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Baron, R. L.

Publications and source records attributed to Baron, R. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

High-Throughput Processes and Structural Characterization of Single-Nanotube Based Devices for 3D Electronics

We have developed manufacturable approaches to form single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 micron deep trenches. These wafer-scale approaches were enabled by chemically amplified resists and inductively coupled Cryo-etchers to form the 3D nanoscale architectures. The tube growth was performed using dc plasmaenhanced chemical vapor deposition (PECVD), and the materials used for the pre-fabricated 3D architectures were chemically and structurally compatible with the high temperature (700 C) PECVD synthesis of our tubes, in an ammonia and acetylene ambient. The TEM analysis of our tubes revealed graphitic basal planes inclined to the central or fiber axis, with cone angles up to 30 deg. for the particular growth conditions used. In addition, bending tests performed using a custom nanoindentor, suggest that the tubes are well adhered to the Si substrate. Tube characteristics were also engineered to some extent, by adjusting growth parameters, such as Ni catalyst thickness, pressure and plasma power during growth.

top-down fabrication↗
NASA NTRS1998

SIM vs. SOS: A Space Interferometry Trade Study

This study was undertaken at the Jet Propulsion Laboratory to identify salient features of two competing instrument designs and to select the design that best meets the goals of the Space Interferometry Mission.

trade-study↗
NASA NTRS1992

Photometric variability of Charon at 2.2 microns

Pluto-Charon images obtained on each of four nights at 2.2, 1.2, and 1.7 microns are presently fitted by a two-source image model in which the position of Charon and the ratio of its signal to that of Pluto are free parameters. At 2.2 microns, Charon is fainter than Pluto by magnitudes which, when combined with Pluto-Charon system photometry, yield apparent magnitudes of 15.01 + or - 0.08 for Charon at 0.06 lightcurve phase and 15.46 + or - 0.05 at lightcurve phase 0.42. In view of these results, Charon is variable in this filter bypass due to geometric albedo changes as a function of longitude.

Bosh, A. S.↗
NASA NTRS1989

Image quality on the Kuiper Airborne Observatory. I - Results of the first flight series

The NASA Kuiper Airborne Observatory (KAO) was flown three times during June and July, 1984 in order to study the causes of the poor seeing obtained with the 0.9-m telescope. High-speed pressure and temperature sensors were placed in the telescope cavity. Several thousand stellar images were recorded under various flight and optical configurations. It is found that the long-exposure image size is affected by telescope tracking errors, imperfect optics, poor optical alignment, telescope and instrument vibration, thermal fluctuations in the telescope cavity, and density fluctuations in the shear layer that forms the boundary between the cavity air and outside air. Possible ways to improve the quality of the images are discussed.

Elliot, J. L.↗
NASA NTRS1986

Signal-to-noise ratios for possible stellar occultations by Pluto

Successful observation of a stellar occultation by Pluto would make it possible to obtain information regarding the presence of an atmosphere at the planet. If an atmosphere is found, the determination of its structure might be feasible. Two or more occultation chords could make it possible to obtain the precise diameter of Pluto. Mink and Klemola (1985) have presented a list of ten stars which might be occulted by Pluto during the period 1985-1990. In this paper, BVR photometry of the occultation candidate stars are presented, and a calculation is conducted of the S/N which could be achieved with a 1-m telescope. It is pointed out that from a photometric standpoint, the best potential occultation (after that of P2) would be that of P8. However, even the faintest stars on the list should give interesting results if their occultations by Pluto can be observed with a 1-m telescope and sensitive photometric equipment.

Bosh, A. S.↗
NASA NTRS1985

The 1983 June 15 occultation by Neptune. I - Limits on a possible ring system

Observations on 15 June 1983 of an occultation of a star by Neptune from Mauna Kea, Mount Stromlo, Siding Spring, and the Kuiper Airborne Observatory show no evidence for equatorial rings between 25,300 and 200,000 km (R/N/ = 25,269 km). Within most of this region, the upper limit on the optical depth along the line of sight, for rings broader than 6 km , is 0.04, which corresponds to a normal optical depth of 0.016. These results rule out a Neptunian ring system similar to that of Saturn or Uranus, but not a system of low optical depth similar to the Jovian rings. The data show no features that appear likely to have been caused by material in the equatorial plane of Neptune near the Roche limit.

Elliot, J. L.↗
NASA NTRS1985

The 1983 June 15 occultation by Neptune. II - The oblateness of Neptune

The oblateness and radius of Neptune were determined from an analysis of photoelectric observations of the June 15, 1983 occultation by Neptune at six stations, combined with the results of the Apr. 7, 1968 Neptune occultation of BD - 17 deg 4388. The oblateness is 0.0191 + or - 0.0017 and the equatorial radius is 25,268 + or - 12 km at the level probed by the occultation. The results are consistent with recent determinations of Neptune's rotation period and J2 (the second-order gravitational harmonic coefficient) and suggest that Neptune is far less centrally condensed than Uranus. Temperature profiles for Neptune's upper atmosphere were also derived from these data.

