Radiometric calibration of the telescope and ultraviolet spectrometer SUMER on SOHO

The prelaunch spectral-sensitivity calibration of the solar spectrometer SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is described. SUMER is part of the payload of the Solar and Heliospheric Observatory (SOHO), which begins its scientific mission in 1996. The instrument consists of a telescope and a spectrometer capable of taking spatially and spectrally highly resolved images of the Sun in a spectral range from 50 to 161 nm. The pointing capabilities, the dynamic range, and the sensitivity of the instrument allow measurements both on the solar disk and above the limb as great as two solar radii. To determine plasma temperatures and densities in the solar atmosphere, the instrument needs an absolute spectral-sensitivity calibration. Here we describe the prelaunch calibration of the full instrument, which utilizes a radiometric transfer-standard source. The transfer standard was based on a high-current hollow-cathode discharge source. It had been calibrated in the laboratory for vacuum UV radiometry of the Physikalisch-Technische Bundesanstalt by use of the calculable spectral photon flux of the Berlin electron storage ring for synchrotron radiation (BESSY)-a primary radiometric source standard.     

Radiometric calibration of the vacuum-ultraviolet spectrograph SUMER on the SOHO spacecraft with the B detector

The Solar Ultraviolet Measurement of Emitted Radiation (SUMER) vacuum-ultraviolet spectrograph was calibrated in the laboratory before the integration of the instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft in 1995. During the scientific operation of the SOHO it has been possible to track the radiometric calibration of the SUMER spectrograph since March 1996 by a strategy that employs various methods to update the calibration status and improve the coverage of the spectral calibration curve. The results for the A Detector were published previously [Appl. Opt. 36, 6416 (1997)]. During three years of operation in space, the B detector was used for two and one-half years. We describe the characteristics of the B detector and present results of the tracking and refinement of the spectral calibration curves with it. Observations of the spectra of the stars alpha and rho Leonis permit an extrapolation of the calibration curves in the range from 125 to 149.0 nm. Using a solar coronal spectrum observed above the solar disk, we can extrapolate the calibration curves by measuring emission line pairs with well-known intensity ratios. The sensitivity ratio of the two photocathode areas can be obtained by registration of many emission lines in the entire spectral range on both KBr-coated and bare parts of the detector's active surface. The results are found to be consistent with the published calibration performed in the laboratory in the wavelength range from 53 to 124 nm. We can extrapolate the calibration outside this range to 147 nm with a relative uncertainty of ?30% (1varsigma) for wavelengths longer than 125 nm and to 46.5 nm with 50% uncertainty for the short-wavelength range below 53 nm.     

Radiometric Calibration Tracking of the Vacuum-Ultraviolet Spectrometer SUMER During the First Year of the SOHO Mission

Detailed radiometric calibration tracking of the vacuum-ultravioletspectrometer SUMER (from solar ultraviolet measurements of emittedradiation) was performed during the first year of the Solar andHeliospheric Observatory (SOHO) mission and will continue. Inview of the flight history of many previous solar UV instruments, thestability of calibration of the extreme-ultraviolet instruments on SOHOhas been a major concern. Results obtained during the first year ofoperation show that excellent radiometric stability has been achievedwith SUMER. These results were accomplished by stringentcleanliness and contamination-control procedures during all phases ofthe project. We describe the strategy and results of the in-flightcalibration tracking program performed with SUMER.     

Polarization sensitivity of the SUMER instrument on SOHO

The Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO) satellite is sensitive to the state of linear polarization of the incident radiation primarily owing to two optical elements, the holographic grating and the wavelength scan mirror. The large angle of incidence of light striking the scan mirror, which varies from roughly 73.3 degrees to 81.6 degrees (with respect to the mirror normal), causes the mirror to act as a linear polarizer. Similarly, the spectrometer grating operates at incidence angles between 16.7 degrees and 35.0 degrees , adding to the polarization effect at some wavelengths. Measurement and characterization of this polarization sensitivity as a function of wavelength were performed with the engineering model optics (scan mirror and grating) and synchrotron radiation, which is nearly 100% linearly polarized, from the Super Anneau de Collisions d'Orsay (SUPERACO) positron storage ring in Orsay. The polarization sensitivity or modulation factor of the SUMER instrument was found to be between 0.4 and 0.6, depending on the wavelength and the angle of incidence of light striking the scan mirror; this agrees with the calculated polarization properties based on the measured optical constants for the silicon carbide mirror and grating.     

