SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

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

88 SPACE SCIENCES (GENERAL)
Includes general research topics related to the natural space sciences.

For specific topics in space sciences see categories 89 through 93.

20060010187 Minnesota Univ., MN, USA

Asteroid Shape Reconstruction From Radar Observations

Busch, Michael J.; Summer Student Research Presentations; August 2005, pp. 30; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

I estimate near-Earth asteroid 1992 SK's physical properties from radar delay-Doppler images, Doppler-only echo spectra and optical lightcurves. The images are not very strong, but place up to 20 (40 m by 160 m) pixels on the asteroid. The radar tracks are confined to subradar latitudes between 20 and 40 degrees but have complete rotational phase coverage. The echo spectra and optical lightcurves span approx.80 degrees of sky motion, providing geometric leverage to constrain the pole direction. The optical lightcurves are essential to accurate determination of the asteroid's shape and spin state. The asteroid is approx.1.4 km in maximum extent and mildly asymmetric, with an elongation of approx.1.5 and relatively subdued topography. The radar albedo is about 0.13 and the optical albedo about 0.3. The circular polarization ratio for the object is about 0.34, implying typical cm-scale surface roughness. I estimate the asteroid's period to be 7.3182+/-0.0003 hours and its pole direction as (99deg+/-5deg,-3deg+/-5deg) in ecliptic coordinates. The radar-refined orbital solution accurately predicts planetary close approaches between the years 826 and 2690. I have used my model to predict salient characteristics of radar images and optical lightcurves obtainable during the asteroid's March 2006 approach. Author

Asteroids; Shapes; Radar Imagery; Radar Tracking; Pixels; Asymmetry; Radar Echoes

20060010200 Portland State Univ., OR, USA

Geographic Information Systems and Martian Data: Compatibility and Analysis

Jones, Jennifer L.; Summer Student Research Presentations; August 2005, pp. 36-37; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

Planning future landed Mars missions depends on accurate, informed data. This research has created and used spatially referenced instrument data from NASA missions such as the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey Orbiter and the Mars Orbital Camera (MOC) on the Mars Global Surveyor (MGS) Orbiter. Creating spatially referenced data enables its use in Geographic Information Systems (GIS) such as ArcGIS. It has then been possible to integrate this spatially referenced data with global base maps and build and populate location based databases that are easy to access. Author

Geographic Information Systems; Mars Missions; Thermal Emission; Mars Global Surveyor; Systems Compatibility; Data Bases; Imaging Techniques

20060010201 Montana State Univ., Bozeman, MT, USA

Qualifying a Bonding Process for the Space Interferometry Mission

Joyce, Gretchen P.; Summer Student Research Presentations; August 2005, pp. 36; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

The Space Interferometry Mission consists of three parallel Michelson interferometers that will be capable of detecting extrasolar planets with a high degree of accuracy and precision. High levels of stability must be met in order to fulfill the scientific requirements of this mission. To attain successful measurements the coefficient of thermal expansion between optics and bonding material must be minimized without jeopardizing the integrity of the bonds. Optic-to-optic bonds have been analyzed to better understand variables such as the effects of the coefficient of thermal expansion differences between optics and bonding materials, and materials have been chosen for the project based on these analyses. A study was conducted to determine if a reliable, repeatable process for bonding by wicking adhesive could be obtained using a low-viscosity epoxy and ultra-low expansion glass. A process of creating a methodology of bonding fused silica optics with Z-6020 silane primer and Epo-Tek 301 epoxy will be discussed. Author

Michelson Interferometers; Extrasolar Planets; Detection; Thermal Expansion; Bonding

20060010224 California Univ., Berkeley, CA, USA

Building the Case for SNAP: Creation of Multi-Band, Simulated Images With Shapelets

Ferry, Matthew A.; Summer Student Research Presentations; August 2005, pp. 32; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

Dark energy has simultaneously been the most elusive and most important phenomenon in the shaping of the universe. A case for a proposed space-telescope called SNAP (SuperNova Acceleration Probe) is being built, a crucial component of which is image simulations. One method for this is 'Shapelets,' developed at Caltech. Shapelets form an orthonormal basis and are uniquely able to represent realistic space images and create new images based on real ones. Previously, simulations were created using the Hubble Deep Field (HDF) as a basis Set in one band. In this project, image simulations are created.using the 4 bands of the Hubble Ultra Deep Field (UDF) as a basis set. This provides a better basis for simulations because (1) the survey is deeper, (2) they have a higher resolution, and (3) this is a step closer to simulating the 9 bands of SNAP. Image simulations are achieved by detecting sources in the UDF, decomposing them into shapelets, tweaking their parameters in realistic ways, and recomposing them into new images. Morphological tests were also run to verify the realism of the simulations. They have a wide variety of uses, including the ability to create weak gravitational lensing simulations. Author

