Study of long path VLF signal propagation characteristics as observed from Indian Antarctic station,Maitri

To examine the quality and propagation characteristics of the Very Low Frequency (VLF) radio waves in a very long propagation path, Indian Centre for Space Physics, Kolkata, participated in the 27th Indian scientific expedition to Antarctica during 2007–2008. One Stanford University made AWESOME VLF receiving system was installed at the Indian Antarctic station Maitri and about five weeks of data were recorded successfully from the Indian transmitter VTX and several other transmitting stations worldwide. The quality of the signal from the VTX transmitter was found to be very good, consistent and highly stable in day and night. The signal shows the evidences of the presence of the 24 h solar radiation in the Antarctic region during local summer. Here we report the both narrow band and broadband VLF observations from this site. The diurnal variations of VTX signal (18.2 kHz) are presented systematically for Antarctica path and also compared the same with the variations for a short propagation path (VTX-Kolkata). We compute the spatial distribution of the VTX signal along the VTX-Antarctica path using the most well-known LWPC model for an all-day and all-night propagation conditions. The calculated signal amplitudes corresponding to those conditions relatively corroborate the observations. We also present the attenuation rate of the dominant waveguide modes corresponding to those propagation conditions where the effects of the Antarctic polar ice on the attenuation of different propagating waveguide modes are visible.     

Contents of Volume 2

Volume Contents

Contents of Volume 2     

Comparative study of spermatogonial survival after x-ray exposure, high LET (HZE) irradiation or spaceflight.

Spermatogonial cell loss has been observed in rats flown on Space Lab 3, Cosmos 1887, Cosmos 2044 and in mice following irradiation with X-ray or with high energy (HZE) particle beams. Spermatogonial loss is determined by cell counting in maturation stage 6 seminiferous [correction of seminferous] tubules. With the exception of Iron, laboratory irradiation experiments (with mice) revealed a similar pattern of spermatogonial loss proportional to the radiation dose at levels less than 0.1 Gy. Helium and Argon irradiation resulted in a 5% loss of spermatogonia after only 0.01 Gy exposure. However, significant spermatogonial loss (45%) occured at this radiation level with Iron particle beams. The loss of spermatogonia during each space flight was less than 10% when compared to control (non-flight) animals. This loss, although small, was significant. Although radiation may be a contributing factor in the loss of spermatogonia during space flight, exposure levels, as determined by dosimetry, were not significant to account for the total cell loss observed.     

SAMBO-GEOS : Electric field measurements in the disturbed ionosphere and magnetosphere

Measurements of the electric field in the ionosphere and the equatorial plane during the pre-onset and actives phases of a substorm (March 4, 1979) are compared. Correlations and disagrements between the measurements are considered. The preliminary conclusion is reached that the model of electrojet polarisation proposed by CORONITI and KENNEL (1972) could possibly explain part of our observations.     

Analysis of nitrogen flow in rice cultivation in CEEF.

In order to control the material circulation in the Closed Ecology Experiment Facilities (CEEF), it is necessary to clarify material flow in the Closed Plant Experiment Facility (CPEF) of CEEF. We tried to grow rice plants and measure the nitrogen contents in rice plant and nutrient solution in plant cultivation bed to trace the material balance in CPEF. The measurements were carried out under the condition of 750 ppm (v/v) CO2 at 26/19 degrees C in the plant cultivation room. The measurements showed the absorbed nitrogen amount in plant was less than the outflow nitrogen amount from nutrient solution. This difference between absorbed and outflow quantity reached to 17%.     

A Herculean task? Economics, politics, and realigning government in the case of US polar-orbiting weather satellites

In 1994 one of the most radical institutional restructurings in the USA's government provision of critical weather information took place after eight previously unsuccessful attempts. The President merged weather data collection by satellites operated by the Department of Defense and satellites operated by the Department of Commerce. Reorganization involving agencies with different objectives, economic constraints, and operating cultures is rare. This paper reviews the decision leading to “convergence,” discusses economic arguments, and addresses the problems confronting the new organization. The paper also discusses the implications of the new organization for incentives to engage in space R&D and the increasingly large role played by these satellites in collecting not only weather but also climate-related data.     

