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(Annex-Jo)SPHERIC OPTICS GROUP
rnals) NICAL NOTE NO. 261 1822 04429 0716
QC
974.5
T43
no. 261
Whole Sky Imagers
For Real-Time Cloud Assessment,
Cloud Free Line of Sight Determinations
and Potential Tactical Applications
For presentation at The Battlespace Atmospheric and Cloud
Impacts on Military Operations (BACIMO) Conference, 2003,
Monterey, CA.
UNIVERSITY
OF
CALIFORNIA
SAN DIEGO
J. E. Shields
R. W. Johnson
M. E. Karr
A. R. Burden
J.G. Baker
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The material contained in this note is to be considered
proprietary in nature and is not authorized for distribution
without the prior consent of the Marine Physical Laboratory.
SCRIPPS
INSTITUTION
OF
OCEANOGRAPHY
MARINE PHYSICAL LAB San Diego, CA 92152-6400
UC SAN DIEGO LIBRARY
UNIVERSITY OF CALIFORNIA, SAN DIEGO
IITT
3 1822 04429 0716
Whole Sky Imagers
For Real-Time Cloud Assessment,
Cloud Free Line of Sight Determinations
and Potential Tactical Applications
For presentation at The Battlespace Atmospheric and Cloud
Impacts on Military Operations (BACIMO) Conference, 2003,
Monterey, CA.
J. E. Shields, R. W. Johnson, M. E. Karr,
A. R. Burden and J. G. Baker
Whole Sky Imagers
For Real-Time Cloud Assessment,
Cloud Free Line of Sight Determinations and
Potential Tactical Applications
Janet E. Shields, Richard W. Johnson, Monette E. Karr, Art R. Burden, and Justin G. Baker
Marine Physical Lab, Scripps Institution of Oceanography, University of California San Diego,
9500 Gilman Dr., La Jolla CA 92093-0701
ABSTRACT
Whole Sky Imagers (WST) have been developed at the Marine Physical Lab for several military and research
applications over many years. This paper discusses several systems useful for real-time monitoring of cloud conditions
and radiance distribution, and for tactical applications. We include a discussion of several data products, including the
results of a Cloud Free Line of Sight (CFLOS) statistical study based on an evaluation of approximately 800,000 WSI
images.
The Day/Night WSI is the most capable of the WSI systems. It can be remotely sited from a user, and can provide near-
real-time assessment of cloud conditions during the day and at night. While each unit is designed for a specific
application, output products can include day and night cloud fraction, cloud condition along selected tracks or in moving
regions of interest, and the absolute sky radiance distribution. The ability to extract earth-to-space beam transmittance is
in development. At the smaller end of the instrument system scale, a light-weight WSI has been developed for use in an
Unmanned Aerial Vehicle, which could be modified for tactical use. Data acquired by earlier versions of the WSI's have
now been processed to yield CFLOS statistics. The data were acquired at one-minute intervals for over two years at
several sites in the late 1980's. CFLOS statistics as a function of location, cloud fraction, and look angle will be
presented, along with persistence results. A new tactical optical system in early development uses one or more fisheye
lenses to enable a user to view the full surround, with simultaneous high-resolution views of selected regions of interest
within the scene. This concept has a patent pending, and we foresee that these capabilities can be used for now-casting
of battlefield environmental conditions.
Key words: Cloud, radiance, tactical imager, now-cast, UAV, visible, NIR, CFLOS, cloud persistence, battlefield,
whole sky imager
1. OVERVIEW
Whole Sky Imagers (WSI) are ground-based sensors which are used in military test site support, global climate research,
UV research, and other applications. They are designed to provide high quality digital imagery of sky conditions and,
when combined with appropriate algorithms, provide assessment of cloud amount and location within the scene, absolute
radiance distribution, and related atmospheric parameters. The Marine Physical Lab (MPL) at Scripps Institution of
Oceanography has been very active in the development of WSI systems for the last two decades. The first WSI systems
the group developed using digital imaging technology were deployed in the early 1980's, and were followed by fully
automated systems in the mid to late 1980s (Johnson et al 1989, and Shields et al., 1993). WSI systems capable of full
24-hour autonomous operation for acquisition of day and night sky parameters were fielded in the early 90's, and have
continued to evolve in capability (Shields et al 1998).
