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NASA NTRS2001

Wireless Subsurface Microsensors for Health Monitoring of Thermal Protection Systems on Hypersonic Vehicles

Health diagnostics is an area where major improvements have been identified for potential implementation into the design of new reusable launch vehicles in order to reduce life cycle costs, to increase safety margins, and to improve mission reliability. NASA Ames is leading the effort to develop inspection and health management technologies for thermal protection systems. This paper summarizes a joint project between NASA Ames and SRI International to develop 'SensorTags,' radio frequency identification devices coupled with event-recording sensors, that can be embedded in the thermal protection system to monitor temperature or other quantities of interest. Two prototype SensorTag designs containing thermal fuses to indicate a temperature overlimit are presented and discussed.

Milos, Frank S.↗
NASA NTRS2001

Wireless Subsurface Sensors for Health Monitoring of Thermal Protection Systems on Hypersonic Vehicles

Health diagnostics is an area where major improvements have been identified for potential implementation into the design of new reusable launch vehicles (RLVs) in order to reduce life cycle costs, to increase safety margins, and to improve mission reliability. NASA Ames is leading the effort to develop inspection and health management technologies for thermal protection systems. This paper summarizes a joint project between NASA Ames and industry partners to develop "wireless" devices that can be embedded in the thermal protection system to monitor temperature or other quantities of interest. These devices are sensors integrated with radio-frequency identification (RFID) microchips to enable non-contact communication of sensor data to an external reader that may be a hand-held scanner or a large portal. Both passive and active prototype devices have been developed. The passive device uses a thermal fuse to indicate the occurrence of excessive temperature. This device has a diameter under 0.13 cm. (suitable for placement in gaps between ceramic TPS tiles on an RLV) and can withstand 370 C for 15 minutes. The active device contains a small battery to provide power to a thermocouple for recording a temperature history during flight. The bulk of the device must be placed beneath the TPS for protection from high temperature, but the thermocouple can be placed in a hot location such as near the external surface.

Milos, Frank S.↗
NASA NTRS1994

Field Experiments using Telepresence and Virtual Reality to Control Remote Vehicles: Application to Mars Rover Missions

This paper will describe a series of field experiments to develop and demonstrate file use of Telepresence and Virtual Reality systems for controlling rover vehicles on planetary surfaces. In 1993, NASA Ames deployed a Telepresence-Controlled Remotely Operated underwater Vehicle (TROV) into an ice-covered sea environment in Antarctica. The goal of the mission was to perform scientific exploration of an unknown environment using a remote vehicle with telepresence and virtual reality as a user interface. The vehicle was operated both locally, from above a dive hole in the ice through which it was launched, and remotely over a satellite communications link from a control room at NASA's Ames Research center, for over two months. Remote control used a bidirectional Internet link to the vehicle control computer. The operator viewed live stereo video from the TROV along with a computer-gene rated graphic representation of the underwater terrain showing file vehicle state and other related information. Tile actual vehicle could be driven either from within the virtual environment or through a telepresence interface. In March 1994, a second field experiment was performed in which [lie remote control system developed for the Antarctic TROV mission was used to control the Russian Marsokhod Rover, an advanced planetary surface rover intended for launch in 1998. Marsokhod consists of a 6-wheel chassis and is capable of traversing several kilometers of terrain each day, The rover can be controlled remotely, but is also capable of performing autonomous traverses. The rover was outfitted with a manipulator arm capable of deploying a small instrument, collecting soil samples, etc. The Marsokhod rover was deployed at Amboy Crater in the Mojave desert, a Mars analog site, and controlled remotely from Los Angeles. in two operating modes: (1) a Mars rover mission simulation with long time delay and (2) a Lunar rover mission simulation with live action video. A team of planetary geologists participated in the mission simulation. The scientific goal of the science mission was to determine what could be learned about the geologic context of the site using the capabilities of imaging and mobility provided by the Marsokhod system in these two modes of operation. I will discuss the lessons learned from these experiments in terms of the strategy for performing Mars surface exploration using rovers. This research is supported by the Solar System Exploration Exobiology, Geology, and Advanced Technology programs.

