Thermal infrared observations of Mars (7.5-12.8 microns) during the 1990 opposition

Thirteen spectra of Mars, in the 7.5 to 12.8 micron wavelength were obtained on 7 Dec. 1990 from the Infrared Telescope Facility (IRTF). For these observations, a grating with an ultimate resolving power of 120 to 250 was used and wavelengths were calibrated for each grating setting by comparison with the absorption spectrum of polystyrene measured prior to each set of observations. By sampling the Nyquist limit at the shortest wavelengths, an effective resolving power of about 120 over the entire wavelength range was achieved. A total of four grating settings were required to cover the entire wavelength region. A typical observing sequence consisted of: (1) positioning the grating in one of the intervals; (2) calibrating the wavelength of positions; and (3) obtaining spectra for a number of spots on Mars. Several observations of the nearby stellar standard star, alpha Tauri, were also acquired throughout the night. Each Mars spectrum represents an average of 4 to 6 measurements of the individual Mars spots. As a result of this observing sequence, the viewing geometry for a given location or spot on Mars does not change, but the actual location of the spot on Mars's surface varies somewhat between the different grating settings. Other aspects of the study are presented

Apse Alignment of Narrow Eccentric Planetary Rings

The boundaries of the Uranian ∈, α, and β rings can be fitted by Keplerian ellipses. The pair of ellipses that outline a given ring share a common line of apsides. Apse alignment is surprising because the quadrupole moment of Uranus induces differential precession. We propose that rigid precession is maintained by a balance of forces due to ring self-gravity, planetary oblateness, and interparticle collisions. Collisional impulses play an especially dramatic role near ring edges. Pressure-induced accelerations are maximal near edges because there (1) velocity dispersions are enhanced by resonant satellite perturbations and (2) the surface density declines steeply. Remarkably, collisional forces felt by material in the last ~100 m of a ~10 km wide ring can increase equilibrium masses up to a factor of ~100. New ring surface densities are derived that accord with Voyager radio measurements. In contrast to previous models, collisionally modified self-gravity appears to allow for both negative and positive eccentricity gradients; why all narrow planetary rings exhibit positive eccentricity gradients remains an open question

GEO debris and interplanetary dust: fluxes and charging behavior

In September 1996, a dust/debris detector: GORID was launched into the geostationary (GEO) region as a piggyback instrument on the Russian Express-2 telecommunications spacecraft. The instrument began its normal operation in April 1997 and ended its mission in July 2002. The goal of this work was to use GORID's particle data to identify and separate the space debris to interplanetary dust particles (IDPs) in GEO, to more finely determine the instrument's measurement characteristics and to derive impact fluxes. While the physical characteristics of the GORID impacts alone are insufficient for a reliable distinction between debris and interplanetary dust, the temporal behavior of the impacts are strong enough indicators to separate the populations based on clustering. Non-cluster events are predominantly interplanetary, while cluster events are debris. The GORID mean flux distributions (at mass thresholds which are impact speed dependent) for IDPs, corrected for dead time, are 1.35x10^{-4} m^{-2} s^{-1} using a mean detection rate: 0.54 d^{-1}, and for space debris are 6.1x10^{-4} m^{-2} s^{-1} using a mean detection rate: 2.5 d^{-1}. Beta-meteoroids were not detected. Clusters could be a closely-packed debris cloud or a particle breaking up due to electrostatic fragmentation after high charging.Comment: * Comments: 6 pages, 4 postscript figures, in Dust in Planetary Systems 2005, Krueger, H. and Graps, A. eds., ESA Publications, SP in press (2006). For high resolution version, see: http://www.mpi-hd.mpg.de/dustgroup/~graps/dips2005/GrapsetalDIPS2005.pd

