The problem of storing, transmitting, and manipulating digital images is considered. Because of the file sizes involved, large amounts of digitized image information are becoming common in modern projects. Our goal is to described an image compression transform coder based on artificial neural networks techniques (NNCTC). A comparison of the compression results obtained from digital astronomical images by the NNCTC and the method used in the compression of the digitized sky survey from the Space Telescope Science Institute based on the H-transform is performed in order to assess the reliability of the NNCTC

Aloy, A.

Gaitan, V.

Garrido, L.

Serra-Ricart, M.

English

NASA Technical Reports Server

20 Workshop on Advanced Technologies for Planetary instruments
INFRARED RUGATES BY MOLECULAR BEAM EPI-
TAXY. M. Rona, Arthur D. Little, Inc., Cambridge MA 02140,
USA.
Rugates are optical structures that have a sinusoidal index of
refraction (harmonic gradient-index field). As their discrete high/
low index filter counterparts, they can be used as narrow rejection
band filters. However, since rugates do not have abrupt interfaces,
they tend to have a smaller absorption, hence deliver a higher in-
band reflectivity. The absence of sharp interfaces makes rugates
even more desirable for high-energy narrowband reflectors. In this
application, the lack of a sharp interface at the maximum internal
standing wave electric field results in higher breakdown strengths.
Our method involves fabricating rugates, with molecular beam
epitaxy -[-lOT on GaAs wafers as an Al(x)Ga(l-x)As single-crystal
film in which x, the alloying ratio, changes in a periodic fashion
between 0 < x < 0.5 [-2-]TThe single-crystal material improves the
rugate performance even further by eliminating the enhanced
optical absorption associated with the grain boundaries. Salient
features of our single-crystal rugate fabrication program, including
the process control system and methodology and some representa-
\
References: [1] Rona M. and Sullivan P. W. (1982) Laser
Induced Damage in Optical Materials: 1982 Proceedings of the
Symposium (NBS-SP-69) (H. E. Bennett et al., eds.), pp. 234-242.
[2] Rona M. (1989) Proceedings of the Topical Meeting in High
Power Laser Optical Components, 30-31 October 1989, Unclassi-
fied Papers, Naval Weapons Center NWC-TP 7080, part 1 (J. L.
Stanford, ed.), pp. 431-436. [3] Rona M., Report to the Materials
Director Wright Laboratory, Air Force Systems Command, Wright
Patterson Air Force Base, Ohio 45433-6533, Report No. WL-TR-
91-4144.
PLASMA, MAGNETIC/AND ELECTROMAGNETIC
MEASUREMENTS AT NONMAGNETIC BODIES. C. T.
\ Russell and J. G. Luhmann, Institute of Geophysics and Planetary
Physics, University of California, Los Angeles CA 90024-1567,
USA.
The need to explore the magnetospheres of the Earth and the
giant planets is widely recognized and is an integral part of our
planetary exploration program. The equal need to explore the
plasma, magnetic, and electromagnetic environments of the
nonmagnetic bodies is not so widely appreciated. The previous,
albeit incomplete, magnetic and electric field measurements at
Venus, Mars, and comets have proven critical to our understanding
of their atmospheres and ionospheres in areas ranging from plan-
etary lightning to solar wind scavenging and accretion. In the cases
of Venus and Mars, the ionospheres can provide communication
paths over the horizon for low-altitude probes and landers, but we
know little about their lower boundaries. The expected varying
magnetic fields below these planetary ionospheres penetrates the
planetary crusts and can be used to sound the electrical conductivity
and hence the thermal profiles of the interiors. However, we have no
knowledge of the levels of such fields, let alone their morphology.
Finally, we note that the absence of an atmosphere and an iono-
sphere does not make an object any less interesting for the purposes
of electromagnetic exploration. Even weak remanent magnetism
such as that found on the Moon during the Apollo program provides
insight into the present and past states of planetary interiors. We
have very intriguing data from our space probes during times of both
close and distant passages of asteroids that suggest they may have
coherent magnetization. If true, this observation will put important
constraints on how the asteroids formed and have evolved. Our
planetary exploration program must exploit its full range of explo-
ration tools if it is to characterize the bodies of the solar system
thoroughly. We should especially take advantage of those tech-
niques that are proven and require low mass, low power, and low
