Assessing the performance limits of internal coronagraphs through end-to-end modeling: a NASA TDEM study

As part of the NASA ROSES Technology Development for Exoplanet Missions (TDEM) program, we are conducting a study of three internal coronagraphs (PIAA, vector vortex, hybrid bandlimited) to understand their behaviors in realistically-aberrated systems with wavefront control (deformable mirrors). This study consists of two milestones: (1) develop wavefront propagation codes appropriate for each coronagraph that are accurate to 1% or better (compared to a reference algorithm) but are also time and memory efficient, and (2) use these codes to determine the wavefront control limits of each architecture. We discuss the results from the study so far, with emphasis on representing the PIAA coronagraph and its wavefront control behavior

End-to-end simulations of different coronagraphic techniques

The NASA exoplanet exploration program is dedicated to developing technologies for detecting and characterizing extrasolar planets. In support of that program we have evaluated three different coronagraphic techniques (bandlimited Lyot, optical vortex, and phase-induced pupil apodization) using optical propagation simulations. These utilized a complete hypothetical telescope+coronagraph system with phase and amplitude aberrations. Wavefront control using dual sequential deformable mirrors was performed. We discuss the different computational techniques necessary to accurately simulate each coronagraph

Performance of Six Vegetative Treatment Systems for Controlling Runoff from Open Beef Feedlots in Iowa

Beef feedlots of all sizes are looking for more cost-effective solutions for managing feedlot runoff. Vegetative treatment systems (VTSs) are one potential option that has been proposed. Iowa State University (ISU) has monitored the performance of six VTSs on open beef feedlots throughout Iowa since 2006. These feedlots have interim, National Pollution Discharge Elimination System (NPDES) permits that allow the use of VTSs to control and treat feedlot runoff. As part of the permit requirements for these feedlots the effluent volumes, nutrient concentrations, and nutrient masses exiting each component of the VTS were monitored. This paper describes the VTSs and monitoring methods used in this study and evaluates the effectiveness, in terms of both effluent concentration and nutrient mass transport reductions, of each system. During the three-year monitoring period, results have shown that VTSs are capable of reducing the nutrient mass exiting the VTSs by 65 – 99% as compared to a settling basin only system, with performance varying by both site and year. In addition to overall mass transport reductions, nutrient concentrations were also reduced, typically reduced by 50-90%, during treatment. Furthermore, monitoring results have shown a consistent improvement in system performance during the three years of the study. Much of this improvement can be attributed to improved management techniques and system modifications that addressed key performance issues