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NASA NTRS1991

On the wind geometry of the Wolf-Rayet star EZ Canis Majoris

Recent models of Wolf-Rayet star winds have been tailored to EZ CMa, and make predictions of the envelope structure and location of line-emitting regions. It is discussed how the wind structure of EZ CMa can be probed observationally through electron distribution integrals as measured by spectropolarimetry, and then present, analyze, and interpret a time-dependent spectropolarimetric data set of EZ CMa. The observations further the view of an electron-scattering wind that is axisymmetric, rotating, and expanding, with a variable mass-loss rate being responsible for the quasi-periodic polarimetric variability. It is demonstrated that the emission lines of EZ CMa are partially polarized, indicating that line photons are electron-scattered in the wind. The polarization in N V lambda 4945 and N IV lambda 4058 is observed to be larger than that of He II lambda 4686 and He I lambda 5876, as expected from ionization stratification.

Schulte-Ladbeck, R. E.↗

NASA NTRS1992

The first linear polarization spectra of Wolf-Rayet stars in the ultraviolet - EZ Canis Majoris and Theta Muscae

During the 1990 December Astro-1 Space Shuttle mission, spectropolarimetry was conducted in the wavelength region from 1400 to 3200 A of the Wolf-Rayet stars EZ CMa (WN5) and Theta Mus (WC6 + O9.5I) with the Wisconsin Ultraviolet Photo-Polarimeter Experiment. The UV polarization of EZ CMa displays features which correspond to emission lines. This indicates a large, about 0.8 percent, intrinsic UV-continuum polarization, and provides further evidence that the wind of EZ CMa is highly distorted. The polarization of Theta Mus does not change across emission lines, or the strong interstellar 2200 A feature. The polarization decreases smoothly to shorter wavelengths, at constant position angle. The combined UV-optical polarization spectrum of Theta Mus can be described well with interstellar polarization following a Serkowski law.

Schulte-Ladbeck, R. E.↗

NASA NTRS1990

A rotating, expanding disk in the Wolf-Rayet star EZ Canis Majoris?

The discovery of linear polarization changes across the extended wings of He II lines, mainly the strong 4-3 transition at 4686 A, in the WN5 star EZ CMa, is reported. When the polarization across the line profiles is plotted in the Stokes parameters plane, it traces loops clockwise from the blue wing through line center to the red, rather than straight lines. Such polarization loops are reminiscent of what is observed in the Balmer lines of Be stars. The continuum polarization in EZ CMa can be understood by an axisymmetric, electron-scattering envelope, with the decrease in polarization in He II being caused by an increase in absorptive opacity in the lines and dilution by unpolarized line emission, while the variations in position angle are due to the Doppler-shifted absorptive opacity and/or scattered line photons. As the sense of rotation in the loops is also independent of phase of this alleged Wolf-Rayet + compact binary, the polarized line profiles are the signature of a rotating, expanding wind geometry around a single star.

Schulte-Ladbeck, R. E.↗

NASA NTRS2000

BOREAS AFM-1 NOAA/ATDD Long-EZ Aircraft Flux data Over the SSA

This data set contains measurements from the Airborne Flux and Meteorology (AFM)-1 National Oceanographic and Atmospheric Administration/Atmospheric Turbulence and Diffusion Division (NOAA/ATDD) Long-EZ Aircraft collected during the 1994 Intensive Field Campaigns (IFCs) at the southern study area (SSA). These measurements were made from various instruments mounted on the aircraft. The data that were collected include aircraft altitude, wind direction, wind speed, air temperature, potential temperature, water mixing ratio, U and V components of wind velocity, static pressure, surface radiative temperature, downwelling and upwelling total radiation, downwelling and upwelling longwave radiation, net radiation, downwelling and upwelling photosynthectically active radiation (PAR), greenness index, CO2 concentration, O3 concentration, and CH4 concentration. There are also various columns that indicate the standard deviation, skewness, kurtosis, and trend of some of these data. The data are stored in tabular ASCII files. The NOAA/ATDD Long-EZ aircraft flux data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Crawford, Timothy L.↗

NASA NTRS1985

The enigmatic star EZ Pegasi - A mystery solved?

EZ Peg, a ninth-magnitude G star that has been classified by various authors as an irregular variable, a U Gem system, and a contact binary, is shown to have all the spectroscopic and photometric characteristics of an active-chromosphere RS CVn binary. It is suggested that the reported outburst of 1943, when the spectrum appeared to be that of a B star, never occurred. The strong Ca II H and K reversals, viewed with low spectral resolution, caused the photospheric Ca II absorption to appear abnormally weak, mimicking a much earlier spectral type.

