May 25, 2008

Nerves Run High for Spacecraft’s Sunday Mars Landing

This story was updated at 5:46 p.m. EDT.

PASADENA, Calif. – Excitement
and nerves are both running high among NASA scientists as they prepare for the
Phoenix Mars Lander's planned Sunday arrival at the red planet, mission
scientists said today.

The spacecraft is
still in good shape and on track as it nears
the finish line
of its 422 million-mile (679 million km) trek to the
Martian arctic.

"Well this is exciting, a very exciting day," said Doug McCuistion,
director of the Mars Exploration program for NASA, at a press briefing at here
at the agency's Jet Propulsion Laboratory (JPL). "The atmosphere here at JPL is

But in addition to excitement, Phoenix scientists are getting a strong
case of nerves.

"The anxiety level is getting high," said Phoenix project manager at JPL
Barry Goldstein.

"I'm getting a real case of the heebie-jeebies now," echoed Joe Guinn,
Phoenix mission manager at JPL.

The craft, now just over 1 million miles (about 1.6 million km) from Mars, is slated to land in the north polar regions of Mars in the
Vastitas Borealis plains
. Mission scientists expect to receive the signal
that Phoenix has landed on Sunday at 7:53 p.m. EDT (2353 GMT). The first images
from the craft could be sent back to Earth as soon as a couple of hours after

The $420-million
mission, which launched last August, plans to dig
to the rock-hard layers of water ice thought to lie under the Martian
soil near the planet's north pole. It is designed to test the soil and ice for
signs that liquid water existed there in the past using some of the instruments
originally created for its ill-fated predecessor, the Mars Polar Lander, which
failed before landing in 1999.

A trajectory
correction maneuver opportunity scheduled for late this evening could be
skipped, mission engineers said, as Phoenix still seems to be flying true after
its last thruster maneuver a week ago. The craft has already skipped one
correction opportunity. The team will have one more opportunity to adjust
Phoenix's trajectory tomorrow morning if required.

The likelihood of
needing to make a correction tomorrow will influence the decision to make a
correction today, Goldstein told Making a maneuver today,
while the landing is still almost 24 hours away, is much less nerve-wracking
than making one tomorrow because there's more time to see if the maneuver
worked, he said. Having to make a maneuver just eight hours before landing
leaves much less wiggle room.

"That's really scary,"
Goldstein said.

Goldstein says the
series of meetings and the work to prepare
for the landing
tomorrow help take his mind off of his nerves, that and
eating lots of ice cream.

He also said that a
long-standing tradition at JPL to kill the butterflies on landing day is to
pass out peanuts to all the people in mission control. The tradition supposedly
goes back to the Ranger missions to the moon; after the first few failed,
people began to eat peanuts to calm their nerves.

"I already have the
peanuts purchased," Goldstein said.

The weather on Mars
also still looks optimal for landing day. Only one dust storm has been spotted
in the area, and was actually seen directly over the landing site yesterday,
but it will likely be out of the way come landing time given its current rate
of movement, Goldstein told reporters on a tour of JPL mission control

"The good news is... that cloud has now passed over our landing site,"
said Phoenix principal investigator Peter Smith of the University of Arizona,
adding that mission scientists are "watching the weather, we're going to be
watching it throughout the mission."

What has scientists
most on edge is Phoenix's "fiery entrance into the atmosphere" tomorrow, as
Goldstein put it. While each of the individual systems that have to deploy
tomorrow, from the parachute, to releasing the back shield and firing the
thrusters, have checked out so far, it's the strict sequence that the systems
have to follow that make mission
scientists most nervous

The last successful
landings on Mars were the two Mars Exploration Rovers, Spirit and Opportunity
in January 2004, with the hardy robots still exploring the planet today.

Phoenix won't use the
same airbag-cushioned landing technique that brought those crafts safely to the
Martian surface. Instead, it will use thrusters to slow its rapid descent
through the atmosphere. This technique has not been used successfully since the
Viking mission in the 1970s and was last used by the failed Mars Polar Lander
(MPL) in 1999.

The mission team has
corrected many of the problems encountered with MPL, but as McCuistion said
during the briefing, "Mars is always there to throw those unknowns at us."

NASA's next Phoenix
mission briefing will be broadcast live on NASA TV at 3:00 p.m. EDT (1900 GMT)
on Sunday, May 25. Click
for's Phoenix mission coverage and a link