Showing papers by "Jet Propulsion Laboratory published in 1972"
TL;DR: In this article, spectral features due to the atmospheric dust storm indicate that large diurnal variations in atmospheric temperature existed up to at least 30 km; winds inferred from the temperature fields show a strong tidal component and significant ageostrophic behavior.
313 citations
TL;DR: The kinds, numbers, and distribution of soil microorganisms in the valleys are investigated in order to gain insight into the practical problems of searching for life in an extreme environment and as they apply to martian exploration.
Abstract: The dry valleys of South Victoria Land, Antarctica, together with a few other ice-free areas on the perimeter
of the Antarctic continent, form what is generally considered to be the most extreme cold-desert region of the earth. During the past S years, we have been interested in the dry valleys as a model environment for investigating questions connected with the biological exploration
o£ Mars. The extraordinary aridity of the region, its low temperature, and its geographical isolation give it a quasimartian character, although it is to be
understood that the actual martian environment is still more hostile than that of the valleys. With our associates, we have investigated the kinds, numbers, and distribution of soil microorganisms in the valleys in order to gain insight into the practical problems of searching for life in an extreme environment. Detailed results of these studies have been published by Cameron and co-workers (1-5). In this-article, we review the major findings of our own and of other groups of investigators in this region,
especially as they apply to martian exploration.
203 citations
TL;DR: In this paper, an efficient and practical method of simulating stationary and non-stationary random envelope processes is presented, in which the stationary envelope processes are simulated by using the fast Fourier transform while the nonstationary envelope process is simulated as the square root of the sum of a series of cosine functions with random phase angles.
195 citations
TL;DR: The surface of the planet was heavily obscured by a global dust storm during the first month in orbit, leaving a residual optical depth of about 0.1 as discussed by the authors, which suggests that the mean radius of the particles responsible for the obscuration was at least 10 microns.
133 citations
TL;DR: Mariner 9 ultraviolet spectrometer observations show that the Mars airglow consists principally of emissions that arise from the interaction of solar ultraviolet radiation with carbon dioxide, the principal constituent of the Mars atmosphere.
107 citations
TL;DR: In this paper, a comparison of averaged limb intensities of the CO2+ doublet and the Cameron bands on four favorable occasions is consistent with the intensities being directly proportional in a ratio of 0.24 to 1.
104 citations
89 citations
TL;DR: In this article, an experiment centering around a mass spectrometer is described, which is aimed at the identification of organic substances present in the top 10 cm of the surface of Mars and an analysis of the atmosphere for major and minor constituents as well as isotopic abundances.
88 citations
Patent•
03 Aug 1972TL;DR: In this paper, a technique and apparatus for optically detonating insensitive high explosives is described, in which an explosive device is formed by containing high explosive material in a housing having a transparent window and a thin metallic film is provided on the interior surface of the window and maintained in contact with the high explosive.
Abstract: A technique and apparatus for optically detonating insensitive high explosives, is disclosed. An explosive device is formed by containing high explosive material in a housing having a transparent window. A thin metallic film is provided on the interior surface of the window and maintained in contact with the high explosive. A laser pulse provided by a Q-switched laser is focussed on the window to vaporize the metallic film and thereby create a shock wave which detonates the high explosive. A plurality of explosive devices may be concurrently or sequentially detonated by employing a fiber optic bundle to transmit the laser pulse to each of the several individual explosive devices.
56 citations
TL;DR: An algorithm is presented for the generation of the Ford sequence of length 2n which does not require storage of the sequence and it is shown that the sequence does not need to be stored.
44 citations
TL;DR: The Mars infrared thermal mapper (IRTM) was carried on the scan platform of the orbiter of the Viking 1975 mission as discussed by the authors, which measured the reflected solar radiation and surface thermal emission from the area viewed by the imaging system with nominal 5 km resolution.
01 Jul 1972
TL;DR: In this paper, range measurements from the orbiting spacecraft to the lunar surface were made during the Apollo 15 mission using a laser altimeter, and the measurements were made in a plane inclined at approximately 26° with respect to the Moon equator.
Abstract: Range measurements from the orbiting spacecraft to the lunar surface were made during the Apollo 15 mission using a laser altimeter. The measurements were made in a plane inclined at approximately 26° with respect to the lunar equator. Analysis of measurements made during one complete lunar revolution indicates that the figure of the Moon is very complex. The lunar far side appears to be considerably rougher than the near side in this plane. There appears to be a very large depression on the far side centered at approximately 180° longitude. The near-side maria are depressed with respect to surrounding terrae. These data provide some proof that there is a displacement between the center of figure and the center of mass of the Moon.
