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HIGHLIGHTS ARCHIVE
11.27.07 Division Highlights

Contents
Initial Development of a Scheduling Algorithm for Very-Closely Spaced Parallel Approaches: The Very Closely-Spaced Parallel Approaches (VCSPA) concept aims to significantly increase arrival traffic throughput. A model for scheduling and sequencing was developed to support the VCSPA concept. The objective function tries to minimize the arrival time of the last aircraft in a sequence given the earliest and latest arrival times of the aircraft in a set. The objective function and the constraints (temporal, separation, pairing, precedence, and constrained position shifting) for this problem were coded using a genetic algorithm to search for feasible solutions. Test runs with an initial sample of 20 aircraft show that the heuristic is capable of providing a solution after a relatively short computation time. The quality of the solutions does not deviate much from the optimal solution. The model was then implemented into a program solved by the CPLEX solver. CPLEX produces an optimal solution using a branch-and-cut algorithm as opposed to heuristics-based solutions, which cannot guarantee optimal solutions. The computation time is highly dependent upon the allowed aircraft sequence shifts (constrained position shifting). Initial comparisons between CPLEX and the genetic algorithm suggest that CPLEX computation times will be greater, with the tradeoff of having a more optimal solution. More simulations with CPLEX and the genetic algorithm will be performed to assess the quality of solutions and the performance for several traffic scenarios.

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Workshop held to understand the impact of non-convective weather constraints on the National Airspace: Metron Aviation is developing models to translate both deterministic and probabilistic meteorological information into a Traffic Flow Management impact model for weather constraints driven by means other than convection. These can include constraints such as clear air turbulence and icing. As part of their work, Metron is hosting three workshops to gather and share information to improve the results. The first and third workshop will be at NASA Ames Research Center, and the second will be at the National Center for Atmospheric Research in Boulder, Colorado. This first workshop had presentations by research meteorologists discussing weather forecast uncertainty, turbulence, icing, and visibility. Discussions during this workshop will be used to plan the second workshop and improve this work. Attendees included researchers from NASA, MITRE, MIT/Lincoln Laboratory, and Mosaic ATM. Mosaic ATM is also working on this same NRA topic using a different approach.

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Space Shuttle Visual Database Development: New, higher-fidelity visual databases have been developed for the Space Shuttle landing and rollout training simulations on the Vertical Motion Simulator (VMS). The recently installed state-of-the-art image generator in the VMS provides an order-of-magnitude improvement in the resolution and detail of the outside visual scene. To make use of the improved visual fidelity, the visual databases of all the Space Shuttle landing sites are being rebuilt. The Shuttle training simulations use 24 visual databases representing potential landing sites used for regular and emergency landings. There are strict requirements on the accuracy of the location and dimensions of the runways and the visual landing aids. Integration of satellite imagery of the areas surrounding the landing sites ensures that the visual scenes are geographically accurate and familiar to the astronauts. Each landing site must be accurate in both day and night visual conditions with correct representation of the color and brightness of the specialized runway lighting and landing aids used for Shuttle landings. The databases are being prepared for check out by the astronaut office prior to the start of the next shuttle training simulation expected in the spring of 2008.

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Last Updated: November 7, 2018

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