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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Trace Contaminant Control Test Bed for Evaluation of TCC Prototypes with Vacuum Regenerable and Non-Regenerable Sorbents

A new Space Suit Exploration Portable Life Support System (xPLSS) is being designed, built, integrated, and tested into the Extra-Vehicular Mobility Unit (xEMU). The Trace Contaminant Control (TCC) system is a component in the oxygen ventilation loop of xPLSS that removes contaminants generated by the crewmembers’ metabolic processes. The primary trace contaminants that must be removed include ammonia (NH3), carbon monoxide (CO), formaldehyde (CH2O), and methyl mercaptan (CH3SH). The current state-of-the-art TCC sorbent is non-regenerable activated carbon. As a non-regenerable sorbent, its use negatively impacts the logistics for future missions. Thus, an ideal solution can be a vacuum-regenerable sorbent integrated with the xPLSS CO2/H2O removal system. To test new designs and sorbents, XploSafe has constructed a recirculating test bed that mimics the environment within the xPLSS by providing concentrations of the trace contaminant analytes generated at the operating temperature, humidity, pressure, and flow rates of the xPLSS. This system can perform regeneration or desorption by exposing the sorbent to a pressure swing from 4.3 psia to <1 torr over approximately 2 minutes. Using this test system, XploSafe evaluated various TCC prototypes constructed using rapid prototyping techniques and identified a process that allows vacuum regenerative TCC designs to be quickly examined for flow, pressure drop, and performance. By using toluene as a segregate for volatile organics, this test system was evaluated using both vacuum regenerable and non-regenerable sorbents to demonstrate the operational effectiveness of these sorbents in maintaining the concentrations of the trace contaminant analytes below the 7-day Spacecraft Maximum Allowable Concentrations.

Nicholas Materer↗
NASA NTRS2011

Object-Based Mapping of the Circumpolar Taiga-Tundra Ecotone with MODIS Tree Cover

The circumpolar taiga tundra ecotone was delineated using an image-segmentation-based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 to 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation procedure was used to group pixels representing similar tree cover into polygonal features (segmentation objects) that form the map of the transition zone. Each polygon represents an area much larger than the 500 m MODIS pixel and characterizes the patterns of sparse forest patches on a regional scale. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values from5 to 20%, or (2) mean adjusted TCC values greater than 5% but with a standard deviation less than 5% were used to identify the ecotone. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1 degree longitudinal interval in North America and Eurasia, (2) Landsat-derived Canadian proportion of forest cover for Canada, and (3) with canopy cover estimates extracted from airborne profiling lidar data that transected 1238 of the TCC polygons. The adjusted TCC from MODIS VCF shows, on average, less than 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. A comparison of the 1238 TCC polygons with profiling lidar measurements yielded an overall accuracy of 67.7%.

Ranson, K. J.↗
NASA NTRS2011

Object-based Mapping of the Circumpolar Taiga-Tundra Ecotone with MODIS Tree Cover

The circumpolar taiga-tundra ecotone was delineated using an image segmentation based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 - 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation grouped pixels representing similar tree cover into polygonal features (objects) that form the map of the transition zone. Eachfeature represents an area much larger than the 500m MODIS pixel to characterize thepatterns of sparse forest patches on a regional scale. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1deg longitudinal interval in North America and Eurasia and (2) Landsat-derived Canadianproportion of forest cover for Canada. The adjusted TCC from MODIS VCF shows, on average, greater than 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values between 5-20% , or (2) mean adjusted TCC values <5% but with a standard deviation > 5% were used to identify the ecotone.

