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This report summarizes a major paper reviewing Canadian work using Landsat imagery for studying changes in lakes and in coastal environments. The nature of environmental change is discussed. For lakes and coastal environments, it is suggested that change is either seasonal, long term, short term or constant; examples of each are given. There is also an important distinction between natural and man-induced change. Outlined in the paper are studies of the filling of the LG2 Reservoir, water level and vegetation changes in the Peace-Athabasca Delta, possible vegetation changes due to the construction of Roberts Bank Port near Vancouver and measurement of surface suspended sediment concentration in the Bay of Fundy using chromaticity analysis.

This report summarizes a major paper reviewing Canadian work using Landsat imagery for monitoring the environmental effects of the development of both renewable and non-renewable resources. Landsat has definite advantages for studying resources. In particular, the data are able to show changes in surface cover indicating in many cases development or the exploitation of resources. Monitoring of areas and rates of change over time is possible. Outlined in the paper are examples related to three aspects of resource development. First is the use of Landsat for updating topographic maps for areas where recent developments have taken place. The second aspect is forestry, and examples related to the detection and measurement of clear cuts and recording of areas affected by spruce budworm are reported. Finally, studies of landscape changes produced by mining activities are presented.

This report summarizes a major paper reviewing the progression of work using Landsat for land use and agricultural monitoring in Canada since 1973. From the launch of Landsat to the present, the focus has moved from using simple visual techniques for interpretation of photographic products to the use of conceptually simple methods which now employ the power of special-purpose image analysis hardware and the standard geometrically corrected products available in Canada. Outlined in the major paper are studies on urban growth, large area land use mapping, crop studies (related to both crop area estimates and erosion potential), assessment of changes in vegetation vigour and clearing of land in areas which were devoted to both dry land farming and forestry. This report emphasizes developments in land use studies.

This paper loosely summarizes the Symposium in the context of estimating the distance to the solar wind termination shock. Thus the major constituents of the heliosphere are first reviewed including the solar wind and its shocks, magnetic structure and stream structure, the interstellar neutral gas and its daughters, the interstellar pickup ions and the cosmic ray anomalous component, and the galactic cosmic rays. Then a direct calculation of the distance to the termination shock is presented, which yields 80 AU but with large error bars. Finally information carried by messengers from the termination shock and heliosheath (the kHz radio bursts observed by Voyager, galactic cosmic rays, the cosmic ray anomalous component, and the interstellar neutral gas and backscattered photons) is assessed and interpreted. The paper concludes that 80 AU is the best bet.

High Gradient Magnetic Fields (HGMFs) offer new opportunities for studying the gravitropic system of plants. However, it is necessary to analyze the influence that HGMF can have on cellular processes and structures that may not be related to amyloplasts displacement. This paper considers possible HGMF effects on plants, which may accompany HGMF stimulation of amyloplasts and contribute to the mechanisms of the HGMF-induced curvature.

Gravitropically tip-growing cell types are attractive unicellular model systems for investigating the mechanisms and the regulation of gravitropism. Especially useful for studying the mechanisms of positive and negative gravitropic tip-growth are characean rhizoids and protonemata. They originate from the same cell type, show the same overall cell shape, cytoplasmic zonation, arrangement of actin and microtubule cytoskeleton, use statoliths for gravisensing, but show opposite gravitropism. In both cell types, actin microfilaments are complexly organized in the apical dome, where a dense spherical actin array is colocalized with spectrin-like epitopes and a unique endoplasmic reticulum aggregate, the structural center of the Spitzenkörper. The opposite gravitropic responses seem to be based on differences in the actin-organized anchorage of the Spitzenkörper and the actin-mediated transport of statoliths. In negatively gravitropic (upward bending) protonemata, the statoliths-induced drastic upward shift of the cell tip is preceded by a relocalization of dihydropyridine-binding calcium channels and of the apical calcium gradient to the upper flank (bending by bulging). Such relocalizations have not been observed in positively gravitropically responding (downward growing) rhizoids in which statoliths sedimentation is followed by differential flank growth (bending by bowing). This paper reviews the current knowledge and hypotheses on the mechanisms of the opposite gravitropic responses in characean rhizoids and protonemata.

The mechanisms proposed to explain gravity sensing can be divided into two groups, “statolith” and “non-statolith” mechanisms. The traditional estimates of the plausibility of these mechanisms are based on the analysis of the signal-to-noise ratio. The existing data indicate that the problem of plant gravisensing may be related to the general problem of the detection of weak signals in mechanoreceptors. This paper reviews the known mechanisms of plant gravisensing as well as the latest nonlinear stochastic models of mechanoreception in which noise promotes detection and amplification of weak signals. These models based on nonlinear stochastic phenomena may be used to explain plant gravisensing, if the cell is considered a dynamic, spatially distributed system of active intracellular cytoskeletal networks and mechanosensitive proteins.