Intercalibration of SUMER and CDS on SOHO. I. SUMER detector A and CDS NIS

The results of an intercalibration between the extreme ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the Solar and Heliospheric Observatory (SOHO) are presented. During the joint observing program Intercal_01, CDS and SUMER were pointed at the same locations in quiet Sun areas and observed in the same wavelength bands located around the spectral lines He i 584 A, Mg x 609 A, and Mg x 624 A. The data sets analyzed here consist of raster images recorded by the CDS normal-incidence spectrometer and SUMER detector A and span the time from March 1996 to August 1996. Effects of the different spatial and spectral resolutions of both instruments have been investigated and taken into account in the analysis. We find that CDS measures generally a 30% higher intensity than SUMER in the He i 584-A line, while it measures 9% and 17% higher intensities in Mg x 609 A and Mg x 624 A, respectively. Both instruments show very good temporal correlation and stability, indicating that solar variations dominate over changes in instrumental sensitivity. Our analysis also provides in-flight estimates of the CDS spatial point-spread functions.     

Intercalibration of SUMER and CDS on SOHO. III. SUMER and CDS-GIS. Solar and Heliospheric Observatory

Simultaneous observation of the same solar sources with different instruments is one way to test prelaunch radiometric calibrations and to detect changes in responsivity with time of extreme-ultraviolet instruments in space. Here we present the results of intercalibration of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrometer (detectors A and B) and the GIS (Grazing Incidence Spectrometer), one of two spectrometers that compose the CDS (Coronal Diagnostic Spectrometer) on the Solar and Heliospheric Observatory (SOHO). The two instruments observed simultaneously radiances of emission lines at or near the center of the solar disk. The emission line chosen for intercomparison was Ne VIII at 770 A. However, such an intercomparison of the SUMER and CDS-GIS measurements means comparing two data sets with large differences in resolution and field of view. The latter difference, especially, introduces differences in the measured intensities caused by the solar variability that is relatively strong in the 770-A line. Using a statistical approach to overcome this problem, we found that the ratio of the GIS to the SUMER average radiances amounted to 2.6 +/- 0.9 before the SOHO's loss of attitude and to 2.1 +/- 0.7 afterward. These findings confirm earlier estimates of the GIS's responsivity being too low, and an update of the GIS calibration is recommended. Despite the large differences in resolution and field of view of the two instruments, the shapes of their normalized and rescaled histograms of the radiances agree well and therefore represent characteristic features of the Ne VIII line.     

Intercalibration of SUMER and CDS on SOHO. II. SUMER Detectors A and B and CDS NIS

Results of an intercalibration between the extreme-ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO) are reported. The results of the joint observing program Intercal_01 are described, and intercalibration results up to July 2000 of both SUMER detectors A and B and of the CDS Normal Incidence Spectrometer (NIS) are presented. The instruments simultaneously observed radiance of emission lines at the center of the Sun, and three lines have been chosen for intercomparison: He i 584 A, Mg x 609 A, and Mg x 624 A. Initially the same area was observed by both instruments, but, after restrictions were imposed by the scanning mechanism of SUMER in November 1996, the instruments viewed areas of different sizes. Nevertheless, the temporal correlation between the two instruments remained good through June 1998, when contact with the SOHO spacecraft was lost. Until then the CDS instrument measured (33 ? 5)% and (38 ? 7)% (?1varsigma) higher intensity than SUMER in the He i 584-A line on average for detectors A and B, respectively. Data from SUMER detector B agreed well for Mg x 609 A and Mg x 624 A with the CDS intensities, showing offsets of (2 ? 10)% and (9 ? 15)%, much less than the data of detector A with offsets of (7 ? 8)% and (16 ? 7)% for the two lines, respectively, relative to CDS. Finally, the intercalibration measurements after the loss and recovery of the SOHO spacecraft are analyzed. The data for observations from November 1998 to July 2000 are compared, and it is shown that, although the responses of the instruments have changed, the CDS and the SUMER still perform well, and their temporal correlation is good.     