Howell, S. B.↗

NASA NTRS1986

EZ Pegasi - The last pieces of the puzzle

Based on UBV differential photometric observations carried out at the Braeside Observatory between October 19, 1984 and January 11, 1985, it is shown that EZ Peg is in synchronous rotation with a photometric period of 11.6626 days. The orbital solution of Griffin (1985) is in good agreement with the present results, and it is employed to analyze the emission properties of the Ca II and H-alpha emission in the system. It is suggested that the emission of the system is almost entirely associated with the primary component, and the two stars appear to be similar in size and luminosity.

Howell, S. B.↗

NASA NTRS1992

Photometry, polarimetry, spectroscopy, and spectropolarimetry of the enigmatic Wolf-Rayet star EZ Canis Majoris

New observations of the peculiar Wolf-Rayet star EZ Canis Majoris collected since 1987 are presented, and photometric, polarimetric, spectroscopic, and spectropolarimetric data are discussed. Linear polarization data are well fitted with an eccentric binary model where an additional free parameter is included to allow for epoch-dependent changes of the geometrical electron distribution in the W-R envelope. This yields a set of basic parameters, including an eccentricity e = 0.39 +/- 0.02 and an orbital inclination i = 114 deg +/- 3 deg. The spectroscopic data show global profile variations for all three observed strong emission lines He II 5412 A, C IV 5807 A, and He I 5876 A. Radial velocities of the lines vary with the 3.766-day period. Radially expanding inhomogeneities are superposed on the line profiles and variable polarization in the lines is observed.

Robert, Carmelle↗

NASA NTRS1998

A Search for X-Ray Evidence of a Compact Companion to the Unusual Wolf-Rayet Star HD 50896 (EZ CMa)

We analyze results of a approx.25 ksec ASCA X-ray observation of the unusual Wolf-Rayet star HD 50896 (= EZ CMa). This WN5 star shows optical and ultraviolet variability at a 3.766 day period, which has been interpreted as a possible signature of a compact companion. Our objective was to search for evidence of hard X-rays (greater than or equal to 5 keV) which could be present if the WN5 wind is accreting onto a compact object. The ASCA spectra are dominated by emission below 5 keV and show no significant emission in the harder 5-10 keV range. Weak emission lines are present, and the X-rays arise in an optically thin plasma which spans a range of temperatures from less than or equal to 0.4 keV up to at least approx. 2 keV. Excess X-ray absorption above the interstellar value is present, but the column density is no larger than N(sub H) approx. 10(exp 22)/sq cm. The absorption-corrected X-ray luminosity L(sub x)(0.5 - 10 keV) = 10(exp 32.85) erg/s gives L(sub x)/ L(sub bol) approx. 10(exp -6), a value that is typical of WN stars. No X-ray variability was detected. Our main conclusion is that the X-ray properties of HD 50896 are inconsistent with the behavior expected for wind accretion onto a neutron star or black hole companion. Alternative models based on wind shocks can explain most aspects of the X-ray behavior, and we argue that the hotter plasma near approx. 2 keV could be due to the WR wind shocking onto a normal (nondegenerate) companion.

Skinner, Stephen L.↗

NASA NTRS2001

Making the EZ Choice

Analytical Mechanics Associates, Inc. (AMA), of Hampton, Virginia, created the EZopt software application through Small Business Innovation Research (SBIR) funding from NASA's Langley Research Center. The new software is a user-friendly tool kit that provides quick and logical solutions to complex optimal control problems. In its most basic form, EZopt converts process data into math equations and then proceeds to utilize those equations to solve problems within control systems. EZopt successfully proved its advantage when applied to short-term mission planning and onboard flight computer implementation. The technology has also solved multiple real-life engineering problems faced in numerous commercial operations. For instance, mechanical engineers use EZopt to solve control problems with robots, while chemical plants implement the application to overcome situations with batch reactors and temperature control. In the emerging field of commercial aerospace, EZopt is able to optimize trajectories for launch vehicles and perform potential space station- keeping tasks. Furthermore, the software also helps control electromagnetic devices in the automotive industry.