Ransom, Kenneth J.↗
NASA NTRS2019

Evaluation of CLARA-A2 and ISCCP-H Cloud Cover Climate Data Records over Europe with ECA&D Ground-Based Measurements

Clouds are of high importance for the climate system but they still remain one of its principal uncertainties. Remote sensing techniques applied to satellite observations have assisted tremendously in the creation of long-term and homogeneous data records; however, satellite data sets need to be validated and compared with other data records, especially ground measurements. In the present study, the spatiotemporal distribution and variability of Total Cloud Cover (TCC) from the Satellite Application Facility on Climate Monitoring (CM SAF) Cloud, Albedo And Surface Radiation dataset from AVHRR data—edition 2 (CLARA-A2) and the International Satellite Cloud Climatology Project H-series (ISCCP-H) is analyzed over Europe. The CLARA-A2 data record has been created using measurements of the Advanced Very High Resolution Radiometer (AVHRR) instrument onboard the polar orbiting NOAA and the EUMETSAT MetOp satellites, whereas the ISCCP-H data were produced by a combination of measurements from geostationary meteorological satellites and the AVHRR instrument on the polar orbiting satellites. An intercomparison of the two data records is performed over their common period, 1984 to 2012. In addition, a comparison of the two satellite data records is made against TCC observations at 22 meteorological stations in Europe, from the European Climate Assessment & Dataset (ECA&D). The results indicate generally larger ISCCP-H TCC with respect to the corresponding CLARA-A2 data, in particular in the Mediterranean. Compared to ECA&D data, both satellite datasets reveal a reasonable performance, with overall mean TCC biases of 2.1 and 5.2% for CLARA-A2 and ISCCP-H, respectively. This, along with the higher correlation coefficients between CLARA-A2 and ECA&D TCC, indicates the better performance of CLARA-A2 TCC data.

Tzallas, Vasileios↗
NASA NTRS2013

An Updated TRMM Composite Climatology of Tropical Rainfall and Its Validation

An updated 15-yr Tropical Rainfall Measuring Mission (TRMM) composite climatology (TCC) is presented and evaluated. This climatology is based on a combination of individual rainfall estimates made with data from the primaryTRMMinstruments: theTRMM Microwave Imager (TMI) and the precipitation radar (PR). This combination climatology of passive microwave retrievals, radar-based retrievals, and an algorithm using both instruments simultaneously provides a consensus TRMM-based estimate of mean precipitation. The dispersion of the three estimates, as indicated by the standard deviation sigma among the estimates, is presented as a measure of confidence in the final estimate and as an estimate of the uncertainty thereof. The procedures utilized by the compositing technique, including adjustments and quality-control measures, are described. The results give a mean value of the TCC of 4.3mm day(exp -1) for the deep tropical ocean beltbetween 10 deg N and 10 deg S, with lower values outside that band. In general, the TCC values confirm ocean estimates from the Global Precipitation Climatology Project (GPCP) analysis, which is based on passive microwave results adjusted for sampling by infrared-based estimates. The pattern of uncertainty estimates shown by sigma is seen to be useful to indicate variations in confidence. Examples include differences between the eastern and western portions of the Pacific Ocean and high values in coastal and mountainous areas. Comparison of the TCC values (and the input products) to gauge analyses over land indicates the value of the radar-based estimates (small biases) and the limitations of the passive microwave algorithm (relatively large biases). Comparison with surface gauge information from western Pacific Ocean atolls shows a negative bias (~16%) for all the TRMM products, although the representativeness of the atoll gauges of open-ocean rainfall is still in question.

(GPCP) Global Precipitation Project analysis↗
NASA NTRS2024

Electrodynamic Dust Shield for Active Dust Mitigation of Thermal Radiators

This project sought to investigate whether the Electrodynamic Dust Shield (EDS) would work with various thermal control coatings (TCC) to remove dust off the TCC. Keeping surfaces dust free is essential for thermal radiators as the dust acts as both a blackbody and a thermal insulator so it will absorb more sunlight and prevent the radiator from radiating heat. The lack of heat rejection on dusty surfaces causes the radiator to be oversized and potentially cause catastrophic system failure due to overheating. With an EDS integrated into the radiator system, dust impacts can be mitigated by removing the dust off the surface using electric fields. This project tested dust removal, solar absorptance, emittance, and limited thermal vacuum with a TCC on an EDS which is bonded to an aluminum plate acting like a radiator. The results of various coatings suggests that the EDS can work with insulative TCC in high vacuum for removing dust, and that after removing dust, the solar absorptance can be restored to within 5-10% of its original value when the EDS works properly. More work is necessary to determine how the EDS impacts the emittance of the whole radiator system and bonding between the different layers needs to be investigated to withstand temperature cycling of the moon without delamination occurring.

