ALBERT

Description: The discovery of concentrations of meteorites in Antarctica by Japanese field parties in 1969, and subsequently by joint U.S.-Japanese and U.S. field parties since 1976 has provided a significant new resource for understanding the origin and evolution of the solar system. The number of meteorites as well as the variety of meteorites has increased dramatically, and substantial amounts of data derived from their study has begun to appear in the scientific literature. The U.S. program of investigation has drawn on curatorial experience derived from the lunar program to: (1) develop specific collection and preliminary examination protocols; (2) provide documented samples for scientific investigations in response to specific requests; and (3) coordinate research by scientific consortia. The productivity of scientific research is significantly enhanced by these management approaches. Some of the results of the curatorial program for Antarctic meteorites carried out over the past three years are described.

Description: A two-axis drive system is described for pointing a high gain antenna. Motion about each axis is provided by identical drive mechanisms. Only three gear passes are required to obtain the necessary 900:1 gear reduction. The drive system is a primary element of an experiment that will provide a real time data link between Nimbus and ground stations. Data are transmitted from Nimbus to the applications technology satellite, which relays the data to ground stations.

Description: The Intelsat 4 communications satellite has two spot beam antennas which are pointed to selected land masses by gimbaled positioners. The positioners employ drive motors with electromagnetic brakes and jackscrews that are self-caging during the launch. The positioner uses dry lubricants for ball bearings, spur gears, screw and nut, and various journal bearings. A coefficient of friction of approximately 0.05 was demonstrated in vacuum operation. Success of the positioner was demonstrated on the first Intelsat 4 placed in orbit in January 1971. The developmental problems that were encountered and their solutions are discussed.

Description: Measurements of the positions of the sources of solar radio bursts at decameter wavelengths, 20- to 60-MHz range, provide information about physical conditions in a region of the corona extending from about one-half to several solar radii from the surface of the sun. Position measurements in the 20- to 60-MHz range were made with the Clark Lake sweep-frequency grating interferometer. Although the resolution of the instrument is sufficient to measure source position accurately, the highly variable effect of refraction in the earth's ionosphere severely limits the observations, distorting position determinations to such an extent as to make much of the position data useless unless ionospheric refraction can be taken into account. A method was developed for the removal of the refractive effect from the data to permit determination of true source position. With this technique it is considered possible to measure spatial extent of radio sources that will provide information about emission processes and physical parameters in the corona.

Description: A technique is described for reducing near-in sidelobes in spacecraft antennas by cancellation. This technique takes a small portion of the radiation from the antenna aperture and generates the near-in lobes, which are then fed out of phase relative to the main signal. Results of sample cases indicate that the first three lobes can be nearly eliminated at a 40% reduction in aperture efficiency.

Description: A design guide for minimizing electromagnetic interference in aerospace communication equipment for ground stations is presented. Specifically treated are the mechanisms of generating unwanted radio emissions that may affect station operations as well as other communications services, the mechanisms by which sensitive receivers become susceptible to interference, means for reducing interference, standard methods of measurement, and the problems of site selection. The sources of interference are viewed primarily as originating from communications transmitters aboard spacecraft and aircraft, ground transmitters within and outside the ground stations, and other electrical sources on the ground that are not intended to radiate.

Description: Water addition to the Gemini 3 exhaust plasma was studied to determine its effectiveness in the establishment of communication links during the entry portion of the flight. Attenuation levels were measured with and without water injection at uhf frequencies of 230.4 and 296.8 megahertz and at the C-band frequency of 5690 megahertz. Ultrahigh frequency signals that had been blacked out were restored to significant levels, during early portions of the water-injection sequence, by the high flow rate injection. The C-band signal was enhanced by medium and high flow rate injections during the latter portion of the injection period. The uhf signal recovered during water injection resulted in an antenna pattern that was beamed in the radial direction of injection from the spacecraft. Postflight analysis showed that the uhf recovery data were consistent with injection-penetration theory.

Description: Impedance behavior of short cylindrical antenna used as diagnostic probe in isotropic and magnetized plasmas

Description: Communications control group teletype line switching equipment for space stations

Description: Antenna rigging angle optimization within structural member design for improved antenna performance

Description: Reflector surface distortions of 210 ft antenna and their effects on radio frequency performance

Description: Polarization diverse S band feed cone for DSIF reflector antennas

Description: Second/third order hybrid phase locked receiver for tracking frequency ramp signals

Description: Examination of deep space Doppler data for terrestrial media contamination

Description: Effects on high temperature microwave antenna breakdown of ionization frequency, collision frequency, diffusion coefficient, and breakdown parameters

Description: Impedance matcher for automatically maximizing power radiated from X band antenna on reentry vehicle by eliminating power dissipated as heat

Description: Computer solution of plane electromagnetic wave interaction with bounded inhomogeneous plasma slab with electron density gradient transverse to wave

Description: Slot antenna radiation pattern distortion produced by boundary layer plasma sheath around conical reentry vehicles

Description: Antenna radiation patterns and electron density profiles in turbulent plasma flow

Description: Reentry plasma effects on RAM C-1 VHF telemetry antenna radiation patterns

Description: Shock tube measurements of admittance of RAM C-2 and RAM C-3 diagnostic antenna admittance to analyze accuracy of calculated electron density

Description: RAM C-3 S band diagnostic antenna systems and calculations of electron density profiles

Description: Coding, synchronization, combinatorial, multiple access, propagation, and permutation studies for telecommunications systems

Description: The fixed and variable Martian features investigated by the TV experiment on Mariner 9 are described. Articles are presented concerning the dust storm of October to November over the Southern Hemisphere; global surface geodesy and cartography; geology; and the satellite astronomy.

