Aboard NASA Research Articles

Ascribing societal benefit to applied remote sensing data products: an examination of methodologies based on the Multi-angle Imaging SpectroRadiometer experience

This paper describes and illustrates frameworks for societal benefits associated with data products from the Multi-angle Imaging SpectroRadiometer (MISR), one of five instruments launched into polar orbit aboard NASA's Terra spacecraft in December 1999. The objective of framing and illustrating benefits is impelled by the January, 2007, U.S. National Research Council's seminal decadal survey of U.S. Earth science. The survey urges that all missions explicitly identify potential societal benefits in mission planning and operation. In this paper, our retrospective look at MISR offers approaches which mission planning for future instruments could operationalize. Societal generally refers to practical applications of data and data products beyond their intrinsic science merit. The paper demonstrates how societal benefit frameworks work, highlights some of these benefits in the case of MISR, and seeks to provide useful guidance for benefit descriptions in future multi-angle and other Earth observation research programs.

Ultrastructural changes in somatosensory cortex of albino rats during space flight

For the first time, mammalian brain has been studied during space flight aboard NASA orbital laboratory Spacelab-2. The main ultrastructural differences in the somatosensory cortex of the brain fixed under microgravity conditions and after landing include an increased number of degenerating presynaptic axon terminals after landing. Apparently, this is due to a sharp increase in afferent impulsation in the cortex during and after landing.

Thank You for Flying the Vomit Comet

This paper describes our flight aboard NASA's C9 “Weightless Wonder,” an aircraft that creates multiple periods of microgravity by conducting a series of parabolic maneuvers over the Gulf of Mexico. Because passengers often develop motion sickness during these parabolic maneuvers, the C9 is more affectionately known as the “Vomit Comet.” To celebrate the 2005 World Year of Physics, AAPT, APS, and NASA co-sponsored a contest in which teams of high school students and their mentors could fly an experiment aboard the Vomit Comet. If selected, students would develop their experiment and travel to Houston to serve as “ground crew” while the mentors would actually fly aboard the C9 to perform the experiment.

Virtual Reality Laparoscopic Skill Assessment in Microgravity

The objective of the study was to assess if performance of basic laparoscopic skills on a virtual reality (VR) simulator is impaired in microgravity relative to normal gravitational influences. Fourteen subjects with various educational backgrounds underwent basic laparoscopy skill training for five consecutive days on the ground before flying aboard NASA's KC-135 zero-gravity laboratory. The participants performed basic laparoscopic exercises (clip applying, grasping, cutting, and suturing) on a VR laparoscopy simulator, both on the ground and during 25-s microgravity windows in parabolic flight. Skill levels after ground training were compared with skill levels in performing the same tasks in microgravity. Blinded reviewers measured the number of tasks successfully completed, tissue damage number, left and right hand path lengths during task execution, and percentage of task attempts that resulted in successful completion. A significant increase in tissue injury (t test, P < 0.05) and task erosion were seen in clip applying, cutting, and grasping in microgravity (45%, 20% and 57% decrease in task attempts that resulted in a successful completion, respectively). However, there was no significant difference in the left and right hand path lengths, and the total number of tasks successfully completed on the ground versus in microgravity, for any of the four laparoscopic exercises (t test, P > 0.05). This study demonstrates decreased efficiency and increased injury to the simulated tissues in performing laparoscopic skills during microgravity as compared to performing these skills in standard gravitational influence. Additional experiments are indicated to further develop and validate VR microgravity surgical simulation.

Virtual reality laparoscopic skill assessment in microgravity

Introduction: The objective of the study was to determine the feasibility of virtual reality training in performance of basic laparoscopic skills in microgravity. Methods: Fourteen subjects with various educational backgrounds underwent basic laparoscopy skill training for five consecutive days on the ground prior to flying aboard NASA’s KC-135 zero-gravity laboratory. The participants performed basic laparoscopic exercises (clip applying, grasping, cutting and suturing) on a virtual reality laparoscopy simulator, both on the ground and during 25-second microgravity windows in parabolic flight. Skill levels after ground training were compared with skill levels in performing the same tasks in microgravity. Blinded reviewers measured the number of tasks successfully completed, tissue damage number, left and right hand path lengths during task execution, and percentage of task attempts that resulted in successful completion. Results: A significant increase in tissue injury (t-test, p<0.05) and task erosion were seen in clip applying, cutting, and grasping in microgravity (60%, 44% and 59% decrease in task attempts that resulted in a successful completion, respectively). However, there was no significant difference in the left and right hand path lengths, and the total number of tasks successfully completed on the ground versus in microgravity, for any of the four laparoscopic exercises (t-test, p>0.05). Conclusion: This study demonstrates decreased efficiency and increased injury to the simulated tissues in performing laparoscopic skills during microgravity as compared to performing these skills in standard gravitational influence. Additional experiments are indicated to further develop and validate virtual reality microgravity surgical simulation.

