50 research outputs found
Systems engineering and the user: Incorporation of user requirements into the SE process
This paper is organized into four parts. In the Gestation Phase, I describe the process of starting a new mission and establishing its rough boundaries. Next I show how the scientific experiments are selected. Then we enter the Preliminary Design Phase, where we incorporate the scientist's instruments into the systems engineering process. Finally, I show how the Preliminary Design Review (PDR) assures NASA management and the scientists that the scientific requirements have been incorporated into the systems engineering process to everyone's satisfaction
First among equals: The selection of NASA space science experiments
The process is recounted by which NASA and the scientific community have, since 1958, selected individual experiments for NASA space missions. It explores the scientific and organizational issues involved in the selection process and discusses the significance of the process in the character and accomplishments of U.S. space activities
The Flux and Energy Spectra of the Protons in the Inner Van Allen Belt
A cylindrical stack of G-5 nuclear emulsions housed in the payload section of a four-stage research rocket was flown into the northern edge of the inner Van Allen belt on September 19, 1960. The experimental design permitted, for the first time, measurements of the particle fluxes and energy spectra as functions of position along the rocket trajectory. Eight points along the trajectory have been selected for analysis. Results are presented herein for three of these points, and they are discussed in the light of various theories on the trapped radiation
Intact Pathway Successfully Buffers Sage Grouse Migration
Landscape conservation is the mechanism for conserving migratory wildlife in sagebrush ecosystems. We studied a greater sage grouse (Centrocercus urophasianus; hereafter ‘sage-grouse’) population with the longest-known annual migration, ? 240 km round-trip, between summer and winter ranges in Saskatchewan, Canada, and northcentral Montana. We asked: Do birds fly quickly through a corridor, or do they use stopovers within a larger pathway? GPS-tracking revealed that migrating grouse frequent stopovers along multiple routes that coalesce to form an integrated pathway. Month-long fall migration in November contrasted with punctuated spring migration lasting ~2 weeks in late March/early April. Individual birds typically spent ~1 day at 9 different stopovers, migrating 71-91 km in 11-15 days. Migrating grouse used native sagebrush rangeland in proportion to its availability and avoided cropland and badlands. Birds responded to record-breaking snowfall in winter 2011 (>274 cm) by migrating another ? 50 km south onto windswept ridge tops where sagebrush remained above snow. Grouse selected habitat on Charles M. Russell National Wildlife Refuge most similar to typical winter habitat. Doing so was without consequence to winter survival; such was not the case for a nearby resident population. Newly identified winter range suggests that high site fidelity is tempered by an ability to adapt quickly when resources become scarce. We recommend public land policy that provides grazing opportunities while precluding large-scale energy development or whole scale removal of sagebrush. Management actions that maintain sagebrush as an emergency food source in newly identified sage grouse wintering grounds will help conserve this migratory population
Low-Tech Riparian and Wet Meadow Restoration Increases Vegetation Productivity and Resilience Across Semiarid Rangelands
Restoration of riparian and wet meadow ecosystems in semiarid rangelands of the western United States is a high priority given their ecological and hydrological importance in the region. However, traditional restoration approaches are often intensive and costly, limiting the extent over which they can be applied. Practitioners are increasingly trying new restoration techniques that are more cost‐effective, less intensive, and can more practically scale up to the scope of degradation. Unfortunately, practitioners typically lack resources to undertake outcome‐based evaluations necessary to judge the efficacy of these techniques. In this study, we use freely available, satellite remote sensing to explore changes in vegetation productivity (normalized difference vegetation index) of three distinct, low‐tech, riparian and wet meadow restoration projects. Case studies are presented that range in geographic location (Colorado, Oregon, and Nevada), restoration practice (Zeedyk structures, beaver dam analogs, and grazing management), and time since implementation. Restoration practices resulted in increased vegetation productivity of up to 25% and increased annual persistence of productive vegetation. Improvements in productivity with time since restoration suggest that elevated resilience may further enhance wildlife habitat and increase forage production. Long‐term, documented outcomes of conservation are rare; we hope our findings empower practitioners to further monitor and explore the use of low‐tech methods for restoration of ecohydrologic processes at meaningful spatial scales