French, R. G.↗
NASA NTRS1985

A high-speed, dual-CCD imaging photometer

The SNAPSHOT is a high-speed, dual-CCD imaging photometer, with special capability for occultation observations. It is capable of recording occultation light curves in the presence of bright, nonuniform background illumination, such as occultations of stars by Saturn's rings or by comets. Such events are difficult or impossible to observe with conventional photometers. The fundamental idea that makes high time-resolution observations possible is to reduce the data rate by digitizing only those pixels in subframes containing the objects of interest.

Dunham, E. W.↗
NASA NTRS1984

Image Quality on the KAO

Three flights of the Kuiper Airborne Observatory (KAO) were taken to study the cause of the point spread function (PSF) degradation. The preliminary conclusions are: (1) the KAO point spread function decreases in size with elapsed time at altitude; (2) image motion is occasionally comparable to the size of the image, but is usually a sub-arcsecond effect; and (3) star images show small scale internal structural changes on a 200 microsecond timescale.

Dunham, E. W.↗
NASA NTRS1984

Results from the occultation of 14 Piscium by (51) Nemausa

Observations of the September 11, 1983 occultation of 14 Psc by the asteroid (51) Nemausa were obtained at six sites distributed across the northern two-thirds of the track. The observations are well represented by an elliptical limb profile with a semimajor axis of 84.9 + or - 2.0 km and oblateness (1-b'/a') 0.20 + or - 0.05. The mean radius of 74 + or - 4 km agrees with the 1979 occultation effective radius of 76.5 + or - 4 km and the published radiometric radius of 75.5 km (Morrison and Zellner, 1979).

Dunham, E. W.↗
NASA NTRS1983

A portable telescope, photometer, and data-recording system

A description is presented of a portable telescope, two-channel photometer and high-speed data-recording system that meet the unique requirements of occultation astronomy. The instrumentation has been designed for portability, high time resolution, accurate absolute timing, and ease of use. The instrumentation includes a light-weight 35.5-cm (14-inch) objective portable telescope, a two-channel high-speed photometer and a data-recording system built into a suitcase. The equipment has been successfully used in field operations and at fixed observatories in India, Australia, and Hawaii.

Baron, R. L.↗
NASA NTRS1981

No evidence of rings around Neptune

The results of two observations of stellar occultations of Neptune to determine if the planet has a ring system are reported. The sightings were made from Mt. Stromlo, Mauna Kea, and Cerro Tololo, noting that an equatorial ring would subtend only two arcsec of view. An upper accretion limit was defined to set the region around Neptune where rings, rather than satellites, could form. The intensities of the starlight from the two selected stars were recorded by photometers on magnetic tape during the occultation period. One of the stars did not occult, but passed through the entire region where a ring system might be present. No definitive evidence for rings was found, although an optical depth for a Neptunian ring was calculated at 0.07, with a width of more than 5 km and a radius of 31,400 km.

Elliot, J. L.↗
NASA NTRS1979

Determination of secondary electron emission characteristics of lunar soil samples

A procedure is described for the determination of the 'apparent crossover voltage', i.e. the value of the primary (bombarding) electron energy at which an insulating sample surface changes the average sign of its charge. This apparent crossover point is characteristic of the secondary emission properties of insulating powders such as the lunar soil samples. Lunar core samples from well-defined, distinct soil layers are found to differ significantly in their secondary emission properties. This observation supports the suggestion that soil layers were deposited by an electrostatic transport process.

Gold, T.↗
NASA NTRS1977

The search for the cause of the low albedo of the moon

The effects of different weathering processes on the albedo of the lunar surface cover is discussed. The surface chemical composition of numerous lunar soil and pulverized rock samples was determined by auger electron spectroscopy. The optical albedo of these samples was also measured. The chemical concentration of iron and titanium is greater on the surface of soil samples than it is on the surface of crushed rock samples with similar bulk composition, whereas the albedo of soil samples is lower than that of the crushed rock samples. A correlation is presented between the surface iron + titanium content and the albedo. Results of solar wind simulation experiments show that irradiation of crushed lunar rock samples with a small dose (corresponding to 3000 years of solar wind) of 2-keV energy protons changed the surface chemistry of the rock to that of the soil. A much larger dose of protons (corresponding to 30,000 years of solar wind) was needed to darken crushed rock to the albedo of the soil of similar bulk chemical composition. The mechanism of darkening by solar wind is discussed, and its effectiveness is compared to that of other darkening processes.

Gold, T.↗