Information Science

Opto-Electronic Oscillator Using Suppressed Phase Modulation

Phase noise would be much lower than in prior OEOs. A proposed opto- electronic oscillator (OEO) would generate a microwave signal having degrees of frequency stability and spectral purity greater than those achieved in prior OEOs. The design of this system provides for reduction of noise levels (including the level of phase noise in the final output microwave signal) to below some of the fundamental limits of the prior OEOs while retaining the advantages of photonic generation of microwaves. Whereas prior OEOs utilize optical amplitude modulation, this system would utilize a combination of optical phase modulation and suppression thereof. The design promises to afford, in the opto-electronic domain, the low-noise advantages of suppression of carrier signals in all-electronic microwave oscillators.

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System for Estimating Horizontal Velocity During Descent

Estimates are generated from images and other sensor outputs. The descent image motion estimation system (DIMES) is a system of hardware and software, designed for original use in estimating the horizontal velocity of a spacecraft descending toward a landing on Mars. The estimated horizontal velocity is used in generating rocket-firing commands to reduce the horizontal velocity as part of an overall control scheme to minimize the landing impact. DIMES can also be used for estimating the horizontal velocity of a remotely controlled or autonomous aircraft for purposes of navigation and control.

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POD Model Reconstruction for Gray-Box Fault Detection

Low-order models that give robust, close approximations can be constructed. Proper orthogonal decomposition (POD) is the mathematical basis of a method of constructing low-order mathematical models for the “gray-box” fault- detection algorithm that is a component of a diagnostic system known as beaconbased exception analysis for multimissions (BEAM). POD has been successfully applied in reducing computational complexity by generating simple models that can be used for control and simulation for complex systems such as fluid flows. In the present application to BEAM, POD brings the same benefits to automated diagnosis.

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Advanced Reference Counting Pointers for Better Performance

A computer program implements reference counting pointers (RCPs) that are lock-free, thread-safe, async-safe, and operational on a multiprocessor computer. RCPs are powerful and convenient means of managing heap memory in C++ software. Most prior RCP programs use locks to ensure thread safety and manage concurrency. The present program was developed in a continuing effort to explore ways of using the C++ programming language to develop safety-critical and mission-critical software.

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NASA Enterprise Visual Analysis

NASA Enterprise Visual Analysis (NEVA) is a computer program undergoing development as a successor to Launch Services Analysis Tool (LSAT), formerly known as Payload Carrier Analysis Tool (PCAT). NEVA facilitates analyses of proposed configurations of payloads and packing fixtures (e.g. pallets) in a spaceshuttle payload bay for transport to the International Space Station. NEVA reduces the need to use physical models, mock-ups, and full-scale ground support equipment in performing such analyses. Using NEVA, one can take account of such diverse considerations as those of weight distribution, geometry, collision avoidance, power requirements, thermal loads, and mechanical loads.

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Tracking-Data-Conversion Tool

A computer program denoted Tracking Data Delivery Software Orbit Data File (TDDSODF) converts deep- space- radiocommunication spacecraft-tracking data from a currently used file format known in the art as “TRK-2-34” to a legacy format denoted “TRK-2-18.” TDDSODF reads standard formatted data units (SFDUs) of several TRK-2-34 types and processes them into an orbit data file (ODF) containing data of one or more of several different TRK-2-18 types. TDDSODF offers the user the following options:

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Efficient Mosaicking of Spitzer Space Telescope Images

A parallel version of the MOPEX software, which generates mosaics of infrared astronomical images acquired by the Spitzer Space Telescope, extends the capabilities of the prior serial version. In the parallel version, both the input image space and the output mosaic space are divided among the available parallel processors. This is the only software that performs the point- source detection and the rejection of spurious imaging effects of cosmic rays required by Spitzer scientists. This software includes components that implement outlier-detection algorithms that can be fine-tuned for a particular set of image data by use of a number of adjustable parameters.

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