ishields@ucsd.edu; phone (858) 534-1769; fax (858) 822-0665

This paper will give an overview of the development of the WSI sensors, and then discuss the Day/Night WSI data
products in more detail, emphasizing those areas that are applicable to military requirements. Sample Cloud Free Line of
Sight
will be presented, including persistence results and multi-station results. These CFLOS
statistics were processed for the Starfire Optical Range using the Day WSI data-base. Finally, we will discuss the
developmental Tactical Full Scene Imager (with patent pending) which can be used to provide unique imagery for a
number of tactical applications and environmental now-casting applications.
2. DEVELOPMENT OF FISHEYE IMAGING SYSTEMS AT MPL
The original concept for the development of calibrated fisheye imaging systems at MPL evolved out of the group's
Atmospheric Optics program, a measurement and modeling program using multiple sensors for monitoring sky radiance,
atmospheric scattering coefficient profiles, and other parameters related to vision through the atmosphere (Johnson et al.,
1980). Beginning in the early 1980's, the group developed a series of ground-based calibrated fisheye imaging systems
known as Whole Sky Imagers (WSI) that used digital imagery and were fully automated. The first automated WSI was
conceived as combining the features of the all-sky cameras used in earlier programs, with the scanning radiometer
systems that provided measurements of sky radiance distribution. The first WSI systems used digital cameras
(sometimes CCD, sometimes Charge Injection Device or CID imagers), with fisheye lenses, optical filter changers, relay
optics to provide the proper image size and location, equatorial sun occultors to provide shading for the fisheye lens, and
early versions of personal computers for automated control. Figure 1 shows some of this evolution. The film-based all-
sky camera in use in a 1963 deployment is shown in Figure 1a, and the automated Day-only WSI developed in the early
and mid-1980's based on CID technology is shown in Figure 1b. With the use of very low noise 16 bit CCD cameras
and an occultor modified to handle both sun and moon, these systems were further developed into the Day/Night WSI
shown in Figure 1c. Some typical images from the Day/Night WSI are shown in Figure 2.
CAMERA'S VIEW
ALL-SKY
CAMERA
ASSEMBLY
(a)
(b)
(C)
Figure 1: Some of the WSI Systems developed at MPL that contributed to the development of the Day/Night WSI: a) the All-Sky
Camera used in 1963; b) the Day-only WSI used in the 1980's; c) the Day/Night WSI used in 1990's and currently in use.
Figure 2: Sample imagery from the Day/Night WSI for sunlight, moonlight, and starlight conditions.

The Day/Night WSI is fully automated, and acquires data continuously 24-hours a day. It has been environmentally
hardened, and there are versions of the D/N WSI running in the desert, Arctic, tropics, and other environments. The lens
covers the full upper hemisphere, down to just below the horizon (with a field of view of 181.5 degrees typically). The
system uses a Series 200 or Series 300 Photometrics 16-bit CCD camera. This camera has a three-stage Peltier cooler on
the chip, and is cooled to approximately 40C. The full dynamic range of the WSI system is over 10 logs (a factor of
1019 due to a combination of the dynamic range of the camera, the neutral density offset filters, changes in camera
exposure time, and changes in spectral filters. With this dynamic range and low noise camera, the WSI acquires imagery
under daylight, moonlight, and starlight; under starlight, even the darkest part of the sky between stars has a signal to
noise ratio of 50 or more under most conditions.
A dual-wheel filter changer enables adjusting flux levels with neutral density filters, and changing spectral filters. The
spectral filter options are blue (450 nm), red (650 nm), NIR (800 nm) and open hole for use at night. The solar/lunar
occultor provides full shading of the front optics, in order to minimize stray light. (A much smaller shade could provide
shading such that the sun does not directly illuminate the CCD, however we feel that it is vital, in order to acquire high
quality data, to shade the full extent of the front optics.) This of course means that the solar/lunar occultor must be held
at a reasonably large distance from the lens so that it does not obscure excessive fractions of the sky dome. A new
occultor has recently been designed, which should shade only 2-3% of the upper hemisphere while still shading the full
optics.