Description: A spacecraft recorder was developed with the objective of functioning continuously for 5 years. The resulting design employed a metallic tape wound in a 200-turn helix. A direct drive, brushless dc torquer and servo speed control drove the recorder at 3 rpm for recording and 54 rpm for playback.

Description: Extreme value theory is examined to explain the cause of the bias and spread in performance of communications systems characterized by low bit rates and high data reliability requirements, for cases in which underlying noise is Gaussian or perturbed Gaussian. Experimental verification is presented and procedures that minimize these effects are suggested. Even under these conditions, however, extreme value theory test results are not particularly more significant than bit error rate tests.

Description: The use of the earth-moon system for radio tracking has several potentially useful aspects, from a scientific standpoint: extension of the baseline by two orders of magnitude, absence of lunar atmosphere, higher-velocity parallax with a longer period, and the moon's more modellable rotation. The facility would be a convenient base station for other research, not directly involving the tracking capability, but utilizing its orbiting data link features.

Description: Range and Doppler measurements for the Mariner 6 and 7 spacecraft are described. The Doppler tracking system and the two systems of spacecraft ranging apparatus being used in the Deep Space Network are illustrated. Charged particle calibration is considered. Equipment characteristics are presented for the ranging apparatus.

Description: The measurement of inhomogeneities in the electron content along the orbital paths of Gemini 8 and Gemini 9 missions was not accomplished because the tracking information was not available. The use of ultrahigh frequency radio transmission was the primary factor in the successful removal of a very high frequency Faraday rotation ambiguity; but, as was expected, this was not very useful for fine-scale polarization studies. Ionosonde data were useful in the computation of the slab thickness at the closest point of approach of the spacecraft.

Description: All digital, single channel command subsystem for spacecraft communication

Description: Spacecraft antenna optimization, receptance coupling program, deformation modes and dynamic response of structures, and holographic measurements

Description: Predictions of surface and near surface blockiness using earth based radar measurements were made. Two polarizations of the radar echoes were measured - polarized and depolarized. Particular attention was given to the depolarized echoes. North Ray and South Ray Craters and a 512-m diameter lunar crater in the Flamsteed Ring were used for the study.

Description: The purpose of the reported experiment was to determine the principal electromagnetic and structural properties of the lunar surface from the observation of command and service module (CSM) radio transmissions that were reflected from the lunar surface and received on earth. These transmissions emanate from the CSM communication systems at wavelengths of 13 cm (S-band) and 116 cm (very high frequency (VHF)). Lunar crustal properties such as dielectric constant, average slope and slope probability, density, small-scale surface roughness, and embedded rocks to a depth of 20 m may be determined. The results are proving to be most useful in understanding the processes that have produced and modified the crust and in distingushing between adjacent and subjacent geological units. The experimental observations are also of intrinsic interest in the study of electromagnetic scattering.

Description: Procedures for achieving electromagnetic compatibility in electronic and electrical equipment for aerospace ground stations are investigated. The application of shielding theory to good design is treated and standards of good practice are outlined for bonding, grounding, wiring, and cabling. Some aspects of filter design are explained, and suggestions are given for the application of filters to electronic and electrical equipment.

Description: Radio wave propagation through plasmas studied for communication with hypersonic vehicles during reentry

Description: Components and techniques for radio and optical space communication

Description: Radio frequency subsystem requirements and estimated reliability data for Thermoelectric Outer Planet Spacecraft

Description: Mechanically despun antenna system design for spin stabilized spacecraft used in ATS and Intelsat systems

Description: The radar augmentation device (RAD) serves to increase the radar response of a target body and thus expedite radar acquisition. The design and development of the RAD are discussed with particular emphasis on technical problems that were encountered and solved. Discussions of the mode of operation of the RAD and the ground test history are also included.

Description: Observations, made by the RAE satellite, of earth magnetospheric noise are reported. The observations show radio noise exists at 700 kHz and below. The results are included in graphs.

Description: Opinions conflict over the role of surface gravity in shaping impact craters on Mercury. One view holds that the effects of g are evident in measurable aspects of crater form; other investigators find little or no evidence for g's geomorphic importance. Ambiguity in the role of g and other variables in cratering on Mercury stems largely from uncertainty in identifying major geomorphic contrasts and the crater sizes at which they occur. One of these, depth/diameter (d/D), undergoes a major change at the transition from simple (bowl shaped) to complex (peaks and terraces) crater interiors. Four least-squares d/D fits for fresh craters on Mercury were attemped. The results are inconsistent. The d/D data that should resolve previous shortcomings is presented. The revised d/D distributions for simple and complex craters, which intersect at a diameter of about 5 km, support the initial thesis that g substantially influences the form of Mercury's craters.

Description: Craters within the Ganymede Jg-7 quadrangle were divided into seven mappable units. The units represent: (1) irregular or elongate craters, (2) craters with dark ejecta, (3) palimpsests, (4) secondary craters, (5) and craters of young, mature, and old age. Symbols used for crater floors include: (1) flat floors, (2) floors with pits, (3) floora with a central dome or peak, (4) and floors with a central dome and pit. Grooved terrains were divided into five mappable units. Three units of light grooved material represent small, medium, and large grooves, which are arbitrarily divided. The other two units of grooved terrain represent dark grooved materials, and reticulate grooves. Two units of ungrooved dark terrain and two units of ungrooved light terrain were defined. In Galileo Regio, two units were defined repesenting large furrowed grooves, and smaller grooves which are orthogonal to the furrowed grooves.