The study of the influence of weightlessness on fertilization and embryonic development of a vertebrate is of importance in the understanding of basic embryogenesis and in the preparation of the future exploration of space. Accordingly, specific hardware was designed to perform experiments on board the MIR space station with an amphibian vertebrate model, taking into account the biological requirements and the multiple constraints of a longterm space mission. This paper describes the biological uses and presents the technological specifications of the device developed under CNES management. The hardware was adapted to and is compatible with biological requirements as confirmed by three experiments performed in space on board the orbital MIR station.

Long-term space missions may increase risks of unfavorable consequences for cosmonauts as a result of radiation effects. This paper presents results of a study of cytogenetic damage in cosmonauts' peripheral blood lymphocytes induced by space radiation. Cultivation of lymphocytes and analysis of chromosomal aberrations were made according to generally accepted methods. It is shown that the yields of dicentrics and centric rings scored after long-term space flights are considerably higher than those scored prior to the flights. An attempt was made to assess individual doses received by cosmonauts. Individual biodosimetry doses received by cosmonauts who showed a reliable increase in the yields of chromosomal-type aberrations after their first flights were estimated to be from 0.02 to 0.28 Gy.

Several advances have been achieved in the knowledge of nuclear architecture and functions during the last decade, thus allowing the identification of interphase chromosome territories and sub-chromosomal domains (e.g. arm and band domains). This is an important step in the study of radiation-induced chromosome aberrations; indeed, the coupling between track-structure simulations and reliable descriptions of the geometrical properties of the target is one of the main tasks in modelling aberration induction by radiation, since it allows one to clarify the role of the initial positioning of two DNA lesions in determining their interaction probability. In the present paper, the main recent findings on nuclear and chromosomal architecture are summarised. A few examples of models based on different descriptions of interphase chromosome organisation (random-walk models, domain models and static models) are presented, focussing on how the approach adopted in modelling the target nuclei and chromosomes can influence the simulation of chromosomal aberration yields. Each model is discussed by taking into account available experimental data on chromosome aberration induction and/or interphase chromatin organisation. Preliminary results from a mechanistic model based on a coupling between radiation track-structure features and explicitly-modelled, non-overlapping chromosome territories are presented.

Many bodies in the outer Solar System display the presence of low albedo materials. These materials, evident on the surface of asteroids, comets, Kuiper Belt objects and their intermediate evolutionary step, Centaurs, are related to macromolecular carbon bearing materials such as polycyclic aromatic hydrocarbons and organic materials such as methanol and related light hydrocarbons, embedded in a dark, refractory, photoprocessed matrix. Many planetary rings and satellites around the outer gaseous planets display such component materials. One example, Saturn's largest satellite, Titan, whose atmosphere is comprised of around 90% molecular nitrogen N2 and less than 10% methane CH4, displays this kind of low reflectivity material in its atmospheric haze. These materials were first recorded during the Voyager 1 and 2 flybys of Titan and showed up as an optically thick pinkish orange haze layer. These materials are broadly classified into a chemical group whose laboratory analogs are termed “tholins”, after the Greek word for “muddy”. Their analogs are produced in the laboratory via the irradiation of gas mixtures and ice mixtures by radiation simulating Solar ultraviolet (UV) photons or keV charged particles simulating particles trapped in Saturn's magenetosphere. Fair analogs of Titan tholin are produced by bombarding a 9:1 mixture of N2:CH4 with charged particles and its match to observations of both the spectrum and scattering properties of the Titan haze is very good over a wide range of wavelengths. In this paper, we describe the historical background of laboratory research on this kind of organic matter and how our laboratory investigations of Titan tholin compare. We comment on the probable existence of polycyclic aromatic hydrocarbons in the Titan Haze and how biological and nonbiological racemic amino acids produced from the acid hydrolysis of Titan tholins make these complex organic compounds prime candidates in the evolution of terrestrial life and extraterrestrial life in our own Solar System and beyond. Finally, we also compare the spectrum and scattering properties of our resulting tholin mixtures with those observed on Centaur 5145 Pholus and the dark hemisphere of Saturn's satellite Iapetus in order to demonstrate the widespread distribution of similar organics throughout the Solar System. Published by Elsevier Science Ltd on behalf of COSPAR.

