Showing papers by "Jet Propulsion Laboratory published in 1974"

Mercury's Surface: Preliminary Description and Interpretation from Mariner 10 Pictures.

Abstract: The surface morphology and optical properties of Mercury resemble those of the moon in remarkable detail and record a very similar sequence of events. Chemical and mineralogical similarity of the outer layers of Mercury and the moon is implied; Mercury is probably a differentiated planet with a large iron-rich core. Differentiation is inferred to have occurred very early. No evidence of atmospheric modification of landforms has been found. Large-scale scarps and ridges unlike lunar or martian features may reflect a unique period of planetary compression near the end of heavy bombardment by small planetesimals.

Magnetic field of Jupiter and its interaction with the solar wind

Abstract: Jupiter's magnetic field and its interaction with the magnetized solar wind were observed with the Pioneer 10 vector helium magnetometer. The magnetic dipole is directed opposite to that of the earth with a moment of 4.0 gauss R_J^3 (R_J, Jupiter radius), and an inclination of 15° lying in a system III meridian of 230°. The dipole is offset about 0.1 R_J north of the equatorial plane and about 0.2 R_J toward longitude 170°. There is severe stretching of the planetary field parallel to the equator throughout the outer magnetosphere, accompanied by a systematic departure from meridian planes. The field configuration implies substantial plasma effects inside the magnetosphere, such as thermal pressure, centrifugal forces, and differential rotation. As at the earth, the outer boundary is thin, nor diffuse, and there is a detached bow shock.

Venus: mass, gravity field, atmosphere, and ionosphere as measured by the mariner 10 dual-frequency radio system.

Abstract: Analysis of the Doppler tracking data near encounter yields a value for the ratio of the mass of the sun to that of Venus of 408,523.9 +/- 1.2, which is in good agreement with prior determinations based on data from Mariner 2 and Mariner 5. Preliminary analysis indicates that the magnitudes of the fractional differences in the principal moments of inertia of Venus are no larger than 10(-4), given that the effects of gravity-field harmonics higher than the second are negligible. Additional analysis is needed to determine the influence of the higher order harmonics on this bound. Four distinct temperature inversions exist at altitudes of 56, 58, 61, and 63 kilometers. The X-band signal was much more rapidly attenuated than the S-band signal and disappeared completely at 52-kilometer altitude. The nightside ionosphere consists of two layers having a peak density of 10(4) electrons per cubic centimeter at altitudes of 140 and 120 kilometers. The dayside ionosphere has a peak density of 3 X 10(5) electrons per cubic centimeter at an altitude of 145 kilometers. The electron number density observed at higher altitudes was ten times less than that observed by Mariner 5, and no strong evidence for a well-defined plasmapause was found.

The Apollo lunar sounder radar system

Abstract: The objectives of the Apollo 17 Lunar Sounder Experiment (ALSE) were to detect subsurface geologic structures, to generate a continuous lunar profile, and to image the moon a radar wavelengths. The first objective is generally impossible on Earth, but is possible on the moon because of the very low EM attenuation found in lunar rocks. A three-wavelength synthetic-aperture radar (SAR) operating at 60 m, 20 m, and 2 m (5, 15, and 150 MHz) was designed to attain these objectives. The design choices reflected a balance of scientific requirements versus Apollo mission and hard-ware constraints. The most difficult choice was that of wavelength, since longer wavelengths have the potential for deeper subsurface penetration at the expense of depth resolution. Shorter wavelengths enhance the ability to generate surface images and accurate profiles. The sounding requirement led to a system requirement for large dynamic range and precise sidelobe control. The radar data from the lunar mission were recorded on photographic film in a conventional SAR format, and were returned to Earth for processing. A combination of optical and digital processing and exploitation techniques was applied to the scientific interpretation of the data. Some preliminary results from the lunar mission have been obtained. The system design and data exploitation techniques developed in support of the ALSE experiment show considerable promise for eventual application to earth-resource survey radar systems.

Mariner 9 observations of the Mars north polar hood

Abstract: Mariner 9 photographs showing variations in the behavior of the Mars atmosphere over 21 consecutive days during northern winter are displayed. The photographs show the north polar cloud hood to be highly variable from day to day, with variations suggestive of development, motion, and decay of baroclinic waves. Lee wave clouds apparently composed primarily of water ice, convective cloud lines inferred to consist of CO2. ice. and dust clouds all occur frequently in the active region between latitudes 40 and 6ON. The wave clouds show that persistent surface westerlies and strong westerly shear occur in this region.

Venus: atmospheric motion and structure from mariner 10 pictures.