Description: The relative time of emplacement of some major rock units on Mars was recognized to some degree from geologic mapping using Mariner Images. Correlation charts showing the map units and their position in sequence, however, displayed little discrimination in their vertical range of occurrence. A more detailed time-stratigraphy is currently being developed as Viking geologic mapping of the planet progresses.

Description: Although many radar profiles and images of the area within 20 deg of Mercury's equator had been obtained from 1971 to 1981, at both Goldstone and Arecibo radar facilities, surprisingly little geological analysis had been done with these data until recently. Topographic profiles and radar roughness reflectivity images which can be derived from these data will be crucial in completing the geological mapping of Mercury now underway at the U.S. Geological Survey. Processing of available radar data must be completed to establish any systematic relationship between radar reflectivities and roughness, density, dielectric constant, and other related geological parameters. Specific tasks accomplished for these purposes include the following. Documentation was located and searched to establish the type and quantity of Goldstone 12.5 cm radar observations which were available for Mercury. Data has been collected during approximately 50 observation periods from 1971 to 1981. About half of the data, collected during 1972 and 1973, have been processed, but without adequate documentation. A standardized, well-documented procedure for processing and analysis for all Goldstone Earth-based observations of Mercury was established.

Description: The origin of Mars surface units and the extent of subsequent cratering play key roles in determining surface texture. At scale sizes of 0.1-10 meters, however, there is a growing body of evidence that wind is the dominant force. The direct and indirect evidence which implies that meter-scale surface texture on Mars is controlled by the wind is presented. Since radar is uniquely sensitive to structure on these scales, radio wave scattering data can provide insight on aeolian activity available from no other source.

Description: Two old volcano-tectonic collapse structures are exposed north and northeast of the huge shield volcano, Olympus Mons. They are semicircular and were probably low shield volcanoes similar to Alba Patera, but whose central portions have subsided or collapsed. They form the basement upon which younger volcanic materials of Alba Patera Olympus Mons have been emplaced. The oldest structure, Acheron Fossae is over 700 km across and is north of Olympus Mons. It has a surface of considerable relief broken by graben and extensive en echelon and parallel fractures and faults with varied displacements. Acheron Fossae is the most densely cratered in the Olympus Mons region. The structure must have formed very early in martian time. The second is Halex Fossae, northeast of Olympus Mons. Where exposed, it is cut by a series of arcuate grabens that become closer spaced toward its center. The radii of the fractures indicate that the structure may be at least 250 km across and centered beneath the Olympus Plains. Lava flows appear to have issued from some of the arcuate fractures and to have flowed radially away from the center of Halex Fossae. North of Halex Fossae, material of the same age as Halex Fossae overlaps Acheron Fossae.

Description: High spatial resolution data from the Viking infrared thermal mapper (IRTM) are used to examine the Tharsis volcanoes which are situated within a vast area of low thermal inertia material very fine particle size or very high porosity, with the volcanoes having the lowest thermal inertias. Thermal infrared images of the 1823 flow on Kilauea's southwest rift zone show lower thermal inertias near the vent area where shelly pahoehoe is common while individual channelized aa flows with abundant broken pahoehoe slabs are higher thermal inertia. The increase in aa flows to the southeast leads to a general trend of increasing thermal inertias from near vent to distal areas. Martian shield volcanoes have thermal inertias equal to or higher than their surrounding plans when atmospheric effects are removed from the data. The general increase in thermal inertias away from the summit calderas is consistent with the trend of the Hawaiian 1823 flow and may be related to changing lava properties away from the summit.

Description: A photometrically and geometrically reduced data base is being produced for the Galilean Satellites using Voyager Imaging data. The basic data set used is essentially all the useful satellite images returned by Voyager. Each frame was radiometrically calibrated and many are projected into cartographic formats. Mosaics of low, medium and high resolution frames being made for each satellite consist of registered digital images with intensity values scaled through a traceable calibration procedure to normal albedo values. Many of the mosaics are being made in two versions. One version is an albedo version and the second is a maximum discrimination version in which large variations in brightness across the picture are suppressed.

Description: One unique feature on Mars is the presence of ring furrows which are apparently produced by inversion of topography at the rims of partially buried craters. Ring furrows are flat-floored trenches, circular in plan view, forming rings 7 to 50 km in diameter. The moat is on the order of 0.5 km deep and 2 to 10 km wide, and it surrounds a flat topped circular mesa or plateau that is 5 to 40 km across. The central plateau is at the same elevation or lower than the surrounding plain outside the ring. The circular nature and size range of ring furrows tend to suggest that these features are related to craters partially buried by younger lava flows. The rings have been formed by preferential removal of the exposed crater rims. Ground ice decay, sapping, or fluvial erosion removed the less resistant, porous material of crater rims while leaving the more resistant volcanic flow material. Differential erosion has thus led to a reversal of topography in which the original positive relief of the rim is reduced to a negative relief feature.

Description: The morphology of channels, valleys, chaotic and fretted terrains and many smaller features on Mars is consistent with the hypothesis that localized deterioration of thick layers of ice-rich permafrost was a dominant geologic process on the Martian surface. Such ground ice deterioration gave rise to large-scale mass movement, including sliding, slumping and sediment gravity flowage, perhaps also catastropic floods. In contrast to Earth, such mass movement processes on Mars lack effective competition from erosion by surface runoff. Therefore, Martian features due to mass movement grew to reach immense size without being greatly modified by secondary erosional processes. The Viking Mission to Mars in 1976 provided adequate measurements of the relevant physical parameters to constrain models for Martian permafrost.

