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Danielson, G. E.

Publications and source records attributed to Danielson, G. E..

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Spacecraft imaging of planets - Camera systems from Mariner to Space Telescope

The purpose of the study is to illustrate how imaging has been used to successfully explore the planets scientifically. The scientific, technological, and systems background for imaging instruments on Mariner, Viking, and Voyager are briefly reviewed, along with the scientific data return. Attention is also given to the present imaging systems on Galileo and the Space Telescope. A comparison of all these imaging systems is included, together with an assessment of their actual or projected science return.

Danielson, G. E.↗
NASA NTRS1980

First Voyager view of the rings of Saturn

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.

Collins, S.A.↗
NASA NTRS1979

The Galilean satellites and Jupiter - Voyager 2 imaging science results

Continuous global observations of Jupiter were made by Voyager 2 for a period of 63 days. Voyager 2 provided images that both complement and supplement the Voyager 1 images. The combined Voyager 1 and 2 observations of Jupiter provide an almost continuous record, over a 6-month period, of the behavior of the Jovian atmosphere at a resolution far better than can be obtained from earth-based studies. The present report briefly describes the changes in the cloud morphologies and local atmospheric motions. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but reveals a system of overlapping bright and dark linear features. Ganymede exhibits at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.

Smith, B. A.↗
NASA NTRS1979

Discovery of a new Jupiter satellite

During detailed analysis of Voyager 2 pictures of the Jupiter ring, a starlike object was identified in the plane of the ring. The same object was subsequently found on a higher-resolution frame and proved to be a satellite of Jupiter. This satellite has a circular orbit whose radius is 1.8 Jupiter radii, a period of 7 hours and 8 minutes, and a diameter of less than 40 kilometers. It is located at the outer edge of the Jupiter ring.

Jewitt, D. C.↗
NASA NTRS1979

Jupiter's rings

Voyager 2 observations of the jovian ring system discovered by Voyager 1 are presented. The rings were observed both above and below the jovian equatorial plane and at extremely low and high phase angles. This ring system seems to represent a steady state configuration for small particles that are slowly moving in toward Jupiter. It must be resupplied from sources well outside Roche's limit.

Owen, T.↗
NASA NTRS1978

Venus in motion

A comprehensive set of television pictures of Venus taken by the Mariner 10 spacecraft is presented. Included is a chronological sequence of television images illustrating the development, variety, and circulation of Venus upper-atmospheric phenomena as viewed in the near-ultraviolet. The higher-resolution images have been assembled into global mosaics to facilitate comparison. Figures and tables describing the imaging sequences have been included to provide a guide to the more complete set of 3400 Venus images on file at the National Space Science Data Center.

Anderson, J. L.↗
NASA NTRS1977

Voyager imaging experiment

The Voyager imaging experiment, which involves two independently operated television systems (a narrow- and a wide-angle camera), is designed to conduct investigations of the atmospheres and surface properties of Jupiter, Saturn, their satellites and Saturn's rings. Objects of the investigations include the horizontal and vertical structure of visible clouds, the vertical structure of high, optically thin scattering layers on Jupiter and Saturn, the Great Red Spot, the South Equatorial Belt, chromophores on Io and Titan, the geology of several satellites, the masses, spin axes and periods of rotation of several satellites, the radial distribution of material in Saturn's rings, and the optical scattering properties of the primaries, rings, and satellites at a variety of wavelengths and phase angles.

Smith, B. A.↗
NASA NTRS1976

Space-time relationships in the UV markings on Venus

A group of geometrically rectified composite pictures taken with the Mariner 10 television cameras is presented which shows the temporal development of UV markings at various locations on Venus over the last seven days of the television experiment. The pictures are of two types: one in which the development of a marking is followed in a reference frame that moves with the apparent motion of the atmosphere and a second in which the development of the markings at fixed angular distances from the subsolar meridian can be seen. By comparing these composites with Mercator projections of single Mariner frames, it is shown that: (1) large-scale markings between + and - 45 deg latitude have lifetimes in excess of four days and move en masse with the apparent motion at the equator; (2) smaller-scale markings have lifetimes between 1.5 and 4 days; (3) the polar ring, bowlike waves, circumequatorial belts, and cellular features all exhibit rapid growth, modulation, or propagation characteristics; and (4) a single dark horizontal Y-shaped marking encircles the planet. It is suggested that both the Y and the polar ring are visible manifestations of propagating waves.

