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NASA NTRS2010

Relating Linear and Volumetric Variables Through Body Scanning to Improve Human Interfaces in Space

Designing space suits and vehicles for the diverse human population present unique challenges for the methods of traditional anthropometry. Space suits are bulky and allow the operator to shift position within the suit and inhibit the ability to identify body landmarks. Limited suit sizing options also cause variability in fit and performance between similarly sized individuals. Space vehicles are restrictive in volume in both the fit and the ability to collect data. NASA's Anthropometric and Biomechanics Facility (ABF) has utilized 3D scanning to shift from traditional linear anthropometry to explore and examine volumetric capabilities to provide anthropometric solutions for design. Overall, the key goals are to improve the human-system performance and develop new processes to aid in the design and evaluation of space systems. Four case studies are presented that illustrate the shift from purely linear analyses to an augmented volumetric toolset to predict and analyze the human within the space suit and vehicle. The first case study involves the calculation of maximal head volume to estimate total free volume in the helmet for proper air exchange. Traditional linear measurements resulted in an inaccurate representation of the head shape, yet limited data exists for the determination of a large head volume. Steps were first taken to identify and classify a maximum head volume and the resulting comparisons to the estimate are presented in this paper. This study illustrates the gap between linear components of anthropometry and the need for overall volume metrics in order to provide solutions. A second case study examines the overlay of the space suit scans and components onto scanned individuals to quantify fit and clearance to aid in sizing the suit to the individual. Restrictions in space suit size availability present unique challenges to optimally fit the individual within a limited sizing range while maintaining performance. Quantification of the clearance and fit between similarly sized individuals is critical in providing a greater understanding of the human body's function within the suit. The third case study presented in this paper explores the development of a conformal seat pan using scanning techniques, and details the challenges of volumetric analyses that were overcome in order to develop a universal seat pan that can be utilized across the entire user population. The final case study explores expanding volumetric capabilities through generation of boundary manikins. Boundary manikins are representative individuals from the population of interest that represent the extremes of the population spectrum. The ABF developed a technique to take three-dimensional scans of individuals and manipulate the scans to reflect the boundary manikins' anthropometry. In essence, this process generates a representative three-dimensional scan of an individual from anthropometry, using another individual's scanned image. The results from this process can be used in design process modeling and initial suit sizing work as a three dimensional, realistic example of individuals from the population, maintaining the variability between and correlation to the relevant dimensions of interest.

Margerum, Sarah E.↗
NASA NTRS2010

Solar Cycle and Anthropogenic Forcing of Surface-Air Temperature at Armagh Observatory, Northern Ireland

A comparison of 10-yr moving average (yma) values of Armagh Observatory (Northern Ireland) surface-air temperatures with selected solar cycle indices (sunspot number (SSN) and the Aa geomagnetic index (Aa)), sea-surface temperatures in the Nino 3.4 region, and Mauna Loa carbon dioxide (CO2) (MLCO2) atmospheric concentration measurements reveals a strong correlation (r = 0.686) between the Armagh temperatures and Aa, especially, prior to about 1980 (r = 0.762 over the interval of 1873-1980). For the more recent interval 1963-2003, the strongest correlation (r = 0.877) is between Armagh temperatures and MLCO2 measurements. A bivariate fit using both Aa and Mauna Loa values results in a very strong fit (r = 0.948) for the interval 1963-2003, and a trivariate fit using Aa, SSN, and Mauna Loa values results in a slightly stronger fit (r = 0.952). Atmospheric CO2 concentration now appears to be the stronger driver of Armagh surface-air temperatures. An increase of 2 C above the long-term mean (9.2 C) at Armagh seems inevitable unless unabated increases in anthropogenic atmospheric gases can be curtailed. The present growth in 10-yma Armagh temperatures is about 0.05 C per yr since 1982. The present growth in MLCO2 is about 0.002 ppmv, based on an exponential fit using 10-yma values, although the growth appears to be steepening, thus, increasing the likelihood of deleterious effects attributed to global warming.

