One of the first steps in spacecraft mission design is the selection of orbit and attitude scenarios that enable the science. This selection process works best when scientists and engineers begin the dialog early to understand the geometry, the science measurements, and the platform orbit and attitude accuracy. Flight Dynamics analysis helps clarify accuracies available with particular sensor complements.

This affects costs both through the hardware and through the need for initial and ongoing ground support. In the first part, this talk presents an overview of general considerations needed for orbit and attitude analysis. The second part gives an introduction to Cloud CubeSat, a very small, but very exciting student spacecraft (picosat) for side-imaging of clouds.

Location: Physics Bldg., Room 401

There will be no seminar Wednesday, April 8, 2009

Today’s High Technology companies, particularly those involved in defense related research, are utilizing advances associated with physics research to an increasing extent. Many of the devices and technologies employed in advanced sensors and computing are leveraging breakthroughs in physics and related disciplines. These breakthroughs encompass quantum optics, quantum information, nano-science, solid state physics, superconductivity, materials science and many other disciplines.

Physics Bldg., room 401

Jianning successfully defended her dissertation on April 22, 2009.

TITLE:
Extended Emission Surrounding Nearby Seyfert Galaxies

ABSTRACT:
We present the results from a search for and survey of any extended X- ray emission surrounding a class of Active Galactic Nuclei (AGN) known as “Seyfert-2” galaxies using data collected using Chandra X-ray observatory (CXO). The mirrors of this work was therefore to determine whether CXO observations help constrain current theories for AGN by probing the smallest spatial scales (> 100 pc) possible. Our sample consists of all the CXO observations of Seyfert-2 galaxies performed using the ACIS-S3 detector during the first 8 years of operation (28 objects). We find extended X-ray emission in all our Seyfert-2 sample of galaxies with a range of luminosities (10³⁸ ∼ 10⁴¹ erg s⁻¹ ). For 18 objects, the morphology is predominately bi-conical centered on the nucleus and typically extending out to a few kpc. Only a single cone is seen in 8 of the remaining ob jects, which may be indicative of intrinsically anisotropic emission. Where data is available, the X-ray cones do appear to occupy the same solid angle as the extended [OIII] emission line gas previously detected in these objects.

Our data suggest that the luminosity of the extended emission is typically a few percent of that of the nuclear source. Our findings are therefore broadly consist with current theories of AGN, but the low signal to noise for many of the observations combined with obscuration and possible contamination prevent any definitive tests of “Unified Schemes” being performed. Unfortunately this is likely to be the case for the foreseeable future.

Mengs successfully defended his dissertation on April 28, 2009.

TITLE:
Investigation of Stable and Unstable Boundary Layer Phenomena Using Observations and a Numerical Weather Prediction Model

ABSTRACT:
Despite significant advances in the simulation of synoptic scale weather events, current numerical weather prediction models show poor skill in their capability to accurately simulate sub-grid scale features, such as cloud-precipitation processes and planetary boundary layer (PBL) evolution, because too many semi-empirical parameterizations are involved. The goal of the work presented here is to evaluate the next-generation mesoscale Weather Research and Forecasting (WRF) model in simulating mesoscale weather phenomena under different PBL stratifications. The work presented in this thesis investigates the performance of the state-of-the-art mesoscale WRF model in simulating the structure and development of a daytime convective boundary layer phenomenon, (the dryline over the Southern Great Plains), and a nocturnal stable boundary layer phenomenon, (the Low-Level-Jet (LLJ) over the Mid-Atlantic region). The dryline and LLJ are two examples of boundary layer phenomena that occur under very different conditions and thus together they provide a good test of the PBL dynamics in the model. Extensive, high spatial and temporal resolution data collected during these case studies is used to evaluate the numerical results. For the unstable boundary layer, a detailed observational analysis of a non-convective dryline investigates an incorrect forecast. For the stable boundary layer, the accuracy of the timing and spatial characteristics of the LLJ for different PBL parameterizations is investigated and discussed in terms of the LLJ forcing mechanisms.