TL;DR: In this paper, the authors study the compression of the remanent magnetic field by the solar wind, based on measurements of remanent magnetization at four Apollo landing sites and of the solar energy at two of these sites.
Abstract: Study of the compression of the remanent lunar magnetic field by the solar wind, based on measurements of remanent magnetic fields at four Apollo landing sites and of the solar wind at two of these sites. Available data show that the remanent magnetic field at the lunar surface is compressed as much as 40% above its initial value by the solar wind, but the total remanent magnetic pressure is less than the stagnation pressure by a factor of six, implying that a local shock is not formed.
TL;DR: The Viking Lander Imaging System as mentioned in this paper consists of two identical facsimile cameras with a high-resolution mode with an instantaneous field of view of 0.04 deg, and survey and color modes with instantaneous fields of view with 0.12 deg.
TL;DR: In this paper, a simple formula useful for predicting leakage through a circular hole array in a metallic flat plate was presented, and the agreement between theory and experiment was typically better than 1 dB at S band and 2 dB at X band.
Abstract: A simple formula useful for predicting leakage through a circular hole array in a metallic flat plate is presented. A correction is given for plate thickness. The formula is applicable to arrays having either a 60/spl deg/ (staggered) or 90/spl deg/ (square) hole pattern, but is restricted to the case of 1) an obliquely incident plane wave with the E field polarized normal to the plane of incidence, and 2) large transmission loss. When theoretical values were compared to experimental data obtained on test samples having transmission losses greater than 20 dB, the agreement between theory and experiment was typically better than 1 dB at S band and 2 dB at X band.
TL;DR: In this article, axisymmetric supersonic nozzles with relatively steep convergent sections and comparatively small radius-of-curvature throats were compared with those obtained in other nozzels tested previously to appraise the influence of contraction shape on performance.
Abstract: Wall static pressure measurements and performance parameters are presented for axisymmetric supersonic nozzles with relatively steep convergent sections and comparatively small radius-of-curvature throats. The nozzle walls were essentially adiabatic. These results are compared with those obtained in other nozzles tested previously to appraise the influence of contraction shape on performance. Both the flow coefficient and the thrust were less than the corresponding values for one-dimensional, isentropic, plane flow for both the axial and radial inflow nozzles considered, but the specific impulse, the most important performance parameter, was found to be relatively unchanged. The thrust decrement for the axial inflow nozzles was established primarily by the shape of the contraction section, and could be estimated reasonably well from a conical sink flow consideration. The radial inflow nozzle has a potential advantage from a cooling point of view if used in a rocket engine.
TL;DR: Preflight error statistics of earth based Doppler tracking for Mariner navigation concerning Mars 1971 and Venus-Mercury 1973 missions are presented.
Abstract: Preflight error statistics of earth based Doppler tracking for Mariner navigation concerning Mars 1971 and Venus-Mercury 1973 missions
TL;DR: In this paper, the major sources of neutrons from plutonium dioxide nuclear fuel are considered in detail, including spontaneous fission of several of the Pu isotopes, reactions with low Z impurities in the fuel, and (alpha, n) reactions with O-18.
Abstract: The major sources of neutrons from plutonium dioxide nuclear fuel are considered in detail. These sources include spontaneous fission of several of the Pu isotopes, (alpha, n) reactions with low Z impurities in the fuel, and (alpha, n) reactions with O-18. For spontaneous fission neutrons a value of (1.95 + or - 0.07) X 1,000 n/s/g PuO2 is obtained. The neutron yield from (alpha, n) reactions with oxygen is calculated by integrating the reaction rate equation over all alpha-particle energies and all center-of-mass angles. The results indicate a neutron emission rate of (1.14 + or - 0.26) X 10,000 n/s/g PuO2. The neutron yield from (alpha, n) reactions with low Z impurities in the fuel is presented in tabular form for one part part per million of each impurity. The total neutron yield due to the combined effects of all the impurities depends upon the fractional weight concentration of each impurity. The total neutron flux emitted from a particular fuel geometry is estimated by adding the neutron yield due to the induced fission to the other neutron sources.
TL;DR: In this paper, the authors studied the popping of liquid jets of hydrazine and nitrogen tetroxide at atmospheric pressure by means of streak photography and suggested a mechanism for the occurrence of popping and its relation to reactive stream separation.
