Strategies for telecommunications and navigation in support of Mars exploration

The planned exploration of Mars will pose new and unique telecommunications and navigation challenges. The full range of orbital, atmospheric, and surface exploration will drive requirements on data return, energy-efficient communications, connectivity, and positioning. In this paper we will summarize the needs of the currently planned Mars exploration mission set, outline design trades and options for meeting these needs, and quantify the specific telecommunications and navigation capabilities of an evolving infrastructure.     

Neural and fuzzy reconstructors for the virtual flight datarecorder

The results are presented of a comparative study evaluating the performance of neural network (NN) and fuzzy logic reconstructors (FLRs) for the development of a virtual flight data recorder (VFDK). Typical flight data recorders (FDRS) on commercial airliners do not record the aircraft control surface deflections. These dynamic parameters are critical in the investigation of an accident or an uncommanded maneuver. The results are shown relative to a VFDR based on a neural network simulator (NNS) along with a neural network reconstructor (NNR) or a FLR The NNS is trained off-line, using available flight data for the particular aircraft, for the purpose of simulating any desired dynamic output recorded in current FDRs. The NNS is then interfaced with the NNR or with the FLR. The output of the two reconstructors are the control surface deflections which minimize a performance index based on the differences between the available data from the FDR and the output from the NNS. The study tested with night data from a B737-300 shows that both schemes, the one with the NNR and the one with the FLR, provide accurate reconstructions of the control surface deflections time histories     

Hard X-ray observations of the Crab Pulsar

The Crab was observed in a balloon flight from Palestine/Texas on 9/28/81 at hard X-ray energies (20–200 keV). The light curve is significantly sharper than reported previously for this energy range. The pulse-averaged as well as the interpulse spectra show breaks in our energy-range. The variation of spectral index across the pulse has an amplitude similar to that found at lower energies by OSO-8 and larger than reported by HEAO-1 A4 at hard X-rays. For a sharp emission line at 77 keV a 99% upper limit of 1.0*10⁻³ photons/ cm² sec can be placed, a factor of 4 lower than line fluxes reported previously. Pulse-shape fits to the optical, X-ray, hard X-ray and gamma ray light-curves reveal a consistent picture of the origin of the interpulse and off-pulse emission, the breaks in the spectra and the variation of spectral index, providing arguments against a thermal component and also a polar cap emission model for NP0532.     

Emesis and space motion sickness in amphibians.

Amphibians possess the ability to vomit in response to a variety of stimuli that provoke emesis in mammals. Pharmacological studies have establish that the ejection of gastric contents and the basic mechanism for vomiting have been phylogenetically conserved among these tetrapods. As part of on-going comparative studies on emesis in vertebrates, we previously documented that some postmetamorphic anurans and salamander larvae experience motion-induced emesis when exposed to the provocative stimulus of parabolic aircraft flight. However, more recent experiments suggest that there are strict conditions for inducing emesis in amphibians exposed to parabolic flight and that amphibians are not as sensitive to this stimulus as mammals. Further studies on emesis in lower vertebrates may help us understand the processes that cause emesis in abnormal gravitational regimes.     

Trickle water and feeding system in plant culture and light-dark cycle effects on plant growth.

Rockwool, as an inert medium covered or bagged with polyethylene film, can be effectively used for plant culture in space station. The most important machine is the pump adjusting the dripping rate in the feeding system. Hydro-aeroponics may be adaptable to a space laboratory. The shortening of the light-dark cycles inhibits plant growth and induces an abnormal morphogenesis. A photoperiod of 12-hr-dark may be needed for plant growth.     

Amorphous Silicon Electronic Devices and their Applications

Hydrogenated amorphous Si (a-Si:H) devices first made a significant impact in photovoltaic application, 70% of the photovoltaic solar cells produced in Japan in 1984 were a-Si:H. More recently, thin film transistor (TFT) and sensor devices have been developed for consumer and business products. The ability to produce large area uniform films of a-Si:H makes the application of TFTs and sensors well suited for input and output imaging devices such as image scanners, display and printers. This paper reviews the operation, material issues and physics of a-Si:H TFTs and sensors. The circuit and technology issues in large area systems incorporating these devices are described.     

The mechanics of air-breathing in anuran larvae: implications to the development of amphibians in microgravity.