Belton, M. J. S.↗
NASA NTRS1976

Planetary imaging - Past, present, and future

Recent exploration of the planets has been highlighted by the development of visual imaging systems carried on board the spacecraft. This paper describes the evolution of planetary camera systems from the earliest reconnaissance flight to Mars in 1965 (Mariner 4) through the planned mission to Jupiter and Saturn in 1977. Advances in telecommunication performance, mission planning and operations, and digital processing of images are also discussed. Science objectives and changes in the imaging systems required to meet these objectives are discussed for the Mariner Mars 1971 (Mariner 9), Mariner Venus-Mercury (Mariner 10), Viking 1975 (Mars Orbiter), and Mariner Jupiter-Saturn 1977 missions. The last section of the paper describes future plans for imaging experiments based on cameras using solid-state sensors, particularly charge-coupled devices.

Masursky, H.↗
NASA NTRS1975

Preliminary imaging results from the second Mercury encounter

The second Mercury encounter has resulted in the acquisition of about 360 pictures of the south polar regions which provide a reliable cartographic and geologic tie between the two sides of the planet photographed on the first encounter. Stereoscopic coverage of large areas of the southern hemisphere was obtained by combining Mercury 1 and 2 pictures taken at different viewing angles. The south polar regions consist of heavily cratered terrain and intercrater plains interspersed with patches of smooth plains. No large areas of smooth plains similar to those surrounding Caloris occur in the south polar regions. No new types of terrain have been recognized, but lobate scarps are common. The second largest basin seen by Mariner 10 has been confirmed on the new photography. At high solar elevations the surface displays an abundance of rays and rayed craters.

Strom, R. G.↗
NASA NTRS1974

Mercury's surface - Preliminary description and interpretation from Mariner 10 pictures

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

Murray, B. C.↗
NASA NTRS1974

Mariner 10 pictures of Mercury - First results

Mercury has a heavily cratered surface containing basins up to at least 1300 kilometers diameter flooded with mare-like material. Many features are closely similar to those on the moon, but significant structural differences exist. Major chemical differentiation before termination of accretion is implied.

Murray, B. C.↗
NASA NTRS1974

Venus - Atmospheric motion and structure from Mariner 10 pictures

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

Murray, B. C.↗
NASA NTRS1974

Television observations of Mercury by Mariner 10

The morphology and optical properties of the surface of Mercury resemble that of the moon in remarkable detail, recording a very similar sequence of events; chemical and mineralogical similarity of the outer layers is implied. Mercury is probably a differentiated planet with an iron-rich core. Differentiation is inferred to have occurred very early. No evidence of atmospheric modification of any landform is found. Large-scale scarps and ridges unlike lunar or Martian features may reflect a unique period of planetary compression near the end of heavy bombardment, perhaps related to contraction of the core.

Murray, B. C.↗
NASA NTRS1971

Imaging of Mercury and Venus from a flyby.

Study of an imaging experiment planned for the 1973 Mariner Venus/Mercury flyby mission. Scientific objectives are presented together with mission constraints, analysis of alternative systems, and the rationale for the final choice. The final selection was a vidicon camera quite similar to that used for Mariner Mars 1971, but with the capability of real time transmission during the Venus and Mercury flybys. Systematic high resolution UV photography of Venus is planned after encounter in an attempt to understand the nature of the mysterious UV markings and their apparent 4- to 5-day rotation period.

Murray, B. C.↗