MLS: a total system approach

A typical approach and landing operation is described. The microwave landing system (MLS) is then examined, its design characteristics and how it works are shown, and how the MLS design fulfils the user's operational requirements by protecting the guidance signal from reflected signal interference is highlighted. MLS angle system accuracy is discussed in great detail, and its reliability, integrity, and coverage volume are briefly considered. MLS availability at any runway to all aircraft types and their landing scenarios, which is accomplished using narrow scanning beam antennas, is examined     

The role of repair in the survival of mammalian cells from heavy ion irradiation: approximation to the ideal case of target theory.

Theories of cellular radiation sensitivity that preclude a significant role for cellular repair processes in the final biological expression of cellular damage induced by ionizing radiation are unsound. Experiments are discussed here in which the cell-cycle dependency of the repair deficiency of the S/S variant, of the L5178Y murine leukemic lymphoblast was examined by treatment with the heavy ions, 20Ne, 28Si, 40Ar, 56Fe and 93Nb. Evidence from those studies, which will be described in detail elsewhere, provide support for the notion that as the linear energy transfer (LET infinity) of the incident radiation increases the ability of the S/S cell to repair radiation damage decreases until effectively it is eliminated around 500 keV/micrometer. In the region of the latter LET infinity value, the behavior of the S/S cell approximates the ideal case of target theory where post-irradiation metabolism (repair) does not influence cell survival. The expression of this phenomenon among different cell types and tissues will depend upon the actual repair systems involved and other considerations.     

Volatile metabolites of higher plant crops as a photosynthesizing life support system component under temperature stress at different light intensities.

The effect of elevated temperatures of 35 and 45 degrees C (at the intensities of photosynthetically active radiation 322, 690 and 1104 micromoles m-2 s-1) on the photosynthesis, respiration, and qualitative and quantitative composition of the volatiles emitted by wheat (Triticum aestuvi L., cultivar 232) crops was investigated in growth chambers. Identification and quantification of more than 20 volatile compounds (terpenoids--alpha-pinene, delta 3 carene, limonene, benzene, alpha- and trans-caryophyllene, alpha- and gamma-terpinene, their derivatives, aromatic hydrocarbons, etc.) were conducted by gas chromatograph/mass spectrometry. Under light intensity of 1104 micromoles m-2 s-1 heat resistance of photosynthesis and respiration increased at 35 degrees C and decreased at 45 degrees C. The action of elevated temperatures brought about variations in the rate and direction of the synthesis of volatile metabolites. The emission of volatile compounds was the greatest under a reduced irradiation of 322 micromoles m-2 s-1 and the smallest under 1104 micromoles m-2 s-1 at 35 degrees C. During the repair period, the contents and proportions of volatile compounds were different from their initial values, too. The degree of disruption and the following recovery of the functional state depended on the light intensity during the exposure to elevated temperatures. The investigation of the atmosphere of the growth chamber without plants has revealed the substances that were definitely technogenic in origin: tetramethylurea, dimethylsulfide, dibutylsulfide, dibutylphthalate, and a number of components of furan and silane nature.     

New model of hair cell bundle functioning in otoliths.

Transformation of the mechanical input in the chain: acceleration of otolithic membrane (OM)-displacement of the OM gel layer -deflection of hair cell bundle (HCB) -deformation of the system of tip-links- formation of temporal pattern of polarization was studied using simplified analytical models of these stages of conversion of mechanical stimulus into the HCB electrical response. The process of transformation of information in this chain was considered for two extreme cases of OM gel-HCB interaction: 1) the HCBs exactly follow the gel displacement; 2) stiff stereocilia and weak surrounding gel allow the relative motion of the bundle with regard to the gel. The analysis of a simplified model of cell polarization based on threshold triggering of the HCB tip-links allows to hypothesize that spatially nonhomogeneous HCB structure with a set of stereocilia of varying heights is designed to perceive spatially nonhomogeneous gel displacements caused by external acceleration. Thus, the HCB-OM gel interaction in the first case leads to formation of temporal pattern of depolarization that corresponds to the temporal pattern of gel displacement. In the second case the kinetics of depolarization reflects time dependence of gel displacement velocity.     

