Engineering topics

Hecht, M.

Publications and source records attributed to Hecht, M..

26 records · Page 2

NASA NTRS1995

Fabricating Sub-collimating Grids for an X-ray Solar Imaging Spectrometer using LIGA Techniques

This paper describes fabrication of sub-collimating X-ray grids that are used in an instrument for the High Energy Solar Spectroscopic Imager ( HESSI ), a proposed NASA mission that will promote understanding of solar particle acceleration and explosive energy release in the magnetized plasmas at the Sun. The HESSI comprises 12 rotating pairs of high-aspect-ratio, high-Z grids; each pair is separated by 1.7 meters and backed by a single Ge detector.

x-ray↗

NASA NTRS1995

Fine Pitch Grids for an X-Ray Solar Imaging Spectrometer Fabricated by Optical Lithography and XeF2 Etching

Fine-pitch, sub-collimating X-ray grids have been developed for an instrument in the High Energy Solar Spectroscopic Imager , a proposed NASA mission. In addition to high-energy x- rays, the instrument requires collimation of photons with energies of less than 4 keV such that free-standing grids are required that have no material between the grid slats. Fabrication of these grids is described.

x-ray↗

NASA NTRS1993

Modulation Collimator Fine Grids for HESP

The proposed High Engergy-Solar Physics (HESP) million will require fine, precise, high aspect ratio modulation collimators for the High Energy Imagin Spectrometer (HEISPEC). The fabrication approach described here rests on the proven precision of semiconductor lithography - the ability to replicate extremely accurate patterns onto different planar substrateds.

LIGA HESP pitch structures solar x-rays gamma rays↗

NASA NTRS1984

Fault-tolerant software for the FIMP

The work reported here provides protection against software failures in the task dispatcher of the FTMP, a particularly critical portion of the system software. Faults in other system modules and application programs can be handled by similar techniques but are not covered in this effort. Goals of the work reported here are: (1) to develop provisions in the software design that will detect and mitigate software failures in the dispatcher portion of the FTMP Executive and, (2) to propose the implementation of specific software reliability measures in other parts of the system. Beyond the specific support to the FTMP project, the work reported here represents a considerable advance in the practical application of the recovery block methodology for fault tolerant software design.

Hecht, H.↗

NASA NTRS1983

Trends in software reliability for digital flight control

Software error data of major recent Digital Flight Control Systems Development Programs. The report summarizes the data, compare these data with similar data from previous surveys and identifies trends and disciplines to improve software reliability.

Hecht, H.↗

NASA NTRS1982

Fault tolerant software modules for SIFT

The implementation of software fault tolerance is investigated for critical modules of the Software Implemented Fault Tolerance (SIFT) operating system to support the computational and reliability requirements of advanced fly by wire transport aircraft. Fault tolerant designs generated for the error reported and global executive are examined. A description of the alternate routines, implementation requirements, and software validation are included.

Hecht, M.↗

NASA NTRS1981

Analysis of DSN software anomalies

A categorized data base of software errors which were discovered during the various stages of development and operational use of the Deep Space Network DSN/Mark 3 System was developed. A study team identified several existing error classification schemes (taxonomies), prepared a detailed annotated bibliography of the error taxonomy literature, and produced a new classification scheme which was tuned to the DSN anomaly reporting system and encapsulated the work of others. Based upon the DSN/RCI error taxonomy, error data on approximately 1000 reported DSN/Mark 3 anomalies were analyzed, interpreted and classified. Next, error data are summarized and histograms were produced highlighting key tendencies.

Galorath, D. D.↗

NASA NTRS1979

An absorption feature in the spectrum of the pulsed hard X-ray flux from 4U0115 + 63

A spectral feature, apparently an absorption line, has been observed at an energy of 20.1 + or - 0.5 keV in the pulsed flux of the 3.61-s X-ray pulsar 4U 0115+63 by using the UCSD/MIT instrument on HEAO 1. The line strength, expressed as equivalent width, is 3.1 + or - 0.5 keV. Although essentially unresolved, the feature has a depth more than 60% of the continuum flux. If the feature arises by cyclotron resonance absorption near the magnetic poles of the neutron star, it implies a magnetic field of between approximately 1.8 and 2.5 x 10 to the 12th G, depending on the gravitational redshift (no more than about 5-40%).

Wheaton, W. A.↗