Wilson, Robert M.↗
NASA NTRS2011

Spacesuit Soft Upper Torso Sizing Systems

The passive sizing system consists of a series of low-profile pulleys attached to the front and back of the shoulder bearings on a spacesuit soft upper torso (SUT), textile cord or stainless steel cable, and a modified commercial ratchet mechanism. The cord/cable is routed through the pulleys and attached to the ratchet mechanism mounted on the front of the spacesuit within reach of the suited subject. Upon actuating the ratchet mechanism, the shoulder bearing breadth is changed, providing variable upper torso sizing. The active system consists of a series of pressurizable nastic cells embedded into the fabric layers of a spacesuit SUT. These cells are integrated to the front and back of the SUT and are connected to an air source with a variable regulator. When inflated, the nastic cells provide a change in the overall shoulder bearing breadth of the spacesuit and thus, torso sizing. The research focused on the development of a high-performance sizing and actuation system. This technology has application as a suit-sizing mechanism to allow easier suit entry and more accurate suit fit with fewer torso sizes than the existing EMU (Extravehicular Mobility Unit) suit system. This advanced SUT will support NASA s Advanced EMU Evolutionary Concept of a two-sizes-fit-all upper torso for replacement of the current EMU hard upper torso (HUT). Both the passive and nastic sizing system approaches provide astronauts with real-time upper torso sizing, which translates into a more comfortable suit, providing enhanced fit resulting in improved crewmember performance during extravehicular activity. These systems will also benefit NASA by reducing flight logistics as well as overall suit system cost. The nastic sizing system approach provides additional structural redundancy over existing SUT designs by embedding additional coated fabric and uncoated fabric layers. Two sizing systems were selected to build into a prototype SUT: one active and one passive. From manned testing, it was found that both systems offer good solutions to sizing a SUT to fit a crewmember. This new system provided improved suit don/doff over existing spacesuit designs as well as providing better fit at suit operational pressure resulting in improved comfort and mobility. It was found that a SUT with a sizing system may solve several problems that have plagued existing HUT designs, and that a SUT with a sizing system may be a viable option for advanced suit architectures.

Graziosi, David↗
NASA NTRS2011

HEXPANDO Expanding Head for Fastener-Retention Hexagonal Wrench

The HEXPANDO is an expanding-head hexagonal wrench designed to retain fasteners and keep them from being dislodged from the tool. The tool is intended to remove or install socket-head cap screws (SHCSs) in remote, hard-to-reach locations or in circumstances when a dropped fastener could cause damage to delicate or sensitive hardware. It is not intended for application of torque. This tool is made of two assembled portions. The first portion of the tool comprises tubing, or a hollow shaft, at a length that gives the user adequate reach to the intended location. At one end of the tubing is the expanding hexagonal head fitting with six radial slits cut into it (one at each of the points of the hexagonal shape), and a small hole drilled axially through the center and the end opposite the hex is internally and externally threaded. This fitting is threaded into the shaft (via external threads) and staked or bonded so that it will not loosen. At the other end of the tubing is a knurled collar with a through hole into which the tubing is threaded. This knob is secured in place by a stop nut. The second assembled portion of the tool comprises a length of all thread or solid rod that is slightly longer than the steel tubing. One end has a slightly larger knurled collar affixed while the other end is tapered/pointed and threaded. When the two portions are assembled, the all thread/rod portion feeds through the tubing and is threaded into the expanding hex head fitting. The tapered point allows it to be driven into the through hole of the hex fitting. While holding the smaller collar on the shaft, the user turns the larger collar, and as the threads feed into the fitting, the hex head expands and grips the SHCS, thus providing a safe way to install and remove fasteners. The clamping force retaining the SHCS varies depending on how far the tapered end is inserted into the tool head. Initial tests of the prototype tool, designed for a 5 mm or # 10SHCS have resulted in up to 8 lb (.35.6 N) of pull force to dislodge the SHCS from the tool. The tool is designed with a lead-in angle from the diameter of the tubing to a diameter the same as the fastener head, to prevent the fastener head from catching on any obstructions encountered that could dislodge the fastener during retrieval.

Bishop, John↗
NASA NTRS2012

Train Like an Astronaut Educational Outreach

In an effort to reduce the incidence of childhood obesity, the National Aeronautics and Space Administration (NASA), capitalizing on the theme of human spaceflight developed two educational outreach programs for children ages 8-12. To motivate young "fit explorers," the Train Like an Astronaut National (TLA) program and the Mission X: Train Like an Astronaut International Fitness Challenge (MX) were created. Based on the astronauts' physical training, these programs consist of activities developed by educators and experts in the areas of space life sciences and fitness. These Activities address components of physical fitness. The educational content hopes to promote students to pursue careers in science, technology, engineering, and math (STEM) fields. At the national level, in partnership with First Lady Michelle Obama's Let?s Move! Initiative, the TLA program consists of 10 physical and 2 educational activities. The program encourages families, schools, and communities to work collaboratively in order to reinforce in children and their families the importance of healthy lifestyle habits In contrast, the MX challenge is a cooperative outreach program involving numerous space agencies and other international partner institutions. During the six-week period, teams of students from around the world are challenged to improve their physical fitness and collectively accumulate points by completing 18 core activities. During the 2011 pilot year, a t otal of 137 teams and more than 4,000 students from 12 countries participated in the event. MX will be implemented within 24 countries during the 2012 challenge. It is projected that 7,000 children will "train like an astronaut".

