits the receiver field of regard for macroscopic coupling optics. This limitation is overcome with a pair of microlens arrays, and a 43% increase in the system's measured space-bandwidth product is demonstrated.

Mathematical Aspects in Meteorological Processing of Infrared Spectral Measurements from the GOES Sounder. Part I: Constructing the Measurement Estimate Using Spatial Smoothing

Abstract The accuracy of temperature and moisture vertical profiles retrieved from infrared spectral measurements is dependent on accurate definition of all contributions from the observed “surface–atmosphere” system to the outgoing radiances. The associated inverse problem is ill posed. Instrument noise is a major contributor to errors in modeling spectral measurements. This paper considers an approach for noise reduction in the Geostationary Operational Environmental Satellite (GOES) spectral channels using spatial averaging that is based upon spectral characteristics of the measurements, spatial properties of atmospheric fields of temperature and moisture, and properties of the inverse problem. Spatial averaging over different fields of regard is studied for the GOES-8 sounder spectral bands. Results of the statistical analysis are presented.

Effects of extremely low frequency electromagnetic fields for ions in solutions?a cyclotron resonance and its threshold

It is known experimentally that biological cell membrane transport of ions such as Ca2+ and K+ is affected by the electromagnetic field when it combines the uniform static magnetic field and the extremely low-frequency (ELF) ac electromagnetic field. This is thought to be caused by a contribution of some type of resonance phenomena that is based on the interaction of the ions and the electromagnetic field. Cyclotron resonance has received attention since it has a window effect in the ELF region. Resonance generation, however, is questionable due to solution viscosity or the collision of the ions with other molecules in solute. In order to understand quantitatively the cyclotron resonance phenomena, the ion behaviors in solutions placed in an electromagnetic field are analyzed using a mathematical model so that the threshold value of the static magnetic field causing resonance is derived. From the computer simulation and analysis results, it is found that the threshold value is determined by the ratio of the magnetic flux density of the static magnetic field and the viscosity coefficient of the solution. The threshold of the magnetic field in regard to the conductivity of the ions was 6.9 × 106 T and 8.8 × 106 T, respectively, for K+ and Ca2+. The magnetic flux density of such a magnitude is not commonly taken. These values are almost identical to the threshold for ion diffusion. The threshold value of the magnetic field for the ion mobility was 5 to 8 larger than the above. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (1): 70–77, 1997

Near Infrared Spectrometer for the Near Earth Asteroid Rendezvous Mission

The Near-Infrared Spectrometer (NIS) instrument on the Near-Earth Asteroid Rendezvous (NEAR) spacecraft is designed to map spectral properties of the mission target, the S-type asteroid 433 Eros, at near-infrared wavelengths diagnostic of the composition of minerals forming S asteroids. NIS is a grating spectrometer, in which light is directed by a dichroic beam-splitter onto a 32-element Ge detector (center wavelengths, 816–1486 nm) and a 32-element InGaAs detector (center wavelengths, 1371–2708 nm). Each detector reports a 32-channel spectrum at 12-bit quantization. The field-of-view is selectable using slits with dimensions calibrated at 0.37° × 0.76° (narrow slit) and 0.74° × 0.76° (wide slit). A shutter can be closed for dark current measurements. For the Ge detector, there is an option to command a l0x boost in gain. A scan mirror rotates the field-of-view over a 140° range, and a diffuse gold radiance calibration target is viewable at the sunward edge of the field of regard. Spectra are measured once per second, and up to 16 can be summed onboard. Hyperspectral image cubes are built up by a combination of down-track spacecraft motion and cross-track scanning of the mirror. Instrument software allows execution of data acquisition macros, which include selection of the slit width, number of spectra to sum, gain, mirror scanning, and an option to interleave dark spectra with the shutter closed among asteroid observations. The instrument was extensively characterized by on-ground calibration, and a comprehensive program of in-flight calibration was begun shortly after launch. NIS observations of Eros will largely be coordinated with multicolor imaging from the Multispectral Imager (MSI). NIS will begin observing Eros during approach to the asteroid, and the instrument will map Eros at successively higher spatial resolutions as NEAR’s orbit around Eros is lowered incrementally to 25 km altitude. Ultimate products of the investigation will include composition maps of the entire illuminated surface of Eros at spatial resolutions as high as as ~300 m.

