Spectropolarimetry of the methane and ammonia bands of Jupiter between 6800 and 8200 Å

Spectropolarimetry of Jupiter at resolutions between 22 and 35 Å reveals a strong increase of linear polarization in the 7250-$\text{A}\text{?}$ CH₄ band. This is very probably due to the decreasing contribution toward the band center of the higher orders of scattering, which have a smaller net polarization than the first few orders. The linear polarization is also enhanced in the band at 7900 $\text{A}\text{?}$ comprising the 7920-$\text{A}\text{?}$ NH₃ and 7600- to 8200-$\text{A}\text{?}$ CH₄ bands. The normalized circular polarization shows a feature at 7250 $\text{A}\text{?}$ with a dispersion shape. This is most probably produced in a double-scattering process involving either a solid or liquid aerosol with an absorption at 7250 $\text{A}\text{?}$. Methane aerosols, the obvious candidates from a spectroscopic point of view, are, however, forbidden if current estimates of the Jovian atmospheric temperature are correct.     

Solar rotation, 1966–1978

Photospheric and chromospheric spectroscopic Doppler rotation rates for the full solar disk are analyzed for the period July, 1966 to July, 1978. An approximately linear secular increase of the equatorial rate of 3.7% for these 12 years is found (in confirmation of Howard, 1976). The high latitude rates above 65 ° appear to vary with a peak-to-peak amplitude of 8%, or more, phased to the sunspot cycle such that the most rapid rotation occurs at, or following, solar maximum. The chromosphere, as indicated by H, has continued to rotate on the average 3% faster than the photosphere agreeing with past observations. Sources of error are discussed and evaluated.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

A remote unmanned ELF/VLF goniometer receiver in Antarctica

In March 1977 an unmanned ELF/VLF goniometer receiving station was deployed on the Antarctic plateau 110 km south south west of the British Antarctic Survey base at Halley. A UHF Telemetry link enabled the ELF and VLF signals to be monitored and recorded at Halley, simultaneously with data from an identical ELF/VLF receiver at Halley. The remote station was designed for unattended operation with a wind driven generator to recharge its battery. Design considerations and problems encountered are discussed and some preliminary results are presented.     

An improved transformation-elimination technique for the solution of perturbed Hamiltonian systems

A Lie transformation technique proposed by the author (1977) utilizing an approach due to Kolmogorov and Arnol'd is modified to eliminate the calculation of unproductive terms. Special features of the original method — the ability to eliminate simultaneously both short- and long-period terms, and [formal] quadratic convergence for non-degenerate system sand nearly quadratic convergence for degenerate systems—are retained in an even more efficient technique. Comparisons of the new method with other available Lie transform techniques is made.     

Galilean satellite eclipse studies: III. Jovian methane abundance

The methane abundance in the lower Jovian stratosphere is measured using Galilean satellite eclipse light curves. Spectrally selective observations in and between absorption bands are compared. An average mixing ratio at the locations measured is [CH₄]/[H₂] ～ 1.3 × 10^?3, larger than the value 0.9 × 10^?3 expected for a solar abundance of carbon. Some zenographic variation of the mixing ratio may occur. Observationally compatible values are 1.3–2.0 × 10^?3 in the STZ, 1.3– 2.6 × 10^?3 on the GRS/STrZ edge, and 0.7–1.3 × 10^?3 in the GRS.     

The evolution of the polar coronal holes

He i 10830 Å synoptic maps, obtained at the Kitt Peak National Observatory during 1974–1979, show that the Sun's polar coronal holes have contracted significantly during 1977–1978. Prior to the accelerated increase of sunspot activity in mid-1977, the area of each polar cap was on the order of 8% of the Sun's total surface area (4R ²), whereas toward the end of 1978 these areas fell below 2% of 4R ². Synoptic polar plots show that the vestigual holes had irregular shapes and were often well removed from the poles themselves. These results are consistent with the changes that one would expect when the polar magnetic fields are weakening just prior to sunspot maximum.     

40Ar39Ar ages of Allende

KAr and/or ⁴⁰Ar³⁹Ar plateau ages of Allende samples—whole rock, matrix, chondrules, white inclusions–range from 3.8 AE for matrix of ?5 AE for some white inclusions, but cluster strongly near 4.53 AE. This age marks the dominant KAr resetting of Allende materials. Age spectra show disturbances due to ³⁹Ar recoil or some other argon redistribution processes. Possible explanations for the apparent presolar ages (>4.6 AE) include: ?20% loss of ³⁹Ar; ?40% loss of ⁴⁰K ～3.8 AE ago with no loss of ⁴⁰Arl trapped argon of unique ⁴⁰Ar/³⁶Ar isotopic composition; admixture of “very old” presolar grains.     