Stoker, Carol↗
NASA NTRS1994

The Utilization of Flight Simulation for Research and Development

The objective of this paper is to review the conventional uses of flight simulation at NASA Ames Research Center for research and development, and to also consider the many new areas that have embraced flight simulation as an effective and economic research tool. Flight simulators have always been a very useful and economic research tool. Component technologies have evolved considerably to meet demands imposed by the aerospace community. In fact, the utilization of flight simulators for research and development has become so widely accepted that non-traditional uses have evolved. Whereas flight dynamics and control, guidance and navigation, vehicle design, mission assessment, and training have been, and perhaps always will be, the most popular research areas associated with simulation, many new areas under the broad categories of human factors and information science have realized significant benefits from the use of flight simulators for research and development. This paper will survey the simulation facilities at NASA Ames Research Center, and discuss selected topics associated with research programs, simulation experiments, and related technology development activities for the purpose of highlighting the expanding role of simulation in aerospace research and development. The information in this paper will in no way provide foreign companies with a competitive advantage over U. S. industry.

Totah, Joseph J.↗
NASA NTRS1994

Survey of Volumetric Grid Generators

This document is the result of an Internet Survey of Volumetric grid generators. As such we have included information from only the responses which were sent to us. After the initial publication and posting of this survey, we would encourage authors and users of grid generators to send further information. Here is the initial query posted to SIGGRID@nas and the USENET group sci.physics.computational.fluid-dynamics. Date: Sun, 30 Jan 94 11:37:52 -0800 From: woo (Alex Woo x6010 227-6 rm 315) Subject: Info Sought for Survey of Grid Generators I am collecting information and reviews of both government sponsored and commercial mesh generators for large scientific calculations, both block structured and unstructured. If you send me a review of a mesh generator, please indicate its availability and cost. If you are a commercial concern with information on a product, please also include references for possible reviewers. Please email to woo@ra-next.arc.nasa.gov. I will post a summary and probably write a short note for the IEEE Antennas and Propagation Magazine. Alex Woo, MS 227-6 woo@ames.arc.nasa.gov NASA Ames Research Center NASAMAIL ACWOO Moffett Field, CA 94035-1000 SPANET 24582::W00 (415) 604-6010 (FAX) 604-4357 fhplabs,decwrl,uunet)!ames!woo Disclaimer: These are not official statements of NASA or EMCC. We did not include all the submitted text here. Instead we have created a database entry in the freely available and widely used BIBTeX format which has an Uniform Resource Locator (URL) field pointing to more details. The BIBTeX database is modeled after those available from the BIBNET project at University of Utah.

Woo, Alex↗
NASA NTRS1994

NASA Activities in Support of the ASTOVL/CTOL CALF Project

A review of the NASA activities in support of the ARPA ASTOVL/CTOL CALF Project will be presented. These supporting activities include large-scale model tests on the Outdoor Aerodynamics Research Facility (OARF) and in the 40-ft by 80-ft wind tunnel at NASA Ames; manned simulations of the candidate concepts on the Ames Vertical Motion Simulator; scale model and component tests at NASA Langley Research Center; and propulsion component tests at NASA Lewis Research Center.

Wilson, Samuel B., III↗
NASA NTRS1994

Information for Lateral Aircraft Spacing Enabling Closely-Spaced Runway Operations During Instrument-Weather Conditions

In an effort to increase airport capacity, the U.S. plans on investing nearly $6 billion a year to properly maintain and improve the nation's major airports. Current FAA standards however, require a reduction in terminal operations during instrument-weather conditions at many airports, causing delays and reducing airport capacity. NASA, in cooperation with the FAA, has developed the Terminal Area Productivity Program to achieve clear-weather capacity in instrument- weather conditions for all phases of flight. This paper describes a series of experiments planned to investigate the conceptual design of different systems that provide information to flight crews regarding nearby traffic during the approach phase of flight. The purpose of this investigation is to identify and evaluate different display and auditory interfaces to the crew for use in closely-spaced parallel runway operations. Three separate experiments are planned for the investigation. The first two experiments will be conducted using part-task flight simulators located at the MIT Aeronautical Systems Laboratory and at NASA Ames. The third experiment will be conducted in the Advanced Concepts Flight Simulator, a generic "glass-cockpit" simulator at NASA Ames. Subjects for each experiment will be current glass-cockpit pilots from major U.S. air carriers. Subject crews will fly several experimental scenarios in which pseudo-aircraft are "blundered" into the subject aircraft simulation. Runway spacing, longitudinal aircraft separation, aircraft performance and traffic information will be varied. Analyses of the subject reaction times in evading the blundering aircraft and the resulting closest points of approach will be conducted. This paper presents a preliminary examination of the data recorded during the part-task experiments. The impact of traffic information on closely-spaced parallel runway operations is discussed, cockpit displays to aid these operations are examined, and topics for future research are suggested.

