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Bolometric magnitudes for a large number of M type dwarf stars, obtained by broadband infrared photometry at 1.65, 2.2, and 3.5 microns, are reviewed. The data obtained indicate that one parameter is sufficient to describe the blanketing in all of the UBVRI bands for all types of M dwarfs. In general, late M dwarfs seem to have lower effective temperatures than are predicted by theoretical models.
Analysis of Morrison and Cruikshank's (1974) infrared flux measurements of Uranus and Neptune shows that Uranus is probably in equilibrium with the incident solar flux, while Neptune probably radiates 2.4 times as much energy as it receives from the sun, implying an internal heat source of 1.4 times the solar input. On the basis of very broadband data (1.5 to 300 micron) Jupiter has been shown to radiate more energy than it receives from the sun. Of the Jovian planets, only Uranus, the least massive, appears to lack an internal heat source.
The solar disturbances of August 1972 produced large-scale solar wind perturbations that were detected by the Pioneer 9 plasma probe, electric field detector, and magnetometer for an extended time period commencing early on August 3. During this ten-day interval the interplanetary plasma parameters at r approximately equal 0.8 AU varied over unusually wide ranges, so that the conditions for generation of high and low VLF wave levels could be identified fairly readily. It is demonstrated that no measurable signals were detected in the broadband electric field channel (sensitive to waves with f greater than or equal to 100 Hz in the spacecraft frame of reference) unless the proton density was high enough to yield a proton plasma frequency with f greater than or about equal to 100 Hz. The analysis suggests that waves related to ion acoustic oscillations were detected throughout the extended storm period.
Plasmaspheric hiss is broadband ELF noise between 100 and 2000 Hz generally occurring inside the plasmasphere. It is proposed that some plasmaspheric ELF hiss is generated by ring current protons. The mechanism by which waves are generated is the anisotropic proton instability magnetospheric (APIM) hiss mechanism. APIM hiss (with a frequency close to the lower hybrid resonance frequency) is a loss-cone, flute instability arising from proton velocity space anisotropies. The energy driving the waves comes from the free energy of the 'inverted population' of the proton loss-cone distribution. The APIM hiss mechanism predicts the bandwidth, center frequency, source location, and wave normal angle of some types of plasmaspheric hiss. APIM hiss is suggested as a possible additional loss mechanism for ring current protons.
Parametric amplification of microwaves was observed using thin-film junctions of the Anderson-Dayem type. A series of 80 such junctions were incorporated into the upper conductor of a broadband 50-ohm microstrip transmission line with no DC bias. The amplifier was operated in the 'doubly degenerate' mode with signal, pump, and idler frequencies closely and equally spaced. An electronic gain of 12 dB at 10 GHz was observed. The bandwidth was measured to be 1 GHz and the noise temperature to be less than 20 K.
An experimental investigation was conducted in an anechoic flow facility to explore problems and methods of measuring the airframe (nonpropulsive) noise associated with a 1/20-scale model of a B-737 transport. The test model geometry simulated the cruise and a landing configuration. Nonpropulsive model noise was detected at various flow velocities and at various angles of attack when turbulent flow was induced over the model. Discrete tones, associated with the extended undercarriage and wheel cavities, and an increase in broadband sound pressure level were observed with the model in a landing configuration.
Charge build-up on spacecraft surfaces and resulting zones of electrostatic contamination have been examined for electrically active and electrically passive spacecraft with both conducting and dielectric surface materials, illuminated and nonilluminated surface conditions, and for both inclusion and neglect of free charge effects from photocurrents and ambient space plasma particles. Techniques for measurement and reduction of electrostatic contamination zone extent have been developed for spacecraft with charge release capability. Indicated limitations for contamination cleanup are about 1 volt potential variation from spacecraft to ambient plasma. Bandwidths of electrostatic monitoring and clamping devices extend to several hundred kilohertz for both DC and 'broadband' AC electrostatic cleanliness.
We have observed Rhea (S5) at 1.6 and 2.2 microns at Mt. Wilson using the Caltech photometer on the 1.52 m and 2.54 m telescopes. The infrared spectral reflectances relative to 0.55 micron are 0.8 at 1.65 micron and 0.6 at 2.2 microns. Such absorption bands in the near infrared are not consistent with spectra of most rocks or minerals; even carbonaceous chondritic materials have nearly flat reflectances over this spectral region. Frosts, however, have strong absorption bands in the 1-3 microns region. In particular, the broadband infrared reflectances of Rhea are similar to those of the Galilean satellites Europa (J2) and Ganymede (J3) and also the rings of Saturn. Rhea's low density, high albedo and relatively flat reflectance from 0.3 to 1.1 micron as well as the low infrared reflectances reported here are consistent with the presence of water ice on Rhea's surface.
Broadband electric field data are presented which show stepped leader wave forms preceding records of distant lightning return strokes. The majority of leader pulses are characterized by a large initial peak with a small and slow opposite overshoot. Total pulse durations range from 15-40 microsec several milliseconds before the return stroke to 2-10 microsec immediately preceding the return stroke. Close to the ground the stepped leader pulses occur at regular 10- to 20-microsec intervals and are almost unipolar with rise times of about 1 microsec and full widths at half maximum in the range from 1 to 3 microsec. The ratio of the peak of the last leader pulse to the subsequent return stroke peak is typically 0.1, which suggests a peak step current near the ground of about 10% of the return stroke peak current.