Because of their rapid development, amphibians have been important model organisms in studies of how microgravity affects vertebrate growth and differentiation. Both urodele (salamanders) and anuran (frogs and toads) embryos have been raised in orbital flight, the latter several times. The most commonly reported and striking effects of microgravity on tadpoles are not in the vestibular system, as one might suppose, but in their lungs and tails. Pathological changes in these organs disrupt behavior and retard larval growth. What causes malformed (typically lordotic) tadpoles in microgravity is not known, nor have axial pathologies been reported in every flight experiment. Lung pathology, however, has been consistently observed and is understood to result from the failure of the animals to inflate their lungs in a timely and adequate fashion. We suggest that malformities in the axial skeleton of tadpoles raised in microgravity are secondary to problems in respiratory function. We have used high speed videography to investigate how tadpoles breathe air in the 1G environment. The video images reveal alternative species-specific mechanisms, that allow tadpoles to separate air from water in less that 150 ms. We observed nothing in the biomechanics of air-breathing in 1G that would preclude these same mechanisms from working in microgravity. Thus our kinematic results suggest that the failure of tadpoles to inflate their lungs properly in microgravity is due to the tadpoles' inability to locate the air-water interface and not a problem with the inhalation mechanism per se.     

Genomic instability and tumorigenic induction in immortalized human bronchial epithelial cells by heavy ions

Carcinogenesis is postulated to be a progressive multistage process characterized by an increase in genomic instability and clonal selection with each mutational event endowing a selective growth advantage. Genomic instability as manifested by the amplification of specific gene fragments is common among tumor and transformed cells. In the present study, immortalized human bronchial (BEP2D) cells were irradiated with graded doses of either 1GeV/nucleon ⁵⁶Fe ions or 150 keV/μm alpha particles. Transformed cells developed through a series of successive steps before becoming tumorigenic in nude mice. Tumorigenic cells showed neither ras mutations nor deletion in the p16 tumor suppressor gene. In contrast, they harbored mutations in the p53 gene and over-expressed cyclin D1. Genomic instability among transformed cells at various stage of the carcinogenic process was examined based on frequencies of PALA resistance. Incidence of genomic instability was highest among established tumor cell lines relative to transformed, non-tumorigenic and control cell lines. Treatment of BEP2D cells with a 4 mM dose of the aminothiol WR-1065 significantly reduced their neoplastic transforming response to ⁵⁶Fe particles. This model provides an opportunity to study the cellular and molecular mechanisms involved in malignant transformation of human epithelial cells by heavy ions.     

The biological clock of Neurospora in a microgravity environment.

The circadian rhythm of conidiation in Neurospora crassa is thought to be an endogenously derived circadian oscillation; however, several investigators have suggested that circadian rhythms may, instead, be driven by some geophysical time cue(s). An experiment was conducted on space shuttle flight STS-9 in order to test this hypothesis; during the first 7-8 cycles in space, there were several minor alterations observed in the conidiation rhythm, including an increase in the period of the oscillation, an increase in the variability of the growth rate and a diminished rhythm amplitude, which eventually damped out in 25% of the flight tubes. On day seven of flight, the tubes were exposed to light while their growth fronts were marked. Some aspect of the marking process reinstated a robust rhythm in all the tubes which continued throughout the remainder of the flight. These results from the last 86 hours of flight demonstrated that the rhythm can persist in space. Since the aberrant rhythmicity occurred prior to the marking procedure, but not after, it was hypothesized that the damping on STS-9 may have resulted from the hypergravity pulse of launch. To test this hypothesis, we conducted investigations into the effects of altered gravitational forces on conidiation. Exposure to hypergravity (via centrifugation), simulated microgravity (via the use of a clinostat) and altered orientations (via alterations in the vector of a 1 g force) were used to examine the effects of gravity upon the circadian rhythm of conidiation.     

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen.

Early Earth and early Mars were similar enough such that past geochemical and climatic conditions on Mars may have also been favorable for the origin of life. However, one of the most striking differences between the two planets was the low partial pressure of dinitrogen (pN2) on early Mars (18 mb). On Earth, nitrogen is a key biological element and in many ecosystems the low availability of fixed nitrogen compounds is the main factor limiting growth. Biological fixation of dinitrogen on Earth is a crucial source of fixed nitrogen. Could the low availability of dinitrogen in the primordial Martian atmosphere have prevented the existence, or evolution of Martian microbiota? Azotobacter vinelandii and Azomonas agilis were grown in nitrogen free synthetic medium under various partial pressures of dinitrogen ranging from 780-0 mb (total atmosphere=1 bar). Below 400 mb the biomass, cell number, and growth rate decreased with decreasing pN2. Both microorganisms were capable of growth at a pN2 as low as 5 mb, but no growth was observed at a pN2 < or = 1 mb. The data appear to indicate that biological nitrogen fixation could have occurred on primordial Mars (pN2=18 mb) making it possible for a biotic system to have played a role in the Martian nitrogen cycle. It is possible that nitrogen may have played a key role in the early evolution of life on Mars, and that later a lack of available nitrogen on that planet (currently, pN2=0.2 mb) may have been involved in its subsequent extinction.