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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions

Saturn was observed by Chandra ACIS-S on 20 and 26-27 January 2004 for one full Saturn rotation (10.7 hr) at each epoch. We report here the first observation of an X-ray flare from Saturn s non-auroral (low-latitude) disk, which is seen in direct response to an M6-class flare emanating from a sunspot that was clearly visible from both Saturn and Earth. Saturn s X-ray emissions are found to be highly variable on time scales of tens of minutes to weeks. Unlike Jupiter, X-rays from Saturn s polar (auroral) region have characteristics similar to those from its disk and varies in brightness inversely to the FUV auroral emissions observed by the Hubble Space Telescope. This report establishes that disk X-ray emissions of the giant planets Saturn and Jupiter are directly regulated by processes happening on the Sun. We suggest that these emissions could be monitored to study X-ray flaring from solar active regions when they are on the far side and not visible to Near-Earth space weather satellites.

Bhardwaj, Anil↗
NASA NTRS1981

Saturn gravity results obtained from Pioneer 11 tracking data and earth-based Saturn satellite data

Improved gravity coefficients for Saturn, its satellites and rings are calculated on the basis of a combination of Pioneer 11 spacecraft Doppler tracking data and earth-based determinations of Saturn natural satellite apse and node rates. Solutions are first obtained separately from the coherent Doppler tracking data obtained for the interval from August 20 to September 4, surrounding the time of closest approach, with the effects of solar plasma on radio signal propagation taken into account, and from secular rates for Mimas, Enceladus, Tethys, Dione, Rhea and Titan determined from astrometric data by Kozai (1957, 1976) and Garcia (1972). Combination of the data by the use of the Pioneer solution and corresponding unadjusted covariance matrix as a priori information for a secular rate analysis results in values for the total ring mass of essentially zero at a standard error level of 1.7 x 10 to the -6th Saturn masses, a ratio of solar mass to that of the Saturn system of 3498.09 + or - 0.22, masses of Rhea, Titan and Iapetus of 4.0 + or - 0.9, 238.8 + or - 3, and 3.4 + or - 1.3 x 10 to the -6th Saturn masses, respectively, and second and fourth zonal harmonics of 16,479 + or - 18 and -937 + or - 38, respectively. The harmonic coefficients are noted to be important as boundary conditions in the modeling of the Saturn interior.

Null, G. W.↗
NASA NTRS1973

Saturn satellite encounter opportunities for Mariner Jupiter-Saturn 1977

The opportunities for close satellite encounters which meet the planetary constraints at Saturn that are imposed by science value return and environmental conditions are investigated. Since the satellites travel at various speeds in their orbits, Saturn arrival time is critical and was chosen as the design parameter. Arrival times are recommended which afford close satellite encounters and also meet important mission constraints. A design chart illustrates the satellite opportunities as a function of Saturn arrival date. Through the use of such a design chart, the Saturn encounter design process, which will take place according to recommendations by the selected science investigators over the next several years, will be considerably streamlined. Potential applications are given to illustrate the use of the Saturn satellite opportunity chart in encounter design.

Wallace, R. A.↗
NASA NTRS1980

Photometry and polarimetry of Saturn's rings from Pioneer Saturn

A profile of the average normal optical depth for Saturn's rings between 1.22 and 2.35 Saturn radii is examined. In the A and B rings, horizontal inhomogeneities make these values deceptive. A thinner component of the B ring with an optical depth below 0.08 covers up to 4% of its surface area. In the A ring, the more transparent component covers more than 7% of its area and has an optical depth greater than 0.10. These thinner parts of the rings would rarely be apparent from earth based observations. The particles of the C ring are larger than 15 microns and differ from those of the B and A rings. The C ring is either homogeneous with high albedo and forward scattering phase functions, or shows a gradient in albedo with distance from Saturn. Polarimetry of Saturn's ring provides only an upper limit (below 15%) which is consistent with ground-based predictions. Polarization in the outer A ring is negative.

Esposito, L. W.↗
NASA NTRS2006

Cassini Observations of Saturn's Dawn-Magnetotail Region and their Relation to Models of Saturn's Aurora: Preliminary Results

Using Cassini plasma and magnetic field observations from the dawn meridian of Saturn s outer magnetosphere to Saturn s magnetotail region, we investigate the applicability of the centrifugal instability model by Sittler et al. [2006] for Saturn s auroral response to the solar wind, versus the reconnection model of Saturn s aurora by Cowley et al. [2005]. We use Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) and Electron Plasma Spectrometer (ELS) observations to characterize the plasma environment. ELS and magnetometer observations are used to map out the morphology of the outer magnetosphere from dawn to midnight local time. IMS observations are used to measure plasma flow velocities from which one can infer rotation versus convective flows. IMS composition measurements are used to trace the source of plasma from the inner magnetosphere (protons, H2 and water group ions) versus an external solar wind source (protons and Heff ions). A critical parameter for both models is the strength of the convection electric field with respect to the rotational electric field for the large scale magnetosphere. Is there a significant return flow from the magnetotail? Pitch angle distributions also play an important role as a discriminator. If the magnetosphere tends to conserve angular momentum as suggested by Sittler et al. [2006], then we expect to see an anti-correlation between rotational flow component and radial flow velocities. All will be investigated.

