Showing papers by "Raytheon published in 2009"

Time Series Prediction Using Support Vector Machines: A Survey

Abstract: Time series prediction techniques have been used in many real-world applications such as financial market prediction, electric utility load forecasting , weather and environmental state prediction, and reliability forecasting. The underlying system models and time series data generating processes are generally complex for these applications and the models for these systems are usually not known a priori. Accurate and unbiased estimation of the time series data produced by these systems cannot always be achieved using well known linear techniques, and thus the estimation process requires more advanced time series prediction algorithms. This paper provides a survey of time series prediction applications using a novel machine learning approach: support vector machines (SVM). The underlying motivation for using SVMs is the ability of this methodology to accurately forecast time series data when the underlying system processes are typically nonlinear, non-stationary and not defined a-priori. SVMs have also been proven to outperform other non-linear techniques including neural-network based non-linear prediction techniques such as multi-layer perceptrons.The ultimate goal is to provide the reader with insight into the applications using SVM for time series prediction, to give a brief tutorial on SVMs for time series prediction, to outline some of the advantages and challenges in using SVMs for time series prediction, and to provide a source for the reader to locate books, technical journals, and other online SVM research resources.

The ACS Nearby Galaxy Survey Treasury

Abstract: The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D 14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

Regulation of Hypoxia-Inducible Factor 2α Signaling by the Stress-Responsive Deacetylase Sirtuin 1

Abstract: To survive in hostile environments, organisms activate stress-responsive transcriptional regulators that coordinately increase production of protective factors. Hypoxia changes cellular metabolism and thus activates redox-sensitive as well as oxygen-dependent signal transducers. We demonstrate that Sirtuin 1 (Sirt1), a redox-sensing deacetylase, selectively stimulates activity of the transcription factor hypoxia-inducible factor 2 alpha (HIF-2α) during hypoxia. The effect of Sirt1 on HIF-2α required direct interaction of the proteins and intact deacetylase activity of Sirt1. Select lysine residues in HIF-2α that are acetylated during hypoxia confer repression of Sirt1 augmentation by small-molecule inhibitors. In cultured cells and mice, decreasing or increasing Sirt1 activity or levels affected expression of the HIF-2α target gene erythropoietin accordingly. Thus, Sirt1 promotes HIF-2 signaling during hypoxia and likely other environmental stresses.

MISR Aerosol Product Attributes and Statistical Comparisons With MODIS

Abstract: In this paper, Multi-angle Imaging SpectroRadiometer (MISR) aerosol product attributes are described, including geometry and algorithm performance flags. Actual retrieval coverage is mapped and explained in detail using representative global monthly data. Statistical comparisons are made with coincident aerosol optical depth (AOD) and Angstrom exponent (ANG) retrieval results from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The relationship between these results and the ones previously obtained for MISR and MODIS individually, based on comparisons with coincident ground-truth observations, is established. For the data examined, MISR and MODIS each obtain successful aerosol retrievals about 15% of the time, and coincident MISR-MODIS aerosol retrievals are obtained for about 6%-7% of the total overlap region. Cloud avoidance, glint and oblique-Sun exclusions, and other algorithm physical limitations account for these results. For both MISR and MODIS, successful retrievals are obtained for over 75% of locations where attempts are made. Where coincident AOD retrievals are obtained over ocean, the MISR-MODIS correlation coefficient is about 0.9; over land, the correlation coefficient is about 0.7. Differences are traced to specific known algorithm issues or conditions. Over-ocean ANG comparisons yield a correlation of 0.67, showing consistency in distinguishing aerosol air masses dominated by coarse-mode versus fine-mode particles. Sampling considerations imply that care must be taken when assessing monthly global aerosol direct radiative forcing and AOD trends with these products, but they can be used directly for many other applications, such as regional AOD gradient and aerosol air mass type mapping and aerosol transport model validation. Users are urged to take seriously the published product data-quality statements.

