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August 25 1997
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August 25 1997

AirMISR Flight of Auguest 25, 1997, Moffett Field, CA

Color-Composite Images Roll-Corrected Images Raw Images

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.

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.

Af-forward view (southward) at 26.1 deg. Aa-aft view (northward) at 26.1 deg.
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

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.

afb afg afr afn
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
aab aag aar aan
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

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.

Af - forward view (southward) at 26.1 deg. Bf - forward view (southward) at 45.6 deg. Cf - forward view (southward) at 60.0 deg. Df - forward view (southward) at 70.5 deg.
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
 
An- nadir view (vertical) at 0.0 deg.      
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
     
 
Aa - aft view (northward) at 26.1 deg. Ba - aft view (northward) at 45.6 deg. Ca - aft view (northward) at 60.0 deg. Da - aft view (northward) at 67.5 deg.
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