Stabilized CO2 gas laser Quarterly report, 1 Jun. - 1 Sep. 1967
Sealed off, 20 watt, stabilized single frequency carbon dioxide laser
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Statistical and stability analyses of neural pulse frequency modulator Semiannual status report, period ending 1 Feb. 1969
Statistical analysis of neural pulse frequency modulator
Hutchinson, C. E.↗
Compensator improvement with an application to a large space vehicle
Compensator improvement program with application to large space vehicles and tables noting relative stability versus frequency response
Mitchell, J. R.↗
Response-produced timeouts under a progressive-ratio schedule with a punished reset option
An attempt is made to extend the generality of timeouts from positive reinforcement to more complex performances. Pigeons were provided with three continuously available options. Responses on one key resulted in food reinforcement under a progressive-ratio schedule, which requires a larger number of responses for successive reinforcements; responses on a second key, which were shocked, reset the progressive-ratio schedule to its first step; and responses on a third key produced a 3-min timeout. Some of these conditions have been studied previously (Dardano, 1968, 1973; Findley, 1958). Questions of general interest included the frequency and stability of response-produced timeouts, changes in the properties of the progressive-ratio performance resulting from the occurrence of timeouts, and the similarity of the relationships between timeouts and the reinforced behavior to relationships found under simpler conditions of reinforcement.
Dardano, J. F.↗
Influence of thermal distortion on the anomalous behavior of a gravity gradient satellite
Consideration of the problem of determining the influence of solar heating on the low-frequency dynamic stability of a gravity-gradient satellite. The scope of the effort includes the development of a computer program that uses a quasi-static approach for describing a satellite's unsteady orbital motion. The essential feature of the quasi-static approach is that the satellite's long, slender booms reach their thermal equilibrium position solely as a result of thermal bending without consideration of the dynamic effects of boom vibration. A nonlinear analytical model and a corresponding computer program have been developed to study the effect of absorptivity, sun angle, and hinge stiffness on the stability of a satellite's motion.
Goldman, R. L.↗
Low-G fluid behavior technology summaries
This report presents a summarization and categorization of the pertinent literature associated with low-g fluid behavior technology. Initially a literature search was conducted to obtain pertinent documents for review. Reports determined to be of primary significance are summarized in detail. Each summary, where applicable, consists of; (1) report identification, (2) objective(s) of the work, (3) description of pertinent work performed, (4) major results, and (5) comments of the reviewer (GD/C). Pertinent figures are presented on a single facing page separate from the text. Specific areas covered are; interface configuration, interface stability, natural frequency and damping, liquid reorientation, bubbles and droplets, fluid inflow, fluid outflow, convection, boiling and condensation heat transfer, venting effects, and fluid properties. Reports which were reviewed and not summarized, along with reasons for not summarizing, are also listed. Cryogenic thermal control and fluid management systems technology are presented.
Stark, J. A.↗
Processing equations for state-space models
Three computer programs comprising six subroutines are used to calculate matrix stability and frequency response.
Seidel, R. C.↗
The DSN VLBI System, Mark 1-79
Very long baseline interferometry is a new capability being implemented in the DSN to support flight project navigation requirements and provide station frequency standard stability monitoring of sufficient accuracy to effectively validate hydrogen maser performance. A description of the system and the phases of its implementation are provided.
Mulhall, B. D. L.↗
Simple JFET oscillator
Device used in mixers, modulators, and function generators provides stable sine-wave signal compatible with both integrated circuits and discrete-component assemblies. Oscillator's frequency is tunable over narrow band about design value. Frequency range, stability, linearity, and low power drain of device are suited to communications receivers and transmitters and digital microprocessors, computers, and displays. Circuit simplicity allows for easy monolithic construction.
Kleinberg, L. L.↗
Geomagnetic field mapping from a satellite: Spatial power spectra of the geomagnetic field at various satellite altitudes relative to natural noise sources and instrument noise
The spectra for the field are presented together with power spectra of the natural magnetospheric and ionosheric noise and a power spectrum of instrumental noise for a typical fluxgate magnetometer. The source of these data is described. The implications of these data relative to desirable instrument frequency resonse, stability and resolution specification as well as the implications relative to desirable spacecraft position and orientation accuracy specifications and desirable environmental (temperature, magnetic noise) specifications are discussed. Implications of these power spectra relative to choice of a suitable magnetometer and relative to desirable methods of data processing are considered. Finally, implications for desirable orbit and mission duration are discussed.
Mcleod, M. G.↗
Practical gust load alleviation and flutter suppression control laws based on a LQG methodology
A modified linear quadratic Gaussian (LQG) synthesis procedure has been used to design low-order robust multiloop controllers for a flexible airplane. The introduction of properly constructed fictitious Gauss-Markov processes in the control loops allowed meeting classical frequency-domain stability criteria using the direct synthesis procedures of modern time-domain control theory. Model reduction was used to simplify the control laws to the point where they could be easily implemented on onboard flight computers. These control laws provided excellent gust load and flutter mode control with good stability margins and compared very favorably to other control laws synthesized by the classical root-locus technique.