Discontinuous Pore Fluid Distribution under Microgravity‐KC‐135 Flight Investigations

Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity.

Evaluation of surgical skills in microgravity using force sensing

Introduction: Force measurements can be used to characterize surgical maneuvers in microgravity. Methods: A series of surgical tasks was performed by a group of 20 participants ( n = 20) both in 1 g on the ground and in 0 g aboard NASA's KC-135 aircraft in parabolic flight. The group included astronauts, a flight surgeon, surgeons, physicians, Ph.D.-scientists, and technical personnel. The interaction forces between the surgical instruments and the mock tissue were measured for a clip-applying, suturing, grasping, and cutting. Seven evaluations in 1 g and a single evaluation in 0 g were performed by each of the participants. Results: The data from a single participant are examined in detail. Statistical results for the group of 20 participants do not show significant differences in the average or peak forces during clip-applying or in the average forces applied during suturing in 0 g versus in 1 g. However, the results do show statistically greater (43% higher) peak forces during suturing in microgravity. Discussion: These data show the usefulness of analyzing force information to assess surgical task performance in microgravity. Although peak suturing forces were statistically higher in microgravity, their clinical relevance is unknown, but likely would not result in a change in clinical outcome. Overall, the data suggest that forces exerted during surgical tasks will not pose a significant barrier to effective surgery in microgravity.

The Search for Dark Matter via Gamma Rays from Astronomical Sources Using EGRET and GLAST

EGRET, aboard NASA's CGRO satellite, has made important contributions to establishing limits on WIMP dark matter in the galaxy. This paper will review these EGRET results. Based on past limits and theoretical estimates, future potential dark matter results from GLAST are projected.

Consistency of MODIS surface bidirectional reflectance distribution function and albedo retrievals: 1. Algorithm performance

The first consistent year (November 2000 to November 2001) of global albedo product was produced at 1‐km resolution every 16 days from the observations of the Moderate‐Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Terra spacecraft. We evaluated the quality of the operational albedo retrievals in two ways: (1) by examining the algorithm performance using the product quality assurance (QA) fields (this paper) and (2) by comparing retrieved albedos with those observed at ground stations and by other satellite instruments (in a companion paper). The internal diagnostics of the retrieval algorithm adequately reflect the goodness of the model fit and the random noise amplification in the retrieved albedo. Global QA statistics show that the RossThick‐LiSparse‐Reciprocal model fits the atmospherically corrected surface reflectances very well, and the random noise amplification factors for white sky albedo and reflectance are generally less than 1.0. Cloud obscuration is the main reason for the activation of the backup magnitude retrieval algorithm. Over the 60°S to 60°N latitude band, 50% of the land pixels acquire more than six clear looks during 14–29 September 2001, and only 5% of these pixels are inverted with the backup algorithm. The latitude dependence and temporal distribution of the QA fields further demonstrate that the retrieval status mainly follows the pattern of angular sampling determined by cloud climatology and the instrument/orbit characteristics. A case study over the west coast of the United States shows that white sky shortwave albedos retrieved from magnitude inversions agree on average with those from full inversions to within 0.033 in reflectance units and have a slightly lower bias ranging from 0.014 to 0.023. We also explored the effect of residual cloud and aerosol contamination in the atmospherically corrected surface reflectance inputs in another case study over southern Africa. The quality assurance procedure of the operational MODIS bidirectional reflectance distribution function and albedo algorithm compensates for some of these residual effects and improves the albedo retrieval results by an order of 0.005 (10%) in the visible for more than 12% of pixels.

A high-energy (35–500MeV) proton monitor for the Gravity Probe-B Mission

Abstract An innovative fault tolerant, high-energy particle monitor designed to record protons in the range 35–500 MeV when in polar orbit aboard NASA's Gravity Probe B spacecraft, is described. This device, which is configured to provide continuous, reliable operation in the hostile particle environment traversed by the spacecraft, can potentially be used either as an onboard monitor or as a scientific experiment.