In this paper we describe a three-dimensional, multicellular tissue-equivalent model, produced in NASA-designed, rotating wall bioreactors using mammalian cells engineered for genomic containment of multiple copies of defined target genes for genotoxic assessment. Rat 2λ fibroblasts, genetically engineered to contain high-density target genes for mutagenesis (Stratagene, Inc., Austin, TX), were cocultured with human epithelial cells on Cytodex beads in the High Aspect Ratio Bioreactor (Synthecon, Inc, Houston, TX). Multi-bead aggregates were formed by day 5 following the complete covering of the beads by fibroblasts. Cellular retraction occurred 8–14 days after coculture initiation culminating in spheroids retaining few or no beads. Analysis of the resulting tissue assemblies revealed: multicellular spheroids, fibroblasts synthesized collagen, and cell viability was retained for the 30-day test period after removal from the bioreactor. Quantification of mutation at the LacI gene in Rat 2λ fibroblasts in spheroids exposed to 0–2 Gy neon using the Big Blue color assay (Stratagene, Inc.), revealed a linear dose-response for mutation induction. Limited sequencing analysis of mutant clones from 0.25 or 1 Gy exposures revealed a higher frequency of deletions and multiple base sequencing changes with increasing dose. These results suggest that the three-dimensional, multicellular tissue assembly model produced in NASA bioreactors are applicable to a wide variety of studies involving the quantification and identification of genotocity including measurement of the inherent damage incurred in Space.

The Mole, an hammer based penetrometer to be used as a sampling tool on the Beagle2 Lander (ESA Mars Express 2003 mission) was the object of several investigations, to identify the main parameters ruling its intrusion process and subsequently optimize and improve it. The working environment of the Mole (Martian sand-like soil) was simulated and fully characterized to allow repeatable test conditions. For this characterization a Piezocone able to detect the frontal force and the lateral friction during the penetration was also used. A Mole simulator was used for fast testing of the frontal resistance. Once a good and “repeatable” Mars simulant was obtained the Mole performed several intrusions and extractions. An accelerometer mounted behind the tip was used to investigate the dynamical behaviour of the Mole. From the data acquired it was possible to implement a mathematical model of the Mole, used to study the intrusion dynamics vs. the change of the internal and external variables. For sake of brevity, in the following paper just the most important results are presented.

The particle dynamics and their non-thermal emission in the magnetospheres of collapsing stars are considered. When the stellar magnetosphere compresses under the collapse, its magnetic field increases considerably. Charged particles will be accelerated in this field. These particles will generate radiation when moving in the magnetic field. The collapsing stars can be a powerful sources of non-thermal radiation produced by the interaction of the charged particles with the magnetic field (Kryvdyk, 1999). The effect can be observed by modern instruments. The radiation flux grows during stellar collapse by a factor of millions and can be observed in the form of radiation pulse with duration equal to the stellar collapse time. The flux depends on the distance to the star, its magnetic field, and the particle spectrum in the magnetosphere. In this paper the radiation fluxes are calculated for various collapsing stars with initial dipole magnetic fields and initial power-law, relativistic Maxwell, and Boltzmann particle energy distributions in the magnetosphere.

The Rossi X-ray Timing Explorer (RXTE) has produced many excellent observations of active galaxies, providing so far the best sensitivity over the bandpass of 10 - 20 keV. This paper reports selected RTXE data for X-ray bright Seyfert galaxies in the context of the currently popular models. One is the recent result for two Seyfert 1 galaxies, NGC 5548 and IC 4329a: both show the "canonical" Seyfert 1 X-ray spectra, with an underlying power law, plus iron Kα fluorescence line and Compton reflection. Interestingly, in both cases, the profile of the Fe K line does not extend as far to the red as seen in the famous MCG-6-30-15, and this indicates that the regions where the Fe K lines originate in AGN are diverse. Independently, in both objects we see a strong spectral variability of the primary continua, which soften as the sources brighten. The second result is for the heavily absorbed Seyfert 2 NGC 4945. The RXTE data confirm the strong absorption corresponding to the optical depth to electron scattering of about 2, but also reveal rapid variability of the hard (8 - 30 keV) X-ray emission on a time scale of a day or less. This suggests that for NGC 4945, the putative parsec-size molecular torus cannot be both geometrically and optically thick. It also implies that if the Cosmic X-ray Background is made up of heavily absorbed sources, they are unlikely to have the absorber confined to a geometrically thin disk as inferred for NGC 4945.