3. WSI DATA PRODUCTS
The primary WSI data products are the displayed images such as shown in Fig. 3a, the cloud fraction images shown in
Fig. 3b, the total cloud fraction and cloud fraction in selected regions of interest, and absolute radiance distribution. The
ability to extract earth-to-space beam transmittance at night is also working in its preliminary version. The raw data are
automatically converted to an 8-bit display on the computer monitor. This displayed imagery is useful for a number of
applications even without further processing. For example, some of our sponsors have used this data to evaluate the sky
condition visually during tests, for determining an appropriate window of opportunity for specific tests, and for
evaluating conditions along satellite tracks during tests.
A number of current and potential applications require an automated cloud algorithm. These applications include
automated analysis of cloud fraction for modeling, automated assessment of cloud conditions in specific regions of the
image, and potentially automated alarms. During the daytime, the cloud decision algorithm identifies each pixel as
opaque cloud, thin cloud, no cloud, or no data. Results of the daytime cloud algorithm are shown in Figure 3.
(a)
(d)
Figure 3: Day Cloud Algorithm Result: a) Raw data with cumulus or alto-cumulus clouds; b) Cloud decision result for image a,
where white is optically opaque, yellow is optically thin, blue is no cloud, and black is no data; c) Cloud decision result for thin clouds
associated with contrails; d) Cloud decision result 2 hours after image c.
For opaque clouds, the daytime cloud algorithm is based on the red/blue ratio at each pixel. For thin clouds, it is based
on a ratio between the measured red/blue ratio and the pre-determined red/blue ratio for a clear sky for the same solar
zenith angle. That is, the thin cloud algorithm takes into account the variation in spectral signature of the sky as a
function of look angle and solar zenith angle. The algorithm generally works well for opaque clouds and moderately thin
clouds. Under hazy conditions, however, it has difficulty distinguishing very thin clouds from the haze or aerosols. An

upgrade to use the NIR filter data is in development with the Day WSI, and we hope to apply the new work to the
Day/Night WSI in the future. It should also be mentioned that DOE's Atmospheric Radiation Measurement (ARM)
Program uses an alternative algorithm, which is beyond the scope of this article.
Most of the military D/N WSI systems developed for Starfire Optical Range and other sponsors have the cloud algorithm
running in near-real time. These systems also use a first-version night algorithm. A typical night algorithm result is
shown in Figure 4. The night algorithm currently uses 357 cells in the sky, and makes an assessment within each cell of
the cloud condition. We consider the algorithm result shown in Figure 4 to be somewhat preliminary. It was based on
detection of stars from a star library, in conjunction with an angular calibration of the image. The angular calibration is
accurate to within approximately half a
pixel. For each star, the image is
inspected to determine if the star can be
detected. If it is detected, the area under
the point spread function for the star is
evaluated, and a contrast between this
integrated signal and the background is
determined. The clouds are identified
using contrast thresholds that depend on
star magnitude, moon phase, and look
angle. We would like to update this
algorithm using the transmittance work
described below. We also feel that in the
future it should be possible to develop a
higher spatial resolution night algorithm
(a)
(b)
Figure 4: Night algorithm results: a) Raw image; b) Cloud decision image.
based on the absolute radiance.
DLRG
Using these automated algorithms, it is possible to design systems that provide automatic alarms for unacceptable test
conditions, and assess a variety of satellite tracks or other regions of the sky to make optimized test decisions. The data
can also be used for studying CFLOS statistics and for other modeling efforts.