Description: High-resolution pictures of talus slopes on Mars show small, dark streaks that characteristically widen downward. These streaks are different from the thin and even streaks of various albedos that stream from cliffs on talus slopes, but gradations between the two streak types occur and not all streaks can be classified with confidence. In order to study the nature and origin of the small, widening, dark streaks, all Viking pictures with a resolution of less than 100 m/pixel were surveyed. To date several hundred streaks were located, but only few are of high enough resolution to be confidently identified as widening downwards. The approximate dimensions of the streaks were measured and their shapes, numbers, position, and spacing on slopes were noted. They were plotted on a topographic map, and their relation to topography, geologic units, and regions of distinct thermal inertia and albedo were studied. Also noted was the season at which images containing streaks were acquired and the direction of illumination. Albedo measurements are in progress. Several streaks can be seen stereoscopically, but none are observed on color images. The observation of small dark streaks on talus slopes on Mars is compatible with an interpretation of their origin as eruptions of small masses of wet debris in places where steep walls intersect aquifers or where seasonal equatorial warming permits the local melting of ground ice.

Description: The valley networks of Mars are widely believed to have formed at a time when climatic conditions on the planet were significantly different from those that currently prevail. This view arises from the following observations: (1) the valleys form integrated branching networks which suggests fluid drainage, and water is the most plausible fluid, (2) the present atmosphere contains only minute amounts of water, (3) the networks appear to be more akin to terrestrial valleys that are eroded by streams of modest discharges than features that form by catastrophic floods, and (4) small streams of water will rapidly freeze under present climatic conditions. Climatic conditions at the time of formation of the valleys are studied based on the assumption that they were cut by running water.

Description: Images of the surface of Venus obtained by the Soviet Venera 9, 10, 13 and 14 landers are analyzed to provide a basis for understanding the nature of geologic processes operating there. Bedrock is exposed at the Venera 10, 13 and 14 sites and is characterized by semi-continuous, flat polygonal to subrounded patches up to several meters in width. The bedrock surface is often dominated by sub horizontal to horizontal layered plates with thicknesses of several cm and abundant linear and polygonal vertical fractures. Soils (particles 1 cm) are abundant at the Venera 9, 10 and 13 sites, but are uncommon at Venera 14. Features indicative of a strong aeolian influence (moats, dunes, wind tails) are not observed. Several hypotheses are considered for the origin of the bedrock surfaces, and it is concluded that bedrock originated from surface lava flows. The relative freshness of features observed by the Veneras suggests that erosion rates are very low or that some bedrock surfaces are geologically young.

Description: A tectonic orgin for Venus banded terrain is consistent with band spacing. Both compressional (folding) and extensional models for band formation can fit present observations. Band spacing cannot distinguish among scenarios for global heat loss and for the origin of highland terrain. Tectonic models for band formation indicate that the surface brittle layer in the venus highlands is no more than a few kilometers thick.

Description: A study to determine the feasibility of conducting experiments to simulate the aeolian environment on Venus as related to wind abrasion was completed. Ideally, such experiments should involve complete investigation of weathering, in which mechanical, thermal, and chemical parameters are taken into account. This is particularly important for Venus, where atmospheric temperatures and pressures at the surface produce an environment which is equivalent to low or medium grade metamorphic conditions on Earth. Details that describe the Venus Aeolian Abrasion Device (VAAD) are included. The VAAD device would enable experiments to be conducted with the same chemistry, temperature, pressure, and other physical properties of the Venus atmosphere near the surface. The proposed device enables the important aeolian parameters to be controlled and monitored, including particle size, velocity, impact-angle and flux, atmospheric pressure, temperature, and gas composition.

Description: Why the lowlands of Mars are concentrated in the Northern Hemisphere and the highlands in the Southern Hemisphere is probably the most fundamental unsolved problem in martian geology. No explanation that accounts both for this asymmetric distribution and for the isostatic equilibrium across the scarp or sloping transition zone dividing the two provinces has been generally accepted; thinning of the lithosphere in the northern hemisphere by internal processes has been suggested. Because other lowland-highland distributions on Mars, Moon, and Mercury are controlled by impact basins, it is proposed that a giant basin formed early in Mars' history has caused the martian hemispheric dichotomy as well.

Description: A number of researchers have concluded that saturation equilibrium cratering exists nowhere in the solar system, and therefore that diameter distributions in even the most heavily cratered provinces reveal initial production functions related to impacting bodies. Based on this premise, different populations of impactors are identified in different epochs and regions of the solar system. These hypotheses are clearly crucial to interpreting planetary history and need further independent examination. The production function in the outer solar system may differ from that in the inner solar system, but it is also possible that viscous relaxation of ice craters or immediate flooding of craters that penetrate through an ice lithosphere into watery substrate may explain the greater deficiency of large craters on icy moons. This problem is controversial and needs more study.

Description: Properties of the planetary surface and subsurface can affect the morphology of impact craters. A mechanism was proposed to explain pedestal craters and domed floors within fresh craters on Ganymede. Voyager 1 and 2 images with resolutions = to or 3.2 km/lp were examined and 523 fresh craters were identified. For each crater, the rim and ejecta diameters were measured, and the crater was characterized by ejecta class(es), interior features, floor morphology and target terrain. Of the craters examined, 97 show moderate to prominent doming of the crater floor; 340 craters have continuous ejecta which terminates in a scarp pedestal craters, of which 86 (25%) have a high albedo diffuse deposit beyond the pedestal.

