Towards a Global Unified Model of Europa’s Tenuous Atmosphere

Despite the numerous modeling efforts of the past, our knowledge on the radiation-induced physical and chemical processes in Europa’s tenuous atmosphere and on the exchange of material between the moon’s surface and Jupiter’s magnetosphere remains limited. In lack of an adequate number of in situ observations, the existence of a wide variety of models based on different scenarios and considerations has resulted in a fragmentary understanding of the interactions of the magnetospheric ion population with both the moon’s icy surface and neutral gas envelope. Models show large discrepancy in the source and loss rates of the different constituents as well as in the determination of the spatial distribution of the atmosphere and its variation with time. The existence of several models based on very different approaches highlights the need of a detailed comparison among them with the final goal of developing a unified model of Europa’s tenuous atmosphere. The availability to the science community of such a model could be of particular interest in view of the planning of the future mission observations (e.g., ESA’s JUpiter ICy moons Explorer (JUICE) mission, and NASA’s Europa Clipper mission). We review the existing models of Europa’s tenuous atmosphere and discuss each of their derived characteristics of the neutral environment. We also discuss discrepancies among different models and the assumptions of the plasma environment in the vicinity of Europa. A summary of the existing observations of both the neutral and the plasma environments at Europa is also presented. The characteristics of a global unified model of the tenuous atmosphere are, then, discussed. Finally, we identify needed future experimental work in laboratories and propose some suitable observation strategies for upcoming missions.     

Evolution of the Sunspot Number and Solar Wind $$ Time Series

The past two decades have witnessed significant changes in our knowledge of long-term solar and solar wind activity. The sunspot number time series (1700-present) developed by Rudolf Wolf during the second half of the 19th century was revised and extended by the group sunspot number series (1610–1995) of Hoyt and Schatten during the 1990s. The group sunspot number is significantly lower than the Wolf series before ～1885. An effort from 2011–2015 to understand and remove differences between these two series via a series of workshops had the unintended consequence of prompting several alternative constructions of the sunspot number. Thus it has been necessary to expand and extend the sunspot number reconciliation process. On the solar wind side, after a decade of controversy, an ISSI International Team used geomagnetic and sunspot data to obtain a high-confidence time series of the solar wind magnetic field strength (\(B\)) from 1750-present that can be compared with two independent long-term (> ～600 year) series of annual \(B\)-values based on cosmogenic nuclides. In this paper, we trace the twists and turns leading to our current understanding of long-term solar and solar wind activity.     

The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument

Space Science Reviews - Modern observatories have revealed the ubiquitous presence of magnetohydrodynamic waves in the solar corona. The propagating waves (in contrast to the standing waves) are...     

Adaptive Resource Allocation in a Spatial Spectral Processor

A method for achieving an optimal allocation of fixed computational resources in a spatial/spectral filtering system is developed. Specifically, clock cycles per unit time for a given processor are to be optimally allocated. The system is a cascade of three subsystems: an adaptive beamformer, a bandpass filter, and a spectral whitener. Each subsystem has adjustable parameters which are related to required arithmetic operations. A gradient projection algorithm is used to find a best allocation according to specified criteria. Two simulation examples are presented to show how the algorithm operates and to indicate the kind of improvement that is possible in a system design.     

Gamma-ray Lines From cr Source Regions

Gamma-ray lines arise from radioactivities produced in nucleosynthesis sites, and from deexcitation of nuclei which have been activated through energetic particle collisions. Since the bulk of nucleosynthesis activity relates to activities inside massive stars, both these processes are related to the likely sources of cosmic rays: Supernova remnants show radioactivity afterglows at time scales which bracket their likely phases of relevance as CR acceleration sites; ²⁶Al radioactivity may trace regions of intense wind interactions from groups of massive stars, and also encode information about the possible injection of matter into CR acceleration environments through interstellar dust grains. The status of -ray line measurements after the Compton Observatory mission is presented, with models and interpretations of current results, and the prospects of upcoming measurements.     

Cellular Mobile Telephone Environment

Cellular mobile telephone systems are rapidly going into service throughout the Continental United States. They are being installed in a large variety of vehicles both of domestic and of foreign manufacture. In this paper we discuss the physical, climatic, and electronic environments which cellular telephones may expect to encounter in nationwide service. We also discuss procedures used to evaluate the ability of a cellular phone to operate without failure in these environments and to avoid interfering with the increasingly complex vehicular electronic systems.     

Estimation of Spectral Moments without Weighting

Quantitative bounds for the normalized second moment of a random signal process are expressed in terms of the statistics of measured quantities. No weighting is used, and, essentially, the only assumption made on the signal process is that its spectrum be bandlimited.     

Telerobotics and orbital laboratories: an end-to-end analysis and demonstration

A preliminary analysis of the United States Laboratory (USL) module of the International Space Station has been completed. A major conclusion was that one of the most limited resources within the USL will be crew time. A laboratory robot would alleviate these constraints, improve safety, and reduce operational costs. A laboratory experiment manipulator system (LEMS) is proposed, made up of an on-board mobile manipulator and a computer-assisted operator control station. The on-board manipulator concept was tested with an Intelledex 660 industrial robot. Operator joystick command capability and delayed video feedback were added to simulate a Space Station Teleoperation system. The implementation of a unique predictive display was chosen for further evaluation because of its promise as a partial solution to the classical problem of robot remote control in the presence of time delay. The incorporation of various correction factors to calibrate the robot predictor model, including geometric distortion and spherical aberration caused by the video optics, is described.     

Developing a stratospheric climatology from NMC analyses

The National Meteorological Center of the National Oceanic and Atmospheric Administration (NOAA) has archived global, daily synoptic analyses and computer gridded fields of geopotential height and temperature for 8 stratospheric pressure levels (70, 50, 30, 10, 5, 2, 1 and 0.4 mb) since the Autumn of 1978. More restricted analyses are available since 1964. The fields are discussed, with special emphasis on improvement of the data bases and analysis procedures. Included in the discussions are screening procedures for the climatological data base. Examples are given with regard to monthly mean energy, wind and hemispheric temperature patterns calculated as the initial development of a stratospheric dynamic climatology.     

The International Space Station human life sciences experiment implementation process.

The selection, definition, and development phases of a Life Sciences flight research experiment has been consistent throughout the past decade. The implementation process, however, has changed significantly within the past two years. This change is driven primarily by the shift from highly integrated, dedicated research missions on platforms with well defined processes to self contained experiments with stand alone operations on platforms which are being concurrently designed. For experiments manifested on the International Space Station (ISS) and/or on short duration missions, the more modular, streamlined, and independent the individual experiment is, the more likely it is to be successfully implemented before the ISS assembly is completed. During the assembly phase of the ISS, science operations are lower in priority than the construction of the station. After the station has been completed, it is expected that more resources will be available to perform research. The complexity of implementing investigations increases with the logistics needed to perform the experiment. Examples of logistics issues include- hardware unique to the experiment; large up and down mass and volume needs; access to crew and hardware during the ascent or descent phases; maintenance of hardware and supplies with a limited shelf life,- baseline data collection schedules with lengthy sessions or sessions close to the launch or landing; onboard stowage availability, particularly cold stowage; and extensive training where highly proficient skills must be maintained. As the ISS processes become better defined, experiment implementation will meet new challenges due to distributed management, on-orbit resource sharing, and adjustments to crew availability pre- and post-increment.