Gangsaas, D.↗
Absorption technique for OH measurements and calibration
An absorption technique is described which utilizes a stabilized frequency-doubled tunable dye laser and a long-path White cell with high mirror reflectivities both in the red and UV. In laboratory conditions it has been possible to routinely obtain a detection sensitivity of 3 parts in 1,000,000 over absorption paths less than 1 m in length and a detection sensitivity of approximately 6 parts in 100,000 over an absorption path of the order of 1 km. The latter number corresponds to 3,000,000 OH molecules/cu cm, and therefore the technique should be particularly useful for calibration the fluorescence instrument for OH measurements. However, the presence of atmospheric fluctuations coupled with intensity variation accompanying frequency scanning appears to degrade the detection sensitivity in outdoor ambient conditions, thus making it unlikely that this technique can be employed for direct OH monitoring.
Bakalyar, D. M.↗
Standards for Epoxies Used in Microelectronics
Improved qualification standards and test procedures for epoxy adhesives used in assembly of high-reliability hybrid microcircuits listed in new report. Objective of standards to resolve problems in areas of outgassing, bond shear strength, corrosivity, volume resistivity, ionic impurities, electrical stability, and frequency of qualification testing. pp
Caruso, S. V.↗
Temperature stability of transit time delay for a single-mode fibre in a loose tube cable
The effect of temperature on the transit-time delay of a loose-tube-type single-mode optical-fiber cable is investigated experimentally. A 1058-m length of cable was placed loosely coiled in an oven and used to connect a 820-nm single-mode laser diode to a high-speed avalanche-photodiode detector feeding a vector voltmeter; the signal was provided by a high-stability frequency-synthesized generator. Measurements were made every 2 C from -50 to 60 C and compared to those obtained with a 200-m lacquered bare fiber. The phase change of both fibers varied with temperature at a positive slope of 6-7 ppm/C. This value is significantly better than those reported for other cable types, suggesting the application of loose-fiber cables to long-haul gigabit digital transmissions or precision time-base distribution for VLBI.
Bergman, L. A.↗
Stability investigation of the quadripod structure for the NASA/JPL 70-meter antenna
A new, slim-profiled, low-blockage quadripod structure was designed to support the 7.7-m-diameter subreflector for the 70-m antenna. Detailed analyses of quadripod structural stability (in frequency and buckling) are presented. The results indicate that the new quadripod design has an adequate safety margin for buckling, and its lowest natural frequency is above the control system bandwidth. The analytical design frequencies were confirmed by actual field measurements made in Spain in February 1986.
Chian, C. T.↗
Ultra-Stable Superconducting-Maser Oscillator
Unprecedented stability of frequency in superconducting, triple-cavity ruby maser oscillator achieved by incorporation of amplitude-control subsystem. New design enhances ultra-stable measurements of time by reducing fluctuations to 2 X 10 to negative 19th power routinely, and to as little as 10 to negative 20th power in exceptional cases. Currents induced in superconducting pickup coil by changes in magnetic field in ruby. Currents from coil fed to superconducting quantum-interference device (SQUID) magnetometer, output used to generate control signal for electronically variable attenuator. Attenuator varies pump-signal amplitude in response to magnetic-field fluctuations in ruby. Very high feedback-loop gain used for sensitivity of control and adequate compensation of fluctuations.
Strayer, Donald M.↗
Aeroelasticity and structural optimization of rotor blades with swept tips
In the present FEM scheme for the aeroelastic modeling of a swept-tip rotor blade, the swept tip of the blade is assumed to undergo moderate deflections in the flap, lag, and torsion degrees-of-freedom. The nonlinear PDEs of motion are discretized by a Galerkin-type FEM. This aeroelastic stability-and-response computational capability is combined with a structural optimization analysis to minimize the n/rev vertical hub shears in forward flight, subject to aeroelastic stability and frequency placement constraints. Tip sweep is used as a design variable to reduce vibration levels in forward flight.
Friedmann, P. P.↗
Radiometer system requirements for microwave remote sensing from satellites
An area of increasing interest is the establishment of a significant research program in microwave remote sensing from satellites, particularly geosynchronous satellites. Due to the relatively small resolution cell sizes, a severe requirement is placed on beam efficiency specifications for the radiometer antenna. Geostationary satellite microwave radiometers could continuously monitor several important geophysical parameters over the world's oceans. These parameters include the columnar content of atmospheric liquid water (both cloud and rain) and water vapor, air temperature profiles, and possibly sea surface temperature. Two principle features of performance are of concern. The first is the ability of the radiometer system to resolve absolute temperatures with a very small absolute error, a capability that depends on radiometer system stability, on frequency bandwidth, and on footprint dwell time. The second is the ability of the radiometer to resolve changes in temperature from one resolution cell to the next when these temperatures are subject to wide variation over the overall field-of-view of the instrument. Both of these features are involved in the use of the radiometer data to construct high-resolution temperature maps with high absolute accuracy.
Juang, Jeng-Nan↗