Hydromagnetic motions in the magnetosphere

Following a brief specification and historical review of hydromagnetic motions in the magnetosphere, the principles of the governing and limiting processes are surveyed. A formal proof of the well-known hydromagnetic theorem is included, and its interpretation in terms of frozen fields is discussed. Some consequences of its application to the magnetosphere are then described, and the value of equipotentials as a means of illuminating the discussion is established. Departures from the hydromagnetic approximation are then evaluated, and their resultant currents described.The general principles find application in a number of processes: rotation, high-latitude circulation in quiet and disturbed conditions, more widespread convection under continuous dynamo action, and irregular motion both of an unstable and of a forced type. All these are reviewed, and one emergent point is emphasized: that direct evidence for the hydromagnetic motions is lacking, but that it can and should be sought.     

14.5-14.8 GHz Frequency Sharing by Data Relay Satellite Uplinks and Broadcasting-Satellite Uplinks

Data relay satellites are being developed to provide real-time data links between research satellites in low earth orbits and central data acquisition and processing facilities. Frequency assignments for data relay satellite links will be made in bands allocated internationally to the space research service. One of the bands which will be used lies between 14.5 and 15.35 GHz, where the space research service has had a frequency allocation as a secondary service since 1971. During the General World Administrative Radio Conference of the International Telecommunication Union, held in Geneva in 1979, a primary frequency allocation was made in the band 14.5-14.8 GHz to the fixed-satellite service, specifically for use by earth-to-space links of the broadcasting satellite service. The feasibility of shared band operation is evaluated between data relay satellite uplinks and broadcasting-satellite feeder links in the band 14.5-14.8 GHz. Relationships for predicting interference power levels are formulated, as functions of satellite separation and of earth station separation. Tradeoffs between satellite separation angle and earth station separation are explored, and conclusions are drawn regarding the feasibility of band sharing. Co-channel operation is demonstrated to be technically feasible for typical systems, provided appropriate separations are maintained.     

Performance of MAX family of order-statistic CFAR detectors

The MAX family of constant-false-alarm-rate (CFAR) detectors is introduced as a generalization of the greatest of CFAR (GO-CFAR) or MX mean-level detector (MX-MLD). Members of the MAX family use local estimators based on order statistics and generate both a near-range and a far-range noise-level estimate. Local estimates are always combined through a maximum operation; this insures false-alarm control at clutter edges. At the same time, order-statistic-based estimators result in a high-resolution detector. A complete detection analysis is provided for SWII targets and a reference channel contaminated by large outliers. Results are presented for the MX censored MLD (MX-CMLD) operating in clutter. The MX order statistic detector (MX-OSD) based on only a single-order statistic per window, is analyzed, and curves showing the required threshold, CFAR loss, optimum censoring point, and signal-to-noise ratio (SNR) loss in the presence of outliers are given. Simulations are used to compare the dynamic responses of various MX-OSD detectors in a clutter and a multiple-target environment     

Medical and surgical applications of space biosensor technology

Researchers in space life sciences are rapidly approaching a technology impasse. Many of the critical questions on the impact of spaceflight on living systems simply cannot be answered with the limited available technologies. Research subjects, particularly small animal models like the rat, must be allowed to function relatively untended and unrestrained for long periods to fully reflect the impact of microgravity and spaceflight on their behavior and physiology. These requirements preclude the use of present hard-wired instrumentation techniques and limited data acquisition systems. Implantable sensors and miniaturized biotelemetry are the only means of capturing the fundamental and critical data. This same biosensor and biotelemetry technology has direct application to Earth-based medicine and surgery. Continuous, on-line data acquisition and improved measurement capabilities combined with the ease and flexibility offered by automated, wireless, and portable instruments and data systems, should provide a boon to the health care industry. Playing a key role in this technology revolution is the Sensors 2000! (S2K!) Program at NASA Ames Research Center. S2K!, in collaboration with space life sciences researchers and managers, provides an integrated capability for sensor technology development and applications, including advanced biosensor technology development, spaceflight hardware development, and technology transfer and commercialization. S2K! is presently collaborating on several spaceflight projects with dual-use medical applications. One prime example is a collaboration with the Fetal Treatment Center (FTC) at the University of California at San Francisco. The goal is to develop and apply implantable chemical sensor and biotelemetry technology to continuously monitor fetal patients during extra-uterine surgery, replacement into the womb, through birth and beyond. Once validated for ground use, the method will be transitioned to spaceflight applications to remotely monitor key biochemical parameters in flight animals. Successful application of NASA implantable biosensor and biotelemetry technologies should accelerate the advancement of this and other modern medical procedures while furthering the exploration of life in space.     