Dark Energy; Spaceborne Telescopes; Detection; Simulation; Supernovae; Gravitational Lenses

20060010257 Michigan Univ., MI, USA

Test Frame for Gravity Offload Systems

Murray, Alexander R.; Summer Student Research Presentations; August 2005, pp. 40; In English; See also 20060010186; No Copyright; Available from CASI only as part of the entire parent document

Advances in space telescope and aperture technology have created a need to launch larger structures into space. Traditional truss structures will be too heavy and bulky to be effectively used in the next generation of space-based structures. Large deployable structures are a possible solution. By packaging deployable trusses, the cargo volume of these large structures greatly decreases. The ultimate goal is to three dimensionally measure a boom's deployment in simulated microgravity. This project outlines the construction of the test frame that supports a gravity offload system. The test frame is stable enough to hold the gravity offload system and does not interfere with deployment of, or vibrations in, the deployable test boom. The natural frequencies and stability of the frame were engineered in FEMAP. The test frame was developed to have natural frequencies that would not match the first two modes of the deployable beam. The frame was then modeled in Solidworks and constructed. The test frame constructed is a stable base to perform studies on deployable structures. Author

Spaceborne Telescopes; Microgravity; Gravitation; Vibration; Resonant Frequencies; Apertures

20060010506 NASA Johnson Space Center, Houston, TX, USA

JSC Orbital Debris Website Description

Johnson, Nicholas L.; January 2006; 2 pp.; In English Contract(s)/Grant(s): 104-07-06-OD; No Copyright; Avail.: CASI: A01, Hardcopy

Purpose: The website provides information about the NASA Orbital Debris Program Office at JSC, which is the lead NASA center for orbital debris research. It is recognized world-wide for its leadership in addressing orbital debris issues. The NASA Orbital Debris Program Office has taken the international lead in conducting measurements of the environment and in developing the technical consensus for adopting mitigation measures to protect users of the orbital environment. Work at the center continues with developing an improved understanding of the orbital debris environment and measures that can be taken to control its growth. Major Contents: Orbital Debris research is divided into the following five broad efforts.

Each area of research contains specific information as follows:

1) Modeling - NASA scientists continue to develop and upgrade orbital debris models to describe and characterize the current and future debris environment. Evolutionary and engineering models are described in detail. Downloadable items include a document in PDF format and executable software.

2) Measurements - Measurements of near-Earth orbital debris are accomplished by conducting ground-based and space-based observations of the orbital debris environment. The data from these sources provide validation of the environment models and identify the presence of new sources. Radar, optical and surface examinations are described. External links to related topics are provided.

3) Protection - Orbital debris protection involves conducting hypervelocity impact measurements to assess the risk presented by orbital debris to operating spacecraft and developing new materials and new designs to provide better protection from the environment with less weight penalty. The data from this work provides the link between the environment defined by the models and the risk presented by that environment to operating spacecraft and provides recommendations on design and operations procedures to reduce the risk as required. These data also help in the analysis and interpretation of impact features on returned spacecraft surfaces.

4) Mitigation - Controlling the growth of the orbital debris population is a high priority for NASA, the USA, and the major space-faring nations of the world to preserve near-Earth space for future generations. Mitigation measures can take the form of curtailing or preventing the creation of new debris, designing satellites to withstand impacts by small debris, and implementing operational procedures ranging from utilizing orbital regimes with less debris, adopting specific spacecraft attitudes, and even maneuvering to avoid collisions with debris. Downloadable items include several documents in PDF format and executable software.and

5) Reentry - Because of the increasing number of objects in space, NASA has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth. One method of postmission disposal is to allow reentry of these spacecraft, either from orbital decay (uncontrolled entry) or with a controlled entry. Orbital decay may be achieved by firing engines to lower the perigee altitude so that atmospheric drag will eventually cause the spacecraft to enter. However, the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses. Controlled entry normally occurs by using a larger amount of propellant with a larger propulsion system to drive the spacecraft to enter the atmosphere at a steeper flight path angle. It will then enter at a more precise latitude, longitude, and footprint in a nearly uninhabited impact region, generally located in the ocean. Derived from text

Websites; Aerospace Environments; Space Debris; Protection; Collisions; Environment Models

Source: NASA