[meteorite-list] Opportunity Closes in on the Red Planet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:08 2004
Message-ID: <200401232003.MAA08243_at_zagami.jpl.nasa.gov>

http://space.com/missionlaunches/opportunity_update_040123.html

Opportunity Closes in on the Red Planet
By Leonard David
space.com
23 January 2004

PASADENA, Calif. -- Early Jan. 25, at about 12:05 a.m. EST, NASA's
second Mars Exploration Rover -- Opportunity -- will arrive on Mars.
It's headed for a region known as Meridiani Planum, halfway around
the planet from where its sister robot, the Spirit rover now resides.

What Opportunity might find at that landing site could be the
geological mother lode at Mars that scientists seek -- a type of
mineral that cries out: "Water was here!"

As was the case three weeks ago, engineers are again faced with risk,
worry, and high anxiety in getting another robot
successfully down on Mars.

One thing for sure: It doesn't get any easier
the second time around.

Good dose of edginess

"I am almost as nervous as I was for Spirit,"
admitted Rob Manning, Mars Exploration
Rover (MER) Entry, Descent and Landing
Lead at JPL. "Even though Meridiani is an
easier landing site in some respects - less
winds, less slopes, and the rocks aren't as
bad. I'm going to be almost as nervous," he
told SPACE.com .

In reconstructing how Spirit made it down
at Gusev Crater, Manning has reason to
retain a good dose of edginess.

"We had a wild day in landing Spirit,"
Manning said. An unexpectedly large wind
gust played havoc with the spacecraft's
approach and touchdown at Gusev. That
burst of wind pushed Spirit's parachute and
other landing gear in a horizontal direction
toward a crater.

An inertial measurement unit, computer
software, special camera gear, and small
rockets onboard Spirit worked in concert to
counter what could have been a deadly drift
into the walls of the crater -- "all within a
handful of seconds," Manning noted.

"I don't know if we would have been toast.
On the other hand, it's an experiment I don't
think I would want to perform," Manning
added.

Once cut free from its parachute,
retro-rocket engines, and long bridle, the
set of airbags with the Spirit rover tucked
inside fell onto Mars from a height of about
31 feet (9.5 meters).

The airbags bounced 28 times across the
martian landscape before coming to a full
stop.

Glue gun and duct tape

At the end of the day, Spirit's safe and sound
landing comes down to one engineering rule
of thumb: margin.

Margin equates to elbow room. There is a
delicate balance between margins and how
close-to-the-edge engineers feel is
tolerable. But then add in the vagaries of the
Mars environment, well, those uncertainties
can give you a bad day.

"From what I see, we have a lot of margin.
We are confident that we made the right
design choices in our rover landing system to
make it reliable," Manning said. "But you
never know. If I could land a thousand of
these things, then I could tell you. We're
still in the infant stages of this stuff."

Lessons learned from getting Spirit down
and dirty on Mars are being applied to the
landing of Opportunity.

For example, Opportunity's parachute is to
be deployed higher and five seconds earlier
than planned over Meridiani Planum.
Secondly, gas generators to inflate the airbag
landing system have been tweaked to reduce
their warm-up time during the plummet
toward Mars' surface.

Opportunity's landing system is good to go,
Manning said. "Our mission is not to do
engineering, although it's fun, exciting, and
a lot of work. It doesn't matter if you took a
glue gun and duct tape to get to Mars. As
long as you get there safely - and we get good
science for the mission - that's the most
important thing," he explained.

Colorful territory

At Meridiani Planum, the Opportunity
rover becomes a stranger in a strange land.

"This site will truly be an alien landscape. It
will not look like anywhere we have been before on
Mars," said James Rice, a Mars Exploration Rover
scientist from the Arizona State University in Tempe.

Rice said he expects Opportunity to drop into colorful
territory, perhaps a deeper, darker reddish brown with
splashes of gray.

"All that pesky bright dust that we are familiar with
will be absent," Rice told SPACE.com . The chances of
encountering fantastic layered sediments will be much
higher in Meridiani than at Gusev Crater, he explained.

These layers may be visible in small mesas and buttes.
Moreover, the landscape appears to have been stripped
by the wind. There will also be far fewer rocks than at
Gusev, roughly half the rock abundance seen in the
images returned by Spirit, Rice said.

"We may also see dune forms and small impact craters
depending on where we put down in the landing ellipse,"
Rice added.

Gray hematite

Opportunity's targeted landing area is an ellipse about
53 miles (85 kilometers) long and 6.8 miles (11 kilometers)
wide.

This zone is within a large region near the planet's
arbitrarily designated prime meridian, or line of zero
longitude. "Planum" means plains. So the name suits the
territory. Meridiani Planum is one of the smoothest,
flattest places on Mars.

Meridiani Planum has been found to contain the detectable
mineral signatures for coarse grained gray hematite - a
type of iron oxide mineral. This type of hematite generally
forms in water.

On Earth, gray hematite usually -- but not always - forms
in association with liquid water. Some environmental
conditions that can produce gray hematite, such as a
lake or hot springs, could be quite hospitable to life.
Others, such as hot lava, would not.

On course cruise

Like its twin on the other side of Mars, Opportunity will
use a rock abrasion tool and two spectrometers attached to
the rover's arm to resolve what martian environment
produced the hematite at Meridiani Planum.

"I think we're going to see some very interesting terrain,"
said Steve Squyres, Principal Investigator for the MER program
and a space scientist from Cornell University.

Mission planners decided Thursday to skip an optional
trajectory correction maneuver for Opportunity as it cruises
toward Mars. There is still time to fine-tune the spacecraft's
aim point within Meridiani Planum, although it appears such a
final action item is not needed.

Opportunity is right on course to land halfway around Mars from
Spirit.

"We expect everything to work nominally on Opportunity," said
Charles Elachi, Director of JPL. "But still you have the risk
of any entry, descent and landing - it's always risky."

Editor's Note: Opportunity's landing is slated for 12:05 a.m.
EST on Sunday, Jan. 25. That corresponds to 9:05 p.m. PST on
Saturday, Jan. 24 in the mission control
room at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Received on Fri 23 Jan 2004 03:03:34 PM PST