Source record↗

NASA NTRS2002

The Unusual Wolf-Rayet Star EZ CMa

The XMM-Newton observations were obtained on 29 - 30 October 2001 during the AO-1 Guest Observer program. Our X-ray analysis focused on data from the European Photon Imaging Camera (EPIC). The VLA observations were obtained during a 3.5 hour interval on 1999 Oct. 19 with the array in hybrid BnA configuration. Radio continuum data were acquired at five different frequencies 1.42 GHz (21 cm), 4.86 GHz (6 cm), 8.44 GHz (3.6 cm), 14.94 GHz (2 cm), and 22.46 GHz (1.3 cm). These radio data are unique since they provide an excellent snapshot picture of the dependence of the radio flux on frequency obtained over a short time interval and are thus immune to the variability effects which can distort results obtained from non-contemporaneous observations at different frequencies.

Skinner, Stephen L.↗

NASA NTRS2006

Daily Planet Redesign: eZ Publish Web Content Management Implementation

This viewgraph presentation reviews the process of the redesign of the Daily . Planet news letter as a content management implementation project. This is a site that is an internal news site that acts as a communication vehicle for a large volume of content. The Objectives for the site redesign was: (1) Clean visual design, (2) Facilitation of publication processes, (3) More efficient maintenance mode, (4) Automated publishing to internal portal, (5) Better navigation through improved site IA, (6) Archiving and retrieval functionality, (7) Back to basics on fundamental business goals. The CM is a process not a software package

web content management↗

NASA NTRS2016

Human Mars Landing Site and Impacts on Mars Surface Operations

This paper describes NASA's initial steps for identifying and evaluating candidate Exploration Zones (EZs) and Regions of Interests (ROIs) for the first human crews that will explore the surface of Mars. NASA's current effort to define the exploration of this planet by human crews, known as the Evolvable Mars Campaign (EMC), provides the context in which these EZs and ROIs are being considered. The EMC spans all aspects of a human Mars mission including launch from Earth, transit to and from Mars, and operations on the surface of Mars. An EZ is a collection of ROIs located within approximately 100 kilometers of a centralized landing site. ROIs are areas relevant for scientific investigation and/or development/maturation of capabilities and resources necessary for a sustainable human presence. The EZ also contains one or more landing sites and a habitation site that will be used by multiple human crews during missions to explore and utilize the ROIs within the EZ. With the EMC as a conceptual basis, the EZ model has been refined to a point where specific site selection criteria for scientific exploration and in situ resource utilization can be defined. In 2015 these criteria were distributed to the planetary sciences community and the in situ resource utilization and civil engineering communities as part of a call for EZ proposals. The resulting "First Landing Site/Exploration Zone Workshop for Human Missions to the Surface of Mars" was held in October 2015 during which 47 proposals for EZs and ROIs were presented and discussed. Proposed locations spanned all longitudes and all allowable latitudes (+/- 50 degrees). Proposed justification for selecting one of these EZs also spanned a significant portion of the scientific and resource criteria provided to the community. Several important findings resulted from this Workshop including: (a) a strong consensus that, at a scale of 100 km (radius), multiple places on Mars exist that have both sufficient scientific interest to sustain multiple crews of exploring astronauts, AND potential resource deposits for ISRU indicating the current EZ definition is viable and should be retained for now, (b) new data types (needed for more definitive analysis of EZs) argued strongly for a new orbiter mission, and possibly one or more surface missions, to obtain these data, (c) a general consensus that this Workshop was an excellent start to identifying a place where future human missions to Mars can productively explore this planet and learn to live and work there for the long term. Building on these findings, HEOMD and SMD are: (a) refining the EZ selection criteria and overall selection process to improve on lessons learned from the first EZ workshop, (b) using these proposed locations to develop "reference EZs" for assessment purposes (primarily engineering assessments), (c) gathering data and conducting analyses to better understanding the different potential sources for water, including the ease of extraction and purification, and (d) assessing trends in additional data that are needed to better characterize EZs proposed at the workshop and how these data needs impact the design and operation of future robotic Mars missions.

