Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

A brief description is given of the origin of Kapteyn’s ”Plan of Selected Areas” in which he proposed that the structure of
the Galaxy could be determined by taking samples at regularly spaced intervals across the sky. The Plan was also a call for international
co-operation to expedite specific programs. Many observatories embraced the Plan and worked on these programs. The
Selected Areas also provided photometric calibration and other support for observational programs other than those in Kapteyn’s
original proposal. Examples were Fath’s early galaxy counts and the early studies of faint blue stars. Baade’s thoughts on the
Mount Wilson work in Selected Areas and the importance and difficulties of early photometric work are discussed. The call for
co-operation and coordination in Galactic research that was implicit in Kapteyn’s Proposal was renewed at IAU Symposium No.1
(Groningen in 1955). The Palomar-Groningen variable star survey, proposed at this conference, was an example of this new type
of co-ordination.
Author
Blue Stars; Galaxies; Surveys; Variable Stars
20000062309 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA USA
Precise Image-Based Motion Estimation for Autonomous Small Body Exploration Final Report
Johnson, Andrew Edie, Jet Propulsion Lab., California Inst. of Tech., USA; Matthies, Larry H., Jet Propulsion Lab., California
Inst. of Tech., USA; [2000]; 3p; In English; 5th; Artificial Intelligence, Robotics and Automation in Space, Unknown; No Copyright;
Avail: CASI; A01, Hardcopy; A01, Microfiche
We have developed and tested a software algorithm that enables onboard autonomous motion estimation near small bodies
using descent camera imagery and laser altimetry. Through simulation and testing, we have shown that visual feature tracking
can decrease uncertainty in spacecraft motion to a level that makes landing on small, irregularly shaped, bodies feasible. Possible
future work will include qualification of the algorithm as a flight experiment for the Deep Space 4/Champollion comet lander
mission currently under study at the Jet Propulsion Laboratory.
Author
Estimating; Autonomy; Spacecraft Motion; Optical Tracking; Image Analysis; Algorithms
20000062726 NASA Ames Research Center, Moffett Field, CA USA
The Galactic Distribution of Aliphatic Hydrocarbons in the Diffuse Interstellar Medium
Sandford, Scott A., NASA Ames Research Center, USA; Pendleton, Yvonne J., NASA Ames Research Center, USA; Allamandola,
Louis J., NASA Ames Research Center, USA; Astrophysical Journal; Feb. 20, 1995; Volume 440, pp. 697-705; In English
Contract(s)/Grant(s): RTOP 199-52-12-04; RTOP 185-52-12-09; RTOP 452-33-93-03; RTOP 188-44-21-04; Copyright; Avail:
Issuing Activity
The infrared absorption feature near 2950/ cm (3.4 microns), characteristic of dust in the diffuse interstellar medium (ISM),
is attributed to C-H stretching vibrations of aliphatic hydrocarbons. We show here that the strength of the band does not scale linearly
with visual extinction everywhere, but instead increases more rapidly for objects near the center of the Galaxy, a behavior
that parallels that of the Si-O stretching band due to silicate materials in the diffuse ISM. This implies that the grains responsible
for the diffuse medium aliphatic C-H and silicate Si-O stretching bands are different from those responsible for much of the
observed visual extinction. It also suggests that the distribution of the carbonaceous component of the diffuse ISM is not uniform
throughout the Galaxy, but instead may increase in density toward the center of the Galaxy. The similar behavior of the C-H and
Si-O stretching bands suggests that these two components may be coupled, perhaps in the form of silicate-core, organic-mantle
grains. Several possible models of the distribution of this material are presented and it is demonstrated that the inner parts of the
Galaxy has a carrier density that is 5 to 35 times higher than in the local ISM. Depending on the model used, the density of aliphatic
material in the local ISM is found to be about 1 to 2 -CH3 groups /cc and about 2 to 5 -CH2- groups/cc. These densities are consistent
with the strengths of the 2955 and 2925/ cm (3.38 and 3.42 microns) subfeatures (due to -CH3 and -CH2- groups, respectively)
within the overall 2950/ cm (3.4 microns) band being described by the relations A(sub upsilon)/tau(sub 2925/cm) = 270 +/- 40
and A(sub upsilon)/tau(sub 2925/cm) = 250 +/- 40 in the local diffuse ISM.
Author
Aliphatic Hydrocarbons; Galaxies; Interstellar Matter; Distribution (Property); Dust
20000063499 Smithsonian Astrophysical Observatory, Cambridge, MA USA
Investigating the Near-Infrared Properties of Planetary Nebulae II. Medium Resolution Spectra, 2, Medium Resolution
Spectra
Hora, Joseph L., Smithsonian Astrophysical Observatory, USA; Latter, William B., SIRTF Science Center, USA; Deutsch, Lynne
K., Boston Univ., USA; [1998]; 34p; In English
Contract(s)/Grant(s): RTOP 399-20-61; No Copyright; Avail: CASI; A03, Hardcopy; A01, Microfiche
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