Mars Exploration Rover Spirit Mission Status
January 3, 2004
Navigators for NASA's Spirit Mars Exploration Rover put the
spacecraft so close to a bull's-eye with earlier maneuvers that
mission managers chose to skip the final two optional maneuvers
for adjusting course before arrival at Mars.
With less than four hours of flight time remaining, Spirit was
on course to land within a targeted ellipse 62 kilometers long
by 3 kilometers wide (39 miles by 2 miles) within Mars' Gusev
Crater. A trajectory correction maneuver scheduled for four
hours before landing was cancelled.
"The navigation status is truly excellent," said Dr. Lou
D'Amario, the mission's navigation team chief at NASA's Jet
Propulsion Laboratory, Pasadena, Calif. A slight trajectory
adjustment on Dec. 26 was the fourth and final for the flight.
Preparations in the past two days for arrival at Mars have
included an adjustment that will open Spirit's parachute about
two seconds earlier than it would have been without the change,
in order to compensate for recent weather on Mars. "A dust storm
seen on the other side of the planet has caused global heating
and thinning of the atmosphere at high altitudes" said JPL's Dr.
Mark Adler, Spirit mission manager.
Also, engineers sent commands today to alter the timing when
several pyro devices (explosive bolts) will be put into an
enabled condition prior to firing. Enabling will begin 40
minutes earlier than it would have under previous commands.
These pyro devices will be fired to carry out necessary steps of
descent and landing, such as deploying the parachute and
jettisoning the heat shield.
Mars is 170 million kilometers (106 million miles) away from
Earth today, a distance that takes nearly 10 minutes for radio
signals to cross at the speed of light. Counting that
communication delay, Spirit will hit the top of Mars' atmosphere
at about 04:29 Jan. 4, Universal Time (8:29 p.m. Jan. 3, Pacific
Standard Time), and reach the surface six minutes later.
JPL, a division of the California Institute of Technology
in Pasadena, manages the Mars Exploration Rover project for
NASA's Office of Space Science, Washington, D.C. Additional
information about the project is available at
http://marsrovers.jpl.nasa.gov , www.nasa.gov and from
Cornell University, Ithaca, N.Y., at
http://athena.cornell.edu .
