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Showing papers by "Jet Propulsion Laboratory published in 1980"



Journal ArticleDOI
TL;DR: The IAU/IAG Working Group on cartographic coordinates and rotational elements of the planets and satellites revises tables giving the directions of the north poles of rotation and the prime meridians of the asteroids as discussed by the authors.
Abstract: Every three years the IAU/IAG Working Group on cartographic coordinates and rotational elements of the planets and satellites revises tables giving the directions of the north poles of rotation and the prime meridians of the planets, satellites, and asteroids. Also presented are revised tables giving their sizes and shapes. Changes since the previous report are summarized in the Appendix.

526 citations


Journal ArticleDOI
TL;DR: The role of bromine compounds in the photochemistry of the natural and perturbed stratosphere has been reexamined using an expanded reaction scheme and the results of recent laboratory studies of several key reactions as discussed by the authors.
Abstract: The role of bromine compounds in the photochemistry of the natural and perturbed stratosphere has been reexamined using an expanded reaction scheme and the results of recent laboratory studies of several key reactions. The most important finding is that through the reaction BrO + CIO → Br + Cl + O2, there is a synergistic effect between bromine and chlorine which results in an efficient catalytic destruction of ozone in the lower stratosphere. One-dimensional photochemical model results indicate that BrO is the major bromine species throughout the stratosphere, followed by BrONO2, HBr, HOBr and Br. We show from the foregoing that bromine is more efficient than chlorine as a catalyst for destroying ozone, and discuss the implications for stratospheric ozone of possible future growth in the industrial and agricultural use of bromine. Bromine concentrations of 20 pptv (2 × 10^−11), as suggested by recent observations, can decrease the present-day integrated ozone column density by 2.4%, and can enhance ozone depletion from steady-state chlorofluoromethane release at 1973 rates by a factor of 1.1–1.2.

363 citations


Journal ArticleDOI
01 Dec 1980-Icarus
TL;DR: The response of Martian climate to changes in solar energy deposition caused by variations of the Martian orbit and obliquity is examined in this paper, where a new theory for the formation of the polar laminae is developed on the basis of this systematic examination.

361 citations




Journal ArticleDOI
01 Jul 1980-Geology
TL;DR: In this article, a comparison of length, volume, and effusion rate for 87 historic Hawaiian basaltic lava flows shows little support for a direct relationship between flow length and the total volume of material extruded.
Abstract: Comparison of length, volume, and effusion rate for 87 historic Hawaiian basaltic lava flows shows little support for a direct relationship between flow length and effusion rate. A statistically more significant relationship exists between flow length and total volume of material extruded. Cross-sectional area, effusion rate, and volume all play important roles in governing the emplacement of lava flows in Hawaii; no single factor appears most important. One reason for the observed relationships in Hawaii may be that tube-fed flows, with approximately constant cross-sectional area, advance farther than other types of flows for similar effusion rates and volumes.

139 citations


Journal ArticleDOI
17 Jul 1980-Nature
TL;DR: In this paper, the changing three-dimensional form of the solar wind is presented which help relate some of the modulations observed in geomagnetic activity, the ionosphere, and the flux of galactic cosmic rays.
Abstract: It is noted that although the 11 year solar cycle was first recognized in 1843, it is still only poorly understood. Further, while there are satisfactory models for the magnetic variations, the underlying physics is still obscure. New observations on the changing three-dimensional form of the solar wind are presented which help relate some of the modulations observed in geomagnetic activity, the ionosphere, and the flux of galactic cosmic rays.

116 citations


Journal ArticleDOI
01 Jul 1980-Icarus
TL;DR: In this article, photoelectric observations of 32 asteroids observed from Table Mountain Observatory during the second half of 1978 are reported, and the geometric mean rotation period of the objects observed is 14.2 + or - 1.6 hr, as compared to 9.38 + or 0.35 hr for 182 asteroids analyzed in Harris and Burns (1979).

91 citations


Proceedings ArticleDOI
01 Jan 1980
TL;DR: In this article, a six degree-of-freedom joystick with feedback motors, called the Force-Reflecting Hand Controller (FRHC), is used as control input for the human operator in a teleoperator system.
Abstract: A six degree-of-freedom joystick with feedback motors, called the Force-Reflecting Hand Controller (FRHC) is used as control input for the human operator in a teleoperator system. The geometric and dynamic properties of the FRHC are entirely different from those of the manipulator being controlled. The paper discusses the analysis and synthesis of the control loop between the FRHC and the robot arm and examines the necessary position and force transformations. The controller is implemented through a dedicated minicomputer.

