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AirMISR Flight of 25 Auguest 1997, Moffett Field, CA
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| Introduction to Engineering Flights |
A general description of the Airborne Multi-angle Imaging Spectro-Radiometer
(AirMISR) is given on the AirMISR page. The images
included below are from the so-called engineering flights of AirMISR, which were
the series of trial flights undertaken while the instrument was new and being
tested, prior to its being certified for operational use.
These images are all from Engineering Flight No. 3, which occurred
mid-afternoon on August 25, 1997. (Certification occurred after a subsequent
flight in November 1997. The first operational science flights are expected in
early 1998.)
The images are of the area surrounding Moffett Field, which is a NASA
airfield at the southern end of San Francisco Bay, California, each covering an
area approximately 10 km on a side, and were acquired from the NASA ER-2
aircraft flying at 20 kilometers altitude in an approximately southward
direction. The imaged area straddles the waters at the southern end of San
Francisco Bay near the inlet of Coyote Creek, an area of mudflats, marshes, and
tidelands that are in part utilized as salt evaporation ponds, and urban areas
of Mountain View, Sunnyvale, and adjacent communities that provide a grid of
city streets, buildings, and freeways. North is toward the top of these images,
and the sun is shining roughly from the south.
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| Color-composite images |
The following images illustrate how the color
(spectral) bands of AirMISR, each of which is a monochromatic image, can be
combined to make a color picture. MISR has four color bands, the red, green,
blue, and near-infrared. That is, the AirMISR camera takes four pictures
simultaneously, in four different colors. Each of the above color-composite
images has been formed by combining the red, green, and blue bands of AirMISR.
As with the following images (see next section below,) radiometric scaling and a
simple line-by-line roll correction algorithm have been applied.
North is toward the top of these images, and the sun is shining roughly from
the south. For the first image, the camera was pointing at 26.1 degrees forward
of nadir, whereas the second image was taken with the camera pointing 26.1
degrees aftward of nadir. The rivers and tidal areas are brighter in the
forward-viewing (first) image, illustrating that these wet surfaces produce
mirror-like reflections that are observable at this viewing geometry.
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Af-forward view
(southward) at 26.1 deg.
browse resolution, GIF
550 x 474, 226 KB
full resolution, TIFF
1496 x 1288, 1.8 MB |
Aa-aft view
(northward) at 26.1 deg.
browse resolution, GIF
550 x 474, 226 KB
full resolution, TIFF
1457 x 1244. 1.7 MB |
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| Roll-Corrected Images |
Here are the four individual camera channels from each of two AirMISR views
used to make the color composites in the previous section. In contrast to the original raw images,
these images have been radiometrically scaled and the effects of roll angle
movements of the aircraft have been removed.
There are eight images shown here, consisting of all four spectral bands of
the A-forward (Af) and A-aft (Aa) camera positions. These are the innermost
off-nadir viewing positions, i.e. view angles of ±26.1 degrees from the nadir.
The differences in the images for the respective spectral bands can be seen.
Even more obvious is the difference between the forward and aft views. The
forward imagery is viewing reflected sunlight that has been forward scattered
from the scene, while the aftward imagery is viewing backscattered light. The
effect of this change in viewing geometry is especially noticeable in the water
and salt pan areas near the tops of the images.
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A-forward Blue
browse resolution, GIF
507 x 411, 124 KB |
A-forward Green
browse resolution, GIF
507 x 411, 124 KB |
A-forward Red
browse resolution, GIF
507 x 411, 124 KB |
A-forward Near-IR
browse resolution, GIF
507 x 411, 124 KB |
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A-aft Blue
browse resolution, GIF
507 x 411, 124 KB |
A-aft Green
browse resolution, GIF
507 x 411, 124 KB |
A-aft Red
browse resolution, GIF
507 x 411, 124 KB |
A-aft Near-IR
browse resolution, GIF
507 x 411, 124 KB |
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| Raw Images |
Here, in the unmodified, raw form, for just the red color band, are all nine
multi-angle AirMISR views of the target area, all from the one run of the
aircraft.
The above AirMISR red-band (670 nm) images are "raw" in that they have
undergone minimal processing at this stage, having not yet been radiometrically
calibrated, georectified, or co-registered. The images have been flipped and
rotated into the correct geographic orientation with north roughly toward the
top. The heading of the ER-2 aircraft was toward the south. Subsequent
processing (see previous section) will georectify the images, eliminating the
visible effects of rapid aircraft pitch, roll, and yaw changes, e.g., the wiggly
appearance of linear features such as the Moffett Field runways and some blurred
stripes at the more oblique views. From the aircraft altitude of 20,000 meters,
the nadir (An) view has a resolution of 7 meters.
The view angles at Earth's surface are included in the table above for
each of the images. The D-aft view is ultimately intended to be at 70.5 degrees;
however, at the time of this flight the instrument was capable of reaching only
67.5 degrees in this direction because of a temporary mechanical clearance
issue.
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Af - forward view
(southward) at 26.1 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1235, 1.3 MB |
Bf - forward view
(southward) at 45.6 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1684, 1.5 MB |
Cf - forward view
(southward) at 60.0 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 3227, 3.2 MB |
Df - forward view
(southward) at 70.5 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 3227, 3.2 MB |
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An- nadir view
(vertical) at 0.0 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1235, 1.3 MB |
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Aa - aft view
(northward) at 26.1 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1235, 1.3 MB |
Ba - aft view
(northward) at 45.6 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1235, 1.3 MB |
Ca - aft view
(northward) at 60.0 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1235, 1.3 MB |
Da - aft view
(northward) at 67.5 deg.
browse resolution, GIF
600 x 444, 223 KB
full resolution, GIF
1520 x 1235, 1.3 MB |
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