Approved for public release; distribution is unlimited / NOAA-7 AVHRR data from April 1982 and 1983 were used to perform a global scale analysis of aerosol particle characteristics. Several improvements were incorporated into an AVHRR multichannel satellite data technique developed by Pfeil (1986). This included better cloud and sunglint discrimination, removal of Rayleigh radiance and accounting for ozone absorption. The characteristics analyzed were optical depth and Aerosol Particle Size Index (S₁₂). S₁₂ provides the slope of the aerosol particle size distribution curve. Both of these parameters were evaluated during several naturally occurring events, foremost of which were the 1982 El Chicon eruption and the 1982-1983 El Nino-Southern Oscillation event. The results provided evidence that a significant amount of aerosol particles over marine regions are from land-derived sources. However, the results also provided evidence that some marine aerosol particles may be of biogenic origins, / http://archive.org/details/globalscaleestim00fros / Lieutenant, United States Navy

Host star metallicity provides a measure of the conditions in protoplanetary disks at the time of planet formation. Using a sample of over 20,000 Kepler stars with spectroscopic metallicities from the LAMOST survey, we explore how the exoplanet population depends on host star metallicity as a function of orbital period and planet size. We find that exoplanets with orbital periods less than 10 days are preferentially found around metal-rich stars ([Fe/H] similar or equal to 0.15 +/- 0.05 dex). The occurrence rates of these hot exoplanets increases to similar to 30% for super-solar metallicity stars from similar to 10% for stars with a sub-solar metallicity. Cooler exoplanets, which reside at longer orbital periods and constitute the bulk of the exoplanet population with an occurrence rate of greater than or similar to 90%, have host star metallicities consistent with solar. At short orbital periods, P < 10 days, the difference in host star metallicity is largest for hot rocky planets (< 1.7 R-circle plus), where the metallicity difference is [Fe/H] similar or equal to 0.25 +/- 0.07 dex. The excess of hot rocky planets around metal-rich stars implies they either share a formation mechanism with hot Jupiters, or trace a planet trap at the protoplanetary disk inner edge, which is metallicity dependent. We do not find statistically significant evidence for a previously identified trend that small planets toward the habitable zone are preferentially found around low-metallicity stars. Refuting or confirming this trend requires a larger sample of spectroscopic metallicities.

We present new spatially resolved astrometry and photometry from the Gemini Planet Imager of the inner binary of the young multiple star system V343 Normae, which is a member of the beta Pictoris (beta Pic) moving group. V343 Normae comprises a K0 and mid-M star in a similar to 4.5 year orbit (AaAb) and a wide 10 '' M5 companion (B). By combining these data with archival astrometry and radial velocities we fit the orbit and measure individual masses for both components of M-Aa = 1.10 +/- 0.10M(circle dot) and M-Ab= 0.290 +/- 0.018 M-circle dot. Comparing to theoretical isochrones, we find good agreement for the measured masses and JHK band magnitudes of the two components consistent with the age of the beta Pic moving group. We derive a model-dependent age for the beta Pic moving group of 26 +/- 3 Myr by combining our results for V343 Normae with literature measurements for GJ. 3305, which is another group member with resolved binary components and dynamical masses.

We study the formation of planetesimals in protoplanetary disks from the gravitational collapse of solid over-densities generated via the streaming instability. To carry out these studies, we implement and test a particle-mesh self-gravity module for the ATHENA code that enables the simulation of aerodynamically coupled systems of gas and collisionless self-gravitating solid particles. Upon employment of our algorithm to planetesimal formation simulations, we find that (when a direct comparison is possible) the ATHENA simulations yield predicted planetesimal properties that agree well with those found in prior work using different numerical techniques. In particular, the gravitational collapse of streaming-initiated clumps leads to an initial planetesimal mass function that is well-represented by a power law, dN / dM(p) proportional to M-p(-p), with p similar or equal to 1.6 +/- 0.1, which equates to a differential size distribution of dN / dR(p) proportional to R-p(-q), with q similar or equal to 2.8 +/- 0.1. We find no significant trends with resolution from a convergence study of up to 512(3) grid zones and N-par approximate to 1.5 x 10(8) particles. Likewise, the power-law slope appears indifferent to changes in the relative strength of self-gravity and tidal shear, and to the time when (for reasons of numerical economy) self-gravity is turned on, though the strength of these claims is limited by small number statistics. For a typically assumed radial distribution of minimum mass solar nebula solids (assumed here to have dimensionless stopping time tau = 0.3), our results support the hypothesis that bodies on the scale of large asteroids or Kuiper Belt Objects could have formed as the high-mass tail of a primordial planetesimal population.