Garcia, Yamil L.↗
NASA NTRS2013

Hidden Connections between Regression Models of Strain-Gage Balance Calibration Data

Hidden connections between regression models of wind tunnel strain-gage balance calibration data are investigated. These connections become visible whenever balance calibration data is supplied in its design format and both the Iterative and Non-Iterative Method are used to process the data. First, it is shown how the regression coefficients of the fitted balance loads of a force balance can be approximated by using the corresponding regression coefficients of the fitted strain-gage outputs. Then, data from the manual calibration of the Ames MK40 six-component force balance is chosen to illustrate how estimates of the regression coefficients of the fitted balance loads can be obtained from the regression coefficients of the fitted strain-gage outputs. The study illustrates that load predictions obtained by applying the Iterative or the Non-Iterative Method originate from two related regression solutions of the balance calibration data as long as balance loads are given in the design format of the balance, gage outputs behave highly linear, strict statistical quality metrics are used to assess regression models of the data, and regression model term combinations of the fitted loads and gage outputs can be obtained by a simple variable exchange.

Ulbrich, Norbert↗
NASA NTRS2013

Estimating the Properties of Hard X-Ray Solar Flares by Constraining Model Parameters

We wish to better constrain the properties of solar flares by exploring how parameterized models of solar flares interact with uncertainty estimation methods. We compare four different methods of calculating uncertainty estimates in fitting parameterized models to Ramaty High Energy Solar Spectroscopic Imager X-ray spectra, considering only statistical sources of error. Three of the four methods are based on estimating the scale-size of the minimum in a hypersurface formed by the weighted sum of the squares of the differences between the model fit and the data as a function of the fit parameters, and are implemented as commonly practiced. The fourth method is also based on the difference between the data and the model, but instead uses Bayesian data analysis and Markov chain Monte Carlo (MCMC) techniques to calculate an uncertainty estimate. Two flare spectra are modeled: one from the Geostationary Operational Environmental Satellite X1.3 class flare of 2005 January 19, and the other from the X4.8 flare of 2002 July 23.We find that the four methods give approximately the same uncertainty estimates for the 2005 January 19 spectral fit parameters, but lead to very different uncertainty estimates for the 2002 July 23 spectral fit. This is because each method implements different analyses of the hypersurface, yielding method-dependent results that can differ greatly depending on the shape of the hypersurface. The hypersurface arising from the 2005 January 19 analysis is consistent with a normal distribution; therefore, the assumptions behind the three non- Bayesian uncertainty estimation methods are satisfied and similar estimates are found. The 2002 July 23 analysis shows that the hypersurface is not consistent with a normal distribution, indicating that the assumptions behind the three non-Bayesian uncertainty estimation methods are not satisfied, leading to differing estimates of the uncertainty. We find that the shape of the hypersurface is crucial in understanding the output from each uncertainty estimation technique, and that a crucial factor determining the shape of hypersurface is the location of the low-energy cutoff relative to energies where the thermal emission dominates. The Bayesian/MCMC approach also allows us to provide detailed information on probable values of the low-energy cutoff, Ec, a crucial parameter in defining the energy content of the flare-accelerated electrons. We show that for the 2002 July 23 flare data, there is a 95% probability that Ec lies below approximately 40 keV, and a 68% probability that it lies in the range 7-36 keV. Further, the low-energy cutoff is more likely to be in the range 25-35 keV than in any other 10 keV wide energy range. The low-energy cutoff for the 2005 January 19 flare is more tightly constrained to 107 +/- 4 keV with 68% probability.