Radiation measurements aboard nasa ER-2 high altitude aircraft with the liulin-4J portable spectrometer

The risks to aircrew health posed by prolonged exposure to low levels of ionizing radiation at aircraft altitudes have recently received renewed attention. Civil and military aircraft currently on the drawing board are expected to operate at higher altitudes (>12 km) and fly longer ranges than do existing aircraft, thereby exposing their crews to higher levels of ionizing radiation. for longer periods of time. We are currently carrying out dosimetric measurements of the ionizing radiation environment at ∼20 km altitude using portable Si detectors aboard NASA's two ER-2 high altitude research aircraft. The instruments, Liulin-4J, have been extensively calibrated at several particle accelerators. With these instruments, we can measure not only absorbed dose, but also variation of the absorbed dose as a function of time. We report radiation dose measurements as function of time, altitude, and latitude for several ER-2 missions.

Early radiometric validation results of the CERES Flight Model 1 and 2 instruments onboard NASA's Terra Spacecraft

The CERES Flight Model 1 and 2 instruments were launched aboard NASA's Earth Observing System (EOS) Terra Spacecraft on December 18, 1999 into a 705 Km sun-synchronous orbit with a 10:30 a.m. equatorial crossing time. These instruments supplement measurements made by the CERES Proto Flight Model (PFM) instrument launched aboard NASA's Tropical Rainfall Measuring Mission (TRMM) spacecraft on November 27, 1997 into a 350 Km, 38-degree mid-inclined orbit. An important aspect of the EOS program is the rapid archival and dissemination of datasets measured by EOS instruments to the scientific community. On September 22, 2000 the CERES Science Team voted to archive the Edition 1 CERES/Terra Level 1b and Level 2 and 3 ERBE-Like data products. These products consist of instantaneous filtered and unfiltered radiances through temporally and spatially averaged TOA fluxes. CERES filtered radiance measurements cover three spectral bands including shortwave (0.3 to 5 μm), total (0.3 to <100 μm) and an atmospheric window channel (8 to 12 μm). The current work summarizes both the philosophy and results of validation efforts undertaken to quantify the quality of the Terra data products as well as the level of agreement between the Terra and TRMM datasets.

Turbulence-induced preferential concentration of solid particles in microgravity conditions

A box of near-isotropic, particle-laden turbulence was flown aboard NASA's reduced gravity aircraft in order to measure the turbulence-induced preferential concentration of solid particles in microgravity. Three particle sets of Stokes numbers based on the fluid Kolmogorov time scale of approximately 0.5, 5, and 50 were tested for relative amounts of preferential concentration. Eight fans in each corner of a Lexan box generated fluid turbulence. Particle concentrations were measured using an imaging system consisting of a camera viewing perpendicular to a white light sheet. Post-processing of video images found largest concentration gradients for the intermediate-sized particles of Stokes number 5, closely followed by the Stokes number 0.5 particles. The experimental results agreed well with the trends seen in direct numerical simulations. The quantitative effects of turbulence modulation by the presence of particles were not measured in the experiment, but were most likely present.

Response of NaI(Tl) to X-rays and electrons

Measurements of the light output response of NaI(Tl) to X-rays were taken as part of the pre-flight calibrations of the High Energy X-ray Timing Experiment (HEXTE), currently in orbit aboard NASA's Rossi X-ray Timing Explorer. These measurements cover the energy range 12–159 keV. Radionuclides and fluorescent sources were used to provide a coarse sampling of this energy range, and a tunable X-ray monochromator was used to provide a fine scale mapping around the iodine K-edge (33.17 keV), where the light output response of NaI(Tl) varies rapidly with energy. The light output response to X-rays is measured to an accuracy of ± 0.7%. In addition to presenting the results of these X-ray calibrations, we use these data to infer the response of NaI(Tl) to electrons in the energy range 0.1–125 keV. This is done using the procedure of Collinson and Hill [Proc. Phys. Soc. 81 (1963) 883], modified to take into account systematic effects that have been noted in the literature and to improve the model that is used to describe the cascade liberation of electrons that follows the absorption of an X-ray in the crystal. The Collinson and Hill procedure is particularly well suited to work with X-ray data, such as ours, that include detail at energies just above the iodine K-edge; the data here are used to determine the response of NaI(Tl) to low energy electrons, a point of contention in the literature. Our measurements of the electron response extend down to lower energies than have been examined in the past. The light output response to electrons is measured to an accuracy of ±90% at 0.1 keV, ±50% at 1 keV, ±5% at 10 keV, and ±4% at 100 keV.

Microgravity processing of immiscible aluminum-indium alloys

This paper addresses the Coupled Growth in Hypermonotectics experiment carried out aboard NASA's Life and Microgravity Spacelab Mission which took place from June 10 to July 7, 1996. The experiment involved the directional solidification of hypermonotectic (immiscible) alloys in an attempt to obtain steady-state, coupled growth conditions by processing under microgravity conditions. Processing was carried out utilizing the Advanced Gradient Heating Facility directional solidification furnace in order to obtain the high thermal gradients and controlled growth rates required for stability. Solidification under the proper growth conditions was expected to lead to interface stability and the production of a desired aligned fibrous microstructure even for hypermonotectic alloys. The paper covers the objectives of the experiment and a discussion of the anticipated results. While microstructural information is not yet available at the time of writing, results will be presented on the thermal gradients and growth rates obtained and how these compared with predictions.

