IMF Direction Derived from Cycloid-Like Ion Distributions Observed by Mars Express

Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser (IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF is relatively uniform on a scale larger than the proton gyroradius. During bow shock outbound crossings, MEX often observed cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most likely newly ionized hydrogen atoms, which are picked up by the solar wind.     

Three-dimensional transgenic cell model to quantify genotoxic effects of space environment.

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 2 lambda 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 2 lambda 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 genotoxicity including measurement of the inherent damage incurred in Space.     

Ground probing radar system

Two types of battery-powered, compact, ground probing radar (GPR) systems have been developed. The systems have CRT displays mounted on antenna units and are used to locate such underground objects as gas pipes, water pipes, and transmission cables. The performance of the systems and results of field tests are reported. The GPR detected 59 of 64 underground gas pipes; a 200-mm-diameter pipe is clearly detected at a depth of 2.3 m     

Understanding Interplanetary Coronal Mass Ejection Signatures

While interplanetary coronal mass ejections (ICMEs) are understood to be the heliospheric counterparts of CMEs, with signatures undeniably linked to the CME process, the variability of these signatures and questions about mapping to observed CME features raise issues that remain on the cutting edge of ICME research. These issues are discussed in the context of traditional understanding, and recent results using innovative analysis techniques are reviewed.     

The extravehicular mobility unit: A review of environment, requirements, and design changes in the US spacesuit

Requirements are rarely static, and are ever more likely to evolve as the development time of a system stretches out and its service life increases. In this paper, we discuss the evolution of requirements for the US spacesuit, the extravehicular mobility unit (EMU), as a case study to highlight the need for flexibility in system design. We explore one fundamental environmental change, using the Space Shuttle EMU aboard the International Space Station, and the resulting EMU requirement and design changes. The EMU, like other complex systems, faces considerable uncertainty during its service life. Changes in the technical, political, or economic environment cause changes in requirements, which in turn necessitate design modifications or upgrades. We make the case that flexibility is a key attribute that needs to be embedded in the design of long-lived, complex systems to enable them to efficiently meet the inevitability of changing requirements after they have been fielded.     

On adaptive multiband signal detection with GLR algorithm

An adaptive multiband detector based on the principle of the generalized likelihood ratio test (GLR) is presented. Its detection performance is studied and compared with that of the corresponding single-band GLR detector. The multiband detector is shown to significantly outperform the single-band under the chosen system constraint, especially when the amount of data available from a single frequency band is severely limited by the environment     

Dust emission phenomena of cometary analogues

Experiments with cometary analogues are reported, which were performed at DLR - Köln in a small vacuum chamber and in the Space Simulator. The results apply to the emission processes of ice-dust grains from the surface of mineral-ice mixtures during insolation. The emission phenomena were observed with CCD-video-cameras. The camera used at the small chamber was equipped with a magnifying (10x) macro-lens. The magnified pictures show that the ice-dust agglomerates carry tiny ice particles on their surfaces. These may play the role of interlinking bonds between one grain and its neighbors. In the enlarged view it can be seen that the ice-dust grains do not erupt with high velocity out of the surface. The upstreaming gas jet originating from the sublimation of the volatile components first erodes the interlinking bonds between the particles. When the drag force exerted on the particles exceeds the force of gravity, the particles lift off. In most of the observed cases this initial lift off velocity is very small e.g. a few cm/s.

During a comet-simulation experiment in the Space-Simulator in November 1989 the trajectories of emitted dust particles were recorded for the first time with a high speed shutter video system 60 cm from the model comet. The video tapes were evaluated with a computerized image processing system. Unique insights in the gas-dust-interaction immediately at and above the insolated icy body were obtained. The trajectories differ markedly in all cases from the the ballistic parabolas calculated from the measured starting conditions: elevation angle and speed. The trajectory is mainly dominated by the momentum transfer from the gas jet to the dust particles. Many of the particles have millimeter sizes. The observed velocities at the end of the visible trajectory are in the order of a few meters per second.     

Swimming behaviour and calcium incorporation into inner ear otoliths of fish after vestibular nerve transection.

