Physical sciences research plans for the International Space Station

The restructuring of the research capabilities of the International Space Station has forced a reassessment of the Physical Sciences research plans and a re-targeting of the major scientific thrusts. The combination of already selected peer-reviewed flight investigations with the initiation of new research and technology programs will allow the maximization of the ISS scientific and technological potential. Fundamental and applied research will use a combination of ISS-based facilities, ground-based activities, and other experimental platforms to address issues impacting fundamental knowledge, industrial and medical applications on Earth, and the technology required for human space exploration. The current flight investigation research plan shows a large number of principal investigators selected to use the remaining planned research facilities.     

An online astrobiology course for teachers

A continuing challenge for scientists is to keep K-12 teachers informed about new scientific developments. Over the past few years, this challenge has increased as new research findings have come from the field of astrobiology. In addition to trying to keep abreast of these new discoveries, K-12 teachers must also face the demands of the content and pedagogical goals imposed by state and national science education standards. Furthermore, many teachers lack the scientific content knowledge or training in current teaching methods to create their own activities or to implement appropriately new teaching materials designed to meet the standards. There is a clear need for special courses designed to increase the scientific knowledge of K-12 science teachers. In response to this need, the authors developed a suite of innovative, classroom-ready lessons for grades 5-12 that emphasize an active engagement instructional strategy and focus on the recent discoveries in the field of astrobiology. They further created a graduate-level, Internet-based distance-learning course for teachers to help them become familiar with these astrobiology concepts and to gain firsthand experience with the National Science Education Standards-based instructional strategies.     

Electrification of Polymer Films in Laboratory and under Space Conditions

A simplified theory of the electrification of polymer films, which permits estimation of the internal electric fields of films irradiated by monoenergetic electrons simulating real streams of plasma electrons during magnetic substorms at a geosynchronous orbit, is suggested. To determine the depth behavior of the forward current and the dosage rate in the irradiated polymer, numerical calculations are made by the Monte Carlo technique. The appearance of electrostatic discharges in thin (5 m) mylar films is shown to be very probable in the orbit's shadow sector under magnetic substorm conditions.     

Study of the psychological adaptation of the crew during a 135 days space simulation

The purpose of this study is to examine human adaptation of a three members' crew during a 135 days MIR flight simulation and to compare and validate psychological methods for monitoring and support in flight. The main findings showed that isolation was not a key factor for the subjects who were more concerned by recreational activities, family, and work. The individual reactions to stress of the crew members were to project their problems on the others. These reactions had some consequences upon the group: Although the three subjects developed a weak tendency to "group think", one of the crew members was considered as less integrated to the group by the other two subjects, who, however, acted to protect (successfully) the general cohesion and mood of the crew. From a methodological point of view, baseline data predicted the difficulties that occurred for one of the crew member. Both quantitative and qualitative tools were adequate, although qualitative tests gave a closer approach to the actual situation that developed during the simulation.     

Solar particle event dose distributions: parameterization of dose-time profiles

Calculations of total dose and dose equivalent as a function of time since the start of the event are presented for four of the major solar particle events that occurred during the period from August to December 1989. Results are presented for exposures to the skin, ocular lens and bone marrow shielded by a nominal thickness of aluminum shielding, comparable to that provided by a spacesuit. The calculated curves of organ dose and dose equivalent versus time are parameterized using a Weibull functional form for the fitting equation. The fitting parameters are determined using least squares regression techniques. These results provide a useful starting point for the development of methods to predict the cumulative doses and times to reach various dose limits from a limited number of dose measurements early in a solar particle event.     

The NASA Performance Assessment Workstation: cognitive performance during head-down bed rest

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 degrees head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.     

Anomalous Cosmic Rays and Solar Modulation

We review aspects of anomalous cosmic rays (ACRs) that bear on the solar modulation of energetic particles in the heliosphere. We show that the latitudinal and radial gradients of these particles exhibit a 22-year periodicity in concert with the reversal of the Sun's magnetic field. The power-law index of the low energy portion of the energy spectrum of ACRs at the shock in 1996 appears to be -1.3, suggesting that the strength of the solar wind termination shock at the helioequatorial plane is relatively weak, with s 2.8. The rigidity dependence of the perpendicular interplanetary mean free path in the outer heliosphere for particles with rigidities between 0.2 and 0.7 GV varies approximately as R2, where R is particle rigidity. There is evidence that ACR oxygen is primarily multiply charged above 20 MeV/nuc and primarily singly-charged below 16 MeV/nuc. The location of the termination shock was at 65 AU in 1987 and 85 AU in 1994.     

Eigenstructure Assignment for Linear Systems

The use of feedback (full state, output, and constrained output) is considered as a means of shaping the transient response of linear time invariant systems. The underlying importance of the eigenstructure (eigenvalues/eigenvectors) is highlighted. Also, the important results and techniques are presented along with a brief literature review. An extensive flight control example is presented which should give direction to the application of eigenstructure assignment in diverse areas.     

An operational system implementation of the ESPIRIT DF algorithm

The practical implementation of the ESPRIT algorithm into direction-finding system architecture is considered. In particular, the problems of phase ambiguity resolution for extended array separations and multidimensional azimuth/elevation estimation are addressed. Generalized solutions for these problems are proposed, and a bearing quality indicator that provides a measure of credibility associated with each angle-of-arrival estimate is developed. Plots of computer simulated performance are presented in order to assess the probability of detection, of failure to alarm, and of false alarm as a function of azimuthal separation and period of signal observation     

Atmospheric Ion-induced Aerosol Nucleation

Ion-induced nucleation has been suggested to be a potentially important mechanism for atmospheric aerosol formation. Ions are formed in the background atmosphere by galactic cosmic rays. A possible connection between galactic cosmic rays and cloudiness has been However, the predictions of current atmospheric nucleation models are highly uncertain because the models are usually based on the liquid drop model that estimates cluster thermodynamics based on bulk properties (e.g., liquid drop density and surface tension). Sulfuric acid (H₂SO₄) and water are assumed to be the most important nucleating agents in the free troposphere. Measurements of the molecular thermodynamics for the growth and evaporation of cluster ions containing H₂SO₄ and H₂O were performed using a temperature-controlled laminar flow reactor coupled to a linear quadrupole mass spectrometer as well as a temperature-controlled ion trap mass spectrometer. The measurements were complemented by quantum chemical calculations of the cluster ion structures. The analysis yielded a complete set of H₂SO₄ and H₂O binding thermodynamics extending from molecular cluster ions to the bulk, based on experimental thermodynamics for the small clusters. The data were incorporated into a kinetic aerosol model to yield quantitative predictions of the rate of ion-induced nucleation for atmospheric conditions. The model predicts that the negative ion-H₂SO₄-H₂O nucleation mechanism is an efficient source of new particles in the middle and upper troposphere.