74 citations


Journal ArticleDOI
25 Jan 1980-Science
TL;DR: Several interesting cloud and atmospheric features of the Saturn system have been observed by the long-wavelength channel of the two-channel ultraviolet photometer aboard the Pioneer Saturn spacecraft, including a Titan-associated cloud, a ring cloud, and the variation of atmospheric emission across Saturn's disk.
Abstract: Several interesting cloud and atmospheric features of the Saturn system have been observed by the long-wavelength channel of the two-channel ultraviolet photometer aboard the Pioneer Saturn spacecraft. Reported are observations of the most obvious features, including a Titan-associated cloud, a ring cloud, and the variation of atmospheric emission across Saturn's disk. The long-wavelength data for Titan suggest that a cloud of atomic hydrogen extends at least 5 Saturn radii along its orbit and about 1.5 Saturn radii vertically. A ring cloud, thought to be atomic hydrogen, has also been observed by the long-wavelength channel of the photometer; it shows significant enhancement in the vicinity of the B ring. Finally, spatially resolved observations of Saturn's disk show significant latitudinal variation. Possible explanations of the variation include aurora or limb brightening.

Journal ArticleDOI
TL;DR: In this article, the quantum yield for O(3P) production was determined to be 0.12 + or - 0.02 at this wavelength, which confirmed the qualitative observations of two previous photofragment studies.

Journal ArticleDOI
20 Nov 1980-Nature
TL;DR: The Oort cloud radius is 100,000 AU, the mean "thermal" velocity in the cloud is about 110 m/s, and the resulting perihelion distribution in the planetary region is uniform with the number based on the radius of the circle within which the comets are falling as discussed by the authors.
Abstract: The paper demonstrates that the Oort cloud radius is 100,000 AU, the mean 'thermal' velocity in the cloud is about 110 m/s, and the resulting perihelion distribution in the planetary region is uniform with the number based on the radius of the circle within which the comets are falling. Stars passing through the Oort cloud during the history of the solar system have ejcted a minimum of the initial population and randomized the orbits of the remaining comets leaving little record of their initial state.

Proceedings ArticleDOI
19 Sep 1980
TL;DR: In this paper, the Sagnac effect was applied to the design of fiber optic inertial frame rotation sensors based on the SAGAC effect, and two general categories: (1) single frequency interferometers which generate a phase shift proportional to inertial rotation rate, and (2) dual frequency interferers for which the beat frequency is proportional to rotation rate.
Abstract: Possible approaches to the design of fiber optic inertial frame rotation sensors based on the Sagnac effect are reviewed under two general categories: (1) single frequency interferometers which generate a phase shift proportional to inertial rotation rate, and (2) dual frequency interferometers for which the beat frequency is proportional to rotation rate. The principal variations within the single frequency class involve the way in which the nonreciprocal phase bias is used and techniques for generating the nonreciprocal bias. Within the dual frequency class, the various approaches differ principally in the way in which the counter-circulating frequencies are established.

Journal ArticleDOI
01 Nov 1980-Icarus
TL;DR: In the outer solar system, high pressure polymorphs will be created by and may remain after large cratering events as mentioned in this paper, and those high-pressure ices should be ubiquitous.

Journal ArticleDOI
TL;DR: In this article, a procedure for correcting antenna temperature measurements and retrieving the true brightness temperatures is developed for the Scanning Multichannel Microwave Radiometer (SMMR) flown on the Seasat-A and Nimbus-G satellites.
Abstract: Procedures for correcting antenna temperature measurements and retrieving the true brightness temperatures are developed for the Scanning Multichannel Microwave Radiometer (SMMR) flown on the Seasat-A and Nimbus-G satellites. These procedures are necessary to meet the measurement accuracies required for deriving sea surface temperatures and wind speeds. It is shown that sidelobe contributions and polarization cross-coupling are major effects to be accounted for, in addition to some unique features of the SMMR instrument such as integration times and antenna scan characteristics. Methods are presented for data averaging and data reformatting, these are to be used with geophysical parameter retrieval algorithms.

Journal ArticleDOI
TL;DR: The MARINER 10 spacecraft measured the hydrogen Lyman α emmission resonantly scattered in the Venus exosphere at several viewing aspects during the encounter period and concluded that the non-thermal source is on the sunward side of the planet.

