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Calculations are presented of the brightness temperature emission spectra of the 60-GHz O2 absorption band lines. Approximately 14 of these lines are predicted to be sufficiently strong for being measurable with state-of-the-art instruments. The intensity of the emission from these lines is shown to be quite sensitive to atmospheric temperature.
The Materials and Processing Laboratory at NASA Marshall Space Flight Center is developing Powder Metallurgy (PM) processing techniques for high temperature cermet and carbide material consolidation. These new group of materials would be utilized in the nuclear core for Nuclear Thermal Rockets (NTR). Cermet materials offer several advantages for NTR such as retention of fission products and fuels, better thermal shock resistance, hydrogen compatibility, high thermal conductivity, and high strength. Carbide materials offer the highest operating temperatures but are sensitive to thermal stresses and are difficult to process. To support the effort, a new facility has been setup to process refractory metal, ceramic, carbides and depleted uranium-based powders. The facility inciudes inert atmosphere glove boxes for the handling of reactive powders, a high temperature furnace, and powder processing equipment used for blending, milling, and sieving. The effort is focused on basic research to identify the most promising compositions and processing techniques. Several PM processing methods including Cold and Hot Isostatic Pressing are being evaluated to fabricate samples for characterization and hot hydrogen testing.
Advanced combustor concepts are evaluated as a means of accommodating possible future broad specification fuels. The three advanced double annular combustor concepts consisted of (1) a concept employing high pressure drop fuel nozzles for improved atomization, (2) a concept with premixing tubes in the main stage, and (3) a concept with the pilot stage on the inside and the main stage on the sideout, which is the reverse of the other two concepts. All of the advanced concepts show promise for reduced sensitivity to fuel hydrogen content. Some hardware problems were encountered, but these problems could be quickly resolved if refinement tests were conducted. The design with the premixing main stage was selected for a parametric test because of its low NOx emissions level, carbon free dome, and very low dome temperatures which were essentially independent of fuel type. The other advanced designs also had low done temperatures. The premixing dome design liner temperatures exhibited less sensitivity to fuel type than did the base-line combustor, although more sensitivity than observed for concept 1. The inner liner hot spot and the observed smoke results for the premixing design suggest that the fuel-air mixture was not as uniform as desired.
The angular distributions of oxygen atoms incident on surfaces in low earth orbit have been calculated for a number of ambient gas temperatures. Atom fluxes to surfaces were modeled by integrals over all permitted angles of incidence. Angles of incidence are limited by masking structures, and a number of types of mask were considered. Combustible surfaces exposed to the orbital atmosphere are heavily etched, creating profiles in mask shadows that are sensitive to ambient temperatures. The influence of the angular distributions on the characteristics of etched surfaces is discussed. Profiles measured for a September, 1983 flight were fitted to this model profile with a temperature of 750 + or - 50 K, which agrees with estimates based on solar activity at that time. Applications to sensing ambient temperatures and oxygen atom densities are discussed.
The temperature stabilization requirements of unchopped thermistor bolometers and thermopile detectors are analyzed. The detector temperature, on which the bolometer output signal depends, is quite sensitive to changes in instrument temperature but relatively insensitive to changes in scene temperature. In contrast, the difference in temperature between detector and substrate (instrument), on which the thermopile signal depends, is equally sensitive to changes in instrument and scene temperature. Expressions for these dependencies are derived based on a simplified instrument model. It is shown that for a typical uncooled thermal imager, the temperature stabilization requirements for a bolometer are two orders of magnitude more stringent than those for a thermopile detector. Keywords: thermistor, bolometer, thermopile, detector, IR, thermal, temperature stabilization
The following aspects of continuous flow electrophoresis were studied: (1) flow and temperature fields; (2) hydrodynamic stability; (3) separation efficiency, and (4) characteristics of wide gap chambers (the SPAR apparatus). Simplified mathematical models were developed so as to furnish a basis for understanding the phenomena and comparison of different chambers and operating conditions. Studies of the hydrodynamic stability disclosed that a wide gap chamber may be particularly sensitive to axial temperature variations which could be due to uneven heating or cooling. The mathematical model of the separation process includes effects due to the axial velocity, electro-osmotic cross flow and electrophoretic migration, all including the effects of temperature dependent properties.