Radiometric calibration of SeaWiFS in the near infrared

The radiometric calibration of the Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) in the near infrared (band 8, centered on 865 nm) is evaluated by use of ground-based radiometer measurements of solar extinction and sky radiance in the Sun's principal plane at two sites, one located 13 km off Venice, Italy, and the other on the west coast of Lanai Island, Hawaii. The aerosol optical thickness determined from solar extinction is used in an iterative scheme to retrieve the pseudo aerosol phase function, i.e., the product of single-scattering albedo and phase function, in which sky radiance is corrected for multiple scattering effects. No assumption about the aerosol model is required. The aerosol parameters are the inputs into a radiation-transfer code used to compute the SeaWiFS radiance. The calibration method has a theoretical inaccuracy of plus or minus 2.0-3.6%, depending on the solar zenith angle and the SeaWiFS geometry. The major source of error is in the calibration of the ground-based radiometer operated in radiance mode, assumed to be accurate to +/- 2%. The establishment of strict criteria for atmospheric stability, angular geometry, and surface conditions resulted in selection of only 26 days for the analysis during 1999-2000 (Venice site) and 1998-2001 (Lanai site). For these days the measured level-1B radiance from the SeaWiFS Project Office was generally lower than the corresponding simulated radiance in band 8 by 7.0% on average, +/- 2.8%.     

Dynamic behavior of a masonry civic belfry under operational conditions

Slender structures, such as towers, are characterized by a high sensitivity to dynamic excitation. As a consequence, meaningful information about their behavior under operational conditions can be obtained by monitoring their response to ambient vibrations. Furthermore, significant stresses could be induced to the ancient masonry walls when the dynamic forces due to the swinging of a bell are acting. To assess the structural conditions of a case study representative of such type of structures and to plan an adequate retrofit, numerical analyses are carried out on a model whose modal parameters are calibrated based on the elaboration of the results from the ambient vibrations tests. In particular, full time histories analyses are performed using as input either the signal recorded while the bell was hit by a hammer, or the numerically calculated dynamic forces that would be produced by the actual swinging of the bell. The first set of analyses aims to investigate the capability of an equivalent linear elastic model to capture the actual dynamic response of the structure. The second set of analyses provides an evaluation of the tower response when dynamic loads of higher intensity and likely occurrence are considered.     

The size refinement of Cu crystallites under mechanical processing conditions: a phenomenological modeling approach

A phenomenological model is developed for describing the kinetics of the crystallite size refinement process of Cu powder under mechanical treatment conditions. Based on the evidence that collisions represent the elementary events of energy transfer, the rate of crystallite size decrease is related on a statistical basis to the amount of powder trapped at each collision, to the number of collisions and to the collision energy. The mathematical approach allows for identifying the approximate functional form of the kinetic curves obtained at largely different impact energies. The values of the apparent kinetic constants and of the model parameters involved can be thus estimated by fitting the model curves to the experimental data. The results obtained provide a deeper insight into the details of the crystallite size refinement process.     

Rate of the thaumasite form of sulfate attack under laboratory conditions

In order to give confidence to those responsible for the management of infrastructure, it is necessary to investigate the structural effects of the thaumasite form of sulfate attack (TSA) on buildings and structures. Whereas TSA is less common than other forms of structural concrete deterioration, its consequences can be quite serious.To investigate TSA deterioration of concrete within a reasonable time scale, it is generally necessary to accelerate TSA in the laboratory. Using such an accelerated testing procedure, this paper is concerned with predicting the rate of TSA depending on varying mix designs and aggressive solutions. A methodology was developed to estimate the annual deterioration rate of TSA. It was shown that a combined carbonate and sulfate solution is less aggressive than a pure sulfate solution, and that deterioration rates of up to 1.8 mm/year are possible in commonly used concrete.     

Bioremediation of chromium contaminated soil: optimization of operating parameters under laboratory conditions

Bacterial strains were isolated and enriched from the contaminated site of Tamil Nadu Chromates and Chemicals Limited (TCCL) premises, Ranipet, Tamil Nadu, India. The strain which was isolated from the highly contaminated location had shown high Cr(VI) reduction potential. Cr(VI) reduction was evaluated both in aerobic and anaerobic conditions. Though the aerobic system performed better than the anaerobic one, further study were carried out in the anaerobic condition due to its economic viability. At higher initial concentration, Cr(VI) reduction was not complete even after 108 h, however, specific Cr(VI) reduction, unit weight of Cr reduced/unit weight of biomass was greater at higher concentration. It was found that a bacterial concentration of 15+/-1.0 mg/g of soil (wet weight) 50 mg of molasses/g of soil as carbon source were required for the maximum Cr(VI) reduction. The bioreactor operated at these conditions could reduce entire Cr(VI) (5.6 mg Cr(VI)/g of soil) in 20 days. The Cr(III) thus formed was found to be strongly attached to the soil matrix and the mobility of Cr(III) was negligible as evident from the low concentration of Cr(III) in the leachate. This study showed that bioremediation is a viable, environmental friendly technology for cleaning-up the chromium contaminated site at TCCL, Ranipet, Tamil Nadu, India, and optimal operating conditions under laboratory conditions were evaluated.     

