SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Device accomplishes simultaneous optical pumping using single flashlamp and electrical driver. Dye lasers require relatively low energy to operate (low-threshold pumping requirement) and provide simple method for producing simultaneous independent laser output at number of different wavelengths.
The relative cross sections for simultaneous ionization and excitation of helium by 200 eV electrons into the 4S, 4P, 4D and 4F levels have been measured via a fast delayed coincidence technique. Results are in poor agreement with Born approximation calculations for simultaneous ionization and excitation of helium, the 4P component being larger than expected.
Simultaneous observations of the GEOS-I and II flashing lamps by the NASA MOTS and SPEOPT cameras on the North American Datum (NAD) were analyzed using geometrical techniques to provide an adjustment of the station coordinates. Two separate adjustments were obtained. An optical data only solution was computed in which the solution scale was provided by the Rosman-Mojave distance obtained from a dynamic station solution. In a second adjustment, scaling was provided by processing simultaneous laser ranging data from Greenbelt and Wallops Island in a combined optical-laser solution. Comparisons of these results with previous GSFC dynamical solutions indicate an rms agreement on the order of 4 meters or better in each coordinate. Comparison with a detailed gravimetric geoid of North America yields agreement of 3 meters or better for mainland U.S. stations and 7 and 3 meters, respectively, for Bermuda and Puerto Rico.
The existence of large terrestrial impact crater doublets and Martian crater doublets that have been inferred to be impact craters demonstrates that simultaneous impact of two or more bodies occurs at nearly the same point on planetary surfaces. An experimental study of simultaneous impact of two projectiles near one another shows that doublet craters with ridges perpendicular to the bilateral axis of symmetry result when separation between impact points relative to individual crater diameter is large. When separation is progressively less, elliptical craters with central ridges and central peaks, circular craters with flat floors containing ridges and peaks, and circular craters with deep round bottoms are produced. These craters are similar in structure to many of the large lunar craters.
The theory of transient mode-locking for an active modulator in a laser with a homogeneously broadened line is presented. The theory is applied to simultaneously Q-switched and mode-locked Nd:YAG lasers and good agreement between theory and experiment is obtained. The main conclusion is that under usual Q-switched operating conditions the mode-locking process does not have sufficient time to build up to steady-state conditions. We also present a method to overcome this problem by allowing the laser to prelase before the Q-switch is opened. Mode-locked pulses whose width approaches the steady-state value are obtained. The transient mode-locking theory presented here also applies to actively mode-locking TEA CO2 lasers and to other types of simultaneously pulsed and mode-locked lasers.
A method and apparatus is described for obtaining simultaneous tracking data from two ground stations relative to a spacecraft, and in particular for obtaining two-way range and Doppler measurements with respect to the spacecraft using only one transponder on the spacecraft. The technique employs simultaneous transmission from two stations to produce a return signal with upper and lower sidebands resulting from the interference of the two transmissions. A transponder transmits the upper and lower sidebands centered about a carrier received by both stations. One station tracks the carrier and the other tracks a sideband aided by the carrier.
Two sequential methods of planimetric SLAR (Side Looking Airborne Radar) block adjustment, with and without splines, and three simultaneous methods based on the principles of least squares are evaluated. A limited experiment with simulated SLAR images indicates that sequential block formation with splines followed by external interpolative adjustment is superior to the simultaneous methods such as planimetric block adjustment with similarity transformations. The use of the sequential block formation is recommended, since it represents an inexpensive tool for satisfactory point determination from SLAR images.