Thrush, Trent↗
NASA NTRS1995

Natural Displays: Anticipating the Future at NASA

There are two ways in which the human factors discipline is called upon to contribute to the development of new products or systems at NASA Ames Research Center. First, there is the application of known human factors principles in the design of a product. This type of application of human factors expertise can be called upon at any time in the evolution of a system or product, with the probability of success a direct function of how early in the system development cycle that the human factors experts are called in. This dependence on timing is due to two things. First, late in the development cycle many decisions have been made that cannot be unmade, and human factors solutions by necessity take on the nature of work-arounds. Second, in many cases where highly innovative or unusual systems are being proposed, known principles are not sufficient to answer design questions. Since most projects work to deadlines, there is generally not enough time late in a project for time-consuming human factors research efforts. In fact, due to the nature of project management, intermediate deadlines often preclude significant research efforts even when the human factors effort is brought in at the beginning. Therefore, critical research, a second function of the human factors effort at NASA Ames, is needed before projects are initiated. How do we determine the necessary research?

Johnson, Walter W.↗
NASA NTRS1995

Supersonic Transport Analysis on the IBM Parallel System SP2

Several studies of supersonic transport (SST) configurations have been undertaken by members of the High Speed Aerodynamics branch at NASA Ames. These computational investigations involved the analysis of shapes to study the sonic boom signatures, aerodynamic performance characteristics, as well as studies of nacelle/airframe integration. A variety of different computer codes were employed including both structured and unstructured codes. The AIRPLANE code has been used extensively in these investigations. This computer code solves the Euler equations for inviscid flow by exploiting an explicit finite volume method on a mesh of tetrahedral cells. AIRPLANE is capable of handling complete aircraft configurations including nacelles and diverters. An example of a generic SST configuration is shown and a comparison of computed and experimental force coefficients is presented. Most of the computations in support of the SST investigations have been run on the YMP and C-90 computers currently installed at NASA Ames. Additional information is contained in the original extended abstract.

Jameson, Antony↗
NASA NTRS1995

Parallel CFD Algorithms for Aerodynamical Flow Solvers on Unstructured Meshes

The Advisory Group for Aerospace Research and Development (AGARD) has requested my participation in the lecture series entitled Parallel Computing in Computational Fluid Dynamics to be held at the von Karman Institute in Brussels, Belgium on May 15-19, 1995. In addition, a request has been made from the US Coordinator for AGARD at the Pentagon for NASA Ames to hold a repetition of the lecture series on October 16-20, 1995. I have been asked to be a local coordinator for the Ames event. All AGARD lecture series events have attendance limited to NATO allied countries. A brief of the lecture series is provided in the attached enclosure. Specifically, I have been asked to give two lectures of approximately 75 minutes each on the subject of parallel solution techniques for the fluid flow equations on unstructured meshes. The title of my lectures is "Parallel CFD Algorithms for Aerodynamical Flow Solvers on Unstructured Meshes" (Parts I-II). The contents of these lectures will be largely review in nature and will draw upon previously published work in this area. Topics of my lectures will include: (1) Mesh partitioning algorithms. Recursive techniques based on coordinate bisection, Cuthill-McKee level structures, and spectral bisection. (2) Newton's method for large scale CFD problems. Size and complexity estimates for Newton's method, modifications for insuring global convergence. (3) Techniques for constructing the Jacobian matrix. Analytic and numerical techniques for Jacobian matrix-vector products, constructing the transposed matrix, extensions to optimization and homotopy theories. (4) Iterative solution algorithms. Practical experience with GIVIRES and BICG-STAB matrix solvers. (5) Parallel matrix preconditioning. Incomplete Lower-Upper (ILU) factorization, domain-decomposed ILU, approximate Schur complement strategies.

