[meteorite-list] Scientists Find Obstacle at Heart of Beagle Landing Zone

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:05 2004
Message-ID: <200312291620.IAA19455_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/mars/marsexpress/031229crater.html

Scientists find obstacle at heart of Beagle landing zone
BY JUSTIN RAY
SPACEFLIGHT NOW
December 29, 2003

The first clear view of the specific area where the British Beagle 2 lander should
have touched down Christmas Day has revealed a one-kilometer crater dead
center in the target landing zone, but officials are quick to say the discovery
doesn't dash their optimism of finding the missing craft.

"This would be an incredibly unlucky situation," Colin Pillinger, lead scientist
for the Beagle 2 project, said this morning.

To date, all attempts using the American Mars Odyssey orbiter and radio
telescopes in the U.K. and California have failed to detect a peep from Beagle.

NASA's Mars Global Surveyor orbiter snapped the landing site image 20
minutes after Beagle's scheduled 0254 GMT arrival December 25. The view
isn't sharp enough to show the two-meter wide spacecraft. However, the
image did uncover a crater not unlike the famous meteor impact crater in the
southwest United States.

"Meteor Crater out in Arizona is a 1.2-kilometer crater...several hundred
meters deep. This crater is comparable in size," Pillinger said.

Although Beagle scientists had examined numerous photographs of the broad
Isidis Planitia region near the Martian equator while selecting that area to send
the lander, the new Global Surveyor image is the first good view of the
ellipse-shaped zone where Beagle was expected to land.

"When we were choosing this site in the first place, we avoided the obvious
craters that we could see at relatively low-resolution. You cannot avoid every
crater on Mars, you'd never go there," Pillinger said.

"We'd chosen the area that we were landing because we believed it was the
right sort of area to risk a landing -- no slopes, low altitude, rock abundance
less than 15 percent. It was repeatedly said 'enough to keep the geologists
happy but not so many (rocks) that it frightens the engineers to death.'"

Global Surveyor's camera is operated by Malin Space Science Systems.

"Something which came out of Mike Malin taking pictures of the actual area in
which we believe we were targeted to land is right at the center, right at the
center of the ellipse that we were aiming at, is a one-kilometer-across crater,"
Pillinger said.

"This is the first picture that he has actually taken in detail anywhere near
where we were supposed to be. Of course, he wasn't able to do that
until we had the absolute ellipse that we were able to compute after Mars
Express had set Beagle on its way."

"When we started to plan the mission, the estimate of the landing ellipse was
480 by 300 (kilometers), which is a very large area. As Mars Express has
flown out to Mars, navigation has gotten better and better," mission manager Mark
Sims said.

Following Beagle's deployment from the Mars Express orbiter on December 19, mission
officials were able to narrow the landing zone to an ellipse-shaped swath
70 kilometers long and 10 kilometers wide.

"There is absolutely no way you could target to avoid a one-kilometer crater.
The target got smaller the better we knew the trajectory of Mars Express. The
best, the absolute best that could be done, was we were targeting 70 by 10
kilometers. There are an awful lot of one-kilometer craters that you can put into
an ellipse that size," Pillinger said.

Despite this new revelation, officials say the chances of Beagle reaching the
crater are slim.

"We must stress this a low probability, it is only one of a number of
possibilities," Sims said of why Beagle has yet to phone home.

"We would have to be incredibly accurate and also incredibly unlucky that we
went down this crater, which would not be good news -- one would not want
to go into a crater, one would not want bounce on the edge and bounce into it,"
Pillinger added.

"For obvious reasons, there is going to impact debris around it, which
means more rocks than the 15 percent, and if we get to the bottom of the
crater we actually reduce our attempts to be able to signal out of it. It
isn't any good trying to signal off to one side if you've got the
rim of crater blocking out half of the picture."

The highly ambitious Beagle lander used parachutes to slow its
descent and then three balloon-like airbags around the craft to cushion
multiple bounces on the surface before coming to
rest. Designers said the landing system needed to avoid bouncing on slopes
and rocky terrain. Also, landing in a crater could cause shadows on the craft's
power-generating solar panels that would create more trouble.

The Martian landscape is covered by impact craters. Such places have their
certain risks to robotic spacecraft but also rewards for scientists.

"There are two ways of looking at craters -- you don't want to land right by
them but you want to land near enough to them so you can take advantage. The
impact excavates rocks and gives you a nice, diverse suite of rocks that you can
analyze," Pillinger said.

Over the coming days, further tries are planned to receive a signal from Beagle
with the Odyssey spacecraft and the Stanford University radio telescope. The
European Mars Express orbiter will begin searching in early January using a
communications link previously tested with the lander.

"We are working under the assumption that Beagle 2 is on the surface of Mars
and for some reason cannot communicate to us. In particular, we're looking at
two major issues. One is communications, and there are also related timing and
software issues," Sims said.

"We've got a few more Odyssey contacts, the last one being on December 31.
Then we have four contacts with Mars Express already pre-programmed into
Beagle, assuming the software is running, on (January) 6, 12, 13 and 17. The
6th and 12th are when Mars Express is maneuvering into its final orbit, so they
are not optimum for Beagle 2 communications. The 13th and 17th are very good
opportunities for Mars Express."

Attempts using the Jodrell Bank radio telescope concluded last night since the
side of Mars where the landing site is located is no longer visible to the
observatory when Beagle should be transmitting its call.
Received on Mon 29 Dec 2003 11:20:08 AM PST