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The Planetary Society BlogBy Emily LakdawallaButtoning up the Mars Orbiter Camera science investigationJan. 15, 2010 | 15:21 PST | 23:21 UTC
The science team for Mars Orbiter Camera, or "MOC" (pronounced "mock") has just published a paper that attempts to summarize an investigation that spanned more than two decades. MOC's first image of Mars was taken on July 2, 1997, while Mars Global Surveyor was still more than 17 million kilometers from Mars orbit insertion; the final image was taken on October 17, 2006 as part of MOC's routine weather monitoring, a few weeks before contact was lost with the orbiter, on November 3, 2006. Between those two dates were nearly ten Earth years, and, more importantly, more than four Mars years, of nearly continuous observations, including 62,571 images from MOC's wide-angle camera and 97,097 from the narrow-angle camera. The wide-angle camera covered all of Mars nearly every day of the mission, while the narrow-angle camera provided high-resolution shots covering 5.45% of the planet's surface.
Starting in August 2003, the MOC team began soliciting broad public and science community suggestions for MOC narrow angle camera targets through an interface available on the Internet. The MOC Public Targeting Program resulted in a total of 4,636 requests, 1,086 of which were satisfied by acquisition of one or more narrow angle images (and, usually, a red wide angle context frame) by the time of the abrupt end of the MGS mission. About a quarter of the public requests came from members of the Mars scientific community, but this resource was generally underutilized by Mars scientists. A little more than half of the requests came from a single individual, a member of the general public. Some of the science community requests resulted in publications....One member of the public who [participated in the target request effort expressed his experience in a letter to The Planetary Society's The Planetary Report, saying, "For two years, I made suggestions and received many pictures back from Mars. It was one of the most exciting ventures I've ever attempted. It was like a football fan being able to run a few plays in the Super Bowl." Another interesting tidbit: The MOC on Mars Observer acquired a total of four images of Mars on approach: two through the narrow-angle camera, and one each through the red and blue wide angle cameras (the last two show Mars as only one pixel). The article states that "The PDS elected not to receive this data." That seems like a loaded sentence but I can't interpret the subtext. Here's one of the two narrow-angle camera images of Mars from Mars Observer; the whole Mars Observer imaging data set, all four pictures, is available here, part of the supplemental data provided with the article.
The timing of the final images is kind of interesting. The last images taken by MOC were on October 17, just before the spacecraft went into solar conjunction. In fact, the very last images were very strongly affected by the spacecraft being so close to the Sun in Earth's sky. They were taken and relayed normally by the spacecraft, but it was difficult for the DSN antennae to receive the signal and the data as received on the ground is really really cruddy. I dug in to the PDS to retrieve the very last image of Mars taken by Mars Orbiter Camera, and it was this one; I checked with Ken Edgett and confirmed that yes, this is how the image appears to him, too. This is what happens when you try to transmit data too close to the Sun!
On top of the geology, MOC provided a resource for continuous monitoring of Mars' weather over four Mars years, and what they learned is pretty cool. I don't read many publications about Mars weather because, to be totally honest, reading about atmospheric stuff makes me yawn violently. But there were several statements in the weather section that made me sit up and take interest. For instance, they presented a fascinating set of observations where they saw the same storm appear at the same time (calendrically speaking) in the same place on Mars for four Mars years straight. Also, they drew a careful distinction between planet-encircling dust clouds (which do exist) and "global dust storms" (which don't). The distinction has to do with the violence of local weather. Local dust storms with dust-raising winds can loft dust to where it gets transported around the whole globe; but the whole globe is not experiencing dust-raising winds in those global dust events. All in all, a fascinating -- and relatively easy -- read; go check it out for yourself!
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