Multi-Criteria Decision Analysis integrated with GIS and remote sensing for astronomical observatory site selection in Antalya province,Turkey

Astronomical observatory site selection is a complex problem that involves evaluation of multiple factors from different sources. The aim of this study is to select the best possible candidates for astronomical observations sites using Multi-Criteria Decision Analysis integrated with Geographical Information Systems and remote sensing technologies. The study was implemented in the Antalya province of Turkey, which is convenient for astronomical site observatory facilities with its appropriate climate properties and weather conditions. Eleven factors (cloud cover, precipitable water, earthquake zones, geology, landslide inventory, active fault lines, Digital Elevation Model, city lights, mining activities, settlement areas, roads) were determined, splitting into three categories; meteorological, geographical and anthropogenic criteria. These factors were evaluated using Analytical Hierarchy Process method and the weights of criteria layers were determined. As a result, the most suitable areas were located extensively in western and eastern part of Antalya. This study offers a robust, accurate, cost and time effective procedure for preliminary site selection for astronomical observatory. However, for a final decision of the best location of astronomical observatory, site testing measurements and atmospheric seeing observations will be further required in these preliminary areas.     

A boundary value problem of aerohydrodynamics in designing an axisymmetric body with jet blowout

A numerical and analytical method for constructing a shape of the axisymmetric body streamlined with jet blowout by the specified velocity distribution along its meridian section is proposed. The foundation of the method is the iteration process based on the solutions of an inverse problem in the plane case and a primal problem for the axisymmetric body. A program realizing the iteration process is set up and examples of numerical calculations are given.     

Cycle slip detection using multi-frequency GPS carrier phase observations: A simulation study

The detection and repair of the cycle slip or gross error is a key step for high precision global positioning system (GPS) carrier phase navigation and positioning due to interruption or unlocking of GPS signal. A number of methods have been developed to detect and repair cycle slips in the last two decades through cycle slip linear combinations of available GPS observations, but such approaches are subject to the changing GPS sampling and complex algorithms. Furthermore, the small cycle slip and gross error cannot be completely repaired or detected if the sampling is quite longer under some special observation conditions, such as Real Time Kinematic (RTK) positioning. With the development of the GPS modernization or Galileo system with three frequencies signals, it may be able to better detect and repair the cycle slip and gross error in the future. In this paper, the cycle slip and gross error of GPS carrier phase data are detected and repaired by using a new combination of the simulated multi-frequency GPS carrier phase data in different conditions. Results show that various real-time cycle slips are completely repaired with a gross error of up to 0.2 cycles.     

Minimizing energy utilization for growing strawberries during long-duration space habitation

Strawberry is a candidate crop for space that is rich in protective antioxidants and could also have psychological benefits as a component of crew diets during long-duration space habitation. Energy for electric lighting is a major input to a controlled-environment crop-production system for space habitation. Day-neutral strawberry cultivars were evaluated at several different photoperiods to determine minimum lighting requirements without limiting yield or negatively impacting fruit quality. The cultivars ‘Tribute’, ‘Seascape’, and ‘Fern’ were grown at 14, 17, or 20 h of light per day, and fruit yield was evaluated over a 31-week production period. This amounted to a difference of 2418 kWh m⁻² in energy usage between the longest and shortest photoperiods. All cultivars produced similar total fresh weight of fruit regardless of photoperiod. Volunteer tasters rated organoleptic characteristics including sweetness, tartness, texture, and overall appeal as measures of fruit quality. Generally, organoleptic attributes were not affected by photoperiod, but these attributes were somewhat dependent upon cultivar and harvest time. Cultivars under different photoperiods varied in their production of fruit over time. ‘Seascape’ was the most consistent producer, typically with the largest, most palatable fruit. ‘Seascape’ plants subsequently were grown at 10-, 12-, or 14-h photoperiods over a treatment period of 33 weeks. Photoperiod again had no significant effect on total fruit weight, although there were periodic flushes of productivity. Fruit under all photoperiods had acceptable approval ratings. A large-fruited, day-neutral strawberry cultivar such as ‘Seascape’ remains productive under shortened photoperiods, allowing reductions in energy and crew labor while maintaining flexibility for mixed-cropping scenarios in space.     