Another standard data product of the WSI is the absolute radiance distribution. Each pixel in the camera is calibrated, so
the instrument provides approximately 180,000 measurements of radiance simultaneously. The systems are calibrated in
each wave band. We are quite careful with the calibrations, measuring the impact of non-linearity, shutter opening time,
non-uniformity, lens roll-off, pixel cross-talk, and so on. Absolute calibrations are traceable to NIST. A discussion of
the calibration is beyond the scope of this paper, however the calibrations are generally self-consistent to within fractions
of a percent. The lamps are accurate to 2-3%, depending on age, so we believe that the overall calibration is generally
accurate to within 3 – 5%. At the present time, the sky radiance distributions are processed in archival mode, and are not
an automated real-time product. Conversion to a real-time product, if an application required it, is straight forward.
The most recent data product is the distribution of earth-to-space beam transmittance over the night sky. Although a
detailed development of the theory is beyond the scope of this paper, we can present an overview of the technique and
the results. The 5th edition NSSDC Bright Star Catalog (Hoffleit, 1991) is used to determine the magnitude and color
temperature of stars down to visual magnitude 7.96. From these values, the expected inherent irradiances of the stars in
the WSI open hole passband are determined. By “inherent”, we mean the effective irradiance of the stars above the
atmosphere. A very accurate angular calibration of angle in object space vs. pixel position in image space enables a
reasonably accurate determination of the association between the stars in the image, and the stars in the library. The
images are calibrated for absolute radiance. We have found that the Point Spread Function of the atmosphere and the
optics can be reasonably well described by a Gaussian with a width of 0.45 pixels over the full image. By integrating
over this PSF and subtracting the background, we can make reasonably good determinations of the apparent irradiance of
the stars in the image. By "apparent', we mean the irradiance as seen from the observer or WSI position. The ratio of
apparent to inherent irradiance should yield the total earth-to-space beam transmittance.
Figure 5 shows the resulting relationship when the inherent and apparent star irradiances are compared. In this data set
of 1555 stars of magnitude down to approximately 3.9, the correlation is very good, with a correlation constant of .968.

If stars down to a magnitude of approximately 7.0 are used, yielding a data set of nearly 33,000 stars for this night, the
correlation is .847. We believe that this may be due to uncertainties in the star magnitude values. The ability of the WSI
to observe the full upper hemisphere with a calibrated sensor simultaneously is a very strong capability, and should
enable us to further improve the inherent star irradiance values.
Spectral Irradiances For WŞI Passband, Zenith < 60 Degrees
Spectral Irradiance > 10- (W/m²-um), Method: Integral Under Gaussian
10-6 FTTTTT
TTTO
TTTTT
Unit 12, February 14, 1999
TTTT
Measured Spectral Irradiance (W/m²-um)
Linear Coefficients:
A = 2.80535e-011
B =
1.02100
Correlation coeff =
0.987696
TTTTTT
The resulting transmittance map is shown
for a sample case in Figure 6. The raw data
are shown in image a, and the total earth-to-
space beam transmittance is shown in
image b. For this plot, we used stars to
magnitude 6.0 that were not too close to
other stars. We determined from a series of
clear nights that an earth-to-space beam
transmittance of approximately 0.8 is
typical for this filter; the residual
transmittance corrected for the clear night
transmittance is shown in image c.
Although it is not obvious in this display of
the raw data, there were clouds present in
the bright band near the horizon. Although
the variance in these results is somewhat
higher than we would like, we are very
pleased with this as a first result, and feel
that it can be improved by modifying the
inherent star values based on measurements
on clear nights. Similar simultaneous
measurements of the full star field in a
variety of wavelengths from high altitude
could be quite useful.
10-9
10-9
10-8
10-7
10-6
Theoretical Spectral Irradiance (W/m²-um)
Figure 5: Observed relationship between the measured, or apparent
star irradiance, and the computed, or inherent star irradiance on a clear
night.
Resulting
Cloud Trans.
0.8 - 1.0
0.6 - 0.8
0.4 -0.6
0.2 - 0.4
0.0 -0.2
Star Not
detected
(a)
(b)
(C)
Figure 6: Transmittance Map Results: a) Raw data, b) the total earth-to-space beam transmittance result, c) the residual transmittance
corrected for a clear-night vertical earth-to-space transmittance of 0.8.
