If all goes as planned Friday, the University of Arizona's High Resolution Imaging Science Experiment (HiRISE) will begin doing for Mars a little of what Google Earth has done for the home planet.
HiRISE, a UA-designed, high-resolution camera aboard the Mars Reconnaissance Orbiter (MRO), is in a polar orbit — doing laps around Mars from north pole to south pole, rather than circling its girth.
Scientists and technicians at UA's Lunar and Planetary Lab will command it to photograph roughly 1 percent of the planet's surface in the first Earth year of HiRISE's operation, according to UA Planetary Science Professor Alfred S. McEwen, the project's principal investigator.
The photos — in 3.6-mile-wide-by-10.8-mile-long swaths taken as HiRISE races across Mars' surface at 7,800 mph, at 150 to 186 miles altitude — are stored and then beamed back to Earth from the MRO's 3-meter antenna.
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Each pixel will capture about 12 inches of Mars, said Chris Okubo, a HiRISE team member involved in setting up the camera. Okubo said that compares to the resolution Web users get when viewing metropolitan areas using Google Earth.
"It's like imaging grains of sand on the side of the road at 125 mph," says McEwen.
Possibly as soon as Friday afternoon, an image sent back from HiRISE through the MRO will be put up on Internet for all to see and use.
Some of the "will it work?" drama has already been defused; the camera was turned on in March, before the MRO began dipping into Mars' atmosphere, like a kid on a swing dragging his feet, to scrub off speed and lower its orbit.
The camera worked, though the images it sent back weren't nearly as detailed as close-ups the team expects now that the camera is much closer.
Today, the team will upload a set of commands that will tell HiRISE — a digital camera with a telescope, the largest ever to leave Earth orbit, for a lens — what to photograph and what settings to use.
HiRISE has 14 devices called CCDs, much like the chips used in digital cameras, says McEwen. But, unlike an off-the-shelf digital camera, it doesn't have automatic settings.
So Monday, McEwen and three of HiRISE's six targeting specialists — Okubo, Lisa McFarlane and Anjani Polit — huddled in front of a pair of Mac computer screens, setting the camera for the anticipated conditions at each of the swaths to be photographed in the first group.
McEwen explained that Mars' atmosphere contains fine dust, which can scatter light, varying light angles and objects with widely varied reflectivity — from sparkling carbon dioxide frost to dull dirt. Gather too much light, by using the wrong settings, and the image could be "blown out," unusable. The same for too little light.
McEwen says success is not only having the camera work and transmit images, but using this information to reveal something about Mars.
For instance, despite the marvelous images captured by earlier orbiting Mars cameras — which piqued further interest in the "canals" and other features seen from Earth — surface details were sketchy.
And Mars landers, although they sent back photos with better surface detail, have only visited a tiny portion of the planet.
McEwen says areas that look flat in photos taken from earlier orbiting cameras, may not be flat enough for a successful landing. Though those areas are no doubt generally flat, McEwen says the existing cameras haven't provided enough detail to pick out possible landing site deal-breakers such as boulders.
"From orbit, the best we had was the Mars Orbital Camera," says McEwen. That camera could not pick out images under about 16 feet in diameter, he says. "Ours should be about five times better, with better color and pointing capability — a number of things that will be cumulative improvements."
Among HiRISE's priority tasks, says McEwen, is scouting landing sites for upcoming missions, including the UA's own Phoenix Mars Lander, set to launch next August for May 2008 touchdown on Mars. To do that safely, McEwen says, HiRISE's high resolution, its ability to "see" objects smaller than a meter in diameter, is crucial.
After landing-site investigations, answers to questions about the geologic history of Mars top HiRISE's to-do list. Was it once covered in an ice sheet? Were there large lakes or oceans? Is there water near the surface? What is the origin of those gullies? Was it ever wet enough for life to have evolved? How has the climate changed?
Not only are scientists from all over the world invited to make photo requests, but the uncredentialed, Mars-curious public, too.
HiRISE has a second name, "The People's Camera," say McEwen and McFarlane, because as soon as this fall people all over the world will be able to make suggestions about what it should photograph on Mars.
● HiRISE and Mars Reconnaissance Orbiter Web sites:
The Planetary Image Resource Laboratory: pirlwww.lpl.arizona.edu
