Engineering topics
Publications and source records attributed to Lane, A. L..
Results are reported for optical-wavelength photopolarimetry of Ganymede from Voyager 1. A phase coefficient of 0.011 + or - 0.001 mag/deg and an opposition effect of 0.17 + or - 0.03 mag are derived. It is shown that Ganymede's surface is probably more porous than Callisto's and that micrometeoroids may continuously roughen the surface of Ganymede.
Ultraviolet absorption bands of sulfur dioxide have been detected in the reflectance spectrum of Venus using the high resolution spectrometer of the International Ultraviolet Explorer (IUE). The identification of these bands in the 2080 to 2180 A range has been verified by comparison with laboratory absorption spectra. An estimate of the SO2 vertical column density using a reflecting layer model is 4 x 10 to the 16th sq cm.
IUE observations indicate that the spectrum of 3C 273 is similar to that of other large-redshift quasars. There is a large excess of flux in the range 2400 A to 5300 A, which encompasses the Balmer jump region but which does not appear to be explainable by Balmer emission. The intensity ratio of Lyman-alpha to H-beta is 5.5, in agreement with other measures and a factor 6 smaller than the recombination value. The only absorption lines in the spectrum are due to our Galaxy. There is marginal evidence for a depression of the continuum shortward of the Lyman-alpha emission line, but the errors are too large to warrant any conclusion that 3C 273 has a rich absorption-line spectrum such as that seen in large-redshift quasars. The absence of emission and absorption lines of Fe II leads to the conclusion that resonance fluorescence probably produces the visual Fe II emission lines.
An overview of the Voyager 1 encounter with Jupiter is presented. Voyager conducted close range measurements of the atmosphere, satellites and magnetosphere of Jupiter from January 6, 1979 to April 13, 1979, coming as close as 348,890 km to the planet. The three-axis stabilized spacecraft carries radioisotope thermoelectric generators providing 445 W of power to the instruments and transmitters and makes use of an X-band telemetry rate of up to 115.2 kbit/sec, a scan platform providing pointing control of 0.15 deg/axis for the instruments carried on it, and three interconnected computer systems. The trajectory of Voyager through the Galilean satellites is illustrated, noting that the trajectory allows for periods of sun and earth occultation, south polar passage by Io, close encounters with Ganymede and Callisto and earth-Jupiter communications distances supporting 21 to 22 h of maximum data rates daily. Highlights of the results of the investigations are presented.
Observations of atmospheric ultraviolet emission between 1350 and 2200 A from the night side of Venus, made by the International Ultraviolet Explorer (IUE), are reported. Low dispersion spectra taken by the short and long wavelength IUE spectrographs clearly show the (0,0) band of the NO delta system at 1909 A; the delta (0,1) band at 1980 A and the delta (0,2) band are indicated, while the (2,0) Cameron band of CO at 1928 A does not seem to be present. The relative band intensities appear to be the same as in earth airglow, where the excitation mechanism has been identified as radiative association of O and N atoms. The column emission rate of 0.5 kR implies a larger N to O ratio in the atmosphere of Venus than in that of the earth.
During the scientific commissioning phase of IUE several spectra were acquired from objects residing in the Solar System. The activities focused on testing numerous parameters which would indicate the usefulness of IUE for planetary science. It seems that IUE can successfully tackle many important questions and the data analysis and interpretation of the initial set of observations has begun.
In connection with a need for more definitive information concerning the composition of Phobos in a study of its origin, an ultraviolet-visible-infrared reflectance spectrum of the Martian satellite was compiled from the Mariner 9 ultraviolet spectrometer, Viking lander imaging, and ground-based photometric data. The probable surface composition of Phobos was deduced by comparing the obtained spectrum with the spectra of asteroids of known composition. The considered data show that the reflectivity of Phobos is flat from 1100 to 400 nm but decreases sharply in the ultraviolet to about 1 percent at 212 nm. The reflectance spectrum is similar to the spectra of asteroids Ceres and Pallas which were found to have surface compositions similar to that of carbonaceous chondrites. It is concluded that the surface composition of Phobos is also similar to that of carbonaceous chondrites. The results of the investigation point to different modes of origin for Mars and Phobos.
The reflectivity of Phobos has been determined in the spectral region from 0.4 to 1.1 micrometers from images taken with a Viking lander camera. The reflectivity curve is flat in this spectral interval and the geometric albedo equals 0.05 + or - 0.01. These results, together with Phobos's reflectivity spectrum in the ultraviolet, are compared with laboratory spectra of carbonaceous chondrites and basalts. The spectra of carbonaceous chondrites are consistent with the observations, whereas the basalt spectra are not. These findings raise the possibility that Phobos may be a captured object rather than a natural satellite of Mars.
Solid state filter with active crystal element increases sensitivity and resolution of passive and active spectrometers. Filter is capable of ranging through infrared and visible spectra, can be built as portable device for field use, and is suitable for ecological surveying, for pollution detection, and for pollutant classification.