X-rays↗
NASA NTRS2014

Quantification of In-flight Physical Changes: Anthropometry and Neutral Body Posture

Currently, NASA does not have sufficient in-flight anthropometric data gathered to assess the impact of physical body shape and size changes on suit sizing. For developing future planetary and reduced gravity suits, NASA needs to quantify the impacts of microgravity on anthropometry, body posture, and neutral body postures (NBP) to ensure optimal crew performance, fit, and comfort. To obtain these impacts, anthropometric data, circumference, length, height, breadth, and depth for body segments (i.e. chest, waist, bicep, thigh, calf) from astronauts for pre, in-, and postflight conditions needs to be collected. Once this data has been collected, a comparison between pre, in-, and postflight anthropometric values will be analyzed, yielding microgravity factors. The NBP will be used to determined body posture (joint angle) changes between subjects throughout the duration of a mission. Data collection, starting with Increments 37/38, is still in progress with the completion of 3 out of 12 subjects. NASA suit engineers and NASA's Extravehicular Activity (EVA) Project Office have identified that suit fit in microgravity could become an issue. It has been noted that crewmembers often need to adjust their suit sizing once they are in orbit. This adjustment could be due to microgravity effects on anthropometry and postural changes, and is necessary to ensure optimal crew performance, fit, and comfort in space. To date, the only data collected to determine the effects of microgravity on physical human changes have been during Skylab, STS-57, and a recent HRP study on seated height changes due to spinal elongation (Spinal Elongation, Master Task List [MTL] #221). The Skylab and the STS-57 studies found that there is a distinct neutral body posture (NBP) based on photographs. The still photographs showed that there is a distinguishable posture with the arms raised and the shoulder abducted; and, in addition, the knees were flexed with noticeable hip flexion and the foot plantar flexed [1,2]. This is the one standard set of body joint angles for a NBP in microgravity. A recent simulated microgravity NBP study [3] has shown an individual variability and inconsistencies in defining NBP. This variation may be influenced by spinal growth, the type of suit fit, and other potential anthropometry factors such as spinal curvature, age, and gender. The variation aspect of this essential data is required for all kinds of space device designs (e.g. suits, habitat, mobility aids, etc.). The method proposed considers the dynamic nature of body movement and will use a measurement technique to continually monitor posture and develop a probability likelihood of the natural posture and how the NBP postures are affected by anthropometry. Additionally, Skylab studies found that crewmembers experienced a stature growth of up to 3%. The data included 3 crewmembers that showed that there is a bi-phasic stature growth once the crew enters into weightlessness. However, the Spinal Elongation study identified that the crewmembers could experience about a 6% growth in seated height and a 3% stature growth, when exposed to microgravity. The results prove that not all anthropometric measurements have the same microgravity percent growth factor. For EVA and suit engineers to properly update the sizing protocol for microgravity, they need additional anthropometric data from space missions. Hence, this study is aimed to gather additional in-flight anthropometric measurements, such as length, depth, breadth, and circumference, to determine the changes to body shape and size due to microgravity effects. It is anticipated that by recording the potential changes to body shape and size, a better suit sizing protocol will be developed for ISS and other space missions. In essence, this study will help NASA quantify the impacts of microgravity on anthropometry to ensure optimal crew performance, fit, and comfort. This study will use simplistic data collection techniques, 3D laser scanning, digital still, and video data, and perform photogrammetric analyses to determine the changes that occur to the body shape, size, and NBP when exposed to a microgravity environment.

Young, K. S.↗
NASA NTRS2013

Properties of Polycyclic Aromatic Hydrocarbons in the Northwest Photon Dominated Region of NGC 7023. I. PAH Size, Charge, Composition, and Structure Distribution

Polycyclic aromatic hydrocarbon (PAH) emission in the Spitzer Infrared Spectrograph spectral map of the northwest photon dominated region (PDR) in NGC 7023 was analyzed exclusively using PAH spectra from the NASA Ames PAH IR Spectroscopic Database (www.astrochem.org/pahdb). The 5-15 micron spectrum at each pixel is fitted using a non-negative-least-squares fitting approach. The fits are of good quality, allowing decomposition of the PAH emission into four subclasses: size, charge, composition, and hydrogen adjacency (structure). Maps tracing PAH subclass distributions across the region paint a coherent astrophysical picture. Once past some 20 seconds of arc from HD 200775, the emission is dominated by the more stable, large, symmetric, compact PAH cations with smaller, neutral PAHs taking over along the lines-of-sight toward the more distant molecular cloud. The boundary between the PDR and the denser cloud material shows up as a distinct discontinuity in the breakdown maps. Noteworthy is the requirement for PANH cations to fit the bulk of the 6.2 and 11.0 micron features and the indication of PAH photo-dehydrogenation and fragmentation close to HD 200775. Decomposition of the spectral maps into "principal" subclass template spectra provides additional insight into the behavior of each subclass. However, the general applicability of this computationally more efficient approach is presently undetermined. This is the first time the spectra of individual PAHs are exclusively used to fit the 5-15 micron region and analyze the spatial behavior of the aromatic infrared bands, providing fundamental, new information about astronomical PAH subpopulations including their dependence on, and response to, changes in local conditions.