Use of a coupled ice‐ocean model to investigate the sensitivity of the Arctic ice cover to doubling atmospheric CO2

A coupled ice‐ocean Arctic ocean model is forced with output from a Canadian Climate Center (CCC) model of the atmosphere. Two cases are considered, the first where the atmospheric CO2 is “normal” and the second where the atmospheric CO2 is “doubled.” The CCC normal forcing data are also compared with observed fields, It is found that the forcing fields from the CCC normal model run are quite similar to observed values of surface temperature and humidity. The wind stresses are, however, lower than observed geostrophic values and are hence scaled to more closely match observed values. Significant differences are found between the normal and doubled CO2 forcing fields in regard to temperature and humidity forcing fields. In particular, the surface air temperature is typically 10° Celsius warmer in the doubled case for the winter months, and the relative humidity is up to 50% higher in the summer months. The surface moisture flux from the CCC data is found to be relatively insensitive to doubling of CO2, with more precipitation less evaporation (P–E) in winter months. When the ice‐ocean model is run, less ice volume and increased areas of open ocean are observed with the doubled forcing, however, the decrease in ice volume is not as large as previous, simpler models have suggested and the model ice cover differs significantly from the ice cover from the atmospheric model. It is also found that there are differences in the oceanic temperature and salinity fields consistent with the forcing inputs, but these appear to be minimized by the insulating properties of the ice cover. On balance, the Arctic ice field appears to act as a regulator of climate change, rather than an accelerator.

Learning Via Queries With Teams And Anomalies

Most work in the field of inductive inference regards the learning machine to be a passive recipient of data. In a prior paper the passive approach was compared to an active form of learning where ...

Short-wavelength imaging laser radar using a digicon detector

532-nm direct-detection imaging laser radar using a prototype digicon receiver was constructed and has demonstrated rapid multiple retargeting over a wide field of regard, obtaining single-shot images with intensity and three-dimensional position data for each target. Such laser radar capability is important for discrimination and targeting. The digicon receiver system obtains 8 x 8 pixel images of multiple targets at a rate of 15 Hz. Each image provides both intensity and range-to-target at each pixel. Results of experiments involving seven targets located at various distances along a 60-m light tunnel are presented. Future directions discussed are acquisition and hand-off, tracking, long-range outdoor experiments (~ 1 km), and a 16 x 16 array digicon tube with magnification.

Spatial statistics of transformer core noise

The tonal nature of the core noise, the difference in pathlength and the different phasing of the sound radiated from the various tank surfaces result in complex spatial interference patterns which characterize the farfield which can be described only in statistical terms. This paper deals with the consequences of the statistical nature of sound field in regard to: (1) Developing meaningful techniques to measure farfield transformer core noise, (2) predicting the expected value and spatial statistics of the farfield noise on the basis of near/field measurements, and (3) defining meaningful performance evaluation measures to determine the effectiveness of such retrofit noise control measures as barriers and enclosures.

Experimental study of the external fringing field on integrated head

We have presented calculations of write field from an integrated head. These approach was based on a micromagnetism analysis. We have shown that it was possible to modify the magnetic potential on finite pole tips surface, in order to minimize the extra-pulse effect caused by negative trailins pde fields, by changing the multilayered structure of pole tips. The purpose of this paper is to show the practical recording efficiency of such structure. We have chosen tape recording, because the phenomenon is more significant on thick recording medium. Like conventional heads, it is the last gap corner field in regard to the tape motion which gives the magnetization distribution in the medium. On a integrated head it's the last pole piece field which drive the tape magnetization. When the write head is symmetric in regard to its gap axis (y), it appears as read-back distortion due to the magnetization distribution in the medium. If we change the multilayered structure only on the writing (last) pole tip, the magnetization distribution in the medium is modified, and the distortion can be made to disappear. It's of course a write phenomenon because the read head is symmetric and the same in the both cases. A discussion explains why the distortion with symmetric write heads is more significant when there are transitions interacting.

