NASA's Mars-Bound Phoenix Adjusts Course Successfully August 10, 2007
NASA's Phoenix Mars Lander today accomplished the first and largest
of six course corrections planned during the spacecraft's flight
from Earth to Mars.
Phoenix left Earth Aug. 4, bound for a challenging touchdown on May 25,
2008, at a site farther north than any previous Mars landing. It will
robotically dig to underground ice and run laboratory tests assessing
whether the site could ever have been hospitable to microbial life.
Phoenix today is traveling at about 33,180 meters per second (74,200
miles per hour) in relation to the sun. The first trajectory-correction
maneuver was calculated to tweak the velocity by about 18.5 meters per
second (41 miles per hour). The spacecraft fired its four mid-size
thrusters for three minutes and 17 seconds to adjust its trajectory.
"All the subsystems are functioning as expected with few deviations
from predicted performance," said Joe Guinn, Phoenix mission system
manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Key activities in the next few weeks will include checkouts of science
instruments, radar and the communication system that will be used during
and after the landing.
The second trajectory-correction maneuver is planned for mid-October.
"These first two together take out the bias intentionally put in at launch,"
said JPL's Brian Portock, Phoenix navigation team chief. Without the
correction maneuvers, the spacecraft's course after launch day would miss
Mars by about 950,000 kilometers (590,000 miles), an intentional offset to
prevent the third stage of the launch vehicle from hitting Mars. The launch
vehicle is not subject to the rigorous cleanliness requirements that the
spacecraft must meet as a protection against letting Earth organisms get
a foothold on Mars.
The burn began at 11:30 a.m. Pacific Daylight Time. Each of the four
trajectory-correction thrusters provides about 15.6 newtons (3.5 pounds) of
force. Smaller, attitude-control thrusters pivoted the spacecraft to the
desired orientation a few minutes before the main burn and returned it afterward
to the right orientation for catching solar energy while communicating with
Earth. Their thrust capacity is about 4.4 newtons (1 pound) apiece. The twelve
largest thrusters on Phoenix, delivering about 293 newtons (66 pounds) apiece,
will operate only during the final minute before landing on Mars.
The Phoenix mission is led by Peter Smith of the University of Arizona,
Tucson, with project management at JPL and development partnership at Lockheed
Martin, Denver. International contributions are provided by the Canadian Space
Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen
and Aarhus, Denmark; the Max Planck Institute, Germany; and the Finnish
Meteorological Institute. JPL is a division of the California Institute
of Technology in Pasadena.