Use of service history for certification credit for COTS [avionic software]

Much has been written in the last ten years about how the use of commercial-off-the-shelf (COTS) components would revolutionize the aerospace industry avionics, communication, navigation, surveillance/air traffic management (CNS/ATM) as well as global air traffic management (GATM). Civil aviation authorities around the world have been faced with numerous requests to certify aircraft containing increasing percentages of COTS components, much of it never designed or intended for use in the safety critical environment of an aircraft. Product service history is one method for demonstrating that such software is acceptable for use. In theory, product service history would seem to be a fairly simple concept, both to understand and to apply. However, in practice, such use has proven extremely problematic, as questions of how to measure the historic performance and the relevance of the provided data have surfaced. This paper elaborates a research effort funded by the United States Federal Aviation Administration to collect, analyze, and synthesize what is known and understood about applying product service history. The effort is limited to the topic of software product service history as applied in the certification of airborne systems and equipment.     

Growth and development in higher plants under simulated microgravity conditions on a 3-dimensional clinostat.

Growth and development of etiolated pea (Pisum sativum L. cv. Alaska) and maize (Zea mays L. cv. Golden Cross Bantam) seedlings grown under simulated microgravity conditions were intensively studied using a 3-dimensional clinostat as a simulator of weightlessness. Epicotyls of etiolated pea seedlings grown on the clinostat were the most oriented toward the direction far from cotyledons. Mesocotyls of etiolated maize seedlings grew at random and coleoptiles curved slightly during clinostat rotation. Clinostat rotation promoted the emergence of the 3rd internodes in etiolated pea seedlings, while it significantly inhibited the growth of the 1st internodes. In maize seedlings, the growth of coleoptiles was little affected by clinostat rotation, but that of mesocotyls was suppressed, and therefore, the emergence of the leaf out of coleoptile was promoted. Clinostat rotation reduced the osmotic concentration in the 1st internodes of pea seedlings, although it has little effect on the 2nd and the 3rd internodes. Clinostat rotation also reduced the osmotic concentrations in both coleoptiles and mesocotyls of maize seedlings. Cell-wall extensibilities of the 1st and the 3rd internodes of pea seedlings grown on the clinostat were significantly lower and higher as compared with those on 1 g conditions, respectively. Cell-wall extensibility of mesocotyls in seedlings grown on the clinostat also decreased. Changes in cell wall properties seem to be well correlated to the growth of each organ in pea and maize seedlings. These results suggest that the growth and development of plants is controlled under gravity on earth, and that the growth responses of higher plants to microgravity conditions are regulated by both cell-wall mechanical properties and osmotic properties of stem cells.     

Magnetic resonance image enhancement using V-filter

A method for enhancing the boundaries of magnetic resonance images (MRIs) using a V-filter (a spatial nonlinear filter) is presented. By iterated V-filtering the signal-to-noise ratio of the MRI can be increased while preserving edge sharpness. A simulation experiment was carried out to evaluate the filter, using clinical brain images. The boundaries of the brain tumor and edematous region were precisely extracted by the region segmentation techniques     

Effects of hypergravity on the development of cell number and asymmetry in fish brain nuclei.

Larval cichlid fish (Oreochromis mossambicus) siblings were subjected to 3 g hypergravity (hg) and total darkness for 21 days during development and subsequently processed for conventional histology. Further siblings reared at 1 g and alternating light/dark (12h:12h) conditions served as controls. Cell number counts of the visual Nucleus isthmi (Ni) versus the vestibular Nucleus magnocellularis (Nm) revealed that in experimental animals total cell number was decreased in the Ni, possibly due to retarded growth as a result of the lack of visual input whereas no effect was observed in the Nm. Calculating the percentual asymmetry in cell number (i.e., right vs. the left side of the brain), no effects of hg/darkness were seen in the Ni, whereas asymmetry was slightly increased in the Nm. Since the asymmetry of inner ear otoliths is decreased under hg, this finding may indicate efferent vestibular action of the CNS on the level of the Nm by means of a feedback mechanism.