March 2001

Briefs : Information Technology
Partial Subtractive Dither for Lossy Data Compression

A technique of partial subtractive dither has been developed to improve the performance of any of a variety of near-lossless data-compression algorithms. The technique may be applicable to compression of scientific and medical image data.

Briefs : Electronics & Computers
Acquisition, Tracking, and Pointing in Optical Communication

A document in the form of lecture slides outlines a program of development of capabilities for acquisition of signals, tracking of signal sources, and pointing of transmitters and receivers in deep-space optical communications. Topics addressed on the first few slides include the...

Briefs : Information Technology
Software for Preprocessing of Raw SAR Data

The SAR Processing System Raw Data Processor (SPS RDS) computer program is used in the Alaska SAR Facility (ASF) to scan and decode raw data that have been downlinked from the European Remote Sensing Satellite (ERS), the Japanese Earth Resources Satellite (JERS), and the RADARSAT (a Canadian...

Briefs : Electronics & Computers
Variable Telemetry Playback Rate for Increased Data Return

In a scheme to increase the overall data return from a phase-modulation, suppressed-carrier telemetry transmitter, the telemetry playback symbol rate is adjusted essentially continuously. More precisely, the playback symbol rate is adjusted frequently (as often as once per symbol...

Briefs : Information Technology
Software for Locating Heterogeneous Data in Different Places

The Object Oriented Data Technology group at NASA's Jet Propulsion Laboratory is developing software for locating data — especially scientific data — stored in various formats on heterogeneous computer systems at different locations. The software is intended to exploit and extend...

Briefs : Test & Measurement
Measuring Contact Angles of a Sessile Drop and Imaging Convection Within It

Figure 1 depicts an apparatus that simultaneously and synchronously records magnified ordinary top-view video images and laser-shadowgraph video images of a sessile drop. The real-time values of contact angle and rate of evaporation of the drop as functions of time can...

Briefs : Electronics & Computers
Improved Encryption-Mode GPS Receiver

An improved Global Positioning System (GPS) receiver, which processes an encrypted P-code signal without knowledge of the encryption code (denoted here as A-codeless mode), includes an auxiliary antenna and associated additional signal-processing circuitry. The improved design of this receiver makes it...

Briefs : Electronics & Computers
Low-Power, Sparse-Sampling GPS Receiver

The term "microGPS" denotes a Global Positioning System (GPS) receiver design concept that combines relatively simple, lightweight, low-power-consumption hardware with portable, efficient software. The power demand of a microGPS receiver can be made low because it is designed to sample sparsely; that is,...

Briefs : Software
Software Models Spacecraft Dynamics and Space Environment

The Spacecraft Control Toolbox (SCT) helps design control systems and attitude estimators, analyze station-keeping requirements, generate fuel and pointing budgets, and analyze spacecraft dynamics. The SCT provides a comprehensive set of over five hundred functions including:

Briefs : Software
Web-Based Software for Distributed Planning

The RecDel System is a low-cost software application that helps different groups of a complex project negotiate interfaces between interdependent schedules. The RecDel system is based on a concept of distributed planning, wherein the cognizant persons retain control over, and responsibility for, their...

Briefs : Software
Software for Detecting Tones in Beacon Monitoring

A software package for use in a ground receiving station detects a beacon-monitor tone transmitted by a spacecraft. To recapitulate from previous NASA Tech Briefs articles on beacon monitoring: An onboard computer processes data from onboard sensors to summarize the condition of the spacecraft...

Briefs : Software
Automated Real-Time Spacecraft Navigation System

The Automated Real-Time Spacecraft Navigation (ARTSN) system is a prototype of a class of software systems for automated navigation and monitoring of spacecraft from stations on the Earth. The system processes radio metric tracking data (principally, range and Doppler measurements) in real time to...

Briefs : Materials
Metal-Supported Catalyst Beds for Reacting CO2 With CH4

Metal-supported catalyst beds with improved thermal and flow characteristics for promoting endothermic chemical reactions are undergoing development. In the proposed original application, catalyst beds of this type would be used on Mars to produce hydrogen from an endothermic reaction...

