Calibrating Array Detectors

The development of sensitive large format imaging arrays for the infrared promises to provide revolutionary capabilities for space astronomy. For example, the Infrared Array Camera (IRAC) on SIRTF will use four 256 x 256 arrays to provide background limited high spatial resolution images of the sky in the 3 to 8 micron spectral region. In order to reach the performance limits possible with this generation of sensitive detectors, calibration procedures must be developed so that uncertainties in detector calibration will always be dominated by photon statistics from the dark sky as a major system noise source. In the near infrared, where the faint extragalactic sky is observed through the scattered and reemitted zodiacal light from our solar system, calibration is particularly important. Faint sources must be detected on this brighter local foreground. We present a procedure for calibrating imaging systems and analyzing such data. In our approach, by proper choice of observing strategy, information about detector parameters is encoded in the sky measurements. Proper analysis allows us to simultaneously solve for sky brightness and detector parameters, and provides accurate formal error estimates. This approach allows us to extract the calibration from the observations themselves; little or no additional information is necessary to allow full interpretation of the data. Further, this approach allows refinement and verification of detector parameters during the mission, and thus does not depend on a priori knowledge of the system or ground calibration for interpretation of images.Comment: Scheduled for ApJS, June 2000 (16 pages, 3 JPEG figures

Adaptive Pareto Set Estimation for Stochastic Mixed Variable Design Problems

Many design problems require the optimization of competing objective functions that may be too complicated to solve analytically. These problems are often modeled in a simulation environment where static input may result in dynamic (stochastic) responses to the various objective functions. System reliability, alloy composition, algorithm parameter selection, and structural design optimization are classes of problems that often exhibit such complex and stochastic properties. Since the physical testing and experimentation of new designs can be prohibitively expensive, engineers need adequate predictions concerning the viability of various designs in order to minimize wasteful testing. Presumably, an appropriate stochastic multi-objective optimizer can be used to eliminate inefficient designs through the analysis of simulated responses. This research develops an adaptation of Walston’s [56] Stochastic Multi-Objective Mesh Adaptive Direct Search (SMOMADS) and Paciencia’s NMADS [45] based on Kim and de Weck’s [34] Adaptive Weighted Sum (AWS) procedure and standard distance to a reference point methods. This new technique is compared to standard heuristic based methods used to evaluate several real-world design problems. The main contribution of this paper is a new implementation of MADS for Mixed Variable and Stochastic design problems that drastically reduces dependence on subjective decision maker interaction

Optimal Control of Fully Routed Air Traffic in the Presence of Uncertainty and Kinodynamic Constraints

A method is presented to extend current graph-based Air Traffic Management optimization frameworks. In general, Air Traffic Management is the process of guiding a finite set of aircraft, each along its pre-determined path within some local airspace, subject to various physical, policy, procedural and operational restrictions. This research addresses several limitations of current graph-based Air Traffic Management optimization methods by incorporating techniques to account for stochastic effects, physical inertia and variable arrival sequencing. In addition, this research provides insight into the performance of multiple methods for approximating non-differentiable air traffic constraints, and incorporates these methods into a generalized weighted-sum representation of the multi-objective Air Traffic Management optimization problem that minimizes the total time of flight, deviation from scheduled arrival time and fuel consumption of all aircraft. The methods developed and tested throughout this dissertation demonstrate the ability of graph-based optimization techniques to model realistic air traffic restrictions and generate viable control strategies

Assessment Of The Probability Of Loggerhead Sea Turtle (Caretta caretta) Recovery In The Northwest Atlantic Ocean Within 50 Years Of Federal And State Protection In The US

Systematic implementation of sea turtle conservation measures have occurred in the U.S. since the 1970’s. As such, this dissertation assessed the probability that loggerhead sea turtles (Caretta caretta) in the NW Atlantic will meet or exceed recovery criteria in the minimum timeframe (i.e., 50 years) specified by the Recovery Plan. Mathematical modeling (Chapter 1) of a theoretical population resembling an important nesting assemblage in a stochastic environment for 200 years revealed broad (\u3c20k to \u3e106k) fluctuation in annual nest counts without extinction, as well as strong contemporary environmental influence on annual nest counts. Modeling also substantiated the importance of monitoring the relative abundance of juvenile females as the most reliable forecasting metric for nest count trajectories up to two decades into the future. In-water monitoring of loggerhead sea turtle demographic structure at a coastal foraging ground between South Carolina and north Florida suggests a shift away from a stable size distribution during 2000–2015, but which may eventually be tempered by the relative abundance of cohorts hatched near the turn of the last century (Chapter 2). The high relative abundance of juvenile females captured in this coastal trawl survey bodes well for sustained annual nest counts in the coming decade (Chapter 3). Slightly elevated female frequency among the smallest loggerhead sea turtles captured is consistent with a warming climate, but a 100-year association with the Atlantic Multi-decadal Oscillation suggests that reduced female production should begin to occur in the coming decade

Exploratory Field Evaluation of Hook-Release Mortality in Tautog (Tautoga onitis) in Lower Chesapeake Bay, Virginia

In April 1996, the Atlantic States Marine Fisheries Commission approved a Tautog Fishery Management Plan (FMP) requiring states to systematically adopt a 14 in. (356 mm) TL minimum size limit. Release-mortality was assumed to be 25%. Between October and December 1997-1998, 299 tautog (235-520 mm TL; 9-20 in.) were caught using angling gear to estimate release mortality in Virginia\u27s tautog fishery. Fishing occurred at shallow (3-10 m; 10-33 ft.) and deep (12-17 m; 39-56 ft.) water depths at temperatures between 9-l 8°C ( 48-64°F). Tautog were tagged, accumulated in aerated livewells, then returned to depth of capture in galvanized wire cages. Mean fish density per cage was six tautog and mean soak time per cage was 115 h (4.8 days). Releasemortality for tautog (n=5) for both years was 1.67%, all occurring in fish taken from deeper water. Mortality rates were comparable to rates reported in Connecticut waters (1994-98)