Previous investigations on neonate swordtail fish (Xiphophorus helleri) revealed that otolithic calcium incorporation (visualized using the calcium tracer alizarin complexone) and thus otolith growth had ceased after nerve transection, supporting a hypothesis according to which the gravity-dependent otolith growth is regulated neuronally. Subsequent investigations on larval cichlid fish (Oreochromis mossambicus) yielded contrasting results, repeatedly depending on the particular batch of cichlids investigated. Like most neonate swordtails, Type I cichlids revealed a stop of calcium incorporation after unilateral vestibular nerve transection. Their behaviour after transection was normal, and the otolithic calcium incorporation in controls of the same batch was symmetric. In Type II cichlids, however, vestibular nerve transection had no effect on otolithic calcium incorporation. They behaved kinetotically after transection (this kind of kinetosis was qualitatively similar to the swimming behaviour exhibited by larval cichlids during microgravity in the course of parabolic aircraft flights). The otolithic calcium incorporation in control animals was asymmetric. These results show that the effects of vestibular nerve transection as well as the efficacy of the mechanism, which regulates otolith growth/otolithic calcium incorporation, are--depending on the particular batch of animals--genetically predispositioned. In conclusion, the regulation of otolithic calcium incorporation is guided neuronally, in part via the vestibular nerve and, in part, via a further pathway, which remains to be addressed in the course of future investigations.     

Large light X-ray optics: basic ideas and concepts

One of the main guidelines for future X-ray astronomy projects like, e.g., XEUS (ESA) and Generation-X (NASA) is to utilize grazing-incidence focusing optics with extremely large telescopes (several tens of m² at 1 keV), with a dramatic increase in collecting area of about two order of magnitude compared to the current X-ray telescopes. In order to avoid the problem of the source's confusion limit at low fluxes, the angular resolution required for these optics should be superb (a few arcsec at most). The enormous mirror dimensions together with the high imaging performances give rise to a number of manufacturing problems. It is basically impossible to realize so large mirrors from closed Wolter I shells which benefit from high mechanical stiffness. Instead the mirrors need to be formed as rectangular segments and a series of them will be assembled in a petal. Taking into account the realistic load capabilities of space launchers, to be able to put in orbit so large mirror modules the mass/geometric-area ratio of the optics should be very small. Finally, with a so large optics mass it would be very difficult to provide the electric power for an optics thermal active control, able to maintain the mirrors at the usual temperature of 20 °C. Therefore, very likely, the optics will instead operate in extreme thermal conditions, with the mirror temperature oscillating between −30 and −40 °C, that tends to exclude the epoxy replication approach (the mismatch between the CTE of the substrate and that of the resin would cause prohibitively large deformations of the mirror surface profiles). From these considerations light weight materials with high thermal–mechanical properties such as glass or ceramics become attractive to realize the mirrors of future Xray telescopes. In this paper, we will discuss a segments manufacturing method based on Borofloat^TM glass. A series of finite element analysis concerning different aspects of the production, testing and integration of the optics are also presented as well.     

Effect of hypergravity on carboanhydrase reactivity in inner ear ionocytes of developing cichlid fish.

It has been shown earlier that hypergravity slows down inner ear otolith growth in developing fish. Otolith growth in terms of mineralization mainly depends on the enzyme carboanhydrase (CA), which is responsible for the provision of the pH-value necessary for calcium carbonate deposition. Larval siblings of cichlid fish (Oreochromis mossambicus) were subjected to hypergravity (3 g, hg; 6 h) during development and separated into normally and kinetotically swimming individuals following the transfer to 1 g (i.e., stopping the centrifuge; kinetotically behaving fish performed spinning movements). Subsequently, CA was histochemically demonstrated in inner ear ionocytes (cells involved in the endolymphatic ion exchange) and enzyme reactivity was determined densitometrically. It was found that both the total macular CA-reactivity as well as the difference in reactivities between the left and the right maculae (asymmetry) were significantly lower (1) in experimental animals as compared to the 1 g controls and (2) in normally swimming hg-animals as compared to the kinetotically behaving hg-fish. The results are in complete agreement with earlier studies, according to which hypergravity induces a decrease of otolith growth and the otolithic calcium incorporation (visualized using the calcium-tracer alizarin complexone) of kinetotically swimming hg-fish was higher as compared to normally behaving hyper-g animals. The present study thus strongly supports the concept that a regulatory mechanism, which adjusts otolith size and asymmetry as well as otolithic calcium carbonate incorporation towards the gravity vector, acts via activation/deactivation of macular CA.