Hoffman, Stephen J.↗

NASA NTRS2016

Human Mars Landing Site and Impacts on Mars Surface Operations

NASA has begun a process to identify and discuss candidate locations where humans could land, live and work on the Martian surface. These locations are referred to as Exploration Zones (EZs). Given current mission concepts, an EZ is a collection of Regions of Interest (ROIs) that are located within approximately 100 kilometers of a centralized landing site. ROIs are areas that are relevant for scientific investigation and/or development/maturation of capabilities and resources necessary for a sustainable human presence. The EZ also contains a landing site and a habitation site that will be used by multiple human crews during missions to explore and utilize the ROIs within the EZ. These candidate EZs will be used by NASA as part of a multi‐year process of determining where and how humans could explore Mars. In the near term this process includes: (a) identifying locations that would maximize the potential science return from future human exploration missions, (b) identifying locations with the potential for resources required to support humans, (c) developing concepts and engineering systems needed by future human crews to conduct operations within an EZ, and (d) identifying key characteristics of the proposed candidate EZs that cannot be evaluated using existing data sets, thus helping to define precursor measurements needed in advance of human missions. Existing and future robotic spacecraft will be tasked to gather data from specific Mars surface sites within the representative EZs to support these NASA activities. The proposed paper will describe NASA's initial steps for identifying and evaluating candidate EZs and ROIs. This includes plans for the "First Landing Site/Exploration Zone Workshop for Human Missions to the Surface of Mars" to be held in October 2015 at which proposals for EZs and ROIs will be presented and discussed. It will also include a discussion of how these considerations are (or will be) taken into account as future robotic Mars missions are defined and developed. One or more representative EZs, drawn from similar previous studies involving Mars sites, will be used in the proposed paper to illustrate the process NASA envisions for gathering additional data from robotic precursor missions to assist in making a final selection of an EZ for human crews as well as the steps likely to occur during the buildup of a habitation site. Examples of the systems and operations likely to be used by human crews, assisted by robotic vehicles, to explore the scientific ROIs as well as developing the resource ROIs within the example EZs will be discussed.

Bussey, Ben↗

NASA NTRS2016

Mars Surface System Common Capabilities and Challenges for Human Missions

NASA has begun a process to identify and evaluate candidate locations where humans could land, live and work on the martian surface. These locations are referred to as Exploration Zones (EZs). Given current mission concepts, an EZ is a collection of Regions of Interest (ROIs) that are located within approximately 100 kilometers of a centralized landing site. ROIs are areas that are relevant for scientific investigation and/or development/maturation of capabilities and resources necessary for a sustainable human presence. The EZ also contains a landing site and a habitation site that will be used by multiple human crews during missions to explore and utilize the ROIs within the EZ. In parallel with this process, NASA continues to make progress on the Evolvable Mars Campaign examining alternatives that can pioneer an extended human presence on Mars that is Earth independent. This involves ongoing assessments of surface systems and operations to enable a permanent, sustainable human presence. Because of the difficulty in getting equipment and supplies to the surface of Mars, part of these assessments involve identifying those systems and processes that can perform in multiple, sometimes completely unrelated, situations. These assessments have been performed in a very generic surface mission carried out at a very generic surface location. As specific candidate EZs are identified it becomes important to evaluate the current suite of surface systems and operations as they are likely to perform for the specific locations and for the types of operations - both scientific and development - that are proposed for these EZs. It is also important to evaluate the proposed EZs for their suitability to be explored or developed given the range of capabilities and constraints for the types of surface systems and operations being considered within the EMC. This means looking at setting up and operating a field station at a central location within the EZ as well as traversing to and exploring the scientific ROIs within the boundaries of the EZ. The proposed paper will describe the current status of common systems and operations as they can be applied to actual EZ locations on Mars. Initially these EZs will be the four locations identified MEPAG's Human Exploration of Mars Science Analysis Group (HEM‐SAG) that will be used as representative of the EZs that will emerge from the process that NASA has initiated. An example process that could be commonly applied is an approach for developing a field station site plan that would be demonstrated by applying this process to each of the four HEM‐SAG sites. Examples of common systems include (a) mobility systems that can be used to off‐load and move payloads to specific locations at the central field station location that could also be used to traverse long distances to reach some of the more remote ROIs or (b) robotic systems that can support various activities (such as system set up and maintenance) at the field station that could also be used to explore scientific ROIs and used to support site‐specific ISRU production activities.