A thin-film heat flux sensor has been fabricated on a stainless steel substrate. The thermocouple elements of the heat flux sensor were nickel and nichrome, and the temperature resistance sensor was platinum. The completed heat flux microsensor was calibrated at the AEDC radiation facility. The gage output was linear with heat flux with no apparent temperature effect on sensitivity. The gage was used for heat flux measurements at the NASA Langley Vitiated Air Test Facility. Vitiated air was expanded to Mach 3.0 and hydrogen fuel was injected. Measurements were made on the wall of a diverging duct downstream of the injector during all stages of the hydrogen combustion tests. Because the wall and the gage were not actively cooled, the wall temperature reached over 1000 C (1900 F) during the most severe test.
Validation of the HIRS2/MSU cloud parameters began with the cloud/climate feedback problem. The derived effective cloud amount is less sensitive to surface temperature for higher clouds. This occurs because as the cloud elevation increases, the difference between surface temperature and cloud temperature increases, so only a small change in cloud amount is needed to effect a large change in radiance at the detector. By validating the cloud parameters it is meant 'developing a quantitative sense for the physical meaning of the measured parameters', by: (1) identifying the assumptions involved in deriving parameters from the measured radiances, (2) testing the input data and derived parameters for statistical error, sensitivity, and internal consistency, and (3) comparing with similar parameters obtained from other sources using other techniques.
We compare 27 wheat models' yield responses to interannual climate variability, analyzed at locations in Argentina, Australia, India, and The Netherlands as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Wheat Pilot. Each model simulated 1981e2010 grain yield, and we evaluate results against the interannual variability of growing season temperature, precipitation, and solar radiation. The amount of information used for calibration has only a minor effect on most models' climate response, and even small multi-model ensembles prove beneficial. Wheat model clusters reveal common characteristics of yield response to climate; however models rarely share the same cluster at all four sites indicating substantial independence. Only a weak relationship (R2 0.24) was found between the models' sensitivities to interannual temperature variability and their response to long-termwarming, suggesting that additional processes differentiate climate change impacts from observed climate variability analogs and motivating continuing analysis and model development efforts.
Projections of future ozone levels are made using models that couple a general circulation model with a representation of atmospheric photochemical processes, allowing interactions among photochemical processes, radiation, and dynamics. Such models are known as chemistry and climate models (CCMs). Although developed from common principles and subject to the same boundary conditions, simulated ozone time series vary for projections of changes in ozone depleting substances (ODSs) and greenhouse gases. In the upper stratosphere photochemical processes control ozone level, and ozone increases as ODSs decrease and temperature decreases due to greenhouse gas increase. Simulations agree broadly but there are quantitative differences in the sensitivity of ozone to chlorine and to temperature. We obtain insight into these differences in sensitivity by examining the relationship between the upper stratosphere annual cycle of ozone and temperature as produced by a suite of models. All simulations conform to expectation in that ozone is less sensitive to temperature when chlorine levels are highest because chlorine catalyzed loss is nearly independent of temperature. Differences in sensitivity are traced to differences in simulated temperature, ozone and reactive nitrogen when chlorine levels are close to background. This work shows that differences in the importance of specific processes underlie differences in simulated sensitivity of ozone to composition change. This suggests a) the multi-model mean is not a best estimate of the sensitivity of upper ozone to changes in ODSs and temperature; b) the spread of values is not an appropriate measure of uncertainty.
