Research Communications
Ohio State University

Ron Li, (614) 292-6946

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



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

“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 ]