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Jackson, J.

Publications and source records attributed to Jackson, J..

27 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Cosmic background explorer (COBE) navigation with TDRSS one-way return-link Doppler in the post-helium-venting phase

A navigation experiment was performed which establishes Ultra-Stable Oscillator (USO) frequency stabilized one way return link Doppler TDRSS tracking data as a feasible option for mission orbit determination support at the Goddard Space Center Flight Dynamics Facility. The study was conducted using both one way and two way Tracking and Data Relay Satellite System (TDRSS) tracking measurements for the Cosmic Background Explorer (COBE) spacecraft. Tracking data for a 4 week period immediately follow the depletion of the helium supply was used. The study showed that, for both definitive orbit solution and short term orbit prediction (up to 4 weeks), orbit determination results based on one way return link Doppler tracking measurements are comparable to orbit determination results based on two way range and two way Doppler tracking measurements.

Nemesure, M.↗
NASA NTRS1991

A survey of the 158 micron forbidden C II fine-structure line in the central 50 parsecs of the Galaxy

NASA's Kuiper Airborne Observatory has been used to conduct an extensive, velocity-resolved survey at 1-arcsec resolution of the 158-micron forbidden C II fine-structure line emission in the central 50 pc of the Galaxy. The emission is found to be strongest toward the rotating circumnuclear disk surrounding Sgr A West; a continuous bridge of the emission connects the Sgr A complex to the thermal radio filaments in the radio arc 10 arcmin north of the center. This suggests a direct physical connection. The brightest emission occurs preferentially near the edges of the massive Galactic center molecular clouds. It is concluded that these clouds are predominantly ionized by external UV photons.

Poglitsch, A.↗
NASA NTRS1986

Effects of stellar outflows on interstellar sulfur oxide chemistry

Interferometer Maps with 2" to 6" resolution of a number of regions with active star formation (Orion A, W49, W51, SGRB2) show that the distribution of the molecule SO is very compact around stellar outflow sources. Both SO and SO2 were studied near three outflows, OrionA/IRc2 and two sources in W49. The two molecules have similar distributions and abundances. More than 95% of the emission comes from regions whose extents are only .05 to .2 pc., being larger around the more energetic sources. Their spectra are broad, 30 km/sec or more, suggesting that the oxide production is associated with the flows. The outflows are identified by water masers and by extended bipolar flows in SiO. Maps in other molecules, such as HCO+ and CS, which have similar collisional excitation requirements, have much greater spatial extent. Thus it appears that the SO and SO2 abundances are truly compact and are closely associated with the outflows.

Welch, W. J.↗
NASA NTRS1984

State estimation Kalman filter using optical processings Noise statistics known

Reference is made to a study by Casasent et al. (1983), which gave a description of a frequency-multiplexed acoustooptic processor and showed how it was capable of performing all the individual operations required in Kalman filtering. The data flow and organization of all required operations however, were not detailed in that study. Consideration is given here to a simpler Kalman filter state estimation problem. Equally spaced time-sampled intervals (k times T sub s, with k the iterative time index) are assumed. It is further assumed that the system noise vector w and the measurement noise vector v are uncorrelated and Gaussian distributed and that the noise statistics (Q and R) and the system model (Phi, Gamma, H) are known. The error covariance matrix P and the extrapolated error covariance matrix M can thus be precomputed and the Kalman gain matrix K sub k can be precomputed and stored for each input time sample.

Jackson, J.↗
NASA NTRS1983

Optical systolic array processor using residue arithmetic

The use of residue arithmetic to increase the accuracy and reduce the dynamic range requirements of optical matrix-vector processors is evaluated. It is determined that matrix-vector operations and iterative algorithms can be performed totally in residue notation. A new parallel residue quantizer circuit is developed which significantly improves the performance of the systolic array feedback processor. Results are presented of a computer simulation of this system used to solve a set of three simultaneous equations.

Jackson, J.↗
NASA NTRS1983

Frequency-multiplexed and pipelined iterative optical systolic array processors

Optical matrix processors using acoustooptic transducers are described, with emphasis on new systolic array architectures using frequency multiplexing in addition to space and time multiplexing. A Kalman filtering application is considered in a case study from which the operations required on such a system can be defined. This also serves as a new and powerful application for iterative optical processors. The importance of pipelining the data flow and the ordering of the operations performed in a specific application of such a system are also noted. Several examples of how to effectively achieve this are included. A new technique for handling bipolar data on such architectures is also described.

Casasent, D.↗
NASA NTRS1977

Semiconductor grade, solar silicon purification project

The conversion of metallurgical grade silicon into semiconductor grade silicon by way of a three step SiF2 polymer transport purification process was investigated. Developments in the following areas were also examined: (1) spectroscopic analysis and characterization of (SiF2) sub x polymer and Si sub x F sub y homologue conversion; (2) demonstration runs on the near continuous apparatus; (3) economic analysis; and (4) elemental analysis.

Ingle, W. M.↗
NASA NTRS1973

Design and fabrication of an augmentor wing model for acoustic tests

The design and fabrication of a full-scale section of an augmentor wing to be used for acoustic testing at the Lewis Research Center are discussed. This hardware will be used primarily to investigate scaling effects of acoustic data obtained during the Boeing-run model tests. Typical model test data is shown in the report, together with predictions on both performance and acoustics that can be expected from the full-scale section to be built. Areas covered include: the aerodynamic and acoustic criteria of the flap system and nozzles, detailed discussion of the hardware, test system operation procedure, and stress analysis of the entire test system.

Jackson, J.↗