Experimental design testing was conducted to identify critical parameters of an aqueous spray process intended for cleaning solid rocket motor metal components (steel and aluminum). A two-level, six-parameter, fractional factorial matrix was constructed and conducted for two cleaners, Brulin 815 GD and Diversey Jettacin. The matrix parameters included cleaner temperature and concentration, wash density, wash pressure, rinse pressure, and dishwasher type. Other spray parameters: nozzle stand-off, rinse water temperature, wash and rinse time, dry conditions, and type of rinse water (deionized) were held constant. Matrix response testing utilized discriminating bond specimens (fracture energy and tensile adhesion strength) which represent critical production bond lines. Overall, Jettacin spray cleaning was insensitive to the range of conditions tested for all parameters and exhibited bond strengths significantly above the TCA test baseline for all bond lines tested. Brulin 815 was sensitive to cleaning temperature, but produced bond strengths above the TCA test baseline even at the lower temperatures. Ultimately, the experimental design database was utilized to recommend process parameter settings for future aqueous spray cleaning characterization work.
We compare AIRS, IASI-A and CrIS under the cold conditions encountered in the daily overpasses of Dome Concordia, which is located on a high plateau in Antarctica, between May 2012 and March 2016. The brightness temperatures at DomeC for the 900 cm-1 atmospheric window channel is 218K on average, but varies seasonally from 185K to 255K. Averaged over all simultaneous overpass data AIRS is 26±13 mK warmer than IASI-A, AIRS is 116±7 mK colder than CrIS. However, we find that differences for both AIRS/IASI-A and AIRS/CrIS are temperature dependent, with AIRS being 250mK colder than IASI-A at 200K. These effects have been independently verified by other investigators. AIRS and CrIS bt900 results for simultaneous overpasses and daily mean values agree within 100 mK. AIRS and IASI simultaneous overpasses agree within 100 mK, but AIRS is 2K warmer than IASI for daily mean values. We attribute this effect to an overactive IASI QC which is sensitive to scene temperature above about 240K. The DomeC data do not reveal if this QC effect is present at temperatures warmer than 255K. These effects need to be taken into account when comparing results from AIRS, IASI and CrIS, and even more so when analyzing data from vintage instruments with respect to climate change.
We compare AIRS, IASI-A and CrIS under the cold conditions encountered in the daily overpasses of Dome Concordia, which is located on a high plateau in Antarctica, between May 2012 and March 2016. The brightness temperatures at DomeC for the 900 cm-1 atmospheric window channel is 218K on average, but varies seasonally from 185K to 255K. Averaged over all simultaneous overpass data AIRS is 26±13 mK warmer than IASI-A, AIRS is 116±7 mK colder than CrIS. However, we find that differences for both AIRS/IASI-A and AIRS/CrIS are temperature dependent, with AIRS being 250mK colder than IASI-A at 200K. These effects have been independently verified by other investigators. AIRS and CrIS bt900 results for simultaneous overpasses and daily mean values agree within 100 mK. AIRS and IASI simultaneous overpasses agree within 100 mK, but AIRS is 2K warmer than IASI for daily mean values. We attribute this effect to an overactive IASI QC which is sensitive to scene temperature above about 240K. The DomeC data do not reveal if this QC effect is present at temperatures warmer than 255K. These effects need to be taken into account when comparing results from AIRS, IASI and CrIS, and even more so when analyzing data from vintage instruments with respect to climate change.
The difficulty in establishing the temperature structure and temperature gradient within coronal holes from limb observations is due to the frequent veiling of coronal holes by hotter and denser quiet regions often surrounding them and shaping their boundaries. Nevertheless probing the coronal hole medium itself can be made with a judicious choice of spectral lines. We show how a set of visible forbidden Fe lines, namely Fe IX 3801, Fe X 6374 and Fe Xl 7892 A which are sensitive to plasma temperatures less than or equal to 10(exp 6) K can achieve this purpose. We propose to use these lines in a coordinated manner with coronagraph observations. In addition observations made with the Fe XIV 5303 A line should yield information about any hot material intercepting the line of sight. The proposed combination of these Fe lines offers a very powerful diagnostic tool for coronal hole temperatures and structures.