Journal ArticleDOI
TL;DR: In this paper, the authors present an analysis of the fundamental dynamical requirements for such a mission and show the performance attainable using present-day ion drive technology in terms of stay time at the pole and imaging resolution as a function of viewing distance.
Abstract: The concept and rationale are presented and the fundamental dynamical requirements set forth for a spacecraft that remains stationary in space above the North or South Pole of the Earth for an extended period of time. The mathematical basis and acceleration characteristics are shown. Performance capability using present-day ion drive technology is evaluated in terms of stay time at the pole and imaging resolution as a function of viewing distance. The analysis shows that a polesitter spacecraft can be maintained without difficulty for one or two years at several (~5) lunar distances from the Earth, admitting low-resolution (3 km) visual imagery and yet lower resolution (12-70 km) measurements in the infrared regime. Microwave measurements are not practical using today's technology. Sensitivity calculations show that substantial improvement in performance capability must await major advances in available technology. Introduction and Rationale L ANDSAT, Nimbus, Tiros, and other low-Earth-orbiting spacecraft have demonstrated the potential for gathering valuable Earth applications data from near-Earth space using remote sensing devices. This great potential for weather analysis, Earth resource surveys, and high-resolution imagery is somewhat diluted because of the limited spacecraft time over a region of particular interest and long times to repeat coverage. The desire for more continuous coverage can be satisfied somewhat by using multiple satellites or wide-swath instruments. Measurements from a geosynchronous equatorial orbit provide an alternative for continuous coverage of a particular region at some cost in resolution due to the greater distance. Coverage is limited primarily to the temperate zone where viewing incidence angles are adequate. A polesitter spacecraft presents the potential for continuous coverage in the polar regions—a new dimension in ap- plications satellite utilization. Such a spacecraft would remain in a fixed position above the North or South Pole for a year or more, allowing long-term, multi-instrument measurements in the polar region as frequently as desired. At mission end the spacecraft could spiral down to low Earth orbit for possible retrieval, refurbishment or replenishment, and reuse. This paper presents an analysis of the fundamental dynamical requirements for such a mission and shows the performance attainable using present-day technology. The analysis establishes the mathematical basis, determines the required acceleration characteristics, and shows the propulsion needed to do such a mission. It takes into account perturbations due to lunar and solar gravity with their variation through the year and assesses the impact of solar radiation pressure. A computer program was constructed and used to compute and plot stay time at the pole for a wide range of spacecraft distances and propulsion parameter assumptions.

Journal ArticleDOI
11 Jan 1980-Science
TL;DR: Two rocket flights of an absolute pyrheliometer indicate an increase in solar luminosity (solar constant) of 0.4 percent, which is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyr Heliometers.
Abstract: Two rocket flights of an absolute pyrheliometer, separated by 30 months, indicate an increase in solar luminosity (solar constant) of 0.4 percent. The significance of this result is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyrheliometers. There is a high probability that the measured difference is real. Additional observations are required to determine whether the difference results from random fluctuations in solar luminosity, a nonrandom change of short duration, or a sustained change that has climatological significance.

Journal ArticleDOI
TL;DR: In this paper, the authors give a corresponding recipe for deciding when two such maps are conjugate in a compact oriented surface of genus g having a single boundary component, i.e., iff the defining curves separate M into pieces of the same genus.
Abstract: Let M be a compact oriented surface of genus g having a single boundary component, ~ f its mapping class group (that is, the group of orientation preserving homeomorphisms of M which are 1 on the boundary rood the subgroup of homeomorphisms which are isotopic to 1 by an isotopy which is pointwise fixed on the boundary), and J the subgroup of J r which acts trivially on HI (M,Z ). Powell has produced (an infinite set of) generators for J of two particularly simple types, namely: a) a twist on a bounding simple closed curve of M, b) opposite twists on two disjoint homologous simple closed curves of M. Algebraic statements concerning these generators frequently can be translated into convenient geometric ones ; for example, two such maps of the same type are conjugate in ~ ' iff the defining curves separate M into pieces of the same genus. Our main result here is to give a corresponding recipe for deciding when two such maps are conjugate in J . This recipe will then be extended to conjugacy classification of such maps in fq for any f~ containing J . Our second goal is to compute certain commutator quotients of J . If ~ is as above, then J/[fq, J ] = X , is abelian. Because of their algebraic simplicity, abelian quotients of J are particulary attractive as objects of study. All known such

Journal ArticleDOI
TL;DR: In this paper, the authors give a complete analysis of the size of these codes and give a construction for a class of binary codes capable of correcting a single asymmetric error, which is the smallest binary code known.
Abstract: Constantin and Rao [(1979), Inform. Contr. 40, 2036] have given an ingenious construction for a class of binary codes capable of correcting a single asymmetric error. In this paper we shall give a complete analysis of the size of these codes.

Journal ArticleDOI
29 May 1980-Nature
TL;DR: An upper limit to the global abundance of SO2 gas in the atmosphere of Io has been derived from observations of near-UV reflectivity made from earth orbit as mentioned in this paper, which was confirmed by ratio spectra of Vesta.
Abstract: An upper limit to the global abundance of SO2 gas in the atmosphere of Io has been derived from observations of near-UV reflectivity made from earth orbit. Spectra in the range 2900-3100 A were obtained by the long-wavelength spectrograph of the IUE, and compared with the convolved solar spectrum of Broadfoot (1972). From the apparent solar origin of all the spectral features, an upper limit of 0.008 cm atm was calculated for the abundance of SO2, which was confirmed by ratio spectra of Vesta. Discrepancies between the upper limit obtained and the detection of a column abundance of 0.2 cm atm by the Voyager 1 IRIS experiment have a number of possible explanations, the most likely of which is that the SO2 atmosphere in Io is patchy, being confined to regions over solid deposits and volcanic vents.