This paper reports the detection of a series of X-ray dips in the superluminal black hole source GRS 1915+105 during 1999 June 6-17 from observations carried out with the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment on board the Indian satellite IRS--P3. The observations made in the soft state after the source had made a transition from a low-hard state to a high-soft state, reveal large number of x-ray dips each lasting for about 100- 150 seconds on most of the days. Quasi periodic oscillation (QPOs) with characteristics similar to those of the 0.5-10 Hz QPOs, seen during the low-hard state of the source, were detected in the non-dip portions of the data. The QPOs are, however, not present during the onset or in the dip-period data. During the dips the energy spectrum is soft and the variability is low compared to the non-dip periods. These features re-appear as the dip gradually recovers. Coincident with the occurrence of a large number of X-ray dips, a huge radio flare of strength 0.48 Jy (at 2.25 GHz) was found from the NRAO archival data. It is suggested that the X-ray dips represent mass ejection due to the evacuation of matter from an accretion disk around the black hole and that a super-position of a large number of such dip events leads to production of huge radio jet in GRS 1915+105.

This paper presents a brief description of measurements of backscatter spectra from 15 m ionospheric irregularities in the auroral electrojets by the CUTLASS Iceland coherent HF radar. The scanning nature of the radar allows the flow angle dependence of the spectral characteristics to be determined and interferometric techniques allow the altitude of the scatter volume (E-, upper E-, or F-region) to be estimated. Several populations of backscatter spectra are observed, each with distinct velocity-spectral width and velocity-flow angle behaviours. At E-region altitudes, two populations appear to correspond to the type I (two-stream instability) and type II (gradient drift instability) spectra observed with VHF radars. However, two E- or upper E-region spectral populations with velocities up to 1000 ms−1, above the typical ion-acoustic speed, are also observed. Furthermore, a population with Doppler shifts of the opposite sense to the main body of backscatter is found.

HF waves measurements performed in the cusp area on board the altitude orbiting satellite Magion-3 reveal the existence of two types of emission: whistler mode waves and strong wide band emissions, reaching the local electron plasma frequency. The HF emissions restricted to the cusp region, provide a spatial picture of the ionospheric region and are good tools to describe the plasma properties both in situ and at remote distance from the satellite. Thermal measurements detected at the topside ionosphere are presented. This paper infers about the mechanism of broadband emission in the cusp region at low altitudes.

The waveform capture receiver onboard the Geotail spacecraft has discovered Electrostatic Solitary Waves (ESW) as waveforms of the Broadband Electrostatic Noise (BEN) in the plasma sheet boundary layer. They mainly contribute to the high frequency parts of the broadband spectra. Several spacecraft before and after the Geotail observations have also reported similar solitary waveforms in other regions. They are observed in the polar magnetosphere, magnetosheath and bow shock regions. Some of them have not been discussed in relation to BEN. However, it is evident that their solitary waveforms contribute to broadband spectral structures in frequency space. In the present paper, we summarize the nature of the ESW observed by Geotail in the magnetotail region and discuss the generation mechanisms of solitary waves observed in other regions by comparing their properties.

Shoots of higher plants exhibit negative gravitropism. However, little is known about the site of gravity perception in shoots and the molecular mechanisms of shoot gravitropic responses. Our recent analysis using shoot gravitropism1(sgr1)/scarecrow(scr)and sgr7/short-root (shr)mutants in Arabidopsis thalianaindicated that the endodermis is essential for shoot gravitropism and strongly suggested that the endodermis functions as the gravity-sensing cell layer in dicotyledonous plant shoots. In this paper, we present our recent analysis and model of gravity perception and gravitropic response of inflorescence stems in Arabidopsis thaliana.

The paper summarizes the data on proliferation and gravity-related gene expression of osteoblasts that were obtained from an experiment conducted under simulated and real microgravity conditions.

In this paper we discuss the effect of microgravity on T cells and we present the data of studies with two new machines for 0 g simulations. Several experiments in space show that mitogenic T cell activation is lost at 0 g. Immunocytochemistry indicates that such effect is associated with changes of the cytoskeleton. Biochemical studies suggest that the lack of expression of the interleukin-2 receptor is one of the major causes of the loss of activity. In fact, interleukin-2 is the third signal required for full activation. In order to deepen our investigations we are now working with the free-fall machine, FFM, invented by D. Mesland, and with the random positioning machine, RPM, or three-dimensional clinostat, developed by T. Hoson. The FFM produces periods of free-fall lasting approximately 800 ms followed by bounces of 15–30 g lasting 45–60 ms. The RPM eliminates the effect of gravity by rotating biological specimen randomly around two orthogonal axes. While the FFM failed to reproduce the results obtained with T lymphocytes in space, the data from the RPM are in good agreement with those in real microgravity. In fact, the inhibition of the mitotic index in the RPM is 89% compared to static controls. The RPM (as the FFM) can carry markedly larger specimen than the fast rotating clinostat and thus allows to conduct comprehensive studies to select suitable biological objects for further investigations in space.

