Mars Global Surveyor
Mars Orbiter Camera

Mars Global Surveyor MOC Celebrates 2 Years in Orbit!

MGS MOC Release No. MOC2-177, 13 September 1999


It seems like only yesterday. Mars Global Surveyor (MGS) first reached the red planet two years ago on September 11, 1997 (Pacific Daylight Time). The very first high resolution picture acquired by the Mars Orbiter Camera (MOC) was obtained on the spacecraft's third orbit on September 15, 1997. This first picture was also the first twilight image obtained by MOC--the sun had already set and was about 1° below the local horizon. Scattering of sunlight reflected off airborne dust allowed a small portion of the floor of Lasswitz Crater--a 122 km (76 mi) diameter basin located at 9.4°S, 221.6°W--to be seen by the MOC on this first of many thousands of images that were to be obtained. The MGS spacecraft flew over Lasswitz Crater again on July 9, 1999--almost 1 martian year later. The new image taken by MOC had much better viewing conditions--the sun was in a 2 p.m. configuration, the camera was in focus, and the spacecraft altitude was low enough that the picture obtained has a resolution of about 1.8 meters (6 feet) per pixel.

Figure 177-A (top, above) shows Lasswitz Crater as it appeared on July 9, 1999. Sunlight illuminated the scene from the upper left. The two white boxes indicate the locations of the very first MOC narrow angle image taken from orbit around Mars (15 SEPT 97) and a higher-resolution view taken during a recent Mapping Phase orbit (09 JULY 99). The picture was taken by the MOC red wide angle camera at the same time that the 09 JULY 99 narrow angle frame was acquired. The picture has been map-projected so that north is up.

Figure 177-B (middle, above) shows what the first MOC narrow angle view of Mars looked like before it was map-projected. This image, AB-1-003/05, was taken from an elliptical, 45-hour orbit on September 15, 1997. The local time of day on the ground was just after sunset. Each pixel in this image represents 2.7 meters (9 ft) in the crosstrack (left-right) dimension and 23.7 meters (78 ft) in the downtrack (top-bottom) dimension.

Figure 177-C (bottom, left) shows the September 15, 1997, MOC narrow angle picture in map-projected form. Here, north is up and illumination is from the left. The image covers a portion of the floor of Lasswitz Crater that is about 5.5 km (3.4 miles) wide and 12 km (7.5 miles) long. Low hills and a few small impact craters can be discerned.

Figure 177-D (bottom, center) shows a portion of the same area on Lasswitz Crater floor that was covered by MOC in September 1997---only this time the image was acquired from the ~380 kilometers-(236 miles)-high, 2-hour MGS Mapping Orbit on July 9, 1999. The Mapping Orbit was finally achieved in late February 1999, after nearly 1 extra year of careful aerobraking to reduce stress on one of the spacecraft's solar panels that was damaged shortly after launch in November 1996. The image shown here covers an area only 1.5 km (0.9 mi) wide. It shows a relatively smooth mantle--presumably of dust--covering the hills that were also visible in the earlier, September 1997 image. Small meteoroids have punctured the dust cover in places, leaving small, bright-rimmed craters. A few, small, bright windblown drifts are visible in the lower half of the scene. This picture is a simple cylindrical map-projected view, north is up and illumination is from the upper left. For a full-resolution (1.8 meters--6 feet--per pixel) view of this image (1.1 Mbytes), Click HERE.

Figure 177-E (bottom, right) shows the September 1997 image overlain by the July 1999 image (darker inset) to show where the more recent image is located within the earlier view. North is up and illumination is from the left. The larger image covers an area approximately 5.5 km (3.4 miles) wide and 12 km (7.5 miles) long. The smaller view is 1.5 km (0.9 mi) wide.

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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