NASA Scientific and Technical Aerospace Reports

uncertainties and sets of uncertainties modified to produce increased and reduced atmospheric variability. For the reference
uncertainties, the 0.8 L/D flatbottom ellipsled vehicle achieves 100% successful capture and has a 99.87 probability of
attaining the science orbit with a 360 m/s V budget for apoapsis and periapsis adjustment. Monte Carlo analyses were also
performed for a guidance system that modulates both bank angle and angle of attack with the reference set of uncertainties.
An alpha and bank modulation guidance system reduces the 99.87 percentile DELTA V 173 m/s (48%) to 187 m/s for the
reference set of uncertainties.
Author
Aerocapture; Neptune (Planet); Space Missions; Triton; Systems Analysis; Spacecraft Performance; Space Exploration
20040111267 Brown Univ., Providence, RI, USA
Reflectance and Thermal Infrared Spectroscopy of Mars: Relationship Between ISM and TES for Compositional
Determinations
Boyce, Joseph, Technical Monitor; Mustard, John; [2004]; 8 pp.; In English
Contract(s)/Grant(s): NAG5-9589; No Copyright; Avail: CASI; A02, Hardcopy
Reflectance spectroscopy has demonstrated that high albedo surfaces on Mars contain heavily altered materials with some
component of hematite, poorly crystalline ferric oxides, and an undefined silicate matrix. The spectral properties of many low
albedo regions indicate crystalline basalts containing both low and high calcium pyroxene, a mineralogy consistent with the
basaltic SNC meteorites. The Thermal Emission Spectrometer (TES) experiment on the Mars Geochemical Surveyor has
acquired critical new data relevant to surface composition and mineralogy, but in a wavelength region that is complementary
to reflectance spectroscopy. The essence of the completed research was to analyze TES data in the context of reflectance data
obtained by the French ISM imaging spectrometer experiment in 1989. This approach increased our understanding of the
complementary nature of these wavelength regions for mineralogic determinations using actual observations of the martian
surface. The research effort focused on three regions of scientific importance: Syrtis Major-Isidis Basin, Oxia Palus-Arabia,
and Valles Marineris. In each region distinct spatial variations related to reflectance, and in derived mineralogic information
and interpreted compositional units were analyzed. In addition, specific science questions related to the composition of
volcanics and crustal evolution, soil compositions and pedogenic processes, and the relationship between pristine lithologies
and weathering provided an overall science-driven framework for the work. The detailed work plan involved colocation of
TES and ISM data, extraction of reflectance and emissivity spectra from areas of known reflectance variability, and
quantitative analysis using factor analysis and statistical techniques to determine the degree of correspondence between these
different wavelength regions. Identified coherent variations in TES spectroscopy were assessed against known atmospheric
effects to validate that the variations are due to surface properties. With this new understanding of reflectance and emission
spectroscopy, mineralogic interpretations were derived and applied to the science objectives of the three regions.
Author
Thermal Emission; Imaging Spectrometers; Mars Surface; Albedo; Infrared Spectroscopy; Emission Spectra
20040111321 NASA Marshall Space Flight Center, Huntsville, AL, USA
Meteoroid Engineering Model (MEM)A Meteoroid Model for the Inner Solar System
McNamara, H.; Jones, J.; Kaufman, B.; Suggs, R.; Cook, W.; Smith, S.; [2004]; 1 pp.; In English; Meteoroids Conference
2004, August 2004, Ontario, Canada; No Copyright; Avail: CASI; A01, Hardcopy
In an attempt to overcome some of the deficiencies of existing meteoroid models, NASA’s Space Environments and
Effects Program sponsored a three year research effort at the University of Western Ontario. The resulting understanding of
the sporadic meteoroid environment - particularly the nature and distribution of the sporadic sources - was then incorporated
into a new meteoroid environment model (MEM) by members of the Space Environments Team at NASA’s Marshall Space
Flight Center. This paper discusses some of the revolutionary aspects of MEM which include: a) identification of the sporadic
radiants with real sources of meteoroids, such as comets, b) a physics-based approach which yields accurate fluxes and
directionality for interplanetary spacecraft anywhere from .2 AU to 2 AU, and c) velocity distributions obtained from theory
and validated against observation. Use of the model, which gives penetrating fluxes and average impact speeds on the surfaces
of a cube-like structure are also described, along with its current limitations and plans for future improvements.
Author
Meteoroid Concentration; Solar System; Sporadic Meteoroids; Environment Models
20040111367 Michigan Univ., Ann Arbor, MI, USA
Modeling of Cometary Atmospheres
Gombosi, Tamas; [2004]; 5 pp.; In English
Contract(s)/Grant(s): NAG5-11041; No Copyright; Avail: CASI; A01, Hardcopy
321