Generalized Theory of Code Tracking with an Early-Late Discriminator Part I: Lower Bound and Coherent Processing

Abstract: Code tracking is an important attribute of receivers for Global Positioning System (GPS) and other global navigation satellite systems (GNSS). This paper and its sequel provide analytical expressions for performance of code-tracking loops using early-late discriminators, under small-error conditions. Expressions are provided for output signal-to-noise-plus-interference ratio (SNIR) and code-tracking error for arbitrary signal spectra, and Gaussian noise and interference having arbitrary spectral shapes. This first paper addresses coherent early-late processing (ELP) for given receiver precorrelation bandwidth and given early-late spacing, also providing a tight lower bound on code-tracking error independent of discriminator design. Theoretical expressions are derived, showing that code-tracking accuracy depends on more than merely signal-to-noise ratio and early-late spacing - the shape of signal and interference spectra are important, as is the receiver precorrelation bandwidth.

Using immersive game-based virtual reality to teach fire-safety skills to children

Abstract: Virtual reality (VR) has been used both to simulate situations that are too dangerous to practice in real life and as a tool to help children learn. This study was conducted as part of a larger more comprehensive long-term research project which aims to combine the two techniques and demonstrate a novel application of the result, using immersive VR to help children learn about fire hazards and practice escape techniques. In the current study, a CAVE was used to immerse participants in a fire scene. To improve the children’s motivation for learning over prior VR fire-safety training methods, game-like interface interaction techniques were used and students were encouraged to explore the virtual world. Rather than being passive viewers, as in prior related studies, the children were given full control to navigate through the virtual environment and to interact with virtual objects using a game pad and a 6DOF wand. Students identified home fire hazards with a partner and then practiced escaping from a simulated fire in the virtual environment. To test for improved motivation, a user study was completed. Results indicate that students were more engaged by the new game-like learning environment and that they reported that they found the experience fun and intriguing. Their enhanced enthusiasm for what is relatively standard fire-safety information demonstrates the promise of using game-based virtual environments for vital but otherwise tedious fire-safety skills training for children.

Experimental Critical-Exponent Values for Fluids

Abstract: After a review of the history and an assessment of the current status of the subject, we present light-scattering data to determine the critical correlation-function exponents for an aqueous electrolyte solution yielding the experimental values γ=1.238±0.012, ν=0.629±0.003, η=0.032±0.013. We conclude the paper with some comments concerning the temperature dependence of non-asymptotic effective critical-exponent values of fluids.

The Detection of Inside-Out Disk Growth in M33

Abstract: We present resolved stellar photometry of four fields along the major axis of the M33 disk from images taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope. The photometry provides a detailed census of the red clump in all fields and reaches the ancient main sequence in the outermost field. Through detailed modeling of the color-magnitude diagrams, we find that the percentage of the stellar mass formed prior to z = 1 changes from 71 ± 9% in the innermost field to 16 ± 6% in the outermost field. The disk shows a clear trend of increasing scale length with time, evolving from rs = 1.0 ± 0.1 kpc 10 Gyr ago to rs = 1.8 ± 0.1 at times more recent than 5 Gyr ago, in agreement with analytical predictions for disk growth. Beyond the disk truncation radius, however, the stellar density profile steepens with time and the age gradient reverses, in agreement with recent simulations. The late and slow growth of the stellar disk may be due in part to the low mass of M33.

The true durations of starbursts: hubble space telescope observations of three nearby dwarf starburst galaxies

Abstract: The duration of a starburst is a fundamental parameter affecting the evolution of galaxies yet, to date, observational constraints on the durations of starbursts are not well established. Here we study the recent star formation histories of three nearby dwarf galaxies to rigorously quantify the duration of their starburst events using a uniform and consistent approach. We find that the bursts range from ~200 to ~400 Myr in duration resolving the tension between the shorter timescales often derived observationally with the longer timescales derived from dynamical arguments. If these three starbursts are typical of starbursts in dwarf galaxies, then the short timescales (3-10 Myr) associated with starbursts in previous studies are best understood as "flickering" events which are simply small components of the larger starburst. In this sample of three nearby dwarfs, the bursts are not localized events. All three systems show bursting levels of star formation in regions of both high and low stellar density. The enhanced star formation moves around the galaxy during the bursts and covers a large fraction of the area of the galaxy. These massive, long-duration bursts can significantly affect the structure, dynamics, and chemical evolution of the host galaxy and can be the progenitors of "superwinds" that drive much of the recently chemically enriched material from the galaxy into the intergalactic medium.