Abstract: The Mariner 10 television camieras imaged the planet Venus in the visible and near ultraviolet for a period of 8 days at resolutions ranging from 100 meters to 130 kilometers. Tle general pattern of the atmospheric circulation in the upper tropospheric/lower stratospheric region is displayed in the pictures. Atmospheric flow is symmetrical between north and south hemispheres. The equatorial motions are zonal (east-west) at approxiimnately 100 meters per second, consistent with the previously inferred 4-day retrograde rotation. Angular velocity increases with latitude. The subsolar region, and the region downwind from it, show evidence of large-scale convection that persists in spite of the main zonal motion. Dynamical interaction between the zonal motion and the relatively stationary region of convection is evidenced by bowlike waves.

Identification of human driver models in car following

Abstract: This paper presents the development of two new mathematical models of driver behavior in single-lane car following situations. Optimum parameter values in each of these models were obtained using standard parameter identification algorithms. The basic approach to model development was to derive the model structure using optimal control theory. The problem was formulated as a model-tracking problem and a quadratic cost function was minimized. Model parameters were optimized by comparing model behavior with freeway data obtained on Interstate 71 in Ohio by Clear and Treiterer. The results indicate that the models fit the data very well during acceleration and deceleration phases, but not during constant velocity regions. To obtain a better fit during transitions between acceleration and deceleration phases, a second model was postulated based on the hypothesis that the driver tracks not only the car directly in front of him, but also cars directly ahead of the lead car. An adaptive controller structure with a mode switching algorithm has been derived and its parameters optimized.

Carrier Synchronization and Detection of QASK Signal Sets

Abstract: A carrier regeneration loop which generates highly coherent quadrature reference signals for quadrature amplitude-shift keying (QASK) demodulation is presented. The loop employs the principle of decision feedback and has a structure analogous to a decision feedback loop for quadriphase signals suggested earlier in the literature. The error probabihty performance of QASK is computed in the presence of the noisy carrier reference signals provided by the above loop. It is demonstrated that when the ratio of data rate to loop bandwidth is 50 or greater, then for all practical purposes, ideal QASK error probability performance is achieved.

Positive Curvature of the H c 2 -versus- T c Boundaries in Layered Superconductors

Abstract: We have found what we believe to be a universal characteristic of layered superconductors: a positive curvature of the Hc2-versus-Tc boundary. The origins of the effect are believed to be associated with strong anisotropies of the Fermi surface and electron-phonon interaction.

A comparison of infrared, radar, and geologic mapping of lunar craters

Abstract: Between 1000 and 2000 infrared (eclipse) and radar anomalies have been mapped on the nearside hemisphere of the Moon. A study of 52 of these anomalies indicates that most are related to impact craters and that the nature of the infrared and radar responses is compatible with a previously developed geologic model of crater aging processes. The youngest craters are pronounced thermal and radar anomalies; that is, they have enhanced eclipse temperatures and are strong radar scatterers. With increasing crater age, the associated thermal and radar responses become progressively less noticeable until they assume values for the average lunar surface. The last type of anomaly to disappear is radar enhancement at longer wavelengths. A few craters, however, have infrared and radar behaviors not predicted by the aging model. One previously unknown feature - a field strewn with centimeter-sized rock fragments - has been identified by this technique of comparing maps at the infrared, radar, and visual wavelengths.

Latex spheres as markers for studies of cell surface receptors by scanning electron microscopy.

Abstract: THE distribution of antigens and carbohydrate residues on the surfaces of cells, notably erythrocytes and lymphocytes, can be determined by binding antibodies or lectins to such macromolecules as ferritin1,2, haemocyanin3,4 or peroxidase2,5, which serve as markers for transmission electron microscopy. Improved techniques in high resolution scanning electron microscopy (SEM), however, make it possible to determine the topographical distribution of molecular receptors on the surfaces of cells and tissues by similar histochemical techniques involving markers resolvable by SEM. LoBuglio et al.6 used commercial polystyrene latex particles, 2,300A in diameter, as immunological markers for SEM work. But applications of this reagent are limited because the hydrophobic surface of the particles makes them stick non-specifically to many surfaces and molecules.

Computer interface system

Abstract: An interface logic circuit permitting the transfer of information between two computers having asynchronous clocks is disclosed. The information transfer involves utilization of control signals (including request, return-response, ready) to generate properly timed data strobe signals. Noise problems are avoided because each control signal, upon receipt, is verified by at least two clock pulses at the receiving computer. If control signals are verified, a data strobe pulse is generated to accomplish a data transfer. Once initiated the data strobe signal is properly completed independently of signal disturbances in the control signal initiating the data strobe signal. Completion of the data strobe signal is announced by automatic turn-off of a return-response control signal.

Mercury: results on mass, radius, ionosphere, and atmosphere from mariner 10 dual-frequency radio signals.