northwest photon↗
NASA NTRS2016

Assessment of Models of Galactic Thermal Dust Emission Using COBE/FIRAS and COBE/DIRBE Observations

Accurate modeling of the spectrum of thermal dust emission at millimeter wavelengths is important for improving the accuracy of foreground subtraction for cosmic microwave background (CMB) measurements, for improving the accuracy with which the contributions of different foreground emission components can be determined, and for improving our understanding of dust composition and dust physics. We fit four models of dust emission to high Galactic latitude COBE/FIRAS and COBE/DIRBE observations from 3 mm to 100m and compare the quality of the fits. We consider the two-level systems (TLS) model because it provides a physically motivated explanation for the observed long wavelength flattening of the dust spectrum and the anti-correlation between emissivity index and dust temperature. We consider the model of Finkbeiner et al. because it has been widely used for CMB studies, and the generalized version of this model that was recently applied to Planck data by Meisner and Finkbeiner. For comparison we have also fit a phenomenological model consisting of the sum of two-graybody components. We find that the two-graybody model gives the best fit and the FDS model gives a significantly poorer fit than the othermodels. The Meisner and Finkbeiner model and the TLS model remain viable for use in Galactic foreground subtraction, but the FIRAS data do not have a sufficient signal-to-noise ratio to provide a strong test of the predicted spectrum at millimeter wavelengths.

Odegard, N.↗
NASA NTRS2019

Bit Error Rate and Frame Error Rate Data Processing for Space Communications and Navigation-Related Communication System Analysis Tools

One of the capabilities that the Space Communications and Navigation (SCaN) Strategic Center for Networking, Integration, and Communications (SCENIC) user interface (UI) web application intends to provide its users is the addition of network protocol and link encryption augmentations of communication system analyses. Before any of these analyses capabilities can be modeled, the simulations of bit error rate (BER) and frame error rate (FER) against signal-to-noise ratio (SNR) have been conducted, requiring parameters from several known coding types (low-density parity-check (LDPC), convolutional, etc.), signal modulations (binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), etc.), coding rates (1/2, 1/3, etc.), and frame sizes (1,280, 3,580, etc.). However, in order to extract useful information from the results of these simulations, a curve fitting technique has been applied to each resulting dataset to extend and extrapolate the curve fit of BER and FER down to 10–30 using MATLAB® Curve Fitting Toolbox™ (The MathWorks, Inc.). This is a necessary step because simulations of BER and FER were only performed to around 10–9 due to the extensive simulation time that would be required to obtain significant simulation results at the error levels desired. Furthermore, the fitted curve results were applied to a finer resolution for the SNR at 0.01-dB interval instead of the 0.05-dB interval limitation used in the simulation. All the possible combinations of the coding types, signal modulations, coding rates, frame sizes, and the extension of BER and FER curves would enable users to capture a wide range of link performances that directly relates to the addition of higher level networking data encapsulated in a frame. The curve fitting results also led to the modeling of the optical link error rate performance by solving for coding gain, FER_BER SNR delta, coded optical BER-SNR, and coded optical FER–SNR.

Communication link analysis↗
NASA NTRS2019

Development of Human-Spacesuit Interaction Models

Today’s astronaut corps represents a wide range of various anthropometric dimensions. Accommodating this wide range of anthropometry and protecting for size variations in future crews, makes spacesuit sizing and fit a challenging and necessary aspect of suit development. Spacesuit fit can play an important role in performance, but a suit fit assessment, especially in dynamic postures, is difficult without extensive human-in-the-loop testing. One approach to address this issue is to model and simulate the human-spacesuit interactions for a target population early in the design process. The Anthropometry and Biomechanics Facility (ABF) at the NASA Johnson Space Center has been working to incorporate parametric human models based on 3D full-body scan data with spacesuit CAD models that can be driven by the user or imported motion capture data. An articulated spacesuit model combined with a poseable high-fidelity human model allows comparisons to be made between spacesuit capabilities and normal human ranges of motion. Furthermore, predictions can be made as to how a specific individual or population may perform in the suit from the perspective of reach and mobility. In this paper, we will present case study examples of reach, mobility, and fit analyses that can be done with these models and the methodology developed thus far. These models have the potential to become powerful tools for evaluating future spacesuit design architectures from the perspective of optimizing fit and performance.