Harmonics in a.c. rotating machines

A general approach to harmonic phenomena in a.c. rotating machines is developed. A flux-density component, b = B sin (kωt ± qθs + o), where k and q are integral constants, is taken as the central concept-This b-distribution is, in general, harmonic in time and space, and a series of such components can represent any cyclic flux distribution encountered. The effects of such a field in regard to voltage and torque production are analysed, with quite simple results when used with the concept that any machine winding may be treated as equivalent to a series connection of sinusoidal space-harmonic windings. Various common causes of harmonics are next analysed using these general results. Appendix 9.1 develops expressions for harmonic winding turns in terms of the actual winding distribution, while Appendix 9.2 examines some effects of saliency in synchronous machines.

On the gyration of light by multiplet lines

1. In the last few years thee has been a great development of the theory of the intensities of spectral lines, and in its turn this theory has reacted on the general theory of spectra; so that any experimental method which throws new light on the subject has a great importance. It has not apparently been explicitly noticed that a study of the dispersive effect of the rotation of polarised light by a vapour can be made to yield information on the second approximations to the intensities of the ┴ Zeeman components. Since tire difficulties of direct intensity measurement and of obtaining strong magnetic fields must always lie very great, there would seem to lie an advantage in having a method of attach which is, it is true, difficult, but only with the difficulty of a very well-known technique, the study of polarised light. The present work is a theoretical investigation of some of the properties that may be expected to lie found. In a recent paper the present writer worked out some results on the subject using tbs purely mechanical models of the type discussed by Voigt, and obtained the result that any atom which exhibits the Paschen bacf effect should show a similar effect in a magnetic field in regard to the gyration of light, provided that the frequency of this light is not too close to the lines of the multiplet . (Of course light in the immediate neighbourhood will not be affected in this way, but will exhibit the actual Zeeman effect inversely.) In other words, the equation of Becquerel relating the gyratory constant V with the refractive index - n V = e / 2 mc 2 λ dn / dλ will give the normal value of e/m , and all trace of the anomalous Zeeman effect will disappear. If this result is true for a single multiplet, it will remain true in regions where more than one contribute sensibly to the retraction, and will only fail for light of frequency very close to that of one of the multiplets of ths spectrum.

Our Book Shelf

ALTHOUGH published in 1890, it is right to say that this compilation only brings our knowledge down to the beginning of the year 1885. It is intended to have a supplement ready soon, and to bring the work up to date.In the meantime we can speak highly of the evident care and labour bestowed on this volume by the compiler. The arrangement is based on that of Mr. Daydon Jackson's “Vegetable Technology.” There is a catalogue of authors, a list of anonymous publications, a list of periodicals, a list of Parliamentary publications, and a chronological table. The first part of the latter is taken from Dr. Falconer's “Sketch of Sugar in Early Times” (1796).The comprehensive subject-index forms a very valuable part of the work. It is arranged in sections as follows:— Bibliography and History, Statistics and General Economy,Illustrations, Geographical Distribution, Chemistry, Origin of Vegetable Sugars (the various plants yielding sugars), Beet Sugar, Cane Sugar, Parasites, and Distillation. It will be easily seen that this guide to the literature of sugar covers practically the whole field in regard to vegetable sugars. It is a work that will prove of much interest to numerous readers having to do with the cultivation and manufacture of sugar, whether derived from the sugar-cane, beet, sorghum, palm, maple, or maize. We only hope the compiler will be encouraged to bring out the promised supplement. During the last five years considerable activity has been displayed in the United States in regard to the production of sugar from sorghum; and there is, besides, the very important fact that the sugar-cane has recently been shown to produce mature seed, and possibly capable of improvement by seminal selection. The literature in regard to this point alone is well worthy of being carefully traced. A Guide to the Literature of Sugar: a Book of Reference for Chemists, Botanists, Librarians, Manufacturers, and Planters, with a Comprehensive Subject-Index. By H. Ling Roth. (London: Kegan Paul, Trench, Trübner, and Co., Limited, 1890.)