telemetry rates to undertake.
A COMPACT IMAGINGDETECTOR OF POLARIZATION
ANDSPECTRALCONTENT. D. M. Rust, A. Kumar, and K.E.
Thompson, Applied Physics Laboratory, The Johns Hopkins
University, Johns Hopkins Road, Laurel MD 20723, USA.
A new type of image detector will simultaneously analyze the
polarization of light at all picture elements in a scene. The Integrated
Dual Imaging Detector (IDID) consists of a polarizing beam splitter
bonded to a charge-coupled device (CCD), with signal-analysis
circuitry and analog-to-digital converters, all integrated on a silicon
chip. The polarizing beam splitter can be either a Ronchi ruling, or
an array of cylindrical lenslets, bonded to a birefringent wafer. The
wafer, in turn, is bonded to the CCD so that light in the two
orthogonal planes of polarization falls on adjacent pairs of pixels.
The use of a high-index birefringent material, e.g., rutile, allows the
IDID to operate at f-numbers as high as f/3.5.
Without an auxiliary processor, the IDID will output the polar-
ization map of a scene with about 1 % precision. With an auxiliary
processor, it should be capable of 1 : 104 polarization discrimination.
The IDID is intended to simplify the design and operation of imaging
polarimeters and spectroscopic imagers used, for example, in
planetary, atmospheric and solar research. Innovations in the IDID
include (1) two interleaved 512 x 1024-pixel imaging arrays (one
for each polarization plane), (2) large dynamic range (well depth of
1 06 electrons per pixel), (3) simultaneous read-out of both images
at 10 million pixels per second each, (4) on-chip analog signal
processing to produce polarization maps in real time, and (5) on-
chip 10-bit A/D conversion. When used with a lithium-niobate
Fabry-Perot etalon or other color filter that can encode spectral
information as polarization, the IDID can collect and analyze
simultaneous images at two wavelengths. Precise photometric
analysis of molecular or atomic concentrations in the atmosphere is
one suggested application.
DIGITAL IMAGE COMPRESSION USING ARTIFICIAL
NEURAL NETWORKS. M. Serra-Ricart1, LI. Garrido2-3, V.
Gaitan2, and A. Aloy4, 'Institute de Astrofisica de Canarias, E-
38200 La Laguna (Tenerife), Spain, 2Departament d'Estructura i
Constituens de la Materia, Universitat de Barcelona, Diagonal 647,
E-08028 Barcelona, Spain, 3Institut de Fisica d'Altes Energies,
Universitat Autoriomade Barcelona, E-08 1 93 Bellaterra (Barcelona),
Spain, 4Digital Equipment Enterprise Espana SA., Provenza, 204-
208, 08036 Barcelona, Spain.
The problem of storing, transmitting, and manipulating digital
images is considered. Because of the file sizes involved, large
amounts of digitized image information are becoming common in
( * «
https://ntrs.nasa.gov/search.jsp?R=19930019622 2020-03-24T07:32:03+00:00Z
LP1 Technical Report 93-02 21
modern projects. Transmitting images will always consume large
amounts of bandwidth, and storing images will always require
special devices. Our goal is to describe an image compression
transform coder based on artificial neural networks techniques
(hereafter Neural Network Compression Transform Coder or
NNCTC). Like all generic image compression transform coders, the
NNCTC embodies a three-step algorithm: invertible transformation
to the image (transform), lossy quantization (quantize), and entropy
coding (remove redundancy). Efficient algorithms have already
been developed to achieve the two last steps, quantize and remove
redundancy [4]. The NNCTC offers an alternative invertible trans-
formation based on neural network analysis [3].
A comparison of the compression results obtained from digital
astronomical images by the NNCTC and the method used in the
compression of the digitized sky survey from the Space Telescope
Science Institute based on the H-transform [3] is performed in order
to assess the reliability of the NNCTC.
Artificial neural network techniques are based on the dot-
product calculation, which is very simple to perform in hardware
[4]. It is in this sense that the NNCTC can be useful when high
compression and/or decompression rates are required (e.g., space
applications, remote observing, remote database access).
References: [1] Wickerhauser M. V. (1992) Digital Signal
Processing, 2, 204. [2] Serra-Ricart M. et al. (1993) Astron. J., in
press. [3] Fritze K. et al. (1977) Astr. Nachr.,298, 189. [4] Morgan
M. etal.,eds. (1990) Artificial Neural Networks Electronic Imple-
mentations, IEEE Computer Society, Los Alamitos.
PROTOTYPE BACKSCATTER MOSSBAUER SPEC-
TROMETER FOR MESURment OF MARTIAN SURFACE
MINERALOGY. T. D. Shelfer', R. V. Morris1, D. G. AgrestP, T.
Nguyen', E. L. Wills2, and M. H. Shen2, 'Code SN4, NASA Johnson
