Simulation of Dropping of Cargo With Parachutes

Decelerator System Simulation (DSS) is a computer program for predicting and analyzing the dynamics of a load of cargo dropped with parachutes from an aircraft. A DSS simulation runs from the first motion in the aircraft until the payload reaches the ground. Intended for use in support of airdrop tests for the X- 38 program, DSS was developed by modifying and augmenting an older program, denoted UD233A, used for simulating the dynamics of a space-shuttle solid rocket booster falling with a parachute. The main effort in converting UD233A into DSS involved development of computational models for simulating the inflation of one or more parachute( s), the dynamics of the payload and the slings connecting the parachute( s) with the payload, and the extraction of the payload and parachutes from the aircraft.

Posted in: Briefs, Software, Computer simulation, Fabrics, Booster rocket engines, Aerodynamics

Aspect-Oriented Subprogram Synthesizes UML Sequence Diagrams

The Rational Sequence computer program described in the immediately preceding article includes a subprogram that utilizes the capability for aspect-oriented programming when that capability is present. This subprogram is denoted the Rational Sequence (AspectJ) component because it uses AspectJ, which is an extension of the Java programming language that introduces aspect-oriented programming techniques into the language. The Rational Sequence (AspectJ) component is compiled with a target Java application program on an AspectJ compiler. The user then starts the Java application program. Thereafter, the Rational Sequence (AspectJ) component publishes every visible method call to a Universal Modeling Language (UML) sequence diagram. When the Java application program ends, a sequencer proceeds to generate a UML model that contains packages, classes, and all method calls that occurred during the execution of the program. The user can control the way the UML model is generated by specifying, via the aspect source code, packages and/or classes to be included in the diagrams. Like the rest of Rational Sequence, the AspectJ component complies with the UML specification.

Posted in: Briefs, Software, Architecture, Computer software / hardware, Computer software and hardware, Architecture, Computer software / hardware, Computer software and hardware

Program Synthesizes UML Sequence Diagrams

A computer program called “Rational Sequence” generates Universal Modeling Language (UML) sequence diagrams of a target Java program running on a Java virtual machine (JVM). Rational Sequence thereby performs a reverse engineering function that aids in the design documentation of the target Java program. Whereas previously, the construction of sequence diagrams was a tedious manual process, Rational Sequence generates UML sequence diagrams automatically from the running Java code. Moreover, there is no need to insert instrumentation code into the target Java program. Rational Sequence employs the Java Native Interface application programming interface to create a software profiler that plugs into the JVM. Once the user starts the target Java program, Rational Sequence acts as a nonintrusive observer, generating UML diagrams representing the observed activity. Every method call, object instantiation, or thread event of the target Java program is tracked by the profiler. Once the Java program has ended, the profiler generates a UML model that contains packages, classes, and all method calls observed during the execution of the target program. The user can control the way the UML model is generated by specifying packages and/or classes to be included in the diagrams.

Posted in: Briefs, Software, CAD / CAM / CAE, CAD, CAM, and CAE, Mathematical models, Imaging, Imaging and visualization, Imaging, Imaging and visualization

Updated Computational Model of Cosmic Rays Near Earth

An updated computational model of the galactic-cosmic-ray (GCR) environment in the vicinity of the Earth, Earth’s Moon, and Mars has been developed, and updated software has been developed to implement the updated model. The GCR model and software in their original forms, developed during the early 1990s, were based on balloon and satellite data from 1954 to 1992. This model accounts for solar modulation of the cosmic-ray contribution for each element from hydrogen through iron by computationally propagating the local interplanetary spectrum of each element through the heliosphere. The propagation is effected by solving the Fokker-Planck diffusion, convection, energy-loss boundary-value problem. Since August 1997, the Advanced Composition Explorer NASA satellite has provided new data on GCR energy spectra. These new data were used to update the original model and greatly improve the accuracy of prediction of interplanetary GCR. The updated software was also simplified significantly, relative to the original software. The updated model and software are expected to provide highly accurate GCR-environment data for use by interplanetary- mission planners in planning for protecting astronauts against radiation and ensuring radiation hardness of electronic equipment.

Posted in: Briefs, Software, Computer simulation, Reliability, Reliability, Radiation, Radiation protection, Spacecraft

Quantum Entanglement Molecular Absorption Spectrum Simulator

Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating twophoton molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixedfrequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QE-MASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled- photon spectroscopy for development and implementation of emerging quantum- spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad® software package.