Description: A systematic survey of the entire Mariner 10 coverage of Mercury was performed to determine the number, distribution and dimensions of additional ancient basins on the planet. Ancient multi-ringed basins on Mercury can be recognized by the following criteria: (1) arcs of massif chains and isolated massifs that protrude through younger units, (2) arcuate segments of lobate ridges (rupes) that align with massifs in circular patterns, (3) arcuate scarps that are aligned with ridges and massif, and (4) isolated regions of anomalously high topography within the intercrater regions of heavily cratered terrain. All of the newly identified basins predate the mercurian intercrater plains, previously held to be the oldest geologic unit on the planet. Subsequent structural evolution of various regions was influenced by the presence of these basins. Smooth plains units appear to be more extensive than mapped by Mariner 10 and more than 90 percent of them appear to be basin contained or basin related. The concentration of extensive smooth plains material within and associated with basin structural and depositional environments suggests a volcanic origin for most of this unit, analogous to the lunar maria. Basins appear to provide the basic structural pattern of early terrestrial planetary crusts.

Description: An improved version of the Pionner-Venus orbital data was used for a statistical analysis of global radar roughness and (alpha(0)) (rho) reflectivity. Classification maps of the venusian surface are produced in a supervised manner on the basis of statistical and empirical studies of the individual data sets. The primary objective is to assess the degree of homogeneity of surface radar properties within topographic provinces in order to map possible geologic boundaries. Maps were produced by correlating two data sets at a time. Classification of specific regions, such as Ishtar, has demonstrated that distinct geological units can be identified.

Description: Interest on Venus has centered on three regions; (1) Aphrodite Terra, especially east of the main uplant portion, (2) Ishtar Terra, especially Lakshmi Planum and its bounding scarp and massifs, and (3) Beta Regio-Phoebe Regio. The last region is topographically similar to the East African rift system, and has been inferred to have a similar tectonic origin. The Aphrodite region is part of a 21,000 km long tectonic zone that seems best explained as due to extension, and that may represent hot spots clustered along an incipient divergent plate boundary. The most interesting and complex portion of this tectonic zone is that part of eastern Aphrodite between Thetis Regio and Atla Regio. In contrast, the Lakshmi Planum region has many topographic characteristics suggesting that it is a true continent, and thus indicative of convergence and a thick crust. Detailed topographic contour maps of eastern Aphrodite Terra and of Lakshmi Planum are included.

Description: The results of analyses of near infrared reflectance spectra are inconsistent with numerous previous interpretations of the Reiner Gamma Formation. These include: (1) nue ardente or volcanic ash deposits, (2) volcanically derived sublimates, (3) high albedo volcanic deposits, and (4) highlands debris emplaced as impact ejecta. These results, strongly suggest that the selective preservation of high albedo features (formed by secondaries) by a local magnetic field enhancement is not a viable hypothesis. The results are generally consistent with, but place constraints on, the cometary impact hypothesis of Schultz and co-workers. While the presence of a magnetized component was not detected in either the bright or dark portions of the Reiner Gamma Formation, this material may be present in amounts under the current detection limits.

Description: On the basis of the icy conglomerate model of cometary nuclei, various observations demonstrate the spotted nature of many or most nuclei, i.e., regions of unusual activity, either high or low. Rotation periods, spin axes and even precession of the axes are determined. The observational evidence for variations in activity over the surfaces of cometary nuclei are listed and discussed. On June 11 the comet IRAS-ARAKI-ALCOCK approached the Earth to a distance of 0.031 AU, the nearest since C/Lexell, 1770 I, providing a unique opportunity for near-nucleus observations. Preliminary analysis of these images establishes the spin axis of the nucleus, with an oblioquity to the orbit plane of approximately 50 deg, and a lag angle of sublimation approximately 35 deg from the solar meridian on the nucleus. Asymmetries of the inner coma suggests a crazy-quilt distribution of ices with differing volatility over the surface of the nucleus. The observations of Comet P/Homes 1892 III, exhibiting two 8-10 magnitude bursts, are carefully analyzed. The grazing encounter produced, besides the first great burst, an active area on the nucleus, which was rotating retrograde with a period of 16.3hr and inclination nearly 180 deg. After the first burst the total magnitude fell less than two magnitudes from November 7 to November 30 (barely naked eye) while the nuclear region remained diffuse or complex, rarely if ever showing a stellar appearance. The fading was much more rapid after the second burst. The grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks.

Description: Dione is one of the most geologically complex of the Saturnian satellites. Crater counts and surface morphology indicates the geologic units observed are of variable age and origin. In an attempt to understand the processes which have affected Dione, a geologic map was prepared. Several geologic units were identified; ancient heavily cratered terrain, two plains units: cratered plains and lightly cratered plains, lobate deposits, crater rim deposits and bright wispy materials.

Description: For large parts of the surfaces of the Galilean satellites there is no stereoscopic high resolution imagery, and so for shadow-free regions far from the terminator, the only method of obtaining topograpic information is photoclinometry, the technique of converting brightness variations into local surface tilts and hence into topographic profiles and contour maps. The conversion from brightness changes to slopes require knowledge of the angular photometric function for the type of planetary surface terrain being analyzed, i.e., the relationship describing the brightness of the surface as a function of the angles of incidence (I) and emergence (E) of light at a surface element. In order to investigate the effects of these changes on the shapes of topographic profiles deduced from the functions, an area of grooved terrain (lines 500-505, samples 550-650 on frame 20640.27 0060J2) using wide ranges of values of all the adjustable parameters in Hapke's new photometric function were analyzed.

Description: Exploratory work on the structure of the Ionian lithosphere is reported. The approach is to examine temperature profiles within the lithosphere that result from different distributions of sulfur and silicates and different conductive heat fluxes, then compare such profiles with observations in the expectation that only a limited set of the profiles are possible. In this preliminary work some rather simplistic assumptions were taken and the report should be viewed more as a demonstration of a method rather than a presentation of results.

