20,292 research outputs found
Research in orbit determination optimization for space trajectories
Research data covering orbit determination, optimization techniques, and trajectory design for manned space flights are summarized
The Composition of Dust in Jupiter-Family Comets as Inferred from Infrared Spectroscopy
We review the composition of Jupiter-family comet dust as inferred from
infrared spectroscopy. We find that Jupiter-family comets have 10 micron
silicate emission features with fluxes roughly 20-25% over the dust continuum
(emission strength 1.20-1.25), similar to the weakest silicate features in Oort
Cloud comets. We discuss the grain properties that change the silicate emission
feature strength (composition, size, and structure/shape), and emphasize that
thermal emission from the comet nucleus can have significant influence on the
derived silicate emission strength. Recent evidence suggests that porosity is
the dominant parameter, although more observations and models of silicates in
Jupiter-family comets are needed to determine if a consistent set of grain
parameters can explain their weak silicate emission features. Models of 8 m
telescope and Spitzer Space Telescope observations have shown that
Jupiter-family comets have crystalline silicates with abundances similar to or
less than those found in Oort Cloud comets, although the crystalline silicate
mineralogy of comets 9P/Tempel and C/1995 O1 (Hale-Bopp) differ from each other
in Mg and Fe content. The heterogeneity of comet nuclei can also be assessed
with mid-infrared spectroscopy, and we review the evidence for heterogeneous
dust properties in the nucleus of comet 9P/Tempel. Models of dust formation,
mixing in the solar nebula, and comet formation must be able to explain the
observed range of Mg and Fe content and the heterogeneity of comet 9P/Tempel,
although more work is needed in order to understand to what extent do comets
9P/Tempel and Hale-Bopp represent comets as a whole.Comment: 21 pages, 4 figures, 2 tables. Accepted for publication in Planetary
and Space Scienc
Conjugate points on extremal rocket paths
Existence of conjugate points on extreme rocket flight paths in trajectory optimization analysi
On the Density of Coprime m-tuples over Holomorphy Rings
Let be a finite field, be a function field of
genus having full constant field , a set of
places of and the holomorphy ring of . In this paper we
compute the density of coprime -tuples of elements of . As a side result,
we obtain that whenever the complement of is finite, the
computation of the density can be reduced to the computation of the
-polynomial of the function field. In the rational function field case,
classical results for the density of coprime -tuples of polynomials are
obtained as corollaries.Comment: To appear in International Journal of Number Theor
Examination of accelerated first order methods for aircraft flight path optimization
Accelerated first order methods for aircraft flight path optimizatio
Convergence Rates for Newton’s Method at Singular Points
If Newton’s method is employed to find a root of a map from a Banach space into itself and the derivative is singular at that root, the convergence of the Newton iterates to the root is linear rather than quadratic. In this paper we give a detailed analysis of the linear convergence rates for several types of singular problems. For some of these problems we describe modifications of Newton’s method which will restore quadratic convergence
Energy management of three-dimensional minimum-time intercept
A real-time computer algorithm to control and optimize aircraft flight profiles is described and applied to a three-dimensional minimum-time intercept mission
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