Krystal Acosta↗
NASA NTRS1992

Test and control computer user's guide for a digital beam former test system

A Digital Beam Former Test System was developed to determine the effects of noise, interferers and distortions, and digital implementations of beam forming as applied to the Tracking and Data Relay Satellite 2 (TDRS 2) architectures. The investigation of digital beam forming with application to TDRS 2 architectures, as described in TDRS 2 advanced concept design studies, was conducted by the NASA/Lewis Research Center for NASA/Goddard Space Flight Center. A Test and Control Computer (TCC) was used as the main controlling element of the digital Beam Former Test System. The Test and Control Computer User's Guide for a Digital Beam Former Test System provides an organized description of the Digital Beam Former Test System commands. It is written for users who wish to conduct tests of the Digital Beam forming Test processor using the TCC. The document describes the function, use, and syntax of the TCC commands available to the user while summarizing and demonstrating the use of the commands wtihin DOS batch files.

Alexovich, Robert E.↗
NASA NTRS2016

Analysis of the Ability of United States and Russian Trace Contaminant Control Systems to Meet U.S. 180-Day and Russian 360-Day Spacecraft Maximum Allowable Concentrations

As the Space Station Freedom program transitioned to become the International Space Station (ISS), uncertainty existed concerning the performance capabilities for U.S.- and Russian-provided trace contaminant control (TCC) equipment. In preparation for the first dialogue between NASA and Russian Space Agency personnel in Moscow, Russia, in late April 1994, an engineering analysis was conducted to serve as a basis for discussing TCC equipment engineering assumptions as well as relevant assumptions on equipment offgassing and cabin air quality standards. The analysis presented was conducted as part of the efforts to integrate Russia into the ISS program via the early ISS Multilateral Medical Operations Panel's Air Quality Subgroup deliberations. This analysis, served as a basis for technical deliberations that established a framework for TCC system design and operations among the ISS program's international partners that has been instrumental in successfully managing the ISS common cabin environment.

Perry, J. L.↗
NASA NTRS2017

Trace Contaminant Control During the International Space Station's On-Orbit Assembly and Outfitting

During the International Space Station’s (ISS’s) on-orbit assembly and outfitting, a series of engineering analyses was conducted to evaluate how effective the passive trace contaminant control (TCC) methods were relative to providing adequate operational margin for the active TCC equipment’s capabilities aboard the ISS. These analyses were based on habitable module and cargo vehicle offgassing test results. The offgassing test for the fully assembled module or cargo vehicle is an important preflight spacecraft evaluation method that has been used successfully during all crewed spacecraft programs to provide insight into how effectively the passive contamination control methods limit the equipment offgassing component of the overall trace contaminant generation load. The progression of TCC assessments beginning in 1998 with the ISS’s first habitable element launch and continuing through the final pressurized element’s arrival in 2010 are presented. Early cargo vehicle flight assessments between 2008 and 2011 are also presented as well as a discussion on predictive methods for assessing cargo via a purely analytical technique.

Contamination control↗
NASA NTRS2026

Dynamic Regulation of Sub-Atmospheric Pressure for Constant and Cyclic Gas Loads During Testing of Spacesuit Components

New iterations of the various subsystems within the spacesuit will benefit from a new sorbent technology. For example, sorbents used in the Trace Contaminant Control (TCC) and the Rapid Cycle Amine (RCA) systems within the Exploration Portable Life Support System (xPLSS), part of the Extra-Vehicular Mobility Unit (xEMU). For proper validation, the sub-atmospheric pressure needs to be maintained within a simulated 2 ft 3 spacesuit volume. The traditional approach, which involves placing the entire vent loop within a hypobaric chamber, is not practical for the widespread testing of components and prototypes, as these specialized chambers are costly and not widely available. A two-stage regulator based sub-atmospheric pressure system is presented in this work. The method regulates the pressure based on pressure differentials between the pressure regulation pump, the test system, and the ambient environment. The performance of this system is demonstrated using data collected during a 150+ hour non-regenerative TCC sorbent evaluation, several 24-hour regenerative TCC sorbent evaluations with different regeneration cycles, and an 8-hour RCA sorbent evaluation, all under xEMU operating conditions. For regulation, the inlet regulator was set to propagate a small leak to increase the stability of the system as the gas load from the testing system changes. It was also found that controlling the input flow rate that replaces the material lost during regeneration is critical for ensuring the stability of the system. This system provided excellent pressure regulation, without adjustments, for constant loads during shorter time evaluations (hours), while longer time evaluations (days) are easily obtainable with periodic regulator adjustments. A second method is under development to address longer-term stability and to automate pressure regulation. It will incorporate flow and pressure measurements to dynamically control a set of electronically controlled proportional valves for adjusting the pumping speed and air bleed supply.