Systematic reductions of 19th century planetary observations

Systematic reductions of nineteenth century observations to the system of the FK4 are discussed. Reductions made on a nightly basis are described and compared with the results obtained through the use of conventional tables. The series of observations made at the Paris Observatory from 1837 to 1881 was used to compare the two methods, and a combined system of 24 000 FK4, FK4 Sup and AGK 3R positions and proper motions provided the reference stars. The results show that for Uranus the mean error of a single observation in right ascension is ±1..33 when tables are used for the reductions, and ±1.12 when nightly reductions are made, while in declination the corresponding mean errors are ±0.88 and ±0.80. The observations of Neptune show an even greater difference between the two methods; the mean errors for the tabular and nightly reductions are ±1.57 and ±1.09 in right ascension and ±0.88 and ±0.75 in declination. Secular rates in the (0–C)'s of Uranus of –0.029/year in right ascension and ±0.030/year in declination are present when the observations are reduced with tables. These rates are reduced to –0.007/year and +0.015/year, respectively, when nightly reductions are made.Presented at the Symposium Star Catalogues, Positional Astronomy and Celestial Mechanics, held in honor of Paul Herget at the U.S. Naval Observatory, Washington, November 30, 1978.     

Spectral analyses of solar photospheric fluctuations

Successful subtraction of instrumental background variations has permitted spectral analyses of two-dimensional measurement arrays of granulation brightness fluctuations at the center of the disk, arrays obtained from Stratoscope I, 1959B-flight, high-resolution frames B1551 and B3241.

1. RMS's, uncorrected for instrumental blurring, are 0.0850 of mean intensity for B1551 and 0.0736 for B3241, somewhat higher than other determinations. These between-frame and between-investigation differences probably result from a combination of calibration errors, frame resolution differences, and, most likely, granulation pattern differences.
2. Significant variations over each array of mean intensities and RMS's, determined for sub-arrays with dimensions in the 2500–10000 km range, indicate spatial brightness and RMS variations larger than the ‘scale’ of the granulation pattern, supporting a turbulent interpretation of photospheric convection.
3. One-dimensional power-spectra shapes provide objective and discriminating criteria for determining granulation pattern differences and, possibly, frame resolution.
4. Two-dimensional power spectra show small, essentially random deviations from axial symmetry which lie almost entirely within the 50% confidence limits.
5. Spectral densities and fluctuation power spectra, computed from the two-dimensional power spectra and corrected for instrumental blurring, noise, and blemishes, have a useable radial wavenumber range nearly double that of earlier Stratoscope I analyses.
6. Corrected RMS's obtained from the corrected fluctuation power spectra, 0.145 ± 0.046 for B1551 and 0.136 ± 0.048 for B3241, depend critically on the accuracy of the correction.
7. The spectra's wavenumber range includes the granulation-fluctuation-producing domain but not the Kolmogoroff domain of turbulence spectra.

     

Operational requirements and the geometry of a station-keeping maneuver

In this paper station-keeping is regarded as the specialization of relative motion referred to a moving, orbiting origin. For this study a well-known linear solution to this problem serves as a base formulation from which the investigation begins.Even though the overall problem could be separated into three parts—necessitating two distinct studies for coverage—this paper examines only the last phase of the operation. That is, it is the continuation, or retention, of a relative motion sub-orbit which is of interest in this analysis.The situation becomes one of determining what is needed to maintain the sub-orbit, and/or to adjust it. In addition, the consequences of these actions, and the results predicted from theory are established, examined, and commented upon. In the presentation of information gathered from this study, various graphs have been prepared; however, these are expressed in a dimensionless format so that the results apply equally to all reasonable reference orbits.For this analysis the separate and combined influences, due to both the initial relative motion state and to a thrusting condition, are examined. Also, the consequences of referencing the acquired sub-orbits to an inertially aligned frame of reference (rather than the familiar rotating one) are illustrated, discussed, and commented upon.Formerly: Sr. Analyst and Manager, Seabrook Office, AMA, Inc., Seabrook, Md., U.S.A.