Abstract: The propellant spray resulting from the impingement of liquid jets of hydrazine and nitrogen tetroxide has been studied at atmospheric pressure by means of streak photography. The streak photographs show periodic small explosions that originate near the impingement point and propagate through the propellant spray at velocities of 3000 to 5000 fps, consuming all propellant droplets over a distance of up to 6 in. Typical streak photographs are presented. The frequency of the explosions or pops ranged up to several hundred cps, and could be controlled by varying the contact time in the liquid phase. Below a minimum threshold contact time, popping did not take place. At high values of contact time, the popping rate was controlled by the transit time of the free jet before impingement. Flashing of the oxidizer prior to impingement prevented popping under certain conditions. It is postulated that popping is initiated by liquid phase reactions. A mechanism for the occurrence of popping and its relation to reactive stream separation is suggested.
Patent•
01 Dec 1972TL;DR: In this article, a single mirror is employed in the path of both split beams of an incoming ray to cause them to double back through separate retroreflectors, and the optical path length is achieved by linear displacement of both retro reflectors using a motor driven lead screw on one for large, low-frequency changes, a moving-coil actuator on the other for smaller, midfrequency changes and a piezoelectric actuators on one of these two two for small, highfrequency changes.
Abstract: In a Fourier interference spectrometer of the double-pass retroreflector type, a single mirror is employed in the path of both split beams of an incoming ray to cause them to double back through separate retroreflectors Changes in optical path length are achieved by linear displacement of both retroreflectors using a motor driven lead screw on one for large, low-frequency changes, a moving-coil actuator on the other for smaller, midfrequency changes and a piezoelectric actuator on one of these two for small, high-frequency changes
TL;DR: This paper studies the performance of a noncoherent frequency-shift keying receiver when it is preceded by a bandpass limiter and obtains expressions for signal suppression- factor, output signal-to-noise ratio (SNR), and error probability to assess the degradation in performance of the receiver due to the presence of the limiter.
Abstract: Many applications of the bandpass limiter involve either coherent or noncoherent demodulation following the limiter. In this paper we study the performance of a noncoherent frequency-shift keying (FSK) receiver when it is preceded by a bandpass limiter. In particular, we obtain expressions for signal suppression- factor, output signal-to-noise ratio (SNR), and error probability from which one can assess the degradation in performance of the receiver due to the presence of the limiter. Both narrow-band and wide-band cases are treated thus covering situations where no frequency uncertainty exists (i.e., known carrier frequency) as well as large-frequency uncertainties. Also discussed is the first-order signal plus noise probability density function (pdf) following noncoherent demodulation.
TL;DR: The spectral factorization algorithm is extended to time-varying systems having periodic coefficient matrices for cases of both discrete and continuous systems, suitable for sensitivity studies in formulating navigation and guidance strategies of low-thrust interplanetary missions.
Abstract: Spectral factorization is a powerful tool in deriving the steady-state solution of Kalman filtering equations. It is an algebraic, nortrecursive method, thus economical in terms of computing cost, when compared with the conventional iterative algorithm. In this paper the technique is extended to time-varying systems having periodic coefficient matrices for both discrete and continuous systems. The tracking of low-thrust spacecraft from an Earth-based station is used as an example and a sensitivity study is performed using a computer program incorporating the algorithm.
TL;DR: In this article, a laminar boundary layer is considered in which only the velocity profile is locally similar and fluid properties are assumed to change uniformly in the gas flow direction, and it is shown that for moderate current densities, the velocity and temperature distributions are insensitive to current.
01 Sep 1972
TL;DR: In this paper, the positions of the observed lunar features are solved for, or estimated directly from, angular measurements made from the orbiting spacecraft (Apollo missions 8, 10, 11, 12, 14, and 15) to the landmark, using least-squares techniques.
Abstract: The selenographic positions of the observed lunar features are solved for, or estimated directly from, angular measurements made from the orbiting spacecraft (Apollo missions 8, 10, 11, 12, 14, and 15) to the landmark, using least-squares techniques. It appears that the radius values derived from the Apollo landmark data provide some proof of the existence of a displacement between the center of figure and center of mass of the moon along the earth-moon line. In addition, all three components of the estimated crater locations should be useful toward establishing a selenodetic reference system for interpreting or reducing earth-based observation data.