The O/OREOS mission: first science data from the Space Environment Survivability of Living Organisms (SESLO) payload

We report the first telemetered spaceflight science results from the orbiting Space Environment Survivability of Living Organisms (SESLO) experiment, executed by one of the two 10?cm cube-format payloads aboard the 5.5?kg Organism/Organic Exposure to Orbital Stresses (O/OREOS) free-flying nanosatellite. The O/OREOS spacecraft was launched successfully to a 72° inclination, 650?km Earth orbit on 19 November 2010. This satellite provides access to the radiation environment of space in relatively weak regions of Earth's protective magnetosphere as it passes close to the north and south magnetic poles; the total dose rate is about 15 times that in the orbit of the International Space Station. The SESLO experiment measures the long-term survival, germination, and growth responses, including metabolic activity, of Bacillus subtilis spores exposed to the microgravity, ionizing radiation, and heavy-ion bombardment of its high-inclination orbit. Six microwells containing wild-type (168) and six more containing radiation-sensitive mutant (WN1087) strains of dried B. subtilis spores were rehydrated with nutrient medium after 14 days in space to allow the spores to germinate and grow. Similarly, the same distribution of organisms in a different set of microwells was rehydrated with nutrient medium after 97 days in space. The nutrient medium included the redox dye Alamar blue, which changes color in response to cellular metabolic activity. Three-color transmitted intensity measurements of all microwells were telemetered to Earth within days of each of the 48?h growth experiments. We report here on the evaluation and interpretation of these spaceflight data in comparison to delayed-synchronous laboratory ground control experiments.     

Mars habitat modules: launch, scaling and functional design considerations

The Sasakawa International Center for Space Architecture (SICSA) is undertaking a multi-year research, planning and design study that is exploring near- and long-term commercial space development opportunities. The central goal of this activity is to conceptualize a scenario of sequential, integrated private enterprise initiatives that can carry humankind forward to Mars. Each development stage is planned as a building block to provide the economic foundation, technology advancements and operational infrastructure to support others that follow. This report presents fundamental issues and requirements associated with planning human Mars initiatives that can transfer crews, habitats and equipment from Earth to Mars orbit, deliver them to the planet's surface, and return people and samples safely back to Earth. The study builds in part upon previous studies which are summarized in SICSA's: Commercial Space Development Plan and the Artificial Gravity Science and Excursion Vehicle reports. Information and conclusions produced in this study provide assumptions and a conceptual foundation for a subsequent report titled The First Mars Outpost: Planning and Concepts.     

Performance of max-mean level detector with and without censoring

The maximum-mean-level detector (MX-MLD) is a constant false-alarm rate (CFAR) detector designed to eliminate the excessively high false-alarm rate seen with the MLD at the edges of contiguous clutter regions. The concomitant high target suppression effect led M. Weiss (1982) to suggest a censored modification. The authors analyze the detection performance of the maximum-censored-mean-level detector (MX-CMLD). A homogeneous Swerling II target and clutter environment are assumed, and only single-pulse detection is considered. Analytic results apply equally to the MX-MLD and extend previous analysis. Simulation results are presented that demonstrate the qualitative effects of various CFAR detectors in nonhomogeneous clutter environments