The 7.3 kg cameras for the 1976 Viking Mars expedition feature an array of 12 silicon photodiodes, including six spectral bands for color and near-infrared imaging with an angular resolution of 0.12 deg and four focus steps for broadband imaging, with an improved angular resolution of 0.04 deg. The field of view in elevation ranges from 40 deg above to 60 deg below the horizon, and in azimuth ranges to 342.5 deg. The cameras are mounted 0.8 m apart to provide a stereo view of the area accessible to a surface sampler for biological and chemical investigations. The scanning rates are synchronized to the lander data transmission rates of 16000 bits per sec to the Viking orbiters as relay stations and 250 bits per sec directly to earth. However, image data can also be stored on a lander tape recorder. About 10 million bits of image data will be transmitted during most days of the 60-day-long mission planned for each lander.
A set of acoustically-treated long-chord vanes was designed to replace the vanes in an existing fan stage to investigate the noise reduction possibilities of both increased stator chord length and a method of incorporating acoustic damping material. The vanes were tested with both active and inactive acoustic surfaces. Results of the inactive tests show significant broadband noise effects with noise reductions in the middle to high frequencies and an increase at low frequencies. No reduction in blade passage tone was observed, but decreases in the overtones were observed. Results of the tests with the active acoustic treatment show large noise reductions over a wide frequency range.
Narrowband analysis revealed grossly similar sound pressure level spectra in each facility. Blade passing frequency (BPF) noise and multiple pure tone (MPT) noise were superimposed on a broadband (BB) base noise. From one-third octave bandwidth sound power analyses the BPF noise (harmonics combined), and the MPT noise (harmonics combined, excepting BPF's) agreed between facilities within 1.5 db or less over the range of speeds and flows tested. Detailed noise and aerodynamic performance is also presented.
The fourth ASSESS Spacelab simulation mission utilizing a Lear Jet aircraft featured trained experiment operators (EOs) in place of the participating scientists, to simulate the role and functions of payload specialists in Spacelab who may conduct experiments developed by other scientists. The experiment was a broadband infrared photometer coupled to a 30-cm, open port, IR telescope. No compromises in equipment design or target selection were made to simplify operator tasks; the science goals of the mission were selected to advance the mainline research program of the principle investigator (PI). Training of the EOs was the responsibility of the PI team and consisted of laboratory sessions, on-site training during experiment integration, and integrated mission training using the aircraft as a high-fidelity simulator. The EO permission experience in these several disciplines proved adequate for normal experiment operations, but marginal for the identification and remedy of equipment malfunctions. During the mission, the PI utilized a TV communication system to assist the EOs to overcome equipment difficulties; both science and operations were successfully implemented.
Narrow band Ross filter measurements of the Fe 25 line flux around 0.185 nm and simultaneous broadband measurements during a solar flare were used to determine the relationship between the solar coronal abundances of iron and helium. The Fe 25 ion population was also determined as a function of time. The proportional counter and the Ross filter on OSO-7 were utilized. The data were analyzed under the separate assumptions that (1) the electron density was high enough that a single temperature could characterize the continuum spectrum and the ionization equilibrium, and that (2) the electron density was low so that the ion populations trailed the electron temperature in time. It was found that the density was at least 5x10 to the 9th power, and that the high density assumption was valid. It was also found that the iron abundance is 0.000011 for a helium abundance of 0.2, relative to hydrogen.
An existing fan stage, redesigned to reduce stator lift fluctuations, was acoustically tested for reduced noise generation. The lift fluctuations on the stator were reduced by increasing the stator chord, adjusting incidence angles, and by adjusting the rotor velocity diagrams. The experiments showed significantly reduced broadband noise levels in the middle to high frequencies. Blade passage tone power was not reduced, but decreases in the harmonics were observed. Aerodynamic improvements in both performance and efficiency were obtained.
The results of the evaluation of two response prediction methods relating to the prediction of structural responses of stiffened shell structures with or without attached components, and subjected to broadband acoustic excitations are presented. The methods under evaluation were the constant mass attenuation method and the impedance ratio method. Example problems were used to illustrate the application procedures of these two methods and to compare their predicted results with the experimentally measured data. It is found that more realistic estimates of the structural response can be obtained by the impedance ratio method.
Noise spectra were measured in three dimensions for several surfaces immersed in turbulent flow from a jet and over a range of flow conditions. The data are free field and were corrected to remove the small contributions of jet noise, atmospheric attenuation and feedback tones. These broadband data were compared with the results of available theories which are only strictly applicable to simple geometries over a limited range of conditions. The available theories proved to be accurate over the range of flow, chord length, thickness, angle of attack, and surface geometries defined by the experiments. These results apply to the noise generated by fixed surfaces in engine passages, the lifting surfaces of aircraft and also to fan noise.
The results of a fan noise data analysis and prediction effort using experimental data obtained from tests on the QF-1B research fan are described. Surface pressure measurements were made with flush mounted sensors installed on selected rotor blades and stator vanes and noise measurements were made by microphones located at the far field. Power spectral density analysis, time history studies, and calculation of coherence functions were made. The emphasis of these studies was on the characteristics of tones in the spectra. The amplitude behavior of spectral tones was found to have a large, often predominant, random component, suggesting that turbulent processes play an important role in the generation of tonal as well as broadband noise. Inputs from the data analysis were used in a prediction method which assumes that acoustic dipoles, produced by unsteady blade and van forces, are the important source of fan noise.