4. CUSTOMIZED WSI’S FOR SPECIALIZED APPLICATIONS
Over the years, several versions of the WSI have been designed and deployed. This section will provide a very brief
overview of these systems. Most of the WSI systems utilize cable bundles communicating between the controller and
the sensor, and require that the sensor be within 230' of the controller. For the Day/Night WSI shown in Figure 7, the
controller package was integrated into the sensor environmental housing. As a result, it can be sited remotely from the
user. The WSI sends data via Ethernet link to a second computer, where data are processed in near-real time. The

computer can also accept instructions from another computer controlling another application or model. This computer
can request moving regions of interest (ROI), and the WSI returns the information on cloud cover within this ROI to the
user or model.
The original Day WSI developed in the 80's is obsolete, and a new version of the Day WSI has been developed based in
part on the upgrades used in the Day/Night WSI systems. The Day WSI is shown in Figure 8, and an image near sunset
(with the occultor nearly below the horizon) is shown in Figure 9. This system acquires imagery in seven user-selected
passbands in the visible and NIR at approximately 1024 x 1024 resolution. It provides calibrated radiance distributions
in all wavebands, as well as cloud fraction. This is the system for which a new daylight cloud algorithm is in
development. It is further documented in Shields et al (2003 a). Like the Day/Night WSI, it provides high quality, fully
shaded imagery appropriate for a variety of applications.
Figure 7: Day/Night WSI for Remote Sites
Figure 8: Day Visible/NIR WSI
Figure 9: Raw image from Day WSI
A small calibrated fisheye imaging system has recently been developed for airborne use on a UAV. It consists of two
camera packages, a visible system near 645 nm using Silicon CCD technology, and a NIR system near 1610 nm using
InGaAs CMOS technology. The NIR camera and a visible image are shown in Figure 10. Both of the systems are fully
calibrated, to provide the radiance distribution of the lower hemisphere, and the cloud top radiances in particular.
Although this was designed for use with the ARM program, we feel that it has great potential for tactical and other
military applications. This system is documented in Feister et al (2000) and Shields et al (2003b). We have also
determined how we could develop similar systems at 3 -5 um and 8 - 12 um.
Figure 10: One of two airborne fisheye systems designed for use with a UAV. The
first figure illustrates the camera that acquires images near 1.6 um in the NIR, and the
second image illustrates data from the visible system near 650 nm.

5. CLOUD FREE LINE OF SIGHT STATISTICAL STUDY
An early version of the Day WSI developed by MPL was fielded in the mid-to-late 1980's at several sites throughout the
U.S., acquiring data once a minute for over two years. The data were originally acquired for support of ground-based
high-energy laser applications, and approximately one year of data from each of several of the sites were processed
through the cloud algorithm in those years. These processed data were recently further processed to extract statistics on
Cloud Free Line of Sight (CFLOS) with funding from the Air Force's Starfire Optical Range. This section presents a
sampling of the results extracted from this data set.
CLOUD DECISION IMAGE
STATION: COLUMBIA
DATE: 7 AUGUST 1989
Tisse: *20 GMT
The processed data consisted of cloud algorithm results such as those shown in Figure 11. This was a fairly early
version of the algorithm, but comparisons with observers over a limited test case showed very good agreement with the
observer. Approximately 82,000 images such as given in Figure 11 were available at 10-minute intervals, and used for
the CFLOS determinations. Approximately 820,000 images at 1-minute intervals were used for the Persistence studies.
The PCFLOS data were extracted as a function of cloud fraction, zenith
angle, station location, and season. Figure 12 shows some very preliminary
data extracted from a limited sample of WSI data, in comparison with two
models. The straight line “model”, one minus cloud fraction, represents the
relationship that might be expected if clouds were uniformly small, evenly
distributed, and essentially had no physical thickness. If one takes into
account the thickness of clouds, the result is similar to that shown by the
curve labeled SRI model. These results were provided to us courtesy of
TASC, Inc. The WSI data showed an interesting drop near 80% cloud cover.