Space Center, Houston TX 77058, USA, 2Physics Department,
University of Alabama at Birmingham, Birmingham AL 35294,
USA, 3Lockheed Engineering and Sciences Co., Houston TX 77058,
USA.
We have designed and successfully tested a prototype of a
backscatter Mossbauer spectrometer (BaMS) targeted for use on
the martian surface to (1) determine oxidation states of iron and
(2) identify and determine relative abundances of iron-bearing
mineralogies. No sample preparation is required to perform mea-
surements; it is only necessary to bring sample and instrument into
physical contact. The prototype meets our projected specifications
for a flight instrument in terms of mass (<500 g), power (<2 W), and
volume (<300 cm3).
A Mossbauer spectrometer on the martian surface would provide
a wide variety of information about the current state of the martian
surface:
1 . Oxidation state: Iron Mossbauer spectroscopy (FeMS) can
determine the distribution of iron among its oxidation states. Is soil
oxidized relative to rocks?
2. Mineralogy: FeMS can identify iron-bearing mineralogies
(e.g., olivine, pyroxene, magnetite, hematite, ilmenite, clay, and
amorphous phases) and their relative abundances. FeMS is not
blind to opaque phases (e.g., ilmenite and magnetite), as are visible
and near-IR spectroscopy.
3. Magnetic properties: FeMS can distinguish between mag-
netite and maghemite, which are putative mineralogies to explain
the magnetic nature of martian soil.
4. Water: FeMS can distinguish between anhydrous phases
such as hematite, olivine, pyroxene, and hydrous phases such as
clay, ferrihydrite, goethite, and lepidocrocite. What are the relative
proportions of hydrous and anhydrous iron-bearing mineralogies?
In summary, a BaMS instrument on MESUR would provide a
very high return of scientific information about the martian surface
(with no sample preparation) and would place a very low resource
demand (weight, power, mass, data rate) on spacecraft and lander.
Our BaMS instrument can be flight-qualified within two years and
is also suitable for lander missions to the Moon, comets, and
asteroids.
References: [ 1 ] Agresti D. G. et al. ( 1 992) Hyperfine Interac-
tions, 72, 285. [2] Bell J. F. Ill et al. (1990) JGR, 95, 14447.
[3] KlingelhoferG. etal. (1992) Hyperfine Interactions, 71, 1449.
[4] Morris R. V. et al. (1989) JGR, 94, 2760. [5] Morris R. V. and
Lauer H. V. Jr. (1990) JGR, 95, 10257.
SPACECRAFT COMPUTER TECHNOLOGY AT SOI
WEST RESEARCH INSTITUTE. D. J. Shirley, Southwest
Research Institute, San Antonio TX 78228-0510, USA.
Southwest Research Institute (SwRI) has developed and deliv-
ered spacecraft computers for anumber of different near-Earth-orbit
spacecraft including shuttle experiments and SDIO free-flyer ex-
periments. Here we describe the evolution of the basic SwRI
spacecraft computer design from those weighing in at 20 to 25 Ib and
using 20 to 30 W to newer models weighing less than 5 Ib and using
only about 5 W, yet delivering twice the processing throughput.
Because of their reduced size, weight, and power, these newer
designs are especially applicable'to planetary instrument require-
ments. The basis of our design evolution has been the availability of
more powerful processor chip sets and the development of higher-
density packaging technology, coupled with more aggressive design
strategies in incorporating high-density FPGA technology and use
of high-density memory chips. In addition to reductions in size,
weight, and power, the newer designs also address the necessity of
survival in the harsh radiation environment of space. Spurred by
participation in such programs as MSTI, LACE, RME, Delta 181,
Delta Star, and RADARS AT, our designs have evolved in response
to program demands to be small, low-powered units, radiation
tolerant enough to be suitable for both Earth-orbit microsats and for
planetary instruments. Present designs already include MIL-STD-
1750 and Multi-Chip Module (MCM) technology with near-term
plans to include RISC processors and higher-density MCMs. Long-
term plans include development of whole-core processors on one or
two MCMs.
THE BACKGROUNDS DATA CENTER. W. A. Snyder', H.
Gursky', H. M. Heckathom', R. L. Lucke1, S. L. Berg2, E. G.
Dombrowski3, and R. A. Kessel2, 'Code. 7604, Naval Research
Laboratory, Washington DC 20375-5352, USA, Computational
Physics, Inc., Suite 600, 2750 Prosperity Avenue, Fairfax VA
22031, USA, 3Sachs-Freeman Associates, 1401 McCormick Drive,
Landover MD 20785, USA.
The Strategic Defense Initiative Organization (SDIO) has cre-
ated data centers for midcourse, plumes, and backgrounds
i
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