Jarvis, Sarah↗
NASA NTRS2020

Thermal Analysis, Compressibility, and Decomposition of Synthetic Bastnäsite-(La) to Lanthanum Oxyfluoride

Understanding basic material properties of rare earth element (REE) bearing minerals such as their phase stability and equations of state can assist in understanding how economically viable deposits might form. Bastnäsite is the most commonly mined REE bearing mineral. We synthesized the lanthanum-fluoride end member, bastnäsite-(La) (LaCO3F), and investigated its thermal behavior and decomposition products from 298 K to 1173 K under ambient pressure conditions through thermogravimetric analysis, differential scanning calorimetry, evolved gas analysis, and high temperature powder X-ray diffraction. We also investigated the compressibility of bastnäsite-(La) via single crystal X-ray diffraction in diamond anvil cells at an ambient temperature up to 11.3 GPa and from 4.9 GPa to 7.7 GPa up to 673 K. At ambient pressure, bastnäsite-(La) was stable up to 598 K in air, where it decomposed into CO2 and tetragonal γ-LaOF. Above 948 K, cubic α-LaOF is stable. High temperature X-ray diffraction data were used to fit the Fei thermal equation of state and the thermal expansion coefficient α(sub 298) for all three materials. Bastnäsite-(La) was fit from 298 K to 723 K with V(sub 0) = 439.82 Å(exp 3), α(sub 298) = 4.32 × 10(exp -5) K(exp -1), a(sub 0) = −1.68 × 10(exp -5) K(exp -1), a(sub 1) = 8.34 × 10(exp -8) K(exp -1), and a(sub 2) = 3.126 K(exp -1). Tetragonal γ-LaOF was fit from 723 K to 948 K with V(sub 0) = 96.51 Å(exp 3), α(sub 298) = 2.95×10(exp -4) K(exp -1), a(sub 0) = −2.41×10(exp -5) K(exp -1), a(sub 1) = 2.42×10(exp -7) K(exp -1), and a(sub 2) = 41.147 K(exp -1). Cubic α-LaOF was fit from 973 K to 1123 K with V(sub 0) = 190.71 Å(exp 3), α(sub 298) = −1.12×10(exp -5) K(exp -1), a(sub 0) = 2.36×10(exp -4) K(exp -1), a(sub 1) = −1.73 × 10(exp -7) K(exp -1), and a(sub 2) = −17.362 K(exp -1). An ambient temperature third order Birch–Murnaghan equation of state was fit with V(sub 0) = 439.82 Å(exp 3), K(sub 0) = 105 GPa, and K’ = 5.58.

Bastnäsite↗
NASA NTRS2021

Retrieval Algorithm for the Column CO2 Mixing Ratio from Pulsed Multi-Wavelength Lidar Measurements

The retrieval algorithm for the column mixing ratio of CO2 from the measurements of a pulsed multi-wavelength integrated path differential absorption (IPDA) lidar is described. The lidar samples the shape of the 1572.33 nm CO2 absorption line at 15 or 30 wavelengths. The algorithm uses a least-squares fit between the CO2 line shape computed from a layered 10 atmosphere model to that sampled by the lidar. In addition to the column average CO2 dry air mole fraction (XCO2), several other parameters are also solved simultaneously from the fit. These include the Doppler shift in the received laser signal wavelengths, the product of the surface reflectivity and atmospheric transmission and a linear trend in the lidar receiver’s spectral response. The algorithm can also be used to solve for the average water vapor mixing ratio, which causes a secondary absorption in the wings of the CO2 absorption line under high humidity conditions. The least-squares fit is linearized about the 15 expected XCO2 value which allows the use of a standard linear least-squares fitting method and software tools. The standard deviation of the retrieved XCO2 is obtained from covariance matrix of the fit. An averaging kernel is defined similarly to that used for passive trace-gas sounding. Examples are presented of using the algorithm to retrieve XCO2 from the measurements from NASA Goddard’s airborne CO2 Sounder lidar made at a constant altitude and during spiral-down maneuvers.

Xiaoli Sun↗
NASA NTRS2021

Dealing with Ion LET Uncertainties: An Application of Generalized Linear Models

Although most SEE rate estimation methods presume a fit to SEE cross section vs. LET, fitting SEE data is challenging because the data are not compatible with the assumptions of many common fitting techniques (e.g. linear regression. The difficulty of fitting such data is compounded when the LET of the ion responsible for an SEE is uncertain. We modify a Generalized Linear Model SEE data fitting methodology to accommodate uncertain LET and apply the method to the problem of backside heavy-ion SEE testing to demonstrate the utility of the method, explore the dependence of systematic errors that arise from improper treatment of LET uncertainty and develop guidelines for minimizing such systematic errors when proper treatment is not possible. Additional applications are suggested and assessed for suitability of treatment by the model.