One year of Galileo dust data from the Jovian system: 1996

The dust detector system onboard Galileo records dust impacts in circumjovian space since the spacecraft has been injected into a bound orbit about Jupiter in December 1995. This is the sixth in a series of papers dedicated to presenting Galileo and Ulysses dust data. We present data from the Galileo dust instrument for the period January to December 1996 when the spacecraft completed four orbits about Jupiter (G1, G2, C3 and E4). Data were obtained as high resolution realtime science data or recorded data during a time period of 100 days, or via memory read-outs during the remaining times. Because the data transmission rate of the spacecraft is very low, the complete data set (i. e. all parameters measured by the instrument during impact of a dust particle) for only 2% (5353) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data for 2883 particles detected during Galileo's interplanetary cruise and published earlier, complete data of 8236 particles detected by the Galileo dust instrument from 1989 to 1996 are now available. The majority of particles detected are tiny grains (about 10 nm in radius) originating from Jupiter's innermost Galilean moon Io. These grains have been detected throughout the Jovian system and the highest impact rates exceeded $\rm 100 min^{-1}$. A small number of grains has been detected in the close vicinity of the Galilean moons Europa, Ganymede and Callisto which belong to impact-generated dust clouds formed by (mostly submicrometer sized) ejecta from the surfaces of the moons (Kr\"uger et al., Nature, 399, 558, 1999). Impacts of submicrometer to micrometer sized grains have been detected thoughout the Jovian system and especially in the region between the Galilean moons.Comment: accepted for Planetary and Space Science, 33 pages, 6 tables, 10 figure

Multiplicity Distributions and Charged-neutral Fluctuations

Results from the multiplicity distributions of inclusive photons and charged particles, scaling of particle multiplicities, event-by-event multiplicity fluctuations, and charged-neutral fluctuations in 158$\cdot A$ GeV Pb+Pb collisions are presented and discussed. A scaling of charged particle multiplicity as $N_{part}^{1.07\pm 0.05}$ and photons as $N_{part}^{1.12\pm 0.03}$ have been observed, indicating violation of naive wounded nucleon model. The analysis of localized charged-neutral fluctuation indicates a model-independent demonstration of non-statistical fluctuations in both charged particles and photons in limited azimuthal regions. However, no correlated charged-neutral fluctuations are observed.Comment: Talk given at the International Symposium on Nuclear Physics (ISNP-2000), Mumbai, India, 18-22 Dec 2000, Proceedings to be published in Pramana, Journal of Physic

Inflight Radiometric Calibration of New Horizons' Multispectral Visible Imaging Camera (MVIC)

We discuss two semi-independent calibration techniques used to determine the in-flight radiometric calibration for the New Horizons' Multi-spectral Visible Imaging Camera (MVIC). The first calibration technique compares the observed stellar flux to modeled values. The difference between the two provides a calibration factor that allows the observed flux to be adjusted to the expected levels for all observations, for each detector. The second calibration technique is a channel-wise relative radiometric calibration for MVIC's blue, near-infrared and methane color channels using observations of Charon and scaling from the red channel stellar calibration. Both calibration techniques produce very similar results (better than 7% agreement), providing strong validation for the techniques used. Since the stellar calibration can be performed without a color target in the field of view and covers all of MVIC's detectors, this calibration was used to provide the radiometric keywords delivered by the New Horizons project to the Planetary Data System (PDS). These keywords allow each observation to be converted from counts to physical units; a description of how these keywords were generated is included. Finally, mitigation techniques adopted for the gain drift observed in the near-infrared detector and one of the panchromatic framing cameras is also discussed

A novel method to improve temperature simulations of general circulation models based on ensemble empirical mode decomposition and its application to multi-model ensembles

A novel method based on the ensemble empirical mode decomposition (EEMD) method was developed to improve model performance. This method was evaluated by applying it to global surface air temperatures, which were simulated by eight general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The temperature simulations of the eight models were separated into their different components by EEMD. The model's performance improved after the first high-frequency component was removed from the original simulations by EEMD for each model, on both the global and continental scale. Moreover, EEMD was more effective in improving the model's performance compared to the wavelet transform method. The multi-model ensembles (MMEs) were calculated based on the EEMD-improved model simulations using the Average Ensemble Mean, Multiple Linear Regression, Singular Value Decomposition and Bayesian Model Averaging methods. The results showed that the MME forecasts performed better when the calculations were based on the EEMD-improved simulations as opposed to the original simulations on both the global and continental scale. Therefore, the results of the MME were further improved by using the EEMD-improved model simulations. This new method provides a simple way to improve model performance and can be easily applied to further improve MME simulations