SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 8 - April 21, 2006

89 ASTRONOMY
Includes observations of celestial bodies; astronomical instruments and techniques; radio, gamma-ray, x-ray, ultraviolet, and infrared astronomy; and astrometry.

20060010230 Oregon State Univ., OR, USA

A Perfect View of Vesta: Creating Pointing Observations for the Dawn Spacecraft on Asteroid 4 Vesta

Hay, Katrina M.; Summer Student Research Presentations; August 2005; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

The Dawn spacecraft has a timely and clever assignment in store. It will take a close look at two intact survivors from the dawn of the solar system (asteroids 4 Vesta and 1 Ceres) to understand more about solar system origin and evolution. To optimize science return, Dawn must make carefully designed observations on approach and in survey orbit, high altitude mapping orbit, and low altitude mapping orbit at each body. In this report, observations outlined in the science plan are modeled using the science opportunity analyzer program for the Vesta encounter. Specifically, I encoded Dawn's flight rules into the program, modeled pointing profiles of the optical instruments (framing camera, visible infrared spectrometer) and mapped their fields of view onto Vesta's surface. Visualization of coverage will provide the science team with information necessary to assess feasibility of alternative observation plans. Dawn launches in summer 2006 and ends its journey in 2016. Instrument observations on Vesta in 2011 will supply detailed information about Vesta's surface and internal structure. These data will be used to analyze the formation and history of the protoplanet and, therefore, complete an important step in understanding the development of our solar system. Author

Asteroids; Vesta Asteroid; Solar System; Solar System Evolution; Optical Equipment; Protoplanets

20060010250 California Univ., Berkeley, CA, USA

A Population Study of Wide-Separation Brown Dwarf Companions to Main Sequence Stars

Smith, Jeffrey J.; Summer Student Research Presentations; August 2005, pp. 47; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

Increased interest in infrared astronomy has opened the frontier to study cooler objects that shed significant light on the formation of planetary systems. Brown dwarf research provides a wealth of information useful for sorting through a myriad of proposed formation theories. Our study combines observational data from 2MASS with rigorous computer simulations to estimate the true population of long-range (greater than 1000 AU) brown dwarf companions in the solar neighborhood (less than 25 pc from Earth). Expanding on Gizis et al. (2001), we have found the margin of error in previous estimates to be significantly underestimated after we included orbit eccentricity, longitude of pericenter, angle of inclination, field star density, and primary and secondary luminosities as parameters influencing the companion systems in observational studies. We apply our simulation results to current L- and T-dwarf catalogs to provide updated estimates on the frequency of wide-separation brown dwarf companions to main sequence stars. Author

Brown Dwarf Stars; Main Sequence Stars; Populations; Planetary Systems

20060010269 California Inst. of Tech., CA, USA

Determining the Locations of Brown Dwarfs in Young Star Clusters

Porter, Lauren A.; Summer Student Research Presentations; August 2005, pp. 43-44; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

Brown dwarfs are stellar objects with masses less than 0.08 times that of the Sun that are unable to sustain nuclear fusion. Because of the lack of fusion, they are relatively cold, allowing the formation of methane and water molecules in their atmospheres. Brown dwarfs can be detected by examining stars' absorption spectra in the near-infrared to see whether methane and water are present. The objective of this research is to determine the locations of brown dwarfs in Rho Ophiuchus, a star cluster that is only 1 million years old. The cluster was observed in four filters in the near-infrared range using the Wide-Field Infra-Red Camera (WIRC) on the 100' DuPont Telescope and Persson's Auxiliary Nasymith Infrared Camera (PANIC) on the 6.5-m Magellan Telescope. By comparing the magnitude of a star in each of the four filters, an absorption spectrum can be formed. This project uses standard astronomical techniques to reduce raw frames into final images and perform photometry on them to obtain publishable data. Once this is done, it will be possible to determine the locations and magnitudes of brown dwarfs within the cluster. Author

Brown Dwarf Stars; Position (Location); Star Clusters; Astronomical Photometry

20060010270 Idaho Univ., ID, USA

Irregular Wavelike Structure in Saturn's Rings

Pollard, Benjamin J.; Summer Student Research Presentations; August 2005, pp. 43; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

We have searched Saturn's A, B, and C rings for irregular wavelike structure using Voyager Photopolarimeter (PPS), Ultraviolet Spectrometer (UVS), and Radio Science (RSS) occultation datasets, as well as ring reflectivity profiles derived from Voyager images. A maximum entropy technique for conducting spectral analysis was used to estimate wave frequency power in relation to radial location for each dataset. Using this method we have found irregular structure in the PPS and UVS inner B Ring occultation datasets previously identified in Voyager imaging data. Both finer structure, with a wavelength of around 20 km, and large structure with wavelengths of 200 to 1000 km, are visible in the occultation data and appear similar to that seen in the imaging data. After removing ringlets from the C-Ring data, we have identified what appears to be a 1000-km wave sustained throughout the ring. The large dominant wavelength appears in all datasets; however, tests are currently being conducted in an attempt to verify its existence. Irregular structure with a wavelength of approximately 20 km has been observed in the C Ring reflectivity profiles, but not within the occultation datasets. This leads us to doubt it is caused by ring surface mass density fluctuations detectable by the occultation experiments. Author

Saturn Rings; Planetary Surfaces; Irregularities

20060010323 Geological Survey, Menlo Park, CA, USA

Cretaceous-Tertiary Boundary Interval in Badlands National Park, South Dakota

Stoffer, P. W.; Messina, P.; Chamberlain, J. A.; Terry, D. O.; January 2001; 54 pp.; In English Report No.(s): PB2006-105428; USGS/OFR-01-56; No Copyright; Avail.: National Technical Information Service (NTIS)

A marine K-T boundary interval has been identified throughout the Badlands National Park region of South Dakota. Data from marine sediments suggest that deposits from two asteroid impacts (one close, one far away) may be preserved in the Badlands. These impact generated deposits may represent late Maestrichtian events or possibly the terminal K-T event. Interpretation is supported by paleontological correlation, sequence stratigraphy, magnetostratigraphy, and strontium isotope geochronology. This research is founded on nearly a decade of NPS approved field work in Badlands National Park and a foundation of previously published data and interpretations. NTIS

Badlands; Cretaceous-Tertiary Boundary; Earth Mantle; Geochemistry; Geochronology; National Parks

20060011027 Astrophysical Advances, Inc., Palo Alto, CA, USA

Comparing Ultraviolet Spectra against Calculations: Year 2 Results

Peterson, Ruth C.; [2004]; 6 pp.; In English; Original contains black and white illustrations Contract(s)/Grant(s): NAS5-02052 Report No.(s): LTSA-03; No Copyright; Avail.: CASI: A02, Hardcopy

The five-year goal of this effort is to calculate high fidelity mid-W spectra for individual stars and stellar systems for a wide range of ages, abundances, and abundance ratios. In this second year, the comparison of our calculations against observed high-resolution mid-Wspectra was extended to stars as metal-rich as the Sun, and to hotter and cooler stars, further improving the list of atomic line parameters used in the calculations. We also published the application of our calculations based on the earlier list of line parameters to the observed mid-UV and optical spectra of a mildly metal-poor globular cluster in the nearby Andromeda galaxy, Messier 3 1. Author

Ultraviolet Spectra; High Resolution; Abundance; Stellar Systems; Globular Clusters

Source: NASA