Abstract: Analysis of the radio-tracking data from Mariner 10 yields 6,023,600 plus or minus 600 for the ratio of the mass of the sun to that of Mercury, in very good agreement with values determined earlier from radar data alone. Occultation measurements yielded values for the radius of Mercury of 2440 plus or minus 2 and 2438 plus or minus 2 kilometers at latitudes of 2 N and 68 N, respectively, again in close agreement with the average equatorial radius of 2439 plus or minus 1 kilometers determined from radar data. The mean density of 5.44 grams per cubic centimeter deduced for Mercury from Mariner 10 data thus virtually coincides with the prior determination. No evidence of either an ionosphere or an atmosphere was found.

Real time analysis of voiced sounds

Abstract: A power spectrum analysis of the harmonic content of a voiced sound signal is conducted in real time by phase-lock-loop tracking of the fundamental frequency, fo, of the signal and successive harmonics hl through hn of the fundamental frequency, measuring the quadrature power and phase of each frequency tracked, differentiating the power measurements of the harmonics in adjacent pairs and analyzing successive differentials to determine peak power points in the power spectrum for display or use in analysis of voiced sound, such as for voice recognition.

Transcontinental baselines and the rotation of the Earth measured by radio interferometry.

Abstract: Nine separate very-long-baseline interferometry experiments, carried out in 1972 and 1973 with radio telescopes 3900 kilometers apart, yielded values for the baseline length with an rms deviation about the mean of less than 20 centimeters. The corresponding fractional spread is about five parts in 100,000,000. Changes in universal time and in polar motion were also determined accurately from these data. The rms scatter of these results with respect to those based on optical methods was 2.9 msec and 1.3 m, respectively. Solid-earth tides were apparently detected, but no useful estimate of their amplitude was extracted.

A Discrete-Time Model for Cell-Age, Size, and DNA Distributions of Proliferating Cells, and its Application to the Movement of the Labeled Cohort

Abstract: The dynamics of cell cycle and proliferating kinetics are characterized by the state equations, which are linear difference matrix equations with their state vectors consisting of variables representing cells in a particular compartment for cell-age, cell-size, and cell-DNA content. The transformation required from the cell-age distribution to the cell-size and DNA distributions in this discrete-time model under various assumptions is derived. The asymptotic behavior (as the time approaches infinity) of the cell age, cell size, and cell DNA is studied. The time course of the cell-size distribution of labeled cells under flash labeling is investigated by computer simulation and favorably evaluated with the experimental results obtained for spontaneous AKR leukemia-cell population.

Microwave Doppler Shift Technique for Determining Solid Propellant Transient Regression Rates

Abstract: A microwave Doppler shift system, with increased resolution over earlier microwave techniques, was developed for measuring the regression rates of solid propellants during rapid pressure transients (104 to 10 5 IN cirr-sec). The system was used in two different transient combustion experiments: a rapid depressurization bomb and in the high-frequency acoustic pressure environment of a T-burner. In the rapid depressurization tests the measured apparent regression rates generally fell near or below the steady-state rate at the corresponding pressure and exhibited oscillations in tests near the critical depressurization rates for extinguishment. Unreasonably high oscillatory regression rates were obtained in the T-burner experiments. The results of a set of parameteric calculations indicated that flame ionization effects could be of sufficient magnitude to account for these anomalies. A direct comparison of the analytical predictions and experimental results yielded the conclusion that flame ionization effects probably produced some errors in the absolute values, but not the general characteristics, of the rapid depressurization regression rate measurements.

Viewing Phobos and Deimos for Navigating Mariner 9

Abstract: A new on-board optical navigation data technique has been successfully demonstrated on Mariner 9. Science TV pictures of Phobos and Deimos against star fields were used in the real time navigation process to insert Mariner 9 into orbit about Mars. Real time and post flight evaluation results have shown that the satellite/star data taken by Mariner 9 was more accurate than preflight analysis indicated. In fact the orbital insertion phase of the mission could have been achieved using only optical data to determine encounter parameters. The use of a science TV camera to obtain this data was successfully demonstrated. Stars as dim as 9th magnitude were detected and measurement accuracies of 3 arc sec (1 sigma) were achieved. The success of the optical navigation techniques developed for Mariner 9 has placed a new class of demanding missions (e.g., multiple outer planet, satellite tour, etc) within realized navigation capability.