Barth, Timothy J.↗
NASA NTRS1995

Optimal Trajectories and Control Strategies for the Helicopter in One-Engine-Inoperative Terminal-Area Operations

Engine failure represents a major safety concern to helicopter operations, especially in the critical flight phases of takeoff and landing from/to small, confined areas. As a result, the JAA and FAA both certificate a transport helicopter as either Category-A or Category-B according to the ability to continue its operations following engine failures. A Category-B helicopter must be able to land safely in the event of one or all engine failures. There is no requirement, however, for continued flight capability. In contrast, Category-A certification, which applies to multi-engine transport helicopters with independent engine systems, requires that they continue the flight with one engine inoperative (OEI). These stringent requirements, while permitting its operations from rooftops and oil rigs and flight to areas where no emergency landing sites are available, restrict the payload of a Category-A transport helicopter to a value safe for continued flight as well as for landing with one engine inoperative. The current certification process involves extensive flight tests, which are potentially dangerous, costly, and time consuming. These tests require the pilot to simulate engine failures at increasingly critical conditions, Flight manuals based on these tests tend to provide very conservative recommendations with regard to maximum takeoff weight or required runway length. There are very few theoretical studies on this subject to identify the fundamental parameters and tradeoff factors involved. Furthermore, a capability for real-time generation of OEI optimal trajectories is very desirable for providing timely cockpit display guidance to assist the pilot in reducing his workload and to increase safety in a consistent and reliable manner. A joint research program involving NASA Ames Research Center, the FAA, and the University of Minnesota is being conducted to determine OEI optimal control strategies and the associated optimal,trajectories for continued takeoff (CTO), rejected takeoff (RTO), balked landing (BL), and continued landing (CL) for a twin engine helicopter in both VTOL and STOL terminal-area operations. This proposed paper will present the problem formulation, the optimal control solution methods, and the key results of the trajectory optimization studies for both STOL and VTOL OEI operations. In addition, new results concerning the recently developed methodology, which enable a real-time generation of optimal OEI trajectories, will be presented in the paper. This new real-time capability was developed to support the second piloted simulator investigation on cockpit displays for Category-A operations being scheduled for the NASA Ames Vertical Motion Simulator in June-August of 1995. The first VMS simulation was conducted in 1994 and reported.

Chen, Robert T. N.↗
NASA NTRS1996

Comparison of Hover/Ground-Effect Characteristics for a Joint Strike Fighter Configuration

Hover and ground-effect tests were conducted with the Lockheed-Martin Large Scale Powered Model (LSPM) during June-November 1995 at the NASA Ames Research Center's Outdoor Aerodynamics Research Facility (OARF). This was done in support of the Joint Strike Fighter (JSF) Program being lead by the Department of Defense. The program was previously metered to as the Joint Advanced Strike Technology (JAST) Program. The tests at the OARF included: engine thrust calibrations out of ground effect, measurements of individual nozzle jet pressure decay characteristics, and jet-induced hover force and moment measurements in and out of ground effect. The engine calibrations provide data correlating propulsion system throttle and nozzle settings to thrust forces and moments for the bare fuselage with the wings, canards, and tails removed. This provides propulsive forces and moments while minimizing any of the effects due to the presence of the airframe. The engine calibrations were used later to determine thrust for hover testing at the OARF and for transition testing which took place in the NASA Ames 80 by 120 foot Wind Tunnel. The jet decay characteristics reflect the jet entrainment properties and are related to the aircraft suckdown characteristics. The JSF program provided the opportunity to obtain model scale effects using two models; one at small scale and one at large scale. Examples of data from these tests will be presented out of ground effect which will demonstrate the effect of scale. For one JSF configuration, two small-scale models and one large-scale model were tested and obtained different values for the lift loss out of ground effect. These differences were examined and are found to be largely dependent on the jet efflux characteristics. The jet-induced hover forces and moments are presented in and out of ground effect. For the hover testing the model is methodically built up from the bare fuselage, to include the wings, canards, and vertical tails, to determine the effects of each. Other components such as weapons bay doors, landing gear doors, and other lift improvement devices and their effect on the jet-induced forces and moments are examined.

