Determination of Angular Distribution Models for Indian desert scene: Comparison with other desert models

In this paper, the shortwave and longwave anisotropy for clear sky Indian desert scene has been estimated using long-term surface data, radiative transfer calculations and Helmholtz reciprocity for missing values. This study is important in the perspective of the low inclination satellites like Megha–Tropiques (MT) mission, carrying Scanner for Radiation Budget (ScaRaB) payload, which will provide broadband radiative fluxes at the top of the atmosphere (TOA). Due to low inclination angle, the angular models for clear sky land scenes for the MT-ScaRaB orbits will be dominated by desert points.The Angular Distribution Models (ADMs) determined in this study were compared with existing desert models. It is observed that for longwave radiation, the largest disagreement is observed for higher values of viewing zenith angle, especially for the summer season, where the difference in flux can reach up to 13 W/m². For the shortwave radiation, higher values of both solar zenith angle and viewing zenith angle cause largest incongruity in the computed albedo from the different models, suggesting the need of caution in interpretation of the flux computations from these bins. In fact at the higher solar zenith angle bin, the disparity in albedo can go up to 6.4%.     

Exposure of Arabidopsis thaliana to hypobaric environments: implications for low-pressure bioregenerative life support systems for human exploration missions and terraforming on Mars

Understanding how hypobaria can affect net photosynthetic (P (net)) and net evapotranspiration rates of plants is important for the Mars Exploration Program because low-pressured environments may be used to reduce the equivalent system mass of near-term plant biology experiments on landers or future bioregenerative advanced life support systems. Furthermore, introductions of plants to the surface of a partially terraformed Mars will be constrained by the limits of sustainable growth and reproduction of plants to hypobaric conditions. To explore the effects of hypobaria on plant physiology, a low-pressure growth chamber (LPGC) was constructed that maintained hypobaric environments capable of supporting short-term plant physiological studies. Experiments were conducted on Arabidopsis thaliana maintained in the LPGC with total atmospheric pressures set at 101 (Earth sea-level control), 75, 50, 25 or 10 kPa. Plants were grown in a separate incubator at 101 kPa for 6 weeks, transferred to the LPGC, and acclimated to low-pressure atmospheres for either 1 or 16 h. After 1 or 16 h of acclimation, CO(2) levels were allowed to drawdown from 0.1 kPa to CO(2) compensation points to assess P (net) rates under different hypobaric conditions. Results showed that P (net) increased as the pressures decreased from 101 to 10 kPa when CO(2) partial pressure (pp) values were below 0.04 kPa (i.e., when ppCO2 was considered limiting). In contrast, when ppCO(2) was in the nonlimiting range from 0.10 to 0.07 kPa, the P (net) rates were insensitive to decreasing pressures. Thus, if CO(2 )concentrations can be kept elevated in hypobaric plant growth modules or on the surface of a partially terraformed Mars, P (net) rates may be relatively unaffected by hypobaria. Results support the conclusions that (i) hypobaric plant growth modules might be operated around 10 kPa without undue inhibition of photosynthesis and (ii) terraforming efforts on Mars might require a surface pressure of at least 10 kPa (100 mb) for normal growth of deployed plant species.     

A synthesis of our present knowledge of interstellar dust

The present state of knowledge as regards interstellar dust is reviewed in Section 1 (Introduction); Section 2 (Composition of Dust Grains: graphite, silicate, dirty-ice, diamond); Section 3 (Size of Grains: mainly r 10^–6 cm); Section 4 (Charge and Temperature of Grains: charge varies from 1–10 electrons (H i clouds) to 500 electrons (H ii clouds); temperature of grain material is about 10–20 K); Section 5 (Distribution and Origin of Grains: confined mainly to discs and arms of spiral galaxies, having had a passive origin by efflux from late-type stars or carbon-stars); Section 6 (Cosmogonical and Cosmological Aspects of Interstellar Grains: accretion by electrical-image forces of one dust grain onto a similarly-charged grain links up the absence of dust and gas in elliptical galaxies with the absence of a magnetic field of the type found in spirals. The origin of the 3 K background radiation field could be produced by a population of rotating silicate grains of r 10^–7 cm); Section 7 (Conclusion).     

Avionics Development and Integration System Methods

This paper describes a set of life cycle methods that were developed in 1980 and 1981 and used in the later phases of the 757/767 airplane programs. They have been used as a framework to establish and guide the introduction of a wide use of similar methods for the future avionics of Boeing's next airplane, the 7J7. The methods were designed to improve communication of the system's requirements, architecture and implementation to a wide group of interested parties ? not just the development engineers but also the users, maintainers, customers and support organizations. A major aspect of these methods is that they were designed to be used for systems in general not just software systems. This paper will describe the background and goals and objectives leading to the need for systems engineering methods, describe the methods and give an example of their use. It will conclude with remarks on steps taken to introduce methods of this type on a wide scale to support the next Boeing airplane.     

Characteristic γ- and X-radiation in the planetary system

Conclusions Passive observation of the naturally occurring γ-ray and X-ray from the planets is potentially an important technique for determining their gross chemical composition and on the basis of natural γ-radiation determining if the planetary surface is composed of differential material. If the planet is not covered by a thick atmosphere then it is possible to map the distribution of the most abundant elements on a scale of spatial resolution that is of the order of the altitude at which the observations are made. Initial observations carried out from lunar orbit have shown that the flux levels are approximately as expected and that the lunar surface is not characterized by any widespread distribution of acidic rocks in the region observed by the Luna 10 spacecraft.     

Reliability of electron density profiles

Deviations from horizontal stratification in the F-region can cause significant errors in electron density profile calculations from ionograms. Such situations exist every day during sunrise and sunset. Angle of arrival measurements and studies of the variation of other F-region parameters indicate that gravity waves are frequently strong enough to produce effects of comparable magnitudes. Ray tracing model studies permit a first order estimate of the resulting errors which are largest for the peak parameters.