Generalized Theory of Code Tracking with an Early-Late Discriminator Part II: Noncoherent Processing and Numerical Results

Abstract: Code tracking is an important attribute of receivers for Global Positioning System (GPS) and other global navigation satellite systems (GNSS). This paper and its antecedent provide analytical expressions for performance of code-tracking loops using early-late discriminators, under small-error conditions. Expressions are provided for output signal-to-noise-plus-interference ratio (SNIR) and code-tracking error, for arbitrary signal spectra, and Gaussian noise and interference having arbitrary spectral shapes. This second paper addresses noncoherent early-late processing (NELP) for given receiver precorrelation bandwidth and given early-late spacing, comparing the results to results for coherent early-late processing (CELP) and to a lower bound (LB) on code-tracking error. Theoretical expressions are derived and compared, and numerical results are provided to examine the effect of different modulation designs and interference conditions.

Development, implementation and evaluation of a data-assimilative ocean forecasting system off the central California coast

Abstract: The development and implementation of a real-time ocean forecast system based on the Regional Ocean Modeling System (ROMS) off the coast of central California are described. The ROMS configuration consists of three nested modeling domains with increasing spatial resolutions: the US West coastal ocean at 15-km resolution, the central California coastal ocean at 5 km, and the Monterey Bay region at 1.5 km. All three nested models have 32 vertical sigma (or terrain-following) layers and were integrated in conjunction with a three-dimensional variational data assimilation algorithm (3DVAR) to produce snapshots of the ocean state every 6 h (the reanalysis) and 48-h forecasts once a day. This ROMS forecast system was operated in real time during the field experiment known as the Autonomous Ocean Sampling Network (AOSN-II) in August 2003. After the field experiment, a number of improvements were made to the ROMS forecast system: more data were added in the reanalysis with more careful quality control procedures, improvements were made in the data assimilation scheme, as well as model surface and side boundary conditions. The results from the ROMS reanalysis are presented here. The ROMS reanalysis is first compared with the assimilated data as a consistency check. An evaluation of the ROMS reanalysis against the independent measurements that are not assimilated into the model is then presented. This evaluation shows the mean differences in temperature and salinity between reanalysis and observations to be less than 1 °C and 0.2 psu (practical salinity unit), respectively, with root-mean-square (RMS) differences of less than 1.5 °C and 0.25 psu. Qualitative agreement is found between independent current measurements and the ROMS reanalysis. The agreement is particularly good for the vertically integrated current along the offshore glider tracks: the ROMS reanalysis can realistically reproduce the poleward California Undercurrent. Reasonably good agreement is found in the spatial patterns of the surface current as measured by high-frequency (HF) radars. Preliminary results concerning the ROMS forecast skill and predictability are also presented. Future plans to improve the ROMS forecast system with a particular focus on assimilation of HF radar current measurements are discussed.

MIMO radar: Snake oil or good idea?

Abstract: MIMO communication is theoretically superior to conventional communication under certain conditions, and MIMO communication also appears to be practical and cost-effective in the real world for some applications. It is natural to suppose that the same is true for MIMO radar, but the situation is not so clear. Researchers claim many advantages of MIMO radar relative to phased array radars (e.g., better detection performance, better angular resolution, better angular measurement accuracy, improved robustness against RFI, ECM, multipath, etc.). We will evaluate such assertions from a system engineering viewpoint. In particular, there are serious trade-offs of MIMO vs. phased array radars relative to cost, system complexity, and risk considering numerous real world effects that are not included in most theoretical analyses. Moreover, in many cases one can achieve essentially the same radar system improvement with phased array radars using simpler, less expensive, and less risky algorithms. We evaluate roughly a dozen asserted advantages of MIMO radar relative to phased arrays.