Single-event effects↗
NASA NTRSDate not supplied

Mitigating Headward Fluid Shifts with Venoconstrictive Thigh Cuffs during Spaceflight

Venoconstrictive thigh cuffs (VTC) are a mechanical countermeasure capable of attenuating the spaceflight induced headward fluid shift, and thus may be a viable spaceflight associated neuro-ocular syndrome (SANS) countermeasure. Crewmembers can use VTC to mitigate the headward fluid shift to aid in adapting to spaceflight. However, data are needed to determine if VTC affect ocular structures. PURPOSE The purpose of this study is to determine the efficacy of long duration use of VTC application to mitigate the spaceflight-induced headward fluid shift. We hypothesize that a VTC countermeasure will temporarily reverse the headward fluid shift and attenuate spaceflight-induced changes of internal jugular vein (IJV) cross-sectional area, IJV pressure, stroke volume, cardiac output, intraocular pressure (IOP), and optic nerve head and retinal morphology. METHODS This study will evaluate the effectiveness of VTC countermeasure application on the headward fluid shift, as well as cardiovascular and ocular variables. VTC during spaceflight will be worn for an extended duration (up to 6 hours) with data collected at three time points (30 minutes, 3 hours, and 6 hours) to characterize the temporal profile of key fluid shift outcome measures of the vascular fluid shift, IOP, and ocular structure changes. Ten astronauts will be recruited to participate and will be studied before and during approximately 180-day International Space Station (ISS) spaceflight missions. Baseline data collection will occur approximately 90-days before launch (Figure). Preflight, each leg of the crewmember will be measured to determine the VTC cuff size and a cuff fit check session will occur prior to the preflight baseline ground imaging to verify the appropriate fit measured via a surface contact pressure. Prior to donning the VTC, baseline measures without VTC will be collected seated, supine, and supine followed by data collection with the VTC. The baseline data collection will include ultrasound (IJV area and pressure, stroke volume and cardiac output), brachial blood pressure and heart rate, optical coherence tomography (OCT) imaging (total retinal thickness and choroid thickness), and IOP. An inflight cuff fit check session, same as the preflight fit check, will occur prior to VTC use on ISS. The inflight VTC experiment will be conducted early (FD45) and late (R-45) to determine if mission duration affects VTC fit and the efficacy of fluid redistribution. A system usability scale comfort questionnaire will be included in each VTC session to capture feedback from crewmembers regarding the comfort and usability of the VTC. SCIENTIFIC & MISSION IMPACT Results will narrow knowledge gaps described in the Human Research Roadmap to mitigate the headward fluid shift during spaceflight and help NASA to 1) determine the efficacy of extended use VTC application to mitigate the spaceflight-induced headward fluid shift and 2) further the understanding of the use of VTC on vascular fluid shifts, IOP, and ocular structure during spaceflight. Supported by NASA Human Research Program Directed Research. Figure. Detailed Testing Schedule. Baseline data collection at L-90 will be performed in a randomized order of position.