Coordinated Continual Planning Methods for Cooperating Rovers

Eight evaluation metrics are used to compare and contrast three coordination schemes for a system that continuously plans to control collections of rovers (or spacecraft) using collective mission goals instead of goals or command sequences for each spacecraft. These schemes use a central coordinator to either: 1) micromanage rovers one activity at a time; 2) assign mission goals to rovers; or 3) arbitrate mission goal auctions among rovers. A self-commanding collection of rovers would autonomously coordinate itself to satisfy high-level science and engineering goals in a changing partially understood environment - making the operation of tens or even a hundred spacecraft feasible     

Mean winds of the mesosphere and lower thermosphere (60–110 km): A global distribution from radar systems (MF,Meteor, VHF)

During the last decade a large number of radars (～12) have been developed, which have produced substantial quantities of tidally-corrected mean winds data. The distribution of the radars is not global, but many areas are well covered: the Americas with Poker Flat (65°N), Saskatoon (52°N), Durham (43°N), Atlanta (34°N), Puerto Rico (18°N); Europe with Kiruna (68°), Garchy (47°N) and Monpazier (44°N); and Oceania with Christchurch (44°S), Adelaide (35°S), Townsville (20°S), and Kyoto (35°N). Zonal and meridional wind height-time cross-sections from $\text{60}\text{80}$ km (MF/Meteor Radar) to ～110 km have been prepared for the last 5–6 years. They are compared with cross-sections from CIRA-72 for zonal winds, and Groves (1969) for meridional winds.It is shown that while CIRA-72 is still a useful model for many purposes, significant differences exist between it and the new radar data. The latter demonstrate important seasonal, latitudinal, longitudinal and hemispheric variations. The new meridional cross-sections are of great value. The common features with Groves (1969) are the equatorward cells in summer near 85 km; however their strength (～10 ms^?1) and size are less. Systematic and somewhat different variations emerge at higher (?52°N) and middle (35–44°) latitudes.     

A balloon-borne sun-tracking multichannel photometer for atmospheric aerosol measurements

A balloon borne multichannel photometer for measurement of atmospheric scattering in the near ultraviolet and the visible wavelength regions has been developed at the Physical Research Laboratory, Ahmedabad for study of the size distribution and number density of aerosols at tropospheric and lower stratospheric altitudes. The instrumentation involves tracking the sun in elevation and scanning in azimuth. The payload was recently flown on a 100 kg. balloon from the Hyderabad Balloon Facility on 18 April 1984. The balloon reached a float altitude of 35 km and good quality data has been obtained from an altitude of 6 km upto float altitude. Data analysis is still in progress. The present paper details the instrument design and presents a few illustrations of the instrument performance from this flight.     

Synthetic Environments for Simulated Missions

Synthetic environments offer Space Flight projects an opportunity to perform rapid, comprehensive, and rigorous modeling of the critical elements of a mission in order to compute quantitative measures of design performance, associated risk, and actual mission utility value. Significantly, these studies can be performed early in the mission cycle. These synthetic terrains are generated on parallel, high-performance computers and served to remote simulations at near-interactive speeds. The terrain creation uses a realistic sequence of physical phenomena such as cratering and dusting with parametric control of features such as surface roughness and rock density. Terrain resolution may be arbitrary but typically ranges from 0.01 to 10 meters. The terrain server has been used for two rover simulations, one using the actual Sojourner autonomy flight code, and the other a more general algorithm. Monte Carlo studies of rover designs interacting with synthetic environments were executed in parallel to quickly compute performance statistics and risk estimates.     

Tide-associated biological rhythms of some White Sea littoral invertebrates.

We report the results from two years of laboratory observations of the tide-associated rhythms of activity of White Sea intertidal invertebrates, Mya arenaria (Bivalvia) and Gammarus finmarchicus (Amphipoda). The tidal associated activity of these invertebrates could not be estimate as a clear circatidal clock. Gammarus activity could be phase shifted by a 0.5 h exposure to turbulent water twice a day for 2-3 days. Mya's rhythm could be changed by a single drainage of aquariums lasting about 15 min. This kind of timing system may be a relatively primitive evolution feature.     

Study of the radiation environment on MIR space station with SILEYE-2 experiment.

In this work we present preliminary results of nuclear composition measurements on board space station MIR obtained with SILEYE-2 particle telescope. SILEYE-2 was placed on MIR in 1997 and has been working since then. It consists of an array of 6 active silicon strip detectors which allow nuclear and energetic identification of cosmic rays in the energy range between approximately 30 and 200 MeV/n. The device is attached to an helmet and connected to an eye mask which shields the cosmonaut eyes from light and allow studies of the Light Flashes (LF) phenomenon. In addition to the study of the causes of LF, the device is used to perform real time long term radiation environment monitoring inside the MIR, performing measurements in solar quiet and active days.