Selected results are presented for an analysis of Mariner 9 1304-A data from the first 100 passes. Based on a comparison of limb data, the exospheric temperature appears lower on several Mariner 9 passes than when Mariner 6 and 7 encountered the planet in 1969. Temperatures of 300 and 350 K are considered in the atmospheric modeling. At 300 K, derived values of the atomic oxygen concentration are typically between 0.5 and 1 percent of the total density at 135 km, based on fitting theoretical intensities to limb data from several passes. Structure in the limb data below 200 km suggests the possibility that approximately 0.2 kR of the observed approximately 0.8 kR near 150 km is due to dissociative excitation of CO2. There is variability in limb profiles indicating changes in the O distribution with time. The variability does not appear to follow a recognizable pattern. Interpretation of the 1304-A disc data shows a correlation in intensity with the 10.7 cm solar flux and larger O concentrations in the afternoon than in the morning. The correlation in intensity with the 10.7 cm flux is probably due largely to variation in the solar 1304-A fluxes. Selected disc data show localized and random enhancements in the intensity.
Analysis of the bright-limb profiles obtained by the Mariner 9 ultraviolet spectrometer during the December 1971 dust storm on Mars shows that the dust extended to an altitude of plus or minus 10 km, with a sharp cutoff in altitude distribution. Above the dust layer, the reflected signal is characterized by Rayleigh scattering in the wavelength interval 2100 to 3500 A. Detached haze layers were detected at an altitude of 70 plus or minus 10 km at the top of the dust layer. The haze layers have a nominal optical thickness of about 0.0001 and a geometrical thickness of 3 to 10 km and are probably a condensate of small CO2 or H2O ice particles (mean radius less than 0.1 micron). Similar features were revealed in Mariner 9 TV pictures of the limb.
The photoionization efficiency curves of H2(+), O2(+), and HO2(+) have been studied in a mixture of hydrogen and oxygen over the wavelength range from 650 to 810 A. The HO2(+) ion appears at 804 A, the threshold for ionization of H2, by the reaction H2(+) + O2 yields HO2(+) + H. The relative photoionization efficiency curves of H2(+) and HO2(+) are the same from 804 to 764 A. Below 764 A production of the 4 Pi u metastable electronic state of O2(+) leads to the formation of HO2(+) by the reaction O2(+)(a 4 Pi u) + H2 yields HO2(+) + H.
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The original scientific objectives and the achieved results are discussed. The upper atmosphere was found to have a variable temperature, with a mean exospheric temperature of 325 K; composed predominantley of CO2. Measurements of hydrogen and ozone are analyzed.
Selected results are presented for an analysis of Mariner 9 1304-A data from the first 100 passes. Based on a comparison of limb data, the exospheric temperature appears lower on several Mariner 9 passes than when Mariner 6 and 7 encountered the planet in 1969. Temperatures of 300 and 350 K are considered in the atmospheric modeling. At 300 K, derived values of the atomic oxygen concentration are typically between 0.5 and 1% of the total density at 135 km, based on fitting theoretical intensities to limb data from several passes. Structure in the limb data below 200 km suggests the possibility that approximately 0.2 kR of the observed approximately 0.8 kR near 150 km is due to dissociative excitation of CO2. There is variability in limb profiles, thus indicating changes in the O distribution with time. The variability does not appear to follow a recognizable pattern. Interpretation of the 1304-A disk data shows a correlation in intensity with the 10.7-cm solar flux and larger O concentrations in the afternoon than in the morning. The correlation in intensity with the 10.7-cm flux is probably due largely to variation in the solar 1304-A fluxes.
It is possible to model the ultraviolet terminator observations of Mariner 9 either with a homogeneous atmosphere or with a scattering layer in addition to a homogeneous atmosphere. The characteristic shape of the twilight intensity variation is dependent on the latitude of observation. Observations north of 55N require a homogeneous model. Twilight measurements south of 55N indicate that a scattering layer may be a general Martian occurrence, at least in the evening. The day-to-day surveillance of the Martian terminator during the first 216 Mariner 9 revolutions indicates haze formation in the evening, and its continued presence until early morning is a daily occurrence in mid-latitudes up to 50N.
Selected results are presented for a considerable quantity of Mariner 9 1304-A data for the first 100 revolutions from both the bright limb and disk of Mars. The limb data suggest that the exospheric temperature is less than it was in 1969 when Mariners 6 and 7 encountered the planet. Similar (O) concentrations (0.5 to 1%) are derived for a temperature of about 300 K. Structure in the limb profiles below 200 km suggests the possibility that about 0.2 kR of the observed approximately 0.8 kR near 150 km is due to dissociative excitation of CO2. Significant differences in selected limb profiles suggest that local as well as random variations in (O) occur.
On Mars, the Mariner observations show a twenty-fold variation in the amount of ozone, depending on the presence or absence of another minor constituent, water vapor, in the atmosphere. In the evolution of earth's primitive atmosphere, the formation of an ozone layer may have played an important role in the prebiotic chemistry that took place on the surface. The seasonal formation and disappearance of ozone in the contemporary Martian atmosphere may be of consequence in any prebiotic chemistry that may be occurring there.