Engineering topics

Bell, James F., III

Publications and source records attributed to Bell, James F., III.

44 records · Page 3

NASA NTRS1992

Surface vs. atmospheric origin of 2.1-2.5 micron absorption features in the Martian spectrum

For 20 years the origin of subtle absorption features in the spectrum of Mars near 2.3 micro-m ('K' band: 1.9-2.5 micro-m) has been debated. This spectral region contains gaseous absorption features predominantly from CO2 and CO on Mars and from telluric H2O and CO2. The authors have obtained new higher spectral resolution telescopic K band spectra of 10 surface regions using the Infrared Telescope Facility (IRTF) at Mauna Kea during 1990. The goals were to confirm the existence of broad features seen at lower spectral resolution and to determine whether these bands are caused by atmospheric gases, surface (or airborne dust) minerals, or a combination of both.

Bell, James F., III↗

NASA NTRS1992

Mars: Compositional variability of ferric/ferrous minerals and polar volatiles from groundbased imaging spectroscopy

In an attempt to further constrain the ferric and ferrous mineralogy of Mars, Bell et al. (1989; 1990) obtained high resolution imaging spectroscopic data of much of the Martian surface in the visible and near-infrared (0.4-1.1 micron) during the 1988 opposition. Preliminary analysis of these data showed further evidence of crystalline hematite absorption features at 0.8-0.9 microns and 0.6-0.7 microns. Additionally, the 0.6-0.7 micron Fe(III) band was shown to vary across the surface, with a substantial correlation with albedo in the region studied. Calibration of this 1988 data set (along with a similar data set obtained during the 1990 opposition) has been ongoing, and some of the most recent results of the analysis of these data using linear spectral mixture modeling are reported.

Bell, James F., III↗

NASA NTRS1992

A high-resolution radar and CCD imaging study of crater rays in Mare Serenitatis and Mare Nectaris

Radar and spectral image processing techniques are reviewed and their application to the rays in Mare Serenitatis and Mare Nectaris is discussed. Analysis of data for Mare Serenitatis shows that the ray that passes west of the Bessel Crater is characterized by up to 40 percent highland ejecta. Radar data show that optically bright ray deposits are characterized by enhanced 1-50 cm scale roughness within the upper meter of the regolith, but not by enhanced 1-10 m blockiness. Stokes vector analysis of the 3.0 cm radar echoes shows that the western portion of the Bessel ejecta blanket is characterized by an anomalously high nondiffuse depolarized return. The ray analyzed in Mare Nectaris passes close to Rosse Crater and is characterized by a cluster of bright secondary craters within a radar-rough halo downrange of Tycho. This downrange deposit is attributed to excavation of local fragmental material by a secondary debris surge.

Campbell, Bruce A.↗

NASA NTRS1992

Charge-coupled device imaging spectroscopy of Mars. I - Instrumentation and data reduction/analysis procedures

This paper describes the collection, reduction, and analysis of 0.4-1.0-micron Mars imaging spectroscopy data obtained during the 1988 and 1990 oppositions from Mauna Kea Observatory and provides a general outline for the acquisition and analysis of similar imaging spectroscopy data sets. The U.H. 2.24-m Wide Field Grism CCD Spectrograph was used to collect 13 3D image cubes covering 90 percent of the planet south of 50 deg N in the 0.4-0.8 micron region and covering 55 percent of the planet south of 50 deg N in the 0.5-1.0 micron region. Spectra extracted from these image cubes reveal the detailed character of the Martian near-UV to visible spectrum. Images at red wavelengths reveal the 'classical' albedo markings at 100-500 km spatial resolution while images at blue wavelengths show little surface feature contrast and are dominated by condensate clouds/hazes and polar ice.

Bell, James F., III↗

NASA NTRS1991

Imaging spectroscopy of Mars during 1990

Preliminary results are presented of observations of Mars using three telescopes and a CCD camera, grating-array spectrometers, and a near-IR array camera. Martian albedo features are shown to be similar in the visible and 1.3-3.5-micron range, and reflectances of nearly zero are noted in the image at 3.02 microns. The results demonstrate that these techniques provide effective maps of spatial variations in spectral absorption features caused by Martian atmospheric volatiles and by surface minerals.

Bell, James F., III↗

NASA NTRS1990

Observational evidence of crystalline iron oxides on Mars

A series of new spectral observations of Mars was obtained at Mauna Kea Observatory in the 0.4-1.0-micron wavelength range during the extremely favorable 1988 opposition, which yielded new spectral reflectance and relative reflectance data for a number of distinct spots on the Martian surface at 500-600 km spatial resolution. The new spectra revealed absorptions at 0.62-0.72 micron and at 0.81-0.94 micron, both seen clearly for the first time. These absorption features are interpreted as Fe(3+) electronic transition bands that indicate the presence of crystalline ferric oxide or hydroxide minerals on the Martian surface.

Bell, James F., III↗

NASA NTRS1989

Mars - Near-infrared comparative spectroscopy during the 1986 opposition

Near-IR, 0.7-2.5 micron spectra were obtained for several Martian locations during the 1986 opposition, using a continuously variable filter spectrometer; approximately 60 distinct spots were observed at 0.5-1.5 arcsec (200-460 km) resolution which are distinguishable into eight distinct geologic types: (1) volcanic regions, (2) ridged plains, (3) ridged volcanic plains, (4) scoured plains, (5) impact basins, (6) channels and canyons, (7) densely-cratered regions, and (8) layered terrain and ice. Spectral features observed in the spot-to-spot ratios for spectra from different geologic regions are used as indicators of mineralogic differences. Little difference is found among spectra from areas that appear to have very different morphologies in Viking Orbiter images.

Bell, James F., III↗

NASA NTRS1987

Mars: Near-infrared comparative spectroscopy during the 1986 opposition

Near-infrared spectral observations of Mars during the 1986 opposition were performed at the Mauna Kea Observatory utilizing the University of Hawaii's 88 inch telescope. Spectra were obtained of several Martian locations using a continuously variable filter (CVF) spectrometer with a resolution of 1.25 percent. Spot-to-spot ratios were produced between spectra taken in different geological regions.

Bell, James F., III↗