The Detection of Inside-out Disk Growth in M33

Abstract: We present resolved stellar photometry of 4 fields along the major axis of the M33 disk from images taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope The photometry provides a detailed census of the red clump in all fields and reaches the ancient main sequence in the outermost field Through detailed modeling of the color-magnitude diagrams, we find that the percentage of the stellar mass formed prior to z=1 changes from 71 +/- 9% in the innermost field to 16 +/- 6% in the outermost field The disk shows a clear trend of increasing scale-length with time, evolving from 10 +/- 01 kpc 10 Gyr ago to 18 +/- 01 kpc at times more recent than 5 Gyr ago, in agreement with analytical predictions for disk growth Beyond the disk truncation radius, however, the stellar density profile steepens with time and the age gradient reverses, in agreement with recent simulations The late and slow growth of the stellar disk may be due in part to the low mass of M33

Solving systems of nonlinear equations with continuous GRASP

Abstract: A method for finding all roots of a system of nonlinear equations is described. Our method makes use of C-GRASP, a recently proposed continuous global optimization heuristic. Given a nonlinear system, we solve a corresponding adaptively modified global optimization problem multiple times, each time using C-GRASP, with areas of repulsion around roots that have already been found. The heuristic makes no use of derivative information. We illustrate the approach using systems found in the literature.

The ACS Nearby Galaxy Survey Treasury. I. The Star Formation History of the M81 Outer Disk

Abstract: The Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury is a large Hubble Space Telescope (HST)/ACS treasury program to obtain resolved stellar photometry for a volume-limited sample of galaxies out to 4 Mpc. As part of this program, we have obtained deep ACS imaging of a field in the outer disk of the large spiral galaxy M81. The field contains the outskirts of a spiral arm as well as an area containing no current star formation. Our imaging results in a color-magnitude diagram (CMD) reaching to m F814W = 28.8 and m F606W = 29.5, one magnitude fainter than the red clump. Through detailed modeling of the full CMD, we quantify the age and metallicity distribution of the stellar populations contained in the field. The mean metallicity in the field is –1 < [M/H] < 0 and only a small fraction of stars have ages 1 Gyr. The results show that most of the stars in this outer disk field were formed by z ~ 1 and that the arm structure at this radius has a lifetime of 100 Myr. We discuss the measured evolution of the M81 disk in the context of surveys of high redshift disk galaxies and deep stellar photometry of other nearby galaxies. All of these indicate that massive spiral disks are mostly formed by z ~ 1 and that they have experienced rapid metal enrichment.

A Revised Characterization of the WFPC2 CTE Loss

Abstract: Charge transfer loss on the Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope is a primary source of uncertainty in stellar photometry obtained with this camera. This effect, discovered shortly after the camera was installed, has grown over time and can dim stars by several tenths of a magnitude (or even more, in particularly bad cases). The impact of CTE loss on WFPC2 stellar photometry was characterized by several studies between 1998 and 2000, but has received diminished attention since ACS became HST's primary imager. After the failure of ACS in January 2007, WFPC2 once again became the primary imaging instrument on board HST, restoring the importance of ensuring accurate CTE corrections. This paper reexamines the CTE loss of WFPC2, with three significant changes over previous studies. First, the present study considers calibration data obtained through 2007, thus increasing the confidence in the reliability of the CTE corrections when applied to recent observations. Second, the change in CTE loss during readout is accounted for analytically. Finally, a reanalysis of the CTE dependencies on counts, background, and observation date was made. The resulting correction is significantly more accurate than that provided in the WFPC2 Instrument Handbook (Dolphin 2002 and updates through 2004), resulting in photometry that can be enhanced by over 5% in certain circumstances.

Overhead imagery research data set — an annotated data library & tools to aid in the development of computer vision algorithms

Abstract: When failures occur in machine object recognition algorithms, researchers may have limited information on the root causes of the failure. For example, did the algorithm fail to detect a target due to occlusion, shadow, contrast, or some other known computer vision shortcoming? The Overhead Imagery Research Data Set (OIRDS) project will help advance the state of the art in image processing and computer vision by providing an open-access, annotated overhead imagery library that will allow researchers to break down algorithm performance by image and target attributes. The OIRDS project has produced a data set with almost 1,000 labeled images suitable for developing automated vehicle detection algorithms. These images contain approximately 1,800 labeled targets. For each target, the OIRDS provides over 30 annotations and over 60 statistics that describe the target within the context of the image.

