Contents
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Figure 1
This picture shows a spectacular view of Earth as seen from the
Polar spacecraft from intermediate altitudes. The altitude of the
spacecraft is 25,740 km and the geographic latitude and longitude of its
position are 57.7° and 201.4°, respectively. The picture was
taken at 00:37 UT on March 25, 1996. Earth's northern auroral oval is
seen as a "crown" at the top of the image. The extended region of light
in the center and bottom of the image is the glow from the sun's
illumination of Earth's upper atmosphere. The filter for this image
passes ultraviolet emissions that are not directly visible to the human
eye. The intensities of this light from atomic oxygen in Earth's
atmosphere at altitudes in the range of about 100 to 500 km are
color-coded in the image with dark red as lowest intensities and whitish
yellow as the brightest intensities. A coastline has been superposed on
the image. Note that the aurora is positioned just north of the Great
Lakes. Advances in technology for the construction of these cameras
allow images of the auroral oval to be acquired for the sunlit atmosphere
with unprecedented clarity, as amply demonstrated by this picture of a
complete auroral oval that extends into the sunlit atmosphere. The image
was taken with the Earth Camera that is one of three cameras in the
Visible Imaging System which was designed and constructed at The
University of Iowa.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
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Figure 1a
Same as Figure 1, but without the geographic coast lines superposed.
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Figure 2
The dramatic beginning or "onset" of an auroral substorm is displayed in
this image of Earth acquired from high above the Northern Hemisphere of
Earth. the northern auroral oval is located in the center of the image
while the bright dayside of Earth is located below it. The bulge of
bright intensities corresponding to the onset of the auroral display
occurs in the auroral oval near local midnight over northern Norway and
Sweden. A coastline map has been superposed on the image. This image
has bee acquired by the Earth Camera that is one of the three cameras in
the Visible Imaging System on board the Polar spacecraft. The
spacecraft has passed apogee and has begun its descent toward perigee.
The spacecraft is positioned at an altitude of 48,280 km and the
geographic latitude and longitude of its position are 57.7° and
62.1°, respectively. The image was acquired at 20:59 UT on April 3,
1996. The filter for this image passes ultraviolet emissions that are not
directly visible to the human eye. The intensities of this light from
atomic oxygen in Earth's atmosphere at altitudes in the range of about
100 to 500 km are color-coded in the image with dark red as lowest
intensities and whitish yellow as the brightest intensities. The Visible
Imaging System was designed and constructed at The University of
Iowa.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
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Figure 3
A closeup view of part of the sourhern aurora oval is seen in the upper
right quadrant of this image that was acquired with the Earth Camera on
the Visible Imaging System on board the Polar spacecraft. The
altitude of the spacecraft is 8,800 km as it approaches perigee and the
geographic latitude and longitude of its position are -43.9° and
158.6°, respectively. The coastal outlines of the island of Tasmania
and the southeast coast of the continent of Australia, as well as the
islands of New Zealand, have been superposed in yellow on the image.
This image was taken at 15:15 UT on March 25, 1996. The Earth Camera is
one of the three cameras of the Visible Imaging System that was designed
and constructed a The University of Iowa. The filter for this image
passes ultraviolet emissions that are not directly visible to the human
eye. The intensities of this light from atomic oxygen in Earth's
atmosphere at altitudes in the range of about 100 to 500 km are
color-coded in the image with dark red as lowest intensities and whitish
yellow as the brightest intensities.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
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Figure 4
A sudden, intense bulge in the auroral oval signals the start of an
auroral substorm over North America. The bulge can be seen easily over
northern United States and southern Canada. A map of the coastal
outlines has been superposed on the image. This image has been acquired
by the Earth Camera that is one of the three cameras in the Visible
Imaging System (VIS) on board the Polar spacecraft. In this mode,
an image of Earth can be acquired every 53 seconds with the VIS Earth
Camera. This image was taken at 07:13 UT on May 15, 1996. At the time
of this image, the Polar spacecraft is located at 82.1°
latitude, 74.2° longitude, and is at an altitude of 41,900 km as it
approaches apogee. The filter for this image passes ultraviolet
emissions that are not directly visible to the human eye. The
intensities of this light from atomic oxygen in Earth's atmosphere at
altitudes in the range of about 100 to 500 km are color-coded in
the image with dark red as lowest intensities and whitish yellow as the
brightest intensities. The Visible Imaging System was designed and
constructed at The University of Iowa.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
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Figure 5
A global view of Earth as it would be seen from the Polar Visible
Imaging System (VIS). This is an image of Earth's Northern Auroral Oval
in the ultraviolet spectrum superposed on an image of Earth's surface for
25 March 1996 (96/085) at 00:37:04 UT.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
The underlying Earth surface image is a subset of the Face of the
EarthTM © 1996, ARC
Science simulations.
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Figure 6
A global view of Earth as it would be seen from the Polar Visible
Imaging System (VIS). This is an image of Earth's Northern Auroral Oval
in the ultraviolet spectrum superposed on an image of Earth's surface for
30 August 1996 (96/243) at 00:12:42 UT.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
The underlying Earth surface image is a subset of the Face of the
EarthTM © 1996, ARC
Science simulations.
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Figure 7
A global view of Earth as it would be seen from the Polar Visible
Imaging System (VIS). This is an image of Earth's Northern Auroral Oval
in the ultraviolet spectrum superposed on an image of Earth's surface for
23 September 1996 (96/267) at 03:17:43 UT.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
The underlying Earth surface image is a subset of the Face of the
EarthTM © 1996, ARC
Science simulations.
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Figure 8
A global view of Earth as it would be seen from the Polar Visible
Imaging System (VIS). This is an image of Earth's Northern Auroral Oval
in the ultraviolet spectrum superposed on an image of Earth's surface for
23 September 1996 (96/267) at 03:25:50 UT.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
The underlying Earth surface image is a subset of the Face of the
EarthTM © 1996, ARC
Science simulations.
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Figure 9
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
(320 kB)
Figure 10
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
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Figures 11a & 11b
The image on the left is one of the first images of the nighttime sector of
the visible northern auroral oval obtained with the Low Resolution Sensor
of the Visible Imaging System (VIS). This image was acquired with the filter
that has peak tranmission at the atomic oxygen emission line wavelength of
557.7 nm and is displayed in a false color presentation with dark red for
low intensities through brilliant yellow for high intensities. In this
image acquired at 23:40:56 UT on 26 November, 1996, the bright glow of the
discrete auroral oval can be seen sweeping across the image from the left
side of the field-of-view to the top. The nighttime limb of the earth can
be seen at the bottom of the image. Clouds and snow cover on the surface
of the Earth illuminated by the waning full moon can be seen as low
intensity regions at lower latitudes in the image.
For comparison, the image on the right is the global view of Earth obtained
at ultraviolet wavelengths with the VIS Earth Camera. This image was
obtained at 23:42:21 UT on 26 November, 1996 (i.e. within 2 minutes of the
visible image). The VIS Earth Camera is predominantly sensitive to the
atomic oxygen emissions at 130.4 nm and 135.6 nm. In this image the
complete northern auroral oval can be seen on the nightside of Earth. The
sunlit dayside of Earth can be seen as the higher intensity crescent to the
upper left.
The Principal Investigator is Dr. L. A. Frank and the Instrument
Scientist and Manager is Dr. John. B. Sigwarth.
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Last Revised: January 21, 2005