In this paper, the problem of searching for gravitationally sensitive mechanisms of polymerization in natural earth gravitational field and in artificial high gravity conditions is considered. Laboratory experiments and numerical modeling have revealed the existence of at least four reasons for gravitational sensitivity: sedimentation of polymeric microglobules, thermal and concentration convection, instability of polymerization front, immediate effect of the mass forces on a deformable polymer. The distinguishing features of the discovered mechanisms and their operation regions have been identified. It is shown that these mechanisms influence the polymerization processes and the final polymeric structure. The results of experimental investigation in microgravity conditions are given for comparison. It has been found, that in the orbital environment on “Mir” station the convective flows of reaction mixture are absent and polymerization develops as a frontal process, which provides homogeneity of the final polymer structure.

Protein crystals, grown under reduced gravity conditions, are either superior or inferior in their structural perfection than their Earth-grown counterparts. A reduction of the crystals' quality due to low-gravity effects on the growth processes cannot be understood from existing models. In this paper we put forth a rationale which predicts either advantages or disadvantagesof microgravity growth. This rationale is based on the changes in the effective solute and impurity supply rates in microgravity and their effects on the intrinsic growth rate fluctuations that arise from the coupling of bulk transport to nonlinear interfacial kinetics and cause severe inhomogeneities. Depending on the specific diffusivity and kinetic coefficient of a protein and the impurities in the solution, either transport enhancement through forced flow or transport suppression under reduced gravity can result in a reduction of the kinetic fluctuations and, thus, growth with higher structural perfection. Investigating this mechanism of microgravity effects, we first demonstrate a one-to-one correspondence between these fluctuations, that are due to the bunching of growth steps, and the formation of defects in the crystals. We have confirmed the forced flow aspects of this rationale in ground-based experiments with lysozyme utilizing flowing solutions with varying, well characterized impurity contents.

Global measurements of nitric oxide (NO) in the earth's upper atmosphere have now been obtained by two satellite experiments during the declining phases of the last two solar cycles. In the 1980's, NO was measured by the Solar Mesosphere Explorer while in the 1990's, NO has been observed by the Halogen Occultation Experiment (HALOE) on board the UARS satellite. The SME data cover the altitude range from 95 to 160 km and extend from pole to pole. The HALOE data used here cover the altitude range from 50 to 125 km and extend from 70N to 70S. Both datasets show a well defined decrease in NO during the decline of solar activity. Also, large perturbations due to auroral activity are seen at middle and high latitudes. In addition, the HALOE data show large increases in the high latitude winter mesosphere which are associated with downward transport from the thermosphere. This paper presents a reference NO model which is based upon the two datasets and which covers a wide range of solar, geomagnetic and seasonal conditions.

The Cryogenic Limb Array Etalon Spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite obtained global distributions of CF2Cl2 and CFCl3 in the stratosphere between October 1991 and May 1993. This paper discusses the seasonal and interannual behavior of a number of prominent dynamical features observed in the zonal mean fields for both gases over the period January 1992 through February 1993 and compares these features with a two-dimensional model. The CFC fields are shown to exhibit many of the same seasonally variant features seen in other conserved tracer fields. These include a semiannual oscillation signature in the tropical upper-level mixing ratios; the development of a double-peaked tropical structure near the vernal equinox and its weakening, or absence, at the autumnal equinox; steep descent at winter high latitudes in both hemispheres with an associated midlatitude surf zone, which is stronger and more sustained in the southern hemisphere; and sharp subtropical gradients in the mixing ratio isopleths in the northern winter hemisphere. Distinct interannual variability is also observed in the CF2Cl2 morphology, particularly for the northern hemisphere for the periods January–February 1992 and 1993. Other than this latter feature, the two-dimensional model is generally found to reproduce the observed behavior, although usually with weaker manifestation than seen in the data, especially in regard to the double-peaked equinoctial structure.