Briefs : Materials
Chemical Reactors Based on Catalyzed Wires

In catalytic flow-through chemical reactors being explored for space vehicle applications, the catalysts would be supported on the surfaces of wires, instead of on particles, as are typically used in traditional packed beds. The original intent of the proposal was to make it possible to build...

Briefs : Materials
Chemical Reactors Based on Catalyzed Microtubes

In an extension of the concept reported in the preceding article, catalytic flow-through chemical reactors of a proposed type would contain catalyst-coated microtubes, possibly in combination with catalyst-coated wires. In addition to the advantages afforded by the catalyst-coated wires described...

Briefs : Mechanical & Fluid Systems
Thrust-Control System for Emergency Control of an Airplane

Extensive redundancy is designed into aircraft flight-control systems to ensure a low probability of failure. During recent years, however, major failures of flight-control systems have occurred in several airplanes, leaving engine thrust as the flight-control mode of last resort. In...

Briefs : Manufacturing & Prototyping
Weld Repair of a Directionally Solidified Superalloy Article

An arc-welding technique for repair of a directionally solidified (DS) nickel-base superalloy article (e.g., a turbine blade or vane) has been devised. The technique equally is applicable to a part as cast or a part that has been damaged in use. Unlike ordinary gas tungsten arc (GTA)...

Briefs : Physical Sciences
Field-Reversed Magnetic Mirrors for Confinement of Plasmas

A field-reversed configuration (FRC) has been proposed for a magnetic mirror — a solenoidal electromagnet configured and operated in such a way as to effect at least partial confinement of a plasma. Magnetic mirrors had been investigated for potential use as plasma-confinement devices...

Briefs : Physical Sciences
Updated Multidisciplinary Optical-System-Analysis Software

Version 5.0 of the Integrated Modeling of Optical Systems (IMOS) software has been released. A previous version was described in "Software for Multidisciplinary Analysis of Optical Systems" (NPO-20536), NASA Tech Briefs, Vol. 24, No. 11 (November 2000), page 36. In both versions, IMOS...

Briefs : Physical Sciences
RVSM Certification of Dryden DC-8 Airborne Laboratory

The NASA Dryden DC-8 Airborne Science Laboratory (see Figure 1) performs research around the globe, recently in support of the SAGE III Ozone Loss and Validation Experiment (SOLVE). This experiment operated in the North Atlantic airspace region, which is subject to reduced vertical separation...

Briefs : Information Technology
Wavelet Analysis To Predict Limit Cycles

A method to predict the onset of a limit cycle for an aeroelastic testbed has been developed. The prediction is based on wavelet processing of measurement data that have been recorded under various flight conditions. The method has been considered for only a small testbed; however, the concepts may lead...

Briefs : Photonics/Optics
Using Ferromagnetism and Giant Magnetoresistance To Sense IR

Infrared (IR) sensors of a proposed type, and integrated-circuit imaging devices containing planar arrays of such sensors, would be based on a combination of (1) temperature-dependent ferromagnetism and (2) the use of giant magnetoresistance (GMR) to detect changes in ferromagnetism....

Briefs : Photonics/Optics
Leakage-Compensated, Frame-Differencing APS Imager

A proposed complementary metal oxide/semiconductor (CMOS) integrated-circuit imaging device of the active-pixel sensor (APS) type is capable of simultaneously generating the pixel-by-pixel sum and difference of two successive image frames at high speed for real-time operation, while...

Briefs : Electronics & Computers
Software for Analyzing Telecommunication Link Performance

The Telecom Forecaster Predictor (TFP) is a multi-mission computer program for analyzing deep space telecommunication links. Analysts use the TFP for link planning, performance prediction, and post-pass trending analysis. For each mission, multiple users access a controlled set of TFP...

Briefs : Photonics/Optics
Magnetic Microimagers Based on Giant Magnetoresistance

Integrated-circuit imaging devices of a proposed type would contain planar arrays of microscopic sensors that would exploit giant magnetoresistance (GMR). Each GMR sensor in such a device would define one pixel in an image with a pixel pitch of the order of tens of microns. With the...

Technology Leaders