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Digital Radar-Signal Processors Implemented in FPGAs

Processing can be performed onboard at relatively low power. High-performance digital electronic circuits for onboard processing of return signals in an airborne precipitation - measuring radar system have been implemented in commercially available field - programmable gate arrays (FPGAs). Previously, it was standard practice to downlink the radar-return data to a ground station for postprocessing - a costly practice that prevents the nearly - real - time use of the data for automated targeting. In principle, the onboard processing could be performed by a system of about 20 personal - computer-type microprocessors; relative to such a system, the present FPGA-based processor is much smaller and consumes much less power. Alternatively, the onboard processing could be performed by an application-specific integrated circuit (ASIC), but in comparison with an ASIC implementation, the present FPGA implementation offers the advantages of (1) greater flexibility for research applications like the present one and (2) lower cost in the small production volumes typical of research applications.

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Partitioning a Gridded Rectangle Into Smaller Rectangles

A relatively simple algorithm yields nearly square, nearly equally sized segments. A relatively simple algorithm, devised for use in an imagedata- compression application, partitions a rectangular pixelated image (or any other rectangle on which a regular rectangular grid has already been superimposed) into a specified number of smaller rectangles, hereafter denoted segments. The algorithm has the following properties: No floating-point operations are needed. The segments tend to be nearly square (in the sense that their widths and heights in pixel units tend to be nearly equal). The segments tend to have nearly equal areas. The algorithm yields valid results (no zero-width or zeroheight segments) as long as the specified number of segments, s, does not exceed the number of pixels (equivalently, the number of grid cells).

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Hybrid Image-Plane/Stereo Manipulation

This method is robust in the face of calibration errors. Hybrid Image-Plane/Stereo (HIPS) manipulation is a method of processing image data, and of controlling a robotic manipulator arm in response to the data, that enables the manipulator arm to place an end-effector (an instrument or tool) precisely with respect to a target (see figure). Unlike other stereoscopic machine-vision-based methods of controlling robots, this method is robust in the face of calibration errors and changes in calibration during operation.

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Computationally-Efficient Minimum-Time Aircraft Routes in the Presence of Winds

Minimum-time routes are achieved using 10 times less computational effort. A computationally efficient algorithm for minimizing the flight time of an aircraft in a variable wind field has been invented. The algorithm, referred to as Neighboring Optimal Wind Routing (NOWR), is based upon neighboring-optimal- control (NOC) concepts and achieves minimum-time paths by adjusting aircraft heading according to wind conditions at an arbitrary number of wind measurement points along the flight route. The NOWR algorithm may either be used in a fast-time mode to compute minimum-time routes prior to flight, or may be used in a feedback mode to adjust aircraft heading in real-time. By traveling minimum-time routes instead of direct great-circle (direct) routes, flights across the United States can save an average of about 7 minutes, and as much as one hour of flight time during periods of strong jet-stream winds. The neighboring optimal routes computed via the NOWR technique have been shown to be within 1.5 percent of the absolute minimum-time routes for flights across the continental United States. On a typical 450-MHz Sun Ultra workstation, the NOWR algorithm produces complete minimum-time routes in less than 40 milliseconds. This corresponds to a rate of 25 optimal routes per second. The closest comparable optimization technique runs approximately 10 times slower.

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Evaluating Performance of Components

Parallel Component Performance Benchmarks is a computer program developed to aid the evaluation of the Common Component Architecture (CCA) — a software architecture, based on a component model, that was conceived to foster high-performance computing, including parallel computing. More specifically, this program compares the performances (principally by measuring computing times) of componentized versus conventional versions of the Parallel Pyramid 2D Adaptive Mesh Refinement library — a software library that is used to generate computational meshes for solving physical problems and that is typical of software libraries in use at NASA's Jet Propulsion Laboratory.

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Tools for Administration of a UNIX-Based Network

Several computer programs have been developed to enable efficient administration of a large, heterogeneous, UNIX-based computing and communication network that includes a variety of computers connected to a variety of sub-networks. One program provides secure software tools for administrators to create, modify, lock, and delete accounts of specific users. This program also provides tools for users to change their UNIX passwords and log-in shells. These tools check for errors. Another program comprises a client and a server component that, together, provide a secure mechanism to create, modify, and query quota levels on a network file system (NFS) mounted by use of the VERITAS File System software. The client software resides on an internal secure computer with a secure Web interface; one can gain access to the client software from any authorized computer capable of running web-browser software. The server software resides on a UNIX computer configured with the VERITAS software system. Directories where VERITAS quotas are applied are NFS-mounted. Another program is a Web-based, client/server Internet Protocol (IP) address tool that facilitates maintenance lookup of information about IP addresses for a network of computers.

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Collaborative Planning of Robotic Exploration

The Science Activity Planner (SAP) software system includes an uplink-planning component, which enables collaborative planning of activities to be undertaken by an exploratory robot on a remote planet or on Earth. Included in the uplink-planning component is the SAP-Uplink Browser, which enables users to load multiple spacecraft activity plans into a single window, compare them, and merge them. The uplink-planning component includes a subcomponent that implements the Rover Markup Language Activity Planning format (RML-AP), based on the Extensible Markup Language (XML) format that enables the representation, within a single document, of planned spacecraft and robotic activities together with the scientific reasons for the activities. Each such document is highly parseable and can be validated easily. Another subcomponent of the uplink-planning component is the Activity Dictionary Markup Language (ADML), which eliminates the need for two mission activity dictionaries — one in a human-readable format and one in a machine-readable format. Style sheets that have been developed along with the ADML format enable users to edit one dictionary in a user-friendly environment without compromising the machine-read-ability of the format.

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