New satellite measurements from instruments on the Upper Atmosphere Research Satellite (UARS) have provided much more detailed information on the relatively long-lived tracers in the stratosphere, CH4 and N2O, than previously available with respect to global distributions. These data represent an excellent opportunity to construct new reference atmospheres appropriate to modelling studies and retrievals of data from remote sensing experiments. This paper considers the nature of the new information from UARS instruments by focussing on a case study of CH4 data obtained for April and May of 1992. A zonal latitude cross-section from the Halogen Occultation Experiment is compared to averaged zonal mean data from the Improved Stratospheric and Mesospheric Sounder (ISAMS) and the Cryogenic Limb Emission Spectrometer (CLAES). The differences are shown to be strongly altitude dependent but to also depend on atmospheric features. For such features, sampling is shown to be an important consideration. The effect of aerosol contamination is demonstrated for the ISAMS and CLAES data. Atmospheric variability is considered and calculations presented and compared for different datasets. Such estimates are recommended for inclusion in new reference atmospheres. The implications of these issues for the construction of a reference atmosphere for N2O are also discussed.

The paper briefly reviews some investigations realized mainly in Southern Spain of possible coupling between middle atmosphere, lower thermosphere and ionosphere. It draws attention to abnormal circulation changes in the winter stratosphere, detected through variations of D-region ionospheric radiowave absorption; the response of the lower ionosphere to the stratospheric warmings; quasi-periodic fluctuations in ionospheric absorption in relation to planetary wave activity in the stratosphere; the statistically significant correlations between variations of total ozone content considered as a parameter of the stratospheric changes; and radio waves absorption as an indicator of the electron density in the lower ionosphere. There is some difference in the behaviour of the lower ionosphere in relation to meteorological parameters in Southern Spain and Central and East Europe, and this is discussed as partly due to latitudinal variations of ionospheric parameters and to longitudinal inhomogeneity of lower atmosphere processes.

The atmospheric effect on the radiance of sunlight scattered from the Earth-atmosphere system is greatly dependent on the surface reflectance pattern, the contrast between adjacent fields, and the optical properties of the atmosphere. In addition, the atmospheric effect is described by the range and magnitude of the adjacency effects, the atmospheric modulation transfer function, and the apparent spatial resolution of remotely sensed imagery. This paper discusses the atmospheric effect on classification of surface features and shows that surface nonuniformity can be used for developing procedures to remove the atmospheric effect from the satellite imagery.

When imaging the surface from satellites or aircraft, “cross radiance” diminishes the information content of the pictures. In this paper a simple method is presented to estimate the value of cross radiance. This method includes a height-dependent aerosol size distribution model and the calculations refer to the single scattering approximation. The height variation of aerosol size distribution has significant effect on the value of cross radiance, while the areal distribution does not change much in comparison with that of the height-independent aerosol model.

In a previous paper the authors showed that the aerosol size distribution can be estimated with reasonable accuracy from spectral extinction measurements in a limited spectral region (λ ≤ 1 μm) only. Using the same method it will be discussed if the anticipated WMO turbidity network with four spectral channels has the potential of estimating the aerosol size distribution.

Since the fall of 1978, two Earth-orbiting spacecraft sensors, SAM II, for Stratospheric Aerosol Measurement II, and SAGE, for Stratospheric Aerosol and Gas Experiment have been monitoring the global stratospheric aerosol. These experiments use the Sun as a source to make Earth-limb extinction measurements during each spacecraft sunrise and sunset. This paper describes the global aerosol data base (climatology) that is evolving. Seasonal and hemispheric variations such as the springtime layer expansion with warming temperatures and the local wintertime polar stratospheric clouds (PSC's) will be described. The PSC's enhance extinction by up to two orders of magnitude and optical depths by as much as an order of magnitude over the background 1000 nm values of about 1.2 × 10−4km−1and 1.3 × 10−3, respectively. The detection and tracking of a number of volcanoes whose effluents penetrated the tropopause are also described. The mass of new aerosol injected into the stratosphere from each volcano is estimated. The May 1980 eruption of Mount St. Helens, for example, produced about 0.32 × 109kg of new stratospheric aerosol enhancing the Northern Hemispheric aerosol by more than 100 percent.

The paper presents the results of laser sounding of water droplet crystal and mixed clouds carried out using an airborne lidar. A new method of determining the phase state of a cloud is described. The results are given on numerical experiments of laser sounding of various clouds using a polarization lidar for large variety of geometrical parameters of sounding schemes and optical characteristics of clouds. Numerical simulation of the results of laser sounding of aerosols from outer space for different lidar parameters and geometrical schemes of sounding is carried out using new models of vertical profiles of aerosol characteristics.