Nicholas F Materer↗
NASA NTRS2008

Results of the Trace Contaminant Control Trade Study for Space Suit Life Support Development

As the United States plans to return astronauts to the moon, designing the most effective and efficient life support systems is of extreme importance. The trace contaminant control system (TCCS) will be located within the Portable Life Support System (PLSS) of the Constellation Space Suit Element (CSSE), and is responsible for removing contaminants, which at increased levels can be hazardous to a crewmember s health. These contaminants come from several sources including metabolic production of the crewmember (breathing, sweating, etc.) and offgassing of the space suit material layers. This paper summarizes the results of a trade study that investigated TCC technologies used in NASA space suits and vehicles as well as commercial and academic applications, to identify the best technology options for the CSSE PLSS. The trade study also looked at the feasibility of regeneration of TCC technologies, specifically to determine the viability of vacuum regeneration for on-back, realtime EVA.

Jennings, Mallory A.↗
NASA NTRS2009

Results of the Trace Contaminant Control Trade Study for Space Suit Life Support Development

As the United States plans to return astronauts to the moon, designing the most effective and efficient life support systems is of extreme importance. The trace contaminant control system (TCCS) will be located within the Portable Life Support System (PLSS) of the Constellation Space Suit Element (CSSE), and is responsible for removing contaminants, which at increased levels can be hazardous to a crewmember's health. These contaminants come from several sources including metabolic production of the crewmember (breathing, sweating, etc.) and offgassing of the space suit material layers. This paper summarizes the results of a trade study that investigated TCC technologies used in NASA space suits and vehicles as well as commercial and academic applications, to identify the best technology options for the CSSE PLSS. The trade study also looked at the feasibility of regeneration of TCC technologies, specifically to determine the viability of vacuum regeneration for on-back, real-time EVA.

Paul, Heather L.↗
NASA NTRS2019

Dynamic Modeling of Gaseous Multicomponent Trace Contaminant Adsorption

Activated carbon is a porous material in the Trace Contaminant Control (TCC) system that physically adsorbs volatile organic compounds (VOCs) generated within spacecraft and spacesuit environments. Several isotherm models exist to predict adsorption equilibria for processes involving multicomponent systems. This paper investigates the use of Ideal Adsorbed Solution Theory (IAST) for predicting multicomponent trace contaminant adsorption behavior using single-component isotherms based on potential theory. Developing simulations for experimental breakthrough curves will gauge the validity on the sizing and design of TCC architecture. Model results on predicting bed performance and roll-up effects are compared with available multicomponent test data.

Ideal Adsorbed Solution Theory (IAST)↗
NASA NTRS2020

The bioclimatic extent and pattern of the cold edge of the boreal forest: the circumpolar taiga-tundra ecotone