Apparatus and method of controlling an unmanned vehicle

Abstract: In one or more embodiments, an apparatus and method for operating an unmanned and autonomous vehicle (115) includes a sensor management module configured to direct sensors as to what function they are to provide; a mission management module configured to provide execute function capabilities; an effects management module configured to provide launching and directing weapons to their target capabilities; a vehicle management module; a situation awareness management module configured to provide correlate sensor data of objects, threats, targets, geographic points of interest that the pilot requires in the immediate environment; a communications management module; an information management module configured to provide a database of intelligence-related data; a middleware module configured to interface with the sensor management module, the mission management module, the effects management module, the vehicle management module, the situation awareness management module, the communications management module, and the information management module.

The ngc 300 transient: an alternative method for measuring progenitor masses

Abstract: We present an alternative technique for measuring the precursor masses of transient events in stars undergoing late stage stellar evolution. We use the well-established techniques of stellar population modeling to age-date the stars surrounding the site of the recent transient event in NGC 300 (NGC 300 OT2008-1). The surrounding stars must share a common turnoff mass with the transient, since almost all stars form in stellar clusters that remain physically associated for periods longer than the lifetime of the most massive stars. We find that the precursor of NGC 300 OT2008-1 is surrounded by stars that formed in a single burst between 8 and 13 Myr ago, with 70% confidence. The transient was therefore likely to be due to a progenitor whose mass falls between the main sequence turnoff mass (12-17 M{sub sun}) and the maximum stellar mass (16-25 M{sub sun}) found for isochrones bounding this age range. We characterize the general applicability of this technique in identifying precursor masses of historic and future transients and supernovae (SNe), noting that it requires neither precursor imaging nor sub-arcsecond accuracy in the position of the transient. It is also based on the well-understood physics of the main sequence, and thus may bemore » a more reliable source of precursor masses than fitting evolutionary tracks to precursor magnitudes. We speculate that if the progenitor mass is {approx}>17 M {sub sun}, there may be a connection between optical transients such as NGC 300 OT2008-1 and the missing type II-P SNe, known as the 'red supergiant problem'.« less

Positioning, detection and communication system and method

Abstract: A positioning, communication, and detection system designed to provide a three dimensional location of an object, navigation tools, and bidirectional surface-to-subsurface communications, and methods of using the system. The system can include one or multiple transmitters comprising electromagnetic beacons, software defined radio receivers with an associated processing unit and data acquisition system, and magnetic antennas. The system may use theoretical calculations, scale model testing, signal processing, and sensor data.

Segmented thermally insulating coating

Abstract: A gas turbine article includes a substrate, a plurality of geometric surface features that protrude from the substrate, and a thermally insulating topcoat disposed over the plurality of geometric surface features. The thermally insulating topcoat includes segmented portions that are separated by faults that extend through the topcoat from the geometric surface features.

Overlay information over video

Abstract: In accordance with a particular embodiment of the invention, a method for geotagging an image includes receiving an image of a real-world scene. Location information may be received corresponding to the image. The location information may identify the location of the real-world scene. The image may be synchronized with the location information corresponding to the image such that a two-dimensional point on the image corresponds to a three-dimensional location in the real world at the real-world scene. A geotag may be received. The geotag may tag the image at the image at the two-dimensional point and provide additional information concerning the real-world scene. The geotag and the three-dimensional location in the real world at the real-world scene may be stored in a geotag database.

Impact of Humidity on Dielectric Charging in RF MEMS Capacitive Switches

Abstract: A novel technique is used to distinguish the charging of the surface from that of the bulk of the dielectrics of different types of RF MEMS capacitive switches under different electric fields and humidity levels. In general, bulk charging dominates in dry air, while surface charging increases linearly with increasing humidity. Under comparable electric fields and humidity levels, switches made of silicon dioxide are less susceptible to surface charging than switches made of silicon nitride. These quantitative results not only underscore the importance of packaging the switches in a dry ambient atmosphere, but also validate the novel technique for evaluating the effectiveness of dielectric preparation and packaging.