This paper presents a review of ultraviolet photometry and spectroscopy of globular clusters and blue horizontal branch stars. Current observations with IUE are placed within the framework of earlier photometric studies carried out by OAO and ANS. In order to provide basic information on the nature of the horizontal branch star, whose light dominates in the ultraviolet, observations of field horizontal branch stars as well as individual stars in globular clusters are discussed. Finally the IUE observations of globular clusters in the Magellanic Clouds are examined, since they provide a sequence spanning the age range from 7 × 106years to 1010years.

With the advent of high resolution space observations with high sensitivity, stellar atmospheric research has entered a new phase of rapid development. All stars, and especially hot stars, are now recognized to have atmospheric characteristics that were not suspected before. All hot stars that we can observe with sufficient accuracy show chromospheres and coronae indicative of non-radiative energy fluxes as well as mass loss; these phenomena exhibit a very great range in magnitude among different stars and, in several cases, they are variable in time. These discoveries have pointed out the need for determining the atmospheric structures of hot stars and, ultimately, of determining the mechanisms responsible for the likely common origin of chromospheres-coronae and mass fluxes. This paper will focus on these observational aspects of hot stars -mainly Be stars and OB-normal stars will be treated here- and on the constraints that the observations impose upon models for these stellar atmospheres.

Aerosols modify scattered solar radiation leaving the atmosphere and this fact will be exploited to determine the aerosol optical depth. The interaction processes between solar radiation and aerosol particles are outlined. A quasi-linear relationship (‘conversion curves’) between the radiance at the satellite, Lsat, and the aerosol optical depth, aDλ, is found from both numerical and empirical studies. Because Lsatis not only controlled by aDλ, but also by a series of other atmospheric parameters (perturbing quantities), the concept of ‘favourable viewing conditions’ is presented, where the effects of the perturbing quantities are minimal. The paper ends with some lines of thought on a concept for a turbidity satellite.

Numerical modelling is used to search for the most suitable conditions, with the object of determining the atmospheric turbidity (aerosol optical depth) from upward emerging spectral radiances in cloudfree pixels over water surfaces. The most suitable conditions are those where the influence of the turbidity on the radiance most strongly outweighs that of the other optically acting constituents. Since the actual values of these constituents of atmosphere and surface are usually known only within certain limits, using the most suitable conditions minimizes the uncertainty in the turbidity to be derived from satellite measurements. As a result, favorable zenith angles of the satellite and favorable wavelengths are presented for an atmosphere with maritime aerosols with and without Saharan dust. The results represent an advance on a paper published by the authors in 1981 [1].

In this paper IUE observations of two type II and three type I Supernovae (see Table I and Table II) are reviewed. The type II events were also observed by Einstein and SN 1980k was detected in the soft X-ray energy band. Combining UV spectra available of the same events one has the elements to construct a physical picture which accounts for all observations. For the type II events it appears that the progenitor star was a massive supergiant which underwent a severe mass loss before becoming Supernova. For the type I events there is neither X-ray nor, for the time being, radio detection. The high similarity of the optical and UV spectra for the three events indicates that type I Supernovae are the end products of one and the same phenomenon.

The scope and degree of land transformation depends on the system of land use by man. Therefore research on land use systems is of considerable importance, both for better knowledge of resulting processes as well as for more rational land management. To start such research a classification of land use systems is necessary. The paper presents an attempt at such a classification, preceded by an information on the studies carried on in the past as well as an explanation of reasons why such an attempt has been made, followed by the discussion of possible criteria, methods and techniques of land use systems identification.

This paper outlines the aspects of land transformation processes in Japan due to urbanization and agricultural development, with special attention to the recent drastic changes of landscape and related natural hazards. Mention is made of the tasks of environmental risk assessment and management and the role of remote sensing.

Agriculture in semi-arid tracts of the world depends on water to sustain its irrigation systems. Such agricultural systems either derive from government investments in the control of surface flow or they have been developed through the exploitation of groundwater sometimes by a large community of unsupervised individuals seeking to maximise their own advantage without concern for the resource upon which they depend in the medium and long term. In both cases government agencies need data on the area irrigated and the volume of water used. In countries with highly developed scientific and agricultural institutions the contribution of remote sensing, though significant, may only provide between five and ten per cent of the data required to guide regional and national managers. In countries without such institutions the proportion contributed by remote sensing can be very much higher, as shown in a recent study in North Africa. The paper will emphasise the importance of carefully structured sampling procedures, both to improve the areal estimates from satellite imagery and the estimates of water use based upon them. The role of satellite imagery in providing information on the status of water resources, on trends in water use and in the implementation of policies to extend or diminish irrigated land are discussed.