Hoffman, Stephen J.↗

NASA NTRS2016

Human Mars Landing Site and Impacts on Mars Surface Operations

This paper describes NASA's initial steps for identifying and evaluating candidate Exploration Zones (EZs) and Regions of Interests (ROIs) for the first human crews that will explore the surface of Mars. NASA's current effort to define the exploration of this planet by human crews, known as the Evolvable Mars Campaign (EMC), provides the context in which these EZs and ROIs are being considered. The EMC spans all aspects of a human Mars mission including launch from Earth, transit to and from Mars, and operations on the surface of Mars. Studies related to Mars surface operations and related system capabilities have led to the current definition of an EZ as well as ROIs. An EZ is a collection of ROIs that are located within approximately 100 kilometers of a centralized landing site. ROIs are areas that are relevant for scientific investigation and/or development/maturation of capabilities and resources necessary for a sustainable human presence. The EZ also contains one or more landing sites and a habitation site that will be used by multiple human crews during missions to explore and utilize the ROIs within the EZ. With the EMC as a conceptual basis, the EZ model has been refined to a point where specific site selection criteria for scientific exploration and in situ resource utilization can be defined. In 2015 these criteria were distributed to the planetary sciences community and the in situ resource utilization and civil engineering communities as part of a call for EZ proposals. The resulting "First Landing Site/Exploration Zone Workshop for Human Missions to the Surface of Mars" was held in October 2015 during which 47 proposals for EZs and ROIs were presented and discussed. Proposed locations spanned all longitudes and all allowable latitudes (+/- 50 degrees). Proposed justification for selecting one of these EZs also spanned a significant portion of the scientific and resource criteria provided to the community. Workshop results will be used to prepare for follow-on workshops to refine our understanding of proposed EZs and ultimately select a single location to be explored and utilized by human crews. Another significant workshop outcome was a recognition that new data will be needed to refine our understanding of the value of proposed EZs. These new data will come in part from existing spacecraft at Mars and may come from future robotic Mars missions as appropriate consideration is given to these new data needs during mission definition and development.

Bussey, Ben↗

NASA NTRS2016

Mars Surface Systems Common Capabilities and Challenges for Human Missions

This paper describes the current status of common systems and operations as they are applied to actual locations on Mars that are representative of Exploration Zones (EZ) - NASA's term for candidate locations where humans could land, live and work on the Martian surface. Given NASA's current concepts for human missions to Mars, an EZ is a collection of Regions of Interest (ROIs) located within approximately 100 kilometers of a centralized landing site. ROIs are areas that are relevant for scientific investigation and/or development/maturation of capabilities and resources necessary for a sustainable human presence. An EZ also contains a habitation site that will be used by multiple human crews during missions to explore and utilize the ROIs within the EZ. The Evolvable Mars Campaign (EMC), a description of NASA's current approach to these human Mars missions, assumes that a single EZ will be identified within which NASA will establish a substantial and durable surface infrastructure that will be used by multiple human crews. The process of identifying and eventually selecting this single EZ will likely take many years to finalized. Because of this extended EZ selection process it becomes important to evaluate the current suite of surface systems and operations being evaluated for the EMC as they are likely to perform at a variety of proposed EZ locations and for the types of operations - both scientific and development - that are proposed for these candidate EZs. It is also important to evaluate proposed EZs for their suitability to be explored or developed given the range of capabilities and constraints for the types of surface systems and operations being considered within the EMC. Four locations identified in the Mars Exploration Program Analysis Group (MEPAG)'s Human Exploration of Mars Science Analysis Group (HEM-SAG) report are used in this paper as representative of candidate EZs that will emerge from the selection process that NASA has initiated. A field station site plan is developed for each of these four HEM-SAG sites. Because of the difficulty in getting equipment and supplies to the surface of Mars, specific assessments have been conducted to identify those systems and processes that can perform in multiple, sometimes completely unrelated, situations. Examples of common systems that are assessed at all of these sites include: (a) habitation and associated logistics storage systems, (b) a centralized power plant capable of supplying power to a geographically distributed (but within the central habitation zone) set of systems, (c) mobility systems that can be used to off-load and move payloads to specific locations at the central field station location that could also be used to traverse long distances to reach some of the more remote ROIs and (d) robotic systems that can support various activities (such as system set up and maintenance) at the field station that could also be used to explore scientific ROIs and used to support site-specific ISRU (In Situ Resource Utilization) production activities.

Toups, Larry↗

NASA NTRS2016

Mars Surface Systems Common Capabilities and Challenges for Human Missions

Toups, Larry↗

NASA NTRS1973

Ion kinematics in a plasma focus.

The results of numerical integrations of three-dimensional equations of motion of ions subject to given electric and magnetic fields are presented. The fields represent those which may exist in the pinch phase of the plasma focus, although here they depend only on the radial coordinate. The ions initially have Maxwellian velocity distributions, and their trajectories are interpreted in terms of single-particle constants of the motion. Two models of the axial electric field Ez are considered. For strong Ez away from the axis, there is a cyclotron acceleration which leads to ion heating. For positive Ez on the axis, ions within a Larmor radius of the axis undergo very efficient acceleration; the results for this new model are in general agreement with experimental results.

Gary, S. P.↗