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NASA NTRS1975

Procedure for locating 10 km UTM grid on Alabama County general highway maps

Each county highway map has a geographic grid of degrees and tens of minutes in both longitude and latitude in the margins and within the map as intersection crosses. These will be used to locate the universal transverse mercator (UTM) grid at 10 km intervals. Since the maps used may have stretched or shrunk in height and/or width, interpolation should be done between the 10 min intersections when possible. A table of UTM coordinates of 10 min intersections is required and included. In Alabama, all eastings are referred to a false easting of 500,000 m at 87 deg W longitude (central meridian, CM).

Paludan, C. T. N.↗
NASA NTRS1975

Recent increase in Jupiter's decimetric radio emission

Observations of the linear polarization properties of Jupiter's decimetric radioemission showed the planet's total intensity to increase between late summer 1973 and July 1974. Measurements were made with the NASA 64-m parabolic antenna operating at a wavelength of 13.1 cm. Data were plotted as a function of the longitude of the central meridian. Both data sets showed similar periodic intensity variation with longitude. However, the 1974 data points were consistently above the corresponding 1973 values. The flux density difference was attributed to the increase in the planet's decimetric radio emission. Measured at wavelengths of 21 cm and 11 to 13 cm the average peak flux densities were plotted as a function of the epoch of each observation.

Klein, M. J.↗
NASA NTRS1975

Galilean satellite mutual occultation data processing

Results of processing seven mutual occultation lightcurves are presented. The lightcurves were obtained using the 60-in. telescope (152 cm) at Mt. Wilson to observe six J1 occulting J2 events and one J3 occulting J2 event. Using a uniformly illuminated disk model, local satellite Jovicentric longitude corrections of 675 plus or minus 150 km, 275 plus or minus 240 km, and 1175 plus or minus 350 km for J1, J2, and J3, respectively, were determined. These corrections enabled the event midpoint times to be computed to within 5 sec of the observed midpoint times for all seven events. These longitude corrections have been verified by Pioneer 10 and recent (1973 and 1974) conventional Jovian eclipse observations. A relative J1:J2 out-of-plane error of less than a few hundred kilometers has been indicated; however, it appears that the relative J3:J2 out-of-plane error is larger than 600 km. Deficiencies in both the uniformly illuminated disk model and Sampson's theory of the Galilean satellite motions for the reduction of mutual event data are described.

Duxbury, T. C.↗
NASA NTRS1975

Results of long-term synoptic monitoring of Jupiter's decametric radiation

Results of the analysis of the large, homogeneous set of measurements of Jupiter's emission at 16.7 and 22.2 MHz for the apparitions during the period 1966-1974 were presented. An update of the radio rotation period determination which includes provision for beaming effects due to variations in the Jovicentric declination of the earth was presented. Some estimates of the magnitude of possible long-term variations in the rotation period were also discussed. The data clearly shows the Io-independent emission features associated with the System III central meridian longitudes of all three major Io-related source regions. There is also some evidence for heretofore unrecognized Io-related emission features which are apparently independent of the central meridian longitude. The possibility of three kinds of emission are suggested: (1) Io-stimulated, sharply beamed emission, (2) Io-independent, sharply beamed emission, and (3) Io-stimulated, broadly beamed emission.

Alexander, J. K.↗
NASA NTRS1975

Real-time orbit estimation for ATS-6 from redundant attitude sensors

A program installed in the ATSOCC on-line computer operates with attitude sensor data to produce a smoothed real-time orbit estimate. This estimate is obtained from a Kalman filter which enables the estimate to be maintained in the absence of T/M data. The results are described of analytical and numerical investigations into the sensitivity of Control Center output to the position errors resulting from the real-time estimation. The results of the numerical investigation, which used several segments of ATS-6 data gathered during the Sensor Data Acquisition run on August 19, 1974, show that the implemented system can achieve absolute position determination with an error of about 100 km, implying pointing errors of less than 0.2 deg in latitude and longitude. This compares very favorably with ATS-6 specifications of approximately 0.5 deg in latitude-longitude.

Englar, T. S., Jr.↗
NASA NTRS1975

A possible correlation between maxima of the far ultraviolet solar irradiance and central meridian passages of solar magnetic sector boundaries

Satellite observations of the sun over almost 5 yrs show that principally two UV active longitudes have persisted over a significant portion of this observational period. A comparison between the position of solar magnetic sector boundaries and UV enhancements of the sun seems to show, at least during the year 1969, that the UV maxima tend to occur near the times when a solar sector boundary is near central meridian. An estimate of the magnitude of the variable UV solar energy input into the atmosphere resulting from the rotation of active solar longitudes is that for wavelengths less than 175 nm and down to H Lyman-alpha it exceeds the annual variation, whereas at longer wavelengths it is less.

