Issue 10 Volume 41 May 16, 2003

ecently. The existence of a connection between unstable regions enables mission designers to envision scenarios of multiple
spacecraft traveling cheaply from system to system, rendezvousing, servicing, and refueling along the way. This paper presents
examples of transfers between the Sun-Earth and Earth-Moon systems using a true ephemeris and perturbation model. It shows
the (Delta)V costs associated with these transfers, including the costs to reach the staging region from the Earth. It explores
both impulsive and low thrust transfer trajectories. Additionally, analysis that looks specifically at the use of nuclear power
in libration point orbits and the issues associated with them such as inadvertent Earth return is addressed. Statistical analysis
of Earth returns and the design of biased orbits to prevent any possible return are discussed. Lastly, the idea of rendezvous
between spacecraft in libration point orbits using impulsive maneuvers is addressed.
Author
Costs; Deployment; Earth-Moon System; Refueling; Rendezvous Spacecraft; Spacecraft Orbits; Sun; Trajectories
20030032416 Hawaii Univ., Honolulu, HI, USA
A Study of Planetary System Formation and Evolution Using a Dual Channel Adaptive Optics Imaging Polarimeter
Potter, Daniel E.; [2003]; 4 pp.; In English; Original contains black and white illustrations
Contract(s)/Grant(s): NGT5-50357; No Copyright; Avail: CASI; A01, Hardcopy
The award I received from the Graduate Student Research Program in 2001, and the renewal award in 2002, supported
the gathering and processing of my thesis data, and the presentation of my scientific results at astronomy conferences.
Ultimately, this led to a successful defense of my PhD thesis. In the thesis work, I built, calibrated, and observed with the first
dual imaging polarimeter ever used in series with a high order adaptive optics system and on an 8 meter class telescope. The
instrument was arguably the most sensitive instrument for the high-contrast detection of the scattered light from circumstellar
disks. The success of the instrument has provided the impetus for the construction of several similar simultaneous adaptive
optics imaging polarimeters. In the course of the observations, a number of circumstellar disks were resolved for the first time
in their scattered light, such as the disk around the classical T-tauri stars, LkCa 15 and LkHa 262. A sample of 24 young,
nearby, solar-analog stars were observed with the instrument in search of the scattered light signature from debris disks around
these stars. Although none of the stars revealed any obvious scattered light signatures, a meaningful limit was placed on the
dust population around these stars. Also, a brown dwarf binary system was found to be a companion to one of the solar-analog
stars observed, HD130948. A careful monitoring of the orbit of the binary brown dwarf will result in a dynamical mass
determination of the objects, providing a valuable calibration of the physical models explaining brown dwarf evolution.
Author
Planetary Evolution; Polarimeters; Astronomical Polarimetry; Stellar Envelopes
20030032428 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Where was the Iron Synthesized in Cassiopeia A?
Hwang, Una; Laming, J. Martin; [2003]; 22 pp.; In English; Original contains black and white illustrations; No Copyright;
Avail: CASI; A03, Hardcopy
We investigate the properties of Fe-rich knots on the east limb of the Cassiopeia A supernova remnant observed with
Chandra/AXAF CCD Imaging Spectrometer (ACIS). Using analysis methods developed in a companion paper, we constrain
the ejecta density profile and the Lagrangian mass coordinates of the knots from their fitted ionization age and electron
temperature. Fe-rich knots which also have strong emission from Si, S, Ar, and Ca are clustered around mass coordinates q
approx. equal to 0.35 - 0.4 in the shocked ejecta of 2 solar masses; this places them 0.7 - 0.8 solar masses out from the center
(or 2 - 2.1 solar masses, allowing for the mass of a compact object). We also find an Fe clump that is evidently devoid of line
emission from lower mass elements, as would be expected for a region that had undergone alpha-rich freeze out. This clump
has a similar mass coordinate to the other Fe knots.
Author
Cassiopeia A; Supernova Remnants; Iron; Ejecta; Lagrange Coordinates; Ionization; Electron Energy
20030032430 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Evaluation of Models for Diffuse Continuum Gamma Rays in EGRET Range
Strong, A.; Moskalenko, I. V.; Reimer, O.; March 07, 2003; 1 pp.; In English; 28th ICRC, 31 Jul. - 7 Aug. 2003, Japan;
Copyright; Avail: Other Sources; Abstract Only
The GALPROP model for cosmic-ray propagation produces explicit predictions for the angular distribution of
gamma-rays. We compare our current models with EGRET spectra for various regions of the sky. This allows a critical test
of alternative hypotheses for the observed GeV excess. We show that a population of hard-spectrum sources cannot be solely
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