Mars orbiting cameras debut as MRO adjusts orbit
Thu Apr 13, 2006 at 20:27 UTC
Researchers today released the first Mars images from two of the three science cameras on NASA's Mars Reconnaissance Orbiter.
Images taken by the orbiter's Context Camera and Mars Color Imager during the first tests of those instruments at Mars confirm the performance capability of the cameras even though the test images were taken from nearly 10 times as far from the planet as the spacecraft will be once it finishes reshaping its orbit. Test images from the third camera of the science payload were released previously.
"The test images show that both cameras will meet or exceed their performance requirements once they're in the low-altitude science orbit. We're looking forward to that time with great anticipation," said Dr. Michael Malin of Malin Space Science Systems, San Diego. Malin is team leader for the Context Camera and principal investigator for the Mars Color Imager.
The cameras took the test images two weeks after the orbiter's March 10 arrival at Mars and before the start of "aerobraking," a process of reshaping the orbit by using controlled contact with Mars' atmosphere. This week, the spacecraft is dipping into Mars' upper atmosphere as it approaches the altitude range that it will use for shrinking its orbit gradually over the next six months.
The orbiter is currently flying in very elongated loops around Mars. Each circuit lasts about 35 hours and takes the spacecraft about 27,000 miles (43,000 kilometers) away from the planet before swinging back in close.
On Wednesday, a short burn of intermediate sized thrusters while the orbiter was at the most distant point nudged the spacecraft to pass from approximately 70 miles (112 kilometers) to within 66 miles (107 kilometers) of Mars' surface.
"This brings us well into Mars' upper atmosphere for the drag pass and will enable the mission to start reducing the orbit to its final science altitude," said Dan Johnston of NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., deputy mission manager.
Image Credit: NASA/JPL/MSSS
The Mars Color Imager (MARCI) camera on Mars Reconnaissance Orbiter acquired a seven-band color, wide-angle view of Mars on March 24, 2006, as part of a checkout of the orbiter's payload. This image shows a color composite made from the MARCI red, green, and blue bands. The view looks northward and includes the large Argyre Basin in Mars' southern hemisphere.
One use of the test imaging is an opportunity to fine-tune calibrations used for processing the separate bands into "true" color -- as it would appear to a human eye looking down from orbit. Further calibration will be needed. Regular use of MARCI and the other science instruments on Mars Reconnaissance Orbiter will begin in autumn 2006, after the spacecraft's orbit has been reshaped to a nearly circular, low-altitude path.
Image Credit: NASA/JPL/MSSS
This is the first image of Mars taken by the Context Camera on NASA's Mars Reconnaissance Orbiter. The spacecraft began orbiting the red planet on March 10, 2006. During its 10th close approach to Mars, on March 24, it turned its cameras to view the planet's surface. Although the images acquired were about 10 times lower in resolution than will ultimately be obtained when the spacecraft has finished reshaping its orbit for the mission's primary science phase, these test images provide important confirmation of the performance of the cameras and the spacecraft.
This first image by the Context Camera includes some chaotic terrain at the east end of Mars' Valles Marineris, seen along the top (northern) edge of the image. The image has a scale of about 87 meters (285 feet) per pixel, which is 14.5 times lower resolution than will be acquired during the primary science phase. Typical images from the Context Camera acquired during that phase of the mission will have a resolution of 6 meters (20 feet) per pixel, and will cover an area about 30 kilometers (18.6 miles) wide.
Note that, because these are initial, test images, there is some linear striping in the images. This results from incomplete removal of pixel-to-pixel variations in the Context Camera detector by the present calibration software. One use of the test imaging is an opportunity to fine-tune the calibrations before the primary science phase begins.
Image Credit: NASA/JPL/MSSS
This is a comparison of a wide-angle, red-filter image from the Mars Orbiter Camera on NASA's Mars Global Surveyor (left) with the first Mars image from the Context Camera. The image from the Mars Orbiter Camera was taken the same day, but about 6.2 hours after the image from the Context Camera, at a local solar time of 1:42 p.m. The Context Camera image was taken at roughly 7:32 a.m., local solar time.
Image Credit: NASA/JPL/MSSS
This image shows a color view cropped from a Mars Orbiter Camera daily global map acquired on the same day as the first two Mars images by the Context Camera. The map shows the planet as if every part could be imaged at some time between 1 p.m. and 3 p.m., that is, with early afternoon illumination. The cameras on Mars Reconnaissance Orbiter, conversely, imaged the planet during morning hours. The Mars Orbiter Camera view was obtained about four hours later in the day than the Context Camera data. Inserted into the daily global map are two grayscale views from the Context Camera. This shows that the Context Camera began imaging when it was over the southernmost portion of the chaotic terrain at the east end of the Valles Marineris. A second image was acquired several minutes later, as Mars Reconnaissance Orbiter flew southward towards the west side of the large Argyre impact basin. The tops of the two Context Camera images were obtained about 13 minutes apart.
Image Credit: NASA/JPL/MSSS
This image contains the northernmost portion of the second Context Camera image, reproduced at one-half its original scale (because of its large file size). The white box outlines the location of the first image from the orbiter's High Resolution Imaging Science Experiment. The Context Camera image and the High Resolution Imaging Science Experiment image were acquired simultaneously. As with the Context Camera, the first image from the High Resolution Imaging Science Experiment was of a much lower resolution than will be obtained during the primary science phase of the Mars Reconnaissance Orbiter mission, owing to the higher altitude during this test. This figure illustrates one of the key roles that Context Camera will play during the mission -- acquiring context images for the other science instruments aboard the Mars Reconnaissance Orbiter.
After hundreds of passes through the upper atmosphere, the drag will gradually reduce the far point of the orbit until the spacecraft is in a nearly circular orbit every two hours.
After the spacecraft gets into the proper orbit for its primary science phase, the six science instruments on board will begin their systematic examination of Mars. The Mars Color Imager will view the planet's entire atmosphere and surface every day to monitor changes in clouds, wind-blown dust, polar caps and other changeable features.
Images from the Context Camera will have a resolution of 20 feet (6 meters) per pixel, allowing surface features as small as a basketball court to be discerned. The images will cover swaths 18.6 miles (30 kilometers) wide.
The Context Camera will show how smaller areas examined by the High Resolution Imaging Science Experiment camera -- which will have the best resolution ever achieved from Mars orbit -- and by the mineral-identifying Compact Reconnaissance Imaging Spectrometer fit into the broader landscape. It will also allow scientists to watch for small-scale changes, such as newly cut gullies, in the broader coverage area.
NASA's Mars Reconnaissance Orbiter is managed by JPL, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor.
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