Heath, D. F.↗
NASA NTRS1976

SAS-2 galactic gamma ray results, 1

Continuing analysis of the data from the SAS-2 high energy gamma-ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitude 310 and 45 deg, corresponding to a region within 7kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315 deg, 330 deg, 345 deg, 0 deg, and 35 deg. These peaks appear to be correlated with such galactic features and components as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic ray concentrations, and photon fields.

Thompson, D. J.↗
NASA NTRS1975

Dynamical consequences of meteorite impacts on the moon

The magnitudes of the excitation of free precession of the lunar spin axis about the position defined by Cassini's laws, free libration in longitude, and free wobble are determined as a function of meteorite angular momentum relative to the lunar center of mass and the position of impact on the lunar surface. Angular-momentum conservation suffices for the estimates of precession and libration excitation, but a cratering model for the ejecta distribution is necessary for the estimate of the wobble excitation. The simultaneous excitation of free wobble is always associated with the excitation of precession, and the angular amplitude is at least comparable to, but may exceed, that of the induced precession by a factor of 3 or 4. It is possible to excite a free libration in longitude with no first-order excitation of free wobble, but generally, all three free motions are excited simultaneously. The induced libration will nearly always have the largest amplitude. For crater sizes scaled as powers of impact energy, impacts leaving craters as small as a few kilometers in diameter can excite free motions which will ultimately be observable by the lunar laser-ranging experiment.

Peale, S. J.↗
NASA NTRS1976

An observation of the diffuse soft X-ray/extreme-ultraviolet background

Results are reported for observations of diffuse radiation in the spectral bands from 114 to 150 A and from 44 to 120 A, which were made with rocket-borne proportional counters in areas of the sky near galactic coordinates 150 deg longitude, -15 deg latitude and 189 deg longitude, 3 deg latitude. The observed fluxes are 0.125 photon per sq cm/s/sr/eV at 180 eV, which is consistent with previous measurements, and 3.2 photons per sq cm/s/sr/eV at 100 eV, which indicates a steeply rising spectrum. It is noted that these fluxes are significantly smaller than those detected by Yentis et al. (1972), and the differences are attributed to either a terrestrial origin of the fluxes or the direction of observation. Constraints are placed on the parameters of simple emission models of celestial origin, and a rigorous upper limit is determined for the space density of white dwarfs at a blackbody temperature of at least 100,000 K.

Cash, W.↗
NASA NTRS1975

Molecular hydrogen in the galaxy and galactic gamma rays

Estimates made of column densities of H2 at galactic longitude equals 0 deg indicate that H2 is far more abundant than HI in the inner galaxy and is the key to an explanation of the gamma-ray observations. This is also reflected in the correlation of galactic longitude and latitude distributions of gamma-rays and molecular clouds. Particularly strong evidence is found from the galactic survey of CO emission at 2.64 mm. The cosmic-ray distribution inferred from the calculations is not uniform but only weakly dependent on the total gas distribution in the inner galaxy.

Stecker, F. W.↗
NASA NTRS1975

Relation of large-scale coronal X-ray structure and cosmic rays. II - Coronal control of interplanetary injection of 300 keV protons

We report the striking coronal control of low-energy solar particles from the solar flare of September 7, 1973. The flare was at S18, W46 (Carrington longitude 188 deg) in McMath Plage Region 12307. We find strong intensity gradients in heliolongitude (about 10% per deg) that are nearly identical in protons, helium, and medium nuclei at energies about 0.5 MeV/nuc, as well as relativistic electrons and 3 MeV protons. This pervasive gradient occurs at longitudes over bright X-ray emission structures east of the flare site which interconnect large-scale chromospheric polarity regions identifiable in H-alpha filtergrams.

Roelof, E. C.↗
NASA NTRS1976

Prediction of the diffuse far-infrared flux from the galactic plane

A basic model and simple numerical relations useful for future far-infrared studies of the Galaxy are presented. Making use of recent CO and other galactic surveys, the diffuse far-infrared flux distribution from the galactic plane is predicted as a function of galactic longitude for longitudes between 4 and 90 deg; the far-infrared emissivity is predicted as a function of galactocentric distance. Future measurements of the galactic far-infrared flux would yield valuable information on the physical properties and distribution of dust and molecular clouds in the Galaxy, particularly the inner region.