Description: A very broad band of electromagnetic radiation is emitted during solar flares, especially at the explosive phase. The existence of a large variety of plasmas with various densities and a wide range of temperatures or energies is proposed as the initiating agent. The manner in which the plasmas are heated and accelerated to subrelativistic and relativistic energies is discussed. Observational evidence on the characteristics of active regions which produced proton flares and on the structure of the associated nonthermal microwave bursts of the sun is presented. The behavior of subrelativistic electrons on the sun is described.

Description: The effects of external mechanical and climatic actions on the efficient operation of magnetic tape recording equipment are analyzed. The efficiency and reliability of the recording system are determined by the structural parameters and the characteristics of the individual elements of the transport mechanism circuit. The resistance of tape recording equipment to the effects of vibration is considered essential for reliable operations. Methods for insuring reliable tape transport and recording action are discussed.

Description: Problems in measurement of irregularities in angular velocity of rotating assemblies in memory devices with rigid and flexible magnetic data carriers are discussed. A device and method for determination of change in angular velocities in various frequency and rotation rate ranges are examined. A schematic diagram of a photoelectric sensor for recording the signal pulses is provided. Mathematical models are developed to show the amount of error which can result from misalignment of the test equipment.

Description: There are two types of experimental measurement errors of the Doppler data associated with the radio occultation, random and systematic. Random errors are due to thermal noise in the transmission channel, and the phase lock loop, and quantization error in the digital circuitry. These are called noise type errors. The systematic errors are due to geometric uncertainty and equipment phase instability. Considered is the amount of uncertainty, due to random measurement errors, in the refractivity profiles reconstructed by this type of indirect sensing experiment. A class of refractivity profiles is defined which approximately fit the set of measured data. Bounds are placed on the extent of this class of solution profiles. To accomplish this, the sensivity of the reconstructed refractivity profiles to errors in the measured quantity and the statistics of the errors in the measurement are examined.

Description: A review of exact techniques for determining the surface of a three-dimensional perfectly conducting body is given, followed by some new results on the uniqueness question concerning the number of measurements that may be required to explicitly determine the surface of the body. It is then shown that the inhomogeneous but spherically symmetric dielectric electromagnetic case is reducible to a scalar inverse problem that can be treated by known techniques.

Description: An estimate of the antenna noise temperature and the uplink signal-to-noise ratio has been made for Bremsstrahlung radiation emitted by a spacecraft ion beam; a worst-case situation in which the spacecraft antenna is located in the exit plane of the ion beam and directed at varying angles into the ion beam is assumed. Numerical results of the antenna noise temperature versus antenna pointing angle are given for a typical set of ion beam and antenna pattern parameters. The uplink signal-to-noise ratio due to the ion beam noise alone is given in terms of a critical range in AU at which a typical ranging transmission is received with S/N = 0 db. The effects of the ion beam divergence angle and antenna distance on the ion beam are also presented. Results of the study show typical increases in the antenna noise temperature of about 0.2 K and critical ranges of the order of 3-5 AU. An ion engine thus generally introduces an undetectable level of noise into a spacecraft receiver.

Description: Optimal design concepts are presented for two- and three-channel telemetry modes in the context of the Mariner Venus-Mercury 1973 mission and the usefulness of interplex modulation techniques is discussed. These ideas are applied as an example to one Mariner Venus-Mercury 1973 telemetry mode to demonstrate that interplex can reduce the required total average power by more than 2 dB in some cases.

Description: A peripheral drive belt on the Mariner Mars 1971 tape recorder failed when a thin longitudinal strip separated off one edge. Analysis showed that the most probable cause of failure occurred from flexural fatigue initiating in mechanically weak locations which are introduced into the belt during fabrication. Methyl ethyl ketone, which is employed as a cleaning solvent during fabrication, was found to cause permanent reduction in engineering properties of polyester and could have contributed to the reduction of the fatigue resistance. Fatigue properties of the polyester drive belt are reviewed for the operating condition, as well as the sensitivity of polyester to cleaning solvents and the origin of mechanically weak locations.

Description: Methods were developed for measuring frictional forces acting on a magnetic tape in motion or at rest, as well as the extent of stick slip. The effects of factors such as temperature, humidity, kind of gaseous atmosphere, and tape speed on the frictional interaction between various tapes and heads were investigated. Results were instrumental in the selection of a tape for the Mariner Mars 1971 spacecraft. Studies are reported on the stick slip behavior of tapes and the performance of a metallic tape, compared with the usual plastic tapes.

Description: Improvements to the design of the Mariner spacecraft resulted in the Viking spacecraft. The Viking spacecraft would consist of two major systems - an orbiter and a lander, while the lander would provide the means for safely delivering the scientific instruments to the surface, house, and provide the necessary power source and communication links for those experiments, the orbiter would transport the lander to Mars, rovide a platform for the Viking imaging system so that proposed landing sites could be surveyed and certified, relay lander science information back to Earth, and conduct scientific observations in its own right.

Description: Computer program for calculating radiation pattern of ATS 6 flexible rib-reinforced reflector

Description: Amplifier gain control for Apollo scan television signal enhancement

Description: The results of the reduction of simultaneous observations of 29 meteors are presented in tabular form. Fragmentation of the observations is discussed along with the 50 meteors not yet reduced.

Description: The procedures used in the analysis of television and simultaneous observations are described. Starting with the right ascension and declination of the meteor, the celestrial triangle formed by Sidell and the meteor is solved, and the epochs of the beginning and end of the meteor observation as recorded on the video tape are determined.

Description: The original image-orthicon equipment used for simultaneous radar and optical observations is described. The adaptations made to enhance its usefulness for meteor observations, and the specialized calibration and photometric procedures developed for this purpose are also described. Some brief comments concerning the use of the secondary electron conduction vidicon are included.