Hange, Craig↗
NASA NTRS1996

Comparison of Aero/Propulsion Transition Characteristics for a Joint Strike Fighter Configuration

NASA Ames conducted a series tests of a large-scale powered model of Lockheed Martin Skunk Works' JSF STOVL configuration at the 80- by 120-Foot Wind Tunnel. The model uses a modified version of an F-16 fighter engine (a Pratt & Whitney F100-229 engine). To provide vertical flight capability, the Lockheed aircraft incorporates a forward fuselage mounted vertical lift fan in addition to an aft mounted vectoring nozzle all driven by a single engine. The lift fan is driven off the engine by means of a shaft and gear system. The data presented is for STOVL configuration 140, a wing-body-canard planform. The main goal of this testing was to obtain propulsion induced data for evaluating differences between small- and large-scale model testing during the transition flight regime between jet- and wing-borne flight. The data presented is from aerodynamic testing of the model in both the unpowered (engine-off) and powered (engine running) configurations. This data, when combined with the propulsion system thrust calibration data from the NASA Ames' Outdoor Aerodynamic Research Facility (OARF), is used to determine the propulsion induced effects during transition.

Naumowicz, Tim↗
NASA NTRS1996

A Virtual Audio Guidance and Alert System for Commercial Aircraft Operations

Our work in virtual reality systems at NASA Ames Research Center includes the area of aurally-guided visual search, using specially-designed audio cues and spatial audio processing (also known as virtual or "3-D audio") techniques (Begault, 1994). Previous studies at Ames had revealed that use of 3-D audio for Traffic Collision Avoidance System (TCAS) advisories significantly reduced head-down time, compared to a head-down map display (0.5 sec advantage) or no display at all (2.2 sec advantage) (Begault, 1993, 1995; Begault & Pittman, 1994; see Wenzel, 1994, for an audio demo). Since the crew must keep their head up and looking out the window as much as possible when taxiing under low-visibility conditions, and the potential for "blunder" is increased under such conditions, it was sensible to evaluate the audio spatial cueing for a prototype audio ground collision avoidance warning (GCAW) system, and a 3-D audio guidance system. Results were favorable for GCAW, but not for the audio guidance system.

Begault, Durand R.↗
NASA NTRS2001

Airborne Sunphotometry of Aerosol Optical Depth and Columnar Water Vapor During ACE-Asia

During the Intensive Field Campaign (IFC) of the Aerosol Characterization Experiment - Asia (ACE-Asia), March-May 2001, the 6-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) operated during 15 of the 19 research flights aboard the NCAR C- 130, while its 14-channel counterpart (AATS- 14) was flown successfully on all 18 research flights of a Twin Otter aircraft operated by the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS), Monterey, CA. ACE-Asia was the fourth in a series of aerosol characterization experiments and focused on aerosol outflow from the Asian continent to the Pacific basin. Each ACE was designed to integrate suborbital and satellite measurements and models so as to reduce the uncertainty in calculations of the climate forcing due to aerosols. The Ames Airborne Tracking Sunphotometers measured solar beam transmission at 6 (380-1021 nm, AATS-6) and 14 wavelengths (353-1558 nm, AATS-14) respectively, yielding aerosol optical depth (AOD) spectra and column water vapor (CWV). Vertical differentiation in profiles yielded aerosol extinction and water vapor concentration. The wavelength dependence of AOD and extinction indicates that supermicron dust was often a major component of the aerosol. Frequently this dust-containing aerosol extended to high altitudes. For example, in data flights analyzed to date 34 +/- 13% of full-column AOD(525 nm) was above 3 km. In contrast, only 10 +/- 4% of CWV was above 3 km. In this paper, we will show first sunphotometer-derived results regarding the spatial variation of AOD and CWV, as well as the vertical distribution of aerosol extinction and water vapor concentration. Preliminary comparison studies between our AOD/aerosol extinction data and results from: (1) extinction products derived using in situ measurements and (2) AOD retrievals using the Multi-angle Imaging Spectro-Radiometer (MISR) aboard the TERRA satellite will also be presented.

Redemann, Jens↗
NASA NTRS1997

Reduction of Gun Erosion and Correlation of Gun Erosion Measurements

Gun barrel erosion is serious problem with two-stage light gas guns. Excessive barrel erosion can lead to poor or failed launches and frequent barrel changes, with the corresponding down time. Also, excessive barrel erosion can limit the maximum velocity obtainable by loading down the hydrogen working gas with eroded barrel material. Guided by a CFD code, the operating conditions of the Ames 0.5-inch gun were modified to reduce barrel erosion. The changes implemented included: (1) reduction in the piston mass, powder mass and hydrogen fill pressure; and (2) reduction in pump tube volume, while maintaining hydrogen mass. The latter change was found, in particular, to greatly reduce barrel erosion. For muzzle velocity ranges of 6.1 - 6.9 km/sec, the barrel erosion was reduced by a factor of 10. Even for the higher muzzle velocity range of 7.0 - 8.2 km/sec, the barrel erosion was reduced by a factor of 4. Gun erosion data from the Ames 0.5-inch, 1.0-inch, and 1.5-inch guns operated over a wide variety of launch conditions was examined and it was found that this data could be correlated using four different parameters: normalized powder charge energy, normalized hydrogen energy density, normalized pump tube volume and barrel diameter. The development of the correlation and the steps used to collapse the experimental data are presented. Over a certain parameter range in the correlation developed, the barrel erosion per shot is found to increase very rapidly. The correlation should prove useful in the selection of gun operating conditions and the design of new guns. Representative shapes of eroded gun barrels are also presented.