Gamma-Ray Line Spectroscopy Results from COMPTEL

Comptel aboard NASA's Compton Observatory has led to a major progress in the field of astronomical gamma-ray line spectroscopy. Highlights are the all-sky map of the 1.8 MeV line from radioactive 26Al, the first detection of the 1.156 MeV line from radioactive 44Ti from a Supernova remnant (Cas A), and the detection of excessive MeV emission from the Orion complex that may be ascribed to excitation of 12C and 16O nuclei.

Heat transfer to annular gas-liquid mixtures at reduced gravity

A series of fluid flow and heat transfer experiments was conducted for annular gas-liquid mixtures at reduced gravity aboard NASA's KC-135 aircraft. Air and two liquids, water and 50% aqueous glycerine, were used to produce a range of liquid Reynolds numbers from 1.4 x 10 to 1.4 x 10 in a 25.4-mm-i.d. tube. Pressure drop measurements compare reasonably well with the Lockhart and Martinelli and Wallis correlations. Film thickness measurements compare reasonably well with correlations derived from ground-based vertical annular flow data. The asymptotic Nusselt numbers for 50% glycerine compare well with a turbulent flat-film model, whereas the model overpredicts the water data. For both fluids at higher Reynolds numbers, the asymptotic Nusselt numbers follow a common dependence on Reynolds and Prandtl numbers, Nu = ARePr.

Boiling heat transfer in the quenching of a hot tube under microgravity

Quenching of a hot tube by injection of a subcooled liquid was investigated under microgravity conditions. Liquid Freon (R-113) was injected at mass fluxes between 160-850 kg/ms into an initially hot, thin-walled stainless steel tube, 11.3 mm i.d. and 914 mm long. Data collected in microgravity aboard NASA's KC-135 aircraft were compared with quenching tests in a horizontal tube under normal gravity. The re wetting temperatures were found to be 15°-25°C lower in microgravity than those obtained under 1 g, and the film boiling heat transfer coefficients in microgravity were only 20-50% of the values obtained in 1 g. This resulted in much longer precursory cooling periods in microgravity, and hence, the time to totally quench the initially hot tube in microgravity was greatly extended. However, once the tube was cooled sufficiently to allow axial propagation of the quench front, the re wetting velocity was found to be slightly greater in microgravity. The boiling curves showed that the nucleate and transition boiling curves in microgravity were shifted to lower wall superheats as compared to 1 g as a result of the lower re wetting temperature. The heat flux profiles were otherwise quite similar, indicating that these boiling regimes are little affected by reduction in gravity.

On purported observations of partially ionized galactic cosmic rays

Galactic cosmic rays are generally believed to be bare nuclei, fully stripped of all orbital electrons during passage through several g/sq cm of interstellar matter. Over the years there have been numerous reports of so-called 'below-cutoff' Fe-group cosmic rays, with momentum below the minimum required for a fully ionized particle to reach Earth's inner magnetosphere. These reports comprised just a few tens of ions, but stimulated much speculation about partially ionized Galactic cosmic rays, suggesting a nearby source of Galactic cosmic rays. In this Letter we compare these previous reports to new observations of below-cutoff Fe-group ions from passive track detectors exposed for nearly 6 years in low-Earth orbit aboard NASA's Long Duration Exposure Facility (LDEF) satellite. The LDEF fluxes are only a few percent of the previously reported fluxes. This comparison suggests that the flux of below-cutoff ions must be out of phase with the observed solar-cycle variation of other (nonsolar) cosmic-ray sources and/or must strongly increase with decreasing altitude in low-Earth orbit. Both of these features are inconsistent with the notion of partially ionized Galactic cosmic rays as the source of the observed below-cutoff ions.

The influence of gravity level during directional solidification of immiscible alloys

During directional solidification of immiscible (hypermonotectic) alloys itis theoretically possible to establish a stable macroscopically-planar solidification front, and thus avoid sedimentation. Unfortunately, convective instabilities often occur which interfere with the directional solidification process. In this paper, stability conditions are discussed and results presented from directional solidification studies carried out aboard NASA's KC-135 zero- g aircraft. Samples were directionally solidified while the effective gravity level was varied from approximately 0.01 g for 25 s to 1.8 g for 45 s. Dramatic variations in microstructure were observed with gravity level during solidification.