Satellite broadband has the potential to provide Internet connectivity to people and places that are unreachable using other wired/wireless technologies. It is therefore a critical component of any service seeking to provide universal coverage. A universal service needs to support a range of Internet applications. While there is existing work on bulk and interactive applications with a characteristic transmission rate, popular Internet applications such as web browsing, web video download or variable-rate voice result in a network traffic that varies its transmission rate. This thesis first investigates the interaction of satellite resource request mechanisms with the quality of service offered to these variable-rate applications using a satellite platform based on DVB-RCS2. It shows that a flexible QoS architecture can be achieved by a combination of resource request methods and network-layer queuing. Variable-rate traffic also poses challenges to the widely deployed Transport Control Protocol (TCP). Previous work analysed the interaction with the congestion control algorithms and proposed Congestion Window Validation (CWV) to constrain the congestion window to the amount of traffic a transport has sent. TCP JAGO studied this problem for variable-rate bursty applications and proposed new algorithms; but these were shown to have drawbacks and there were no guidance on how to implement. This thesis therefore presents, newCWV, a practical mechanism to provide an appropriate estimate of the available path capacity and corresponding congestion control behaviour. This benefits variable-rate applications with shorter transfer durations, but has a consequence of allowing larger traffic bursts into the network that can increase packet loss. Burst mitigation techniques, such as TCP pacing, are proposed to deal with this. These techniques are implemented and tested in the Linux TCP/IP stack, where newCWV improves the burst transfer time. This benefit is particularly significant for the large delay of broadband satellite systems.

Approved for public release; distribution is unlimited / This research is part of a continued effort to simulate the effects of total dose radiation on the performance of single and composite operational amplifiers using PSPICE. This research provides further verification that the composite operational amplifier has a superior performance to the single operational amplifier while operating in a radiation flux. In this experiment, a single and composite op amp were constructed in PSPICE and implemented in a finite gain amplifier circuit. The effects of ionizing radiation were simulated by varying the parameters of the components that made up the op amps. These component parameters were varied in ways that would mimic the response of the actual components that were irradiated in previous research. The simulations were incrementally run to simulate an increasing radiation dose. The results of these simulations were then compared with the results of an actual study conducted at Naval Postgraduate School where similar circuits were irradiated using the school's LINAC. This procedure proved to be an improved method for predicting the effects of total dose radiation for radiation hardened devices and provided additional confirmation of the superior performance of the composite op amp over the single op amp. / Lieutenant, United States Navy

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Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / M.S.

Orientador: Rodolpho Vilhena de Moraes / Coorientador: Jean Paulo dos Santos Carvalho / Banca: Ernesto Vieira Neto / Banca: Sandro da Silva Fernandes / Resumo : Neste trabalho buscam-se formulações de modelos analíticos e d aelaboração de programas computacionais para realizar uma busca por órbitas estáveis em torno de satélites planetários que poderão contribuir no planejamento de missões espaciais a serem conduzidas para o esudo destes corpos celestes. O estudo leva em consideração órbitas de satélites artificiais em torno de satélites plenetários sob a influência da petubação de terceiro corpo (a atração gravitacional de Júpiter ) e das pertubações devidas à distribuição não uniforme de massa (J2 e J3) do corpo principal (central) ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work seeks to formulations of analytical models and the development of computer programs to perform a search for stable orbits around planetary satellites that maybe helpful in planning space missions to be conducted to study these celestial bodies. The study takes into account artificial satellite orbits around planetary satellites under the influence of the third body pertubation (gravitational attraction of Jupiter) and the pertubations due to non-uniform distribution of mass (J2 and J3) of the main (central) body ... (Complete abstract click eletronic access below) / Mestre

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