Multitarget sequential sputtering apparatus

Abstract: A sputtering apparatus includes a single cathode on which a plurality of targets of different materials are supported, with a rotatable anode, supporting a substrate and/or substrates, spaced apart from the cathode in a chamber containing an inert gas at a selected pressure A potential difference is applied between the cathode and anode to produce a plasma for each target, which is sputtered by accelerated ions within the plasma Apertured plates and shields are positioned between the targets and the anode to effectively separate the plasmas into separate columns The sputtered material from each target having access to the substrate/substrates only through that target's column The shields are biasable by a voltage gradient to sumultaneously and equally control the current in each plasma Each column has a separate bias ring associated therewith, which is biasable to a separate voltage to individually control the plasma in its associated column Also included are movable shutters The various parts are assembled so that when the substrate is aligned with any target only sputtered material from that target reaches the substrate through the plasma column and from no other target As the anode is rotated from the first target to align with the second target, during the transition the deposition takes place continuously, first from the first target, followed by deposition from both targets and finally from the second target, thereby controlling the interface structure and preventing any inter-layer contamination and providing a near perfect controlled interface

Detonation Propulsion for High Pressure Environments

Abstract: One limitation encountered by chemical rocket propulsion in high-pressure planetary atmospheres is illustrated by the conflict between the dependence of specific impulse on the ratio of chamber pressure to ambient pressure and the dependence of the motor structural design on the difference between the pressures. This work proposes to resolve the difficulty by employing detonating propellant in which the high pressures necessary for efficient propulsion are developed over a short time and need not be contained statically. Experimental results are presented to substantiate this claim of relatively high performance, together with an analytical development that approximately describes the flow dynamics. Nomenclature A = nozzle cross-sectional area ca — speed of sound in ambient gas CD = flow coefficient ea = specific energy released in explosion, EJme Ea — energy released in explosion Ea' = energy released per solid angle, Ejai /i/2 = functions of y, Eq. (15) /3 = function, Eq. (19) F = axial thrust g = acceleration of gravity gc = conversion constant G = integral, Eq. (16) H = integral, Eq. (16) Ht = total enthalpy A/I = height / = specific impulse L = axial length of nozzle m = mass of gas ma = mass of ambient gas contained in nozzle me = mass of explosive material ra = mass flow rate M = mass of equipment Mw = molecular weight P = static pressure Pa = ambient pressure Po = plateau pressure Ap = pressure difference, Pt — Pa r — radial distance from apex of cone re = effective radial length of nozzle, Table 4 R = gas constant Ru = universal gas constant Ri = characteristic radial length, Eq. (17) t — time T = temperature u = velocity V = volume z = elevation a = function of y, Table 3 y = specific heat ratio

Lunar gravity: apollo 15 doppler radio tracking

Abstract: New detailed gravity measurements were obtained over a 10- to 70-km surface strip from − 70° to + 70° long. during low-altitude orbits (≈ 12 km at periapsis). The trajectory path (Figure 1) went over the centers of both Maria Serenitatis and Crisium, providing a complete center gravity profile of two large mascons. Consistent with the previous results for Mare Nectaris and Mare Humorum, both Serenitatis and Crisium mascons are approximately disk-shaped near-surface mass anomalies of net uncompensated loading, 800 kg cm−2. This strengthens Booker's contention that all mascons are approximately the same thickness. Also revealed for the first time are significant positive gravity measurements over mountain ranges - Apennines (near Hadley Mountain) and the Marius Hills. The data suggests that the Apennines have undergone some isostatic compensation, whereas the Marius Hills have not. The crater anomalies detected are all consistently negative as observed before, implying loss of mass from the impact event which formed them.

DC-to-DC converters employing staggered-phase power switches with two-loop control

Abstract: Boost, buck and buck-boost dc-to-dc converters employing a plurality of parallel staggered-phase power switches with two-loop control. A switched inductor voltage is coupled to a sense winding in each phase, and all sense windings are connected in series to one of two feedback loops to provide a signal that indicates when one of the power switches is on as the principal determinant of switching instants. A sequencer is triggered each time a pulse generator is triggered to turn on a different power switch in sequence at each switching instant.

Orbit design concepts for Jupiter orbiter missions

Abstract: Advanced mission and orbit planning efforts are currently in progress for a Mariner-class Jupiter orbiter. Baseline spacecraft and orbit design criteria are the goals of a NASA effort to define such a mission. Orbit design concepts that have been discovered during the early stages of mission planning are both challenging and exciting. A description is given of several such concepts that may greatly increase the flexibility and scientific return of orbiters designed for close study of the Galilean satellites and exploration of the Jovian system. Some new jargon is introduced in discussions to describe the exploitation of gravity-assist trajectories using the giant satellites for orbit control. Orbit 'pumping' and 'cranking' and 'resonance hopping' are defined and shown to be dynamically feasible means of controlling the orbit and, thus, the scientific return. A candidate encounter sequence is presented for an equatorial tour of the Galilean moons.