Current configurations of forest structure at the cold edge of the boreal may help understand the future of ecosystem functioning in high northern latitudes. The circumpolar biome boundary at the boreal (taiga) forest and tundra interface is an ecological transition zone (taiga-tundra ecotone; TTE) experiencing changes that affect its forest structure. We accounted for the TTE's horizontal forest structure with an estimate of its extent and pattern as represented by tree canopy cover (TCC). We quantified TCC patterns with an algorithm that describes its spatial gradient, and summarized landscape patterns of structure to represent heterogeneity, capturing abrupt, diffuse, and uniform forest at mesoscales. We used these landscape patterns to constrain the spatial extent of sparse and open canopy forest, and non-forest (forest-adjacent) edge that defines the TTE extent. The resulting map of the TTE extent is based on forest structure spatial patterns resolved at 30 m, highlights structural variability across landscapes, and helps distinguish tundra from boreal domains. We classified 14 594 landscapes as those associated with the TTE within a circumpolar bioclimatic envelope (11.575 million km2), where 44.83% of the area of these landscapes were forest and non-forest edge, yet 36.43% contributed to the TTE extent. We report the overall extent of the TTE (3.032 million km2) across North America and Greenland (53%), and Eurasia (47%), where 0.697 million km2 is non-forest edge, 0.549 million km2 is sparse forest, and 1.787 million km2 is open canopy forest. Diffuse forest landscapes dominate the TTE (79%), and abrupt landscapes (~19%) indicate portions of the TTE where sparse forest and non-forest edge are the prevailing structural patterns. This account of the TTE quantifies the area of the cold edge of the boreal forest where previous global estimates show high discrepancies, and can help target monitoring and prediction of circumpolar dynamics.

Paul M Montesano↗
NASA NTRS2021

Estimating Bare Earth in Sparse Boreal Forests With WorldView Stereo Imagery

Circumboreal forests are currently experiencing rapid climate warming which is altering their structure, productivity, and status as a carbon sink. Very-high resolution (VHR, <2 m) stereo derived digital surface models are available to monitor these forests, but, a similar resolution digital terrain model (DTM) is required to extract information about tree height, which is often used to estimate carbon content. To our knowledge, no openly available VHR DTM currently exists. To address this need, we developed approaches to extract DTMs by filtering VHR stereo point clouds (PCs) in sparse canopies of Alaska. Our evaluation consisted of two stereo processing methods with three PC search radii, at six different tree canopy cover (TCC) intervals. We found VHR DTMs were robust for estimating bare ground at TCC intervals less than 40% with vertical errors <1.6 m using airborne small footprint light detection and ranging (LiDAR) as reference.

Christopher S R Neigh↗
NASA NTRS2020

Mapping tree canopy cover and canopy height with L-band SAR using LiDAR data and Random Forests

Light detection and ranging (LiDAR) data can provide direct measurements of vegetation structures but are limited by the sparse spatial coverage. Polarimetric synthetic aperture radar (SAR) can perform large-scale high-resolution mapping without weather constraints but the information about vegetation and ground subsurface are mixed in the backscatter data. In this paper, we adopted the Random Forests algorithm to train an upscaling function using tree canopy cover (TCC) and canopy height model (CHM) derived from Goddard’s LiDAR, Hyperspectral and Thermal Imager (G-LiHT) data. The regression model is then applied to the L-band Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data acquired during the 2017 Arctic-Boreal Vulnerability Experiment (ABoVE) airborne campaign to map the TCC and CHM over the Delta Junction area in interior Alaska.

Moghaddam, Mahta↗
NASA NTRS2021

Estimating Bare Earth in Sparse Boreal Forests With WorldView Stereo Imagery

Circumboreal forests are currently experiencing rapid climate warming which is altering their structure, productivity, and status as a carbon sink. Very-high resolution (VHR, <2 m) stereo derived digital surface models are available to monitor these forests, but, a similar resolution digital terrain model (DTM) is required to extract information about tree height, which is often used to estimate carbon content. To our knowledge, no openly available VHR DTM currently exists. To address this need, we developed approaches to extract DTMs by filtering VHR stereo point clouds (PCs) in sparse canopies of Alaska. Our evaluation consisted of two stereo processing methods with three PC search radii, at six different tree canopy cover (TCC) intervals. We found VHR DTMs were robust for estimating bare ground at TCC intervals less than 40% with vertical errors <1.6 m using airborne small footprint light detection and ranging (LiDAR) as reference.

Christopher S. R. Neigh↗
NASA NTRS2008

Modeling and Simulation at Tidewater Community College

Investment of $1.5 million in medical simulation technology. Integration of medical simulation activities into the curriculum. Support from TCC leadership. Individual and team activities. Skill development and critical thinking/problem solving skills.

Summers, Michael↗