Software helps Mars rovers find winter havens (Forwarded)

Research Communications
Ohio State University

Contact:
Ron Li, (614) 292-6946

Written by:
Pam Frost Gorder, (614) 292-9475

12/7/07

SOFTWARE HELPS MARS ROVERS FIND WINTER HAVENS

COLUMBUS , Ohio -- New software is helping NASA find safe places for the
Spirit rover to ride out future Martian winters -- and also plan where
Spirit and its companion rover, Opportunity, will explore in the future.

The steep Martian mesa dubbed "Von Braun" would be a safe haven, the
software and data analysis determined -- but the path that Spirit would
have to follow to get there is a little too risky to travel with winter on
the way, explained Ron Li, professor of civil and environmental
engineering and geodetic science at Ohio State University.

That's one reason why Spirit is currently headed to the northern rim of a
depression called "Home Plate" for the winter -- though, as of early
December, it was rolling through loose soil that was hampering its
progress.

Li and his research team are developing several software programs to help
the rovers navigate. The latest program used satellite images, as well as
rover images, to determine that Von Braun's more than 25-degree incline is
steep enough for the rover's solar panels to gather critical energy from
the low winter sun. But it also determined that there are no safe winter
sites on the route to Von Braun where the rover could hide out in a pinch.

Should Spirit set out on the 400-foot journey to Von Braun and not be able
to reach it, there are not enough bail out spots along the route where it
could take refuge, the software found. Even in ideal driving conditions,
the trip would take a number of days. And with the winter approaching,
Spirit might need to stop at steep slopes where it could better angle its
solar panels to gather light.

"Once we identified Von Braun as a good winter site, our job was to help
the rover find a safe path there from Home Plate, and identify a few 'bail
out' spots in case anything happened in between," Li said. "But we
couldn't find any bail out spots with a steep enough slope."

The Ohio State software uses images from the High Resolution Imaging
Science Experiment (HiRISE) camera onboard the Mars Reconnaissance
Orbiter. It compares those images to panoramas taken by the rovers on the
ground to precisely map features on the surface.

Li described the software Wednesday, December 12, 2007, in a poster
session at the American Geophysical Union meeting in San Francisco.

Previously, his team used similar software to map Opportunity's path as it
descended into Victoria Crater. The new software does more, by helping
scientists identify Martian surface features that the rovers can
investigate.

"HiRISE gives us 0.3-meter (one foot) resolution on the ground, so we can
combine those orbital images with ground images to identify rocks from the
orbiter and the ground," Li said.

The key, he said, is to combine panoramas taken by the rovers to give a
wide view of the terrain. The rover takes one panorama, then travels a
distance from several feet to 300 feet, depending on the terrain and tasks
it's performing at the time.

The software combines two or more rover panoramas in a way analogous to
how our brain combines the images from our left eye and right eye to give
us a stereo view of our surroundings. Only the software is able to
calculate where features on the landscape are located, and match them to
features on HiRISE images at high accuracy.

One of the new functions of the software is this so-called wide baseline
stereo. "It's as if the rover had a baseline view that was bigger than the
rover itself," Li said.

The Mars Exploration Rover team expects it may find some very interesting
geologic features on Von Braun, so Spirit may travel there next year --
after winter's danger has passed.

This continuing research is funded by NASA. The Ohio State scientists are
working to further develop the software so that future rovers can use it
to navigate automatically.

In the meantime, they have joined the European Space Agency mission
ExoMars, which will launch a Mars mission with a rover of its own in 2013.
Li will be working on the science team for the PanCam instrument, which
will let the ExoMars rover take 3D panoramas of the red planet.

Editor's note: During the meeting, Li can be reached through Pam Frost
Gorder. She can be reached by email or in the AGU press room (2012 Moscone
West) at (415) 348-4440.

Poster #0432, "Rigorous Photogrammetric Processing of HiRISE Stereo Images
for Topographic and Geomorphologic Analysis at MER landing sites," will be
available starting at 8:00 a.m. PT (11:00 a.m. ET) Wednesday, December 12,
2007 as part of session P31B in room MS Exhibit Hall B.

[NOTE: An image supporting this release is available at
http://researchnews.osu.edu/archive/wintersitepix.htm ]