Where on Mars is Opportunity?
Summary (Jan 25, 2004): Using images taken by Opportunity during its descent to the martian surface, mission scientists have begun to pinpoint the rover's location. Nearby, a large crater beckons as a long-range scientific target.

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Where on Mars is Opportunity?

By Henry Bortman
Pasadena, Opportunity Mission Sol 2

In the pre-dawn hours of sol 2, Opportunity sent back to Earth dramatic new images of Meridiani Planum. Mission scientists continued to be intrigued and astonished by what they see.

Image of Meridiani landing ellipse from Mars Orbital Camera on Mars Global Surveyor. The blue arrow shows the 150 meter crater, estimated at about one-half mile driving distance, from current lander location. Banner image from MOC shows the full landing ellipse, with the blue square covering the zoom-view shown here. Credit: MSSS/MOC

Included in the new images were the three low-resolution DIMES (Descent Image Motion Estimation System) images taken by the lander during its descent through the martian atmosphere. The images show a largely featureless surface, but one large crater stands out clearly.

The crater is roughly 150 meters across, and has been tentatively estimated to be about 0.8 kilometers (about 0.5 miles) away from the lander, within easy driving distance of the rover.

DIMES images serve two purposes. The first is as a navigational aid. They help the lander determine how fast it's moving horizontally as it nears the surface. Too much horizontal motion is undesirable. The lander can compensate for this motion by firing onboard rockets. Spirit used these rockets during descent; they weren't necessary for Opportunity's descent.

The DIMES images also help mission scientists determine the lander's precise location. By comparing prominent landforms in the DIMES images with higher-resolution images taken by the MOC (Mars Orbital Camera) on the MGS (Mars Global Surveyor) orbiter, science team members can figure out precisely where Opportunity first impacted the martian surface.

Descent image (DIMES) of same 150 m wide crater likely to be an important science target. The solar glare spot just left of the crater shows the shadow of the lander's parachute as a black dot. The DIMES system takes 3 rapid images, processes them with hardware and software, then estimates the vehicle's horizontal velocity during descent. The Opportunity rover is thought to be in a 20 meter wide crater presently, based on surface panoramas. The DIMES image is 1 mile across and shot from an altitude of about 4000 feet. Credit:NASA/JPL/EDL Team

Scientists believe Opportunity came to rest inside one of the small craters visible in the DIMES image. It could take as long as another week for them to figure out exactly which crater, however. While being in a crater is great for scientific exploration, it makes it difficult to see any of the surrounding landforms that might help pinpoint the lander's location.

That process, however, could take several more days. The lander used an airbag system to cushion it's impact, and the airbags can bounce and roll for as much as a kilometer before coming to rest. But no-one knows just how far - or in which direction it bounced.

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Related Web Pages

Malin Space Systems Mars Orbital Camera
Opportunity image gallery and slideshow
Two for Two: Opportunity Lands on Mars
A Bazarre New Mars
Location Is Everything
Finding Spirit
Spirit Condition Serious

Mars Time

Note: Mars Life

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Sunday, January 25, 2004