J V Jasien↗
NASA NTRSDate not supplied

Evaluation of Aerobic Standards for Lunar Surface Extravehicular Activities

Introduction: As NASA prepares to return to the Moon, astronauts will need to be physically primed to successfully execute Extravehicular Activities (EVA) on the Lunar surface. Compared to past Apollo missions, Artemis missions will include EVAs of increased physical demand, frequency, intensity, and duration, thus requiring adequate fitness to successfully and safely complete mission objectives. The physical demand associated with partial gravity (g) EVAs on the Moon is expected to be greater compared to microgravity EVAs based on initial workload estimation. Currently, aerobic fitness standards for partial g EVAs are not well supported by high-fidelity data and require further research for establishing standards to protect crew health and performance during Lunar surface missions. Therefore, the aim of this investigation is to characterize metabolic data from Lunar analog simulations and in-flight crew population aerobic capacity data to validate the current NASA 3001 standard for celestial partial g aerobic fitness (aerobic capacity (VO_2pk) ≥36.5ml/kg/min). Methods: In order to evaluate aerobic fitness requirements for Lunar EVAs, the following were performed: 1) preliminary analysis of long-duration (6 hr) EVA analog simulations in the Neutral Buoyancy Laboratory (NBL) and the Active Response Gravity Offload System (ARGOS) to evaluate expected metabolic rates for 1/6 g EVAs (NBL: n=1 female; ARGOS: n=1 male) and 2) assessment of the current NASA 3001 celestial surface EVA aerobic standard (aerobic capacity (VO_2pk) ≥36.5ml/kg/min) with data from an ISS astronaut population (n=30 male + 13 female) captured before and during space flight (flight day 15). Preliminary Results: Average fractional aerobic capacity during simulated EVAs were 33%±7% VO_2pk and 23.3±7% VO_2pk in the NBL and ARGOS, respectively. This was within a previously predicted 30–40% sustainable work rate. Average metabolic rates for some tasks performed in the NBL, such as traverse (40.4% VO_2pk) and ingress (47.1% VO_2pk) were higher than the predicted sustainable work range. In ARGOS, the tasks with the greatest metabolic rates were object relocation (34.2% VO_2pk) and incapacitated crew rescue (27.0% VO_2pk). Characterization of ISS crewmember aerobic capacity determined that the average preflight VO_2pk was 42.1±5.4 ml/kg/min for females and 37.5±5.4 ml/kg/min for males. At preflight, 21.5% of crewmembers were below the 36.5 ml/kg/min in-mission aerobic standard for celestial surface EVA as outlined in NASA-STD-3001. In-flight, both female and male crewmembers experienced reductions in VO_2pk (11.7% and 10.9%, respectively), such that, during the mission, 62% of crewmembers were below the standard aerobic capacity level for celestial surface EVAs. Conclusions: Our preliminary data suggest that while average metabolic rates for simulated Lunar EVA fall within the 30–40% sustainable work range, task specific metabolic rates exceed this range and may indicate that greater fitness is necessary for more strenuous tasks expected to be performed on the Lunar surface. Additionally, deconditioning due to space flight results in most crewmembers falling below the current celestial partial g EVA standard, which may increase risk to crew health and performance and completing mission objectives for surface missions. Further research is necessary in Artemis-specific analog environments to validate the current NASA-3001 aerobic standard for celestial EVAs. Additionally, work is ongoing to validate the current NASA-3001 strength standard for celestial EVAs.

N.C. Strock↗
NASA NTRSDate not supplied

Evaluation of Aerobic Capacity in Relation to Simulated Lunar Surface Extravehicular Activities

INTRODUCTION Astronauts will need to be physically prepared to successfully execute strenuous Extravehicular Activities (EVA)on the Lunar surface. Compared to Apollo missions, Artemis missions will include EVAs of increased physical demand, frequency, and duration, thus requiring adequate fitness to successfully and safely complete mission objectives and potential contingency scenarios. Currently, aerobic fitness standards for partial gravity (g)surface EVAs are not well supported by high-fidelity EVA analog data. This investigation aims to characterize metabolic demands from Lunar analog EVA simulations in relation to the current NASA standards for celestial partial-g aerobic fitness(aerobic capacity (VO2pk) ≥36.5ml/kg/min). METHODS To evaluate current Lunar EVA aerobic fitness requirements, a pilot study was performed to characterize metabolic ratesduring6 hour simulated EVAs. The EVAs were performed in pressurized MKIII (n=2male) and xEMU (n=3 female) spacesuits offloaded to 1/6 g in the NASA Active Response Gravity Offload System. VO2pk was assessed via graded exercise testing on acycle ergometer and physical workload was quantified as percent ofVO2pk. RESULTS Four out of five subjects did not meet the current NASA celestial surface EVA aerobic standard (3 xEMU, 1MKIII;35.1±0.9 ml/kg/min). During simulated EVAs, subjects (xEMU: 35±1ml/kg/min; MKIII: 44±10ml/kg/min) worked at an average 36%VO2pk(xEMU) and 31% VO2pk(MKIII). For xEMU subjects, the tasks with the greatest average metabolic rates were 2km treadmill traverse(0% grade: 47.2%VO2pk[max 69.1%]), object relocation (45.2%VO2pk[max 60.5%]), and 1.5km traverse (0% grade: 45%VO2pk[max 59.7%]). For MKIII subjects, the tasks with the greatest average metabolic rates were 0.5km treadmill traverse (30% grade: 35.4% VO2pk[max 45.5%]), object relocation(31% VO2pk[max 40.8%]), and treadmill traverse (0% grade: 29.9%VO2pk[max 45.9%]). CONCLUSIONS While average metabolic rates for simulated Lunar EVA fall within sustainable work ranges of30–40% VO2pkand life support system limitations, task-specific metabolic rates exceed this range and may indicate that greater fitness is necessary for more strenuous tasks expected to be performed on the Lunar surface. As few subjects met the standard, more data is needed to adequately evaluate the NASA 3001 standard.

N C Strock↗