Evaluation of global ocean data assimilation experiment products on south florida nested simulations with the hybrid coordinate ocean model

Abstract: The South Florida Hybrid Coordinate Ocean Model (SoFLA-HYCOM) encompasses a variety of coastal regions (the broad Southwest Florida shelf, the narrow Atlantic Keys shelf, the shallow Florida Bay, and Biscayne Bay) and deep regions (the Straits of Florida), including Marine Protected Areas (the Florida Keys Marine Sanctuary and the Dry Tortugas Ecological Reserve). The presence of the strong Loop Current/Florida Current system and associated eddies connects the local and basin-wide dynamics. A multi-nested approach has been developed to ensure resolution of coastal-scale processes and proper interaction with the large scale flows. The simulations are free running and effects of data assimilation are introduced through boundary conditions derived from Global Ocean Data Assimilation Experiment products. The study evaluates the effects of boundary conditions on the successful hindcasting of circulation patterns by a nested model, applied on a dynamically and topographically complex shelf area. Independent (not assimilated) observations are employed for a quantitative validation of the numerical results. The discussion of the prevailing dynamics that are revealed in both modeled and observed patterns suggests the importance of topography resolution and local forcing on the inner shelf to middle shelf areas, while large scale processes are found to dominate the outer shelf flows. The results indicate that the successful hindcasting of circulation patterns in a coastal area that is characterized by complex topography and proximity to a large scale current system requires a dynamical downscaling approach, with simulations that are nested in a hierarchy of data assimilative outer models.

Information rights management

Abstract: In certain embodiments, a method for providing information rights management (IRM) includes receiving, from a user having an associated security access profile, a request to access an object. The object has a corresponding IRM wrapper stored with the object both when the object is stored in a document management system (DMS) database and external to the DMS database, the IRM wrapper including an IRM profile and one or more IRM permission sets. The object also has encrypted data. The method further includes determining whether the user is authorized to access the object based on a comparison of the security access profile of the user and the IRM profile of the IRM wrapper corresponding to the object and communicating to the user, in response to a determination that the user is authorized to access the object, a decryption key associated with object.

Effects of Temperature, Pressure, and Metal Promoter on the Recrystallized Structure and Optical Transmission of Chemical Vapor Deposited Zinc Sulfide

Abstract: Structural changes from processing in polytype-rich zinc sulfide (ZnS) are complex and poorly understood. In this study, recrystallization was induced in chemical vapor deposited ZnS by annealing and hot isostatic pressing (HIPping). Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder X-ray diffraction, and transmission spectroscopy. Recrystallization was found to reduce the hexagonality and increase the {111} texture of as-deposited ZnS. Changes in hexagonality and texture can occur independently of each other. HIPped ZnS with superior transmission exhibits both a change in texture and a reduction in hexagonal content. Reduction in hexagonality, alone, was not sufficient to improve optical transmission from the visible to the infrared. For the first time, the effects of pressure, temperature, and the presence of platinum on recrystallization during commercial ZnS HIPping are separated and identified. Platinum was found to actively promote recrystallization and silver demonstrated a similar effect. Several theories focusing on the unique polytypic nature of ZnS are offered to explain the changes in structure and properties occurring during recrystallization. These findings contribute to a broader understanding of the nature of order–disorder and martensitic phase transformations in ceramic materials.

The sensitivity of CO and aerosol transport to the temporal and vertical distribution of North American boreal fire emissions

Abstract: . Forest fires in Alaska and western Canada represent important sources of aerosols and trace gases in North America. Among the largest uncertainties when modeling forest fire effects are the timing and injection height of biomass burning emissions. Here we simulate CO and aerosols over North America during the 2004 fire season, using the GEOS-Chem chemical transport model. We apply different temporal distributions and injection height profiles to the biomass burning emissions, and compare model results with satellite-, aircraft-, and ground-based measurements. We find that averaged over the fire season, the use of finer temporal resolved biomass burning emissions usually decreases CO and aerosol concentrations near the fire source region, and often enhances long-range transport. Among the individual temporal constraints, switching from monthly to 8-day time intervals for emissions has the largest effect on CO and aerosol distributions, and shows better agreement with measured day-to-day variability. Injection height substantially modifies the surface concentrations and vertical profiles of pollutants near the source region. Compared with CO, the simulation of black carbon aerosol is more sensitive to the temporal and injection height distribution of emissions. The use of MISR-derived injection heights improves agreement with surface aerosol measurements near the fire source. Our results indicate that the discrepancies between model simulations and MOPITT CO measurements near the Hudson Bay can not be attributed solely to the representation of injection height within the model. Frequent occurrence of strong convection in North America during summer tends to limit the influence of injection height parameterizations of fire emissions in Alaska and western Canada with respect to CO and aerosol distributions over eastern North America.