The suggested association of X Persei with the weak X-ray source 3U 0352+30 raises the possibility of detection of X-ray/optical covariability. The paper reports a successfully conducted simultaneous optical/X-ray observation utilizing ground-based photometry and a satellite-borne proportional counter. Photoelectric photometry of X Persei was obtained on five out of seven consecutive nights in January 1975. The observations yield the faintest and bluest photoelectric magnitudes and colors ever reported for X Per; this change apparently occurred relatively uniformly during 1973-74 and is reminiscent of behavior last observed in about 1900. On January 21, 7 hr of data were obtained simultaneously with OAO Copernicus X-ray observations of 3U 0352+30. The X-ray flux varied during this period by a factor of 2, but there is no obviously correspondent optical activity, to a level of 0.02 mag. The optical data are also used to limit the 0.01-mag variations coincident with the X-ray periodicity reported by White et al. (1976).
Results are presented for simultaneous observations of whistlers at two Alaskan stations (L roughly 4) during one occasion lasting 24 hr, another lasting 10 hr, and a third lasting 6 hr. Of the three periods of simultaneous observations studied, two showed patterns of equatorial electron density which were stationary in L-LMT space and which were unchanging for at least 1.5 hr of UT. The third showed a marked change, the nature of which being accounted for by east-west gradients corotating with the stations. All three periods exhibited persistent stationary patterns of whistler duct tracks, each thin in the cross-L direction and extensive in the east-west direction. It would appear that either the ducts are stable shells or there is a succession of ducts arrayed along the contours and possibly corotating with the earth along the stationary tracks. Multistation direction finding on the whistler exit points may elucidate the relevant interpretations.
Eighteen events of large-amplitude (0.4-6 gammas) waves which may be propagating in the ion cyclotron mode have een observed by Explorer 45. Comparison with simultaneously measured proton distributions has allowed the events to be divided into two categories. The first category consists of waves accompanied by enhanced ion fluxes apparently injected into the plasmasphere with anisotropic pitch-angle distributions. This simultaneity suggests that these waves may be generated by the observed ring-current ions. Waves in the second category were found near or outside the plasmapause and were not correlated with any identifiable changes in the observed proton distribution. The generation mechanism for these waves remains unknown.
A method for simultaneous reproduction of images, requiring different amounts of time to reproduce, on a cathode ray tube (CRT) screen is disclosed. Ultrasonic sectional views and electrocardiogram curves are simultaneously reproduced on the CRT screen by producing the images on different areas of a screen with two phosphors having different persistence times and luminous colors, within the times required for the appearance of the images. In front of the area on which is produced the image requiring the shorter time is a color filter which is permeable to the color of the phosphor with the shorter persistence time by which absorbs the color of the other phosphor.
Energetic proton bursts were observed simultaneously on Imp 6, 7, and 8 both inside and outside the earth's magnetosphere during the period October 1972 through August 1974. It is found that proton bursts are present nearly simultaneously in the vicinity of the outer belt trapping boundary, in the low-latitude magnetotail, in the magnetosheath, and upstream from the bow shock. Large intensity differences, time delays, and differences in energy spectra recorded by the three spacecraft are described. It is suggested that energetic protons and electrons are probably accelerated inside the plasma sheet and propagate to various regions both inside and outside the magnetosphere.
Results are reported for simultaneous Copernicus UV and X-ray observations of the massive binary system V861 Sco (possibly associated with the X-ray source OAO 1653-40) over a period of five orbital cycles from April to September 1978. It is found that the UV spectrum of V861 Sco is similar to that of a normal supergiant and that the X-ray flux from OAO 1653-40 is highly variable. A simultaneous change in the C III 1176-A line and the 3.8-8.8-keV X-ray flux is discussed which was detected when V861 Sco was observed in September 1978. The close correlation between the X-ray and UV events is taken to imply that the X-ray source OAO 1653-40 is coincident with V861 Sco. The event energetics and physical conditions in the region responsible for the C III 1176-A emission are considered. It is concluded that the most likely X-ray production mechanism is accretion by a gas stream onto a black hole.
