However, as the spacecraft has moved from the low illumination conditions near the evening terminator towards higher sun elevation angles, the images have been improving. Two of the best images are presented here in several versions, along with "context" frames derived from Viking Orbiter images.
Mars Global Surveyor Mars Orbiter Camera Release: MOC2-11A,-11B,-11C
Mars Global Surveyor Mars Orbiter Camera Image IDs: 559142748.503
A: Viking Orbiter Context Image (250 KB) B: MOC Image P005_03 (593 KB)
Oblique view of P005_03 (132 KB)
MOC image P005_03 was acquired at 6:25 AM PDT on September 19, 1997, about 11 minutes after Mars Global Surveyor passed close to the planet for the fifth time. During the imaging period, the spacecraft was canted towards the sun-lit hemisphere by 25°, and the MOC was obliquely viewing features about 1600 km (1000 miles) away. The resolution at that distance was about 6 meters (20 feet) per picture element (pixels), but in order to improve the number of gray levels, the pixels were summed in both the cross-track and along-track directions, yielding final resolution of about 12 meters (40 feet) per pixel. The MOC image covers an area about 12 km X 12 km (7.5 X 7.5 miles).
Shown above are three pictures:
(A) is excepted from the U.S. Geological Survey's Mars Digital Image Mosaic, showing the Labyrinthus Noctis area west of the Valles Marineris. This image is about 175 km (109 miles) square. The outline of the MOC high resolution (Narrow Angle ) camera image is centered at 4.6°S, 102.6°W.
(B) is the MOC frame P005_03. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to distort the image slightly.
(C) shows P005_03 skewed and rotated to the perspective that MOC was viewing at the time the image was taken.
Mars Global Surveyor Mars Orbiter Camera Release: MOC2-12A,-12B,-12C
Mars Global Surveyor Mars Orbiter Camera Image IDs: 559303731.605
A: Viking Orbiter Context Image (146 KB) B: MOC Image P006_05 (655 KB)
C: MOC P006_5 (enlargement) (794 KB)
D: Oblique view of P006_05 (175 KB)
E: Oblique view of P006_05 (Enlargement)(628 KB)
At 3:08:30 AM on September 21, 1997, the MOC field of view swept across the highland valley network Nirgal Vallis at 28.5°S, 41.6 W. Although the MGS spacecraft was at an altitude of about 400 km (250 miles), the MOC was pointed obliquely across the planet at about 35°, so the distance to Nirgal Vallis was closer to 800 km (500 miles). At that range and viewing angle, the MOC field of view was about 16 km (10 miles) wide, and the resolution was about 9 meters (30 feet) per pixel. The acquired image is 36 km (23 miles) long.
Five images are shown above:
(A) is an excerpt from the USGS MDIM, roughly 180 km (112 mile) square. The small box outlines the MOC image acquisition.
(B) is MOC frame P006_05, shown here at reduced resolution because the full image is almost 7 MBytes in size. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to significantly distort the image. However, even in this reduced resolution version, dunes can be seen in the canyon and in areas on the upland surface around the canyon.
(C) shows a portion of P006_05 at the full resolution of the data. This view shows the dunes more clearly, and also illustrates better the distortion introduced by the method of data acquisition.
(D) shows P006_05 skewed and rotated to the perspective that MOC was viewing at the time the image was taken.
(E) shows a full-resolution version of a portion of the rotated perspective view.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
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