Publications

Operation of a CCD imager on a curved focal surface offers advantages to flat focal planes, especially for lightweight, relatively simple optical systems. The first advantage is that the modulation transfer function can approach diffraction-limited performance for a spherical focal surface employed in large field-of-view or large-format imagers. The second advantage is that a curved focal surface maintains more uniform illumination as a function of radius from the field center. Examples of applications of curved imagers, described here, include a small compact imager and the large curved array used in the Space Surveillance Telescope. The operational characteristics and mechanical limits of an imager deformed to a 15 mm radius are also described.

The issues in the dual lane runway problem were investigated via computer real time (man in the loop) and fast time (no human input during the simulation run) simulations in order to identify a dual lane runway configuration and determine operation strategies. The real time experiments were conducted using experienced ATC controllers and a pilot to observe the situation at interactive graphics CRT displays. Headsets and microphones were utilized to permit the normal controller/pilot interchanges. Flight strips as used in control tower cabs were employed to further simulate controller workload. Based on information gained during early real time controller experiments, a programmed controller concept (fast time) was adopted. A series of dual lane runway computer simulation experiments were performed to investigate the pertinent dual lane issues: centerline spacing, arrival/departure preference, parallel taxiway, threshold stagger, and hiqh speed exits. In addition, time was spent analyzing operational high density airport terminal facilities. Airport administrative and operations personnel were interviewed to obtain their views on high density operations and the dual lane concept. Peak rush hour periods were sought out to detenTIine control strategies employed indirecting peak period traffic. Air crews utilizing these high density airport terminals were interviewed in the course of their operations into and out of these major hub airports.

An overview of the issues involved in the design of dual lane runways is presented. These issues include: centerline spacing, parallel taxiway, high speed exits, midpoint versus end point crossing, threshold stagger, and departure/arrival runway preference. An interactive graphics simulation was developed on the TX-2 computer. The simulation provides the capability for an airport designer to easily input dual lane runway configurations. ATC controllers were employed for over 100 hours to control and direct simulated traffic to various dual lane configurations. A set of preliminary criteria for dual lane runway configurations are presented along with recommendations for future work.

A concept formulation study of the control aspects of the fourth generation air traffic control system is presented. The results of this study are not strongly influenced by present-day equipment. They are influenced by certain aspects of present airspace utilization and procedures which appear necessary for the design of an effective system. The inputs to the control system design include the fourth generation air traffic demand, characteristics of fixed elements (types of aircraft, etc.), and disturbances such as weather effects. The control system which has been formulated includes flight plan generation, flow control, conformance monitoring, and collision avoidance as control functions. A baseline control system is given as a first iteration of the fourth generation system. The baseline system is defined by classifying types of airspace, conformance requirements, and required segregation of classes of flight paths. The airspace is divided into three categories: positive control air space containing only controlled aircraft, controlled (mixed) air space containing both controlled and cooperative aircraft, and uncontrolled airspace containing uncontrolled aircraft. Cooperative aircraft must be able to accept IPC co-ands as well as simplified flight plans when flying in high density retied air space. The surveillance, navigation, and communications systems complete the interacting parts of the control system. Candidate fourth generation system concepts ranging from the completely tactical to the highly strategic have been described both in this report and elsewhere. In order to characterize a proposed concept we have drawn up a list of decisions which we find must be made in the course of a flight. We then consider where these decisions are made and thereby characterize the system. The feasibility of generating conflict free flight plans is investigated with the aid of analytical models. A consideration of the factors which influence the flight planning process is presented. Use is made of a generally accepted traffic density model for the 1995 time period. The expected number of conflicts for selected routes and the distances required to resolve conflicts are evaluated. The use of aircraft performance characteristics in evaluating the effectiveness of conflict resolution maneuvers is discussed. The level of conformance necessary for conflict free flight plans is determined for each maneuver. For cases in which the required conformance was unrealistically high, it was determined that providing velocity structure in high density airspace permitted a decrease in conformance requirements. Factors which directly influence the capability of aircraft to conform to flight plans in a strategic system as well as the relevant technology areas peculiar to the implementation of conflict free flight plans are considered. The conclusions reached during this study are followed by recommendations for future work in specific areas.