Fazio, G. G.↗
NASA NTRS1976

Mutual phenomena of the Galilean satellites in 1973. III - Final results from 91 light curves

This paper presents an analysis of photoelectric light curves of 91 mutual eclipses and occultations of the Galilean satellites that occurred from June to December 1973. From the deepest curves, radii and standard errors are deduced for J2, J3, and J4. It is shown that the substantial differences between the depths and midtimes observed and those predicted by Sampson's theory can be used in a clear and definite way to revise the orbital constants of that theory. The present analysis, which reduces all the data provided by these mutual events in one body, diminishes the latitude and longitude residuals of the unrevised theory by as much as a factor of about 10. The resulting overall consistency and the demonstrated inadequacy of an explanation based solely on surface-brightness variations argue that these corrections do represent the dominant effects required to account for the light curves. In order that these mutual events can be used with other astrometric data, the separations between a satellite pair at midevent are given. A small systematic (with solar phase angle) and unexplained difference in the longitude corrections is found for Io and Europa as obtained from nearly simultaneous pairs of occultations and eclipses.

Aksnes, K.↗
NASA NTRS1976

Prediction of the diffuse far-infrared flux from the galactic plane

A basic model and simple numerical relations useful for future far-infrared studies of the Galaxy are presented. Making use of recent CO and other galactic surveys, the diffuse far-infrared flux distribution from the galactic planes is predicted as a function of galactic longitude for the region between 4 and 90 deg longitude; the far-infrared emissivity is predicted as a function of galactocentric distance. Future measurements of the galactic far-infrared flux would yield valuable information on the physical properties and distribution of dust and molecular clouds in the Galaxy, particularly the inner region.

Fazio, G. G.↗
NASA NTRS1977

SAS-2 galactic gamma-ray results. 1: Diffuse emission

Continuing analysis of the data from the SAS-2 high energy gamma ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitudes 310 deg and 45 deg, corresponding to a region within 7 kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315, 330, 345, 0, and 35 deg. These peaks appear to be correlated with galactic features and components such as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic-ray concentrations, and photon fields.

Thompson, D. J.↗
NASA NTRS1977

The galactic halo question: New size constraints from galactic gamma-ray data

The SAS-2 gamma-ray data is analyzed making use of recent CO line emission and other data for determining the large-scale distribution of galactic gas. A nonuniform distribution of cosmic rays in the galaxy is implied. This fact rules out large trapping halo models and extragalactic origin models. Detailed models of diffusion halos of various sizes perpendicular to the galactic plane are considered. In such models, the scale perpendicular to the plane has a strong effect in determining the radial distribution of cosmic rays. Such radial distributions are calculated for cylindrical coordinate models. The implied gamma-ray longitude distributions are then calculated and compared with the SAS-2 data for goodness-of-fit. Assuming the sources to be supernova remnants or pulsars, cosmic ray nucleon halo models with scale heights greater than 3 kpc are found to provide a poor fit to the gamma-ray longitude data (probability of 6% or less). Thin halo, or source dominated diffusion models are found to provide a good fit to the gamma-ray data, with an upper limit scale height of approximately 3 kpc.

Stecker, F. W.↗
NASA NTRS1976

Frequency of coronal transients and solar activity

The white light coronagraph aboard Skylab observed at least 110 coronal transients during 227 days of observations. It is shown that these transients occurred preferentially at longitudes where the sunspot number and the area times brightness index of calcium plages were high. The number of transients observed to arise from each of four quadrants in heliographic longitude, rotation by rotation, was strongly correlated with the average value of these measures of solar activity. From this it is inferred that coronal transients occur more commonly where magnetic fields are stronger, more complex, and varying more rapidly.

Hildner, E.↗
NASA NTRS1976

The occultation of Mariner 10 by Mercury

Analysis of Mariner 10 dual-frequency radio-occultation recordings has yielded new information on the radius and atmosphere of Mercury. The ingress measurements, which were conducted near 1.1 deg north latitude and 67.4 deg east longitude on the night side of the planet, gave a value for the radius of 2439.5 + or - 1 km. Egress near 67.6 deg north latitude and 258.4 deg east longitude on the sunlit side yielded a radius of 2439.0 + or - 1 km. The atmospheric measurements showed the electron density to be less than 1000 per cu cm on both sides of the planet. From the latter result one may infer an upper limit to the dayside surface gas density of 1 million molecules per cu cm.

Fjeldbo, G.↗