Posted in: Briefs, TSP, Software, Computer simulation, Downsizing, Lasers, Spectroscopy, Lasers, Spectroscopy


Fuzzy Feature Observation Planner for Small Body Proximity Observations (FuzzObserver) is a developmental computer program, to be used along with other software, for autonomous planning of maneuvers of a spacecraft near an asteroid, comet, or other small astronomical body. Selection of terrain features and estimation of the position of the spacecraft relative to these features is an essential part of such planning. FuzzObserver contributes to the selection and estimation by generating recommendations for spacecraft trajectory adjustments to maintain the spacecraft’s ability to observe sufficient terrain features for estimating position. The input to FuzzObserver consists of data from terrain images, including sets of data on features acquired during descent toward, or traversal of, a body of interest. The name of this program reflects its use of fuzzy logic to reason about the terrain features represented by the data and extract corresponding trajectory-adjustment rules. Linguistic fuzzy sets and conditional statements enable fuzzy systems to make decisions based on heuristic rule-based knowledge derived by engineering experts. A major advantage of using fuzzy logic is that it involves simple arithmetic calculations that can be performed rapidly enough to be useful for planning within the short times typically available for spacecraft maneuvers.

Posted in: Briefs, TSP, Software, Fuzzy logic, Attitude control, Spacecraft guidance, Attitude control, Spacecraft guidance, Autonomous vehicles

Internet Distribution of Spacecraft Telemetry Data

Remote Access Multi-mission Processing and Analysis Ground Environment (RAMPAGE) is a Java-language server computer program that enables near-real-time display of spacecraft telemetry data on any authorized client computer that has access to the Internet and is equipped with Web-browser software. In addition to providing a variety of displays of the latest available telemetry data, RAMPAGE can deliver notification of an alarm by electronic mail. Subscribers can then use RAMPAGE displays to determine the state of the spacecraft and formulate a response to the alarm, if necessary. A user can query spacecraft mission data in either binary or comma-separated-value format by use of a Web form or a Practical Extraction and Reporting Language (PERL) script to automate the query process. RAMPAGE runs on Linux and Solaris server computers in the Ground Data System (GDS) of NASA’s Jet Propulsion Laboratory and includes components designed specifically to make it compatible with legacy GDS software. The client/server architecture of RAMPAGE and the use of the Java programming language make it possible to utilize a variety of competitive server and client computers, thereby also helping to minimize costs.

Posted in: Briefs, TSP, Software, Architecture, Computer software / hardware, Computer software and hardware, Internet, Telemetry, Architecture, Computer software / hardware, Computer software and hardware, Internet, Telemetry, Spacecraft

Semi-Automated Identification of Rocks in Images

Rock Identification Toolkit Suite is a computer program that assists users in identifying and characterizing rocks shown in images returned by the Mars Explorer Rover mission. Included in the program are components for automated finding of rocks, interactive adjustments of outlines of rocks, active contouring of rocks, and automated analysis of shapes in two dimensions. The program assists users in evaluating the surface properties of rocks and soil and reports basic properties of rocks. The program requires either the Mac OS X operating system running on a G4 (or more capable) processor or a Linux operating system running on a Pentium (or more capable) processor, plus at least 128MB of random-access memory.

Posted in: Briefs, TSP, Software, Cartography, Computer software / hardware, Computer software and hardware, Cartography, Computer software / hardware, Computer software and hardware, Soils, Terrain, Identification, Spacecraft

Pattern-Recognition Algorithm for Locking Laser Frequency

A computer program serves as part of a feedback control system that locks the frequency of a laser to one of the spectral peaks of cesium atoms in an optical-absorption cell. The system analyzes a saturation absorption spectrum to find a target peak and commands a laser-frequency-control circuit to minimize an error signal representing the difference between the laser frequency and the target peak. The program implements an algorithm consisting of the following steps:

Acquire a saturation absorption signal while scanning the laser through the frequency range of interest. Condition the signal by use of convolution filtering. Detect peaks. Match the peaks in the signal to a pattern of known spectral peaks by use of a pattern-recognition algorithm. Add missing peaks. Tune the laser to the desired peak and thereafter lock onto this peak.
Posted in: Briefs, TSP, Software, Calibration, Mathematical models, Computer software / hardware, Computer software and hardware, Lasers, Optics, Computer software / hardware, Computer software and hardware, Lasers, Optics

Processing EOS MLS Level-2 Data

A computer program performs level-2 processing of thermal- microwave-radiance data from observations of the limb of the Earth by the Earth Observing System (EOS) Microwave Limb Sounder (MLS). The purpose of the processing is to estimate the composition and temperature of the atmosphere versus altitude from ≈8 to ≈90 km. “Level-2” as used here is a specialists’ term signifying both vertical profiles of geophysical parameters along the measurement track of the instrument and processing performed by this or other software to generate such profiles. Designed to be flexible, the program is controlled via a configuration file that defines all aspects of processing, including contents of state and measurement vectors, configurations of forward models, measurement and calibration data to be read, and the manner of inverting the models to obtain the desired estimates. The program can operate in a parallel form in which one instance of the program acts a master, coordinating the work of multiple slave instances on a cluster of computers, each slave operating on a portion of the data. Optionally, the configuration file can be made to instruct the software to produce files of simulated radiances based on state vectors formed from sets of geophysical data-product files taken as input.
Posted in: Briefs, TSP, Software, Measurements, Architecture, Computer software / hardware, Computer software and hardware, Radar, Architecture, Computer software / hardware, Computer software and hardware, Radar, Weather and climate

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