This paper reviews the application of Landsat to transformation monitoring and a selection of current Australian research projects on land transformation processes. The projects reviewed include forest, rangeland, agriculture, urbanization and wetland monitoring.

This paper describes a procedure for detecting and mapping changes in vegetation cover using LANDSAT digital analysis techniques, and demonstrates how the procedure can be used as an aid to environmental monitoring. Digital image analysis is used to perform a historical comparison, and a computerized colour plotter is used to map the changes in vegetation.

The inventory of large often non-homogeneous tracts of land by resource agencies has led to the development of estimation methods and sampling strategies that produce estimates of the aereal extent of various features from ‘limited’ observations of the universe of interest. Landsat data has furnished a tool that allows for potential improvement in estimates of resource parameters over extensive areas. This paper examines the methodology and results of a procedure which uses an economical sampling procedure allied with the large area covering qualities of the satellite imaging system to make improved estimates of irrigated land in a more timely, efficient and ‘accurate’ manner.

The capability of making stereoscopic observations of clouds from meteorological satellites is a new basic analysis tool with a broad spectrum of applications. Stereoscopic observations from satellites were first made using the early vidicon tube weather satellites (e.g., Ondrejka and Conover [1]). However, the only high quality meteorological stereoscopy from low orbit has been done from Apollo and Skylab, (e.g., Shenk et al.[2] and Black [3], [4]). Stereoscopy from geosynchronous satellites was proposed by Shenk [5] and Bristor and Pichel [6] in 1974 which allowed Minzner et al.[7] to demonstrate the first quantitative cloud height analysis. In 1978 Bryson [8] and desJardins [9] independently developed digital processing techniques to remap stereo images which made possible precision height measurement and spectacular display of stereograms (Hasler et al.[10], and Hasler [11]). In 1980 the Japanese Geosynchronous Satellite (GMS) and the U.S. GOES-West satellite were synchronized to obtain stereo over the central Pacific as described by Fujita and Dodge [12] and in this paper. Recently the authors have remapped images from a Low Earth Orbiter (LEO) to the coordinate system of a Geosynchronous Earth Orbiter (GEO) and obtained stereoscopic cloud height measurements which promise to have quality comparable to previous all GEO stereo. It has also been determined that the north-south imaging scan rate of some GEOs can be slowed or reversed. Therefore the feasibility of obtaining stereoscopic observations world wide from combinations of operational GEO and LEO satellites has been demonstrated.

Estimates of clear and low, middle and high cloud amount in fixed geographical regions approximately (160km)2are being made routinely from 11.5μm radiance measurements of the Nimbus-7 Temperature-Humidity Infrared Radiometer (THIR). The purpose of validation is to determine the accuracy of the THIR cloud estimates. Validation requires that a comparison be made between the THIR estimates of cloudiness and the “true” cloudiness. The validation results reported in this paper use human analysis of concurrent but independent satellite images with surface meteorological and radiosonde observations to approximate the “true” cloudiness. Regression and error analyses are used to estimate the systematic and random errors of THIR derived clear amount.

The accuracy of atmospheric transmittances is important in remote sensing applications. In this paper the atmospheric ozone transmittances in the 1042 cm−1ozone band were calculated for different temperatures and ozone profiles using line-by-line integration method. The absorption line parameters were taken from McClatchey's line parameter compilation. The transmittances were used to derive the main characteristics of the atmospheric ozone profile and the total ozone amount from radiance measurements of Meteor satellites.

GIRL is a liquid helium cooled 50 cm telescope equipped with four focal plane instruments dedicated to astronomical and aeronomical observations. These instruments, a detector array, a photopolarimeter, an Ebert-Fastie-spectrometer and a Michelson-interferometer make up an “infrared observatory” having high sensitivity and high spectral and spatial resolution. Si:Ga-, Si:Sb-, Si:As-, Si:P-, Ge:Be-, Ge:Cu- and Ge:Ga-detectors with NEP-values as low as 3 10−17W Hz−12have been tested and will be used to cover the wavelength range 3…120 μm. A full size “thermal model” of the GIRL cryostat containing 300 1 of superfluid helium at 1.6 K has been tested at the industrial prime contractor MBB; results of these tests will be presented in a following paper by F. Dahl et al. Several new techniques for cold telescopes are used in GIRL, for instance a glass ceramics primary mirror, a low power chopping secondary and an active helium phase separator. The scientific objectives include studies of star formation regions and active galaxies as well as measurements of spurious gases in the earth atmosphere. GIRL will be pointed by the Instrument Pointing System (IPS) and is scheduled to fly on Spacelab in 1986/87.