A more detailed study of the WSI, based on 24,000 cases near White Sands
Missile Range (WSMR) shows the same behavior in Figure 13. We believe
MPIN
this behavior is real, and reflects the fact that clouds often are not evenly
distributed small clumps. If the 80% cloud cover is associated with a front,
Figure 11: Sample Day WSI Cloud
and 80% of the sky is covered, then the zenith will also not be cloud free.
Algorithm Data Product for CFLOS Study This behavior is of course inverted near the horizon, as shown in the 75
degree zenith angle curve in Figure 13.
0.8
1 . SKY COVER
L
00.6F
0.61
SRI MODEL
75
S
PCFLOS
0.4
at
0.4
DATA-DERIVED
0.2
e 0.2
n.
no
0.0
0.0
0.2
0.4
0.6
0.8
Cloud Fraction
Cloud Fraction
Figure 12: Model and Sample WSI Data for PCFLOS
At the zenith as a function of Cloud Fraction.
Figure 13: PCFLOS at Zenith and at 75 degrees zenith
angle as a function of Cloud Fraction; data from WSMR,
24,000 cases.
Table 1
Conditional Probability for a
Cloud Free Line of Sight to GOES-8
Another type of data product extracted from the
CFLOS data is the conditional probability. As an
example, in Table 1 column 2, we show the
probability that the sky is clear in the direction
toward GOES-8, for each of 5 sites. These
probabilities range from around 66% for the desert
sites, to 35% for the coast of Florida. However, if
we look at the conditional probility that the line of
sight towards GOES-8 is clear given that the line of
sight toward Polaris is clear, now the probabilities
increase to 92% to 84%.
Location
Albuquerque, NM
White Sands, NM
Columbia, MO
Malmstrom AFB, MT
Malabar Tracking
Station, FL
PCFLOS in
GOES-8
Direction
0.66
0.63
0.46
0.38
0.35
PCFLOS
for GOES-8
if Polaris is clear
0.92
0.90
0.86
0.72
0.84

1 Minute Cloud-Free Persistence for COES-8 at Five Stations
Relative Frequency
It is also interesting to evaluate the persistence. Figure 14
shows a sample persistence result. For those cases which
had a clear line of sight in a given direction at Time To, we
determined what fraction of these cases remained clear
throughout the interval from time To to time T. The upper
plot shows five stations for the GOES-8 direction, and the
lower plot shows the GOES-9 direction. At some of the
stations, such as those in the desert, the probability of
persistence was quite high. For example, at WSMR, the
probability fell to 50% only after over 5 hours. At the
Florida site, the probability fell to 50% after less than an
hour. Similar studies were made as a function of season,
and also studies of the persistence of cloudy conditions
were made. These results are shown in Table 2.
SOL
WÁG
BR
5 10 20 30 1
3 5 7 9
Minutes
Hours
-Minute Cloud-Free Persistence for COES 9 ot Five Stations
5
1
085
Table 2
Persistence Results:
Time (hr) Required for Yearly Persistence
Probabilities for Polaris to drop below 0.5
Relative Frequency
Cloud-free
4.1
Location
Albuquerque, NM
White Sands, NM
Columbia, MO
Malmstrom AFB, MT
Malabar Tracking
Station, FL
Cloudy
1.1
0.7
2.6
5.1
BAR
3.1
1.5
0.8
2.9
0.4
aaL
mit
S 10
Minutes
20 30
1
3 5 7 911
Hours
Figure 14: Cloud-free Persistence results for yearly
Averages at five stations and in two directions.
In Table 2, the persistence of cloud-free conditions is quite long for the desert sites, and shorter for the other sites, as
expected. The persistence of cloudy conditions is short for the desert sites. For the first four sites in the table, the cloudy
persistence increases, as the cloud-free persistence decreases. However, for the coastal Florida site, where we often
seemed to observe small fast-moving clouds, both the cloud-free and cloudy persistences were short.
While the above CFLOS and Persistence data give a small sampling of the type of statistics that were extracted from the
WSI data-base, there are many statistics that can be extracted. For example, we evaluated multi-station behavior, in
terms of both CFLOS and Persistence, and conditional probabilities such as the time persistence for having N stations
with a clear line of sight, if M stations were available.