TDI CCD相机实验室辐射定标的研究

TDI CCD相机辐射定标的目的是建立输入辐亮度和探测器数字化输出之间的关系,为相机提供调光参数.本文推导了辐射定标的原理,并针对特定的TDI CCD相机在应用光学国家重点实验室里使用积分球对其进行了基于光谱辐照度灯的辐射定标,标定了TID CCD相机响应的线性度、TDI CCD相机响应分别与增益和级数的关系,根据实验结果我们得到了在不同的辐亮度值下的增益和级数参考值,从而确定了TDI CCD相机的调光参数,并给出了标定的误差和各项误差源的影响.     

Development of crumb rubber reinforced bituminous binder under laboratory conditions

Bituminous binders are widely used in the construction of flexible pavements. However, in some applications, the performance of conventional binders is not considered to be satisfactory. Reinforcing these binders with selected polymers prevents premature failure of a pavement by improving the properties of the binder. Another source of reinforcement comes from crumb (ground) rubber produced from waste tyres. After they have been worn-out during their limited service life, millions of used tyres are discarded every year and are hauled to a dump. The fatigue resistance at temperatures below normal service temperatures (25°C), one of the key engineering properties of crumb rubber reinforced binders, has been found to be lower than that of neat binders. This paper is concerned with the development of a rubber reinforced binder. It was shown that the binder has the potential to be used as an all-weather wearing course in flexible roads, whilst at the same time recycling a considerable amount of waste rubber.     

The generation of free concentrated air vortexes under laboratory conditions

Video filming is used to investigate the dynamics of free concentrated vortexes which arise over a heated underlying surface as a result of unstable stratification of air. Various types of trajectories of motion of the base of vortex structures are revealed. Parameters are analyzed such as the temperature of underlying surface, the region of emergence of vortex structures, the lifetime, and the direction of motion, which define the type of trajectory of vortex base.     

Properties of 13KhMF steel after operation and degradation under the laboratory conditions

The influence of cooling rate in the process of thermal treatment on the formation of the microstructure of 13KhMF heat-resistant steel is investigated. The relationships between the microstructure, strength characteristics, crack-resistance characteristics, and creep resistance of the material are determined. The transformations of the structure are modeled by the changes in the duration of tempering. The bainitemartensite structure is characterized by the best combination of properties and the largest period of transformation of the structure. The comparison of the results of laboratory and long-term in-service degradation and their influence on the structure, strength, and crack-resistance characteristics shows that they are similar.     

A program of equivalent tests for turbine blades under laboratory conditions

A method of conducting equivalent tests of turbine blades under laboratory conditions, which ensures reproduction of the operational pattern of the loading in its most heavily loaded components, is proposed. A method for construction of the equivalent-test program is analyzed on a stage-I turbine blade of one of the high-temperature aviation gas-turbine engines.Translated from Problemy Prochnosti, No. 7, pp. 89–92, July, 1991.     

Comparison of carbon and corrugated diamond stripper foils under operational conditions at the Los Alamos PSR

To accumulate high-intensity proton pulses, the Los Alamos Proton Storage Ring (PSR) uses the charge-exchange injection method. H⁻ ions merge with already circulating protons in a bending magnet, and then are stripped off their two electrons in a carbon stripper foil. The circulating protons continue to interact with the foil. Despite efforts to minimize the number of these foil hits, like “painting” of the vertical phase space, they cannot totally be eliminated. As a result, foil heating and probably also radiation damage limit the lifetime of these foils. In recent years, LANL has collaborated with KEK to improve the carbon foils in use at PSR, and these foils now last typically for about 2 months. Recently, an alternative in the form of corrugated diamond foils has been proposed for use at SNS. These foils have now been tested in PSR production for a year, and have already shown to be at least as enduring as the LANL/KEK carbon foils. Advantages of the diamond foil concept, as well as some noteworthy differences that we observed with respect to the LANL carbon foils, will be discussed here.