Description: Performance of mercury cadmium telluride photovoltaic infrared mixer for ATS 6 carbon dioxide laser communication system

Description: Median noon absorption values for each month from 1964 through 1967, the diurnal variations of absorption on the regular world days, and the seasonal variations of absorption are given. The dependence of the absorption coefficient on sunspot number is analyzed.

Description: Based on the assumption that the ionized column left behind a moving meteroroid is underdense, it is shown that radar observations of the column yield resonable aproximations to the meteoriod's speed and trajectory. The principles and procedures for finding a meteor's position and vector velocity from the observed data are also presented.

Description: The procedures for calibrating the antenna patterns of the Havana radar system are described along with the reduction of the measurements made using a dipole towed behind an airplane. The power-gain pattern for the north, south, and joint troughs of sites 3 and 4 are plotted.

Description: A general description is given of the eight-station system at Havana which incorporated high-gain antennas and a powerful transmitter to reach faint meteors on the order of magnitude of plus 12. The station location, principle of system design, systems connections, transmitter, receivers, logics, range measurement, and recording are described.

Description: The Tharsis ridge system appears to form a great circle around the major volcanoes. The roughly circumferential orientation of these ridges could be interpreted as the formation of a ridge system in response to a single stress field with a center near Pavonis Mons. Wise, et al. (1979) plotted the perpendiculars to strikes of ridges on the eastern flanks of Tharsis as great circles on the upper hemisphere of an equal area net. In order to further test for circular symmetry and possible other influences on ridge orientations, normals to vector means of ridge orientations were calculated using over 1850 digitized ridge segments sampled in 10 degree boxes. Orientations of individual ridge segments were weighted by their lengths, and the magnitudes of normals to vectors means were weighted by cummulative length of the ridge segments. Normals to vector means with magnitudes less than 100 km are not shown. Assuming a single fold origin for ridges, the resulting plot shows compressive stress trajectories for the ridges in the Tharsis region. The averaged compressive stress orientation around Tharsis confirm the suggestion by Wise, et al. that the ridge system is not concentric to any single point.

Description: In this paper the tectonic features of the Elysium region are identified and characterized. Identification of features was made using USGS controlled photomosaics (Elysium quadrangle, and portions of Amenthes and Cebrenia quadrangles); Viking Orbiter photographic data were used in individual cases to assist in identification. The positions and orientations of tectonic features can then be used, in conjunction with estimates of the mass of the volcanic load obtained from gravity modelling, to constrain the thickness of the elastic lithosphere in the region.

Description: Several 3.8 cm radar frames were calibrated empirically by histogram fitting, because no instrument background data is available. Then data were corrected for geometric distortion by: (1) redetermining position of individual frames using most accurate recent lunar ephemerides; (2) reprojecting frames into simple cylindrical map projection; (3) using most recent catalog of lunar craters to determine the exact positions of features identifiable on radar frames; and (4) correcting for apparent distortion (misplacement of features in frames) by resampling using a different bilinear interpolation derived for each of the parallelopideds of the set defined for each frame. A hardcopy set of corrected frames was produced. Attempts to produce a mosaic of such corrected frames continue. The resulting mosaic can be used to show the systematic relationship between photographic thermal IR and radar data at different wavelengths in a region dominated by both mare and highland terrain.

Description: Studies of the stratigraphy of southwest Coprates have led to further constraints on both the geographic extent and the relative age of the major compressional ridge forming events in the Tharsis region of Mars. Southwestern Coprates is characterized by curvilinear ridges that are regularly spaced, suggestive of harmonic folding. The western edge of the ridged plains unit of Coprates is marked by volcanic flow fronts. In an enhanced Viking-Orbiter image, a ridge can be seen completely surrounded by a flow with only a small portion of the ridge crest still exposed. Comparison of partially buried ridges on the western edge of the ridged plains to those in central Coprates suggests that flooding of the inter-ridge plains does not exceed a few hundred meters. The morphological relationship between the flow units to the west and the ridged plains indicates that the deformational events in this region predates the emplacement of the younger units.

Description: Layered deposits within Valles Marineris and its associated system of canyons have been considered to consist of two different rock types: (1) thick, competent, cliff-forming, light and dark bedded material in canyon walls, and (2) relatively thin, alternating series of light and dark layered material, both horizontal and inclined, that form rounded hills and large flat-topped mesas rising above the canyon floors. The dissimilarity in appearance between canyon wall and floor materials, as well as their contrasting patterns of erosion, have been considered strong evidence that their modes of origin were different.

Description: The scarps along the margins of the Vales Marineris display a complex assemblage of forms that have been related to a variety of mass wasting and sapping processes. These scarp segments display variations in the degree of development of spur and gully topography, the number and density of apparent sapping features and the frequency of large scale landslides which reflect the age, geology and processes of slope development throughout the Valles Marineris. This regional analysis should provide more information on the geologic evolution of the Valles Marineris as well as new insight into the relative importance of different processes in the development of the scarp forms. In order to evaluate the regional variation in scarp form and the influence of time and structure on scarp development geomorphic mapping and morphometric analysis of geologically distinct regions of Valles Marineris is being undertaken.