6. A TACTICAL FULL SCENE IMAGER (PATENT PENDING)
Another development that has come out of the Whole Sky Imager family of systems is the concept for a Tactical Full
Scene Imager. In its simplest concept, this system uses a single fisheye lens with a beam splitter behind the lens to create
two image planes, as shown in Figure 15. One of the image planes is used to provide an image of the full hemisphere
scene, either using a tapered fiber optic bundle as shown, or using a lens, or by using imaging directly onto a chip if
feasible. The second image plane is interrogated with a microscope objective, in order to provide a high-resolution view
of a portion of the scene.
This concept is demonstrated in Figures 16 and 17. Figure 16 shows the full fisheye view (180 degrees in field of view)
of the test room. Image (a) has been displayed to show the room, and image (b) has been displayed to show the optical
target.

ZOOMING FISHEYE
SIMPLE CONFIGURATION
FISHEYE
FOCAL
PLANES
FISCALEA
FIBER-OPTIC
TAPER
FIBER OPTIC
Figure 17 shows the image through the
microscope objective. The image plane has a
high spatial frequency content, well beyond that
which is acquired in the imagery shown in
Figure 16. As a result, it is possible to extract
high resolution imagery with a behind-the-lens
optical zoom using a microscope objective.
Image (b) of Figure 17 shows a small portion of
image (a) further enhanced using electronic
zoom. Image (c) of Fig. 17 shows the best we
could achieve with electronic zoom alone.
B
------
FISHEYE
LENS
MICROSCOPE
RIGHT
ANGLE
PRISM
(SPLITTER)
Figure 15: The simplest concept for the Tactical Full
Scene Imager concept
(a)
(b)
Figure 16: Image of the full scene in a test room: a) displayed to show the room, b) displayed to show the target
(a)
Figure 17: Images using Zooming: a) Image of the image plane through a microscope, b) Image of the target using both optical and
Electronic zoom, c) Image of the target using electronic zoom alone.
This concept could be used with human interaction, or could be fully automated. For example, a human in a tank could
view an image such as in Figure 16, chose an area of interest using a touch-screen monitor, and the system could display
the high resolution view of the selected area of interest. Similarly, a motion detection algorithm could be used to
automatically select the area of interest. A number of different lens and camera configurations is possible. For example,
use of three fisheye lenses would enable the full spherical surround to be viewed continuously with a completely staring
system. The system should be far more robust, dust-resistant, and covert in comparison with external optical zoom, and
we have developed methods for doing very fast changes to the region of interest. The system currently has a patent
pending, and is in mock-up stage. We feel that it has many applications both for tactical applications in unattended
ground sensors, tanks, and ships, as well as for now-casting in the battlefield environment.
7. SUMMARY
The Whole Sky Imagers have been developed for a number of applications, including military and general research
applications. The data products can include the raw images, cloud decision images, and absolute radiance distributions.
More recently the ability to determine the distribution of beam transmittance over the full sky at night has been
developed but not yet integrated into the real-time processing software. Several versions of the instrument have been
developed, including a Day/Night WSI, Day/Night WSI with automated real-time processing, Day WSI, and an airborne
fisheye system. Cloud Free Line of Sight statistics have been extracted from part of the WSI data base. Concepts for
tactical systems and now-casting are in development.
8. ACKNOWLEDGEMENTS
We would like to express our appreciation to the Starfire Optical Range, for their support of much of this work, as well
as for providing partial support to enable the presentation of these results. We would especially like to thank Ann Slavin
for her advice and technical support in this work. In addition, we would like to thank Dr. Tim Tooman at Sandia
National Laboratories, and the DOE's Atmospheric Radiation Measurements Program administered by Battelle's Pacific
Northwest National Laboratories, for their support of much of the D/N WSI development. Thanks also to the Air Force
Research Labs, and to Deutsche Wetterdienst, the German Weather Service which supported some aspects of the
research. We would like to recognize Roper Scientific, for their assistance with the Photometrics camera products.
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