A Clutter Reduction Technique for Random Signal Radars

The performance of certain radars is degraded in environments with significant clutter returns, and since the clutter is signal-generated, increasing the transmitted power does not improve the situation. However, changing the pulse width and pulse period of the transmitted signal can increase the input signal-to-interference ratio. In this correspondence, the transmitted signal is made up of pulses of random waveforms and the receiver is a correlator where the reference signal extends over many pulses. An expression for input signal-to-interference ratio as a function of pulse width and period is obtained for the case of a distributed target. This expression could be maximized by any of several methods, but to further elucidate the clutter reduction technique, contour plots of the input signal-to-interference ratio are presented.     

Compressible Aspects of Slow Solar Wind Formation

Recently we have shown how the slow solar wind can be formed within a coronal helmet streamer. The solar wind is modeled by a "wake-neutral" sheet, whose subsequent linear and nonlinear evolution provides clues to the development of the wind. In this paper we describe the first results of our extension of this model to the compressible regime. In particular, we show that traveling density enhancements are formed, similar to those observed by LASCO. The compressible equations are solved by an extension to MHD of the SPECLS algorithm. This revised version was published online in June 2006 with corrections to the Cover Date.     

Haze aerosols in the atmosphere of early Earth: manna from heaven

An organic haze layer in the upper atmosphere of Titan plays a crucial role in the atmospheric composition and climate of that moon. Such a haze layer may also have existed on the early Earth, providing an ultraviolet shield for greenhouse gases needed to warm the planet enough for life to arise and evolve. Despite the implications of such a haze layer, little is known about the organic material produced under early Earth conditions when both CO(2) and CH(4) may have been abundant in the atmosphere. For the first time, we experimentally demonstrate that organic haze can be generated in different CH(4)/CO(2) ratios. Here, we show that haze aerosols are able to form at CH(4) mixing ratios of 1,000 ppmv, a level likely to be present on early Earth. In addition, we find that organic hazes will form at C/O ratios as low as 0.6, which is lower than the predicted value of unity. We also show that as the C/O ratio decreases, the organic particles produced are more oxidized and contain biologically labile compounds. After life arose, the haze may thus have provided food for biota.     

Gravitation Maneuver Using the Families of Super-Unstable Orbits around the Libration Points

The families of periodic solutions to an autonomous Hamiltonian system in that part where the solutions are unstable have their specific field of influence. Under strong instability, the orbits that have fallen in such a field of influence are drawn into the family as in a whirlpool and then are thrown away from it. In the particular case of the restricted three-body problem, the orbits around the libration points L ₁ and L ₂ are super-unstable and the Keplerian elements in motion over these orbits change drastically. When the orbits fall into such a domain, for some time the motion is close to the motion around the libration point, and after being thrown out of this domain, the Keplerian orbital elements also change essentially.     

Certain approaches to the development of on-board automated training system

Perspectives of long-term space programs make it necessary to develop autonomous computer expert system for crew-members physical state control. The purpose of the work--to develop a set of objective formalizable physiological indices of working capacity suitable for reliable algorithmization of physical state control. Investigations were performed in on-earth microgravity simulation (3- and 7-day dry immersion, 6 subjects; 4-month antiorthostatic hypokinesy, 10 subjects) with volunteers' participation as well with 34 members of MIR-station expeditions during flights. Model exercise investigations were made also with 20 young male volunteers to evaluate the validity of different physical state indices. A set of indices was found which, being simple enough for measuring, performs to get satisfactory adequate evaluations of current organism physical state in long-term real or simulated microgravity. It was proved that some ergometric indices along with heart rate derivatives could reflect real working ability even better than traditional characteristics of organism energy systems state.     

Adaptation of neuromuscular activation patterns during treadmill walking after long-duration space flight

The precise neuromuscular control needed for optimal locomotion, particularly around heel strike and toe off, is known to he compromised after short duration (8- to 15-day) space flight. We hypothesized here that longer exposure to weightlessness would result in maladaptive neuromuscular activation during postflight treadmill walking. We also hypothesized that space flight would affect the ability of the sensory-motor control system to generate adaptive neuromuscular activation patterns in response to changes in visual target distance during postflight treadmill walking. Seven crewmembers, who completed 3- to 6-month missions, walked on a motorized treadmill while visually fixating on a target placed 30 cm (NEAR) or 2 m (FAR) from the subject's eyes. Electronic foot switch data and surface electromyography were collected from selected muscles of the right lower limb. Results indicate that the phasic features of neuromuscular activation were moderately affected and the relative amplitude of activity in the tibialis anterior and rectus femoris around toe off changed after space flight. Changes also were evident after space flight in how these muscles adapted to the shift in visual target distance.