Sittler, E. C.↗
NASA NTRS1993

The occultation of 28 Sgr by Saturn - Saturn pole position and astrometry

Saturn's ring plane-defined pole position is presently derived from the geometry of Saturn's July 3, 1989 occultation of 28 Sgr, as indicated by the timings of 12 circular edges in the Saturn C-ring as well as the edges of the Encke gap and the outer edge of the Keeler gap. The edge timings are used to solve for the position angle and opening angle of the apparent ring ellipses; the internal consistency of the data set and the redundancy of stations indicates an absolute error of the order of 5 km. The pole position thus obtained is consistent with the pole and ring radius scale derived from Voyager occultation observations.

Hubbard, W. B.↗
NASA NTRS2024

The Plasma Proton Environment within Saturn’s F-G Ring Gap as Observed by the Cassini Plasma Spectrometer Ion Mass Spectrometer during Saturn Orbit Insertion

We report on the detection of protons and the potential detection of H 2 + between Saturn's F and G rings based on Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) time-of-flight (TOF) composition measurements acquired during Saturn Orbit Insertion (SOI) outbound pass. The range in dipole L shell is 2.3 < L < 2.8. Initial results based on TOF data were presented in E. C. Sittler et al., 2017. Here we present the latest results of our analysis. During the SOI outbound pass between the F and G rings the CAPS IMS was in a mode of reduced post-acceleration voltage at -6 kV instead of the usual -14.6 kV. This reduced voltage still allows the analysis of protons since 6 keV protons are minimally scattered by the instrument’s ultrathin carbon foils when compared to heavier ions O + and O 2 + , scattering. Background noise from penetrating radiation and ghost peaks produced by foil-scattered O + ions within the instrument were considered in our analysis. The analysis allowed determination of the proton density, temperature and flow velocity, accounting for spacecraft potential by assuming a convected Maxwellian for the proton velocity distribution function. We find average proton density n P = 3.2 ± 1.1 #/cm 3 , proton temperature T P = 1.74 ± 0.12 eV, proton rotational flow speed V P = 24 ± 1.5 km/s and spacecraft potential  SC = -0.8 ±1.5 V. These results are compared with previous theoretical estimates of H + and H 2 + ions within Saturn’s inner magnetosphere.

E C Sittler↗
NASA NTRS1972

Saturn 1B and Saturn 5 computer programs, software

Information on the progress and development of all Saturn 1B and Saturn 5 computer programs is presented. On-line, operating systems, test programs, and on-line display descriptions are given along with off-line programs. All programs are listed in tabular form.

Source record↗
NASA NTRS1976

The formation of Saturn's satellites and rings, as influenced by Saturn's contraction history

The paper investigates constraints imposed on the ice content of Saturn's satellites and rings by the planet's high luminosity during the early part of its quasi-equilibrium contraction phase. It is assumed that the addition of ices to the satellites was not completed until after the start of the quasi-equilibrium contraction and that the condensation of ices ceased at the same time within the primordial nebulae of Jupiter and Saturn. Using previously derived limits on the time of condensation cessation for Jupiter's system, the following tentative conclusions are made: (1) Titan is the innermost satellite at whose position a methane-containing ice could condense; (2) water ice could have condensed at the positions of all the satellites; (3) the systematic decrease in the mass of the regular satellites with decreasing distance from the planet may have been caused, in part, by the larger time intervals, for the closer satellites, between the start of contraction and the first condensation of ices at their positions; and (4) ammonia ices, primarily NH4SH, were able to condense at the positions of all but the innermost satellites. It is also shown that water ice could have condensed in the region of the rings near the end of the condensation period.

Pollack, J. B.↗
NASA NTRS1979

On seasonal phenomena in Saturn's atmosphere - New observations of Saturn's 3nu3 methane band

Saturn's 3nu3 CH4 band has been reobserved during April-June 1976, using the same telescope and spectrographic set-up used to study this band during the 1970 apparition. Direct comparison of the ratio spectra Saturn/moon reveals greater absorption in the manifold cores during 1976, but the increase is not as pronounced as that for the stronger CH4 bands. The rotational temperature and effective pressure of this band did not change significantly. These results are interpreted in terms of a possibly seasonal settling of the upper boundary of Saturn's atmospheric haze layer.

Trafton, L.↗