Description: Parallel studies of Martian geomorphic features and their analogs on Earth continue to be fruitful in deciphering the geologic history of Mars. In the context of rock weathering, the Earth-analog approach is admirably served by the study of meteorites recovered from ice sheets in Antarctica. The weathering environment of Victoria Land possesses several Mars-like attributes. Four of the five Antarctic meteorites being studied contain rust and EETA79005 further possesses a conspicuous, dark, weathering rind on one side. Secondary minerals (rust and salts) occur both on the surfaces and interiors of some of the samples and textural evidence indicates that such secondary mineralization contributed to physical weathering (by salt riving) of the rocks. Several different rust morphologies occur and emphasis is being placed on identifying the phase compositions of the various rust occurrances. A thorough understanding of terrestrial weathering features of the meteorites is a prerequisite for identifying possible Martian weathering features (if such features exist) that might be postulated to occur in some meteorites.

Description: Photometric studies of crater related bright and dark streaks have strongly supported the hypothesis that the bright streaks are excess dust deposits and dark streaks are erosional windows in a partial dust cover. Red-blue (and red-violet) plots show that bright streaks are consistent with mosaics of bright red dust and background material. Here the plains are also consistent with a partial dust cover; the dark streak is the least covered area. Bright and dark streaks both reverse contrast relative to surrounding plains at phase angles over 100 deg in violet filter images. The similar phase behavior of both bright and dark streaks supports the idea that they are both changes in the amount of dust cover. Red-violet plots of bright streaks are most easily explained by mosaics of optically thick dust and plains material. Lengths of bright streaks are independent of their contrasts. This suggests the streak deposition, if in the mosaic patterns indicated above, is a function of available sites of deposition, rather than atmospheric dust loading. Contrasts of dark streaks with plains indicate the plains have fractional dust covers nealy as great as the maximum additional cover in bright streaks. The bright streaks thus store little of the global supply of dust.

Description: Viking Lander 1 observations on Mars were punctuated by a strong local dust storm after two martian years of mild wind conditions. Tens of micrometers of dust settled to the surface during global dust storms of the first two falls and winters; some of this dust was locally removed during the second year. A late winter local dust storm of the first year caused little or no erosion of the surface materials despite wind speeds of 25 to 30 m/s. The strong local dust storm occurred during late winter of the third martian year. Winds of this storm altered and demolished small conical piles of surface materials constructed at the onset the first winter, removed 4 to 5 mm size fragments, displaced centimeter size fragments, destroyed clouds in areas disrupted by the sampler and footpad, eroded impact pits, and darkened the sky. Movement of erosional products and tiny wind tails indicate easterly to northeasterly winds. If the 4 to 5 mm size fragments were entrained and removd by the wind, threshold friction speeds near 3 to 5 m/s would have been required for the atmospheric temperatures and pressures that prevailed during the late winter of the third year.

Description: There are classes of landforms whose presence on Mars is strongly suggestive, if not confirmatory, of the participation of volatiles, presumably water, in its geomorphic development: (1) valley networks, (2) outflow channels, (3) landslides, and (4) flow-ejecta blankets. The first two may represent landforms generated by the movement of volatiles from sources, while the latter two probably represent the dissipation of energy generated by forcing inputs (e.g., kinetic energy and gravity) modulated by volatiles. In many areas on Mars, all four processes have acted on the same lithologic materials and were influenced by the composition of those units, and possibility by the climatic regime at the time of their formation. One of the approaches discussed to this specific problem of landform genesis, and to the general problem of the present and past states of martian volatiles, is to attempt to constrain the distribution, amount, and history of available volatiles by using possible evidence of volatile participation expressed in the morphology of other related landforms (e.g., flow-ejecta blankets and landslides) coupled with physical models for landform genesis.

Description: Most cratering experiments are designed to study the effects of a single hypervelocity impact into a target of uniform properties. Experiments involving multiple impacts are usually limited to low velocity projectiles and unconsolidated target materials. Gault described saturation cratering in an unconsolidated target. Quaide and Oberbeck studied crater forms produced by hypervelocity impact into layered targets. Several investigators have modeled the generation of either a regolith or megaregolith by repeated impact on planetary surfaces. Studies now in progress examine changes in crater morphology and target properties by repeated impact into an initially consolidated target. Current studies employ low velocity projectiles (2 g at 0.5 km/sec) and consolidated salt targets. Records of crater size, morphology, and accumulated ejecta thickness are maintained as impacts collect on the surface.

Description: The crater size/frequency distributions of large ( 8 km) craters on the Moon and terrestrial planets display two very different curves representing two crater populations. The heavily cratered regions of the Moon, Mercury, and Mars show the same highly structured curve which cannot be represented by a single slope distribution function. In contrast, the lunar post mare crater population has a size/frequency distribution which differs significantly from that in the highlands over the same diameter range, and can be represented by a single-slope distribution function of -2.8 differential. On areas of martian lightly cratered northern plains, the crater population is essentially identical to that of the post mare population. This indicates that the same two families of impacting objects were responsible for the cratering records on both Moon and Mars. The thickness of mantling material varies among the various plains units, and can be calculated from the depth/diameter scaling relations for martian craters.

Description: A generalized model for short period comets is developed which integrates in a fairly rigorous manner the isolation history of regions on rotating comets with specified axial orientation and the complex feedback processes involving heat, gas and dust transport, dust mantle development and coma opacity. Attention is focused on development, reconfiguration and partial or complete launching of dust mantles and the reciprocal effects of these three processes on ice surface temperature and gas and dust production. The dust mantle controls the H2O flux not only by its effect on the temperature at the ice interface but (dominantly) by its dynamic stability which strongly influences vapor diffusivity. The model includes the effects of latitude, rotation and spin axis orientation are included and applied to an initially homogeneous sphere of H2O ice and silicate using the orbital parameters of comet Encke. Numerous variations of the model, using combinations of grain size distribution, dust-to-ice ratio, latitude and spin axis orientation, are presented and discussed. Resulted for a similar nonrotating, constant Sun orientation models are also included.