Technique developed to deconvolve period and relative amplitude of fluctuations of heat flow inBridgman crystal growth. Temperature-measuring device with enough sensitivity and frequency response to make desired measurements inserted close as possible to substance monitored. Time-dependent temperature response recorded, and time domain response converted to frequency domain for further analysis. Fast fourier transform (FFT) of data on temperature oscillations shows particular behavior at some specific frequencies corresponding with striations, or defects observed on crystal. Useful procedure to help determine sources of some growth-induced crystalline defects. Other processes sensitive to small temperature fluctuations, such as diffusion, precipitation, and corrsion, benefit from technique.
In 1982, the VISSR Atmospheric Sounder (VAS) on the GOES satellite performed the Atmospheric Variability Experiment (AVE) to verify VAS's mesoscale-sounding capabilities. Attention is given to the AVE network in the late afternoon of March 6, 1982, after a winter storm had passed over Texas, in order to ascertain whether such temperature profile deviations from the average lapse rate as a midlevel cold pool (which should decrease the brightness of several IR channels) can be retrieved from VAS radiances. Two simple enhancements are introduced: the regression matrix is calculated using the AVE asynoptic radiosondes launched from NWS sites in the region, and a change of the statistical conditioning factor from the conservative 10/1 SNR to a more optimistic 100/1 for those VAS channels that are more sensitive to tropospheric temperature.
An all-solid-state replacement for high-frequency Gunn diode oscillators (GDOs) has been proposed for use in NASA s millimeter- and submillimeter-wave sensing instruments. Highly developed microwave oscillators are used to achieve a low-noise and highly stable reference signal in the 10-40-GHz band. Compact amplifiers and high-power frequency multipliers extend the signal to the 100-500-GHz band with minimal added phase noise and output power sufficient for NASA missions. This technology can achieve improved output power and frequency agility, while maintaining phase noise and stability comparable to other GDOs. Additional developments of the technology include: a frequency quadrupler to 145 GHz with 18 percent efficiency and 15 percent fixed tuned bandwidth; frequency doublers featuring 124, 240, and 480 GHz; an integrated 874-GHz subharmonic mixer with a mixer noise temperature of 3,000 K DSB (double sideband) and mixer conversion loss of 11.8 dB DSB; a high-efficiency frequency tripler design with peak output power of 23 mW and 14 mW, and efficiency of 16 and 13 percent, respectively; millimeter-wave integrated circuit (MMIC) power amplifiers to the 30-40 GHz band with high DC power efficiency; and an 874-GHz radiometer suitable for airborne observation with state-of-the-art sensitivity at room temperature and less than 5 W of total power consumption.
We are developing magnetic penetration thermometers (MPTs) for applications in X-ray astronomy. These non-dissipative devices consist of an X-ray absorber in good thermal contact to a superconducting thin film with a transition temperature around T=100mK. A microfabricated superconducting planar inductor underneath is used to store a persistent current and couple the superconductor's diamagnetic response to a readout SQUID. The strong temperature dependence of the diamagnetic response make these devices suitable for highly sensitive macroscopic thermometers that are capable of achieving very high energy resolution. We present results achieved with MPTs consisting of MoAu bilayer sensors attached to overhanging square 250 micron by 250 micron gold absorbers that have demonstrated an energy resolution of delta E_FWHM=2.3eV at an X-ray energy of 5.9keV. A similar device has shown delta E_FWHM=2.0eV at 1.5 keV. Under certain conditions and for specific device geometries, the temperature responsivity of the MPTs can vary on long timescales degrading the spectral performance. We present the characterization of different inductor geometries to optimize the design for the highest possible temperature sensitivity and compare different device designs with respect to responsivity stability.