May 13, 2008

Phoenix Spacecraft on Track for Mars Landing

This story was updated at 1:33 p.m. EDT.

WASHINGTON — With just 12 days to go until its Mars arrival, NASA's Phoenix lander is
functioning well and on course to be the first mission to land in the frigid, arctic
regions of the red planet, NASA officials said today.

A planned
maneuver to adjust Phoenix's course was canceled last Saturday because the
spacecraft is on track for its May
25 landing
, said Barry Goldstein, Phoenix project manager at NASA's Jet
Propulsion Laboratory in Pasadena, Calif. Another maneuver is set for this
coming Saturday.

NASA also
released enhanced images of Phoenix's
landing site
, located at 68 degrees north latitude, 233 degrees east
longitude in Vastitas Borealis, the northern arctic planes of Mars. This
latitude corresponds to northern Canada, just below the Arctic sea, said
Phoenix principal investigator Peter Smith of the University of Arizona,

Below the
surface layer of dust in these plains lies a layer of water ice mixed with sand
and dust. During its three-month mission, Phoenix will use its 7.7-foot
(2.3-meter) robotic arm to dig up samples of this dirty ice and analyze it with
onboard science instruments to shed light on the history of water in the
Martian arctic and see if the icy
soil could support life

In these polar
regions, "there's a very large abundance of water," Smith said. "We expect a
tremendous abundance of ice in the landing site."

Phoenix is
picking up where its ill-fated brother, the Mars Polar Lander (MPL), left off
after it failed to make a safe landing in at the Martian south pole in 1999.
Though it will use nearly the same landing strategy, Phoenix contains different
instrumentation to explore the planet.

"Phoenix is
truly an appropriate name for this lander as it has risen from two Mars
failures," said Ed Weiler, associate administrator of NASA's Science Mission

$420-million mission launched
last August
and has traveled about 422 million miles (679 million km) to
reach our red-hued neighbor. The lander currently has about 10 million miles
(about 16 million km) left to go before setting down in the Martian arctic.

Phoenix is
slated to touchdown at 7:53 p.m. EDT (2353 GMT) on May 25. Unlike its rover
cousins Spirit and Opportunity (currently exploring closer to Mars' equator),
Phoenix will not use airbags to land. Instead, it will rely on a set of rocket
thrusters that will fire in slow pulses to slow the craft down during its
descent, similar to the design for the MPL.

The last
successful use of this landing approach was 32 years ago with NASA's
Viking landers
in the 1970s.

scientists said that the known problems with the MPL have been addressed and
fixed, along with several other problems engineers later identified, though
they cautioned that that doesn't rule out unforeseen issues.

we've fixed all the known issues from the MPL, remember, there is always the
unknown unknown," Weiler said.

Ray Arvidson,
chairman of the Phoenix landing site working group, said that the team at the
University of Arizona, Tucson, where the new lander's operations will be based,
will be taking the instruments through their paces in the critical first days
after landing.

"It's all
scripted," said Arvidson, adding that Phoenix scientists and engineers have
prepared for a number of contingencies after landing.

Such issues
may include problems with instruments, power failures and obstacles such as a
rock lying in the way of the deployment of the solar arrays that will power the
lander throughout its three-month mission, until the sun sets at the end of the
Martian summer.

"The risks
will certainly be there, but the rewards will absolutely pay off," said Doug
McCuistion, director of the Mars Exploration Program. The Phoenix mission's
potential wealth of information about Martian soil, the history of weather of
Mars, as well as the state of water in the planet's current climate outweigh the
risks of another failure, he added.

NASA's Mars
Reconnaissance Orbiter and Mars Odyssey have been repositioned to track descent
of Phoenix and relay communications between the lander and Earth during its
"seven minutes of terror" falling through the Martian atmosphere, as Goldstein
put it, and once the spacecraft is settled on the planet.