TL;DR: The computer programs developed to prepare optical data for use in a navigation filter are discussed and the experiment provides a basis for the design of equivalent systems for future missions.
Abstract: The Mariner 9 spacecraft's science television camera provided an optical navigation experiment with TV pictures containing images of Mars' natural satellites against star backgrounds. Required TV image data and spacecraft engineering data were extracted from the spacecraft telemetry stream in this near-real time experiment designed to validate the navigation content of spacecraft-based optical data. This paper discusses the computer programs developed to prepare optical data for use in a navigation filter. Ground and in-flight calibration allowed pointing knowledge of better than 6 arc seconds. System performance during Mars approach was excellent, leading to extremely accurate trajectory estimates. The experiment provides a basis for the design of equivalent systems for future missions.
Patent•
16 Mar 1972TL;DR: In this paper, a digital servo control system for random noise excitation of a test object in a reverberant acoustic chamber employs a plurality of sensors spaced in the sound field to produce signals in separate channels which are decorrelated and averaged.
Abstract: A digital servo control system for random noise excitation of a test object in a reverberant acoustic chamber employs a plurality of sensors spaced in the sound field to produce signals in separate channels which are decorrelated and averaged. The average signal is divided into a plurality of adjacent frequency bands cyclically sampled by a time division multiplex system, converted into digital form, and compared to a predetermined spectrum value stored in digital form. The result of the comparisons are used to control a time-shared up-down counter to develop gain control signals for the respective frequency bands in the spectrum of random sound energy picked up by the microphones.
TL;DR: In this article, the problem of replacing a time-varying linear system with a stationary one is investigated, and several quadratic criteria are proposed to aid in determining suitable candidate systems.
Abstract: The problem of replacing the time-varying linear system \dot{X} = A(t)X by a stationary one \dot{Y} = BY is investigated. The matrix B is selected so that X(t) = Y(t) in the interval [ 0, T ]. Several quadratic criteria are proposed to aid in determining suitable candidate systems. One criterion for choosing B is initial condition dependent, and another bounds the "worst case" homogeneous system performance. Both of these criteria produce weighted least squares fits to A(t) .
TL;DR: A trajectory design philosophy for Jupiter orbiter missions that is based on the gravity thrust concept developed for interplanetary trajectories is introduced in this article, which is accomplished by utilizing the moving gravitational fields of the four Galilean satellites.
Abstract: A trajectory design philosophy is introduced for Jupiter orbiter missions that is based on the gravity thrust concept developed for interplanetary trajectories. This is accomplished by utilizing the moving gravitational fields of the four Galilean satellites. A general theorem, applicable to any existing planetary satellite system, is developed to show how the effects of small satellite perturbations can be magnified by incorporating multiple revolutions between encounters.-
TL;DR: In this paper, the power series solutions to the matrix covariance differential equation and the transition differential equation are reexamined, and the truncation error bounds are derived by exploiting the functional equations satisfied by the transition and covariance matrices.
Abstract: Power series solutions to the matrix covariance differential equation \dot{P} = AP + (AP)' + Q and the transition differential equation \dot{\Phi} = A\Phi are reexamined. Truncation error bounds are derived which are computationally attractive and which extend previous results. Polynomial approximations are obtained by exploiting the functional equations satisfied by the transition and covariance matrices. The series-functional equation propagation technique represents a fast and accurate alternative to the numerical integration of the time-invariant transition and covariance equations.
TL;DR: In this paper, the implication of actual cometary observations for the physical nature of comets is briefly reviewed, bringing out the complete conflict with observation of the ice-dust solid nucleus model put forward in recent years as representing the fundamental structure of the comets.
Abstract: The implication of actual cometary observations for the physical nature of comets is briefly reviewed, bringing out the complete conflict with observation of the ice-dust solid nucleus model put forward in recent years as representing the fundamental structure of comets. That under increasing solar heat the nucleus develops an expanding atmosphere is inconsistent with the well-established phenomenon that the coma contracts with decreasing distance from the sun. Several comets remaining always beyond Mars have nevertheless been strongly active and produced fine tails. That some comets show at times a star-like point of light is readily explicable on the dust-cloud structure and by no means establishes that a solid nucleus exists. With the nucleus-area corresponding not to a small solid mass but to an optical phenomenon, there would be no reason to expect that it would describe a precise dynamical orbit. On the hypothesis of a nucleus, it is necessary to postulate further some internal jet-propulsion mechanism to account for the orbital deviations.