Species-Specific Scaling to Define and Conserve the Northern Great Plains Region
Prairie ecosystems are in a continuous state of flux, shifting by processes that include variable weather patterns and climatic conditions, disturbance regimes, and more recently, human-induced modification. Similarly, wildlife resources fluctuate across the landscape as a result of these ever-changing conditions; however, human alterations have increased, removed, and manipulated the ecological processes of the prairie. Specifically, the spatial scales at which humans manage and interact with the landscape are often inconsistent or incompatible with the scales required for the persistence of wildlife populations. Our synthesis demonstrates how the spatial scales at which wildlife in the Northern Great Plains of North America operate have been constrained by human intervention. This process of anthropogenic scaling has affected the decline of many native wildlife populations and in some cases has resulted in the complete extirpation of species from the landscape. We use historical observations and recent quantitative data to describe the primary cause of spatial scale alteration for prairie focal species (i.e. plains bison, pronghorn, grassland birds, Greater Sage-grouse, black-tailed prairie dogs, swift fox, prairie rattlesnakes) using migration, home range, distribution, and dispersal distances as metrics. We then describe the role that spatial scale plays in wildlife management of the prairie landscape from the non-profit, state, and federal perspective and how these entities are managing at the scales of each focal species
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Saving sage-grouse from the trees: A proactive solution to reducing a key threat to a candidate species
Conservation investment in management of at-risk species can be less costly than a delay-and-repair approach implemented after species receive legal protection. The United States Endangered Species Act candidate species designation represents an opportunity to implement proactive management to avoid future listing. Such efforts require substantial investments, and the challenge becomes one of optimization of limited conservation funds to maximize return. Focusing on conifer encroachment threats to greater sage-grouse (Centrocercus urophasianus), we demonstrated an approach that links species demographics with attributes of conservation threats to inform targeting of investments. We mapped conifer stand characteristics using spatial wavelet analysis, and modeled lek activity as a function of conifer-related and additional lek site covariates using random forests. We applied modeling results to identify leks of high management potential and to estimate management costs. Results suggest sage-grouse incur population-level impacts at very low levels of encroachment, and leks were less likely to be active where smaller trees were dispersed. We estimated costs of prevention (treating active leks in jeopardy) and restoration (treating inactive leks with recolonization potential) management across the study area (2.5 million ha) at a total of US8.75 million can potentially address encroachment issues near all known Oregon leks within the next decade. Investments in proactive conservation with public and private landowners can increase ecosystem health to benefit species conservation and sustainable land uses, replace top-down regulatory approaches, and prevent conservation reliance of at-risk species.Keywords: Conifer encroachment, Spatial wavelet analysis, Sage-Grouse Initiative, Random forest models, Ecological economics, Juniperus occidentalis, Proactive managementKeywords: Conifer encroachment, Spatial wavelet analysis, Sage-Grouse Initiative, Random forest models, Ecological economics, Juniperus occidentalis, Proactive managemen
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with
new instrumentation and new surveys focused on Galactic structure and chemical
evolution, measurements of the baryon oscillation feature in the clustering of
galaxies and the quasar Ly alpha forest, and a radial velocity search for
planets around ~8000 stars. This paper describes the first data release of
SDSS-III (and the eighth counting from the beginning of the SDSS). The release
includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap,
bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a
third of the Celestial Sphere. All the imaging data have been reprocessed with
an improved sky-subtraction algorithm and a final, self-consistent photometric
recalibration and flat-field determination. This release also includes all data
from the second phase of the Sloan Extension for Galactic Understanding and
Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars
at both high and low Galactic latitudes. All the more than half a million
stellar spectra obtained with the SDSS spectrograph have been reprocessed
through an improved stellar parameters pipeline, which has better determination
of metallicity for high metallicity stars.Comment: Astrophysical Journal Supplements, in press (minor updates from
submitted version