Bogdanoff, Dave↗
NASA NTRS1997

Research on the Effects of Fatigue within the Corporate/Business Aircraft Environment

In 1980, responding to a Congressional request, NASA Ames Research Center created a program to examine whether 'there is a safety problem of uncertain magnitude, due to transmeridian flying and a potential problem due to fatigue in association with various factors found in air transport operations.' The NASA Ames Fatigue/Jet Lag Program was created to collect systematic, scientific information on fatigue, sleep, circadian rhythms, and performance in flight operations. Three Program goals were established and continue to guide research efforts to: (1) determine the extent of fatigue, sleep loss, and circadian disruption in flight operations; (2) determine the impact of these factors on flight crew performance; (3) develop and evaluate countermeasures to mitigate the adverse effects of these factors and maximize flight crew performance and alertness. Since 1980, studies have been conducted in a variety of aviation environments, in controlled laboratory environments, as well as in a full-mission flight simulation. Early studies included investigations of short-haul, long-haul, and overnight cargo flight crews. In 1991, the name of the program was changed to the Fatigue Countermeasures Program to provide a greater emphasis on the development and evaluation of countermeasures. More recent work has examined the effects of planned cockpit rest as an operational countermeasure and provided analyses of the pertinent sleep/duty factors preceding an aviation accident at Guantanamo Bay, Cuba. The Short-Haul study examined the extent of sleep loss, circadian disruption, and fatigue engendered by flying commercial short-haul air transport operations (flight legs less than eight hours). This was one of the first field studies conducted by the NASA program and provided unique insight into the physiological and subjective effects of flying commercial short-haul operations. It demonstrated that a range of measures could be obtained in an operational environment without disturbing the regular performance of duties. The Long-Haul study examined how long-haul flight crews organized their sleep during a variety of international trip patterns and examined how duty requirements, local time, and the circadian system affected the timing, duration, and quality of sleep. Duty requirements and local time can be viewed as external/environmental constraints on time available for sleep, while the internal circadian system is a major physiological modulator of sleep duration and quality. The Overnight Cargo study documented the psychophysiological effects of flying overnight cargo operations. The data collected clearly demonstrated that overnight cargo operations, like other night work, involve physiological disruption not found in comparable daytime operations.

Neri, David F.↗
NASA NTRS1997

Regional Application of an Ecosystem Production Model for Studies of Biogeochemistry in the...

The degree to which primary production, soil carbon, and trace gas fluxes in tropical forests of the Amazon are limited by moisture availability and other environmental factors was examined using an ecosystem modeling application for the country of Brazil. A regional geographic information system (GIS) serves as the data source of climate drivers, satellite images, land cover, and soil properties for input to the NASA Ames-CASA (Carnegie-Ames-Stanford Approach) model over a 8-km grid resolution. Simulation results supports the hypothesis that net primary production (NPP) is limited by cloud interception of solar radiation over the humid northwestern portion of the region. Peak annual rates for NPP of nearly 1.4 kg C m-2yr -1are localized in the seasonally dry eastern Amazon in areas that we assume are primarily deep-rooted evergreen forest cover. Regional effects of forest conversion on NPP and soil carbon content are indicated in the model results, especially in seasonally dry areas. Comparison of model flux predictions along selected eco-climatic transects reveal moisture, soil, and land use controls on gradients of ecosystem production and soil trace gas emissions (CO2, N2O, and NO). These results are used to formulate a series of research hypotheses for testing in the next phase of regional modeling, which includes recalibration of the light-use efficiency term in CASA using field measurements of NPP, and refinements of vegetation index and soil property (texture and potential rooting depth) maps for the region.

Potter, C. S.↗