It has been suggested that the very bright IR bursts observed from the Rapid Burster (MXB 1730-335) are due to Type I X-ray bursts. If the suggestion is correct, similar bright IR bursts may, in general, accompany Type I X-ray bursts. This paper investigates this possibility for one specific case. During the 1977 coordinated worldwide burst watch, simultaneous X-ray and IR observations were made. On 00 h 00 min 25s June 17 UT, a Type I X-ray burst was observed, which was almost certainly emitted by Ser X-1 (MXB 1837+05, 4U1837+04). Simultaneous IR observations failed to detect any bursts.
Results of coordinated program of observations in the X-ray, UV, optical and radio regions of the dM5e flare star Proxima Centauri are presented. Simultaneous observations of the star were obtained on March 6 and March 7, 1979, by the Einstein Observatory IPC, the IUE SWP and LWR cameras at low dispersion, three ground-based optical telescopes in Australia and the Parkes 64-m radio telescope. A total of 10 radio bursts and six optical flares was detected during three nights of simultaneous radio and optical observations, which appear to be broadly correlated. A major X-ray flare event was detected with temperatures of 1.7 x 10 to the 7th and 1.2 x 10 to the 7th K during the rise and decay phases, respectively, respective X-ray fluxes of 3.0 x 10 to the -11th and 3.7 x 10 to the -11th ergs/sq cm per sec, and changes in spectral flux distribution. No radio, optical or UV flare emission corresponding to the X-ray flare was detected. The X-ray flare is interpreted in terms of an arch model with cooling predominantly by X-ray radiation, with an electron density of 1.0 x 10 to the 11th/cu cm during the decay phase and a total arch length comparable to the size of the star itself. The X-ray flare observed is thus more similar to a typical strong solar flare than heretofore seen on a flare star.
A program for the measurement of latitudinal, seasonal, and diurnal variations in stratospheric N2O, NO, NO2 and HNO3 is described, which uses airborne Fourier transform absorption spectroscopy to simultaneously determine columns, above 12 km, of the four molecules. The data may prove useful for comparison with two-dimensional models of stratospheric chemistry, since simultaneous measurement of several species with the same technique provides an inherently more reliable set for model comparisons, by eliminating uncorrelated atmospheric variability and reducing differences in instrumental biases.
The possibility of improving the accuracy of geodetic results by use of simultaneously observed ranges to Lageos, in a differencing mode, from pairs of stations was studied. Simulation tests show that model errors can be effectively minimized by simultaneous range differencing (SRD) for a rather broad class of network satellite pass configurations. The methods of least squares approximation are compared with monomials and Chebyshev polynomials and the cubic spline interpolation. Analysis of three types of orbital biases (radial, along- and across track) shows that radial biases are the ones most efficiently minimized in the SRC mode. The degree to which the other two can be minimized depends on the type of parameters under estimation and the geometry of the problem. Sensitivity analyses of the SRD observation show that for baseline length estimations the most useful data are those collected in a direction parallel to the baseline and at a low elevation. Estimating individual baseline lengths with respect to an assumed but fixed orbit not only decreases the cost, but it further reduces the effects of model biases on the results as opposed to a network solution. Analogous results and conclusions are obtained for the estimates of the coordinates of the pole.
Methods of obtaining information about the geometry of X-ray burster systems from simultaneous optical and X-ray observations are discussed, and such simultaneous observations of 4U/MXB 1636-53 are reported. The physical idea of an optical burst being due to reprocessing of an X-ray burst in material in the vicinity of the compact object is discussed. The resulting modification of the X-ray burst signal is described in terms of an optical response function. Delay and smearing due to radiative processes are discussed along with those due to the geometry. For 4U/MXB 1636-53, the estimated delay is 2.5 seconds, the smearing is less than four seconds, and the maximum temperature of the reprocessing region is about 75,000 K. The projected area of the reprocessing region is about 6 x 10 to the 21st square cm. The neutron star is about 1.4 solar masses, the radius of the accretion disk is greater than 1.5 lt-sec, and the mass of the Roche lobe filling companion star is less than 2.0 solar masses, corresponding to a binary period between about one and ten hours.