Journal ArticleDOI
TL;DR: In this paper, current practices and future requirements for the storage, transmission and distribution of hydrogen are reviewed in order to identify inadequacies to be corrected before hydrogen can achieve its full potential as a substitute for fossil fuels.

Patent
03 Jul 1980
TL;DR: In this paper, a single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed, where each beam illuminates a separate "footprint" (i.e., range and azimuth interval).
Abstract: A single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed. Each beam illuminates a separate "footprint" (i.e., range and azimuth interval). The distinct azimuth intervals for the separate beams produce a distinct Doppler frequency spectrum for each beam. After range correlation of raw data, an optical processor develops image data for the different beams by spatially separating the beams to place each beam of different Doppler frequency spectrum in a different location in the frequency plane as well as the imaging plane of the optical processor. Selection of a beam for imaging may be made in the frequency plane by adjusting the position of an aperture, or in the image plane by adjusting the position of a slit. The raw data may also be processed in digital form in an analogous manner.

Journal ArticleDOI
TL;DR: The conditions for growth, the crystallographic texture and the solar cell properties of silicon-on-ceramic (SOC) material are quite similar to those of EFG ribbon.

Journal ArticleDOI
TL;DR: For any positive integer N, there are a finite number of non-isomorphic groups of order N. as mentioned in this paper dealt with the 3,58 groups and their classification into families.

Journal ArticleDOI
TL;DR: In this article, the performance of an L-band, 25-cm wavelength imaging synthetic aperture radar (SAR) for soil moisture determination, and to study the temporal variability of radar returns from a number of agricultural fields.
Abstract: The objectives of this experiment were to assess the performance of an L-band, 25-cm wavelength imaging synthetic aperture radar (SAR) for soil moisture determination, and to study the temporal variability of radar returns from a number of agricultural fields. A series of three overflights was accomplished during March 1977 over an agricultural test site in Kern County, CA. Soil moisture samples were collected from bare fields at nine sites at depths of 0-2, 2-5, 5-15, and 15-30 cm. These gravimetric measurements were converted to percent of field capacity for correlation to the radar return signal. The initial signal film was optically correlated and scanned to produce image data numbers. These numbers were then converted to relative return power by linear interpolation of the noise power wedge which was introduced in 5-dB steps into the original signal film before and after each data run. Results of correlations between the relative return power and percent of field capacity (%FC) demonstrate that the relative return power from this imaging radar system is responsive to the amount of soil moisture in bare fields. The signal returned from dry (15%FC) and wet (130%FC) fields where furrowing is parallel to the radar beam differs by about 15 dB. Problems remain to be resolved before this technique can be operationally employed. First, adequate calibration of the radar system is required to insure comparability of data both from area to area within a single flight and between different flights.

Journal ArticleDOI
04 Dec 1980-Nature
TL;DR: Voyager 1 imaging data of the Saturn rings, taken at a resolution of 1000 km/line pair between September 3 and October 13, 1980 are discussed in this paper, where it is shown that the fine structure observed in the rings cannot, for the most part, be attributed to classical resonances with the known inner satellites.
Abstract: Voyager 1 imaging data of the Saturn rings, taken at a resolution of 1000 km/line pair between September 3 and October 13, 1980 are discussed. It is pointed out that as the spacecraft approached Saturn, finer radial structure in the rings between and within the major divisions became apparent, together with extensive azimuthal structure in the B ring. It is shown that the fine structure observed in the rings cannot, for the most part, be attributed to classical resonances with the known inner satellites. Preliminary model calculations of ring brightness based on photometry data indicate that the particles of the A and B rings are characterized by a greater degree of diffuse backscattering ability than previously suspected, behaving like Lambert spheres, while those of the C ring are either darker or more highly forward scattering than the A or B ring particles.

Journal ArticleDOI
01 Jun 1980

Journal ArticleDOI
09 Oct 1980-Nature
TL;DR: In this paper, a study of nitrous oxide formation mechanisms indicates that N2O concentrations greater than 10 to the 9th per cu cm could be produced in IBC III aurora or by lower-level activity lasting for many hours.
Abstract: A study of nitrous oxide formation mechanisms indicates that N2O concentrations greater than 10 to the 9th per cu cm could be produced in IBC III aurora or by lower-level activity lasting for many hours, and, in favorable conditions, the N2O concentration could exceed the local nitric oxide density. An upper limit on the globally averaged N2O production rate from auroral activity is estimated at 2 x 10 to the 27th per second.